Abstract
Heavy mineral assemblages of sandstones of the Miocene Yaeyama Group were examined using core samples from a borehole of MITI Miyakojima-Oki drilled at the sea floor off Miyako-jima, Ryukyu Islands.
Identified heavy mineral species are garnet, zircon, tourmaline, amphibole, epidote, rutile, pyroxene, glauconite, chlorite, monazite, staurolite and anatase, and among them, garnet appears in highest frequency in all specimens. Characteristic mineral as staurolite is found in many samples inspite of its low frequency. These minerals are presumed to have been supplied from the source area consisting of granitic rocks and metamorphic ones. Such assemblages resemble to those of the same group and its equivalents distributed in small islands such as Iriomote-jima, Yonaguni-jima and also in Formosa. This fact may suggest a paleogeographical relevancy between a source land near Miyako-jima and that adjacent eastward to Formosa which were named as the East China Old Land (LIEW and LIN, 1974).
