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Geodynamika metamorfních reakcí

Metamorphic Petrology Group at the Faculty of Science, Charles University consists of faculty members, graduate and undergraduate students who work together on various aspects of field and microstructural relations of metamorphic rocks in order to decipher the tectonic evolution of orogenic belts. Our group uses an integrated approach, notably combining:

  • Fieldwork e.g. in the Bohemian Massif (Czech Republic), Hindu Kush (Afghanistan), Western Carpathians (Slovak Republic), Western Alps (Austria), Central Iran Blocks (Iran).
  • Mineral forming processes (high pressure rocks, decompression reactions, partial melting)
  • Significance of metamorphic textures and the phase relations
  • Quantification and interpretation of pressure-temperature-deformation-time paths
  • Characterization and interpretation of solid phase inclusions in high-pressure and high-temperature in collisional orogens
  • Studies of ultrahigh-pressure rocks to understand large-scale processes and phenomena that occur along plate boundary in lower crustal and upper mantle levels.

People

Facilities

Laboratory of scanning electron microscopy equipped by SEM with the EDS and EBSD detectors allows phase study of the samples using BSE and CL imaging as well as quantitative microanalysis of major elements, compositional mapping and study of preferred crystal lattice orientation.

Conference

Research

Eclogites and ultrahigh-pressure metamorphic rocks in the Bohemian Massif

Most eclogites and UHPM rocks, exposed in collision orogenies, reveal reequilibration in granulite or amphibolite facies conditions and their peak pressure or prograde minerals and textures are usually obliterated by low-pressure assemblages. Recent progress in micro- and nanoscale techniques allow to investigate solid- or fluid phase inclusions and reaction textures and to reconstruct the pre-amphibolite/granulite facies history of the rocks subjected to subduction or simply exhumed from the mantle depth. The Bohemian Massif is one of the best studied part of the Variscan Collision Orogeny, where lenses and boudins of eclogites and mantle peridotites are distributed in various lithotectonic units. UHP conditions were confirmed by index minerals only for some rocks, but mineral textures and thermobarometric calculations indicate that most of these rocks experienced subduction history. Our research group focuses on solid phase inclusions and their equilibrium products to trace the evidence of peak pressure history and to understand the process of partial or total equilibrium of these rocks.

Selected publications

  • Faryad, S.W.  2012. High-pressure polymetamorphic garnet growth in eclogites from the Mariánské Lázně Complex (Bohemian Massif). European Journal of Mineralogy, 24, 483–497.
  • Faryad, S.W., 2011. Distribution and geological position of high-/ultrahigh-pressure units within the European Variscan Belt: a review, in: Dobrzhinetskaya, L., Faryad, S.W., Wallis, S., Cuthbert, S. (Eds.), Ultrahigh Pressure Metamorphism: 25 Years After the Discovery of Coesite and Diamond, Elsevier, p. 361–397.
  • Faryad, S. W., Jedlička, R., Ettinger, K., 2013. Subduction of lithospheric upper mantle recorded by solid phase inclusions and compositional zoning in garnet: example from the Bohemian Massif. Gondwana Research, 23, 3, 944-955.
  • Hrouda, F., Faryad, S. W., Franěk, J., Chlupáčová, M., 2012. Magnetic fabrics in garnet peridotites–pyroxenites and host felsic granulites in the South Bohemian Granulites (Czech Republic): Implications for distinguishing between primary and metamorphism induced fabrics: Gondwana Research, 23, 3, 956-972.
  • Racek, M., Štípská , P., Pitra, P., Schulmann, K. & Lexa, O., 2006. Metamorphic record of burial and exhumation of orogenic lower and middle crust: new tectonothermal model for the Drosendorf window (Bohemian Massif, Austria). Mineralogy and Petrology, 86, 221–251.
  • Racek, M., Štípská, P. & Powell, R., 2008. Garnet-clinopyroxene intermediate granulites in the St. Leonhard massif of the Bohemian Massif: ultrahigh temperature metamorphism at high pressure? Journal of Metamorphic Geology, 26, 253-271.

Blueschist facies metamorphism along orogenic zones

The Jurassic Meliata Zone (Western Carpathians)

 

The Meliata unit with ophiolites and blueschist facies rocks occurs along southwards dipping tectonic zone between the Pannonian basin and the Western Carpathians. It was formed by closure of the Triassic Meliata-Hallstatt oceanic basin that related to the European Tethys. The blueschists form isolated slices overthrusting the basement units to the north and occur as tectonic blocks within very low-grade sedimentary sequences. The HP/LT rocks are represented by marbles with lenses and layers of metabasites and by phyllites. Tectonic slices of former amphibolite facies basement rocks, overprinted by blueschist facies metamorphism, are also present. The blueschist facies minerals in metabasites are glaucophane, epidote, albite, phengite and rarely paragonite, garnet and Na pyroxene with maximum 70 % jadeite component. Pelitic rocks may additionally contain chloritoid. Geochronological data indicates Middle Jurassic age for blueschit facies and Upper Jurassic for the very low-grade mélange matrix.

Selected papers

  • Faryad, S.W. and Frank, W. 2011. Textural and age relations of polymetamorphic rocks in the HP Meliata Unit (Western Carpathians). Journal of Asian Earth Sciences, 42, 111-122
  • Faryad, S.W. and Henjes-Kunst, F. (1997): K-Ar and Ar-Ar age constraints of the Meliata blueschist facies rocks, the Western Carpathians (Slovakia). Tectonophysics, 280, 141-156.
  • Faryad, S.W (1995b): Phase petrology of mafic blueschists of the Meliata Unit (West Carpathians)-Slovakia. J. metamorphic Geol, 13, .432-448.
  • Faryad, S.W. (1995a): Low-grade high-pressure metapelites and metapsammites of the Meliata Unit (West Carpathians) - Slovakia. Eur.J. Mineralogy, 7, 57-74.

 

 

The Bohemian Massif

Several occurrences of high-pressure low-temperature rocks occurs alongthe northern border of the Bohemian Massif. They form a discontinuous belt rimming the Krkonoše-Jizera complex from east and south and occur also in the Krušné hory Mts. The presence of blueschist facies rocks along the northern border of the Bohemian Massif (the Saxothuringian Zone and the Sudetes) is not restricted only to lenses and boudins of metabasites within greenschists and phyllites, but in some areas the surrounding lithologies also experienced HP/LT metamorphism.

X-ray map with Mg concentration and compositional profile from zoned white mica in chloritoid schists.

  • Faryad, S.W., Kachlík, V., 2012. New evidence of blueschist facies rocks and their geotectonic implication for Variscan suture(s) in the Bohemian Massif. Journal of Metamorphic Geology, 31, 63-82.

 

 

The Pieniny Klippen Belt (Western Carpathians)

In the absence of requisite outcrops, pebbles of critical rock types in younger sedimentary sequences contribute important and otherwise unobtainable information on the geodynamics of orogenic belts. In this respect, high-pressure metabasites occurring as pebbles in the Albian conglomerates along the Klippen Belt indicate subduction history of parts of the Western Carpathians. They comprise three different types ranging from pumpellyite (I)- through lawsonite (II) - to omphacite-bearing blueschists (III).

 

  • Faryad, S.W. and Schreyer, W.(1997): Petrologica and geological significances of  high-pressure metabasites,  occurring as pebbles in the Cretaceous  conglomerates in the Klippen Belt (Western Carpathians, Slovakia). Eur.J.Mineralogy, 9, 547-562.

The Proterozoic Kabul block and its rule during India convergence with the Afghan Central blocks

The Kabul block records a polymetamorphic history within amphibolite to granulite facies rocks of Palaeo-Proterozoic age. The block was one of the last of the accreted terranes to ‘dock’ within the complex terrane-montage of the Hindu-Kush mountain system prior to the collision of the Indian continent. It is bounded on all sides by terrane boundaries, most notably the Chaman Fault (A prominent linear feature that stretches from the Hindu Kush through Afghanistan and into Pakistan and represents the extreme western margin of the modern Indian Plate). The high-grades of metamorphism recorded in the Kabul Block are restricted to the Proterozoic by the apparent lack of deformation in overlying Phanerozoic sediments. As despite the position of the block within the Himalayan-Hindukush system where Alpine events had a significant effect on the formation of mountain belts, the Proterozoic Kabul Block seems to have only been affected by a low-degree of metamorphism. Understanding the metamorphic character of this block is essential for interpretation of  its geotectonic evolution during the Proterozoic period and during collision between the Indian plate and the Afghan Central Blocks.

  • Faryad, S.W, Collett, C. , Ptterson, M. and Sergeev, A.S. Magmatism and metamorphism linked to the accretion of continental blocks south of the Hindu Kush, Afghanistan, Lithos (in review).

Metamorphism and deformation in the Iranian Central Block

The Shotur Kuh complex, exposed in the NE part of the Great Kavir block, is composed of amphibolite facies metaigneous rocks and micaschist, and of lower-grade Permian–Miocene cover sequences. Major- and trace-element geochemistry in combination with U–Pb age dating of zircon showed that the protoliths formed during Late Neoproterozoic continental arc magmatism that has also been identified in other tectonic blocks of Central Iran. The rocks underwent two stages Middle Jurassic amphibolite facies metamorphism.

  • Rahmati-Ilkhchi M. Faryad SW, Holub F.V.. Košler J., Frank W. (2011): Magmatic and metamorphic evolution of the Shotur Kuh metamorphic complex (Central Iran). Int. J. Earth Sci.,100, 1, 45-62

  • Rahmati-Ilkhchi M., Jeřábek P., Faryad S. W., Koyi H. A. (2010): Mid-Cimmerian, Early Alpine and Late Cenozoic orogenic events in the Shotur Kuh metamorphic complex, Great Kavir block, NE Iran. Tectonophysics, 494, 1-2, 101-117.

Greenschist facies to amphibolite facies basement units incorporated within Alpine collisional front in the Western Carpathians

The Gemer basement unit with strong Alpine overprint

The Gemer tectonic unit is located in the south-eastern part of the Western Carpathians. It consists of Pre-Alpine greenschist facies rocks with a few slices of gneiss-amphibolites. It is a typical example of low-grade polymetamorphic terrane, where older metamorphic minerals and textures were obliterated by a younger process. By investigation of mineral textures in various lithologies we were able to distinguish and quantify PT conditions of Variscan and Alpine metamorphic event. In addition to greenschist facies metamorphism, part of Variscan basement preserve evidence of low-pressure blueschist facies conditions. The younger metamorphic produced barrovian type mineral assemblages and related collisional process during Alpine events.

Selected publications

  • Faryad, S.W. and Dianška, I. 1999. Alpine overprint in the early Paleozoic of the Gemericum. Mineralia Slovaca, 31, 485-490.
  • Faryad, S.W. and H.J. Bernhardt (1996): Taramite-bearing metabasites from Rakovec (Gemeric Unit, The Western Carpathians). Geologica Carpathica, 47, 349-357.
  • Faryad, S.W (1994): Mineralogy of Mn-rich rocks from greenschist facies sequences of the Gemericum, West Carpathians, Slovakia. N. Jb. Miner. Mh., 10, 464-480

 

The Tatra-Vepor units

Both units are represented by thick-skinned crustal sheets composed of pre-Alpine (generally Variscan) basement and its Mesozoic sedimentary cover. The basement rocks underwent amphibolite to greenschist facies metamorphism. The amphibolite facies metamorphism of the Tatricum and Veporicum had medium- (Pre- or Early Variscan) to low-pressure (Variscan) character. During Alpine Orogeny, they were affected by very low-grade metamorphism.

Garnet formation with prehnite and pumpellyite at very low-grade metamorphism

  • Faryad, S.W. and Dianiška, I. (2003): Ti-bearing andradite-prehnite-epidote assemblage from the Malá Fatra granodiorite and tonalite (Western Carpathians). Swiss Bull. Min. Petrol. 83, 47-56.
  • Faryad, S. W., Ivan, P. and Jacko, S. 2005. Metamorphic petrology of metabasites from the Branisko and Čierna Hora Mts. Western Carpathians (Slovakia). Geologica Carpathica, 56, 3-16
  • Faryad, S.W. and Balogh, K. 2002. Variscan pegmatite and K-Ar and Ar/Ar dating from basement rocks of the Zemplin Unit, Western Carpathians. Acta Geologica Hungarica, 45/2, 193-204.

Amphibolite-eclogite facies rocks from the Esatern Alps

Subject of this research was the Austroalpine basement units, along a SSE-NNW from Saualpe Complex through Wölz Tauern to the Speik Complex in the Rottenmann Tauern. An early Variscan eclogite facies metamorphism (397 Ma) was confirmed in the Speik Complex. Different compositional zoning and inclusion patterns in garnet porphyroblasts from the Rappold and Wölz Units allowed to distinguish two Pre-Alpine metamorphic events: a Permian (246 Ma) low-P/high-T and an Upper Carboniferous (330 Ma ?) medium-pressure metamorphism of amphibolite facies conditions. The Eo-Alpine metamorphism (~ 100 Ma) was grading from upper greenschist facies in the Permian cover sequences in the north, through high-pressure amphibolite facies in the Wölz Tauren to eclogite facies in the Saualpe Complex in the south.

Two metamorphic events recognized by compositional zoning in garnet. Rapid change from the low-Ca core to high-Ca rim is due to Alpine high-pressure metamorphic overprint on low-pressure Pre-Alpine garnet.

Selected papers

 

  • Frayad, SW and Chakraborty, S. 2005. Duration of Eo-Alpine metamorphic events obtained from multicomponent diffusion modeling of garnet: A case study from the Eastern Alps. Contr. Mineral Petrol. 150, 305-318.
  • Faryad, S.W. and Hoinkes, G. 2004. Complex growth textures in a polymetamorphic metabasite from the Kraubath Massif (Eastern Alps). J. Petrology, 45, 1441-1451.
  • Faryad, S.W. and Hoinkes, G .2003. P-T gradient of Eo-Alpine metamorphism within the Austroalpine basement units, east of the Tauern Window (Austria). Mineralogy and Petrology, Springer 77, 129-159.
  • Faryad, S.W., Hoinkes, G., Melcher, F., Puhl, J., Meisel, T. and Frank, W. 2002. Relics of eclogite facies metamorphism in the Austroalpine basement, Hochgrößen (Speik Complex), Austria. Mineralogy and Petrology, Springer 74, 49-73.

 

High-grade amphibolite facies metaevaporite and surrounding rocks from Sare Sang (Hindukosh, Afghanistan)

Scapolite and other halogen-rich minerals (phlogopite, amphibole, apatite, titanite and clinohumite) occur in some high-pressure amphibolite facies calc-silicates and orthopyroxene-bearing rocks at Sare Sang, northeast Afghanistan. Peak P-T conditions of 1.4 GPa/750 oC and XCO2 = 0.03 – 0.15 were estimated. XNaCl (fluid), obtained for scapolite, ranges between 0.04 and 0.99. Partitioning of F and Cl between coexisting phases was calculated for apatite-biotite and amphibole-biotite. Cl preferentially partitions into amphibole with respect to biotite. All these rocks have suffered various degrees of retrogression, which resulted in removal of halogens, CO2 and S. Halogen- and S-bearing minerals formed during retrogression and metasomatism are flourapatite, sodalite, amphibole, scapolite, clinohumite, haüyne, pyrite, and lazurite, which either form veins or replace earlier formed phases.

 

 

  • Faryad, S.W. 1999. Metamorphic evolution of the Precambrian South Badakhshan block, based on mineral reactions in metapelites and metabasites associated with whiteschists from Sare Sang (Western Hindu Kush, Afghanistan). Precambrian research, 98, 223-241.
  • Faryad, S.W. 2002.Metamorphic conditions and fluid compositions of scapolite-bearing rocks from the lapis lazuli deposit at Sare Sang Afghanistan. J. Petrology 43, 4, 725-747.

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