Structural and metamorphic evolution of the Nanga Parbat syntaxis, Pakistan Himalayas, on the Indus gorge transect: The importance of early events. Phase equilibria modeling of kyanite-bearing eclogitic metapelites in the NCKFMASHTO system from the Egere terrane (Central Hoggar, South Algeria). A metamorphic facies is a set of mineral assemblages in metamorphic rocks formed under similar pressures and temperatures. The third major kind of regional tectonic overprint is the Early Cretaceous mélange that is present as belts in and between the Rakaia and Pahau terranes. Figure 6.12. The duration of granulite (G) and ultra–high temperature (UHT) conditions in regional metamorphism is critical to arguments regarding the tectonic settings of … Concentrated aqueous solutions of strong electrolytes, including (Na,K)Cl, would have low aH2O, as would CO2-rich fluids. Chinese Journal of Geochemistry, vol. A.B. In the host Ama Drime orthogneiss, the granulite event is correlated with synkinematic sillimanite-grade metamorphism and muscovite dehydration melting. tectonic setting.One by one tectonic unit will be correlated according to its similarities and different. Thermal perturbation on a regional scale might have been induced by asthenospheric upwelling following slab break-off at relatively shallow depth and consequent production of basaltic magma emplaced in the lower crust. 8.3). Metamorphism probably took place in the deep parts of a Jurassic–Early Cretaceous accretionary wedge. However, muscovite is coarse grained and cuts across the schistosity and was possibly formed during the cooling phase. Farther north is a granulite facies gneiss complex, the Qinling Group, which has ultramafic slivers and includes the remnants of an island arc with two bounding suture zones. Experimental Study of the Melting Reaction and Genetic Mechanism of Mineral Phase Transformation in Granulite Facies Metamorphism. Other workers consider the formation of orthopyroxene to be typical of granulite facies conditions, although this occurs at significantly higher temperatures (100–150 ¯C higher) than does formation of K-feldspar + Al-silicate. The fundamental change in the Earth’s history at the Archaean–Palaeoproterozoic boundary was linked to the transition from Archaean “microplate tectonics” to Palaeoproterozoic “supercontinent tectonics” (or “micro-ocean tectonics” having in mind the limited size of the predominantly Red Sea-type oceans that originated within a partially disrupted supercontinent) (sections 3.4 and 3.6). Local post-and anorogenic events (bimodal magmatism including gabbro–anorthosite and rapakivi–granite intrusions, and high-grade metamorphism) in different places within a reborn Palaeoproterozoic supercontinent developed at various times after termination of the collisional and accretionary processes, generally after 1.7 Ga. The Takhsang Formation is composed of garnet–sillimanite–biotite gneiss largely devoid of muscovite (Golani, 1995, p. 96), which, if present, occurs as a second-generation grain. Veevers (2009) summarized and illustrated the assembly and breakup history of Antarctica and India (Fig. See also Palin et al. Lithologic and geochemical comparisons show that supracrustal assemblages in the amphibolite- and granulite-facies terrains of southern India formed in different tectonic settings and had different sediment sources. The stability of osumilite in metapelitic granulites. The postkinematic mineral assemblages, however, formed at around 640°C and 6 kb. The northern limit of these occurrences is traditionally marked as Charnockite Line (Fermor, 1936). The 90 Ma Kigluaik pluton forms the core of a granulite facies gneiss dome and is In mafic rocks, the presence of orthopyroxene, which forms at the expense of hornblende and/or biotite, is considered indicative of granulite facies conditions. In mafic rocks, the greenschist–amphibolite facies transition is designated by the appearance of hornblende and Ca-rich plagioclase and the disappearance of actinolite and Na-rich plagioclase. Large‐scale fluid infiltration, metasomatism and re‐equilibration of Archaean basement granulites during Palaeoproterozoic thrust belt construction, Ungava Orogen, Canada. Orthophosphate and biotite chemistry from orthopyroxene-bearing migmatites from California and South India: The role of a fluid-phase in the evolution of granulite-facies migmatites. A well-documented example of a Barrovian-type metamorphic zoning is exposed on the island of Naxos, Greece (see later). granulitic slab suggest emplacement in a brittle extensional setting whereas garnet coronas attest to subsequent burial under high-pressure (HP) granulite facies at relatively high temperature. N. Mortimer, in Encyclopedia of Geology, 2005. Geochemical signatures of metasedimentary rocks of high-pressure granulite facies and their relation with partial melting: Carvalhos Klippe, Southern Brasília Belt, Brazil. When water activity is low, pervasive partial (dry) melting will occur at much higher temperatures and hydrous minerals (muscovite, biotite, and amphibole) may decompose to anhydrous ones by local dehydration melting. Contrasting garnet parageneses in a composite Grenvillian granitoid pluton, Newfoundland. If you do not receive an email within 10 minutes, your email address may not be registered, The ages of granulite facies metamorphism in the southern part of the Dharwar Protocontinent range between 2500 ± 50 and 2540 ± 17 Ma (Hansen et al., 1997). This model, combined with the natural observations, suggests that it is possible to form granulite facies assemblages without participation of external fluid and without major extraction of silicate melt. Thermal granulite‐facies metamorphism with diffuse retrogression in Archaean orthogneisses, Fiskefjord, southern West Greenland. Cordierite as a sensor of fluid conditions in high‐grade metamorphism and crustal anatexis. Orthopyroxene‐bearing, mafic migmatites at Cone Peak, California: evidence for the formation of migmatitic granulites by anatexis in an open system. The flow of dense CO2-rich fluid would be limited by the inability of CO2 to wet grain boundaries effectively, unlike chlorine-rich brines (Watson and Brenan, 1987). Anatectic melt volumes in the thermal aureole of the Etive Complex, Scotland: the roles of fluid‐present and fluid‐absent melting. We use cookies to help provide and enhance our service and tailor content and ads. After Veevers, J.J. (2009). Mineral assemblages and microstructures indicate that these rocks were affected by granulite-facies metamorphism and anatexis followed by decompression and cooling. The geochemical characteristics of granites from the NGB indicate a dominant calc–alkaline nature consistent with their formation in a convergent margin in an island arc setting at around 2.5 Ga. Isotopic constraints on fluid infiltration from an eclogite facies shear zone, Holsenøy, Norway. According to them, their data from the Bhutan terrain suggest that the central portion of the Tibetan Slab was heated by the migmatitic upper portion of the sequence and that this migmatite was uplifted from lower crustal depth and thrust over the central portion, possibly predating MCT movement. These include metamorphosed amphibolite facies mafic volcanics, carbonates, and iron formation of the Hutchison Group >1860 Ma (Figure 2). In metapelites, the amphibolite–granulite transition is considered by some workers to be indicated by the assemblage K-feldspar + Al-silicate forming at the expense of muscovite + quartz. Roy, Ritesh Purohit, in Indian Shield, 2018. Granulite facies metamorphism in the Mallee Bore area, northern Harts Range: implications for the thermal evolution of the eastern Arunta Inlier, central Australia. Melting, carbonic fluids and water recycling in the deep crust: an example from the Limpopo Belt, South Africa. Metamorphism of Pelitic Rocks (Metapelites). In the northern part of the Oman Mountains in the Bani Hamid area, United Arab Emirates, ~870 m of granulite facies rocks (enstatite + spinel ± diopside quartzites, garnet … Following accretion to the North Australian Craton, the site of subduction may have moved to the south-western Gawler Craton (Figure 4) with the development of the first tectonic episode of the Kararan Orogeny (1710–1670 Ma) and the intrusion of voluminous granitic rocks of the Tunkillia Suite in a possible back-arc setting. In a certain sense, they can be interpreted as the beginning of a new Meso-Neoproterozoic evolutionary cycle. Granulite facies xenoliths from the Yuhuashan complex, central Jiangxi, South China constraints on Late Palaeozoic orogeny and middle-lower crust components Charnockitization of feldspar-free orthopyroxene-clinopyroxene-phlogopite metaultramafite in the lapland granulite belt, southern Kola Peninsula: Compositional trends of rocks and minerals, P-T parameters, and fluid regime. Metamorphism and Plate Tectonics At present, the geothermal gradients observed are strongly affected by plate tectonics. The Yixingzhai granitoid plutons are chemically similar to the Hengshan TTG gneisses, but are only metamorphosed to greenschist to lower-amphibolite facies and are less deformed, locally preserving igneous textures. 7.3 Plate Tectonics and Metamorphism – Physical Geology Thus, if we know the facies of metamorphic rocks in the region, we can determine what the geothermal gradient must have been like at the time the metamorphism occurred. Charnockitic alteration: evidence for CO2 infiltration in granulite facies metamorphism. mean1 Median ±1σ 1 Archaean gneisses 95 3000– 2500 Dominantly tona-litic to granitic gneisses Early Proterozoic (c. 2.0–1.8 Ga) amphibo-lite- to granulite-facies metamorphism. According to them, the P-T condition of the last equilibration in the HSL was about 630°C and 4 kb. Geochronology and geochemistry of the enderbite series in the Lapland Granulite Belt: generation, tectonic setting, and correlation of the belt11NORDSIM Publication No. P–T Conditions, Mechanism and Timing of the Localized Melting of Metapelites from the Petronella Shear Zone and Relationships with Granite Intrusions in the Southern Marginal Zone of the Limpopo Belt, South Africa. The third phase of the orogeny took place between 1745 and 1690 Ma and involved deformation, medium-grade metamorphism, and further granite intrusion (Figure 4). In the Curnamona Craton, the shallow-marine, immature clastic sedimentary rocks and bimodal volcanics of the Willyama Supergroup were deposited between ∼1715 and ∼1645 Ma. medium-pressure granulite-facies metamorphism in the southern Nawa Domain (Cutts et al. The latest, most widespread and intense event at c.1150 Ma gave rise to low-P granulites which record an anticlockwise P-T path and were accompanied by gneissic granite and charnockite. This means that assemblages of both facies occur in the same metabasalt. Ex: Usually Granodiorite, Tonalite. All the tectonothermal events in the region including the UHT metamorphism can be considered as part of this accretionary process. Melting of the continental crust during orogenesis: the thermal, rheological, and compositional consequences of melt transport from lower to upper continental crustThis article is one of a selection of papers published in this Special Issue on the the theme Gansser (1964) marked a tectonic contact at the locale of garnetiferous amphibolite between sillimanite-bearing gneiss and metasediments (see Golani, 1964, p. 97–98). Rb depletion in biotites and whole rocks across an amphibolite to granulite facies transition zone, Tamil Nadu, South India. Exhumation of the Haast Schist belt was episodic, with most of the schist being at the surface by 105 Ma and deeper levels being exhumed along the Alpine Fault from 20 Ma to the present day. The segregations have modes consistent with the hypothesis that they are the solid and liquid products of the dehydration‐melting reactions: Bt + Sil + Qtz + PI = Grt ° Crd + Kfs + L (metapelite), Bt + Qtz + Pl = Opx + Kfs + L (biotite gneiss), and Hbl + Qtz = Opx + Cpx + Pl + L (metabasic gneiss). On the other hand, the style of crustal evolution during the Palaeoproterozoic differs significantly not only from that in the Archaean, but also from that in the Phanerozoic. You may make use of these … Besides, the mafic granulite lenses hosted within the opx–ksp gneiss also show a metamorphic age of ∼255 Ma (Chen et al., 2006). Geologic setting 2.1 Regional geology The eastern Himalayan syntaxis (EHS) (Fig.1) is the eastern termination of the In metapelites, staurolite-bearing assemblages gradually replace chloritoid-bearing assemblages. The assemblage is typical of what is formed in conditions corresponding to an area on the two dimensional graph of temperature vs. pressure (See diagram in Figure 1). 322. The interpretation was further extended that the EGMB-south represents a part of an exotic terrane, which was transferred to proto-India in the late Paleoproterozoic as part of a linear accretionary orogenic belt that may also have included south-west Baltica and southeastern Laurentia. At low temperature, albite-bearing mafic rocks are replaced by assemblages with sodic amphibole (line 4, in Figure 5). The model endorses that the EGMB–south represents a fraction of an exotic terrane that was transferred to proto-India in the late Paleoproterozoic (1.68–1.6 Ga). The internal domain corresponds to the crystalline core of the orogen and comprises high amphibolite to granulite facies rocks of the Juiz de Fora Complex (Alkmim et al., 2007). K. Bucher, in Encyclopedia of Geology, 2005. Episodes of tectonic activity were previously described as orogenies. Thus, the tectonic setting of the eclogite facies was somewhat enigmatic. Tectonic setting of the Ottawa River ... granulite‐ and eclogite‐facies rocks in the aMP Belt commonly exhibit evidence for an amphibolite‐facies overprint of variable severity. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. Rocks which contain certain minerals can therefore be linked to certain tectonicsettings, times and places in the geological history of the area. Outcrop features of granulite-facies migmatites; Vein-like and patchy charnockite in southern India; Metamorphic history of the Namaqualand granulites. The mass balance of dehydration melting in typical biotite gneiss and metapelite shows that the proportion of melt in the product assemblage at T± 850°C is relatively small (10–20%), and probably insufficient to mobilize a partially melted rock body.
2020 granulite facies tectonic setting