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内瀚岩体位于云开地块西北缘,总体沿罗定—广宁断裂呈北东向展布,出露面积超过600 km2,岩性以中细粒黑云母二长花岗岩为主。对内瀚花岗岩代表性岩石样品进行LA-ICP-MS锆石U-Pb同位素测年,得到其结晶年龄为246.7±7.1 Ma,为印支期岩浆活动的产物。结合区域构造背景及岩石地球化学分析认为,内瀚岩体侵位结晶与区域上印支期广泛的碰撞造山、地壳增厚存在密切的关系,与地壳局部熔融具有动力成因联系。
Neihan rock body is located in the northwestern margin of the Yunkai block. It is generally distributed along the Luodong-Quang Ninh fault in the northeast direction with an exposed area exceeding 600 km2. The lithology is dominated by medium-fine biotite monzogranite. LA-ICP-MS zircon U-Pb isotope dating of the representative Hu Neo-granite samples was performed. The crystallization age was 246.7 ± 7.1 Ma, which was the product of Indosinian magmatism. According to the regional tectonic setting and lithogeochemical analysis, it is concluded that there is a close relationship between the intrusion crystallization of Neihan rock mass and the extensive collision orogeny and crustal thickening in the Upper Indosinian in the area, and the dynamic contact with local melting of the crust.