内蒙古呼伦贝尔盟北部地区花岗岩特征与金矿化的关系

内蒙古呼伦贝尔盟北训地区蕴藏着丰富的砂金矿产资源,已探明中小型砂金矿床数十个,砂金矿中金主要来源于该区花岗岩.在野外工作及室内研究基础上,从岩石学、岩石化学、锶同位素、稀士元素等方面,对两种成因的花岗岩即深熔成因(I)型和陆壳改造成因(S)型的金成矿地质条件进行研究,认为"S"型花岗岩因交代重熔金丰度较高的基底岩石(板岩、片岩等)而使其金含量大大提高,是本区砂金矿床的主要金源体."S"型花岗岩的人工重砂中金粒的出现说明一部分金以自然金的形式存在。今后本区应注重在"S"型花岗岩发育的地区寻找原生金矿及砂金矿.

THE RELATIONSHIP BETWEEN GOLD MINERALIZATION ANDCHARACTERISTICS OF GRANITE IN NORTH HULUNBERLEAGUE OF INNER MONGOLIA AUTONOMOUS REGION

North Hulunber League of Inner Mongolia is rich in placer gold deposits,where dozens of small madium scale deposits have been explored There exists two stages of granits,i e ,Caledonian stage (442 Ma)and Hercynian stage (383 230 Ma) Based on its characteristics on petrology,lithochemistry,Sr isotope and rare earth elements,the granitic rocks can be divided into two types of genesis,i e ,anatectic type (Ⅰ) and continental crust transformation type (S) The S type contain higher abundance of gold,because it metasomatized and remelted basement rock with high gold abundance (slate, schist, etc ) This proves that the S type provided gold source directly to placer gold deposits in this region Moreover, the fact that natural gold grains are found in artifical heavy placer minerals from S type granite also confirms that a part of gold exist in natural form These suggest that we should pay attention to searching gold deposit in the area where S type granite is developed