湖南桃江地区印支期辉绿岩成因——地球化学、年代学和Sr-Nd-Pb同位素约束  

Petrogenesis of diabase from Jiangshiqiao in Taojiang City,Hu'nan Province:Constrains from geochemistry, geochronology and Sr-Nd-Pb isotopes

作　　者：金鑫镖 王磊[1,2] 向华[3] 刘重芃[1] 段桂玲[1] 李子云[3] JIN Xinbiao;WANG Lei;LIU Zhongpeng;DUAN Guiling;XIANG Hua;LI Ziyun(Wuhan Center of Geological Survey, CGS, Wuhan 430205, Hubei, China;Research Center of Granitic Diagenesis and Mineralization, CGS, Wuhan 430205, Hubei, China;Team 413, Bureau of Geology and Mineral Exploration and Deveopment of Hu'nan Province, Changde 415000, China)

机构地区：[1]中国地质调查局武汉地质调查中心,湖北武汉430205 [2]中国地质调查局花岗岩成岩成矿地质研究中心,湖北武汉430205 [3]湖南省地质矿产勘查开发局四一三队,湖南常德530023

出　　处：《地质通报》2017年第5期750-760,共11页Geological Bulletin of China

基　　金：中国地质调查局项目<雪峰古陆及邻区金刚石找矿选区评价>(编号:12120113063000);国家自然科学基金项目<粤北大宝山多金属矿床成因研究>(批准号:41302068)

摘　　要：对湖南桃江地区江石桥辉绿岩进行了LA-ICP-MS锆石U-Pb定年,获得的岩浆侵位年龄为229±2.3Ma(n=8,MSWD=1.8,2σ)。其低钾(K_2O/Na_2O=0.14~0.16),贫碱(K_2O+Na_2O=2.89%~2.96%),富集大离子亲石元素(Rb、Ba、Th、U),亏损高场强元素(Nb、Ta、Ti),呈轻稀土元素弱富集,无Eu、Ce异常,富集放射性成因Pb,低(^(87)Sr/^(86)Sr)_i(0.706052~0.706437),较低正ε_(Nd)(t)(1.54~1.86)的特征,表明岩石来源于下地壳物质和亏损地幔的混合源区。综合前人的研究结果认为,在印支运动造山后的伸展背景下,软流圈上涌导致区域下地壳及部分地幔物质发生熔融,形成辉绿岩岩浆并向上侵位而成。Zircon LA-ICP-MS U-Pb dating for diabase from Jiangshiqiao in Taojiang City of Hu'nan Province yielded an emplace?ment age of229±2.3Ma(n=8,MSWD=1.8,2σ).The diabase is characterized by low values of potassium(K2O/Na2O=0.14~0.16),and alkali(K2O+Na2O=2.89%~2.96%),enrichment of large ion lithophile elements and LREE and depletion of high field strength el?ements,low(87Sr/86Sr)i ratios(0.70606~0.70644),low positiveεNd(t)values(1.55~1.87)and enrichment of radioactive Pb,suggestinga mixed source of the depleted mantle(DM)and the lower crustal.In combination with previous studies,the authors hold that the di?abase was formed through partial melt of the mantle and lower crustal components by the upwelling asthenosphere during the Indo?sinian post-orogenic lithosphere extension in Hu'nan Province.

关 键 词：辉绿岩 地球化学 年代学 SR-ND-PB 同位素 岩石成因 桃江地区 

分 类 号：P588.12[天文地球—岩石学] P597[天文地球—地质学]