retrograde metamorphism

retrograde metamorphism

[′re·trə‚grād ‚med·ə′mȯr‚fiz·əm]
(petrology)
Formation of metamorphic minerals of a lower grade of metamorphism at the expense of minerals which are characteristic of a higher grade. Also known as diaphthoresis; retrogressive metamorphism.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Metamorphic rocks of the Silgara Formation show evidence of a complex metamorphic history characterized by crustal thickening during heating and a regional retrograde metamorphism after the peak metamorphic temperature (Rios et al., 2003).
These rocks frequently contain evidence of retrograde metamorphism, involving hydration processes, including partial replacement of garnet, biotite and staurolite by chlorite, staurolite by muscovite and plagioclase and staurolite by sericite.
This obduction process, possibly caused by the arrival at the subduction zone of some oceanic relief (guyots chain, oceanic ridge, oceanic plateau, etc.), that was unable to enter in the subduction zone (X terrane of Mpodozis and Kay, 1990), implied exhumation and retrograde metamorphism of the rocks of the ChMC (Fig.
In most contact metamorphic settings, periclase does not survive the retrograde metamorphism that follows a metamorphic climax and it rehydrates to form brucite according to reaction (2).
The amount of retrograde metamorphism varies from relatively minor with preserved pseudomorphs of garnet or idocrase, to extensive involving the nearly complete recrystallisation of the lower amphibolite facies assemblage to a lower greenschist assemblage.
Abundant serpentine (antigorite, replacing olivine and chlorite) reflects hydration of the metadunites during retrograde metamorphism. Mineral assemblages at Dark Ridge therefore preserve a record of a range of metamorphic conditions.
In addition, there is textural evidence of retrograde metamorphism in amphibolites (sample Arq59Al in Figure 1), such as the presence of muscovite, epidote minerals, hornblende and garnet as inclusions into the plagioclase (Figure 3g).
Metamorphic P-T-time history of the Sanbagawa Belt in central Shikoku, Japan and implications for retrograde metamorphism during exhumation, Lithos.
1, Ernst (1988), indicates that retrograde metamorphism that some of these units present is typical for subduction zones as part of its tectonic history in HP--LT rocks like blueschists and eclogites, produced an ascent of subducted material toward to surface after detachment takes place of descending slab, adding in this process mantle material like ultrabasics rocks.
With the above-mentioned, the tectonic--stratigraphic disposition along of RFS showing retrograde metamorphism phenomena being observed in Arquia Complex and rocks associated in the places like Pijao and Barragan in Colombia and equally in the Raspas Metamorphic Complex in Ecuador (Maya, 2001; Mojica et al., 2001; Gonzalez, 1997; Bosch et al., 2002, Gabrielle, 2002; Arculus et al., 1999).

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