Timing and development of sedimentation of the Cleaverville Formation and a post‐accretion pull‐apart system in the Cleaverville area, coastal Pilbara Terrane, Pilbara, Western Australia

Abstract

In the Cleaverville area of Western Australia, the Regal, Dixon Island, and Cleaverville Formations preserve a Mesoarchean lower-greenschist-facies volcano-sedimentary succession in the coastal Pilbara Terrane. These formations are distributed in a rhomboidal-shaped area and are unconformably overlain by two narrowly distributed shallow-marine sedimentary sequences: the Sixty-Six Hill and Forty-Four Hill Members of the Lizard Hills Formation. The former member is preserved within the core of the Cleaverville Syncline and the latter formed along the northeast-trending Eighty-Seven Fault. Based on the metamorphic grade and structures, two deformation events are recognized: D 1 resulted in folding caused by a collisional event, and D 2 resulted in regional sinistral strike-slip deformation. A previous study reported that the Cleaverville Formation was deposited at 3020 Ma, after the Prinsep Orogeny (3070-3050 Ma). Our SHRIMP U-Pb zircon ages show that: (i) graded volcaniclastic-felsic tuff within the black shale sequence below the banded iron formation in the Cleaverville Formation yields an age of (3 114 ±14) Ma; (ii) the youngest zircons in sandstones of the Sixty-Six Hill Member, which unconformably overlies pillow basalt of the Regal Formation, yield ages of 3090-3060 Ma; and (iii) zircons in sandstones of the Forty-Four Hill Member show two age peaks at 3270 Ma and 3020 Ma. In this way, the Cleaverville Formation was deposited at 3114-3060 Ma and was deformed at 3070-3050 Ma (D 1 ). Depositional age of the Cleaverville Formation is at least 40-90 Myr older than that proposed in previous studies and pre-dates the Prinsep Orogeny (3070-3050 Ma). After 3020 Ma, D 2 resulted in the formation of a regional strike-slip pull-apart basin in the Cleaverville area. The lower-greenschist-facies volcano-sedimentary rocks are distributed only within this basin structure. This strike-slip deformation was synchronous with crustal-scale sinistral shear deformation (3000-2930 Ma) in the Pilbara region.

Thematic section: Special topics in 4th IGS ‘Precambrian World 2’

“…2.1 | Age constrain for the Creaverville Formation (3.1 Ga) Kiyokawa, Aihara, Takehara, and Horie (2019) boundary. The main lithology of the Embry Lake Formation is a continuous sandstone-shale turbidite sequence, which was previously identified as an oceanic sequence.…”

“…Kiyokawa, Aihara, Takehara, and Horie (2019) provide important new age data for sedimentation of the Cleaverville Formation, coastal Pilbara terrane, Australia, which is one of the most important Banded Iron formation (BIF) records of the Mesoarchean world which is formed 6 million years ago before Great Oxidation Event (GOE). Onset of the Cleaverville deposition was newly dated as 3114 ± 14 Ma, 40–90 Ma older than previous estimates.…”