Experimental settling, floatation and compaction of plagioclase in basaltic melt and a revision of melt density

Abstract Centrifuge-assisted piston cylinder experiments were conducted on plagioclase in basaltic melt at 1140–1250 °C, 0.42–0.84 GPa and mostly 1000 g. One set of assesses the settling velocity a dilute suspension; second sinks or floats MORB-type exploring conditions neutral buoyancy; third examines floatation from an evolved lunar magma ocean composition. A compaction rate for cumulates is established. The demonstrate that density An 74 MOR-type tholeiitic basalt occurs 0.59 ± 0.04 (1200 °C), contrasting predictions by present models which yield inversion pressure 0.10–0.15 GPa. In nature, level buoyancy depends composition; nevertheless, onset crystallization dry basalts, our result robust. As molar volume well known, experimentally determined indicates correction -1.6% to previous silicate melts. It follows (tholeiitic) layered mafic intrusions, negatively buoyant early, relatively primitive, parent contrast, extreme Fe enrichment fractionating leads densities let anorthite always float. Compaction ? / 0 experimental quantified = ? 0.0582 log (? ? · h t ) + 1.284, where porosity after (67 2%), cumulate pile height, acceleration as function time . Gravitational-driven tens m -thick magmas reaches down ~ 40% within hundreds years, timescales competing with characteristic cooling times layers intrusions. To achieve modes > 80% due compaction, additional overload 100 (layers) minerals would be required. anorthosite crust 35 km 20% (i.e. 90% interstitial melt) require 30 kyrs.