新疆东准噶尔松喀尔苏斑岩型铜金矿床的火山构造系统及其控矿作用

摘要

The Songkaersu Cu-Au deposit is located in the south part of the Karamaili tectonic belt and is related to the continental volcanic rocks in Carboniferous continental volcanic belt. Based on studying the lithofacies, patterns, features and stress field of the ore-controlling volcanic structural systems, this paper discusses its evolution, mechanism and model. Our study indicated that (1) the volcanic structural systems are composed of regional continental volcanic belt, volcano-tectonic depression, and caldera (dome), at different scales;(2) The ore-forming processes are controlled by the volcanic structural systems. It has proved that the volcano-tectonic depression is restricted by regional NW-trending deep-seated faults, and one of the caldera groups with ring and radial faults defined by the Devonian basement in the ore field. Both host porphyry and its mineralization extent are defined by the convergence of the SN- and EW-trending volcanic faults. Moreover, the ore-bodies and mineralization type are related to their spatial association with the host porphyry, and the NE-trending faults also contributed to the superposition of the Au mineralization;(3) Tectonic systems include levels from dominant fault systems to basement fault systems, volcanic fault systems, and intrusive contact structure systems. Ore-controlling tectonic processes are related to stress of different period, with SN stress from Late Devonian to Early-Middle Carboniferous and NW stress from Late Carboniferous to Permian. The SN stress could display as NW-trending dextral strike-slip faults, clockwise rotary of adjacent block, and beginning of volcano-tectonic systems. The NW stress could show as volcano faults, superimposed the NE trend slip joints, with linear distribution of volcanic rocks, and epithermal Au mineralization; (4) The conversion of the SN stress and NW stress resulted in lithospheric delamination and asthenosphere mantle underplating under post-collisional environment; (5) The ore mineralization occurs mainly in the contact of the porphyry and the origin of the deposit is of porphyry-type. The main exploration targets are inferred to be the NE part of host porphyry and the contact.%松喀尔苏铜金矿床位于卡拉麦里石炭纪陆相火山岩带，属于与陆相火山–侵入岩有关的斑岩型铜金矿床。文章分析了火山构造系统、及其控制作用和构造应力场，结合区域构造演化，探讨了矿床控矿火山构造演化和机制，构建了控矿模式。研究表明：(1)火山构造系统依次分类为陆相火山岩带→火山构造盆地→破火山口(火山穹窿)。控矿火山构造类型是具有环状和放射状断裂的破火山口构造。(2)火山构造系统控矿作用表现在 NW 走向的区域深大断裂控制火山构造盆地， NW走向的基底断层控制串珠状破火山口构造，赋存于泥盆系基底内的破火山口构造以及派生的EW走向和SN走向的火山断裂交汇部位控制含矿斑岩体侵入和矿化带形成，岩体侵入过程中发生的侵入接触带构造控制矿体和矿化类型， NE走向断裂和剪切裂隙密集带则有利于矿化的叠加。(3)构造系统从主断裂构造带系统向基底断层系统、火山断裂系统和岩体接触带系统依次演化。控矿构造作用与晚泥盆世–早石炭世早中期SN向构造作用和早石炭世晚期–二叠纪NW向构造作用有关：晚泥盆世–早石炭世早中期， SN向挤压构造作用引发NW走向的断层右行走滑剪切、块体顺时针旋转和火山构造控矿系统；早石炭世晚期–二叠纪，来自SN方向和EW方向联合挤压作用下产生的NW方向的构造作用，使得火山断裂构造进一步发育，引起 NE 走向剪切面理的叠加改造、陆相火山岩线状分布和浅成低温金成矿作用。(4)后碰撞早期挤压–伸展转换环境，早期SN向持续缩短和后期NW向构造作用使构造体制转换，诱发深部岩石圈拆沉作用和软流圈地幔底侵作用，是斑岩型铜金成矿作用和控矿火山构造演化的重要机制。(5)控矿模式明确接触带和斑岩型为主要矿化部位和勘查类型，外围北东侧岩体与接触带是重要勘查区域。