UNDERSTANDING THE MAGMATIC EVOLUTION AND PROCESSES ASSOCIATED WITH THE FORMATION OF THE LAVA FLOWS FOUND IN LAVERICKS BAY, BANKS PENINSULA, NEW ZEALAND

The volcanic deposits of Akaroa Volcano found in Lavericks Bay, Banks Peninsula, New Zealand are the result of millions of years of intraplate volcanism. This type of volcanism is unique in that it occurs away from plate boundaries (Conrad, 2011). Numerous studies have been done in an attempt to learn more about the processes associated with intraplate volcanism on Banks Peninsula, though fewer studies have focused on the processes that occurred during the formation of Akaroa’s volcanic deposits. This study focuses on the volcanic deposits of Lavericks Bay and is among the first to study the bay from a geologic point of view. It uses geochemical analysis to understand the magmatic evolution and processes associated with the formation of the lava flows and to provide insight into Akaroa’s magmatic system. Geochemical analysis indicates that the lava flows range in composition from picrite basalt to mugearite, and have relatively low silica content, from 45 to 51 wt %. Trends within variation diagrams of major and trace element data indicate that fractional crystallization played a role in the formation of the lava flows found in Lavericks Bay. Within the stratigraphy, there are compositional fluctuations between picrite basalt and more evolved compositions. This fluctuation can be explained by the eruption of small, distinct collections of magma from multiple eruptive centers. This evidence is consistent with the model for Akaroa’s magmatic system proposed by Johnson et al. (in prep). The complexities of such a system, however, necessitate that future research be done to investigate additional small-scale or localized processes that occurred during the formation of Lavericks Bay’s lava flows.