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Geoscience CanadaJournal of the Geological Association of CanadaJournal de l’Association Géologique du Canada

Igneous Rock Associations 16. The Late Permian EmeishanLarge Igneous ProvinceJ. Gregory Shellnutt

Volume 42, Number 1, Spring 2015

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Cite this articleShellnutt, J. G. (2015). Igneous Rock Associations 16. The Late PermianEmeishan Large Igneous Province. Geoscience Canada, 42(1), 169–180.

Article abstractThe Late Permian Emeishan large igneous province (ELIP) covers ~0.3 x 106km2 of the western margin of the Yangtze Block and Tibetan plateau of SWChina with displaced, correlative units in northern Vietnam (Song Da zone).The ELIP is of particular interest because it contains numerous world-classbase metal deposits and is contemporaneous with the Late Capitanian massextinction. The flood basalts are the signature feature of the ELIP but there arealso picritic and silicic volcanic rocks and layered mafic–ultramafic and silicicplutonic rocks exposed. The ELIP is divided into three zones (i.e. inner, middleand outer) which correspond to a decrease in crustal thickness from the innerto the outer zone. The eruptive age of the ELIP is ~260 Ma and is constrained bypaleomagnetic observations to an interval of ≤ 3 m.y. The presence of picriticand basaltic volcanic rocks is evidence for a high temperature regime;however, it is uncertain if these magmas were derived from subcontinentallithospheric mantle or sublithospheric mantle (i.e. asthenosphere or mantleplume) sources or both. The range of Sr (ISr ≈ 0.7040 to 0.7132), Nd (εNd(T) ≈–14 to +8), Pb (206Pb/204PbPbI ≈ 17.9 to 20.6) and Os (gOs ≈ –5 to +11) isotopevalues of the ultramafic and mafic rocks does not permit a conclusive answerto source origin but it is clear that some rocks were affected by crustalcontamination. However, the identification of depleted isotope compositionssuggests that there is a sub-lithospheric mantle component in the system. TheELIP is considered to be a mantle plume-derived large igneous province andmay have contributed to ecosystem collapse during the latest Capitanian.

GEOSCIENCE CANADA

Igneous RockAssociations 16.The Late PermianEmeishan Large IgneousProvince

J. Gregory Shellnutt

Department of Earth Sciences National Taiwan Normal University 88 Tingzhou Road Section 4Taipei 11677, Taiwan E-mail: jgshelln@ntnu.edu.tw

SUMMARYThe Late Permian Emeishan largeigneous province (ELIP) covers ~0.3 x106 km2 of the western margin of theYangtze Block and Tibetan plateau ofSW China with displaced, correlativeunits in northern Vietnam (Song Dazone). The ELIP is of particular inter-est because it contains numerousworld-class base metal deposits and iscontemporaneous with the Late Capi-tanian mass extinction. The floodbasalts are the signature feature of theELIP but there are also picritic andsilicic volcanic rocks and layeredmafic–ultramafic and silicic plutonic

rocks exposed. The ELIP is dividedinto three zones (i.e. inner, middle andouter) which correspond to a decreasein crustal thickness from the inner tothe outer zone. The eruptive age ofthe ELIP is ~260 Ma and is con-strained by paleomagnetic observationsto an interval of ≤ 3 m.y. The pres-ence of picritic and basaltic volcanicrocks is evidence for a high tempera-ture regime; however, it is uncertain ifthese magmas were derived from sub-continental lithospheric mantle or sub-lithospheric mantle (i.e. asthenosphereor mantle plume) sources or both. Therange of Sr (ISr ≈ 0.7040 to 0.7132),Nd (εNd(T) ≈ –14 to +8), Pb(206Pb/204PbPbI ≈ 17.9 to 20.6) and Os(gOs ≈ –5 to +11) isotope values ofthe ultramafic and mafic rocks doesnot permit a conclusive answer tosource origin but it is clear that somerocks were affected by crustal contami-nation. However, the identification ofdepleted isotope compositions sug-gests that there is a sub-lithosphericmantle component in the system. TheELIP is considered to be a mantleplume-derived large igneous provinceand may have contributed to ecosys-tem collapse during the latest Capitan-ian.

SOMMAIRELa grande province ignée d’Emeishande la fin du Permien (ELIP) s’étendsur environ 0,3 x 106 km2 à la margeouest du bloc Yangtze et du plateautibétain du sud-ouest de la Chine, avecdes unités corrélatives déplacées dansle nord du Vietnam (zone de SongDa). L’ELIP est intéressant parce qu’ilrenferme de nombreux gisements demétaux de base de classe mondiale et

qu’il est contemporain de l’extinctionde masse de la fin du Capitanien. Lesbasaltes de plateau sont la signaturegéologique de l’ELIP, bien qu’on y ren-contre aussi des roches volcaniquespicritiques et siliciques ainsi que desformations stratifiées de rochesmafiques à ultramafiques et plu-toniques acides. L’ELIP est divisé entrois zones (interne, médiane etexterne) correspondant à une diminu-tion de l’épaisseur crustale de la zoneinterne vers la zone externe. L’éruptionde l’ELIP date d’environ 260 Ma maisles observations paléomagnétiques lim-itent sa durée à ≤ 3 m.a. La présencede roches volcaniques picritiques etbasaltiques indique un régime à hautetempérature mais on ne sait pas si cesmagmas proviennent de sources man-telliques lithosphériques sous-continen-tales ou sous-continentales man-telliques (c.-à-d. asthénosphère oupanache mantellique) ou des deux. Lagamme des valeurs isotopiques Sr (ISr≈ 0,7040 à 0,7132), Nd (εNd(T) ≈ –14 à+8), Pb (206Pb/204PbPbI ≈ 17,9 à 20,6)et Os (gOs ≈ –5 à +11) des rochesultramafiques et mafiques ne permetpas de décider de l’origine de la sourcemais il est clair que certaines rochesont subis de contaminations crustales.Cependant l’existence de compositionsisotopiques appauvries indique laprésence dans le système d’une com-posante mantellique sous-lithos-phérique. L’ELIP est considéré commeune grande province ignée dérivée d’unpanache mantellique qui pourrait bienavoir contribué à l'effondrement de l’é-cosystème à la toute fin du Capitanien.

INTRODUCTIONThe Late Permian Emeishan large

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Geoscience Canada, v. 42, http://dx.doi.org/10.12789/geocanj.2014.41.060 © 2015 GAC/AGC®

SERIES

igneous province (ELIP) is a relativelysmall, continental mafic large igneousprovince but is the focus of a tremen-dous amount of geological, geochemi-cal, paleomagnetic, geochronologicaland biostratigraphic research since the1980s. In spite of its stature as a‘smaller’ large igneous province, theELIP is an important geological fea-ture of SW China, not only because ithosts a number of Fe–Ti–V oxide andNi–Cu– (PGE) sulphide deposits, butis also contemporaneous with the latestperiod of the Late Capitanian–EarlyWuchiapingian mass extinction (i.e.end-Guadalupian) indicating that theremay be a link between the two (Zhouet al. 2002a; Ganino and Arndt 2009;Sun et al. 2010; Shellnutt et al. 2012).Beyond the economic and biogeologi-cal significance, the ELIP contains adiverse set of volcanic and plutonicigneous rocks (i.e. picrite, basalt, lay-ered gabbroic intrusions, basalticandesite, andesite, trachyte, rhyolite,syenite, and granite). The fact that themagmatic plumbing system of theELIP is well exposed at the surface isrelatively special because plutonic andhypabyssal rocks of LIPs are not oftenobserved together. The bulk of thegeological and petrological research,including evidence of structural dom-ing of the crust, suggests that theELIP formed by a mantle plume. Con-sequently, it is considered to be one ofthe best examples of a mantle plume-derived LIP and is used as a bench-mark for comparison with other conti-nental mafic LIPs (Campbell 2005).

There are some widely accept-ed ideas on the formation of the ELIP(e.g. mantle plume-derived) but recent-ly many older interpretations (e.g. evi-dence for uplift) are giving way to newand alternative ideas. There are ongo-ing debates regarding the source of theflood basalts, the formation of theoxide-ore deposits and whether crustaldoming occurred prior to volcanism(Xu et al. 2001, 2004; Song et al. 2001;He et al. 2003; Zhou et al. 2005;Utskins Peate and Bryan 2008; Sun etal. 2010; Zhong et al. 2011, Shellnuttand Jahn 2011; Kamenetsky et al.2012).

The objective of this reviewpaper is to introduce the salient fea-tures of the ELIP and provide a gener-al synthesis of its formation. The

paper is divided into six principal sec-tions which focus on a specific aspectof the ELIP. The first sectiondescribes the geological background ofthe ELIP, including its size, shape andzonation. The second section discussesthe age of the ELIP and the durationof magmatism. The third section pri-marily describes and discusses the mag-matic rocks which are unrelated tomineral deposits (i.e. picrite, basalticand silicic volcanic and plutonic rocks).The fourth section discusses some ofthe structural features of the ELIP (i.e.crustal doming) that are interpreted tobe evidence for a mantle plume andthe effect that it may have had on thelate Capitanian ecosystem. The fifthsection describes the layered gabbro-hosted Ni–Cu–(PGE) sulphide andFe–Ti–V oxide deposits. The final sec-tion presents a general synthesis of theELIP.

GEOLOGICAL BACKGROUNDThe ELIP is located on the westernedge of the Yangtze Block near theboundary with the Songpan-Ganze ter-rane (Figs. 1 and 2). The wedge-shapeddistribution of ELIP rocks is related toMesozoic faulting associated with theformation of the Songpan-Ganze ter-rane and the Cenozoic India–Eurasiancollision (Chung and Jahn 1995; Chunget al. 1997). The ELIP covers an areaof at least 0.3 x 106 km2 of SW Chinaand northern Vietnam (Song Da zone)and is subdivided into three roughlyconcentric zones (i.e. inner, intermedi-ate and outer) which correspond tocrustal thickness estimates (Fig. 2a, b).The centre of the ELIP is known asthe inner zone and has the thickestcrust which progressively thins fromthe intermediate to outer zone (Zhonget al. 2002; Xu et al. 2004; Zhou et al.2005). The volcanic successions rangein thickness from 0.1 to 5.0 km andconsist mostly of flood basalts withpicrite in the lower half and basalticandesite and silicic volcanic rocks inthe upper half. The volcanic rockserupted at equatorial latitudes of east-ern Pangaea on top of middle Permianlimestone or directly on Precambriancratonic rocks of the Yangtze Block.The ELIP is an important host ofNi–Cu–(PGE) sulphide and Fe–Ti–Voxide mineral deposits. The inner zone,chiefly the Panxi region, contains many

giant orthomagmatic Fe–Ti–V oxidedeposits, whereas Ni–Cu–(PGE) andPGE deposits are found within theinner and outer zones but none havebeen found within the intermediatezone yet (Shellnutt 2014).

AGE AND DURATION OF ELIP MAGMATISMThe sedimentology and biostratigraphyconstrain the eruption of the Emeis-han flood basalts to the late Permian(He et al. 2007; Sun et al. 2010). TheEmeishan basalts erupted onto theMiddle Permian fusulinid-bearingNeomisellina-Yabeina zone of the Maok-ou Limestone Formation which indi-cates they erupted no earlier than 263Ma (He et al. 2003). The deposition ofthe Xuanwei Formation at 257 ± 4 Mamarks the end of subaerial volcanismin the region suggesting that it lasted ≤10 million years (He et al. 2007). Paleo-magnetic data collected from basaltsections show evidence for an earlyperiod of normal magnetic polarityfollowed by reverse polarity coincidingwithin one normal polarity episode (i.e.≤ 1.5 m.y.) thereby reducing the likelyeruption duration to < 3 m.y. (Ali et al.2005; Zheng et al. 2010). However, theradiometric ages of all magmatic rocksreveals a more complicated scenario.Over 70 published radiometric agedates have been measured by 40Ar/39Ar(11) and U/Pb (65) methods on vol-canic and plutonic rocks of the ELIPand they range from ~236 Ma to ~266Ma (Fig. 3). The range of dates may, infact, be an artifact of different radio-metric methods used (c.f. Shellnutt etal. 2012), misinterpreting rocks, poordata processing and the rock type (i.e.volcanic vs. plutonic). The first highprecision zircon U/Pb chemical abra-sion ID–TIMS geochronology resultsfrom a suite of diabase dykes andgranitic rocks yielded ages between257.6 ± 0.5 Ma and 259.6 ± 0.5 Maand currently is the best emplacementage available for the ELIP (Shellnutt etal. 2012).

MAGMATIC ROCKS OF THE ELIPMafic continental large igneousprovinces represent the physical andchemical transfer of material from themantle to the crust and are related tolithospheric thinning and/or a mantleplume (Coffin and Eldholm 1994;

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Bryan and Ernst 2008). A number ofgeological, geochemical and thermalcriteria indicate whether a given LIPwas generated by a mantle plume. Themain geological features associatedwith a mantle plume-derived LIPincludes: short duration of magmatism(e.g. ≤ 1 m.y.), the eruption of ultra-mafic lava, thermal anomalies, volumi-nous flood basalt and doming of thecrust (Campbell 2007). Some of thecriteria are difficult to assess, in partic-ular the eruption duration and domingof the crust. The ELIP is consideredto be a mantle plume-derived largeigneous province and exhibits, to vary-ing degrees, the criteria outlined for

mantle plume-LIPs (Xu et al. 2004:Xiao et al. 2004; Hou et al. 2006;Kamenetsky et al. 2012). This sectionsummarizes the magmatic features ofthe ELIP.

Ultramafic Volcanic RocksHigh temperature ultramafic volcanicrocks are recognized within the innerzone of the ELIP (Hanski et al. 2004,2010; Hou et al. 2006; Zhang et al.2006; Wang et al. 2007; Ali et al. 2010;He et al. 2010; Kamenetsky et al.2012). There are also correlative units,including picrite, in the Song Da zoneof northern Vietnam which was trans-lated by ~600 km sinistral offset dur-

ing the Paleogene activation of theAilao Shan–Red River fault system(Chung et al. 1997). The picritic rockscontain between 14 wt.% and 27 wt.%MgO but, in some cases, their compo-sition and textures (i.e. spinifex) bearsome resemblance to the komatiite ofGorgona Island (Hanski et al. 2004;Kamenetsky et al. 2012). The picritelayers are found no higher than thelower half of the volcanic successionwhich suggests they were amongst theearliest eruptive rocks (Xu et al. 2001;Hanski et al. 2004; Zhang et al. 2006;Li et al. 2010). The eruption and man-tle potential temperatures (Tp) of theELIP picrite layers have been estimat-

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Figure 1. Major tectonic divisions of China and the location of the Emeishan large igneous province (ELIP).

ed using different techniques but calcu-lated temperatures are consistently >1540°C which is at least 150°C abovethe Tp estimates of primitive MORB(Xu et al. 2001; Ali et al. 2010; He etal. 2010).

The ultramafic rocks eruptedrelatively early, consist of ‘low-Ti’ and‘high-Ti’ varieties, are high temperaturemelts, and represent a large (i.e. >20%) amount of melting from a gar-net-bearing mantle source (Hanski etal. 2004, 2010; Zhang et al. 2006; Wanget al. 2007; Kamenetsky et al. 2012).However, there are different interpreta-tions regarding the nature of theirsource. The prevailing view is that theultramafic rocks are pristine primitivemelts from the starting plume-headthat were modified, in some cases, viainteractions with one of, or a combina-tion of crustal material and lithospher-ic mantle melts and assimilation–frac-tional crystallization (AFC) processes(Hanski et al. 2004, 2010; Zhang et al.2006; Wang et al. 2007; Li et al. 2010;He et al. 2010). Some of the picriteshows the most depleted Sr–Nd–Osisotope signatures (i.e. ISr ≈ 0.7040;εNd(T) ≈ +8; gOs ≈ +11) in the entireELIP and implies there is a depletedmantle-like (i.e. sub-lithosphere) com-ponent in the source (Hanski et al.2004; C. Li et al. 2010; J. Li et al. 2012).Kamenetsky et al. (2012) have suggest-ed that the two series (i.e. high-Ti andlow-Ti) of picrite were derived fromseparate mantle sources; a peridotitesource for the low-Ti series and a gar-

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Figure 2. (a) Regional distribution of the Emeishan large igneous province (ELIP)showing the concentric zones (dashed red lines) of the ELIP and location of Ti–Voxide and Ni–Cu–PGE sulphide deposits. (b) Seismic P-wave velocity (km/s)structure of the lower crust and upper mantle beneath the western Yangtze Block.The profile is from Lijiang (A) to Zhehai (B) (modified from Xu et al. 2004).HVLC = high velocity lower crust.

Figure 3. Frequency distribution ofwhole rock 40Ar/39Ar and zircon U/Pbradioisotopic age dates of rocks fromthe Emeishan large igneous province(ELIP).

net pyroxenite for the high-Ti series,and originated from the subcontinentallithospheric mantle which may be com-posed of variable proportions ofeclogite, garnet pyroxenite and peri-dotite rather than a deep-seated mantleplume source or asthenosphericsource.

The Emeishan Flood BasaltsThe early themes of Emeishan basaltstudies focused on their division intohigh- and low-Ti groups and their spa-tial–temporal distribution (Xu et al.2001; Song et al. 2001; Xiao et al. 2004;He et al. 2010; Lai et al. 2012). Thedivision into ‘high-Ti’ and ‘low-Ti’groups corresponded to a petrologicaldistinction as the ‘high-Ti’ (i.e. TiO2 >2.5 wt.%) basalts are considered to bederived by low degrees (< 8%) of par-tial melting of the pristine source,whereas the ‘low-Ti’ basalts (i.e. TiO2< 2.5 wt.%) are considered to bederived from either the subcontinentallithospheric mantle (SCLM) or picriticmagmas that assimilated upper crust(Fig. 4) (Xiao et al. 2004; Wang et al.2007; Fan et al. 2008; Song et al. 2008;Zhou et al. 2008; Qi et al. 2010). Thesignificance of the basalt groups is thatthe composition is indicative of thetype of mineral deposit (i.e. sulphideor oxide) which may be present in theimmediate area (Zhou et al. 2008; Songet al. 2009; Wang et al. 2011). Theintrusive equivalents of the basalts areoften associated with mineral depositsand have textures indicative of cumu-lus textures; consequently, they will bediscussed with the orthomagmaticdeposits. Initial interpretations of thegeographic distribution of the basaltsfrom the inner and outer zones sug-gested that there is a consistent spatial,temporal and chemical relationship,where the ‘higher-Ti’ basalts are locat-ed mostly in the outer zone and the‘lower-Ti’ basalts are located mostly inthe inner zone (Xu et al. 2001). Fur-thermore, it was thought that the‘lower-Ti’ basalts erupted before the‘high-Ti’ basalts. The spatial–composi-tional variation is debatable and maynot exist. For example, there are strati-graphic profiles within the inner zonethat have basal ‘high-Ti’ basalt flows,whereas ‘lower-Ti’ basalts are identifiedwithin the outer zone (Shellnutt 2014).

The Emeishan basalts range in

composition from subalkaline to alka-line (Fig. 5a). The whole rock Sr andNd isotopes of the Emeishan basaltsindicate that they could be derivedfrom a heterogeneous mantle sourceand/or experienced variable degrees ofcrustal assimilation (Figs. 5d, 6a). Thetypical range of the εNd(T) values ofthe Emeishan basalts is between –5and +6 as both the ‘high-Ti’ basalts(i.e. εNd(T) = –3.6 to +4.8) and the‘low-Ti’ basalts (i.e. εNd(T) = –14.2 to+6.4) completely overlap. Isotope dataand trace elements can usually distin-guish between possible source contri-butions but in the case of the ELIPthey are not particularly insightfulbecause of the large range in values(i.e. ISr ≈ 0.7040 to 0.7132; gOs ≈ –5to +11; 206Pb/204PbPb1 ≈ 17.9 to 19.7)(Fig. 6). Trace elements are no more orless useful as there is a continuouscompositional range across all of thebasalts (i.e. ‘high- and low-Ti’) and thechemical trends attributed to crustalassimilation may in fact represent mix-

ing between a subducted sedimentcomponent (e.g. global subducting sed-iments - GLOSS) and the mantlesource (Fig. 5b, c, d).

The chemical diversity of theEmeishan basalts may also reflect theinfluence of magmatic rocks from anearlier period. During the Neoprotero-zoic (~800 Ma) there was an activecontinental margin located in the sameplace as the ELIP (Zhou et al. 2002b).It is possible that underplated maficrocks from the arc magmatism servedas a source or acted as a contaminantfor some Emeishan magmas. There-fore the ELIP basaltic magmas couldbe derived from a ‘pristine’ mantlesource (i.e. mantle plume), and/or alithospheric mantle source and/ormelting of mafic crustal rocks. In addi-tion to the multiple sources of thebasaltic magmas, they likely experi-enced shallow level crustal assimilationand fractional crystallization, andreflect differences in the amount ofsource melting. Constraining the pre-

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Figure 4. Frequency distribution plots of (a) Ti/Y showing the 500 division lineand (b) TiO2 (wt.%) showing the 2.5 wt.% division. (c) Range of eNd vs. Ti/Y and(d) Sm/Yb ratio vs. Ti/Y of the Emeishan basalts showing a continuous trend.

cise source characteristics and influ-ence of crustal material on the compo-sition of the flood basalts remains animportant issue.

Silicic RocksThe silicic volcanic and plutonic rocksof the ELIP are volumetrically minor(i.e. ≤ 5%) components but testify tothe diversity of magmas that were pro-duced. In general, the silicic volcanicrocks are exposed in the upper por-tions of the volcanic stratigraphy,whereas the plutonic rocks haveintruded the basement rocks of theYangtze Block and also have intrudedthe lowermost flows of the floodbasalts. The ELIP is an excellentregion to study within-plate silicicrocks because both the volcanic andplutonic rocks are well exposed.

The silicic rocks classify asandesite, trachyandesite, trachyte, rhyo-lite, ignimbrite, granite and syenite and

have peraluminous, metaluminous andperalkaline compositions (Xu et al.2010; Anh et al. 2011; Shellnutt et al.2011a, b). Geochemical modelling indi-cates that the peralkaline rocks arederived by fractional crystallization ofmafic magmas resembling the ‘high-Ti’Emeishan basalt with minimal, if any,crustal assimilation (Xu et al. 2010;Shellnutt et al. 2011a, b). The peralu-minous rocks are considered to bederived almost exclusively from crustalsources, although Anh et al. (2011)suggested that some peraluminous vol-canic rocks were derived by extensivefractionation of ‘high-Ti’ basalticmagma with crustal assimilation. Incontrast, the formation of the metalu-minous rocks is a little more compli-cated as some were derived bybasalt–crust AFC (assimilation–frac-tional crystallization) processes, where-as others were derived by partial melt-ing of basaltic underplated rocks relat-

ed to ELIP (Shellnutt and Zhou 2007;Xu et al. 2008; Shellnutt et al. 2011b).

STRUCTURAL FEATURES AND ECOLOGICAL IMPACT OF THE ELIP

High Velocity in the CrustPerhaps one of the most intriguinginterpretations in support of the ELIPmantle plume model is the presence ofhigh seismic velocity layers within theYangtze Block beneath the region con-sidered to be the epicentre of magma-tism (i.e. inner zone). The inner zone isshown to have thicker average crustthan the middle and outer zones (Xu etal. 2004). The interpretation is that thedeep (i.e. > 100 km) high seismicvelocity layers represent the ‘fossilized’mantle plume head, whereas the lowercrust (i.e. 40–60 km) high velocity lay-ers represent underplated mafic andultramafic rocks that were injected intothe lower crust and fed the surfaceflows and shallow crustal intrusions(Fig. 2b). The seismic data interpreta-tion is a compelling argument in favourof the ELIP mantle plume model butthe same region experienced an older(i.e. ~800 Ma) period of continentalarc magmatism. Therefore, it is possi-ble that the older arc-related magmaswere also preserved in the lower crust;however, they cannot be distinguishedfrom the younger ELIP-related materi-al and thus the crustal seismic velocitylayers may consist of rocks derivedfrom two separate periods of magma-tism.

Flexure of the CrustIt is theorized that excessive heat (i.e.100°C to 350°C above ambient condi-tions) from a mantle plume is suitableto induce maximum uplift of the sur-face directly beneath the plume head toan area within a 200 km radius (Camp-bell 2005). The amount of vertical dis-placement may be in excess of ~ 1 km(Campbell 2005). The ELIP is consid-ered to be one of the best examples ofmantle plume-induced surficial upliftand doming (Campbell 2005, 2007).The progressive thickening of theMaokou Limestone from the innerzone to the outer zone of the ELIP isinterpreted as evidence for uplift relat-ed to a mantle plume (He et al. 2003)(Fig. 7). However, the uplift model forthe ELIP has come under scrutiny and

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Figure 5. (a) Comparison of the Emeishan basalts using the discriminating param-eters of Winchester and Floyd (1977). (b) Sm/YbPM vs. Th/NbPM of the basalticrocks of the ELIP. (c) Nb/La versus εNd of the Emeishan basalts showing thetrend of the Parana basalts for comparison. (d) εNd vs. Th/NbPM of the basalticand picritic rocks of the ELIP. PM = Primitive mantle normalized to values of Sunand McDonough (1989). EMI (enriched mantle I) range taken from Zindler andHart (1986). GLOSS (global subducting sediment) values taken from Plank andLangmuir (1998) and Chauvel et al. (2008). UC = upper crust, MC = middle crustvalues of Rudnick and Gao (2003).

alternative ideas have been presented(Utskins Peate and Bryan 2008; Sun etal. 2010; Ali et al. 2010; Wang et al.2014). The evidence against uplift istwofold: 1) carbonate platform collapseis documented with deep water faciessuch as radiolarian chert and subma-rine fans (Sun et al. 2010; Ali et al.2010; Wang et al. 2014), and 2) that theflood basalts were emplaced at sea-level (i.e. pillow basalt erupted aftersubaerial basalt) and that previouslyinterpreted alluvial fan sedimentaryrocks are actually hydromagmaticdeposits (Utskins Peate and Bryan2008; Wang et al. 2014). The core ofthe debate is focused on whether thegeological evidence (i.e. alluvial fansediments vs. hydromagmatic deposits;presence of mid-eruption pillowbasalts) presented by He et al. (2003,2007) is actually documenting uplift,

not whether the ELIP is or is not man-tle plume-derived.

Effect on the Late Permian EcosystemSome mass extinctions are coeval withthe eruption of flood basalt (Courtillotet al. 1999; Wignall 2005; White andSaunders 2005). In many cases there iscompelling evidence to link specificvolcanic episodes to biological crises;however, there are many large igneousprovinces (e.g. Tarim, Panjal, Karoo,Ethiopia, Columbia River) that are notcontemporaneous with ecosystem col-lapse. The basic premise is that due torapidly emplaced basaltic magma, dra-matic climatic changes occur at a pacewhich is faster than the ability of anecosystem to adapt (Wignall 2005).

Compared to the end-Permianmass extinction, the end-Guadalupian

mass extinction (~260 Ma) affectedfewer genera but was contemporane-ous with the earliest eruption of theEmeishan flood basalts, and as a con-sequence is considered to have beenthe cause of, or at least contributed to,the decline in biota at that time (Zhouet al. 2002a; Wignall 2005; He et al.2007; Retallack and Jahren 2008; Gani-no and Arndt 2009). If atmosphericcomposition is to be affected by mag-matism then emplacement rates haveto be high. It is suggested thatdegassing of carbonate-rich countryrocks and a rapid (i.e. < 2 m.y.)emplacement rate was sufficient toinduce climate change or at least affectmarine chemistry to the point wheresome genera would be vulnerable anddie out (Ganino and Arndt 2009; Shell-nutt et al. 2012). It is possible that theELIP either directly caused or acceler-ated the end-Guadalupian mass extinc-tion; however, there are larger erup-tions of flood basalt during the earlyPermian which did not affect globalecosystems (e.g. Tarim and PanjalLIPs).

MINERAL DEPOSITS OF THE ELIP

Ni–Cu–Sulphide and PGE DepositsThe magmatic sulphide deposits areconcentrated within ultramafic and/ormafic intrusive rocks and are foundthroughout the entire ELIP. Thedeposits contain variable proportionsof Ni, Cu and platinum group ele-ments (PGE) within sulphide mineralsor platinum group minerals (Zhong etal. 2002; Song et al. 2005; Wang et al.2011). The propensity of sulphideand/or PGE deposits to form is sug-gested to be linked with the type (i.e.‘low-Ti’) of parental magma (Song etal. 2009; Zhou et al. 2008; Wang et al.2011). Song et al. (2005) grouped thesulphide and PGE deposits into fourgenetic types based on inferred petro-genetic processes, and host rock andmineral associations. The four types ofdeposits are: 1) Ni–Cu–(PGE) by insitu sulphide segregation, 2) PGE-enriched layers within layered intru-sions, 3) Ni–Cu sulphide related to sul-phide-bearing mush, and 4) PGE sul-phide ores in ultramafic rocks. NativeCu and Au deposits have also beenidentified but they appear to be relatedto post-ELIP hydrothermal processes.

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Figure 6. (a) Sr-Nd isotope plot showing the known range of Emeishan ultramaficand mafic volcanic rocks. (b) 87Sr/86Sr(I) vs. 206Pb/204Pb (I) plot of the Emeishanbasalts from Guangxi and ultramafic rocks from Lijiang (western ELIP). (c)207Pb/204Pb (I) vs. 206Pb/204Pb (I) of the Emeishan basalts from Guangxi and ultramaf-ic rocks from Lijiang (western ELIP). (d) 208Pb/204Pb (I) vs. 206Pb/204Pb (I) of theEmeishan basalts from Guangxi and ultramafic rocks from Lijiang (western ELIP).EMI and HIMU range taken from Zindler and Hart (1986). GLOSS (global sub-ducting sediment) values taken from Plank and Langmuir (1998) and Chauvel et al.(2008). FOZO range taken from Hart et al. (1992) and Campbell (2007). The rangeof Yangtze Block lower crust rock compositions taken from Wang et al. (2007).EMI= enriched mantle I, FOZO = focal zone component, HIMU = high μ[μ=((U+Th)/Pb) reservoir].

Fe–Ti–V Oxide-Ore DepositsThere are at least five world-class mag-matic oxide deposits within the Panxiregion of the inner zone, at least threeof which are spatially and temporallyassociated with alkaline granitoid rocks.Zhou et al. (2005) reported that ~7%and ~35% of global production of Vand Ti, respectively, is from China withmost of the metals originating fromthe layered gabbroic complexes of theELIP. The formation of the layeredintrusions and their ore deposits is ahighly debated issue. For instance,

some consider the gabbro ore bodiesto be a separate magma system fromthe neighbouring silicic plutons, where-as others suggest they are part of thesame intrusion (Zhong et al. 2009,2011; Shellnutt et al. 2011a). Further-more, the formation of the actual oredeposits is debated and may involve anumber of magmatic processes such assilicate immiscibility, fractional crystal-lization and fluxing of CO2-rich fluids(Zhou et al. 2005, 2013; Zhang et al.2009; Pang et al. 2010, 2013; Shellnuttet al. 2011a, b; Ganino et al. 2013).

The parental liquids of theoxide deposits are considered to be‘high-Ti’ Emeishan basalt. It is thoughtthat the gabbro bodies are derivedfrom ‘high-Ti’ Emeishan basaltbecause of the evolved compositionsof the olivine (e.g. Fo<82) and clinopy-roxene (e.g. Mg# < 80) and the traceelement budget (i.e. incompatible ele-ment enrichment in silicic plutons).There is evidence for open systembehaviour (i.e. multiple magma pulses)and internal redistribution (i.e. mineralchemistry variation) of crystals but theoverall process which affected themagma system was crystallization andthe consequences of an evolvingmagma. The ideas on silicate immisci-bility are difficult to reconcile in theformation of the oxide ore depositbecause the trace element budget (i.e.depletion of the large ion lithophileand high field strength elements) ofthe layered gabbro bodies is not suffi-ciently accounted for unless a residualsilicic liquid is considered (Pang et al.2010). A candidate for the residual liq-uid is the neighbouring peralkalinegranitic rocks (Shellnutt et al. 2011a).The hypothesis is that a basalticparental magma, as represented by a‘high-Ti’ Emeishan basalt, is injected inthe shallow crust and crystallizesolivine, plagioclase and clinopyroxene.Large quantities of titanomagnetite willcrystallize as soon as the magmaticconditions allow (i.e. early or later) butthe net result will be that the residualliquid composition becomes more sili-cic (Shellnutt et al. 2011a).

TECTONOMAGMATIC SYNTHESIS OFTHE ELIPA unifying theory of the formation ofthe ELIP is a difficult issue to addressbecause there are many different ideasregarding its genesis. This sectionbrings together the main geologicaland geochemical features of the ELIPin order to constrain its likely tectono-magmatic history.

During the Late Capitanian toEarly Wuchiapingian, the YangtzeBlock was a stable carbonate platformat tropical latitudes. It is uncertainwhat the exact topography (i.e. flat orundulatory) of the carbonate platformwas but it is possible that some portionof the Yangtze Block was exposed,whereas most of the platform was sub-

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Figure 7. Schematic model of uplift and doming of the crust due to the arrival ofthe Emeishan mantle plume.

merged. The volcanic rocks erupted atthe same time as several plutonic com-plexes were emplaced at ~260 Ma. Vol-canism was short-lived and probablywithin one magnetic reversal cycle. It isunlikely that ELIP volcanism was con-tinuously active for ~20 m.y.

The volcanic and the plutonicrocks were likely derived from magmasgenerated from a mantle plume source,some of which was contaminated bycrustal material (Fig. 8). The major andtrace elemental and isotope composi-tion of the magmatic rocks indicatethat the source was heterogeneous.The subcontinental lithospheric mantlemay or may not have been involvedbut probably cannot be discerned easi-ly due to the isotope heterogeneity ofthe rocks. Whether uplift and domingof the crust occurred is not a prerequi-site. The injection of mafic magmaslikely induced partial melting of the

Yangtze Block which led to the forma-tion of some peraluminous to metalu-minous silicic rocks, whereas minglingbetween mafic magmas and crustalmelts produced other metaluminousplutonic silicic rocks. Some mafic mag-mas reached shallow crustal levels (i.e.< 3 km) and crystallized to form thecumulate layered mafic–ultramaficcomplexes, some of which producedthe plutonic peralkaline silicic rocksand the Fe–Ti–V oxide deposits (Fig.8).

The precise cause of the ELIPis uncertain but it could be due to therandom formation of a mantle plumerelated to plate tectonics or due to theplate dynamics of the North China–South China–Indochina Block amalga-mation. Many LIPs are associated withcontinental break-up and mantleplumes but not all are related to both.The emplacement of the ELIP was

within a tensional environment; how-ever, it did not cause the YangtzeBlock to split, unlike that of otherLIPs (i.e. Central Atlantic MagmaticProvince, Karoo).

ACKNOWLEDGEMENTSI would like to thank Jean Bédard andan anonymous reviewer for their com-ments on the manuscript and the edi-torial handling by Brendan Murphyand type setting by Cindy Murphy. Spe-cial thanks to Mei-Fu Zhou, Jason Ali,Sun-Lin Chung, Steve Denyszyn,Clement Ganino, Eero Hanski, Bor-Ming Jahn, George Ma, Kwan-NangPang, Liang Qi, Xie-Yan Song, Christi-na Wang, Kuo-Lung Wang and Yi-Gang Xu for their opinions on all mat-ters related to the ELIP over the years.

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Figure 8. At 260 Ma the ELIP plume head arrives at the base of the lithosphere possibly inducing uplift of the crust anddecompressional melting of the plume source. Mafic magmas were injected into the lower crust or upper mantle forming cham-bers and the HVLC (high velocity lower crust) layer. Some magmas erupted onto the surface, whereas others reached relativelyshallow depths and formed the oxide ore-bearing layered intrusions and sulphide ore-bearing intrusions. The continuous injec-tion of mafic magmas likely induced partial melting of the crust which led to the formation of the crust-derived silicic plutonsand possible the hybrid silicic plutons.

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Received April 2014Accepted as Revised October 2014First published on the web November 2014

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