湖南鲁塘石墨矿Re-Os同位素研究

发布时间：2018-05-13 12:10

本文选题：鲁塘 + 石墨矿　；参考：《岩矿测试》2017年03期

【摘要】：石墨具有较高的Re、Os含量,可望成为理想的Re-Os同位素测年对象,但迄今国内外研究较少,尤其在煤层经变质作用形成石墨过程中,其中Re-Os同位素体系的变化还有待研究。湖南鲁塘石墨矿是我国典型的隐晶质石墨矿床之一,矿体产于二叠系龙潭组煤系地层中。本文采用Carius管逆王水溶解样品,直接蒸馏、微蒸馏分离纯化Os,丙酮萃取法分离富集Re,热表面电离质谱法对鲁塘矿区石墨样品以及外围原煤进行了Re-Os同位素分析。结果表明:鲁塘石墨的Re含量为0.901~9.794 ng/g,Os含量为7.3~189.5 pg/g,Re-Os同位素等时线年龄为155.6±3.6 Ma,该年龄与鲁塘石墨矿东侧骑田岭岩体第二阶段中粒黑云母花岗岩锆石U-Pb年龄153~157 Ma一致,表明了龙潭组煤层受到骑田岭岩体"烘烤"作用,发生热接触变质作用,使得靠近骑田岭岩体原煤变质为石墨,形成石墨矿床。通过对比石墨、原煤和骑田岭岩体Re、Os含量及比值,发现石墨中的Re、Os主要来源于原煤,并根据石墨Re-Os等时线初始(187Os/188Os)i值(0.686±0.032),推测骑田岭岩体在侵入煤系地层过程中,有少量具有较低187Os/188Os值的Os被碳质吸附。
[Abstract]:Graphite is expected to be an ideal Re-Os isotopic dating object due to its high content of Reo Os, but little research has been done at home and abroad, especially in the process of coal seam metamorphism to form graphite, in which the change of Re-Os isotopic system remains to be studied. Lutang graphite deposit in Hunan Province is one of the typical cryptic graphite deposits in China. The orebody occurs in the coal measure strata of Longtan formation of Permian system. In this paper, Carius tube reverse Wang Shui dissolved sample, direct distillation, microdistillation separation and purification, acetone extraction and thermal surface ionization mass spectrometry were used to analyze the Re-Os isotopes of graphite samples and peripheral raw coal in Lutang mine area. The results show that the re content of Lutang graphite is 0.901g / g 9.794 ng / g / Os = 7.3N 189.5 PG / g Re-Os isochron age of 155.6 卤3.6Ma. this age is in agreement with the zircon U-Pb age of 153157Ma in the second stage of the Qitianling granite in the east side of the Qitianling granite, Lutang graphite deposit, which is similar to the zircon age of 153157Ma in the second stage of the Qitianling granite in the east of the Lutang graphite deposit. It is indicated that the coal bed of Longtan formation is "baked" by Qitianling rock mass, and thermal contact metamorphism occurs, which makes the raw coal near Qitianling rock body metamorphism into graphite and forms graphite deposit. By comparing the content and ratio of Reos in graphite, raw coal and Qitianling rock mass, it is found that the Reo Os in graphite are mainly derived from raw coal, and according to the initial value of 1877 Osr 1888 Ossii of graphite Re-Os isochron, it is inferred that the Qitianling rock mass is in the process of intruding into coal measure strata. A small amount of Os with low 187Os/188Os value was adsorbed by carbon.
【作者单位】：中国地质科学院矿产资源研究所;北京大学造山带与地壳演化教育部重点实验室;国家地质实验测试中心;
【基金】：国家自然科学基金面上项目(41673060) 中国地质调查局地质调查项目(DD20160095)
【分类号】：P597;P619.252

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