Spherules with pure iron cores from Myanmar jadeitite: Type-I deep-sea spherules?

doi:10.1016/j.gca.2011.01.005

	Spherules with pure iron cores from Myanmar jadeitite: Type-I deep-sea spherules?
	Shi, Guang-Hai 1,2; Zhu, Xiang-Kun 3; Deng, Jun 1; Mao, Qian 2; Liu, Ying-Xin 1; Li, Guo-Wu 1
刊名	GEOCHIMICA ET COSMOCHIMICA ACTA
	2011-03-15
卷号	75 期号:6 页码:1608-1620
ISSN号	0016-7037
DOI	10.1016/j.gca.2011.01.005
文献子类	Article
英文摘要	Here we report spherules in Myanmar jadeitite, a rock forming from jadeitic fluids within mantle-derived serpentinized rocks in subduction zones under high-pressure conditions (>1.0 GPa) and rather low temperatures of about 250-370 degrees C. The spherules have off-centre iron nuclei and dendritic wustite cortexes, with tiny wustite crystals perpendicular to the surface of iron core. Within the spherules are vesicles occupied by calcite, jadeite, albite? or mixtures of these phases, and the cortexes contain about 10 wt.% SiO(2) + Al(2)O(3) + Na(2)O filling materials within wustite. The spherules are in direct contact with jadeite crystals. Contrasting patterns of some individual spherules are obvious between a front area with a crowd of hill-like prominences and a rear zone with one or more rings on the surface. Such surface features and internal textures suggest that they experienced movement at high temperature and then rapid cooling. Chemical compositions of the nuclei are homogenous and consist of nearly pure iron with minor Cr (<0.05 wt.%), Mn (<0.80 wt.%), and Ni (0.142-0.23 wt.%), and a trend of Ni decreasing and Cr increasing from core to cortex. Mn in the cortex (up to about 2.00 wt.%) is far more enriched than the nucleus. The bulk ratios (average) of delta(56)Fe and delta(57)Fe in the core and cortex are 0.51 and 0.78, respectively. Such features suggest that there is a very low possibility of origin associated with volcanic explosive eruption, impact ejecta, chemical reduction or oxidation of iron on seafloor. Since biological reduction processes are not significant under high PIT condition in subduction zones, this origin is excluded. Considering their low Ni contents, it is more likely that they belong to the minor type-I deep-sea cosmic spherules/dusts of low isotope fractionation. This discovery shows that such spherules could remain stable under low-temperature and high-pressure conditions during recycling processes, and therefore could be found in rocks related to slab-derived sediments within subduction zones. This also suggests that subducted oceanic slab sediments contribute to the formation of jadeitite, coupled with dehydration of sediments and altered oceanic crust. (C) 2011 Elsevier Ltd. All rights reserved.
WOS关键词	MOTAGUA FAULT ZONE ; EASTERN HIMALAYAN SYNTAXIS ; COSMIC SPHERULES ; ISOTOPE FRACTIONATION ; NORTHWESTERN MYANMAR ; SURROUNDING REGIONS ; METAMORPHIC BELT ; SUBDUCTION-ZONE ; ORIGIN ; AREA
WOS研究方向	Geochemistry & Geophysics
语种	英语
出版者	PERGAMON-ELSEVIER SCIENCE LTD
WOS记录号	WOS:000287682500012
资助机构	National Basic Research Program of China(2009CB421008) ; National Basic Research Program of China(2009CB421008) ; National Basic Research Program of China(2009CB421008) ; National Basic Research Program of China(2009CB421008) ; National Science Foundation of China(40672046 ; National Science Foundation of China(40672046 ; National Science Foundation of China(40672046 ; National Science Foundation of China(40672046 ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; 40325008) ; 40325008) ; 40325008) ; 40325008) ; National Basic Research Program of China(2009CB421008) ; National Basic Research Program of China(2009CB421008) ; National Basic Research Program of China(2009CB421008) ; National Basic Research Program of China(2009CB421008) ; National Science Foundation of China(40672046 ; National Science Foundation of China(40672046 ; National Science Foundation of China(40672046 ; National Science Foundation of China(40672046 ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; 40325008) ; 40325008) ; 40325008) ; 40325008) ; National Basic Research Program of China(2009CB421008) ; National Basic Research Program of China(2009CB421008) ; National Basic Research Program of China(2009CB421008) ; National Basic Research Program of China(2009CB421008) ; National Science Foundation of China(40672046 ; National Science Foundation of China(40672046 ; National Science Foundation of China(40672046 ; National Science Foundation of China(40672046 ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; 40325008) ; 40325008) ; 40325008) ; 40325008) ; National Basic Research Program of China(2009CB421008) ; National Basic Research Program of China(2009CB421008) ; National Basic Research Program of China(2009CB421008) ; National Basic Research Program of China(2009CB421008) ; National Science Foundation of China(40672046 ; National Science Foundation of China(40672046 ; National Science Foundation of China(40672046 ; National Science Foundation of China(40672046 ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; Program for the New Century Excellent Talents in China(NCET-07-0771) ; 40325008) ; 40325008) ; 40325008) ; 40325008)
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/73794]
专题	中国科学院地质与地球物理研究所
通讯作者	Shi, Guang-Hai
作者单位	1.China Univ Geosci, State Key Lab Geol Proc & Mineral Resources, Beijing 100083, Peoples R China 2.Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China 3.China Univ Geosci, Inst Geol, Beijing 100037, Peoples R China
推荐引用方式 GB/T 7714	Shi, Guang-Hai,Zhu, Xiang-Kun,Deng, Jun,et al. Spherules with pure iron cores from Myanmar jadeitite: Type-I deep-sea spherules?[J]. GEOCHIMICA ET COSMOCHIMICA ACTA,2011,75(6):1608-1620.
APA	Shi, Guang-Hai,Zhu, Xiang-Kun,Deng, Jun,Mao, Qian,Liu, Ying-Xin,&Li, Guo-Wu.(2011).Spherules with pure iron cores from Myanmar jadeitite: Type-I deep-sea spherules?.GEOCHIMICA ET COSMOCHIMICA ACTA,75(6),1608-1620.
MLA	Shi, Guang-Hai,et al."Spherules with pure iron cores from Myanmar jadeitite: Type-I deep-sea spherules?".GEOCHIMICA ET COSMOCHIMICA ACTA 75.6(2011):1608-1620.