浙江建德铜矿成矿流体、成矿物质来源与矿床成因探讨

摘要

The Jiande copper deposit is located in the northeast part of Qinzhou-Hangzhou suture belt between Yangtze and Cathaysia blocks,and it is one of the largest copper deposits in Zhejiang Province,China.The genesis of the Jiande copper deposit is still hotly debated.The aim of this paper is to present new field observations,fluid inclusions,H-O-S isotope data to constrain the metallogenic mechanism and ore genesis of the Jiande copper deposit.Based on petrographic observations of ore-bearing quartz collected from the massive ores,primary inclusions of the Jiande deposit have three types:two-phase liquid-rich (type Ⅰ),two-phase vapor-rich (type Ⅱ),and halite-bearing (type Ⅲ) fluid inclusions.Type Ⅰ inclusions occur widely in the Jiande deposit,and show homogenization temperatures of 280 ～ 340℃ and salinities of 0.63％ ～ 8.00％ NaCleqv.Type Ⅱ and type Ⅲ inclusions primarily coexist in the ore veins.Homogenization temperatures of type Ⅱ and type Ⅲ reveal peaks at 296 ～ 334℃ and 290 ～ 326℃ respectively,and their salinities at 1.22％ ～ 2.00％ NaCleqv and 31.87％ ～ 38.16％ NaCleqv,respectively.It indicates that fluid boiling process took place,and metal precipitation probably induced by extensive fluid boiling events during the ore stage.Hydrogen and Oxygen isotopic compositions are also within the range of magmatic water.o34 S of sulfides show positive values within a narrow range,close to zero in average,which points to a magmatic source.Based on geological observations,fluid inclusions,and H-O-S isotope data,the Jiande copper deposit is interpreted as a magmatic-hydrothermal deposit which is determined by "Calcium-Silicon Interface".%浙江建德铜矿位于钦杭结合带北东段,是浙江省最大的铜矿之一,该矿床的成因一直存在争议.本文在详细的野外调查基础上,对建德铜矿成矿期流体包裹体及氢、氧、硫同位素进行了系统测定.流体包裹体研究表明,建德铜矿主要发育三类包裹体:Ⅰ类富液相气液两相包裹体,Ⅱ类富气相气液两相包裹体,以及Ⅲ类含子晶包裹体.显微测温结果显示:Ⅰ类富液相包裹体加热后均一到液相,均一温度分布范围主要集中在280～ 340℃,流体包裹体盐度0.63％ ～8.00％ NaCleqv;Ⅱ类富气相包裹体加热均一到气相,均一温度296 ～ 334℃,盐度1.22％ ～ 2.00％ NaCleqv,属低盐度范围;Ⅲ类含子晶包裹体加热均一到液相,均一温度范围与Ⅱ类包裹体基本相同,分布范围为290～326℃,盐度很高,分布范围为31.87％～38.16％ NaCleqv.Ⅱ类与视域内共存的Ⅲ型流体包裹体的均一温度相似,盐度相差很大,表明发生强烈的流体沸腾作用.流体的强烈沸腾作用是造成建德铜矿成矿物质沉淀富集的原因.氢氧同位素测试结果(618 OH2o值在8.1‰ ～ 10.6‰,δDH2O变化范围从-78‰～-61‰)显示成矿流体主要为岩浆流体.硫化物硫同位素研究显示,634S值的总体变化范围是0.78‰ ～ 4.77‰,并且总体分布在零值附近呈塔式分布,这也暗示着建德铜矿硫化物的硫主要来自于岩浆.流体包裹体及氢、氧、硫同位素研究,并结合地质特征,表明建德铜矿是与晚侏罗世燕山期花岗闪长斑岩有关的,受石炭系灰岩、白云岩和泥盆系砂岩之间“硅钙面”控制的岩浆热液矿床.