Petrogenetic links between the Dunedin Volcano and peripheral volcanics of the Karitane Suite

Abstract

ABSTRACTThe Karitane Suite of East Otago marks the northern extent of evolved magmas erupted contemporaneously on the periphery of the Miocene Dunedin Volcano. Compositions range from relatively primitive basalts to highly evolved trachyandesites and phonolites with strong geochemical affinity to Dunedin Volcano magmas and their fractionation trends. Karitane trachyandesites are abundant with fluidal, hornblende-rich mafic inclusions interpreted as remnant features of magma mingling between basanitic dikes and evolved magma reservoirs dispersed in the crust. Mineral data reveals discrete populations of Mg-rich diopside within evolved members that suggest they were inherited during mixing with basanite magmas prior to eruption. It is proposed that the overall distribution and concentration of evolved magmas within the Dunedin volcanic system is source-controlled and a function of mantle productivity. The Karitane Suite is therefore the product of low-volume, dispersed peripheral magma reservoirs recharged and mixed with rapidly ascending basanitic dikes of the surrounding Waipiata volcanic field.