新疆北部二叠纪基性岩墙群岩浆作用及其动力学背景  

Magmatism and Dynamic Settings of Permian Mafic Dyke Swarms in the Northern of Xinjiang

作　　者：林瑶[1] 汤庆艳[1] 张铭杰[1] 焦建刚[2] 陈思童[1] 虎啸[1] 

机构地区：[1]兰州大学地质科学与矿产资源学院,甘肃兰州730000 [2]长安大学地球科学与资源学院,陕西西安710054

出　　处：《地球科学与环境学报》2014年第3期73-82,共10页Journal of Earth Sciences and Environment

基　　金：国家自然科学基金项目(41372095;41072056;40772058);中国地质调查局地质大调查项目(1212011121092;12120114044401);教育部高等学校博士学科点专项科研基金项目(20120211110023)

摘　　要：新疆北部西准噶尔、吐哈盆地、东天山、西天山以及塔里木东北缘广泛发育的二叠纪（260-290Ma）基性岩墙群与塔里木大火成岩省形成时代相近。基性岩墙群主量元素与MgO含量具有较好的相关性,富集Rb、Ba和Sr等大离子亲石元素以及轻稀土元素,亏损Nb、Ta和Ti等高场强元素,无明显Eu异常,与岛弧岩浆特征相似。εNd（t）值为-11.25-7.86,初始N（87Sr）/N（86Sr）值为0.703-0.710。西天山基性岩墙群亏损轻稀土元素,塔里木东北缘亏损Sr。新疆北部二叠纪基性岩墙群岩浆可能起源于富集型软流圈地幔源区,岩浆演化过程中存在不同程度的地壳物质或俯冲交代岩石圈地幔的混染,其中西准噶尔、东天山、西天山和吐哈盆地岩墙经历了板片俯冲流体交代的岩石圈地幔混染,东天山及塔里木东北缘基性岩墙在岩浆演化过程中受到明显的地壳物质混染。新疆北部二叠纪基性岩墙群可能是地幔柱岩浆作用不同演化过程的产物。Permian（260-290Ma）mafic dyke swarms in the northern of Xinjiang widely develop in West Junggar,Turpan-Hami Basin,East Tianshan,West Tianshan and the northeast margin of Tarim.The formation age of mafic dyke swarm is similar to that of Tarim large igneous provinces.The correlations between contents of major elements and MgO of mafic dyke swarms are obvious.Mafic dykes are enriched in large ion lithophile elements（Rb,Ba,Sr,etc.）and light rare earth elements（LREE）,and depleted in high field strength element（Nb,Ta,Ti,etc.）,and there is no obvious Eu anomaly,the characteristics are similar to island arc magma.εNd（t）values of mafic dykes are-11.25-7.86,and the initial N（87Sr）/N（86Sr）values are 0.703-0.710.Mafic dyke swarms in West Tianshan are depleted in LREE,and those in the northeast margin of Tarim are depleted in Sr.The magma of Permian mafic dyke swarm in the northern ofXinjiang is probably originated from enriched asthenosphere mantle source,and experiences different degrees of contamination of crust materials or metasomatic lithospheric mantle with subduction in the process of magmatic evolution.The dykes in West Junggar,East Tianshan,West Tianshan and Turpan-Hami Basin experience the contamination of lithospheric mantle with metasomatism of fluids from plate subduction;the mafic dykes in East Tianshan and the northeast margin of Tarim experience obvious contamination of crustal materials in the process of magmatic evolution.The Permian mafic dyke swarms in the northern of Xinjiang could be the products of mantle plume magmatism in different processes of evolution.

关 键 词：地幔柱 混染 岩浆演化 基性岩墙 二叠纪 新疆 

分 类 号：P583[天文地球—岩石学] P595[天文地球—地质学]