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.
are composed of orthoclase and reach 2-3 cm in size.
Lavas from the northwestern knoll are fresh, slightly ollvine-phyric lavas with abundant vesicles and rare, partially resorbed plagioclase xenocrysts
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.
Unit D is a relatively fresh, mostly dense but locally scoriaceous, porphyritic trachyandesite with ten to fifteen percent large plagioclase xenocrysts
Pellet-rich tuffistic (volcaniclastic) serpentine kimberlite breccia occupies the southern fissure appendage of the pipe which is extremely rich in mantle xenocrysts
, megacrysts and xenoliths.
It proves that the magma carried numerous mantle-derived xenocrysts
in the 1723 scoria are unrimmed euhedral hornblende crystals, indicating a rapidly ascended magma of a few days or hours (Fig.
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.
2004, Discovery of Archean continental and mantle fragments inferred from xenocrysts
in komatiites, the Belingwe greenstone belt, Zimbabwe: Geology, v.
We consider the first interpretation to be the best explanation for the Brazil Lake tantalite U-Pb results because tantalite is generally quite rare in crustal rocks and it seems remote that there would be tantalite xenocrysts
originally present in the Brazil Lake magma.