摘要
玛依勒蛇绿岩出露于玛依勒蛇绿混杂岩带中,该带位于西准噶尔造山带西南缘,是区内规模较大的一条蛇绿混杂岩带,蛇绿岩中镁铁-超镁铁质岩研究对探讨古亚洲洋古生代构造演化具有重要意义。本文选取玛依勒蛇绿岩中的镁铁-超镁铁质岩进行系统的岩石学、地球化学和年代学研究。结果表明,玛依勒蛇绿混杂岩中超镁铁质岩以富集Al_2O_3、CaO为特征,TiO_2含量与俯冲带之上地幔橄榄岩中含量相当,稀土配分曲线为轻稀土富集型,微量元素受蚀变作用影响,呈现出两种不同的曲线特征。镁铁质岩石可分为两组:I组镁铁质岩具有高MgO、低Al_2O_3,LREE轻微富集,富集大离子亲石元素,亏损Nb、Ta的特征,形成于消减带相关的岛弧环境;Ⅱ组镁铁质岩具有富碱、TiO_2,且呈LREE显著富集的右倾稀土配分曲线特征,富集大离子亲石元素,Nb、Ta正异常特征,代表了洋盆中海山或洋岛的残片。I组镁铁质岩中两个辉长岩岩块的LA-ICP-MS锆石UPb年龄分别为512.1±7.2Ma(MSWD=0.014)和531±12Ma(MSWD=0.17),与巴尔鲁克蛇绿岩、唐巴勒蛇绿岩中镁铁质岩岩块获得的锆石U-Pb年龄相吻合,且这三条蛇绿岩都具有SSZ型蛇绿岩的地球化学特征,可能为不同环境下同一洋盆的演化产物。
Mayile ophiolitic mélange belt is located in the southwest of the West Junggar orogenic belt,which is the largest ophiolitc mélange belt in the region. The ultramafic and mafic rocks of the ophiolite are crucial to study the tectonic evolutionary history of the Paleo-Asian. This article selects the ultramafic rock in Mayile ophiolite that makes systematic petrology,geochemistry and chronology study. The result shows that the ultramafic rock in Mayile ophiolite is characterized by abundant Al_2O_3 and CaO,and the content of TiO_2 is equal to the mantle peridotite＇s of subduction zone. The curve of REE is LREE-enriched type,and trace element is affected by corrosion,which presents two different kinds of curve characteristic. Mafic rock is divided into two groups. The first is high in MgO and low in Al_2O_3,and slightly rich in LREE and rich in lithophile elements and loss in Nb and Ta,which formed the island environment with the related subduction zone. The second is rich in alkali and TiO_2 and characterized significantly by the right deviation rare earth distribution curve,and rich in large ion lithophile elements. The Nb and Ta are positive anomaly characteristic,which represents the fragments of the seamount and ocean island. In the first one,the LA-ICP-MS zircon U-Pb age of two gabbro rocks are 512. 1 ± 7. 2Ma（ MSWD = 0. 014） and 531 ± 12Ma（ MSWD = 0. 17）,which are consistent with the Baerluke ophiolite＇s and Tangbale ophiolite ultramafic rock＇s. These three ophiolite all characterized by the SSZ ophiolite of geochemical,which can be the the product of the one ocean basin in different environment.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2016年第5期1420-1436,共17页
Acta Petrologica Sinica
基金
国家自然科学基金项目(41272089)
中国地质调查局地质调查项目(1212011085009
1212011085055
12120115066701)
中央高校基本科研基金项目(310827161021)联合资助
