A new paleomagnetic constraint on Mesoarchean plate motion from the Pilbara Craton, Western Australia
Abstract
The modes and rates of tectonic processes and lithospheric growth - or lack thereof - in the Archean are subjects of considerable debate. Traditional approaches to this problem have been based on geochemical proxies, field relations of possible syn-tectonic rocks, and geodynamical modeling. Paleomagnetic methods may contribute to the discussion by quantifying past plate velocities. Here we report a new paleomagnetic pole for the c. 3180 Ma Honeyeater Basalt of the Pilbara craton, Western Australia. Several lines of evidence support a primary origin of the measured high temperature component of magnetization, which points south-southwest and moderately down: (1) it robustly passes a fold test within the Soanesville Syncline, a c. 2930 Ma structure; (2) its minimum unblocking temperature (>435°C) is much higher than the peak metamorphic temperature of the host basalt ( 250°C - prehnite-pumpellyite facies), making a thermal overprint origin unlikely; and (3) it is distinct from any pole previously reported from the Pilbara. Our inferred paleolatitude of the Honeyeater Basalt ( 26°), when compared with previously reported paleolatitudes from the Black Range Dike (2772±2 Ma) and Euro basalt (3350-3335 Ma), requires that the average latitudinal drift rate of the East Pilbara Terrane was at least 0.1°/My or 1 cm/y during the 580 My interval between 3350 and 2772 Ma, making its velocity roughly comparable with slow modern plates. Assuming this motion is a consequence of plate motion instead of true polar wander (TPW), this result is consistent with a uniformitarian model of tectonic processes in the Mesoarchean and an initiation of plate tectonic motion prior to 3.2 Ga.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMDI33C0048B
- Keywords:
-
- 5430 Interiors;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 8103 Continental cratons;
- TECTONOPHYSICSDE: 8149 Planetary tectonics;
- TECTONOPHYSICSDE: 8170 Subduction zone processes;
- TECTONOPHYSICS