洛南—豫西中酸性小岩体岩石化学特征与钼成矿的关系

THE RELATIONSHIP BETWEEN CHEMICAL CHARACTERISTICS AND MOLYBDENUM METALLOGENIC PROPERTIES OF THE MIDDLE ACID SMALL ROCKS IN LUONAN-WEST OF HENAN PROVINCE

东秦岭洛南—豫西地区包含陕西华县金堆城和河南栾川南泥湖两个超大型钼矿田。两个矿田的几乎所有钼矿床均为斑岩型钼矿床,南泥湖矿田内矿床的一部分属于矽卡岩型钨钼矿床,但仍然属于广义上的斑岩型钼矿床。这些超大型、大型钼矿床的成矿母岩都是小岩体。确切地说,这些小岩体均是属于高硅、高钾、高碱低钙镁的"三高一低"的强酸性钙碱性的超浅成侵入岩—花岗斑岩岩株。它们的演化过程离不开区域巨大型的花岗岩基,花岗岩基是花岗斑岩岩株演化的物质基础。一般地,成矿岩体的SiO_2含量下限为72.5%,上限为76%左右;K_2O含量5%~6%,K_2O+Na_2O界于8%~9%之间,K_2O/Na_2O为1~2,超大型、大型钼矿床成矿母岩K_2O/Na_2O为2~3。里特曼指数σ限制在1.8~2.6对成矿有利。SiO_2/K_2O限制在11~16之间。我们说只有强酸性小岩体才能构成钼矿床的成矿母岩,这就是岩浆岩尤其是花岗岩成矿专属性的具体体现,也是小岩体成大矿的找矿地质成果的实践结论。

The area of Luonan-west of Henan province includes two super large molybdenum deposits,Jinduicheng in Shaanxi province and Nannihu in Henan province.Almost all molybdenum deposits in the mine are porphyry molybdenum deposits.Some of the deposits in Nannihu mine belong to the silicon-type tungsten molybdenum deposit,but still belong to the porphyry molybdenum deposit in the broad sense.The metallogenic rocks of these large molybdenum deposits are small rock masses.These little rocks are,to be exact,the ultra-shallow and intrusive rocks of high-silicon,high-potassium,high-alkali,low-calcium magnesium,and the granite porphyry.The evolution process cannot be separated from the large granite base of the region,and the granite base is the material basis of the evolution of granite rock.In general,the lower limit of SiO2 in the ore body is 72.5%,and the upper limit is about 76%.K2O content is 5%~6%,K2O+Na2O is between 8%and 9%,K2O/Na2O is 1~2,and super large and large molybdenum deposit is 2~3.The Reitman indexσis limited to 1.8~2.6 in favor of ore.SiO2/K2O is limited to 11~16.We say that only small strongly acidic rock mass can constitute a molybdenum deposit ore-forming parent rock,which is the embodiment of magmatic rocks,especially granite mineralization specificity,is also a little rock into the big ore prospecting geological results of practical conclusion.