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U-Pb dating of overpressure veins in late Archean shales reveals six episodes of Paleoproterozoic deformation and fluid flow in the Pilbara craton

Rasmussen, Birger and Zi, Jian-Wei and Muhling, Janet R. and Dunkley, Daniel J. and Fischer, Woodward W. (2020) U-Pb dating of overpressure veins in late Archean shales reveals six episodes of Paleoproterozoic deformation and fluid flow in the Pilbara craton. Geology, 48 (10). pp. 961-965. ISSN 0091-7613. https://resolver.caltech.edu/CaltechAUTHORS:20200624-101732608

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Abstract

Fluid flow in the upper crust not only impacts the redistribution of heat and elements, driving the formation of economic ore deposits, but it also exerts control on metamorphism, metasomatism, and deformation. However, reconstructing the history of fluid flow in ancient basins is exceedingly difficult, particularly in Archean sedimentary rocks because of extensive overprinting and recrystallization. Here, we report U-Pb ages for monazite and xenotime that grew in bedding-parallel veins in 2.63–2.5-b.y.-old shales along the southern Pilbara craton, Australia. The U-Pb ages define six discrete populations, at 2.41 Ga, 2.30 Ga, 2.20 Ga, 2.10 Ga, 2.05 Ga, and 1.66 Ga, which formed ≥200 m.y. after deposition. The abundance of bedding-parallel crack-seal and fibrous veins in banded iron formations (BIFs) and underlying shales suggests a history of episodic buildup of fluid pressure followed by microfracturing, fluid expulsion, and mineral growth. Thermometry of vein minerals indicates temperatures between 230 °C and 320 °C, implicating the migration of hydrothermal fluids. The development of bedding-parallel veins at 2.41 Ga, 2.20 Ga, and 1.66 Ga was coeval with regional orogenic events known to have affected the craton, whereas vein growth at 2.30 Ga, 2.10 Ga, and 2.05 Ga reveals new episodes of deformation and fluid flow. Our results show that well-preserved Archean shales devoid of structural fabrics and >150 km inboard of the craton margin preserve a cryptic history of fluid overpressure, crack-seal vein development, and hydrothermal fluid flow between 2.41 and 1.66 b.y. ago.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1130/g47526.1DOIArticle
ORCID:
AuthorORCID
Rasmussen, Birger0000-0001-5052-6797
Fischer, Woodward W.0000-0002-8836-3054
Additional Information:© 2020 Geological Society of America. Manuscript received 17 February 2020; Revised manuscript received 24 April 2020; Manuscript accepted 29 April 2020. We acknowledge support from the Australian Research Council (DP140100512 to Rasmussen; DP190102237 to Rasmussen and Muhling), the State Key Laboratory of Geological Processes and Mineral Resources (China) Open Research Grant GPMR201802 (Rasmussen), and the National Natural Science Foundation of China grant 4187306 (Zi). Scanning electron microscopy was performed at the Centre for Microscopy, Characterization and Analysis at the University of Western Australia (Perth), a node of Microscopy Australia, funded from university and government sources. Ion microprobe analyses were done at the John de Laeter (JdL) Centre, Perth, Australia. We thank Fernando Corfu and two anonymous reviewers for their comments.
Funders:
Funding AgencyGrant Number
Australian Research CouncilDP140100512
Australian Research CouncilDP190102237
State Key Laboratory of Geological Processes and Mineral ResourcesGPMR201802
National Natural Science Foundation of China4187306
Issue or Number:10
Record Number:CaltechAUTHORS:20200624-101732608
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200624-101732608
Official Citation:Birger Rasmussen, Jian-Wei Zi, Janet R. Muhling, Daniel J. Dunkley, Woodward W. Fischer; U-Pb dating of overpressure veins in late Archean shales reveals six episodes of Paleoproterozoic deformation and fluid flow in the Pilbara craton. Geology ; 48 (10): 961–965. doi: https://doi.org/10.1130/G47526.1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103992
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:24 Jun 2020 17:27
Last Modified:21 Oct 2020 21:26

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