A COMPARATIVE STUDY OF EARLY MIOCENE VOLCANIC ACTIVITY ON SAKHALIN AND EARLY-MIDDLE MIOCENE ACTIVITY IN THE EASTERN SIKHOTE-ALIN: PETROCHEMISTRY, LOCATION, AND PALEOGEOGRAPHY OF EARLY MIOCENE VOLCANICS ON SAKHALIN

Abstract

In terms of their chemistry, most of the Early Miocene volcanic rocks of Sakhalin can be referred to a tholeiitic series and merely a small amount, to a calc-alkalic series. Early Miocene volcanic eruptions occurred mainly in subaqueous conditions and were replaced by subaerial events after some of the volcanic cones had emerged from the sea. Eight central-type volcanoes have been identified. In terms of their average chemical composition, the Sakhalin volcanics approximate the Lesser Antilles rocks and volcanics from some other primitive island arcs.