Behavior of iron,uranium, and thorium during formation of secondary quartzites |
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| Abstract: | This paper presents data on the age, composition, and origin of rare-metal granites and associated tin tungsten mineralization in the region of the Tigrin deposit, in the Central Sikhote-Alin' mountain range (Primor'ye). These granites were formed in two successive subphases. The porphyritic protolithionite granites constituting the upper stock belong to the first, and the zinnwaldite granites of the lower (Main) stock belong to the second. The age of the granites of the lower and upper stocks (67 and 73.2 Ma, respectively) was determined for the first time, by the Rb-Sr method. The rare-metal granites crystallized from a magma enriched in fluids, rare alkalies, and ore elements. The tin-tungsten ores of the Tigrin deposit, related to these granites, are classified as deposits of the cassiterite-quartz association, but they differ from such deposits in other regions in the extensive development of stannite, the presence of a substantial amount of varlamoffite in the zone of oxidation, and an insignificant amount of sulfides in the presence of extensive development of topaz and lithium-iron micas. Sc-W-Nb minerals were found for the first time-scandium minerals proper, scandian ixiolite, and scandian-tungsten ixiolite occurring in the form of inclusions in wolframite and cassiterite. In the Tigrin deposit, tin mineralization of the greisen association is genetically related to the rare-metal granites, and extensive vein-veinlet ore zones in hornfels and granites are paragenetically related to them. |
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