甘肃北山地区怪石山含铜镍矿化镁铁质-超镁铁质杂岩体的地球化学特征及成因机制  

Geochemical characteristics and petrogenesis of Guaishishan copper-nickel mineralized mafic-ultramafic complex in Beishan region of Gansu

作　　者：李丽[1] 杨永强[2] 王育习[1] 

机构地区：[1]中国地质调查局西安地质调查中心,西安710054 [2]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

出　　处：《世界地质》2010年第1期16-27,共12页World Geology

基　　金：中国地质调查局战略性矿产远景调查项目(K47E015001;K47E016001)

摘　　要：甘肃北山怪石山镁铁质-超镁铁质杂岩体为一具铜镍矿化的基性岩体。岩石地球化学数据显示,基性岩相Mg#为74,超基性岩相为84-90,表明其具有原生岩浆及早期堆晶的特征。稀土和微量元素特征为∑REE偏低;球粒陨石标准化配分曲线属轻微右倾的平坦型,（La/Sm）N为0.99-1.95,（La/Yb）N为1.13-2.96,（Ce/Yb）N为1.16-2.37,δEu为0.93-1.02,δCe为0.91-0.95,基本无异常。结合该岩体产出的构造环境分析,认为这一岩体应产于活动大陆边缘的构造背景下,锆石SHR IMPU-Pb测年确定为泥盆纪。甘肃北山地区古生代的俯冲活动可能持续到泥盆纪,在这一过程中上地幔的尖晶石橄榄岩相发生部分熔融,产生的上升岩浆并未受到明显混染作用,从而形成了怪石山镁铁质-超镁铁质岩体,并伴随有铜-镍矿化。Guaishishan mafic-ultramafic complex in Beishan region of Gansu is a copper-nickel mineralized basic rocks.Their geochemical data show that the Mg# of basic rock is 74,and the Mg# of ultrabasic rock is 84~90,which indicates the primary magma and early cumulation in characteristics.The total content of rare-earth and trace elements is low in ΣREE,the chondrite-normalized REE distribution pattern is slightly right enriched,and with 0.99~1.95（La / Sm）N,1.13~2.96（La / Yb）N,1.16~2.37（Ce / Yb）N,0.93~1.02（δEu） and 0.91~0.95（δCe） in contents.Combining with the tectonic setting analysis of the rock,the authors consider that the mafic-ultramafic complex was produced in the active continental margin environment,and aged in Devonian with SHRIMP U—Pb dating.The subduction activity in Beishan area of Gansu in Paleozoic might continue to Devonian,in which the spinel peridotite in upper mantle partially melted in this process,and the rising magma was not contaminated significantly so that formed this copper-nickel mineralized mafic-ultramafic complex in Guanshishan.

关 键 词：地球化学 成因机制 分离结晶 地壳混染 怪石山镁铁质-超镁铁质杂岩体 

分 类 号：P595[天文地球—地球化学]