4 research outputs found
URANYL DEPOSITION IN UNCONFORMITY-RELATED DEPOSITS IN THE ATHABASCA BASIN: EVIDENCE FROM URANIUM SPECIATION IN HEMATITE AND GOETHITE
No full textWith the exception of the recently discovered stable U4+ chloride complex at high temperatures under reduced conditions, genetic models for the formation of uranium deposits had almost invariably invoked the pivotal roles of soluble U6+ species for the transport of uranium-bearing fluids and their reduction to sparingly soluble U4+ as the deposition mechanism. However, the questions of when and how this reduction in most uranium deposits such as those in the Athabasca basin (Canada) occurred are often not clear. The unconformity-related uranium deposits in the Athabasca basin are commonly accompanied by extensive and intensive hematite-rich alteration halos. Previous U L3-edge XANES studies of uranium-bearing fluid inclusions and thermodynamic modeling demonstrated uranium transport as uranyl (UO22+) species in hypersaline fluids in the Athabasca basin. Electron microprobe analyses reveal that hematite inclusions in two early generations of secondary quartz overgrowth, as well as some disseminated hematite in clay mineral (illite-chlorite) matrices, in both orebodies and associated alteration haloes from five uranium deposits (Arrow, Cigar Lake, Key Lake, McArthur River, and Phoenix) in the Athabasca basin, contain anomalously high contents of uranium (up to 2.16 wt.% UO3). Synchrotron U L3-edge X-ray absorption spectroscopy (XAS) and U 4f X-ray photoelectron spectroscopy (XPS) analyses show that uranium in hematite occurs dominantly as the uranyl species, providing unambiguous evidence for direct uranyl deposition in the Athabasca basin. This mechanism of direct uranyl deposition with hematite and other minerals such as quartz (or their amorphous or microcrystalline precursors) during a single episode of hydrothermal alteration can account for low-grade uranium mineralization, but high-grade uranium deposits in the Athabasca basin required multiple episodes of hydrothermal alteration and reduction-induced deposition mechanisms. In addition, synchrotron U L3-edge XAS analyses show that uraniferous goethite associated with boltwoodite in late alteration assemblages of mineralized metapelites at the Eagle Point deposit is also dominated by the uranyl species, supporting its roles in late uranium remobilization
URANYL DEPOSITION IN UNCONFORMITY-RELATED DEPOSITS IN THE ATHABASCA BASIN: EVIDENCE FROM URANIUM SPECIATION IN HEMATITE AND GOETHITE
No full textWith the exception of the recently discovered stable U4+ chloride complex at high temperatures under reduced conditions, genetic models for the formation of uranium deposits had almost invariably invoked the pivotal roles of soluble U6+ species for the transport of uranium-bearing fluids and their reduction to sparingly soluble U4+ as the deposition mechanism. However, the questions of when and how this reduction in most uranium deposits such as those in the Athabasca basin (Canada) occurred are often not clear. The unconformity-related uranium deposits in the Athabasca basin are commonly accompanied by extensive and intensive hematite-rich alteration halos. Previous U L3-edge XANES studies of uranium-bearing fluid inclusions and thermodynamic modeling demonstrated uranium transport as uranyl (UO22+) species in hypersaline fluids in the Athabasca basin. Electron microprobe analyses reveal that hematite inclusions in two early generations of secondary quartz overgrowth, as well as some disseminated hematite in clay mineral (illite-chlorite) matrices, in both orebodies and associated alteration haloes from five uranium deposits (Arrow, Cigar Lake, Key Lake, McArthur River, and Phoenix) in the Athabasca basin, contain anomalously high contents of uranium (up to 2.16 wt.% UO3). Synchrotron U L3-edge X-ray absorption spectroscopy (XAS) and U 4f X-ray photoelectron spectroscopy (XPS) analyses show that uranium in hematite occurs dominantly as the uranyl species, providing unambiguous evidence for direct uranyl deposition in the Athabasca basin. This mechanism of direct uranyl deposition with hematite and other minerals such as quartz (or their amorphous or microcrystalline precursors) during a single episode of hydrothermal alteration can account for low-grade uranium mineralization, but high-grade uranium deposits in the Athabasca basin required multiple episodes of hydrothermal alteration and reduction-induced deposition mechanisms. In addition, synchrotron U L3-edge XAS analyses show that uraniferous goethite associated with boltwoodite in late alteration assemblages of mineralized metapelites at the Eagle Point deposit is also dominated by the uranyl species, supporting its roles in late uranium remobilization
Synthesis of jadarite in the Li2O–Na2O–B2O3–SiO2–NaCl–H2O system: FTIR, Raman, and Li and B K-edge XANES characterizations and theoretical calculations
No full text<jats:p>Abstract. The occurrence of jadarite (LiNaSiB3O7OH) as a major ore mineral in the world-class lithium–boron deposit of the Miocene Jadar lacustrine basin (western Serbia) raises interesting questions about its formation conditions and potential associations for lithium mineralization in other sedimentary basins. This contribution reports on the first successful synthesis of jadarite in the Li2O–Na2O–B2O3–SiO2–NaCl–H2O system at temperatures from 180 to 230 ∘C and pH values from 6 to 12. Synthetic jadarite has been characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, laser Raman spectroscopy, and synchrotron Li and B K-edge X-ray absorption near-edge structure (XANES). First-principles theoretical calculations reproduce the measured FTIR and Raman spectra and allow definitive assignments of vibration modes. Similarly, the measured Li and B K-edge XANES spectra are reasonably reproduced by first-principles theoretical calculations. Our synthesis results, together with its association with searlesite in the Jadar basin, suggest jadarite forms in deep sediments derived from Li-rich alkaline brines under high-temperature diagenetic conditions.
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Burhâneddîn el-Fezârî’nin Risâle fî sıhhati icâreti’l-iktâ‘ İsimli Risâlesinin Tahkikli Neşri
No full textThe present study consists of a critical edition of Burhan al-Din al-Fazari's -one of the Shafiite Islamic scholars of the 8/14. century- Risalah fi ?ı??at ijara al- iq?a?. The concept of iq?a? has followed a continuous line of change and development throughout the history of Islam. The type of iq?a? mentioned by the author, who lived in Mamluk Damascus, is the assignment of income-generating real estate that belongs to the public treasury (bayt al-mal) to military officers in exchange for the service they provided. This type of iq?a? was also known as "military iq?a?”. One of the main debates between the jurists related to this type of iq?a? is about the ability of the military officers (muqta?) to lease these lands. This issue was directly related to whether the military officers had the right of usufruct of the property or not. As far as can be determined, the first scholars expressing their opinion are Muhyi al-Din al-Nawawi (676/1277) and Taj al-Din al-Fazari (690/1291), the father of the mentioned author. The first opinion is positive and the second one is negative. Our author, who agrees with his father, wrote this treatise to defend the negative view. In this respect, this is the only known independent study written by scholars who hold the negative opinion. According to the author, the iq?a? alone does not establish for the assignee (muqta‘) rights of property or usufruct on the granted real estate; it only has the meaning of ibaha, that is, it provides a limited right of use. Therefore, it was not appropriate for the muqta‘ to lease the real estate unless he had a special permission from the Imam. This is because one cannot assign an interest that one does not own to someone else. The only copy of the work that is the subject of this study is in Kutubhane-i Umumi-i Ayetullah Mar?ashi in Iran.Elinizdeki çalışma 8./14. yüzyıl Şâfiî fakihlerinden Burhâneddîn el-Fezârî'nin Risâle fî sıhhati icâreti'l-iktâ‘ isimli eserinin inceleme ve tahkikinden oluşmaktadır. İktâ müessesi İslam tarihi boyunca sürekli bir değişim/gelişim çizgisi seyretmiştir. Memlük Suriye'sinde yaşamını sürdüren Fezârî’nin bahis konusu ettiği iktâ türü “askerî iktâ” olarak da bilinen ve ana hatlarıyla sundukları hizmet karşılığında gelirinden yararlanmaları için beytülmale ait gelir getiren gayrimenkullerin askerlere tahsisini ifade etmektedir. Bu iktâ türü ile ilgili fukahâ arasında cereyan eden ana tartışmalardan biri beytülmale ait arazilerin kendilerine tahsis edildiği askerlerin (mukta) bu arazileri kira akdine konu edebilme salahiyetleri ile ilgilidir. Başka bir deyişle Fezârî’nin de risâlesinde cevap aradığı soru kendisine beytülmal arazisi iktâ edilen askerin burayı kira ve ortakçılık gibi akitlerle işletme hakkına sahip olup olmadığı sorusudur. Bu sorunun cevabı muktaın kendisine iktâ edilen gayrimenkulün menfaatine mâlik olup olmaması ve eğer mâlik ise bu mülkiyetin keyfiyeti ile doğrudan ilgilidir. Tespit edebildiğimiz kadarıyla bu mesele hakkında görüş belirten ilk isimler sırasıyla Muhyiddîn Nevevî ve tahkikini sunduğumuz risâlenin müellifinin babası olan Tâceddîn el-Firkâh’dir. Bunlardan birincisi müsbet, ikincisi menfi görüş beyan etmiştir. Babasıyla aynı fikirde olan müellif bu görüşü savunmak için tahkikini sunduğumuz risâleyi kaleme almıştır. Bu yönüyle bu risâle bildiğimiz kadarıyla menfi kanaate sahip fakihler tarafından bu konuya dair müstakil olarak kaleme alınmış tek monografik çalışmadır. Fezârî’ye göre tek başına iktâ işlemi akarın menfaati üzerinde herhangi bir mülkiyet tesis etmemekte; sadece ibaha anlamı taşımakta yani intifa hakkı temin etmektedir. Dolayısıyla muktaın kendisine iktâ edilen akarı kiraya vermesi -eğer devlet başkanının bu hususta özel bir izni yoksa- sahih değildir. Zira kişi malik olmadığı bir menfaati başkasına temlik edememektedir. Eserin tespit edebildiğimiz tek nüshası İran’da bulunan Kütübhâne-i Umûmî-i Âyetullâh Mar‘aşî’dedir. Bunun dışında İbn Hacer el-Heytemî risâlenin yaklaşık yarısına tekabül eden bir kısmını Fetâvâ’sında nakletmiştir. Eserin tahkikinde Heytemî’nin naklettiği metin mukabelede kullanılmış, fakat tam bir nüsha muamelesi yapılmayarak sadece gerekli görülen yerlere işaret edilmiştir
