黔西南碱性超基性脉岩的铂族元素地球化学  

PGE Geochemistry of Alkaline Ultramafic Dykes in Southwestern Guizhou Province,China

作　　者：冯光英[1,2] 刘燊[1] 苏文超[1] 冯彩霞[1] 王涛[1,2] 杨毓红[1,2] 

机构地区：[1]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,贵州贵阳550002 [2]中国科学院研究生院,北京100039

出　　处：《矿物学报》2010年第2期207-214,共8页Acta Mineralogica Sinica

基　　金：国家973项目(2007CB411402);国家自然科学基金项目(批准号:4067302940773020);西北大学大陆动力学国家重点实验室开放课题基金(08LCD08)

摘　　要：黔西南出露大范围的碱性超基性脉岩,其成因研究对了解该地区大规模的金矿形成具有重要意义。采用卡洛斯管同位素稀释法结合ICP-MS分析了黔西南4个岩区碱性超基性脉岩中的Ni、Ir、Ru、Rh、Pt、Pd和Cu的含量。结果显示：研究区脉岩铂族元素（PGE）的含量普遍较低,原始地幔标准化PGE分布模式呈正斜率型;并具有较高的Cu/Pd比值（11903-60210）。综合对比研究表明,研究区脉岩为地幔低程度部分熔融作用的产物,原始岩浆具有硫不饱和的特征,岩浆在上升过程中没有发生明显的硫化物分异,但发生了一定程度的岩浆分离结晶。此外,陇要脉岩可能经历了岩浆上升时铬铁矿的分离结晶作用。Studies on the petrogenesis of alkaline ultramafic dykes are helpful to understand the formation of the gold deposits widely distributed in southwestern Guizhou Province,China.The platinum-group elements（PGE） are sensitive indicators of the petrogenesis（e.g.,partial melting and silicate fractionation） of mafic-ultramafic rocks.Thus,in this paper,contents of Ni,Cu and PGE（Ir,Ru,Rh,Pt and Pd） were measured by using isotope dilution（ID）-ICP-MS with an improved Carius tube.The studied samples are characterized by low PGE contents,high Cu/Pd（11903—60210） ratios and positive slope in the primitive mantle normalized patterns.Synthetic and comparative studies on the PGE indicate that the ultramafic rocks were derived from low-degree partial melting of the MORB-like mantle.These dyke rocks were formed by the crystallization of the S-unsaturated magma,which had not experienced obvious sulfide segregation.The primary magma of the ultramafic rocks,however,underwent extensive fractionation of clinopyroxene,olivine,Ti-bearing phases（e.g.,rutile,ilmenite,titanite） and apatite,prior to emplacement.In addition,the Longyao ultramafic dykes experienced differentiation of chromite during primary magma ascent.

关 键 词：PGE 超基性脉岩 成因 黔西南 

分 类 号：F588.12[经济管理—产业经济] P595[天文地球—地球化学]