scholarly journals Finite lattice distortion patterns in plastically deformed zircon grains

2014 ◽  
Vol 6 (2) ◽  
pp. 1799-1861 ◽  
Author(s):  
E. Kovaleva ◽  
U. Klötzli ◽  
G. Habler ◽  
E. Libowitzky
Keyword(s):  
Lattice Distortion ◽  
Subgrain Boundary ◽  
Microstructural Analysis ◽  
Finite Lattice ◽  
Shear Zones ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Type I ◽  
Slip Systems ◽  
Type Iii

Abstract. This study examines finite deformation patterns of zircon grains from high-temperature natural shear zones. Various zircon-bearing rocks were collected in the Western Tauern Window, Eastern Alps, where they were deformed under amphibolite facies conditions, and in the Ivrea-Verbano Zone (IVZ), Southern Alps, where deformation is related with granulite-facies metamorphism. Among the sampled rocks are: granitic orthogneisses, meta-lamprophyres and paragneisses, all of which are highly deformed. The investigated zircon grains ranging from 10 to 50 microns were studied in situ using a combination of scanning electron microscope (SEM) techniques, including secondary electron (SE), backscattered electron (BSE), forward scattered electron (FSE), cathodoluminescence (CL) imaging, and crystallographic orientation mapping by electron backscatter diffraction analysis (EBSD), as well as micro-Raman spectroscopy. Energy-dispersive X-ray spectrometry (EDS) was applied to host phases. Microstructural analysis of crystal-plastically deformed zircon grains was based on high-resolution EBSD maps. Three general types of finite lattice distortion patterns were detected: Type (I) is defined by gradual bending of the zircon lattice with orientation changes of about 0.6° to 1.4° per μm without subgrain boundary formation. Type (II) represents local gradual bending of the crystal lattice coupled with the formation of subgrain boundaries that have concentric semicircular shapes in 2-D sections. Cumulative grain-internal orientation variations range from 7° to 40° within single grains. Type (III) is characterized by formation of subgrains separated by a well-defined subgrain boundary network, where subgrain boundaries show a characteristic angular closed contour in 2-D sections. The cumulative orientation variation within a single grain ranges from 3° to 10°. Types (I) and (II) predominate in granulite facies rocks, whereas type (III) is restricted to the amphibolite facies rocks. Investigated microstructures demonstrate that misorientation axes are usually parallel to the ⟨ 001 ⟩ and ⟨ 100 ⟩ crystallographic directions; dominant slip systems operating along tilt boundaries are ⟨ 010 ⟩{001}, ⟨ 010 ⟩{100} and ⟨ 001 ⟩{010}. In case of twist boundaries the slip systems ⟨ 010 ⟩{001} and ⟨ 100 ⟩ {001} are active, whereas in some grains cross-slip takes place. This study demonstrates that activation of energetically preferable slip systems is mostly controlled by the degree of coupling with the host phase and by the viscosity ratio between inclusion and host, and defined by crystallographic and elastic anisotropy of the zircon lattice.

scholarly journals Finite lattice distortion patterns in plastically deformed zircon grains

Solid Earth ◽  
2014 ◽  
Vol 5 (2) ◽  
pp. 1099-1122 ◽  
Author(s):  
E. Kovaleva ◽  
U. Klötzli ◽  
G. Habler ◽  
E. Libowitzky
Keyword(s):  
Lattice Distortion ◽  
Subgrain Boundary ◽  
Microstructural Analysis ◽  
Finite Lattice ◽  
Shear Zones ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Type I ◽  
Soft Phase ◽  
Type Iii

Abstract. This study examines finite deformation patterns of zircon grains from high-temperature natural shear zones. Various zircon-bearing rocks were collected in the Western Tauern Window, eastern Alps, where they were deformed under amphibolite facies conditions, and in the Ivrea–Verbano Zone (IVZ), southern Alps, where deformation is related with granulite-facies metamorphism. Among the sampled rocks are granitic orthogneisses, metalamprophyres and paragneisses, all of which are strongly deformed. The investigated zircon grains ranging from 10 to 50 μm were studied in situ using a combination of scanning electron microscope (SEM) techniques, backscattered electron (BSE) imaging, forward-scattered electron (FSE) imaging, cathodoluminescence (CL) imaging, and crystallographic orientation mapping by electron backscatter diffraction (EBSD), as well as micro-Raman spectroscopy. Energy-dispersive X-ray spectrometry (EDS) was applied to host phases. Microstructural analysis of crystal-plastically deformed zircon grains was based on high-resolution EBSD maps. Three general types of finite lattice distortion patterns were detected: type (I) is defined by gradual bending of the zircon lattice with orientation changes of about 0.6–1.8° per micrometer without subgrain boundary formation. Cumulative grain-internal orientation variations range from 7 to 25° within single grains. Type (II) represents local gradual bending of the crystal lattice accompanied by the formation of subgrain boundaries that have concentric semicircular shapes in 2-D sections. Cumulative grain-internal orientation variations range from 15 to 40° within single grains. Type (III) is characterized by formation of subgrains separated by a well-defined subgrain boundary network, where subgrain boundaries show a characteristic angular closed contour. The cumulative orientation variation within a single grain ranges from 3 to 10°. Types (I) and (II) predominate in granulite facies rocks, whereas type (III) is restricted to the amphibolite facies rocks. The difference in distortion patterns is controlled by strain rate and by ratio between dislocation formation and dislocation motion rates, conditioned by the amount of differential stress. Investigated microstructures demonstrate that misorientation axes are usually parallel to the < 001 > and < 100 > crystallographic directions; dominant slips are < 010 > {001}, < 010 > {100} and < 001 > {010}, whereas in some grains cross-slip takes place. This study demonstrates that activation of energetically preferable slip systems is facilitated if zircon grain is decoupled from the host matrix and/or hosted by a soft phase.

scholarly journals Metamorphic fingerprints of Fe-rich chromitites from the Eastern Pampean Ranges, Argentina

2020 ◽  
Vol 72 (3) ◽  
pp. A080420
Author(s):  
Vanessa Colás ◽  
Ignacio Subías ◽  
José María González-Jiménez ◽  
Joaquín A. Proenza ◽  
Isabel Fanlo ◽  
...  
Keyword(s):  
Granulite Facies ◽  
Amphibolite Facies ◽  
Phase Iii ◽  
Type I ◽  
Type Ii ◽  
Prograde Metamorphism ◽  
Slow Cooling ◽  
Rich Phase ◽  
Type Iii ◽  
Suprasubduction Zone

Chromitites hosted in the serpentinized harzburgite bodies from Los Congos and Los Guanacos (Eastern Pampean Ranges, north Argentina) record a complex metamorphic evolution. The hydration of chromitites during the retrograde metamorphism, their subsequent dehydration during the prograde metamorphism and the later-stage cooling, have resulted in a threefold alteration of chromite: i) Type I is characterized by homogeneous Fe3+- and Cr-rich chromite; ii) Type II chromite contains exsolved textures that consist in blebs and fine lamellae of a magnetite-rich phase hosted in a spinel-rich phase; iii) Type III chromite is formed by variable proportions of magnetite-rich and spinel-rich phases with symplectitic texture. Type I chromite shows lower Ga and higher Co, Zn and Mn than magmatic chromites from chromitites in suprasubduction zone ophiolites as a consequence of the redistribution of these elements between Fe3+-rich non-porous chromite and silicates during the prograde metamorphism. Whereas, the spinel-rich phase in Type III chromite is enriched in Co, Zn, Sc, and Ga, but depleted in Mn, Ni, V and Ti with respect to the magnetite-rich phase, due to the metamorphic cooling from high-temperature conditions. The pseudosection calculated in the fluid-saturated FCrMACaSH system, and contoured for Cr# and Mg#, allows us to constrain the temperature of formation of Fe3+-rich non-porous chromite by the diffusion of magnetite in Fe2+-rich porous chromite at <500 ºC and 20 kbar. The subsequent dehydration of Fe3+-rich non-porous chromite by reaction with antigorite and chlorite formed Type I chromite and Mg-rich olivine and pyroxene at >800 ºC and 10 kbar. The ultimate hydration of silicates in Type I chromite and the exsolution of Type II and Type III chromites would have started at ~600 ºC. These temperatures are in the range of those estimated for ocean floor serpentinization (<300 ºC and <4 kbar), the regional prograde metamorphism in the granulite facies (800 ºC and <10 kbar), and subsequent retrogression to the amphibolite facies (600 ºC and 4-6.2 kbar) in the host ultramafic rocks at Los Congos and Los Guanacos. A continuous and slow cooling from granulite to amphibolite facies produced the exsolution of spinel-rich and magnetite-rich phases, developing symplectitic textures in Type III chromite. However, the discontinuous and relatively fast cooling produced the exsolution of magnetite-rich phase blebs and lamellae within Type II chromite. The P-T conditions calculated in FCrMACaSH system and the complex textural and geochemical fingerprints showed by Type I, Type II and Type III chromites leads us to suggest that continent-continent collisional orogeny better records the fingerprints of prograde metamorphism in ophiolitic chromitites.

Proterozoic geological evolution of the northern Vestfold Hills, Antarctica

1991 ◽  
Vol 128 (4) ◽  
pp. 307-318 ◽  
Author(s):  
C. W. Passchier ◽  
R. F. Bekendam ◽  
J. D. Hoek ◽  
P. G. H. M. Dirks ◽  
H. de Boorder
Keyword(s):  
Large Scale ◽  
Structural Evolution ◽  
Shear Zones ◽  
Granulite Facies ◽  
Strike Slip ◽  
Amphibolite Facies ◽  
Tectonic Event ◽  
Vestfold Hills ◽  
Two Phases ◽  
Brittle Faulting

AbstractThe presence of polyphase shear zones transected by several suites of dolerite dykes in Archaean basement of the Vestfold Hills, East Antarctica, allows a detailed reconstruction of the local structural evolution. Archaean and early Proterozoic deformation at granulite facies conditions was followed by two phases of dolerite intrusion and mylonite generation in strike-slip zones at amphibolite facies conditions. A subsequent middle Proterozoic phase of brittle normal faulting led to the development of pseudotachylite, predating intrusion of the major swarm of dolerite dykes around 1250 Ma. During the later stages and following this event, pseudotachylite veins were reactivated as ductile, mylonitic thrusts under prograde conditions, culminating in amphibolite facies metamorphism around 1000–1100 Ma. This is possibly part of a large-scale tectonic event during which the Vestfold block was overthrust from the south. In a final phase of strike-slip deformation, several pulses of pseudotachylite-generating brittle faulting alternated with ductile reactivation of pseudotachylite.

Pre-Caledonian granulite and gabbro enclaves in the Western Gneiss Region, Norway: indications of incomplete transition at high pressure

2000 ◽  
Vol 137 (3) ◽  
pp. 235-255 ◽  
Author(s):  
M. KRABBENDAM ◽  
A. WAIN ◽  
T. B. ANDERSEN
Keyword(s):  
High Pressure ◽  
Shear Zones ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Ultrahigh Pressure ◽  
Western Gneiss Region ◽  
Ultrahigh Pressure Metamorphism ◽  
Mountain Belts ◽  
Orogenic Cycle ◽  
Highly Strained

The Western Gneiss Region of Norway is a continental terrane that experienced Caledonian high-pressure and ultrahigh-pressure metamorphism. Most rocks in this terrane show either peak-Caledonian eclogite-facies assemblages or are highly strained and equilibrated under late-Caledonian amphibolite-facies conditions. However, three kilometre-size rock bodies (Flatraket, Ulvesund and Kråkenes) in Outer Nordfjord preserve Pre-Caledonian igneous and granulite-facies assemblages and structures. Where these assemblages are preserved, the rocks are consistently unaffected by Caledonian deformation. The three bodies experienced high-pressure conditions (20–23 kbar) but show only very localized (about 5%) eclogitization in felsic and mafic rocks, commonly related to shear zones. The preservation of Pre-Caledonian felsic and mafic igneous and granulite-facies assemblages in these bodies, therefore, indicates widespread (∼ 95%) metastability at pressures higher than other metastable domains in Norway. Late-Caledonian amphibolite-facies retrogression was limited. The degree of reaction is related to the protolith composition and the interaction of fluid and deformation during the orogenic cycle, whereby metastability is associated with a lack of deformation and lack of fluids, either as a catalyst or as a component in hydration reactions. The three bodies appear to have been far less reactive than the external gneisses in this region, even though they followed a similar pressure–temperature evolution. The extent of metastable behaviour has implications for the protolith of the Western Gneiss Region, for the density evolution of high-pressure terranes and hence for the geodynamic evolution of mountain belts.

scholarly journals Tectonic and chemical implications of cathodoluminescent microstructures in quartz, Parry Sound domain, Ontario, Canada

2017 ◽  
Vol 54 (6) ◽  
pp. 677-692 ◽  
Author(s):  
Stephanie G. Mills ◽  
Christopher Gerbi ◽  
Jeffrey H. Marsh ◽  
Martin G. Yates ◽  
Sheila J. Seaman ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Shear Zones ◽  
Granulite Facies ◽  
Element Distribution ◽  
Amphibolite Facies ◽  
Trace Element Distribution ◽  
Scanning Transmission ◽  
Mechanisms Of Formation ◽  
Lower Temperature ◽  
Straight Lines

Cathodoluminescence (CL) imaging of quartz in orthogneiss of the Parry Sound domain, Grenville Province, Ontario, Canada, reveals four dark microstructures—medium-dark grains, mantles, sinuous lines, and straight lines. The Parry Sound domain experienced granulite-facies deformation and metamorphism followed by variable degrees of amphibolite-facies retrogression associated with the development of retrograde shear zones. We integrate our observations of CL-visible quartz microstructures with structures observable with optical and scanning transmission electron microscopy, analyses of water species concentration, and trace element distribution in quartz, as well as with microstructures in plagioclase, to determine their characteristics and elucidate their timing and mechanisms of formation relative to the deformational history. Medium-dark grains are primarily located in and near kilometer-scale shear zones at the margins of the Parry Sound domain, have notably darker cores than most samples in the interior, and may have higher water contents than other samples in the interior. These grains formed during late shearing, at a lower temperature than CL-bright grains; they thus provide evidence that the large shear system narrowed with time. Dark mantles occur at grain boundaries and correlate with higher concentrations of Fe. They formed after the first shearing event, but while still at amphibolite facies, and they provide evidence for post-kinematic alteration at grain boundaries. Dark sinuous lines correspond to subgrain boundaries that formed after retrograde shearing, but while still at amphibolite facies. Dark straight lines correspond to fluid inclusion trails and most likely formed at low temperatures and pressures during exhumation.

scholarly journals The northern boundary of the Proterozoic (Nagssugtoqidian) mobile belt of South-East Greenland

1989 ◽  
Vol 146 ◽  
pp. 54-65
Author(s):  
P.R Dawes ◽  
N.J Soper ◽  
J.C Escher ◽  
R.P Hall
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Mobile Belt ◽  
Basic Dyke ◽  
Northern Boundary ◽  
East Greenland ◽  
Diffuse Region

The Proterozoic mobile belt of South-East Greenland has been regarded as a classic example of amphibolite facies reworking of an Archaean granulite facies gneiss terrain. Its northern boundary has been interpreted as a transcurrent shear zone in which reworking was associated with major basic dyke emplacement. A re-examination of the northern boundary shows it to be a diffuse region more than 50 km wide in which retrogression, unrelated to dykes or shear zones, gradually intensifies southwards. Superimposed on this are discrete belts of retrogression associated with dykes and shear zones. The sense of displacement on the latter is compatible with thrusting of the northern Archaean block southwards over the reworked terrain of the mobile belt.

scholarly journals Metamorphism of the Kangâmiut dykes and the metamorphic and structural evolution of the southern Nagssugtoqidian boundary in the Itivdleq – Ikertôq region, West Greenland

1979 ◽  
Vol 89 ◽  
pp. 63-75
Author(s):  
J.A Korstgård
Keyword(s):  
Structural Evolution ◽  
Shear Zones ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Mobile Belt ◽  
Metamorphic Evolution ◽  
West Greenland ◽  
Subsequent Deformation ◽  
Affected Country

The structural evolution of the Nagssugtoqidian mobile belt is characterised by reworking of pre-existing Archaean rocks. At the southern Nagssugtoqidian boundary swarms of basic dykes, the Kangamiut dykes, intruded after the earliest Nagssugtoqidian movements. These dykes aet as time markers separating tectono-metamorphic events and record degree and extent of post-dyke metamorphism and deformation. The structural and metamorphic evolution at the southern Nagssugtoqidian boundary ean be summarised as follows. The rocks now exposed were stabilised in granulite and amphibolite facies in Archaean times. Uplift brought the rocks under low amphibolite facies conditions. Subsequent deformation (Nag. 1) caused the retrogression to low amphibolite facies and transformed the rocks into strongly schistose rocks along duetile, transcurrent, E-W trending shear zones. The Nag. 1 deformation was followed by intrusion of the mainly NE trending Kangamiut dykes. Later Nagssugtoqidian deformation (Nag. 2) affected country rocks with Nag. 1 fabrics as well as dykes and probably also Archaean gneisses unaffected by Nag. 1 deformation. In areas with intense Nag. 2 movements the deformation was characterised by duetile overthrusting towards the SSE along a linear zone striking ENE. New Nag. 2 fabrics were imposed on the country gneisses and dykes were transformed into strongly deformed amphibolites. The duetile overthrusting brought granulite facies rocks into juxtaposition with amphibolite facies rocks so that across the areas affected by Nag. 2 deformation a prograde metamorphic sequence with facies boundaries parallel to the overthrusting zone was established.

Methionine-Specific Staining of Collagen

1982 ◽  
Vol 40 ◽  
pp. 294-295
Author(s):  
E.M. Kuhn ◽  
K.D. Marenus ◽  
M. Beer
Keyword(s):  
Amino Acids ◽  
Collagen Fibers ◽  
Type Iii Collagen ◽  
Type I ◽  
Electron Microscopic ◽  
Good Correspondence ◽  
Specific Staining ◽  
Type Iii ◽  
Different Types ◽  
Sulfur Containing

Fibers composed of different types of collagen cannot be differentiated by conventional electron microscopic stains. We are developing staining procedures aimed at identifying collagen fibers of different types.Pt(Gly-L-Met)Cl binds specifically to sulfur-containing amino acids. Different collagens have methionine (met) residues at somewhat different positions. A good correspondence has been reported between known met positions and Pt(GLM) bands in rat Type I SLS (collagen aggregates in which molecules lie adjacent to each other in exact register). We have confirmed this relationship in Type III collagen SLS (Fig. 1).

Labelling of non-A, non-B hepatitis infected chimpanzee hepatocytes with nuclease-gold conjugates

1984 ◽  
Vol 42 ◽  
pp. 250-251
Author(s):  
G. D. Gagne ◽  
M. F. Miller ◽  
D. A. Peterson
Keyword(s):  
Endoplasmic Reticulum ◽  
Experimental Infection ◽  
Uranyl Acetate ◽  
Type I ◽  
Cellular Injury ◽  
Type Ii ◽  
Tubular Structures ◽  
Type Iii ◽  
Type Iv ◽  
Infected Chimpanzee

Experimental infection of chimpanzees with non-A, non-B hepatitis (NANB) or with delta agent hepatitis results in the appearance of characteristic cytoplasmic alterations in the hepatocytes. These alterations include spongelike inclusions (Type I), attached convoluted membranes (Type II), tubular structures (Type III), and microtubular aggregates (Type IV) (Fig. 1). Type I, II and III structures are, by association, believed to be derived from endoplasmic reticulum and may be morphogenetically related. Type IV structures are generally observed free in the cytoplasm but sometimes in the vicinity of type III structures. It is not known whether these structures are somehow involved in the replication and/or assembly of the putative NANB virus or whether they are simply nonspecific responses to cellular injury. When treated with uranyl acetate, type I, II and III structures stain intensely as if they might contain nucleic acids. If these structures do correspond to intermediates in the replication of a virus, one might expect them to contain DNA or RNA and the present study was undertaken to explore this possibility.

Human non-parenchymal liver cells produce type I and type III interferons in response to poly I:C, thereby mediating an antiviral state against HCV

2014 ◽  
Vol 52 (01) ◽  
Author(s):  
M Lutterbeck ◽  
R Broering ◽  
K Kleinehr ◽  
A Paul ◽  
G Gerken ◽  
...  
Keyword(s):  
Liver Cells ◽  
Poly I:C ◽  
Type I ◽  
Antiviral State ◽  
Type Iii ◽  
Parenchymal Liver
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