Greisen-vein type tin deposits are the most important mineralization type in Huashan granite, Guangxi, South China:
The Huashan granite is an oxidized-type granite. In this granite body the element tin predominantly exists as Sn4+
in primary tin-
bearing minerals, such as biotite, amphibole, titanite, rutile, ilmenite and cassiterite. Based on the comprehensive mineralogical
study, we recognize that greisenization developed through interaction of the medium-fine-grained biotite granite with a residual
magmatic fliud formed by adequate differentiation and evolution. At the early stage of alteration, the tin in the primary tin-bearing
minerals was leached out by magmatic fliud, and entered into fluid or secondary mineral phases, such as rutile, muscovite etc.
to accomplish the first concentration. Then, at the later stage of alteration, the mineralizing fluid was able to redissolve earlier
precipitated tin-bearing minerals, and tin entered into mineralizing fluid to accomplish the second concentration. Tin dissolved
in fluid combined with ligands, such as F-
, Cl
-
etc. to form stable complexes and transported. During greisenization, there was an
increase in pH, a decrease in temperature and a decrease in ligand concentration, the stabilities of tin complexes in fluid were
dropped down, and then the tin mineral deposits were formed
