The role played by Paleoproterozoic cratons in southern South America from the Mesopro- terozoic to the Early Cambrian is reconsidered here. This period involved protracted continental amal- gamation that led to forma...The role played by Paleoproterozoic cratons in southern South America from the Mesopro- terozoic to the Early Cambrian is reconsidered here. This period involved protracted continental amal- gamation that led to formation of the supercontinent Rodinia, followed by Neoproterozoic continental break-up, with the consequent opening of Clymene and Iapetus oceans, and finally continental re-assembly as Gondwana through complex oblique collisions in the Late Neoproterozoic to Early Cambrian. The evidence for this is based mainly on a combination of precise U-Pb SHRMP dating and radiogenic isotope data for igneous and metamorphic rocks from a large area extending from the Rio de la Plata craton in the east to the Argentine Precordillera in the west and as far north as Arequipa in Peru. Our interpretation of the paleogeographical and geodynamic evolution invokes a hypothetical Paleoproterozoic block （MARA） embracing basement ultimately older than 1.7 Ga in the Western Sierras Pampeanas （Argentina）, the Arequipa block （Peru）, the Rio Apa block （Brazil）, and probably also the Paraguaia block （Bolivia）.展开更多
We study light rays in the static and spherically symmetric gravitational field of the null aether theory(NAT).To this end,we employ the Gauss-Bonnet theorem to compute the deflection angle formed by a NAT black hole ...We study light rays in the static and spherically symmetric gravitational field of the null aether theory(NAT).To this end,we employ the Gauss-Bonnet theorem to compute the deflection angle formed by a NAT black hole in the weak limit approximation.Using the optical metrics of the NAT black hole,we first obtain the Gaussian curvature and then calculate the leading terms of the deflection angle.Our calculations indicate how gravitational lensing is affected by the NAT field.We also illustrate that the bending of light stems from global and topological effects.展开更多
基金Financial support over the last years was through Spanish MEC and MICINN grants CGL2005-02065/BTE and CGL2009-07984UCM-Santander grant GR58/08Argentinian grant 1728 AR PICT 1009
文摘The role played by Paleoproterozoic cratons in southern South America from the Mesopro- terozoic to the Early Cambrian is reconsidered here. This period involved protracted continental amal- gamation that led to formation of the supercontinent Rodinia, followed by Neoproterozoic continental break-up, with the consequent opening of Clymene and Iapetus oceans, and finally continental re-assembly as Gondwana through complex oblique collisions in the Late Neoproterozoic to Early Cambrian. The evidence for this is based mainly on a combination of precise U-Pb SHRMP dating and radiogenic isotope data for igneous and metamorphic rocks from a large area extending from the Rio de la Plata craton in the east to the Argentine Precordillera in the west and as far north as Arequipa in Peru. Our interpretation of the paleogeographical and geodynamic evolution invokes a hypothetical Paleoproterozoic block （MARA） embracing basement ultimately older than 1.7 Ga in the Western Sierras Pampeanas （Argentina）, the Arequipa block （Peru）, the Rio Apa block （Brazil）, and probably also the Paraguaia block （Bolivia）.
文摘We study light rays in the static and spherically symmetric gravitational field of the null aether theory(NAT).To this end,we employ the Gauss-Bonnet theorem to compute the deflection angle formed by a NAT black hole in the weak limit approximation.Using the optical metrics of the NAT black hole,we first obtain the Gaussian curvature and then calculate the leading terms of the deflection angle.Our calculations indicate how gravitational lensing is affected by the NAT field.We also illustrate that the bending of light stems from global and topological effects.
