摘要
为探讨陕西凤太矿集区八卦庙金矿床绿泥石的成岩成矿意义,运用电子探针分析了矿床中围岩、不同成矿阶段及煌斑岩脉中的绿泥石。结果显示,矿区内绿泥石的分布特征可以分为4类:分布在围岩中由黑云母蚀变而成(Ⅰ型)、叶片状或鳞片状、与石英硫化物共(伴)生的绿泥石脉(Ⅱ型)、蠕虫状包裹在石英颗粒中(Ⅲ型)及由钠长石蚀变具钠长石假晶的绿泥石(Ⅳ型)。前3种主要为蠕绿泥石(铁绿泥石),含少量密绿泥石,Ⅳ型分布在铁镁绿泥石和蠕绿泥石(铁绿泥石)的范围,均指示形成于偏还原环境。在其结构的离子置换中既有Fe对Mg的置换,也有Mg对Fe的置换,表明绿泥石的形成既与泥质碎屑岩围岩有关,也受到富铁、镁的成矿流体影响。由绿泥石地质温度计估算出4类绿泥石的形成温度为198~255℃,均属于中-低温热液蚀变范围。在金成矿过程中,随着温度不断下降热液流体性质由弱酸性→近中性→弱酸性演化。金矿化的有利形成环境为近中性。
In order to discuss petrogenic and ore-forming significances of chlorite of the Baguamiao gold deposit in Shaanxi province,the chlorite minerals from wall rocks,lamprophyre and ores of different stages were chemically analyzed by means of electron-microprobe.Four types of the chlorite in the deposit were identified,namely chlorite derived from altered biotite in wall rocks(typeⅠ),chlorite in(with)quartz-sulfide veins(typeⅡ),wormlike chlorite included in quartz(typeⅢ)and chlorite in altered albite in lamprophyre(typeⅣ).The former three types of chlorites are mainly Fe-rich prochlorite and minor pycnochlorite,indicating that they could be formed in a partial reducing environment.The phenomenon that Mg ions were mainly substituted with Fe ions in its lattice suggests that the formation of those chlorites is closely associated with the argillaceous wall rocks under several metamorphisms,and affected by mafic hydrothermal fluid.According to the chlorite geothermometer,these chlorites were formed in low-moderate temperature ranging from 198℃to 255℃.It is believed that the hydrothermal fluid was gradually evolved from faintly acid to nearly neutral and finally to faintly acid with the continuous decrease of temperature in the mineralization process.Favorable formation environment of gold is close to neutral conditions.
作者
张娟
刘新星
王义天
陈绍聪
胡乔青
刘协鲁
ZHANG Juan;LIU Xinxing;WANG Yitian;CHEN Shaocong;HU Qiaoqing;LIU Xielu(Hebei key Laboratory of strategic Critical Mineral Resources/Hebei GEO University,Shijiazhuang 050031,Hebei,China;MNR Key Laboratory of Metallogeny and Mineral Assessment/Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;Beijing Institute of Exploration Engineering,Beijing 100083,China)
出处
《地质通报》
CAS
CSCD
北大核心
2021年第4期586-603,共18页
Geological Bulletin of China
基金
中国地质调查局项目《秦岭-大巴山-大别山成矿规律及找矿方向研究》(编号:1212011220869)
河北省高等学校科学技术研究项目《冀东峪耳崖金矿床黄铁矿中矿物包裹体微区研究》(编号:QN2019144)。
关键词
绿泥石
电子探针
组成特征
形成环境
八卦庙金矿床
陕西
chlorite
electronmicroprobe
characteristics of compositions
forming environment
Baguamiao gold deposit
Shaanxi Province
