Topic
Terrane
About: Terrane is a research topic. Over the lifetime, 11025 publications have been published within this topic receiving 442596 citations. The topic is also known as: tectonostratigraphic terrane.
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TL;DR: In this paper, the authors reported new U-Pb data from the southern sector of the Brasilia belt in order to provide temporal limits for the deposition and ages of provenance of sediments accumulated in passive margin successions around the south and southwestern margins of the Sao Francisco Craton, and date the orogenic events leading to the amalgamation of West Gondwana.
162 citations
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TL;DR: The Namaqualand metamorphic complex is a well-exposed, INTRODUCTION Mesoproterozoic, low-pressure, amphibolite-granulite-facies terrane flanking the Archaean Kaapvaal Craton of southern Africa as discussed by the authors.
Abstract: The Namaqualand Metamorphic Complex is a well-exposed, INTRODUCTION Mesoproterozoic, low-pressure, amphibolite–granulite-facies terrane flanking the Archaean Kaapvaal Craton of southern Africa. Previous isotopic dating in the region suggests an ~150 my period of prograde granulite-facies metamorphism and episodic granite emplacement The mid-crustal granulite-facies problem in the mid-crust. In contrast, thermal modelling suggests that Granulite-facies terranes are rocks of the Earth’s lower suband superjacent magmatic accretion should not have exceeded and middle crust that equilibrated at high pressures (P ) 30 my in duration. This enigma is resolved by precise U–Pb zircon and temperatures (T ). Their petrology and geoSHRIMP dating of the major orthogneissic units of the region. chronology commonly preserve both prograde and retroThese data point to Kibaran crustal growth at 1220–1170 Ma, grade characteristics. Because these terranes reflect a which occurred on the margins of a Palaeoproterozoic (2000–1800 number of different crustal and tectonic processes, their Ma) continental nucleus. A later, distinct, orogenic episode, here origin is important in understanding the nature of contermed the Namaquan (time equivalent of the Grenvillian), involved tinental growth and crustal evolution. crustal thickening and magmatism at 1060–1030 Ma and was Granulite-facies rocks typically reflect P–T conditions responsible for, and coeval with, the peak of metamorphism. Lowof 6–9 kbar and 750–850°C and comprise anhydrous P granulite-facies metamorphism resulted from advective heating mineral assemblages that point to conditions of reduced and crustal thickening by magmatic accretion over a 30 my interval. water activity (Harley, 1989). In the lower crust some granulite-facies rocks are thought to be residues of partial melting that has moved melt and volatiles to higher crustal levels. Alternatively, granulite-facies rocks may form where mutually soluble CO2–H2O-rich fluids stream upwards through the crust, causing local reduction in volatile content and accompanying mineral phase changes along the fluid flow paths (Harley, 1989). In the
162 citations
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TL;DR: In this article, the authors presented a detailed analysis of the ultrawide high pressure metamorphic terrane of the North Qaidam eclogite-gneiss region.
162 citations
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TL;DR: In this paper, a single grain evaporation technique was used to estimate the age of the Onverwacht Group in the Barberton greenstone belt (BGB) of South Africa and Swaziland.
Abstract: One of the central issues in early Precambrian crustal evolution is the age and genetic relationship between greenstone belt supracrustal assemblages and nearby high-grade gneiss terranes. The crucial question, in most cases, is which of the two is older. We report zircon ages, using the new single grain evaporation technique, from a metaquartzite and a felsic volcanic flow of the Onverwacht Group in the Barberton greenstone belt (BGB), South Africa and Swaziland, that constrain the age of this basal part of the greenstone sequence between 3451 ± 15 and 3438 ± 6 Ma. This is almost 100 Ma younger than previous age estimates assigned to the Onverwacht and agrees well with recent Sm-Nd, Pb-Pb and zircon ion-microprobe dating. Tonalitic orthogneisses of the Ancient Gneiss Complex (AGC) adjacent to the BGB have ages up to 3644 ± 4 Ma and are thus demonstrably older than the greenstones; also, they cannot be derived from them by partial melting as has been proposed previously. This age relationship as well as the presence of metaquartzites and thrust slices of pregreenstone tonalite in the Onverwacht tectonic sequence rule out an entirely oceanic evolution for the early history of the BGB and suggest that continental crust was either below or nearby.
161 citations
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TL;DR: In this article, the authors presented new geochronological and geochemical (whole-rock major and trace element and Sr-Nd and zircon Hf isotope) data for recently identified volcanic rocks exposed in Changguo area, southernmost part of the Lhasa terrane.
161 citations