多宝山斑岩铜矿区水热蚀变矿物的激光显微探针^（40）Ar／^（39）Ar定年  

￣(40)Ar/￣(39)Ar LASER MICROPROBE DATING ON HYDROTHERMAL MINERALS FROM DUOBAOSHAN PORPHYRY COPPER MINING DISTRICT, HEILONGJIANG PROVINCE, CHINA

作　　者：刘驰[1] 穆治国[1] 刘如曦 黄宝玲[1] 

机构地区：[1]北京大学地质学系

出　　处：《地质科学》1995年第4期329-337,共9页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金

摘　　要：在利用脉冲显微激光探针４０Ａｒ／３９Ａｒ定年技术测定标准样品的Ｊ值和年龄适用范围的基础上，研究了黑龙江省嫩江县北部多宝山斑岩铜矿区水热成因矿物的年代学。结果表明，高钾含量的水热蚀变矿物适合于激光探针的表面微区测定，并且可以克服水热蚀变矿物中的３９Ａｒ“反冲”丢失对年龄结果的影响。矿区的岩浆－水热事件主要有两期，分别为２５３－２２０Ｍａ和１８４－１６２Ｍａ，前者代表了成矿时代，后者反映出由成矿期后岩浆活动所引起的水热叠加事件。The hydrothermal alteration assemblages of Duobaoshan porphyry copper district indicate a spatial distribution of ore bodies and ore belts. They are mainly divided into K-silicate alteration zone, quartz-sericite alteration zone and chlorite-epidotecalcite alteration zone. Some K-rich hydrothermal minerals, produced in K-silicate zone and quartz-sericite zone: K-feldspar, biotite, sericite and illite, are considered to be directly associated with the hydrothermal events of mineralization and ore forming period.The experiment used laser microprobe 40Ar/39Ar dating technique equipped with a Nd-YAG pulsing laser. The background level of mass spectrometer is 36Ar≈1×10-15mol, 37Ar≈4×10-16 mol, 39Ar≈2×10-15 mol, 40Ar≈9×10-15 mol, with a measurement of atmospheric Ar isotopes being (40Ar/36Ar)A≈295.3±1.0(1σ). We determined two K-rich standard samples: K-feldspar (SB-778, K-Ar method, recommend.ed as (1 .84±0.08)Ma) and muscovite (KF-1M, Rb-Sr method, recommended as 803Ma). The results of laser microprobe 40Ar/39Ar dating are (2.6±0.1 ) Ma and (785.5 ±6.5) Ma, respectively.Following electron microprobe studies, the whole rock samples collected from mineralization zone were made of a thin section about 0.5 mm in thickness. Then,the hydrothermal minerals are measured in situ by means of laser microprobe 40Ar/39Ar technique under a microscope's location. The age results of ten samples show that there are two major periods of hydrothermal events: 253-220 Ma and 184-162 Ma,respectively, corresponding to the Late-Variscan and the Early-Yanshanian magmatic activities in the district.It is considered that Late-Variscan magmatic activities formed the mineralization intrusion of granodiorite and granodiorite porphyry bodies, and Early-Yanshanian magmatic intrusion mostly emerged in the northwest of structural belts of the district without porphyry copper mineralization. Therefore, the period of hydrothermal mineralization is 253-220 Ma while another hydrothermal period, 184-162 Ma,reflects an superimposed infl

关 键 词：定年 水热蚀变矿物 氩同位素 激光探针 铜矿床 

分 类 号：P618.410.4[天文地球—矿床学]