摘要
川西呷村黑矿型矿床产于酸性流纹质火山岩系上部。矿区蚀变可分为矿化热液蚀变和区域低温蚀变。后者广布矿区:前者绕网脉矿(硅矿)形成蚀变岩筒,并具明显的蚀变分带:自内而外由石英-钡冰长石带向绢云母-石英带递变,自下而上由绿泥石带向石英-绢云母带递进。采用"惰性"微量元素方法恢复了含矿岩系原岩成分,定量估算了蚀变引起的物质-化学变化。在蚀变岩筒中,Cu、Pb、Zn 强烈富集,远离蚀变岩筒,Cu 略有亏损,Pb 和 Zn 显著亏损,证明成矿物质 Pb 和 Zn 主要来自被热液交代淋滤的酸性火山岩系。根据蚀变岩石的物质变化,概略性地固定了呷村矿区蚀变火山岩物质变化图,可准确地追溯热液流体运移轨迹,进行矿体圈定。
The Gacun kuroko-type deposit in western Sichuan is distributed in the inter-arc rift zone within the Triassic Yidun island arc and occurs in the upper part of the rhyolitic volcanic rocks in bimodal suite.Alterations in the ore district include mineralizing hydrothermal alteration and re- gional low-temperature alteration.The former has formed an altered pipe around the stockwork ore(Silica ore)and exhibits obvious alteration zoning:from the inner part outward,there exists gradual change from the quartz-adularia zone to the sericite-quartz zone,and from the lower part upward,the change is progressively from the chlorite zone to the quartz-sericite zone.The inert trace element method was employed to restore protolith composition of the ore-bearing rocks and make quantitative estimation of mass chemical change caused by alteration.Protoliths included dacite rhyolite,rhyolite and high-silica rhyolite.With the evolution of magma towards strong acidity,lead and zinc increased,and copper was obviously depleted,implying that copper might have entered magmatic fluids.In the altered pipe,copper,lead and zinc are remarkably concen- trated;distant from the altered pipe,copper is somewhat depleted,and lead and zinc are obvi- ously depleted,indicating that lead and zinc in ore-forming substance were mainly derived from acid volcanic rocks which had suffered hydrothermal metasomatism and leaching.According to mass change of altered rocks,the authors outlined mass change of altered volcanic rocks in the Gacun ore district.The method that accurately traces the migration focus of hydrothermal fluids to outline orebodies is proposed on the basis of the calculation of mass change of the altered uol- canic rocks.
出处
《矿床地质》
CAS
CSCD
北大核心
1996年第2期97-108,共12页
Mineral Deposits
基金
日本国际产业技术研究事业基金资助
关键词
火山岩
热液蚀变
含矿
黑矿型矿床
物质变化
Gacun kuroko-type deposit
hydrothermal alteration
mass chemical change
