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Lead isotopes constrain Precambrian crustal architecture, thermal history, and lithospheric foundering in Laurentia

Terra Nova
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https://doi.org/10.1111/ter.12748

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Abstract

Laurentia (ancestral North America) records nearly 4 billion years of crustal evolution. Here, a newly compiled continental-scale Pb isotopic database is used to evaluate the Precambrian crustal evolution of Laurentia. Pb model ages yield a 2.7 Ga peak, a 2.5–1.8 Ga minimum and 1.8–0.9 Ga continuum. Pb model ages yield thermochronometric data and track crustal growth via arc-related magmatism and accretionary orogenesis. Model 232Th/204Pb and 238U/204Pb broadly correlate with mapped crustal domains. More homogeneous and less radiogenic 238U/204Pb and 232Th/238U after 2.7 Ga suggests a shift to more juvenile sources, loss of early isotopic reservoirs and greater crustal reworking. U and Th are fractionated from Pb in Proterozoic orogens with abundant ferroan and anorthosite–mangerite–charnockite–granite(AMCG)-suite magmatism. This fractionation suggests the removal of Pb-rich lower crust, supporting petrogenetic models involving lithospheric foundering and magmatic underplating. Lithospheric thinning and associated magmatism may have contributed to high middle Proterozoic geothermal gradients.

Suggested Citation

Hillenbrand, I.W., 2024, Lead isotopes constrain Precambrian crustal architecture, thermal history, and lithospheric foundering in Laurentia: Terra Nova, v. 37, no. 2, p. 65-76, https://doi.org/10.1111/ter.12748.

Publication type Article
Publication Subtype Journal Article
Title Lead isotopes constrain Precambrian crustal architecture, thermal history, and lithospheric foundering in Laurentia
Series title Terra Nova
DOI 10.1111/ter.12748
Volume 37
Issue 2
Publication Date September 10, 2024
Year Published 2024
Language English
Publisher Wiley
Contributing office(s) Geosciences and Environmental Change Science Center
Description 12 p.
First page 65
Last page 76
Additional publication details