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Deformation fabrics of faulted rocks, and some syntectonic stress estimates from the active Woodlark Basin detachment zone

Roller, S. and Behrmann, J. H. and Kopf, A.
Wilson, R. C. L. and Whitmarsh, R. B. and Taylor, B. and Froitzheim, N. (eds.) (2001):
Deformation fabrics of faulted rocks, and some syntectonic stress estimates from the active Woodlark Basin detachment zone.
In: Non-Volcanic Rifting of Continental Margins: A Comparison of Evidence from Land and Sea, London, Geological Society, pp. 319-334, [Online-Edition: http://sp.lyellcollection.org/cgi/content/abstract/187/1/319],
[Book Section]

Abstract

Ocean Drilling Program (ODP) Leg 180 investigated, in the western Woodlark Basin off Papua New Guinea, the nature and evolution of continental extension, eventually leading to crustal break-up and sea-floor spreading. At Moresby Seamount, the rift-related extension is localized at a recently active low-angle (30°) detachment fault, partly buried beneath a Pliocene-Pleistocene sedimentary synrift sequence. Data from three drillsites sample the detachment fault itself, secondary faults in its hanging wall and a steep normal fault cutting the footwall. The fault plane itself is manifested as a strongly altered fault gouge. Deformation of turbiditic sediments in several fault zones in the hanging wall is dominated by brittle mechanisms, and accompanied by intensive veining and pervasive diagenetic cementation. The metabasic rocks of the footwall below the detachment show an unusual transition from ductile to brittle deformation fabrics with increasing depth. Many fracture systems show evidence of repeated opening and healing during multistage hydrothermal mineralization. Syn-mylonitic microstructures and vein fill mineralogy suggest exhumation of the detachment footwall from considerable depth in the crust. Two palaeo-piezometers were applied to calcite-filled veins that show evidence of plastic deformation. Differential stress values of similar magnitude and probably close to the rock failure strength are found in both the hanging wall and footwall.

Item Type: Book Section
Erschienen: 2001
Editors: Wilson, R. C. L. and Whitmarsh, R. B. and Taylor, B. and Froitzheim, N.
Creators: Roller, S. and Behrmann, J. H. and Kopf, A.
Title: Deformation fabrics of faulted rocks, and some syntectonic stress estimates from the active Woodlark Basin detachment zone
Language: English
Abstract:

Ocean Drilling Program (ODP) Leg 180 investigated, in the western Woodlark Basin off Papua New Guinea, the nature and evolution of continental extension, eventually leading to crustal break-up and sea-floor spreading. At Moresby Seamount, the rift-related extension is localized at a recently active low-angle (30°) detachment fault, partly buried beneath a Pliocene-Pleistocene sedimentary synrift sequence. Data from three drillsites sample the detachment fault itself, secondary faults in its hanging wall and a steep normal fault cutting the footwall. The fault plane itself is manifested as a strongly altered fault gouge. Deformation of turbiditic sediments in several fault zones in the hanging wall is dominated by brittle mechanisms, and accompanied by intensive veining and pervasive diagenetic cementation. The metabasic rocks of the footwall below the detachment show an unusual transition from ductile to brittle deformation fabrics with increasing depth. Many fracture systems show evidence of repeated opening and healing during multistage hydrothermal mineralization. Syn-mylonitic microstructures and vein fill mineralogy suggest exhumation of the detachment footwall from considerable depth in the crust. Two palaeo-piezometers were applied to calcite-filled veins that show evidence of plastic deformation. Differential stress values of similar magnitude and probably close to the rock failure strength are found in both the hanging wall and footwall.

Title of Book: Non-Volcanic Rifting of Continental Margins: A Comparison of Evidence from Land and Sea
Series Name: Special Publications
Number: 187
Place of Publication: London
Publisher: Geological Society
Divisions: 11 Department of Materials and Earth Sciences > Earth Science
11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Earth Science > Applied Sedimentary Geology
Date Deposited: 28 Jan 2010 13:15
Official URL: http://sp.lyellcollection.org/cgi/content/abstract/187/1/319
Identification Number: doi:10.1144/GSL.SP.2001.187.01.16
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