华南某大型铀矿床成因新识

华南某大型铀矿床具典型的岩溶特征。研究发现矿石中铀主要以微脉浸染状沥青铀矿形式存在，沥青铀矿的晶胞参数ａ０＝５．４１６～５．４２８，含氧系数为２．３１～２．３４，属低、中温热液成因。矿床中出现一套低、中温热液矿物组合。测得成矿温度为１５０～１８１℃（均一法）。矿床中热水叠加改造特征明显，故建议称之为岩溶热造铀矿床，是一种特殊的新成矿类型。

A NEW GENETIC UNDERSTANDING FOR A HIGH-TONNAGE URANIUM DEPOSIT IN SOUTH CHINA

The Bentou uranium deposit in Hunan Province of South China is a high-tonnage,high-grade and shallow depth ore body. The host rocks include limestones of the early Carboniferous Shidengzi Formation,which are overlain by shales and sandstones of early Carwere schistoided and mylonitized. Mineralizing ages are 135, 119 and 65 m. y. . On the basis of fluid inclusion data, hydrothermal fluids had temperatures of 150～181℃. Uranium was deposited as microveinet-disseminated pitchblende with unit cell parameter a of 5.416～5. 428 and oxidation coefficient of 2. 31～2. 34, indicating its low-intermediate temperature hydrothermal genesis. Antimonselite, violarite, ullmannite, niccolite and nickel-pyrite are the principal hydrothermal minerals in the deposit. Carbon, oxygen, sulfer and lead isotopic analyses of the ores and the host rocks suggest that hydrothermal system of Bentou deposit was by meteoric fluids and mineralizing matter derived from the host rocks. Therefore, authors may suppose that the Indosinian paleokarst facilitated uranium enrichment in the paleokarst system. Then, uraniumbearing underground water heated by the Yanshanian and the Himalayan tectonic movements transformed and superimposed the uranium-bearing paleokarst sediment. As a result, Bentou uranium deposit, called paleokarst hydrothermal superimposition and transformation type deposit,was formed. Mixing of uranium-bearing warm tectonic water with cool paleokarst water may play an important role in deposition of mineralizing matter.