Record of mega-earthquakes in subduction thrusts: The black fault rocks of Pasagshak Point (Kodiak Island, Alaska)
On Kodiak Island, Alaska, decimeter-thick black fault rocks are at the core of foliated cataclasites that are tens of meters thick. The cataclasites belong to melange zones that are regarded as paleodecollements active at 12-14 km depth and 230-260 degrees C. Each black layer is mappable for tens of...
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GEOLOGICAL SOC AMER, INC, PO BOX 9140, BOULDER, CO 80301-9140 USA
2010
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Online Access: | http://hdl.handle.net/11577/2424176 https://doi.org/10.1130/B30049.1 |
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ftunivpadovairis:oai:www.research.unipd.it:11577/2424176 2024-02-27T08:42:33+00:00 Record of mega-earthquakes in subduction thrusts: The black fault rocks of Pasagshak Point (Kodiak Island, Alaska) Meneghini F. Rowe, C. D. Moore J. C. Tsutsumi A. Yamaguchi A. DI TORO, GIULIO Meneghini, F. DI TORO, Giulio Rowe, C. D. Moore, J. C. Tsutsumi, A. Yamaguchi, A. 2010 STAMPA http://hdl.handle.net/11577/2424176 https://doi.org/10.1130/B30049.1 eng eng GEOLOGICAL SOC AMER, INC, PO BOX 9140, BOULDER, CO 80301-9140 USA info:eu-repo/semantics/altIdentifier/wos/WOS:000278351300022 volume:122 firstpage:1280 lastpage:1297 numberofpages:18 journal:GEOLOGICAL SOCIETY OF AMERICA BULLETIN http://hdl.handle.net/11577/2424176 doi:10.1130/B30049.1 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-77954022327 earthquake pseudotachylyte frictional melting megathrust cataclasite fault rocks info:eu-repo/semantics/article 2010 ftunivpadovairis https://doi.org/10.1130/B30049.1 2024-01-31T17:47:47Z On Kodiak Island, Alaska, decimeter-thick black fault rocks are at the core of foliated cataclasites that are tens of meters thick. The cataclasites belong to melange zones that are regarded as paleodecollements active at 12-14 km depth and 230-260 degrees C. Each black layer is mappable for tens of meters along strike. The black fault rocks feature a complex layering made at microscale by alternation of granular and crystalline micro textures, both composed of micronscale subrounded quartz and plagioclase in an ultrafine, phyllosilicate-rich matrix. In the crystalline microlayers, tabular zoned micro lites of plagioclase make up much of the matrix. No such feldspars have been found in the cataclasite. We interpret these crystalline microlayers as pseudotachylytes. The granular microlayers show higher grain-size variability, crushed microlites, and textures typical of fluidization and granular flow deformation. Crosscutting relationships between granular and crystalline microlayers include flow and intrusion structures and mutual brittle truncation. This suggests that each decimeters-thick composite black fault rock layer records multiple pulses of seismic slip. In each pulse, ultracomminuted fluidized material and friction melt formed and deformed together in a ductile fashion. Brittle truncation by another pulse occurred after solidification of the friction melt and the fluidized rock. Article in Journal/Newspaper Kodiak Alaska Padua Research Archive (IRIS - Università degli Studi di Padova) Geological Society of America Bulletin 122 7-8 1280 1297 |
institution |
Open Polar |
collection |
Padua Research Archive (IRIS - Università degli Studi di Padova) |
op_collection_id |
ftunivpadovairis |
language |
English |
topic |
earthquake pseudotachylyte frictional melting megathrust cataclasite fault rocks |
spellingShingle |
earthquake pseudotachylyte frictional melting megathrust cataclasite fault rocks Meneghini F. Rowe, C. D. Moore J. C. Tsutsumi A. Yamaguchi A. DI TORO, GIULIO Record of mega-earthquakes in subduction thrusts: The black fault rocks of Pasagshak Point (Kodiak Island, Alaska) |
topic_facet |
earthquake pseudotachylyte frictional melting megathrust cataclasite fault rocks |
description |
On Kodiak Island, Alaska, decimeter-thick black fault rocks are at the core of foliated cataclasites that are tens of meters thick. The cataclasites belong to melange zones that are regarded as paleodecollements active at 12-14 km depth and 230-260 degrees C. Each black layer is mappable for tens of meters along strike. The black fault rocks feature a complex layering made at microscale by alternation of granular and crystalline micro textures, both composed of micronscale subrounded quartz and plagioclase in an ultrafine, phyllosilicate-rich matrix. In the crystalline microlayers, tabular zoned micro lites of plagioclase make up much of the matrix. No such feldspars have been found in the cataclasite. We interpret these crystalline microlayers as pseudotachylytes. The granular microlayers show higher grain-size variability, crushed microlites, and textures typical of fluidization and granular flow deformation. Crosscutting relationships between granular and crystalline microlayers include flow and intrusion structures and mutual brittle truncation. This suggests that each decimeters-thick composite black fault rock layer records multiple pulses of seismic slip. In each pulse, ultracomminuted fluidized material and friction melt formed and deformed together in a ductile fashion. Brittle truncation by another pulse occurred after solidification of the friction melt and the fluidized rock. |
author2 |
Meneghini, F. DI TORO, Giulio Rowe, C. D. Moore, J. C. Tsutsumi, A. Yamaguchi, A. |
format |
Article in Journal/Newspaper |
author |
Meneghini F. Rowe, C. D. Moore J. C. Tsutsumi A. Yamaguchi A. DI TORO, GIULIO |
author_facet |
Meneghini F. Rowe, C. D. Moore J. C. Tsutsumi A. Yamaguchi A. DI TORO, GIULIO |
author_sort |
Meneghini F. |
title |
Record of mega-earthquakes in subduction thrusts: The black fault rocks of Pasagshak Point (Kodiak Island, Alaska) |
title_short |
Record of mega-earthquakes in subduction thrusts: The black fault rocks of Pasagshak Point (Kodiak Island, Alaska) |
title_full |
Record of mega-earthquakes in subduction thrusts: The black fault rocks of Pasagshak Point (Kodiak Island, Alaska) |
title_fullStr |
Record of mega-earthquakes in subduction thrusts: The black fault rocks of Pasagshak Point (Kodiak Island, Alaska) |
title_full_unstemmed |
Record of mega-earthquakes in subduction thrusts: The black fault rocks of Pasagshak Point (Kodiak Island, Alaska) |
title_sort |
record of mega-earthquakes in subduction thrusts: the black fault rocks of pasagshak point (kodiak island, alaska) |
publisher |
GEOLOGICAL SOC AMER, INC, PO BOX 9140, BOULDER, CO 80301-9140 USA |
publishDate |
2010 |
url |
http://hdl.handle.net/11577/2424176 https://doi.org/10.1130/B30049.1 |
genre |
Kodiak Alaska |
genre_facet |
Kodiak Alaska |
op_relation |
info:eu-repo/semantics/altIdentifier/wos/WOS:000278351300022 volume:122 firstpage:1280 lastpage:1297 numberofpages:18 journal:GEOLOGICAL SOCIETY OF AMERICA BULLETIN http://hdl.handle.net/11577/2424176 doi:10.1130/B30049.1 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-77954022327 |
op_doi |
https://doi.org/10.1130/B30049.1 |
container_title |
Geological Society of America Bulletin |
container_volume |
122 |
container_issue |
7-8 |
container_start_page |
1280 |
op_container_end_page |
1297 |
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1792050299288944640 |