论文部分内容阅读
针对南秦岭光头山岩体群的岩相学和黑云母地球化学分析,进而对秦岭造山带晚三叠世花岗岩形成的温度、压力和氧逸度等物理化学条件进行专门的研究。其中岩相学观察表明,光头山岩体群主要由黑云母二长花岗岩和花岗闪长岩组成。电子探针分析结果表明黑云母二长岗岩中的黑云母是铁质黑云母,花岗闪长岩中的黑云母是镁质黑云母,所测黑云母的Fe2+/(Fe2++Mg)比值变化范围较小,表明其未受到后期改造,为原生黑云母,可以用来估算岩体的成岩物理化学条件。根据黑云母地球化学成分计算的成岩温度为(645~710)℃,压力为(126~309)MPa,logfo2为-12~-15,岩体侵位于中上地壳层次(约8.6km)。黑云母地球化学分析还表明,光头山岩体群主要为过铝质-造山带钙碱性花岗岩,岩浆以壳源为主兼具壳幔混源的特征。
According to the petrography and biotite geochemical analysis of the Guangtoushan rock mass in the South Qinling Mountains, the physical and chemical conditions such as temperature, pressure and oxygen fugacity of late Triassic granite in the Qinling orogenic belt are studied. The observation of petrography shows that the Guangtoushan rock mass mainly consists of biotite monzogranite and granodiorite. The results of electron probe analysis showed that the biotite in biotite monzogranite is iron biotite, the biotite in granodiorite is magnesian biotite, and the biotite Fe2 + / (Fe2 + + Mg) The range of change of the ratio is small, indicating that it has not been transformed later. It is a native biotite that can be used to estimate the diagenetic physicochemical conditions of the rock mass. The diagenesis temperature (645 ~ 710) ℃, pressure (126 ~ 309) MPa and logfo2 -12 ~ -15 are calculated according to the biochemical composition of biotite. The biotite geochemical analysis also shows that the Guangtoushan rock mass is mainly a peraluminous-orogenic calc-alkaline granite, and the magma is characterized by a crust-source and a crust-mantle mixed source.