Rhenium-osmium isotope and platinum-group elements in the Xinjie layered intrusion, SW China: Implications for source mantle composition, mantle evolution, PGE fractionation and mineralization

CORC > 地球化学研究所 > 中国科学院地球化学研究所 > 矿床地球化学国家重点实验室 > 期刊论文

	Rhenium-osmium isotope and platinum-group elements in the Xinjie layered intrusion, SW China: Implications for source mantle composition, mantle evolution, PGE fractionation and mineralization
	Wei-Guang Zhu; Bing-Guang Liu; Zhu-Yin Chu; Liang Qi; Rui-Zhong Hu; Mei-Fu Zhou; Ti-Zhong Gou; Hong Zhong
刊名	Geochimica et Cosmochimica Acta
	2011
卷号	75 期号:6 页码:1621-1641
英文摘要	The Xinjie mafic–ultramafic layered intrusion in the Emeishan large igneous province (ELIP) hosts Cu–Ni–platinum group element (PGE) sulfide ore layers within the lower part and Fe–Ti–V oxide-bearing horizons within the middle part. The major magmatic Cu–Ni–PGE sulfide ores and spatially associated cumulate rocks are examined for their PGE contents and Re–Os isotopic systematics. The samples yielded a Re–Os isochron with an age of 262 ± 27 Ma and an initial 187Os/188Os of 0.12460 ± 0.00011 (cOs(t) = 0.5 ± 0.1). The age is in good agreement with the previously reported U–Pb zircon age, indicating that the Re–Os system remained closed for most samples since the intrusion emplacement. They have near-chondritic cOs(t) values ranging from 0.7 to 0.2, similar to those of the Lijiang picrites and Song Da komatiites. Exceptionally, two samples from the roof zone and one from upper sequence exhibit radiogenic cOs(t) values (+0.6 to +8.6), showing minor contamination by the overlying Emeishan basalts. The PGE-rich ores contain relatively high PGE and small amounts of sulfides (generally less than 2%) and the abundance of Cu and PGE correlate well with S, implying that the distribution of these elements is controlled by the segregation and accumulation of a sulfide liquid. Some ore samples are poor in S (mostly <800 ppm), which may due to late-stage S loss caused by the dissolution of FeS from pre-existing sulfides through their interaction with sulfide-unsaturated flowing magma. The combined study shows that the Xinjie intrusion may be derived from ferropicritic magmas. The sharp reversals in Mg#, Cr/FeOT and Cr/TiO2 ratios immediately below Units 2–4, together with high Cu/Zr ratios decreasing from each PGE ore layer within these cyclic units, are consistent with multiple magma replenishment episodes. The sulfides in the cumulate rocks show little evidence of PGE depletion with height and thus appear to have segregated from successive inputs of fertile magma. This suggests that the Xinjie intrusion crystallized from in an open magma system, e.g., a magma conduit. The compositions of the disseminated sulfides in most samples can be modeled by applying an R factor (silicate–sulfide mass ratio) of between 1000 and 8000, indicating the segregation of only small amounts of sulfide liquid in the parental ferropicritic magmas. Thus, continuous mixing between primitive ferropicritic magma and differentiated resident magma could lead to crystallization of chromite, Cr-bearing magnetite and subsequently abundant Fe–Ti oxides, thereby the segregation of PGE-rich Cu-sulfide. When considered in the light of previous studies on plume-derived komatiites and picrites worldwide, the close-to-chondritic Os isotopic composition for most Xinjie samples, Lijiang picrites and Song Da komatiites suggest that the ferropicritic 0magma in the ELIP were generated from a plume. This comprised recycled Neoproterozic oceanic lithosphere, including depleted peridotite mantle embedded with geochemically enriched domains. The ascending magmas thereafter interacted with minor (possibly <10%) subducted/altered oceanic crust. This comparison suggests that the komatiitic melts in the ELIP originated from a greater-than normal degree of melting of incompatible trace element depleted, refractory mantle components in the plume source.
学科主题	矿床地球化学
语种	英语
公开日期	2017-12-29
内容类型	期刊论文
源URL	[http://ir.gyig.ac.cn:8080/handle/352002/7010]
专题	地球化学研究所_矿床地球化学国家重点实验室_矿床地球化学国家重点实验室_期刊论文
推荐引用方式 GB/T 7714	Wei-Guang Zhu,Bing-Guang Liu,Zhu-Yin Chu,et al. Rhenium-osmium isotope and platinum-group elements in the Xinjie layered intrusion, SW China: Implications for source mantle composition, mantle evolution, PGE fractionation and mineralization[J]. Geochimica et Cosmochimica Acta,2011,75(6):1621-1641.
APA	Wei-Guang Zhu.,Bing-Guang Liu.,Zhu-Yin Chu.,Liang Qi.,Rui-Zhong Hu.,...&Hong Zhong.(2011).Rhenium-osmium isotope and platinum-group elements in the Xinjie layered intrusion, SW China: Implications for source mantle composition, mantle evolution, PGE fractionation and mineralization.Geochimica et Cosmochimica Acta,75(6),1621-1641.
MLA	Wei-Guang Zhu,et al."Rhenium-osmium isotope and platinum-group elements in the Xinjie layered intrusion, SW China: Implications for source mantle composition, mantle evolution, PGE fractionation and mineralization".Geochimica et Cosmochimica Acta 75.6(2011):1621-1641.