Rock formed by solid-state mineralogical, chemical and/or structural changes to a pre-existing rock, in response to marked changes in temperature, pressure, shearing stress and chemical environment.
Robertson (1999) defines the boundary between diagenesis and metamorphism in sedimentary rocks as follows: “…the boundary between diagenesis and metamorphism is somewhat arbitrary and strongly dependent on the lithologies involved. For example changes take place in organic materials at lower temperatures than in rocks dominated by silicate minerals. In mudrocks, a white mica (illite) crystallinity value of < 0.42D.2U obtained by X-ray diffraction analysis, is used to define the onset of metamorphism (Kisch, 1991). In this scheme, the first appearance of glaucophane, lawsonite, paragonite, prehnite, pumpellyite or stilpnomelane is taken to indicate the lower limit of metamorphism (Frey and Kisch, 1987; Bucher and Frey, 1994; Frey and Robinson, 1998). Most workers agree that such mineral growth starts at 150 ± 50° C in silicate rocks. Many lithologies may show no change in mineralogy under these conditions and hence the recognition of the onset of metamorphism will vary with bulk composition.”
See Also: buchite, fulgurite
Parents: Composite genesis rock (65)
Children: Amphibolite (10); Quartzite (221); Serpentinite (235); Chlorite actinolite epidote metamorphic rock (53); Eclogite (80); Foliated metamorphic rock (110); Glaucophane lawsonite epidote metamorphic rock (122); Granofels (128); Granulite (129); Marble (157); Migmatite (162)
[Description taken from GeoSciML SimpleLithology201012.rdf]
Category: Analysed material
The different kinds of sample material collected in the field have been classified hierarchically. Examples: “till”, “soil”, “vegetation”. Taken from the “Sample_Types_SHARED” database table.
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