The origin of olistoliths in proterozoic rocks of the Ashburton trough, Western Australia, using zircon U‐Pb isotopic characteristics

Pidgeon, R. T.; Horwitz, R.C.

doi:10.1080/08120099108727955

Cited by 35 publications

(25 citation statements)

References 12 publications

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“…In the present paper we combine the SHRIMP data for the Barley et al . (1997) sample W17 with data we had obtained previously from a nearby sample (W101) of the same unit, from which Pidgeon and Horwitz (1991) had earlier reported a TIMS U–Pb zircon age. Trendall et al .…”

Section: Previously Published Geochronologymentioning

confidence: 69%

“…Some initial thermal ionisation mass spectrometric (TIMS) multigrain and single‐grain zircon analyses were made (Compston et al . 1981; Pidgeon & Horwitz 1991), but since the advent of the first SHRIMP in Canberra (Compston 1996) it has been the preferred analytical method, and this brief review is mainly confined to the SHRIMP results. Some Pb–Pb carbonate isochron work has also been published (Jahn & Simonson 1995; Woodhead et al .…”

Section: Previously Published Geochronologymentioning

confidence: 99%

“…1998); and geochronological work has also been carried out by Barley et al . (1997), Pidgeon and Horwitz (1991) and Pickard (2002).…”

Section: Introductionmentioning

confidence: 99%

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SHRIMP zircon ages constraining the depositional chronology of the Hamersley Group, Western Australia*

et al. 2004

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The Mt Bruce Supergroup of Western Australia was laid down between ca 2.8 Ga and ca 2.2 Ga in the Hamersley Basin, unconformably over a basement of the older, granite-greenstone, component of the Pilbara Craton. The Mt Bruce Supergroup consists of three groups: the Fortescue Group, Hamersley Group and Turee Creek Group in upward sequence. The Hamersley Group, which is divided into eight formations, has a general thickness of ~2.5 km, and is characterised by major banded iron-formation (BIF) units. Reported here are SHRIMP U-Pb zircon results (406 grain analyses) from 13 samples taken from the Hamersley Group and near the top of the underlying Fortescue Group. In combination with SHRIMP results previously published from 12 Hamersley Group samples, the present results provide significant new constraints on the depositional chronology of the group, and suggest that the average (compacted) depositional rates of each of the main depositional lithologies (BIF, carbonate, shale) were ~180 m per million years, 12 m per million years and 5 m per million years, respectively. Some recently published SHRIMP ages from the Joffre Member differ slightly from those that are interpreted from the present data, and it is suggested that the two datasets may be reconciled if non-zero-age Pb loss is taken into account. The total body of zircon U-Pb age data from the Fortescue and Hamersley Groups is consistent with a model involving continuous accumulation of basin-fill for at least 330 million years, from ca 2780 Ma to the top of the Hamersley Group at ca 2449 Ma. The word 'continuous' in this context means that there may have been no breaks in deposition longer than 1 million years. However, this model is not proven, and a major challenge for future work is to measure the length of any proposed non-depositional intervals.

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Section: Previously Published Geochronologymentioning

confidence: 69%

Section: Previously Published Geochronologymentioning

confidence: 99%

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SHRIMP zircon ages constraining the depositional chronology of the Hamersley Group, Western Australia*

et al. 2004

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“…According to Thorne and Seymour (1991) additional siliciclastic sediments were derived from the southwest during the final stages of deposition of the Ashburton Formation. The Ashburton Formation disconformably overlies the June Hill Volcanics, which contain zircons dated by conventional U-Pb methods at 1843 Ϯ 2 Ma (Table 1) (Pidgeon & Horwitz 1991).…”

Section: Regional Geologymentioning

confidence: 99%

Basin setting and age of the Late Palaeoproterozoic Capricorn Formation, Western Australia

Hall¹,

Powell²,

Bryant³

2001

Aust J Earth Sci

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The Palaeoproterozoic Capricorn Formation near Ashburton Downs in northwestern Australia formed during the latter stages of the convergence of the Pilbara and Yilgarn Cratons. Palaeocurrent and facies analyses show that the southwesterly derived sediments were deposited in terrestrial environments and in a lake or shallow sea with a shoreline trending southeast. Intraformational debris flows suggest instability during sedimentation. Zircon grains from an accretionary lapilli tuff, dated at 1804 Ϯ 7 Ma by the SHRIMP U-Pb method, show that the Capricorn Formation was deposited at the same time as granitic plutons were intruded in the Gascoyne Complex to the south and west. Although the Capricorn Formation was deposited with marked angular unconformity over the turbiditic Ashburton Formation, both formations could have been deposited in a foreland basin on the northeast flank of the growing Ashburton Fold Belt.

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“…1 Geologic map of the Pilbara-Hamersley district (simplified after Ho et al, 1990;modified after Trendall, 1983 (Morris, 1980). The age of the Upper Wyloo Group was determined to be 1,843±2 Ma for the June Hill Volcanics at the upper part of the Upper Wyloo Group (Pidgeon and Horwitz, 1991).…”

Section: Generalmentioning

confidence: 99%

Chemical, Isotopic, and Fluid Inclusion Evidence for the Hydrothermal Alteration of the Footwall Rocks of the BIF‐Hosted Iron Ore Deposits in the Hamersley District, Western Australia

et al. 2003

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. The petrography, chemical, fluid inclusion and isotope analyses (O, Rb‐Sr) were conducted for the shale samples of the Mount McRae Shale collected from the Tom Price, Newman, and Paraburdoo mines in the Hamersley Basin, Western Australia. The Mount McRae Shale at these mines occurs as a footwall unit of the secondary, hematite‐rich iron ores derived from the Brockman Iron Formation, one of the largest banded iron formations (BIFs) in the world. Unusually low contents of Na, Ca, and Sr in the shales suggest that these elements were leached away from the shale after deposition. The δ18O (SMOW) values fall in the range of + 15.0 to +17.9 per mil and show the positive correlation with calculated quartz/sericite ratios of the shale samples. This suggests that the oxygen isotopic compositions of shale samples were homogenized and equilibrated by postdepositional event. The pyrite nodules hosted by shales are often rimmed by thin layers of silica of varying crystallinity. Fluid inclusions in quartz crystals rimming a pyrite nodule show homogenization temperatures ranging from 100 to 240d̀C for 47 inclusions and salinities ranging from 0.4 to 12.3 wt% NaCl equivalent for 18 inclusions. These fluid inclusion data give direct evidence for the hydrothermal activity and are comparable to those of the vein quartz collected from the BIF‐derived secondary iron ores (Taylor et al, 2001). The Rb‐Sr age for the Mount McRae Shale is 1,952 ± 289 Ma and at least 200 million years younger than the depositional age of the Brockman Iron Formation of ∼ 2.5 Ga in age. All the data obtained in this study are consistent with the suggestion that high temperature hydrothermal fluids were responsible for both the secondary iron ore formation and the alteration of the Mount McRae Shale.

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The origin of olistoliths in proterozoic rocks of the Ashburton trough, Western Australia, using zircon U‐Pb isotopic characteristics

Cited by 35 publications

References 12 publications

SHRIMP zircon ages constraining the depositional chronology of the Hamersley Group, Western Australia*

SHRIMP zircon ages constraining the depositional chronology of the Hamersley Group, Western Australia*

Basin setting and age of the Late Palaeoproterozoic Capricorn Formation, Western Australia

Chemical, Isotopic, and Fluid Inclusion Evidence for the Hydrothermal Alteration of the Footwall Rocks of the BIF‐Hosted Iron Ore Deposits in the Hamersley District, Western Australia

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