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Titolo:
CONDITIONS OF FORMATION OF LIZARDITE, CHRYSOTILE AND ANTIGORITE, CASSIAR, BRITISH-COLUMBIA
Autore:
OHANLEY DS; WICKS FJ;
Indirizzi:
TRINITY SCH RIVER RIDGE,2300 E 88TH ST BLOOMINGTON MN 55425 ROYAL ONTARIO MUSEUM,DEPT MINERAL TORONTO ON M5S 2C6 CANADA
Titolo Testata:
Canadian Mineralogist
, volume: 33, anno: 1995,
parte:, 4
pagine: 753 - 773
SICI:
0008-4476(1995)33:<753:COFOLC>2.0.ZU;2-3
Fonte:
ISI
Lingua:
ENG
Soggetto:
CONSISTENT THERMODYNAMIC DATA; SERPENTINIZATION; MINERALS; STABILITY; MAGNETITE; MOUNTAIN; ORIGIN;
Keywords:
SERPENTINITE; SERPENTINE; RECRYSTALLIZATION; REPLACEMENT; INFILTRATION METAMORPHISM; MINERAL STABILITY; CASSIAR; BRITISH COLUMBIA;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
43
Recensione:
Indirizzi per estratti:
Citazione:
D.S. Ohanley e F.J. Wicks, "CONDITIONS OF FORMATION OF LIZARDITE, CHRYSOTILE AND ANTIGORITE, CASSIAR, BRITISH-COLUMBIA", Canadian Mineralogist, 33, 1995, pp. 753-773

Abstract

Observations at the Cassiar (British Columbia) chrysotile asbestos deposit have defined a continuous series of serpentine textures, betweenpseudomorphic and nonpseudomorphic. These minerals and textures are distributed with respect to shear zones in the interior of the serpentinite such that the degree of recrystallization and replacement increases as the shear zones are approached. Patterns of spatial distributionsuggest that recrystallization and replacement were caused by infiltration-driven metamorphism as the serpentinite equilibrated with an externally derived fluid. The shear zones served as conduits for the fluid. The recrystallization and replacement of lizardite formed after olivine and of that formed after enstatite proceed independently early inthe process, such that composition of the various serpentine mineralswas controlled by the bulk composition of the precursor. Later in theprocess, Fe2+/Mg, Cr/Al and Fe3+/(Mg + Si) values, and the distribution of boron, between serpentine after olivine and that formed after enstatite indicate that equilibrium was closely approached. The formation of a chrysotile + antigorite assemblage marks this transition. The recrystallization of lizardite and its replacement by chrysotile + antigorite occurred at 250 +/- 25 degrees C and a P(H2O) of less than 1 kbar. The temperatures and pressures of serpentinization can be modeled in the system MgO-SiO2-H2O (MSH) because: 1) clinochlore is stabilizedby the breakdown of chromite, rather than a serpentine mineral, and 2) magnetite is both a product and a reactant in the conversion of lizardite to antigorite, indicating that it is not an essential compound in the conversion of lizardite to antigorite. The mineralogy, textures and compositions of lizardite and chrysotile indicate that they are polymorphs in the MSH system.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 03/12/20 alle ore 15:56:35