南金山金矿稳定同位素组成特征及成因意义

Stable Isotopic Composition Characteristics and the Genesis Significance of NanJinshan Gold Deposit,Gansu Province

南金山金矿产于北山北部晚古生代活动大陆边缘,次生石英岩化火山碎屑岩内,是受近东西向和北东向断裂控制的浅成低温热液型金矿。矿床稳定同位素地球化学特征表明,成矿热液来源复杂,可能有岩浆水和大气降水的混合作用。矿石硫同位素值与自然界中花岗岩、玄武岩相似,反映出与花岗质岩浆有一定的亲缘关系。矿石硫可能是来自于由地壳火成岩源区熔融形成的岩浆,在岩浆侵入地层后形成含矿气水热液。铅同位素特征表明铅来自于造山带。同样,矿区附近侵入岩体的铅同位素投绘点也位于造山带附近,反映了南金山金矿床的成矿作用与其附近侵入岩体之间可能具有内在联系,因此推断成矿物质主要来自于岩浆活动。

Nanjinshan gold deposit is an epithermal deposit in North mountain area,which was an active continental margin in late Paleozioc.The orebodies occur as in secondary pyroclastic rocks,mainly controlled by E-W and N-E trending fault.The results show that： ore-forming fluid maybe originated from magmatic water and meteoric water;Ore sulfur isotope value is similar with nature of granite,basalt,reflects a certain relationship with the granitic magma.Ore sulfur may be from molten magma which is the source area of crust igneous rock,after magma intrusion in the formation,it can format ore-bearing water and gas hydrothermal.The study of lead isotope indicates that Pb in ore is mainly from orogenic belt.As the same,the mining area nearby intrusive bodies＇lead isotope throws draws also to be located at nearby the orogenic belt.It reflectes that metallization of Nanjinshan gold deposit may have the inner link with its nearby intrusive bodies.Thus,the authors consider that ore-forming materials are from magmatic activity.