摘要
浙东新昌-永嘉银(铅-锌)矿带中,主要有嵊县毫石、新昌拔茅、天台大岭口及黄岩五部等大一中型银矿床或含银铅-锌矿床。在这些典型矿床的专题研究基础上,本文根据它们的成岩成矿年龄时差及氢、氧、硫和铅同位素地球化学特征,提出了“中生代地热水淋滤汲取成矿”的成因机制和成矿模式。地热水环流-汲取成矿活动的主体部分发生在火山岩层内。成矿流体是大气降水来源的浅循环地热水,在其环流过程中淋滤汲取周围岩石中的成矿物质(银、铅、锌及硫等成矿元素主要来源于已固结的火山岩),从而形成了中低温热液银(铅-锌)矿床。
In the Xinchang-Yongjia silver (lead, zinc) ore zone of eastern Zhejiang Province, more than thirty deposits (or occurrences) are densely distributed, mainly including the large and intermediate-sized Haoshi, Bamo, Dailinkou and Wubu silver or silver-bearing lead-zinc deposits. On the basis of studies on individual typical deposits, the authors deal with the isotopic geochemical characteristics of the zone and the genesis of the deposits therein.In this paper the leaching-drawing mineralization mechanism of the Mesozoic geothermal water is put forward; the following are its main arguments:1. Ore-forming ages obtained from the altered minerals or rocks and the fluid inclusions of quartz in ore veins are in the range of 70-100Ma, while rock-forming ages of the related volcanic and intrusive rocks are in the range of 110-130Ma. It is indicated that the time interval between the formation of host volcanic rocks and the silver mineralization was up to 30-40Ma. Therefore, the mineralization in the zone was not directly associated with the volcanic activity.2.The hydrogen and oxygen isotopic data of the gangue minerals, such as quartz, calcite, baritite and rhodochrosite, show that the ore-forming hydrothermal water has δD values of - 55‰ to - 70‰ and δ18O values of -8.3‰ to +4.19‰. Through the an investigation of the variation curve of isotopic composition for water-rock exchange, it is considered that the ore fluids in the zone were circulating geothermal water derived from the Mesozoic meteoric water.3. The sulphur and lead isotopic composition characters of the ore minerals, such as pyrite, galena, and sphalerite, are consistent with that of the host volcanic rocks, reflecting that the ore materials were mainly derived from the Mesozoic volcanic rocks. The two-component mixing model for lead isotopic composition suggests that more than 94% ore lead came from the Mesozoic volcanic rocks, while lead derived from the metamorphosed rocks of the Precambrian basement underlying the volcanic rocks was scarce. This result shows that the ore materials were leached and drawn by circulating geothermal water from a shallower depth and that the main part of the circulation lies in the volcanic cover. Thus, the silver (lead, zinc) deposit in the zone belongs to epithermal one.
出处
《地质学报》
EI
CAS
CSCD
北大核心
1994年第3期255-267,共13页
Acta Geologica Sinica
关键词
铅锌矿床
矿带
同位素地质学
isotope geochemistry, silver (lead, zinc) ore zone, genesis of ore deposit, Zhejiang Province
