Few olivine crystals can be identified in the thin section and they show oxidized rounded borders and alteration to iddingsite, suggesting that they may be xenocrysts
instead of phenocrysts from the new batch of magma.
Several factors can influence the reproducibility of the chemical signature of the studied samples: a) the percentage of glass and phenocrysts, b) the presence of xenocrysts
and, c) the presence of xenoliths or lithic clasts.
The andalusite xenocryst
displays a homogeneous composition (Si[O.
A second data set comes from a xenocryst
in the Orano porphyry, a unit characterized by extensive captured crystals from the Monte Capanne system (Dini et al.
The relatively coarse grain size of xenoliths and xenocrysts
indicate origin from subjacent plutonic sources, and the gabbro of Christmas Mountain and syenitic rocks of Dominguez Mountain show that such plutons exist in the Big Bend region.
The KL-2 pipe, meanwhile, is a multiphase diatreme facies complex with at least four distinct phases of tuffistic (volcaniclastic) serpentine kimberlite breccia which, again, are locally rich in mantle xenoliths and xenocrysts
in the 1723 scoria are unrimmed euhedral hornblende crystals, indicating a rapidly ascended magma of a few days or hours (Fig.
The dyke contains abundant large (up to at least 9 cm) phenocrysts and xenocrysts
in addition to a wide variety of xenoliths that include granulite, dunite, lherzolite, werhlite, harzburgite, and pyroxene peridotite (Ross et al.
2004, Discovery of Archean continental and mantle fragments inferred from xenocrysts
in komatiites, the Belingwe greenstone belt, Zimbabwe: Geology, v.
The latter occurrence probably represent xenocrysts
Additionally, limited exchange of xenocrysts
(labradorite, edenitic amphibole, and bronzite in dacites, oligoclase and andesine in andesitic enclaves) might have occurred during this entrainment stage.
The presence of ferrous clinopyroxene cores suggests xenocrysts
removed from diferentiated magmas while unusual occurence of acmite in basaltic rocks emphazises their strong peralkaline evolution.