CH4 inclusions in orogenic harzburgite: Evidence for reduced slab fluids   and implication for redox melting in mantle wedge

doi:10.1016/j.gca.2008.12.008

CORC > 北京大学 > 地球与空间科学学院

	CH4 inclusions in orogenic harzburgite: Evidence for reduced slab fluids and implication for redox melting in mantle wedge
	Song, Shuguang ; Su, Li ; Niu, Yaoling ; Lai, Yong ; Zhang, Lifel
刊名	geochimica et cosmochimica acta
	2009
关键词	NORTH QILIAN MOUNTAINS BENEATH OCEAN RIDGES SUBDUCTION ZONES OXIDATION-STATE OXYGEN FUGACITY ARC MAGMAS ABYSSAL PERIDOTITES METAMORPHIC BELT SOURCE REGIONS NW CHINA
DOI	10.1016/j.gca.2008.12.008
英文摘要	Fluids released from the subducting oceanic lithosphere are generally accepted to cause mantle wedge peridotite melting that produces arc magmas. These fluids have long been considered to be dominated by highly oxidized H2O and CO2 as inferred from erupted arc lavas. This inference is also consistent with the geochemistry of peridotite xenoliths in some arc basalts. However, the exact nature of these fluids in the mantle wedge melting region is unknown. Here, we report observations of abundant CH4 + C + H-2 fluid inclusions in olivine of a fresh orogenic harzburgite in the Early Paleozoic Qilian suture zone in Northwest China. The petrotectonic association suggests that this harzburgite body represents a remnant of a Paleozoic mantle wedge exhumed subsequently in response to the tectonic collision. The mineralogy, mineral compositions and bulk-rock trace element systematics of the harzburgite corroborate further that the harzburgite represents a high-degree melting residue in a mantle wedge environment. Furthermore, existing and new C, He, Ne and Ar isotopes of these fluid inclusions are consistent with their being of shallow (i.e., crustal vs. deep mantle) origin, likely released from serpentinized peridotites and sediments of the subducting oceanic lithosphere. These observations, if common to subduction systems, provide additional perspectives on mantle wedge melting and subduction-zone magmatism. That is, mantle wedge melting may in some cases be triggered by redox reactions; the highly reduced (similar to Delta FMQ-5, i.e., 5 log units below the fayalite-magnetite-quartz oxygen fugacity buffer) CH4-rich fluids released from the subducting slab interact with the relatively oxidized (similar to Delta FMQ-1) mantle wedge peridotite, producing H2O and CO2 that then lowers the solidus and incites partial melting for arc magmatism. The significance of slab-component contribution to the geochemistry of are magmatism would depend on elemental selection and solubility in highly reduced fluids, for which experimental data are needed. We do not advocate the above to be the primary mechanism of arc magmatism, but we do suggest that the observed highly reduced fluids are present in mantle wedge peridotites and their potential roles in arc magmatism need attention. (C) 2008 Elsevier Ltd. All rights reserved.; http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000264258600015&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701 ; Geochemistry & Geophysics; SCI(E); 37; ARTICLE; 6; 1737-1754; 73
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/155905]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	Song, Shuguang,Su, Li,Niu, Yaoling,et al. CH4 inclusions in orogenic harzburgite: Evidence for reduced slab fluids and implication for redox melting in mantle wedge[J]. geochimica et cosmochimica acta,2009.
APA	Song, Shuguang,Su, Li,Niu, Yaoling,Lai, Yong,&Zhang, Lifel.(2009).CH4 inclusions in orogenic harzburgite: Evidence for reduced slab fluids and implication for redox melting in mantle wedge.geochimica et cosmochimica acta.
MLA	Song, Shuguang,et al."CH4 inclusions in orogenic harzburgite: Evidence for reduced slab fluids and implication for redox melting in mantle wedge".geochimica et cosmochimica acta (2009).