Segregation vesicles in basaltic lava

Segregation Vesicles and Immiscible Liquid Droplets in Oceanfloor Basalt of Hole 396B, IPOD/DSDP Leg 46

“…Segregation vesicles in Leg 46 basalts are similar to those in the Australian pillow lavas (Smith, 1968) and in Leg 37 basalts (Barager et al, 1976). The common features between the fillings of the segregation vesicles and the intersticies of the surrounding groundmass observed in Leg 46 basalt confirm the argument of Smith that the fillings represent the residual melt infiltrated into vesicles at a certain period during the crystallization of groundmass.…”

“…The supercooling effect is also implied by the overwhelming spherulitic and dendritic textures of Ca-rich clinopyroxene in the groundmass. Smith (1968) discussed how the once gas-filled vesicles could be infiltrated by the residual silicate melt, and deduced that the infiltration is due to the movement of lava into the deeper part of a shallow sea floor, which increases the Clague and Bunch (1976). Dot-dash lines represent approximate cotectic boundaries of olivine, plagioclase, and Ca-rich clinopyroxene (Shibata, 1976).…”

“…In the ocean-floor basalts of Leg 46, Hole 396B, mafic spherules similar to the segregation vesicles of Smith (1968) are common. Segregation vesicles are the vesicles infilled with the residue from the crystallizing magma surrounding them and may retain the composition of the residual melt at a certain period of the crystallization of groundmass.…”

The Roza Member, Columbia River Basalt Group: A gigantic pahoehoe lava flow field formed by endogenous processes?

“…A few good quality partial sections are also included. Detailed graphic logs were made at each locality, recording the texture, vesiculation, and jointing style on a decimeter to [Kuno, 1965] or vesicle sheets [Goff, 1996] irregular, spherical to elongate vesicles lined with segregation material [Smith, 1967];…”

Site 648

“…In individual thin sections, they commonly occur in a consistent orientation that probably indicates the gravity field in which the basalts cooled. Totally filled segregation vesicles are recognized by their darker color and finer grain size, compared with the surround ing groundmass, and are similar to those observed in Australian pillow lavas (Smith, 1968) 1977), and in Leg 46 basalts (Sato, 1978). They appear to have formed late in the crystallization history of a lava by infiltration of residual melt into vesicles that were previously filled with volatiles.…”