Paleozoic-aged brine and authigenic helium preserved in an Ordovician shale aquiclude

Clark, Ian D.; Al, Tom; Kennell, Laura; Mazurek, Martin; Mohapatra, Ratan; Raven, Ken G. (2013). Paleozoic-aged brine and authigenic helium preserved in an Ordovician shale aquiclude. Geology, 41(9), pp. 951-954. Geological Society of America 10.1130/G34372.1

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Consideration of the geosphere for isolation of nuclear waste has generated substantial interest in the origin, age, and movement of fl uids and gases in low-permeability rock formations. Here, we present profi les of isotopes, solutes, and helium in porewaters recovered from 860 m of Cambrian to Devonian strata on the eastern fl ank of the Michigan Basin. Of particular interest is a 240-m-thick, halite-mineralized, Ordovician shale and carbonate aquiclude, which hosts Br–-enriched, post-dolomitic brine (5.8 molal Cl) originating as evaporated Silurian seawater. Authigenic helium that has been accumulating in the aquiclude for more than 260 m.y. is found to be isolated from underlying allochthonous, 3He-enriched helium that originated from the rifted base of the Michigan Basin and the Canadian Shield. The Paleozoic age and immobility of the pore fl uids in this Ordovician aquiclude considerably strengthen the safety case for deep geological repositories, but also provide new insights into the origin of deep crustal brines and opportunities for research on other components of a preserved Paleozoic porewater system.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Institute of Geological Sciences > Rock-Water Interaction

UniBE Contributor:

Mazurek, Martin

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0091-7613

Publisher:

Geological Society of America

Language:

English

Submitter:

Martin Mazurek

Date Deposited:

08 Aug 2014 12:40

Last Modified:

07 Oct 2015 11:41

Publisher DOI:

10.1130/G34372.1

BORIS DOI:

10.7892/boris.47452

URI:

https://boris.unibe.ch/id/eprint/47452

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