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CO2-rich intraplate alkaline magmatism in the Levant: melt inclusion insights into source-to-surface evolution of the Ramon volcanics, Israel
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DOI：10.1093/petrology/egag053.png)
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Abstract
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Continental alkaline magmatic provinces are notable for their exceptional compositional diversity, making them valuable recorders of mantle source heterogeneity, magma differentiation processes, and volatile behaviour. Some of these provinces occur in intraplate settings where evidence for rifting or plume activity is absent, leaving the cause of mantle melting and magma ascent enigmatic. Here, olivine-hosted melt inclusions provide insight into the source-to-surface evolution of the Ramon volcanics, the most diverse series of the Early Cretaceous intraplate Levant magmatic province, whose origin is enigmatic. Most data are derived from the well-preserved nephelinite-basanite-alkaline basalt series of the Ga’ash Hill edifice, complemented by additional exposures in Makhtesh Ramon, Negev Desert, Israel. Trace-element systematics indicate that compositional diversity is mostly dominated by low-degree melting of a garnet-bearing mantle source near the garnet-spinel transition, with contributions from peridotite and pyroxenite lithologies. Melt inclusions are CO2-rich (≤ 3.19 wt.%), while H2O contents are moderate with reconstructed values of up to 0.95 wt.%. Volatile saturation pressures recorded in melt inclusions span a wide range (1300–230 MPa), further constrained by clinopyroxene geobarometry to indicate magma storage at lower-crustal levels (~25–35 km), near the reconstructed Moho. Fluid-behaviour modelling suggests a two-stage volatile control on melt mobilization: CO2 dominating deep transport and H2O becoming increasingly important at shallow levels below ~ 250 MPa, where eruptibility increases. Minimal interaction between ascending melts and crustal rocks is indicated by oxygen isotope ratios of olivine phenocrysts. Compositional diversity stems from the melting of a fertile lithospheric mantle source previously affected by carbonate-rich metasomatism, deep storage, and rapid ascent. Small perturbations in tectonic or thermal conditions may be sufficient to generate alkaline mafic melts from readily fusible carbonate- and pyroxenite-bearing lithospheric mantle, thus providing a possible explanation for magmatism in stable continental interiors that lack structural evidence for extension.
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