【摘要】 本文报道了东天山沙泉子地区石炭纪火山岩的主量、微量及铂族元素(PGE)地球化学特征,初步探讨了岩浆源区特征和岩浆演化过程。采用改进的溶样方法,即Teflon密闭溶样-Te共沉淀富集PGE,阳离子交换树脂结合P507萃淋树脂分离干扰元素方法,测定了玄武岩及玄武安山岩中的PGE含量。结果表明,沙泉子火山岩具有较低的MgO含量,且整体表现为强烈的PGE亏损,暗示其可能形成于较低的部分熔融程度(<10%),可能有少量硫化物(～0.001%)残留于地幔。火山岩较低的Cu/Zr值表明原始岩浆有了亲铜元素的亏损。玄武岩较稳定的Pd/Ir和Pt/Pd值,较高且变化较大的Cu/Pd值,表明岩浆上升或侵位过程达到过S饱和而发生硫化物熔离。IPGE与Cr、Ni的相关性表明,原始岩浆可能发生了橄榄石和铬铁矿的分离结晶作用。更多还原

【Abstract】 This paper reports the geochemical characteristics of major,trace and platinum-group elements(PGEs) in Carboniferous volcanic rocks from the Shaquanzi area,East Tianshan,Xinjiang.The magma source and the magma evolution of these rocks are discussed.PGEs concentrations in basalt and basaltic andesite are determined by ID-ICP-MS using screw-top,PTFE-lined,stainless steel pressure bombs for sample digestion.PGEs are depleted in the whole volcanic rocks with low MgO suggests that the primary magma has experienced low degree partial melting(<10%) and that some sulfides(~0.001%) were remained in the mantle source.Low Cu/Zr ratios in the volcanic rocks mean depletion of chalcophile elements.The relative stable Pd/Ir and Pt/Pd ratios but high and variable Cu/Pd ratios of basalt suggest that the magmas reached sulfide saturation and segregated PGE-rich sulfides during magma ascent.The strong correlations of Rh and Ir,Ru,as well as IPGE and Cr,Ni,suggest that magmatic differentiation may experience the fractional crystallization of olivine and chromite.更多还原