Some IR features of SiO4 and OH in coesite, and its amorphization and   dehydration at ambient pressure

doi:10.1016/j.jseaes.2017.03.016

CORC > 北京大学 > 地球与空间科学学院

	Some IR features of SiO4 and OH in coesite, and its amorphization and dehydration at ambient pressure
	Liu, Xi ; Ma, Yunlu ; He, Qiang ; He, Mingyue
刊名	JOURNAL OF ASIAN EARTH SCIENCES
	2017
关键词	Coesite IR features Water content Dehydration Subduction zone fluid Amorphization X-RAY-DIFFRACTION THERMODYNAMIC PROPERTIES SPINEL LHERZOLITE ALPHA-QUARTZ SYSTEM CAO-MGO-AL2O3-SIO2 1-CENTER-DOT-1 GPA LATTICE-VIBRATIONS SILICA POLYMORPHS HIGH-TEMPERATURES CRYSTAL-STRUCTURE
DOI	10.1016/j.jseaes.2017.03.016
英文摘要	Coesite (Coe) with grain size in the range of 30-80 mu m has been synthesized at 5 GPa and 1600 degrees C for 12 h by using a cubic press. Its unpolarized single-crystal absorption infrared (IR) spectra show 14 IR bands in the range of similar to 1200-650 cm(-1), five of which have high intensity (at similar to 1161, 1109, 1063, 1028 and 994 cm(-1)) and are preliminarily assigned to the SiO4 asymmetric stretching (nu(3)). In addition, three sharp but relatively weak bands at similar to 838, 814 and 796 cm(-1) are tentatively attributed to the SiO4 asymmetric bending (nu(4)). The IR data also show six OH peaks in the range of 3700-3300 cm(-1), with an estimated H2O content of similar to 30(4) wt ppm. Following previous studies, we have assigned the peaks at similar to 3464 (#7), 3421 (#8), 3406 (#9) and 3377 cm(-1) (#10) to the Type-II hydrogarnet substitution, and the peaks at similar to 3500 (#6a) and 3534 cm(-1) (#6b) to the B-based defects, with the latter aroused by possible B contamination in the synthesizing experiments. Annealing experiments conducted consecutively at similar to 200, 400, 600, 800, 1000 and 1200 degrees C, with every heating step lasting for 24 h, demonstrate that water diffuses quickly out of Coe at T as low as similar to 600 degrees C. The material annealed at 1200 degrees C is completely dehydrated and amorphous. A quick response of the water content in Coe to the changes of P, T and composition is thus possible, which may be critical to the preservation of natural Coe in relevant geological processes. It further implies that water in Coe, and possibly in other nominally anhydrous minerals (NAMs), may behave distinctively different from the water located in the hydrous phases such as amphibole and mica, and potentially makes significant contribution to the subduction zone-related fluids.; Chinese Academy of Sciences [XDB18000000]; DREAM of MOST, China [2016YFC0600408]; Data Integration and Standardization in the Geological Science and Technology from MOST, China [2013FY110900-3]; SCI(E); ARTICLE; 315-323; 148
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/484681]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	Liu, Xi,Ma, Yunlu,He, Qiang,et al. Some IR features of SiO4 and OH in coesite, and its amorphization and dehydration at ambient pressure[J]. JOURNAL OF ASIAN EARTH SCIENCES,2017.
APA	Liu, Xi,Ma, Yunlu,He, Qiang,&He, Mingyue.(2017).Some IR features of SiO4 and OH in coesite, and its amorphization and dehydration at ambient pressure.JOURNAL OF ASIAN EARTH SCIENCES.
MLA	Liu, Xi,et al."Some IR features of SiO4 and OH in coesite, and its amorphization and dehydration at ambient pressure".JOURNAL OF ASIAN EARTH SCIENCES (2017).