摘要
本文着重讨论了我国北方地区几个主要金矿床的形成时代、矿源及其与铅同位素的关系。认为:①从内蒙到东部沿海(包括东北),金矿的形成时代从海西中期(311×10~6a)到燕山晚期(100×10~6a),并且大多数金矿与中生代的岩浆活动有关;②在由岩石铅(包括花岗岩和变质岩)和矿石铅同位素组成的^(207)Pb/^(204)pb-^(208)Pb/^(204)Pb图解上,矿石铅同位素组成更靠近花岗岩一端;③变质岩和花岗岩中的金具有很高的淋洗率,均可作为金矿的矿源岩石。
The present paper summarizes geological features of some major gold deposits in North China and their mineralization ages from the angle of geochronology. These gold deposits are mostly hosted by various old metamorphic rocks and are closely related to the Mesozoic intermediate-acid intrusions. Their mineralization ages appear to become younger from 311 Ma in the west (Inner Mongolia) to 100 Ma in the east(coastal areas of East and Northeast China). The lead isotope composition of the ores and that of host rocks lie on the same line in the ^(207)Pb/^(204)Pb versus ^(208)Pb/^(204)Pb diagram, with the lead isotope composition of granites and that of metamorphic rocks just occupying the two end members. Thus a mixed or two-stage evolutionary model of lead isotopes is advanced in this paper. It is concluded that the gold deposits have a genetic connection with granites and metamorphic rocks. Lead in the ores came from these two types of host rocks and the sizes of the ore deposits are directly proportional to the amount of lead provided by the related granites. Experiments under the conditions of 450—100℃ (with an interval of 50℃)and 50×10~5Pa and 100×10~5Pa were conducted to examine the leaching ratios of Au in different rocks of North China, which commonly host gold deposits. The results show that the leaching ratios of Au in the metamorphic, igneous and sedimentary rocks are 14.75%, 14.03% and 0.7% respectively, indicating convincingly that igneous and metamorphic rocks serve as the source rocks of Au and are closely related to the formation of gold deposits in North China.
出处
《矿床地质》
CAS
CSCD
北大核心
1993年第2期168-173,共6页
Mineral Deposits
