东秦岭钼矿带南泥湖-上房沟花岗斑岩成因及其对钼成矿作用的制约  

Geochemistry and petrogenesis of the ore-related Nannihu and Shangfanggou granite porphyries from east Qinling belt and their constaints on the molybdenum mineralization.

作　　者：包志伟[1] 曾乔松[1] 赵太平[1] 原振雷[2] 

机构地区：[1]中国科学院广州地球化学研究所成矿动力学实验室,广州510640 [2]河南省国土资源科学研究院,郑州450016

出　　处：《岩石学报》2009年第10期2523-2536,共14页Acta Petrologica Sinica

基　　金：国家重点基础研究发展计划(批准号:2006CB403504);国家自然科学基金(批准号:40672070)资助项目

摘　　要：河南省栾川县南泥湖-上房沟斑岩-矽卡岩型钼(钨)矿田是我国最重要的钼矿产区,钼矿探明储量(金属量)达205万吨。区内钼成矿与南泥湖和上房沟两个花岗斑岩小岩体关系密切,两岩体产于华北克拉通南缘,岩石为高硅、富碱和较高分异指数的碱性-碱钙性、过铝质花岗岩。其微量元素地球化学组成具有显著亏损Eu、Sr、Ba、Ti的特征,表明岩浆经历过相当高程度的分异演化。较低的εNd(t)值(-12.7～-15.5)和年轻的Nd模式年龄(1.48～1.71Ga)表明其成岩物质来源主要为年轻的地壳物质。南泥湖和上房沟岩体的锆石LA-ICPMS U-Pb年龄分别为149.56±0.36Ma(MSWD=1.5)和135.38±0.29Ma(MSWD=1.4)。结合现有的秦岭-大别造山带中生代花岗岩类的有关地球化学研究成果,东秦岭钼成矿带内的燕山期成矿花岗岩小岩体及大岩基应为扬子克拉通北缘中生代向华北克拉通A型俯冲的地壳物质在碰撞后伸展构造环境下部分熔融的产物并可能有部分地幔物质的参与。成矿小岩体是花岗岩大岩基高度分异演化的结果,花岗岩大岩基结晶分异导致其中挥发分的过饱和、挥发分对正在固结的岩浆体中成矿元素的淋滤是小岩体成矿的关键。The Nannihu-Shangfanggou porphyry-skarn molybdenum (tungten) mining area in Luanchuan County, Henan Province, which boasts more than two million tons of molybdenum metal, is the most important molybdenum producer in China. The molybdenum mineralization is closely related to the Nannihu and Shangfanggou granite porphyries. The two granite porphyries occur in the southern margin of North China craton and are of alkalic to alkalic-calcic peraluminous, characterized by high SiO(2), K(2)O, and Na(2)O contents and high DI. The rocks are significantly depleted in Eu, Sr, Ba, and Ti, which might have resulted from high degree crystallization diffractionation of feldspar, iron and titanium oxides. The relative low epsilon(Nd) (t) values (-12.7 similar to -15.5) and young Nd model ages (1.48 similar to .71Ga) of the rocks suggest that the granite porphyries were most likely derived mainly from partial melting of rather young crustal material. LA-ICPMS U-Pb data on zircons from the Nannihu and Shangfanggou granite porphyries indicate that they were crystallized at 149.56 +/- 0.36Ma (MSWD = 1.5), and 135.38 +/- 0.29Ma (MSWD = 1.4), respectively. Considering the geochemical characteristics of the other Mesozoic granitic rocks from the Qinling-Dabie orogen in literatures, we suggest that the Yanshanian orerelated granite porphyries and granite plutons from the east Qinling molybdenum mineralization belt were formed under post-collisional tectonic regime and were derived from the crustal material originally from northern margin of the Yangtse craton which subducted beneath the southern margin of North China craton and possibly with the involvement of mantle derived material. It can be inferred that the ore-related granite porphyries are highly diffractionated parts of granite plutons, as the magmas crystallizing and the volatile componer is becoming over-saturated, the volatites, which leach and extract ore metals from the subsolidus magmas, ascend along with the remain highly evolved magma and, then, result in the ore-related

关 键 词：东秦岭 钼成矿带 南泥湖 岩成因 成矿作用 过铝质花岗岩 小岩体 华北克拉通南缘 地壳物质 分异演化 扬子克拉通北缘 中生代 岩基 挥发分 化学研究成果 地球化学组成 成岩物质来源 燕山期成矿 大别造山带 岩浆 

分 类 号：P58[天文地球—岩石学]