Showing papers in "Precambrian Research in 1993"

TL;DR: A new image of the Precambrian in the northeastern half of Europe has been created by recent work in the Baltic Shield and its continuation in the basement of the East European Platform, which can be traced to a Proterozoic system of palaeorifts in the Eastern European Platform.

TL;DR: In this article, a model of varying supply of materials for the medley of mesoband types, particularly of iron and silica in the oxide BIF, can be accommodated by the interaction of two major oceanic supply systems: surface currents and convective upwelling from mid-oceanic ridge (MOR) or hot-spot activity, both modified by varied input of pyrochastic material.

TL;DR: In this paper, 120 detrital zircons from Svecofennian metasediments in Sweden and Finland were analysed using the SHRIMP ion microprobe and the oldest materials in this array are a 344 Ga old zircon from the Tampere Schist Belt in Finland and a 332 Ga old crystal from southeastern Sweden.

TL;DR: A12O3 trondhjemitic gneisses are found in enclaves within granites at Markampara in the Bastar Craton, Central India.

TL;DR: The early Precambrian Hamersley Group of Western Australia contains both major and minor occurrences of well-preserved carbonate sedimentary rock as mentioned in this paper, and the Carawine Dolomite and the Paraburdoo Member of the Wittenoom Formation are two most extensive occurrences.

TL;DR: Sulfur isotopic compositions of Precambrian sulfates, both new and previously measured, are summarized and critically evaluated in relation to a seawater sulfate sulfur isotope age curve as discussed by the authors.

TL;DR: The late Svecofennian granite-migmatite (LSGM) zone in southwestern Finland is a ∼ 100 km wide and 500 km long belt transecting the southern Svecodides from WSW to ENE.

TL;DR: In this article, a model is proposed of an initial calc-alkalic enderbitic mass extracted from the mantle at ∼1050 Ma and emplaced in the lower crust; this ender bituminous parent is considered as the source for successive alkali-rich melts which were emplaced synkinematically between 1050 and 850 Ma.

TL;DR: In this paper, a holistic tectonostratigraphic framework is presented that pairs the supracrustal and crustal rock records to test the conformity of stratigraphic cause and response.

TL;DR: RbSr analyses of leached phlogopite macrocrysts from kimberlite pipes 1, 2, 5 and 7 in south India give concordant ages of 1091±20, 1092±15, 1093±20 and 1091 ± 10 Ma, respectively, indicating contemporaneous emplacement of these pipes as mentioned in this paper.

TL;DR: The Mount Bruce Megasequence Set as discussed by the authors is a succession of volcanic and sedimentary rocks that was deposited on the Pilbara Craton of Western Australia in the late Archaean to early Proterozoic.

TL;DR: Rb-Sr and SmNd model ages of basement gneisses in the Caledonian fold belt of North-East Greenland show that most of these rocks are related to a Palaeoproterozoic event of crust formation around 2000 Ma ago as discussed by the authors.

TL;DR: In this article, the authors provide constraints on the bulk geometry, the progressive deformation and the kinematic history of this region of the Archaean continental crust in Dharwar craton, southern India.

TL;DR: In this article, a detailed Moho depth map for the Fennoscandian part of the Baltic Shield has been compiled from a variety of seismic refraction and reflection profiling results, and a complementary crystalline crustal thickness map was compiled for Denmark, the Skagerrak Sea, offshore western Norway and adjacent areas where sedimentary strata reach maximum thicknesses of 10 km and even more.

TL;DR: The Warrawoona Megasequence as discussed by the authors contains a 3.46 Ga assemblage of tholeiitic and calc-alkaline volcanic rocks interlayered with cherty sedimentary rocks.

TL;DR: In this article, it was shown that the Hook massif contains a single, moderate- to high-temperature, solid-state foliation that is continuous with the regionally developed S1 fabric in the adjacent lower-grade Kundelungu metasedimentary rocks.

TL;DR: In this article, a minor plutonic phase was found in the Shaw Batholith of the east Pilbara Block, Western Australia, and was dated at 3338±52 Ma, which is the same age as the Mt Edgar Batholith.

TL;DR: For layered basic-ultrabasic intrusions of the Kola Peninsula and northern Karelia in the northeastern part of the Baltic Shield, the ages are in the range between 2.5 and 2.4 Ga as mentioned in this paper.

TL;DR: A geochemical and isotopic study has been carried out on the Paleoproterozoic Kuandian Complex and some associated granitoids in the eastern Liaoning Province, China as discussed by the authors.

TL;DR: In this paper, zircons from mafic and felsic volcanic rocks in the type area of the Warrawoona Group, the basal Archaean greenstone succession of the eastern Pilbara Block, have been dated precisely using the ion-microprobe SHRIMP.

TL;DR: In this article, the authors used SmNd isotopic analyses of Proterozoic granitoids and metavolcanics to delineate the Archaean palaeoboundary.

TL;DR: In this paper, the authors show that the BIFs of the Sandur belt are a product of hybridity between the hydrothermal emplacement of Si and Fe and divergent clastic sediments to ambient cold ocean water.

TL;DR: In this paper, the authors considered UPb zircon ages and some geochemical and lithostratigraphic features of the Svecofennian in the continental margin area between the Skellefte ore district and the boundary of the Archaean craton farther north in Sweden.

TL;DR: The Ammassalik area in South-East Greenland forms a link between the Precambrian terrains of West Greenland and northwest Scotland as discussed by the authors, which consists mainly of Archaean orthogneisses reworked during a Proterozoic tectonothermal event.

TL;DR: The Nama foreland basin is subdivided into three basins, from north to south the Zaris, Witputs, and Vanrhynsdorp basins.

TL;DR: In this paper, the authors propose that Southeast Rae and North Rae provinces were separate prior to ∼ 1.92 Ga, when regional tectonism changed from extension to contraction.

TL;DR: In this paper, four samples of granitoids and gneisses from the Contendas-Mirante area of the Sao Francisco Craton of Bahia State, Brazil were used for zircon geochronology.

TL;DR: The age of the granulite facies metamorphism in the Bamble Belt has long been a matter of debate as discussed by the authors, and several localities in the coastal section of the belt have been used to obtain SmNd mineral ages.

TL;DR: The northwestern Pontiac Subprovince is dominated by a monotonous greywacke sequence, metamorphosed and deformed during the Late Archaean Kenoran orogeny as mentioned in this paper.

TL;DR: The Oribi Gorge Suite can thus be regarded as late (syn)tectonic and not partly post-tectonically as previously envisaged as discussed by the authors, an age similar to both the main regional tectogenesis and syntectonic granites of the Margate Suite.