A case study of impact-induced hydrothermal activity: The Haughton impact structure, Devon Island,...

Meteoritics amp Planetary Science 40 Nr 12 1859ndash1877 (2005)Abstract available online at httpmeteoriticsorg

1859 copy The Meteoritical Society 2005 Printed in USA

A case study of impact-induced hydrothermal activityThe Haughton impact structure Devon Island Canadian High Arctic

Gordon R OSINSKI1dagger Pascal LEE2 John PARNELL3 John G SPRAY4 and Martin BARON3

1Lunar and Planetary Laboratory University of Arizona 1629 East University Boulevard Tucson Arizona 85721ndash0092 USA2SETI InstituteNASA Ames Research Center MS 245-3 Moffett Field California 94035ndash1000 USA

3Geofluids Research Group Department of Geology and Petroleum Geology University of Aberdeen Aberdeen AB24 3UE UK4Planetary and Space Science Centre Department of Geology University of New Brunswick

2 Bailey Drive Fredericton New Brunswick E3B 5A3 CanadadaggerCanadian Space Agency 6767 Route de lrsquoA roport Saint-Hubert Quebec J3Y 8Y9 Canada

Corresponding author E-mail osinskilycoscom

(Received 14 April 2004 revision accepted 25 October 2004)

AbstractndashThe well-preserved state and excellent exposure at the 39 Ma Haughton impact structure23 km in diameter allows a clearer picture to be made of the nature and distribution of hydrothermaldeposits within mid-size complex impact craters A moderate- to low-temperature hydrothermalsystem was generated at Haughton by the interaction of groundwaters with the hot impact meltbreccias that filled the interior of the crater Four distinct settings and styles of hydrothermalmineralization are recognized at Haughton a) vugs and veins within the impact melt breccias with anincrease in intensity of alteration towards the base b) cementation of brecciated lithologies in theinterior of the central uplift c) intense veining around the heavily faulted and fractured outer marginof the central uplift and d) hydrothermal pipe structures or gossans and mineralization along faultsurfaces around the faulted crater rim Each setting is associated with a different suite of hydrothermalminerals that were deposited at different stages in the development of the hydrothermal systemMinor early quartz precipitation in the impact melt breccias was followed by the deposition of calciteand marcasite within cavities and fractures plus minor celestite barite and fluorite This occurred attemperatures of at least 200 degC and down to sim100ndash120 degC Hydrothermal circulation through thefaulted crater rim with the deposition of calcite quartz marcasite and pyrite occurred at similartemperatures Quartz mineralization within breccias of the interior of the central uplift occurred intwo distinct episodes (sim250 down to sim90 degC and lt60 degC) With continued cooling (lt90 degC) calciteand quartz were precipitated in vugs and veins within the impact melt breccias Calcite veining aroundthe outer margin of the central uplift occurred at temperatures of sim150 degC down to lt60 degCMobilization of hydrocarbons from the country rocks occurred during formation of the highertemperature calcite veins (gt80 degC) Appreciation of the structural features of impact craters hasproven to be key to understanding the distribution of hydrothermal deposits at Haughton

INTRODUCTION

It is well-known that hydrothermal systems will developanywhere in the Earthrsquos crust where water coexists with a heatsource with magmatic heat sources being predominant onEarth today (eg Pirajno 1992 Farmer 2000) A growingbody of evidence also suggests that hydrothermal activity iscommonplace after the impact of an asteroid or comet intoH2O-rich solid planetary surfaces (see Naumov 2002 for areview) Hypervelocity impact events generate shockpressures and temperatures that can melt andor heat

substantial volumes of target material providing heat sourcescapable of sustaining a hydrothermal system The interactionof impact-melted or impact-heated materials with H2O in thenear surface of a planet will induce a hot rock-watercirculatory system that can dissolve transport and precipitatevarious mineral species This may have importantastrobiological implications because hydrothermal systems ingeneral might have provided habitats or ldquocradlesrdquo for theorigin and evolution of early life on Earth and possibly otherplanets such as Mars (eg Shock 1996 Farmer 2000 Kring2000 Cockell and Lee 2002) Hydrothermal systems are

1860 G R Osinski et al

considered plausible candidates because they represent siteswhere liquid H2O warmth and dissolved chemicals andnutrients may have been available for extended periods oftime Although impact-induced hydrothermal systems aretransient in nature because they lack the usually longer-lastingheat sources that characterize volcanogenic hydrothermalsystems they might still have subsisted long enough to haveexperienced colonization by thermophilic (heat-loving)microbial communities particularly in the case of the largerimpact structures (Cockell and Lee 2002 Rathbun andSquyres 2002)

Hydrothermal processes have also played an importantrole in the formation of many different types of mineral andore deposits (eg porphyry copper-molybdenum depositstin-tungsten-copper greisen-related deposits copper-zinc-richvolcanogenic massive sulfide deposits lead-zinc MississippiValley-type deposits) (Pirajno 1992) More recently it hasbeen noted that impact-induced hydrothermal activity canalso result in economic mineralization as has been the case atthe Sudbury (ie zinc-lead-copper-silver-gold Ames et al1998) and Vredefort (ie gold) (Grieve and Masaitis 1994)impact structures

Evidence for impact-induced hydrothermal activity hasnow been recognized at over sixty terrestrial craters (Naumov2002) from the sim18 km diameter Lonar Lake structure India(eg Hagerty and Newsom 2003) to the sim250 km diameterSudbury structure Canada (eg Ames et al 1998) Despitethe potential economic and astrobiological importance ofhydrothermal activity the nature and distribution of suchdeposits within impact craters remains poorly studied This isdue in part to the lack of surface exposure and preservationof hydrothermal deposits at many terrestrial impact sitesMoreover it is only in the past few years that hydrothermalactivity has been recognized as a fundamental processassociated with impact events The sim39 Ma Haughton impactstructure in Canadian High Arctic is well-exposed and well-preserved and as such offers an exceptional opportunity togain a better understanding of the different types ofhydrothermal deposits within impact craters and theirdistribution

Evidence for hydrothermal activity associated with theHaughton impact event was first recognized during the 1998and 1999 field seasons of the NASA Haughton-Mars Project(reported in Osinski et al 2001) Since this discoveryextensive mapping has revealed important new informationregarding the nature and distribution of hydrothermal depositsat Haughton (see map insert) This will be described herealong with analytical data that builds upon the studies ofOsinski et al (2001) New fluid inclusion data on a series ofhydrothermal minerals is also presented that helps toconstrain the temperature conditions during post-impacthydrothermal activity This data will be discussed andsynthesized with new work on the impactites (Osinski andSpray 2001 2003 Osinski et al 2005a) and tectonics

(Osinski and Spray 2005) of Haughton Collectively thesestudies enable an improved model for the impact-inducedhydrothermal system at Haughton to be presented

GEOLOGICAL SETTING OF THE HAUGHTON IMPACT STRUCTURE

Haughton is a well-preserved complex impact structure23 km in diameter that is situated on Devon Island in theCanadian Arctic Archipelago (75deg22primeN 89deg41primeW) Theimpact event occurred sim39 Myr ago (Sherlock et al 2005) in atarget comprising sim1880 m of Lower Paleozoic sedimentaryrocks of the Arctic Platform overlying Precambrianmetamorphic basement of the Canadian Shield (Thorsteinssonand Mayr 1987 Osinski et al 2005b) The unmetamorphosedsedimentary succession consists of thick units of dolomite andlimestone with subordinate evaporite horizons and minorshales and sandstones (Thorsteinsson and Mayr 1987)

Allochthonous crater-fill deposits form a virtuallycontinuous sim54 km2 unit covering the central area of thestructure (Fig 1) (Osinski et al 2005a) Recent field studiesand analytical scanning electron microscopy indicate thatthese rocks are carbonate-rich impact melt breccias or clast-rich impact melt rocks (Osinski and Spray 2001 2003Osinski et al 2005a) The impact melt breccias have amaximum current thickness of sim125 m although the presenceof this unit up to sim140 m above the central topographic lowarea suggests that they originally completely occupied thecentral area to depths of 200 m or more (Osinski et al 2005a)The present-day exposure of the allochthonous crater-filldeposits therefore represents a minimum The pale gray-weathering rocks comprise variably shocked mineral andlithic clasts set within a groundmass of calcite + silicate glassplusmn anhydrite (Osinski et al 2005a) The lithic clasts aretypically angular and are predominantly dolomite andlimestone with minor sandstones shales and evaporites andsubordinate lithologies from the crystalline basement(Metzler et al 1988)

Post-impact lacustrine sediments of the HaughtonFormation occupy the central part of the structure (Hickeyet al 1988) (Fig 1) These sediments were laid down in acrater lake and consist of dolomitic silts and muds withsubordinate fine-grained dolomitic sands Recent field studiessuggest that the Haughton Formation was deposited gt104ndash106 yr following the impact event following a period oferosion during which significant quantities of impact meltbreccias and the bulk of any original intra-crater sedimentswere removed (Osinski and Lee 2005)

SAMPLES AND ANALYTICAL TECHNIQUES

Over 100 samples of hydrothermally altered rocks werecollected from around the Haughton impact structurePolished thin sections were investigated using a JEOL 6400

A case study of impact-induced hydrothermal activity 1861

digital scanning electron microscope (SEM) The SEM wasequipped with a Link Analytical eXL energy dispersivespectrometer (EDS) and Si(Li) LZ-4 Pentafet detector Beamoperating conditions were 15 kV and 25 nA at a workingdistance of 37 mm and count times of 100 sec SEM data werereduced using a ZAF procedure incorporated into theoperating system and calibrated using a multi-elementstandards block (Type 202-52) produced by the CM Taylor

Corporation of Sunnyvale California USA SEMbackscattered electron (BSE) imagery was used to investigatethe microtextures of the hydrothermal phases The presenceor absence of hydrothermal phases was also recorded duringthe study of gt150 samples of impactites (Osinski et al2005a) X-ray diffraction (XRD) was performed on powderedsamples using a Philips 1710 diffractometer and generatorwith operating conditions of 40 kV and 20 mA

Fig 1 A simplified geological map of the Haughton impact structure showing the location of various types of hydrothermal deposits See themap insert for a more detailed version


Fluid inclusion studies were carried out at the GeofluidsResearch Group University of Aberdeen UK Fluidinclusions are a sample of fluid trapped during crystal growth(primary inclusions) or at some later time along fractures(secondary inclusions) after the crystal has formed (Roedder1981) Non-destructive freezing and heating experimentswere performed on polished wafers using a LinkhamTHM600 heating-freezing stage attached to an Olympus BH-2 petrographic microscope Organic chemicals of knownmelting point were used as standards Fluorescence under UVlight was determined using a Nikon Eclipse 600 microscopewith a UV-2a filter block The temperature of homogenization(Th) was recorded on disappearance of the vapor bubbleHomogenization occurred into the liquid state for all (liquid +vapor) inclusions Freezing studies were used to determinethe salinity of the inclusions by measuring the final icemelting temperature (Tm) on reheating the frozen inclusionThe depression of the freezing point of water is directlyproportional to the amount of salt in solution This varieshowever according to the nature of the salt present thereforeTm is conventionally reported as weight NaCl equivalent(Shepherd et al 1985)

LOCATION DISTRIBUTION AND NATURE OF HYDROTHERMAL DEPOSITS

Detailed 110000 to 125000 scale mapping carried outover the course of five field seasons reveals a series of distincthydrothermal deposits at Haughton each associated withdifferent structuralstratigraphic settings (Fig 1 map insert)

Mineralization within Crater-Fill Impact Melt Breccias

Hydrothermal alteration assemblages at Haughton aretypically restricted to the lower sim20ndash50 m of the crater-fillimpact melt breccia unit and occur as open-space cavity andfracture fillings Three distinct alteration types identifiedwithin impact melt breccias are marcasite-calcite calcite andselenite (Osinski et al 2001) with minor quartz-filled vugsand veins

Sulfide-Carbonate Mineralization

The largest sulfide deposits occur at two closely spacedlocalities in a well-exposed cliff section along the HaughtonRiver valley in the southeastern sector of the structure(Fig 1) (Osinski et al 2001) The irregularly shaped vugs are5ndash10 m3 in volume with the hydrothermal minerals lining theinterior surface of the cavity walls (Fig 2a) Both outcrops arelt5ndash10 m above the basal contact of the crater-fill meltbreccias with the underlying pre-impact target rocks XRDand EDS analysis indicate that the hydrothermal phases arein decreasing order of abundance calcite (CaCO3) marcasite(FeS2) fibroferrite (Fe(SO4)(OH)5H2O) celestite (SrSO4)barite (BaSO4) fluorite (CaF2) and quartz (SiO2) (Figs 3andashc

Table 1) In addition sim05ndash20 mm thick calcite-marcasiteveins have been recognized in four out of more than 150samples of impact melt breccias studied (Fig 3d) Fieldstudies together with SEM backscattered electron imageryreveal that marcasite occurs in several different formsand settings and is usually the last precipitating phase(Figs 3andashd) although clear coarse-grained calcite andfibroferrite were observed after marcasite on the surfaces ofsome samples (Osinski et al 2001) It is notable that quartzalways occurs as isolated relatively large grains (sim1 mmlong) enclosed in calcite and possessing highly corrodedcrystal faces Abundant two-phase (liquid + vapor) fluidinclusions both primary and secondary are present in thislate stage calcite (eg sample 99-135) (Table 2) Fluidinclusions also occur in fine-grained calcite associated themarcasite but are too small to accurately measure

Carbonate Mineralization

Large calcite vugs up to sim15 cm across occur within lt10ndash60 m from the base of the impact melt breccia layer Thesevugs comprise large (up to sim7 mm long) clear euhedralcalcite crystals projecting into a void (ie a typical open-space filling texture) Thin veins of calcite sim05ndash25 mmthick have also been recognized in 8 out of more than 150samples of impact melt breccias studied These veins cross-cut clasts and groundmass phases (eg silicate glass calcite)(Fig 3e) Two-phase (liquid + vapor) and one-phase (liquid-filled) primary fluid inclusions are common in the vuggycalcite (eg sample 092) (Table 2)

Quartz Mineralization

Quartz vugs very similar in their mode of occurrence tothe calcite vugs described above are present in the lowerlevels of the impact melt breccia layer although they are lesscommon than their carbonate counterparts and of smaller size(lt8ndash10 cm across) The large majority of fluid inclusions inthe quartz are one-phase (liquid-filled) However sufficienttwo-phase (liquid + vapor) primary fluid inclusions wererecognized to allow non-destructive heating experiments tobe carried out (eg sample 091) (Table 2)

Sulfate Mineralization

Field mapping reveals that selenite (CaSO42H2O) atransparent variety of gypsum is widespread throughout thelower levels of the crater-fill impact melt breccias (Fig 1map insert) It is notable that the majority of the mappedoccurrences of selenite occur in the eastern quadrants (Fig 1)Selenite occurs both as large tabular plates from 01 m2 to1 m2 and as single well-formed prismatic crystals growingon clasts within the breccia (Fig 2b) (Osinski et al 2001)Veins of selenite (sim1ndash10 mm thick) are also common in thebasal impact melt breccias (Fig 3f) (Osinski and Spray 2003)


Fig 2 Field photographs showing the different types of hydrothermal alteration at Haughton a) Intra-impact melt breccia marcasite (green)and calcite mineralization Pale yellow accumulations of fibroferrite can be seen to the right of the rock hammer point (40 cm long)428110 mE 8364341 mN b) Eroded selenite deposit within the impact melt breccias A 15 cm high GPS is shown for scale 424772 mE8371440 mN c) Quartz-cemented brecciated carbonates of the Eleanor River Formation in the central uplift at Haughton A 14 cm longpencil is shown for scale 425 821 mE 8371650 mN d) An image showing two sets of calcite veins (sim09570 S and sim15570 N) cross-cutting limestones of the Bay Fiord Formation in the outer edge of the central uplift One set is in the plane of the image while the other issub-vertical and is approximately perpendicular to the orientation of the image (arrows) A 10 cm long penknife is shown for scale 426140mE 8362201 mN e) The primary author standing within an eroded hydrothermal pipe structure characterized by Fe-hydroxide alterationof the carbonate wall rocks 419830 mE 8365602 mN f) A field photograph of two sub-parallel fault surfaces along which calcitemineralization (pale yellow) has occurred A 40 cm long rock hammer is shown for scale 424890 mE 8360903 mN


and in uplifted blocks of the Bay Fiord Formation evaporitesthat lie directly beneath the impact melt breccias One-phase(liquid-filled) primary fluid inclusions are common in theselarge selenite crystals (Fig 4a Table 2)

Mineralized Breccias in the Interior of the Central Uplift

Hydrothermal alteration associated with the centraluplift at Haughton is generally restricted to its outer margins

Fig 3 Backscattered electron (BSE) photomicrographs of hydrothermal alteration products within impact melt breccias (a) through (c) showa series of BSE images of marcasite-calcite vugs showing the different forms and settings of marcasite In detail a) An individual grain ofmarcasite in a groundmass of hydrothermal calcite and fluorite b) A layer of radiating marcasite crystals projecting into a void that form acoating on calcite c) Euhedral to subhedral marcasite grains in a groundmass of hydrothermal calcite Note the individual tetragonal octahedrain a micro-cavity in the upper right of the image d) A hydrothermal marcasite-calcite vein that cross-cuts the silicate glass-calcite groundmassof the impact melt breccias e) Two sub-parallel hydrothermal veins of calcite that cross-cut clasts and groundmass phases in the impact meltbreccias f) As with calcite veins hydrothermal selenite veins cross-cut both clasts and groundmass phases in the impact melt breccias (cfOsinski and Spray 2003)

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usio

ns


(see below) However minor mineralization has beenobserved and studied at three locations in uplifted strata ofthe Eleanor River Formation in the center of the crater(Figs 1 and 2c map insert) Quartz is the only hydrothermalmineral observed and its occurrence is typically limited tothe cementation of highly fractured and brecciatedcarbonate lithologies (Fig 2c) Several lt05ndash10 mm thickveins have also been observed Two phases of quartz aredistinguishable in hand specimen and using plane-polarizedlight a creamndashpale blue colored milky variety and clearquartz that cross-cuts the former Primary fluid inclusions arepresent within both varieties (eg samples 99-063 and 02-121) (Table 2) In the volumetrically significant clear quartzthe inclusions are one-phase (liquid filled) whereas in themilky quartz two-phase (liquid + vapor) inclusions arepresent which are also larger in size than the inclusions inthe clear quartz (Table 2)

Veining Around the Outer Margin of the Central Uplift

A zone of (sub-) vertical faults and bedding occurs at aradial distance of 55ndash60 km from the center of the crater(Fig 1) (Osinski and Spray 2005) These highly fracturedrocks contain a pervasive network of thin (lt2ndash5 mm thick)calcite veins that are notably more common in the eastern andsouthern regions (Figs 1 and 2d) Two phases of calcite arediscernible under plane polarized light clear calcite and atranslucent sometimes pale brown variety Abundant fluidinclusions are present in both types of calcite however thetype of inclusions always differs between the two varieties(eg samples 99-104 and 02-048) (Table 2) It is notable thatfluid inclusions of liquid hydrocarbon have been found inboth calcite types These inclusions are typically two-phasewith a high degree of liquid fill Hydrocarbon-bearing fluidinclusions are both primary and secondary (in cross-cuttingtrails) up to sim25 μm in diameter and fluoresce yellow-greento blue-white under ultraviolet light (Fig 4b Table 2) (Parnellet al 2003) In sample 99-104 the fluorescing inclusions ofliquid hydrocarbon are far more abundant in areas in closeproximity to clasts of argillaceous host rock that aresuspended in the veins Secondary two-phase fluid inclusionsof liquid hydrocarbon also occur within the carbonate crystalsof the vein host rock (eg sample 99-098) (Table 2) Similarhydrocarbon-bearing fluid inclusions are present withindolomite crystals of an unshocked reference sample collectednear the crater rim (sample 02-248) (Table 2) Theseinclusions fluoresce yellow and appear to have been trappedduring crystal growth (Parnell et al 2003)

Hydrothermal Pipe Structures Around the CraterPeriphery

Detailed field mapping has revealed the presence of overseventy hydrothermal pipe structures or gossans at Haughton

(Fig 1 map insert) It is notable that they are developedexclusively around the rim of the impact structure wherefaulting occurs and have not been found developed in the

Fig 4 Photomicrographs of fluid inclusions a) Two-phasehydrocarbon inclusions within calcite See Fig 5c for results of fluidinclusion studies b) Monophase inclusions (F) in selenite from a vugimpact melt breccias Gemini Hills c) Two-phase primary aqueousinclusions in quartz from the interior of the central uplift atHaughton


crater-fill impactites or in central uplift lithologies (Fig 1)These features are therefore different to the degassing pipesfound at the Ries impact structure Germany that aredeveloped exclusively within impactites (Newsom et al1986) The highly brecciated cylindrical pipe-like structuresat Haughton are typically 1ndash5 m in diameter and are exposedover vertical lengths of up to 20 m although the quality ofexposure is generally poor (Fig 2e) (Osinski et al 2001)They are always sub-vertical and are characterized bypronounced Fe-hydroxide (goethite FeO(OH)) alteration ofthe carbonate wall rocks The brecciated interior of the pipesare lined andor cemented with either calcite or quartz andseries of sulfide minerals (marcasite + pyrite plusmn chalcopyrite(CuFeS2)) The textural relationships between the varioussulfide minerals is unknown due to highly friable and fine-grained nature of the samples in which they have been

documented At higher structural levels the pipe structuresare characterized by being very porous with cavities andfractures lined by calcite andor gypsum

Mineralization Along Faults and Fractures in the CraterRim Area

Fault surfaces within the heavily faulted rim of theHaughton structure are frequently lined by cream or paleyellow calcite (Fig 2f) Fe-hydroxide andor oxide alterationof fault surfaces can also occur Occasionally fault surfacesdisplay crystal fiber lineations produced by the preferreddirectional growth of calcite or quartz during movement(Osinski et al 2001) The presence of crystal fiber lineationsindicates that fluids migrated along the faults after the impactevent

Fig 5 Frequency plots of fluid inclusion homogenization temperatures (Th) from representative hydrothermal phases at Haughton a) Resultsfrom fluid inclusion studies of calcite associated with marcasite in the impact melt breccias b) Isolated quartz vug from the impact meltbreccias c) and d) Calcite veins from the periphery of the central uplift The hydrocarbon-bearing veins (c) record higher temperatures thanthe hydrocarbon-free veins (d)


GEOTHERMOMETRY AND MINERAL PARAGENESIS

New fluid inclusion studies combined with data onmineral paragenesis (Osinski et al 2001) allows a moreaccurate model of the hydrothermal system at Haughton to bedeveloped


Marcasite associated with calcite occurs predominantlyas open-space fillings in cavities and fractures within thecrater-fill impact melt breccias Minor sulfide-carbonatemineralization also occurs within the hydrothermal pipestructures Field and analytical data from Haughton (Osinski

Fig 6 The paragenetic sequence for hydrothermal mineralization within the Haughton impact structure Quartz appears to have been the firstmineral to precipitate from the hydrothermal fluids probably at temperatures of sim340ndash200 degC Calcite precipitation followed during the mainstage of hydrothermal activity associated with marcasite celestite and barite in the impact melt breccias at temperatures of sim210 down tosim120 degC The formation and mineralization of the hydrothermal pipe structures around the crater rim area was probably initiated in a similartemperature range Calcite veining and mobilization of hydrocarbons occurred shortly thereafter in the faulted periphery of the central upliftat temperatures of sim150ndash80 degC A decrease in the pH of the hydrothermal solutions circulating through the impact melt breccias led todeposition of radiating marcasite crystals that typically form a crust on calcite The resumption in calcite precipitation during the late stage ofhydrothermal activity in association with a substantial increase in the amount of fluorite deposited was associated with an increase in pHLate-stage deposition of fibroferrite occurred on some marcasite surfaces The final stages of hydrothermal alteration at Haughton consistedof widespread selenite and minor quartz and calcite deposition in cavities near the base of the impact melt breccias Calcite veining withoutthe involvement of hydrocarbons also continued down to sim60 degC around the periphery of the central uplift Modified from Osinski et al (2001)using additional data from this study


et al 2001) coupled with experimental data on marcasiteformation (Murowchick and Barnes 1986 Goldhaber andStanton 1987 Schoonen and Barnes 1991a 1991b 1991c)suggests that the conditions of formation of primary marcasiteat Haughton includes (a) acidic mineralizing fluids with pHlt50 (b) temperature of deposition gt100 to lt240 degC and (c)presence of neutral polysulfide species (H2Sn) at the site ofdeposition (ie monovalent or divalent polysulfide specieswould favor pyrite formation which did not occur within theimpact melt breccias at Haughton)

Calcite is the most dominant hydrothermal phaseassociated with marcasite at Haughton and likely exsolveddue to the degassing of CO2 through boiling and precipitatedby cooling associated with a rise in pH (Osinski et al 2001)Fluid inclusion studies performed on late-stage clear calcite(sample 99-135) yield temperatures of homogenization (Th)of primary inclusions of 118ndash210 degC (Fig 5a Table 2) Thistemperature range represents the final stages of intrameltbreccia marcasite-calcite mineralization at this particularlocality (Fig 6) and is consistent with experimental studies(Schoonen and Barnes 1991a 1991b 1991c) It is thereforelikely that marcasite-calcite mineralization commenced athigher temperatures possibly up to sim240 degC based on theexperimental evidence for marcasite formation (see above)By analogy it is suggested that sulfide-carbonate formationwithin the hydrothermal pipe structures occurred at similartemperatures

Calcite Mineralization

In addition to being associated with sulfides (see above)calcite also occurs as monomineralic vugs and veins withinimpact melt breccias and around the outer margin of thecentral uplift and as cement within brecciated pipe structuresaround the crater periphery

For calcite vugs within the impact melt breccias Th ofprimary fluid inclusions range from sim70 to 95 degC (egTable 2) (sample 99-092) The relationship between thiscarbonate mineralization and the sulfide-carbonatemineralization is unclear However the presence of calciteand calcite-marcasite veins cross-cutting impact melt brecciasin the same outcrop would suggest a close temporal andgenetic relationship between the two types of mineralizationThe presence of abundant one-phase (liquid-filled) fluidinclusions indicates that calcite formation continued down totemperatures of lt60 degC within the impact melt breccias

Fractures around the outer margin of the central uplift arefilled with two main varieties of calcite Calcite veinscontaining no hydrocarbons record temperatures of sim65ndash145 degC with lt90 degC being typical (eg Fig 5c Table 2)(samples 99-104 00-098 02-048) Calcite formationcontinued down to temperatures of lt60 degC as evidenced byabundant one-phase fluid inclusions Higher temperatures (upto 209 degC) were recorded but petrographic evidence showsthat they are due to stretching of primary fluid inclusions andare therefore not reliable In contrast Th of primaryinclusions from hydrocarbon-bearing calcite typically rangesfrom 91 to 175 degC (eg Fig 5c Table 2) (samples 99-10499-098) although one sample yielded slightly lowertemperatures (Fig 5d Table 2) (sample 02-048) The widerange of Th of the fluid inclusions suggests that calciteveining around the outer margin of the central uplift wasrelatively long-lived This is consistent with the presence ofseveral cross-cutting series of veins and the pervasive natureof the veining in places

Parnell et al (2003) have shown that liquid hydrocarbonsare present in the Lower Paleozoic target lithologies atHaughton especially dolomites of the Allen Bay Formation(Table 2) (sample 02-248) Fluid inclusion and geochemicaldata from the dolomites suggest that the dolomite texture and

Fig 7 A schematic cross-section showing the nature of the hydrothermal system shortly after commencement of hydrothermal activityfollowing the Haughton impact event See text for details


its enclosed hydrocarbons are a product of deep burialdiagenesis at depths of sim3ndash4 km (Parnell et al 2003) Thus itis clear that hydrocarbons at Haughton survived the impactevent at least near the crater rim and were mobilized andentrained during impact-induced hydrothermal activity (cfParnell et al 2005)


Quartz vugs within the impact melt breccias at Haughtoncontain fluid inclusions that yield homogenizationtemperatures of 71ndash92 degC with a mean of 78 degC (eg Fig 5bTable 2) (sample 99-091) One-phase fluid inclusions are alsoabundant which indicates that quartz mineralizationcontinued down to lt60 degC Minor quartz is also associatedwith the sulfide-carbonate mineralization within the impactmelt breccias It is notable that this quartz displays evidenceof dissolution (eg highly corroded crystal faces) which isunusual and requires special hydrothermal conditions Mooreet al (2000) suggest that the production of fluids capable ofquartz dissolution is only possible in a vapor-dominatedhydrothermal system

The quartz-cemented carbonate breccias within theinterior of the central uplift contain two distinct generations ofquartz The early-stage milky quartz contains abundant two-phase (liquid + vapor) fluid inclusions that record a range ofTh from 84 to 250 degC (Table 2) (sample 02-121) It is notablethat this milky quartz can also occur as a thin (lt1 mm thick)coating displaying botryoidal textures on the brecciatedcentral uplift lithologies These coatings were not amenable tofluid inclusion studies however given the high temperaturesrecorded by other milky quartz varieties and the distinctivetextures displayed by this phase it is suggested thatdeposition of milky quartz commenced during an early vapor-dominated stage at temperatures gt250 degC (cf endogenousvapor-dominated hydrothermal systems eg White et al1971 Moore et al 2000 2002) The preponderance of one-phase (liquid-filled) fluid inclusions in the later cross-cuttingclear quartz indicates that this variety formed at temperatureslt60 degC Thus two distinct episodes of quartz mineralizationoccurred within the interior of the central uplift


It is known that sulfate minerals can form at lowtemperatures (lt100 degC) which is consistent with thepreponderance of one-phase (liquid-filled) fluid inclusions inselenite from the impact melt breccias at Haughton (Fig 4a)A possible explanation for the precipitation of selenite is themixing of late-stage hydrothermal fluids with cooler moreoxygenated groundwaters resulting in an increase in pH andoxidation state of the solution (Osinski et al 2001) Fluidsrich in CaSO4 were almost certainly derived from gypsumand anhydrite beds of the Bay Fiord Formation that underliethe impact melt breccias which may explain the restriction of

selenite mineralization to the lower reaches of the brecciadeposits This is also consistent with the concentration ofselenite mineralization in the eastern parts of the impact meltbreccia layer as this mirrors the outcropping of the Bay FiordFormation evaporites (ie Bay Fiord Formation strata onlyoutcrop in the eastern half of the Haughton structure) (mapinsert) However it is notable that abundant selenite depositsoccur in impact melt breccias preserved in a down-faultedgraben in the southwest of the structure (Fig 1) At thislocation Bay Fiord Formation evaporites are currently at adepth of sim300ndash500 m indicating the importance of impact-generated faults for fluid flow

POST-IMPACT HYDROTHERMAL MODEL

The comprehensive post-impact hydrothermal modeloutlined below for Haughton is based on extensive fieldanalytical and fluid inclusion studies This model may also beapplicable as a working model for other complex impactstructures in the size range sim5ndash100 km in diameterparticularly in terms of the distribution and style ofhydrothermal alteration However hydrothermal systems andtheir deposits are also strongly dependant on host rockcomposition (eg Naumov 2002 Ames et al Forthcoming)For example the carbonate- and sulfate-dominated targetsequence at Haughton ensured that clays zeolites and K-feldspar were not formed (Osinski et al 2001) in contrast tothe typical alteration products of terrestrial impact structuresdeveloped in silicate-rich crystalline targets (Naumov 2002)In general hypervelocity impact events generate structures(eg faults fractures) enhanced permeability and a heatsource(s) that drive and focus hydrothermal fluids if H2O ispresent in the target (cf Ames et al 2000)

Early Stage gt200 degC

Impact events generate extreme pressures andtemperatures that will disrupt andor eliminate the originalwater table in a substantial portion of the target sequenceFollowing readjustment of the initial or transient crater duringthe modification stage the hydrological ldquovoidrdquo left by theimpact event would cause replacing waters to rise from depthas well as being drawn in laterally from the water table in therelatively undisturbed rocks surrounding the crater (Fig 7)The interaction of the re-established hydrosphere with hotimpact-generated and impact-heated rocks will create ahydrothermal system within the crater following impact (egKieffer and Simonds 1980 Newsom 1980 Allen et al 1982)Some exceptions may occur with small craters and in extremearid environments (Osinski et al 2001)

The heat source for the hydrothermal system at Haughtonwas primarily the hot impact melt breccias that filled thecrater interior to depths of gt200 m (Osinski et al 2005a) Theinitial temperature of these impactites is difficult to estimatehowever impact melts originating from crystalline targets are


generally assumed to be superheated with initialtemperatures gt2000 degC (eg Grieve et al 1977) Little isknown about the emplacement temperatures of sediment-derived impact melts however the presence of immiscibletextures between carbonate and SiO2 glass at Haughton(Osinski et al 2005a) would suggest initial textures ofgt1500ndash2000 degC Such temperatures are consistent withevidence for high-temperature sediment-derived impact meltsfrom Ries impact structure Germany (Graup 1999 Osinski2003 Osinski et al 2004) although the glassy nature of thesilicate phases in the Haughton and Ries impactites indicatessubsequent rapid cooling below the liquidus for these melts(sim600ndash900 degC)

Within the country rocks directly below the hot impactmelt breccias more water would be boiled off than could bereplaced resulting in the development of a short-lived vapor-dominated regime (Osinski et al 2001) whereas at deeperlevels it is likely that a two-phase (vapor + liquid) zonewould form In addition the re-established now boiling watertable would be deflected downwards due to heat from theoverlying melt breccias (Newsom 1980) Minor quartzdeposition within cavities and fractures in the interior of thecentral uplift and impact melt breccias occurred during thisvapor-dominated stage

Main Stage sim200ndash80 degC

Our studies at Haughton have revealed the importance ofimpact-generated fault systems in governing the location andnature of post-impact hydrothermal alteration (cfendogenous hydrothermal systems eg Park andMacDiarmid 1975) For example hydrothermal pipestructures are developed exclusively around the rim of theHaughton structure where faulting occurs and have not beenfound developed in the impact melt breccias or in the interiorof the central uplift The concentric listric faults andinterconnecting radial faults would have acted as fluidpathways enabling hot fluids and steam to travel along them(Fig 7) Hydrothermal fluids were also focused into a zone ofintense faulting and fracturing around the periphery of thecentral uplift (Fig 7) By analogy with volcanogenichydrothermal systems the vapor and liquid phases can travelindependently with liquid phases traveling laterally forseveral kilometers away from the boiling zone (Nicholson1993) This is evidenced at Haughton in the form ofhydrothermal pipe structures around the periphery of thecrater some several kilometers from the heat source

The main stage of hydrothermal activity at Haughtonwould have been characterized by a progressive cooling ofthe impact melt breccias and the development of a two-phase(vapor + liquid) zone (Osinski et al 2001) Field andanalytical evidence suggests that a simple convection systemwas developed with hot liquids and steam rising up andflowing laterally from the boiling water table These fluids

then cooled and may have been discharged in the outerreaches of the crater or may have descended for recirculation(Fig 7) The fluids circulating in a hydrothermal system maybe derived from a number of source reservoirs The lowsalinities of fluid inclusions in carbonates and quartz (lt3 wtNaCl equivalent) at Haughton suggest that the dominantcomponents of the system were a combination of surface ormeteoric waters Indeed this appears to be the case for themajority of impact-induced hydrothermal systems formed incontinental settings (Naumov 2002) The higher salinities offluid inclusions from the Paleozoic target rocks (gt17 wtNaCl equivalent) indicate that trapped pore waters did notsignificantly contribute to the hydrothermal system atHaughton

Within the impact melt breccias early quartzprecipitation was followed by the deposition of calcite whichcontinued until the final stages of hydrothermal activity It islikely that precipitation of calcite occurred due to boiling ofthe hydrothermal fluids resulting in the decrease in theconcentration of CO2 in the liquid phase concomitant with anincrease in pH (cf Nicholson 1993) Marcasite together withminor celestite barite and fluorite were then co-precipitatedwith calcite in the impact melt breccias at temperatures ofsim110ndash200 degC (Fig 6) The most likely mechanism formarcasite precipitation within the impact melt breccias wasthrough partial oxidation of H2S gas in the vapor phasetogether with condensation of the steam in more oxygenatedgroundwaters (Fig 7) (Osinski et al 2001)

Fluid flow and precipitation of calcite associated withhydrocarbons in the fractured and faulted margins of thecentral uplift was initiated in a similar temperature range (sim80to 150 degC) Although evidence from fluid inclusions islacking the presence of marcasite and pyrite within thehydrothermal pipe structures would suggest the flow ofmineralizing fluids with temperatures on the order of sim100ndash200 degC in this region during the main stage of hydrothermalactivity at Haughton

Late Stage lt80 degC

The circulation of fluids during the final stages of thehydrothermal system at Haughton was areally extensive Bythis time the impact breccias would have been cooled byconduction with the cooler underlying country rocks and byconvection via waters from an overlying crater lake(s)Calcite mineralization within veins and isolated cavities inimpact melt breccias and around the margins of the centraluplift continued down to sim60ndash90 degC (Fig 6) This wasfollowed by selenite and quartz deposition in cavities withinthe impact melt breccias at low temperatures (lt60 degC)Selenite deposition likely occurred through the mixing ofhydrothermal fluids with cooler more oxygenatedgroundwater (Osinski et al 2001) The abundance of selenitesuggests that the fluids were saturated in sulfate ions most


probably derived from the underlying uplifted Bay FiordFormation gypsum and anhydrite beds The higher salinity offluid inclusions in late-stage selenite (up to sim6 wt NaClequivalent) supports this conclusion

A second episode of quartz mineralization occurredwithin brecciated lithologies in the interior of the centraluplift at temperatures lt60 degC It is important to note thatsilica-rich (eg sandstone) horizons are most common in theoldest Paleozoic target rocks implying that SiO2 may havebeen leached from deeper levels of the stratigraphy(gt1400 m) Seismic reflection studies indicate that some ofthe impact-generated faults penetrate to depths of 15 km ormore (Scott and Hajnal 1988) These faults may havefacilitated SiO2 transport from depth

DISCUSSION

Heat Sources in Impact-Induced Hydrothermal Systems

There are three main potential sources of heat forcreating impact-generated hydrothermal systems (a) impact-generated melt rocks and melt-bearing breccias (b) elevatedgeothermal gradients in central uplifts and (c) energydeposited in central uplifts due to the passage of the shockwave The relative importance of each of these heat sources isnot clear at present Preliminary studies by Daubar and Kring(2001) suggest that impact melt rocks contribute sim10ndash100times more energy than elevated geothermal gradients incentral uplifts However when shock heating is factored in tothe models it appears that the heat contribution from upliftedtarget rocks is approximately the same as that from impactmelt rocks (Thorsos et al 2001) This is supported bypreliminary modeling studies of a 30 km diameter craterunder Martian conditions which suggest that the heatingcomes mainly from shock wave propagation combined withthe structural uplift of rocks underneath the crater althoughthis is highly dependant upon the impact conditions (Pierazzoet al 2005)

For Haughton with a structural uplift of sim2 km theelevated geothermal gradient would have provided amaximum temperature of sim70 degC (assuming a geothermalgradient of 30 degC kmminus1 and a surface temperature of sim10 degC)Given such a relatively low temperature hydrothermalactivity at Haughton cannot exclusively be attributed to theelevated geothermal gradient in central uplift (Osinski et al2001) although an additional heat component from thepassage of the shock wave is likely but as yet remainsunquantified However the greater amount of hydrothermalalteration of the impact melt breccias as compared to theinterior of the central uplift suggests that the bulk of the heatmust have come from the impact melt breccias

For larger craters however the central uplift will likelycontribute more energy to post-impact hydrothermal systemsdue to increasing structural uplift and contributions from the

passage of the shock wave Indeed the concentration of thehighest temperature alteration minerals in the deeper centralpeak lithologies of the sim35 km diameter Manson (McCarvilleand Crossey 1996) and the sim80 km diameter Puchezh-Katunki (Naumov 2002) impact structures would suggest thisto be the case However mineralization with the uplift of thesim100 km Popigai impact structure like Haughton is verylimited in nature (Naumov 2002) It also appears that thedominant heat source for the hydrothermal system developedwithin the large sim250 km diameter Sudbury impact structureCanada was the impact melt sheet (Ames et alForthcoming) suggesting that more controlling factors are atwork (see below)

Intensity of Impact-Induced Hydrothermal Alteration

It is notable that impact-associated hydrothermal activityat Haughton is discrete in nature and restricted to vugs andveins in the lower levels of the impact melt breccias in theheavily faulted outer margin of the central uplift and in thefaulted crater periphery This suggests that the impact meltbreccias acted as a cap to the hydrothermal system a viewsupported by the pristine unaltered nature of impact melt anddiaplectic glass clasts within the preserved impact meltbreccias (Osinski et al 2005a) In addition the low overallintensity of alteration at Haughton is consistent with thecontinental setting of the impact site so that the limited supplyof fluids may have been a constraining factor

The paleogeographic setting of the Kara and Puchezh-Katunki impact structures has also been used to explain whyhydrothermal alteration is more intense in these structuresthan at the larger Popigai structure (Naumov 2002) Theformer two craters formed in shallow shelf or intra-continentbasins while Popigai occurred in a continental setting(Naumov 2002) Similarly the large sim250 km diameterSudbury impact structure formed in a shallow subaqueousenvironment resulting in an extensive hydrothermal system inthe crater-fill impact breccias and below the impact melt sheet(Ames et al 1998 Ames et al 2000 Forthcoming) Recentstudies of impactites in the Yaxcopoil-1 drill hole located inthe annular trough of the Chicxulub impact structure Mexicosuggest that alteration was facilitated and enhanced by thepercolation of seawater into the underlying impactites (Ameset al 2004 Hecht et al 2004 L ders and Rickers 2004Z rcher and Kring 2004) Thus in general it appears that themost intensive impact-induced hydrothermal alteration takesplace in craters that form in shallow continental shelf or inintra-continent shallow basins (cf Naumov 2002)

Location of Hydrothermal Deposits within ImpactCraters

Based on our studies at the Haughton impact structureand a review of the existing literature five main locations in


an impact crater where post-impact hydrothermal depositscan form are identified

Interior of Central UpliftsCentral uplifts are formed during the modification stage

of complex impact crater formation in structures on Earththat are gt2ndash4 km in diameter (eg Melosh 1989) Widespreadmineralization within central uplifts has been discoveredthough deep drilling (hundreds to thousands of meters) of ahandful of terrestrial structures (eg the Manson andPuchezh-Katunki impact structures noted above) Thesestudies reveal that the temperature of crystallization ofhydrothermal minerals increases with depth as well as intowards the crater center (Naumov 2002) At Haughtonmineralization within the interior of the central uplift is minorand limited to the cementation of brecciated lithologies Thiscould be due to the smaller size of Haughton for it is wellknown that the amount of structural uplift increases withincreasing crater size (Grieve and Pilkington 1996) Howeverfrom the discussions above it is suggested that mineralizationwithin central uplifts in particular may be very sensitive to thepaleogeographic conditions with widespread alteration of theinterior of central uplifts only occurring in craters formed inshallow shelf or intra-continent basins

Outer Margin of Central UpliftsOur field studies at Haughton indicate that the edge of the

central uplift is characterized by a sim05ndash10 km wide zone ofhighly fractured (sub-) vertical faults and bedding in whichhydrothermal calcite veins are abundant The concentration ofhydrothermal vein mineralization around the outer margin ofcentral uplifts has also been documented at the sim65 kmdiameter Siljan impact structure Sweden (Hode et al 2003)As with Haughton the outer margin of the central uplift atSiljan is intensely and complexly faulted Mineralizationoccurs in the form of quartz veins in granitic rocks andcalcite-fluorite-pyrite-galena veins in carbonates (Hode et al2003) In larger peak-ring and multi-ring impact structureshydrothermal alteration also appears to be enhanced aroundthe edge of central uplifts (eg mineralization in the LevackGneiss Complex at the Sudbury structure that is interpretedas the remnants of the peak ring [Ames et al 1998Forthcoming])

Hydrothermal Pipe Structures and Mineralization in the Faulted Crater Periphery

Detailed field mapping carried out at Haughton hasrevealed the presence of over seventy pipe structures orgossans (Fig 1b) distributed around the faulted rim of theHaughton impact structure They have not been observed inthe impact melt breccias in the craterrsquos central area (Fig 1b)Alteration and evidence for fluid flow along fault planes isalso widespread at Haughton indicating the importance ofimpact-generated fault systems in governing the location and

nature of hydrothermal deposits around impact craters This isto be expected as the locations of many mineral and oredeposits formed by sedimentary- and magmatic-relatedhydrothermal systems are also fault-controlled (eg Park andMacDiarmid 1975)

Impact Melt Rocks and Melt-Bearing BrecciasThe first recognition of secondary minerals such as clays

and carbonates at terrestrial impact structures came fromstudies of impact melt rocks and impact breccias (egEngelhardt 1972 Grieve 1978 Floran et al 1978) Howeverit was not until the work of Newsom (1980) and Allen et al(1982) that the importance and role of hydrothermal activityas an agent of alteration was recognized Mineralizationwithin impact melt rocks and impact breccias is typicallyrestricted to cavity and fracture fillings and the minorreplacement of glassy materials (eg Newsom 1980 Osinskiet al 2001 Naumov 2002) An exception is the Sudburyimpact structure where pervasive hydrothermal alteration ofcrater-fill impact breccias (Onaping Formation) resulted in aseries of regionally extensive semiconformable alterationzones above which are associated zinc-lead-copper oredeposits (Ames et al 1998 Forthcoming)

Fieldwork carried out as part of the present study revealsthat mineralization occurs preferentially towards the base andedge of the planar impact melt breccia layer at Haughton Atthe Kara and Popigai structures the mineral assemblages alsoindicate an increase in temperature of alteration from the topto the base of impact melt rocks (Naumov 2002) It isinteresting to note that numerical modeling of hydrothermalcirculation around near-surface sills which are somewhatanalogous to impact melt sheets has shown that there is astrong tendency for the concentration of fluid flow and theproduction of larger convective cells at the edges of sills(Cathles et al 1997) These studies are therefore consistentwith the suggestion that hydrothermal systems arepreferentially focused at the edge of planar impact melt sheetson Mars (Newsom 2001 Newsom et al 2001)

Post-Impact Sedimentary Crater-Fill DepositsIntra-crater sedimentary deposits overlying crater-fill

impactites (eg impact melt rocks and melt-bearing breccias)have been documented at many terrestrial impact structures Ifthese deposits were laid while the hydrothermal system wasstill active then we might expect hydrothermal alterationproducts to be present This is the case at the sim24 km diameterRies impact structure Germany where smectite clays andvarious zeolite minerals are found throughout the sim400 mthick sequence of intra-crater paleolacustrine sedimentaryrocks (eg St ffler et al 1977) Importantly the onset ofsedimentation at the Ries was rapid (Riding 1979) andoccurred while the impact-induced hydrothermal system wasstill active (eg Newsom et al 1986) This is also true at themuch larger Sudbury structure where crater-fill impactites are


overlain by gt2000 m of intra-crater sedimentary rocksDetailed field and geochemical studies reveal that the lower-most sim5ndash50 m thick Vermilion Formation consists ofchemical sedimentary rocks or ldquoexhalitesrdquo that wereprecipitated from bicarbonate-rich fluids derived from calcitealteration in the underlying impactites (Ames 1999) There isalso a metalliferous alteration halo in the overlyingcarbonaceous mudstones of the sim600ndash1000 m thick OnwatinFormation which has been attributed to hydrothermal plumeactivity in the water column during deposition of intra-cratersediments (Rogers et al 1995)

In contrast no evidence of hydrothermal alterationproducts has been found within the intracrater sedimentarydeposits at Haughton (Osinski and Lee 2005) This can beattributed to the fact that these sedimentary lithologies weredeposited gt104ndash106 years following the impact eventfollowing a period of erosion during which the bulk of theoriginal intracrater sedimentary deposits were removed(Osinski and Lee 2005) Thus while post-impact sedimentarycrater-fill deposits may offer the opportunity for samplinghydrothermal deposits it is critical that the timing ofdeposition with respect to the impact event be ascertained

Duration of Impact-Induced Hydrothermal Systems

One of the outstanding questions regarding hydrothermalactivity at Haughton and within impact craters in general isthe duration of these systems Calculations made for thecomparably sized sim200ndash300 m thick suevite layer at the Riesimpact structure in Germany show that cooling from sim600down to 100 degC took several thousand years (Pohl et al1977) However since the first recognition of hydrothermalactivity at Haughton (Osinski et al 2001) it has beenrecognized that the crater-fill impactites are clast-rich impactmelt rocks or impact melt breccias and not clastic matrixbreccias as previously thought (Osinski et al 2005a) Thusthe heat source at Haughton may have taken substantiallylonger than several thousand years to cool down to ambienttemperatures thereby prolonging the lifetime of the post-impact hydrothermal system

One of the best quantified impact-induced hydrothermalsystems is that of the Sudbury impact structure (eg Ames etal Forthcoming and references therein) Geochronologicaldata suggests that the hydrothermal system persisted for up to2 Ma based on purely conductive cooling of the impact meltsheet (Ames et al 1998) However convection was alsoimportant at Sudbury as evidenced by the pervasive alterationof the crater-fill Onaping Formation so that ldquothe duration ofthe resulting hydrothermal system may have beensignificantly less from tens to hundreds of thousands ofyearsrdquo (Ames et al 1998) Recent numerical modeling of thesim4 km diameter K rdla crater Estonia (Kirsim e et al 2006)suggests that hydrothermal activity can persist for a fewthousand years even in relatively small structures

SUMMARY

Over the past few years it has been recognized thathydrothermal activity is a fundamental process during andfollowing the modification stage of hypervelocity impactevents on Earth and probably elsewhere in the solar systemThe nature and distribution of hydrothermal deposits atHaughton provides critical constraints on the plumbing withinmid-size complex impact structures Understanding thedistribution of hydrothermal deposits within impact craters isimportant if we are to truly understand any possible economicbenefits of such deposits and implications for the origin andevolution of life on Earth and other planets including Mars

The dominant heat source for the hydrothermal system atHaughton was the crater-fill impact melt breccias thatoriginally filled the central area of the crater to depths ofgt200 m At larger diameter craters (gt30ndash50 km) it is likelythat heat contributions from the central uplift will becomemore important however in even larger diameter impactstructures gt200 km (eg Sudbury) the crater-fill impact meltrocks appear to be the predominant heat source (Ames et alForthcoming) Fluid inclusion data indicate that the bulk ofthe mineralization at Haughton occurred at moderatetemperatures of sim200ndash240 degC down to lt60 degC Calcite andselenite are the major alteration products in terms of volumewith minor marcasite quartz and goethite and subordinatebarite celestite fibroferrite fluorite and pyrite Thisalteration assemblage is distinctly different to that developedat many other terrestrial impact structures (eg clayszeolites K-feldspar) (Naumov 2002) thus demonstrating theimportance of host lithology in governing the type ofhydrothermal alteration products that are formed

Detailed mapping has revealed the presence of a series ofhydrothermal deposits at Haughton each associated withdifferent structuralstratigraphic settings (a) cavity andfracture fillings within crater-fill impact melt breccias (b)mineralized breccias within the interior of the central uplift(c) fracture fillings around the outer margin of the centraluplift (d) hydrothermal pipe structures and mineralizationalong fault surfaces in the down-faulted crater rim region Thereport of hydrothermal deposits in similar settings at otherless well exposed impact structures lends credence to ourproposal that Haughton may serve as a template for locatinghydrothermal deposits at other impact sites

AcknowledgmentsndashThis study was funded in part by theNatural Sciences and Engineering Research Council ofCanada (NSERC) through research grants to JGS andrepresents a component of the PhD thesis of GRO Fundingfor GRO for the 2003 field season came from the CanadianSpace Agency through a post-doctoral research grantDouglas Hall provided valuable help during SEM studies Wethank Alain Berinstain Colleen Lenahan Samson OotoovakNesha Trenholm and everyone involved in the NASA


Haughton-Mars Project for their assistance during the HMP1999ndash2003 field seasons Doreen Ames and Horton Newsomare sincerely thanked for their constructive and helpfulreviews This is contribution HMP-SCI 2004-002 PASSCpublication 39

Editorial HandlingmdashDr Elisabetta Pierazzo

REFERENCES

Allen C C Gooding J and Keil K 1982 Hydrothermally alteredimpact melt rock and breccia Contributions to the soil of MarsJournal of Geophysical Research 8710083ndash10101

Ames D E Watkinson D H and Parrish R R 1998 Dating of aregional hydrothermal system induced by the 1850 Ma Sudburyimpact event Geology 26447ndash450

Ames D E 1999 Geology and regional hydrothermal alteration ofthe crater-fill Onaping Formation Association with Zn-Pb-Cumineralization Sudbury Structure Canada PhD thesisCarleton University Ottawa Ontario Canada

Ames D E Gibson H L and Watkinson D H 2000 Controls onmajor impact-induced hydrothermal system Sudbury StructureCanada (abstract 1873) 31st Lunar and Planetary ScienceConference CD-ROM

Ames D E Golightly J P Lightfoot P C and Gibson H L 2002Vitric compositions in the Onaping Formation and theirrelationship to the Sudbury Igneous Complex SudburyStructure Economic Geology 971541ndash1562

Ames D E Kjarsgaard I M Pope K O Dressler B O andPilkington M 2004 Secondary alteration of the impactite andmineralization in the basal Tertiary sequence Yaxcopoil-1Chicxulub impact crater Mexico Meteoritics amp PlanetaryScience 391145ndash1167

Ames D E Jonasson J R Gibson H L and Pope K OForthcoming Impact-generated hydrothermal systemConstraints from the large Paleoproterozic Sudbury craterCanada In Biological processes associated with impact eventsedited by Cockell C S Gilmour I and Koeberl C BerlinSpringer-Verlag 376 p

Cathles L M Erendi A H J and Barrie T 1997 How long can ahydrothermal system be sustained by a single intrusive eventEconomic Geology 92766ndash771

Cockell C S and Lee P 2002 The biology of impact craters Areview Biological Reviews 77279ndash310

Daubar I J and Kring D A 2001 Impact-induced hydrothermalsystems Heat sources and lifetimes (abstract 1727) 32nd Lunarand Planetary Science Conference CD-ROM

Engelhardt W V 1972 Shock produced rock glasses from the Riescrater Contributions to Mineralogy and Petrology 36265ndash292

Farmer J D 2000 Hydrothermal systems Doorways to earlybiosphere evolution GSA Today 1071ndash9

Floran R J Grieve R A F Phinney W C Warner J L SimondsC H Blanchard D P and Dence M R 1978 Manicouaganimpact melt Quebec I Stratigraphy petrology and chemistryJournal of Geophysical Research 832737ndash2759

Goldhaber M B and Stanton M R 1987 Experimental formation ofmarcasite at 150ndash200 degC Implications for carbonate-hosted PbZn deposits (abstract) Geological Society of America AnnualMeeting p 678

Graup G 1999 Carbonate-silicate liquid immiscibility upon impactmelting Ries Crater Germany Meteoritics amp Planetary Science34425ndash438

Grieve R A F 1978 The melt rocks at the Brent Crater Ontario

Proceedings 9th Lunar and Planetary Science Conference pp2579ndash2608

Grieve R A F and Masaitis V L 1994 The economic potential ofterrestrial impact craters International Geology Reviews 36105ndash151

Grieve R A F and Pilkington M 1996 The signature of terrestrialimpacts Australian Geology and Geophysics Journal 16399ndash420

Grieve R A F Dence M R and Robertson P B 1977 Crateringprocesses As interpreted from the occurrence of impact melts InImpact and explosion cratering edited by Roddy D J PepinR O and Merrill R B New York Pergamon Press pp 791ndash814

Hagerty J J and Newsom H E 2003 Hydrothermal alteration at theLonar Lake impact structure India Implications for impactcratering on Mars Meteoritics amp Planetary Science 38365ndash382

Hecht L Wittmann A Schmitt R T and St ffler D 2004Composition of impact melt particles and the effects of post-impact alteration in suevitic rocks at the Yaxcopoil-1 drill coreChicxulub crater Mexico Meteoritics amp Planetary Science 391169ndash1186

Hickey L J Johnson K R and Dawson M R 1988 Thestratigraphy sedimentology and fossils of the HaughtonFormation A post-impact crater fill Meteoritics 23221ndash231

Hode T von Dalwigk I and Broman C 2003 A hydrothermalsystem associated with the Siljan impact structure SwedenmdashImplications for the search for fossil life on Mars Astrobiology3271ndash289

Kieffer S W and Simonds C H 1980 The role of volatiles andlithology in the impact cratering process Reviews of Geophysicsand Space Physics 18143ndash181

Kirsim e K Jotildeeleht A Plado J Versh E and Ainsaar L 2006Development of ecological niches in impact-inducedhydrothermal systemsmdashThe case of the K rdla Crater (abstract)In Biological processes associated with impact events edited byCockell C Koeberl C and Gilmour I Berlin Springer 376 p

Kring D A 2000 Impact events and their effect on the originevolution and distribution of life GSA Today 1081ndash7

L ders V and Rickers K 2004 Fluid inclusion evidence for impact-related hydrothermal fluid and hydrocarbon migration inCretaceous sediments of the ICDP-Chicxulub drill core Yax-1Meteoritics amp Planetary Science 391187ndash1197

McCarville P and Crossey L J 1996 Post-impact hydrothermalalteration of the Manson impact structure In The Manson impactstructure Iowa Anatomy of an impact crater Special Paper302 edited by Koeberl C and Anderson R R BoulderColorado Geological Society of America pp 347ndash376

Melosh H J 1989 Impact cratering A geologic process New YorkOxford University Press 245 p

Metzler A Ostertag R Redeker H J St ffler D 1988 Compositionof the crystalline basement and shock metamorphism ofcrystalline and sedimentary target rocks at the Haughton impactcrater Meteoritics 23197ndash207

Moore J N Adams M C and Anderson A J 2000 The fluidinclusion and mineralogic record of the transition from liquid- tovapor-dominated conditions in the Geysers geothermal systemCalifornia Economic Geology 951719ndash1737

Moore J N Allis R Renner J L Mildenhall D and McCulloch J2002 Petrologic evidence for boiling to dryness in the Karaha-Telaga Bodas geothermal system Indonesia Proceedings 27thWorkshop on Geothermal Reservoir Engineering pp 98ndash108

Murowchick J B and Barnes H L 1986 Marcasite precipitationfrom hydrothermal solutions Geochimica et Cosmochimica Acta502615ndash2629

Naumov M V 2002 Impact-generated hydrothermal systems Data


from Popigai Kara and Puchezh-Katunki impact structures InImpacts in Precambrian shields edited by Plado J and PesonenL J Berlin Springer-Verlag pp 117ndash171

Newsom H E 1980 Hydrothermal alteration of impact melt sheetswith implications for Mars Icarus 44207ndash216

Newsom H E 2001 Central remnant craters on MarsmdashLocalizationof hydrothermal alteration at the edge of crater floors (abstract1402) 32nd Lunar and Planetary Science Conference CD-ROM

Newsom H E Graup G Sewards T and Keil K 1986 Fluidizationand hydrothermal alteration of the suevite deposit in the RiesCrater West Germany and implications for Mars Journal ofGeophysical Research 91239ndash251

Newsom H E Hagerty J J and Thorsos I E 2001 Location andsampling of aqueous and hydrothermal deposits in martianimpact craters Astrobiology 171ndash88

Nicholson K 1993 Geothermal fluids Chemistry and explorationtechniques Berlin Springer-Verlag 263 p

Osinski G R 2003 Impact glasses in fallout suevites from the Riesimpact structure Germany An analytical SEM studyMeteoritics amp Planetary Science 381641ndash1667

Osinski G R and Lee P 2005 Intra-crater sedimentary deposits ofthe Haughton impact structure Devon Island Canadian HighArctic Meteoritics amp Planetary Science 40 This issue

Osinski G R and Spray J G 2001 Impact-generated carbonatemelts Evidence from the Haughton structure Canada Earth andPlanetary Science Letters 19417ndash29

Osinski G R and Spray J G 2003 Evidence for the shock meltingof sulfates from the Haughton impact structure Arctic CanadaEarth and Planetary Science Letters 215357ndash270

Osinski G R and Spray J G 2005 Tectonics of complex craterformation as revealed by the Haughton impact structure DevonIsland Canadian High Arctic Meteoritics amp Planetary Science40 This issue

Osinski G R Spray J G and Lee P 2001 Impact-inducedhydrothermal activity within the Haughton impact structureArctic Canada Generation of a transient warm wet oasisMeteoritics amp Planetary Science 36731ndash745

Osinski G R Grieve R A F and Spray J G 2004 The nature of thegroundmass of the Ries impact structure Germany andconstraints on its origin Meteoritics amp Planetary Science 391655ndash1684

Osinski G R Spray J G and Lee P 2005a Impactites of theHaughton impact structure Devon Island Canadian High ArcticMeteoritics amp Planetary Science 40 This issue

Osinski G R Lee P Spray J G Parnell J Lim D S S Bunch TE Cockell C S and Glass B 2005b Geological overview andcratering model of the Haughton impact structure Devon IslandCanadian High Arctic Meteoritics amp Planetary Science 40 Thisissue

Park C F and MacDiarmid R A 1975 Ore deposits San FranciscoW H Freeman and Company 529 p

Parnell J Osinski G R Lee P Baron M Pearson M J andFeely M 2003 Hydrocarbons in the Haughton impact structureDevon Island Nunavut Canada (abstract 1118) 34th Lunar andPlanetary Science Conference CD-ROM

Parnell J Lee P Osinski G R and Cockell C S 2005 Applicationof organic geochemistry to detect signatures of organic matter inthe Haughton impact structure Meteoritics amp Planetary Science40 This issue

Pirajno F 1992 Hydrothermal mineral deposits Principles and

fundamental concepts for the exploration geologist BerlinSpringer-Verlag 709 p

Pierazzo E Artemieva N A and Ivanov B 2005 Startingconditions for hydrothermal systems underneath martian cratersHydrocode modeling In Large meteorite impacts III SpecialPaper 384 edited by Kenkmann T H rz F and Deutsch ABoulder Colorado Geological Society of America

Pohl J St ffler D Gall H and Ernstson K 1977 The Ries impactcrater In Impact and explosion cratering edited by Roddy D JPepin R O and Merrill R B New York Pergamon Press pp343ndash404

Rathbun J A and Squyres S W 2002 Hydrothermal systemsassociated with martian impact craters Icarus 157362ndash372

Riding R 1979 Origin and diagenesis of lacustrine algal bioherms atthe margin of the Ries Crater upper Miocene southern GermanySedimentology 26645ndash680

Roedder E 1981 Origin of fluid inclusions and changes that occurafter trapping In Short course in fluid inclusions Applications toPetrology edited by Hollister L S and Crawford M L CalgaryMineralogical Association of Canada pp 107ndash137

Rogers D F Gibson H L Whitehead R Checetto J and JonassonE R 1995 Structure and metal enrichment in the hanging wallcarbonaceous argillites of the Paleoproterozoic Vermilion andErrington Zn-Cu-Pb massive sulfide deposits Sudbury Canada(abstract) Proceedings Geological Association of CanadandashMineralogical Association of Canada 20A90

Schoonen M A A and Barnes H L 1991a Reactions forming pyriteand marcasite from solution I Nucleation of FeS2 below 100 degCGeochimica et Cosmochimica Acta 551495ndash1504

Schoonen M A A and Barnes H L 1991b Reactions forming pyriteand marcasite from solution II Via FeS precursors below 100degC Geochimica et Cosmochimica Acta 551505ndash1514

Schoonen M A A and Barnes H L 1991c Mechanisms of pyriteand marcasite formation from solution III Hydrothermalprocesses Geochimica et Cosmochimica Acta 553491ndash3504

Scott D and Hajnal Z 1988 Seismic signature of the Haughtonstructure Meteoritics 23239ndash247

Sherlock S C Kelley S P Parnell J Green P Lee P Osinski G Rand Cockell C S 2005 Re-evaluating the age of the Haughtonimpact event Meteoritics amp Planetary Science 40 This issue

Shepherd T J Rankin A H and Alderton D H M 1985 Apractical guide to fluid inclusions Glasgow Blackie 239 p

Shock E L 1996 Hydrothermal systems as environments for theemergence of life In Evolution of hydrothermal ecosystems onEarth (and Mars) edited by Bock G R and Goode J AChichester John Wiley amp Sons Ltd pp 40ndash82

St ffler D Ewald U Ostertag R and Reimold W U 1977Research drilling N rdlingen 1973 (Ries) Composition andtexture of polymict impact breccias Geologica Bavarica 75163ndash189

Thorsteinsson R and Mayr U 1987 The sedimentary rocks of DevonIsland Canadian Arctic Archipelago Geological Survey ofCanada Memoir 411 Ottawa Geological Survey of Canada182 p

White D E Muffler L J P and Truesdell A H 1971 Vapor-dominated hydrothermal systems compared with hot watersystems Economic Geology 6675ndash97

Z rcher L and Kring D A 2004 Hydrothermal alteration in the coreof the Yaxcopoil-1 borehole Chicxulub impact structureMexico Meteoritics amp Planetary Science 391199ndash1221


considered plausible candidates because they represent siteswhere liquid H2O warmth and dissolved chemicals andnutrients may have been available for extended periods oftime Although impact-induced hydrothermal systems aretransient in nature because they lack the usually longer-lastingheat sources that characterize volcanogenic hydrothermalsystems they might still have subsisted long enough to haveexperienced colonization by thermophilic (heat-loving)microbial communities particularly in the case of the largerimpact structures (Cockell and Lee 2002 Rathbun andSquyres 2002)

Hydrothermal processes have also played an importantrole in the formation of many different types of mineral andore deposits (eg porphyry copper-molybdenum depositstin-tungsten-copper greisen-related deposits copper-zinc-richvolcanogenic massive sulfide deposits lead-zinc MississippiValley-type deposits) (Pirajno 1992) More recently it hasbeen noted that impact-induced hydrothermal activity canalso result in economic mineralization as has been the case atthe Sudbury (ie zinc-lead-copper-silver-gold Ames et al1998) and Vredefort (ie gold) (Grieve and Masaitis 1994)impact structures

Evidence for impact-induced hydrothermal activity hasnow been recognized at over sixty terrestrial craters (Naumov2002) from the sim18 km diameter Lonar Lake structure India(eg Hagerty and Newsom 2003) to the sim250 km diameterSudbury structure Canada (eg Ames et al 1998) Despitethe potential economic and astrobiological importance ofhydrothermal activity the nature and distribution of suchdeposits within impact craters remains poorly studied This isdue in part to the lack of surface exposure and preservationof hydrothermal deposits at many terrestrial impact sitesMoreover it is only in the past few years that hydrothermalactivity has been recognized as a fundamental processassociated with impact events The sim39 Ma Haughton impactstructure in Canadian High Arctic is well-exposed and well-preserved and as such offers an exceptional opportunity togain a better understanding of the different types ofhydrothermal deposits within impact craters and theirdistribution

Evidence for hydrothermal activity associated with theHaughton impact event was first recognized during the 1998and 1999 field seasons of the NASA Haughton-Mars Project(reported in Osinski et al 2001) Since this discoveryextensive mapping has revealed important new informationregarding the nature and distribution of hydrothermal depositsat Haughton (see map insert) This will be described herealong with analytical data that builds upon the studies ofOsinski et al (2001) New fluid inclusion data on a series ofhydrothermal minerals is also presented that helps toconstrain the temperature conditions during post-impacthydrothermal activity This data will be discussed andsynthesized with new work on the impactites (Osinski andSpray 2001 2003 Osinski et al 2005a) and tectonics

(Osinski and Spray 2005) of Haughton Collectively thesestudies enable an improved model for the impact-inducedhydrothermal system at Haughton to be presented

GEOLOGICAL SETTING OF THE HAUGHTON IMPACT STRUCTURE

Haughton is a well-preserved complex impact structure23 km in diameter that is situated on Devon Island in theCanadian Arctic Archipelago (75deg22primeN 89deg41primeW) Theimpact event occurred sim39 Myr ago (Sherlock et al 2005) in atarget comprising sim1880 m of Lower Paleozoic sedimentaryrocks of the Arctic Platform overlying Precambrianmetamorphic basement of the Canadian Shield (Thorsteinssonand Mayr 1987 Osinski et al 2005b) The unmetamorphosedsedimentary succession consists of thick units of dolomite andlimestone with subordinate evaporite horizons and minorshales and sandstones (Thorsteinsson and Mayr 1987)

Allochthonous crater-fill deposits form a virtuallycontinuous sim54 km2 unit covering the central area of thestructure (Fig 1) (Osinski et al 2005a) Recent field studiesand analytical scanning electron microscopy indicate thatthese rocks are carbonate-rich impact melt breccias or clast-rich impact melt rocks (Osinski and Spray 2001 2003Osinski et al 2005a) The impact melt breccias have amaximum current thickness of sim125 m although the presenceof this unit up to sim140 m above the central topographic lowarea suggests that they originally completely occupied thecentral area to depths of 200 m or more (Osinski et al 2005a)The present-day exposure of the allochthonous crater-filldeposits therefore represents a minimum The pale gray-weathering rocks comprise variably shocked mineral andlithic clasts set within a groundmass of calcite + silicate glassplusmn anhydrite (Osinski et al 2005a) The lithic clasts aretypically angular and are predominantly dolomite andlimestone with minor sandstones shales and evaporites andsubordinate lithologies from the crystalline basement(Metzler et al 1988)

Post-impact lacustrine sediments of the HaughtonFormation occupy the central part of the structure (Hickeyet al 1988) (Fig 1) These sediments were laid down in acrater lake and consist of dolomitic silts and muds withsubordinate fine-grained dolomitic sands Recent field studiessuggest that the Haughton Formation was deposited gt104ndash106 yr following the impact event following a period oferosion during which significant quantities of impact meltbreccias and the bulk of any original intra-crater sedimentswere removed (Osinski and Lee 2005)

SAMPLES AND ANALYTICAL TECHNIQUES

Over 100 samples of hydrothermally altered rocks werecollected from around the Haughton impact structurePolished thin sections were investigated using a JEOL 6400




























ble

1 A

vera

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99

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2ndash

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200

48ndash

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d0

040

120

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08ndash

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FeO

338

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07ndash

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MgO

ndashndash

021

028

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dndash

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534

30

410

510

13ndash

nd

CaO

ndashndash

547

31

740

580

400

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73ndash

120

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7032

44

076

Na 2

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18ndash

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659

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ndashndash

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288

264

390

ndashn

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920

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100

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372

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Qua

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rtzP2

2ndash5

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minus01

ndash05

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99-0

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369

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2ndash1

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ndash10

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nite

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plift

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679

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Vein

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ndash09

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7ndash1

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2142

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Inte

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f ce

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l upl

ift

Cem

bre

ccia

Ml

Qtz

P2

3ndash11

092

ndash09

784

3ndash2

498

nd

dn

dd

Cem

bre

ccia

Cl

Qtz

P1

3ndash4

1n

dc

minus02

ndash08

04ndash

14

02-2

4841

966

08

373

870

Cra

ter r

im

regi

onU

nsho

cked

D

olom

iteP2

2ndash6

096

ndash09

764

5ndash1

187

minus13

4ndash14

617

3ndash1

83

Targ

et ro

ckD

olom

iteP2

HC

2ndash5

095

ndash09

862

7ndash1

014

nd

nd

a Abb

revi

atio

ns T

h =

tem

pera

ture

of h

omog

eniz

atio

n T

m =

fina

l ice

mel

ting

tem

pera

ture

P =

prim

ary

S =

seco

ndar

y 1

= o

ne-p

hase

2 =

two-

phas

e H

C =

hyd

roca

rbon

-bea

ring

nd

= n

ot d

eter

min

able

Cal

=

calc

ite Q

tz =

qua

rtz C

em =

cem

ente

d C

l cl

ear

Br

= br

own

Tr

= tra

nslu

cent

Ml

= m

ilky

ES

= ea

rly st

age

LS

= la

te st

age

b The

deg

ree

of fi

ll is

def

ined

as t

he v

olum

etric

pro

porti

on o

f liq

uid

rela

tive

to th

e to

tal v

olum

e of

the

incl

usio

nc I

t is n

ot p

ossi

ble

to c

arry

out

hea

ting

expe

rimen

ts o

n on

e-ph

ase

fluid

incl

usio

ns

d It

is n

ot p

ossi

ble

to c

arry

out

hea

ting

expe

rimen

ts o

n on

e-ph

ase

fluid

incl

usio

ns

























































DISCUSSION































SUMMARY








REFERENCES





































































































ble

1 A

vera

ge c

ompo

sitio

n of

sel

ecte

d po

st-im

pact

hyd

roth

erm

al p

hase

s at

Hau

ghto

na

Sam

ple

99

-136

99-1

3599

-133

99-1

3502

-087

02-0

8800

-258

bPh

ase

Mar

casi

teC

alci

teC

eles

tite

Bar

iteC

alci

teC

alci

teSe

leni

teN

umbe

r of

anal

yses

710

45

55

7D

escr

iptio

nC

rust

Inte

rstit

ial

Inte

rstit

ial

Inte

rstit

ial

Vein

Vein

Vein

wt

sd

wt

sd

wt

sd

wt

sd

wt

sd

wt

sd

wt

sd

SiO

2ndash

ndash0

200

48ndash

nd

ndashn

d0

040

120

020

08ndash

nd

FeO

338

40

52ndash

nd

009

034

ndashn

d0

15n

d0

020

07ndash

nd

MgO

ndashndash

021

028

ndashn

dndash

nd

534

30

410

510

13ndash

nd

CaO

ndashndash

547

31

740

580

400

350

73ndash

120

531

41

7032

44

076

Na 2

Ondash

ndash0

040

18ndash

nd

045

065

ndashn

dndash

nd

ndashn

dK

2Ondash

ndashndash

nd

ndashn

dndash

nd

004

nd

ndashn

dndash

nd

SO3

659

70

14ndash

nd

433

11

1133

73

073

ndash0

17ndash

nd

473

31

16B

aOndash

ndashndash

nd

103

334

630

34

35ndash

nd

ndashn

dndash

nd

SrO

ndashndash

ndashn

d55

13

288

264

390

ndashn

dndash

nd

ndashn

dC

lndash

ndashndash

nd

ndashn

d0

450

920

15n

dndash

nd

ndashn

dTo

tal

998

10

4655

18

151

100

141

3210

065

137

536

11

5253

69

159

797

71

74a C

r N

i P

and

Ti w

ere

belo

w d

etec

tion

for a

ll an

alys

es A

bbre

viat

ions

wt

= m

ean

com

posi

tion

in w

eigh

t s

d =

stan

dard

dev

iatio

n (2

σ) n

d =

not

det

erm

ined

The

firs

t fou

r gro

ups o

f ana

lyse

s are

from

a ca

lcite

-mar

casi

te v

ug w

ithin

the

impa

ct m

elt b

recc

ias

The

last

thre

e gr

oups

of a

naly

ses a

re fr

om h

ydro

ther

mal

vei

ns fr

om th

e im

pact

mel

t bre

ccia

s


ble

2 S

umm

ary

of fl

uid

incl

usio

n da

ta fo

r rep

rese

ntat

ive

sam

ples

of h

ydro

ther

mal

dep

osits

at H

augh

ton

a

UTM

Pos

ition

Sam

ple

Ea

stin

gN

orth

ing

Loca

tion

in c

rate

rSe

tting

Hos

tm

iner

alIn

clus

ion

type

Size

rang

e(μ

m)

Fillb

Th (degC

)Tm (deg

C)

Salin

ity(w

t N

aCl e

q)

99-0

6342

501

08

369

020

Inte

rior o

f ce

ntra

l upl

iftC

em b

recc

iaC

l Q

tz

P12ndash

61

nd

cn

dd

nd

d

99-0

9142

963

08

372

930

Impa

ct m

elt

brec

cias

Vug

Qua

rtzP1

2ndash6

1n

dc

nd

dn

dd

Vug

Qua

rtzP2

2ndash5

097

ndash09

871

0ndash9

16

minus01

ndash05

02ndash

07

99-0

9242

850

08

369

760

Impa

ct m

elt

brec

cias

Vug

Cal

cite

P12ndash

61

nd

cn

dd

nd

d

Vug

Cal

cite

P22ndash

50

96ndash0

98

701

ndash94

9n

dd

nd

d

99-1

0442

946

08

370

350

Perip

hery

of

cent

ral u

plift

Vein

Tr C

al

P12ndash

81

nd

cminus0

2ndash1

10

4ndash2

0

Vein

Tr C

al

P22ndash

80

95ndash0

98

814

ndash144

4minus0

4ndash1

40

7ndash2

4Ve

inC

l C

al

P2S

2 H

C3ndash

250

94ndash0

96

141

3ndash17

48

nd

dn

dc

99-1

3542

800

08

364

390

Impa

ct m

elt

brec

cias

Vug

Cal

cite

P22ndash

40

92ndash0

96

117

7ndash21

01

minus01

ndash06

02ndash

11

Vug

Cal

cite

S23ndash

40

90ndash0

96

143

5ndash18

48

nd

dn

dd

00-0

9841

775

08

368

430

Perip

hery

of

cent

ral u

plift

Vein

(LS)

Cl

Cal

P1

2ndash3

1n

dc

minus04

ndash10

07ndash

21

Vein

(ES)

Cl

Cal

S2

HC

2ndash4

095

ndash09

691

0ndash1

426

nd

dn

dd

Hos

t roc

kC

l C

al

S2 H

C2ndash

40

94ndash0

96

910

ndash142

6n

dn

dH

ost r

ock

Br

Cal

S2

2ndash3

095

ndash09

683

8ndash1

183

minus13

5 17

400

-136

420

570

835

989

0Pe

riphe

ry o

f ce

ntra

l upl

iftVe

inC

alci

teP2

2ndash3

094

ndash09

613

66ndash

142

8minus0

3ndash0

40

7

00-2

5842

783

08

367

980

Impa

ct m

elt

brec

cias

Vug

Sele

nite

P12ndash

51

nd

cminus0

1ndash3

70

2ndash6

0

02-0

3541

865

08

363

780

Impa

ct m

elt

brec

cias

Vug

Sele

nite

P1 S

12ndash

51

nd

cminus0

5ndash0

80

7ndash1

4

02-0

4842

654

08

361

980

Perip

hery

of

cent

ral u

plift

Vein

Cl

Cal

P2

20

97ndash0

98

679

ndash85

1minus1

1ndash2

01

9ndash3

4

Vein

Br

Cal

S2

HC

2ndash3

095

ndash09

662

7ndash1

014

nd

dn

dd

02-1

2142

582

08

371

650

Inte

rior o

f ce

ntra

l upl

ift

Cem

bre

ccia

Ml

Qtz

P2

3ndash11

092

ndash09

784

3ndash2

498

nd

dn

dd

Cem

bre

ccia

Cl

Qtz

P1

3ndash4

1n

dc

minus02

ndash08

04ndash

14

02-2

4841

966

08

373

870

Cra

ter r

im

regi

onU

nsho

cked

D

olom

iteP2

2ndash6

096

ndash09

764

5ndash1

187

minus13

4ndash14

617

3ndash1

83

Targ

et ro

ckD

olom

iteP2

HC

2ndash5

095

ndash09

862

7ndash1

014

nd

nd

a Abb

revi

atio

ns T

h =

tem

pera

ture

of h

omog

eniz

atio

n T

m =

fina

l ice

mel

ting

tem

pera

ture

P =

prim

ary

S =

seco

ndar

y 1

= o

ne-p

hase

2 =

two-

phas

e H

C =

hyd

roca

rbon

-bea

ring

nd

= n

ot d

eter

min

able

Cal

=

calc

ite Q

tz =

qua

rtz C

em =

cem

ente

d C

l cl

ear

Br

= br

own

Tr

= tra

nslu

cent

Ml

= m

ilky

ES

= ea

rly st

age

LS

= la

te st

age

b The

deg

ree

of fi

ll is

def

ined

as t

he v

olum

etric

pro

porti

on o

f liq

uid

rela

tive

to th

e to

tal v

olum

e of

the

incl

usio

nc I

t is n

ot p

ossi

ble

to c

arry

out

hea

ting

expe

rimen

ts o

n on

e-ph

ase

fluid

incl

usio

ns

d It

is n

ot p

ossi

ble

to c

arry

out

hea

ting

expe

rimen

ts o

n on

e-ph

ase

fluid

incl

usio

ns

























































DISCUSSION































SUMMARY








REFERENCES











































































ble

2 S

umm

ary

of fl

uid

incl

usio

n da

ta fo

r rep

rese

ntat

ive

sam

ples

of h

ydro

ther

mal

dep

osits

at H

augh

ton

a

UTM

Pos

ition

Sam

ple

Ea

stin

gN

orth

ing

Loca

tion

in c

rate

rSe

tting

Hos

tm

iner

alIn

clus

ion

type

Size

rang

e(μ

m)

Fillb

Th (degC

)Tm (deg

C)

Salin

ity(w

t N

aCl e

q)

99-0

6342

501

08

369

020

Inte

rior o

f ce

ntra

l upl

iftC

em b

recc

iaC

l Q

tz

P12ndash

61

nd

cn

dd

nd

d

99-0

9142

963

08

372

930

Impa

ct m

elt

brec

cias

Vug

Qua

rtzP1

2ndash6

1n

dc

nd

dn

dd

Vug

Qua

rtzP2

2ndash5

097

ndash09

871

0ndash9

16

minus01

ndash05

02ndash

07

99-0

9242

850

08

369

760

Impa

ct m

elt

brec

cias

Vug

Cal

cite

P12ndash

61

nd

cn

dd

nd

d

Vug

Cal

cite

P22ndash

50

96ndash0

98

701

ndash94

9n

dd

nd

d

99-1

0442

946

08

370

350

Perip

hery

of

cent

ral u

plift

Vein

Tr C

al

P12ndash

81

nd

cminus0

2ndash1

10

4ndash2

0

Vein

Tr C

al

P22ndash

80

95ndash0

98

814

ndash144

4minus0

4ndash1

40

7ndash2

4Ve

inC

l C

al

P2S

2 H

C3ndash

250

94ndash0

96

141

3ndash17

48

nd

dn

dc

99-1

3542

800

08

364

390

Impa

ct m

elt

brec

cias

Vug

Cal

cite

P22ndash

40

92ndash0

96

117

7ndash21

01

minus01

ndash06

02ndash

11

Vug

Cal

cite

S23ndash

40

90ndash0

96

143

5ndash18

48

nd

dn

dd

00-0

9841

775

08

368

430

Perip

hery

of

cent

ral u

plift

Vein

(LS)

Cl

Cal

P1

2ndash3

1n

dc

minus04

ndash10

07ndash

21

Vein

(ES)

Cl

Cal

S2

HC

2ndash4

095

ndash09

691

0ndash1

426

nd

dn

dd

Hos

t roc

kC

l C

al

S2 H

C2ndash

40

94ndash0

96

910

ndash142

6n

dn

dH

ost r

ock

Br

Cal

S2

2ndash3

095

ndash09

683

8ndash1

183

minus13

5 17

400

-136

420

570

835

989

0Pe

riphe

ry o

f ce

ntra

l upl

iftVe

inC

alci

teP2

2ndash3

094

ndash09

613

66ndash

142

8minus0

3ndash0

40

7

00-2

5842

783

08

367

980

Impa

ct m

elt

brec

cias

Vug

Sele

nite

P12ndash

51

nd

cminus0

1ndash3

70

2ndash6

0

02-0

3541

865

08

363

780

Impa

ct m

elt

brec

cias

Vug

Sele

nite

P1 S

12ndash

51

nd

cminus0

5ndash0

80

7ndash1

4

02-0

4842

654

08

361

980

Perip

hery

of

cent

ral u

plift

Vein

Cl

Cal

P2

20

97ndash0

98

679

ndash85

1minus1

1ndash2

01

9ndash3

4

Vein

Br

Cal

S2

HC

2ndash3

095

ndash09

662

7ndash1

014

nd

dn

dd

02-1

2142

582

08

371

650

Inte

rior o

f ce

ntra

l upl

ift

Cem

bre

ccia

Ml

Qtz

P2

3ndash11

092

ndash09

784

3ndash2

498

nd

dn

dd

Cem

bre

ccia

Cl

Qtz

P1

3ndash4

1n

dc

minus02

ndash08

04ndash

14

02-2

4841

966

08

373

870

Cra

ter r

im

regi

onU

nsho

cked

D

olom

iteP2

2ndash6

096

ndash09

764

5ndash1

187

minus13

4ndash14

617

3ndash1

83

Targ

et ro

ckD

olom

iteP2

HC

2ndash5

095

ndash09

862

7ndash1

014

nd

nd

a Abb

revi

atio

ns T

h =

tem

pera

ture

of h

omog

eniz

atio

n T

m =

fina

l ice

mel

ting

tem

pera

ture

P =

prim

ary

S =

seco

ndar

y 1

= o

ne-p

hase

2 =

two-

phas

e H

C =

hyd

roca

rbon

-bea

ring

nd

= n

ot d

eter

min

able

Cal

=

calc

ite Q

tz =

qua

rtz C

em =

cem

ente

d C

l cl

ear

Br

= br

own

Tr

= tra

nslu

cent

Ml

= m

ilky

ES

= ea

rly st

age

LS

= la

te st

age

b The

deg

ree

of fi

ll is

def

ined

as t

he v

olum

etric

pro

porti

on o

f liq

uid

rela

tive

to th

e to

tal v

olum

e of

the

incl

usio

nc I

t is n

ot p

ossi

ble

to c

arry

out

hea

ting

expe

rimen

ts o

n on

e-ph

ase

fluid

incl

usio

ns

d It

is n

ot p

ossi

ble

to c

arry

out

hea

ting

expe

rimen

ts o

n on

e-ph

ase

fluid

incl

usio

ns

























































DISCUSSION































SUMMARY








REFERENCES


































































































































DISCUSSION































SUMMARY








REFERENCES






























































































SUMMARY








REFERENCES













































































REFERENCES










































































A case study of impact-induced hydrothermal activity: The Haughton impact structure, Devon Island,...

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Transcript of A case study of impact-induced hydrothermal activity: The Haughton impact structure, Devon Island,...