aphyric

aphyric

[ā′fir·ik]
(petrology)
Of the texture of fine-grained igneous rocks, showing two generations of the same mineral but without phenocrysts.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The maficdykes in Wadhrai show considerable variation in texture and modal composition from distinctly porphyritic to aphyric, medium to (mostly) fine-grained, and fairly fresh to completely altered (Fig.
Trachyphonolites and trachytes are porphyritic to aphyric. The phenocrysts are alkali feldspar (Or60-65) [+ or -] clinopyroxene (Wo46-49Fs14-20) [+ or -] plagioclase (An14-16), pseudomorphosed leucite, amphibole, and biotite in a hypocrystalline to glassy groundmass containing microlites of alkali feldspar, biotite, and clinopyroxene [+ or -] biotite [+ or -] amphibole [+ or -] magnetite [+ or -] Ti-andradite [+ or -] haematite.
The Endeavour Seamount lava is highly plagioclasephyric, but all others are aphyric to sparsely phyric (plagioclase +/- olivine, rare clinopyroxene).
The settling and flotation of cumulus crystals is also restricted to low viscosity aphyric magmas, which would allow rapid and unimpeded vertical movements of cumulus crystals.
They present quartz and K-feldspar phenocrysts in an aphyric matrix composed by quartz, K-feldspar(orthoclase?) and clinopyroxene.
Unit F is composed of essentially aphyric basalt of varied petrography and chemistry, which suggests that it consists of at least two flows, although they were not distinguished in the field.
The mafic rocks are porphyritic to aphyric and consist of calcic plagioclase, clinopyroxene +- olivine or hornblendic amphibole, ilmenite, titanite, and a range of secondary minerals.
Dacites are minor in the Sabalan region and occur mostly as aphyric lavas associated with trachyandesites.
This is close to the composition of aphyric komatiites and chilled margins of komatiitic flows.