青海东昆仑三通沟北沉积锰矿地质特征及形成时代探讨

东昆仑三通沟北锰矿床是近年来青海省发现的规模最大的海相沉积型锰矿。但目前该矿床研究程度较低,地质文献很少,尤其是赋矿岩系的形成时代及区域成矿地质背景存在争议。本文在赋矿岩系组成和矿床地质观察的基础上,重点对与锰矿关系密切的粉砂岩开展了碎屑锆石U-Pb年代学研究,同时对矿区硅质岩中发现的放射虫化石进行了种属鉴定。结果表明：最年轻碎屑锆石U-Pb年龄优势峰为478 Ma,硅质岩中放射虫化石属奥陶纪—志留纪海底生物分子中的贝奥苏克虫。综合研究表明,研究区赋锰岩系应形成于奥陶纪—志留纪,不是前人认为的中-晚元古代;通过对比研究表明青海东昆仑南带在早古生代的构造环境为弧后（裂谷）盆地,该裂谷盆地与原特提斯洋北向俯冲的动力学背景有关。

Geological characteristics and discussion on formation age of Santonggoubei sedimentary manganese deposit in eastern Kunlun of Qinghai

The Santonggoubei manganese deposit is the largest marine sedimentary manganese deposit found in Qinghai Province in recent years. At present, the research degree of the deposit is low and there are few geological documents. In particular, the formation age of ore-bearing rock series and regional geological background is controversial. On the basis of geological observation of host rock series and manganese deposit, the author analyzed the U-Pb age of detrital zircon from siltstone of the host rock, at the same time, radiolarian fossils found in siliceous rocks were identified. The results show that the dominant peak of the youngest detrital zircon U-Pb age is 478 Ma, and radiolarian fossils in siliceous rocks are benthic biomolecules from Ordovician to Silurian. The comprehensive results show that the manganese-bearing rock series in the study area should be formed in Ordovician to Silurian, rather than the Middle-Late Proterozoic thought by predecessors. It further provides a geological evidence for the tectonic environment of back arc (rift) basin by north subduction in eastern Kunlun in the Early Paleozoic.