Mantle—crust transition zone and origin of wehrlitic magmas: Evidence from the Oman ophiolite

Birth, death, and resurrection: The life cycle of suprasubduction zone ophiolites

“…gabbros of the lower crust [Benn et al, 1988;Browning, 1984;Ernewein et al, 1988;Juteau et al, 1988a;Juteau et al, 1988b;Pallister and Hopson, 1981]. Basalts of the Geotimes unit (along with most of the sheeted dike complex) have been attributed to formation at a mid-ocean spreading axis because they resemble MORB in many aspects of their geochemistry.…”

“…[51] Gabbros associated with the stage 1 magma series are layered on a centimetric to decimetric scale, with layers defined by variations in modal proportions, by the appearance or loss of a cumulus phase, and by variations in the size of the cumulus crystals [Benn et al, 1988;Browning, 1984;Ernewein et al, 1988;Juteau et al, 1988aJuteau et al, , 1988bPallister and Hopson, 1981]. The layers display both synmagmatic deformation textures (e.g., ductile normal faults with amphibolite facies minerals [Ernewein et al, 1988;Lippard et al, 1986]) and subsolidus ductile deformation (Figure 8a).…”

“…[52] Stage 2 in the Semail ophiolite (Figure 7c) is represented most clearly by ultramafic rocks that intrude the earlier layered gabbros [Benn et al, 1988;Ernewein et al, 1988;Juteau et al, 1988a;Juteau et al, 1988b;Lippard et al, 1986] and by olivine-clinopyroxene-phyric and orthopyroxene-phyric volcanic rocks that overlie the Geotimes volcanic unit [Alabaster et al, 1982;Ernewein et al, 1988;Umino et al, 1990].…”

“…[53] Plutonic rocks associated with stage 2 include dunite, wehrlite, pyroxenite, troctolite, and pegmatoidal gabbro [Benn et al, 1988;Juteau et al, 1988a;Juteau et al, 1988b;Lippard et al, 1986;Pallister and Hopson, 1981]. The ultramafic intrusive series forms stocks and dikes that crosscut the layered series at high angles (Figure 8b), as well as sills that penetrate parallel to the older layering and mimic cumulus layering [Benn et al, 1988;Juteau et al, 1988a;Juteau et al, 1988b;Umino et al, 1990].…”

“…The ultramafic intrusive series forms stocks and dikes that crosscut the layered series at high angles (Figure 8b), as well as sills that penetrate parallel to the older layering and mimic cumulus layering [Benn et al, 1988;Juteau et al, 1988a;Juteau et al, 1988b;Umino et al, 1990]. Early studies recognized the intrusive nature of these ultramafic rocks but attributed their origin tò`m obilization'' of preexisting cumulates, rich in interstitial magma, that formed at deeper levels in the cumulate pile [e.g., Lippard et al, 1986;Pallister and Hopson, 1981].…”