南秦岭汉阴北部金斗坡矿区S<sub>2</sub>面理和黑云母-石榴石变斑晶矿物温压条件与控矿关系-《地球科学与环境学报》

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Title:: Study on S₂ Foliation, Conditions of Temperature-pressure on Biotite-garnet Metacryst Minerals and the Relation of Ore-control in Jindoupo Ore Area of the Northern Hanyin, South Qinling

作者:: 高雅宁; 杨兴科; 韩珂; 吴旭; 樊培贺; 1.长安大学地球科学与资源学院,陕西西安 710054;2.长安大学西部矿产资源与地质工程教育部重点实验室,陕西西安 710054

Author(s):: GAO Ya-ning; YANG Xing-ke ; HAN Ke; WU Xu; FAN Pei-he; 1. School of Earth Science and Resources, Chang’an University, Xi’an 710054, Shaanxi, China; 2. Key Laboratory of Western Mineral Resource and Geological Engineering of Ministry of Education, Chang’an University, Xi’an 710054, Shaanxi, China

Keywords:: S₂foliation; factor of ore-control; gold deposit; Meiziya Group; garnet-biotite geothermometer; Hanyin area; South Qinling

摘要:: 南秦岭汉阴北部金斗坡矿区志留系梅子垭组面理以S₂面理为主。大比例尺构造-岩相填图和剖面实测所获得的大量S₂面理产状数据显示,S₂面理倾向305°~355°,倾角为25°~50°,为稳定北倾的平直面理。通过S₂面理产状数据连图和综合分析,S₂面理与金矿化具有相同的展布特征及变化规律,对成矿具有制约作用。此外,选取梅子垭组含石榴石黑云母变斑晶绢云母石英片岩中的共生矿物石榴石-黑云母进行电子探针测试,运用Holdaway石榴石-黑云母地质温度计方法,估算出该区热蚀变温度为590 ℃~670 ℃。综合研究表明,印支晚期—燕山早期为金矿的成矿期,在此期间岩浆热液的强烈活动引起热蚀变作用的发生,生成石榴石与黑云母变斑晶;热变质作用促使Au元素发生活化,有利于后期Au元素富集成矿。

Abstract:: The foliation of Silurian Meiziya Group in Jindoupo ore area of the northern Hanyin, South Qinling is mostly S₂ foliation. The massive occurrence data from mapping as well as section plane based on large measuring scale indicate that the tendency of S₂foliation are 305°-355° with the dip angle of 25°-50°; the S₂ foliation, which inclines towards the north, is stable as well as placid. After comprehensive mapping and analysis, the distribution direction of S₂ foliation is mainly the same as that of gold mineralization, and has obvious constraint on mineralization. In addition, after testing the biotite-garnet paragenetic mineral assemblage from garnet-bearing biotite metacrysta sericite-schist of Meiziya Group by electron probe microanalysis, the thermal alteration temperature (590 ℃-670 ℃) was estimated by the means of Holdaway biotite-garnet geothermometer method. Comprehensive study indicates that Late Indosinian-Early Yanshanian is the metallogenic period of Au deposit, and the intense magmatic hydrothermal activities cause hydrothermal alteration and give birth to biotite metacrysta as well as garnet; the thermometamorphism accelerates the activity of Au, which has the advantage of later mineralization.