东昆仑五龙沟金矿田控矿构造带的变形条件——来自EBSD组构的启示

Deformation Conditions of Ore-controlling Structural Zone in the Wulonggou Gold Orefield,Eastern Kunlun Mountains:Evidence from EBSD Fabrics Analysis

五龙沟金矿田是东昆仑地区最重要的金矿集中区之一,金矿田主要控矿构造为偏脆性断裂破碎带,在三条控矿构造带中仅在萤石沟—红旗沟构造带邻近北侧的局部出露韧性变形带。本文作者运用电子背散射衍射技术(EBSD)技术方法,对东昆仑五龙沟金矿田萤石沟—红旗沟构造带变形岩石的组构分析显示,花岗质糜棱岩韧性变形强烈,大部分样品石英变形机制是以中温I级柱面(1010)<1120>滑移为主,变形式样比较单一;少量样品为中高温II级柱面(101—0)<0001>滑移和中低温底面(0001)<112—0>滑移。从岩石组构特点结合宏观构造分析,五龙沟金矿田萤石沟—红旗沟构造带及其邻近北侧经历了中-中深层次、中-中高温条件(15~25 km,t=350~550°C,P=0.40~0.60 Gpa)的韧性变形,局部叠加中浅层次、中低温条件(10~15 km,t=250~350°C,P=0.25~0.40 Gpa)的韧脆性变形;而岩金沟和三道梁—苦水泉构造带为低温低压条件的脆性破碎带。结合变形花岗闪长岩年代学资料,确定构造变形时代为早中生代。

The Wulonggou gold orefield is one of the most important gold ore concentration areas in Eastem Kunlun Mountains, and three brittle ore-controlling fault fracture zones are developed in the orefield, i.e., Yanjingou zone, Yinshigou-Hongqigou zone and Sandaoliang-Kushuiquan zone. The ductile deformation is only outcropped in some areas near the northern side of the Yinshigou-Hongqigou structural zone. Based on the EBSD petro-fabrics analysis of deformed rocks from Yinshigou-Hongqigou structural zone of the Wulonggou gold orefield, the authors have drawn the conclusions as follows. （1） There happened a strong deformation of the rocks in some area near the northern side of the Yinshigou-Hongqigou structural zone in the orefield. （2） Quartz in most granitic mylotite samples was mainly deformed along its prismatic I glide system with a single deformation type, while quartz in partial samples was deformed along its prismatic II and basal or basal-near glide system. （3） The deformation of the mylotite occurred mostly at a medium and medium-great depth of 15-25 km, at a middle and med-high temperature of 350-550℃ and under a middle pressure of 0.40-0.60 GPa, with only part of them being superimposeddeformation late at a low-medium depth of 10-15 km and a low-middle of pressure of 0.25-0.40 GPa. （4） There developed brittle fracture 250-350℃ and under a low-middle zone in Yanjingou zone and Sandaoliang-Kushuiquan zone. （5） Combined with the age of deformed granodiorite, the authors consider that the ductile deformation in the orefield occurred in early Mesozoic.