Showing papers on "Granulite published in 1971"
TL;DR: In this article, liquid inclusions in quartz found in rocks of amphibolite and granulite facies were studied in the presence of CO2 (probably juvenile) and gave values (800°C, 8 kb) comparable to those obtained by the petrological study (7-800 °C, 6-8 kb).
227 citations
TL;DR: The basement of Southern Norway is a genetically homogeneous migmatite complex in which old supracrustals produced granitic and granodioritic "neosome" during a late Precambrian (109 years ago) regional metamorphism.
126 citations
TL;DR: In this paper, the trace element concentrations of granulite and amphibolite facies were analyzed for major elements and trace elements Rb, Sr, Ba, Zr, Pb, Th and U.
119 citations
TL;DR: In equilibrated metamorphic rocks containing coexisting garnet, cordierite, quartz and sillimanite, the exchange of iron and magnesium between cordierites and garnet offers a highly favorable geological thermometer and barometer, because this exchange reaction is insensitive to pressure.
Abstract: In equilibrated metamorphic rocks containing coexisting garnet, cordierite, quartz and sillimanite, the exchange of iron and magnesium between cordierite and garnet offers a highly favourable geological thermometer and barometer, because this exchange reaction is insensitive to pressure. Thermodynamic analysis shows that this thermometer may be calibrated from knowledge of the breakdown reactions for iron and magnesian cordierite end members to garnet. The thermometer was experimentally calibrated using cordierites of intermediate composition. When applied to rocks showing petrographic evidence of equilibrium, and chemical evidence of reaction between garnet and cordierite, the thermometer yielded temperatures of 600–750:C, and pressures of 5.7–6.7 kilobars. Similar conditions are indicated by other literature data on cordierite-garnet gneisses, and are believed to represent hornblende granulite grade of metamorphism.
102 citations
TL;DR: In this paper, a melting mechanism involving several stages and hypotheses concerning the possible composition of the depleted melting fractions are proposed, which have a bearing on the genesis of granitic materials.
93 citations
TL;DR: Sapphirine and magnetite are closely associated in elongate pods in the granulites of Wilson Lake, central Labrador, where quartz, hypersthene, sillimanite, kyanite, corundum, and spinel also occur in textural equilibrium.
65 citations
01 Jul 1971
TL;DR: The Arltunga Nappe Complex as mentioned in this paper was formed by a combination of recumbent folding and overthrusting, and the uppermost and largest nappe was transported at least 24 km across strike and developed by a combined recumbence folding and overthrowing.
Abstract: The Arltunga Nappe Complex trends east‐west along the northeastern margin of the Amadeus Basin, approximately in the centre of the Australian continent. The nappes formed in a stratigraphic sequence consisting of the crystalline Precambrian Arunta Complex overlain unconformably by Upper Proterozoic Heavitree Quartzite and carbonate rocks of the Bitter Springs Formation. The uppermost and largest nappe was transported at least 24 km across strike and developed by a combination of recumbent folding and overthrusting. The lower nappes formed by overthrusting alone. The nappes root to the north in a belt of crystalline rocks of the Arunta Complex, originally in the amphibolite facies, that are retrograded to the greenschist facies. North of the retrograded zone a belt of rocks belonging to the granulite facies and amphibolite facies is exposed. There is a sharp discontinuity in the style and pattern of deformation along the thrust fault surface that defines one of the lower thrust nappes. The autocht...
58 citations
01 Nov 1971
TL;DR: In this article, retrograde schistzones intersect high-grade, regional metamorphic rocks of the lower granulite facies (or the amphibolite-granulite transition).
Abstract: Aluminous, mafic, felsic, calcareous, and sulphide‐rich rocks have been involved in localized deformation and retrograde metamorphism at Broken Hill, western New South Wales, where retrograde schist‐zones intersect high‐grade, regional metamorphic rocks of the lower granulite facies (or the amphibolite‐granulite facies transition). Although technically retrograde, the schists contain mineral assemblages indicative of the lower amphibolite facies. The schist‐zones were formed by local folding, apparently as part of the third stage of deformation in the Broken Hill area.
51 citations
TL;DR: In this paper, a pluton of biotite hornblende quartz monzonite (amphibolite facies) and hypersthene quartz monzoneite (granulite faces) was analyzed for K, Th, U and U. The authors concluded that the distribution of the fluid phase has been the decisive factor in determining the concentrations of U and Th.
21 citations
TL;DR: In this article, the Nussbaum Riegel petrography and the structure of three small areas, the nussbaum riegel and the north and south sides of the Garwood valley in the “Dry Valleys” region of Victoria Land, Antarctica are described and discussed.
Abstract: The petrography and structure of three small areas, the Nussbaum Riegel and the north and south sides of the Garwood Valley in the “Dry Valleys” region of Victoria Land, Antarctica, are described and discussed. The rocks are mostly pure or impure marbles plus lesser quantities of amphibolite, schist and quartz‐feldspar rocks, and mineral assemblages indicate that they have been metamorphosed under conditions of the amphibolite fades, and possibly, locally under conditions transitional to the granulite facies. In general they have not suffered retrograde metamorphism. Nussbaum Riegel is characterized by isoclinal folds and very well‐developed boudinage structure. Examination of the boudins reveals that the competent beds behaved in a ductile manner when failing parallel to the fold axis and in a brittle manner when failing perpendicular to the fold axis. An explanation for this observation is offered, based on variation in strain rate in various directions during the development of the fold. The G...
19 citations
TL;DR: In this paper, the authors have studied the weathering of a deeply weathered boulder conglomerate of Middle Old Red Sandstone (Devonian) age in north-east Scotland and found that all the feldspars in these rocks weather to a Cheto-type montmorillonite, poor in iron.
Abstract: The clay minerals formed in a deeply weathered boulder conglomerate of Middle Old Red Sandstone (Devonian) age in north-east Scotland have been studied by a variety of physical and chemical techniques. The granite and granulite boulders in this deposit are completely weathered. With the exception of microcline, all the feldspars in these rocks—orthoclase feldspar, orthoclase-microperthite, albite, and oligoclase—weather to a Cheto-type montmorillonite, poor in iron. Electron and optical microscopy indicate that the weathering transformation is a direct one, without the intervention of any intermediate crystalline or well-defined amorphous phase. Structural control of the primary mineral over the formation of the montmorillonite seems to have been a minimal factor and the evidence suggests that the clay mineral crystallized from the soluble or colloidal products arising from the decomposed feldspars. Smaller amounts of kaolinite also formed during weathering but largely from the weathering of muscovite. The environment in which these changes occurred seems to have been alkaline in a relatively closed system. Chemical analyses of related cores and weathered shells of granite and granulite bounders show only a slight decrease of silica and an increase in magnesia. Judging from the extent of alteration to secondary clay minerals, the order of resistance towards weathering of the primary minerals in these rocks is plagioclase = orthoclase < muscovite < biotite < microcline < quartz.
TL;DR: The Lake Hopatcong area is divisible into several northeast-trending fault blocks, each of which contains a mappable stratigraphic sequence of paragneisses and granitic or syenitic rocks.
Abstract: Precambrian rocks near Lake Hopatcong, New Jersey, form a part of the intensely deformed and metamorphosed Reading Prong. The Lake Hopatcong area is divisible into several northeast-trending fault blocks, each of which contains a mappable stratigraphic sequence of paragneisses and granitic or syenitic rocks. The paragneisses generally are well foliated and well layered. They consist chiefly of biotite-feldspar-quartz gneisses and quartz-oligoclase leucogneisses that are interpreted as metamorphosed potassium-rich sandstones and quartz keratophyres, respectively. A thin well-foliated unit of biotite-plagioclase gneiss is thought to be a metamorphosed sill of gabbroic anorthosite. The granitic and syenitic rocks generally form thick, regionally concordant sheets. They are typically foliated and are composed chiefly of microcline microperthite and plagioclase (or mesoperthite), quartz, and iron-rich hornblende and clinopyroxene. These foliated granitic and syenitic rocks are viewed as syntectonic magmatic intrusives. One regionally discordant, unfoliated sheet of clinopyroxene quartz syenite is probably a late tectonic magmatic intrusive. Mineral assemblages in Lake Hopatcong paragneisses may be assigned to the hornblende granulite subfacies of metamorphism. The presence of Ca-bearing mesoperthite in biotite-feldspar-quartz gneiss indicates that metamorphic temperatures exceeded 700° C, and the assemblage garnet-sillimanite-quartz without cordierite indicates that load pressure was greater than 2.5 kb. The rocks have thus probably been buried to depths in excess of 10 km.
TL;DR: The Namaqualand granite-gneiss complex in South Africa covers an area of approximately 70,000 km 2. The southern portion consists of mainly mesozonal biotite gneiss and a fine-grained granulite as mentioned in this paper.
TL;DR: In this article, the role of tectonic overpressure and magmatic superheat in orogenic PT-regimes is assessed on the strength of structural relations in the high PT-facies series of Cabo Ortegal, and of recently reported high-temperature minerals (wollastonite, sapphirine, sanidine, etc.) from granulite facies terrains in the vicinity of charnockitic and other relatively dry magmatic intrusives.
TL;DR: Corundum laths have been identified as exsolution products from both ilmenite and spinel in granulite facies rocks from central Australia as discussed by the authors, which is interpreted as having occurred during a decrease in the P•T conditions under which the minerals initially crystallized.
Abstract: Corundum laths have been identified as exsolution products from both ilmenite and spinel in granulite facies rocks from central Australia. The exsolution is interpreted as having occurred during a decrease in the P‐T conditions under which the minerals initially crystallized. The ilmenite + corundum possibly indicate the existence of a former homogeneous iron‐hogboemite. The spinel + corundum suggests that under conditions of high Ps‐T (granulite facies) and low fo2 there exists a field where aluminous spinel is stable.
01 Dec 1971
TL;DR: In granulites of South-Bohemia not only the usually occurring Al2SiO5 polymorphs, kyanite and sillimanite, were found but also andalusite.
Abstract: In granulites of South-Bohemia not only the usually occurring Al2SiO5 polymorphs, kyanite and sillimanite, were found but also andalusite. Its presence indicates that the metamorphic development of these granulites is characterized by a high PT-gradient. The granulitic rocks of the Bohemian Massif can be regarded as a facies series ranging from the granulite facies through the amphibolite facies to the hornblende-hornfels facies. The lower limit of the PT-conditions of this series should be placed below the position of the triple point of Al2SiO5.
TL;DR: Work on the Isortoq granulite facies rocks of the Nagssugtôqidian mobile belt in West Greenland has revealed an area where the rocks show features believed to be caused by shock metamorphism, while in neighbouring areas small veins of glass-mylonite (hyalomylonite) have been generated in pre-existing regional thrust zones.
Abstract: WORK on the Isortoq granulite facies rocks of the Nagssugtoqidian mobile belt1 in West Greenland has revealed an area where the rocks show features believed to be caused by shock metamorphism, while in neighbouring areas small veins of glass-mylonite (hyalomylonite) have been generated in pre-existing regional thrust zones.
Journal Article•
TL;DR: The field and petrological observations suggest that these orthopyroxene-bearing rocks are variants of the metapelites, derived by the metamorphism of appropriate sediments and have no connection with the associated charnockites of the area as discussed by the authors.
Abstract: Orthopyroxene-bearing rocks viz., quartz-norite, cordierite-biotite-hypersthene granulite, leptynite and hypersthene-biotite quartzite containing minerals like hypersthene (aluminous), diopside, brown hornblende, biotite, garnet, cordierite, plagioclase and quartz, occur constituting an integral part of the high-grade metapelites of the area. The field and petrological observations suggest that these orthopyroxene-bearing rocks are variants of the metapelites, derived by the metamorphism of appropriate sediments and have no connection with the associated charnockites of the area.
TL;DR: In this paper, a review of the available data indicated that the granulite fades of metamorphism is not restricted to Precambrian rocks, but is found also in younger complexes, some of which outcrop on the surface of the ground, although they were subjected to intensive autodiaphthoresis.
Abstract: Relatively high geothermal gradient and greater depths of the erosion plane may account for certain distinctions of the Lower Archean metamorphic complexes. Their granulites and amphibolites could not have been formed at depths shallower than 15-16 and 10 km, respectively, as indicated by review of the available data. The granulite fades of metamorphism is not restricted to Precambrian rocks, but is found also in younger complexes, some of which outcrop on the surface of the ground, although they were subjected to intensive autodiaphthoresis, which usually accompanied crystallization of anatectic melts within the amphibolitic range of the temperature.