TEXTURAL AND MICROANALYSIS OF IGNEOUS ROCKS: TOOLS ...

a limited picture of CSD variation across this thick flow, but CSD fanning of
co-magmatic lavas may indicate progressive deeper sampling of the solidification
fronts lining the magma chamber [146]. The deeper portions of solidification fronts
lining the magma chamber contain larger and older crystals, and as this region is
increasingly scoured by passing magma en-route to the surface the resulting lava
will have a flatter CSD slope (e.g., [146]). In the case of this single thick flow the
steeper CSD from the bottom of the flow is representative of the earliest and lowest
crystallinity magma emptied from the magma chamber, and as evacuation of the
magma chamber progressed and fed the flow, deeper portions of the solidification
fronts lining the chamber were eroded leading to a shallower sloped CSD near the
top of the flow (i.e., the terminus of magma chamber evacuation).
I conclude that flow sorting of plagioclase was a ubiquitous process during
the formation of Detroit Seamount and that measurement of one plagioclase CSD
per flow is inadequate for making robust interpretations based solely upon CSD
results. Crystal size distribution results do, however, provide insight into when
and where crystal accumulation or magma mixing most heavily influenced bulk
magma composition. Based upon the fact that everywhere I looked for evidence of
crystal sorting I found convincing evidence of this process, I suggest that sorting
was not limited to plagioclase. Indeed, the greater density of olivine relative to
basaltic melt and plagioclase may have accentuated olivine sorting and sorting
due to both flow sorting and gravitational settling. Indeed Tarduno et al. [128]
noted olivine cumulate picritic basalts at Site 1203
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