The origin of shoshonites: new insights from the Tertiary high-potassium intrusions of eastern Tibet

CORC > 南海海洋研究所 > 中国科学院南海海洋研究所 > 中科院边缘海地质重点实验室

	The origin of shoshonites: new insights from the Tertiary high-potassium intrusions of eastern Tibet
	Campbell, IH ; Stepanov, AS ; Liang, HY ; Allen, CM ; Norman, MD ; Zhang, YQ ; Xie, YW
刊名	CONTRIBUTIONS TO MINERALOGY AND PETROLOGY
	2014
卷号	167 期号:3 页码:-983
关键词	Shoshonite High-potassium magmas High-potassium intrusions Eastern Tibet Red River-Ailao Shan-Batang-Lijiang fault system
ISSN号	0010-7999
通讯作者	ian.campbell@anu.edu.au
中文摘要	The shoshonitic intrusions of eastern Tibet, which range in age from 33 to 41 Ma and in composition from ultramafic (SiO2 = 42 %) to felsic (SiO2 = 74 %), were produced during the collision of India with Eurasia. The mafic and ultramafic members of the suite are characterized by phenocrysts of phlogopite, olivine and clinopyroxene, low SiO2, high MgO and Mg/Fe ratios, and olivine forsterite contents of Fo(87) to Fo(93), indicative of equilibrium with mantle olivine and orthopyroxene. Direct melting of themantle, on the other hand, could not have produced the felsic members. They have a phenocryst assemblage of plagioclase, amphibole and quartz, high SiO2 and lowMgO, with Mg/Fe ratios well below the values expected for a melt in equilibrium with the mantle. Furthermore, the lack of decrease in Cr with increasing SiO2 and decreasing MgO from ultramafic to felsic rocks precludes the possibility that the felsic members were derived by fractional crystallization from the mafic members. Similarly, magma mixing, crustal contamination and crystal accumulation can be excluded as important processes. Yet all members of the suite share similar incompatible element and radiogenic isotope ratios, which suggests a common origin and source. We propose that melting for all members of the shoshonite suite was initiated in continental crust that was thrust into the upper mantle at various points along the transpressional Red RiverAilao Shan-Batang-Lijiang fault system. The melt formed by high-degree, fluid-absent melting reactions at high-T and highP and at the expense of biotite and phengite. Themelts acquired their high concentrations of incompatible elements as a consequence of the complete dissolution of pre-existing accessory minerals. The melts produced were quartz-saturated and reacted with the overlying mantle to produce garnet and pyroxene during their ascent. The felsic magmas reacted little with the adjacent mantle and preserved the essential features of their original chemistry, including their high SiO2, low Ni, Cr and MgO contents, and low Mg/Fe ratio, whereas the mafic and ultramaficmagmas are the result of extensive reaction with the mantle. Although the mafic magmas preserved the incompatible element and radiogenic isotope ratios of their crustal source, buffering by olivine and orthopyroxene extensively modified their MgO, Ni, Cr, SiO2 contents and Mg/Fe ratio to values dictated by equilibrium with the mantle.
学科主题	Geochemistry & Geophysics ; Mineralogy
收录类别	SCI
资助信息	Chinese Academy of Sciences [XDB03010302]; China Scholarship Council; Chinese NSF [41121002, 41272099, 41172080]
原文出处	SPRINGER
WOS记录号	WOS:000332585700006
公开日期	2014-12-11
内容类型	期刊论文
源URL	[http://ir.scsio.ac.cn/handle/344004/10639]
专题	南海海洋研究所_中科院边缘海地质重点实验室
推荐引用方式 GB/T 7714	Campbell, IH,Stepanov, AS,Liang, HY,et al. The origin of shoshonites: new insights from the Tertiary high-potassium intrusions of eastern Tibet[J]. CONTRIBUTIONS TO MINERALOGY AND PETROLOGY,2014,167(3):-983.
APA	Campbell, IH.,Stepanov, AS.,Liang, HY.,Allen, CM.,Norman, MD.,...&Xie, YW.(2014).The origin of shoshonites: new insights from the Tertiary high-potassium intrusions of eastern Tibet.CONTRIBUTIONS TO MINERALOGY AND PETROLOGY,167(3),-983.
MLA	Campbell, IH,et al."The origin of shoshonites: new insights from the Tertiary high-potassium intrusions of eastern Tibet".CONTRIBUTIONS TO MINERALOGY AND PETROLOGY 167.3(2014):-983.