阿尔金南缘构造带西段辉绿岩墙群的地球化学特征及构造环境  

Geochemical characteristics and tectonic settings of the diabase dyke swarms in the western segment of the southern Altun tectonic belt

作　　者：覃小锋[1] 夏斌[1] 李江[2] 陆济璞[2] 许华[2] 周府生[2] 胡贵昂[2] 李乾[2] 

机构地区：[1]中国科学院广州地球化学研究所,广东广州510640 [2]广西区域地质调查研究院,广西桂林541003

出　　处：《岩石矿物学杂志》2008年第1期14-22,共9页Acta Petrologica et Mineralogica

基　　金：广西自然科学基金资助项目(桂科自0728089);中国地质调查局地质大调查项目资助(19991300008091)

摘　　要：对阿尔金南缘构造带西段辉绿岩墙群的岩石学和地球化学的详细研究表明，该区辉绿岩墙群为拉斑系列岩石，其主量元素以中等TiO2（1．19％～1．59％）、高MgO（5．51％～7．88％）、贫K2O（0．04％～0．84％）和P2O5（0．10％～0．20％）、Na2O〉K2O为特征；高场强元素（HFSE）丰度特征显示其为E-MORB型或过渡型玄武岩质岩石；稀土元素总量相对较高，轻重稀土元素分馏不显著[（La/Yb）N=1．93～3．61，LREE／HREE：3．01～4．10]，在球粒陨石标准化配分模式图上呈略富集型。结合玄武岩构造环境判别图解综合分析推测，它们可能形成于一种裂谷向MORB环境过渡的构造环境，即初始小洋盆构造环境。Detailed petrographic and geochemical studies show that the diabase dyke swarms in the western segment of the southern Altun tectonic belt belong to tholeiite series. The major elements of the diabase dykes are characterized by intermediate TiO2 （1.19% - 1.59% ）, high MgO （5.51% - 7.88% ）, poor K2O （0.04%-0.84 % ） and P2O5 （0.10 % -0.20 % ） and Na2O〉K2O; Characteristics of high field strength elements contents show that the diabase dyke swarms are of E-type MORB or transitional types from continental （intraplate） rift basalt to mid-ocean ridge basalt. The diabase dyke swarms have high contents of ∑REE and unremarkable fractionation between LREE and HREE [ （La/Yb）N = 1.93- 3.61, LREE/HREE = 3.01 - 4.10 ]. Chondrite-normalized REE diagrams show a slightly enriched LREE patterns. Combined with the basalt tectonic discrimination diagrams, it is held that the diabase dyke swarms in the western segment of the southern Altun tectonic belt might have been formed in a transitional tectonic environment from rift to MORB, i.e. , the tectonic environment of an initial small oceanic basin.

关 键 词：辉绿岩墙群 地球化学 构造环境 阿尔金南缘构造带西段 

分 类 号：P588.1[天文地球—岩石学] P618.51[天文地球—地质学]