云南兰坪金顶铅锌矿床构造特征与演化分析

Tectonic features and evolution of the Jinding Zn-Pb deposit of Lanping basin inYunnan

金顶超大型铅锌矿床赋存于三江褶皱带南段兰坪盆地北部,成矿条件优越。为详细厘定矿区构造特征及其演化过程,在矿区范围内实施了大比例地质修测。矿区复杂多变的地层-构造格架为区域上大规模走滑事件、褶皱-逆冲推覆事件、成矿后伸展事件3期构造作用叠加的产物。赋矿层位古新统勐野井组(E_1m)沉积形成于大规模走滑系统期间,经东西向挤压形成早期轴向近南北的开阔复式褶皱。矿区位于区域上逆冲推覆构造系统的前锋带,在大规模挤压作用下形成逆冲断裂系主推覆面F_8,以及次级层间滑动断裂F_2。金顶构造穹隆为早期开阔复式褶皱与褶皱-逆冲推覆事件中形成的冲断褶皱横跨式构造叠加的结果,不协调褶皱之间的虚脱部位为金属元素沉淀提供重要的容矿空间。成矿后高原隆升与伸展事件中形成的以F_5、F_4、F_(27)、F_(24)为代表的断裂,叠加改造早阶段形成的构造,形成矿区不规则网格状的构造格架,加上差异性剥蚀,共同制约着矿体的变化与保存。

The large-scale Jinding Zn-Pb deposit,located in the north of Lanping Basin,south of the Sanjiang orogenic belt,with advantageous metallogenic conditions.In order to determine the structural characteristics and evolution process of the mining area in detail,the authors have implemented a large-scale geological revision survey in the mining area.The complex and changeable stratigraphic-tectonic framework of the mining area is the product from three times regional tectonic superposition,including large-scale strike-slip,bidirectional foldthrust nappe and post-mineralization extension.The ore-bearing strata of Paleocene Mengyejing Formation(E1m)was formed during a large-scale strike-slip fault,as an early open complex fold in axial and near northsouth direction under east-west compression.The mining area is located in the front zone of the regional thrust nappe system.The main thrust fault F8 and the secondary interlayer sliding fault F2 are formed under the action of large-scale compression.The Jinding structural dome is the result of the superimposition of thrust fold straddling tectonics formed in the events of early open composite fold and fold-thrust nappe.The collapse locations between discordant folds provide space for metal elements’precipitation.The faults represented by F5,F4,F27 and F24 were formed during the uplift and extension of the plateau after mineralization,and the irregular grid structure framework of the mining area is come from superimposing and transforming of earlier structures.This structure framework,coupled with differential denudation,restrict the transformation and preservation of ore bodies.