摘要
摘要:为了探讨塔里木北缘构造岩浆演化，采用锆石年代学、岩石地球化学方法对柯坪辉绿岩进行研究。LA-ICP-MS锆石U-Pb结果表明其为中-晚三叠世岩浆活动的产物。辉绿岩SiO₂含量为45.68%～46.97%、TiO₂为3.98%～4.03%、Al₂O₃为14.81%～14.90%、K₂O/Na₂O为0.39～0.42，属于高钾碱性系列。微量元素特征表明，有微弱的Ce负异常（δCe=0.95～0.99），Eu异常不明显（δEu=0.98～1.00），总体富集大离子亲石元素和LREE，高场强元素相对亏损。柯坪辉绿岩、阿图什辉绿岩与柯坪玄武岩、巴楚辉绿岩等具有相似的源区和一致的构造背景，均为拉张背景下形成，但却分属不同的构造事件。研究表明早石炭世南天山洋闭合，晚石炭世—早二叠世柯坪地区为塔里木北缘的具有前陆盆地性质的残留海盆，受地幔柱影响柯坪—巴楚地区出现大规模岩浆活动。二叠纪之后塔里木北缘为后碰撞伸展背景。三叠纪南天山—塔里木北缘为拉伸走滑的构造背景，本文的辉绿岩，正是在这种背景下形成的。
关键词: 辉绿岩/
地球化学特征/
柯坪/
三叠纪

Abstract:In order to discuss the tectonomagmatic evolution of the northern margin of Tarim, zircon geochronology and petrochemistry are used to study the Keping diabase. The results of LA-ICP-MS zircon U-Pb indicate that it is the product of magmatic activity in the Middle-Late Triassic. The diabase, with an average abundance of SiO₂=45.68%~46.97%, TiO₂=3.98%~4.03%, Al₂O₃=14.81%~14.90%, K₂O/Na₂O=0.39~0.42, belongs to the rock series of high potassium calc-alkaline. The trace element characteristics, with weak Ce(δCe=0.95~0.99) negative anomalies, Eu(δEu=0.98~1.00) abnormality is not obvious, exhibit depletion in LILE and LREE, relative loss of HFSE. Keping diabase, Atush diabase and Keping basalt, Bachu diabase had similar source area and consistent structural background. They are all formed under the tension background, but they belong to different tectonic events. The study shows that the South Tianshan ocean is closed in the Early Carboniferous, and the Keping area in the Late Carboniferous-Early Permian is a residual basin with foreland basin nature in the northern margin of Tarim, and large-scale magmatic activity occurs in the Keping Bachu area under the influence of mantle plume. After Permian, the northern margin of Tarim is in the background of post collisional extension. In this paper, diabase is formed under the tectonic background of extensional strike slip in the northern margin of South Tianshan Tarim in Triassic.
Key words:Diabase/
Geochemical characteristics/
Keping/
The Triassic period



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