西昆仑慕士塔格岩体锆石U-Pb和黑云母40Ar-39Ar年龄及其地质意义

西昆仑造山带作为古特提斯洋消减、洋盆闭合的重要构造域，对古特提斯洋的演化研究有着重要意义，并且其与青藏高原、塔里木盆地的构造演化和气候变化有着密切的联系。以西昆仑西北段慕士塔格岩体为研究对象，对其中的暗色包体进行锆石U-Pb同位素分析和黑云母⁴⁰Ar-³⁹Ar同位素分析，探讨岩体的演化历史。锆石U-Pb同位素分析给出n(²⁰⁶Pb)/n(²³⁸U)加权平均年龄为(218.8±1.9)Ma，为晚三叠世，解释为岩体的结晶年龄，结合区域资料可推断岩体形成于古特提斯洋闭合后的后碰撞阶段；黑云母⁴⁰Ar-³⁹Ar同位素分析得到坪年龄为(6.018±0.072)Ma和(5.675±0.059)Ma，解释为岩体的隆升冷却年龄，表明西昆仑地区中新世晚期经历了冷却隆升事件，该隆升事件使西昆仑地区中新世晚期以来地形地貌及区域构造强烈改变，造成了区域内的干旱气候，并加速了在塔里木盆地形成塔克拉玛干沙漠。

Zircon U-Pb and Biotite 40Ar-39Ar Ages of Muztag Pluton in West Kunlun and Their Geological Significance

As a key tectonic regime of the subduction and closure of Paleo-Tethys Ocean, the West Kunlun orogenic belt has great significance in the study on the tectonic thermal history of Paleo-Tethys Ocean. Moreover, it has close connection with the tectonic and climatic evolution of Tibetan Plateau and Tarim Basin. In order to reveal the evolution history of Muztag pluton in the northwest section of West Kunlun orogenic belt, several isotopic characteristics of zircon U-Pb ages and biotite ⁴⁰Ar-³⁹Ar ages of melanocratic enclaves hosted in it were discussed. The zircon U-Pb isotopic analysis returns a weighted average U-Pb age of (218.8±1.9)Ma, which is interpreted as the crystallization age of the pluton. Combined with regional geological data, it is inferred that Muztag pluton emplaces in an extensional regime related to the post-collisional setting following the closure of Paleo-Tethys Ocean. Biotite ⁴⁰Ar-³⁹Ar isotopic analysis yields the plateau ages of (6.018±0.072)Ma and (5.675±0.059)Ma, respectively, which are considered as uplifting and cooling ages of the pluton, indicating that West Kunlun area undergoes a cooling-uplift event in Late Miocene. The event vehemently changes the tectonics, topography and geomorphology of West Kunlun and its adjacent area, gives rise to a regional arid climate, and impels the formation of Taklimakan Desert in Tarim Basin.