Abstract
Abstract Typically porphyritic basaltic to basaltic andesitic pyroclastic rocks (mainly tuff, tuffbreccia and agglomerate), together with subordinate massive and pillowed lava flows, dikes, and interbedded volcaniclastic sediments, comprise the 2400 m thick sequence of Brook Street Volcanics at west D'Urville Island, New Zealand. The Brook Street rocks show a trend of moderate iron enrichment and possess anomalously low Ti, Zr, and Nb abundances, as well as low Zr/Y, Ti/Y, and Nb/Zr ratios, features typical of island arc tholeiites. Rare earth element (REE) abundance patterns are relatively unfractionated and show only slight light rare earth element (LREE) enrichment. The lack of Eu anomalies, as well as the increase of Al2O3 contents with decreasing MgO and the large range of Ni and Cr contents, indicate that fractionation was dominated by ferromagnesian phases over most of the observed range of compositions, typical of island-arc tholeiitic suites. Some of the basalts possess ankaramitic affinities. Ve...
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