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义敦岛弧南段的中甸岛弧印支期浅成-超浅成斑岩体与成矿密切相关,本文对该地区代表性的成矿斑岩如西侧的雪鸡坪、东侧的欠虽等岩体开展了高精度的LA-ICPMS锆石U-Pb定年,获得雪鸡坪成矿斑岩的年龄为213.4±1.5Ma,欠虽石英闪长玢岩年龄为217.1±1.5Ma。本研究和近几年发表的高精度锆石U-Pb年代学成果发现前人划分的中甸岛弧地区东、西成矿斑岩带的斑岩体形成时代没有明显的差异,这些斑岩体呈面状分布,其形成时代集中在223~211Ma,应该属于同一构造作用的产物。同时,这些成矿斑岩的锆石REE配分模式图显示一致的成分趋势,具有强烈的Ce正异常和相对较低的Eu负异常,指示出岩浆过程具有高的氧逸度。结合它们埃达克质的地球化学研究成果,我们认为中甸岛弧成矿斑岩以及相关的斑岩矿床是在东侧的甘孜-理塘洋晚三叠世俯冲过程中形成的,俯冲板片熔体的参与形成了高氧逸度富金属的岩浆,其对区内成岩和成矿过程具有重要意义。
The Indosinian epicanthic epicontinental porphyry in Zhongdian Island in the southern section of Yidun Island is closely related to metallogenesis. In this paper, representative ore-forming porphyries in the area, such as Xuejiping on the west side, east side , The zircon LA-ICPMS zircon U-Pb dating with high accuracy has been carried out. The age of the Xuejiubing mineralized porphyry is 213.4 ± 1.5Ma, and the age of the quartz diorite porphyrite is 217.1 ± 1.5Ma . In this study and the high-accuracy zircon U-Pb dating published in recent years, it is found that there is no obvious difference in the age of porphyry formation of the eastern and western mineralized porphyry belts in the Zhongdian arc area previously distributed. The porphyry bodies It is distributed in the shape of surface and its formation time is concentrated in 223 ~ 211Ma, which belongs to the product of the same tectonic effect. At the same time, zircon REE partitioning patterns of these mineralized porphyries show a consistent compositional trend with strong Ce positive anomalies and relatively low Eu anomalies, indicating that the magmatic processes have high oxygen fugacity. Combined with their adakitic geochemical findings, we believe that the Zhongdian arc-forming porphyry and related porphyry deposits were formed during the late Triassic subduction of the Garzê-Litang Ocean in the east, The involvement of sheet melts forms a magma with high oxygen and fugacity, which is of great significance to diagenesis and mineralization in the area.