THE ANDESITE EXTRUSION OF MOUNT MISHENNAYA, KAMCHATKA, AND ITS AGE

Abstract

The hornblende andesite extrusion of Mount Mishennaya belongs to the andesite subcomplex of the Avacha Neopleistocene-Holocene basalt-andesite volcanic complex. The Mishennaya dome belongs to the extrusive areal field found on the north bank of Avacha Creek. It is believed that the subcomplex took a long time to develop from the Early to Late Neopleistocene. Three K-Ar age determinations of the Mishennaya andesites have been made using a hornblende monofraction for one determination and the nonmagnetic fraction of the rocks for the other two. The resulting age values are 0.60, 0.57, and 0.59 Myr. These are consistent with previous paleomagnetic determinations and with results from fission track analysis (0.7 Myr).