黔东北燕山期构造变形特征及对华南"大塘坡式"锰矿勘查的影响——以普觉锰矿床犁式正断层为例

黔东北地区大地构造位置位于扬子板块西南部,自元古宙以来经历了多期次构造变形。不同期次的构造叠加对区内早期形成的沉积型矿产的埋藏和保存产生了重要影响。文章针对黔东北地区燕山期构造变形,采用中小尺度构造解析的方法开展露头尺度的构造样式、叠加关系剖析研究,同时,对研究区广泛发育的犁式正断层及其对南华纪"大塘坡式"锰矿的找矿勘查进行深入探讨。现有勘查成果认为犁式正断层为燕山早期—燕山晚期应力体制转换产物,该类断层倾角随深度增加而渐趋于缓,断距和断层错断区域伴随深度增加而加大,并伴生少量次级陡倾角分支断裂。冷水溪犁式断裂及其分支断裂将贵州松桃普觉超大型锰矿床体切割为多个独立单元,造成锰矿层不连续,且在矿区内形成了大小规模不等的断层错断区域。同时,由于冷水溪断层上盘下降,上盘锰矿体的埋藏深度增加,断层错断区域亦伴随深度加深而加大。对冷水溪犁式断层及其对锰矿体之间关系的分析,有利于深入研究整个黔湘渝地区"大塘坡式"锰矿的埋藏与保存特征,对助推区域上深部锰矿勘查,合理规避勘探风险具有重要的现实意义。

Structural deformation of northeastern Guizhou during Yanshanian period and its influence on exploration of Datangpo manganese deposits in South China: A case study of plow-type normal faults in Pujue Mn deposit

Northeastern Guizhou is located in the southwest of Yangtze plate, which has undergone multiple tectonic de-formation since Proterozoic. Structural superimposition at different stages had an important influence on the burial and preservation of sedimentary deposit of the early stage. In this paper, tectonic deformation in northeastern Guizhou in Yanshanian period was analyzed by using analytical method for meso- and micro-scale geological structures, and outcrop-scale structural styles and superposition relation were studied. In addition, extensively developed listric normal fault in the study area and ore-search prospective of "Datangpo type" manganese deposits were investigated. Listric normal fault is considered to be stress regime transition products of Early Yanshanian to Late Yanshanian period. The fault dip gradually decreases with depth, while the fault throw and fault gap increase with depth, associated with a few secondary steep dip branching faults. Denudational fault and its branching faults in Lengshuixi cut the superlarge manganese deposit into several independent units at Pujue Town in Songtao County, which caused discontinuity of manganese ore and gaps of varying sizes in the mining area. Moreover, the burial depth of manganese ore in the hanging wall and the gap increases with depth because of the declining of upper wall of Lengshuixi fault. The analysis of the relation between Lengshuixi listric fault and manganese orebody is conducive to the further study of the burial and preservation characteristics of "Datangpo type" manganese deposits in the whole region of Guizhou, Hunan and Chongqing; besides, it could help to promote the exploration of manganese deposits in upper and deep regions, and it has important practical significance for reasonable avoidance of exploration risk.