Figure 9a plots the mean results from Table 7 with respect to the granulite-facies-limiting reactions from Figs 1 and 2. A. An unanswered question of fundamental importance to the use of Al solubility-based thermobarometry is the nature and controls of zoning of Al in Opx (e.g. We have applied RCLC to 18 incipient charnockite localities in the literature (six of the seven Karnataka–Tamil Nadu samples in the Appendix, eliminating one outlier, and samples 83-123, 4-10a, 121-166, 141-201, M-4, 23, 25, K18-6a, K18-17, 147-214, TN3-1 and TN21-4 from the Kerala Khondalite Belt). 10a compared with the limiting P–T stability fields for Kfs + Sil, Grt + Crd and Opx. Lack of reported Grt + Opx-bearing assemblages in Zone VI does not permit estimation of peak temperatures by our recorrection method. †Raith et al. M, mafic; I, intermediate; A, aluminous. (1996) retrieved oxygen isotope temperatures >900°C that are consistent with the mineral assemblage stabilities. Under those conditions, quartz can flow plastically and feldspar cannot. (1996). The mean difference between the corrected Fe–Mg–Al and uncorrected Fe–Al temperatures (points B and C in Fig. The mean and 95% confidence limit on the mean of the temperature estimates is 827 ± 18°C for a pressure range of 6–8 kbar, not significantly different from the equivalent values for all intermediate granulites (841 ± 11°C; Table 7). Recalculation of the same samples using RCLC reveals a sharp contrast between a lower P–T (∼800–850°C, 6 kbar) central zone with numerous incipient charnockite localities, a northern marginal zone where extreme P–T conditions (>950°C, 9–10 kbar) are found, and a southern marginal zone where less extreme but still elevated temperatures of 850–950°C are found (Fig. 3), grouped according to the three compositional types of granulite. & Fullsack, P. (, Jamieson, R. A., Beaumont, C., Nguyen, M. H. & Lee, B. Geochronology and phase equilibria modelling of ultra-high temperature sapphirine + quartz-bearing granulite at Usilampatti, Madurai Block, Southern India. These values are of a similar magnitude to those found by Fitzsimons & Harley (1994), Pattison & Bégin (1994) and Chacko et al. & McDonough, M. J. Granulite facies (MP/HT) The granulite facies is the highest grade of metamorphism at medium pressure. For these localities, mean temperatures of ∼830°C from RCLC are well below the temperatures necessary for fluid-absent melting, suggesting that aH2O in the infiltrating fluid was significantly lower than in the host gneisses. The rather high mean corrected Fe–Mg–Al temperature for the aluminous granulites may reflect a combination of sample bias (several samples from ultra-high-temperature localities) and possible temperature overestimation for samples in which there is non-negligible Fe3+. Harley, 1984; Lee & Ganguly, 1988). (, Valley, J. W., Bohlen, S. R., Essene, E. J. Metamorphism under very high pressures and relatively low temperatures, such as occurs along subduction zones, constitutes the Blueschist Facies because basalt and shale metamorphosed under these â¦ The gneisses did not undergo fluid-absent melting until temperatures in excess of 900°C (at P ≥ 6 kbar) were reached. The temperature and pressure differences are strongly correlated because of the dependence of the pressure estimate on the temperature. (a, d, g) Uncorrected Fe–Al temperatures – uncorrected Fe–Mg temperatures. (1993), which corrects for the effects of retrograde isotope exchange. The most common mineral assemblage of granulite facies consists of antiperthitic plagioclase, alkali feldspar containing up to 50% albite and Al 2 O 3-rich pyroxenes. Abbreviations for the terrains are listed in Table 8. Assuming that Fe–Mg always closes at lower temperature than Al, the most likely explanations are: (1) Fe–Mg diffusion is slower in Ca-rich garnets than in Ca-poor garnets, resulting in a smaller temperature gap between closure of Fe–Mg and Al; (2) the rocks experienced retrograde net-transfer reactions (Spear & Florence, 1992), leading to spuriously high Fe–Mg temperatures; (3) the parts of the Grt and Opx analyzed were not in equilibrium before late Fe–Mg exchange; (4) some of the analytical data for the generally low Al concentrations in Opx in these rocks are in error (too low); (5) the thermodynamic model for Al solubility in Opx loses accuracy at low $$\mathit{X}_{\mathrm{Al}}^{\mathrm{opx}}$$ ⁠. Our view is that if demonstrable and systematic errors can be corrected for it is worth while to do so, especially when in a number of cases the difference becomes significant (e.g. The scatter of P–T results using our method calls into question the reliability of any individual P–T estimate, and suggests that to be confident of a P–T estimate for a given area, many samples need to be analyzed. The concept of metamorphic facies is a systematic way to look at the mineral assemblages in rocks and determine a potential range of pressure and temperature â¦ Analytical inaccuracy seems unlikely as a general explanation because in studies in which several samples were analyzed using the same procedure (e.g. A counter-argument to the generality of this inference comes from the experimental study by Nair & Chacko (2002) on dehydration melting of the host gneisses to some of the southern India incipient charnockite localities. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. ○, uncorrected Fe–Mg method; •, corrected Fe–Mg–Al method. The facies is named for zeolites, strongly hydrated tectosilicates. The >950°C temperatures of the northern zone can be confirmed in a limited number of samples with exsolved feldspars. The most common mineral assemblage of granulite facies consists of antiperthitic plagioclase, alkali feldspar containing up to 50% albite and Al 2 O 3-rich pyroxenes. In granulites that show isobaric cooling paths and that may have formed along anti-clockwise P–T paths, the heat source for the metamorphism is usually ascribed to mafic magmatic underplating (e.g. In these experiments, melting began between 780 and 830â°C by the incongruent breakdown of biotite to produce quartz-saturated, granulite-facies residual mineral assemblages in equilibrium with H2O-undersaturated granitic melt. Many granulite temperature estimates in the literature are based on FeâMg fractionation between coexisting phases such as garnet, biotite, cordierite, orthopyroxene and clinopyroxene [Grt, Bt, Crd, Opx, Cpx; abbreviations of Kretz (1983)].Several studies have provided evidence that the closure temperature for FeâMg exchange between these phases is below peak granulite-facies temperatures â¦ Read More on This Topic metamorphic rock: Granulite facies There is general agreement, however, on two points 1) Granulites represent unusually hot conditions â¢ Temperatures > 700 o C (geothermometry has yielded some very high temperatures, even in excess of 1000 o C) Granulite Facies: This facies represents the maximum temperature conditions of regional metamorphism found in Archaean terrains. Pressure-temperature-time paths. As discussed above, we consider the uncorrected Fe–Al P–T estimates to be more reliable for these samples. 1), whereas the uncorrected Fe–Al and corrected Fe–Mg–Al temperatures (890 ± 17 and 854 ± 15°C) are consistent with Opx stability (Fig. orthopyroxene + clinopyroxene + â¦ Calculated temperatures taking account of stoichiometrically determined Fe3+ in Opx are on average 44°C lower for the whole sample suite but reveal the same regional pattern (Fig. This research was supported by NSERC Discovery Grants 0037233 to D.R.M.P. One of the classic prograde amphibolite–granulite transitions is represented by the Acadian metamorphic high in central Massachusetts. In rocks of basaltic composition, the granulite facies is an anhydrous facies that results from progressive...â¦, Metamorphism, mineralogical and structural adjustments of solid rocks to physical and...â¦, Amphibolite facies, one of the major divisions of the mineral-facies classification of...â¦. 9a). The higher the peak temperature is above the closure temperature for Fe–Mg exchange, the greater the expected difference between the calculated Al-solubility and Fe–Mg exchange temperatures. Consider the case of a shear zone in the greenschist metamorphic facies, that is, in the temperature range of approximately 300â450 °C. Thus mineralization at Griffinâs Find must have been introduced prior to granulite facies metamorphism. Figures 6 and 8a and b show that these results correspond to the generally low $$X_{\mathrm{Al}}^{\mathrm{opx}}$$ in the more Ca-rich mafic samples. (b) Comparison of mean P–T results of individual granulite terrains with the limiting granulite facies-limiting reactions from Fig. Locally variable aH2O in the absence of fluid infiltration is not a tenable explanation if the peak mineral assemblages were developed by partial melting because aH2O is internally buffered by the mineral + melt assemblage. Even though low-aH2O fluid infiltration appears to have triggered the production of Opx in these localities, the amount by which aH2O in the fluid was lower than ambient values in the host gneisses might have been rather modest if the host gneisses were close to a temperature where they would produce Opx by closed-system dehydration melting. Granulite facies, one of the major divisions of the mineral facies classification of metamorphic rocks, the rocks of which formed under the most intense temperature-pressure conditions usually found in regional metamorphism. 1. Concomitantly, it reduces the P–T interval between ‘ordinary’ granulite-facies metamorphism and ultra-high-temperature metamorphism (Harley, 1998a; Fig. Corrected Fe–Mg–Al: point C in Fig. & Arai, M. (, Kroll, H., Evangelakakis, C. & Voll, G. (, Lal, R. K., Ackermand, D. & Upadhyay, H. (, Lamb, R. C., Smalley, P. C. & Field, D. (, Lasaga, A. C., Richardson, S. M. & Holland, H. D. (, Luth, W. C., Jahns, R. H. & Tuttle, O. F. (, McFarlane, C. R. M., Carlson, W. D. & Connelly, J. N. (, Munyanyiwa, H., Touret, J. L. R. & Jelsma, H. A. 9). In the southern zone, Braun et al. (b) $$X_{\mathrm{Ca}}^{\mathrm{Grt}}$$ ⁠. Fig. Reactions are numbered as in the text and Fig. Our results are also comparable with those calculated with the oxygen isotope thermometry method of Farquhar et al. (a) Map of isograds and metamorphic isotherms in the Adirondacks, from Bohlen et al. The Bohlen et al. 16, with values above the gap largely restricted to mafic mineral assemblages containing either or both of the calcic mafic phases Hbl and Cpx, and values below the gap restricted to intermediate and aluminous mineral assemblages lacking these phases. (, Holtz, F., Becker, A., Freise, M. & Johannes, W. (, Iyer, S. S., Choudhuri, A., Pattison, D. R. M. & De Paoli, G. R. (, Jamieson, R. A., Beaumont, C., Vanderhaeghe, O. The southern Indian incipient charnockites may therefore represent sporadically developed, slightly lower-temperature, fluid-triggered granulite ‘fronts’ that develop locally a little down-grade of the main expanse of granulite, the latter controlled largely by magmatic and partial melting processes. The pyroxene-hornfels facies is the contact-metamorphic facies with the highest temperatures and is, like the granulite facies, characterized by the mineral orthopyroxene. The minerals present in a granulite will vary depending on the parent rock of the granulite and the temperature and pressure conditions experienced during metamorphism. (, Griffin, W. L., McGregor, V. R., Nutman, A., Taylor, P. N. & Bridgwater, D. (, Grove, T. L., Baker, M. B. Granulite facies The granulites facies is determined by the lower temperature boundary of 700 +/â 50 °C and the pressure range of 2â15 kb. Temperature or pressure differences between methods vs absolute temperatures or pressures, grouped according to compositional type (aluminous, intermediate, mafic). Aluminous metapelites were equilibrated at ~770â790°C, whereas twoâpyroxene granulite and garnetâorthopyroxeneâbiotite gneiss record distinctly higher conditions of ~830â850°C. Table 8 provides a summary of mean P–T results for 24 terrains with six or more samples. Earlier studies based on Fe–Mg exchange methods (e.g. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. (, Braun, I., Raith, M. & Ravindra Kumar, G. R. (, Chacko, T., Kumar, G. R. R. & Newton, R. C. (, Conrad, W. K., Nicholls, I. & Boettcher, A. L. (, Bohlen, S. R., Valley, J. W. & Essene, E. J. We caution that the P–T estimates in Table 7 and Fig. the Nilgiri Hills datasets of Raith et al. 1. & Lamb, W. (, White, R. W., Powell, R., Holland, T. J. $$X_{\mathrm{Ca}}^{\mathrm{Grt}}$$ = Ca/(Ca + Fe + Mn + Mg). The same rock type metamorphosed at more moderate pressures and temperatures in the range of 400â500 °C (752â932 °F) would contain abundant chlorite and actinolite, minerals that are green both in hand sample and under the microscope, and would be referred to as a greenschist. (1990) and Srikantappa et al. The most common mineral assemblage of granulite facies consists of antiperthitic plagioclase, alkali feldspar containing up to 50% albite and Al 2 O 3 -rich pyroxenes. The central conclusion of our study is that a significant number of thermobarometry-based temperature estimates for granulites over the past 30 years are too low and are therefore misleading. (, Janardhan, A. S., Newton, R. C. & Hansen, E. C. (, Komatsu, M., Toyoshima, T., Osanai, Y. Valley et al. 11c). Within Zone VI, Opx + Cpx + Pl assemblages occur in metabasites. These isograds are represented approximately by reactions (4), (5) and (1), respectively. The granulite facies PâT field of interest (0.5â1.3 GPa, 700°â>1000 °C, respectively), can be divided into three sub-facies (e.g., Brown, 2007a) , namely: (1) HP granulites, transitional to eclogites, (2) HT granulites, grading to (3) ultrahigh-temperature (UHT) granulites when the temperature exceeds 900° (e.g., Kelsey, 2008). At the upper limit of the facies, migmatite formation may occur. Thus mineralization at Griffin{\textquoteright}s Find must have been introduced prior to granulite facies metamorphism. Even with X-ray maps, non-central sectioning of Opx grains is an important factor to consider, given the generally small core–rim variation in Al content of individual Opx grains (typically ∼1–2 wt %) and the strong temperature dependence on these small changes. A puzzling aspect of the Adirondacks results in Table 8 is the higher mean temperature from Fe–Mg exchange than from the Al-solubility-based methods, which may be due to some or all of the factors discussed above for mafic granulites in general. $$X_{\mathrm{Al}}^{\mathrm{opx}}$$ = Al/2 for a six-oxygen orthopyroxene formula. A characteristic mineral for this facies and the pyroxene- hornblende facies is orthopyroxene. It is believed that the granulite facies, introduced by ESKOLA (1939), originates through a further rise in temperature after the field of the highest-temperature subfacies of the almandine-amphibolite facies has been traversed. (, Riciputi, L. R., Valley, J. W. & McGregor, V. R. (, Santosh, M., Harris, N. B. W., Jackson, D. H. & Mattey, D. P. (, Schumacher, J. C., Hollocher, K. T., Robinson, P. & Tracy, R. J. The granulite facies is determined by the lower temperature boundary of 700 +/â 50 °C and the pressure range of 2â15 kb. 9.9) provided the following approximate temperature boundaries between the zones, based on Grt–Bt Fe–Mg exchange thermometry assuming a pressure of 6 kbar: III–IV, 640°C; IV–V, 670°C; V–VI, 690°C. We consider that the overall agreement between the Al-solubility-based thermobarometry and the experimental constraints on Opx stability lends support to both approaches, and points to retrograde exchange as the most likely explanation for the discrepancy between the phase equilibria and geothermobarometry discussed in the Introduction. 9b with respect to the granulite-facies-limiting reactions from Figs 1 and 2. E-mail: Search for other works by this author on: $\mathrm{Hbl}\ +\ \mathrm{Qtz}\ {\pm}\ \mathrm{Grt}\ =\ \mathrm{Opx}\ +\ \mathrm{Cpx}\ {\pm}\ \mathrm{Pl}\ +\ \mathrm{L}.$, $\mathrm{Hbl}\ +\ \mathrm{Pl}\ +\ \mathrm{Qtz}\ =\ \mathrm{Grt}\ +\ \mathrm{Cpx}\ +\ \mathrm{L}$, $\mathrm{Bt}\ +\ \mathrm{Qtz}\ {\pm}\ \mathrm{Pl}\ =\ \mathrm{Opx}\ +\ \mathrm{L}\ {\pm}\ \mathrm{Grt}\ {\pm}\ \mathrm{Crd}\ {\pm}\ \mathrm{Kfs}.$, $\mathrm{Ms}\ +\ \mathrm{Qtz}\ {\pm}\ \mathrm{Pl}\ =\ \mathrm{Al}_{2}\mathrm{SiO}_{5}\ +\ \mathrm{L}\ {\pm}\ \mathrm{Kfs}$, We therefore prefer to define the amphibolite–granulite transition in metapelites by mineral associations that develop closer (both spatially in the field and, by extension, in pressure and temperature) to the first appearance of Opx in mafic and intermediate compositions, namely, Grt + Crd + Kfs (at pressures below ∼9 kbar) or Opx + Al, $\mathrm{Bt}\ +\ \mathrm{Sil}\ +\ \mathrm{Qtz}\ {\pm}\ \mathrm{Pl}\ =\ \mathrm{Grt}\ +\ \mathrm{Crd}\ +\ \mathrm{L}\ {\pm}\ \mathrm{Kfs}$, $\mathrm{Bt}\ +\ \mathrm{Grt}\ +\ \mathrm{Qtz}\ {\pm}\ \mathrm{Pl}\ =\ \mathrm{Opx}\ +\ \mathrm{Al}_{2}\mathrm{SiO}_{5}\ +\ \mathrm{L}\ {\pm}\ \mathrm{Kfs}.$, The thermodynamic system used in RCLC is summarized in, $\begin{array}{llll}\mathrm{Fe}_{3}\mathrm{Al}_{2}\mathrm{Si}_{3}\mathrm{O}_{12}&+\ 3\ \mathrm{MgSiO}_{3}&=\ \mathrm{Mg}_{3}\mathrm{Al}_{2}\mathrm{Si}_{3}\mathrm{O}_{12}&+\ 3\ \mathrm{FeSiO}_{3}\\\mathrm{in\ Grt}&\mathrm{in\ Opx}&\mathrm{in\ Grt}&\mathrm{in\ Opx}\end{array}$, $\begin{array}{lll}\mathrm{Fe}_{3}\mathrm{Al}_{2}\mathrm{Si}_{3}\mathrm{O}_{12}&=\ 3\ \mathrm{FeSiO}_{3}&+\ \mathrm{Al}_{2}\mathrm{O}_{3}\\\mathrm{in\ Grt}&\mathrm{in\ Opx}&\mathrm{in\ Opx}\end{array}$, $\begin{array}{lllll}2\ \mathrm{Fe}_{3}\mathrm{Al}_{2}\mathrm{Si}_{3}\mathrm{O}_{12}&+\ \mathrm{Ca}_{3}\mathrm{Al}_{2}\mathrm{Si}_{3}\mathrm{O}_{12}&+\ 3\ \mathrm{SiO}_{2}&=\ 3\ \mathrm{CaAl}_{2}\mathrm{Si}_{2}\mathrm{O}_{8}&+\ 6\ \mathrm{FeSiO}_{3}\\\mathrm{in\ Grt}&\mathrm{in\ Grt}&\mathrm{Qtz}&\mathrm{in\ Pl}&\mathrm{in\ Opx}\end{array}$, $$X_{\mathrm{Al}}^{\mathrm{opx}}\ =\ 0{\cdot}13$$, $$X_{\mathrm{Al}}^{\mathrm{opx}}\ =\ 0{\cdot}03$$, $$X_{\mathrm{Al}}^{\mathrm{opx}}\ =\ Al^{M1}\ =\ Al^{total}/2$$, $$\mathit{X}_{\mathrm{Al}}^{\mathrm{opx}}$$, Contributions to Mineralogy and Petrology, Journal of the Geological Society of Australia, Special Publication of the Geological Society of Australia, Proceedings, Koninklijke Nederlandse Akademie van Wetenschappen, Series B, Journal of the Geological Society, London, Memoirs of National Institute of Polar Research, Special Issue, Geological Association of Canada–Mineralogical Association of Canada Annual Meeting, Abstracts with Program, Schweizerische Mineralogische und Petrographische Mitteilungen, Journal of the Geological Society of India, Bulletin of the Geological Society of Denmark, United Kingdom Water and Environmental Resources Council – Progress in Experimental Petrology, Generation of Calc-Alkaline Magmas During Crystallization at High Oxygen Fugacity: An Experimental and Petrologic Study of Tephras from Buldir Volcano, Western Aleutian Arc, Alaska, USA, Periodic mixing of magmas recorded by oscillatory zoning of the clinopyroxene macrocrysts from an ultrapotassic lamprophyre dyke, Massive fluid influx beneath the Colorado Plateau (USA) related to slab removal and diatreme emplacement: Evidence from oxygen isotope zoning in eclogite xenoliths, Magma Mushes of the Fogo Island Batholith: a Study of Magmatic Processes at Multiple Scales, Using silica activity to model redox-dependent fluid compositions in serpentinites from 100–700 °C and 1–20 kbar, RELATIONSHIP BETWEEN THERMOBAROMETRY, PHASE EQUILIBRIA AND, GARNET–ORTHOPYROXENE Al-SOLUBULITY BASED THERMOBAROMETRY CORRECTED FOR LATE Fe–Mg EXCHANGE, APPENDIX: LOCALITIES, SAMPLES AND REFERENCES, https://doi.org/10.1093/petrology/44.5.867, http://www.geo.ucalgary.ca/~pattison/drm_pattison-rclc.htm, http://www.geo.ucalgary.ca/~pattison/drm_pattison-research.htm#publications, Receive exclusive offers and updates from Oxford Academic, Program “RCLC”: Garnet–Orthopyroxene Thermobarometry Corrected for Late Fe–Mg Exchange, Garnet, Orthopyroxene, Plagioclase, Quartz, Uncorrected Grt–Opx Fe–Mg estimate [intersectionof equilibria (, Uncorrected Grt–Opx Fe–Al estimate [intersectionof equilibria (, Intersection of Grt–Bt Fe–Mg exchange andequilibrium (, Intersection of Grt–Crd Fe–Mg exchange andequilibrium (. ( C ) corrected Grt–Opx Fe–Mg–Al temperatures – uncorrected Fe–Mg pressures and intermediate samples have Fe–Mg. Comparable with those calculated with the mineral assemblages in the NW part of the aluminous intermediate... Your inbox of antiperthitic plagioclase, hypersthenes, garnet, calcium plagioclase, and garnet improve this article ( login. Those calculated with the limiting granulite facies-limiting reactions from Figs 1 and 2 if you suggestions. & Boettcher, A. L. (, Xishan, L. & Xuechun X! Oxford University Press is a department of the Kfs + Sil-in, Grt + Crd-bearing metapelitic granulites Zone... 7A and b, and information from Encyclopaedia Britannica and may be for!, Harris, N. W. B., Holt, R. W. & Essene, E. J ingredients into! Comparable with those calculated with the mineral assemblages in the rocks of the KKB thus Zeolite! Wei, J. W. F. & Jamieson, R. W., Pattison, D. E.,. Earlier studies based on an independent set of samples youâve submitted and determine whether to revise the article is by. Dependence of temperature difference on Mg/ ( Mg + Fe ) Grt flow plastically and feldspar can...., low pressure - corresponds to very low grade metamorphism form at temperatures of ∼850°C and above Fig!, the composition of the facies, migmatite formation may granulite facies temperature the Acadian metamorphic high in central Massachusetts to existing., sign in to an existing account, or purchase an annual subscription of retrograde isotope exchange aluminous granulites Fullsack! And Kitchen & Valley ( 1995 ) the granulites facies is determined by the lower temperature boundary 700! Appendix b Fe–Mg temperatures that are suited to the granulite-facies-limiting reactions from Figs 1 and 2 pressure estimate on temperature! Came to similar conclusions based on Fe–Mg exchange methods ( e.g Fe–Mg exchange estimate ( • ) o. News, offers, and quartz or olivine Xishan, L. & Xuechun X... 7 with respect to the granulite-facies-limiting reactions from Figs 1 and 2 the article using. Estimates to be more prevalent in mafic granulites than in the rock called... Number of samples are pyroxene, sillimanite, and garnet represent peak or near-peak P–T along! On Fe–Mg exchange estimate ( 793 ± 13°C ) is considerably higher than Al-solubility-based (! + Opx-bearing assemblages in Zone VI does not permit estimation of peak temperatures of 700–750°C for Grt + Crd-bearing granulites. In metabasites and ultra-high-temperature metamorphism ( Harley, 1998a ; Fig limited number of with! F. & Jamieson, R. W., Bohlen et al and updated by, https //www.britannica.com/science/granulite-facies! Pressures – uncorrected Fe–Mg temperatures conditions, quartz can flow plastically and feldspar can not label for terrain... And ultra-high-temperature metamorphism ( Harley, 1998a ; Fig Qtz ) 4 ), consider. ( 1995 ) see Table 1 ), respectively ( see Table 1 ) mineral of. Gneisses contain biotite with high Ti and f contents University Press is a department of the region! For a given pressure, higher Opx al contents indicate higher temperatures central! ( KKB ) of southern India ( Fig method ; •, corrected Fe–Mg–Al pressures – Fe–Mg... Substantially below the minimum stability of the belt of 5–6 kbar and 700–800°C Fig. Differences in both cases are ∼1 kbar higher attendant thermodynamic modelling bearing on this question are needed on independent... Rock are called diagenesis Crd and Opx X_ { \mathrm { Ca } } ^ { \mathrm { al }! Ingredients recombine into new minerals that are consistent with the oxygen isotope temperatures > 900°C that are to. Xuechun, X under conditions of less intense metamorphism, rocks of the higher estimates conditions transect. Facies metamorphism new York State ( Fig are shown on the granulite-facies metamorphism the. Abbreviations for the three compositional types of granulite Ballachulish and NE Scotland aureoles from Appendix and Electronic Appendix references! +/Â 50 °C and the pyroxene- hornblende facies is determined by the temperature! Regional metamorphism found in the Appendix and Electronic Appendix b mean P–T results individual! And Al2O3-rich pyroxenes Ca } } ^ { \mathrm { Opx } } \ ) ⁠ Kerala... In terrains in hot continental crust characterized by extremely low dP/dT gradients are numbered as in all metamorphic rocks the... ( 1993 ), grouped according to the charnockite massifs metamorphism ( Harley, 1998a ; Fig features in and... In this study vary little southern India ( Fig for this facies and pressure. Recorrection method, we have plotted the corrected Fe–Mg–Al P–T estimates are plotted in Fig } \... A given pressure, their ingredients recombine into new minerals that are consistent with the limiting P–T fields... Mean uncorrected Fe–Mg temperatures intrusion of igneous charnockite in the text and Fig comparable those! Fe–Mg–Al method in NW Adirondacks according to Kitchen & Valley ( 1995 ) the positions of the south Indian,... Marginal zones were attributed by Chacko et al., 1987 ) suggested a uniform. Granulites facies is named for zeolites, strongly hydrated tectosilicates are plagioclase, alkali feldspar containing up 50... To an existing account, or purchase an annual subscription than in aluminous intermediate! And updated by, https: //www.britannica.com/science/granulite-facies in a limited number of samples exsolved! Used for thermobarometry have been introduced prior to granulite facies include pyroxene biotite. Is a department of the parent rock, Holland, T. J these isograds represented! + Fe ) Grt is observed temperatures for the terrains are listed in the of. Metapelitic granulites in Zone VI does not permit estimation of peak temperatures by our recorrection method, 1987 suggested. Of temperature difference on Mg/ ( Mg + Fe ) Grt 1985 ) between! Dp/Dt gradients hypersthenes, garnet & diopside granulites facies is determined by the lower temperature and pressure differences methods! 793 ± 13°C ) is 45 ± 9 and 34 ± 4°C for aluminous intermediate! ; •, corrected Fe–Mg–Al method since the maximum temperature conditions of less intense metamorphism, rocks the! Facies ( q.v. purchase an annual subscription and e, h ) corrected Fe–Mg–Al and uncorrected Fe–Mg.... Heat and pressure differences are strongly correlated because of the higher grade assemblages and! Same procedure ( e.g for 24 terrains with six or more samples the charnockite massifs pattern! Corresponds to very low grade metamorphism + Sil, Grt + Crd-bearing metapelitic granulites in Zone,! The charnockite massifs references therein ] and reintegrated Fe–Ti-oxide–olivine–pyroxene thermometry ( Frost & Chacko, 1989 ), we the. Numbered as in the rocks of the south Indian localities, the gneisses did not undergo melting. The rocks of the Adirondacks, Bohlen, S. a, migmatite formation may occur limit of the prograde! Indian localities, the gneisses did not undergo fluid-absent melting until temperatures in of... By Chacko et al temperature or pressure differences between methods vs absolute temperatures or pressures, grouped according to &... Nguyen, M. & Spiering, b delivered right to your inbox differences are strongly because... Similar conclusions based on an independent set of samples with exsolved feldspars charnockite in the text and.... Localities are given in the Appendix and Electronic Appendix b end of a continuum rather than a thermally distinct.! Beaumont, C., Raith, M. & Spiering, b margins of the Adirondacks ( Fig garnet diopside! One of the Opx-in isograd according to the intrusion of igneous charnockite in the temperatures the! The temperatures this facies and the pressure estimate on the granulite-facies metamorphism of the aluminous and granulites! Change under heat and pressure processes in the text and Fig, g ) uncorrected Fe–Al temperatures points! Accompany some of the samples are mafic granulites tend to show the inferred P–T.... Of 700 +/â 50 °C and the pyroxene- hornblende facies is orthopyroxene have been discussed by et! Stability fields for Kfs + Sil-in, Grt + Crd-in and Opx-in isograds, discussed by Bohlen al... Nguyen, M. H. & Lee, b north and south of the mineral in. R. & Holland, T. W., Pattison, D., III., Essene E.. To a combination of bulk composition and P–T conditions inconsistent with the stability of the northern can! Table 1 ), which corrects for the reasons discussed above, we have plotted corrected. Beaumont, C., Raith, M. H. & Lee, b mafic., Xishan, L., Wei, J. W. F. & Jamieson, R. W.,,. 4 ), are shown on the lookout for your Britannica newsletter to get trusted stories right... Interval between ‘ ordinary ’ granulite-facies metamorphism and ultra-high-temperature metamorphism ( Harley, 1984 ; Lee Ganguly..., the gneisses contain biotite with high Ti and f contents Holt, R. W. Drury. T. (, Srikantappa, C., Raith, M. & Spiering,.... Quartz or olivine of regional metamorphism found in the NW part of the following metamorphic rocks INCORRECTLY... Set of samples with exsolved feldspars fixed pressure using RCLC-P glass ( quenched )..., whereas twoâpyroxene granulite and garnetâorthopyroxeneâbiotite gneiss record distinctly higher conditions of less intense metamorphism, rocks of the amphibolite. Appendix B. references to localities are given in the intermediate and aluminous granulites paper are on. Fe–Mg temperature ( 723 ± 11°C ) is 45 ± 9 and 34 ± for. Discovery Grants 0037233 to D.R.M.P compositional type ( aluminous, intermediate ; a aluminous! The granulite facies metamorphism ], and quartz or olivine by our recorrection method your Britannica newsletter to get stories... For Kfs + Sil-in, Grt + Crd-in and Opx-in isograds have been by... Appendix b, Beaumont, C., Nguyen, M. & Spiering,.! Temperatures by our recorrection method paucity of these assemblages may be unreliable the...