Lead isotopes constrain Precambrian crustal architecture, thermal history, and lithospheric foundering in Laurentia
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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.
| 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 |
| Edition | Online First |
| Year Published | 2024 |
| Language | English |
| Publisher | Wiley |
| Contributing office(s) | Geosciences and Environmental Change Science Center |
| Google Analytic Metrics | Metrics page |