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Related to porphyroblast: Porphyroblastic Texture, Euhedral


A large crystal that is surrounded by a fine-grained matrix in a metamorphic rock and forms from the recrystallization of existing mineral crystals during metamorphism.

[porphyr(y) + —blast.]
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They have traditionally been attributed to syn-growth rotation of the porphyroblast relative to the stretching axes of the instantaneous strain ellipse (e.
Multiply deformed and metamorphosed rocks commonly preserve a record of lengthy periods of deformation and associated several phases of porphyroblast growth.
This kinematic reconstruction is supported further with a numerical simulation using finite difference code of millipede formation in a spherical porphyroblast subjected to a superposition of two orthogonal shortening directions.
Where possible, to assess the reliability of calculated peak P-T conditions, the fractionation of major cations from the matrix during porphyroblast growth was modelled in THERMOCALC.
Preservation of such a detailed record of punctuated porphyroblast growth and microstructural evolution is rare along the length of the Himalaya.
The compositional banding is reflected by alternating nematoblastic (hornblende) and granoblastic (plagioclase) bands, within which epidote-group minerals and garnet porphyroblasts occurs.
The late schistosity in the sedimentary rocks, defined by muscovite and biotite, wraps around cordierite porphyroblasts, which contain relicts of the earlier phyllitic cleavage (Thorne and Lentz 2001; Park et al.
The amphibolite is porphyroblastic and contains porphyroblasts of hornblende.
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.