四川大水沟楚碲铋矿的两类显微文像结构

根据大水沟楚碲铋矿的产状、“客晶”磁黄铁矿的形态、展布和化学成分，其显微文像结构可分成传统意义上的“交代型”、“出溶型”两类，但它们形成的根 本原因是由于富碲、铋流体在相对封闭环境中交代了早期硫化物（磁黄铁矿为主）。交代强 度及其环境的稳定程度决定了显微文像结构的特征：强度弱、稳定性差，可形成具明显“交代”特征的楚碲铋矿；强度大、环境稳定则早期硫化物在交代流体中充分“溶解”，形成的文像结构往往具有 “出溶”特征。

Two Types of Micrographic Textures in the Tsumoite of Dashuigou Independent Tellurium Deposit, Sichuan Province

According to the textural features of the guttate, myrmeki tic, or threa dlike minerals and the occurrences of host tsumoites under optical and scann ing electronic microscopes, the micrographic textures of tsumoite and sulfides i n Dashuigou tellurium deposit are of two types. The first type shows metasomatic relicts of earlier pyrrhotites hosted in tsumoite, while the second type has t he `guest minerals or mineral mixtures' elongated in specific directions and d istributed metrically in tsumoite `hoster'. They suggest simultaneously two co ntradictory formation mechanisms in traditional meaning-metasomatism and exso lution. However, the mineral paragenesis and occurrence, similarity in chemical comp ositions by EPMA between the "guest minerals" and accompanying sulfides and tell urides of earlier stages, and contrast letween the 2nd texturetype and the ideal model of `exsolution' eliminate the possibility of `exsolution' and conclude a comprehensive metasomatism under varying environments by which these two types o f textures have been formed. From the first to the second type texture, metasoma tism of earlier pyrrhotite and chalcopyrite by Te, Bi rich fluids is intensified with the fluid/sulfides ratios increased and the environment stabilized. Weak a lteration in fluctuational environments would produce tsumoites with typical met asomatic features, whereas complete alteration in a stable environment could dis solve earlier pyrrhotites and/or chalcopyrites in the fluids and produce exsolut ion-like micrographic texture.