aphyric

aphyric

[ā′fir·ik]
(petrology)
Of the texture of fine-grained igneous rocks, showing two generations of the same mineral but without phenocrysts.
References in periodicals archive ?
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?
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.
This host unit is underlain by a sequence of aphyric andesite or latite volcanic flows which to date have not been found to host mineralization.
The marginal zones of the dyke are aphyric and free of xenoliths and megacrysts, both of which were concentrated in the dyke interior by flow differentiation and show varying degrees of flow alignment (Fig.
This is close to the composition of aphyric komatiites and chilled margins of komatiitic flows.
Thus, the porphyritic rock types are the result of mineral accumulation, and the aphyric rock types are the result of mineral separation.
All three holes intersected interbedded units of massive grey aphyric ryholite and intermediate to felsic tuffaceous rocks and bottomed in K-feldspar-quartz augen schist.
The fragmentation depth for the aphyric magma occurs near the base of the conduit for water contents of 10% or more.
The rarer type of tuff is a foliated, green-grey aphyric felsite with a porcelain-like texture.
At least a few aphyric basalts on most oceanic islands have Mg# values around 0.