新疆阿吾拉勒山西段下二叠统陆相火山岩岩石地球化学特征、成因及构造背景  

Geochemistry, Petrogenesis and Tectonic Settings of the Lower Permian Series Volcanic Rocks from Western Awulale Mountain, Xinjiang

作　　者：赵军[1,3] 张作衡[2] 张贺[4] 刘敏[2] 洪为[2] 蒋宗胜[2] 

机构地区：[1]长安大学地球科学与资源学院,西安710054 [2]中国地质科学院矿产资源研究所,北京100037 [3]中国人民武装警察部队黄金第八支队,乌鲁木齐830057 [4]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地质学报》2013年第4期525-541,共17页Acta Geologica Sinica

基　　金：国家重点基础研究发展计划(编号2012CB416803);国家科技支撑计划(编号2011BAB06B02);地质矿产调查评价项目(编号1212011085060)共同资助的成果

摘　　要：新疆阿吾拉勒山西段是伊犁石炭—二叠纪裂谷的重要组成部分,本文对该区下二叠统典型的双峰式玄武岩-流纹岩组合进行了系统的岩相学和岩石地球化学研究。岩石整体高Na2O、高Al2O3、低TiO2、富碱。玄武岩富集大离子亲石元素Ba、K、LREE和P,亏损高场强元素Th、U、Ta、Nb。粗面斑岩和流纹斑岩富集大离子亲石元素Rb、K、LREE、高场强元素Th、Zr、Hf,亏损Ta、Nb、Sr、Ti和P。玄武安山玢岩的蛛网图与粗面斑岩和流纹斑岩较为一致,但少量元素的特征与玄武岩相似。玄武岩浆来源于弱亏损地幔,并受到了下地壳物质的混染,而玄武安山玢岩、粗面斑岩和流纹斑岩则可能来源于地壳物质的部分熔融。双峰式火山岩的形成可能与上地幔玄武岩浆的底侵作用有关。裂谷演化导致的陆相火山活动持续到早二叠世晚期达到顶峰,中二叠世以后,构造环境由拉伸转为挤压,裂谷演化趋于终止。该区石炭纪末—早二叠世的裂谷活动与整个天山地区晚古生代的构造演化背景具有一致性。The western Awulale Mountain is an important section of the Carboniferous-Permian Rift in Yili in Xinjiang Province. Typical bimodal volcanic rocks (basalts-rhyolite) in lower Permian series in this area was studied using petrography and lithochemistry. These rocks are generally characterized with higher Na2O and Al2O3 contents, lower TiO2 content and alkali-rich. The basalts are enriched in large-ion-lithophile elements(LILE), such as Ba, K, P and light rare earth elements(LREE), depleted in high-field-strength elements (HFSE), such as Th, U, Ta and Nb..Comparatively, the other rocks are enriched with Rb, K , LREE and Th, U, Zr and Hf, depleted of Ta, Nb, Sr and Ti. The basaltic magma was derived from weakly-depleted mantle and possibly contaminated by lower crust. In contrast, the rhyolite, trachytic porphyry and rhyrolite porphyry were likely the products of partial melting of crustal material. Spider diagram of basaltic porphyry is in agreement with that of trachytic porphyry and rhyrolite porphyry, with features of minor elements similar to that of basalt. The formation of bi-modal volcanic rock was likely related to the underplating of upper mantle basaltic magma. The development of rifting in western Awulale Mountain resulted in that continental volcano activity lasted and reached peak at early Permian. After the middle Permian, tectonic settings changed into compression from extension, resulting in end of rifting development. Rift activity of western Awulale Mountain in the late Carboniferous and early Permian period had the similar tectonic evolution as the Tianshan orogen in late Paleozoic.

关 键 词：阿吾拉勒山西段 伊犁古裂谷 双峰式火山岩 岩石地球化学 构造背景 

分 类 号：P588.14[天文地球—岩石学]