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.

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.

scholarly journals Depositional constraints and age of metamorphism in southern India: U–Pb chemical (EMPA) and isotopic (SIMS) ages from the Trivandrum Block

2005 ◽  
Vol 142 (3) ◽  
pp. 255-268 ◽  
Author(s):  
M. SANTOSH ◽  
A. S. COLLINS ◽  
T. MORIMOTO ◽  
K. YOKOYAMA
Keyword(s):  
Electron Microprobe ◽  
Secondary Ion Mass Spectrometry ◽  
Granulite Facies ◽  
Southern India ◽  
Biotite Gneiss ◽  
Metamorphic History ◽  
Gondwana Supercontinent ◽  
Late Neoproterozoic ◽  
Formed Part ◽  
Tectonothermal Event

We report U–Pb electron microprobe (zircon and monazite) and Secondary Ion Mass Spectrometry (SIMS) U–Pb (zircon) ages from a granulite-facies metapelite and a garnet–biotite gniess from Chittikara, a classic locality within the Trivandrum Block of southern India. The majority of the electron-microprobe data on zircons from the metapelite define apparent ages between 1500 and 2500 Ma with a prominent peak at 2109±22 Ma, although some of the cores are as old as 3070 Ma. Zircon grains with multiple age zoning are also detected with 2500–3700 Ma cores, 1380–1520 mantles and 530–600 Ma outer rims. Some homogeneous and rounded zircon cores yielded late Neoproterozoic ages that suggest that deposition within the Trivandrum Block belt was younger than 610 Ma. The outermost rims of these grains are characterized by early Cambrian ages suggesting metamorphic overgrowth at this time. The apparent ages of monazite grains from this locality reveal multiple provenance and polyphase metamorphic history, similar to those of the zircons. In a typical case, Palaeoproterozoic cores (1759–1967 Ma) are enveloped by late Neoproterozoic rims (562–563 Ma), which in turn are mantled by an outermost thin Cambrian rim (∼515 Ma). PbO v. ThO*2 plots for monazites define broad isochrons, with cores indicating a rather imprecise age of 1913±260 Ma (MSWD=0.80) and late Neoproterozoic/Cambrian cores as well as thin rims yielding a well-defined isochron with an age of 557±19 Ma (MSWD=0.82). SIMS U–Pb isotopic data on zircons from the garnet–biotite gneiss yield a combined core/rim imprecise discordia line between 2106±37 Ma and 524±150 Ma. The data indicate Palaeoproterozoic zircon formation with later partial or non-uniform Pb loss during the late Neoproterozoic/Cambrian tectonothermal event. The combined electron probe and SIMS data from the metapelite and garnet–biotite gneiss at Chittikara indicate that the older zircons preserved in the finer-grained metapelite protolith have heterogeneous detrital sources, whereas the more arenaceous protolith of the garnet–biotite gniess was sourced from a single-aged terrane. Our data suggest that the metasedimentary belts in southern India may have formed part of an extensive late Neoproterozoic sedimentary basin during the final amalgamation of the Gondwana supercontinent.

Pre-Caledonian granulite and gabbro enclaves in the Western Gneiss Region, Norway: indications of incomplete transition at high pressure

2000 ◽  
Vol 137 (3) ◽  
pp. 235-255 ◽  
Author(s):  
M. KRABBENDAM ◽  
A. WAIN ◽  
T. B. ANDERSEN
Keyword(s):  
High Pressure ◽  
Shear Zones ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Ultrahigh Pressure ◽  
Western Gneiss Region ◽  
Ultrahigh Pressure Metamorphism ◽  
Mountain Belts ◽  
Orogenic Cycle ◽  
Highly Strained

The Western Gneiss Region of Norway is a continental terrane that experienced Caledonian high-pressure and ultrahigh-pressure metamorphism. Most rocks in this terrane show either peak-Caledonian eclogite-facies assemblages or are highly strained and equilibrated under late-Caledonian amphibolite-facies conditions. However, three kilometre-size rock bodies (Flatraket, Ulvesund and Kråkenes) in Outer Nordfjord preserve Pre-Caledonian igneous and granulite-facies assemblages and structures. Where these assemblages are preserved, the rocks are consistently unaffected by Caledonian deformation. The three bodies experienced high-pressure conditions (20–23 kbar) but show only very localized (about 5%) eclogitization in felsic and mafic rocks, commonly related to shear zones. The preservation of Pre-Caledonian felsic and mafic igneous and granulite-facies assemblages in these bodies, therefore, indicates widespread (∼ 95%) metastability at pressures higher than other metastable domains in Norway. Late-Caledonian amphibolite-facies retrogression was limited. The degree of reaction is related to the protolith composition and the interaction of fluid and deformation during the orogenic cycle, whereby metastability is associated with a lack of deformation and lack of fluids, either as a catalyst or as a component in hydration reactions. The three bodies appear to have been far less reactive than the external gneisses in this region, even though they followed a similar pressure–temperature evolution. The extent of metastable behaviour has implications for the protolith of the Western Gneiss Region, for the density evolution of high-pressure terranes and hence for the geodynamic evolution of mountain belts.

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.

Slave River delta: geomorphology, sedimentology, and Holocene reconstruction

1988 ◽  
Vol 25 (12) ◽  
pp. 1990-2004 ◽  
Author(s):  
Sandy Vanderburgh ◽  
Derald G. Smith
Keyword(s):  
River Delta ◽  
Delta Front ◽  
Average Width ◽  
Sand Waves ◽  
Isostatic Rebound ◽  
Great Slave Lake ◽  
Sand Body ◽  
Fort Smith ◽  
River Rapids ◽  
Slave River Delta

The Holocene Slave River delta (8300 km2) is a long (170 km), narrow (42 km average width) alluvial sand body, which extends north from the Slave River rapids at Fort Smith to Great Slave Lake, Northwest Territories. The delta is flanked by the Talston and Tethul rivers and Canadian Shield to the east and by the Little Buffalo River to the west. Wave-associated sedimentary structures in lithostratigraphic logs from river cutbanks indicate that the sandy delta was wave influenced. Most of the logs (34) consist of three facies: basal laminated mud (unknown thickness), interbedded mud and sand (2.5 m), and planar-tabular ripple sets interbedded with cross-laminated to flat-bedded sand (3.0–14.5 m).Eleven radiocarbon-dated wood samples from river cutbanks were used to reconstruct the delta paleoshoreface and to calculate the rate of progradation, which averaged 20.7 m/year from 8070 BP to the present. In the same period isostatic rebound of the delta region relative to the Liard River delta averaged 12 cm/km (a total rebound of 48 m). The data were calculated normal to the retreating Laurentide ice front.From the surface to depths of 59 m, the subaerial and subaqueous delta front exhibits barrier islands, lagoons, offshore bars or sand waves, tensional cracks, slumps and pressure ridges. The barriers and offshore bars consist of medium grain-sized sand, whereas the slumps and pressure ridges are interpreted as mud.

A Discussion on global tectonics in Proterozoic times - The Grenville Province in Helikian times: a possible model of evolution

1976 ◽  
Vol 280 (1298) ◽  
pp. 499-515 ◽  
Keyword(s):  
Continental Crust ◽  
Granulite Facies ◽  
Continental Collision ◽  
Canadian Shield ◽  
Grenville Province ◽  
East Central ◽  
Metasedimentary Rocks ◽  
Grenvillian Orogeny ◽  
Triangular Area ◽  
Global Tectonics

It is suggested that the Helikian (1650-1000 million years (Ma) ago) evolution of the Grenville Province in the Canadian Shield was marked by three events: emplacement of anorthosites around 1450-1500 Ma ago, rifting associated with opening of a proto-Atlantic ocean between 1200 and 1300 Ma ago, and continental collision responsible for the Grenvillian ‘orogeny’ about 1100-1000 Ma ago. Emplacement of rocks of the anorthosite suite (anorthosites and adamellites or mangerites) into continental crust was accompanied by formation of aureoles in the granulite facies. The Grenville Group was deposited in the southern part of the Province between 1300 and 1200 Ma ago and comprises marbles, clastic metasedimentary rocks and volcanics. It occupies a roughly triangular area limited on the northwest by the Bancroft—Renfrew lineament and on the southeast by the Chibougamau—Gatineau lineament. It is thought to have been accumulated in an aulacogen that would have developed along a fracture zone separating two basement blocks. The Grenvillian thermotectonic event may represent a Tibetan continental collision in the sense of Burke & Dewey. The suture zone would now be hidden under the Appalachians. Collision would cause reactivation of continental crust and renewed movement on pre-existing lineaments. The east—central part of the Grenville Province appears to have been more intensively reactivated than the western part.

scholarly journals Ba- and Ti-enriched dark mica from the UHP metasediments of the Seve Nappe Complex, Swedish Caledonides

Mineralogia ◽  
2015 ◽  
Vol 46 (1-2) ◽  
pp. 41-50
Author(s):  
Jarosław Majka ◽  
Łukasz Kruszewski ◽  
Åke Rosén ◽  
Iwona Klonowska
Keyword(s):  
Granulite Facies ◽  
Stability Field ◽  
Metasedimentary Rocks ◽  
High Pressure Metamorphism ◽  
Nappe Complex ◽  
Crystallochemical Formula ◽  
Seve Nappe Complex ◽  
The Mean ◽  
End Members ◽  
Parental Rock

AbstractWe report on the occurrence of peculiar Ba- and Ti-enriched dark mica in metasedimentary rocks that underwent high-pressure metamorphism in the diamond stability field followed by decompression to granulite facies conditions. The mica occurs as well-developed preserved laths in a quartzofeldspathic matrix. The mean concentrations of BaO and TiO2in the mica are 11.54 and 7.80wt%, respectively. The maximum amounts of these components are 13.38wt% BaO and 8.45wt% TiO2. The mean crystallochemical formula can be expressed as (K0.54Ba0.39Na0.02Ca0.01)Σ0.96(Fe1.37Mg0.85Ti0.50Al0.29Mn0.01Cr0.01)Σ3.03(Si2.59Al1.41)Σ4.00O10(OH1.30O0.66F0.02S0.01)Σ1.99, withoxyannite,oxy-ferrokinoshitaliteand siderophyllite as dominating end-members. Based on the petrographical observations, it is proposed that the dark mica was formed at a rather late stage in the evolution of the parental rock, i.e. under granulite facies conditions.

scholarly journals Investigation of Road Bank Failures based on Mineralogical Composition Studies in Kano-Abuja Road Northern, Nigeria

2018 ◽  
Vol 7 (4.34) ◽  
pp. 167
Author(s):  
Mohd Khairul Amri Kamarudin ◽  
Musa Garba Abdullahi ◽  
Mohd Hariri Arifin ◽  
Roslan Umar ◽  
Muhammad Hafiz Md Saad ◽  
...  
Keyword(s):  
Composition Studies ◽  
Sedimentary Rocks ◽  
Granite Gneiss ◽  
Mineralogical Composition ◽  
Poor Quality ◽  
Coarse Grained ◽  
Bank Failures ◽  
Mica Schist ◽  
The Road ◽  
Metasedimentary Rocks

This article investigated the general compositions of the areas (the road) including the geology, mineralogy, and geochemistry to explore the reason for the road failure. The zone is underlain basement (storm cellar) and sedimentary rocks of different textures, mineralogy, and geochemistry. The results implies that the areas that is most stable along the road portions is underlain by the granite-gneiss, granites, amphibole schist and quartz, schist and small sandstone while portions with the failures are underlain by mica schist, phyllite, and coarse-grained granite. It is apparently sure from this study that poor quality metasedimentary rocks constitute the formation of the failed portions. However, the high numbers of the sediment and sandstone present in the area that can easily be weathered due to the climate variation have increased the failure. In conclusion, the result will help the engineers during reconstruction of these parts need to be excavating deeply and replace with granite-gneiss, granites, amphibole schist and quartz for better result.  

Metamorphic evolution and zircon geochronology of early Proterozoic granulites in the Aravalli Mountains of northwestern India

2005 ◽  
Vol 142 (3) ◽  
pp. 287-302 ◽  
Author(s):  
A. B. ROY ◽  
ALFRED KRÖNER ◽  
P. K. BHATTACHAYA ◽  
SANJEEV RATHORE
Keyword(s):  
Granite Gneiss ◽  
Granulite Facies ◽  
Granulite Facies Metamorphism ◽  
Granulite Metamorphism ◽  
History Of ◽  
Single Zircon ◽  
Northwest India ◽  
Orogenic Cycle ◽  
Age Range ◽  
Rock Association

Granulites including a charnockite suite, mafic granulites, pelitic granulites, metanorite dykes and their retrograde varieties occur as discontinuous shear zone-bounded bodies within the Archaean basement comprising a granite gneiss–amphibolite–metasedimentary rock association in the central part of the Aravalli Mountains, northwest India. The entire suite, named the Sandmata Complex, preserves a complex history of tectonothermal evolution. Except for their strongly foliated margins, the granulite bodies are largely massive. Partial melting in the ‘country rocks’ led to the development of migmatite gneisses close to the contact of the granulite, a feature not as common in the rocks further away from the granulite contact. Geothermobarometry of massive granulites indicates Tmax>900°C and Pmax∼7.5 kbar. The retrograde granulites, which formed at lower amphibolite/upper greenschist-facies conditions, experienced channelized hydration reactions concomitant with shearing. These rocks locally appear as hornblende–biotite-bearing foliated granulite with or without Cpx or Opx. The rocks seem to have followed an inverse PTt path and have undergone an earlier phase of near-isobaric cooling. Our single zircon Pb–Pb ages indicate that the exhumation of granulites to the shallower amphibolite-facies levels with concomitant melting in the country rocks took place between 1690 Ma and 1621 Ma. Assuming that the granulite-facies metamorphism took place at around 1725 Ma, we relate the entire process of granulite metamorphism and exhumation covering an age range between 1725 and 1621 Ma to the rift basin opening stages of the Delhi Orogenic cycle that culminated at c. 1450 Ma.

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.

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