Nitrogen-rich fluid in the upper mantle: fluid inclusions in spinel dunite from Lanzarote, Canary Islands

Article Abstract:

A study of fluid inclusions varying from pure N2 to CO2 in olivine porphyroclasts in spinel dunite xenoliths at two places in the alkaline lavas of Lanzarote, Canary Islands, suggests that pure N2 had been formed in upper mantle and earlier than nitrogen-free CO2. It might have formed in-situ through destabilizing reactions of ammonia in silicate minerals, which can be connected to CO2 evolution, melting of silicates and formation of the mantle beneath the site. These observations may help researchers understand the mantle below Canary Islands and formulate theories about the global nitrogen balance.

Composition, Rocks, Metamorphic, Metamorphic rocks, Inclusions, Spinel group

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Sr-Nd-Pb isotope data for ultramafic xenoliths from Hierro, Canary Islands: melt infiltration processes in the upper mantle

Article Abstract:

Sr-Nd-Pb isotope data shows that dunite-pyroxenite suite xenoliths, from the island of Hierro, Canary Island, could have been foisted by Hierro-type basalt. Harzburgite suite has a greater range of isotopic composition as compared to dunite-pyroxenite suite xenoliths. Systematic analysis of these two suites is done by applying a leaching technique to whole-rock powder samples. In upper mantle beneath Hierro, before and during volcanic events, complex interactions occur with penetrating basaltic melts.

Observations, Isotopes

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Infiltration of refractory melts into the lowermost oceanic crust: evidence from dunite- and gabbro-hosted clinopyroxenes in the Bay of Islands ophiolite

Article Abstract:

The composition and variability of melts entering the base of the oceanic crust were determined by examining the clinopyroxene trace element pattern of dunitic, wehrlitic and mafic rocks found in the Blow Me Down massif of the Bay of Islands Ophiolite. Results showed that highly refractory melts can be found under oceanic spreading centers dominated by a mid-ocean ridge basalt-like cumulate and volcanic sequence.

Analysis, Ophiolites, Bay of Islands (Pacific Ocean)

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