塔里木盆地西部中生代早期伸展作用的辉绿岩证据  

Diabase evidence for the early Mesozoic extension in the western Tarim basin,NW China

作　　者：罗金海[1] 车自成[1] 周新源[2] 李勇[2] 李建立[2] 张敬艺[1] 

机构地区：[1]西北大学地质学系大陆动力学国家重点实验室,陕西西安710069 [2]中国石油塔里木油田分公司,新疆库尔勒841000

出　　处：《中国地质》2006年第3期566-571,共6页Geology in China

摘　　要：塔里木盆地西北缘出露的辉绿岩墙的SiO2含量为44.34%～49.34%,Na2O+K2O(4.32%～6.04%)和Na2O/K2O均较高(2.23～9.15),主量元素反映板内玄武岩的特点。稀土总量较低(∑REE=35.71～47.95μg/g),(La/Yb)N高达11.66～14.77,呈轻稀土强烈富集的稀土配分型式,基本不显示明显的Eu异常,具有富集地幔源的地球化学特点。对辉绿岩的40Ar/39Ar年龄测定为235.6Ma和203.7Ma。结合塔里木盆地西部,特别是西邻塔吉克盆地和卡拉库姆盆地三叠—侏罗纪沉积与构造背景的综合分析表明,塔里木盆地西部三叠—侏罗纪时期是白垩纪—古近纪强烈沉降作用的前奏,主体处于伸展背景下的隆起状态。Diabase dikes exposed on the northwestern margin of the Tarim basin contain 44.34%-49.3% SiO2 have higher values of Na2O＋K2O （4.32%- 6.04%） and Na2O/K2O （2.23-9.15）, showing the features of intraplate basalt. The diabase is also characterized by a lower total REE content （∑REE=35.71-47.95μg/g） and a higher ratio of （La/Yb）N （11.66-14.77） and no pronounced Eu anomaly. The geochemistry of the diabase suggests that it was derived from enriched mande sources. ^40Ar/^39Ar dating of the diabase yields ages of 235.6 and 203.7 Ma. The above-mentioned geochemical characteristics combined with an integrated analysis of the Triassic-Jurassicsedimentary and tectonic settings of the western Tarim basin, especially the Tajikistan basin and Karakumy basin west of the Tarim basin suggest that：in the Triassic-Jurassic the western Tarim basin was in a prelude stage of Cretaceous-Paleogene intense subsidence and its main part was still in an uplift stage against the general extensional setting.

关 键 词：塔里木盆地 辉绿岩 地球化学 ^40Ar/^39Ar年龄测定 三叠-侏罗纪 伸展作用 

分 类 号：P534.5[天文地球—古生物学与地层学]