摘要:
南岭以花岗岩广泛分布闻名于世,但也存在基性超基性侵入岩。位于赣南安远蔡坊镇的路迳似金伯利岩(金伯利质煌斑岩)就是其中之一。本研究在野外调研的基础上,利用高灵敏高分辨离子探针(SHRIMP)锆石定年技术对其成岩时代进行了研究,获得其U-Pb年龄为132.0 Ma(变化于128.7~135.4 Ma)。同时还发现了早期锆石捕获晶,其年龄为1945 Ma,意味着赣南地区存在古元古代的基底。这一结果一方面弥补了原先根据K-Ar法和Rb-Sr法将似金伯利岩定为新生代的不足,为探讨赣南地区大地构造演化历史提供了准确资料;同时也表明燕山晚期的构造体制转换与壳幔相互作用是有关的,似金伯利岩岩浆可能起源于富集地幔。
Abstract:
The Nanling area is famous for its widely distributed granites, however, there are also many mafic to ultra-mafic intrusion, Lujing kimberlite-like rock (kimberlitic lamprophyre), located in Caifang Town, Anyuan Country of South Jiangxi province, being one of these intrusions. Based on a field survey, we investigated the rock formation time of Lujing by SHRIMP zircon U-Pb dating, and determined its age as 132.0 Ma (range in 128.7-135.4 Ma). Meanwhile, early xenocryst of 1945 Ma old was found, which indicates that there is a Palaeoproterozoic basement in the South Jiangxi area. Firstly, this result revises the previous determination of the Lujing kimberlite-like rock as Caenozoic by K-Ar and Rb-Sr dating method, and provides new correct data for investigating the evolutionary history of tectonic structures of the South Jiangxi area. Secondly, this result indicates that the transformation of the tectonic system in the late Yanshanian period is related to the interaction of crust and mantle, and the magma of the Lujing kimberlite-like rock may have originated from enriched mantle.
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