The petrogenesis of Gorgona komatiites, picrites and basalts: new field, petrographic and geochemical constraints

摘要: Abstract Gorgona Island, Colombia is remarkable not only because it contains the Phanerozoic komatiites, but also has mafic to ultramafic lavas with a wide range of compositions, from moderately enriched extremely depleted (relative Bulk Earth). The komatiite flows are, in many respects similar Archaean komatiites; they formed MgO-rich (18%) liquids and have upper spinifex zones lower cumulate zones. komatiites contain solid grains, contrast more than 90% olivine cumulates highly skeletal. This combined fact that are thinner those suggests magma became strongly superheated en route surface. trace element contents intermediate between basalts tuffs. Some isotope compositions indicative long-term enrichment incompatible elements, whereas other volcanics isotopic signatures imply corresponding depletion. It apparent plume source region magmas was markedly heterogeneous, at least two components contributing observed variation composition. heterogeneity may resulted incorporation different into source, or be result complex melting melt extraction processes during ascent heterogeneous plume. Despite earlier suggestions there been significant age gap basalt basalts, new 40Ar-39Ar dating gabbros consistent all being generated 87 Ma formation Caribbean/Colombian plateau, possibly Galapagos hotspot.