华南—古岩溶型铀矿床中有机质的热成熟异常及其矿床成因意义

THERMAL MATURATION ANOMALIES OF ORGANIC MATERIALS IN A URANIUM DEPOSIT OF SOUTH CHINA AND ITS SIGNIFICANCE IN METALLOGENY

华南某层控铀矿床中有机质可分为原生沉积型、热液变质型和运移型三种类型,其母质类型为腐泥-腐殖型,主要来源于海相微体生物、藻类及少量源于陆相高等植物。根据镜质体反射率、饱和烃气相色谱和某些地球化学指标,表明矿石中有机质呈现异常热成熟特征,这对揭示该矿床热水叠造成矿机制具有指纹意义。本文还首次合理解释矿石中铀与有机碳含量间复杂关系的原因。

This paper presents the results of preliminary researches on types, origin and thermal maturation anomalies of organic materials in the largest paleokarst uranium deposit of China. On the basis of their modes of occurrence and characteristics, the organic materisls may be divided into three types: (a) indigenous type, (b) hydrothermal metamorphic type and (c) migration type. The organic materials of both migration type and hydrothermal metamorphic type are closely associated with uranium mineralization. The original substance of the organic materials is of sapropelic-humic type. According to bitumen reflectances, infrared spectra and gas chromatogram, the organic materials in the ores are considered to be more mature than those in the wall rocks, which is attributed to hydrothermal reaction. This phenomenon is quite important in the genetic study of uranium deposits where hydrothermal transformation mineralization is indistinct. The complex correlation between uranium content and organic carbon amount is studied and explained.