鞍本地区早前寒武纪地质体铅同位素组成及铀源条件定量计算方法研究

Researches on the Quantitative Calculation of Uranium Origin and the Lead Isotope Compositions of Precambrian Terrains in the Anshan-Benxi Area

本文对比了鞍本地区前寒武纪铅-锌-银矿区和铀矿区的硫化物矿石和花岗岩长石Pb同位素组成,分别用矿石铅二阶段普通铅法、铅构造模式图解和全岩铅同位素组成三阶段拟合法计算了年龄和全岩原始铀含量。结果表明,矿石铅和长石铅模式年龄约为2000 Ma,在铅构造模式图上投影于2000~1600 Ma间,花岗岩和辽河群全岩拟合年龄为2000~1800 Ma;铅同位素组成显示铅-锌-银来自早元古代辽河群地层,连山关地区明显为放射性成因Pb同位素组成,源于富铀花岗岩。连山关矿石铅年龄和全岩三阶段年龄与该区铀矿床沥青铀矿的年龄基本一致;花岗岩原始铀的得失计算表明,该地区不同地质体均经历了约2000~1800 Ma花岗岩重熔改造,花岗质岩石发生了铀的丢失,是连山关地区铀矿的主要来源。

This paper studied and compared lead isotope compositions among the different terrains,such as granites,metal deposits,and metamorphic rocks in the Anshan-Benxi area.Figure prospective plumbotectonics model,two stage common lead H-H model,and three stage model were applied to estimate the correspondent isotopic ages.The results indicated that the correspondent isotopic ages are from 2000Ma to 1600Ma.These isotope ages are similar to that of pitchblende.The lead isotope compositions correspond to the different geological settings.The abnormally high compositions of radioactive lead in the Lianshanguan granites implicited that they rich of uranium.The paleoproterozoic granite source and the metal deposit regions,with normal ore lead isotope compositions originated mainly from the metamorphic rocks of the Liaohe group,and both of them underwent the synchronized tectonic and granites remelting events in the early paleoproterozoic.The primitive uranium lost by the granitic rocks results in the uranium metallogenetic zone of the Lianshanguan area.