Heavy mineral assemblages of sandstones in the Shiiya and Nishiyama formations, the Higashiyama oil belt, Niigata Prefecture

Abstract

The total content by weight of heavy minerals is large in A-type sandstone, medium in B-type sandstone and small in C-type sandstone. The heavy mineral assemblages of the A-type sandstone; rich in augite and hypersthene, no epidote, no glaucophane: the B-type sand-stone; rich in hornblende and magnetite including ilmenite, poor in augite, rare in epidote and garnet, no glaucophane: the C-type sandstone; rare in oxy-hornblende, rich in hornblende, poor in augite and hypersthene, rare in epidote and glaucophane.
From these facts, A-type sandstones are concluded to be originated from Tertiary pyroxene andesitic rocks, B-type sandstones from Tertiary hornblende dacitic rocks, and C-type sandstones from the pre-Tertiary basements including glaucophane bearing metamorphic rocks.