川西南大梁子铅锌矿区F15主控断裂及其控矿作用机制

大梁子铅锌矿是川西南矿集区典型的大型矿床之一, 矿床(体)的空间展布严格受F15主控断裂及其次级构造控制, 它们为成矿流体运移和矿质沉淀提供了有利场所。针对该矿床成矿构造体系、F15主控断裂及其控矿作用的核心问题, 应用矿田地质力学理论与方法, 通过主控断裂几何学、运动学、力学、构造岩、构造期次等方面的解析, 结合地球化学研究, 认为F15主控断裂在成矿期具有导矿和容矿的特征, 主走滑-断褶构造组合样式(负花状构造)是该矿床的主要构造组合样式。F15主控断裂主要表现出2期构造活动: 早期(印支中晚期—燕山早期)因NW—SE向主压应力作用, 形成右行扭张-张扭性构造, 晚期(燕山中—晚期)因NE—SW向主压应力作用, 断层转化为左行扭性-扭压性, 右行扭张-张扭性及派生出的一系列NWW—NW向张性断裂、NE向压扭性断裂及NE向SW倾伏主背斜组合而成的NE向构造带, 为主要成矿构造体系。与铅锌成矿有关的Zn-Pb-Cd-Sb-Hg-Ag-As等元素组合和与深部流体有关的Mo-Tl等成矿元素组合均表现为明显富集现象; 成矿流体沿F15导矿构造"贯入", 沿次级NWW—NW向断裂和NE向SW倾伏主背斜、层间断裂构造系统发生"贯入"-交代作用, 形成矿床。该研究不仅对大梁子铅锌矿深部及外围找矿具有实际意义, 对于川西南铅锌多金属矿集区构造控矿规律研究也具有科学价值。

F15 master-control fault and its ore-controlling effect of the Daliangzi lead-zinc deposit of southwestern Sichuan

The Daliangzi lead-zinc deposit is one of the typical large-scale deposits in the southwestern Sichuan ore concentration area whose spatial distribution is strictly controlled by F15 main control fault and the supporting secondary structure, which provide a favorable place for ore-forming fluid migration and mineral precipitation.Aiming at the core issues of the metallogenic tectonic system of the deposit, the F15 main controlled fault and its ore-controlling effect, appling Mining Field Geomechanics Theory and Method, by analyzing the geometry, kinematics, mechanics, tectonic rocks, and tectonic stages of the dominant faults and combining geochemical research, it is considered that the F15 main control fault has the characteristics of ore-conducting and ore-hosting during the metallogenic period.The main strike-slip-fault-fold structural combination(negative flower-like structure)is the main structural combination of this deposit.The F15 main ore control fault obviously shows two stages of tectonic activity: In the early stage(middle late Indosinian to early Yanshanian), right strike-slip tensional to right tensional strike-slip structures were formed due to NW-SE trending principal compressive stress.In the late stage(middle late Yanshanian), the fault was transformed into left strike-slip to left strike-slip compressional due to NE-SW trending principal compressive stress.The main metallogenic structural system is the NE structural belt composed of the right strike-slip tensional to right tensional strike-slip structures and its derivation of a series of NWW-NW trending extensional faults, NE compressional fracture and NE trending SW side dipping main anticline.The combination of elements such as Zn-Pb-Cd-Sb-Hg-Ag-As related to lead-zinc mineralization and the combination of metallogenic elements such as Mo-Tl related to deep fluids are obviously enriched.The ore-forming fluids "penetration" along the F15 ore-conducting structure, and "penetrates"-metasomatism occurs in the structural system along the secondary NWW-NW-trending faults and the NE-trending SW-trending main anticlines and interlayer faults.This study is not only of practical significance to the deep and peripheral prospecting of Daliangzi lead-zinc mine, but also of scientific value to the study of the structural ore control law of the lead-zinc polymetallic ore concentration area in the southwestern Sichuan.