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.
TheParaná-Etendeka Large Igneous Province (PE-LIP) (orParaná and Etendeka Plateau; orParaná and Etendeka Province) is alarge igneous province that includes both the main Paranátraps (inParaná Basin, aSouth Americangeological basin) as well as the smaller severed portions of theflood basalts at the Etendeka traps (in northwestNamibia and southwestAngola). 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 million km3.[1][2]
The basalt samples at Paraná and Etendeka have an age of about 132 Ma, during theValanginian stage of theEarly Cretaceous.[3] Indirectly, the rifting andextension are probably the origin of the Paraná and Etendeka traps and it could be the origin of theGough andTristan da Cunha Islands as well, as they are connected by theWalvis Ridge (Gough/Tristan hotspot). The seamounts of theRio Grande Rise (25°S to 35°S) that go eastwards from the Paraná side[4][5] are part of this traps system.[6]
Interpretations of geochemistry, includingisotopes, have led geologists to conclude that the magmas forming the traps and associatedigneous rocks originated bymelting ofasthenosphic mantle due to the arrival of amantle plume to the base of Earth'slithosphere. Then much of the magma wascontaminated withcrustal materials prior to their eruption. Someplutonic rocks related to the traps escaped crustal contamination reflecting more directly the source of the magmas in the mantle.[7]
In Paraná, thesilicic 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 ofquartz latite are grouped into high-Ti and low-Tisuites. The high-Ti suit is composed of sixmembers: 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-Atlanticchemostratigraphy, 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]
In Etendeka, the quartz latite units are interpreted to be rheomorphicignimbrites, which are emplaced byexplosive eruptions of high-temperatureash-flows. Each eruption produced voluminous and widespread pyroclastic sheets with thicknesses 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 Messumigneous 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 thelargest 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 oldWah Wah Springs and 28 million year oldFish 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 samemagmatic 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 locallava flows andlava domes produced byeffusive eruptions,[18][19][20] and were emitted from nearbysilicic conduits andfeeder dikes. The extremely large volume estimations and explosive style of them, therefore, are questioned.[21][22] On the other hand, a study has foundpyroclastic-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 unitsintercalated with lava domes.[15] These ignimbrites were characterzied by low-explosivity, high eruptive mass-flux, andlow-column fountains.[23]
^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.
^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.
^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.
^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.
^abSato, 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. InCongresso de Iniciação Científica UNESP (Vol. 1, No. 1, pp. 43-49).
