ABSTRACT The Mantiqueira Province in SE Brazil and Uruguay is a complex Brasiliano/Pan-African orogenic province that has recently been the topic of conflicting geodynamic models focusing the possibility of multiple collision events... more
ABSTRACT The Mantiqueira Province in SE Brazil and Uruguay is a complex Brasiliano/Pan-African orogenic province that has recently been the topic of conflicting geodynamic models focusing the possibility of multiple collision events during the Ediacaran–Ordovician assembly of the Western Gondwana Supercontinent. A thorough compilation of recently obtained high-resolution U-Pb geochronology and geochemistry in the Mantiqueira Province provided the following results: a) considering the entire orogenic system, the pre-, syn- and post-orogenic periods range from >670–595 Ma, 620–550 Ma and 560–490 Ma, respectively, and are coeval with the intrusion of 3 distinct magmatic sequences within each geographic segment of this large orogenic province, evolving from: i) calc-alkaline, arc-related magmatism; to ii) syn-orogenic, anatectic magmatism coeval with the metamorphic climax; to iii) calc-alkaline/alkaline (including shoshonitic and A-type affinity) magmatism that reveal significant lower crust and mantle contribution; b) progressively younger ages are present from south to north, irrespective of the orogenic period considered, implying that the different geographic sectors were, from south to north, diachronically amalgamated into the Mantiqueira Province. Results provide important evidence for the existence of a single diachronic collision event at 630–590 Ma, followed by the thermal climax at 615–560 Ma, slab break-off, asthenospheric upwelling and mantle underplating that sustained long-term high heat flux conditions until 540–490 Ma, when post-tectonic calc-alkaline/alkaline granitoids (probably admixed with small amounts of slab melts formed at depth) intruded the middle/low-crust magmatic and metamorphic sequences during the final stages of thermal and orogenic collapse of the Mantiqueira Province belts.
This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45°–48°S), where an active spreading center is presently subducting beneath the Andean continental margin. Updated sea-floor kinematics... more
This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45°–48°S), where an active spreading center is presently subducting beneath the Andean continental margin. Updated sea-floor kinematics associated with a comprehensive review of geologic, geochemical, and geophysical data provide new constraints on the geodynamics of this puzzling area. We discuss: (1) the emplacement mode for the Pleistocene Taitao Ridge and the Pliocene Taitao Peninsula ophiolite bodies. (2) The occurrence of these ophiolitic complexes in association with five adakite-like plutonic and volcanic centers of similar ages at the same restricted locations. (3) The inferences from the co-occurrence of these sub-coeval rocks originating from the same subducting oceanic lithosphere evolving through drastically different temperature–pressure (P–T) path: low-grade greenschist facies overprint and amphibolite-eclogite transition, respectively. (4) The evidences that document ridge-jump events and associated microplate individualization during subduction of the SCR1 and SCR-1 segments: the Chonos and Cabo Elena microplates, respectively. The ridge-jump process associated with the occurrence of several closely spaced transform faults entering subduction is controlling slab fragmentation, ophiolite emplacement, and adakite-like production and location in the CTJ area. Kinematic inconsistencies in the development of the Patagonia slab window document an 11- km westward jump for the SCR-1 spreading segment at ~6.5-to-6.8 Ma. The SCR-1 spreading center is relocated beneath the North Patagonia Icefield (NPI). We argue that the deep-seated difference in the dynamically sustained origin of the high reliefs of the North and South Patagonia Icefield (NPI and SPI) is asthenospheric convection and slab melting, respectively. The Chile Triple Junction area provides the basic constraints to define the basic signatures for spreading-ridge subduction beneath an Andean-type margin.
During the Pliocene, subduction of the Chile ridge beneath the South American margin was coeval with the emplacement of the Cabo Raper pluton located at the seaward edge of the Taitao peninsula. The chemical characteristics of the Cabo... more
During the Pliocene, subduction of the Chile ridge beneath the South American margin was coeval with the emplacement of the Cabo Raper pluton located at the seaward edge of the Taitao peninsula. The chemical characteristics of the Cabo Raper pluton combined with the available tectonic data allow us to reconstruct the paleogeometry of the Chile margin 3–4.2 m.y. ago. When compared to the modern configuration, the volume of material removed by subduction erosion can be estimated quantitatively. From 3–4.2 to 1.5–1.6 Ma, 625 km3 of rock were removed along each kilometre of margin along the Taitao peninsula transect. This leads to a conservative subduction-erosion rate of 231–443 km3zkm21zm.y.21, significantly higher than those calculated along the Japan and Peru convergent margins. It is proposed that subduction of the Chile ridge contributes fluids in addition to the subducted sediment, resulting in a higher rate of subduction erosion
This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45–48S), where an active spreading center is presently subducting beneath the Andean continental margin. Updated sea-floor kinematics... more
This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45–48S), where an active spreading center is presently subducting beneath the Andean continental margin. Updated sea-floor kinematics associated with a comprehensive review of geologic, geochemical, and geophysical data provide new constraints on the geodynamics of this puzzling area. We discuss: (1) the emplacement mode for the Pleistocene Taitao Ridge and the Pliocene Taitao Peninsula ophiolite bodies. (2) The occurrence of these ophiolitic complexes in association with five adakite-like plutonic and volcanic centers of similar ages at the same restricted locations. (3) The inferences from the cooccurrence of these sub-coeval rocks originating from the same subducting oceanic lithosphere evolving through drastically different temperature–pressure (P–T) path: low-grade greenschist facies overprint and amphibolite-eclogite transition, respectively. (4) The evidences that document ridge-jump events and associated microplate individualization during subduction of the SCR1 and SCR-1 segments: the Chonos and Cabo Elena microplates, respectively. The ridge-jump process associated with the occurrence of several closely spaced transform faults entering subduction is controlling slab fragmentation, ophiolite emplacement, and adakite-like production and location in the CTJ area. Kinematic inconsistencies in the development of the Patagonia slab window document an 11- km westward jump for the SCR-1 spreading segment at*6.5-to-6.8 Ma. The SCR-1 spreading center is relocated beneath the North Patagonia Icefield (NPI). We arguethat the deep-seated difference in the dynamically sustained origin of the high reliefs of the North and South Patagonia Icefield (NPI and SPI) is asthenospheric convection and slab melting, respectively. The Chile Triple Junction area provides the basic constraints to define the basic signatures for spreading-ridge subduction beneath an Andean-type margin.
