新疆哈图早二叠世富镁闪长岩的时代、地球化学特征和可能的成因机制  

Age,geochemical features and possible petrogenesis mechanism of Early Permian magnesian diorite in Hatu,Xinjiang

作　　者：尹继元[1,2] 袁超[1] 孙敏[3] 龙晓平 邱华宁[1] 王毓婧[1] 任江波[4] 关义立[1] 

机构地区：[1]中国科学院广州地球化学研究所,广州510640 [2]中国地质科学院地质研究所,北京100037 [3]香港大学地球科学系 [4]国土资源部广州海洋地质调查局,广州510760

出　　处：《岩石学报》2012年第7期2171-2182,共12页Acta Petrologica Sinica

基　　金：国家973项目(2007CB411308);国家自然科学基金(40721063;40772130)联合资助

摘　　要：西准噶尔别鲁阿嘎希地区广泛发育富镁闪长质小岩体和岩墙。对岩墙全岩样品的Ar-Ar测年获得了292±3Ma的坪年龄,显示其主要形成于早二叠世。这些小岩体和岩墙均为钙碱性系列岩石,具有宽的SiO2(51.9%～62.6%)、高的MgO(Mg#>60)、Cr(45.8×10-6～539×10-6)、Ni(17.2×10-6～197×10-6)含量,富集大离子亲石元素(LILE)(如K、Rb、Ba、Th和U)、亏损高强场元素(如Nb、Ta、Ti),富集LREE,亏损HREE。这些特征类似于日本中新世Setouchi火山岩带中的赞岐岩。这些岩体/岩墙很可能是在俯冲过程中,经洋壳板片的脱水形成流体与地幔橄榄岩相互作用而成。这表明,西准噶尔别鲁阿嘎希地区早二叠世为岛弧环境。而富镁闪长岩的形成过程也有利于铜-金矿床的形成,显示该区有良好的成矿远景。Magnesian dioritic dikes and plutons widely occur in the Bieluagaxi region, Western Junggar and recorded the Late Paleozoic tectonic evolutionary history of the area. Ar-Ar dating on rock chips of the dikes has yielded a plateau age of 292Ma, indicating an Early Permian age for the dikes. The magnesian diorites are calc-alkaline suite with variable SiO2 （ 51.9% - 62. 6% ）, and characterized by high Mg（ Mg^＂ 〉 60）, Cr（45.8× 10^ -6 - 539 × 10^ -6 ）, Ni （ 17.2× 10 ^-6 - 197× 10 ^-6 ） contents. The magnesian diorites are strongly enriched in large-ion-lithophile elements（ such as K, Rb, Ba, Th and U）and light rare earth elements, and are characterized by depletion of high-field-strength elements（ such as Nb,Ta,Ti）and heavy rare earth element. These geochemical features are analogous to those of sanukitoids in Setouchi volcanic belt. The Bieluagaxi magnesian diorite is generated by interaction of mantle peridotite with supercritical fluid derived from dehydration of subducting oceanic slab. The occurrence of Early Permian sanukitic rocks in the Bieluagaxi region suggest that the Western Junggar was dominated by subdnction-related environment. The interaction between high oxygen fugacity supercritical fluid and mantle peridotite caused the decomposition of metal sulfides and the Cu and Au mineralization which have good metallogenic prospects in the Bieluagaxi region.

关 键 词：富镁闪长岩 岩墙 俯冲带 铜-金矿化 西准噶尔 

分 类 号：P588.122[天文地球—岩石学] P597.3[天文地球—地质学]