Chemical characteristics of the mineralized granitoids (I) : Mo and W provinces of the Inner Zone of Southwest Japan.

Abstract

In order to know chemical parameters useful for mineral exploration including Mo, W and Sn, selected granitoids of 47 samples from the Mo province, W province and barren province were analyzed by polarized XRF spectrometer, XLAB 2000. The granitoids of the Mo province are least in Al₂O₃ and ASI, Ga, K₂O and Rb, compared with those of the W and barren provinces. Mafic trace elements such as V, Cr, Zn and Co are controlled by ferric/ferrous state of the granitoids.Trace amounts of Mo is high in the granitoids of the Mo province and least in the barren province. It is rather strange that W is high in both W and Mo provinces. Mo appears to be a useful indicator for molybdenum deposits, and both W and Sn could be useful parameter for mineral exploration of Sn-bearing tungsten deposits in rock geochemical exploration. Compared with conventional wet-chemical analyses of the 1960s, low correlation coefficients (ρ) are obtained from MnO (0.83), P₂O₅ (0.85), Al₂O₃ (0.87) and Na₂O (0.88). Diversity from unity (m) is low on P₂O₅ (0.79) and MnO (0.83), but high on K₂O (1.15), implying that the Lawrence Smith's method gives consistently low values on K₂O contents relative to the XRF. Good correlations between the two methods are seen on CaO and SiO₂ , and also on trace amount of Sn with AA method.