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Metamorphism and geodynamics of the Proterozoic Kabul Block: Preservation and modification of crustal fragments within an orogenic zone
Collett, Stephen ; Faryad, Shah Wali (advisor) ; Kotková, Jana (referee) ; Krenn, Kurt (referee)
The Kabul Block is a lenticular crustal fragment that, along with the Farah, Helmand, and Nuristan terranes, is situated within a tectonic zone known as the Afghan Central Blocks. The Afghan Cent- ral Blocks form within the collision zone between the Indian, Eurasian, and Arabian plates. The Kabul Block consists of a highly-deformed crystalline basement overlain by weakly-deformed Late Paleozoic- Mesozoic sediments. U/Pb SHRIMP analysis of zircon cores from the lowermost basement formations (the Sherdarwaza and/or Khair Khana) indicates the presence of a Neoarchean component (~ 2700 Ma), while the majority of zircon cores yield a range of Early Paleoproterozoic ages (2200 - 2500 Ma). The Sherdarwaza and Khair Khana Formations are comprised of migmatite and orthogneiss with minor marble, quartzite, and amphibolite that reached granulite-facies conditions. Conventional geother- mobarometry and phase equilibria modelling on well preserved granulite-facies assemblages indicates that the rocks reached conditions of approximately 850 řC at up to 7 kbar of pressure. Textural relations indicate that this was a strongly temperature dominated event. U/Pb SHRIMP dating of zircon rims and U-Th-Pb dating of monazite inclusions in granulite-facies garnet suggest that this event occurred in the late...
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Reconstruction of PT path in the eclogites facies micaschists from the Krušné Hory
Kulhánek, Jan ; Faryad, Shah Wali (advisor) ; Racek, Martin (referee)
English abstract This work focuses on garnet bearing micaschist in the vicinity of the Měděnec village on the czech side of the Krušné hory Mountains (Saxothuringian Zone, Bohemian Massif). Micaschist is a part of nappe units with eclogites which reached high pressure conditions during subduction of the Saxhothuringian plate beneath the Teplá-Barrandien unit and they were subsequently exhumed into the upper parts of this subduction-collisional system. The rock-forming minerals present in micaschist are phengite, quartz and porphyroblastic garnet with inclusions of quartz, rutile, phengite, paragonite, apatite, monazite, florencite, zircon, chlorite, chloritoid, ilmenite, titanite, Co-arsenopyrite and graphite. Small amount of kyanite, retrograde chlorite and tourmaline are present in the matrix. Detailed chemical composition of garnet was studied using compositional maps of major and trace elements. The garnet shows prograde zoning with decrease of Mn and Ca and increase of Fe and Mg from the core towards the rim. Pressure and temperature conditions of the micaschist were calculated using thermodynamic modeling in Perple_X in the system of MnNCKFMASHTO. Based on the pseudosection, the mineral assemblage with kyanite is stable at higher pressure above 18 kbar and 600 řC. The pressure-temperature path of...
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Structural and petrological characterization of Melechov massif host-rock migmatites
Zelinková, Tereza ; Lexa, Ondrej (advisor) ; Faryad, Shah Wali (referee)
English abstract This work deals with the structural and petrological characteristics of migmatites surrounding Melechov massif near Humpolec. The aim was to assess the existence of multiple anatectic events that could be caused by intrusion of late granites. The results are based on fieldwork, petrographic observations in thinsections of the collected rocks, study of major minerals chemistry in both melanosome and the leucosome of selected migmatites and a comparison of bulk chemical analyses of selected samples. Studied migmatites are characterized by SSW-NNE oriented migmatitic vertical banding S2, which is intensively transposed into subhorizontal foliation S3 via folding and solid state deformation. Rocks of all studied sites bears common mineral assamblage (Bt + Crd + Sil + Pl + Kfs + Qtz + Ms + Mag). While overall chemical analysis of selected samples do not vary significantly, the chemistry of biotite and cordierite exhibits a significant increase in xMg a slight decrease in Ti from the first to the third locality. Chemistry of other rock-forming minerals do not vary significantly. These differences correlate well with different modal abundance of magnetite, which reaches up to 3% on the locality TM3. Based on the obtained data it can be stated that the studied rocks form a homogeneous domain of the...
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Solid phase inclusions in minerals from eclogites, peridotites and granulites in the Kutná Hora Complex
Jedlička, Radim ; Faryad, Shah Wali (advisor) ; Svojtka, Martin (referee)
Studium pevných inkluzí vybraných minerálů eklogitů, peridotitů a granulitů Kutnohorské oblasti English abstract Felsic granulites with lenses and boudins of garnet peridotites and eclogites, for which UHP conditions have been obtained, commonly occur in the Moldanubian Zone of the Bohemian Massif. However, it is not clear when and how the HP-UHPM rocks were emplaced into the host granulites. The most important question that remains is, whether the felsic granulites also experienced UHP metamorphism. By studying solid phase inclusions and compositional zoning in resistant phases as garnet, we provide evidence of prograde metamorphism of felsic rocks prior to their granulite facies overprint. Finding mono-mineral inclusion of Ti-rich phengite point to prograde evolution of the rocks.Polyphase inclusions of phengite and biotite indicate that it was previously Ti-poor phengite. Another important inclusion is graphite, which could be remnant of micro-diamond inclusion. Well-preserved prograde zoning of major elements in garnet from the felsic granulites is supported by zoning patterns of trace elements, such as titanium, chromium and yttrium and rare earth elements. Both these groups of elements remain heterogeneous at a micro-scale. The garnet profiles reveal that the rocks preserved signs of multiple stages...
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Preservation of HP minerals and textures in felsic and mafic granulites from the Rychleby Mts.
Schlöglová, Kateřina ; Faryad, Shah Wali (advisor) ; Kotková, Jana (referee)
Diploma thesis - Kateřina Schlöglová - 2011 1/2 English abstract Granulites of the Rychleby Mts. represent relics of high-pressure eclogite-facies metamorphic rocks that are scattered in various crustal and mantle segments of the Variscan orogen in central Europe. These rocks may provide important insights into early stages of Variscan plate convergence and burial as well as exhumation mechanisms. We use mineral assemblages and chemistry to reconstruct the pressure-temperature paths, mechanisms of melting, and conditions of mineral preservation of high-pressure granulites, as well as whole- rock geochemistry to aid in interpretation of granulite precursors and their geodynamic setting. The mafic granulites consist of garnet, omphacite, two feldspars, and quartz with accessory rutile and zircon. The peak assemblage was partly replaced by pargasitic amphibole and biotite. Garnet grains are zoned from Grs36Py10Alm54 (core) to Grs20Py38Alm42 (rim), and host inclusions of phengite, omphacite, unmixed feldspars, kyanite, and rutile. Omphacite composition varies from Di44Hd14Jd42 (inclusions in garnet) through Di63Hd20Jd17 (porphyroblasts) and Di63Hd24Jd13 (symplectitic intergrowths with plagioclase). Reintegrated composition of the feldspar porphyroblasts is Or43Ab53An04. The felsic granulite variety is composed...
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Thermobarometry of garnet peridotites and granulites from the Blanský Les Massif
Urychová, Michala ; Faryad, Shah Wali (advisor) ; Racek, Martin (referee)
English abstract Granulites of Moldanubian Zone are usually characterized by the presence of HP/UHP rocks of mafic and ultramafic compositions. The relationships between UHP rocks and granulites and their metamorphic history are subjects of many discussions. The Blanský Les Granulite Massif is the largest body of this type and includes numerous budines and bodies of serpentinized garnet peridotites, pyroxenites and amphibolic eclogites. PT conditions of granulites and garnet peridotites were estimated using different thermobarometric calculations. Temperatures 850-1050řC and pressures 15-20 kbar were calculated for granulites and 800-1000řC/25-40 kbar were estimated for garnet peridotites. Similar to other granulite bodies in the Moldanubian zone, the Blanský Les Granulite Massif is interpreted either as a segment of orogenic root, which was exhumed by viscous flow from low crust or the rocks reached eclogite facies conditions in the subduction channel first and then were overprinted by granulite facies metamorphism. Maximum depths of emplacement of garnet peridotites and other UHP rocks into granulites are limited by their pressure conditions. For these granulites the pressure is 22 kbar.
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Solid phase inclusions in minerals from eclogites, peridotites and granulites
Jedlička, Radim ; Faryad, Shah Wali (advisor) ; Jelínek, Emil (referee)
English abstract Felsic granulites in the Bohemian Massif are characterized by the presence of small (from decimetres to several houndred metres in size) boudins and lenses of garnet peridotites and high-pressure eclogites. Pressure conditions of the granulites and their mutual metamorphic history with garnet peridotites and eclogites are subject of long discussion. For this purpose, minerals and textures formed at peak pressure conditions were investigated using thin-sections and mineral separates of these rocks from the Kutná Hora complex. As all these rocks underwent granulite facies reequilibrium and subsequent cooling, most inclusions are transformed to lower pressure and temperature phases. In addition to olivine, orthopyroxene and clinopyroxene, garnet from garnet peridotites contains frequent chromium spinel. The host garnet around inclusions shows Cr-rich domains as result of diffusion from spinel to garnet. Rare ilmenite inclusions with high MgO content and pentlandite were also observed in garnet. Orthopyroxene in matrix and rims of large grains have low amounts of Al and the associated clinopyroxene has relatively high jadeite content. Two varieties of eclogites are present in the granulite: eclogites with pyroxenites and garnetites occur within or adjacent to garnet peridotites. Garnets of...
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High-pressure partial melting and its relationship to the granulite facies metamorphism: Implications for the origin of felsic high-PT granulites in the Bohemian Massif, central Europe
Nahodilová, Radmila ; Faryad, Shah Wali (advisor) ; Janák, Marian (referee) ; Kryza, Ryszard (referee)
Felsic granulites from the Kutná Hora complex in the Moldanubian zone of central Europe preserve mineral assemblage that record transition from early eclogite to granulite facies conditions, and exhibit discordant leucocratic veining, which is interpreted as evidence for melt loss during the decompression path. The granulites are layered and consist of variables proportions of quartz, ternary feldspar, garnet, biotite, kyanite, and rutile. In the mesocratic layers, garnet grains show relatively high Ca contents corresponding to 28-41 mol. % grossular end member. They have remarkably flat compositional profiles in their cores but their rims exhibit an increase in pyrope and a decrease in grossular and almandine components. In contrast, garnets from the leucocratic layers have relatively low Ca contents (15-26 mol. % grossular) that further decrease towards the rims. In addition to modelling of pressure-temperature pseudosections, compositions of garnet core composition, garnet rim- ternary feldspar-kyanite-quartz equilibrium, ternary feldspar composition, and the garnet- biotite equilibrium provide five constraints that were used to constrain the pressure- temperature path from eclogite through the granulite and amphibolite facies. In both layers, garnet cores grew during omphacite and phengite dehydration...
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Metamorphism and Geotectonic Position of the Shotur Kuh Complex, Central Iranian Block
Ilkhchi, Rahmati Mahmoud ; Faryad, Shah Wali (advisor) ; Janák, Marian (referee) ; Reza Ghassemi, Mohammed (referee)
The thesis focuses on tectonics and petrology of the Shotur Kuh complex and it is subdivide into four chapters. The first chapter involves a brief summary of information on regional geology, metamorphism and geochronology from different basement units in Iran. Chapters 2 and 3 include results of my research work that are in print or submitted for publication to international journals, respectively. In general, these two chapters provide an interdisciplinary approach to the metamorphism and tectono-metamorphic evolution of the Shotur Kuh complex and emphasizing the related links between geochronology, metamorphic petrology, micro-structural and macro-structural analyses, and tectonics. The last chapter (4) is a summary of achieved results with their possible interpretation and some future directions of research in the basement units of Iran. Consolidation of the Iranian basement units by metamorphism with partial granitization and partly intense folding occurred during Late Precambrian. This process continued during several major orogenic phases that were accompanied by syntectonic metamorphism and magmatic events. The most important orogenic events were during Paleozoic, Middle Triassic, Middle Jurassic, Late Jurassic and late Cretaceous periods. Some authors assume only epeirogenic movements during...
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Geochemistry of upper mantle rocks from Kozákov and Horní Bory, Bohemian Massif
Ackerman, Lukáš ; Jelínek, Emil (advisor) ; Faryad, Shah Wali (referee) ; Becker, Harry (referee)
The purpose ofthis dissertation is geochemical study ofupper mantle rocks at two sites from diÍlěrent geological settings of the Bohemian Massif (Czech Repub|ic) - Koziíkov and Homí Bory. The first part of dissertation represents a review of petrological and geochemical studies of upper mantle Íocks found in the Bohemian Massi{ which have been pub|ished or presented so far' These include information about ýpe and occuÍTences of mantle{erived rock with individual Bohemian Massif units and summarized present state of knowledge on depletion and metasomatism ofthese rocks. The principal questions related to the mantle beneath the Bohemian Massif which remďn opened are presented at the end of this part. The most important paÍt of the dissertation represents three comprehensive papers on geochemical studies of upper mant|e rocks from Koziíkov and Horní Bory. In the second part, a geochemical study of major elements, trace elements, and Sr-Nd isotopes combined with mineral chemistry of upper mantle xenoliths from the Koziíkov volcano have been presented. This unique suite of xenoliths samples upper 2/3 of the upper mantle in this region and, therefore' provides a great possibility to study uppeÍ mantle composition variations with depth. The results show that upper mantle beneath Koziíkov volcano underwent...
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