Abstract

Coexisting fluid inclusions and silicate melt inclusions, trapped as primary inclusions in clinopyroxene rims and as secondary inclusions along healed fractures in orthopyroxene, were studied in two amphibole-bearing spinel lherzolite peridotite xenoliths from the Bakony–Balaton Highland Volcanic Field (western Hungary). The composition of both Cpx-hosted and Opx-hosted inclusions suggests that they were entrapped from the same silicate melt, which was saturated in volatiles at mantle P– T conditions. Raman spectroscopy, combined with microthermometry and FTIR analyses, proved the existence of CO 2, H 2O and H 2S in the fluid inclusions. Trace element compositions of silicate melt and fluid inclusions were determined by LA–ICP–MS, although the results of fluid inclusions are only semi-quantitative. Trace element distributions revealed significant similarities in the compositions of silicate melt and fluid inclusions, especially with respect to K, Rb, Sr, Pb, Nb, Th and U content. This confirms the same parental melt for both silicate melt and fluid inclusions and suggests that the trace element content of the CO 2-rich end-member (containing some dissolved melt) resulted from high P– T immiscibility in deep lithospheric environments and is controlled by the trace element content of the parent silicate melt.

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