Petrology, Mineralogy and Geochemistry of the Emeishan Continental Flood Basalts, SW China: Evidence for Activity of Mantle Plumes

Abstract Electronic microprobe analyses for olivine, clinopyroxene and Cr‐spinel in picrites, which we have discovered recently in the Emeishan continental flood basalt province (ECFBP), show that the olivine is rich in Mg, and that Cr‐spinel is rich in Cr. Based on the olivine‐melt equilibrium, the primary parental melt compositions are calculated. The high‐Mg olivine‐hosted picrite can be regarded as parental melt. Thus, the melting temperature and pressure are estimated: T=1600°C and P=4.5 GPa. It suggests that the picrites are connected with the activity of mantle plumes. Their major element composition is comparable to many other CFBs by their high Fe8, (CaO/Al2O3)8 and low Na8, indicating a high pressure. All rocks display a similar chondrite‐normalized REE patterns, i.e., enrichment of LREE, relative depletion of HFSE and absence of negative Nb and Ta but depletion in P and K. Some incompatible element ratios, such as La/Ta, La/ Sm, (La/Nb)pM, (Th/Ta)pM, are in a limited range, show that they were derived from the mantle plume, and there was no or little crustal contamination during magma ascent en route to the surface. They were generated by 7% partial melting of garnet peridotite. The axis of the plume might be located beneath Lijiang Town, Yunnan province.

[1]  Wan Fu-sheng.  Sr, Nd and Pb Isotopic Characteristics of Emeishan Basalt Province and Discussion on Their Source Region , 2003 .

[2]  J. Mahoney,et al.  Mantle sources and the highly variable role of continental lithosphere in basalt petrogenesis of the Kerguelen Plateau and Broken Ridge LIP : Results From ODP Leg 183 , 2002 .

[3]  Zhang Zhaochong,et al.  Geochemistry of Two Types of Basalts in the Emeishan Basaltic Province: Evidence for Mantle Plume‐Lithosphere Interaction , 2002 .

[4]  C. Lo,et al.  Age of the Emeishan flood magmatism and relations to Permian–Triassic boundary events , 2002 .

[5]  J. Malpas,et al.  A temporal link between the Emeishan large Igneous Province (SW China) and the end-Guadalupian mass extinction , 2002 .

[6]  K. Breddam.  Kistufell: Primitive Melt from the Iceland Mantle Plume , 2002 .

[7]  Sun-Lin Chung,et al.  Petrologic and geochemical constraints on the petrogenesis of Permian Triassic Emeishan flood basalts in southwestern China , 2001 .

[8]  J. Ali,et al.  Emeishan Basalts, SW China: reappraisal of the formation’s type area stratigraphy and a discussion of its significance as a large igneous province , 2001, Journal of the Geological Society.

[9]  S. Eggins,et al.  Primary magmas and mantle temperatures , 2001 .

[10]  Mei-Fu Zhou,et al.  Geochemical Constraints on the Mantle Source of the Upper Permian Emeishan Continental Flood Basalts, Southwestern China , 2001 .

[11]  Xu Yi.  The Emeishan Large Igneous Province: Evidence for mantle plume activity and melting conditions , 2001 .

[12]  M. J. Bas.  IUGS Reclassification of the High-Mg and Picritic Volcanic Rocks , 2000 .

[13]  N. Arndt.  Geochemistry: Hot heads and cold tails , 2000, Nature.

[14]  R. Thompson,et al.  Transient high temperatures in mantle plume heads inferred from magnesian olivines in Phanerozoic picrites , 2000, Nature.

[15]  L. Larsen,et al.  Processes in High-Mg, High-T Magmas: Evidence from Olivine, Chromite and Glass in Palaeogene Picrites from West Greenland , 2000 .

[16]  K. Gopalan,et al.  Olivine Compositions in Picrite Basalts and the Deccan Volcanic Cycle , 2000 .

[17]  Yu-gan Jin,et al.  The Permian of China and its interregional correlation , 2000 .

[18]  G. Shi,et al.  Permian-Triassic evolution of Tethys and Western Circum-Pacific , 2000 .

[19]  A. Kerr,et al.  Petrogenesis of picrites from the Caribbean Plateau and the North Atlantic magmatic province , 1999 .

[20]  U. Christensen,et al.  The dynamical origin of Hawaiian volcanism , 1999 .

[21]  H. Hansen,et al.  Crustal contamination in Palaeogene East Greenland flood basalts: plumbing system evolution during continental rifting , 1999 .

[22]  S. Solomon,et al.  Seismic evidence for a lower-mantle origin of the Iceland plume , 1998, Nature.

[23]  G. Czamanske,et al.  Demise of the Siberian Plume: Paleogeographic and Paleotectonic Reconstruction from the Prevolcanic and Volcanic Record, North-Central Siberia , 1998 .

[24]  Sun‐Lin Chung,et al.  Plume-lithosphere interaction in generation of the Emeishan flood basalts at the Permian-Triassic boundary , 1995 .

[25]  J. Mahoney,et al.  Drillhole lavas from the northwestern Deccan Traps, and the evolution of Réunion hotspot mantle , 1995 .

[26]  E. Stolper,et al.  Determining the composition of high-pressure mantle melts using diamond aggregates , 1994 .

[27]  N. Arndt,et al.  Constraining the potential temperature of the Archaean mantle: A review of the evidence from komatiites , 1993 .

[28]  K. Hirose,et al.  Partial melting of dry peridotites at high pressures: Determination of compositions of melts segregated from peridotite using aggregates of diamond , 1993 .

[29]  G. V. Nesterenko,et al.  Temporal Sr-, Nd- and Pb-isotopic variations in the Siberian flood basalts: Implications for the plume-source characteristics , 1992 .

[30]  R. Carlson,et al.  Evidence from Re–Os isotopes for plume–lithosphere mixing in Karoo flood basalt genesis , 1992, Nature.

[31]  P. Wyllie,et al.  High-pressure apatite solubility in carbonate-rich liquids: Implications for mantle metasomatism , 1992 .

[32]  Yin Hongfu,et al.  The effects of volcanism on the Permo-Triassic mass extinction in South China , 1992 .

[33]  D. McKenzie,et al.  Partial melt distributions from inversion of rare earth element concentrations , 1991 .

[34]  D. McKenzie,et al.  Melt Generation by Plumes: A Study of Hawaiian Volcanism , 1991 .

[35]  C. Devey,et al.  Source and Differentiation of Deccan Trap Lavas: Implications of Geochemical and Mineral Chemical Variations , 1990 .

[36]  L. Zhili,et al.  The Emei Taphrogenesis of the upper Yangtze Platform in south China , 1990, Geological Magazine.

[37]  N. Rogers,et al.  Continental mantle lithosphere, and shallow level enrichment processes in the Earth's mantle , 1990 .

[38]  R. White,et al.  Magmatism at rift zones: The generation of volcanic continental margins and flood basalts , 1989 .

[39]  C. Langmuir,et al.  Local versus global variations in ocean ridge basalt composition: A reply , 1989 .

[40]  J. Mutter,et al.  Deep crustal structure and magmatic processes: the inception of seafloor spreading in the Norwegian-Greenland Sea , 1988, Geological Society, London, Special Publications.

[41]  M. Ernesto,et al.  Continental Flood Volcanism From the Paraná Basin (Brazil) , 1988 .

[42]  C. Langmuir,et al.  Global correlations of ocean ridge basalt chemistry with axial depth and crustal thickness , 1987 .

[43]  E. Watson.  Apatite and phosphorus in mantle source regions: An experimental study of apatite/melt equilibria at pressures to 25 kbar , 1980 .

[44]  W. J. Morgan,et al.  Plate Motions and Deep Mantle Convection , 1972 .

[45]  P. Roeder,et al.  Olivine-liquid equilibrium , 1970 .

[46]  T. Simkin,et al.  Minor-Element Distribution in Olivine , 1970, The Journal of Geology.