670矿床火山围岩铀赋存状态及配分研究

A STUDY OF THE EXISTING FORM AND DISTRIBUTION OF URANIUM IN HOST VOLCANIC ROCK IN THE 670 DEPOSIT

670矿床是中国东南部中生代火山岩带内典型的火山岩型铀钼矿床;矿床具有叠加成矿特点.本文利用诱发裂变径迹的方法研究了矿床火山围岩中铀的赋存状态及配分.结果表明火山围岩中的铀主要有三种赋存状态:(一)分布在火山基质及晶屑内均匀分散的质点铀,其裂变径迹是弥散状或弧立星射状分布;(二)吸附在蚀变矿物表面、矿物隙间及微裂隙内的聚合态铀,其裂变径迹为密集带状及团块状;(三)分布在副矿物中或呈铀矿物存在的铀,其裂变径迹为聚合星射状及团块状.矿物的蚀变过程,如绿泥石化、碳酸盐化等可改变火山围岩铀的赋存状态,造成铀在岩石中的活化和预富集,从而有利于矿化.因此火山围岩中铀的含量虽然较低,但对火山岩型铀矿的形成仍有重要意义.

The 670 deposit is a typical volcanogenic uranium deposit in Mesozoic volcanic rock belt in Zhejiang. With the method of fission track, the author studied the existing form and distribution of uranium in the wall volcanic rock and the effects of alteration on them. The results show that the existing form of uranium may be divided into three types: (1) the uranium particles scattered uniformly in the volcanic groundmass; (2) the uranium absorbed in the iron oxides, alterated minerals, microfissures or interqranular cracking of minerals; (3) the microcrys-tal of uranium minerals and uranium - bearing accessory minerals. The latter two existing forms of uranium are in the majority. Carbonatization and chloritization change the existing forms of uranium and mobilize the uranium in host volcanic rock. This contributes to the mineralization. Therefore, the author considers that the mobilized uranium in alteralization is very important for the mineralization, in spite of the minor content of uranium in host volcanic rock of 670 deposit.