Distributed deformation in the lower crust and upper mantle beneath a continental strike-slip fault zone: Marlborough fault system, South Island, New Zealand

Geology ◽  
2004 ◽  
Vol 32 (10) ◽  
pp. 837 ◽  
Author(s):  
Charles K. Wilson ◽  
Craig H. Jones ◽  
Peter Molnar ◽  
Anne F. Sheehan ◽  
Oliver S. Boyd
Keyword(s):  
New Zealand ◽  
Fault Zone ◽  
Upper Mantle ◽  
Lower Crust ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Fault System ◽  
Crust And Upper Mantle

The Andaman Basin Central Fault Zone, Andaman Sea: Characteristics of a major deepwater strike-slip fault system in a polyphase rift

2021 ◽  
pp. 104997
Author(s):  
Thananchai Mahattanachai ◽  
Christopher K. Morley ◽  
Punya Charusiri ◽  
Pitsanupong Kanjanapayont
Keyword(s):  
Fault Zone ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Andaman Sea ◽  
Fault System

scholarly journals Constraints on the rheology of lower crust in a strike-slip plate boundary: Evidence from the San Quintin xenoliths, Baja California, Mexico

2017 ◽  
Author(s):  
Thomas van der Werf ◽  
Vasileios Chatzaras ◽  
Leo M. Kriegsman ◽  
Andreas Kronenberg ◽  
Basil Tikoff ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Lower Crust ◽  
Baja California ◽  
Volcanic Field ◽  
Strike Slip ◽  
Mafic Granulite ◽  
Dislocation Creep ◽  
Diffusion Creep ◽  
Plate Boundaries ◽  
Crust And Upper Mantle

Abstract. The rheology of lower crust and its time-dependent behavior in active strike-slip plate boundaries remain poorly understood. To address this issue, we analyzed a suite of mafic granulite and lherzolite xenoliths from the Holocene San Quintin volcanic field, of northern Baja California, Mexico. The San Quintin volcanic field is located 20 km east of the Baja California shear zone, which accommodates the relative movement between the Pacific plate and Baja California microplate. Combining microstructural observations, geothermometry and phase equilibria modeling we constrain that crystal-plastic deformation took place at temperatures of 750–900 °C and pressures of 400–580 MPa, corresponding to 15–22 km depth. A hot crustal geothermal gradient of 40 °C/km is required to explain the estimated deformation conditions. Infrared spectroscopy shows that plagioclase in the mafic granulites is dry. Microstructural evidence suggests that the mafic granulite and peridotite xenoliths were dominantly deforming by processes transitional between dislocation creep and diffusion creep. Recrystallized grain size paleopiezometry yields similar differential stresses in both the uppermost lower crust and upper mantle. Using dry-plagioclase and dry-olivine flow laws we demonstrate that the viscosity of the lower crust and upper mantle is low (2.2 × 1018 – 1.4 × 1020 Pa s). Comparing the viscosity structure of the lithosphere constrained from the San Quintin xenoliths with results from post-seismic relaxation studies from western US, we suggest that lower crust is stronger during transient deformation (e.g., post-seismic relaxation period) while the upper mantle is stronger during long-term deformation (e.g., interseismic period).

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