Relations between chemical composition of granitic rocks and metallization in the Outer Zone of Southwest Japan

702001-101300-1096-B
Author : N. Oba & M. Miyahisa
Publication : Bulletin of the Geological Society of Malaysia
Page : 67-74
Volume Number : 9
Year : 1977
DOI : https://doi.org/10.7186/bgsm09197705

Bulletin of the Geological Society of Malaysia, Volume 9, Nov. 1977,  pp. 67 – 74

 

Relations between chemical composition of granitic rocks and metallization in the Outer Zone of southwest Japan

NOBORU OBA

Institute of Earth Sciences, Faculty of Science, Kagoshima University, Kagoshima, Japan 890

and

MICHITOSHI MIYAHISA

Geological Institute, Faculty of Science, Ehime University, Matsuyama, Japan 790

 

Abstract: In the outer zone of southwest Japan, Tertiary granitic rocks of the Southwestern Outer Zone-type are genetically related to the associated metallic ore deposits represented by the Obira-type, which are characterized by a wide range of complex metallization, such as, pneumatolytic, hypothermal and xenothermal types, with most of the ores having extremely variable mineral assemblages.

The physical conditions of formation suggested by mineral assemblage, type of metallization and mode of occurrence, show that the ore deposits formed at high temperatures and shallow depths, and harmonize with those of the Southwestern Outer Zone-type granitic rocks. Throughout that region, granitic rocks of high silica-content are commonly accompanied by many ore deposits; but, in contrast, those of low silica-content by little or no ore deposits. Plots on AKF diagram representing granitic rocks accompanied by many ore deposits suggest concentration in alkali and aluminium during the differentiation and contamination-assimilation of magmas. 

https://doi.org/10.7186/bgsm09197705