A δ26Mg Record of the Paleozoic Oceans
A δ26Mg Record of the Paleozoic Oceans
Previously Published Material: Background information on the site from which the cores were taken has been published, however the focus of the presentation will be on new (unpublished) δ26Mg data.
Abstract ID#: 36002
English Abstract:
The prospect of storing nuclear waste in the deep geosphere (ie. 600-800 m below ground surface (mbgs)) has generated considerable interest in the provenance and movement of deep crustal fluids in the Michigan Basin, where the construction of a deep geologic repository (DGR) for radioactive waste has been proposed. This waste management strategy seeks to isolate radioactive waste from the biosphere on geologic timescales, which demands a detailed understanding of the pore waters in low-permeability environments. A halite-mineralized Ordovician carbonate aquiclude is the proposed host of the DGR. The associated pore waters are a post-dolomitic brine of evaporated Silurian seawater, which has resided in the aquiclude for more than 260 m.y.1. Cores reaching depths of 861 mbgs, and spanning Cambrian to Devonian strata taken from a Bruce Power nuclear site near Kincardine, Ontario, have already been used to investigate several geochemical and isotopic tracers at this site. Mg isotopes are an emerging tool in the investigation of dolomite formation, magnesium cycling, and may be useful in the investigation of past and continental weathering fluxes. This study employs Ca (δ44Ca) and Mg (δ26Mg) isotopes measured by MC-ICP-MS to trace the movement of dolomitization fluids through Devonian, Silurian, and Orovician carbonates. The first segment of this research focuses on the δ26Mg of dolostones throughout the core to establish a baseline expectation of the δ26Mg of the pore waters if they are primary, while generating a record of δ26Mg of the oceans through the Paleozoic and investigating dolomite formation in deep time.
1 - Clark, ID et al. (2013) Geology. 41: 951–954.