scholarly journals Textural analysis and emplacement conditions of well-preserved Orosirian felsic volcanic rocks of Northern Amazon Craton, Brazil

2021 ◽  
Author(s):  
Carla Joana Barreto ◽  
Mauricio Haag ◽  
Jean Michel Lafon ◽  
Carlos Sommer ◽  
Lúcia Travassos da Rosa-Costa
Keyword(s):  
Volcanic Rocks ◽  
Rheological Parameters ◽  
Systematic Classification ◽  
Igneous Provinces ◽  
Long Time ◽  
Volcaniclastic Rocks ◽  
Felsic Volcanic ◽  
Textural Analyses

Located in the Amazon Craton, the Uatumã magmatism (1.89-1.87 Ga) consists in one of the oldest Silicic Large Igneous Provinces (SLIPs) on Earth. For a long time, the access to these deposits in the northern Amazon Craton (Erepecuru–Trombetas Domain) has been set back for volcanological studies due to dense vegetation cover and the absence of roads. Recent studies identify two Orosirian volcanic units in the region: the Iricoumé Group (1.89-1.87 Ga) related to the Uatumã magmatism, and the Igarapé Paboca Formation (1.99-1.94 Ga), associated to an older magmatism. Both units are widespread in the Erepecuru–Trombetas Domain and include effusive and explosive deposits. In this paper, we apply textural analyses and rheological estimations to determine the eruption and emplacement conditions of these two volcanic sequences. Textural analyses were carried out through fieldwork and petrography, including a systematic classification of lavas and volcaniclastic rocks. Rheological parameters were determined using geochemistry data to obtain melt viscosity (η) and temperature, zircon saturation (TZr), liquidus (TL), and glass transition temperatures (TG), for anhydrous and hydrous compositions. Textural analyses indicate the predominance of volcaniclastic facies with abundant eutaxitic and parataxitic textures. Rheological estimations reveal TL of 1020ºC, TZr 650-905ºC, and TG 640-753ºC for anhydrous Iricoumé Group melts. Eruptive viscosity estimations range from 8.4 to 11.7 log η (Pa.s). Igarapé Paboca melts present higher temperatures, with TL of 1050ºC, TZr 710-880ºC, and TG 670-740 ºC. Modeling using hydrous compositions indicate that minute amounts of water can strongly affect the rheology of the studied melts, reducing η, TL, TZr, and TG. The petrographic features indicative of hydrous magma reinforces the role of H2O as a controlling agent in the fragmentation of Iricoumé and Igarapé Paboca melts. The pyroclastic samples are marked by elevated ∆TZr - TG relationships indicative of high emplacement temperatures above the TG. Our results indicate that the high temperatures and the presence of network-modifier cations in the studied melts favored the development of extensive welded ignimbrites associated with low-eruption columns, likely developed in fissural and/or caldera systems.

Permian magmatism in the Carpathian–Panonnian region (Hungary and Romania): New geochronological and geochemical results

2020 ◽  
Author(s):  
Máté Szemerédi ◽  
Réka Lukács ◽  
Andrea Varga ◽  
István Dunkl ◽  
Ioan Seghedi ◽  
...  
Keyword(s):  
Pannonian Basin ◽  
Volcanic Rocks ◽  
Rock Types ◽  
Regional Correlation ◽  
Ne Germany ◽  
Long Time ◽  
Spider Diagrams ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks ◽  
European Variscides

<p>In the Carpathian–Pannonian region (Pannonian Basin, Hungary and the Apuseni Mts, Romania) several Late Paleozoic magmatic episodes were revealed by zircon U-Pb geochronology. These events were genetically controlled by a post-collisional to extensional tectonic regime and occurred along the European Variscan Orogenic Belt. Detailed geochronological and geochemical information about the products of this magmatism play crucial role in the regional correlation studies which is the main goal of our research.</p><p>In the Tisza Mega-unit, including southern Transdanubia and the eastern Pannonian Basin (Hungary) as well as the Apuseni Mts (Romania), Permian felsic (dominantly rhyodacitic-dacitic) ignimbrites are common. In the western–central part of the Apuseni Mts, they are accompanied by basaltic and subordinate andesitic lavas, corresponding to a bimodal volcanic suite. Cogenetic plutonic (granites, diorites, gabbros) and subvolcanic rocks (felsic–intermediate dykes) occur in the SW part of the Apuseni Mts, Highiş massif. Immobile element features (REE patterns and multi-element spider diagrams) are similar for all of the aforementioned rock types, suggesting fractional crystallization from a common or similar source. Zircon U-Pb ages of this cogenetic rock assemblage overlap each other and fall within a ~10 Myr long time-span (269–259 Ma, Guadalupian). In contrast to the previous assumptions, the Permian felsic volcanites in the Tisza Mega-unit are not in connection with the granitoid rocks known in the basement of the eastern Pannonian Basin (e.g., Battonya granite). Based on our new data, the granitoids represent a Variscan (~356 Ma, Mississippian) plutonic body.</p><p>The dacitic subvolcanic rocks (dykes) and lavas in the ALCAPA Mega-unit, Central Transdanubia (Hungary) represent an older (~281 Ma, Cisuralian) and geochemically distinct volcanic episode than the magmatism in the Tisza Mega-unit. Associated plutonic rocks, however, are not known in the study area.</p><p>Regarding a broader correlation, the zircon U-Pb ages of the studied Permian plutonic and volcanic rocks of the Tisza Mega-unit are significantly younger than the ages of other well-studied parts of the Central European Variscides (e.g., Intra-Sudetic Basin, NE Germany) where much older ages were identified (300–280 Ma). On the other hand, felsic volcanic rocks of the ALCAPA Mega-unit do not differ from the aforementioned parts of the European Variscides in age. Based on whole-rock geochemistry and zircon geochronology, all of the observed Permian magmatic rocks show similarity with the Permian felsic volcanites of the Western Carpathians (Slovakia). Some further assumptions have been raised: (1) felsic volcanic rocks of the Tisza Mega-unit could correlate with similar rocks of the Southern Gemeric (Vozárová et al. 2009) and Silicic Units (Ondrejka et al. 2018) of the ALCAPA Mega-unit, while (2) the studied samples of Central Transdanubia might be in relationship with the felsic volcanites of the Northern Veporic Unit, ALCAPA Mega-unit (Vozárová et al. 2016). This study was financed by NRDIF (K131690).</p><p>Ondrejka, M., Li, X.H., Vojtko, R., Putiš, M., Uher, P., Sobocký, T. (2018). Geol Carpath 69(2):187–198.</p><p>Vozárová, A., Šmelko, M., Paderin, I. (2009). Geol Carpath 60(6):439–448.</p><p>Vozárová, A., Rodionov, N., Vozár, J., Lepekhina, E., Šarinová, K. (2016). Geol Carpath 61:221–237.</p>

scholarly journals Tectonic History of the South Tannuol Fault Zone (Tuva Region of the Northern Central Asian Orogenic Belt, Russia): Constraints from Multi-Method Geochronology

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 56
Author(s):  
Evgeny Vetrov ◽  
Johan De Grave ◽  
Natalia Vetrova ◽  
Fedor Zhimulev ◽  
Simon Nachtergaele ◽  
...  
Keyword(s):  
Fault Zone ◽  
Volcanic Rocks ◽  
The South ◽  
Mafic Rocks ◽  
Tectonic History ◽  
Central Asian ◽  
Igneous Provinces ◽  
Late Neogene ◽  
History Of ◽  
Felsic Volcanic

In this study, we present zircon U/Pb, plagioclase and K-feldspar 40Ar/39Ar and apatite fission track (AFT) data along the South Tannuol Fault Zone (STFZ). Integrating geochronology and multi-method thermochronology places constraints on the formation and subsequent reactivation of the STFZ. Cambrian (~510 Ma) zircon U/Pb ages obtained for felsic volcanic rocks date the final stage of STFZ basement formation. Ordovician (~460–450 Ma) zircon U/Pb ages were obtained for felsic rocks along the structure, dating their emplacement and marking post-formational local magmatic activity along the STFZ. 40Ar/39Ar stepwise heating plateau-ages (~410–400 Ma, ~365 and ~340 Ma) reveal Early Devonian and Late Devonian–Mississippian intrusion and/or post-magmatic cooling episodes of mafic rocks in the basement. Permian (~290 Ma) zircon U/Pb age of mafic rocks documents for the first time Permian magmatism in the study area creating prerequisites for revising the spread of Permian large igneous provinces of Central Asia. The AFT dating and Thermal history modeling based on the AFT data reveals two intracontinental tectonic reactivation episodes of the STFZ: (1) a period of Cretaceous–Eocene (~100–40 Ma) reactivation and (2) the late Neogene (from ~10 Ma onwards) impulse after a period of tectonic stability during the Eocene–Miocene (~40–10 Ma).

scholarly journals Basaltic to andesitic volcaniclastic rocks in the Blake River Group, Abitibi Greenstone Belt: 1. Mode of emplacement in three areas1This article is a companion paper to Ross et al. 2011. Basaltic to andesitic volcaniclastic rocks in the Blake River Group, Abitibi Greenstone Belt: 2. Origin, geochemistry, and geochronology. Canadian Journal of Earth Sciences, 48: this issue.2MRNF Contribution BEGQ 8439-2010/2011-1. Natural Resources Canada, Earth Science Sector Contribution 20100253.

2011 ◽  
Vol 48 (4) ◽  
pp. 728-756 ◽  
Author(s):  
Pierre-Simon Ross ◽  
Jean Goutier ◽  
Patrick Mercier-Langevin ◽  
Benoît Dubé
Keyword(s):  
Greenstone Belt ◽  
Earth Science ◽  
Volcanic Rocks ◽  
Companion Paper ◽  
Density Currents ◽  
Abitibi Greenstone Belt ◽  
Volcaniclastic Rocks ◽  
Emplacement Processes ◽  
Felsic Volcanic ◽  
High Level

The Archean Blake River Group (BRG) of Ontario and Quebec is dominated by submarine mafic to intermediate lavas, with more restricted felsic volcanic rocks. Given the good quality of outcrop, and high level of preservation of some BRG rocks, the mafic to intermediate lavas were used in the 1970s and 1980s to better understand the evolution of massive and pillowed submarine flows, and their associated fragmental facies (pillow breccias, hyaloclastite). Potentially, the BRG could also represent a useful volcanic succession for the study of explosive submarine eruption products in the ancient record. Before this is possible, however, a regional inventory of the mafic to intermediate volcaniclastic units is needed to clarify their characteristics and origins. In this paper, we compare and contrast volcaniclastic rocks from three areas within the same formation of the northern BRG in Quebec: the Monsabrais area, the Lac Duparquet area, and the D’Alembert tuff area. Close examination reveals pronounced differences in terms of lateral continuity, thickness, grading, bedding, clast shapes, textures, etc. in the volcaniclastic rocks. These differences are interpreted to reflect vastly different emplacement processes, ranging from hyaloclastite generation as a result of self-fragmentation and lava contact with water (dominant in the Monsabrais and Lac Duparquet areas) to aqueous density currents likely fed directly by explosive submarine eruptions (dominant in the D’Alembert tuff).

scholarly journals From Ordovician nascent to early Permian mature arc in the southern Altaids: Insights from the Kalatage inlier in the Eastern Tianshan, NW China

Geosphere ◽  
2021 ◽  
Author(s):  
Qigui Mao ◽  
Jingbin Wang ◽  
Wenjiao Xiao ◽  
Brian F. Windley ◽  
Karel Schulmann ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Evolutionary Model ◽  
Early Permian ◽  
Calc Alkaline ◽  
Eastern Tianshan ◽  
Central Asian ◽  
Intrusive Rocks ◽  
Volcaniclastic Rocks ◽  
Felsic Volcanic ◽  
Potassium Enrichment

The Kalatage inlier in the Dananhu-Haerlik arc is one of the most important arcs in the Eastern Tianshan, southern Altaids (or Central Asian orogenic belt). Based on outcrop maps and core logs, we report 16 new U-Pb dates in order to reconstruct the stratigraphic framework of the Dananhu-Haerlik arc. The new U-Pb ages reveal that the volcanic and intrusive rocks formed in the interval from the Ordovician to early Permian (445–299 Ma), with the oldest diorite dike at 445 ± 3 Ma and the youngest rhyolite at 299 ± 2 Ma. These results constrain the ages of the oldest basaltic and volcaniclastic rocks of the Ordovician Huangchaopo Group, which were intruded by granite- granodiorite-diorite plutons in the Late Ordovician to middle Silurian (445–426 Ma). The second oldest components are intermediate volcanic and volcaniclastic rocks of the early Silurian Hongliuxia Formation (S1h), which lies unconformably on the Huangchaopo Group and is unconformably overlain by Early Devonian volcanic rocks (416 Ma). From the mid- to late Silurian (S2-3), all the rocks were exhumed, eroded, and overlain by polymictic pyroclastic deposits. Following subaerial to shallow subaqueous burial at 416–300 Ma by intermediate to felsic volcanic and volcaniclastics rocks, the succession was intruded by diorites, granodiorites, and granites (390–314 Ma). The arc volcanic and intrusive rocks are characterized by potassium enrichment, when they evolved from mafic to felsic and from tholeiitic via transitional and calc-alkaline to final high-K calc- alkaline compositions with relatively low initial Sr values, (87Sr/86Sr)i = 0.70391–0.70567, and positive εNd(t) values, +4.1 to +9.2. These new data suggest that the Dananhu-Haerlik arc is a long-lived arc that consequently requires a new evolutionary model. It began as a nascent (immature) intra-oceanic arc in the Ordovician to early Silurian, and it evolved into a mature island arc in the middle Silurian to early Permian. The results suggest that the construction of a juvenile-to-mature arc, in combination with its lateral attachment to an incoming arc or continent, was an important crustal growth mechanism in the southern Altaids.

Geochemistry of the late Archean Banting Group, Yellowknife greenstone belt, Slave Province, Canada: simultaneous melting of the upper mantle and juvenile mafic crust

2002 ◽  
Vol 39 (11) ◽  
pp. 1635-1656 ◽  
Author(s):  
Brian Cousens ◽  
Kathy Facey ◽  
Hendrik Falck
Keyword(s):  
Upper Mantle ◽  
Greenstone Belt ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Heavy Rare Earth Element ◽  
Element Abundances ◽  
Slave Province ◽  
Volcaniclastic Rocks ◽  
Felsic Volcanic ◽  
Felsic Rocks

This study investigates the geochemistry and tectonic setting of the 2.66 Ga Banting Group, the younger sequence of volcanic rocks in the Yellowknife greenstone belt, and its relationship to older tholeiitic volcanic rocks of the 2.72–2.70 Ga Kam Group. The Banting Group includes a much higher proportion of felsic volcanic and volcaniclastic rocks than the Kam Group, but mafic to intermediate volcanic rocks are common. Banting basalts are tholeiitic and are melts of Archean depleted upper mantle, as are basalts of the Kam Group. In contrast, Banting dacites and rhyolites have much lower heavy rare earth element abundances and generally have higher initial 143Nd/144Nd than Kam felsic rocks. The chemistry of the felsic rocks provides a geochemical signature to distinguish rocks of Kam versus Banting age where complex structures have obscured the stratigraphy. Whereas Kam felsic rocks evolved from mafic parents by assimilation – fractional crystallization processes, Banting felsic rocks have compositions similar to Archean tonalite–trondhjemite–dacite suites, as well as modern adakites, and appear to be melts of juvenile, garnet-bearing, hydrated mafic crust, possibly underplated Kam basalts. The nearby 2.66 Ga felsic complex at Clan Lake mimics the geochemical systematics of the Banting Group, and thus Banting-like rocks may reflect a regional crustal melting event at this time.

Raiders Activity on the Market for Corporate Control as a Product of Coercive Entrepreneurship Evolution

2007 ◽  
pp. 80-92
Author(s):  
A. Kireev
Keyword(s):  
Corporate Control ◽  
Role Of Government ◽  
Market For Corporate Control ◽  
Basic Characteristics

The paper studies the problem of raiders activity on the market for corporate control. This activity is considered as a product of coercive entrepreneurship evolution. Their similarities and sharp distinctions are shown. The article presents the classification of raiders activity, discribes its basic characteristics and tendencies, defines the role of government in the process of its transformation.

The Problem of Identifying and Modeling the Relationship between Monetary Factor and Inflation in the Russian Economy

2008 ◽  
pp. 61-76
Author(s):  
A. Porshakov ◽  
A. Ponomarenko
Keyword(s):  
Money Supply ◽  
Money Demand ◽  
Russian Economy ◽  
Long Run ◽  
Complex Approach ◽  
Wide Range ◽  
Long Time ◽  
The Relationship ◽  
Supply Side Factors

The role of monetary factor in generating inflationary processes in Russia has stimulated various debates in social and scientific circles for a relatively long time. The authors show that identification of the specificity of relationship between money and inflation requires a complex approach based on statistical modeling and involving a wide range of indicators relevant for the price changes in the economy. As a result a model of inflation for Russia implying the decomposition of inflation dynamics into demand-side and supply-side factors is suggested. The main conclusion drawn is that during the recent years the volume of inflationary pressures in the Russian economy has been determined by the deviation of money supply from money demand, rather than by money supply alone. At the same time, monetary factor has a long-run spread over time impact on inflation.

ASPECTS IN BUILDING A COMPANY WEB-SITE AND ITS ROLE FOR THE DEVELOPMENT OF BUSINESS

2018 ◽  
pp. 117-124
Author(s):  
Petar Halachev ◽  
Victoria Radeva ◽  
Albena Nikiforova ◽  
Miglena Veneva
Keyword(s):  
Life Cycle ◽  
Web Site ◽  
The Internet ◽  
A Company ◽  
The Web ◽  
Design Construction ◽  
Made In ◽  
Site Types

This report is dedicated to the role of the web site as an important tool for presenting business on the Internet. Classification of site types has been made in terms of their application in the business and the types of structures in their construction. The Models of the Life Cycle for designing business websites are analyzed and are outlined their strengths and weaknesses. The stages in the design, construction, commissioning, and maintenance of a business website are distinguished and the activities and requirements of each stage are specified.

ПОЕТИЧНА МОВОТВОРЧІСТЬ ЯК ВІДОБРАЖЕННЯ КОНЦЕПТУАЛЬНОЇ КАРТИНИ СВІТУ

2018 ◽  
pp. 166-174
Author(s):  
М. В. Дзисюк
Keyword(s):  
Semantic Space ◽  
Spiritual Values ◽  
Spatial Features ◽  
Filling Ability ◽  
Material Reality ◽  
Space Saving ◽  
Long Time ◽  
Literary Techniques ◽  
Linguistic Process

Definitions of concept and sphere of the concept are widely used in different aspects of modern linguistics. There is no single understanding of these notions and universal methodology of research has not been invented by linguists yet. This predetermines topicality of the article. The aim of our research is analysis, generalization, and systematization of different approaches to the interpretation of the notion ‘concept’ that exist in modern linguistics. It results in the following tasks: analysis of existing definitions of concept and its division into certain ranges and defining classification features. Modern linguists raise the questions of the conceptual and linguistic image of the world, the role of a human factor in its formation and interaction as in a linguistic process more frequently and it is defined as a fact in today’s linguistic scientific literature. The problem of individual language formation, poetic one in particular gains important meaning in this context. Ukrainian linguists use the notion of ‘concept’ for a long time now although they adhere to different views on its definition. Researches of the question define two major approaches in the analysis of the notion ‘concept’ that is linguistic-cognitive and linguistic-cultural. We can claim that words-concepts are agents between material reality and the ideal world that is synthesized in poetry, carriers of sense since with their help the versatility of the real world correlates with eternal spiritual values. Therefore, main features of the notion ‘concept’ in which objectively-cognitive and subjectively-creative features are combines are as follow sensual authenticity, time-spatial features, mediation between material and spiritual, semantic filling, ability to polysemy. A word with a generally symbolic meaning that is implemented in a language process through literary techniques typical for poet’s idiotype is the main core of the concept. The concept in poetic language formation by modern Uman poets is semantically integral, fulfilled, able to penetrate into other concepts and absorb semantically narrower images saving unity and semantic independence, varying numerous interpretations that project it in a certain semantic space, saving potential of real reflection.

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