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published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--Open University. BLDSC no. DXN046377.

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TRUMPA DARBO APŽVALGA Magistrinio darbo tema „Feldšpatų izomorfinės eilės narių nustatymas gemologiniais tyrimų metodais“. Darbo vadovas dok. A. Kleišmantas. Magistrinis darbas yra bakalaurinio darbo tęsinys. Bakalauro darbe gemologiniais metodais buvo ištirti 67 feldšpatų grupės pavyzdžiai ir padaryta išvada, kad jų identifikavimas gemologiniais metodais yra įmanomas. Darbo objektas: feldšpatų grupės mineralai ir mineralų agregatai iš skirtingų pasaulio kasyklų, radimviečių. Jų fizinių, bei optinių savybių priklausomybė nuo cheminės sudėties, kitų mineralų priemaišų, bei kristalo gardelės susitvarkymo laipsnio. Pagrindinis darbo tikslas - įvertinti gemologinių tyrimų metodo pritaikomumą bei efektyvumą identifikuojant feldšpatų grupės mineralus. Pagrindiniai darbo uždaviniai - Naudojantis įvairia literatūra, aprašyti feldšpatų grupę, išskiriant tris pogrupius, bei atskirai apibūdinti kiekvieną grupės mineralą, sudaryti lenteles, susiejant kiekvieno grupės mineralo optines savybes su jo radimvietėmis. Surinkus kuo įvairesnių pavyzdžių paruošti juos tyrimams, nustatyti jų lūžio rodiklį, ir dvejopą lūžį, apskaičiuoti jų masę ir tankį, pagal pasirinktą schemą atskirai aprašyti kiekvieną pavyzdį ir jį identifikuoti. Chemijos institute atlikti kristalocheminius tyrimus, pavyzdžiuose nustatant Ca; K ir Na procentinę sudėtį, palyginti abiejų metodų rezultatus, tokiu būdu įvertinant gemologinių tyrimų metodų pritaikomumą bei efektyvumą identifikuojant feldšpatų grupės mineralus. Darbe... [toliau žr. visą tekstą] / SUMMARY KRISTIJONAS UNDZĖNAS IDENTIFICATION OF THE FELDSPAR GROUP ISOMORPHIC ROW MEMBERS USING GEMOLOGICAL METHODS The main objective of this dissertation is to assess the gemological methods affectivity and reliability for the identification of feldspar group minerals. The main task of this dissertation is to investigate and identify minerals of the feldspar group by using gemological investigation methods. After that to the part of the samples, which are representing the different kind of feldspar group minerals, to make crystal chemical analysis in Vilnius chemistry Institute. And after that to compare the results of the crystal chemical analysis and gemological investigation methods. Thereby to assess the affectivity and reliability of the gemological investigation methods in identification of feldspar group minerals. In this dissertation there were 86 minerals of the feldspar group investigated. 56 samples were identified like plagioclases and 30 were classified to the alkaline feldspar subgroup. From the plagioclases group there were indicated 32 Labradorites, 17 oligoclases, 4 albites, 3 andesines. And from the alkaline feldspar, there were 6 amazonites, 2 microclines, 22 orthoclases. Proceeding the job, there were made next finding: 1. It is easily possible to separate the plagioclases subgroup from the alkaline feldspar subgroup minerals, even to indicate the approximate plagioclase number, by using the gemological methods. 2. Performed crystal chemical analysis... [to full text]

The potential for valid dating using feldspar minerals has recently been increasingly questioned with the recognition of a range of effects capable of giving rise to age shortfalls. The intention here was to investigate the more serious of these, and to simultaneously extend the surprisingly meagre body of knowledge on the luminescence of the feldspar minerals. A suite of feldspars representative of all major mineral species of the feldspar ternary system was assembled and mineralogically classified by XRD and SEM techniques. Characterization of some luminescence properties relevant to dating (radiation dose-sensitivities, emission spectra, thermal sensitization and bleaching by IR and green light) was conducted to enable comparison of these properties with the anomalous fading behaviour in each feldspar (IRSL and OSL intensities being subsequently measured as a function of storage duration at 10°C and 100°C). Examples of feldspars representative of each major compositional regime of the ternary system were found to fade, and similarly some were stable; no luminescence characteristics or storage duration at these temperatures permitted reliable separation of stable signals. A new method for analysis of localised transition-type anomalous fading was successfully tested on zircon; however the fading mechanism operant in feldspars was found to be tunnelling-type fading. Such fading cannot be circumvented by any feasible laboratory procedure and it was concluded that monitoring of samples for the presence of fading is essential: discovery of fading is a rejection criteria. The long-term trapping stability of the IRSL source traps was investigated by "conventional" kinetic means, and also by a combined optical and thermal approach in which the bleaching response curves of five selected feldspars were measured along with their low temperature (= 100-400 K) response. It was concluded that the IRSL signal originates from one trap type only in all feldspars, which possesses a constant ground state-to-excited state transition energy of 1.44 ± 0.01 eV. However, the excited state-to-conduction band energy varies depending on the major element composition of the feldspar. Lifetimes of microcline TL from glow curve temperatures > 300°C greatly exceed the minimum required for dating and this work and complementary experiments showed no physical basis for the existence of an age limit for coarse grain feldspars, other than dose saturation. Supplementary work supported the existence of an upper age limit of = 100 ka for fine grain materials.

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Thesis (Ph. D.)--University of Chicago, 1915. / "A private edition distributed by the University of Chicago libraries." "Reprinted from the Journal of geology, vol. XXIV, no. 2, February-March, Chicago, 1916."

Thesis (Ph. D.)--University of Chicago, 1915. / "A private edition distributed by the University of Chicago libraries." "Reprinted from the Journal of geology, vol. XXIV, no. 2, February-March, Chicago, 1916."

Thesis (Ph. D.)--University of Wisconsin--Madison, 1936. / Typescript. Includes abstracts and vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.