北山花岗岩S型/I型空间变化规律及含矿性

Spatial Variation Regularity and Ore Potential of S-type and I-type Granites in the Beishan Mountain

北山地区花岗岩十分发育,出露面积接近总面积的30%,形成时代以华力西期为主,约占80%以上。笔者根据岩石化学判别统计,本区花岗岩的S型/I型个数比例,北带0.33,中带0.54,南带0.59,说明从北向南,I型花岗岩逐渐减少,S型花岗岩逐渐增多。区内花岗岩类为重要的含矿岩石,其中典型斑岩铜矿床与I型花岗质斑岩有关,当出现铜铅组合时则与S型花岗质斑岩有关;钼矿床有关花岗岩一般属I型,当出现钨钼组合时则向S型花岗岩过渡;钨锡矿床主要与S型花岗岩有关;金矿床有关的花岗岩既有I型,也有S型,专属性不明显。

Granites are well developed in Beishan area, with the outcrop making up nearly 30% of the total area. Over 80% of the granites were formed in the Variscan epoch. According to petrochemical discrimination, the ratio of S-type to I-type granites is 0.33 in the north belt, 0.54 in the middle belt and 0.59 in the south belt respectively. From north to south, the I-type granite gradually decreases whereas the S-type granite increases. The granites in this area constitute important ore-bearing rocks. The typical porphyry Cu deposits are related to the I-type granitic porphyry, and the Cu-Pb combination has to do with the S-type granitic porphyry. The Mo deposits are associated with the I-type granite, which grades off into the S-type granite when the W-Mo combination appears. The W-Sn deposits are mainly linked with the S-type granite. The granites related to gold deposits are S-type and I-type ones, with indistinct specialization.