1:25万郴州幅区域地质调查主要进展及成果

通过地面地质调查、样品分析测试以及前人资料收集利用,全面查明了区内地层、岩浆岩和构造发育特征,系统总结了区内矿产资源概况和成矿地质条件.针对有关区域地质问题进行了深入研究,取得以下主要进展及成果:确定了南华系—寒武系中砂岩的主量元素和微量元素特征,反映其形成于被动大陆边缘环境;确定了中三叠世后期印支运动表现为NWW—SEE向区域挤压下的陆内俯冲造山,提出了印支运动中NW向基底隐伏断裂的左行走滑导致部分地区构造线走向偏转,炎陵—汝城一带发育的印支期隔槽式褶皱形成于基底(厚皮式)横向收缩与压扁作用;确定了中生代印支期、燕山早期和燕山晚期3阶段花岗岩的时限分别为233~210 Ma、174~135 Ma、130~85 Ma,形成构造环境分别为后碰撞、后造山和陆内裂谷;通过热年代学分析揭示了湘东南地区中、新生代山体隆升过程;厘定出湘东南及湘粤赣边区中生代构造发展框架;分析表明构造体制差异可能是造成湘东南燕山早期花岗岩成矿能力强于印支期花岗岩的关键原因,燕山早期钨锡多金属和铅锌多金属2类矿床组合的形成可能主要与岩石圈结构和深部热扰动强度有关.

Major progress and achievements in regional geological survey of 1:250000 Chenzhou sheet

Through surface investigation, sample testing and using previous data, the regional geological survey of 1∶250 000 Chenzhou sheet has studied the overall characteristics of the strata, magmatic rocks and structures, and has summarized the general situation of mineral resources. The regional geological survey has studied the granitic magmatism, the tectonic regime, the deformation dynamic mechanisms, the uplift process of mounts, the tectonic evolution and the tectonic-magmatic-mineralization dynamic mechanisms in Mesozoic, and studied the nature of the Nanhuan-Cambrian basin in southeastern Hunan in the central segment of the Nanling Mountains, and achieved progress as follows: ①the characteristics of major and trace elements suggested that the Nanhuan-Cambrian sandstones from southeastern Hunan were formed in a tectonic setting of passive continental margin; ②the Indosinian Movement in late Middle Triassic in southeastern Hunan was characterized by the intracontinental subduction-convergence controlled by the NWW-SEE compression; we suggested that the sinistral strike-slip motions of the NW-trending basement hidden faults in Indosinian Movement caused N-S-directed lineament in Shuikoushan-Xianghualing area and NWW-directed lineament in Jiangjunmiao-Anren area; we proposed that the trough like folds in Yanling-Rucheng area were formed by the transverse shrinking and flattening of the basement (thick-skin); ③the forming ages of the Indosinain, the Early Yanshanian and the Late Yanshanian granitoids were 233-210 Ma, 174-135 Ma and 154-163 Ma, and their forming tectonic settings were post-collisional setting, post-orogenic setting and intraplate rift setting, respectively; ④through the thermochronological dating study, we revealed that the Meso-Cenozoic uplift process of southeast Hunan could be divided into 4 stages, developing in order of fairly rapid uplift→rapid uplift→slow uplift→rapid uplift; ⑤studying on multiple geological elements, we defined the framework of Mesozoic tectonic evolution in southeastern Hunan and the Hunan-Guangdong-Jiangxi border area, which is of the Early Triassic-early Middle Triassic pre-orogenic stage, the late Middle Triassic-early Middle Jurassic intracontinental orogenic stage, the early Middle Jurassic-Late Jurassic post-orogenic stage and the Cretaceous intraplate rift stage; ⑥we also revealed that the first cause for the fact that the ore-forming capacity of the early Yanshanian granites in southeastern Hunan was far larger than that of the Indosinian granites is the differences in tectonic setting and tectonic regime, and the second cause is the difference in geochemistry of granites; we suggested that the formation of the W-Sn-polymetallic and Pb-Zn-polymetallic deposit assemblage is probably mainly related to such factors as the structure (or thickness) of the lithosphere, intensity of thermal perturbations in the deep interior of the Earth and corresponding scale of magmatism and depth of pluton emplacement.