TEXTURAL AND MICROANALYSIS OF IGNEOUS ROCKS: TOOLS ...

een referred to as Singgalo, Kwaimbaita, and Kroenke basalts [46, 131, 133]
(Fig. 1.4). The uniformity of basalt composition over the Greenland-size OJP is
remarkable [46, 110, 131, 133]. Three different basalt types have been recovered
from this vast LIP, and of these three types the Kwaimbaita basalt makes up >
90% of the OJP [110, 131, 133]. My study is focused on plagioclase cumulate
xenoliths from the Kwaimbaita basalt. Kwaimbaita basalt is the most widespread
OJP basalt type and the only one of the three that contains cumulate xenoliths,
and the magma chamber processes that produced this ubiquitous composition
were the most common and important during formation of the OJP.
Key OJP research questions include: What are the physical processes (i.e.,
magma chamber dynamics) of differentiation that led to the repeated production
of the same basalt type (Kwaimbaita basalt) over a Greenland-size geographic
area? Hypothesis 1: OJP magma chambers were crystal-mush dominated, where
differentiation was heavily influenced by residence time of magmas in the crys-
tal mush. Near steady state flow of melt into and out of a vast crystal-mush-
dominated magma chamber system is amenable to repeated production of the
same type of basalt over a wide area. Crystals will be isotopically similar to
their host basalt, but will contain greater ranges of trace element enrichments and
depletions than the whole-rock host basalt.
Hypothesis 2: Nucleation and growth of crystals occurred homogenously through-
out the magma chamber interior. Plagioclase crystals will contains similar isotopic
and trace element compositions as the whole-rock host basalt.
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