Garnet compositions as recorders of P–T–t history of metamorphic rocks

2010 ◽  
Vol 18 (1) ◽  
pp. 138-146 ◽  
Author(s):  
Massimiliano Tirone ◽  
Jibamitra Ganguly
Keyword(s):  
Metamorphic Rocks ◽  
History Of

scholarly journals Thermal history of the Sanbagawa metamorphic rocks.

1985 ◽  
Vol 93 (7) ◽  
pp. 515-527
Author(s):  
Shohei BANNO ◽  
Chihiro SAKAI ◽  
Masayuki OTSUKI
Keyword(s):  
Thermal History ◽  
Metamorphic Rocks ◽  
History Of

scholarly journals Mesostructures and deformational history of the Central Crystallines: an example from Garhwal Himalaya, India

1998 ◽  
Vol 17 ◽  
Author(s):  
V. K. Singh ◽  
S. P. Singh ◽  
P. S. Saklani ◽  
C. S. Dubey
Keyword(s):  
Large Scale ◽  
Ductile Deformation ◽  
Metamorphic Rocks ◽  
Geochronological Data ◽  
Deformational History ◽  
Crenulation Cleavage ◽  
Ductile Shearing ◽  
History Of ◽  
Transcurrent Faults ◽  
East West

Structural analysis reveals that the Central Crystallines in the Garhwal region were subjected to four phases of deformations (D1 to D4). The D1 deformational phase is highly obliterated and usually found as F1 intrafolial (rootless) tight isoclinal folds in migmatites and gneisses. The D2 deformational phase produced strong pervasive S2 schistosity and asymmetric and open fold (F2) plunging 20-30° towards ENE-WSW. The L2 lineation plunge 5-10° towards east-west is well developed in medium grade metamorphic rocks. The D1 deformations were responsible for F3 folds reflected in large scale anticlinal and synclinal, overturned and recumbent folds, which have 10-40° plunges towards NW. The late D3 deformational stresses were responsible for shearing along the middle limbs of F1 folds and they ultimately initiated thrusting. The NNE­ SSW plunging mineral or stretching lineation (L3), S3 crenulation cleavage and S-C fabrics were developed during the dominant ductile shearing related to the late D3 deformation. The D4 phase characterised by brittle-ductile deformation (minor kinks, puckers, transverse/transcurrent faults, and S-C' fabrics) and extensive cataclasis along thrust- and fault-zones reflects the last episode of deformation. The structural and geochronological data indicate that D1 and D2 deformation episodes may be related to the Precambrian time while D3 and D4 are exclusively of the Tertiary age.

scholarly journals HISTORY OF THE SOLOTVYNO HOLLOW OF TRANSCARPATHIA RELIEF DEVELOPMENT

2021 ◽  
pp. 129-137
Author(s):  
Yaroslav Kravchuk ◽  
Vasyl Chalyk
Keyword(s):  
Metamorphic Rocks ◽  
Main Attention ◽  
Palynological Analysis ◽  
Second Stage ◽  
Modern Period ◽  
Lower Pleistocene ◽  
History Of ◽  
River Valleys ◽  
Tectonic Movements

The analysis of four stages of relief development is done, which created the corresponding complexes within the Solotvyno hollow. The main attention is paid to the morphostructural and morphosculptural features. The morphostructures of the third and fourth orders are distinguished. Among the elements of morphosculpture the main attention is paid to denudation and denudation-accumulative surfaces (Kycherska, Skrydeyska, Boronyavska). The role of the new technological movements in the formation of these surfaces and river valleys was rated. The second stage of the upper baden is associated with the retreat of the sea basin and the division of the land into mountains. The main features of the modern relief were formed in the Pliocene Pleistocene stage - a river network with a complex of terraces, denudation and denudation-accumulative surfaces, quest forms in the marginal zone. Age of the Kicherska denudation surface is pannon-pont. According to the palynological analysis, the estimated age of the Skrydei denudation-accumulative surface is upper pliocene-lower pleistocene. The age of the Boronyava surface is considered to be Eopleistocene, and pebbles of metamorphic rocks are present in its alluvium (up to 5%). In the modern period, newer differentiated tectonic movements have become more active, which have contributed to the active manifestation of exogenous processes: erosion, landslides, and halogen karst. Key words: denudation and denudation-accumulative surfaces; power of ancient alluvium; modern morphodynamic processes.

THE TECTONIC SIGNIFICANCE OF MESOSCOPIC SUBFABRICS IN THE SOUTHERN ROCKY MOUNTAINS OF ALBERTA AND BRITISH COLUMBIA

1967 ◽  
Vol 4 (1) ◽  
pp. 39-70 ◽  
Author(s):  
R. A. Price
Keyword(s):  
Rocky Mountains ◽  
Metamorphic Rocks ◽  
Southern Rocky Mountains ◽  
Relative Extension ◽  
Discrete Surfaces ◽  
Tectonic Significance ◽  
Dynamic Analyses ◽  
History Of ◽  
Principal Elements ◽  
Layered Sequence

Deformation throughout much of the southern Rocky Mountains was characterized by brittle failure in a strongly anisotropic layered sequence of non-metamorphic rocks. On a megascopic scale, the overall structure is dominated by an interlocking system of imbricate thrust plates that have moved relatively eastward or northeastward and upward. On a mesoscopic scale, the principal elements in the fabric of these rocks are fractures that are statistically parallel or perpendicular to the bedding, or else intersect it at preferred angles of approximately 25° or 70°. During deformation many of these fractures obviously were kinematically active, as discrete surfaces of slip that became slickensided, as zones of dilation that became filled with vein minerals, or as surfaces of pressure solution that are now marked by stylolites. Each of these fractures provides a partial record of the kinematics of some stage of the deformation, even when they are considered individually rather than as components in a fracture array whose symmetry is related to that of the movement picture during deformation. Each defines a unique line of slip and axis of rotation for slip, or a unique direction of relative extension or compression. Collectively, they provide a direct and succinct record of the kinematic history of an individual fabric domain, and a sound basis for dynamic analyses of deformation.Some preliminary results of a reconnaissance study of these mesoscopic subfabrics illustrate their tectonic significance.A movement picture can be established for the deformation that occurs within an individual thrust plate during its development and translation. Kinematic relationships between and among the interlocking thrust plates can. be studied.Within a broad area centered along the prominent structural reentrant that crosses the Rocky Mountains near Crowsnest Pass, two different movement pictures occur in superposition. Movement about both northerly and north westerly trending axes can be outlined on the basis of the mesoscopic subfabrics of rocks which, on a megascopic scale, have either a northwesterly or a northerly trending fabric axis. Movement patterns for the deformation associated with each of two regional structural salients converge in the vicinity of the reentrant.The mesoscopic subfabrics associated with transverse faults in parts of the Front Ranges outline a pattern of movement which indicates that they did not originate as tear faults related to the translation of the thrust plates, but instead are probably older gravity faults, whose orientation may be controlled by the fabric of the Hudsonian basement extending beneath the mountains from the Canadian Shield.

How Himalayan collision stems from subduction

Geology ◽  
2021 ◽  
Author(s):  
M. Soret ◽  
K.P. Larson ◽  
J. Cottle ◽  
A. Ali
Keyword(s):  
Foreland Basin ◽  
Continental Collision ◽  
Ultrahigh Pressure ◽  
Metamorphic Rocks ◽  
Conductive Heat ◽  
Plate Interface ◽  
Continental Subduction ◽  
Metamorphic History ◽  
Orogenic Wedge ◽  
History Of

The mechanisms and processes active during the transition from continental subduction to continental collision at the plate interface are largely unknown. Rock records of this transition are scarce, either not exposed or obliterated during subsequent events. We examine the tectono-metamorphic history of Barrovian metamorphic rocks from the western Himalayan orogenic wedge. We demonstrate that these rocks were buried to amphibolite-facies conditions from ≤47 Ma to 39 ± 1 Ma, synchronously with the formation (46 Ma) and partial exhumation (45–40 Ma) of the ultrahigh-pressure eclogites. This association indicates that convergence during continental subduction was accommodated via development of a deep orogenic wedge built through successive underplating of continental material, including the partially exhumed eclogites, likely in response to an increase in interplate coupling. This process resulted in the heating of the subduction interface (from ~7 to ~20 °C/km) through advective and/or conductive heat transfer. Rapid cooling of the wedge from 38 Ma, coeval with the formation of a foreland basin, are interpreted to result from indentation of a promontory of thick Indian crust.

Re-investigating the Barrovian metamorphic rocks of the Isbjørnhamna Group, Svalbard Caledonides

2021 ◽  
Author(s):  
Margot Patry ◽  
Iwona Klonowska ◽  
Karolina Kośmińska ◽  
Jarosław Majka
Keyword(s):  
High Arctic ◽  
Metamorphic Rocks ◽  
Metamorphic History ◽  
South West ◽  
Science Centre ◽  
National Science ◽  
History Of ◽  
Orogenic Events ◽  
Preliminary Phase

<p>The Isbjørnhamna Group, which crops out in the south-west of Svalbard in the High Arctic, is crucial for understanding Svalbard’s regional geology. It can be traced in southern Wedel Jarlsberg Land and Sørkapp Land, and it consists of a Barrovian-type series of metapelites that were metamorphosed during the Torellian (c. 640Ma; Majka et al. 2008) and overprinted during the Caledonian orogenesis (Majka & Kośmińska, 2017). Although relatively recent petrological study exists, there are certain gaps in it. In order to fill these gaps, we decided to re-investigate these rocks using the most up-to-date petrochronological approach. Hence, we aim to determine the metamorphic history of these rocks in detail, test the hypothesis if there are indeed several orogenic events registered by these rocks and what was a possible exhumation mechanism responsible for uplift of this sequence.</p><p>The studied garnet-bearing mica schists preserve four different parageneses, ranging from chloritoid to kyanite metamorphic zones. Here we report on the samples containing chlorite and chloritoid, kyanite, staurolite and both staurolite and kyanite. The studied samples are the same exact rocks that have been previously studied by Majka et al. (2008, 2010) using both geothermobarometry and petrogenetic grids in the KFMASH system. According to those authors the estimated pressure-temperature conditions (P-T) were c. 655°C at 11kbar for the kyanite-bearing shist, c. 624°C at 6.6 to 8.7kbar for the staurolite + kyanite pelite and c. 580°C at 8-9kbar for the staurolite-bearing rock. The chloritoid schist has not been studied previously.</p><p>Our preliminary phase equilibrium modelling in the MnNCKFMASHTO system using the Theriak-Domino software indicates P-T conditions of c. 660°C at 7 kbar for the kyanite-schist and c. 575°C at 8 to 9.5kbar for the staurolite-schist, respectively. The chloritoid schist yielded conditions of c. 560°C at 7.5kbar. Further P-T modelling coupled with in-situ Ar-Ar and U-Pb geochronology should allow for much better understanding of the complex geological history of these rocks as well as potential flaws in the previous studies.</p><p> </p><p>Research funded by National Science Centre (Poland) project no. 2019/33/B/ST10/01728.</p><p> </p><p>References:</p><p>Majka & Kośmińska (2017): Arktos, 3:5, 1.17.</p><p>Majka et al. (2008): Geological Magazine, 145, 822-830.</p><p>Majka et al. (2010): Polar Research, 29, 250-264.        </p>

Forestry

1983 ◽  
Vol 84 ◽  
pp. 141-170
Author(s):  
J. D. Matthews
Keyword(s):  
Alnus Glutinosa ◽  
Metamorphic Rocks ◽  
Historical Sources ◽  
Black Alder ◽  
Deciduous Woodland ◽  
Ulmus Glabra ◽  
History Of ◽  
Mineral Soils ◽  
River Valleys ◽  
Oak Ash

Anderson (F.R.S.E. 1952), in A History of Scottish Forestry (1967), pieced together from many varied historical sources a picture of the natural indigenous woodlands of Scotland, which has been confirmed by scientific studies based on pollen counts and botanical analysis (McVean 1964; Durno 1973; Godwin 1975). The species composition of these natural indigenous woodlands was closely associated with geology, soil and elevation. Around the coast and in the lower parts of the river valleys, the moist, fertile mineral soils carried deciduous woodland comprising oak (Quercus robur and Q. petraea), Wych elm (Ulmus glabra), ash (Fraxinus excelsior) and Black alder (Alnus glutinosa). On the drier soils, there was less ash and elm but more birch (Betula pendula and B. pubescens) along with the oak. Above the oak-ash-elm woodlands, on the lower and middle slopes of hills composed of igneous and rich metamorphic rocks, the woodlands included birch, alder, aspen (Populus tremuld), rowan (Sorbus aucuparia), willow (Salix species) and hazel (Corylus avellana). Above this zone were short scrubby stands of birch and willow.

Les bassins sedimentaires du nord de la Corse; essai de synthese stratigraphique et apercu tectonique

1964 ◽  
Vol S7-VI (3) ◽  
pp. 322-333
Author(s):  
Roland Delcey ◽  
Jean Claude Limasset ◽  
Pierre Routhier
Keyword(s):  
Metamorphic Rocks ◽  
Pillow Lavas ◽  
Tectonic History ◽  
Basement Rocks ◽  
Structural Nature ◽  
History Of

Abstract The Saint Florent, Balagne, and Francardo basins of northern Corsica, surrounded by Paleozoic granitic and metamorphic rocks, are occupied by Permian to Triassic arkosic clastics and rhyolite overlain by dolomitic limestones, Jurassic limestones and spilite pillow lavas, Cretaceous flysch and overlying Globotrunca marly and sandy limestones, Eocene arkosic clastics, Nummulite limestone, and flysch. Although the paleogeographic history of the three basins differs in details, it was essentially the same in major features. The tectonic history, however, differed considerably depending on the structural nature of the underlying basement rocks of the basins. Presence of nappes of distant origin is suspected from relationships of the Cretaceous flysch and the Paleozoic schists east of Francardo.

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