摘要
胶东西部地区金矿床硫同位素组成以变异小和富集34 S为突出特征。不同类型金矿床有其特征的δ34 S值 :石英脉型 4‰～ 7‰ ;蚀变岩型 7‰～ 12‰ ;银、铅锌矿床为 - 4‰～+ 4‰。金矿床矿石硫直接来自交代 -深熔花岗岩 ,间接来自原始矿源岩 ,δ34 SΣS=10‰。区域上金矿床δ34 S沿控矿脆韧性剪切带形成高值带 ,且自西向东递降。矿田范围内 ,控矿构造—矿化类型—矿床δ34 S三者呈谐和水平分带。构造热力学分馏效应和构造动力学分馏 (即扩散分馏 )效应可能是构造作用力制约δ34 S分布的主要机制。
Statistics of sulphur isotope data from 500 ore samples has shown that the sulphur isotopic composition of gold deposits in western Jiaodong district are remarkably characterized by small variance and concentrated on 34 S.Different mineralization types of gold deposits are of its own characteristics of δ 34 S value:Mid Yanshanian(140～100Ma)mesothermal quartz vein type gold deposits are of 4‰～7‰;altered rock type gold deposits are 7‰～12‰;Late Yanshanian epithermal gold ,silver,and Pb-Zn deposits are -4‰～4‰.From the statistic aspect,the higher of δ 34 S value,stronger the intensity of gold mineralization and larger the scale of gold deposits,thus the δ 34 S value of ore deposit maybe used as the major geochemistry indices for the evaluation of gold prospecting in Western Jiaodong. The comparison of rock sulphur and ore sulphur shows;the ore sulphur of mid Yanshanian mesothermal gold deposits are originated from the ore source rock of Mesozoic re activated area,i.e directly sourced from structural altered granite in long term tectonic activated area and altered by deep source alkali (mainly potash)fluid,indirectly from Jiaodong and Jinshan Group.(Neo Archaeozoic～Early Proterozoic greenstone terrain of 'O'type).The ore sulphur of Late Yanshanian epithermal Au,Ag,Pb,Zn deposits are mainly from the syntactic magma source.According to the calculation of Ohmoto Model,the composition of total sulphur isotope of mesothermal gold deposit δ 34 S ΣS =10‰,it pertains to crustal source sulphur. Constrained by regional controlling structure of rocks & ores,the regional distribution pattern of δ 34 S of gold deposits in Western Jiaodong district is formed by four δ 34 S high value zones (NE NNE direction )alternatively with three low value zones. The additional static gradient pressure structure is the original dynamic force of sulphur isotopic fractionation.The high gradient dilatent area of high stress energy is easy to induce quick accumulation and the release of energy and favorable for diffusional fractionation of sulphur isotope.This is the cause that within the same metallogenic tectonic system,the ore forming solution of same stage and same source under the analogue physicochemical condition,the relative enrichment of 32 S in quartz vein ores occurred in the upper continuous free space( δ 34 S value decreased),while the 34 S of altered rock type ore body is enriched( δ 34 S value increased)in the lower connected diffusive space.The tectonic stress field does not only control the forming and concentration of ore body,but also the mineralization type .In special case(such as tectonic pulse),the detectable fractional effect of sulphur isotope may also by formed.Thus distribution pattern of δ 34 S may be used as major geochemistry indicating tracer for the discussion of ore controlling mechanism of various structures.
出处
《黄金》
CAS
2002年第4期1-16,共16页
Gold
关键词
金矿床
硫同位素分布
地球化学
构造运输分馏
胶东地区
gold deposits
distribution pattem of δ 34 S
tectonic kinetic fractionation
Jiaodong Area
