User:Martuny/Weezerite

Weezerite refers to a symplectic intergrowth of muscovite plus quartz that commonly forms during retrograde metamorphism of pelitic rocks that have experienced upper amphibolite facies metamorphism and partial melting (Brown, 2002). These conditions are above the stability field for muscovite plus quartz. Formation of weezerite occurs when the rocks cool and re-enter the the stability field for muscovite plus quartz. The simplified chemical reaction:

K-feldspar + sillimanite + water => Muscovite + Quartz

KAlSi3O8 + Al2SiO5 +H2O => KAl2[Si3Al]O10(OH)2

Formation of the weezerite texture is limited by diffusion (Schramke et al., 1987). The distinguishing feature of weezerite are vermicular (wormy) intergrowths and unreacted "islands" of K-feldspar surrounded by quartz. Symplectic intergrowths of plagioclase plus quartz (myrmekite) are commonly associated with weezerite (Phillips et al., 1972).

References

Brown, M, 2002, Retrograde processes in migmatites and granulites revisited. Journal of Metamorphic Geology, v. 20, p. 25-40, DOI: 10.1046/j.0263-4929.2001.00362.x

Schramke, JA, Kerrick, DM, Lasaga, AC (1987) The reaction muscovite + quartz = andalusite + K-feldspar + water. 1. Growth kinetics and mechanism. Am J Sci 287, p. 517-559.

Phillips, ER, Ransom, DM, Vernon, RH, Myrmekite and muscovite developed by retrograde metamorphism at Broken Hill, New South Wales. Mineralogical Magazine, v.38, p. 570-578.