Eastern Laurentia in Rodinia:Constraints from whole-rock Pb and U/Pb geochronology

• Published in: Tectonophysics
• Main Authors: Loewy, Staci L., Connelly, James N., Dalziel, Ian W.D., Gower, Charles F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2003
• Subjects: Amazonia; Arequipa-Antofalla Basement; Common lead; Laurentia; Rodinia; U/Pb; Greenland
• Online Access: https://curis.ku.dk/portal/da/publications/eastern-laurentia-in-rodinia(ae378169-75eb-46fb-982b-3713faa0f26c).html; https://doi.org/10.1016/S0040-1951(03)00338-X; http://www.scopus.com/inward/record.url?scp=0242658747&partnerID=8YFLogxK

Whole-rock Pb isotopic signatures and U/Pb geochronology refute a Rodinian correlation of northeastern Laurentia and proto-Andean Amazonia. According to this previously proposed model, the Labrador-Scotland-Greenland Promontory (LSGP) of northeastern Laurentia collided with the proto-Andean margin of Amazonia, at the Arica Embayment, during the Grenville/Sunsás Orogeny (ca. 1.0 Ga). Links between the two margins were based upon the correlation of the LSGP with Arequipa-Antofalla Basement (AAB), a Proterozoic block along the proto-Andean margin of Amazonia adjacent to the Arica Embayment. Specifically, similarities in 1.8-1.0 Ga basement rocks in both regions suggested that the AAB was originally a piece of the LSGP. Furthermore, similarities in unique, post-collisional, but pre-rift, glacial sedimentary sequences also supported a link between the AAB and LSGP. Tests of these apparent similarities fail to support correlation of the AAB and the LSGP and, thus, eliminate a direct link between northeastern Laurentia and southwestern Amazonia in Rodinia. However, Pb isotopic compositions and U/Pb geochronology provide the basis for two new correlations, namely, (1) the ca. 1.3-1.0 Ga basement in the central and southern Appalachians may be an allochthonous block that was transferred to Laurentia from Amazonia at ca. 1.0 Ga, and (2) an allochthonous AAB may be a piece of the Kalahari Craton that was transferred to Amazonia at ca. 1.0 Ga. Based on these new correlations and a previously proposed Grenvillian connection between southern Laurentia (Llano) and Kalahari, we propose that Amazonia may have collided with a contiguous southeastern Laurentia/Kalahari margin at ca. 1.0 Ga.