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GoldGold andand CopperCopper DisseminationDisseminationin in thethe IgneousIgneous--VolcanicVolcanic
SaldaSaldaa a FormationFormation, Colombia, Colombiaandand ExtensionExtension ofof thethe Mineral Mineral ProvinceProvince
in in thethe AndeanAndean CordilleraCordillera
Prepared by:Prepared by:Alberto LoboAlberto Lobo--Guerrero S.Guerrero S.GeologistGeologist, , M.ScM.Sc., ., MinExMinEx
EconomicEconomic GeologyGeology ResearchResearch InstituteInstituteUniversityUniversity ofof thethe WitwatersrandWitwatersrand
JohannesburgJohannesburg, , SouthSouth AfricaAfrica, , JuneJune, 2003, 2003
CONTENTS
Introduction Saldaa Formation
LocationDescriptionLithologyPetrographyExtensionEnvironment of EmplacementStructural Geology
MineralizationTypes KnownPotentialProspects
Extension of ProvinceIn Colombian AndesPerij ChainIn Andean CordilleraInto Mexico
INTRODUCTION-1
Saldaa region constitutes
one of the best exploration targets
for large-tonnage Au + Cu disseminationsin Colombian Andes, South America
Saldaa Formation =Jurassic hypabissal + volcanic rocks
INTRODUCTION-2
Aulacogen extends throughout the Andes
from Venezuela into Argentina
Mineralization known all along
conformscontinent-wide metallogenic province
INTRODUCTION
SALDAA FORMATION-1
Natagaima region =isolated stretch of Colombian Central Cordillera
complex vulcano-sedimentarysequence of faulted blocks
Saldaa Formation composed by:
tuffs, agglomerates, lava flows,continental + shallow marine sedimentary rocks
+ small subvolcanic porphyritic bodies
GENERALIZED LITHOLOGIC UNITS, NATAGAIMA, COLOMBIA
UNIT NAME AGE LITHOLOGY/ENVIRONMENT
RELATEDINTRUSIVES
MINERALIZATION
Volcaniclasticdeposits
Q Continental clastic andvolcanic deposits
Not exposed Au placers, exotic Cu
HondaFormation
TContinental shales,siltstones, sandstones,mudflows and volcanic ash
T porphyriticstocks
Gypsum veinlets, exotic Cu
Cretaceous toTertiary
sedimentarysequence
K-T
Marine to continentalsiliciclastics:conglomerates,sandstones, shales,limestones
None known
Au placers, Paleoplacers(Gualanday Fm.)Exotic Cu
SaldaaFormation
JContinental volcanic rocks,sediments, shallow marinedeposits, lava flows
J stocks,batholiths, dikes
+ sills
Low+high sulf. Epithermal Au veins;low sulfidation Au diss. in stkwks;Au+Cu porph., Fe oxide-Cu-Au,Sediment-hosted Au, gypsumveins, Mo-Cu porph.
PayandFormation J-TR
Limestones, sandstonesand shales
None known Sediment-hosted Au; Cu skarnAu veins + skarn, Replacementdeposits
LuisaFormation
TRContinental red beds:conglomerates,sandstones and shales,(evaporites)
Mafic smallbodies
Sediment hosted Au, Manto typePb-Zn, evaporites, Sediment-hosted Cu, Sabkhas
TierradentroGneiss &Granulites
pEHigh grade metamorphicrocks (granulites andgneisses)
Pz stocksShear zones with Au,Mesothermal Au
LOCATION
INTRODUCTION
LOCATION
Isolatedwedge ofColombianCentralCordillera
SALDAA FORMATION-2
size of andesitic-daciticporphyritic bodies seldom >4km2
Most outcrops of intrusive rocks =apophysis of larger bodies
too small to map at 1:100,000 scale
porphyritic bodies composed bywell-formed plagioclase phenocrystals
up to a few centimeters longthat occur in gray-green aphanitic matrix
SALDAA FORMATION-3
PETROGRAPHY
composition varies from tonalite togranodiorite and quartzmonzonite
some rocks grade into diorite + basaltfew = syenitic
Numerous augite phenocrystals + abundantamygdules filled by chalcedony, calcite, chlorite, epidote, zeolites and native Cu are evident in the matrix
GeneralizedGeologicalMap
GeneralizedGeologicalMap
SALDAA FORMATION-4
In t/ region of study, extends for 1200 km2
evidence of fertile intrusive rocks, hydrothermalalteration and mineralization occur throughout
15,400 hectares within region have high potentialto host disseminated Au associated with the upperportion of Cu-Au porphyry systems
study area = approx.1/3 of total known Saldaa outcrops in Colombian Andes
= 1/10 of similar age/composition rocks in country
SALDAA FORMATION-5
ENVIRONMENT OF EMPLACEMENT
deposited in aborted rift basin
overlying Triassic continental red beds andcarbonate platform
Jurassic subductionproduced magmatism + vulcanism
Unconformably overlain by thick pile of Cretaceous+ Tertiary sediments
INTRODUCTION
SALDAA FORMATION-6
Mineral deposits = result of Jurassic, porphyriticforced intrusions emplaced along weak zones oftuffs and other Saldaa units
Repetitive intrusion == overprinting of hydrothermalalteration + mineralization
Extensional faults run parallel to main branches ofaulacogen = offered sites for fluid migration + mineral deposition
circular structures are not uncommon
INTRODUCTION
MINERALIZATION-1
Several types of mineralization are knownin region
world-class Au placersabundant sub-vertical high and low
sulphidation Au- & Cu-rich qtz veinsAg, Cu, barite, fluorite, Sb, Fe +
gypsum deposits exploited at smallscale since pre-Columbian times
MINERALIZATION-2
Au + Cu diss. mineralization detected in:
-stockworks-breccioid qtz veins-individual porphyritic bodies-hydrothermal bxs along contact
between intrusive + volcanic rocks
MINERALIZATION-3
Region has significant potential forexploration of various mineral deposit types
-high and low sulfidation epithermal Au-Au porphyry-Cu porphyry-sediment-hosted Au
(so-called Carlin type)-Fe Oxide-Cu-Au-REE-exotic Cu accumulations
INTRODUCTION
MINERALIZATION-4
Primary Cu mineralization generally associated w/ local intense sericitization and silicification
large portion of Saldaa Formation = covered by secondary Cu minerals + epidote
Numerous gossans with high contents of free Auhave been mapped
>22 zones of interest with potential large-tonnageAu + Cu mineralization identified to date
Zooming in on amineralized
stockwork
Intense argillizationoverprints mineralizedstockwork
MINERALIZATION-5
Few prospects have been studied in detail, mapped or explored under moderntechniques.
Old, small-scale Au miners only workedrock deposits >6gAu/tplacers >5gAu/m3
No disseminated deposits were sampledbefore 1990s
EXTENSION INTOCOLOMBIAN ANDES
Geological environment and associated Auand Cu mineralization of Saldaa Formation
extends thoughout Colombian Andes
from Guajira to Putumayo
INTRODUCTION
EXTENSION INTOANDEAN CORDILLERA
Saldaa Formation equivalentsextend furthermore
along Andean Cordillera
from Venezuela to Argentina
Venezuela:Perij and Mrida
Argentina: Patagonia
WORLD-CLASS DEPOSITS
occur in correlatives of Saldaa Formation
and fall within similar age spanin continent-wide metallogenic province
WORLD-CLASS DEPOSITS
COLOMBIAEl Silencio, Antioquia ~1500 ton AuAngostura, Santander >700 ton AuSerrana de San Lucas, Bolvar >>500 tonAu
ECUADORNambija, Serrana del Cndor >300 ton AuSan Carlos, Sna del Cndor >~5x10^6 ton Cu
ARGENTINACerro Vanguardia, Patagonia ~500 ton Au
EXTENSION INTOANDEAN CORDILLERA
Serrana de Perij(stretches between
Colombia + Venezuela)
contains numerous,under-explored Au + Cu depositsassociated to Saldaa-typeJurassic events
EXTENSION INTOOTHER REGIONS
Part of this provinceextends into Mexico
Guerrero and Oaxaca terranes
GoldGold andand CopperCopper DisseminationDisseminationin in thethe IgneousIgneous--VolcanicVolcanic
SaldaSaldaa a FormationFormation, Colombia, Colombiaandand ExtensionExtension ofof thethe Mineral Mineral ProvinceProvince
in in thethe AndeanAndean CordilleraCordillera
Prepared by:Prepared by:Alberto LoboAlberto Lobo--Guerrero S.Guerrero S.GeologistGeologist, , M.ScM.Sc., ., MinExMinEx
EconomicEconomic GeologyGeology ResearchResearch InstituteInstituteUniversityUniversity ofof thethe WitwatersrandWitwatersrand
JohannesburgJohannesburg, , SouthSouth AfricaAfrica, , JuneJune, 2003, 2003