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昆仑关岩体位于广西南丹—昆仑关燕山期花岗岩带西南端,岩石类型为黑云母花岗岩.岩相学及化学成分显示其属高钾钙碱性岩系,具高硅、富碱和铝、低磷和钛的特点,SiO2含量为68.13～72.61,K2O/Na2O比值介于1.28～1.69之间,铝指数A/CNK=0.72～1.28,属准铝质一强过铝质岩石.富集Ga、Rb、Th、U、Pb等元素,而强烈亏损13a、Nb、Sr、P和Ti.稀土元素具明显负Eu异常,总体呈现轻稀土富集的右倾“V”形配分模式.昆仑关古民单元锆石LA-ICP-MSU-Pb定年结果为93±1Ma,形成于晚白垩世.矿物组成及地球化学特征确定了南丹—昆仑关花岗岩带是华南西南端一条重要的铝质A型花岗岩带,控岩断裂构造为NW向南丹一昆仑关深大断裂.岩石学及主量和微量元素(含稀土)特征表明岩体侵位于后碰撞阶段的张性构造环境.结合研究范围在晚白垩世的构造背景及区域应力场匹配组合关系,认为其与印度板块在该时期北移所引起的古太平洋板块高角度俯冲所导致的弧后拉张有关,与浙闽沿海A型花岗岩或碱性岩分别代表了匹配构造体制下的两条A型花岗岩带.
The Kunlun Pass Rock is located at the southwestern end of Yanshan granite belt of Nandan-Kunlun Pass in Guangxi Province, and the rock type is biotite granite.The petrographic and chemical compositions show that it is a high-K calc-alkaline rock series with high silicon, alkali-rich and aluminum , Low phosphorus and titanium, the content of SiO2 is 68.13 ~ 72.61, the ratio of K2O / Na2O is between 1.28 and 1.69, and the aluminum index A / CNK is 0.72 ~ 1.28, Ga, Rb, Th, U, Pb and other elements, and strongly depleted in 13a, Nb, Sr, P and Ti. The REEs have obvious negative Eu anomaly and generally show a light Rare Earth enrichment right-leaning “V” The result of LA-ICP-MSU-Pb zircon dating from ancient Kunlun Pass was 93 ± 1Ma, formed in the Late Cretaceous.The mineral composition and geochemical characteristics of the Nandan-Kunlunguan Granite Belt were identified as an important aluminum A Type granite belt and the controlled rock fracture are NW deep to the Nandan-Kunlunguan deep fault.The petrology and the characteristics of major and trace elements (including rare earth) indicate that the intrusive rock intrusive in the post-collision extensional tectonic environment.Based on the research scope In Late Cretaceous tectonic setting and regional stress field match the combination of relations, that the Indian plate in the After the arc ancient Pacific plate high angle northward period caused by the subduction caused tension related to Zhejiang and Fujian coastal A-type granite or alkaline rocks represent the two A-type granite belt in the match tectonic regime.