U–Pb SHRIMP ages of detrital granulite-facies rutiles: further constraints on provenance of Jurassic sandstones on the Norwegian margin

2010 ◽  
Vol 148 (3) ◽  
pp. 473-480 ◽  
Author(s):  
GUIDO MEINHOLD ◽  
ANDREW C. MORTON ◽  
C. MARK FANNING ◽  
ANDREW G. WHITHAM
Keyword(s):  
Granulite Facies ◽  
Hydrocarbon Exploration ◽  
Age Dating ◽  
High Grade ◽  
Provenance Analysis ◽  
Granulite Facies Metamorphism ◽  
Metasedimentary Rocks ◽  
Major Cluster ◽  
Norwegian Margin ◽  
Clastic Sedimentary

AbstractElectron microprobe analyses of 128 detrital rutile grains from two Jurassic sandstone samples (Hettangian and Bajocian–Bathonian in age) from hydrocarbon exploration wells on the Norwegian margin confirm that more than 85 % of the rutiles were derived from metapelitic rocks. Zr-in-rutile geothermometry confirms that about 83 % of the rutile was formed under high-grade metamorphism (>750 °C). Sixty-two rutile grains, including 60 of the identified high-temperature rutile population, were also analysed for U–Pb geochronology using SHRIMP. The 206Pb–238U rutile ages range from approximately 485–292 Ma, with a major cluster between 450 and 380 Ma. These data suggest that the detrital rutile was predominantly derived from a felsic source that experienced granulite-facies metamorphism about 450–380 Ma ago. This conclusion is consistent with derivation from high-grade Caledonian metasedimentary rocks, probably the Krummedal sequence in central East Greenland, as previously suggested by an earlier provenance study using conventional heavy mineral analysis, garnet geochemistry and detrital zircon age dating. The present study underscores the importance of rutile geochemistry and geochronology in quantitative single-mineral provenance analysis of clastic sedimentary rocks.

New constraints on metamorphism in the Highjump Archipelago, East Antarctica

2016 ◽  
Vol 28 (6) ◽  
pp. 487-503 ◽  
Author(s):  
Naomi M. Tucker ◽  
Martin Hand
Keyword(s):  
Granulite Facies ◽  
East Antarctica ◽  
Partial Replacement ◽  
Granulite Facies Metamorphism ◽  
Metasedimentary Rocks ◽  
Facies Metamorphism ◽  
Antarctic Expedition ◽  
Higher Temperature ◽  
Temperature And Pressure

AbstractThe age and conditions of metamorphism in the Highjump Archipelago, East Antarctica, are investigated using samples collected during the 1986 Australian Antarctic expedition to the Bunger Hills–Denman Glacier region. In situ U-Pb dating of monazite from three metasedimentary rocks yields ages between c. 1240–1150 Ma and a weighted mean 207Pb/206Pb age of 1183±8 Ma, consistent with previous constraints on the timing of metamorphism in this region and Stage 2 of the Albany–Fraser Orogeny in south-western Australia. This age is interpreted to date the development of garnet ± sillimanite ± rutile-bearing assemblages that formed at c. 850–950°C and 6–9 kbar. Peak granulite facies metamorphism was followed by decompression, evidenced largely by the partial replacement of garnet by cordierite. These new pressure–temperature determinations suggest that the Highjump Archipelago attained slightly higher temperature and pressure conditions than previously proposed and that the rocks probably experienced a clockwise pressure–temperature evolution.

Petrology of the Fort Smith - Great Slave Lake radiometric high near Pilot Lake, N.W.T.

1981 ◽  
Vol 18 (5) ◽  
pp. 842-851 ◽  
Author(s):  
R. A. Burwash ◽  
D. F. Cape
Keyword(s):  
Granulite Facies ◽  
Mica Schist ◽  
Biotite Gneiss ◽  
Black Sand ◽  
Metasedimentary Rocks ◽  
Great Slave Lake ◽  
Fort Smith ◽  
High Concentrations ◽  
Orogenic Cycle ◽  
Clastic Sedimentary

Near Pilot Lake, the east boundary of the Fort Smith – Great Slave Lake radiometric high coincides with the contact of a well-foliated, porphyroblastic microcline–plagioclase–quartz-garnet–biotite gneiss1 (Pilot Lake Gneiss) with a hybrid assemblage of quartzite, mica schist, garnet–cordierite gneiss, and minor amphibolite (Variable Paragneiss). Anomalously high concentrations of uranium and thorium are associated with mafic-rich, lenticular bodies with a mineral assemblage biotite + monazite + zircon + ilmenite + hematite ± apatite ± plagioclase ± quartz. The mafic pods occur within both the Variable Paragneiss and the Pilot Lake Gneiss. Corundum and spinel occur in the mafic lenses and sillimanite, kyanite, and hypersthene in other inclusions in the Pilot Lake Gneiss.The ilmenite–magnetite–monazite–zircon–apatite assemblage is interpreted as a "black sand" concentration in a clastic sedimentary sequence subsequently metamorphosed by a regional granulite facies event. A granitic pluton intruded during the same orogenic cycle assimilated the clastic metasedimentary rocks containing black sand interlayers, becoming enriched in thorium from the monazite. A second metamorphic event at lower P–T conditions, accompanied by strong cataclasis, developed the texture of the Pilot Lake Gneiss as now observed. Shearing within the gneiss locally concentrated hematite + quartz + uranium.Regional tectonic extrapolations suggest that the pyroxene granulite event was Kenoran and the later amphibolite event Hudsonian.

Granulite-facies metamorphism in the Quetico Subprovince, north of Manitouwadge, Ontario

1994 ◽  
Vol 31 (9) ◽  
pp. 1427-1439 ◽  
Author(s):  
Yuanming Pan ◽  
Michael E. Fleet ◽  
Howard R. Williams
Keyword(s):  
Equilibrium Phase ◽  
Granulite Facies ◽  
Crustal Thickening ◽  
Granulite Facies Metamorphism ◽  
Metasedimentary Rocks ◽  
Thermal Peak ◽  
Mineral Assemblages ◽  
Facies Metamorphism ◽  
Peak Event ◽  
High Temperature Metamorphism

A zone of granulites, defined by an orthopyroxene-in isograd and extending more than 100 km in length and about 10 km in width, occurs near the southern margin of the Quetico Subprovince, north of Manitouwadge, Ontario. Mineral assemblages in metasedimentary rocks and associated migmatites consist of quartz, plagioclase, garnet, orthopyroxene, biotite, cordierite, sillimanite, K-feldspar, hercynite, magnetite, ilmenite, and other accessory phases. Minor mafic gneisses and calc-silicate pods or lenses are also present. From equilibrium phase relations and thermobarometry, the granulites experienced a thermal-peak event (4–6 kbar (1 bar = 100 kPa), 680–770 °C, a(H2O) of 0.15–0.25 and fO2 of 1–2 log units above the FMQ buffer) in association with D2 deformation, followed by a retrogression (550–660 °C and 3–4 kbar) and a later hydrothermal alteration (1–2 kbar and 200–400 °C). The distribution and calculated peak metamorphic conditions of the granulite zone in the Quetico Subprovince are similar to those of granulites in the English River Subprovince and other proposed accretionary terranes. The low-pressure, high-temperature metamorphism in the Quetico Subprovince is interpreted to be related to both crustal thickening and addition of heat from subduction-related magmatism.

Silicate, Oxide and Sulphide Trends in Neo-Archean Rocks from the Nilgiri Block, Southern India: the Role of Fluids During High-grade Metamorphism

2019 ◽  
Vol 60 (5) ◽  
pp. 1027-1062 ◽  
Author(s):  
Vinod O Samuel ◽  
Daniel E Harlov ◽  
Sanghoon Kwon ◽  
K Sajeev
Keyword(s):  
Granulite Facies ◽  
Southern India ◽  
Sulphide Mineral ◽  
High Grade ◽  
Regional Trend ◽  
Granulite Facies Metamorphism ◽  
Facies Metamorphism ◽  
High Grade Metamorphism ◽  
Specific Oxidation

Abstract The Nilgiri Block, southern India represents an exhumed section of lower, late Archean (2500 Ma) crust. The northern highlands of the Nilgiri Block are characterized by metagabbros with pyroxenite inlayers. A two-pyroxene granulite zone acts as a transition between the metagabbros and charnockites, which are exposed in the central and southern part of the Nilgiri highlands. Thermobarometry results indicate a SW–NE regional trend both in temperature (∼650–800°C) and in pressure (700–1100 MPa) over the Nilgiri highlands. In the charnockites, composite rutile–ilmenite grains are the dominant oxide assemblage. In the two-pyroxene granulites, hemo-ilmenite–magnetite is dominant with coexisting rutile–ilmenite composite grains in a few samples in the vicinity of the boundary with the charnockites. In the metagabbros, hemo-ilmenite–magnetite is the dominant oxide assemblage. The principal sulphide mineral in the charnockite is pyrrhotite with minor pyrite–chalcopyrite exsolution lamellae or blebs. In the two-pyroxene granulites and the metagabbros, the principal sulphide assemblage consists of discrete pyrite grains with magnetite rims and pyrite–pyrrhotite–chalcocopyrite associations. From these observations, a specific oxidation trend is seen. The northern granulite-facies metagabbros and two-pyroxene granulites of the Nilgiri highlands are highly oxidized compared with the charnockites from the central and southern regions. This higher oxidation state is proposed to be the result of highly oxidizing agents (probably as SO3) in low H2O activity grain boundary NaCl saline fluids with a dissolved CaSO4 component present during granulite-facies metamorphism of the metagabbros and two-pyroxene granulites. Eventually these agents became more reducing, owing to the inherent buffering of the original tonalite–granodiorite granitoids at the graphite–CO2 buffer, such that S took the form of H2S during the granulite-facies metamorphism of the charnockites. At the same time, these saline fluids were also responsible the solid-state conversion of biotite and amphibole to orthopyroxene and clinopyroxene in the metagabbro, two-pyroxene granulite, and charnockite.

U–Pb zircon age dating of a rapakivi granite batholith in Rangnim massif, North Korea

2007 ◽  
Vol 144 (3) ◽  
pp. 547-552 ◽  
Author(s):  
MINGGUO ZHAI ◽  
JINGHUI GUO ◽  
PENG PENG ◽  
BO HU
Keyword(s):  
North China Craton ◽  
North Korea ◽  
North China ◽  
Granulite Facies ◽  
Age Dating ◽  
Weighted Mean ◽  
Zircon Age ◽  
Metasedimentary Rocks ◽  
The North ◽  
Granite Batholith

Rapakivi granites and several small leucogabbroic and gabbroic bodies are located in the Rangnim Massif, North Korea. The largest batholith in the Myohyang Mountains covers an area of 300 km2 and was intruded into Precambrian metamorphosed rocks. It has a SHRIMP U–Pb zircon weighted mean 207Pb/206Pb age of 1861 ± 7 Ma. The country rocks of rapakivi granites are Neoarchaean orthogneisses and Palaeo-Mesoproterozoic graphite-bearing metasedimentary rocks of granulite facies, and they are similar to those of the rapakivi granites and anorthosites exposed in South Korea and in the North China Craton. We conclude that the three massifs in the Korean Peninsula commonly record an identical Palaeo-Mesoproterozoic anorogenic magmatic event, indicating that they have a common Precambrian basement with the North China Craton.

SHRIMP U–Pb zircon geochronology of gneisses from the Gweta borehole, northeast Botswana: implications for the Palaeoproterozoic Magondi Belt in southern Africa

2001 ◽  
Vol 138 (3) ◽  
pp. 299-308 ◽  
Author(s):  
R. B. M. MAPEO ◽  
R. A. ARMSTRONG ◽  
A. B. KAMPUNZU
Keyword(s):  
Central Zone ◽  
Granulite Facies ◽  
Eastern Africa ◽  
High Grade ◽  
Zircon Geochronology ◽  
Granulite Facies Metamorphism ◽  
Grade Metamorphism ◽  
Facies Metamorphism ◽  
High Grade Metamorphism ◽  
Limpopo Belt

This paper presents new U–Pb zircon analyses from garnet–sillimanite paragneisses from the Gweta borehole in northeast Botswana. Concordant to near-concordant analyses of zircon from these rocks reveal a billion year history from 3015 ± 21 Ma for the oldest detrital grain measured, to the age of high-grade metamorphism, 2027 ± 8 Ma. The maximum age of sedimentation in the Magondi belt is constrained by the age of the youngest concordant detrital zircon at 2125 ± 6 Ma. This contrasts with the age of sedimentation in the Central Zone of the Limpopo belt which is Archaean. The comparison of our results with U–Pb zircon data from the Magondi belt in Zimbabwe suggests that the granulite-facies metamorphism in this belt extended between c. 2027–1960 Ma. Granulite-facies rocks with U–Pb zircon ages in this interval are also known in the Ubendian belt and lend support to the correlation of these two segments of Palaeoproterozoic belts in southern and central–eastern Africa. The granulite facies metamorphism in the Magondi belt is coeval with the high-grade metamorphism and granitoids documented further south in the Central Zone of the Limpopo Belt.

scholarly journals Supracrustal rocks in the Ammassalik region, South-East Greenland

1989 ◽  
Vol 146 ◽  
pp. 17-22
Author(s):  
R.P Hall ◽  
B Chadwick ◽  
J.C Escher ◽  
V.N Vasudev
Keyword(s):  
Relative Stability ◽  
Granulite Facies ◽  
Ultramafic Rocks ◽  
Granulite Facies Metamorphism ◽  
East Greenland ◽  
Great Thickness ◽  
Metasedimentary Rocks ◽  
The North ◽  
Facies Metamorphism ◽  
Pelitic Rocks

Large belts of supracrustal rocks are abundant in the Ammassalik region of S.E. Greenland, and are referred to collectively as the Siportoq supracrustal association. They comprise overwhelmingly metasediments, mainly of quartz-rich or semipelitic composition, with variable proportions of quartz, kyanite, sillimanite, garnet and biotite. Graphitic schists are also common and marble horizons occur up to a kilometre thick. Garnet amphibolites are volumetrically minor, and ultramafic rocks are extremely rare. Lithological banding representing relict bedding and rare cross-bedding are locally well preserved. The compositions of the metasedimentary rocks suggest that their provenance was dominantly sialic and the great thickness of semi-pelitic rocks suggests that additions of immature minerals kept pace with gentle subsidence of a basin or shelf environment. The thick marble horizons indicate periods of relative stability. Unlike the surrounding quartzo-feldspathic gneisses in the north of the area, the supracrustal rocks do not appear to have undergone granulite facies metamorphism.

High-grade metamorphism in metapelites from the western East European Craton, western Lithuania: challenges of deciphering and dating multi-stage metamorphism

2021 ◽  
Author(s):  
Grazina Skridlaite ◽  
Jolanta Putnaite ◽  
Boguslaw Baginski ◽  
Agnieszka Huc ◽  
Laurynas Siliauskas
Keyword(s):  
Local Equilibrium ◽  
Age Groups ◽  
Granulite Facies ◽  
East European Craton ◽  
Complex Nature ◽  
Variable Degree ◽  
Large Area ◽  
Granulite Facies Metamorphism ◽  
East European ◽  
Metasedimentary Rocks

<p>The Precambrian basement of the western East European Craton (EEC) in western Lithuania is covered by ca 2 km thick sediments. The rocks are mostly charnockitoids and granitoids with a large area of metasedimentary rocks crosscut by the Lk1-5, Pc1-7, Sh3, Ls1-3, Ml1, Tr11, and other drillings. The metasediments are mostly Fe-rich pelites with subordinate calcic-silicic and mafic rocks.</p><p>The rocks were metamorphosed in granulite facies with a variable degree of partial melting resulting in domain-like structure. Most of the granulites contain garnet, biotite, sillimanite, plagioclase, K-feldspar, quartz, and opaque minerals with or without cordierite and hercynite spinel. The earlier geothermobarometry investigations in several drillings have revealed a complex nature of the granulite facies metamorphism. Peak conditions of 800-850<sup>o</sup> C at 8.5 -9 kbar (samples Tr11, Lk2, 5, Pc1) were obtained from large garnet, biotite, and plagioclase grains with the presence of sillimanite. A second stage of 600-770<sup>o</sup>C at 6-7 kbar was recorded mainly by the second garnet and cordierite. It was followed by a stage of 550-600<sup>o</sup>C at 4-5 kbar (Skridlaite et al., 2014).</p><p>Using a pseudosection approach (Thermocalc 3.5.0), the preliminary modelling results are the following: in Lk5 sample, the T increases from 790<sup>o</sup>C at 5.5 kbar to 840<sup>o</sup>C at 5 kbar; in Tr11 sample, the garnet is stable at 800<sup>o</sup>C and 7 kbar; in Pc1 sample, a drop of P from 6.5 7.5 to 5 kbar at 760-770<sup>o</sup>C is prominent.</p><p>No metamorphic zircon was produced during the peak metamorphism except for a single metamorphic grain of ca. 1.80 Ga in Lk 2 sample (Bogdanova et al., 2015). Metamorphic overgrowths were too thin to date them. Instead, numerous monazite grains seemed to be promising for dating metamorphic peaks and distinct stages. Two age groups of monazites were distinguished from the preliminary EPMA dating results in Lk1, 2, and 5 samples: 1.79-1.77 Ga and 1.66 Ga - 1.63 Ga. In Tr11 sample, the cores of 1.80-1.79 Ga monazites were overgrown by 1.77-1.76 Ga rims.</p><p>After preliminary attempts to model and date distinct stages of metamorphism, we could evaluate advantages of all the methods applied and to look after some solutions of the arising problems. First, the whole-rock chemistry of distinct domains might be helpful to model PT evolution of those domains. More careful mineral analysis in a greater number of samples should be helpful for finding peak and other assemblages in a local equilibrium. HREE, especially Y-content investigations in monazite grains might provide some clues on monazite and garnet behavior during the distinct stage of metamorphism. Some other solutions would be very welcome.</p><p>Bogdanova, S. et al., 2015. Precambrian Research, 259, 5–33.</p><p>Skridlaite, G. et al., 2014. Gondwana Research, 25, 649-667.</p>

Accretion and evolution of an Archaean high-grade grey gneiss – amphibolite complex: the Fiskefjord area, southern West Greenland

1997 ◽  
pp. 1-115 ◽  
Author(s):  
Adam A. Garde
Keyword(s):  
Continental Crust ◽  
Granulite Facies ◽  
Ductile Deformation ◽  
Repeated Injection ◽  
High Grade ◽  
Volcanic Origin ◽  
Granulite Facies Metamorphism ◽  
West Greenland ◽  
Facies Metamorphism ◽  
Grey Gneiss

NOTE: This monograph was published in a former series of GEUS Bulletin. Please use the original series name when citing this series, for example: Garde, A. A. 1997: Accretion and evolution of an Archaean high-grade grey gneiss – amphibolite complex: the Fiskefjord area, southern West Greenland. Geology of Greenland Survey Bulletin 177, 115 pp. _______________ The Fiskefjord area in southern West Greenland, part of the Akia tectono-stratigraphic terrane, comprises a supracrustal association and two groups of grey quartzo-feldspathic orthogneises c. 3200 and 3000 Ma old. The supracrustal association forms layers and enclaves in grey gneiss and may comprise two or more age groups. Homogeneous amphibolite with MORB-like but LIL element enriched tholeiitic composition predominates; part, associated with cumulate noritic and dunitic rocks, represents fragments of layered complexes. Heterogeneous amphibolite of likely submarine volcanic origin, (basaltic) andesitic amphibolite, leucogabbro-anorthosite, and minor pelitic metasediment occur. Disruption by magmatic and tectonic events and geochemical alteration have obscured primary origin: the supracrustal association may represent oceanic crust. Grey orthogneiss of the tonalite-trondhjemite-granodiorite (TTG) association was generated during continental accretion at c. 3000 Ma, most likely by partial melting of wet and hot tholeiitic basaltic rocks subducted in a convergent plate setting. Most dioritic gneiss is c. 220 Ma older. A 3040 Ma dioritic to tonalitic phase, enriched in P2O5 , Ba, Sr, K, Pb, Rb and LREE, probably was derived from metasomatised mantle. Intense deformation and metamorphism accompanied the 3000 Ma magmatic accretion.Thrusts along amphibolite-orthogneiss contacts were succeeded by large recumbent isoclines, upright to overturned folds, and local domes with granitic cores. Syntectonic granulite facies metamorphism is thought to be due to heat accumulation by repeated injection of tonalitic magma. Strong ductile deformation produced steep linear belts before the thermal maximum ceased, whereby folds were reorientated into upright south-plunging isoclines. Two large TTG complexes were then emplaced, followed by granodiorite and granite. Post-kinematic diorite plugs with unusually high MgO, Cr and Ni, and low LIL and immobile incompatible element contents, terminated the 3000 Ma accretion. Hybrid border zones and orbicular textures suggest rapid crystallisation from superheated magma. The diorites most likely formed from ultramafic magma contaminated with continental crust. Widespread high-grade retrogression preserved a granulite facies core in the south-west; to the east the retrogressed gneiss grades into amphibolite facies gneiss not affected by granulite facies metamorphism and retrogression. LIL elements were depleted during granulite facies metamorphism and reintroduced during retrogression, probably transported in anatectic silicate melts and in fluids. Rb-Sr isotope data, and relationships between retrogression, high-strain zones and granite emplacement, show that retrogression took place shortly after the granulite facies metamorphism, before terrane assembly at c. 2720 Ma, probably by movement of melts and fluids into the upper, marginal zone of granulite facies rocks from deeper crust still being dehydrated. Retrogression during Late Archaean terrane assembly was in narrow reactivated zones of ductile deformation; in the Proterozoic it occurred with faulting and dyke emplacement.Geochemical data are presented for Early Proterozoic high-Mg and mafic dykes. A rare 2085 Ma microgranite dyke strongly enriched in incompatible trace elements was formed by partial anatexis of Archaean continental crust.  

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