scholarly journals Variscan thrusting in I- and S-type granitic rocks of the Tribeč Mountains, Western Carpathians (Slovakia): evidence from mineral compositions and monazite dating

2015 ◽  
Vol 66 (6) ◽  
pp. 455-471 ◽  
Author(s):  
Igor Broska ◽  
Igor Petrík
Keyword(s):  
Early Stage ◽  
Temperature Shift ◽  
Greenschist Facies ◽  
Coarse Grained ◽  
Granitic Rocks ◽  
Western Carpathians ◽  
Lower Carboniferous ◽  
Magmatic Stage ◽  
Leucocratic Granite ◽  
Redox Evolution

AbstractThe Tribeč granitic core (Tatric Superunit, Western Carpathians, Slovakia) is formed by Devonian/Lower Carboniferous, calc-alkaline I- and S-type granitic rocks and their altered equivalents, which provide a rare opportunity to study the Variscan magmatic, post-magmatic and tectonic evolution. The calculatedP-T-Xpath of I-type granitic rocks, based on Fe-Ti oxides, hornblende, titanite and mica-bearing equilibria, illustrates changes in redox evolution. There is a transition from magmatic stage atTca. 800–850 °C and moderate oxygen fugacity (FMQ buffer) to an oxidation event at 600 °C between HM and NNO up to the oxidation peak at 480 °C and HM buffer, to the final reduction at ca. 470 °C at ΔNN= 3.3. Thus, the post-magmatic Variscan history recorded in I-type tonalites shows at early stage pronounced oxidation and low temperature shift back to reduction. The S-type granites originated at temperature 700–750 °C at lower water activity and temperature. TheP-Tconditions of mineral reactions in altered granitoids at Variscan time (both I and S-types) correspond to greenschist facies involving formation of secondary biotite. The Tribeč granite pluton recently shows horizontal and vertical zoning: from the west side toward the east S-type granodiorites replace I-type tonalites and these medium/coarse-grained granitoids are vertically overlain by their altered equivalents in greenschist facies. Along the Tribeč mountain ridge, younger undeformed leucocratic granite dykes in age 342±4.4 Ma cut these metasomatically altered granitic rocks and thus post-date the alteration process. The overlaying sheet of the altered granites is in a low-angle superposition on undeformed granitoids and forms “a granite duplex” within Alpine Tatric Superunit, which resulted from a syn-collisional Variscan thrusting event and melt formation ~340 Ma. The process of alteration may have been responsible for shifting the oxidation trend to the observed partial reduction.

Visean overprint of the Devonian-Early Carboniferous granites: result of Variscan collisional stage revealed by zircon SHRIMP dating (Tribeč Mts., Western Carpathians)

2020 ◽  
Author(s):  
Igor Broska ◽  
Keewook Yi ◽  
Milan Kohút ◽  
Igor Petrík
Keyword(s):  
Early Stage ◽  
Early Carboniferous ◽  
White Mica ◽  
Granitic Rocks ◽  
Western Carpathians ◽  
Variscan Orogeny ◽  
Shrimp Dating ◽  
The West ◽  
Volcanic Arc ◽  
Type Granite

<p>The granites with I- and S-type affinity in the Variscan segments of the Alpine West-Carpathian edifice belong to the oldest intrusions within the European Variscides. Granites and granodiorites of the West-Carpathian crystalline basement are mostly classified as S-type, whereas tonalities and granodiorites belong to the I-type suite. Both suites probably originated in the volcanic arc setting as product of subduction-related regime in the Galatian superterrane (Broska et al. 2013). The I- and S-type granite bodies were firstly identified in the West-Carpathian Tribeč Core Mountains and the new SHRIMP and CHIME datings recognised their Visean geotectonic overprint. The subduction-related I-type granites show the age span 364-358 Ma followed by the intrusion of the S-type granites dated by SHRIMP on 358 Ma. The bimodal SHRIMP data of a dyke placed within S-type granites show ages 351 Ma and 330 Ma, or primary vs. alteration age. The CHIME age from monazite dating shows 347 Ma because monazite indicate probably early stage of massive granite alteration perhaps during collisional process, younger zircons represents later phase of the event.  CHIME dating of newly formed monazite in greisenised S-type granite gives the age 344 Ma. The granite showing strong greisenization (total degradation of feldspars and formation of quartz - white mica assemblages) is dated by SHRIMP on 355 Ma. The greisenised granite contains abundant tourmaline with high dravitic molecule, Sr-rich apatite and common monazite. Abundant tiny stoichiometrically pure apatite grains in this granite indicate their exsolution from feldspars enriched in phosphorus. The S-type granite dyke from the ridge of the Tribeč Mts gives zircon SHRIMP age 355 Ma and CHIME monazite age 342 Ma. The dating results of the Tribeč granites identified: (<strong>1</strong>) older Upper Devonian/Lower Mississippian subduction-related I-type tonalites (ca. 364-351 Ma), and (<strong>2</strong>) S-type granites Middle/Upper Mississippian (Visean) intruding in time span 342-330 Ma reflecting probably of the collisional event in the Variscan orogeny. Dual evolution of the Tribeč Mts. Variscan granitic rocks is partly corroborated by Hf isotopes from the dated zircons with εHf<sub>(t)</sub> = +3.5 ~ –2.4 for the older granites, and εHf<sub>(t)</sub> = –0.3 ~ –4.9 for the younger ones. The evolution of the I- and S-type granites seems to be rather different from the granite evolution known in the Bohemian Massif and therefore the origin of Variscan hybrid granites from the Western Carpathians we placed on the SW side of Galatian volcanic arc as result of Paleo-Tethys subduction (see Stampfli and Borel, 2002, Stampfli et al. 2013).</p><p>Acknowledgments: Support from Slovak Research and Development Agency: APVV SK-KR-18-0008, APVV-14-0278/, APVV-18-0107, and VEGA 2/0075/20 are greatly appreciated.</p>

scholarly journals Ore Genesis of the Takatori Tungsten–Quartz Vein Deposit, Japan: Chemical and Isotopic Evidence

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 765
Author(s):  
Yuichi Morishita ◽  
Yoshiro Nishio
Keyword(s):  
Oxygen Isotope ◽  
Early Stage ◽  
Isotope Ratios ◽  
Equilibrium Temperature ◽  
Granitic Rocks ◽  
Granitic Magma ◽  
Lithium Isotope ◽  
Vein Deposit ◽  
Pressure Independent ◽  
Isotope Equilibrium

The Takatori hypothermal tin–tungsten vein deposit is composed of wolframite-bearing quartz veins with minor cassiterite, chalcopyrite, pyrite, and lithium-bearing muscovite and sericite. Several wolframite rims show replacement textures, which are assumed to form by iron replacement with manganese postdating the wolframite precipitation. Lithium isotope ratios (δ7Li) of Li-bearing muscovite from the Takatori veins range from −3.1‰ to −2.1‰, and such Li-bearing muscovites are proven to occur at the early stage of mineralization. Fine-grained sericite with lower Li content shows relatively higher δ7Li values, and might have precipitated after the main ore forming event. The maximum oxygen isotope equilibrium temperature of quartz–muscovite pairs is 460 °C, and it is inferred that the fluids might be in equilibrium with ilmenite series granitic rocks. Oxygen isotope ratios (δ18O) of the Takatori ore-forming fluid range from +10‰ to +8‰. The δ18O values of the fluid decreased with decreasing temperature probably because the fluid was mixed with surrounding pore water and meteoric water. The formation pressure for the Takatori deposit is calculated to be 160 MPa on the basis of the difference between the pressure-independent oxygen isotope equilibrium temperature and pressure-dependent homogenization fluid inclusions temperature. The ore-formation depth is calculated to be around 6 km. These lines of evidence suggest that a granitic magma beneath the deposit played a crucial role in the Takatori deposit formation.

Geochemistry and geochronology of alkaline dykes from the Finero Phlogopite Peridotite (Ivrea-Verbano Zone): insights into the Triassic-Jurassic tectono-magmatic events of the Southern Alps

2021 ◽  
Author(s):  
Abimbola Chris Ogunyele ◽  
Tommaso Giovanardi ◽  
Mattia Bonazzi ◽  
Maurizio Mazzucchelli ◽  
Alberto Zanetti
Keyword(s):  
Continental Crust ◽  
Southern Alps ◽  
Coarse Grained ◽  
Dyke Swarm ◽  
Fine Grained ◽  
Sector Zoning ◽  
Magmatic Stage ◽  
Late Magmatic Stage ◽  
Mesozoic Magmatism ◽  
Peridotite Mantle

<p>The Ivrea-Verbano Zone (IVZ, westernmost sector of the Southern Alps) represents a unique opportunity to investigate the Paleozoic to Mesozoic geodynamic evolution of the Gondwana and Laurasia boundary from the perspective of the lower continental crust. Only recently, the petrochemical record of Triassic-Jurassic magmatism has been recognized. It mainly affected the northernmost tip, the Finero Complex, where the continental crust was tectonically thinned before opening of Alpine Tethys. However, the Mesozoic magmatism in the Finero Complex is still poorly-constrained. Firstly, its extent is largely unknown, because the mantle and crustal intrusives were already enriched by Paleozoic processes. Secondly, Mesozoic melts migration started when the Finero Complex was still placed at P-T conditions typical of a continental crust-mantle transition (1 GPa): this has promoted the reopening of the geochronological clocks in both Paleozoic and Mesozoic rocks, which usually provides wide time intervals. Lastly, the finding of Mesozoic magmatism as composite veins/pods and metasomatised layers has not allowed an exhaustive reconstruction of the primitive melts geochemistry. To place further constraints on such issue, a new dyke swarm cropping out in the Finero Phlogopite Peridotite mantle unit has been investigated. Dykes usually cut at high angle the mantle foliation and are up to 60 cm thick. They are composed by coarse-grained hornblendite to anorthosite, both phlogopite/biotite-bearing. Many dykes are composite, showing variable proportions of hornblendite and anorthosite. In places, the dyke swam was affected by volatiles overpressure as late magmatic stage, which produced plastic flow and development of a porphyroclastic structure by deformation of the early cumulates, with widespread segregation of a fine-grained mica matrix.</p><p>Dykes mainly consist of pargasite, phlogopite/biotite, albite (An 8-10), in association with apatite, monazite, ilmenite, zircon, Nb-rich oxides, carbonates. Enrichments in Fe (amphibole and biotite) and Na (plagioclase) suggest segregation from evolved melts, strongly enriched in H<sub>2</sub>O, P, C. The large LILE and LREE contents in amphiboles, sometimes associated to high Nb, Ta, Zr and Hf concentrations, as well as the mineral assemblage, support an alkaline affinity of the melts. The strongly positive εHf<sub>t </sub>(+10) of zircons and the isotopic Sr composition of amphiboles (0.7042) point to a derivation of the melts from mildly enriched sources, possibly located at the crust-mantle interface.</p><p>Zircons from anorthosite layers are mostly anhedral fragments. They show homogenous internal structure or sector zoning. Concordant <sup>206</sup>Pb/<sup>238</sup>U zircon ages vary from 221 ± 9 Ma to 192 ± 8 Ma. The results of this study confirm that mantle input to the Southern Alps magmatism was of alkaline affinity from Norian to Sinemurian. A widespread fluids circulation induced by such magmatism at high P-T conditions was likely the main cause of the diffuse geochronological reset towards Mesozoic ages of the northern IVZ.</p>

Alteration and breakdown of xenotime-(Y) and monazite-(Ce) in granitic rocks of the Western Carpathians, Slovakia

Lithos ◽  
2005 ◽  
Vol 82 (1-2) ◽  
pp. 71-83 ◽  
Author(s):  
Igor Broska ◽  
C. Terry Williams ◽  
Marian Janák ◽  
Géza Nagy
Keyword(s):  
Granitic Rocks ◽  
Western Carpathians

Understanding receptor-mediated endocytosis of elastic nanoparticles through coarse grained molecular dynamic simulation

2018 ◽  
Vol 20 (24) ◽  
pp. 16372-16385 ◽  
Author(s):  
Zhiqiang Shen ◽  
Huilin Ye ◽  
Ying Li
Keyword(s):  
Molecular Dynamic Simulation ◽  
Molecular Dynamic ◽  
Dynamic Simulation ◽  
Contact Area ◽  
Late Stage ◽  
Early Stage ◽  
Coarse Grained ◽  
Large Energy ◽  
Receptor Mediated Endocytosis ◽  
Large Contact Area

The membrane wrapping of the soft nanoparticle (NP) is faster than that of the stiff one at the early stage, due to the NP deformation induced large contact area between the NP and membrane. However, because of the large energy penalties induced by the NP deformation, the membrane wrapping speed of soft NPs slows down during the late stage.

Experience with Interface Shear Box Testing for Pipe-Soil Interaction Assessment on Sand

2021 ◽  
Author(s):  
Zack Westgate ◽  
Ricardo Argiolas ◽  
Regis Wallerand ◽  
Jean-Christophe Ballard
Keyword(s):  
Soil Properties ◽  
Normal Stress ◽  
Oil And Gas ◽  
Early Stage ◽  
Soft Clay ◽  
Interface Roughness ◽  
Coarse Grained ◽  
Interface Shear ◽  
Shear Box ◽  
Test Database

Abstract This paper is a companion paper to OTC 28671, titled "Experience with Interface Shear Box Testing for Axial Pipe-Soil Interaction Assessment on Soft Clay", and presents a similar range of experience and best practice recommendations for geotechnical laboratory testing to determine soil properties relevant to pipeline-seabed friction on sandy seabeds. The paper is underpinned by a new database that demonstrates the driving parameters that influence interface friction in granular materials. By accurately quantifying shear resistance along the pipe-soil interface under low normal stresses imposed by subsea pipelines, design ranges in friction can be narrowed and/or tailored to specific pipeline conditions. These improved geotechnical inputs to pipe-soil interaction can alleviate unnecessary axial expansion mitigation and lateral stabilization measures, unlocking cost savings otherwise unavailable through conventional testing. A large database is presented, compiled from both previously published research and unpublished recent industry experience with low normal stress interface shear testing using various modified direct shear box devices. The test database comprises several coarse-grained soil types of both silica and carbonate minerology tested against pipeline coatings of various material, hardness and roughness. The database populates a framework for assessing frictional pipe-soil interaction response, illuminating key trends from normal stress, interface roughness and hardness, and particle angularity, which otherwise remain elusive when examined through individual test datasets. This database and the populated framework provides guidance to pipeline and geotechnical engineers in the form of a basis for initial estimates of axial and lateral friction of pipelines on sand and an approach for improving these estimates via focused site-specific testing. The test database includes previously unreleased project data collected over the past few years for offshore oil and gas projects. Similar to its predecessor paper on soft clays (OTC 28671), this paper shares the authors’ collective experience providing guidance on the planning, execution and interpretation of low stress interface shear tests in sands. The combined databases across both papers provide a significant improvement in early stage guidance for characterization of geotechnical soil properties for subsea pipeline design.

Mineralogy of vesicles in an olivine leucitite at Cosgrove, Victoria, Australia

1980 ◽  
Vol 43 (329) ◽  
pp. 597-603 ◽  
Author(s):  
W. D. Birch
Keyword(s):  
Late Stage ◽  
Rock Type ◽  
Early Stage ◽  
Coarse Grained ◽  
Residual Liquid ◽  
Cooling History ◽  
History Of

SummaryAn olivine-titanomagnetite-apatite-clinopyroxene-mica-nepheline-feldspar assemblage occurs in late-stage vesicles in a small outcrop of olivine leucitite at Cosgrove, Victoria. The vesicles were formed by exsolution of volatiles at an early stage in the cooling history of the lava. Subsequently, a volatile-rich residual liquid filled cavities and fractures, giving rise to a coarse-grained pegmatoid rock type similar in over-all mineralogy to the vesicles. The volatiles facilitating crystallization in both the vesicles and the pegmatoid were probably enriched in F, CO2, and P. A number of geothermometers applied to the vesicle assemblage failed to agree on likely crystallization temperatures.

scholarly journals Cyclic deformation behaviour and stability of grain-refined 301LN austenitic stainless structure

2018 ◽  
Vol 165 ◽  
pp. 06005 ◽  
Author(s):  
Jiří Man ◽  
Antti Järvenpää ◽  
Matias Jaskari ◽  
Ivo Kuběna ◽  
Stanislava Fintová ◽  
...  
Keyword(s):  
Strain Rate ◽  
Volume Fraction ◽  
Early Stage ◽  
Low Cycle Fatigue ◽  
Deformation Behaviour ◽  
Polarized Light ◽  
Constant Strain Rate ◽  
Coarse Grained ◽  
Grain Sizes ◽  
Cyclic Straining

Low cycle fatigue (LCF) behaviour of metastable austenitic 301LN stainless steel with different grain sizes – coarse-grained (13 μm), fine-grained (1.4 μm) and ultrafine-grained (0.6 μm) – produced by reversion annealing after prior cold rolling was investigated. Fully symmetrical LCF tests with constant total strain amplitudes of 0.5% and 0.6% were performed at room temperature with a low constant strain rate of 2×10-3 s-1. Microstructural changes in different positions within the gauge part of the specimens were examined by optical microscopy (polarized light) and electron backscatter diffraction (EBSD) technique; for quantitative assessment of the volume fraction of deformation induced martensite (DIM) a Feritscope FMP 30 was adopted. The cyclic stress-strain response and specific changes of hysteresis loop shapes in the very early stage of cycling are confronted with the character of DIM formation and its distribution in the whole volume of the material. A possible effect of strain rate (frequency of cycling) on the destabilization of austenitic structure during cyclic straining of materials with different grain sizes is highlighted.

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