One grain (Zl), larger and older than the other dated grains, is interpreted as a xenocryst
and has a [sup.206]Pb/[sup.238]U age of 423.3 [+ or -] 0.6 Ma.
(2012): Anomalous xenocryst
dispersion during tonalite-granodiorite crystal mush hybridization in the mid crust: Mineralogical and geochemical evidence from Variscan appinites (Avila Batholith, Central Iberia).
4A), where the same ignimbrite unit shows variations in xenocryst
contents ranging from 5 to 15%.
Mineral compositions were determined for clinopyroxene, plagioclase, opaque minerals, apatite and the andalusite xenocryst
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.
This suggests that some of the phenocrysts that had formed in the rhyolitic magmas were later enclosed (as xenocrysts
) within the more mafic one (i.e., as enclaves).
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 1970 sample from the northwestern knoll is transitional basalt, plotting on the Hawaiian tholeiite-alkalic basalt boundary, whereas the 1994 lava is tholeiitic basalt with a higher Si[O.sub.2] content (Fig.