安徽和县香泉独立铊矿床的地质地球化学特征及成因探讨

Geological-geochemical features and genesis of Xiangquan independent thallium deposit in Hexian County,Anhui Province

安徽和县香泉铊矿床位于长江中下游成矿带北侧的皖东地区,是目前为止发现的罕见独立铊矿床。和县地区位于扬子板块、华北板块和大别造山带之间的过渡带,区内无岩浆岩出露。矿床的赋矿围岩为奥陶系下统仑山组微晶灰岩、泥灰岩和泥岩,主要控矿构造为断裂和褶皱。矿床主要由一个矿体组成,矿体总体上为似层状和透镜状,分布与地层走向大体一致。矿床中铊高度富集,黄铁矿是铊的主要载体矿物,铊主要以类质同象形式替代铁进入黄铁矿晶格,其次以纳米级、次纳米级铊矿物颗粒形式产出。矿床的围岩主要蚀变类型有萤石化、重晶石化、硅化和碳酸盐化等。矿床的地质地球化学特征研究表明,铊矿床的形成经历了两个成矿期,即海底热水沉积成矿期和低温热液改造成矿期。奥陶纪海底热水形成含铊黄铁矿建造,早白垩纪低温成矿流体对黄铁矿建造进行叠加改造,并使铊进一步活化富集。香泉铊矿床的发现和研究表明,分散元素铊不仅可以富集形成伴生型多元素矿床,还可以形成单一元素的独立铊矿床。

This paper deals with geological-geochemical features of the only independent thallium deposit so far discovered in eastern Anhui Province. The Hexian County is located in the transitional area of the Yangtze block, the North China Block and the Dabie Orogenic Belt. The host strata of the Xiangquan thallium deposit are Lower Ordovician Lunshan Formation, and the main ore-control structures are Xiaoshan-Xiaolongshan-Dalongshan anticline and two reversed faults （F1 and F2）. The thallium deposit consists mainly of one ore body which is generally stratoid and lenticular in form and extends in accord with the strike of the strata. Alteration is on the whole weak, and the main alteration types are fluoritization, baritization, quartzification, carbonation and limonitization. Thallium is mainly hosted by pyrite. In pyrite, thallium occurs mainly as tiny individual grains in fractures of pyrite, with the rest in the crystal lattices of pyrite. The deposit was formed during the submarine hydrothermal ore-forming period and the epithermal reformation metallogenic period, with the former being dominant. Studies of the Xiangquan thallium deposit show that thallium, as a disperse element, can form not only polymetallic deposits but also independent thallium deposits.