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Ar~(40)/Ar~(39)同位素计时法是七十年代以后发展起来的一种新方法。和常规方法相比,此法有以下优点:①分析精度比常规 K—Ar 法高;②可追索样品结晶后的热史;③可测定硫化物的年龄。秦(岭)巴(山)地区位于中国东、西、南、北构造块体的交接处,经历了强烈的、多阶段的构造运动,致使常规的计时方法效果不好。1985年,陕西地质矿产局区域地质调查队花岗岩室在秦巴地区采了八个 Ar~(40)/Ar~(39)年龄样,由中国科学院地球化学研究所分析。年龄谱数据见表1。1.路家沟岩体:位于河南登封县,岩性为片麻状混合花岗岩。该岩体贯入登封群郭家窑组,并被嵩山群石英岩不整合覆盖。郭家窑组角闪片麻岩等时年龄为1931Ma~*。路家沟岩体
Ar ~ (40) / Ar ~ (39) isotope timing method is a new method developed since the seventies. Compared with the conventional method, this method has the following advantages: (1) The analysis accuracy is higher than that of the conventional K-Ar method; (2) The thermal history after recrystallization of the sample can be recoded; (3) The age of the sulfide can be determined. The Qin (Ling) Ba (mountain) region is located at the junction of East, West, South and North tectonic blocks in China and has undergone intense and multi-stage tectonic movements, resulting in the ineffectiveness of conventional timing methods. In 1985, the granite chamber of the Regional Geological Survey Team of Shaanxi Bureau of Geology and Mineral Resources collected eight Ar ~ (40) / Ar ~ (39) age samples from Qinba area and was analyzed by Institute of Geochemistry, Chinese Academy of Sciences. Age spectrum data are shown in Table 1.1 Lujiagou rock mass: Located in Dengfeng County, Henan Province, the lithology is gneissic mixed granite. The rock mass penetrates the Guojiayao Formation in Dengfeng Group and is unconformably covered by Songshan Group quartzite. The Guojiayao Formation hornblende gneiss isochronous age is 1931Ma ~ *. Lujiagou rock mass