Lead isotopes constrain Precambrian crustal architecture, thermal history, and lithospheric foundering in Laurentia
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.
Citation Information
Publication Year | 2024 |
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Title | Lead isotopes constrain Precambrian crustal architecture, thermal history, and lithospheric foundering in Laurentia |
DOI | 10.1111/ter.12748 |
Authors | Ian William Hillenbrand |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | Terra Nova |
Index ID | 70258412 |
Record Source | USGS Publications Warehouse |
USGS Organization | Geosciences and Environmental Change Science Center |