miarolitic


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miarolitic

[¦mē·ə·rō¦lid·ik]
(petrology)
Of igneous rock, characterized by small irregular cavities into which well-formed crystals of the rock-forming mineral protrude.
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The abundance of aligned miarolitic cavities parallel to primary flow fabric suggests that these bodies were emplaced at high levels.
Miarolitic cavities are abundant, consistent with high-level emplacement.
The only member of the beryl family with more Fe is stoppaniite, which occurs in miarolitic cavities in volcanic ejecta at Latium, Italy, and contains up to 19.
Foster occurs in miarolitic cavities containing gem-quality fluorite, microcline, phenacite ([Be.
The groundmass is granophyric, partly spherulitic, and contains miarolitic cavities.
The presence of quartz and feldspar ph enocrysts, as well as miarolitic cavities, requires the melt composition (the opposing end of the lever) to lie on the quartz- feldspar boundary line.
Miarolitic cavities are present locally but are generally uncommon (Wolfson 1983).
The upper margin of the granite consists of an almost continuous layer of fine-grained, pink, felsic rock varying from featureless felsite to microgranite with abundant granophyric intergrowth and drusy miarolitic cavities, to rhyolite porphyry that is commonly spherulitic.
Parts of the aplitic to porphyritic phase of the GRII contain miarolitic cavities, comb quartz layers, and unidirectional solidification textures (UST), suggesting fluid saturation and/ or undercooling of the parental magma (Kirkham and Sinclair 1988).
Miarolitic cavities (1 mm to 2 cm in size) are locally abundant, in which very fine-grained sericite, chlorite, fluorite, and carbonate are present, but arsenopyrite, molybdenite, and other metallic minerals are relatively rare (Sinclair et al.
Very low regional metamorphic grade (chlorite and sub-chlorite), low-pressure contact metamorphism (cordierite-andalusite), and miarolitic cavities in granite batholiths indicate that the study area remained at shallow crustal levels throughout this polydeformational history.
Vuggy textures are common in the porphyry due to abundant miarolitic cavities that impart a frothy appearance to the weathered surface.