Nature and significance of haematite-ilmenite solid solution in 540;similar to 600m eclogite of Chinese Continental Scientific Drilling main;borehole: implications for the exhumation of the CCSD eclogites.

	Nature and significance of haematite-ilmenite solid solution in 540;similar to 600m eclogite of Chinese Continental Scientific Drilling main;borehole: implications for the exhumation of the CCSD eclogites.
	Liang FengHua 3; Zeng LingSen ; Xu ZhiQin ; Chen FangYuan ; Chen Jing
刊名	ACTA PETROLOGICA SINICA
	2006
卷号	22 期号:7 页码:1905-1914
关键词	hematite-ilmenite solid exsolution eclogite Chinese Continental Scientific Drilling Sulu UHP metamorphic belt
ISSN号	1000-0569
英文摘要	We document the occurrence of hematite-ilmenite solid solutions in the 540-600m eclogites recovered by the Chinese Continental Scientific Drilling ( CCSD) project. These solid solutions have a very fine intergrowth structure from millimeter to nanometer scale, and can amount up to 30 vol. % of the whole-roek mineral composition. They occur either as fine rounded inclusions in clinopyroxenes and garnets or as interstitial phases among clinopyroxene and garnet boundaries and form a seemingly sponge-like structure. In either case, they have multiple generations of exsolution lamellae, with widths ranging from millimeters to nanometers. Within any single grain, the exsolution lamellae are parallel to the ( 001) plane of the host, but they do not define any overall systematic trend throughout any sample. Chemically, the molar fraction of ilmenite in these solid solutions varies from 23.80% to 89.84%, which may lead to the formation of a series of intergrowths with varying magnetic properties from paramagnetic hematite-ilmenite solid solution to intergrowths of canted antiferromagnetie (CAF) hematite and paramagnetic ilmenite. To form these extraordinary hematite-ilmenite intergrowths, it requires an extremely slow-cooling progress during the tectonic evolution of the CCSD eclogites. This is at odd with commonly acclaimed rapid subduction and exhumation for the formation of Dabie-Sulu UHP rocks, which raises a critical question whether most of the eclogites have lost such key high temperature memories that have obscured our understanding on the tectonic processes responsible for the subduction and exhumation of continental materials. A number of studies have shown that hematite-ilmenite intergrowth has an extraordinary magnetic property. These intergrowths impart an unusually strong and stable remnant magnetization to the host rocks that is extremely difficult to be erased even in a strong alternating demagnetization field. The presence of such intergrowths may be a major factor that contributes to the anomalously high magnetic susceptibilities, high P-wave velocities, and geochemical anomalies (e. g. high TiO(2), V, and V/Sc ratio, but low Nb and Ta) in these eclogites. Whether or not this type of eclogite is more common than what we know at present deserves further studies. Answers to this question have important implications for our understanding on the mechanisms for the subduction and exhumation of large mass of continental materials and regional exploration of vanadium and titanium deposits.
学科主题	固体地球物理学
WOS关键词	FE-TI ORDER ; LAMELLAR MAGNETISM ; HEMO-ILMENITE ; AEROMAGNETIC ANOMALIES ; REMANENT MAGNETIZATION ; ALPHA-FE2O3 SYSTEM ; CRYSTAL CHEMISTRY ; METAMORPHIC ROCKS ; PHASE-TRANSITION ; SOKNDAL REGION
WOS研究方向	Geology
语种	中文
出版者	SCIENCE PRESS
WOS记录号	WOS:000245957000016
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/38308]
专题	中国地质科学院地质研究所
作者单位	1.CAGS, Inst Geol, Key Lab Continental Dynam, MLR, Beijing 100037, Peoples R China. 2.Peking Univ, Sch Phys, Electron Microscopy Lab, Beijing 100871, Peoples R China. 3.中国地质科学院地质研究所
推荐引用方式 GB/T 7714	Liang FengHua,Zeng LingSen,Xu ZhiQin,et al. Nature and significance of haematite-ilmenite solid solution in 540;similar to 600m eclogite of Chinese Continental Scientific Drilling main;borehole: implications for the exhumation of the CCSD eclogites.[J]. ACTA PETROLOGICA SINICA,2006,22(7):1905-1914.
APA	Liang FengHua,Zeng LingSen,Xu ZhiQin,Chen FangYuan,&Chen Jing.(2006).Nature and significance of haematite-ilmenite solid solution in 540;similar to 600m eclogite of Chinese Continental Scientific Drilling main;borehole: implications for the exhumation of the CCSD eclogites..ACTA PETROLOGICA SINICA,22(7),1905-1914.
MLA	Liang FengHua,et al."Nature and significance of haematite-ilmenite solid solution in 540;similar to 600m eclogite of Chinese Continental Scientific Drilling main;borehole: implications for the exhumation of the CCSD eclogites.".ACTA PETROLOGICA SINICA 22.7(2006):1905-1914.