The Tengchong volcanies in western Yunnan Province, China, are located in the eastern part of the collision margin between Indian and Eurasian Plates. Alternating extention and compression controlled the eruption, fro...The Tengchong volcanies in western Yunnan Province, China, are located in the eastern part of the collision margin between Indian and Eurasian Plates. Alternating extention and compression controlled the eruption, from late Tertiary to Holeeno, of at least 5 groups of volcanics consisting of a Major series of hlgh-Al basalts (3 groups), a high-K andesite-dacite group and a high-Mg basalt group. The Major series has a range of GNd from +0.7 to-6.7 and Sr^87/Sr^86 from 0.70595 to 0.70881, exhibiting good linear correlations between Zr/Ni and Zr as well as between Nd. and both Sm/Nd and 1/Nd and similar chondrite-normalized incompatible element patterns. This suggests an ecologitic source metasomatized with fluids derived from parts of thesubducted Indian plate.The high-K andesite-dacite group shows a more extreme isotopic composition of GNd=-12.3, Sr^87/Sr^66=0.71124. It is chemically comparable to the calc-alkaline lavas in Xizang and could be resulted from mixing between shallow mantle zones and lower crust. The high-Mg basalt group has Sr^87/Sr^86-0.708 and slightly negative GNd (-2). They are similar, in chemical composition and possibly also in source, to the intraplate basalts in east China. A partial melting model of isotopic tmequilibrium system has been proposed to explain the isotope and trace element correlations of Tengchong volcanics.展开更多
The Dahongliutan granitic pluton,in the eastern part of the West Kunlun orogenic belt,provides significant insights for studying the tectonic evolution of West Kunlun.This paper presents a systematic study of LA-ICP-M...The Dahongliutan granitic pluton,in the eastern part of the West Kunlun orogenic belt,provides significant insights for studying the tectonic evolution of West Kunlun.This paper presents a systematic study of LA-ICP-MS zircon U Pb age,major and trace elements,Sr-Nd-Hf isotopes,and the first detailed Li isotope analysis of the Dahongliutan pluton.LA-ICP-MS zircon U Pb dating shows that the Dahongliutan granites were emplaced in the Late Triassic((213±2.1)Ma).Geochemical data show relatively high SiO2 contents(68.45 wt%73.62 wt%)and aluminum saturation index(A/CNK=1.111.21)indicates peraluminous high-K calc-alkaline granite.The Dahongliutan granites are relatively high in light rare earth elements(LREE)and large ion lithophile elements(LILEs)(e.g.,Rb,K,Th),and relatively depleted in high field strength elements(HFSEs)(e.g.,Nb,Ta,P,Ti).TheεNd(t)values range from 8.71 to 4.73,and(87Sr/86Sr)i=0.70870.71574.Zircons from the pluton yield 176Hf/177Hf values of 0.2826181 to 0.2827683,andεHf(t)values are around 0;the two-stage Hf model ages range from 0.974 to 1.307 Ga.Theδ7Li values are 0.76‰3.25‰,with an average of 2.53‰.Isotopic compositions of the pluton suggest a mixed trend between the partial melting of the Middle Proterozoic ancient crustal material and a juvenile mantle-derived material.This study infers that the Dahongliutan rock mass is formed in the post-collisional extension environment,when the collision between South Kunlun and the Tianshuihai terranes results in the closure of the Palaeo-Tethys.The mantle-derived magma results in partial melting of the lower crust.展开更多
文摘The Tengchong volcanies in western Yunnan Province, China, are located in the eastern part of the collision margin between Indian and Eurasian Plates. Alternating extention and compression controlled the eruption, from late Tertiary to Holeeno, of at least 5 groups of volcanics consisting of a Major series of hlgh-Al basalts (3 groups), a high-K andesite-dacite group and a high-Mg basalt group. The Major series has a range of GNd from +0.7 to-6.7 and Sr^87/Sr^86 from 0.70595 to 0.70881, exhibiting good linear correlations between Zr/Ni and Zr as well as between Nd. and both Sm/Nd and 1/Nd and similar chondrite-normalized incompatible element patterns. This suggests an ecologitic source metasomatized with fluids derived from parts of thesubducted Indian plate.The high-K andesite-dacite group shows a more extreme isotopic composition of GNd=-12.3, Sr^87/Sr^66=0.71124. It is chemically comparable to the calc-alkaline lavas in Xizang and could be resulted from mixing between shallow mantle zones and lower crust. The high-Mg basalt group has Sr^87/Sr^86-0.708 and slightly negative GNd (-2). They are similar, in chemical composition and possibly also in source, to the intraplate basalts in east China. A partial melting model of isotopic tmequilibrium system has been proposed to explain the isotope and trace element correlations of Tengchong volcanics.
基金Project(2017YFC0602701)supported by the National Key Research and Development Plan,ChinaProject(DD20160004-8-3)supported by the Geological Survey of China
文摘The Dahongliutan granitic pluton,in the eastern part of the West Kunlun orogenic belt,provides significant insights for studying the tectonic evolution of West Kunlun.This paper presents a systematic study of LA-ICP-MS zircon U Pb age,major and trace elements,Sr-Nd-Hf isotopes,and the first detailed Li isotope analysis of the Dahongliutan pluton.LA-ICP-MS zircon U Pb dating shows that the Dahongliutan granites were emplaced in the Late Triassic((213±2.1)Ma).Geochemical data show relatively high SiO2 contents(68.45 wt%73.62 wt%)and aluminum saturation index(A/CNK=1.111.21)indicates peraluminous high-K calc-alkaline granite.The Dahongliutan granites are relatively high in light rare earth elements(LREE)and large ion lithophile elements(LILEs)(e.g.,Rb,K,Th),and relatively depleted in high field strength elements(HFSEs)(e.g.,Nb,Ta,P,Ti).TheεNd(t)values range from 8.71 to 4.73,and(87Sr/86Sr)i=0.70870.71574.Zircons from the pluton yield 176Hf/177Hf values of 0.2826181 to 0.2827683,andεHf(t)values are around 0;the two-stage Hf model ages range from 0.974 to 1.307 Ga.Theδ7Li values are 0.76‰3.25‰,with an average of 2.53‰.Isotopic compositions of the pluton suggest a mixed trend between the partial melting of the Middle Proterozoic ancient crustal material and a juvenile mantle-derived material.This study infers that the Dahongliutan rock mass is formed in the post-collisional extension environment,when the collision between South Kunlun and the Tianshuihai terranes results in the closure of the Palaeo-Tethys.The mantle-derived magma results in partial melting of the lower crust.
