Contents of Arsenic in Granitoids and Their Relation to Mineralization
1976 Volume 26 Issue 139 Pages 327-339
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1976 Volume 26 Issue 139 Pages 327-339
About 850 granitoids from various localities, mostly from the Japanese Islands are analyzed for arsenic by an arsine-generated atomic absorption method. The range varies from 0.1 to 87 ppm in fresh rocks, but generally from 0.2 to 6 ppm. Foliated granitoids of the high T/P type metamorphic belts have the lowest range and the average is 0.7 ppm. Massive granitoids of the nonmetamorphic belts are 2.1 ppm in their average; the Sierra Nevada batholith falls within the same category (avg. 2.1 ppm).
Miocene granitods in the southwestern Outer belt, which is a tin belt, have the widest range as 0.1-87.0 ppm and the highest average as 5.9 ppm. Tin granitoids in other regions, such as the Erzgebirge (avg. 17.3 ppm), Malay Peninsula (avg. 5.0) and Mt. McKinley, Alaska (avg. 19.2 ppm), are also high. Thus arsenic in granitoids becomes to be enriched in the following order: deeply sheeted concordant type, common discordant type, and discordant type tin granite. Generalized average in the previous papers, 2 ppm, corresponds to the average of the common discordant type batholith and stock.
Small granitoid stocks associated with arsenic and tin (plus Cu+Pb+Zn) mineralizations have generally higher contents of arsenic than those unrelated. Pervasively altered granitoids in base metal mining areas are enriched in arsenic. The element may be useful in geochemical exploration.
