Gondwana

About: Gondwana is a research topic. Over the lifetime, 6078 publications have been published within this topic receiving 263050 citations. The topic is also known as: Gondwanaland.

SHRIMP U/Pb Zircon Dating of Neoproterozoic Granitic Magmatism and Collision in the Pelotas Batholith, Southernmost Brazil

Abstract: The introduction of robust geochronological methods for age determinations of the southernmost segment of the Neoproterozoic terranes of Brazil, namely the Dom Feliciano Belt, provides important clues for unraveling the complex evolution of the Brasiliano/Pan-African orogeny in this southwestern portion of the Gondwana supercontinent Except for associated small schist belts and post-orogenic foreland basins, the belt is represented in this region of southeastern South America by the Pelotas Batholith Precise SHRIMP U/Pb zircon geochronological techniques based on the study of 95 individual spots on 74 zircon crystals (three samples) and on Nd-isotopic determinations (three samples) are used to assess the late Neoproterozoic history of the belt, especially the orthogneisses interleaved with the batholithic plutons Three petrotectonic associations were selected for detailed isotopic investigations—the Pinheiro Machado syncollisional monzogranites, the widespread Piratini gneiss tonalitic xenoliths, and t

Structural and Tectonic Controls of Basin Evolution in Southwestern Gondwana During the Phanerozoic

Abstract: The continental lithosphere of southwestern Gondwana, comprising the southern part of South America and southern Africa, was largely assembled before the end of the Proterozoic. Geologic studies indicate that the basement anisotropy that controlled the development of Phanerozoic basins was established by Neoproterozoic-Early Cambrian tectonism. This tectonism reactivated the older terrane boundaries or cut across them. The backbone linking the system of Pan-African and Brasiliano basins was a system of northeast-trending structures. There were four areas of pronounced Neoproterozoic-Early Cambrian basin subsidence in the study area: the Chiquitanas trough in Bolivia, the Puncoviscana basin in Argentina, the Dom Feliciano-Ribeira basins in Brazil, and the Damara-Nama basin complex of southern Africa.

Late Palaeozoic retreating and advancing subduction boundary in the New England Fold Belt, New South Wales

Abstract: Compositions of Carboniferous and Lower Permian mafic and felsic magmatic rocks from the southern New England Fold Belt, combined with a time-space evaluation of appropriate regional geological elements, indicate that Late Palaeozoic tectonic events can be simply explained in terms of ongoing west-dipping subduction. The diversity of igneous rock types and tectonostratigraphic assemblages are interpreted to reflect sequential development of a stationary (Carboniferous), retreating (Early Permian) and advancing (Late Permian) subduction boundary along the active continental margin of East Gondwana. The stationary Carboniferous subduction boundary is expressed as a dual magmatic chain comprising a volcanic arc front of intermediate-felsic volcanic rocks in the Tamworth Belt and a subparallel rear-arc chain of granitoids and rare high-K gabbroic rocks represented by the Bathurst Batholith and satellite plutons. Waning of arc-front magmatism at ca 330 Ma corresponded to climactic activity in the rear-arc between 330 Ma and 320 Ma. Subduction boundary retreat is reflected by outboard migration of magmatism into the former accretionary prism of the Tablelands Complex, represented by the ca 300 Ma S-type Hillgrove Suite granites and coeval Bakers Creek Suite gabbros. Trace-element chemistry of these gabbros, and of Lower Permian basalts in the nascent Sydney Basin, suggests generation in a backarc setting. The 290-270 Ma Sydney Basin basalts record a transition from steep to flat, N-MORB normalised chemical trends, which suggests progressive upper plate (Gondwanan) lithospheric thinning during ongoing subduction boundary retreat. The S-type Bundarra and I-type Barrington Tops granite suites formed from contrasting crustal sources in this Early Permian extensional backarc setting. A reversal to compressional deformation is recorded by the Late Permian Hunter-Bowen Orogeny, which placed the Sydney-Bowen Basin in a foreland setting. An increasing volume of volcanic material, coincident with an increase in the proportion and thickness of conglomeratic units in the Late Permian foreland deposits, is considered to represent the westward translation of the orogenic front and magmatic arc back toward the old Carboniferous continental margin, reflecting an advancing subduction boundary. Voluminous post-tectonic, high-K calc-alkaline plutonism in the New England Batholith indicates establishment of the main magmatic arc in the New England Fold Belt, during the latest Permian - Early Triassic. It completes the cycle of subduction boundary retreat and advancement in the Late Palaeozoic.