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Two zoning patterns in tin deposits are proposed according to geochemical environments. 1. Acidic zoning pattern is characteristic of tin deposits associated with sialic rocks and tin-bearing veinsin carbonate rocks. Six zones may be recognized from the granite mass outwards: (1) Nb-Ta-(Li-Be-Mo), (2)Sn, (3) W-(Sn), (4) Cu-Pb-Zn-(Bi), (5) Sb-Hg, and (6) Au-Ag. This kind of zoning is related with thetemperature difference involved in the deposition of various ore minerals ilx an acidic (or neutral) geochem-ical environment. From the granite outwards, the temperature decreases gradually with increasing distancefrom the heat source. 2. Alkaline zoning pattern is typical of tin deposits occurring in calcareous and magnesian carbonaterocks. Three zones can be recognized from the granite mass outwards: (1) Cu-Zn-Bi, (2) Sn, and (3)Fe-Pb-Zn-Cn. A calcium and magnesium rich alkaline environment is responsible for this zoning pattern.In this case the normal sequence of mineral formation will be greatly changed owing to neutralization whenan acidic ore-forming solution enters the alkaline environment. Zoning structure in tin deposits is very complex and highly variable, depending on: (1) the geochemicalenvironment in which the deposits are formed, (2) the type of shield beds, and (3) the character of ore-forming solutions. However, there are some known examples showing similar zoning patterns for thedeposits that are similar in these three aspects.
Two zoning patterns in tin deposits are according to geochemical environments. 1. Acidic zoning pattern is characteristic of tin deposits associated with sialic rocks and tin-bearing veinsin carbonate rocks. Six zones may be recognized from the granite mass outwards: (1) Nb (2) Sn, (3) W- (Sn), (4) Cu-Pb-Zn- (Bi), (5) Sb- Hg, and -Ag. This kind of zoning is related with the temperature difference involved in the deposition of various minerals minerals ilx an acidic (or neutral) geochem-ical environment. From the granite outwards, the temperature decreases gradually with increasing distancefrom the heat source. Three zones can be recognized from the granite mass outwards: (1) Cu-Zn-Bi, (2) Sn, and (3) Fe-Pb-Zn- Cn. A calcium and magnesium rich alkaline environment is responsible for this zoning pattern. This case the normal sequence of mineral formation will be greatly changed owing to neutralization when an acidic ore-forming solution enters the alkaline environment. (1) the geochemicalenvironment in which the deposits are formed, (2) the type of shield beds, and (3) the character of ore-forming solutions. However, there are some known examples showing similar zoning patterns for the deposits that are similar in these three aspects.