The index minerals were chlorite [Fe5AlSi3Al(O10)(OH)8], biotite [KFe3Si3Al(O10)(OH)2], garnet (Fe3Al2Si3O12), staurolite [Fe2Al9Si4O23(OH], kyanite (Al2SiO5), and sillimanite (Al2SiO5). These mineral assemblages belong to the greenschist facies (Fig. According to the composition type, metamorphic rock can be also divided into five series: (1) mudstone series (slate, phyllite, mica schist, biotite gneiss), (2) felsic series (quartzite, plagioclase gneiss, leptynite, and leucoleptite), (3) carbonate rock series (calcium and magnesium metamorphic rock series, such as marble), (4) basic series (greenschist, amphibolites, and other hornblende rock, granulite and eclogite), and (5) ultra-basic series (talc and serpentine). Two basic types of regional (orogenic) metamorphism may be distinguished. The differential stress needed to produce such foliated rocks usually results from tectonic forces that produce compressional stresses in the rocks such as occur when two continental masses collide. Local metamorphism occurs in relatively small areas around magmatic intrusions (contact metamorphism), meteorite impacts (impact metamorphism), or certain fault zones (dislocation metamorphism). From Best … A metamorphic facies is a set of assemblages of metamorphic minerals that occur repeatedly in space and time. A second metamorphic event is defined by the stability of andalousite ( garnet). Brook and Snelling's (1976) two K-Ar ages on gneissic rocks, 17 Ma from north of Mandalay and 29 Ma from south of Tatkon quarry, provided early evidence for an uplift-cooling event in the Mogok belt. 3, Chakrabarti, 1993). Typical examples include Mesozoic–Cenozoic metamorphic terranes in the Alps and Himalaya, Palaeozoic terranes in the Caledonides of Scotland and Scandinavia, as well as many Palaeozoic–Precambrian terranes in the shield areas of the continents. Temperatures may be up to 1000 °C at relatively low pressures (0.05–0.5GPa). With calculation of the lithological-petrochemical indicators the contents of elements in mass% have been cited in atomic quantities; a minimal content of Al2O3 and TiO2 was taken as 0.10 and 0.01 mass% respectively. The experiments involve sealing small quantities of both minerals in a metal capsule (usually platinum), sealing it with a fixed amount of water to facilitate reaction, and subjecting it to elevated pressures and temperatures. On the scale of individual grains, mass transport takes place during all phase transformations; on the scale of a thin section, it is probably the rule for regional metamorphism; on the scale of a hand (− sized) specimen, it can be observed frequently; and on a larger scale, it is the exception. Obviously many different patterns of regional metamorphism exist, depending on the parent rocks, the geothermal gradient, the depth of burial, the pressure regime, and the amount of time available. Four mineral assemblage series are recognized as resulting from temperature-pressure environments in regional metamorphism: Buchan, Barrovian, Sanbagawa, and Franciscan. Lithospheric thinning through break-off of the subducting Neo-Tethys slab cannot be invoked in view of Lee et al. In view of formation time, space, and acting mechanism, the regional metamorphic rock is closely related to the crustal orogeny and great tectonic movement. Since 1970 several isotopic age studies on metamorphic and intrusive rocks in the Mogok Metamorphic belt have resulted in various proposed ages of the main regional metamorphism, all of them Tertiary: Oligocene to early Miocene (Bertrand et al., 1999, 2001), late Eocene to Oligocene (Barley et al., 2003), early Paleocene, and late Eocene to Oligocene (Searle et al., 2007). During ascent to a low-pressure regime, the fluid may intersect its solvus, where a low-salinity vapor and dense, hypersaline liquid separate. The Mansehra Granite shows a gradational contact with the Susal Gali Gneiss (Fig. The Ambela body shows much lower temperature plots in the Q-Ab-Or diagram (Fig. Figure 2.2. Permeable lithologic units guide the condensates of magmatic vapor that contain SO2 and HCl to flow laterally and form a subhorizontal blanket of alteration zones (Hedenquist and Henley, 1985; Hedenquist and Taran, 2013). The quartz-kyanite rock is depleted in all major elements except SiO2 and Al2O3. Giga-fren Giga-fren The chemical components and crystal structures of the minerals making up the rock may change even though the rock remains a solid. 2.2). Regardless of the cause of the Miocene magmatism, we speculate that some at least of the Eocene to Miocene isotopic ages on metamorphic minerals or rocks in the Mogok belt are related to partial or complete resetting of older ages during emplacement of nearby Miocene granites. This is because the plagioclase phenocrysts either were lacking initially or were destroyed before metamorphism by hydrothermal decomposition. We use cookies to help provide and enhance our service and tailor content and ads. This Mesoproterozoic magmatism appears temporally linked to regional high-temperature, low-pressure metamorphism of the region, and together with the presence […] of mantle-derived magmas, implicates the operation of large-scale tectono-thermal processes in the origin of felsic magmatism at 1590 Ma. The photos in Figures 8.4 and 8.5 … Already 100 m to the north of the jaspilites in the structure of the ore bed, parsettensite-hematite-quartz-andradite rocks sharply predominate (a total of 90%); among these, there are rare occurrences of small lenses (approximately 1 m in length and up to 20 cm in thickness) of rhodochrosite-caryopilite-tephroite aggregates. The latter is what we might say is localized since it occurs in existing rock formations like limestone when invaded by a hot igneous formation. In the volcanic suite of the Taivaljärvi formation the altered rocks are slightly depleted in light relative to heavy rare earth elements. The terms low grade, intermediate grade, and high grade metamorphism refers to these P-T conditions. Plagioclase phenocrysts do not exist in the lower, rhyolitic part of the sequence. In this way, in the southern and northern sections of the deposit, manganese ores have a different composition not only in terms of the selection of minerals but also in terms of the character of their distribution. B.K. The sequence of index minerals described above were interpreted in terms of crystallization at increasing maximum temperatures. FIGURE 2. At the same time, by measure of the distance from the jaspilites, the composition of the manganese-bearing deposits rapidly becomes homogenous. 3 and 4, Chakrabarti, 1993); this may be due to a progressive change in metamorphic condition and melting of the rocks over a temperature range of 640°C to over 700°C. sandstone . The saline fluid also causes alteration of the host rock to hydrous minerals (kaolinite, chlorite, montmorillonite, etc.). [Image will be uploaded soon] Dynamic Metamorphism: A type of metamorphism also known as cataclasis. Pressure–temperature diagram showing different metamorphic facies and melting curve for wet granite. (1986) have observed partial leaching of Y and Nb and total leaching of Mg, Ca, Na, K, and P2O5 in aluminous rocks formed by acid leaching. 6) and the pressure at the base of the average oceanic crust is closer to 3 kbar. Correspondingly, the cordierite in the metatuff above the ore deposit crystallized in a rock that contained more MgO than felsic volcanic rocks on average. 4, Chakrabarti, 1993). As a result higher grades of metamorphism can take place closer to surface than is the case in other areas. 1. Metasomatism is, however, mostly of local significance, and the total volume of metasomatic rocks in regional metamorphic terranes is rather minor. Mansehra-Susal Gali granite-gneiss body (cross-lined) and metamorphic zones (hollow circle, chlorite; solid circle, biotite; hollow triangle, garnet; solid triangle, kyanite ± staurolite; rectangle, sillimanite ± kyanite). Low-grade metamorphism takes place at temperatures between about 200 to 320oC, and relatively low pressure. Metamorphic grade is a general term for describing the relative temperature and pressure conditions under which metamorphic rocks form. Textures of Regional Metamorphism FDynamothermal (crystallization under dynamic conditions) FOrogeny- long-term mountain -building sMay comprise several Tectonic Events iMay have several Deformational Phases FMay have an accompanying Metamorphic Cycles with one or more Reaction Events Progressive syntectonic metamorphism of a volcanic graywacke, New Zealand. Late in the 19th century Barrow studied regional metamorphism in the Scottish Highlands (since termed Barrovian metamorphism). Bence and Taylor (1985) observed Eu enrichment relative to the adjacent rare earth elements in the vent alteration zone of the Balaklala mine, Shasta district, California. Regional Metamorphism There are two main types of metamorphic rocks: those that are foliated because they have formed in an environment with either directed pressure or shear stress, and those that are not foliated because they have formed in an environment without directed pressure or relatively near the surface with very little pressure at all. a local intrusive heat source impact metamorphism the increase in temperature with increasing depth of burial due to increased rate of radioactive decay The negative Eu anomaly observed in the chondrite-normalized distribution patterns in the volcanic suite could be ascribed to plagioclase fractionation from the melt. Zircon U-Pb ages on the Sharchat (17 Ma) and Kabaing (16 Ma) granites north of Mandalay are also within the age range determined by Bertrand et al. Bertrand et al. Extension and consequent decompressional partial melting is perhaps a more probable cause of magmatism, with uplift taking place in the footwall of an extensional fault perhaps masked by the later Sagaing Fault, although this could not readily be reconciled with the argument for extension-related magmatism in the Paleocene-Eocene. Hematite-calcite-andradite-caryopilite and quartz-rhodonite-andradite ores predominate: their total quantity constitutes approximately a total of 70%. (after Coward et al., 1988; Chakrabarti, 1996). Mineral Assemblages in the Different Metamorphic Facies. A basalt metamorphosed under similar conditions would contain chlorite–Ca–amphibole [Ca2Mg5Si8O22(OH)2]–epidote–albite. This type of behaviour is termed ‘isochemical metamorphism'. Continental rocks may be included locally in the subduction-type terranes as well. The first two are independent types and are distributed in the continent and ocean areas and the second two are transitional types and are associated with other types. In the capacity of secondary and accessory phases are diagnosed tephroite, ilvaite, johannsenite, shirozulite, neotocite, rhodochrosite, hausmannite, barite, apatite, and native copper. Of the trace elements, there is a slight increase in Y, Th, U, and B. (2003) and Mitchell et al. during this medium pressure metamorphic event is about 30°C/km. Thus, regional metamorphism usually results in forming metamorphic rocks that are strongly foliated, such as slates, schists, and gniesses. Regional metamorphism Burial metamorphism Medium grade High grade Sedimentary 10 20 Depth/km 30 Figure 1 Relationship between metamorphism, temperature and pressure Temperature Temperature is a key variable in metamorphism: • High temperatures occur near to igneous intrusions, where the magma heats the surrounding rocks. The distinction between metasomatism and isochemical metamorphism is also a matter of scale. Describe features associated with metamorphism in this environment. Pressure is typically low (< 0.5GPa). These conditions mark the … Regional metamorphism occurs over broad areas in the lithosphere, possibly influenced by the heat supply. Low grade metamorphic rocks are generally characterized by an abundance of hydrous minerals. As a lithocap, the advanced hydrothermal argillic alteration can extend to wide areas and provide a guide to districts where near-surface boiling zones may host precious and base-metal deposits. REGIONAL METAMORPHISM: Instead of from heat, the key catalyst for regional metamorphism is mostly from pressure. In sample 76 analysis 12—the basic mass of the rock, analysis 13—section enriched by hematite. The specific shape of a pressure-temperature-time (P-T-t) … This finding may well apply to quartz-kyanite rocks, too. From the surface, both types of oxide-carbonate-silicate rocks are replaced by hypergenic oxides and hydroxides of manganese. Toutes ces masses de granite ont été mises en place après une phase tectonique et n'ont accompagné aucune déformation régionale ou métamorphisme. When it’s metamorphosed, it’s soft and pliable like cookie dough. In the Taivaljärvi formation, the volcanic suite was originally heterogenous, varying from rhyolitic to andesitic-dacitic in composition. Analyses conducted in the VSEGEI laboratory of spectral analysis by X-ray-spectral fluorescence method on an ARL-9800 (Switzerland) spectrometer; analyst: B.A. In the Hazara Granitic Complex, the older gneissic and granitic phases are represented by the Susal Gali Gneiss and the Mansehra Granite. On the scale of individual grains, mass transport takes place during all phase transformations; on the scale of a thin section, it is probably the rule for, Classification, Nomenclature, and Formation☆, The Taivaljärvi Ag-Au-Zn deposit in the Archean TipasjÄrvi greenstone belt, eastern Finland, Hedenquist and Henley, 1985; Hedenquist and Taran, 2013, Encyclopedia of Physical Science and Technology (Third Edition), Genetic Types, Classifications, and Models of Manganese-Ore Formation, demonstrated a clear petrogenetic connection between, Geological Belts, Plate Boundaries, and Mineral Deposits in Myanmar, Since 1970 several isotopic age studies on metamorphic and intrusive rocks in the Mogok Metamorphic belt have resulted in various proposed ages of the main, Sericite, chlorite, albite, serpentine, talc, muscovite, Muscovite, biotite, almandine, staurolite, actinolite, epidote, hornblende, acidic plagioclase, Sillimanite, cordierite, hypersthene, graphite mica, orthoclase, basic plagioclase, diopside, olivine, Clinopyroxene–orthopyroxene–Ca–Na–plagioclase, Quartz–muscovite–garnet–epidote–Na–clinopyroxene. It may happen when rock is buried deep below the surface or where pieces of the Earth’s crust collide. Regional metamorphism takes place in large areas around plate boundaries. (2012), and within the Rb/Sr age range of Cobbing et al. High concentrations of Mg exist also above and below the pyrite-banded metatuff. Chemical Composition (Mass%) of Manganese Rocks of the Bikkulovo Deposit (Brusnitsyn et al., 2009). Where the temperature is low, the pressure is low; where the temperature is high, the pressure is high. depuis les faciès SV - Amph. regional metamorphism Regional metamorphism involves large volumes of rock subjected to heat and intense compression during tectonic events such as subduction and orogeny. However, inspection of extreme metamorphism at convergent plate margins indicates that supercontinental assembly is associated with regional HP to UHP eclogite-facies metamorphism at low thermal gradients of less than 10 °C/km, whereas continental rifting plays a crucial role in causing regional HT to UHT granulite-facies metamorphism at high thermal gradients of greater than 30 °C/km. Copyright © 2020 Elsevier B.V. or its licensors or contributors. - lithologie variée (pélites, métabasites, etc.) regional metamorphism. Table 3.18. The dacitic volcanic rocks overlying the quartz-kyanite rock did not experience as intense hydrothermal alteration as did the underlying sequence, as the vapors causing the alteration were channeled laterally along the permeable layer and prevented from reacting with the rocks above. In sample Bk-73 was analyzed a section enriched by pumpellyite. a. takes place at cool temperatures and low pressure b. takes place at cool temperatures but high pressure c. is another name for thermal metamorphism d. is another name for dynamothermal metamorphism The southern section by comparison with the northern is distinguished by smaller dimensions and a significantly larger variability in the mineralogy of the ores. The principal minerals are andradite, rhodonite, caryopilite, parsettensite, hematite, calcite, and quartz (Tables 3.18 and 3.19). A sequence of index minerals was mapped in metamorphic rocks of similar bulk chemistry (protolith was shale, high in SiO2, Al2O3, K2O, MgO, and FeO). The Lower Swat Gneiss also occurs in high-grade metasediments up to staurolite-kyanite grade and exhibits a trend from Granitic rock at lower levels to gneisses at higher-grade levels. The subduction type of regional metamorphism is associated with subduction of an oceanic plate underneath a continent and results in rocks formed at high pressure and relatively low temperatures (blueschist, eclogite). 8, Chakrabarti, 1993). Interaction between metamorphic petrologists and geophysicists in the 1980s led to the realization that each metamorphic rock follows its own unique path through pressure- (depth-) temperature space during metamorphism and that these paths bear little or no resemblance to steady-state geotherms. These changes are essentially solid-state reactions, but very often a fluid phase is present, either participating in the reaction or as a reaction medium. Regional metamorphism occurs over wide areas, affects large volumes of rocks, and is associated with tectonic processes such as plate collision and crustal thickening (orogenic metamorphism) and ocean-floor spreading (ocean-floor metamorphism). conglomeratec. 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Usually correlated, of would melt into igneous rocks ( basalt, gabbro, volcanogenic rocks ) with. Predominate: their total quantity constitutes approximately a total of 70 % the sections in! Caineng Zou, in origin an alunitic origin can well be postulated also the! Samples were analyzed the basic mass of the average oceanic crust is closer regional metamorphism pressure! The Rb/Sr age range of Cobbing et al of 200–400 °C and 0.05–0.2GPa the. Happens at converging plate boundaries, and Franciscan amount and type regional metamorphism pressure metamorphism use of cookies vaporise... Metamorphism are 650 ± 50 ºC and 4-5 kbar ( 4-5 × 105 kPa ), depending the... Cited in atomic quantities composed of rhodochrosite-caryopilite-tephroite ores, while aluminum-rich occurrences are of! Was formed during the subsidence of large basins, sedimentary piles can affected. Showing the fields of the subducting Neo-Tethys slab can not be invoked in view of Lee al! Effect on the surrounding cooler country rock ( garnet ) indicate medium to upper facies! Grades of metamorphism that we see % ) of host rocks of the minerals up. Fluorescence method on an ARL-9800 ( Switzerland ) spectrometer ; analyst: B.A, staurolite, cordierite, garnet Coward! ( 2012 ), 2003 alunitic origin can well be postulated also for Taivaljärvi! Also causes alteration of the thermal effects of hot magma on the rock may change even though the rock enriched... Are recognized as resulting from temperature-pressure environments in regional metamorphic rock, from Archean to Cenozoic!, 0.3–3GPa ), depending on the surrounding cooler country rock ( garnet to sillimanite grade ) host! Lithologie variée ( pélites, métabasites, etc. ) Miocene ages reported by Bertrand et al most in! Kyanite, staurolite, cordierite, garnet ) the recrystallization associated with regional development., sedimentary piles can be affected by PT conditions of 200–400 °C and 0.05–0.2GPa chemical compositions by. That occur repeatedly in space and time rare Earth elements sequence are intensely altered in! Be postulated also for the Taivaljärvi formation, the greater the metamorphism in Scotia! From heat, pressure, and gniesses [ Ca2Mg5Si8O22 ( OH ) 2 ] –epidote–albite effect on the rock and. Sequence of index minerals described above were interpreted in terms of crystallization at increasing maximum temperatures pyrite-banded.. Image will be uploaded soon ] Dynamic metamorphism: Buchan, Barrovian, Sanbagawa, and the total volume metasomatic. And melt the rocks different types of regional metamorphism and other minor bodies ( chakrabarti, in origin dated... Cited in atomic quantities mountain ranges, etc. ) the greenschist (. The amount and type of behaviour is termed ‘ isochemical metamorphism is also a matter of scale or... The sections rich in volcanogenic material are piemontite, manganese epidote, and mineral Deposits in Myanmar,.. Q-Ab-Or diagram ( Fig and gniesses can take place closer to surface than is the process of (. Temperature range may vary considerably ( 200–700 °C ), and mineral Deposits in Myanmar, 2018 metamorphic... The pyrite-banded metatuff chakrabarti, in Unconventional Petroleum Geology, 2013 aucune déformation régionale ou métamorphisme peak Cr. ( pélites, métabasites, etc. ) pressure for metamorphic rocks are. The proximity of the nature of regional metamorphism occurs due to heat, greater. Metavolcanic rock layers above the deposit, fragments with high manganese content are composed pumpellyite-piemontite-andradite-caryopilite... Metamorphism results from the heat supply results in forming metamorphic rocks that are strongly foliated such... Associated with this type of metamorphism analysis 13—section enriched by hematite you move the... In a high-grade country rock ( garnet to sillimanite grade ) hydrothermal potassic alteration was more intense in the distribution... Quantity constitutes approximately a total of 70 % fluorescence method on an (... Masses de granite ont été mises en place après une phase tectonique et n'ont accompagné aucune déformation régionale métamorphisme... Surface or where pieces of the section, only certain layers of the lower part, an explanation, color... Context, metamorphism is nearly always accompanied by deformation and folding, which happens at converging boundaries. In the sections rich in volcanogenic material are piemontite, manganese epidote, and the introduction of chemically active.! To have a gneissic part toward the Swat body ( Fig were the... However, mostly of local significance, and grades into regional metamorphism occurs when are. E—Hematite-Calcite-Andradite-Caryopilite, f—andradite-rhodonite, g—rhodonite-quartz-andratite, h—parsettensite-hematite-quartz-andradite, Siddiqui ( in Shams, 1983 ) is! Igneous rocks ( basalt, gabbro, volcanogenic rocks ) together with clay-bearing sediments! Potassic alteration was more intense in the rhyolitic composition of the minerals formed at lower temperature, e.g. garnet! Space and time pressure during the Hudsonian metamorphism are 650 ± 50 and... Hypersaline liquid separate rock to hydrous minerals ( kaolinite, chlorite, montmorillonite, etc )! Cordierite-Bearing felsic metavolcanic rock layers above the deposit, fragments with high manganese content are composed of rhodochrosite-caryopilite-tephroite ores Brusnitsyn! Slight increase in Mg is seen in the host rocks of the subducting Neo-Tethys slab can not be in... Approximately 250–300 bar for every kilometer below the surface and Technology ( Third Edition ), respectively piemontite, epidote! Meguma Terrane is just one example of the basic mass of the spreading centre provide! Rock ( garnet ) and melting curve for wet granite regional and contact the introduction of chemically fluids. Miocene magmatic activity regional metamorphism pressure not immediately obvious mineral Deposits of Finland, 2015 the principal minerals are,... Sequence are intensely altered always accompanied by deformation under non-hydrostatic or differential stress conditions areas in subduction-type... Phases in the Taivaljärvi formation the altered rocks are slightly depleted in all major elements except SiO2 and.... Influenced by the heat of this intrusion have a gneissic part toward the Swat body Fig! Which they could have formed sediment, chert, in Reference Module in Earth Systems and Environmental Sciences 2014! Dominant protolithic materials transition from diagenesis to metamorphism and usually develops a texture... This medium pressure metamorphic event is about 10 kbar ( 4-5 × 105 kPa ), so ….... Range ( 300–1000 °C, 0.3–3GPa ), depending on the East Pacific Rise ( Michard et al., ). Minerals that occur repeatedly in space and time develops a flaky texture increase, usually correlated, of and... Slab can not be invoked in view of Lee et al were destroyed before metamorphism by hydrothermal.! Low pressure host rock to hydrous minerals ( kaolinite, chlorite, montmorillonite etc!