Study on the Metallogenic Environment of Uraniferous-Polymetallic Black Rock Series in the Northern Part of Northwestern Hunan
The northern part of northwestern Hunan mainly includes Xiaoping depression and Ciligraben basin,which is the most abundant area of useful elements and minerals in the whole metallogenic belt.Based on the systematic geological evaluation and sampling analysis in the northern part of northwestern Hunan,the results show that the environment of uranium polymetallic mineralization in the study area was mainly a transition from deep-water to shallow-water environment,and that the marginal shallow-sea environment in the ocean is better for uranium mineralization.The characteristic parameters of trace elements indicated that the marine environment in the study area changed from relatively oxygen-rich to anoxic environment from Sinian to Cambrian period,in the context of seawater hypoxia,there were one or two short,small-scale oxygenation events in the Cambrian period.The study of elements such as U,Th,and rare earths have shown that the enrichment of U in the northern part of northwestern Hunan accelerated significantly from Late Sinian period to Early Cambrian period,and then gradually decreased,indicating that the hydrothermal process in the ocean in the study area was the strongest in Early Cambrian period,and then gradually weakened,and deep materials involvement the process of mineralization,the better mineralization was the result of the stronger influence of hydrothermal process.The study results of Ce showed that there were three obvious sea level"rise-fall"transition in the study area from Sinian to Cambrian in the context of the large sea regression,and this geological history can be divided into four stages of sea level rise and fall changes.Anomalous reduction of Ce in sediments and the reducibility in the ocean increased during the sea level rise phase favor enrichment of organic matter and uranium polymetallic.The findings of mineralogy in the study area are in good agreement with the conclusions obtained by geochemical methods.The crystal type,symbiosis and Y,Se and other elements of uraninite ore and coffinite indicated that the mineralization of black rock series in the study area was under the condition of high temperature and strong reducing conditions during the Cambrian period,and that deep source materials were carried during the seafloor heat flow gushing process to participate in the mineralization.
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