P-T conditions of crystallization and origin of plagioclase-mantled alkali feldspar megacrysts in the Mesozoic granitoids in the Qinling orogen (China)

CORC > 中国地质调查局 > 中国地质调查局

	P-T conditions of crystallization and origin of plagioclase-mantled alkali feldspar megacrysts in the Mesozoic granitoids in the Qinling orogen (China)
	Wang, XX (Wang, Xiaoxia); Wang, T (Wang, Tao); Haapala, I (Haapala, Ilmari); Mao, JW (Mao, Jingwen)
刊名	LITHOS
	2008
卷号	103 期号:3-4 页码:289-308
关键词	P-T conditions rapakivi texture magma mixing granitoids qinling
ISSN号	0024-4937
英文摘要	The Qinling orogen between the North China and South China cratons was intruded at 211-217 Ma by calc-alkaline quartz monzonitic to monzogranitic plutons characterized by I- to A-type geochemistry and in many places contain plagioclase-mantled alkali feldspar megacrysts (rapakivi texture sensu lato). The felsic rocks contain mafic to intermediate magmatic enclaves suggestive of mingling and mixing of mafic and felsic magmas. The P-T conditions of crystallization have been determined for early mineral assemblages (inner parts of alkali feldspar megacrysts and their plagioclase, quartz, amphibole and biotite inclusions) and late assemblages (matrix minerals) of the rapakivi-textured granitoids. Al contents in amphibole from the early and late mineral assemblages yield pressures of 1.2-3.0 and 0.7-3.0 kbar, respectively, and indicate only minor pressure change between the crystallization of the early and late assemblages. Amphibole-plagioclase thermometry gives temperatures mainly of the order of 900 to 1000 degrees C for both the early and late assemblages indicating nearly isothermal conditions. Feldspar thermometers yield lower temperatures. Relative abundances of minerals and their chemical compositions indicate that the late mineral assemblages tend to be richer in MgO, Na2O and CaO than the early assemblages. Rapakivi texture is interpreted in this case mainly as a result of compositional changes related to the hybridization between granitic and more mafic magmas. Small release of pressure during crystallization of the magmas may have contributed to the origin of the mantled alkali feldspar megacrysts. (C) 2007 Elsevier B.V. All rights reserved.
学科主题	火成岩岩石学
WOS关键词	SHAHEWAN-RAPAKIVI GRANITE ; IN-HORNBLENDE BAROMETER ; TECTONIC EVOLUTION ; ROCKS ; THERMOMETRY ; AMPHIBOLE ; TEXTURE ; MOUNTAINS ; ENCLAVES ; SANIDINE
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000257907700001
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/38608]
专题	中国地质调查局
作者单位	Chinese Acad Geol Sci, Inst Mineral Resources, Beijing 100037, Peoples R China
推荐引用方式 GB/T 7714	Wang, XX ,Wang, T ,Haapala, I ,et al. P-T conditions of crystallization and origin of plagioclase-mantled alkali feldspar megacrysts in the Mesozoic granitoids in the Qinling orogen (China)[J]. LITHOS,2008,103(3-4):289-308.
APA	Wang, XX ,Wang, T ,Haapala, I ,&Mao, JW .(2008).P-T conditions of crystallization and origin of plagioclase-mantled alkali feldspar megacrysts in the Mesozoic granitoids in the Qinling orogen (China).LITHOS,103(3-4),289-308.
MLA	Wang, XX ,et al."P-T conditions of crystallization and origin of plagioclase-mantled alkali feldspar megacrysts in the Mesozoic granitoids in the Qinling orogen (China)".LITHOS 103.3-4(2008):289-308.