Abstract
The Bogota Peninsula shear zone in New Caledonia (southwest Pacific Ocean) is the exhumed mantle section of an oceanic transform zone. Ductile fabrics in this zone formed at temperatures >820 °C, and differential stresses estimated from microstructures vary spatially and temporally. Along a transform-perpendicular transect, stresses increase toward the high-strain areas. We attribute this stress gradient to an increase in strain rate caused by imposed rather than intrinsic strain localization. Temporal stress variations are indicated by the formation of fine-grained microdeformation zones (MDZs) that truncate and offset coarser grains. We interpret the MDZs to result from zones of brittle deformation caused by earthquake fracture propagation downward in the upper mantle, which are in turn overprinted by ductile deformation at stresses 2-6 times higher (22-81 MPa) than their surrounding steady-state fabrics. We interpret the spatial and temporal variations in microstructures and stresses as reflecting different stages of the seismic cycle in oceanic lithosphere.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 569-573 |
| Number of pages | 5 |
| Journal | Geology |
| Volume | 48 |
| Issue number | 6 |
| DOIs | |
| State | Published - 2020 |
Bibliographical note
Funding Information:We thank the late Chief Isaac Toussi and the Ouassé villagers on New Caledonia for their hospitality. This research was supported by a Marie Curie International Outgoing Fellowship (PIOF-GA-2012-329183) and a research support grant from the University of Sydney (Australia) awarded to Chatzaras; by research funds from Boston College (Massachusetts, USA) awarded to Kruckenberg; and by U.S. National Science Foundation grant EAR-1347309 awarded to Teyssier. We acknowledge the facilities and technical assistance of the Scanning Electron Microscope (SEM) Facility at Boston College, the electron microprobe laboratories at the University of Wisconsin-Madison (USA) and Utrecht University (Netherlands), and Microscopy Australia at the Australian Centre for Microscopy and Microanalysis at the University of Sydney. We thank Luca Menegon, Steve Reddy, an anonymous reviewer, and editor Chris Clark for their constructive comments.
Funding Information:
We thank the late Chief Isaac Toussi and the Ouassé villagers on New Caledonia for their hospitality. This research was supported by a Marie Curie International Outgoing Fellowship (PIOF-GA-2012–329183) and a research support grant from the University of Sydney (Australia) awarded to Chatzaras; by research funds from Boston College (Massachusetts, USA) awarded to Kruckenberg; and by U.S. National Science Foundation grant EAR-1347309 awarded to Teyssier. We acknowledge the facilities and technical assistance of the Scanning Electron Microscope (SEM) Facility at Boston College, the electron microprobe laboratories at the University of Wisconsin–Madison (USA) and Utrecht University (Netherlands), and Microscopy Australia at the Australian Centre for Microscopy and Microanalysis at the University of Sydney. We thank Luca Menegon, Steve Reddy, an anonymous reviewer, and editor Chris Clark for their constructive comments.
Publisher Copyright:
© 2020 Geological Society of America.