1,720,962 research outputs found
GEOCHEMISTRY, PROVENANCE, AND TECTONIC SETTING OF PALEOPROTEROZOIC METAVOLCANIC AND METASEDIMENTARY UNITS OF THE ALUTAGUSE ZONE, NORTH ESTONIA – A COMPARATIVE STUDY WITH THE SOUTH SVECOFENNIAN ZONE
Full text link<p>Nykänen, V., Cook, N. & Kaija, J. (eds) 2023. EU SuperCluster Lapland Geoconference – October 30–31, 2023, Hotel Santa Claus, Rovaniemi, Finland. Geological Survey of Finland, Open File Research Report 55/2023, 212 pages, 69 figures and 9 tables. (pg.255)</p>
Ordoviitsiumi ja Siluri bentoniitide varadiageneetiline areng Balti Paleobasseini põhjaosas
Full text linkBentonites are old tephra layers, which have been transformed into clay mineral dominated sedimentary beds. The authigenic mineral assemblages of bentonites provide information of geothermal-burial history of sedimentary basins, but also about environmental characteristics of old sedimentary and diagenetic environments. The thesis focuses on key variables, which controlled genesis of Estonian lower Palaeozoic multiphase bentonites at different stages of their diagenetic evolution. The studied bentonites are characterized by thermodynamically unstable authigenic assemblages of illite-smectite, K-feldspar and kaolinite. In the clay fractions illitic R1 ordered illite-smectite and kaolinite dominate. Variations in illite-smectite/kaolinite ratio are interpreted to reflect conditions during early diagenesis and were suggestible principally controlled by organic matter content of host rock and ratio of siliciclastic/carbonate matter in enclosing deposits. The special mixed-layer chlorite-smectite assemblages characterize bentonites from the Pirgu Stage. Corrensite formation in these beds was probably induced by reflux of Mg-rich early diagenetic brines and suggests existence of shallow water evaporitic settings within palaeobasin at the end of Ordovician. The unique feature of Estonian Palaeozoic bentonites is occurrence of varieties with almost pure authigenic K-feldspar composition and correspondingly very high K2O content (up to~13%). The K-feldspar formed on account of metastable alkali zeolites, whereas zeolites formation instead of smectite in cause of primary alteration of ash was supported by high pH and silica activities in interstitial solutions of bentonites hosted by carbonate deposits. Alternatively, K-feldspar formation was induced by prolonged episode(s) of low-temperature K-rich hydrothermal fluid flows during final stages of Caledonian orogeny. Bentoniidid on vulkaanilise päritoluga setendikihid, milles algne vulkaaniline tuhk on mattumise ja diageneesi tulemina asendunud valdavalt savimineraalidega. Nende autigeensed kooslused võimaldavad uurida vanade settebasseinide mattumiskulgu ja geotermaalset arengut. Lisaks annavad need teavet ka teiste algse sette- ja diageneesikeskkonna parameetrite kohta. Käesolev doktoritöö keskendub muutujatele, mis kontrollisid Eesti varapaleosoiliste bentoniitide mineraalkoosluse kujunemist, analüüsides seejuures eelkõige varadiageneetiliste ja senini problemaatiliste transformatsiooniprotsesside mõju ja ulatust. Eesti paleosoilisi bentoniite iseloomustab termodünaamiliselt ebastabiilne autigeenne kooslus – illiit-smektiit, kaaliumpäevakivi ja kaoliniit. Bentoniitide savifraktsioonis valdavad illiitne R1 korrastatusega illiit-smektiit ja kaoliniit. Tõenäoliselt kontrollisid kaoliniidi ja smektiidi teket varadiageneesi staadiumis ümbritsevate setendite orgaanikasisaldus ning silikaatsete ja karbonaatsete faaside suhtvahekord. Erilaadse mineraalse koostisega, segakihilist kloriit-smektiiti sisaldavad bentoniidid esinevad Pirgu lademes. Korrensiidi teke neis kihtides on samuti oletatavalt seotud varadiageneesiga kui Mg-rikkad fluidid lõid tingimused saponiidi-tüüpi smektiidi tekkeks. Korrensiidi esinemine bentoniitides lubab rekonstrueerida settejäljes mittesäilinud evaporiitseid faatsiesi paleobasseinis. Uuritud bentoniitide üheks iseärasuseks on peaaegu puhtast K-päevakivist koosnevate ja seega äärmiselt kaaliumirikaste erimite esinemine. K-päevakivi on oletatavalt tekkinud varadiageneetiliste metastabiilsete Na-K-tseoliitide arvel. Viimaste teket primaarsel tuha ümberkristalliseerumisel võisid soodustada lubimudade settesiseste lahuste kõrge pH ja lahustunud räni ning leelismetallide kõrge kontsentratsioon. Alternatiivse hüpoteesi kohaselt võis K-päevakivi tekkida kaaliumirikaste ning madalatemperatuursete hüdrotermaalsete fluidide mõjul samaaegselt Kaledoonia orogeneesi lõpufaasiga
Is the Estonian Alutaguse Section of Eastern Fennoscandia a continuation of the Southern Svecofennian Finnish Terranes, or is it akin to the Swedish Bergslagen region?
No full text<p>This research explores the geochemistry of Paleoproterozoic metasedimentary and metavolcanic units in the Alutaguse region of North Estonia and the South Svecofennian (SS) zones, including Ladoga, Saimaa, Häme Belt, and Uusimaa Belt, to better understand the tectonic evolution of the Svecofennian Orogeny in Eastern Fennoscandia. Metasedimentary units consist of micaceous gneisses (± Grt ± Crd ± Sil), while metavolcanics include amphibolites and pyroxenic gneisses. Historical and new data show that High-SiO₂ (>63 wt%) metasediments have felsic origins similar to the Upper Continental Crust (UCC), whereas Low-SiO₂ (≤63 wt%) metasediments, resembling graywackes and shales, indicate mafic to intermediate origins similar to Post-Archean Australian Shale (PAAS). Various weathering indices, including CIA, PIA, CIW, and ICV for metasediments, and AI, CCPI, WIP, and SI for metavolcanics, were applied to reveal these geochemical trends. The metavolcanics are classified as subalkaline, with geochemical signatures pointing to asthenospheric mantle origins for Alutaguse and subducted oceanic crust origins for SS. Tectonic affinity analyses indicate a predominant oceanic arc setting in both regions. High concentrations of CaO and MnO in Alutaguse and Uusimaa metasediments suggest a genetic link, positioning Alutaguse as a backarc of 1.90-1.89 Ga back-arc to the Uusimaa belt, followed by the accretion of the Uusimaa and Häme belts around 1.87 Ga, marking the closure of the Svecofennian ocean. The Alutaguse zone probably developed as a back-arc to the Tallinn-Uusimaa belt after the accretion of the Bergslagen microcontinent. This interpretation is supported by geophysical anomalies correlated with Zn-Pb-Fe mineralisation, which shows similarities to Bergslagen's VMS provinces and warrants further investigation. </p>
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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