Characteristics and significance of CH4-rich fluid inclusions from the mafic-ultramaflc complex at the Xiangshan, eastern Tianshan Mountains, Xinjiang of China

	Characteristics and significance of CH4-rich fluid inclusions from the mafic-ultramaflc complex at the Xiangshan, eastern Tianshan Mountains, Xinjiang of China
	Pan, XF; Liu, W
刊名	ACTA PETROLOGICA SINICA
	2005
卷号	21 期号:1 页码:211-218
关键词	Laser Raman Spectroscopy Ch4-rich Fluid Inclusion Mantle Transition Zone Post-collisional Mafic-ultramafic Complex Eastern Tianshan Mountains
ISSN号	1000-0569
文献子类	Article
英文摘要	Post-collisional Cu-Ni-bearing mafic-ultramafic intrusive complexes densely occur in the eastern Tianshan Mountains, Xinjiang of China. Compositions of rock and, especially, fluid in their source region remain to be resolved. Xiangshan pluton is typical of the mafic-ultramafic complexes in the eastern Tianshan Mts. It comprises peridotite, gabbro-norite, diorite and gabbro-diabase. Megacrysts of poikilitic hornblende that is abundant in all the rock phases have grown around olivine and labrador, indicating that the parent magma is rich in water. Studied samples were collected from the fresh gabbro-norite in the central body of the Xiangshan pluton. Labrador- and olivine-hosted fluid inclusions occur in isolation or in group without obvious orientation. Fluid inclusion trails were observed occurring parallel to the grain boundary or growth plane of the host mineral. Fluid inclusions are primary or secondary and were trapped during growth of the host mineral or extensive exsolution of fluid from the magma as marked by the crystallization of hornblende. Hence, these fluid inclusions represent fluids derived from the source region. Available stable sulfur and lead isotopic data show meteoric affinity and normal common lead characteristics, respectively. Therefore, crustal contribution for rock and fluid via assimilation or infiltration can be excluded. Bubbles of more than 50 fluid inclusions were analyzed using micro-laser Raman spectrometer. It is shown by the analysis that CH4 and H2O are the dominant gas species, and hydrocarbons C2H2, C2H6, and C4H6, and N-2 are the subordinate gas species in the vapor phase of these fluid inclusions. Four types of vapor compositions are distinguished that include a) CH4-rich vapor, b) H2O-rich vapor, c) H2O + CH4 mixing vapor, and d) multi-species ( C2H6 + N-2 + CH4, C2H6 + CH4 + N-2 + C4H6) mixing vapor. Therefore, fluids that are brought by the Xiangshan pluton from the mantle source region are rich in H2O and reductive volatiles CH4 etc. Because CO2 fluid instead of CH4 fluid is abundant in the upper mantle whose redox state is near to fayalite-magnetite-quartz buffer, it is likely that the parent magma and inclusion fluids of the Xiangshan pluton derive from the transition zone of the mantle or asthenosphere underneath the Paleozoic orogens of the northern Xinjiang. Subducted slab brought water to the un-oxidized deep mantle during the subduction period before the end of the Early Carboniferous. Mixing of water with the reducing CH4-rich C-H fluids played an important role in the melting of the deep mantle, thereby resulting in the production of widespread post-collisional mafic-ultramafic complexes and the related Cu-Ni sulfide ore deposits.
WOS关键词	EARTHS UPPER-MANTLE ; XENOLITHS ; MINERALS ; DIAMOND ; WATER
WOS研究方向	Geology
语种	英语
出版者	SCIENCE CHINA PRESS
WOS记录号	WOS:000227476000020
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/64893]
专题	中国科学院地质与地球物理研究所
通讯作者	Pan, XF
作者单位	Chinese Acad Sci, Inst Geol & Geophys, State Key Lithosphere Tecton Evolut, Beijing 100029, Peoples R China
推荐引用方式 GB/T 7714	Pan, XF,Liu, W. Characteristics and significance of CH4-rich fluid inclusions from the mafic-ultramaflc complex at the Xiangshan, eastern Tianshan Mountains, Xinjiang of China[J]. ACTA PETROLOGICA SINICA,2005,21(1):211-218.
APA	Pan, XF,&Liu, W.(2005).Characteristics and significance of CH4-rich fluid inclusions from the mafic-ultramaflc complex at the Xiangshan, eastern Tianshan Mountains, Xinjiang of China.ACTA PETROLOGICA SINICA,21(1),211-218.
MLA	Pan, XF,et al."Characteristics and significance of CH4-rich fluid inclusions from the mafic-ultramaflc complex at the Xiangshan, eastern Tianshan Mountains, Xinjiang of China".ACTA PETROLOGICA SINICA 21.1(2005):211-218.