湖南城步地区1∶5万区调主要成果与进展

New Progresses in 1:50 000 Regional Geological Survey in Chengbu Area,Hunan Province

在湖南西南部城步地区开展的1∶5万区域地质调查,比较完整地建立了该区地层、构造格架以及岩浆演化序列。在青白口纪黄狮洞组火山岩夹层中获得锆石SHRIMP U-Pb年龄值828±10 Ma,为解决该地区乃至更大区域地层对比等基础地质问题提供了重要的年龄依据。根据岩体的接触关系、岩石学特征以及本次工作获得的同位素年龄资料,首次对测区花岗岩进行了详细的解体,共划分为12个侵入次、31个侵入体,并归并成青白口纪、志留纪、晚三叠世、中侏罗世四个岩浆演化系列,青白口纪片麻状花岗岩的发现提高了测区岩浆岩的研究程度。查明并阐述了"城步-江口大断裂"在区内的表现形式,建立了该区比较完整的构造变形序列,重塑了该区地质发展史。通过水系沉积物测量和异常查证,新发现矿(化)点15处,特别是发现了平滩中型钨矿,并为下一步找矿工作提供了明确的找矿远景区和找矿靶区。

Stratigraphic framework, tectonic framework and magmatic evolutionary series have been established in 1：50 000 regional geological survey in Chengbu, southwestern Hunan province. The deposition of Huangshidong Formation of Qingbaikouan System is at 828＋ 10 Ma which is yielded by zircon SHRIMP U-Pb dating. According to the contact relationship, rock characteristics and the isotope ages new-acquired, we subdivided the granite-bodies in Chengbu area into 12 intrusive periods, 31 intrusive masses, and merged into four magmatic evolutionary series： Qingbaikou Period, Silurian Period, Late Triassic Period and Jurassic Peri- od. The new discovery of gneissose granite of Qingbaikou Period greatly improved the study of magmatic rocks in this area. Structural feature of Chengbu-Jiangkou rupture fault is investigated and the integrated tectonic deformation succession of Chengbu area is rebuilt, so as geological history. 15 ore occurrences （including Pingtan medium-size scheelite deposit） are discovered by stream sediments analysis and mineralized abnormalities check, the newly discovery would provide exploration target for the next step prospecting work.