三山岛西部海域构造带发现及其地质意义

胶东金矿集中区金矿十分发育,截至目前,陆地已探明资源储量的金矿床有200余处,近年来,地质工作者将找矿目标转向近岸海域,2013—2018年,山东省地质调查院利用地质调查专项及省地勘资金项目,在三山岛海域开展地质矿产调查工作。通过开展海上重力测量,在三山岛西部海域发现近似平行于三山岛断裂带的一条重力梯级带。利用海上钻探验证揭露了前寒武纪变质岩与岩体的接触面,通过SHRIMP锆石U-Pb测年,确定该岩体为中生代晚侏罗世玲珑二长花岗岩。对比该梯级带与三山岛断裂带,在重力场均表现为南陡北缓,南端验证均见到前寒武纪变质岩与玲珑二长花岗岩界面,且三山岛断裂带上具有规模的矿床均分布在北段重力场较缓的部位,结合钻探验证及样品分析,推断该梯级带北段具有较好的找矿潜力。

Discovery of Structural Belt in Western Sanshan Island and Its Geological Significance

There are more than 200 gold deposits in Jiaodong gold concentration area. In recent years, geologists have turned their prospecting targets to offshore areas. From 2013 to 2018, by using special funds for geological survey and provincial geological survey funds, geological surveying and mineral resources surveying have been carried out by Shandong Institute of Geological Surveying in Sanshandao sea area. By means of marine gravity survey, a gravity gradient zone approximately parallel to Sanshandao fault zone has been found in western Sanshandao. The contact surface between Precambrian metamorphic rock and rock body is revealed by offshore drilling verification, and the rock body is identified as Linglong monzogranite of Mesozoic late Jurassic by SHRIMP zircon UPb dating. Comparing with Sanshandao fault zone, the gravity field of the cascade zone is steep in the south and gentle in the north. The interface between Precambrian metamorphic rock and Linglong monzogranite can be seen in the south. Moreover, the largescale deposits in Sanshandao fault zone are distributed in gentle gravity field in the north. Combining with drilling verification and sample analysis, it is inferred that the northern part of the cascade zone has good prospecting potential.