内蒙古东升庙矿床火山作用新证据的发现及其意义

NEW EVIDENCES OF BIMODEL VOLCANIC ACTIVITIES IN DONGSHENGMIAO POLYMETALLIC PYRITE DEPOSIT IN INNER MONGOLIA: DISCOVERY AND IMPLICATION

东升庙硫－多金属矿床狼山群二组含矿地层中，除已发现的变质石英角斑岩之外，又找到具有变余斑状结构（斑晶主要为钠质斜长石，另有少量辉石和角闪石）的变质基性火山岩和变质凝灰岩夹层以及火山岩屑与晶屑。这既直接证实本矿在成岩成矿期有明显的间歇性火山喷发活动、成矿与火山喷发作用有关，又可为研究本矿床成矿地质构造背景、成岩成矿历史，进而判别矿区古火山口的位置，进行区域对比与确认同生断层等问题提供岩石学的基本素材。此外。

In the second formation of the Langshan group in the Dongshengmiao polymetallic pyrite deposit, metamorphic basic volcanic rocks have been discovered,except quartz keratophyre, with a blastoporphyritic texture containing albite and oligoclase and minor, pyroxen and hornblende. In addtion,interbeds of metamorphic tuffs in the three members of the formation and lithoclasts and crystalloclasts in the pyrite bearing levels of the columns of deep boreholes have been recognaized. All these findings provide direct evidences of strong but intermittent volcanic eruptions during the sedimentation and metallogenesis of the deposit which might have owed its formation to the sea floor eruptional activities of its kind. The co existence of the metamorphic basic volcanic rocks and quartz keratophyre in fact serves as a indicator of bimodal volcanic activities typical generally of tensional(rift) basins along the margins of the continents. In a certain sence, this is the very environment the deposit was emplaced. Recognization of the bimodel volcanic facies inspires us more than understaning the paleogeographic conditions of the deposit itself-offering reliable knowhows for us, through investigating evolutions of regional diagenesis and metallogenesis, to define the positions of paleocraters in the mining area, carry out stratigraphic correlation and correctly decide synsedimentary faults, as well as efficient index beds for us to use for ore hunting.