SPINEL, KALSILITE, CLINOPYROXENE AND OLIVINE by

Kilbourne Hole, NM, Wikiup, AZ, Potrillo maar, NM, Lunar Crater, NV, and Dish Hill,
CA), Wilshire and Shervais (1975) suggested a model in which Group II inclusions
represent the products of fractional crystallization of partial melts that had generated
under generally similar conditions over a period of time. Frey and Prinz (1978) suggested
the presence of high- and low pressure-cumulates in Group II. All of the examined Group
II samples in this study appear to correspond to the high-pressure cumulates. They also
pointed out that not all are genetically related to the basalt that brought them to the
surface.
Frey and Prinz (1989) noted that metasomatic trace element enrichment was most
widespread in the infertile (refractory) samples (Group I). Based on petrographic and
geochemical analyses, they concluded that SC olivine-rich Group I xenoliths are
comprised of two components: (A) a residue, which determined the modal mineralogy
and major elemental and compatible trace element (e.g., Cr, Co, Ni) compositions, and
(B) a small degree (< 5 %) of garnet peridotite melting, which later introduced large-ion-
lithophile (LIL) elements (e.g., K, U, Th, La, Ce) into the residue. This kind of model has
been proposed in the studies of xenoliths from other localities to account (1) for
inconsistencies between LIL trends and major and compatible trace elemental trends
(Frey and Green 1974), (2) for the presence of hydrous minerals as veins or in interstitial
areas (c.f., Wilshire and Trask 1971), (3) for relative light rare earth element (REE)
enrichment in many refractory peridotite xenoliths (c.f., Ridley and Dawson. 1975), (4)
for the occurrence of primary phlogopite in eclogite and garnet peridotite inclusions (c.f.,
Kushiro and Aoki 1968; Aoki 1975), and (5) for a relative deficiency of radiogenic Pb
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