Granulite Facies Metamorphism in the Coast Range Crystalline Belt

1975 ◽  
Vol 12 (11) ◽  
pp. 1953-1955 ◽  
Author(s):  
Lincoln S. Hollister
Keyword(s):  
British Columbia ◽  
Granulite Facies ◽  
Coast Range ◽  
Geologic History ◽  
Granulite Facies Metamorphism ◽  
Mineral Assemblages ◽  
Facies Metamorphism ◽  
History Of

Mineral assemblages diagnostic of the granulite facies of metamorphism occur between Terrace and Prince Rupert, British Columbia. The estimated pressure (5–8 kb) and temperature (750–850 °C) of metamorphism are important constraints in unravelling the geologic history of the Coast Range batholithic complex.

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.

scholarly journals Trace Elements in Apatite as Genetic Indicators of the Evate Apatite-Magnetite Deposit, NE Mozambique

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1125
Author(s):  
Marek Slobodník ◽  
Veronika Dillingerová ◽  
Michaela Blažeková ◽  
Monika Huraiová ◽  
Vratislav Hurai
Keyword(s):  
Trace Elements ◽  
Inductively Coupled Plasma ◽  
Granulite Facies ◽  
Metasomatic Alteration ◽  
Partial Removal ◽  
Granulite Facies Metamorphism ◽  
Inductively Coupled ◽  
Mineral Assemblages ◽  
Granulite Complex ◽  
History Of

The Evate deposit is a Neoproterozoic (~590 Ma) magnetite-apatite-carbonate body emplaced parallel to foliation of the Monapo granulite complex in NE Mozambique. A complicated history of the deposit is recorded in apatite textures visualized in cathodoluminescence (CL) images. In spite of different solid and fluid inclusions, mineral assemblages, and the CL textures, electron probe microanalyses indicate relatively consistent apatite compositions corresponding to fluorapatite (XF = 0.51–0.73, XOH = 0.21–0.47, XCl = 0.02–0.06) with limited belovite- and cesanite-type substitutions. Laser ablation inductively coupled plasma mass spectrometric analyses show that apatites from unaltered magnetite-forsterite-spinel ores are depleted in Y, REE, Ba, and Sr compared to apatites from carbonate-anhydrite ores. Hydrothermally overprinted apatites with complex patchy domain CL textures are enriched in Y-REE in greenish-grey zones, Fe-U-Th in blue zones, and Mn-Sr-Ba in brown domains. Observed CL-emissions in the Evate apatites result from very subtle variations in REE, Mn, and U contents controlled by the variability of redox conditions. The decreased Th:U ratio in the hydrothermally overprinted apatites reflects the oxidation and partial removal of U4+ from the apatite structure during the interaction with oxidizing aqueous fluids capable of transporting U6+. Flat, LREE (La-Sm)-enriched chondrite-normalized patterns with Eu/Eu* = 0.7–1.4 and Ce/Ce* = 0.9–1.5, together with concentrations of diagnostic trace elements (Sr, Mn, Y, REE) are consistent with apatites from magmatic carbonatites and phoscorites. This study corroborates that the Evate deposit is a post-collisional orogenic carbonatite genetically linked with mafic plutonic rocks intruding the Monapo granulite complex after granulite-facies metamorphism, and later overprinted by intensive hydrothermalism. The Evate apatite is peculiar in retaining its pristine magmatic signature despite the extensive hydrothermal-metasomatic alteration accompanied by dissolution-reprecipitation.

Tectonic history of the Grenville-age Trenton Prong inlier, Central Appalachians, USA: Evidence from SHRIMP U–Pb geochronology

2021 ◽  
Author(s):  
Richard Volkert ◽  
John N. Aleinikoff
Keyword(s):  
Granulite Facies ◽  
Small Population ◽  
Local Source ◽  
Thermal Activity ◽  
Granulite Facies Metamorphism ◽  
Magmatic Arc ◽  
Tectonic History ◽  
Facies Metamorphism ◽  
Minimum Age ◽  
History Of

New zircon U–Pb geochronologic data from the Grenville-age Trenton Prong provide information on the age of magmatism, timing of metamorphism, and post-metamorphic history of the inlier. Diorite gneiss (1318 ± 13 Ma) of the Colonial Lake Suite temporally correlates to magmatic arc sequences that formed along the eastern margin of Laurentia at <1.4 Ga. Metasedimentary gneisses yielded detrital zircon ages of ca. 1319-1133 Ma and ca. 1370-1207, consistent with sediment derived from a similar local source of Laurentian affinity. A small population of zircon (either detrital or igneous in origin) in one sample yielded ages of ca. 1074-1037 Ma. Possible interpretations for their formation are explored. Ca. 1060 Ma overgrowths on zircon in the northern part of the inlier constrain the timing of granulite-facies metamorphism to the Ottawan phase of the Grenvillian Orogeny. The undeformed Assunpink Creek Granite (1041 ± 6 Ma) intruded country rocks as small bodies of late-orogenic syenogranite. It provides a minimum age for amphibolite-facies metamorphism and Ottawan orogenesis elsewhere in the inlier. Regionally, zircon rim ages of ca. 1010–960 Ma record continued thermal activity during the Rigolet phase of the orogen that resulted in migmatization of paragneiss at ca. 1004 Ma and juxtaposition of upper- and mid-crustal rocks during orogenic collapse. The lithologic ages and tectonic history of the Trenton Prong correlate to those in other Appalachian Mesoproterozoic inliers, and parts of the Canadian Grenville Province, confirming it is not an exotic terrane that was accreted to eastern Laurentia during Grenvillian orogenesis.

Regional geothermobarometry in the granulite facies terrane of South India

1983 ◽  
Vol 73 (4) ◽  
pp. 221-244 ◽  
Author(s):  
M. Raith ◽  
P. Raase ◽  
D. Ackermand ◽  
R. K. Lal
Keyword(s):  
South India ◽  
Analytical Data ◽  
Granulite Facies ◽  
Critical Discussion ◽  
Granulite Facies Metamorphism ◽  
Northern Margin ◽  
Mineral Equilibria ◽  
Metamorphic History ◽  
Facies Metamorphism ◽  
History Of

ABSTRACTIn the southern part of the Archaean craton of South India, an approximately 3.4–2.9 b.y. old migmatite–gneiss terrane (Peninsular gneiss complex) has been subjected to granulite facies metamorphism about 2.6 b.y. ago. During this event, the extensive charnockite-khondalite zone of southern India developed. A younger metamorphism (Proterozoic?) led to retrogression of the charnockites and khondalites, mainly under the conditions of the amphibolite facies.The physical conditions of metamorphism have been evaluated by applying methods of geothermobarometry to the widespread charnockitic assemblages with garnet, orthopyroxene, clinopyroxene, plagioclase, and quartz. The interpretation of the P–T estimates includes a critical discussion of potential error sources, e.g. errors of the analytical data and the calibrations of the models, and takes into account the complex metamorphic history of the rocks and the kinetics of the mineral equilibria.P-T estimates were obtained for seven subareas from the rim compositions of the coexisting minerals: Shevaroy Hills 680±55°C—7·4±1 kb; Kollaimalai area 680±40°C—8·6± 1 kb; Nilgiri Hills 680±90°C—6·6±0.8kb (upland massif) and 705±60°C—9·3±0.8 kb (northern margin); Bhavani Sagar area 650±50°C—7·2± 1 kb; Sargur-Mysore area 690±60°C—7·6 kb; Bangalore-Kunigal-Satnur area 760±50°C—6 kb. Except for the last subarea, the P-T model data reflect the conditions of a late annealing stage probably related to the retrogressive metamorphism. Conditions near the peak of granulite facies metamorphism (730–800°C—6·5–9·5 kb) are recorded by the core compositions of the minerals. Although a rather uniform cooling history of the main part of the charnockite-khondalite terrane is suggested from the temperature data, differential uplift of smaller blocks is indicated by the regional variation of the pressure data.

Ilmenite-magnetite geothermometry in trondhjemites from the Scourian complex of NW Scotland

1979 ◽  
Vol 43 (325) ◽  
pp. 165-170 ◽  
Author(s):  
Hugh R. Rollinson
Keyword(s):  
High Temperature ◽  
Oxygen Fugacity ◽  
Large Scale ◽  
Granulite Facies ◽  
Small Scale ◽  
Granulite Facies Metamorphism ◽  
Facies Metamorphism ◽  
Different Temperatures ◽  
History Of ◽  
Lower Temperature

SynopsisThe crystallization history of four trondhjemite samples from the Scourian complex, NW Scotland, has been investigated using composite ilmenite-magnetite grains. A variety of compositions are present both as large- and small-scale exsolution lamellae, which can be used to unravel the complex cooling history of these rocks. The samples were collected near Upper Badcall, Sutherland, where intrusive trondhjemite sheets 1–2 m thick cut banded gabbro. The trondhjemites have a complex history that includes four stages: magmatic intrusions, granulite facies metamorphism, hydration and retrogression to amphibolite facies, and slow cooling with uplift.Ilmenite-magnetite grains in samples HR. 49, 53, 86 display a complex exsolution pattern (fig. 1A). An original titanomagnetite exsolved into large-scale (up to 50 µm wide) ilmenite-magnetite lamellae from which have subsequently exsolved small-scale lamellae (c.4 µm wide) parallel to the earlier lamellae. The ilmenite-magnetite pairs form subhedral grains in a granoblastic aggregate of plagioclase and quartz. A little biotite overgrows some oxide grains. Ilmenite-magnetite grains in sample HR. 56 are composed of broad-zoned lamellae (fig. 1B); small-scale exsolution lamellae are absent. Silicate-grain boundaries are irregular and lower-temperature minerals (chlorite and carbonate) are more common.The experimental results of Buddington and Lindsley (1964) allow the equilibration temperature and oxygen fugacity of coexisting ilmenite and magnetite to be determined from their chemical composition. Subsequent workers have shown that it is possible to determine liquidus temperatures and oxygen fugacity for volcanic rocks (Carmichael, 1967; Anderson, 1968a). Slowly cooled igneous and metamorphic rocks, however, have continued to equilibrate below their solidus and show a range of temperatures and oxygen-fugacity conditions (Anderson, 1968b; Duchesne, 1972; Oliver, 1978; Bowles, 1976, 1977).This paper presents 42 new pairs of analyses made by electron-probe microanalysis, from 13 composite ilmenite-magnetite grains (Table I). Mole % ulvöspinel and R2O3 values have been calculated using the method of Carmichael (1967) and used to determine temperature and oxygen fugacity at equilibration, from the experimental data of Buddington and Lindsley (1964).By using a scanning electron beam it is possible to obtain the average composition of a broad lamella that contains smaller exsolution lamellae in order to estimate its composition prior to exsolution. A −log10ƒo2ν.T °C plot of lamellae whose original composition has been determined in this way shows that they lie on a curve slightly above the Ni-NiO buffer between 1010 and 850 °C (fig. 2). Temperatures of the order of 1000 °C are probably magmatic temperatures since they are higher than is normally recorded for granulite-facies metamorphism; 850 °C is interpreted as the blocking temperature below which diffusion was unable to occur to form large-scale lamellae. A comparison may be made between this oxygen-fugacity curve and the curves determined by Carmichael (1967) (fig. 2) for acid lavas coexisting with different phenocryst phases. If an adjustment is made for the differences in bulk composition and pressure, some correspondence between the analysed points and the curve for hydrous silicates would be expected since hornblende is the earliest Fe-bearing silicate seen in the trondhjemite. However, correspondence is not found, implying that amphibole did not control the oxygen fugacity, either because it was not the main Fe-bearing phase at magmatic temperatures, or because the oxygen fugacity was externally controlled.After the formation of broad high-temperature lamellae Ti diffusion continued on a smaller scale (2–3 µm) so that the lower-temperature history of these grains can be considered in terms of many independent microsystems. Limited diffusion continued across the boundaries of and within early magnetite and ilmenite lamellae. The compositions of small-scale exsolution lamellae in ilmenite and magnetite hosts have been determined. Lamellae of ilmenite in magnetite from different grains define separate log ƒo2-T curves for different grains. Lamellae of magnetite in ilmenite equilibrated at lower temperatures and oxygen fugacities. Individual microsystems have equilibrated at different temperatures and oxygen fugacities within the same grain and similar microsystems in different grains have equilibrated at different temperatures and oxygen fugacities, suggesting that the rock itself has become a series of independent closed systems.The compositions of phases either side of early high-temperature lamellar boundaries have been measured. Analyses from different rocks yield different oxygen-fugacity curves in the same temperature range (765 to 610 °C). Higher temperatures were obtained for grains 49/3 and 86/4, which have exsolved into broad-zoned lamellae with no small-scale exsolution. The sense of the zoning is such that R2O3 in ilmenite decreases as it approaches magnetite. The equilibration temperature and ƒo, at the grain boundary increases from the centre of the grain to the edge.In HR. 56 ilmenite magnetite grains show broad-zoned lamellae with no late small exsolution lamellae. The sense of zoning is such that magnetite grains increase in ulvöspinel content towards ilmenite and ilmenite decreases in R2O3 towards magnetite (fig. 1B). Even though the grains are in disequilibrium, it is assumed that equilibrium was at least established close to the boundary between lamellae. Equilibration temperatures thus obtained are between 410 and 430 °C at an ƒo2 between the Ni-NiO and QFM buffers. Ilmenite-magnetite grains coexist with a biotite richer in Ti and a hornblende depleted in Fe relative to those in samples yielding higher oxide temperatures suggesting that there was continuous Fe-Ti exchange between oxides and silicates as well as between ilmenite and magnetite.

Iron-titanium oxides as an indicator of the role of the fluid phase during the cooling of granites metamorphosed to granulite grade

1980 ◽  
Vol 43 (329) ◽  
pp. 623-631 ◽  
Author(s):  
Hugh R. Rollinson
Keyword(s):  
Fluid Phase ◽  
Granulite Facies ◽  
Granitic Rocks ◽  
Titanium Oxides ◽  
Cooling History ◽  
Granulite Facies Metamorphism ◽  
North West ◽  
Facies Metamorphism ◽  
History Of

SummaryA detailed electron probe study of irontitanium oxide intergrowths from slowly cooled granitic rocks from the granulite grade, Archaean Scourian complex of north-west Scotland has yielded a wealth of information about magmatic and metamorphic temperatures, subsolidus cooling, and the behaviour of the fluid phase during cooling. Five stages are documented in the cooling history of granites and trondhjemites which include: (i) magmatic-subsolidus cooling (1035 °C–890 °C); (ii) granulite facies metamorphism and the accompanied expulsion of a hydrous fluid phase (890 °C–830 °C); (iii) subsolidus cooling following the peak of the granulite facies metamorphism (830 °C–660 °C); (iv) the localized reintroduction of water into the rocks during retrogression (660 °C–530 °C) and (v) subsolidus cooling and re-equilibration in the presence of a finite amount of H2O (530 °C–320 °C).

Metamorphic P–T conditions and retrograde path of high-pressure Barrovian metamorphic zones near Cairn Leuchan, Caledonian orogen, Scotland

2013 ◽  
Vol 151 (3) ◽  
pp. 559-571 ◽  
Author(s):  
K. AOKI ◽  
B. F. WINDLEY ◽  
S. MARUYAMA ◽  
S. OMORI
Keyword(s):  
High Pressure ◽  
Granulite Facies ◽  
Metamorphic Rocks ◽  
Published Data ◽  
Chemical Compositions ◽  
Garnet Amphibolite ◽  
Granulite Facies Metamorphism ◽  
High Pressure Granulite ◽  
Mineral Assemblages ◽  
Facies Metamorphism

AbstractThe metamorphic P–T conditions and associated relationships of the Barrovian zones near Glen Muick were re-examined by focusing on the petrology and thermodynamics of rocks at Cairn Leuchan, where garnetite lenses and layers occur in surrounding garnet amphibolite in the highest-grade sillimanite zone. The representative mineral assemblages in the garnet-rich lenses and garnet amphibolite are garnet + quartz + clinopyroxene + plagioclase + amphibole ± epidote, and garnet + amphibole + quartz + plagioclase ± clinopyroxene ± epidote, respectively. The chemical compositions of constituent minerals are the same in both garnetite and garnet amphibolite. The metamorphic P–T conditions of these rocks were estimated by thermodynamic calculations. The results show that the rocks underwent high-pressure granulite facies metamorphism at P = c. 1.2–1.4 GPa and T = c. 770–800°C followed by amphibolite facies metamorphism at P = c. 0.5–0.8 GPa and T = c. 580–700°C. Integration of our new results with previously published data suggests that the retrograde P–T trajectory of the highest-grade Barrovian metamorphic rocks marks a temperature decrease during decompression from a crustal depth of the high-pressure granulite facies, which is much deeper than previously considered.

Petrology of the Cormacks Lake Complex, Newfoundland: decompressional reaction relations in cordierite+orthoamphibole-bearing gneisses and associated rocks

2000 ◽  
Vol 64 (4) ◽  
pp. 711-724 ◽  
Author(s):  
J. V. Owen ◽  
J. D. Greenough
Keyword(s):  
Granulite Facies ◽  
Moderate Pressure ◽  
High Grade ◽  
Granulite Facies Metamorphism ◽  
Mineral Assemblages ◽  
Facies Metamorphism ◽  
Regional Tectonic ◽  
Tectonic Reconstructions

AbstractCordierite+orthoamphibole (Crd+Oam)-bearing gneisses in the Cormacks Lake complex are regionally associated with metapelites containing prismatic sillimanite and K-feldspar, metabasites that locally contain metamorphic orthopyroxene, and other high-grade rocks in the Central Gneiss (Dashwoods) subzone, in the southwestern Newfoundland Appalachians. Retrograde features formed at the expense of the granulite-facies assemblages are ubiquitous. For example, in some migmatitic rocks, garnet is resorbed by Crd+Oam, and in metapelites, cordierite separates corroded garnet and sillimanite. Mineral thermobarometry suggests that, following granulite-facies metamorphism (T<785°C, P<7.5 kbar), retrogression occurred as the Cormacks Lake gneisses cooled through Mg-Fe diffusional blocking temperatures as they decompressed to a pressure of ∼3–4 kbar. Given the absence of Barrovian (or higher pressure) mineral assemblages in the metapelites, regional tectonic reconstructions involving the thrusting of a neighbouring terrane (Notre Dame subzone) over the Central Gneiss subzone appear to be supported only by the moderate pressure determined for the granulite facies event. Although scarcely discernible given re-equilibration effects and the imprecision of thermobarometers, subsequent decompression nonetheless had a marked impact on the mineralogy of the gneisses.

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