豫西崤山地区金矿成矿年龄的测定及其意义  

Determination of the Ore-forming Age of Gold Deposits in Xiaoshan, Western Henan and Its Geological Significance

作　　者：朱嘉伟 张天义 薛良伟 

机构地区：[1]河南省地质科学研究所,郑州450053

出　　处：《地质论评》1999年第4期418-422,共5页Geological Review

摘　　要：^(40)Ar/^(39)Ar流体包裹体同位素测年法为金矿成矿年龄测定开辟了新的途径。但是,由于次生包裹体的存在及样品中存在过剩氩或氩丢失,常产生复杂的不一致年龄谱,难以获得准确可靠的成矿年龄。本文对豫西崤山地区含金石英脉中的石英和方铅矿样品进行精选,采用阶段升温法测定出了可靠的^(40)Ar/^(39)Ar年龄。^(40)Ar/^(39)Ar等时线线性相关系数>0.99,^(40)Ar/^(39)Ar初始值分别为294.0和297.0,没有过剩氩和氩丢失。测得其全坪年龄分别为130.6±2.6 Ma和127.8±2.8 Ma;等时线年龄分别为133.0±2.7 Ma和126.0±2.5 Ma,不同样品的年龄值相差很小。由此可确定豫西崤山地区金矿的成矿年龄为130±6 Ma,为燕山期。这一年龄值与崤山变质核杂岩内花岗岩的形成年龄(106.0～122.1 Ma,K-Ar法)接近,说明了崤山金矿的形成与燕山期花岗岩浆活动密切相关,金矿找矿工作应围绕燕山期花岗岩这一主导因素开展。It is difficult to determine exactly the ore-forming age of gold deposits even using the 40Ar-39Ar fluid inclusion dating because the existence of secondary fluid inclusions and presence of excess Ar or Ar loss often give rise to complicated and not identical age spectra. The authors determined the accurate 40Ar-39Ar ore-forming age of gold deposits in Xiaoshan western Henan using the method of heating carefully selected quartz and galena samples from gold-bearing quartz veins in stages. The 40Ar-39Ar age spectra are horizontal, saw-tooth-shaped. The linear corelations coefficient of the 40Ar/39Ar isochrons are above 0. 99. The initial '40Ar/39Ar ratios of quartz and galena are 294. 0 and 297. 0 respectively. There is no excess Ar or Ar loss. The 40Ar/39Ar plateau ages of quartz and galena were determined to be 130. 6±2. 6 Ma and 127. 8±2. 8 Ma re-spectivel, and the 40Ar/39Ar isochron ages of quartz and galena were 133. 0±2. 7 Ma and 126. 0 ±2. 5 Ma respectively. The errors of the determined ages of different samples were very small. Thus it may be concluded that the ore-forming ages of the gold deposits in Xiaoshan, western Henan, are 130±6 Ma (Yanshanian Stage). This age range is close to that (106. 0~122. 1 Ma, K-Ar age) of granite in the Xiaoshan metamorphic core complex. It explains the relationship of the formation of gold deposits with Yanshanian granite magmatism. So gold exploration should be carried out around Yanshanian granite.

关 键 词：金矿床 成矿年龄 氩40-氩39 地质年龄 

分 类 号：P618.510.5[天文地球—矿床学] P618.510.2[天文地球—地质学]