论文部分内容阅读
自晚侏罗纪到晚第三纪,在加拿大科迪勒拉山系在地质、地球化学和成因上发生了两类不同的金矿化作用。一类可以称为低温热液型矿床,因其与中性至长英质火山岩、区域破火山口构造,低pH直蚀变带、低Au/Ag值和石英—玉髓—重晶石—萤石脉石共生。第二类可以称为中温热液型矿床,它与加利福尼亚的马瑟卢德(Mother Lode)矿床非常相似。该类矿床与横推断层、中pH值蚀变带和石英士碳酸岩、钠长石、铬硅云母、黄铁矿、毒砂、白钨矿脉共生。与低温热液矿床相比,中温热液矿床有较高的As,W和Au/Ag值,在液态包体内有较高的CO_2,其成矿溶液的~18O值为+3‰筋到+10‰,低温热液矿床则为—14‰到—7‰。 象内华达和科罗拉多的金矿床一样,加拿大科迪勒拉低温热液矿化是大气水在地表中性至长英质火山杂岩体内浅部循环的结果。对比之下,北美科迪勒拉山脉的中温热液金矿床则是大气水在与主要横推断层带共生的断裂内深部循环和演化的结果。科迪勒拉的太古代脉金矿床和中温热液矿床之间的相似性,表明二者的成矿作用相同。
From Late Jurassic to late Tertiary, two different types of gold mineralization occurred in the geology, geochemistry and genesis of the Cordillera in Canada. A class of deposits that can be characterized as low-temperature hydrothermal deposits is characterized by low Au / Ag ratios and quartz-chalcedony-barite- Fluorite gangue symbiosis. The second type can be called a mesothermal hydrothermal deposit, which is very similar to the Mother Lode deposit in California. This type of deposit is intergrowth with transverse thrusting, mid-pH alteration zone and quartz-quartz carbonate, albite, chitosite, pyrite, arsenopyrite and scheelite veins. Compared with the low-temperature hydrothermal deposits, the Meso-temperature hydrothermal deposits have higher As, W and Au / Ag values and higher CO 2 concentrations in the liquid inclusions, and the ~ 18 O value of the ore-forming solution is + 3 ‰ to + 10 ‰, low-temperature hydrothermal deposits is -14 ‰ to -7 ‰. Like the gold deposits of Nevada and Colorado, low-temperature hydrothermal mineralization in Cordillera, Canada, is the result of the shallow water circulation of atmospheric water in the surface to neutral British volcanic complexes. In contrast, the Meso-temperature hydrothermal gold deposits in the Cordillera range in North America are the result of deep circulation and evolution of atmospheric water within the faults that co-occurred with the major thrusting belt. The similarities between Cordillera’s Archaean vein gold deposits and the mesothermal hydrothermal deposit suggest that the two have the same metallogenic potential.