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Paraná and Etendeka traps

Paraná and Etendeka traps
Paraná and Etendeka Plateau or Paraná and Etendeka Province
Large igneous province
The Paraná and Etendeka traps shown as dark purple spot on the geologic map of South America
The Paraná and Etendeka traps shown as dark purple spot on the geologic map of South America
Locationeastern Brazil, Uruguay, northwest Namibia & southwest Angola
Part ofParaná Basin
Offshore water bodiesSouthern Atlantic
AgeEarly Cretaceous
138-128 Ma
Formed byBreak-up of Pangaea
GeologySerra Geral Formation
Area
 • Total1,500,000 km2 (580,000 sq mi)
Last eruptionBarremian
A cliff at the Paraná Magmatic Province. Rio do Rastro, Santa Catarina. One can see the near vertical escarpment of silicic succession from waning-stage volcanism.

The Paraná-Etendeka Large Igneous Province (PE-LIP) (or Paraná and Etendeka Plateau; or Paraná and Etendeka Province) is a large igneous province that includes both the main Paraná traps (in Paraná Basin, a South American geological basin) as well as the smaller severed portions of the flood basalts at the Etendeka traps (in northwest Namibia and southwest Angola). The original basalt flows occurred 136 to 132 million years ago. The province had a post-flow surface area of 1,000,000 square kilometres (390,000 sq mi) and an original volume projected to be in excess of 2.3 x 106 km3.[1][2]

Geodynamics

The basalt samples at Paraná and Etendeka have an age of about 132 Ma, during the Valanginian stage of the Early Cretaceous.[3] Indirectly, the rifting and extension are probably the origin of the Paraná and Etendeka traps and it could be the origin of the Gough and Tristan da Cunha Islands as well, as they are connected by the Walvis Ridge (Gough/Tristan hotspot). The seamounts of the Rio Grande Rise (25°S to 35°S) that go eastwards from the Paraná side[4][5] are part of this traps system.[6]

Description

Interpretations of geochemistry, including isotopes, have led geologists to conclude that the magmas forming the traps and associated igneous rocks originated by melting of asthenosphic mantle due to the arrival of a mantle plume to the base of Earth's lithosphere. Then much of the magma was contaminated with crustal materials prior to their eruption. Some plutonic rocks related to the traps escaped crustal contamination reflecting more directly the source of the magmas in the mantle.[7]

Silicic eruptions

In Paraná, the silicic rocks are divided into two compositional groups, the Palmas volcanics and Chapecó volcanics.[8] Palmas is recognized as composed of the five geochemical subtypes Santa Maria, Caxias do Sul, Anita Garibaldi, Clevelândia and Jacuí, while Chapecó is composed of the three geochemical subtypes Ourinhos, Tamarana and Guarapuav.[9] Eight major eruptive units, labeled PAV-A to -G and BRA-21, are recognized within Palmas volcanics.[10]

In Etendeka, individual eruptive units of quartz latite are grouped into high-Ti and low-Ti suites. The high-Ti suit is composed of six members: Naudé, Sarusas, Elliott, Khoraseb, and Ventura. The low-Ti suite is composed of eight members: Fria, Beacon, Grootberg, Wereldsend, Hoanib, Springbok, Goboboseb, and Terrace.[11] In particular, Goboboseb consists of four eruptive units, labeled Goboboseb-I to -IV.[12]

On the basis of trans-Atlantic chemostratigraphy, the low-Ti suite in Etendeka is equivalent to Palmas volcanics in Paraná,[10] and the high-Ti suite is equivalent to Chapecó volcanics.[11] At a finer scale, geochemical affinities have made tentative correlations in these pairs:[13][10][14] PAV-G of Anita Garibaldi and Beacon, PAV-B of Caxias do Sul and Springbok, PAV-A of Jacuí and Goboboseb-II, Guarapuava and Ventura, Ourinhos and Khoraseb, BRA-21 and Wereldsend, PAV-F of Caxias do Sul and Grootberg. Sarusas may correlate either to Guarapuava or Tamarana, and Fria may correlate either to Santa Maria or Clevelândia.[13][14]

Eruption style and volume

In Etendeka, the quartz latite units are interpreted to be rheomorphic ignimbrites, which are emplaced by explosive eruptions of high-temperature ash-flows. Each eruption produced voluminous and widespread pyroclastic sheet with thickness between 40–300 m (130–980 feet). Individual unit, within Etendeka, has a volume between 400–2,600 km3 (96–624 cubic miles) and covers an area up to 8,800 km2 (3,400 square miles).[12] No air-fall layer associated with the eruptions has been recognized.[12][15] A 18 km (11 miles) diameter, circular structure, called Messum igneous complex, is identified to be the eruptive centre for Goboboseb-I to -IV and Springbok.[16]

It was postulated that Chapecó and Palmas volcanics in Paraná are the eastward extensions of Etendeka ash-flows, so each correlation represents a huge ignimbrite eruption. The volumes of these eruptions would make them the largest known explosive eruptions on Earth.[13][15] Notably, the largest Guarapuava-Tamarana/Sarusas is estimated to have a volume of 8,600 km3 (2,100 cubic miles), which dwarfs other extremely large eruptions such as 30 million year old Wah Wah Springs and 28 million year old Fish Canyon Tuff. This interpretation, however, is disputed. Sarusas member is known to consist of 10 eruptive units hence a product of multiple eruptions.[13][17] Moreover, units of each province are not the exact correlatives of the same eruptive event but may share the same magmatic system.[10]

In contrast, Chapecó and Palmas volcanics in Paraná are not unambiguously identified as the eastward extensions of ash-flows. Most studies have characterized Chapecó and Palmas as stacks of local lava flows and lava domes produced by effusive eruptions,[18][19][20] and were emitted from nearby silicic conduits and feeder dikes. The extremely large volume estimations and explosive style of them, therefore, are questioned.[21][22] On the other hand, a study has found pyroclastic-like textures in Chapecó and Palmas volcanics that are indicative of explosive eruptions. Guarapuava and Clevelândia subtypes are interpreted to be entirely of ignimbrites, while Jacuí, Anita Garibaldi, Caxias do Sul, and Santa Maria are multiple ignimbrite units intercalated with lava domes.[15] These ignimbrites were characterzied by low-explosivity, high eruptive mass-flux, and low-column fountains.[23]

See also

References

  1. ^ Courtillot, Vincent E.; Renneb, Paul R. (January 2003). "Sur l'âge des trapps basaltiques (On the ages of flood basalt events)". Comptes Rendus Geoscience. 335 (1): 113–140. Bibcode:2003CRGeo.335..113C. CiteSeerX 10.1.1.461.3338. doi:10.1016/S1631-0713(03)00006-3.
  2. ^ Fodor, R.V.; McKee, E.H.; Roisenberg, A. (1989). "Age distribution of Serra Geral (Paraná) flood basalts, southern Brazil". Journal of South American Earth Sciences. 2 (4): 343–349. Bibcode:1989JSAES...2..343F. doi:10.1016/0895-9811(89)90012-6.
  3. ^ Stewart, Kathy; Turner, Simon; Kelley, Simon; Hawkesworth, Chris; Kirstein, Linda; Mantovani, Marta (1996). "3-D, 40Ar-39Ar geochronology in the Paraná continental flood basalt province". Earth and Planetary Science Letters. 143 (1–4): 95–109. Bibcode:1996E&PSL.143...95S. doi:10.1016/0012-821X(96)00132-X.
  4. ^ O'Neill, C.; Müller, R. D.; Steinberger, B. (2003). "Revised Indian plate rotations based on the motion of Indian Ocean hotspots" (PDF). Earth and Planetary Science Letters. 215 (1–2): 151–168. Bibcode:2003E&PSL.215..151O. CiteSeerX 10.1.1.716.4910. doi:10.1016/S0012-821X(03)00368-6. Archived from the original (PDF) on 2011-07-26.
  5. ^ O'Connor, J. M.; le Roex, A. P. (1992). "South Atlantic hot spot-plume systems. 1: Distribution of volcanism in time and space". Earth and Planetary Science Letters. 113 (3): 343–364. Bibcode:1992E&PSL.113..343O. doi:10.1016/0012-821X(92)90138-L.
  6. ^ Brazilian 'Atlantis' found - Geologists have announced the discovery of what has been dubbed the 'Brazilian Atlantis', some 900 miles from Rio., Donna Bowater, The Daily Telegraph, 7 May 2013
  7. ^ Owen-Smith, T.M.; Ashwal, L.D.; Sudo, M.; Trumbull, R.B. (2017). "Age and Petrogenesis of the Doros Complex, Namibia, and Implications for Early Plume-derived Melts in the Paraná–Etendeka LIP". Journal of Petrology. 58 (3): 423–442. Bibcode:2017JPet...58..423O. doi:10.1093/petrology/egx021.
  8. ^ BELLIENI, G.; COMIN-CHIARAMONTI, P.; MARQUES, L. S.; MELFI, A. J.; NARDY, A. J. R.; PAPATRECHAS, C.; PICCIRILLO, E. M.; ROISENBERG, A.; STOLFA, D. (1986-08-01). "Petrogenetic Aspects of Acid and Basaltic Lavas from the Paran Plateau (Brazil): Geological, Mineralogical and Petrochemical Relationships". Journal of Petrology. 27 (4): 915–944. doi:10.1093/petrology/27.4.915. ISSN 0022-3530.
  9. ^ Nardy, AJR, Machado, FB, & de Oliveira, MAF (2008). The acidic Mesozoic volcanic rocks of the Paraná Basin: lithostratigraphy and geochemical-stratigraphic considerations. Brazilian Journal of Geology, 38 (1), 178-195.
  10. ^ a b c d Milner, S. C.; Duncan, A. R.; Whittingham, A. M.; Ewart, A. (1995-12-30). "Trans-Atlantic correlation of eruptive sequences and individual silicic volcanic units within the Paraná-Etendeka igneous province". Journal of Volcanology and Geothermal Research. 69 (3): 137–157. doi:10.1016/0377-0273(95)00040-2. ISSN 0377-0273.
  11. ^ a b Marsh, J.S.; Ewart, A.; Milner, S.C.; Duncan, A.R.; Miller, R. McG. (2001-02-01). "The Etendeka Igneous Province: magma types and their stratigraphic distribution with implications for the evolution of the Paraná-Etendeka flood basalt province". Bulletin of Volcanology. 62 (6): 464–486. doi:10.1007/s004450000115. ISSN 1432-0819.
  12. ^ a b c Milner, SC; Duncan, AR; Ewart, A (1992). "Quartz latite rheoignimbrite flows of the Etendeka Formation, north-western Namibia". Bulletin of Volcanology. 54 (3): 200–219. doi:10.1007/bf00278389. ISSN 0258-8900.
  13. ^ a b c d Scott E. Bryan; Ingrid Ukstins Peate; David W. Peate; Stephen Self; Dougal A. Jerram; Michael R. Mawby; J.S. Marsh; Jodie A. Miller (2010). "The largest volcanic eruptions on Earth" (PDF). Earth-Science Reviews. 102 (3–4): 207–229. Bibcode:2010ESRv..102..207B. doi:10.1016/j.earscirev.2010.07.001.
  14. ^ a b Sato, V. S., Nardy, A. J. R., Luchetti, A. C. F., & Navarro, J. (2016). Correlação das unidades ácidas da Província Magmática do Paraná e Província Magmática do Etendeka. In Congresso de Iniciação Científica UNESP (Vol. 1, No. 1, pp. 43-49).
  15. ^ a b c Luchetti, Ana Carolina F.; Nardy, Antonio J.R.; Madeira, José (2018). "Silicic, high- to extremely high-grade ignimbrites and associated deposits from the Paraná Magmatic Province, southern Brazil". Journal of Volcanology and Geothermal Research. 355: 270–286. doi:10.1016/j.jvolgeores.2017.11.010. hdl:11449/170391.
  16. ^ Ewart, A; Milner, S.C; Duncan, A.R; Bailey, M (2002). "The Cretaceous Messum igneous complex, S.W. Etendeka, Namibia: reinterpretation in terms of a downsag-cauldron subsidence model". Journal of Volcanology and Geothermal Research. 114 (3–4): 251–273. doi:10.1016/s0377-0273(01)00266-9. ISSN 0377-0273.
  17. ^ EWART, A. (2004-01-01). "Petrology and Geochemistry of Early Cretaceous Bimodal Continental Flood Volcanism of the NW Etendeka, Namibia. Part 2: Characteristics and Petrogenesis of the High-Ti Latite and High-Ti and Low-Ti Voluminous Quartz Latite Eruptives". Journal of Petrology. 45 (1): 107–138. doi:10.1093/petrology/egg082. ISSN 1460-2415.
  18. ^ Polo, L.A.; Janasi, V.A.; Giordano, D.; Lima, E.F.; Cañon-Tapia, E.; Roverato, M. (2018). "Effusive silicic volcanism in the Paraná Magmatic Province, South Brazil: Evidence for locally-fed lava flows and domes from detailed field work". Journal of Volcanology and Geothermal Research. 355: 204–218. doi:10.1016/j.jvolgeores.2017.08.007. ISSN 0377-0273.
  19. ^ Rossetti, Lucas; Lima, Evandro F.; Waichel, Breno L.; Hole, Malcolm J.; Simões, Matheus S.; Scherer, Claiton M. S. (2018-04-15). "Lithostratigraphy and volcanology of the Serra Geral Group, Paraná-Etendeka Igneous Province in Southern Brazil: Towards a formal stratigraphical framework". Journal of Volcanology and Geothermal Research. The Paraná-Etendeka igneous province and related magmatism. 355: 98–114. doi:10.1016/j.jvolgeores.2017.05.008. ISSN 0377-0273.
  20. ^ GARLAND, F.; HAWKESWORTH, C. J.; MANTOVANI, M. S. M. (1995-10-01). "Description and Petrogenesis of the Paran Rzhyolites, Southern Brazil". Journal of Petrology. 36 (5): 1193–1227. doi:10.1093/petrology/36.5.1193. ISSN 0022-3530.
  21. ^ Simões, M.S.; Lima, E.F.; Sommer, C.A.; Rossetti, L.M.M. (2018). "Structures and lithofacies of inferred silicic conduits in the Paraná-Etendeka LIP, southernmost Brazil". Journal of Volcanology and Geothermal Research. 355: 319–336. doi:10.1016/j.jvolgeores.2017.12.013. ISSN 0377-0273.
  22. ^ de Lima, Evandro Fernandes; Waichel, Breno Leitão; Rossetti, Lucas De Magalhães May; Sommer, Carlos Augusto; Simões, Matheus Silva (2018). "Feeder systems of acidic lava flows from the Paraná-Etendeka Igneous Province in southern Brazil and their implications for eruption style". Journal of South American Earth Sciences. 81: 1–9. doi:10.1016/j.jsames.2017.11.004. ISSN 0895-9811.
  23. ^ Luchetti, Ana Carolina F.; Gravley, Darren M.; Gualda, Guilherme A.R.; Nardy, Antonio J.R. (2018). "Textural evidence for high-grade ignimbrites formed by low-explosivity eruptions, Paraná Magmatic Province, southern Brazil". Journal of Volcanology and Geothermal Research. 355: 87–97. doi:10.1016/j.jvolgeores.2017.04.012. hdl:11449/160358. ISSN 0377-0273.

Further reading

  • Peate DW (1997). "The Parana-Etendeka Province" (PDF). In Mahoney JJ, Coffin MF (eds.). Large Igneous Provinces: continental, oceanic, and planetary flood volcanism. Geophysical Monograph. Vol. 100. Washington, DC: American Geophysical Union. pp. 217–245. Archived from the original (PDF) on 2017-08-09. Retrieved 2010-08-22.
Quelle: http://en.wikipedia.org/wiki/Etendeka