The Lau Basin is an excellent location for studying suprasubduction zone processes due to numerous volcanoes spanning from the forearc, arc, reararc, to backarc settings, providing windows into different aspects of the subduction zone. The young, primarily boninitic submarine Mata Volcanoes, located between the arc and the backarc spreading center, are an important part of this picture. This thesis presents a preliminary study of the Mata Volcanoes, including XRF whole rock and glass, and mineral EPMA analysis of samples, thermometry, and crystallization modeling. Differentiation at the Mata Volcanoes occurred under oxidizing conditions, and over a temperature range of approximately 1000-1200 .C. Starting magmas had high water contents of at least 1.7- 2 wt%. Lavas preserve heterogeneities, suggesting that no well-developed magma storage system/homogenization zone is present. Complex crystal chemistry and compositions suggest that magma mixing played a role in the formation of these magmas.