大兴安岭中南段燕山期三类不同成矿花岗岩中黑云母的化学成分特征及其成岩成矿意义

MINERAL CHEMISTRY OF BIOTITE FROM GRANITES ASSOCIATED WITH DIFFERENT MINERALIZATION IN THREE STAGES OF YANSHANINA PERIOD IN THE SOUTHERN-MIDDLE PARTS OF THE DA HINGGAN LING MOUNTAINS AND ITS PETROGENETIC AND METALLOGENIC SIGNIFICANCE

大兴安岭中南段燕山期三类不同成矿花岗岩中黑云母主要为富铁黑云母和铁黑云母 ,属富铁黑云母 铁叶云母系列。黑云母主要化学成分表明本区花岗岩碱度属正常碱度 过碱性岩石系列 ;本区燕山期花岗岩为壳幔混源成因 ,其岩石系列属于长江深源系列和南岭浅源系列之间的过渡类型。燕山期三个不同期次不同成矿系列的花岗岩中黑云母的化学成分明显不同 ,燕山早期早阶段与铜成矿有关的花岗岩黑云母相对以富镁贫铁为特征 ,燕山晚期早阶段与锡多金属矿化有关的花岗岩其黑云母成分相对以富铁贫镁为特征 ,燕山早期晚阶段与铅锌银矿化有关的花岗岩黑云母成分处于两者之间 ,黑云母的化学成分是判别本区三类不同成矿岩体的有效标志。

Based on the mineralogical composition OF biotite occurring in Yanshanian granites in the southern-middle parts of the Da Hinggan Ling Mountains, it is suggested that the biotites in the Yanshanian granites are mainly lepidomelance and Fe-rich biotite, and they belong to the lepidomelance-annite series. The major composition of biotite shows that its host rocks are alkalic and calc-alkaline series rocks, and the Yanshanian granites have characters of the Nanling granite series and Yangtze river granite series, manifesting the granites in the region are of the mantle-crust mixing type. The granites, which evolved in three different stages of the Yanshanian period, stemmed from the same magma source. Biotites from the granites associated with different mineralization in three stages of the Yanshanian period are different in composition. The biotite is characterized by high contents of Mg and low contents of Fe 2+, which is from granites associated with Cu mineralization in the early stage of the Early Yanshanian period. And the biotite enriched in Fe and depleted in Mg is from granites related to Sn-polymetal mineralization at the early stage of the Late Yanshanian period. The biotite from the late stage of the Early Yanshanian granites related to lead-zinc-silver mineralization is similar to the biotite from the early stage of the Early Yanshanian granites and to that from the early stage of the Late Yanshanian granites.