Las Lozas volcanics

The Las Lozas volcanics are a geological formation in Argentina.

During the Ordovician, the Famatinian orogeny on Gondwana's western margin laid down large volcanic deposits. Some of these were later found to be younger, of Carboniferous-Pennsylvanian age.[1] In the Las Lozas valley, this younger unit is 550 metres (1,800 ft) thick and dominated by rhyolite. It lies beneath Paleozoic sediments and above a metamorphic basement.[2] This volcanic activity occurred concurrently with crustal extension,[3] which may be associated either with the Famatinian orogeny, the Achalian orogeny or a separate event.[4]

The Las Lozas unit has been dated at 320 million years, with previous dates for other units being between 336-298 million years. The rocks erupted during this volcanic episode were formed from much older crust of Cryogenian age, based on isotope dating of zircons. This older crust may have formed when Rodinia broke up.[3]

The structure of the deposits indicates that explosive eruptions involving lava domes were the principal sources of the Las Lozas volcanic deposits. Also present basalts formed lava flows, which may have originated from the lava domes as well. The activity occurred at high temperatures and was issued by fissure vents.[4]

References

  1. ↑ Zappettini et al. 2015, p. 13.
  2. ↑ Zappettini et al. 2015, p. 14.
  3. 1 2 Zappettini et al. 2015, p. 17.
  4. 1 2 Coira, Beatriz; Cisterna, Clara E.; Ulbrich, Horstpeter H.; Cordani, Umberto G. (2016-01-01). "Magmatismo carbonífero en régimen extensional en el margen occidental de Gondwana: valle de Las Lozas, Catamarca, Argentina". Andean geology. 43 (1): 105–126. doi:10.5027/andgeoV43n1-a06. ISSN 0718-7106.

External links

  • Zappettini, E.O.; Coira, B.; Santos, J.O.S.; Cisterna, C.E.; Belousova, E. (April 2015). "Combined U–Pb and Lu–Hf isotope study from the Las Lozas volcanics, northwestern Argentina: Evidence of juvenile Cryogenian-derived, lower Pennsylvanian volcanism in western Gondwana". Journal of South American Earth Sciences. 59: 13–18. doi:10.1016/j.jsames.2015.01.004. 
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