Basalt petrochemistry as a probe of crustal thickness in the Hudson Bay Arc, Quebec

Details Basalt petrochemistry as a probe of crustal thickness in the Hudson Bay Arc, Quebec Basalt petrochemistry as a probe of crustal thickness in the Hudson Bay Arc, Quebec

Oct 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994e%26psl.127...11h&link_type=abstract

Earth and Planetary Science Letters (ISSN 0012-821X), vol. 127, no. 1-4, p, 11-24

Mathematics

Logic

Basalt, Earth Crust, Earth Mantle, Geochemistry, Island Arcs, Peridotite, Petrology, Sediments, Crustal Fractures, Fractionation, Geological Faults, Melts (Crystal Growth), Quebec, Temperature Measurement, Thickness Ratio

Scientific paper

The Belcher Islands, in the center of the Hudson Bay Arc, consist of Early Proterozoic shallow-water sediments and continental tholeiites that were deformed into a thin-skinned thrust-and-fold belt during the Trans-Hudson Orogeny. The chemistry of the continental tholeiites is used to constrain the degree of thinning experienced by the crust during continental rifting. McKenzie and Bickle's parameterization of the physics of melt generation during rifting is combined with several different parameterizations of the chemistry of peridotite melting and Grove et als.'fractionation scheme for basalts to determine which combinations of rifting parameters can best explain the chemistry of the observed tholeiites. The results are insensitive to assumptions about the chemistry of the mantle peridotite (fertile or partly depleted). If the melt is assumed to have been extracted in a fractional way rather than in a batch process, mantle temperatures beneath the Belcher Islands in the Early Proterozoic may have been no higher than in the modern mantle. For a batch-melting process the best-fitting parent melts are produced for mantle temperatures up to 200 deg higher than in the modern mantle. Extension factors for the lithosphere are required to be high for either melt extraction process; they may have been as high as 5 or 6 and were certainly greater than 1.5, implying that continental basement was thinned to less than 70% of its original thickness. The absence of evidence of significant basement involvement in the subsequent thrusting indicates that the continental basement may still be very thin beneath the Belcher Islands and regions farther to the west.

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