准噶尔盆地西缘下侏罗统玄武岩地球化学特征及其地质意义

Geochemical characteristics and geologic significance of the Lower Jurassic basalt on the western margin of Junggar Basin

高山林

GAO Shanlin

中国石化 油田勘探开发事业部, 北京 100728

Exploration and Development Affairs Department, SINOPEC, Beijing 100728, China

对准噶尔盆地西缘下侏罗统火山岩的地球化学特征进行了分析，主量、微量和稀土元素数据表明岩石为碱性玄武岩，富集轻稀土、大离子亲石元素和高场强元素，微量元素具有洋岛玄武岩（OIB）配分模式。玄武岩岩浆来源于未受明显地壳混染的亏损地幔，具有与地幔柱活动有关的大陆板内裂谷火山岩的特征。西北地区吐哈、敦煌等盆地发育与西准噶尔具有类似成因的侏罗系玄武岩，其形成与区域性软流圈界面上升和岩石圈的减薄有关，为侏罗纪早中期伸展盆地的形成提供了动力学条件。西北地区侏罗纪盆地伸展作用具有西早东晚、南早北晚的特征，是盆地烃源岩分布层位、成藏组合差异的基础原因之一。

The geochemical characteristics of the Lower Jurassic volcanic rocks on the western margin of the Junggar Basin were analyzed. The main, trace and rare earth element data indicate that the rocks are alkaline basalts, enriched with light rare earth elements, large ion lithophile elements and high field strength elements. The trace elements show an ocean island basalt (OIB) distribution model. The basalt magma came from the depleted mantle that was not obviously contaminated by crust, and has the characteristics of continental intraplate rift volcanic rocks related to mantle plume activity. The Tubo-Hami, Dunhuang and other basins in the northwest developed Jurassic basalt of similar genesis with the western Junggar Basin. The basalt formation was related to the rising of regional asthenosphere interface and the thinning of lithosphere, providing dynamic conditions for the formation of extension basin during the early and middle Jurassic. The extension of the Jurassic basin took place earlier in the west and the south, which explained the difference of source rock distribution and hydrocarbon accumulation in the basin.

国家科技重大专项（2011ZX05005-004）资助。

https://doi.org/10.11781/sysydz201903420