广东省河台金矿区糜棱岩锆石LA-ICP-MS U-Pb年龄及其地质意义

发布时间：2018-05-05 18:59

本文选题：糜棱岩 + 热液锆石　；参考：《岩石学报》2017年06期

【摘要】：河台金矿区位于广东省高要市境内,普遍认为其是典型的韧性剪切带型金矿。本次对采自韧性剪切带中的糜棱岩和初糜棱岩样品进行了LA-ICP-MS锆石U-Pb定年,以约束剪切带的活动时代,并为金矿化事件提供依据。利用糜棱岩中的热液锆石约束韧性剪切带的变质变形时间,获得两组年龄:糜棱岩中热液锆石增生边加权平均年龄约为240Ma,代表左旋运动的年龄;初糜棱岩中热液锆石加权平均年龄约为204Ma,代表右旋运动的年龄。因此,矿区在印支期可能经历过两期剪切变形,并且这两期变形事件在整个华南都是普遍存在的。结合前人对矿化时间的研究,河台金矿的成矿时间(燕山期)要晚于韧性剪切带的形成时间(印支期)。样品中继承性锆石(糜棱岩中核部锆石)年龄显示云开群最晚沉积时间为早古生代早期,而并非前寒武地层。另外,本次研究还测试了锆石的Lu-Hf同位素,实验表明,可以根据热液锆石与继承性锆石的Lu-Hf同位素关系,判定热液锆石的形成条件。云开群的成岩物质主要来自1.8Ga地壳增生事件所形成的地壳物质发生重熔而产生的岩浆岩。
[Abstract]:The Hetai gold deposit is a typical ductile shear zone gold deposit located in Gaoyao City, Guangdong Province. The LA-ICP-MS zircon U-Pb dating of mylonite and primary mylonite samples from ductile shear zone has been carried out in this paper in order to constrain the active age of shear zone and to provide basis for gold mineralization. Based on the metamorphic deformation time of hydrothermal zircon confined ductile shear zone in mylonite, two groups of ages are obtained: the weighted average age of hydrothermal zircon accretion edge in mylonite is about 240 Ma, representing the age of left-lateral movement; The weighted mean age of hydrothermal zircon in the primary mylonite is about 204 Ma, representing the age of dextral movement. Therefore, the ore area may have experienced two shear deformation periods during the Indosinian period, and these two deformation events are common in the whole South China. In combination with previous studies on mineralization time, the metallogenic time of Hetai gold deposit (Yanshanian period) is later than that of ductile shear zone (Indosinian period). The age of inherited zircon (core zircon in mylonite) indicates that the latest deposition time of Yunkai group is early early Paleozoic and not Precambrian formation. In addition, the Lu-Hf isotopes of zircons have been tested. The results show that the formation conditions of hydrothermal zircons can be determined according to the Lu-Hf isotopic relationship between hydrothermal zircons and inherited zircons. The diagenetic material of Yunkai Group mainly comes from magmatic rock formed by remelting of crustal material formed by 1.8Ga crustal accretion.
【作者单位】：中国科学院广州地球化学研究所中国科学院矿物学与成矿学重点实验室;中国科学院大学;中南大学有色金属成矿预测教育部重点实验室;广东省地质局第五地质大队;
【基金】：国家重点研发计划重点专项(2016YFC0600401) 中南大学有色金属成矿预测教育部重点实验室开放基金项目(2016YSJS003) 中国地质调查局项目(12120114052801)联合资助
【分类号】：P597.3;P618.51

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