Mesoproterozoic Oaxaquia-type basement in peri-Gondwanan terranes of Mexico, the Appalachians, and Europe: T _DM age constraints on extent and significance

摘要

The basement of most peri-Gondwanan terranes in Mexico, the Appalachians, the Caledonides, and the Variscides is buried beneath younger Ediacaran arc, Palaeozoic passive margin, and/or Mesozoic-Cenozoic platformal carbonates. However, it is exposed in the Oaxaquia terrane of Mexico (Oaxacan, Novillo, Huiznopala, and Guichicovi complexes), where it is characterized by ca. 1.0-1.3 billion year protolith ages and igneous rocks with depleted mantle model ages (T _DM) of 1.35-1.77 billion years. The T _DM ages represent a bulk average composition of the source and can be used as a tracer; these T _DM ages overlap with those in ca. 546 Ma arc clasts from the 65.5 Ma Chicxulub bolide breccia, suggesting that the northern Maya block is also underlain by Oaxaquia-type basement. Similar T _DM ages occur in Ediacaran arc rocks in Suwannee (Florida), NW Avalonia, Ganderia, Iberia, Armorica, and Bohemia, and in lower Palaeozoic plutons cutting adjacent Palaeozoic passive margin rocks (Acatlán Complex, Gander Group), suggesting that Oaxaquia-type basement underlies these regions. These T _DM ages are intermediate between those of SE Avalonia/Carolinia (0.75-1.1 billion years) and the ca. 2.0 Ga basement typical of NW Africa and the Channel Islands of the United Kingdom. The lateral extent of this Oaxaquia-type basement suggests that it formed a Precambrian rim around the periphery of northern Gondwana (Amazonia and NW Africa). The Oaxaquia-type basement beneath Ganderia and northwestern Avalonia suggests that these terranes were derived from the Oaxaquia margin of Amazonia. The polarity of the T _DM ages in Avalonia (younger to the SE) suggests that, rather than being transferred orthogonally across Iapetus, these peri-Gondwanan terranes rotated clockwise through 90° before accretion to Laurentia.View full textDownload full textKeywordsOaxaquia, peri-Gondwanan terranes, T DM ages, palaeogeographic reconstructionsRelated var addthis_config = { ui_cobrand: "Taylor & Francis Online", services_compact: "citeulike,netvibes,twitter,technorati,delicious,linkedin,facebook,stumbleupon,digg,google,more", pubid: "ra-4dff56cd6bb1830b" }; Add to shortlist Link Permalink http://dx.doi.org/10.1080/00206814.2010.543783