黑龙江省东部麻山群黑云斜长片麻岩中锆石的年龄及其地质意义  

The Source Componet of 40 Ar/ 36 Ar of the Earth's Atmosphere and It's Geological Implication

作　　者：宋彪[1] 李锦轶[1] 牛宝贵[1] 徐文喜[2] 

机构地区：[1]中国地质科学院地质研究所 [2]黑龙江省地质矿产局第一地质勘查所

出　　处：《地球学报（中国地质科学院院报）》1997年第3期306-312,共7页Acta Geoscientia Sinica

摘　　要：采自西麻山煤矿附近的麻山群黑云斜长片麻岩中，分离出了较多的锆石。采用单颗粒锆石逐级蒸发沉积法对其进行了定年研究，获得的１０粒锆石的２０７Ｐｂ／２０６Ｐｂ年龄相当一致，平均值为５２７．５±４．４Ｍａ。所测岩样经岩石学和矿物学研究均未发现有显著的后期叠加变质作用，因此，可以认为所测样品的主变质作用发生在寒武纪早－中期，而不是早前寒武纪。麻山群的原岩时代可能也不全是早前寒武纪，而更可能是一个较复杂的岩石构造地层单位，需要将其解体、重新认识和命名。The Enshi metorite fell on Dec. 26, 1974, in the Enshi County , Hubei Provence, China (109°51′20″E,30°34′40″N). The total mass recovered is about 9.57kg. The Enshi meteorite is an ordinary chondrite, classified as belonging to group H5. The K Ar and Ar Ar geochronology indicates that the K Ar gas-retention age is 4 503±91Ma, 40 Ar/ 39 Ar plateau age, total gases Ar Ar age and isochron age are 4 518±8Ma, 4 515±23Ma and 4505±16Ma, respectively. The result of ages shows that the parent body of Enshi meteorite has not suffered collisional event probably.A correlation diagram from gases release above 1000℃ gives a primordial trapped 40 Ar/ 36 Ar ratio, 0.89±0.44, using York formula. From the plot of derived K/Ca ratios, it is concluded that the high temperature release of trapped Ar is from Ca rich phases with low K/Ca ratios, almost cerntainly the bronzite.The ratio, 0.89±0.44, is possible that the source compnent of 40 Ar/ 36 Ar of the earth's atmosphere and the trapped Ar originated in the solar wind.

关 键 词：锆石 麻山群 片麻岩 黑云斜长片麻岩 同位素测年 

分 类 号：P588.345[天文地球—岩石学] P597[天文地球—地质学]