Small and short-lived magma batches at composite volcanoes: time windows at Tongariro volcano, New Zealand

Abstract

Many are volcanoes are characterized by frequent eruptions of small ( 3 ) volume. A key question is do such small events represent discrete magma batches or do these magmas share a partial common history and to what depths? The last 1000 years of eruptions at Tongariro volcano, New Zealand, offer a series of time-calibrated 9snap shots9 of an are magmatic system. Complex and abrupt changes in magma chemistry at Tongariro attest to the small size ( 3 ) and short life span (years to decades) of many magma batches and a powerful role for shallow level assimilation, fractional crystallization and mingling in modifying magma compositions on time scales as short as a year.