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

doi:10.1016/j.gexplo.2015.10.012

CORC > 深海科学与工程研究所 > 中国科学院深海科学与工程研究所 > 深海科学研究部 > 深海极端环境模拟研究实验室

	An occurrence of metastable cristobalite in spodumene-hosted crystal-rich inclusions from Jiajika pegmatite deposit, China
	Chou, I-Ming1 ; Li, Jiankang 2
刊名	JOURNAL OF GEOCHEMICAL EXPLORATION
	2016-12-01
卷号	171 期号:2015 页码:29-36
关键词	Cristobalite Crystal-rich Inclusion Pegmatite Jiajika Deposit
DOI	10.1016/j.gexplo.2015.10.012
文献子类	Article
英文摘要	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.
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WOS关键词	FLUID INCLUSIONS ; GRANITIC PEGMATITES ; RAMAN-SPECTROSCOPY ; PHASE-TRANSITION ; SYSTEM ; CRYSTALLIZATION ; SILICA ; TRIDYMITE ; PRESSURE ; H2O
语种	英语
WOS记录号	WOS:000388780200004
内容类型	期刊论文
版本	出版稿
源URL	[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 Sci, Sanya Inst Deep Sea Sci & Engn, Sanya 572000, Hainan, Peoples R China 2.Chinese Acad Geol Sci, MLR Key Lab Metallogeny & Mineral Assessment, Inst Mineral Resources, Beijing 100037, Peoples R China
推荐引用方式 GB/T 7714	Chou, I-Ming,Li, Jiankang. 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	Chou, I-Ming,&Li, Jiankang.(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	Chou, I-Ming,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.