Petrographic thin sections are dominated by anhedral Ca-rich augite
and subhedral to euhedral calcic plagioclase laths in a subophitic
Unit G is oniy slightly porphyritic and has analcite and ophitic augite
, which A does not).
Mason, Pyrope, augite
, and hornblende from Kakanui, New Zealand, New Zealand J.
Although we would not suggest that the diopside (Di) was actively formed by metamorphic processes, the destruction of the Fe-Mg components of augite
will make the remaining pyroxene more calcic.
phenocrysts more strongly Augite
phenocrysts generally pleochroic having purplish-brown, pale-brown and zoning is not as Tirich rims.
Furthermore, minerals common to both series (chromite, olivine, augite
, plagioclase, magnetite and ilmenite) are compositionally distinct reflecting fundamental chemical differences between the two magma series.
Coughlan (1986) recognized five units in the Staples Mountain Gabbro, designated I to V from inferred bottom to top: I--gabbro, anorthositic gabbro, and olivine gabbro; II--subophitic augite
gabbro; III--interlayered norite and anortbosite; IV--unlayered augite
gabbro and minor olivine gabbro; V --unlayered gabbronorite, with increased orthopyroxene and no olivine, in contrast to unit IV.
The samples, which ate all very similar, contain augite
([less than or equal to] 5mm, ~[Wo.
Relict igneous pyroxene of hypersthene composition was observed in rare gabbroic samples, whereas the later diabase dykes contain augite
A typical mineral assemblage for mafic samples includes augite
, albite, chlorite, epidote, biotite, and ilmenite-spinel.
Petrographically, the basalts are described as containing calcic plagioclase, augite
, and rarer pigeonite and bronzite, and Fe-Ti oxides, and vary from holocrystalline to variably vitrophyric ([less than or equal to]30%).
2006, High-Ca augites
do not prove that komatiites were wet: American Geophysical Union, Fall Meeting, 2006, abstract V24B-04.