Cryptic crustal contamination of MORB primitive melts recorded in olivine-hosted glass and mineral inclusions
journal contributionposted on 2023-05-16, 21:32 authored by Vadim KamenetskyVadim Kamenetsky, Gurenko, AA
The origin of compositional heterogeneities among the magmas parental to mid-ocean ridge basalts (MORB) was investigated using a single rock piece of the olivine-phyric basalt from 43Â°N, Mid-Atlantic Ridge (AII D11-177). The exceptional feature of this sample is presence of very primitive olivine crystals (90-91 mol% Fo) that are significantly variable in terms of CaO (0.15-0.35 wt%). A population of low-Ca olivine (0.15-0.25 wt% CaO) is also notably distinct from high-Ca olivine population in AII D11-177, and primitive MORB olivine in general, in having unusual assemblage of trapped mineral and glass inclusions. Mineral inclusions are represented by high-magnesian (Mg# 90.7-91.1 mol%) orthopyroxene and Cr-spinel, distinctly enriched in TiO2 (up to 5 wt%, c.f. <1 wt% in common MORB spinel). Glass inclusions associated with orthopyroxene and high-Ti Cr-spinel have andesitic compositions (53-58 wt% SiO2). Compared to the pillow-rim glass and "normal" MORB inclusions, the Si-rich glass inclusions in low-Ca olivine have strongly reduced Ca and elevated concentrations of Ti, Na, K, P, Cl, and highly incompatible trace elements. Strong variability is recorded among glass inclusions within a single olivine phenocrysts. We argue that the observed compositional anomalies are mineralogically controlled, and thus may arise from the interaction between hot MORB magmas and crystal cumulates in the oceanic crust or magma chamber. Â© Springer-Verlag 2006.
Publication titleContributions to Mineralogy and Petrology
Department/SchoolSchool of Natural Sciences
Place of publicationGermany