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Xuance Wang - One of the best experts on this subject based on the ideXlab platform.
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genesis of the 1 21 ga marnda moorn large Igneous Province by plume lithosphere interaction
Precambrian Research, 2014Co-Authors: Xuance Wang, Zhengxiang Li, Jie Li, Michael T.d. WingateAbstract:Abstract The 1.21 Ga Marnda Moorn large Igneous Province (LIP) of the Yilgarn Craton is important for understanding the final breakup of the Nuna (Columbia) supercontinent. However, its petrogenesis is poorly understood owing to the lack of geochemical data. We conducted geochemical analyses of the Gnowangerup–Fraser Dyke Suite, a major part of the Marnda Moorn LIP, and report the first geochemical and Nd isotope data for this LIP. Results of a complementary paleomagnetic study of these dykes will be published elsewhere. Most of the studied dykes consist of predominately tholeiitic and OIB-like dolerite (Group 1) and one arc-like and more felsic dyke (Group 2). Group 1 samples have incompatible trace element compositions similar to those of tholeiitic Hawaiian plume-induced OIB and typical asthenospheric mantle-derived Nd isotopes with ɛNd(t) varying from +3.7 to +7.5, produced mainly within the spinel stability field (
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the willouran basic Province of south australia its relation to the guibei large Igneous Province in south china and the breakup of rodinia
Lithos, 2010Co-Authors: Zhengxiang Li, Xuance Wang, Xianhua Li, Yueheng YangAbstract:Abstract The Willouran Basic Province in South-Central Australia and the Guibei large Igneous Province (LIP) in the South China Block are two of the most prominent Neoproterozoic LIPs related to the breakup of the supercontinent Rodinia. The Willouran Basic Province is dominated by tholeiitic mafic dykes (the Gairdner dykes), flood basalts (the Wooltana basalts), and mafic intrusions. The basaltic suites across a distance of more than 1000 km have similar immobile major element compositions, uniform tholeiitic OIB-type trace element distribution patterns, and identical Hf–Nd isotopic signatures. Geochemical analyses from this study imply that their generation may have involved both depleted and enriched mantle sources, similar to that of the Guibei LIP. The age distributions of the two LIPs are also comparable, peaking at ca. 825 Ma. This simultaneous flare-up of mafic magmatism in the two continents, including high-temperature lavas found in the South China Block, coincides with the starting up of widespread continental rifting in Rodinia. We thus speculate that the two LIPs could have been parts of a once contiguous LIP, which was dismembered during the breakup of Rodinia. This work thus provides additional support for the proposed South China–Australia connection in Rodinia.
Yigang Xu - One of the best experts on this subject based on the ideXlab platform.
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Geochemical characterization of a reconstructed 1110 Ma Large Igneous Province
Precambrian Research, 2019Co-Authors: Babita R. Choudhary, Michiel O. De Kock, Amarildo Salina Ruiz, Joseph G. Meert, Richard E Ernst, Yigang Xu, Gabrielle Aparecida De LimaAbstract:Abstract 1110 Ma Large Igneous Province (LIP) fragments in the Kalahari craton, southern Africa (Umkondo LIP); Dronning Maud Land, Antarctica; Bundelkhand portion of Indian craton (Mahoba dolerite dykes); Congo craton (Huila-Epembe dolerite dykes); and Amazonia (Rincon del Tigre-Huanchaca LIP) have been reconstructed as a single LIP with plume centre beneath the NW part of the Kalahari Craton. This paper offers the best estimates for the paleoposition of the Indian and Amazonian cratons along with conjoined Kalahari-SF/Congo reconstruction. This 1110 Ma mafic magmatism is dominantly tholeiitic, ranging from basalt to andesitic basalt in composition, generated over a range of mantle melting depths [(Gd/Yb)N = 1.2–2.3], exhibit low to high contamination with crustal components (negative Nb anomalies, eNd (0 to −12), and elevated Th/Yb). The data fall into two Groups based on TiO2 content, with Group 1 (low Ti) of andesitic basalt composition, and Group 2 (high Ti) exhibiting a basaltic affinity. Group 1 magmas were generated in the spinel lherzolite field followed by significant contamination likely during passage through metasomatised lithospheric mantle in crustal magma chambers. A greater melting depth reaching into the garnet lherzolite field is proposed for the Group 2 magmas. The majority of Group 2 units are located in the Kalahari and Congo cratons, and this reflects onset of deeper melting closer to the interpreted plume axis in our reconstruction.
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crustal melting above a mantle plume insights from the permian tarim large Igneous Province nw china
Lithos, 2019Co-Authors: Yigang Xu, Yuting Zhong, Roland Mundil, Teal R Riley, Le ZhangAbstract:Abstract Low Nb Ta rhyolites from the Permian Tarim Large Igneous Province (LIP) represent the melting products of continental crust above a mantle plume. Zircon U Pb dating reveals that the Kuchehe and Dawanqi rhyolites were erupted at 292.6 ± 0.5 Ma and 274 ± 2 Ma respectively. Both rhyolite groups are characterized by pronounced negative Nb Ta anomalies, crust-like trace element ratios and negative eNd-Hf(t) values, consistent with a crustal origin. Newly acquired data, combined with available data in the literature, clearly show that there is an increasing trend of zircon saturation temperature (TZr) from 794 to 827 °C to 886–936 °C for the early to middle stage (293–287 Ma), followed by a decreasing TZr of 803–908 °C for the late stage (287–274 Ma) of the Tarim magmatism. The temporal changes in TZr for the Tarim rhyolites are interpreted to reflect the crustal melting behavior above a mantle plume, such that fusible materials in the crust melt at an earlier stage and refractory materials melt at a later stage. The gradual decrease in TZr, towards the final stage of the Tarim rhyolitic magmatism, reflects the gradual ‘decay’ of thermal input from mantle plume to the lithosphere in the region. This thermal model is also applicable to describe the crustal melting behavior in the Chon Aike silicic LIP of Patagonia and the Snake River Plateau-Yellowstone Plateau volcanic Provinces.
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magmatic underplating and crustal growth in the emeishan large Igneous Province sw china revealed by a passive seismic experiment
Earth and Planetary Science Letters, 2015Co-Authors: Yun Chen, Shaokun Si, Yangfan Deng, Xiaobo Tian, Yigang Xu, Xiaofeng Liang, Tao Xu, Lin Chen, Peng Wang, Yihe XuAbstract:Abstract In an attempt to characterize the subsurface structure that is related to fossil mantle plume activity, a comprehensive geophysical investigation was conducted in the Emeishan Large Igneous Province (ELIP). The nature and geometry of the crust were examined within the scheme of the domal structure of ELIP, which comprises the Inner, Intermediate and Outer zones, which are defined on the basis of the biostratigraphy of pre-volcanic sediments. The bulk crustal properties within the Inner Zone are characterized by high density, high P-wave velocity, high Vp/Vs ratios and large crustal thickness. A visible continuous seismic converter is present in the upper part of the crust in the whole Intermediate Zone and the eastern part of the Inner Zone, but it is absent in the Inner Zone, where another seismic converter is observed in the lower part of the crust. The geometric configuration of these converters is attributable to the addition of mantle-derived melts to the pre-existing crust and subsequent interaction between them. The crustal geometry, which is delineated by the migrated image of receiver functions from the passive seismic experiment, and the crustal properties collectively suggest that a mafic layer of 15–20 km thickness and 150–180 km width exists at the base of the crust in the Inner Zone. Such a mafic layer reflects a vertical crustal growth through magmatic underplating at the base of the crust and intraplating within the upper crust. The salient spatial correlation between the deep crustal structure and the dome strongly supports a genetic link between crustal thickening and plume activity, if the pre-volcanic domal uplift is generated by the Permian Emeishan mantle plume. This arrangement is further supported by the consistency of the extent of crustal uplift estimated by isostatic equilibrium modeling and sedimentary data. This study therefore characterizes and provides evidence for a plume-modified crust in a large Igneous Province.
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ca tims zircon u pb dating of felsic ignimbrite from the binchuan section implications for the termination age of emeishan large Igneous Province
Lithos, 2014Co-Authors: Yuting Zhong, Roland Mundil, Bin He, Yigang XuAbstract:Abstract The age of the Emeishan lavas in SW China remains poorly constrained because the extrusive rocks are (1) thermally overprinted and so represent an open system unsuitable for 40 Ar/ 39 Ar geochronology and (2) in most cases devoid of zircon so that it is impossible for the application of U–Pb geochronology. Existing radiometric age constraints of Emeishan large Igneous Province are mainly from the application of SIMS and LA-ICP-MS U–Pb techniques to zircons from mafic and felsic intrusions, which represent indirect constraints for the lavas. In an attempt to directly determine the age of the Emeishan lava succession, high-resolution chemical abrasion-thermal ionization mass spectrometry (CA-TIMS) zircon U–Pb techniques have been used on the felsic ignimbrite at the uppermost part of the Emeishan lava succession. These techniques have yielded a weighted mean 206 Pb/ 238 U age of 259.1 ± 0.5 Ma (n = 6; MSWD = 0.7). We interpret this age as the termination age of the Emeishan flood basalts. The age of the Guadalupian–Lopingian boundary is still unconstrained by high-resolution geochronology but is likely to be close to our new age for this felsic ignimbrite.
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a permian large Igneous Province in tarim and central asian orogenic belt nw china results of a ca 275 ma mantle plume
Geological Society of America Bulletin, 2010Co-Authors: Chuanlin Zhang, Zhengxiang Li, Yigang Xu, Xianhua Li, Gang Zhou, Haimin YeAbstract:New sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon ages, geochemical data, and a synthesis of existing stratigraphic, geochronologic, and geochemical results from the Tarim block and the Central Asian orogenic belt in northwestern China suggest the presence of a Permian (ca. 275 Ma) large Igneous Province (the Bachu large Igneous Province). The large Igneous Province consists predominantly of coeval mafic rocks (basalts and mafic-ultramafic intrusions) having an aerial coverage of more than 600,000 km 2 , and its formation was accompanied by voluminous emplacement of A-type granites. This large Igneous Province, interpreted to be of mantle plume origin, is ∼15 m.y. older than the ca. 260 Ma Emeishan large Igneous Province in southwestern China and ∼25 m.y. older than the 251 Ma Siberian Trap in Russia. Such a sudden flair up of plume activity in the Permian may represent the early stage of the Pangean superplume event. The Permian plumes likely played a role in late Paleozoic rapid continental crustal growth in the Central Asian orogenic belt. In addition, there appear to be two types of mantle geochemical Provinces (domains) in the region, a long-term enriched Tarim Province and a subduction-metasomatized and depleted Central Asian orogenic belt Province.
Michael T.d. Wingate - One of the best experts on this subject based on the ideXlab platform.
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genesis of the 1 21 ga marnda moorn large Igneous Province by plume lithosphere interaction
Precambrian Research, 2014Co-Authors: Xuance Wang, Zhengxiang Li, Jie Li, Michael T.d. WingateAbstract:Abstract The 1.21 Ga Marnda Moorn large Igneous Province (LIP) of the Yilgarn Craton is important for understanding the final breakup of the Nuna (Columbia) supercontinent. However, its petrogenesis is poorly understood owing to the lack of geochemical data. We conducted geochemical analyses of the Gnowangerup–Fraser Dyke Suite, a major part of the Marnda Moorn LIP, and report the first geochemical and Nd isotope data for this LIP. Results of a complementary paleomagnetic study of these dykes will be published elsewhere. Most of the studied dykes consist of predominately tholeiitic and OIB-like dolerite (Group 1) and one arc-like and more felsic dyke (Group 2). Group 1 samples have incompatible trace element compositions similar to those of tholeiitic Hawaiian plume-induced OIB and typical asthenospheric mantle-derived Nd isotopes with ɛNd(t) varying from +3.7 to +7.5, produced mainly within the spinel stability field (
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warakurna large Igneous Province a new mesoproterozoic large Igneous Province in west central australia
Geology, 2004Co-Authors: Michael T.d. Wingate, Franco Pirajno, Paul A MorrisAbstract:Coeval mafic Igneous rocks emplaced rapidly over;1.5 3 10 6 km 2 in western and central Australia represent the erosional rem- nants of a late Mesoproterozoic large Igneous Province, named here the Warakurna large Igneous Province. SHRIMP U-Pb dating of rocks separated by as much as 1500 km indicates that the main episode of magmatism occurred between 1078 and ca. 1070 Ma. The Warakurna large Igneous Province includes layered mafic- ultramafic intrusions and mafic to felsic volcanic rocks and dikes in central Australia, a 1000-km-long mafic sill Province in Western Australia, and several swarms of mafic dikes. The large areal ex- tent and short duration imply emplacement above a mantle-plume head. Despite their wide separation, the mafic rocks have similar mid-oceanic-ridge basalt-normalized trace element patterns and rare earth element characteristics. West-directed paleocurrents, westward-radiating dike swarms, and the occurrence of high-Mg rocks indicate that the center of the plume head was located be- neath central Australia. Other late Mesoproterozoic large Igneous Provinces, in the Laurentia and Kalahari cratons, appear to be significantly older than the Warakurna large Igneous Province in Australia and thus are unlikely to be related to the same mantle- plume head.
Mei-fu Zhou - One of the best experts on this subject based on the ideXlab platform.
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chalcophile element geochemistry and petrogenesis of high ti and low ti magmas in the permian emeishan large Igneous Province sw china
Contributions to Mineralogy and Petrology, 2011Co-Authors: Christina Yan Wang, Mei-fu ZhouAbstract:Sulfide-poor mafic layered intrusions, sills/dykes and lava flows in the Funing region, SW China, are part of the ~260 Ma Emeishan large Igneous Province. They belong to either a high-Ti group (TiO2 = 1.6–4.4 wt%) with elevated Ti/Y ratios (351–1,018), or a low-Ti group (TiO2 1, low (Y/Pd)PM ratios (0.2–7.1) and nearly constant (Cu/Pd)PM ratios (1.5–3.8). The even and parallel chalcophile element patterns of the high-PGE low-Ti subgroup rocks are likely a result of olivine-dominated fractionation under S-undersaturated condition. The low-PGE low-Ti group rocks have low MgO (4.5–8.9 wt%) and very poor PGE (Pt + Pd 0.5–1.6 ppb, Ir 0.004–0.02 ppb) with low Cu/Zr ratios (0.1–0.5), high (Y/Pd)PM (26–70) and variable (Cu/Pd)PM ratios (2.8–14). The trough-like chalcophile element patterns of the low-PGE low-Ti subgroup rocks indicate that the magmas were sulfide saturation and sulfide melts were extracted from the magmas. The extracted sulfide melts might be potential Ni–Cu sulfide ores at depth in the Funing region.
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flood basalt related fe ti oxide deposits in the emeishan large Igneous Province sw china
Lithos, 2010Co-Authors: Kwannang Pang, Mei-fu Zhou, Gregory J Shellnutt, Liang Qi, Christina Yan Wang, Donggao ZhaoAbstract:In the Panzhihua–Xichang region (Sichuan Province, SW China), there are a number of world-class magmatic Fe–Ti oxide deposits. They are hosted as conformable masses in lower parts of layered mafic–ultramafic intrusions that are part of the end-Guadalupian (∼ 260 Ma) Emeishan large Igneous Province. The ore-bearing Panzhihua, Hongge, Baima, Taihe and Xinjie intrusions are spatially and temporally associated with flood basalts and granitoids in the Province. New mineralogical data for Fe–Ti oxide ores in the Hongge and Baima intrusions, combined with an overview of previously published data, provide a better understanding on the formation of these enigmatic deposits. Geochemical and Sr–Nd isotopic data confirm a genetic relation between the intrusions and high-Ti Emeishan flood basalts. Parental magma compositions, estimated using the most Mg-rich cumulus olivine in the intrusions, are characterized by slight to moderate degrees of fractionation (MgO = 7.2–11 wt.%). Occurrences of rare Cr-bearing titanomagnetite (Cr2O3 = 1.2–10.7 wt.%) in the Panzhihua, Hongge and Xinjie intrusions are consistent with early crystallization of Fe–Ti oxides. Oxide-silicate equilibria and low V concentration (< 4800 ppm) in magnetite are consistent with relatively high oxygen fugacity. Flood basalt-related origin, early Fe–Ti oxide crystallization and relatively high oxygen fugacity, are characteristic of Fe–Ti oxide deposits in the Panxi region but are fundamentally different from those hosted in highly-differentiated, upper parts of large layered intrusions (e.g. the Bushveld Complex). Similar Fe–Ti oxide deposits have not been documented in other well-studied large Igneous Provinces to date, but a number of Fe–Ti oxide ore occurrences worldwide are potentially similar to this type of flood basalt-related oxide deposits.
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zircon lu hf isotopic compositions of metaluminous and peralkaline a type granitic plutons of the emeishan large Igneous Province sw china constraints on the mantle source
Journal of Asian Earth Sciences, 2009Co-Authors: Gregory J Shellnutt, Mei-fu Zhou, Christina Yan Wang, Yueheng YangAbstract:Abstract Permian A-type granitoids of the Emeishan large Igneous Province (ELIP) in the Panxi region, SW China, are predominantly peralkaline and metaluminous in composition. In situ zircon Hf isotopic compositions along with whole rock trace element and Nd isotopic data are used to examine the probable source characteristics of these A-type granitic plutons. Zircons from the Baima and Taihe peralkaline plutons have weighted average eHf (T) values of +8.7 ± 0.4 and +9.2 ± 1.0, whereas the Woshui and Huangcao metaluminous plutons have differing eHf (T) values (+8.6 ± 0.2 and +5.8 ± 0.3, respectively). Previous studies have suggested that the plutons were derived by differentiation (e.g. fractionation or partial melting) of mafic magmas from an enriched mantle source similar to oceanic island basalt with little or no contribution from the crust (eNd (T) = +1.3 to +3.2, Zr/Nb = 0.9–14.4, Rb/Nb = 0.1–8.4 and Th/Ta = (T) values of the Woshui and Baima plutons indicates that spatially and temporally associated peralkaline and metaluminous A-type granitic rocks can originate from the same mantle source without crustal assimilation.
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zircon lu hf isotopic compositions of metaluminous and peralkaline a type granitic plutons of the emeishan large Igneous Province sw china constraints on the mantle source
Journal of Asian Earth Sciences, 2009Co-Authors: Gregory J Shellnutt, Mei-fu Zhou, Christina Yan Wang, Yueheng YangAbstract:Abstract Permian A-type granitoids of the Emeishan large Igneous Province (ELIP) in the Panxi region, SW China, are predominantly peralkaline and metaluminous in composition. In situ zircon Hf isotopic compositions along with whole rock trace element and Nd isotopic data are used to examine the probable source characteristics of these A-type granitic plutons. Zircons from the Baima and Taihe peralkaline plutons have weighted average eHf(T) values of +8.7 ± 0.4 and +9.2 ± 1.0, whereas the Woshui and Huangcao metaluminous plutons have differing eHf(T) values (+8.6 ± 0.2 and +5.8 ± 0.3, respectively). Previous studies have suggested that the plutons were derived by differentiation (e.g. fractionation or partial melting) of mafic magmas from an enriched mantle source similar to oceanic island basalt with little or no contribution from the crust (eNd(T) = +1.3 to +3.2, Zr/Nb = 0.9–14.4, Rb/Nb = 0.1–8.4 and Th/Ta =
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controls on the metal compositions of magmatic sulfide deposits in the emeishan large Igneous Province sw china
Chemical Geology, 2008Co-Authors: Xie-yan Song, Mei-fu Zhou, Jiafei XiaoAbstract:Abstract Magmatic sulfide deposits in the Emeishan large Igneous Province, SW China, have variable chalcophile and siderophile metal contents and can be divided into PGE, Ni–Cu–PGE and Ni–Cu deposits. PGE sulfide deposits include the Jinbaoshan and Zhubu deposits and have ores with very low sulfide contents (~ 1 to 2 vol.%) and very high Pt and Pd (0.3 to 10 ppm) and Ir (0.02 to 0.5 ppm). Typical Ni–Cu–PGE sulfide deposits include the Yangliuping and Qingkuangshan deposits, which contain sulfide ores with more than 10 vol.% sulfides (0.1–6.2 wt.% Ni, 0.03–11 wt.% Cu) and have moderate PGE contents (0.1–5 ppm Pt, 0.01–1.8 ppm Pd, On the 100% sulfide basis, Pt and Pd correlate positively with Ir in the ores from the PGE deposits, whereas they correlate negatively in the Ni–Cu–PGE and Ni–Cu deposits. PGE geochemistry and model calculations indicate that the PGE-rich sulfides were separated from primary basaltic magmas, whereas the Ni–Cu–PGE sulfides were produced from magmas that had experienced minor sulfide removal (about 0.01%), and the Ni–Cu sulfides were separated from magmas that experienced about 0.025% sulfide segregation. Fractionation of monosulfide solid solution resulted in differentiation between IPGE and PPGE in the Ni–Cu–PGE and Ni–Cu deposits.
Xie-yan Song - One of the best experts on this subject based on the ideXlab platform.
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key factors controlling the accumulation of the fe ti oxides in the hongge layered intrusion in the emeishan large Igneous Province sw china
Ore Geology Reviews, 2014Co-Authors: Yan Luan, Xie-yan Song, Wenqin Zheng, Liemeng Chen, Songyue Yu, Xiaoqi Zhang, Xiaolin TianAbstract:Abstract The Hongge layered intrusion hosts the largest Fe–Ti–V oxide ore deposit in the central part of the Emeishan Large Igneous Province, SW China. It is divided into Lower Zone (LZ), Middle Zone (MZ) and Upper Zone (UZ) from the bottom to the top. For the LZ, relatively higher Cr (250–3000 ppm) and Ni (50–200 ppm) contents of clinopyroxene, lower eNd259Ma and higher (87Sr/86Sr)259Ma values (− 2.82 to − 0.07 and 0.7057–0.7076, respectively) and plenty of hornblende demonstrate a more primitive parental hydrous magma. In contrast, relatively low Cr (
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platinum group element geochemistry of the continental flood basalts in the central emeisihan large Igneous Province sw china
Chemical Geology, 2009Co-Authors: Xie-yan Song, Long Xiao, Reid R. Keays, Huowen Qi, Christian IhlenfeldAbstract:In the central zone of the Emeishan Large Igneous Province (ELIP), southwestern China, the Permian Emeishan continental flood basalts (ECFB) can be divided into high- and low-Ti basalts and alkaline basalts. At the southern margins of the central ELIP, the low- and high-Ti basalts comprise the lower and upper parts of the ECFB sequences, respectively; the alkaline basalts occur in the lower part of the ECFB sequence in a few locations. The high-Ti basalts are high in Pd (4-16 ppb) and Pt (7–18 ppb), but have large variations in Ir (0.04–0.88 ppb). The alkaline basalts have low TiO2 contents (1.8–2.15 wt.%) and are depleted in PGE ( 30,000) and very low Pt/Y ratios (230 to as low as 6) strongly suggest that the PGE-depletion in the low-Ti basalts and alkaline basalts is related to sulfide removal. The positive relationship between Pt and Pd depletion and increases in Zr/Nb and Th/Nb ratios indicate that crustal contamination played a role in driving the low-Ti basaltic magmas to S-saturation. In contrast, for the PGE-undepleted high- and low-Ti basalts, Pd decreases slightly with decreasing MgO and Ir, and Pd/Cr ratios increase with decreasing Pt/Y, indicating that fractionation occurred under S-undersaturated conditions. Some PGE-undepleted low-Ti basalts have very high Pd/Pt ratios (up to 6, much higher than that of the primitive mantle ~ 0.6) and extremely low Ir concentrations (< 0.03 ppb), suggesting that the magmas experienced fractionation of olivine, chromite, pyroxene and PGE minerals rich in Os, Ir, Ru, and Pt. The remaining high-Ti basalts have moderate Pd/Pt ratios (< 2.3) and very high Ir concentrations, up to 0.88 ppb, indicating that they possibly contain chromite and PGE minerals rich in Os, Ir, and Ru.
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controls on the metal compositions of magmatic sulfide deposits in the emeishan large Igneous Province sw china
Chemical Geology, 2008Co-Authors: Xie-yan Song, Mei-fu Zhou, Jiafei XiaoAbstract:Abstract Magmatic sulfide deposits in the Emeishan large Igneous Province, SW China, have variable chalcophile and siderophile metal contents and can be divided into PGE, Ni–Cu–PGE and Ni–Cu deposits. PGE sulfide deposits include the Jinbaoshan and Zhubu deposits and have ores with very low sulfide contents (~ 1 to 2 vol.%) and very high Pt and Pd (0.3 to 10 ppm) and Ir (0.02 to 0.5 ppm). Typical Ni–Cu–PGE sulfide deposits include the Yangliuping and Qingkuangshan deposits, which contain sulfide ores with more than 10 vol.% sulfides (0.1–6.2 wt.% Ni, 0.03–11 wt.% Cu) and have moderate PGE contents (0.1–5 ppm Pt, 0.01–1.8 ppm Pd, On the 100% sulfide basis, Pt and Pd correlate positively with Ir in the ores from the PGE deposits, whereas they correlate negatively in the Ni–Cu–PGE and Ni–Cu deposits. PGE geochemistry and model calculations indicate that the PGE-rich sulfides were separated from primary basaltic magmas, whereas the Ni–Cu–PGE sulfides were produced from magmas that had experienced minor sulfide removal (about 0.01%), and the Ni–Cu sulfides were separated from magmas that experienced about 0.025% sulfide segregation. Fractionation of monosulfide solid solution resulted in differentiation between IPGE and PPGE in the Ni–Cu–PGE and Ni–Cu deposits.
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emeishan large Igneous Province sw china
Lithos, 2005Co-Authors: G M Thompson, Mei-fu Zhou, Xie-yan SongAbstract:In recent years, there have been major advances in our understanding of the Emeishan large Igneous Province (LIP) of SW China following publication of a number of LIP-focused investigations of the terrain and associated rocks. This paper reviews the current state of knowledge. The volcanic and upper-intrusive portion of the Province is relatively small (∼0.3×106 km3), even when offset fragments, eroded sections and buried portions are included in the volume calculation. The most reliable radiometric age dates (zircon U–Pb SHRIMP from an associated layered intrusive body several kilometers in area) indicate generation at ∼259 Ma, consistent with the end-Guadalupian (end Middle Permian) stratigraphic age. In addition, several Ar–Ar dating studies have been carried out, mainly on the volcanic rocks, with a number of reported dates ∼253–251 Ma (Late Permian), but a consensus is emerging that these ages are problematic because they are in conflict with the stratigraphic data (possibly due to a monitor standard miscalibration). The Ar–Ar investigations have also yielded a large number of secondary ages, which are clustered at ∼175, ∼142, ∼98 and ∼42 Ma, and these are inferred to record sub-regional tectonic events that affected the western Yangtze Block as East Asia was assembled and later deformed by India’s collision–indentation into Asia. Magnetostratigraphic data and field observations suggest that the bulk of the volcanic sequence formed within 1–2 my. The geochemistry of the volcanic rocks and bio-lithostratigraphic studies of the underlying Maokou Formation suggests a mantle plume generated the Province. The basalts can be classified into low and high Ti groups with different parental magmas. The low Ti basalts are confined to the western part of the Province and are overlain by the high Ti basalts. The low Ti magmas formed at shallow mantle depths in the spinel–garnet field transition zone (60–80 km), whereas the high Ti magmas formed by low degrees of partial melting within the deeper garnet stability field. This observation suggests a deepening of the melting column as the lithosphere thickened due to under-plating and a transition from peak basalt generation to the waning stage. Outstanding issues, which might focus future studies, are also outlined.
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A temporal link between the Emeishan large Igneous Province (SW China) and the end-Guadalupian mass extinction
Earth and Planetary Science Letters, 2002Co-Authors: Mei-fu Zhou, Xie-yan Song, John Malpas, Paul T. Robinson, Min Sun, Allen K. Kennedy, C. Michael Lesher, Reid R. KeaysAbstract:Abstract Previous studies have suggested that there were two mass extinction events in the Late Permian: one that occurred at the Permo-Triassic (P/T) boundary (251 Ma) and a second, smaller mass extinction that occurred 5–8 Myr earlier at the end of the Guadalupian. Many workers have argued that there is a causal relationship between large-scale volcanic activity and mass extinctions. The major mass extinction event at the P/T boundary coincides with the outpouring of huge quantities of lava that formed the Siberian flood basalt Province in Russia. Courtillot et al. [Earth Planet. Sci. Lett. 166 (1999) 177–195] and Wignall [Earth Sci. Rev. 53 (2001) 1–33] suggested that the earlier Late Permian mass extinction coincided with the eruption of the lavas that formed the Emeishan flood basalt (EFB) Province in SW China. However, the age of eruption of the EFB lavas is poorly constrained. Using the Sensitive High-Resolution Ion Microprobe to analyze zircons, we have established the age of the Xinjie intrusion, believed to be a feeder to the main phase of EFB volcanism, to be 259±3 Ma. Hence, the formation of the EFB is coincident with a proposed extinction event at 256–259 Ma. This result supports a temporal link between the Emeishan large Igneous Province and the end-Guadalupian mass extinction.
