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The Paraná-Etendeka Large Igneous Province (PE-LIP) (or Paraná and Etendeka Plateau; or Paraná and Etendeka Province) is a
large igneous province A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive ( sills, dikes) and extrusive (lava flows, tephra deposits), arising when magma travels through the crust towards the surface. The format ...
that includes both the main Paraná traps (in Paraná Basin, a
South American South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
geological basin) as well as the smaller severed portions of the
flood basalt A flood basalt (or plateau basalt) is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava. Many flood basalts have been attributed to the onset of a hotspot (geolo ...
s at the Etendeka traps (in northwest
Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...
and southwest
Angola Angola, officially the Republic of Angola, is a country on the west-Central Africa, central coast of Southern Africa. It is the second-largest Portuguese-speaking world, Portuguese-speaking (Lusophone) country in both total area and List of c ...
). The original basalt flows occurred 136 to 132 million years ago. The province had a post-flow surface area of and an original volume projected to be in excess of 2.3 million km3.


Geodynamics

The basalt samples at Paraná and Etendeka have an age of about 132 Ma, during the
Valanginian In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 137.05 ± 0.2 Ma and 132.6 ± 0.2 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretac ...
stage of the
Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...
. 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 Tristan da Cunha (), colloquially Tristan, is a remote group of volcano, volcanic islands in the South Atlantic Ocean. It is one of three constituent parts of the British Overseas Territories, British Overseas Territory of Saint Helena, Ascensi ...
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 are part of this traps system.


Description

Interpretations of geochemistry, including
isotope Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...
s, have led geologists to conclude that the magmas forming the traps and associated
igneous rock Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...
s originated by
melting Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which inc ...
of asthenosphic mantle due to the arrival of a
mantle plume A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic ho ...
to the base of Earth's
lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time ...
. Then much of the magma was contaminated with crustal materials prior to their eruption. Some
plutonic rock Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form ''intrusions'', such as batholiths, dikes, sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: March ...
s related to the traps escaped crustal contamination reflecting more directly the source of the magmas in the mantle.


Silicic eruptions

In Paraná, the silicic rocks are divided into two compositional groups, the Palmas volcanics and Chapecó volcanics. 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. Eight major eruptive units, labeled PAV-A to -G and BRA-21, are recognized within Palmas volcanics. 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 Member may refer to: * Military jury, referred to as "Members" in military jargon * Element (mathematics), an object that belongs to a mathematical set * In object-oriented programming, a member of a class ** Field (computer science), entries in ...
: Naudé, Sarusas, Elliott, Khoraseb, and Ventura. The low-Ti suite is composed of eight members: Fria, Beacon, Grootberg, Wereldsend, Hoanib, Springbok, Goboboseb, and Terrace. In particular, Goboboseb consists of four eruptive units, labeled Goboboseb-I to -IV. On the basis of trans-Atlantic
chemostratigraphy Chemostratigraphy, or chemical stratigraphy, is the study of the chemical variations within sedimentary sequences to determine stratigraphic relationships. The field is relatively young, having only come into common usage in the early 1980s, but ...
, the low-Ti suite in Etendeka is equivalent to Palmas volcanics in Paraná, and the high-Ti suite is equivalent to Chapecó volcanics. At a finer scale, geochemical affinities have made tentative correlations in these pairs: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). 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.


Eruption style and volume

In Etendeka, the quartz latite units are interpreted to be rheomorphic
ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surrou ...
s, which are emplaced by
explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An ex ...
eruptions of high-temperature ash-flows. Each eruption produced voluminous and widespread pyroclastic sheet with thickness between . Individual unit, within Etendeka, has a volume between and covers an area up to . No air-fall layer associated with the eruptions has been recognized. A diameter, circular structure, called Messum igneous complex, is identified to be the eruptive centre for Goboboseb-I to -IV and Springbok. 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. Notably, the largest Guarapuava-Tamarana/Sarusas is estimated to have a volume of , 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. Moreover, units of each province are not the exact correlatives of the same eruptive event but may share the same magmatic system. 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 dome In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...
s produced by
effusive eruption An effusive eruption is a type of volcanic eruption in which lava steadily flows out of a volcano onto the ground. Overview There are two major groupings of eruptions: effusive and explosive. Effusive eruption differs from explosive eruption ...
s, and were emitted from nearby silicic conduits and feeder dikes. The extremely large volume estimations and explosive style of them, therefore, are questioned. 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. These ignimbrites were characterzied by low-explosivity, high eruptive mass-flux, and low-column fountains.


See also

* Geology of Paraguay * Geology of Uruguay * Paraná Basin * Uruguayan dyke swarms


References


Further reading

*


External links

* {{DEFAULTSORT:Parana And Etendeka Traps Large igneous provinces Barremian Stage Hauterivian Stage Valanginian Stage Early Cretaceous Africa Early Cretaceous South America Cretaceous volcanism Volcanism of Brazil Volcanism of Angola Volcanism of Namibia Cretaceous Argentina Geology of Argentina Cretaceous Brazil Geology of Brazil Cretaceous Uruguay Geology of Uruguay Stratigraphy of Argentina Stratigraphy of Uruguay