山东新泰地区绿岩带金的地球化学特征

本文概述了新泰地区绿岩带的基本特征,构造及其演化规律,提出花岗质岩石是由幔源物质上侵及绿岩带部分重熔形成的。文中用测得κ系数0.37,作为对比太古宙绿岩带中科马提岩的标准,并得出金在科马提岩中初始丰度值,其西带为5.99ppb,东带为2.37ppb,反映了太古宙期间本地区地幔含金的不均一性。运用算术、几何平均法,对绿岩带各岩石类型、地层单元、花岗质岩石及其岩脉的含金性统计结果表明有的岩石变异系数增大,有利于金的分散与集中。文中对金矿化带地质地球化学特征及其成晕机制进行了论述,确定了矿化带的地表与金呈明显正相关元素为Ag、As、Sb、Ph、Zn,负相关元素为Cu、Hg,矿化带的深部与金呈正相关的元素为Sb,而Ag、As、Hg、Cn、Pb、Zn则与金的相关系数趋于零。从而对区内绿岩带金矿成因进行探讨,提出了变质-岩浆-热液充填交代成矿模式,并初步提出找矿地段。

GEOLOGICAL AND GEOCHEMICAL CHARACTERISTICS OF GOLD IN THE GREENSTONE BELT OF XINTAI AREA,SHANDONG

The principal characteristics, structures and their evolution regularity of the greenstone belt of Xintai area are summerised. It is considered that the granitoid rocks were formed as mantle materials were upwelling and the greenstone belt were partially remelted. Coefficient K is got as 0.37 and used as a standard for correlating komatiites in Archean greenstone belts. Initial abundance of gold in the komatiite is 5.79 ppb in western belt and 2.37 ppb in eastern belt, suggesting inequality of gold content in the primitive mantle of this area in Archean. The atatistics of various rock types, stratigraphic units, granitoid rocks and their dikes in the greenstone belt witharithmetic and geometric mean show that increasing of variation coefficient of some rocks is favorable to dispersion and concentration of gold. Geological and geoc-hemical characteristics of gold-mineralization and halo mechanism is discu -ssed.It is recognized that in surficial gold mineralization zone the elements in passitive correlation with gold are Ag, As, Sb, Pb, Zn and in negative correlation with gold are Cu and Hg; in deep gold mineralization zone only element Sb is of passitive correlation with gold while the gold correlation coefficient of elements Ag, As, Hg, Cu, Pb, Zn is tending towards zero. Discussing genesis of greenstone type gold deposits in this area, the author proposes a metamorphic- magmatic- hydrothermal filling alterating minerogenetic mo -del and outlines preliminarily the ore-searching area.