南岭西段花山-姑婆山侵入岩带锆石U-Pb年龄格架及其地质意义

Ziucon U-Pb age framework of Huashan-Guposhan intrusive belt,western part of Naniing Range,and its geological significance.

花山-姑婆山侵入岩带位于南岭西段,由牛庙、同安、花山、金子岭、乌羊山和姑婆山等岩体所组成,10个锆石样品的 SHRIMP U-Pb 法、LA-ICP-MS 法和熔融法定年结果显示,该带中主要的闪长质和花岗质岩体侵位于160～163Ma 这一狭窄的时间范围内,表明中—晚侏罗世之交是本区岩浆活动的高峰时期,它们在时间上、空间上、物质来源上、构造背景上和成因机制上有着十分密切的联系。姑婆山里松花岗岩与其中暗色包体结晶年龄的一致性,从一个重要的方面否定了暗色包体是浅部围岩捕虏体或深部熔融残留体的可能性,并为它们的岩浆混合成因提供了一个重要依据。具有充分分异演化特征的新路晚阶段细粒花岗岩小岩体中锆石的 U-Pb 年龄值为151Ma,比主体花岗岩大约晚10Ma,它可能反映了本区主体花岗岩岩浆房分离结晶和演化的时间跨度。桂岭和大宁岩体侵位于加里东晚期。

Huashan-Guposhan intrusive belt is located in the western part of the Nanling Range. It is composed of Niumiao, Tong＇ an, Huashan, Jinziling, Wuyangshan, Guposhan, etc. granitoid bodies. The U-Pb age dating of 10 samples by SHRIMP, LA-ICP-MS and melting methods reveals that the major phase granitic and dioritic bodies in this belt were emplaced in a narrow time interval of 160 163Ma. These granitoids are closely related in time, space, material sources, geotectonic setting and genetic mechanism. The synchronous age of Lisong granite and Lisong marie enclave excludes the possibility of xenolith from country rocks or restite of remehed metamorphic rocks, and provides an important evidence for magma mingling. The later stage Xinlu fine-grained granite with well evolved fractionation characteristics has a zircon U-Pb age of 151Ma, which is about 10Ma later than the major phase granitoids. It probably represents the time duration of fractional crystallization and evolution of the granitic magmatic chamber in this region. The Guiling and Daning granitoid bodies were emplaced in the late Caledonian period.