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Radiometric dating and temperature history of banded iron formation–associated hematite, Gogebic iron range, Michigan, USA

Farley, K. A. and McKeon, R. (2015) Radiometric dating and temperature history of banded iron formation–associated hematite, Gogebic iron range, Michigan, USA. Geology, 43 (12). pp. 1083-1086. ISSN 0091-7613. https://resolver.caltech.edu/CaltechAUTHORS:20151221-080305404

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Abstract

Newly developed techniques were used to characterize the age, origin, and temperature history of coarse hematite contained in high-grade iron ore. Three botryoidal specimens from two different mines in the Gogebic iron range near Ironwood, Michigan (USA), yielded (U-Th)/^(21)Ne ages concordant with plateau ^4He/^3He ages. These data reveal that while two of the specimens grew at ca. 772 ± 41 Ma, the third formed 300 m.y. later (453 ± 14 Ma). ^4He/^3He polydomain thermochronometry indicates hematite formation at >80 °C for the older specimens and ∼60 °C for the younger. Fe mobilization and recrystallization in open cavities at 3–5 km subsurface has occurred episodically or possibly continuously over hundreds of millions of years despite a quiescent tectonic setting throughout this interval. While the analyzed specimens are distinct from typical Fe ore, their ages along with structural relationships constrain the onset of iron enrichment to between 1060 and 770 Ma. Cooling of ∼0.5 °C/m.y. ensued between ca. 800 and ca. 550 Ma, declining to ∼0.1 °C/m.y. for the last 550 m.y. These data suggest an erosion rate of ∼6 m/m.y. and ∼5 km of total erosion of the Superior Upland province through the Phanerozoic, and limit unroofing associated with Pleistocene glaciation to <1 km.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1130/G37190.1DOIArticle
http://geology.gsapubs.org/content/43/12/1083PublisherArticle
http://geology.geoscienceworld.org/content/43/12/1083PublisherArticle
ORCID:
AuthorORCID
Farley, K. A.0000-0002-7846-7546
Additional Information:© 2015 Geological Society of America. Manuscript received 22 July 2015; Revised manuscript received 7 October 2015; Manuscript accepted 9 October 2015; First published online November 6, 2015. We thank S. Kessler and P. Vasconcelos for helpful suggestions. F. Stuart, W. Cannon, B. Smith, and H. Dalstra provided valuable reviews. This work was supported by National Science Foundation grant EAR-1144500.
Funders:
Funding AgencyGrant Number
NSFEAR-1144500
Issue or Number:12
Record Number:CaltechAUTHORS:20151221-080305404
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20151221-080305404
Official Citation:K.A. Farley and R. McKeon Radiometric dating and temperature history of banded iron formation–associated hematite, Gogebic iron range, Michigan, USA Geology, December 2015, v. 43, p. 1083-1086, First published on November 6, 2015, doi:10.1130/G37190.1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63088
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:22 Dec 2015 20:34
Last Modified:03 Mar 2020 13:01

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