赣杭铀成矿带北禾山地区绿泥石矿物学特征及找矿启示

Mineralogical Characteristics of Chlorite in the Beiheshan Area of the Jiangxi-Hangzhou Uranium Metallogenic Belt and Its Prospecting Implications

玉华山火山盆地位于赣杭成矿带西南段,在全国铀资源潜力评价中被列为重要的火山岩型铀矿找矿远景区。近年来,盆地南侧北禾山地区铀矿勘查出现新突破,发现一批铀矿体。为查明该区矿石的物质组分,通过详细的扫描电镜和电子探针成分分析,发现矿石矿物以沥青铀矿为主,脉石矿物为萤石、钠长石、黄铁矿、绿泥石、水云母等,围岩蚀变主要为绿泥石化、赤铁矿化、黄铁矿化、水云母化、钠长石化,其中绿泥石化与铀矿化关系密切。该区域绿泥石以铁镁绿泥石为主,形成温度为230℃左右,硫逸度平均值约为-2.82,氧逸度平均值约为-44.44,指示该地区铀矿形成于中低温、高硫逸度、低氧逸度的物理化学条件。通过与相山铀矿田对比,发现两区具有相似的控矿规律和矿物学特征,因而认为北禾山地区成矿地质条件优越,找矿潜力较好,可进一步扩大勘查工作范围。

Yuhuashan volcanic basin is located in the southwest of Jiangxi-Hangzhou metallogenic belt.It is listed as an important volcanic rock type uranium mineralization prospect in the national uranium resource potential evaluation.In recent years,new breakthroughs have been made in uranium exploration in Beiheshan area on the south side of the basin,and a number of uranium ore bodies have been found.In order to find out the material composition of the ore in this area,detailed scanning electron microscope and electron probe composition analysis are conducted.It is considered that the ore minerals are mainly pitchblende,and the gangue minerals are fluorite,albite,pyrite,chlorite and hydromica.The wall rock alteration is mainly chloritization,hematite mineralization,pyritization,hydromica and albitization,in which chloritization is closely related to uranium mineralization.The chlorite in this area is mainly Fe-Mg-chlorite,the formation temperature is about 230℃,the average oxygen fugacity is about-44.44,and the average sulfur fugacity is-2.82,indicating that the uranium deposit in this area was formed under the physicochemical conditions of medium low temperature,high sulfur fugacity and low oxygen fugacity.Compared with Xiangshan uranium orefield,there are similar ore-controlling regularity and mineralogical characteristics in Beiheshan area.With superior metallogenetic geological conditions and prospecting potential,the exploration of the Beiheshan area can be further expanded.