V. Puchkov - Academia.edu (original) (raw)
Papers by V. Puchkov
Precambrian Research, 2003
In the SW Urals a change of tectonic conditions occurred at around 620 Ma leading to a detrital i... more In the SW Urals a change of tectonic conditions occurred at around 620 Ma leading to a detrital input from contrasting provenance areas. Fifty-seven detrital zircons were separated from Proterozoic sandstones of this setting to study their typologies and pattern of U-Pb systematics.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2009
The natural garnets from chromite ores associated with pegmatoid pyroxenites of Sangalyk area (Uc... more The natural garnets from chromite ores associated with pegmatoid pyroxenites of Sangalyk area (Uchaly ore district, southern Urals, Russia) were studied by means of micro-Raman spectroscopy. The compositions of these garnets were close to ugrandite, an isomorphous intermediate group of uvarovite-grossularite-andradite, X(3)Y(2)(SiO(4))(3), X = Ca(2+), Y = Al(3+), Fe(3+), Cr(3+), according to Raman spectra and X-ray microprobe analyses. An assignment of most of the observed bands in visible and near infrared Raman spectra is reported.
An integrated geological study of the tectono-metamorphic evolution of the metamorphic complex of... more An integrated geological study of the tectono-metamorphic evolution of the metamorphic complex of Beloretzk (MCB) which is part of the eastern Bashkirian mega-anticlinorium (BMA), SW Urals, Russia shows that the main lithological units are Neoproterozoic (Riphean and Vendian age) siliciclastic to carbonate successions. Granitic, syenitic and mafic intrusions together with subaerial equivalents comprise the Neo-and Mesoproterozoic magmatic rocks. The metamorphic grade ranges from diagenetic and very low grade in the western BMA to high-grade in the MCB. The N-S trending Zuratkul fault marks the change in metamorphic grade and structural evolution between the central and eastern BMA. Structural data, Pb/Pb-single zircon ages, 40 Ar/ 39 Ar cooling ages and the provenance signature of Riphean and Vendian siliciclastic rocks in the western BMA give evidence of Mesoproterozoic (Grenvillian) rifting, deformation and eclogite-facies metamorphism in the MCB and a Neoproterozoic (Cadomian) orogenic event in the SW Urals. Three pre-Ordovician deformation phases can be identified in the MCB. The first SSE-vergent, isoclinal folding phase (D 1 ) is younger than the intrusion of mafic dykes (Pb/Pb-single zircon: 1350 Ma) and older than the eclogite-facies metamorphism. High P/low T eclogite-facies metamorphism is bracketed by D 1 and the intrusion of the Achmerovo granite (Pb/Pb-single zircon: 5970 Ma). An extensional, sinistral, top-down-to-NW directed shearing (D 2 ) is correlated with the first exhumation of the MCB. E-vergent folding and thrusting (D 3 ) occurred at retrograde greenschist-facies metamorphic conditions. The tremolite 40 Ar/ 39 Ar cooling age (7189 5 Ma) of amphibolitic eclogite and muscovite 40 Ar/ 39 Ar cooling ages (about 550 Ma) of mica schists indicate that a maximum temperature of 500 950°C was not reached during the Neoproterozoic orogeny. The style and timing of the Neoproterozoic orogeny show similarities to the Cadomian-aged Timan Range NW of the Polar Urals. : S 0 3 0 1 -9 2 6 8 ( 0 1 ) 0 0 1 8 7 -5 U. A. Glasmacher et al. / Precambrian Research 110 (2001) 185-213 186 Geochronological and thermochronological data together with the abrupt change in structural style and metamorphism east of the Zuratkul fault, suggest that the MCB is exotic with respect to the SE-margin of the East European Platform. Thus, the MCB is named the 'Beloretzk Terrane'. Recognition of the 'Beloretzk Terrane' and the Neoproterozoic orogeny at the eastern margin of Baltica has important implications for Neoproterozoic plate reconstruction and suggests that the eastern margin of Baltica might have lain close to the Avalonian -Cadomian belt.
The mid-Ordovician Grampian Orogen of western Irish Caledonides, the Miocene Bismarck Orogen of N... more The mid-Ordovician Grampian Orogen of western Irish Caledonides, the Miocene Bismarck Orogen of New Guinea, and the early Cretaceous Nevadan Orogen of the Sierra Nevada probably developed by the collision of a supra-subduction zone (SSZ) ophiolite/oceanic arc (s) with a continental margin followed by a flip in subduction polarity, leading to the addition of oceanic arc complexes to the edges of continents and, hence, continental growth. In each, imminent collision is heralded by a switch from mafic to silicic magmatism, fore-arc/ ...
Geological Society, London, Memoirs, 2006
ABSTRACT
Tectonophysics, 1999
... Received 14 October 1998; accepted 9 April 1999. Available online 25 August 1999. Abstract. T... more ... Received 14 October 1998; accepted 9 April 1999. Available online 25 August 1999. Abstract. The reactivation of two sets of pre-existing basement faults provided strong control on the geometric and kinematic evolution of the Paleozoic south Urals foreland thrust and fold belt. ...
Tectonophysics, 1997
The foreland thrust and fold belt of the southern Urals has a number of along-strike structural c... more The foreland thrust and fold belt of the southern Urals has a number of along-strike structural changes in which regional-scale structures terminate abruptly. One important along-strike structural change is the southern termination of the Precambrian-cored Bashkirian Anticlinorium, which plunges southward beneath the synformal Zilair Nappe. Balanced and restored dip cross-sections, a N-S-oriented strike section, together with a geological interpretation of
Tectonophysics, 2000
The southern Urals contain a well-preserved accretionary complex that has overthrust the continen... more The southern Urals contain a well-preserved accretionary complex that has overthrust the continental margin during arc-continent collision between the East European Craton (EEC ) and the Magnitogorsk island arc in the Late Devonian. Within the accretionary complex, we study three tectonic units that differ in deformation style, and each provides a unique geodynamic implication. The Zilair Nappe, the largest and best exposed unit, consists of 5-6 km of syncollisional, arc-derived Upper Devonian to Lower Carboniferous polymictic and graywacke turbidites that were deposited across the continental margin and incorporated by frontal accretion into the accretionary complex. The Zilair Nappe is a bivergent thrust imbricate where the west-vergent thrusts dominate and have associated kilometer-scale ramp anticlines with well developed east-dipping axial planar cleavage. Along its eastern contact, however, the cleavage fans until it dips moderately westward and the folds are east-vergent. Following its emplacement, west-vergent, basement-involved thrusting that breached the whole accretionary complex imbricated the Zilair Nappe. The Timirovo Duplex is structurally beneath the Zilair Nappe, and outcrops for several tens of kilometers along its northwestern margin. The duplex forms a west-vergent thrust stack composed of a highly deformed and sheared Lower and Middle Devonian reef carbonates of the former EEC margin platform. These rocks were shallowly underplated at the base of the accretionary complex during emplacement over the margin. The Suvanyak Complex outcrops along the eastern contact of the Zilair Nappe, and consists of polydeformed greenschist facies metasediments of the former EEC slope that were offscraped, underplated and incorporated at the rear of the accretionary complex.
Tectonics, 2001
The southern Urals of Russia contain a well-preserved example of a Paleozoic arc-continent collis... more The southern Urals of Russia contain a well-preserved example of a Paleozoic arc-continent collision in which the intraoceanic Magnitogorsk volcanic arc and its forearc basin sediments accreted to the East European Craton during the Devonian. The Magnitogorsk arc records the evolution from incipient intraoceanic subduction to a mature arc, and by comparing its surface geological features with those in active arccontinent collision settings it is possible to identfy upper crustal processes that were active in the southern Urals. The arc edifice can be divided into western and eastern volcanic fronts that were active during different stages of arc evolution and for which two distinct phases of forearc basin development can be recognized. The late Lower to Middle Devonian Aktau Formation represents a remnant of the intraoceanic to collisional forearc basin to the Irendyk volcanic front, whereas the Middle Devonian to Lower Carboniferous Ulutau, Koltubanian, and Zilair Formations were deposited in a suture forearc basin to the east Magnitogorsk volcanic front. It was not until the Late Devonian that these two basins were joined. Structural mapping, combined with reflection seismic profiling, shows these basins to be affected by open, nonlinear, volcanic basement-cored synsedimentary folds. The Karamalytash anticline appears to have the geometry of a growth fold that formed during deposition of sediments in the suture forearc basin. The forearc region is affected by minor thrusting that involves the volcanic basement, although it is not clear if these thrusts reactivate preexisting trench-parallel faults. Synsedimentary deformation, slumping, and olistostrome development were common throughout the suture forearc basin history but were especially widespread during the Late Devonian, when the full thickness of the continental crust is interpreted as having arrived at the subduction zone. ], whereas reflection seismic profiling and active seismicity studies have investigated processes at lower crustal and upper mantle levels [Snyder et al., 1996; Abets and McCaffrey, 1994]. In many fossil orogens, arc terranes are often strongly deformed, metamorphosed, and fragmented by postaccretion tectonic activity [e.g., Leggett et al., 1982; van Staal, 1994; Bedard et al., 1998; Puchkov, 1997], making it difficult to determine arc-continent collision processes from the variably preserved tectonostratigraphic units. The southern Uralide orogen of Russia (Figure 1), however, has been shown to contain an exceptionally well-preserved example of a Paleozoic arc-continent collision in which the upper crustal geological features can be determined at a level of detail comparable to those in active settings [e.g., Brown et al., 1998; Brown and Spadea, 1999]. This paper presents a detailed investigation of the structure and evolution of the Magnitogorsk forearc, focusing on the architecture of the forearc basin. It provides a new, detailed data set that allows us to compare the southern Urals arccontinent collision with those now active in the circum-Pacific, helping to identify the upper crustal processes that were active during the accretion of the Magnitogorsk arc to the East European Craton.
Tectonics, 1997
The first balanced and restored cross section through the foreland thrust and fold belt of the so... more The first balanced and restored cross section through the foreland thrust and fold belt of the southern Urals along the Belaya River of Bashkortostan is presented. This cross section is used to discuss the Paleozoic structure and kinematic evolution of the area and to provide quantitative estimates of fault displacement and shortening. The Belaya River thrust stack can be divided
Precambrian Research, 2003
In the SW Urals a change of tectonic conditions occurred at around 620 Ma leading to a detrital i... more In the SW Urals a change of tectonic conditions occurred at around 620 Ma leading to a detrital input from contrasting provenance areas. Fifty-seven detrital zircons were separated from Proterozoic sandstones of this setting to study their typologies and pattern of U-Pb systematics.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2009
The natural garnets from chromite ores associated with pegmatoid pyroxenites of Sangalyk area (Uc... more The natural garnets from chromite ores associated with pegmatoid pyroxenites of Sangalyk area (Uchaly ore district, southern Urals, Russia) were studied by means of micro-Raman spectroscopy. The compositions of these garnets were close to ugrandite, an isomorphous intermediate group of uvarovite-grossularite-andradite, X(3)Y(2)(SiO(4))(3), X = Ca(2+), Y = Al(3+), Fe(3+), Cr(3+), according to Raman spectra and X-ray microprobe analyses. An assignment of most of the observed bands in visible and near infrared Raman spectra is reported.
An integrated geological study of the tectono-metamorphic evolution of the metamorphic complex of... more An integrated geological study of the tectono-metamorphic evolution of the metamorphic complex of Beloretzk (MCB) which is part of the eastern Bashkirian mega-anticlinorium (BMA), SW Urals, Russia shows that the main lithological units are Neoproterozoic (Riphean and Vendian age) siliciclastic to carbonate successions. Granitic, syenitic and mafic intrusions together with subaerial equivalents comprise the Neo-and Mesoproterozoic magmatic rocks. The metamorphic grade ranges from diagenetic and very low grade in the western BMA to high-grade in the MCB. The N-S trending Zuratkul fault marks the change in metamorphic grade and structural evolution between the central and eastern BMA. Structural data, Pb/Pb-single zircon ages, 40 Ar/ 39 Ar cooling ages and the provenance signature of Riphean and Vendian siliciclastic rocks in the western BMA give evidence of Mesoproterozoic (Grenvillian) rifting, deformation and eclogite-facies metamorphism in the MCB and a Neoproterozoic (Cadomian) orogenic event in the SW Urals. Three pre-Ordovician deformation phases can be identified in the MCB. The first SSE-vergent, isoclinal folding phase (D 1 ) is younger than the intrusion of mafic dykes (Pb/Pb-single zircon: 1350 Ma) and older than the eclogite-facies metamorphism. High P/low T eclogite-facies metamorphism is bracketed by D 1 and the intrusion of the Achmerovo granite (Pb/Pb-single zircon: 5970 Ma). An extensional, sinistral, top-down-to-NW directed shearing (D 2 ) is correlated with the first exhumation of the MCB. E-vergent folding and thrusting (D 3 ) occurred at retrograde greenschist-facies metamorphic conditions. The tremolite 40 Ar/ 39 Ar cooling age (7189 5 Ma) of amphibolitic eclogite and muscovite 40 Ar/ 39 Ar cooling ages (about 550 Ma) of mica schists indicate that a maximum temperature of 500 950°C was not reached during the Neoproterozoic orogeny. The style and timing of the Neoproterozoic orogeny show similarities to the Cadomian-aged Timan Range NW of the Polar Urals. : S 0 3 0 1 -9 2 6 8 ( 0 1 ) 0 0 1 8 7 -5 U. A. Glasmacher et al. / Precambrian Research 110 (2001) 185-213 186 Geochronological and thermochronological data together with the abrupt change in structural style and metamorphism east of the Zuratkul fault, suggest that the MCB is exotic with respect to the SE-margin of the East European Platform. Thus, the MCB is named the 'Beloretzk Terrane'. Recognition of the 'Beloretzk Terrane' and the Neoproterozoic orogeny at the eastern margin of Baltica has important implications for Neoproterozoic plate reconstruction and suggests that the eastern margin of Baltica might have lain close to the Avalonian -Cadomian belt.
The mid-Ordovician Grampian Orogen of western Irish Caledonides, the Miocene Bismarck Orogen of N... more The mid-Ordovician Grampian Orogen of western Irish Caledonides, the Miocene Bismarck Orogen of New Guinea, and the early Cretaceous Nevadan Orogen of the Sierra Nevada probably developed by the collision of a supra-subduction zone (SSZ) ophiolite/oceanic arc (s) with a continental margin followed by a flip in subduction polarity, leading to the addition of oceanic arc complexes to the edges of continents and, hence, continental growth. In each, imminent collision is heralded by a switch from mafic to silicic magmatism, fore-arc/ ...
Geological Society, London, Memoirs, 2006
ABSTRACT
Tectonophysics, 1999
... Received 14 October 1998; accepted 9 April 1999. Available online 25 August 1999. Abstract. T... more ... Received 14 October 1998; accepted 9 April 1999. Available online 25 August 1999. Abstract. The reactivation of two sets of pre-existing basement faults provided strong control on the geometric and kinematic evolution of the Paleozoic south Urals foreland thrust and fold belt. ...
Tectonophysics, 1997
The foreland thrust and fold belt of the southern Urals has a number of along-strike structural c... more The foreland thrust and fold belt of the southern Urals has a number of along-strike structural changes in which regional-scale structures terminate abruptly. One important along-strike structural change is the southern termination of the Precambrian-cored Bashkirian Anticlinorium, which plunges southward beneath the synformal Zilair Nappe. Balanced and restored dip cross-sections, a N-S-oriented strike section, together with a geological interpretation of
Tectonophysics, 2000
The southern Urals contain a well-preserved accretionary complex that has overthrust the continen... more The southern Urals contain a well-preserved accretionary complex that has overthrust the continental margin during arc-continent collision between the East European Craton (EEC ) and the Magnitogorsk island arc in the Late Devonian. Within the accretionary complex, we study three tectonic units that differ in deformation style, and each provides a unique geodynamic implication. The Zilair Nappe, the largest and best exposed unit, consists of 5-6 km of syncollisional, arc-derived Upper Devonian to Lower Carboniferous polymictic and graywacke turbidites that were deposited across the continental margin and incorporated by frontal accretion into the accretionary complex. The Zilair Nappe is a bivergent thrust imbricate where the west-vergent thrusts dominate and have associated kilometer-scale ramp anticlines with well developed east-dipping axial planar cleavage. Along its eastern contact, however, the cleavage fans until it dips moderately westward and the folds are east-vergent. Following its emplacement, west-vergent, basement-involved thrusting that breached the whole accretionary complex imbricated the Zilair Nappe. The Timirovo Duplex is structurally beneath the Zilair Nappe, and outcrops for several tens of kilometers along its northwestern margin. The duplex forms a west-vergent thrust stack composed of a highly deformed and sheared Lower and Middle Devonian reef carbonates of the former EEC margin platform. These rocks were shallowly underplated at the base of the accretionary complex during emplacement over the margin. The Suvanyak Complex outcrops along the eastern contact of the Zilair Nappe, and consists of polydeformed greenschist facies metasediments of the former EEC slope that were offscraped, underplated and incorporated at the rear of the accretionary complex.
Tectonics, 2001
The southern Urals of Russia contain a well-preserved example of a Paleozoic arc-continent collis... more The southern Urals of Russia contain a well-preserved example of a Paleozoic arc-continent collision in which the intraoceanic Magnitogorsk volcanic arc and its forearc basin sediments accreted to the East European Craton during the Devonian. The Magnitogorsk arc records the evolution from incipient intraoceanic subduction to a mature arc, and by comparing its surface geological features with those in active arccontinent collision settings it is possible to identfy upper crustal processes that were active in the southern Urals. The arc edifice can be divided into western and eastern volcanic fronts that were active during different stages of arc evolution and for which two distinct phases of forearc basin development can be recognized. The late Lower to Middle Devonian Aktau Formation represents a remnant of the intraoceanic to collisional forearc basin to the Irendyk volcanic front, whereas the Middle Devonian to Lower Carboniferous Ulutau, Koltubanian, and Zilair Formations were deposited in a suture forearc basin to the east Magnitogorsk volcanic front. It was not until the Late Devonian that these two basins were joined. Structural mapping, combined with reflection seismic profiling, shows these basins to be affected by open, nonlinear, volcanic basement-cored synsedimentary folds. The Karamalytash anticline appears to have the geometry of a growth fold that formed during deposition of sediments in the suture forearc basin. The forearc region is affected by minor thrusting that involves the volcanic basement, although it is not clear if these thrusts reactivate preexisting trench-parallel faults. Synsedimentary deformation, slumping, and olistostrome development were common throughout the suture forearc basin history but were especially widespread during the Late Devonian, when the full thickness of the continental crust is interpreted as having arrived at the subduction zone. ], whereas reflection seismic profiling and active seismicity studies have investigated processes at lower crustal and upper mantle levels [Snyder et al., 1996; Abets and McCaffrey, 1994]. In many fossil orogens, arc terranes are often strongly deformed, metamorphosed, and fragmented by postaccretion tectonic activity [e.g., Leggett et al., 1982; van Staal, 1994; Bedard et al., 1998; Puchkov, 1997], making it difficult to determine arc-continent collision processes from the variably preserved tectonostratigraphic units. The southern Uralide orogen of Russia (Figure 1), however, has been shown to contain an exceptionally well-preserved example of a Paleozoic arc-continent collision in which the upper crustal geological features can be determined at a level of detail comparable to those in active settings [e.g., Brown et al., 1998; Brown and Spadea, 1999]. This paper presents a detailed investigation of the structure and evolution of the Magnitogorsk forearc, focusing on the architecture of the forearc basin. It provides a new, detailed data set that allows us to compare the southern Urals arccontinent collision with those now active in the circum-Pacific, helping to identify the upper crustal processes that were active during the accretion of the Magnitogorsk arc to the East European Craton.
Tectonics, 1997
The first balanced and restored cross section through the foreland thrust and fold belt of the so... more The first balanced and restored cross section through the foreland thrust and fold belt of the southern Urals along the Belaya River of Bashkortostan is presented. This cross section is used to discuss the Paleozoic structure and kinematic evolution of the area and to provide quantitative estimates of fault displacement and shortening. The Belaya River thrust stack can be divided