甘肃阳山金矿独居石Th-U-Pb化学年龄及其地质和成矿意义  

Chemical Th-U-Pb ages of monazite from the Yangshan gold deposit,Gansu province and their geologic and metallogenic implications.

作　　者：杨荣生[1] 陈衍景[2] 张复新[3] 李志宏 毛世东[2] 刘红杰[5] 赵成海[5] 

机构地区：[1]北京大学造山带与地壳演化重点实验室,北京100871 [2]中国科学院广州地球化学研究所成矿动力学重点实验室,广州510640 [3]西北大学地质学系,西安710069 [4]武警黄金部队12支队,成都610036 [5]中国科学院地球化学研究所,贵阳550002

出　　处：《岩石学报》2006年第10期2603-2610,共8页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(Nos.40572065;40425006);国家973项目2006CB403508课题;科学院百人计划项目;武警黄金部队科研项目的资助

摘　　要：阳山金矿是西秦岭地区新发现的超大型金矿,作者运用电子探针测定了含矿花岗斑岩脉的独居石 Y-Th-U-Pb含量,采用 ChemAge 软件计算了各测点的表面年龄,各测点表面年龄落入3个组。第一组包括9个数据,来自独居石的核心部位,表面年龄变化于297-251 Ma,等时线年龄为268±4Ma(MWSD=0.24),记录了勉略洋俯冲引发的晚古生代弧岩浆活动。第二组包括12个数据,表面年龄变化于237～207Ma,等时线年龄为220±3Ma(MWSD=0.20),属花岗斑岩侵入结晶年龄,与西秦岭碰撞型花岗岩开始大规模发育的时间一致。第三组包括7件位于独居石边缘的测点,表面年龄变化于200～179Ma,等时线年龄为190±3Ma(MSWD=0.15),属阳山金矿的成矿时间。因此,阳山金矿成矿时间与西秦岭中生代陆陆碰撞体制的大规模流体成矿事件一致。The Yangshan gold deposit is a superlarge deposit recently found in western Qinling Orogen. Using electron microprobe technique, the authors analyzed the contents of Y, Th, U and Pb in monazites from the Au-bearing altered granite-porphyry dykes, and then calculate their apparent ages using ChemAge procedure. The apparent ages cluster into three groups. Group 1 includes nine analyses spotted on the cores of monazites, with apparent ages ranging from 297 to 251Ma, and gives an isochron age of 268 ± 4Ma （MSWD = 0. 24）, representing Late Paleozoic arc-magrnatism induced by northward subduction of the Mian-Lue Ocean. Group 2 includes twelve apparent ages ranging from 237 to 207Ma and yields an isochron age of 220 ±3Ma （MSWD =0. 20）. This age records the crystallization of the granite-porphyry dike and accords with the beginning time of the large-scale collision-type granitic magmatism in western Qinling Orogen. Group 3 contains seven analyses spotted on the margins of monazites, yielding apparent ages of 200 179Ma and an isochron age of 190 ± 3Ma （ MSWD = 0. 15） , which represents the metallogenic time of the Yangshan gold deposit. Hence the Yangshan gold deposit is a typical representative resulted from collisional fluid flow and metallogeny due to its metallogenic time agrees with the large-scale hydrothermal metallogenesis during the Mesozoic continental collision in western Qinling Orogen.

关 键 词：阳山金矿 独居石Th—U—Pb化学年龄 电子探针 成矿时间 晚古生代岩浆弧 碰撞体制流体成矿作用 

分 类 号：P597.3[天文地球—地球化学] P618.51[天文地球—地质学]