Clinopyroxene, mineral chemistry, magma composition, Izu-Bonin volcanic arc
International Ocean Discovery Program Expedition 350 recovered 2000 meters of volcanic rock core in spring, 2014 at the Izu-Bonin-Mariana Rear Arc. The core has been divided into seven lithostratigraphic units, from age 0 at the top to at least 13 million years at the bottom. The major and trace element geochemistry of representative mineral grains in volcaniclastic rocks throughout the core from top to bottom were analyzed and used as a proxy for interpreting magma compositional changes through time. The clinopyroxene from all units and the glass from Unit I were analyzed for major elements (by SEM and electron microprobe) and trace elements (by Laser Ablation Inductively Coupled Plasma Mass Spectrometer, LA-ICP-MS). Six samples from Unit I and two samples each from Units IV, VI, and VII were analyzed. The trace elements were used to calculate host magma trace element compositions through use of trace element partitioning relationships. The mineral chemistry can thus be used as a proxy for understanding magma differentiation trends occurring through time in the rear arc setting. Changes were observed in the mineral chemistry from top the top of the core to the bottom that could reveal more about continental crust growth from island arcs.
Benson, Erin, "Using clinopyroxene mineral chemistry to decipher magma composition changes over the 13 million year history of the Izu-Bonin volcanic arc" (2016). Geology Graduate and Undergraduate Student Scholarship. 3.
Student project; term paper
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