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 Americangeological 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
lave 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]
^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. In Congresso de Iniciação Científica UNESP (Vol. 1, No. 1, pp. 43-49).