博格达上大河沿岩体铷-锶同位素年龄及其地质意义  

Rb-Sr Isotope Age of the Shangdaheyan Intrusion in the Bogda Orogenic Belt and its Geological Implications

作　　者：顾连兴[1] 于春水[1] 李宏宇[1] 肖新建[1] 严正富[1] 

机构地区：[1]南京大学内生金属矿床成矿机制国家重点实验室,江苏南京210093

出　　处：《矿物岩石地球化学通报》2000年第1期19-21,共3页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金!项目(49172094);国家攻关项目!(96915050301);南京大学现代分析中心测试基金

摘　　要：博格达造山带是上古生代裂谷带，于石炭纪末闭合。该带的侵入活动主要表现为大量辉绿岩岩床、岩墙和岩株，并有零星分布的闪长岩和花岗岩岩体。上大河沿侵入体一组矿物岩石样品的ＲｂＳｒ 等时线测定获得其年龄为２９８．４±０．７６ Ｍａ 和８７ Ｓｒ８６ Ｓｒ 初始比０．７０４１。结合野外证据，表明博格达山的大部分侵入岩定位于海西旋回，且是裂谷闭合后初始拉张阶段的产物，同时表明该带海西期以后的侵入活动并不重要。The Bogda region is interpreted to be an upper Palaeozoic continental rift, which was closed towards the end of the Carboniferous period. Intrusive activities in that region are represented by a large number of diabasic sills, dykes and stocks with a few dioritic and granitic bodies. No date of age determination have so far been reported about these intrusive rocks.The Shangdaheyan intrusion is composed of a spectrum from dioritic to granitic rocks. These rocks are characterized mineralogically by the existence of augite with or without other pyroxene, and are thus considered to represent a series of differentiates of a basaltic magma. A group of samples from this intrusion were determined in this paper, which yielded a mineral-rock Rb Sr isochron with an age of 298.4±0.76 Ma and an initial 87 Sr/ 86 Sr ratio of 0.7041. With the support from field evidence, these results indicate that most of , if not all, the intrusions of the Bogda region were emplaced during the Hercynian cycle as a result of initial extension following rift closure.

关 键 词：锶同位素 地质意义 裂谷 海西 拉张 侵入体 上古生代 年龄 闭合 野外 

分 类 号：P597[天文地球—地球化学]