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Upstairs-downstairs: supercontinents and large igneousprovinces, are they related?Kent C. Condiea, Anne Davailleb, Richard C. Asterc & Nicholas Arndtd

a Department of Earth and Environmental Science, New Mexico Institute of Mining andTechnology, Socorro, NM 87801, USAb Laboratoire FAST, CNRS/Universite Paris-Sud, Orsay 91405, Francec Geosciences Department, Colorado State University, Fort Collins, CO 80523, USAd ISTerre (UMR5275), Université Joseph Fourier, Grenoble cedex 9 38041, FrancePublished online: 13 Oct 2014.

To cite this article: Kent C. Condie, Anne Davaille, Richard C. Aster & Nicholas Arndt (2014): Upstairs-downstairs: supercontinents and large igneous provinces, are they related?, International Geology Review, DOI:10.1080/00206814.2014.963170

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Upstairs-downstairs: supercontinents and large igneous provinces, are they related?

Kent C. Condiea*, Anne Davailleb, Richard C. Asterc and Nicholas Arndtd

aDepartment of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA;bLaboratoire FAST, CNRS/Universite Paris-Sud, Orsay 91405, France; cGeosciences Department, Colorado State University, Fort

Collins, CO 80523, USA; dISTerre (UMR5275), Université Joseph Fourier, Grenoble cedex 9 38041, France

(Received 27 June 2014; accepted 4 September 2014)

There is a correlation of global large igneous province (LIP) events with zircon age peaks at 2700, 2500, 2100, 1900, 1750,1100, and 600 and also probably at 3450, 3000, 2000, and 300 Ma. Power spectral analyses of LIP event distributionssuggest important periodicities at 250, 150, 100, 50, and 25 million years with weaker periodicities at 70–80, 45, and18–20 Ma. The 25 million year periodicity is important only in the last 300 million years. Some LIP events are associatedwith granite-forming (zircon-producing) events and others are not, and LIP events at 1900 and 600 Ma correlate with peaksin craton collision frequency. LIP age peaks are associated with supercontinent rifting or breakup, but not dispersal, at2450–2400, 2200, 1380, 1280, 800–750, and !200 Ma, and with supercontinent assembly at 1750 and 600 Ma. LIP peaks at2700 and 2500 Ma and the valley between these peaks span the time of Neoarchaean supercraton assemblies. Theseobservations are consistent with plume generation in the deep mantle operating independently of the supercontinent cycleand being controlled by lower-mantle and core-mantle boundary thermochemical dynamics. Two processes whereby plumescan impact continental assembly and breakup are (1) plumes may rise beneath supercontinents and initiate supercontinentbreakup, and (2) plume ascent may increase the frequency of craton collisions and the rate of crustal growth by acceleratingsubduction.

Keywords: large igneous province (LIP); mantle plume; supercontinent cycle; craton; orogeny

Introduction

A large number of papers have been written about thepossible relationship between the supercontinent cycleand mantle plume events, yet no consensus has emerged(Gurnis 1988; Stein and Hofmann 1994; Storey 1995;Condie 1998; Maruyama et al. 2007). One set of modelsproposes that insulation of mantle beneath growing super-continents leads to the generation of mantle plume clus-ters. Two mantle plume clusters are recognized today asregions of slow seismic velocities in the lower mantle (theLLSVP beneath Africa and the South Paci!c) (Burke et al.2008; Li and Zhong 2009). Other models suggest that it isnot supercontinents but disconnected processes in the deepmantle that lead to production of these plumes, and thatthe generation of plumes is independent of the superconti-nent cycle (LeBars and Davaille 2004).

The distribution of large igneous provinces (LIPs) inspace and time has become the major tracking method ofmantle plume events in Earth history. We readdress thequestion of the relationship of LIPs and supercontinentsbased on new LIP ages and on recent revisions of assem-bly and breakup times of pre-Gondwana supercontinents.We use previously reported LIP ages as well as add newU/Pb zircon and baddleyite isotopic ages and discuss thecorrelation or lack of correlation of LIP ages with zirconage peaks and the supercontinent cycle. Finally, we

propose a new model to explain LIP events of globalextent from mantle plumes generated by thermochemicalinstabilities at the base of the mantle. Our results implythat plate tectonics operates mostly or entirely indepen-dently of plume generation in the deep mantle.

Results

The !rst question is that of how to de!ne a LIP. Althoughmany investigators have used an areal or volume cut-offfor LIPs (commonly 105 km2; Ernst et al. 2008), such amethod is dif!cult to use for ancient LIPs where most ofthe record has either been removed by erosion or is notexposed. This is especially so when greenstone basalts andkomatiites are included in the LIP data base. Because theareal extent of any given LIP is not well constrained forrocks older than about 500 Ma, we adopt a size cut-off ofonly 104 km2. For our purposes, it is the global geographicdistribution of LIPs of a given age and not the areal extentof any given LIP that is most important. In this study, weinclude as LIPs, giant dike swarms, continental "oodbasalts, plume-related basalts and komatiites, and oceanicplateau basalts (from Bryan and Ernst 2008). Plume-related basalts are identi!ed using petrotectonic rock asso-ciations together with incompatible element geochemistry(Condie 1994, 2003). We begin with the Ernst and Buchan

*Corresponding author. Email: kcondie@nmt.edu

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(2001) data base, from which we eliminate LIPs that arenot well dated and add new precisely dated LIPs togetherwith plume-related basalts and komatiites (Appendix 1 inonline supplemental material at http://dx.doi.org/10.1080/00206814.2014.963170). When more than one period ofmagmatism is recorded by a single LIP, we use the majorperiod of magmatism as the age and use the range of agesreported for single LIPs to assign uncertainties to the ages.

The next question to address is that of how to de!ne aLIP ‘event’. Prokoph et al. (2004) identi!ed 304 LIPevents based on the ‘likelihood of their being related toan arriving mantle plume head’. Because we found thisconstraint dif!cult to apply, we use the total geographicdistribution of single LIPs of a given age to de!ne a LIP‘event’. A kernel density estimation (Jones et al. 1995)calculated from a Monte Carlo simulation of 1000 datasets is used to characterize LIP events in time (Figure 1).Closely spaced LIP age peaks are grouped into single LIPevents. For comparison, the kernel density distribution iscompared with various histogram distributions inAppendix 2 (Figure A2-1 in online supplemental materialat http://dx.doi.org/10.1080/00206814.2014.963170). Theduration of LIP events is typically 20–50 million years,but Phanerozoic events may be >100 million years, and insome cases may represent more than one, yet unresolved,LIP event. As shown in Table 1, LIP events of a given ageoccur on as few as 3 and as many as 12 cratons or

orogens; if we include individual oceanic plateaus<300 Ma, this number can increase to 32 depending onhow oceanic LIPs are grouped. Although most LIP events

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Figure 1. Distribution of LIP ages with time as compiled in Appendix 1. Also shown are supercontinent assembly and breakup times.Age spectrum constructed using the adaptive kernel estimation method of Jones et al. (1995). Original age data are randomized using ageuncertainties to create a data vector of multiple (1000) realizations of the data set, and this is used as an input for the kernel densityestimation. Ages given in Ma, total number of sites 444.

Table 1. Geographic distribution of large igneous province events.

Peak age (Ma)^ Number of cratons/orogens Number of sites

3450 (3450–3500) 3 93000 (2980–3000) 4 92800 (2780–2820) 6 72700 (2690–2720) 12 242500 (2500–2520) 6 62400 (2450–2400) 11 132200 (2190–2220) 8 162050 (2040–2060) 8 152000 (1990–2000) 6 61900 (1875–1925) 7 161790 (1770–1800) 3 51750 (1740–1770) 11 131450 (1500–1450) 12 131380 (1370–1400) 9 91270 (1280–1250) 4 71100 (1080–1100) 11 14825 (720–820) 11 13600 (500–620) 9 13200 (180–320) 22* 25*100 (20–150) 32* 39*

Notes: ^range of ages refers to several peaks that are grouped into oneLIP event.*Includes oceanic plateaus in modern ocean basins.

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also leave a record in ocean basins (as oceanic plateausand islands), this record is not well preserved before300 Ma except as minor remnants that were accreted tothe continents. Of the LIP events in Table 1, only twoevents (3450 and 3000 Ma) are not recognized on "6cratons or orogens, which we use as a cut-off for a ‘global’LIP event. From our data base, we recognize 15 globalLIP events ranging in age from 2800 to 600 Ma (17 eventsif we include oceanic plateaus !300 Ma) (Figure 1). All ofthe 15 events have been identi!ed in one or more previousstudies (Isley and Abbott 2002; Prokoph et al. 2004, 2013;Ernst et al. 2008; Ernst and Bleeker 2010). The number ofcratons has remained relatively constant between 12 and15 since the breakup of Archaean supercratons at 1900 Ma(Condie et al. 2014).

There is a correlation of LIP events with zircon agepeaks at 2700, 2500, 2100, 1900, 1750, 1100, and 600 andalso probably at 3450, 3000, 2000, and 300 Ma. However,caution must be used in attaching a great deal of signi!-cance to the height of age peaks (both LIP and zirconpeaks) (Condie and Aster 2010) because of three contri-buting factors: (1) peak height is largely dictated by thenumber of geochronological studies at a given site or in ageographic region; (2) the procedure used to group indi-vidual sites – this is especially important for greenstonebelts that are semi-continuous along strike: do you counteach greenstone separately or do you lump them together;and (3) the bin size is critical to how many peaks areresolved in a given population. We have overcome thebin size problem in this study by using a kernel densityapproximation after Jones et al. (1995) (Figure 1).

Isley and Abbott (2002) report strong LIP periodicityat 800, 270, 35, and 26 million years with weaker periodi-city at 370 and 300 million years. Prokoph et al. (2004)recognize a robust LIP periodicity at 170 million years and

weaker periods at 730–550 and 250–220 million years,and in the last 500 million years, Prokoph et al. (2013)report periodicity at 32, 65, and 140 million years. Usingmulti-taper power spectral analysis, which provides con-!dence intervals and optimizes spectral leakage versusuncertainty (Thomson 1982), we examined our new LIPdata base for possible periodicity. Results and associatedcon!dence intervals suggest well-developed periodicitiesat about 250, 150, 100, 50, and 25 million years, withweaker or poorly de!ned periodicities at 70–80, 45, and18–20 million years (Figure 2). Although some of theseperiods have been recognized in earlier studies, we feelour results based on a greater number of locations andmore precisely dated LIPs render a more accurate pictureof LIP periodicity or aperiodicity. The 25 million yearperiod is most prominent in the last 300 million years(Figure 2). Unlike the results of Isley and Abbott (2002)and Prokoph et al. (2004), we !nd no suggestion in thepower spectrum of periodicities longer than 300 millionyears, which are dominated by spectral reddening.

Discussion

As pointed out in our earlier papers (Condie 1998; Condieand Aster 2010), major zircon age peaks occur at 2700,2500, 2100, 2000, 1900, 1750, 1100, 600, and 300 Ma(Figure 3). Although all of these age peaks have corre-sponding LIP events, LIP events at 2450–2400, 2200,1500–1450, 1380, 1280, 800–750, and !200 Ma are notaccompanied by zircon age peaks. LIP events at 3450,3000, and 2800 Ma may have corresponding zircon agepeaks, although weakly developed (Figure 3). Thus, someLIP events are associated with granite-forming (zircon-producing) events and some are not, and with the excep-tion of zircon age peaks at 3450 and 3000 Ma, both LIP

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and zircon peaks appear to be global in extent. Likewise,some LIP age peaks appear to be associated with super-continent breakup and others do not. LIP peaks at 2700and 2500 Ma, and the valley between these peaks spansthe time of Neoarchaean supercraton assemblies. LIP agepeaks correlate with supercontinent rifting or breakup at2200, 1380, 1280, 800–750, and !200 Ma, and withsupercontinent assembly at 1750 and 600 Ma. The LIPand zircon peaks at about 1100 Ma may correlate witheither or both the late stages of Nuna breakup or earlystages of Rodinia assembly. It is possible that the LIP agepeaks not accompanied by zircon peaks (2450–2400,2200, 1500–1450, 1380, 1280, 800–750, !200 Ma) re"ectinitial rifting and fragmentation of supercontinents withoutwidespread production of granitoids or they may be totallydisconnected from the supercontinent cycle. At 2450 Ma,the supercratons formed in the Neoarchaean (2700–2500 Ma) began to rift apart (Heaman 1997; Vogel et al.1998); and at about 2200–2100 Ma, they completely frag-mented. The large LIP peak at 2000 Ma could representthe onset of dispersal. The 1500–1450 and 1380 Ma LIPpeaks may re"ect the initial rifting of Nuna leading tobreakup between 1300 and 1100 Ma (Pisarevsky et al.2014a, 2014b), and the LIP age peak at 825–750 Ma maycorrespond to the initial rifting of Rodinia followed bybreakup at 750–650 Ma (Wang et al. 2009). Lastly, theLIP peak at 200 Ma correlates with the initial rifting ofGondwana–Pangea, followed by breakup from 150 Maonwards. Many of the LIP events in the last 150 millionyears are not global in extent. For instance, the Atlanticbasin opened progressively in the last 150 million yearsand it is accompanied by three non-global LIP events: the

Central Atlantic Magmatic Province (200 Ma), theEtendeka–Parana event (138 Ma), and the Iceland–NorthAtlantic event (60 Ma) (Courtillot et al. 1999). Otherpeaks seem to be totally disconnected with the supercon-tinent cycle. For example, the largest Mesozoic andCenozoic LIPs such as the Siberian LIP at 250 Ma, theOntong–Java LIP at 90–120 Ma, and the Caribbean LIP at90 Ma are not associated with speci!c continental assem-bly or rifting events.

LIP age peaks at 1900 and 600 Ma also correspondwith peaks in craton collision frequency (Condie et al.2014), but recent re!nements in the timing of the pre-500 Ma supercontinent cycle do not support earlier con-clusions that major zircon age peaks correlate with super-continent assembly (Condie and Aster 2010;Hawkesworth et al. 2010; Condie 2013) (Figure 3).Three zircon age peaks (1750, 1100, and 600 Ma) maycorrelate with the onset but not the duration of super-continent assembly, and the 1900 and 300 Ma peaks donot correlate with supercontinent assembly or breakup.Supercontinent formation is a protracted process whoseduration of several hundred million years is generallylarger than the events registered by zircon peaks. Thesupercontinent cycle begins with the assembly of Nunabetween 1700 and 1500 Ma (Pisarevsky et al. 2014a), yetthe major zircon age peak is at 1900 Ma. The two or threezircon age peaks between 1800 and 1500 Ma that arepartly hidden by the shoulder of the 1900 Ma peak may,at least in part, re"ect collisions in the growth of Nuna. Itis noteworthy that LIPs also show age peaks at 1900 and1750–1700 Ma with only small peaks between 1700 and1500 Ma (Figure 1). We see a similar pattern of ages

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Figure 3. Distribution of U/Pb zircon ages in granitoids and detrital zircons for the last 4 billion years with 1! error envelopes. N isrepresentative of the number of samples as a function of age that would be observed in a histogram with bins of 30 million year width.The detrital ancient sediment data base is multiplied by two for comparative purposes. Modi!ed after Condie and Aster (2010, 2013). LIPevents from Table 1, rifting and breakup refer to supercontinents.

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during the assemblies of Rodinia (at 1000–850 Ma) andGondwana-Pangea (650–350 Ma), with both zircon andLIP age peaks occurring just before or at the beginning ofsupercontinent assembly (1100 and 600 Ma, respectively).

This brings up the question of how to de!ne theduration of supercontinent assembly, and indeed whetherthe duration can be de!ned. For instance, at 1900 Ma,numerous small cratons collided to make ‘supercratons’(Condie et al. 2014), but it was not until 1700–1500 Mathat the supercratons assembled into Nuna (Figure 4). Inthe case of Rodinia, numerous cratons collided at 1200–1000 Ma, but most or all of Rodinia assembly occurredbetween 1000 and 850 Ma (Pisarevsky et al. 2003,2014b). Although most craton collisions related to thegrowth of Gondwana–Pangea occurred at 650–550 Ma,assembly of the Pangea phase continued until about350 Ma (Cawood and Buchan 2007; Li et al. 2013).Thus, in all three of the supercontinents, just before orduring the early stages of assembly, there is a peak infrequency of craton collisions (Figure 4). Should wecount this peak as part of supercontinent assembly oronly count the !nal collisions of large cratons as theassembly? If we include palaeomagnetic constraints(Pisarevsky et al. 2003, 2014a, 2014b), it would appearthat only the !nal supercraton collisions should be desig-nated as supercontinent assembly. If so, what is the causeof the large peaks in craton collision frequency prior tosupercontinent assembly? The increase in frequency of

global LIP events prior to and during each of the cratoncollision events (Figure 4) suggests a cause and effectrelationship. It is possible, as discussed below, that risingmantle plumes enhanced the rate of subduction, which inturn increased the frequency of craton collisions, andperhaps accelerated the rate of growth of continental crust.

Mantle plumes are common features of thermal con-vection at high Rayleigh number (e.g. Olson et al. 1987).They are transient and develop on a characteristic timescale between 30 and 200 million years, for mantle visc-osity between 1019 and 1022 Pa s. However, their distribu-tion in space and time is chaotic so that another ingredientis needed in addition to produce plume/LIP global eventsas reported in the previous section. Previous studies haveproposed that there may be two types of LIP events: thoseassociated with insulation or isolation of mantle beneathsupercontinents (Gurnis 1988; Coltice et al. 2007) andthose not associated with supercontinents, but perhapscreated by the return "ow from slab avalanches from themantle transition zone (Machetel and Weber 1991; Steinand Hofmann 1994; Condie 1998, 2000; Heron andLowman 2010; Brandl et al. 2013). However, slab ava-lanches from the 660 km discontinuity depend on theClapeyron slope of the perovskite reaction, of whichrecent estimates suggest the slope is too small to supportthis process, even at higher mantle temperatures thatexisted in the past (Katsura et al. 2003; Fei et al. 2004).Also, although generation of global plume events by slab

Figure 4. Age distribution of collisional orogens from 2400 to 400 Ma. Data from Condie et al. (2014). Bin size 40 million years.

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avalanches tends to work for 2D models (Machetel andWeber 1991), it does not work well for 3D models(Tackley 1996).

Recent experiments (Davaille 1999; Davaille et al.2005; Arndt and Davaille 2013) suggest that major LIPevents can originate from the sudden destabilization of acompositionally heterogeneous layer at the base of themantle that produces thermochemical instabilities(plumes) that rise rapidly to the base of the lithosphereand undergo extensive melting to produce LIPs. Theseexperiments suggest that global plume episodes needneither the supercontinent cycle nor slab avalanches andthat there is a disconnect between the lithosphere and thedeep mantle (i.e. the downstairs does not know what isgoing on upstairs). The arrival of hot plumes in the uppermantle results in (1) production of large volumes of meltin plume heads (including komatiites) and (2) displace-ment of upper mantle material that enhances the rate ofdownwelling by increasing subduction rates. The lattermay also accelerate rates of craton collision and perhapsof continental growth.

The thermochemical instability model has the advan-tage that it explains all major LIP events by one process,and it is also strongly supported by experimental results. Italso implies that LIP events that do not correspond tosupercontinent breakup (such as at 2700, 2500, 1900,1750, and 600 Ma) are not tied to actions of the litho-sphere, but have deep-seated causes. In the laboratoryexperiments, cooling of rising and spreading plumesresults in increasing their density and sinking back intothe mantle, leading to a repetition of the plume cycle(LeBars and Davaille 2004; Davaille et al. 2005).Several episodes with recurrence times of 200–300 millionyears are predicted by the experiments, with later cyclesbecoming more disorganized. Supporting the thermoche-mical instability model for Earth are the results of ourpower spectral analysis, which suggest periodicities inthe 100–300 million year range (Figure 2).

If the thermochemical instability model is accepted asdominating global plume event production, the relation-ship of mantle plume generation to the supercontinentcycle appears to be a secondary effect: i.e. arrival ofmantle plumes weakens the continental lithosphere andfocuses the site of breakup, but fragmentation of the super-continents is caused by far-!eld tectonic processes(Courtillot et al. 1999). In some cases, the initial breakupof supercontinents is earlier than the onset of plume-induced magmatic events. For instance, extensive conti-nental extension, anorogenic magmatism, and riftingbegan in Rodinia some 30–50 million years before the!rst well-documented mantle plume event at 825–800 Ma (Wang et al. 2009). In contrast, progressivespreading of !rst the Atlantic Ocean and then the IndianOcean is linked to plume arrivals in the last 200 millionyears (with some precursor rifting at 230 Ma). In this case,

plume magmatism may be directly involved in continentalbreakup.

Conclusions

(1) Global peaks in age of LIPs correlate with zirconage peaks at 2700, 2500, 2100, 1900, 1750, 1100,and 600 Ma and also probably at 3450, 3000,2000, and 300 Ma.

(2) LIP age peaks correlate with supercontinent riftingor breakup, but not dispersal, at 2200, 1380, 1280,800–750, and !200 Ma, and with supercontinentassembly at 1750 and 600 Ma. LIP peaks at 2700and 2500 Ma, and the valley between these peaksspans the time of Neoarchaean supercratonassemblies.

(3) LIP age peaks at 1900 and 600 Ma correlate withpeaks in craton collision frequency and may re"ectmantle plume events that enhance subduction rates.

(4) The 1900 Ma LIP age peak correlates with wide-spread collision and amalgamation of micro-cra-tons resulting from breakup and dispersal ofArchaean supercratons.

(5) Of the LIP age peaks without corresponding zirconpeaks, those at 2450–2400, 2200, 1500–1450,1380, 1280, 825–750, and !200 Ma may representinitial rifting and fragmentation of supercontinents,or they may be totally disconnected from thesupercontinent cycle.

(6) Power spectral analyses of LIP events suggestdominant periodicity at 250, 150, 100, 50, and25 million years and weaker periodicities at 70–80, 45, and 18–20 Ma, with the 25 million yearperiod important only after 300 Ma.

(7) Interpreted in light of experimental plume models,our results suggest that global LIP age peaksre"ect episodic destabilization of a composition-ally heterogeneous layer at the base of the mantlethat produces thermochemical instabilities(plumes) with a recurrence time of 100–300 millionyears. These periods of mantle plume generationoperate independently of the supercontinent cycle.

Supplemental dataSupplemental data for this article can be accessed at http://dx.doi.org/10.1080/00206814.2014.963170.

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