Timing of sedimentation of the Cleaverville Formation, coastal Pilbara terrane, Pilbara, Western Australia: new age dating, identified post-accretion pull-apart system and DXCL drilling result
Abstract
The Cleaverville banded iron formation (BIF) of the western Pilbara, Western Australia is one of the important key bed in Mesoarchean Iron formation at Pilbara. This iron formation was collected DXCL drilling projects (2009, 2013) collected fresh black shale and BIF samples. At the Cleaverville area in coastal Pilbara terrane, a low-grade greenstone sequence preserved and stratified sequence because it was affected strike-slip pull-apart deformation and preserved low metamorphic portion of greenstone. The greenstone sequence (Regal, Dixon Island and Cleaverville formations) are unconformably overlain by two narrowly distributed shallow-marine sedimentary sequences: The Sixty-Six Hill and Forty-Four Hill members. The former is preserved within a syncline axis (Cleaverville Syncline) and the latter formed along a northeast-trending fault. Based on the metamorphic grade and deformation in this area, two deformation events are recognized: D1resulted in folding caused by a collisional event and D2resulted in regional sinistral strike-slip deformation. A previously reported age indicates that the Cleaverville Formation pre-dated the Prinsep Orogeny (East and West Pilbara terranes collision event) that occurred at 3.02 Ga. New dating results show that: (1) silicic volcaniclastic rocks within the black shale sequence below the Cleaverville BIF have ages of 3108 ± 11 Ma; (2) the youngest zircons in sandstones of the Sixty-Six Hill Member, which unconformably overlies pillow basalt within the Cleaverville Syncline, have ages of ca. 3.08-3.09 Ga; and (3) the youngest zircons in sandstones of the Forty-Four Hill Member have ages of 3.27 and 3.02 Ga. As such, the Cleaverville BIF was deposited at ca. 3.10-3.09 Ga, which pre-dates the 3.02 Ga Prinsep Orogeny (D1).After the orogeny at about 3.02 Ga, D2resulted in the formation of a pull-apart basin in the Cleaverville area of the same age as the regional Pilbara crustal-scale shear deformation (ca. 2.93-2.90 Ma). In this way, the Dixon Island and Cleaverville formations preserved at remarkably unknow 3.1-3.2 Ga oceanic environment record in the earth history. At 3.1 Ga, oceanic environment may be had pervasive iron depositional condition.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMDI33C0049K
- Keywords:
-
- 5430 Interiors;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 8103 Continental cratons;
- TECTONOPHYSICSDE: 8149 Planetary tectonics;
- TECTONOPHYSICSDE: 8170 Subduction zone processes;
- TECTONOPHYSICS