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CHEMISTRY (593 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 8)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 34)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 18)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 23)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 234)
ACS Photonics     Full-text available via subscription   (Followers: 11)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 21)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription   (Followers: 1)
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 50)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 55)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 14)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 9)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 15)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 19)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 69)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 26)
American Journal of Plant Physiology     Open Access   (Followers: 14)
American Mineralogist     Hybrid Journal   (Followers: 14)
Analyst     Full-text available via subscription   (Followers: 40)
Angewandte Chemie     Hybrid Journal   (Followers: 204)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 214)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 2)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 8)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 15)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 28)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 293)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 124)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 98)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 66)
Catalysis for Sustainable Energy     Open Access   (Followers: 7)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 8)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 13)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 71)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 19)
Chemical Reviews     Full-text available via subscription   (Followers: 176)
Chemical Science     Open Access   (Followers: 22)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 57)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 26)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 143)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 18)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 45)
Chemistry of Materials     Full-text available via subscription   (Followers: 260)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 9)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 2)
Copernican Letters     Open Access   (Followers: 1)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 12)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 58)
Dalton Transactions     Full-text available via subscription   (Followers: 22)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 4)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 2)
Environmental Chemistry     Hybrid Journal   (Followers: 9)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)
Environmental Science : Nano     Partially Free   (Followers: 1)
Environmental Toxicology & Chemistry     Hybrid Journal   (Followers: 18)

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Journal Cover Canadian Mineralogist
  [SJR: 0.591]   [H-I: 54]   [3 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 0008-4476 - ISSN (Online) 1499-1276
   Published by GeoScienceWorld Homepage  [16 journals]
  • Why Are Some Crystals Gem Quality' Crystal Growth Considerations On
           the "Gem Factor"
    • Authors: Fritsch, E; Rondeau, B, Devouard, B, Pinsault, L, Latouche, C.
      Pages: 521 - 533
      Abstract: The purpose of this work is to investigate the crystal growth parameters necessary or sufficient to obtain a crystal specifically of gem quality. We assume adequate chemistry is available. First, nucleation must occur with only a limited number of nuclei, otherwise too many crystals will be produced, and they will be too small to be faceted into a gem. Two growth mechanisms are readily documented for gems: Most commonly there is slow growth, driven by a spiral growth mechanism, leading to large single individuals. There are only a few examples of fast growth leading to gem-quality edifices: examples include "gota de aceite" Colombian emerald or the dendritic "pseudo cube" for gem diamonds. We have not documented the intermediate conditions between these two extremes in the Sunagawa diagram, which would correspond to 2D nucleation growth. The presence of inclusions is to be limited to desirable ones. Thus, in general, a good stability of the growth interface is the best guarantee of good clarity in the final gem. As for the interface, in general, growth conditions must be relatively stable over the period necessary to achieve growth. Perhaps surprisingly, it has become well documented that gem-quality near-colorless diamonds may have experienced quite a complex growth history. Therefore, the term stability has to be re-defined for each system producing a given gem. The length of time it takes to achieve crystallization of the gem has rarely been studied or estimated. Scientific evidence from experimental petrology and the growth of synthetic gems indicates that it does not take millions of years to grow a gem, but that this exercise may be achieved in a week to, arguably, a few years at the most. Available free space to grow does not appear always necessary, but it helps. Otherwise deformation, inclusions, and other negative effects may occur. Finally, no dramatic post-growth events, such as fracturing or etching, should affect the gem crystal.
      PubDate: 2017-07-26T16:13:54-07:00
      DOI: 10.3749/canmin.1700013
      Issue No: Vol. 55, No. 4 (2017)
       
  • The Origin of A New Pargasite-Schist Hosted Ruby Deposit From Paranesti,
           Northern Greece
    • Authors: Wang, K. K; Graham, I. T, Lay, A, Harris, S. J, Cohen, D. R, Voudouris, P, Belousova, E, Giuliani, G, Fallick, A. E, Greig, A.
      Pages: 535 - 560
      Abstract: Gem-quality (cabochon) ruby-bearing occurrences (here termed PAR-1 and PAR-5) located near Paranesti, north eastern Greece have been systematically studied for the first time in this paper. Tectonically, the occurrences are located within the Nestos Shear Zone (NSZ). The NSZ separates two distinct geological units. The Rhodope Terrane is a heterogeneous unit of gneisses, mafic, ultramafic, and meta-sedimentary rocks in the hanging wall. The footwall Pangaion-Pirin Complex consists of marbles and acid gneisses of a Mesozoic carbonate platform on pre-Mesozoic continental basement. In this paper, a range of petrographic and geochemical techniques were used to determine (1) any similarities and differences to other mafic-ultramafic hosted ruby deposits worldwide; (2) distinctive geochemical fingerprints for Paranesti; and (3) the likely P-T conditions of formation.Detailed petrographic and whole-rock analyses utilizing ICP-MS, XRF, and XRD have found the Paranesti corundum to be of a mafic/ultramafic protolith with approximately 40 wt.% SiO2, 16 wt.% Mg, 11000 ppm Cr, and 440 ppm Ni. EMPA major element analysis determined the mineral inclusions within the corundum grains to be picotite and hercynite spinels. Pargasite is the dominant amphibole within the corundum-bearing amphibole schist host. The surrounding non-corundum bearing chlorite schist mainly comprises clinochlore. Petrographic examination of the mineral assemblages within the corundum-bearing schists revealed strong fracturing and alignment (parallel to the main regional foliation) of the corundum grains and margarite reaction rims around the corundum. The surrounding non-corundum amphibolites also contain anorthite, along with relict sillimanite, kyanite, and chlorite/muscovite/epidote overprinting. Detailed LA-ICP-MS trace element analysis of the color range of corundum from the two occurrences showed the corundum to be mainly of metamorphic origin, though pale rubies from PAR-5 suggest some metasomatic influence.The corundum displays distinctive geochemical locality signatures, with a combination of high Cr (average 2300 ppm with 15% sample points on core positions>5000 ppm and maximum 8600 ppm); high Si (average 1400 ppm with 40% over 1500 ppm and maximum 2500 ppm), low Mg (average 30 ppm), and very low V, Ti, and Ga. Based on the literature for similar occurrences, and the mineral assemblages observed at Paranesti, the estimated P-T conditions of corundum formation are
      PubDate: 2017-07-26T16:13:54-07:00
      DOI: 10.3749/canmin.1700014
      Issue No: Vol. 55, No. 4 (2017)
       
  • Genesis of Emerald-Bearing Quartz Veins Associated With the Lened W-Skarn
           Mineralization, Northwest Territories, Canada
    • Authors: Lake, D. J; Groat, L. A, Falck, H, Mulja, T, Cempirek, J, Kontak, D, Marshall, D, Giuliani, G, Fayek, M.
      Pages: 561 - 593
      Abstract: Emerald at the Lened occurrence in the western Northwest Territories is hosted by quartz veins cutting skarn near the Lened granite pluton and older Selwyn Basin strata. Euhedral beryl crystals (
      PubDate: 2017-07-26T16:13:54-07:00
      DOI: 10.3749/canmin.1700025
      Issue No: Vol. 55, No. 4 (2017)
       
  • Trace Element Geochemistry and Metasomatic Origin of Alluvial Sapphires
           From the Orosmayo Region, Jujuy Province, Northwest Argentina
    • Authors: Harris, S. J; Graham, I. T, Lay, A, Powell, W, Belousova, E, Zappettini, E.
      Pages: 595 - 617
      Abstract: This study primarily sought to investigate the trace element composition of alluvial sapphires from the Orosmayo region, Jujuy Province, northwest Argentina. In situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis (n = 69) showed that the sapphires exhibit a predominant metasomatic trace element signature, including low Fe/Mg (4–117) and Ga/Mg (0.3–10.4) ratios. However, the sapphires also display magmatic associations, including elevated Ga (up to 239 ppm) and Si (up to 3890 ppm), which indicates magmatic-metasomatic inputs. Enrichments in LREEs (Y, La, Ce, and Nd), Zn, and Pb, likely contained within remnant formational fluids, and elevated Be, Nb, Ta, Sn, Th, and U contents, likely contained within mineral inclusions, suggest that the sapphires were influenced by highly evolved felsic melts resembling those of granitic composition. The analyses were complemented by mineral inclusion identification using visual microscopy, and confirmed by energy dispersive spectroscopy (EDS). Identifiable co-genetic mineral inclusions include Al and Ti-rich magnetite, pyrochlore, albite, columbite-(Fe), rutile, phlogopite, trikalsilite, pyrite, baryte, monazite-(La), xenotime-(Y), and zircon. Secondary inclusions included hematite and Mg-hercynite which formed as reaction rims surrounding three of the sapphires. The inclusion mineralogy supports the notion of a mixed genetic scenario, with a distinct bimodal nature highlighting interactions between Si-poor and evolved Si-rich melts. Morphological and textural analysis using scanning electron microscopy (SEM) revealed dominant corrosive features on the sapphires. These corrosive features, coupled with the presence of spinel reaction rims, suggests that the sapphires were transported to the surface as xenocrystal fragments that were in chemical dis-equilibrium with their transport medium.Detailed consideration of their geochemical composition in relation to the known geology of the surrounding region was used to narrow down potential sources. Until other evidence surfaces, a working hypothesis for sapphire genesis involves a three-stage process, including: (1) their crystallization via metasomatic fluid exchange between an evolved crustal felsic system, such as crustal pegmatitic/granitic fluids, and intruding coeval mantle-derived carbonatized lamprophyre during the Lower Cretaceous (~150–100 Ma) as part of alkaline magmatism within NW Argentina; (2) their incorporation as xenocrysts within the effusive volcanic products of the Neogene Granadas Volcanic Complex (~9.8 Ma); and (3) subsequent host-rock erosion to form the present-day alluvial placer deposits of Orosmayo. The large trace element variation within individual sapphire grains identified in this work also highlights the importance of detailed in situ analysis across corundum grains in order to better understand the complex changing physiochemical conditions during their growth.
      PubDate: 2017-07-26T16:13:54-07:00
      DOI: 10.3749/canmin.1700015
      Issue No: Vol. 55, No. 4 (2017)
       
  • Fluid Inclusion and Stable Isotope Constraints On the Formation of the
           Ianapera Emerald Deposit, Southern Madagascar
    • Authors: Salvi, S; Giuliani, G, ANDRIANJAKAVAH, P. R, Moine, B, Beziat, D, Fallick, A.
      Pages: 619 - 650
      Abstract: The Ianapera emerald deposit is hosted in the Neoproterozoic Vohibory domain of southern Madagascar, within a tightly folded metamorphic sequence of mafic and ultramafic rocks (M-UMR), gneiss, and marble, a few kilometers north of the major tectonic break known as the Ianapera-Ampanihy Suture. Late-collisional metaluminous to peraluminous felsic intrusions outcrop in the area. Emerald occurs mostly within metasomatic phlogopitite and quartz-tourmaline veins, developed within lenses of M-UMR. Recent work recognized granitic pegmatites as the source of the emerald-forming fluids, leading to the classification of proximal and distal mineralization styles, based on whether or not pegmatites are associated with the phlogopitite, respectively (Andrianjakavah et al. 2009). Considerations of the chemistry of tourmaline and scapolite associated with emerald and beryl, data from fluid and solid inclusions in these minerals, thermodynamic calculations, and mineral thermobarometric data confirm that Be originated from the pegmatites, transported in a moderately saline aqueous fluid that exsolved at about 600 to 680 °C and 4–6 kbars. This fluid was enriched in alkali elements, incompatible elements and dissolved sulfur, and produced the proximal mineralization. Migration along fractures caused loss of at least part of the pegmatitic elements and local mixing with a metamorphic CO2-rich fluid, leading to the more distal mineralization at somewhat lower temperatures (520 to 650 °C). Oxygen and hydrogen stable isotopes were measured from beryl and emerald; the data corroborate a magmatic-hydrothermal origin for the mineralization and a common source for proximal and distal fluids. The calculated 18OH2O of 12.5 at 520 °C for the distal emerald and the DH2O range measured from the channel of the emerald samples fit within the oxygen and hydrogen isotopic range of values defined for peraluminous granitic magmatism. The occurrence of a distal style of emerald mineralization such as typified by Ianapera suggests that metamorphic origin models for similar occurrences worldwide should be taken with care and possibly reconsidered in terms of source and origin of fluids and metals.
      PubDate: 2017-07-26T16:13:54-07:00
      DOI: 10.3749/canmin.1700017
      Issue No: Vol. 55, No. 4 (2017)
       
  • Searching For the Garamantian Emerald: Reconsidering the Green-Colored
           Stone Beads Trade In the Ancient Sahara
    • Authors: Zerboni, A; Vignola, P, Gatto, M. C, Risplendente, A, Mori, L.
      Pages: 651 - 668
      Abstract: In the current literature, Saharan green-colored stone beads are identified with the term émeraude garamantique, while several archaeological investigations on Garamantian contexts referred to them as amazonite. Moreover, according to the hypothesis proposed by Monod, authors identify the only source of amazonite to be the pegmatite swarm at Eghei Zuma (northern Tibesti, Libya). To check this assumption, we characterized the composition of green-colored stone beads found at Fewet, a Garamantian site (2nd century BC – 1st century AD) in the Libyan Sahara. We performed electron microprobe analyses on stone beads from Fewet and ethnographic contexts of Mali, Mauritania, and Sudan. Furthermore, lacking a regional database on amazonite to compare the geochemical properties of archaeological beads, we analyzed amazonite crystals from several African pegmatites, including samples from Eghei Zuma. The results show that green-colored stone beads from Fewet consist of serpentinite and amazonite. The K/Rb versus Rb diagram reveals that the source of the amazonite from Fewet could not be the pegmatite at Eghei Zuma. The raw material for amazonite beads traded in Garamantian times originated from Egypt and Mauritania. We discuss the archaeological implications of our results, which concerns the directions of ancient trade routes for elite goods in Garamantian times.
      PubDate: 2017-07-26T16:13:54-07:00
      DOI: 10.3749/canmin.1600052
      Issue No: Vol. 55, No. 4 (2017)
       
  • Origin Of Scapolite-Hosted Sapphire (Corundum) Near Kimmirut, Baffin
           Island, Nunavut, Canada
    • Authors: Belley, P. M; Dzikowski, T. J, Fagan, A, Cempirek, J, Groat, L. A, Mortensen, J. K, Fayek, M, Giuliani, G, Fallick, A. E, Gertzbein, P.
      Pages: 669 - 699
      Abstract: Gem-quality corundum (sapphire) occurs in scapolite-rich calc-silicate rock hosted in marble of the Lake Harbour Group near Kimmirut, southern Baffin Island. A deposit of blue and colorless gem corundum (Beluga occurrence) is compared to a similar calc-silicate pod generally lacking corundum but containing nepheline (Bowhead occurrence) and located 170 m to the SSW. Corundum formation was made possible by three equally important sequential metamorphic reactions: (1) formation of nepheline, diopside, and K-feldspar (inferred) at granulite facies peak metamorphic conditions; (2) partial retrograde replacement of the peak assemblage by phlogopite, oligoclase, calcite, and scapolite (Me50–Me67) as a result of CO2-, H2O-, Cl-, F-bearing fluid influx at 1782.5 ± 3.7 Ma (P-T < 720 °C, 6.2 kbar); and (3) retrograde breakdown of scapolite + nepheline (with CO2- and H2O-bearing fluid) to form albite, muscovite, corundum, and calcite. Late, low-temperature zeolite mineralization is common in corundum-bearing zones. Based on thermodynamic models, the corundum-forming reaction only occurs in a
      PubDate: 2017-07-26T16:13:54-07:00
      DOI: 10.3749/canmin.1700018
      Issue No: Vol. 55, No. 4 (2017)
       
  • The Precious Opal Deposit At Wegel Tena, Ethiopia: Formation Via
           Successive Pedogenesis Events
    • Authors: Chauvire, B; Rondeau, B, Mazzero, F, Ayalew, D.
      Pages: 701 - 723
      Abstract: Since its discovery in 2008, the opal deposit in the Wegel Tena area of Ethiopia, located within an Oligocene ignimbritic trap, has become a major provider of precious opal. This study provides new field evidence and laboratory results that reinforce the pedogenetic model for gem opal formation. In the eight mines investigated, opal occurs in lenticular horizons within an unwelded ignimbrite bed. Moreover, several deposits are superimposed in the sequence, indicating that gem opal formation occurred several times in the same place. We observed that, in contrast to the other beds, the opal-bearing horizons are strongly weathered: volcanic glass is altered to smectite, rocks with a granular microstructure are apparent, and cavities are covered by illuvial clays. These features are typical of pedogenetic processes. Plant fossils in the opals reveal a well preserved cellular structure composed of chalcedony. These observations are consistent over all the mines, supporting the pedogenetic model for precious opal formation in the Wegel Tena area.
      PubDate: 2017-07-26T16:13:54-07:00
      DOI: 10.3749/canmin.1700010
      Issue No: Vol. 55, No. 4 (2017)
       
  • Formational Conditions For the Binntal Emerald Occurrence, Valais,
           Switzerland: Fluid Inclusion, Chemical Composition, and Stable Isotope
           Studies
    • Authors: Marshall, D; Meisser, N, Ellis, S, Jones, P, Bussy, F, Mumenthaler, T.
      Pages: 725 - 741
      Abstract: Emerald from the Binntal occurrence in the Canton of Valais in Switzerland has been studied to determine its chemical zonation, stable isotopic signatures, depositional-fluid characteristics, pressure-temperature emplacement conditions, and formational model. The emerald is vanadium-rich, with optical and blue cathodoluminescence zoning related to chemical variations, primarily in V2O3 concentrations. The hydrogen isotope signature of the emerald channel fluids is unique and in agreement with previously identified high-altitude (deuterium-depleted) Alpine-age meteoric fluids. Field studies, fluid inclusion analyses, and oxygen isotope thermometry are consistent with a metamorphic formational model for the Binntal emerald at temperatures and hydrostatic pressures ranging from 200 to 400 °C and 100 to 250 Mpa, respectively. This corresponds to formational depths on the order of 4 to 9 km and fluids consistent with a 10–20 Ma CO2-dominant fluid with approximate mole percentages of 84.0, 11.9, 1.5, 1.3, 0.3, and 0.5 for CO2, H2O, CH4, N2, H2S, and NaCl, respectively.
      PubDate: 2017-07-26T16:13:54-07:00
      DOI: 10.3749/canmin.1600090
      Issue No: Vol. 55, No. 4 (2017)
       
  • Pink and Red Spinels In Marble: Trace Elements, Oxygen Isotopes, and
           Sources
    • Authors: Giuliani, G; Fallick, A. E, Boyce, A. J, Pardieu, V, Pham, V. L.
      Pages: 743 - 761
      Abstract: The oxygen isotopic composition of pink to red and other colored spinels hosted by marbles worldwide have been combined with trace elements investigated by electron microprobe analysis (EMPA). For the first time, this database enables the characterization of the geographic origin of the main productive and historical sources of gem spinel. Three consistent sets of 18O values were found for primary and placer deposits: (1) between 5.6 and 8.6 for the historical Kuh-i-Lal spinels from Tajikistan; (2) from 12.1 to 18.5 for spinels from An Phu and Cong Troi in Vietnam, and Namya from Myanmar; and (3) between 19.0 and 24.2 for spinels from Paigutan in Nepal, Kiswila and Ipanko in Tanzania, Pamreso in Kenya, Mogok in Myanmar, and An Phu in Vietnam. The variation in the 18O values for most of the deposits can be related to the buffering of the metamorphic fluids by the oxygen isotope composition of the impure marbles. The 18O values of Kuh-i-Lal spinels result from a metasomatic skarn process between granitic intrusives and marble. Trace elements, such as Fe-Zn-Cr-V-Ti, presented in various new chemical discrimination diagrams allow for the differentiation of all the pink to red spinels. The slight overlaps observed for some chemical domains can be resolved by combination with the O-isotope composition of spinel. The present study shows that it is possible to discriminate gem spinels hosted by marbles from different geographic regions of the world and provides new insights into the traceability of historical spinels such as those from Kuh-i-Lal.
      PubDate: 2017-07-26T16:13:54-07:00
      DOI: 10.3749/canmin.1700009
      Issue No: Vol. 55, No. 4 (2017)
       
  • Age and Origin of the Tsavorite and Tanzanite Mineralizing Fluids In the
           Neoproterozoic Mozambique Metamorphic Belt
    • Authors: Feneyrol, J; Giuliani, G, Demaiffe, D, Ohnenstetter, D, Fallick, A. E, Dubessy, J, Martelat, J.-E, Rakotondrazafy, A. F. M, Omito, E, Ichang'i, D, Nyamai, C, Wamunyu, A. W.
      Pages: 763 - 786
      Abstract: The genetic model previously proposed for tsavorite- (and tanzanite-) bearing mineralization hosted in the Neoproterozoic Metamorphic Mozambique Belt (stretching from Kenya through Tanzania to Madagascar) is refined on the basis of new Sm-Nd age determinations and detailed Sr-O-S isotope and fluid-inclusion studies. The deposits are hosted within meta-sedimentary series composed of quartzites, graphitic gneisses, calc-silicate rocks intercalated with meta-evaporites, and marbles. Tsavorite occurs either in nodules (also called "boudins") oriented parallel to the metamorphic foliation in all of the deposits in the metamorphic belt or in quartz veins and lenses located at the hinges of anticlinal folds (Lelatema fold belt and Ruangwa deposits, Tanzania). Gem tanzanite occurs in pockets and lenses in the Lelatema fold belt of northern Tanzania.The Sm-Nd isotopic data for tsavorites and tanzanites hosted in quartz veins and lenses from Merelani demonstrate that they formed at 600 Ma, during the retrograde metamorphic episode associated with the East African Orogeny. The tsavorites hosted in nodules do not provide reliable ages: their sedimentary protoliths had heterogeneous compositions and their Sm-Nd system was not completely rehomogenized, even at the local scale, by the fluid-absent metamorphic recrystallization.The initial 87Sr/86Sr isotopic ratios of calcite from marble and tanzanites from Merelani fit with the strontium isotopic composition of Neoproterozoic marine carbonates. Seawater sediment deposition in the Mozambique Ocean took place around 720 Ma.The quartz-zoisite O-isotopic thermometer indicates a temperature of formation for zoisite between 385 and 448 °C.The sulfur isotopic composition of pyrite (between –7.8 and –1.3 V-CDT) associated with tsavorite in the Lelatema fold belt deposits suggests the contribution of reduced marine sulfate. The sulfur in pyrite in the marbles was likely derived from bacterial sulfate reduction which produced H2S. Fluid inclusion data from tsavorite and tanzanite samples from the Merelani mine indicate the presence of a dominant H2S-S8±(CH4)±(N2)±(H2O)-bearing fluid. In the deposits in Kenya and Madagascar, the replacement of sulfate by tsavorite in the nodules and the boron isotopic composition of tourmaline associated with tsavorite are strong arguments in favor of the participation of evaporites in garnet formation.
      PubDate: 2017-07-26T16:13:54-07:00
      DOI: 10.3749/canmin.1600085
      Issue No: Vol. 55, No. 4 (2017)
       
  • Reflectance Spectroscopy and Hyperspectral Imaging of Sapphire-Bearing
           Marble From the Beluga Occurrence, Baffin Island, Nunavut
    • Authors: Turner, D; Groat, L. A, Rivard, B, Belley, P. M.
      Pages: 787 - 797
      Abstract: Baffin Island (Nunavut, Canada) is located in the remote arctic where geological exposure is high, terrain is expansive, and field seasons are short. Metacarbonates in the Lake Harbour Group, southern Baffin Island, are considered to be prospective for sapphire (corundum), lapis lazuli (lazurite), and spinel gem deposits. This research is an investigation of the hyperspectral signature of rocks from the Beluga sapphire occurrence near Kimmirut, Nunavut.Thirty-five rock and thin section offcut samples from the Beluga corundum occurrence were studied in a laboratory setting using high spatial resolution imaging spectroscopy in the shortwave infrared region (SWIR, ~975 to 2500 nm). Analysis of hyperspectral imagery successfully reproduced mineralogical and textural information relevant to gem mineralization previously assessed through thin section petrography and scanning electron microscopy. Scapolite, phlogopite, and muscovite from these rocks are shown to have distinct spectral responses from the host marble that is dominated by calcite. Furthermore, spectrally distinct prehnite and zeolite, both locally associated with corundum mineralization, are readily distinguishable.From the perspective of regional exploration, the small footprint of colored gemstone deposits in combination with their unique mineralogical makeup, unusual settings, and unfamiliarity to most geoscientists has resulted in very few discoveries in this remote but otherwise fertile area. These factors, in combination with the unique spectral responses observed from hand samples and thin section offcuts, provide a positive case for mapping and exploration of gem corundum targets by high spatial resolution hyperspectral imaging as part of regional surveys.
      PubDate: 2017-07-26T16:13:54-07:00
      DOI: 10.3749/canmin.1700023
      Issue No: Vol. 55, No. 4 (2017)
       
  • Recent Advances In Understanding the Similarities and Differences of
           Colombian Euclases
    • Authors: Pignatelli, I; Giuliani, G, Morlot, C, Rouer, O, Claiser, N, Chatagnier, P.-Y, Goubert, D.
      Pages: 799 - 820
      Abstract: Colombian euclase is rare and associated with emerald in medium-temperature hydrothermal veins hosted by Lower Cretaceous black shales (BS). The original sources of euclase production were the mining districts of Gachalá and Chivor in the eastern emerald belt, but in 2016 euclases were also found at the La Marina mine in the western emerald belt.The present study is centered on a chemical and mineralogical examination of zoned Colombian euclase sold on the gem market as "trapiche". Its texture is characterized by growth bands and sectors distinguished by the presence of numerous inclusions (mainly pyrite, carbonates, and organic matter) which represent around 0.2% of the total volume of the crystals. X-ray computed tomography showed that the largest inclusions are randomly located, whereas the small inclusions are concentrated in the center of the crystals, along the crystallographic b axis, between neighboring growth sectors and between growth bands in each sector. The texture cannot be defined as "trapiche", like that of Colombian emeralds, because there is no matrix material from the surrounding BS trapped between the growth sectors and accumulated as dendrites. Three-phase fluid inclusions (FI) containing halite, liquid, and vapor phases are also observed in the euclase, and their volume is identical to that of the inclusions in emerald.Chromium and vanadium are the main chromophores, and the highest concentrations (1240 and 400 ppm, respectively) were found in deep blue-colored zones. Surprisingly, the euclase crystals have high Ge contents, between 230 and 530 ppm. The Rare Earth Element (REE) patterns of euclase are inherited from the enclosed BS or albitized and carbonatized BS. Euclase has the same REE pattern as emerald from the Gachalá mines with an Eu anomaly (Eu/Eu* ~ 0.40) and a depletion in Heavy Rare Earth Elements (HREE).The present study allows for the reconstruction of the formation conditions of "trapiche" euclase and discussion about its probable geographic origin, i.e., the eastern emerald belt.
      PubDate: 2017-07-26T16:13:54-07:00
      DOI: 10.3749/canmin.1700011
      Issue No: Vol. 55, No. 4 (2017)
       
 
 
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