甘肃北山公婆泉斑岩铜矿床流体演化与成矿作用

Gongpoquan is a representative porphyry copper deposit in the Beishan porphyry copper metallogenic belt, which is located between the South Mongolia and Eastern Tianshan Tuwu-Yandong porphyry copper metallogenic belt, is a key point in researching the comparison and connection of this two porphyry copper metallogenic belt. The orebody is hosted in granodiorite porphyry and sub-volcanic rock, but systematic fluid evolution and metallogenesis has been lack of research. On the basis of a systematic research of the Gongpoquan porphyry copper deposit geology, the author focus on the granite porphyry, sub-volcanic rock, mineralization type, veins type, alteration zoning and enrichment process of ore-forming elements. This research on the fluid inclusion, isotope geochemistry and geochronology is to find out the corresponding relations among properties, sources and evolution of the fluid, veins type, alteration zoning and the process of aggregation and precipitation of copper sulfide, determine the ages of rock-forming and ore-forming, the time-space relations between granite porphyry and sub-volcanic rock, aiming at discuss the process of metallogenesis and summarize metallogenic regularity. This research is not only conducive to understanding the metallogenic process of porphyry copper deposit in the Beishan porphyry copper metallogenic belt and guide mineral deposit exploration of porphyry copper deposits in Beishan areas, but also provide theoretical basis for the comparison and connection of between the South Mongolia and Eastern Tianshan Tuwu-Yandong porphyry copper metallogenic belt.

公婆泉铜矿是北山斑岩铜矿成矿带中代表性的矿床，处于南蒙古和东天山土屋-延东斑岩铜矿成矿带的中间部位，是研究这两个斑岩铜矿成矿带连接的关键点。矿体赋存于花岗闪长斑岩和（次）火山岩中，矿床的流体演化和成矿作用一直缺乏系统的研究。本文以公婆泉斑岩铜矿为研究对象，以系统的矿床学研究为基础，拟重点对花岗斑岩、（次）火山岩、矿化类型、脉体类型、蚀变分带、成矿元素富集过程进行研究。通过流体包裹体、同位素和年代学研究，查明矿床流体性质、来源及演化与脉体类型、蚀变分带、Cu硫化物聚集沉淀的关系，精确厘定成岩时代和成矿时代，确定（次）火山岩和花岗斑岩与成矿的时空关系，探讨成矿作用和总结成矿规律。本项目的开展不仅有助于认识北山斑岩铜矿成矿带的成矿作用，有效指导北山地区斑岩铜矿的找矿勘查工作，而且为北山斑岩铜矿成矿带与南蒙古和东天山土屋-延东斑岩铜矿成矿带的连接、对比提供理论基础。

项目以公婆泉斑岩铜矿床为研究对象，在研究矿床地质特征研究的基础上，以流体系统研究为重点，确定流体的性质、来源及演化与脉体类型、蚀变分带和Cu硫化物的聚集过程的相互对应关系，精确厘定成岩时代和成矿时代，探讨（次）火山岩和花岗斑岩与成矿作用的关系，总结成矿规律，为指导甘肃北山地区斑岩型铜矿床找矿勘探提供理论基础。. 在详细的野外地质考察和室内分析测试基础上，确定矿床类型为斑岩型，围岩蚀变中心向外依次为石英核带→钾化带→绢英岩化带→青盘岩化带→角岩化带→泥化带。对不同蚀变带的成矿流体进行了系统研究，确定了成矿流体性质为中-低温、中-低盐度的H2O-CO2-NaCl体系，成矿过程中经历了沸腾作用。利用H、O同位素示踪了不同蚀变带的成矿流体，确定了成矿流体来源主要为岩浆水，成矿后期存在大气降水的加入。厘定了公婆泉矿区赋矿岩体的年龄，构建了矿区岩浆序列格架，确定了矿区至少存在晚奥陶-早志留世（449～440 Ma）、晚志留世（429～423 Ma）、早泥盆世（407～413 Ma）三期岩浆活动，主成矿期为晚奥陶-早志留世，同时限定公婆泉群形成时代为早奥陶-早泥盆世。利用40Ar-39Ar定年方法测定了公婆泉铜矿床的黄铁绢云岩中白云母的形成时代，限定了成矿时代的下限早于早泥盆世。结合区域地质构造背景，探讨了成矿作用，为区域找矿方向提供了理论依据。基于公婆泉铜矿床地质特征及地球化学研究，结合找矿勘探中运用的地球物理、地球化学与遥感方法，确立了找矿标志，总结了区域成矿规律，为研究北山造山带与斑岩铜矿奠定了基础。