花牛山地区中生代A型花岗岩特征及其找矿意义

花牛山矿产集中地区与钨、锡、钼、金、银、铅、锌等成矿关系密切的钾长花岗岩是印支期—燕山早期构造—岩浆活动产物。岩石化学和地球化学具A型花岗岩特征:SiO271.51%～77.53%,Al2O311.64%～14.41%,K2O+Na2O7.43%～9.75%,K2O/Na2O1.01～2.04,CaO0.36%～1.9%,MgO0.03%～0.77%,Eu、Ba、Sr贫,富集Nb、Td、Hf、Th、U等元素。结合区域地质和岩浆岩资料,作者认为,钾长花岗岩是同熔型岩浆经一系列分异演化的产物,形成的构造环境是二叠纪—三叠纪EW向裂谷作用和中生代滨西太平洋NE向断裂。北山地区与印支—燕山期"A"型有关的W、Sn、Mo、Au矿的找矿潜力巨大。"A"型花岗岩的区域构造—岩浆演化,对指导区域矿产预测和评价均具有重要的理论和实际意义。

FEATURES OF MESOZOIC A-TYPE GRANITES AND IT'S SIGNIFICANCESFOR PROSPECTING IN HUANIUSHAN AREA

The moyite with which metallogenesis of W, Sn, Mo, Au, Ag, Pb, Zn have the close relations in Huaniushan mineral concentration area are the products originated from Indo-Chinese to early Yanshan tectonicmagmatic activities. The study of petro-chemistry and geochemistry show that the moyite has the features of Atype granites： SiO2 71.51%～77.53%,Al2O3 11.64%～14.41%,K2O＋Na2O 7.43%～9.75%,K2O / Na2O 1.01～2.04,CaO 0.36%～1.9%,MgO 0.03%～0.77%,poor in the elements of Eu, Ba and Sr,but rich in the elements of Nb, Td, Hf, Th and U. Through studying the literature of regional geology and magmatic rock, the author supposes that the moyite are the products of syntexis magma undergone a series of differentiation in the tectonic environment of Permian-Triassic EW-direction rifting and Palaeozoic west marginal Pacific faults. The study on regional tectonic and magmatic evolution of A-type granites will be of theoretical and practical significances in guiding to predict and to evaluate the mineral resources in the study area.