西天山石炭纪火山岩岩石学及Sr-Nd同位素地球化学研究  

Petrology and Sr-Nd isotopic geochemistry of the Carboniferous volcanic rocks in the western Tianshan Mountains, NW China.

作　　者：朱永峰[1] 周晶[1] 郭璇[1] 

机构地区：[1]北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室,北京100871

出　　处：《岩石学报》2006年第5期1341-1350,共10页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划"中国西部中亚型造山与成矿"2001CB409802课题;国家自然科学基金项目(批准号40572033)资助.

摘　　要：西天山石炭纪火山岩连续从玄武岩、粗面质玄武安山岩、粗面安山岩、粗面岩一直演化到流纹岩。不同地区火山岩的同位素组成差别很大。出露在拉尔敦达坂一带的晚石炭世粗面安山岩．粗面岩具有较高的ε_(Nd)(t)值(+2．68～+4．29)和较高的初始^(87)Sr/^(86)Sr值(0．7015～0．7051)。新源城南的早石炭世粗面安山岩-流纹岩具有相对较低的ε_(Nd)(t)值(-0．22～+ 0．87)和变化较大的初始^(87)Sr/^(86)Sr值(0．7045～0．7068)。早石炭世玄武岩的初始^(87)Sr/^(86)Sr值较低且变化范围较小(0．7045～0．7058),ε_(Nd)(t)值高且变化范围大(+0．89～+3．04)。本文的同位素地球化学资料以及前期的年代学研究表明,西天山晚泥盆．早石炭世岛弧自西向东逐渐消亡,取而代之的是晚石炭世碰撞后富钾岩浆的喷发。The Carboniferous volcanic rocks occurring in western Tianshan Mountains range continuously from basalt, basaltic trachyandesite, trachyandesite, trachyte, to rhyolite. The isotopic compositions are variable for Carboniferous volcanic rocks in different regions in western Tianshan Mountains. The Late Carboniferous trachyandesite-trachyte occurring in Laerdundaba region characterize with relatively high εNd （t） values （ ＋ 2. 68 - ＋ 4. 29） and high initial ^87Sr/^86Sr ratios （0. 7015 - 0. 7051 ）. The trachyandesite - rhyolite occurring in the south of Xinyuan city have relatively low εNd （t）values （ -0. 22 - ＋ 0. 87 ） and variable initial ^87Sr/^86Sr values （0.7045 - 0.7068 ）. The basalts in south of Xinyuan city have low and less variable initial ^87Sr/^86Sr ratios （0.7045 - 0.7058 ）, but their εNd （t） values are high and variable （ ＋ 0. 89 - ＋ 3.04）. These Sr-Nd isotopic data and the previous zircon SHRIMP chronology studies suggested that the Early Carboniferous volcanic arc system faded away from west to east at the Late Carboniferous. Potassium-rich volcanic rocks formed in east part of the western Tianshan during the Late Carboniferous at a post-collisional environment.

关 键 词：石炭纪 火山岩 SR-ND同位素 西天山 新疆 

分 类 号：P588.145[天文地球—岩石学] P597.3[天文地球—地质学]