西昆仑山中元古代长城系火山岩地球化学  

Geochemistry of Statherian volcanic rocks in the West Kunlun Mountains

作　　者：郭坤一[1] 张传林[1] 沈家林[1] 叶海敏[1] 王爱国[1] 李春海[1] 

机构地区：[1]中国地质调查局南京地质矿产研究所,江苏南京210016

出　　处：《地质通报》2004年第2期130-135,共6页Geological Bulletin of China

基　　金：中国地质调查局<中国前寒武纪重大地质问题研究>(200113900070)课题<西昆仑前寒武纪构造事件群研究>专题部分成果

摘　　要：西昆仑山长城系塞拉加兹塔格群为一套火山-沉积岩组合,其火山岩主体为基性岩,在顶部出现少量酸性富Na的流纹英安岩。基性火山岩SiO2=47.77%～49.56%,Na2O+K2O=4.64%～5.42%,Na2O/K2O=2.32～8.46,ΣREE=74.29×10-6～137.35×10-6La/YbN=6.5～10.0La/SmN=2.35～2.91微量元素经N-MORB标准化后的配分模式与板内碱性-拉斑玄武岩的相近多种不相容元素HFSE比值及相应的图解表明玄武岩形成于大陆板内裂解背景。酸性火山岩SiO2=70.01%～72.72%Na2O+K2O=7.83%～8.27%ΣREE=402.97×10-6～826.55×10-6,(La/Yb)N=11.58～30.68,(La/Sm)N=5.1～10.5,δEu为0.31～0.32,稀土配分模式具有A型花岗岩特征。火山岩的沉积学、地球化学特征综合分析显示火山岩形成于大陆裂解背景。The Statherian Sailajiazitag Group in the West Kunlun Mountains is an association of volcanic rocks. It consists dominantly of basic volcanic rocks, with some acid, sodium-rich rhyodacite occurring at the top. The chemical composition of the basic volcanic rocks is given as follows: SiO2=47.77% to 49.56%, Na2O+K2O=4.64% to 5.42% with Na2O/K2O=2.32 to 8.46, and ∑REE=74.29×10-6 to 137.35×10-6 with (La/Yb)N=6.5 to 10 and (La/Sm)N=2.35 to 2.91. The N-MORB-normalized trace element patterns are close to those of intraplate alkaline to tholeiitic basalt. Ratios of multiple incompatible elements and their related diagrams indicate that the basalt formed in a setting of intracontinental plate breakup. The chemical composition of acid volcanic rocks is given as follows: SiO2=70.01% to 72.72%, Na2O+K2O=7.83% to 8.27%, ∑REE=402.97×10-6 to 826.55×10-6, (La/Yb)N=11.58 to 30.68, (La/Sm)N=5.1 to 10.5, and δEu=0.31～0.32. Their chondrite-normalized REE distribution patterns show the characteristics of A-type granite. An integrated sedimentologic and geochemical analysis of the volcanic rocks suggests that the volcanic rocks formed in a continental breakup environment.

关 键 词：西昆仑山 长城系火山岩 地球化学 

分 类 号：P534.3[天文地球—古生物学与地层学] P588.14[天文地球—地质学]