Consulta: subjectFacets:"Metamorphism"
Registros recuperados: 3
Data/hora: 01/06/2024 06:17:50

Experimental alteration of the &lt;i&gt;Nautilus&lt;/i&gt; shell by factors involved in diagenesis and metamorphism. Part I. Thermal changes in conchiolin matrix of mother-of-pearl
Provedor de dados: 27
Autores: Grégoire, Ch.
1. This paper is an electron microscope study of the alterations produced by temperatures in range of 100°C to 900°C in mother-of-pearl of the modern &lt;i&gt;Nautilus&lt;/i&gt; shell. 2. Fragments of nacreous layers of the shell wall in the living chamber were exposed for 5 minutes to 21 days to dry heat in open vessels and in quartz tubes sealed under vacuum or argon. Other fragments were boiled in sea mud and sea water. 3. In open vessels and in sealed tubes, conversion of aragonite into calcite took place in the samples heated at 400 °C and above. In the 600 °C-900 °C samples, calcite was mixed with varying amounts of calcium oxide. With elevation of temperature, the original hard, compact and stratified mother-of-pearl became progressively brittle,...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Diagenesis; Metamorphism; Nacre; Nautilus.
Ano: 1968
URL: http://www.vliz.be/imisdocs/publications/294745.pdf

Mid amphibolite facies metamorphism of harzburgites in the Neoproterozoic Cerro Mantiqueiras Ophiolite, southernmost Brazil
Provedor de dados: 42
Autores: HARTMANN,LÉO A.; CHEMALE-JÚNIOR,FARID.
Valuable information is retrieved from the integrated investigation of the field relationships, microstructure and mineral compositions of harzburgites from the Neoproterozoic Cerro Mantiqueiras Ophiolite. This important tectonic marker of the geological evolution of southernmost Brazilian Shield was thoroughly serpentinized during progressive metamorphism, because the oldest mineral assemblage is: olivine + orthopyroxene + tremolite + chlorite + chromite. This M1 was stabilized in mid amphibolite facies - 550-600ºC as calculated from mineral equilibria. No microstructural (e.g. ductile deformation of olivine or chromite) or compositional (e.g. mantle spinel) remnant of mantle history was identified. A metamorphic event M2 occurred in the low amphibolite...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Mineral chemistry; Cerro Mantiqueiras Ophiolite; Metamorphism; Neoproterozoic.
Ano: 2003
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652003000100012

Metamorphic evolution and U-Pb zircon SHRIMP geochronology of the Belizário ultramafic amphibolite, Encantadas Complex, southernmost Brazil
Provedor de dados: 42
Autores: Hartmann,Léo A.; Santos,João O.S.; Leite,Jayme A.D.; Porcher,Carla C.; Mcnaughton,Neal J.
The integrated investigation of metamorphism and zircon U-Pb SHRIMP geochronology of the Belizário ultramafic amphibolite from southernmost Brazil leads to a better understanding of the processes involved in the generation of the Encantadas Complex. Magmatic evidence of the magnesian basalt or pyroxenite protolith is only preserved in cores of zircon crystals, which are dated at 2257 ± 12 Ma. Amphibolite facies metamorphism M1 formed voluminous hornblende in the investigated rock possibly at 1989 ± 21 Ma. This ultramafic rock was re-metamorphosed at 702±21 Ma during a greenschist facies eventM2; the assemblage actinolite + oligoclase + microcline + epidote + titanite + monazite formed by alteration of hornblende. The metamorphic events are probably related...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Ultramafic amphibolite; Zircon geochronology; Encantadas Complex; Trans-Amazonian Cycle; Metamorphism.
Ano: 2003
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652003000300010