WIDESPREAD 1.1 GA INTRAPLATE MAGMATISM IN THE LAURENTIAN, KALAHARI, AND AUSTRALIAN CRATONS DURING ASSEMBLY OF THE RODINIA SUPERCONTINENT: REVIEW AND IMPLICATIONS

Available evidence suggests that Laurentia formed the centerpiece of the late Mesoproterozoic-early Neoproterozoic Rodinia supercontinent, but the relative positions of most of the other cratons within Rodinia are controversial. Major episodes of intraplate magmatism occurred in Laurentia during culminating phases of Rodinia assembly, and correlations between these magmatic episodes and synchronous magmatism within other cratons may help constrain Rodinia configurations. Voluminous tholeiitic magmatism related to the Midcontinent rift (MCR) at 1109-1105 Ma is coeval with emplacement of the Umkondo large igneous province (LIP) over much of the Kalahari craton in southern Africa at 1112-1106 Ma (cited dates are U-Pb zircon or baddeleyite ages in all cases). The close similarity in timing of these episodes suggests that they represent parts of a single LIP emplaced across both cratons, contradicting recent suggestions by some workers that Kalahari was not part of Rodinia. Paleomagnetic data for the two provinces also preclude models that juxtapose the southern Grenville belt at ~1105 Ma with the Namaqua-Natal belt along the present-day southern margin of the Kalahari craton. Younger intraplate magmatism in Laurentia includes renewed magmatism in the MCR at 1102-1087 Ma, as well as emplacement of extensive mafic rocks in the SW US at 1100-1069 Ma, the A-type Pikes Peak batholith in Colorado at 1090-1070 Ma, and gabbro in the subsurface of northern Texas at 1081 Ma. Additional, broadly coeval Laurentian intraplate magmatism includes the enormous Pecos mafic intrusive complex in the subsurface of West Texas and eastern New Mexico, and the Red Bluff/Thunderbird volcano-plutonic complex in the Franklin Mountains of West Texas; however, better age constraints are needed for both of these suites before precise regional correlations are possible. Intraplate magmatism in SW Laurentia overlaps in time with the main magmatic episode in the Warakurna LIP in Australia at 1078-1070 Ma, consistent with models that place Australia against the SW or southern margins of Laurentia. Future work on the time-space relations of these and other intraplate LIPs in the component cratons of Rodinia may help constrain interactions between mantle thermal anomalies and plate motions during Rodinia assembly.