An occurrence of metastable cristobalite in spodumene-hosted crystal-rich inclusions from Jiajika pegmatite deposit, China

doi:10.1016/j.gexplo.2015.10.012

	An occurrence of metastable cristobalite in spodumene-hosted crystal-rich inclusions from Jiajika pegmatite deposit, China
	Li, Jiankang 1; Chou, I-Ming2
	2016-12-01
发表期刊	JOURNAL OF GEOCHEMICAL EXPLORATION
卷号	171 期号:2015 页码:29-36
摘要	Laser Raman spectroscopic analyses showed the occurrence of cristobalite, together with carbonic aqueous fluid phases, in the crystal-rich inclusions (CIs) hosted in spodumene in Jiajika pegmatite deposit, China. In these CIs, cristobalite always coexists with zabuyelite, and occasionally with other minerals, including calcite, spodumene, and possibly cookeite. The rare occurrences of cristobalite in plutonic rocks are commonly considered to be resulted from the lack of H2O, which was thought to be the catalyzer for the conversion of cristobalite to quartz. However, this assumption is not supported by our observed coexistence of cristobalite with aqueous fluid in the CIs of Jiajika pegmatite deposit. The results of microthermometric analyses showed that the carbonic aqueous fluids in CIs had salinities of less than 7 wt.% NaCl equivalent, in which the CO2 phase(s) occupied 60-80 vol.% with the bulk CO2 densities of near 0.70 g/cm(3). Therefore, the estimated internal pressure of CIs are between 200 and 290 MPa at the initial dissolving temperature of daughter minerals (cristobalite at -400 degrees C), much lower than the entrapment pressures of at least 440 MPa. The occurrences of cristobalite in CIs could be ascribed to (1) the pressure decrease within CIs from the entrapment pressures of greater than 440 MPa to 200-290 MPa at -400 degrees C, mainly resulted from the crystallization of zabuyelite, and (2) the extension of the cristobalite stability to low temperatures due to the presence of lithium and H2O in the inclusions. More study is needed for the formation mechanisms of cristobalite in plutonic rocks and the effect of H2O on the conversion of cristobalite to quartz. (C) 2015 Elsevier B.V. All rights reserved.
文章类型	Article
关键词	Cristobalite Crystal-rich Inclusion Pegmatite Jiajika Deposit
WOS标题词	Science & Technology ; Physical Sciences
DOI	10.1016/j.gexplo.2015.10.012
URL	查看原文
收录类别	SCI ; ISTP
语种	英语
关键词[WOS]	FLUID INCLUSIONS ; GRANITIC PEGMATITES ; RAMAN-SPECTROSCOPY ; PHASE-TRANSITION ; SYSTEM ; CRYSTALLIZATION ; SILICA ; TRIDYMITE ; PRESSURE ; H2O
WOS类目	Geochemistry & Geophysics
WOS记录号	WOS:000388780200004
引用统计	被引频次：2[WOS] [WOS记录] [WOS相关记录]
文献类型	期刊论文
版本	出版稿
条目标识符	http://ir.idsse.ac.cn/handle/183446/1470
专题	深海科学研究部_深海极端环境模拟研究实验室
作者单位	1.Chinese Acad Geol Sci, MLR Key Lab Metallogeny & Mineral Assessment, Inst Mineral Resources, Beijing 100037, Peoples R China 2.Chinese Acad Sci, Sanya Inst Deep Sea Sci & Engn, Sanya 572000, Hainan, Peoples R China
推荐引用方式 GB/T 7714	Li, Jiankang,Chou, I-Ming. An occurrence of metastable cristobalite in spodumene-hosted crystal-rich inclusions from Jiajika pegmatite deposit, China[J]. JOURNAL OF GEOCHEMICAL EXPLORATION,2016,171(2015):29-36.
APA	Li, Jiankang,&Chou, I-Ming.(2016).An occurrence of metastable cristobalite in spodumene-hosted crystal-rich inclusions from Jiajika pegmatite deposit, China.JOURNAL OF GEOCHEMICAL EXPLORATION,171(2015),29-36.
MLA	Li, Jiankang,et al."An occurrence of metastable cristobalite in spodumene-hosted crystal-rich inclusions from Jiajika pegmatite deposit, China".JOURNAL OF GEOCHEMICAL EXPLORATION 171.2015(2016):29-36.

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