porphyroblast


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Related to porphyroblast: Porphyroblastic Texture, Euhedral

porphyroblast

[pȯr′fir·ə‚blast]
(petrology)
A relatively large crystal formed in a metamorphic rock.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Inclusion free (or poor) areas in texturally sector-zoned porphyroblasts commonly form when porphyroblast growth is accommodated by dissolution and diffusion of material not needed during growth and or by displacement of insoluble matrix material (Passchier and Trouw, 2005; Ferguson et al., 1981).
Staurolite forms honey-brown large prismatic porphyroblasts which quite frequently reach up to 1.2 cm across and 12 cm in length, elongated along the schistosity and usually displaying reaction rims.
Garnet porphyroblasts which contain inclusions of quartz and biotite are arranged parallel to dominant crenulation cleavage.
Two conflicting hypothesis have been postulated for the asymmetric inclusion trail geometries: porphyroblast rotation and non-rotation.
The earliest deformation event recognized in the Sutlej GHS at the level of the MCT is recorded by straight to sigmoidal (S1) inclusion trails of quartz + ilmenite in the cores of large garnet porphyroblasts. S1 is often observed at high angles to the matrix foliation (S2), and is truncated at inclusion-poor garnet rims.
Albite (Ab) and Grt2 (mineral abbreviations from Whitney and Evans, 2010) are porphyroblasts mainly syn-kinematic with the S2 and frequently helicitic, including a previous foliation (S1) (Figs.
The graphite occurs within "fairly homogeneous, quartz-graphite schist, incorporating minor "porphyroblasts" of muscovlte crystals and small lenses of extremely fine sillimanite".
and Speck, P.J.H.R.: 1994, The kinematic interpretation of obliquely-transected porphyroblasts: an example from the Trois Seigneurs Massif, France, J.
GROWTH OF CENTIMETER-SCALE GARNET PORPHYROBLASTS AT THE