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Titolo:
High-temperature embrittlement of extensional Alpine mylonite zones in themidcrustal ductile-brittle transition
Autore:
Axon, GJ; Selverstone, J; Wawrzyniec, T;
Indirizzi:
Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA Univ Calif Los Angeles Los Angeles CA USA 90095 Los Angeles, CA 90095 USA Univ New Mexico, Dept Earth & Planetary Sci, Albuquerque, NM 87131 USA Univ New Mexico Albuquerque NM USA 87131 y Sci, Albuquerque, NM 87131 USA
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
fascicolo: B3, volume: 106, anno: 2001,
pagine: 4337 - 4348
SICI:
0148-0227(20010310)106:B3<4337:HEOEAM>2.0.ZU;2-2
Fonte:
ISI
Lingua:
ENG
Soggetto:
WESTERN TAUERN WINDOW; PORE PRESSURE EXCESS; LINE NORMAL-FAULT; EASTERN ALPS; PLASTIC TRANSITION; DEFORMATION MECHANISMS; DEHYDRATING SYSTEM; DISLOCATION CREEP; CONTINENTAL-CRUST; DETACHMENT FAULT;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
68
Recensione:
Indirizzi per estratti:
Indirizzo: Axon, GJ Univ Calif Los Angeles, Dept Earth & Space Sci, 595 Charles E Young Dr E, Los Angeles, CA 90095 USA Univ Calif Los Angeles 595 Charles E Young Dr E Los Angeles CA USA 90095
Citazione:
G.J. Axon et al., "High-temperature embrittlement of extensional Alpine mylonite zones in themidcrustal ductile-brittle transition", J GEO R-SOL, 106(B3), 2001, pp. 4337-4348

Abstract

Structural and fluid inclusion analyses of two large-displacement extensional Alpine shear zones show that embrittlement occurred at anomalously hightemperatures and indicate that factors other than gradually changing temperature and pressure can exert primary control on the ductile-brittle transition. Most rocks within the Brenner and Simplon mylonite zones, including abundant weak schists, failed brittlely by distributed faulting, fracturing,and brittle-ductile shearing at T = 450 degrees -575 degreesC and P = 400-750 MPa, conditions in which plastic or semibrittle flow rather than brittle deformation is expected, even in strong orthogneiss. Embrittlement was caused by transiently(?) high fluid pressure and local bending strain rather than by temperature or pressure decrease. Mylonitization shut off permanently in the embrittled parts of the shear zones despite continued high-T denudation of the footwalls. However, mylonitization apparently did continue inthe structurally highest similar to 50 m of the shear zones where brittle structures are absent or rare. A strength contrast evolved between these late, thin mylonite zones and the stronger, deeper parts where mylonitizationended. This contrast probably reflects both weakening of the late mylonitezones and strengthening of the deeper embrittled parts, although differential stress may have ultimately increased in the former due to strain rate increase as the shear zones thinned. The shear zones probably evolved to discrete frictional faults by T approximate to 450 degreesC and P approximate to 400 MPa (similar to 15 km).

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Documento generato il 07/04/20 alle ore 04:18:51