A geochronological review of magmatism along the external margin of Columbia and in the Grenville-age orogens forming the core of Rodinia

A total of 4344 magmatic U-Pb ages in the range 2300 to 800 Ma have been compiled from the Great Proterozoic Accretionary Orogen along the margin of the Columbia / Nuna supercontinent and from the subsequent Grenvillian collisional orogens forming the core of Rodinia. The age data are derived from Laurentia (North America and Greenland, n = 1212), Baltica (NE Europe, n = 1922), Amazonia (central South America, n = 625), Kalahari (southern Africa and Dronning Maud Land in East Antarctica, n = 386), and western Australia (n = 199). Laurentia, Baltica, and Amazonia (and possibly other cratons) most likely formed a ca. 10 000-km-long external active continental margin of Columbia from its assembly at ca. 1800 Ma until its dispersal at ca. 1260 Ma, after which all cratons studied were involved in the Rodinia-forming Grenvillian orogeny. However, the magmatic record is not smooth and even but highly irregular, with marked peaks and troughs, both for individual cratons and the combined data set. Magmatic peaks typically range in duration from a few tens of million years up to around hundred million years, with intervening troughs of comparable length. Some magmatic peaks are observed on multiple cratons, either by coincidence or because of paleogeographic proximity and common tectonic setting, while others are not. The best overall correlation, 0.617, is observed between Baltica and Amazonia, consistent with (but not definitive proof of) their being close neighbours in a SAMBA-like configuration at least in Columbia, and perhaps having shared the same peri-Columbian subduction system for a considerable time. Correlation factors between Laurentia and Baltica, or Laurentia and Amazonia, are below 0.14. Comparison between the Grenville Province in northeastern Laurentia and the Sveconorwegian Province in southwestern Fennoscandia (Baltica) shows some striking similarities, especially in the Mesoproterozoic, but also exhibits differences in the timing of events, especially during the final Grenville-Sveconorwegian collision, when the Sveconorwegian evolution seems to lag behind by some tens of million years. Between the other cratons, the evolution before and during the final Grenvillian collision is also largely diachronous. After 900 Ma, magmatic activity had ceased in all areas investigated, attesting to the position of most of them within the stable interior of Rodinia.publishedVersio

Late Palaeoproterozoic mafic dyking in the Ukrainian Shield of Volgo-Sarmatia caused by rotation during the assembly of supercontinent Columbia (Nuna)

The Ukrainian Shield comprises the exposed crust of the large Palaeoproterozoic protocraton Volgo-Sarmatia, which together with the Fennoscandian crustal segment constitutes the East European Craton ("Baltica"). Geological and geophysical data indicate that 1.80 to 1.75 Ga mafic dykes related to anorthosite-mangerite-charnockite-granite (AMCG) plutons are widespread within the Ukrainian Shield. We examined their ages, distribution patterns, orientations and compositions in three different crustal blocks (Volyn, Ingul and Azov), and found close spatial relationships with major strike-slip fault systems developed during two phases of extension. The early, 1.80-1.77 Ga, generation of mafic dykes mostly follows NW (330 +/- 20 degrees) and more rarely N-S- or E-W-trending faults corresponding to major NE-SW extension (the Submoshorino phase). These dykes contain olivine dolerites, picrites, camptonites, lamprophyres, kimberlites and other rocks belonging to tholeiitic and subalkaline jotunitic series. The compositions of these dykes differ between the host blocks, but all feature upper mantle geochemical signatures such as high contents of Ni and Cr, and positive values of epsilon Nd-(1800) up to + 2.8. High degrees of REE fractionation indicate deep levels of mantle melting, which is particularly characteristic of the Ingul block as marked by the most extensive and dense mafic dyke swarms. The later, 1.76-1.75 Ga, dyke swarms occur close to the most voluminous AMCG suites of similar age and were emplaced during the second (Korsun) phase of faulting when all the older strike-slip fault zones were reactivated and partly transformed to tensional faults by E-W extension. These dyke swarms mainly trend 030 +/- 20 degrees. They are jotunitic and their isotopic signatures indicate a greater participation of crustal sources in the parent melts. The overall transtensional tectonic setting of the mafic dyking associated with the AMCG magmatism in Volgo-Sarmatia was created by convergent tectonics and postcollisional collapse of the thickened lithosphere, as well as by mantle delamination coupled with the rotation of Volgo-Sarmatia between 1.80 and 1.75 Ga. This agrees with palaeomagnetic reconstruction suggesting rotation(s) of Volgo-Sarmatia during its protracted oblique docking with Fennoscandian terranes and Laurentia as supercontinent Columbia (Nuna) was assembled. (C) 2012 Elsevier B.V. All rights reserved

A geochronological review of magmatism along the external margin of Columbia and in the Grenville-age orogens forming the core of Rodinia

A total of 4344 magmatic U-Pb ages in the range 2300 to 800 Ma have been compiled from the Great Proterozoic Accretionary Orogen along the margin of the Columbia / Nuna supercontinent and from the subsequent Grenvillian collisional orogens forming the core of Rodinia. The age data are derived from Laurentia (North America and Greenland, n = 1212), Baltica (NE Europe, n = 1922), Amazonia (central South America, n = 625), Kalahari (southern Africa and Dronning Maud Land in East Antarctica, n = 386), and western Australia (n = 199). Laurentia, Baltica, and Amazonia (and possibly other cratons) most likely formed a ca. 10 000-km-long external active continental margin of Columbia from its assembly at ca. 1800 Ma until its dispersal at ca. 1260 Ma, after which all cratons studied were involved in the Rodinia-forming Grenvillian orogeny. However, the magmatic record is not smooth and even but highly irregular, with marked peaks and troughs, both for individual cratons and the combined data set. Magmatic peaks typically range in duration from a few tens of million years up to around hundred million years, with intervening troughs of comparable length. Some magmatic peaks are observed on multiple cratons, either by coincidence or because of paleogeographic proximity and common tectonic setting, while others are not. The best overall correlation, 0.617, is observed between Baltica and Amazonia, consistent with (but not definitive proof of) their being close neighbours in a SAMBA-like configuration at least in Columbia, and perhaps having shared the same peri-Columbian subduction system for a considerable time. Correlation factors between Laurentia and Baltica, or Laurentia and Amazonia, are below 0.14. Comparison between the Grenville Province in northeastern Laurentia and the Sveconorwegian Province in southwestern Fennoscandia (Baltica) shows some striking similarities, especially in the Mesoproterozoic, but also exhibits differences in the timing of events, especially during the final Grenville-Sveconorwegian collision, when the Sveconorwegian evolution seems to lag behind by some tens of million years. Between the other cratons, the evolution before and during the final Grenvillian collision is also largely diachronous. After 900 Ma, magmatic activity had ceased in all areas investigated, attesting to the position of most of them within the stable interior of Rodinia.