"The Kikiktat Volcanics in Arctic Alaska and the Mount Harper Volcanic Complex of the Yukon are two volcanic complexes with the same age (c. 720 Ma) as the much larger Franklin Large Igneous Province (LIP) in northern Canada. However, despite the overlapping ages, the geochemistry of the Kikiktat and Mount Harper volcanics is distinct from the Natkusiak volcanics near the center of the Franklin LIP, with both seemingly requiring a harzburgitic source. This relationship of "far-flung" volcanic provinces that require a more depleted source than mantle plumes has also been demonstrated for LIPs associated with the break-up of Gondwana. We propose two scenarios that can integrate these distant volcanic provinces into the larger Franklin LIP: 1) that melting occurred within pre-existing harzburgitic mantle underlying Laurentia, possibly heated by an underlying plume, or 2) that they represent second stage melting of the original lherzolite source envisaged for the Franklin plume. The second scenario is appealing insofar as large-scale melting of the Franklin plume head would have left behind a melt-depleted, low-density source, which would then migrate laterally away from the plume center. The two volcanic complexes add to the growing database of Franklin-aged volcanic complexes within and around northern Laurentia. Based on current paleogeographic reconstructions, the Franklin LIP is the largest of several LIP's that were centered on northern Laurentia and adjacent cratons of South China and Australia in the middle Neoproterozoic. The cumulative area of these LIP's is ~6.4 x 10^6 km^2, suggesting that much of Rodinia was covered by a carapace of basalt for much of the early Neoproterozoic (Tonian period). New neodymium isotope data ([epsilon]Nd) on shales and a compilation of data from Neoproterozoic sedimentary successions in Canada, Svalbard, Australia and China reveal that this basaltic carapace was present primarily before the onset of the Sturtian glaciation and that the basalt was largely removed by glaciation. Considering the higher weatherability of basalts, their greater CO2 demand compared to granitic rocks, higher phosphorous content and a paleogeography that places them in the wet tropics, they may have triggered the descent into global glaciation through the drawdown of atmospheric CO2 via a combination of silicate weathering and enhanced primary productivity. The reappearance of iron formation during the Sturtian glaciation and documented shift from euxinic to ferruginous deep waters in the late Tonian is consistent with this hypothesis because basalts have a higher Fe/S than average continental basement. These results highlight the role that LIP emplacement has on long-term environmental change, in addition to the well-documented shorter-term perturbations linked to outgassing of CO2 and S gases." --