Magma fractionation systems beneath the mid-Atlantic ridge at 36?37 � N

An Electron Microprobe Study of Basalt Chemical Variation at Deep Sea Drilling Project Sites 482–485, Gulf of California

“…The glass and whole-rock data usually approximate the overall liquid-type fractionation trend, despite the generally greater scatter of the whole-rock data. This pattern is in contrast to that observed for Atlantic Ocean basalts, where complex phenocryst redistribution patterns involve (notably) the strong accumulation of plagioclase (e.g., Staudigel et al, 1980;Flower et al, 1977Flower et al, , 1980Byerly and Wright, 1978). There are slight but probably significant systematic differences between the Site 482 and Site 483 glass compositional trends.…”

“…Petrologic studies of mid-ocean ridge basalt (MORB) (e.g., Melson et al, 1975;Flower, et al, 1977;Byerly and Wright, 1978;Melson, 1979;Byerly and Sinton, 1980; show that magmatic liquid-fraction trends are indicated by the compositions of fresh glass selvedges, usually, but not always, associated with pillow basalts. In contrast, whole-rock compositional variation will often reflect the complicating effects of syn-and post-eruptive phenocryst accumulation.…”

Petrography and Geochemistry (Trace, Ree and Pge) of Pedda Cherlo Palle Gabbro-Diorite Pluton, Prakasam Igneous Province, Andhra Pradesh, India

“…Such lowpressure cpx crystalisation in oceanic tectonic settings has been described by many workers [43,44]. Petrographic studies indicate the dominance of cumulus plagioclase, clinopyroxenes and olivine in unaltered gabbros.…”

Geochemistry of Basalts: Deep Sea Drilling Project Sites 482, 483, and 485 near the Tamayo Fracture Zone, Gulf of California

“…Previous studies of oceanic basement (e.g., Flower et al, 1977;Byerly and Wright, 1978;Flower and Robinson, 1981a and b;Bryan et al, 1978) suggest that compositional differences between chemical types may reflect the effects of both deep-seated and comparatively shallow-level fractionation. Such processes would be expected to include fractional crystallization, as constrained by polybaric phase equilibria and mixing of magma batches at various stages of the liquids' evolution.…”