phenocryst


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phenocryst

[′fēn·ə‚krist]
(petrology)
A large, conspicuous crystal in a porphyritic rock. Also known as phanerocryst.
References in periodicals archive ?
Small quantities of either clinopyroxene or hornblendic amphibole may occur as an additional phenocryst phase.
Units A, B, D and G contain common to sparse olivine phenocrysts (0.
Both phenocryst and fine grain populations have linear distributions on a plot of Ln n (nucleation density), that is the intercept of the CSD vs Log (Gt) that is log (-1/slope) (Figs.
Francois Mountains Complex regardless of inferred mode or depth of crystallization (volcanic phenocryst versus volcanic matrix versus hypabyssal ring pluton versus subvolcanic massif) or crystallization age (1.
Phenocryst minerals include plagioclase, clinopyroxene, and olivine.
Sanidine phenocryst compositions that have been used in many previous studies for proving the correlations of volcanic ash beds are stable throughout the vertical section and therefore serve as a good discrimination criterion.
The small compositional differences can largely be explained (and numerically modelled) by slight variations in phenocryst populations; relatively large variations in concentrations in some of the LIL elements (e.
Plagioclase phenocryst, euhedral to tabular in form, is the dominant phase which in some cases is partially or completely sauceritized.