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Evolution of the middle and lower crust during the transition from contraction to extension in Fiordland, New Zealand

Keith A. Klepeis and Daniel S. King
Evolution of the middle and lower crust during the transition from contraction to extension in Fiordland, New Zealand (in Crustal cross sections; from the western North American Cordillera and elsewhere; implications for tectonic and petrologic processes, Robert B. Miller (editor) and Arthur W. Snoke (editor))
Special Paper - Geological Society of America (2009) 456: 243-265

Abstract

A deeply eroded orogen in southwest New Zealand preserves a record of changing flow patterns in the middle and lower crust during a transition from contraction and crustal thickening to extension and crustal thinning. The New Zealand exposures show that deformation patterns at mid-lower crustal depths were strongly influenced by local variations in crustal structure, temperature, composition, magmatic activity, and rheology. Kinematic parameters, including the orientation of shear zone boundaries, the degree of non-coaxiality and kinematic partitioning, strain symmetry, and whether shear zones were thickening or thinning in different planes of observation, were extremely variable spatially and changed repeatedly over an 8-10 Ma period. However, despite this variability, several aspects of superposed deformations remained constant and can be assigned to distinctive tectonic settings. All shear zones that formed during the 119-111 Ma period in Northern Fiordland record flow involving bulk horizontal (layer-parallel) shortening, vertical (layer-perpendicular) thickening, and >50% pure shear regardless of shear zone orientation, degree of non-coaxiality, strain symmetry, and temperature conditions. In contrast, all shear zones that formed during the 114-90 Ma period in Central Fiordland record flow involving vertical thinning, subhorizontal stretching, and 40%-50% pure shear. These patterns are correlative with regional contraction and regional extension, respectively. The data suggest that at length scales of approximately 100 km and time scales of ca. 10 Ma, the effects of changing plate boundary dynamics on deformation patterns in the middle and lower crust can be distinguished from the effects of changing local boundary conditions, including steep temperature gradients and variable rheology.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 456
Title: Evolution of the middle and lower crust during the transition from contraction to extension in Fiordland, New Zealand
Title: Crustal cross sections; from the western North American Cordillera and elsewhere; implications for tectonic and petrologic processes
Author(s): Klepeis, Keith A.King, Daniel S.
Author(s): Miller, Robert B.editor
Author(s): Snoke, Arthur W.editor
Affiliation: University of Vermont, Department of Geology, Burlington, VT, United States
Affiliation: San Jose State University, Department of Geology, San Jose, CA, United States
Pages: 243-265
Published: 2009
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 79
Accession Number: 2010-004840
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 1 table, geol. sketch maps
S46°00'00" - S44°30'00", E166°30'00" - E168°00'00"
Secondary Affiliation: University of Wyoming, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 201003
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