Metamorphic micro-textural variations and their bearing on rock technical properties. A case study of the transition from greenschist- to high-pressure granulite-facies in the Eastern Segment, Sveconorwegian orogen

2020 ◽  
Author(s):  
Cindy Urueña ◽  
Charlotte Möller ◽  
Jenny Andersson ◽  
Mattias Göransson ◽  
Jan Erik Lindqvist ◽  
...  
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
Los Angeles ◽  
Partial Melting ◽  
Granulite Facies ◽  
Gradual Change ◽  
Average Grain Size ◽  
High Pressure Granulite ◽  
Eastern Segment ◽  
Technical Properties

<p>The Precambrian shield in southern Sweden exposes a granitic bedrock segment that represents a part of an ancient eroded mountain belt and expose a gradual change in metamorphic grade from cold (<300°C), little affected by recrystallization, to hot (>800°C) and partially molten sections at the west coast (Möller and Andersson, 2018). This area – the Eastern Segment – offers a large scale study of the interdependence of metamorphism, deformation, partial melting, and functional properties of crushed rock aggregates.</p><p>In the petrological community, it is well-known that the evolution of a metamorphic unit (e.g. a high-pressure unit) with respect to pressure, temperature, time, and deformation holds key information on its tectonic history. It has rarely been emphasized, however, that the same factors determine the physical properties of the rock and thus, its technical properties. Basic research in metamorphic petrology thus contributes with a fundament to applied and technical science, e.g. by providing data that lead to quarrying of proper materials.</p><p>This study assesses the variations of technical properties with the metamorphic state, primarily metamorphic temperature and partial melting during metamorphism. Our first results show the correlation between the petrological characteristics and technical properties of felsic orthogneiss within a migmatized eclogite-bearing terrane and its high-pressure granulite-bearing footwall.</p><p>Measurements include the Los Angeles and Micro-Deval value tests. The Los Angeles value is a measure of the resistance to fragmentation (EN 1097-2, 2010). The Micro-Deval test measures the resistance to wear.</p><p>High values of the Los Angeles and Micro-Deval analyses for felsic orthogneiss in the eclogite-bearing domain reflect poor technical properties and are largely linked to that the rocks underwent partial melting. Orthogneisses in the footwall, which recrystallized under high-temperature, dry conditions, and without partial melting, tend to have lower values. This group includes high-quality rocks for the production of aggregates suitable for asphalt base courses and unbound road layers.</p><p>Micro-textures in the orthogneisses are linked with these metamorphic conditions. The clinopyroxene-bearing orthogneisses have complex grain boundaries and micro-perthitic feldspars, finer average grain size, lower biotite content, and absence of migmatitic segregation or penetrative veining. These textures in the footwall orthogneisses contrast with those in the migmatitic orthogneisses from the eclogite-bearing domain, which have a coarser average grain size, even-grained and granoblastic texture, and lack of perthitic texture in feldspars. Thus, these petrographic parameters govern the technical differences.</p><p>Our ongoing research addresses the relations between macro-fabric, micro-texture and technical properties of felsic orthogneiss and metagabbro, respectively, along 120 km profile across the metamorphic field gradient from greenschist- to high-pressure granulite-facies in the Eastern Segment.</p>

Pétrologie des niveaux trondhjémitiques de haute pression associés aux éclogites et amphibolites des complexes leptyno-amphiboliques du Massif Central français

1978 ◽  
Vol 15 (5) ◽  
pp. 696-707 ◽  
Author(s):  
C. Nicollet ◽  
A. Leyreloup
Keyword(s):  
High Pressure ◽  
Partial Melting ◽  
Granulite Facies ◽  
Massif Central ◽  
Granulite Facies Metamorphism ◽  
High Pressure Granulite ◽  
Greenstone Belts ◽  
Metamorphic Terranes ◽  
Archean Greenstone Belts ◽  
Initial Mineral

High pressure trondhjemitic rocks interbedded with eclogites and high pressure amphibolites have been recognized in the leptyno-amphibolitic series of the Rouergue and Marvejols metamorphic terranes. These rocks appear to have been derived by partial melting of the surrounding amphibolites (or amphibole-gabbro) at [Formula: see text] (<7 × 105 kPa). The initial mineral assemblage of these layers (Q, Pl, Ky, Ga, Zo, etc.) is suggested by microstructural evidence to have crystallized directly under high pressure granulite facies conditions (12.5 kbar <PT <20 kbar (12.5 × 105 kPa < PT <20 × 105 kPa); 750 °C<T<840 °C) from the trondhjemitic liquid. The partial melting has taken place before the well-known Barrovian metamorphism that has affected the whole crystalline basement of the French Massif Central. This older metamorphic event is considered to be equivalent to the high pressure granulite facies metamorphism recognized in the Variscan of Europe. This acid–basic high pressure bimodal association argues for a close similarity between Archean greenstone belts and the leptyno-amphibolitic series.

Chapter 15 Polyphase (1.9–1.8, 1.5–1.4 and 1.0–0.9 Ga) deformation and metamorphism of Proterozoic (1.9–1.2 Ga) continental crust, Eastern Segment, Sveconorwegian orogen

2020 ◽  
Vol 50 (1) ◽  
pp. 351-396 ◽  
Author(s):  
Michael B. Stephens ◽  
Carl-Henric Wahlgren
Keyword(s):  
High Pressure ◽  
Variable Temperature ◽  
Active Continental Margin ◽  
Granulite Facies ◽  
Metavolcanic Rocks ◽  
High Pressure Granulite ◽  
Facies Metamorphism ◽  
Eastern Segment ◽  
Sveconorwegian Orogen ◽  
East West

AbstractThe Eastern Segment in the Sveconorwegian orogen comprises Paleoproterozoic–Mesoproterozoic magmatic suites, which formed along an active continental margin, and Mesoproterozoic suites emplaced during intracratonic extension. Zn–Pb sulphide and Fe oxide mineralizations in 1.9 Ga metavolcanic rocks form a significant mineral resource cluster in the northeastern part. Deformation and metamorphism under low-pressure (≤5 kbar) and variable-temperature conditions, including anatexis and granulite facies, prevailed during 1.9–1.8 Ga (Svecokarelian) and 1.5–1.4 Ga (Hallandian) accretionary orogenies. Sveconorwegian tectonothermal reworking initiated at c. 0.99–0.98 Ga in structurally lower levels. Crustal shortening, underthrusting with eclogite facies metamorphism (18 kbar), exhumation by eastwards thrusting (D1) during continued shortening and high-pressure granulite (8–12 kbar) to upper amphibolite facies metamorphism prevailed. Anatexis and folding around east–west axial surfaces with west-northwesterly constrictional strain (D2) followed at c. 0.98–0.95 Ga, being consanguineous with crustal extension. Structurally higher levels, northwards and eastwards, consist of high-pressure (10–12 kbar) orthogneisses, not affected by anatexis but also showing polyphase deformation. Sveconorwegian convergence ceased with upright folding along north–south axial surfaces and, in the uppermost frontal part, greenschist facies shearing with top-to-the-foreland normal followed by reverse displacement after 0.95 Ga. The normal shearing detached the upper compartment from the underlying gneisses.

Thermal Stability of Ultrafine-Grained Pure Titanium Processed by High-Pressure Torsion

2021 ◽  
Vol 1016 ◽  
pp. 338-344
Author(s):  
Wan Ji Chen ◽  
Jie Xu ◽  
De Tong Liu ◽  
De Bin Shan ◽  
Bin Guo ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Grain Size ◽  
High Pressure ◽  
Annealing Temperature ◽  
High Pressure Torsion ◽  
Stored Energy ◽  
Ultrafine Grained ◽  
Average Grain Size ◽  
Thermal Stability Of

High-pressure torsion (HPT) was conducted under 6.0 GPa on commercial purity titanium up to 10 turns. An ultrafine-grained (UFG) pure Ti with an average grain size of ~96 nm was obtained. The thermal properties of these samples were studied by using differential scanning calorimeter (DSC) which allowed the quantitative determination of the evolution of stored energy, the recrystallization temperatures, the activation energy involved in the recrystallization of the material and the evolution of the recrystallized fraction with temperature. The results show that the stored energy increases, beyond which the stored energy seems to level off to a saturated value with increase of HPT up to 5 turns. An average activation energy of about 101 kJ/mol for the recrystallization of 5 turns samples was determined. Also, the thermal stability of the grains of the 5 turns samples with subsequent heat treatments were investigated by microstructural analysis and Vickers microhardness measurements. It is shown that the average grain size remains below 246 nm when the annealing temperature is below 500 °C, and the size of the grains increases significantly for samples at the annealing temperature of 600 °C.

Discussion of ‘Metamorphic P–T and retrograde path of high-pressure Barrovian metamorphic zones near Cairn Leuchan, Caledonian orogen, Scotland’

2014 ◽  
Vol 151 (4) ◽  
pp. 758-763 ◽  
Author(s):  
K. Aoki ◽  
B. F. Windley ◽  
S. Maruyama ◽  
S. Omori
Keyword(s):  
High Pressure ◽  
Granulite Facies ◽  
Geological Structure ◽  
Metamorphic Rocks ◽  
New Paradigm ◽  
Zircon Age ◽  
Tectonic Model ◽  
High Pressure Granulite ◽  
Future Publication ◽  
Western Ireland

K. Aoki, B. F. Windley, S. Maruyama & S. Omori reply: First, we thank Viete, Oliver & Wilde for their interesting and thought-provoking comments on the timing of the high-pressure granulite facies (HGR) metamorphism recorded in metamorphic rocks at Cairn Leuchan, Scotland, published by Aoki et al. (2013). Based on new metamorphic data of garnetites and garnet-amphibolites at Cairn Leuchan and new zircon U–Pb ages of amphibolitized eclogite at Tomatin, we suggested in our publication that the HGR metamorphism was retrograde after eclogite facies before the c. 470 Ma ‘Barrovian metamorphism’. Viete, Oliver & Wilde however speculate that the HGR metamorphism at Cairn Leuchan may have occurred at c. 1000 Ma, as a result of their new U–Pb zircon age of the Cowhythe Gneiss at Portsoy and from previous studies of the geological structure and geochronology. We are grateful for this opportunity to describe, albeit in a preliminary manner, our new understanding and tectonic model of the Caledonian orogen in Scotland and western Ireland of which the Barrovian metamorphism is a key component. A reply to a comment is not the correct place to propose an entirely new paradigm for such a classic orogen, but we will present our model more fully in a future publication.

Asymmetric zoning profiles in garnet from HP-HT granulite and implications for volume and grain-boundary diffusion

1999 ◽  
Vol 63 (2) ◽  
pp. 227-238 ◽  
Author(s):  
P. J. O’Brien
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Grain Boundary ◽  
Boundary Diffusion ◽  
Sharp Decrease ◽  
Fluid Phase ◽  
Granulite Facies ◽  
Grain Boundary Diffusion ◽  
Diffusion Models ◽  
High Pressure Granulite

AbstractDetailed electron-microprobe line profiles and small-area compositional maps of zoned garnets in a sample of high-pressure-high-temperature granulite show features inconsistent with commonly applied diffusion models. Larger grains of an early garnet generation have their highest Ca contents in domains away from the rim or inclusions but show a sharp fall in Ca balanced by increased Mg and Fe (and slightly higher XMg) towards inclusions and the rim. In domains with secondary biotite, the sharp decrease in Ca is accompanied by variations in XMg dependent upon proximity to biotite, thus producing one-sided, asymmetric profiles with XMg lower against biotite. As a consequence, rim compositions of the same grain are different on the sides adjacent and away from biotite and there is no relationship between grain size and rim XMg. Such a zoning pattern requires that grain-boundary diffusion is as slow as volume diffusion and implies the absence of a diffusion-enhancing grain-boundary fluid phase during the majority of the rock's high-temperature exhumation history. Diffusion models ignoring this probability could yield either cooling rates that were too fast, or extrapolated ages based on closure temperature models that were too old.A second garnet generation in the same rock, grown in a Ca-rich domain resulting from kyanite breakdown, has irregularly distributed patches, identified by compositional mapping, containing higher Ca than the first-formed garnet but at lower XMg. Use of such garnet compositions for geothermobarometrical determination of the high-pressure granulite stage would clearly lead to erroneous results. The presence of such contrasting garnet compositions in a granulite-facies rock is clearly evidence of disequilibrium, and further supports the proposition that there was a lack of an effective transport medium even at the mm scale.

Application of Radial Forging and Remelting Treatment to Prepare Semi-Solid Billet of AlMg0.7Si Alloy

2016 ◽  
Vol 256 ◽  
pp. 257-262 ◽  
Author(s):  
Yong Fei Wang ◽  
Sheng Dun Zhao ◽  
Chen Yang Zhang
Keyword(s):  
Grain Size ◽  
Partial Melting ◽  
Starting Material ◽  
Main Mechanism ◽  
Solid Alloy ◽  
Radial Forging ◽  
Area Reduction ◽  
Average Grain Size ◽  
Semi Solid ◽  
Deformation Recovery

Semi-solid AlMg0.7Si alloy was prepared by recrystallization and partial melting (RAP) method which including radial forging (RF) and remelting process. RF was carried out with different area reduction ratios (ARRs) to accumulate strains, effect of ARR and remelting time on microstructure was studied, mechanism of RAP preparing semi-solid AlMg0.7Si alloy was summarized. Results show that, compared with the large and irregular solid grains form remelting of starting material, solid grains of semi-solid alloy prepared by RAP are fine and globular, and the optimum microstructure can be obtained when alloy with 80% ARR is remelted at 630 °C for 10 min. With the increase of ARR, the solid grains are smaller and rounder. With the increase of remelting time, the average grain size is increased, and the spheroidization degree of solid grain is gradually improved. The main mechanism consists of pre-deformation, recovery and recrystallization, grains fragmentation, grains spheroidization and coarsening.

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