Folds in multilayered rocks of Proterozoic age, Rajasthan, India

The principal mineral deposits of Proterozoic age in Australia, not only of uranium but also of base and precious metals, are found within a north-trending belt central to the continent which stretches from Adelaide to Darwin. This belt represents the margin to the West Australian Archaean craton, and comprises orogenic and shelf domains that evolved throughout the Proterozoic; and it is suggested that the formation of the uranium deposits was an integral part of the evolution of the various geosynclines in the belt. The uranium ore bodies occupy structurally prepared features such as shears, faults and breccias, and are clearly introduced, but the source of the mineralizing fluids, and the precise mechanism of deposition, is, in some cases at least, in dispute. Mineralization per ascensum by connate water carrying metals desorbed from the sedimentary pile, or in association with acid magma which may itself be the product of anatexis, is favoured by the author.

Pre-Grenvillian history of the Adirondacks as an anorogenic, bimodal caldera complex of mid-Proterozoic age

Geology ◽

10.1130/0091-7613(1986)14<229:photaa>2.0.co;2 ◽

1986 ◽

Vol 14 (3) ◽

pp. 229 ◽

Cited By ~ 20

Author(s):

James M. McLelland

Keyword(s):

History Of ◽

Proterozoic Age

Provenance of the Old Red Sandstone: Pb isotope evidence from Arran, western Scotland

Transactions of the Royal Society of Edinburgh Earth Sciences ◽

10.1017/s0263593300013870 ◽

1984 ◽

Vol 75 (2) ◽

pp. 239-241 ◽

Cited By ~ 1

Author(s):

A. P. Dickin

Keyword(s):

Significant Contribution ◽

Strike Slip ◽

Pb Isotope ◽

Early Proterozoic ◽

Red Sandstone ◽

Boundary Fault ◽

Crustal Block ◽

Isotope Evidence ◽

Strike Slip Movement ◽

Proterozoic Age

ABSTRACTOld Red Sandstone sediments from Arran in western Scotland yield an array of Pb isotope compositions whose slope corresponds to an age of 1830 ± 400 Ma. These compositions are not consistent with a significant contribution of material from the Southern Highlands, Midland Valley, or Southern Uplands, but are similar to the Torridonian sandstones of NW Scotland. Bearing in mind the probable Laxfordian provenance of the Torridonian assemblage, this points to a source for the Old Red Sandstone in a crustal block of early Proterozoic age corresponding to the age of the Laxfordian episode. Since such a source is not presently in a position to yield the Old Red Sandstone, strike-slip movement along the Highland Boundary fault is a strong possibility.

Proterozoic age and cumulate origin for granulite xenoliths, Lesotho

Nature ◽

10.1038/299409a0 ◽

1982 ◽

Vol 299 (5882) ◽

pp. 409-413 ◽

Cited By ~ 62

Author(s):

N. W. Rogers ◽

C. J. Hawkesworth

Keyword(s):

Granulite Xenoliths ◽

Proterozoic Age

R. N. Annells, C. J. N. Fletcher, M. T Styles, C. C. J. Burton, R. B. Evans, & R. R Harding 1986. The Rincon del Tigre Igneous Complex: a major layered ultramafic-mafic intrusion of Proterozoic age in the Precambrian shield of eastern Bolivia. Overseas Geology and Mineral Resources Memoir no. 63. iv + 63 pp. + map in folder. London: H.M.S.O. Price £10.50 (paperback). ISBN 0 11 884420 2.

Geological Magazine ◽

10.1017/s0016756800009742 ◽

1988 ◽

Vol 125 (2) ◽

pp. 198-199

Author(s):

P.W.F.

Keyword(s):

Mineral Resources ◽

Igneous Complex ◽

Precambrian Shield ◽

Mafic Intrusion ◽

Proterozoic Age

Alkaline rocks of the Ukrainian Shield: Some mineralogical, petrological and geochemical features

Mineralogia ◽

10.2478/mipo-2013-0008 ◽

2013 ◽

Vol 44 (3-4) ◽

pp. 115-124 ◽

Cited By ~ 2

Author(s):

Aleksandr N. Ponomarenko ◽

Stepan G. Kryvdik ◽

Aleksandr V. Grinchenko

Keyword(s):

Wide Distribution ◽

Ukrainian Shield ◽

Alkaline Magmatism ◽

Alkaline Rocks ◽

Precambrian Rocks ◽

Western Province ◽

Rock Types ◽

Alkaline Feldspar ◽

Granite Complex ◽

Proterozoic Age

AbstractThe Ukrainian Shield (USh) is a typical province of Proterozoic alkaline magmatism where about 50 massifs and occurrences of alkaline rocks and carbonatites have been found. In spite of the wide distribution of Devonian basaltic- and alkaline magmatic rocks in the Dnieper-Donetsk depression adjacent to the USh, and in a marginal zone of the USh adjacent to folded Donbass, only alkaline rocks of Proterozoic age (1.8-2.1 Ga) that have been identified in the central interior of the USh. Some discrete bodies of 2.8 Ga subalkaline rocks also occur in Bogdanivka massif (Azov area). Occurrences of both Proterozoic (prevailing) and Phanerozoic (Devonian) alkaline rocks and kimberlites are only found in the eastern part of the USh (Azov area). Kimberlites in the central part of the Ukrainian Shield (Kirovograd region) are also of Proterozoic age (ca 1.8 Ga). It is this predominance of Precambrian rocks that makes the USh so different from other alkaline provinces where Phanerozoic alkaline rocks and kimberlites commonly prevail over Precambrian rocks. The lack of Phanerozoic alkaline magmatism on USh is poorly understood. Two main complexes of alkaline rocks - alkaline-ultrabasic (carbonatitic) and gabbro- syenitic - are distinguished in the USh. There are also rare occurrences of rock types such as alkaline- and alkaline-feldspar granites that may represent one separate alkaline-granite complex. Alkaline rocks present in the Eastern (Azov) province and in the Western province display essentially different geochemical character. Those of the Eastern province show characteristics typical of alkaline-ultrabasic rocks (e.g. high contents of incompatible rare elementssuch as Nb, REE, Zr, Y, Sr, whereas those in the Western province are characterized by low contents of Nb and Zr, and REE in some cases. This fact is interpreted as reflecting different geodynamic conditions of their origin. The Eastern rocks were formed in rift settings, the Western rocks in crustal compressional settings (collision, subduction). Various mineral deposits of phosphorus (apatite), niobium, REE, yttrium and zirconium, including unusually rich ores of REE, Y and Zr (Azov and Yastrybetsky) are associated with the alkaline rocks and carbonatites of the USh.

The Lawson Creek Formation of middle Proterozoic age in east-central Idaho

10.3133/b1482e ◽

1980 ◽

Keyword(s):

East Central ◽

Middle Proterozoic ◽

Proterozoic Age ◽

Central Idaho

UM MODELO PARA A EVOLUÇÃO MICROESTRUTURAL DOS MINÉRIOS DE FERO DO QUADRILÁTEO FERRÍFERO. PARTE I - ESTRUTURAS E RECRISTALIZAÇÃO

Revista Geonomos ◽

10.18285/geonomos.v1i1e2.238 ◽

1993 ◽

Cited By ~ 4

Author(s):

Carlos Alberto Rosière ◽

Farid Chemale Jr. ◽

Marcelo L.V. Guimarães

Keyword(s):

Iron Ore ◽

Banded Iron Formations ◽

Lower Proterozoic ◽

Ore Bodies ◽

Quadrilátero Ferrífero ◽

Textural Relationship ◽

Iron Formations ◽

Ore District ◽

Proterozoic Age

In the Quadrilátero Ferrífero iron ore district, the Cauê Formation of the Minas Supergroup comprise banded iron formations, called itabirites, of Lower Proterozoic age enclosing iron rich ore bodies. Although many ore bodies are associated with syntectonic enrichment processes, due to the leaching of gangue minerals like quartz and carbonates, others are probably of sedimentary origin and were recrystallized during the tectonometamorphic development of the region.Three generations of magnetite and four of hematite are recognized in these rocks. They display a clear textural relationship in zones of high and low strain, with the development of two main deformational events under variable metamorphic conditions and different tectonic levels.The first part of this paper one describes the recrystallization phenomena and its relation to the main structures, while in the second part the developed textures and its association to the strain are presented.

Precambrian Rb-Sr isochron ages from the crystalline complexes of inner Forsblads Fjord, East Greenland fold belt

Rapport Grønlands Geologiske Undersøgelse ◽

10.34194/rapggu.v85.7544 ◽

1977 ◽

Vol 85 ◽

pp. 122-126

Author(s):

D.C Rex ◽

A.R Gledhill ◽

A.K Higgins

Keyword(s):

Standard Technique ◽

Fold Belt ◽

East Greenland ◽

Crystalline Complexes Of ◽

Proterozoic Age

Several collections of samples were made from crystalline units in inner Forsblads Fjord by D.C.R. and A.R.G. in 1974. Result of whole rock Rb-Sr analyes on two of these collections are presented here, and give an Archaean age for banded gneises and amiddle Proterozoic age for quartzitic metasediments. These ages confirm the occurrence of major Precambrian complexes within the East Greenland Caledonian fold belt (Hansen el al., 1973a, b, 1974; Rex & Gledhill, 1974; Rex el al., 1976; Henrik en & Higgins, 1976: Higgins 1976). Analyses were carried out using standard technique (Van Breemen & Dodson, 1972).