广西大厂矿区锡矿床地质特征及硫同位素组成

对大厂矿田进行详细地质调查并对铜坑和大幅楼矿床进行系统观察与研究,结果表明：长坡矿床主要由裂隙脉型、细脉型、似层状、细脉-网脉浸染状等矿化类型组成。裂隙脉型矿化在垂向上通常呈透镜状,细脉型矿化具有稳定的走向与倾向,似层状矿化一般沿地层中的断裂系统充填和交代变化;巴力-龙头山矿床矿物组分复杂、种类繁多。矿石结构以他形-半自形以及细粒为主,其次为填隙结构、固溶体分离结构、溶蚀结构、反应边结构以及压碎结构等;矿石构造包括块状、细脉状、浸染状、条带状、晶洞状、生物残余和角砾状等构造。同时,对金属硫化物的硫同位素进行分析,结果表明：铜坑矿床的硫同位素δ34S值较分散,介于-0.30%-1.38%之间;而大福楼矿床硫同位素δ34S值较集中,变化范围为-0.15%-0.22%,说明不同矿床的硫同位素组成存在较大的差异。大福楼矿床相对铜坑矿床而言,硫同位素组成具有更为集中的特点。同样,不同类型金属矿物的硫同位素组成也不同,磁黄铁矿的硫同位素较为分散,而黄铁矿的硫同位素组成更为均一。总体来看,硫同位素组成的差异既体现在矿床尺度上也表现于不同类型的矿物上,这可能受到矿床不同的硫来源影响。

Geological features and S isotope composition of tin deposit in Dachang ore district in Guangxi

The geological investigation of the Dachang ore field was carried out in detail, and the geological characteristics of the deposits, consisting of the Tongkeng and Dafulou deposits, were observed and researched systematically. It suggests that the mineralization types of Changpo ore are composed of cracking vein, thin vein, bedded vein and thin vein-net vein disseminated types. The cracking vein ore is usually lens-shaped in the vertical direction. The thin vein ore is always characterized by a stable trend and tendency. The bedded ore always occurs along the strata in the way of filling and metasomatism in the fracture system. In terms of Bali-longtoushan ore, it is characterized by complicated mineral components and a variety of minerals. More generally, ore textures consist of the anhedral-subhedral shapes and thin particle, and secondary with the interstitial texture, solid solution separation texture, dissolution texture, corona texture, and crushing texture, yet ore structures include the massive, veinlet, disseminated, banded, miarolitic, biological residual and brecciated structure. In addition, the sulfur isotopes of the metal sulfide were analyzed. The results show that the δ34S values of Tongkeng ore range from-0.30% to 1.38% with more dispersed characteristics, yet in terms of Dafulou ore, the δ34S values are from-0.15% to 0.22% which are characterized by more focused. This indicates that the sulfur isotope composition has large difference between the different deposits. The sulfur isotope values of the Dafulou ore are concentrated relatively, yet are dispersed for the Tongkeng ore. Likewise, there are also divergences of sulfur isotopes for the different minerals. The sulfur isotope values of pyrrhotine are dispersed, yet are homogeneous for pyrite. In short, the divergence of the sulfur isotope is reflected in both the different deposits and minerals, all of these may account for the difference of sulfur sources.