Geochronological and geochemical constraints on the Cuonadong leucogranite, eastern Himalaya
Geochronological and geochemical constraints on the Cuonadong leucogranite, eastern Himalaya
复制标题
喜马拉雅东部错那洞淡色花岗岩的年代学和地球化学约束
DOI：
10.1007/s11631-018-0273-8
复制
发表时间：
2018
期刊：
影响因子：
1.6
通讯作者：
Xia Xiao Ping
中科院分区：
文献类型：
--
作者：
Xie Jia Jia;Qiu Hua Ning;Bai Xiu Juan;Zhang Wan Feng;Wang Qiang;Xia Xiao Ping
首次对藏南北喜马拉雅片麻岩穹隆中的错那洞浅色花岗岩进行了综合研究。振荡锆石环的西姆斯U-Pb年龄分布在34.1 ~ 16.0Ma之间，错那洞浅色花岗岩可能侵位于16.0Ma。对白云母样品进行的高精度40 Ar/39 Ar定年产生了基本平坦的年龄谱，具有一致的平台和等时线年龄，表明Cuonadong浅色花岗岩在14 Ma时冷却到450 °C以下。根据最年轻锆石U-Pb年龄和白云母40 Ar/39 Ar年龄，错那洞浅色花岗岩在16 ~ 14 Ma经历了119 °C/Myr的快速冷却。这种未变形的浅色花岗岩的年代学数据也表明，在喜马拉雅山东部的藏南拆离系的韧性伸展停止约14 Ma。此外，初始Sr-Nd同位素组成和Nd模式年龄表明，浅色花岗岩来自于大喜马拉雅结晶杂岩内的变质源区。高Rb/Sr比值和负Eu异常的明显Ba亏损表明，浅色花岗岩熔体是在流体缺乏的条件下由白云母破裂产生的。
First comprehensive investigations of the Cuonadong leucogranite exposed in North Himalayan gneiss dome of southern Tibet are presented in this study. The SIMS U–Pb ages of oscillatory zircon rims scatter in a wide range from 34.1 to 16.0 Ma, and the Cuonadong leucogranite probably emplaced at 16.0 Ma. High-precision40Ar/39Ar dating on a muscovite sample yields an essentially flat age spectrum with consistent plateau and isochron ages, indicating that the Cuonadong leucogranite cooled below 450 °C at 14 Ma. Based on the youngest zircon U–Pb age and muscovite40Ar/39Ar age, the Cuonadong leucogranite experienced rapid cooling with a rate of 119 °C/Myr from 16 to 14 Ma. The geochronological data of this undeformed leucogranite also suggest that the ductile extension of the South Tibetan Detachment System in the eastern Himalaya ceased byca.14 Ma. Furthermore, the initial Sr–Nd isotopic compositions and Nd model ages demonstrate that the leucogranite was derived from metapelitic source within the Greater Himalayan Crystalline Complex. The distinct Ba depletion with high Rb/Sr ratios and negative Eu anomalies make it clear that the leucogranite melts were generated by breakdown of muscovite under fluid-absent conditions.