Geochemical and morphological characteristics of coarse-grained tabular beryl from the Xuebaoding W-Sn-Be deposit, Sichuan Province, western China

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	Geochemical and morphological characteristics of coarse-grained tabular beryl from the Xuebaoding W-Sn-Be deposit, Sichuan Province, western China
	Liu, Y (Liu, Yan); Deng, J (Deng, Jun); Shi, GH (Shi, Guanghai); Sun, DS (Sun, Daisheng)
刊名	INTERNATIONAL GEOLOGY REVIEW
	2012
卷号	54 期号:14 页码:1673-1684
关键词	beryl tabular habit alkali elements hydrothermal deposit Sichuan China
ISSN号	0020-6814
英文摘要	The dominant crystal faces on beryl are usually hexagonal prisms, a direct reflection of the lattice structure. However, coarse-grained beryl from the Xuebaoding W-Sn-Be deposit, China, has a tabular habit. To evaluate the genesis of this well-crystallized tabular beryl, we analysed the crystals using inductively coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence (XRF) spectrometry, X-ray powder diffraction (XRD), and differential interference contrast microscopy (DICM). The beryl unit cell dimensions are 9.223-9.232 angstrom for a(0) and 9.183-9.244 angstrom for c(0). The ratio c(0)/a(0) = 0.995-1.002. The beryl has a high alkali content, including Li2O (2.60-3.10 wt.%), Rb (65-120 ppm), Cs2O (0.70-0.92 wt.%), and Na2O (1.29-1.66 wt.%); other components include TiO2 (0.00-0.01 wt.%), TFe2O3 (1.03-1.29 wt.%), MnO (0.01 wt.%), MgO (0.09-0.12 wt.%), and CaO (0.03-0.04 wt.%). These analyses indicate that the Xuebaoding material is a Na-Li-Cs beryl with a dominance of tetrahedral substitution in the crystal structure. Based on a systematic statistical study of the relationship between chemical composition and habit, a high content of alkalis leads to a lower growth rate of c {0001} compared with m {10 (1) over bar0}, producing the short prismatic/columnar habit that typifies the Xuebaoding beryl. The difference in the number of pyramidal growth hillocks on s {11 (2) over bar1} faces that face in opposing directions strongly suggests the influence of unidirectional hydrothermal fluid flow on growth rates. The oriented flow also led to variable growth rates for other crystal faces, including m {10 (1) over bar0} and c {0001}, and caused the growth of many thick, distorted crystals of scheelite, cassiterite, tabular apatite, etc. Apparently, the m {10 (1) over bar0} faces were outgrown by other, more rapidly growing faces and consequently tended to disappear. Accordingly, we discuss two mechanisms that underlie the formation of tabular beryl crystals (1) the geochemical compositions and especially the high amount of alkalis at the Be site and in the channel structures of the crystals; and (2) the directional flow and supply of hydrothermal fluids in narrow fractures during crystal growth.
学科主题	结晶学与矿物学
WOS关键词	CRYSTAL-CHEMISTRY ; SOUTHWEST CHINA ; FLUID ; SCHEELITE ; FEATURES
WOS研究方向	Geology
语种	英语
出版者	TAYLOR & FRANCIS INC
WOS记录号	WOS:000307447700004
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/39628]
专题	中国地质调查局
作者单位	China Univ Geosci, State Key Lab Geol Proc & Mineral Resources, Beijing 100083, Peoples R China
推荐引用方式 GB/T 7714	Liu, Y ,Deng, J ,Shi, GH ,et al. Geochemical and morphological characteristics of coarse-grained tabular beryl from the Xuebaoding W-Sn-Be deposit, Sichuan Province, western China[J]. INTERNATIONAL GEOLOGY REVIEW,2012,54(14):1673-1684.
APA	Liu, Y ,Deng, J ,Shi, GH ,&Sun, DS .(2012).Geochemical and morphological characteristics of coarse-grained tabular beryl from the Xuebaoding W-Sn-Be deposit, Sichuan Province, western China.INTERNATIONAL GEOLOGY REVIEW,54(14),1673-1684.
MLA	Liu, Y ,et al."Geochemical and morphological characteristics of coarse-grained tabular beryl from the Xuebaoding W-Sn-Be deposit, Sichuan Province, western China".INTERNATIONAL GEOLOGY REVIEW 54.14(2012):1673-1684.