Pampean orogeny

Source: Wikipedia, the free encyclopedia.
microcontinents such as Cuyania, Pampia and Chilenia
are omitted.

The Pampean orogeny (Spanish: orogenia pampeana) was an orogeny active in the Cambrian in the western margin of the ancient landmass of Gondwana. The orogen's remains can now be observed in central Argentina, in particular at the Sierras de Córdoba[A] and other parts of the eastern[B] Sierras Pampeanas.[1] It is uncertain if the orogeny involved at some point a continental collision. The Pampean orogen can be considered both part of the larger Terra Australis orogen and of the Brasiliano orogeny. The Pampean orogeny was succeeded by the Famatinian orogeny further west.

Magmatic belts

The Pampean orogen contains a

magmatic belt[C] including granodiorites, monzogranites, and volcanic rocks, all of them of calc-alkaline chemistry. The igneous rocks of this belt formed at various times in over the period from 555 to 525 million years ago. From 525 million years ago onward another magmatic belt of peralumineous and mafic rocks developed further amidst gneiss, schist, amphibolites and carbonate rocks. The igneous rocks of this belt formed in the period from 525 to 515 million years ago.[2]

Part of the

dykes of the Pampean Pegmatite Province formed during the orogeny.[3] These dykes are thought to be derived from S-type granitic melts.[3]

Tectonic interpretation

The Pampean orogeny can be considered part of the larger Terra Australis orogeny[2] or of the Brasiliano orogeny.[4] The Pampean orogeny developed at a similar time as the Paraguai Belt of the Brasiliano Orogeny, but in difference to the Paraguay Belt that ended up in the interior of Gondwana the Pampean Orogen remained at a continental margin.[5] The orogen eventually ceased activity and was succeeded by the Famatinian orogeny further west.[6]

The eastern magmatic belt of the Pampean orogeny is interpreted as the remains of a

accretionary prism of the orogen.[2]

There have been differing views among geologists on the tectonic and paleogeographic position of the

Arequipa-Antofalla Craton from Río de la Plata and Guaporé Craton. Following this interpretation the aulacogen would have closed during the Pampean orogeny.[7]

Notes

  1. ^ The modern relief of Sierras de Córdoba is, however, related to the much more recent Andean orogeny in the Tertiary.[1]
  2. ^ All coordinates in this article are in relation to present-day geography and not to the past disposition of continents, terranes and oceans.
  3. ^ A magmatic belt is large-scale elongate arrays of igneous rock outcrops.

References

  1. ^ a b Rapela, C.W.; Pankhurst, R.J; Casquet, C.; Baldo, E.; Saavedra, J.; Galindo, C.; Fanning, C.M. (1998). "The Pampean Orogeny of the southern proto-Andes: Cambrian continental collision in the Sierras de Córdoba" (PDF). In Pankhurst, R.J; Rapela, C.W. (eds.). The Proto-Andean Margin of Gondwana. Vol. 142. Geological Society, London, Special Publications. pp. 181–217. Retrieved 7 December 2015.
  2. ^
    S2CID 129441236
    .
  3. ^
    hdl:20.500.11850/557078
    .
  4. ^ de Brito Neves, Benjamin Bley. "Ciclos Transamazônico e Brasiliano". Glossário Geológico Ilustrado (PDF) (in Portuguese).
  5. doi:10.1130/G30510.1
    .
  6. ^ Gaucher, Claudio; Bossi, Jorge; Blanco, Gonzalo (2010). "Paleogeography". In Gaucher, Claudio; Sial, Alcides; Haverson, Galen (eds.). Neoproterozoic-cambrian tectonics, global change and evolution: a focus on south western Gondwana. Elsevier. p. 137.
  7. ^ a b c Aceñolaza, Florencio G.; Toselli, Alejandro (2010). "The Pampean Orogen: Ediacaran-Lower Cambrian Evolutionary History of Central and Northwest Region of Argentina". In Gaucher, Claudio; Sial, Alcides; Haverson, Galen (eds.). Neoproterozoic-cambrian tectonics, global change and evolution: a focus on south western Gondwana. Elsevier. pp. 239–254.
  8. hdl:11336/92729
    . Retrieved 15 December 2015.
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