广西云开地区那蓬岩体黑云母二长花岗岩年代学、地球化学特征及成因

华南地区印支期经历了强烈的构造运动和岩浆活动，印支期花岗岩的构造背景一直是地学界讨论的热点问题。本文对广西云开地区那蓬黑云母二长花岗岩体进行了详细的锆石年代学、地球化学特征及成因研究。结果显示：那蓬岩体LA-ICP-MS锆石U-Pb年龄加权平均值为（257.8 ±1.2） Ma，结晶年龄为晚二叠世；岩石主量元素具有富钾、富铝质特点，属于钙碱性岩石；微量元素主要富集大离子亲石元素（Rb、Th、U、K、Pb），亏损高场强元素（Nb、Ta、Ti、Zr、Hf）和Ba、Sr元素；稀土元素特征表现为轻稀土元素相对富集，重稀土元素亏损，稀土元素球粒陨石配分曲线呈右倾型，具有较明显轻重稀土分馏特征和负铕异常（δEu=0.41~0.66）。地球化学特征指示了花岗岩的物质来源主要为古老地壳杂砂-泥质源岩部分熔融，构造环境有可能形成于板块碰撞环境的后造山阶段。

Geochronology,Geochemical Characteristics and Genesis of Napeng Granite Biotite Monzogranite in Yunkai Area,Guangxi

The Indosinian period in South China experienced intense tectonic movement and magmatic activity, and the tectonic background of the Indosinian granite has always been a hot topic in earth science. A detailed study was conducted on the chronology, geochemical characteristics and genesis of zircon of the biotite monzogranite of Napeng in Yunkai area, Guangxi. The results show that the weighted average age of zircon U-Pb LA-ICP-MS zircon is (257.8 ±1.2) Ma, and the chemical analyses show that the Late Permian granitoids are classified as alkali-calcic rocks, which are characterized by enrichment of light rare earth elements (LREEs), large ion lithophile elements (LILEs), depletion of heavy rare earth elements (HREEs) and high field strength elements (HFSEs), and Ba, Sr, and obvious negative europium anomaly(δEu=0.41-0.66). All the geochemical characteristics suggest that the Napeng granitoid pluton experienced highly differentiated evolution. Through analyses, the material source of granite may come from the partial melting of the mixed sand-muddy source rocks in the ancient crust, and the tectonic environment may be formed in the post-mountain stage of the plate collision junction environment.