广东大埔岩体LA-ICP-MS锆石U-Pb年龄、地球化学及其地质意义

发布时间：2018-06-08 10:02

本文选题：大埔岩体 + 锆石　；参考：《地质科技情报》2017年06期

【摘要】：大埔岩体位于粤东北地区,呈北东向的大岩基出露,出露面积约2 000km~2,主体岩性为中粒斑状黑云母二长花岗岩。对大埔岩体花岗岩岩石样品进行了LA-ICP-MS锆石U-Pb同位素测年,得到其结晶年龄为(143.8±1.5)~(139.2±1.1)Ma,属于晚中生代早白垩世,为燕山期岩浆活动的产物。岩体w(Al2O3)在11.98%~14.18%之间,A/CNK为1.01~1.15,AKI在0.77~0.89之间,里特曼指数σ为1.72~2.7,Rb/Sr比值为1.32~8.05(平均为4.19),Nb/Ta比值为6.45~12.99。岩石具中等-强的δEu负异常,稀土元素配分模式为海鸥型。结合区域构造背景及岩石地球化学分析认为,大埔岩体侵位结晶与区域上太平洋板块的俯冲后期岩石圈大面积伸展减薄、地幔物质上涌、形成大规模岩浆活动有关,形成于碰撞后的伸展构造环境。
[Abstract]:The Tai Po rock body is located in the northeast of Guangdong Province. It is a large rock base with an area of about 2 000 km / m ~ 2, and the main lithology is a mesomorphic porphyry biotite monzogranite. The LA-ICP-MS zircon U-Pb isotopic dating of granite samples from the Tai Po rock mass has been carried out. The crystallization age is 139.2 卤1.1 MaA, which belongs to the late Mesozoic early Cretaceous and is the product of Yanshanian magmatism. In the range of 11.98% to 14.18%, the ratio of A- / CNK is 1.01 / 1.15A = 0.77 / 0.89 and the Rtman index 蟽 is 1.72 / 2.7N / r / Sr = 1.32 / 8.05 (the average value is 4.19 / nb / Ta = 6.4512.99). The rocks have moderate to strong 未 EU negative anomalies and the REE distribution model is seagull type. Combined with regional tectonic setting and petrogeochemical analysis, it is concluded that the emplacement crystallization of the Tai Po rock mass is related to the large area extension and thinning of lithosphere in the late subduction of the upper Pacific plate, the upwelling of mantle material, and the formation of large-scale magmatic activity. Formed in the post-collision extensional tectonic environment.
【作者单位】：广东省地质调查院;
【基金】：中国地质调查局项目“广东1∶5万明山嶂煤矿、高陂圩、砂田圩、潭江圩四幅区域地质矿产调查”(1212011220554);“广东1∶5万丰顺县、坪上、五经富、揭阳县幅区域地质调查子项目”(DD20160032-18)
【分类号】：P588.1;P59

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