关于湘西北红岩溪地区沉积-构造-成矿研究的一些认识

湘西北红岩溪地区处于湘西—鄂西多金属成矿带的中南部,属上扬子地块东南缘,主要沉积自寒武纪至志留纪地层,沿NE向红岩溪断裂在奥陶系桐梓组、红花园组灰岩中分布了大量铅锌矿点。以地层、岩石、构造特征为研究对象,突出对含矿地层、岩石、构造的刻画,查明了成矿地质背景和成矿条件,总结了成矿规律。通过分析奥陶纪—志留纪的桐梓组风暴沉积岩、红花园组生物礁灰岩、宝塔组龟裂纹构造、新滩组远源浊积岩等现象的形成机理,建立了区内奥陶纪—志留纪的沉积-构造演化模型,指示地质背景从伸展体制的被动大陆边缘演化为挤压体制的前陆盆地; 查明了区内断裂构造与铅锌成矿的关系,认为NE—NNE向断裂为铅锌的导矿构造,而NW向小断裂则为主要容矿构造; 从流体包裹体方面探讨了铅锌成矿环境,成矿热液与盆地热卤水较为相似,成矿流体原始来源为层间水和大气降水,最终建立了区内铅锌成矿模型。

Research on sedimentary tectonic metallogenic of Hongyanxi area in the northwest Hunan

Hongyanxi area in the northwest of Hunan is on the south central of Xiangxi-Exi polymetallic metallogenic belt and it belongs to the southeast of upper Yangtze region. The major sedimentary formations are from Cambrian to Silurian and there are many Pb-Zn deposits along Hongyanxi fracture with northeast strike. These Pb-Zn deposits are in the limestone of Tongzi Formation and Honghuayuan Formation of Ordovician period. Firstly, this paper used stratum, rock and tectonic feature to characterize stratum, rock and tectonic feature about the Pb-Zn mine, found out the metallogenic geological background and qualification, and summarized the metallogenic law. This study also analyzed the forming mechanisms of the storm deposit in Tongzi Formation, bioherm limestone in Honghuayuan Formation, crazing construction in Baota Formation and turbidities of far source in Xintan Formation. So the model of Ordovician-Silurian sedimentary tectonic evolution was built, which was from passive continental margin (extensional system) to foreland basin (compressional system). Secondly, this paper investigates the connection between fracture and Pb-Zn deposits, and found out the faults strike to northeast and north-north-east are the ore-transmission structures, and those pointing to northwest are ore-hosting structures. Also the form of metallogenic environment of Pb-Zn deposit from aspect of fluid inclusion was discussed. The results show the mineralizing hydrothemal is similar to the hot brine in the basin, which is originally coming from interlayer and meteoric water. Finally, the Pb-Zn metallogenic model was built.