新疆阿尔泰山南缘泥盆纪弧型苦橄岩铂族元素地球化学特征及其地质意义  

Platinum Group Element Geochemistry of the Devonian ArcRelated Picrites of the South Margin of the Altai Mountains in Xinjiang and Its Geological Implications

作　　者：张招崇[1] 周刚[2] 闫升好[3] 陈柏林[4] 贺永康 柴凤梅[1] 何立新 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]中国地质科学院地质研究所,北京100037 [3]中国地质科学院矿产资源研究所,北京100037 [4]中国地质科学院地质力学研究所,北京100081 [5]新疆地质矿产局第四地质大队,新疆阿尔泰836500

出　　处：《现代地质》2006年第4期519-526,共8页Geoscience

基　　金：国家自然科学基金项目(40572047);国家"305"项目(2001BA609A-07-02);教育部新世纪优秀人才支持计划(NCET-04-0728);科技部"973"项目(2001CB409807)

摘　　要：全球岛弧火山岩的铂族元素数据非常少。本研究对新疆阿尔泰山南缘中泥盆世北塔山组地层中的苦橄岩的铂族元素进行了分析,结果表明:其铂族元素的含量总体变化不大,其原始地幔标准化曲线总体上和已经报道的大西洋Lesser Antilles岛弧的G renada苦橄岩相似,均以富集钯组铂族元素(PPGE)为特征,但总体含量比后者高,而比大火成岩省的苦橄岩低。一些铂族元素的特征比值指示了苦橄岩和富辉玄武岩起源于软流圈地幔,而高的w(Os)/w(Ir)比值则暗示了源区中有深海沉积物的加入。w(Pd)/w(Ir)-w(N i)/w(Cu)图解说明本区的苦橄岩不是原始岩浆,而是原始的高镁玄武岩中有过剩橄榄石的加入,而w(Pd)-w(Cu)图解则说明原始岩浆硫不饱和。IPGE在俯冲带流体中相对稳定,而PPGE在俯冲带流体中的活动性相对较高。Platinum-group element （PGE） data for global arc lavas are very scarce. PGE analyses for the picrites of the middle Devonian Beitashan Formation at the south margin of Altai Mountains show that the PGE concentrations are within a narrow range, and their primitive mantle normalized PGE patterns resemble those from Grenada picrites, Lesser Antilles Arc in Atlantic, which is characterized by the enrichment of PPGE although the PGE contents of the researched picrites are higher than the latter, and lower than those from large igneous provinces. Some characteristic ratios suggest the picrites and ankaramites were derived from asthenospheric mantle, and high Os/Ir ratios reflect the involvements of pelagic sediments. Pd/Ir versus Ni/Cu diagram implies that the picrites and ankaramites were not primary magmas, but MgO-high basahs with excess olivines, whereas Pd versus Cu diagram suggests a S-undersaturated primary magma. The PPGE may have slightly more transport efficiency in slab-derived fluids than do the IPGE.

关 键 词：苦橄岩 铂族元素 原始岩浆 俯冲带流体 阿尔泰 新疆 

分 类 号：P588.12[天文地球—岩石学]