ORCID Profile
0000-0002-7869-946X
Current Organisation
University of Freiburg
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Publisher: Oxford University Press (OUP)
Date: 09-2000
Publisher: Elsevier BV
Date: 10-2002
Publisher: Elsevier BV
Date: 02-2005
Publisher: Wiley
Date: 06-1999
Publisher: Elsevier BV
Date: 02-2014
Publisher: Elsevier BV
Date: 07-2017
Publisher: Schweizerbart
Date: 25-07-2005
Publisher: Elsevier BV
Date: 06-2000
Publisher: Mineralogical Society
Date: 02-2004
Abstract: Silica sinter masses in the southern portion of the Pliocene Puhipuhi geothermal field of Northland, New Zealand, have recrystallized to microcrystalline quartz and moganite but many primary depositional fabrics of the sinters can still be recognized. Finely disseminated cinnabar, acicular stibnite, pyrite framboids and minor livingstonite are distributed through both massive sinter and stromatolitic fabrics with sulphide mineralization extending from fractured rocks about former spring vents into less disturbed sinter layers. The deposition of sulphides in the sinters is part of a continuum of mineralization resulting from the former hydrothermal regime and which extends to depth in the extinct geothermal system. Periodic changes in the hydrology, such as repeated fracturing following fracture sealing facilitated episodic sulphide deposition. Mercury is considered to have travelled in the liquid phase with antimony and precipitated directly as cinnabar. Remobilization of the sulphides, along with the recrystallization of the sinter masses, have produced complex textural relations. The multifaceted paragenesis of the sulphides is reflected in the range of their minor and trace element compositions revealed by electron microprobe analyses.
Publisher: Wiley
Date: 07-2000
Publisher: Geological Society of America
Date: 07-2000
Publisher: Mineralogical Society
Date: 08-2003
Abstract: A dolostone layer is found in spatial association with the Emirli epithermal Sb-Au deposit in western Turkey. It occurs within an argillic alteration zone adjacent to the major Emirli fault zone, which is the controlling structure for the deposit, and is composed of large closely packed subhedral to anhedral planar and nonplanar dolomites. Pyrite is the only accessory mineral in the layer and occurs as disseminations and veinlets up to 100 μm wide. Dolomite crystals are petrographically homogeneous and have consistent deep-red cathodoluminescence (CL) colour with no zoning which implies single-stage dolomitization of a calcitic precursor which is partly preserved as remnant patches of orange-coloured CL zones. Some crystal boundaries have dark (or no) CL colour. Electron microprobe line-scan analyses across these regions indicate intense enrichment of Fe and Mg depletion, revealing late-stage Fe-metasomatism (ankeritization) especially prevalent near pyrite veinlets and disseminations. Dolomite crystals are composed of 52.4–55.0 mol.% CaCO 3 , 29.9 –41.2 mol.% MgCO 3 , 1.8 – 14.4 mol.% FeCO 3 and 0.75 –3.2 mol.% MnCO 3 indicating ferroan dolomite. The relationship between Ca and Mg is not stoichiometric due to substitution of Mg 2+ by Fe 2+ after dolomitization, as demonstrated by a strong negative correlation between Fe and Mg. Whole-rock Fe contents of the dolostone layer increases toward the Emirli fault zone. The δ 13 C (PDB) compositions of the Emirli dolomite, calcitic marbles, and graphite-schists are in the ranges of –1.6 to 0.8‰, 1.5 to 1.5‰ and –6.6 to –23.5%, respectively, indicating that dolomite was formed due to interaction of light-carbon-enriched fluids with calcitic marbles light-carbon may have been derived from decarboxylation of the graphitic schist layers. δ 18 O (PDB) values of dolomite and marble range –15.2 to – 11.2‰ and –2.4 to – 3.5‰, respectively. This large isotopic difference between dolomite and marble was probably inherited from oxygen isotope exchange between the dolomitizing fluid and the precursor calcites, as well as other minerals enriched in light-oxygen. Fluid inclusions in dolomite are two-phase, and homogenize into liquid within the temperature interval 242 – 362ºC with a mode of 290ºC, and have salinities of 1 – 3 wt.% NaCl equiv. Using this modal temperature, the average δ 18 O (PDB) composition of water in isotopic equilibrium with the Emirli dolostone was estimated to be –19.4±2.1‰, which is interpreted as an indication of modified surface-waters this interpretation is also supported by low fluid salinity and Na and Sr contents. These fluids migrated along graben-related faults, penetrating deeper levels where they were transformed into hydrothermal fluids due to the high heat-flow of the Küçük Menderes graben system, and flowed-up mainly through the Emirli and Haliköy faults that control mineralization in local deposits of Sb-Au and Hg, respectively. Due to interaction with chlorite-bearing graphite-schists, the fluid may have dissolved Mg 2+ from chlorite and been enriched in isotopically-light carbon due to decarboxylation of graphite. Dolomitization occurred as a result of the interaction of these fluids with a calcitic marble band adjacent to the Emirli fault zone. Subsequent introduction of Fe 2+ caused ankeritization along dolomite crystal boundaries during first-stage Sb-Au mineralization.
Publisher: Mineralogical Society
Date: 08-2003
Abstract: Compreignacite, a naturally occurring potassium uranyl oxide hydrate, is an expected alteration product of spent nuclear fuel subjected to oxidative corrosion in the presence of water. Ion-exchange experiments were performed using natural crystals of compreignacite in a 2 M CsCl solution at 180°C for 24 h, and in a 100 ppm CsCl solution at 90°C for 14 days. Exchange of Cs into crystals of compreignacite was demonstrated by crystal-structure analysis for a crystal from 2 M solution and chemical analysis for crystals from both exchange experiments. The structure of Cs-exchanged compreignacite is hexagonal, space group P 2m, a = 14.1014 (18) Å, c = 15.127(3) Å, V = 2605.1(7) Å 2 . It was solved by direct methods and refined on the basis of F 2 for all unique reflections to a final R 1 = 6.37%. The structure determination demonstrated almost complete exchange of Cs for K in the interlayer of the structure, as confirmed by compositional analysis of the crystals, and provided the formula Cs 6 [(UO 2 ) 12 (OH) 10 O 10 ](H 2 O) 3.5 , Z = 2. The structure of Cs-exchanged compreignacite contains α-U 3 O 8 -type sheets of uranyl pentagonal bipyramids that are topologically identical, although compositionally distinct, to those in compreignacite. Compreignacite crystals placed in 100 ppm CsCl solution also incorporated substantial Cs by ion exchange. Ion exchange experiments, using Cs-exchanged compreignacite from earlier experiments, in 2 M KCl solution at 90°C for 14 days showed that compreignacite will retain significant Cs in the presence of a solution rich in K. These experiments indicate that formation of compreignacite structure-type phases in a geological repository due to alteration of nuclear waste may significantly impact upon the mobility of Cs, either by direct incorporation of Cs into growing crystals, or by exchange of Cs into earlier-formed crystals of compreignacite when they contact Cs-bearing solutions.
Publisher: Springer Science and Business Media LLC
Date: 09-01-2016
Publisher: Royal Society of Chemistry (RSC)
Date: 1998
DOI: 10.1039/A801286E
Publisher: Elsevier BV
Date: 03-2004
Publisher: Oxford University Press (OUP)
Date: 10-2008
Publisher: Mineralogical Society of America
Date: 05-2001
Publisher: Mineralogical Society of America
Date: 05-2001
Publisher: Mineralogical Society of America
Date: 2004
Publisher: Elsevier BV
Date: 2009
DOI: 10.1016/J.JENVMAN.2007.10.002
Abstract: A susceptibility indexing method was developed based on vulnerability and quality indices. The contamination susceptibility index (SI) at a given location was calculated by taking the product of the vulnerability index (VI) and the quality index (QI): SI=VIxQI. This method incorporates both hydrogeological and hydrochemical data for a comprehensive index mapping. The DRASTIC index methodology was used for the hydrogeological data evaluations. The quality index calculation procedure based on a water quality classification scheme was introduced to evaluate hydrochemical data. The suggested susceptibility indexing method was applied to the Küçük Menderes river basin located in western Turkey. The susceptibility index map shows both hydrogeological and hydrochemical data related to the contamination problem including areas that should be taken into consideration during water management planning. The index map indicates that the most susceptible groundwater is located along the river channel between Kiraz and Tire towns, in the Selçuk area and along the Fertek stream channel to the north of Torbali town. The results indicate that the incorporation of both hydrogeological and hydrochemical datasets enables more realistic evaluations than those of an in idual dataset to estimate the groundwater contamination susceptibility of an aquifer. The numerical procedure applied could be extended further by including other parameters such as retardation, potential contaminant sources, etc. that affect the water quality in a given basin.
Publisher: Mineralogical Society of America
Date: 2003
DOI: 10.2113/0530469
Publisher: Springer Science and Business Media LLC
Date: 12-05-2000
Publisher: Mineralogical Society of America
Date: 2003
DOI: 10.2113/0530027
Publisher: Springer Science and Business Media LLC
Date: 11-12-1998
Publisher: Mineralogical Society
Date: 06-2015
DOI: 10.1180/MINMAG.2015.079.3.04
Abstract: Gem minerals at Lava Plains, northeast Queensland, offer further insights into mantle-crustal gemformation under young basalt fields. Combined mineralogy, U-Pb age determination, oxygen isotope and petrological data on megacrysts and meta-aluminosilicate xenoliths establish a geochemical evolution in sapphire, zircon formation between 5 to 2 Ma. Sapphire megacrysts with magmatic signatures (Fe/Mg ∼100–1000, Ga/Mg 3–18) grew with ∼3 Ma micro-zircons of both mantle (δ 18 O 4.5–5.6%) and crustal (δ 18 O 9.5–10.1‰) affinities. Zircon megacrysts (3±1 Ma) show mantle and crustal characteristics, but most grew at crustal temperatures (600–800°C). Xenolith studies suggest hydrous silicate melts and fluids initiated from hibolized mantle infiltrated into kyanite+sapphire granulitic crust (800°C, 0.7 GPa). This metasomatized the sapphire (Fe/Mg ∼50–120, Ga/Mg ∼3–11), left relict metastable sillimanite-corundum-quartz and produced minerals enriched in high field strength, large ion lithophile and rare earth elements. The gem suite suggests a syenitic parentage before its basaltic transport. Geographical trace-element typing of the sapphire megacrysts against other eastern Australian sapphires suggests a phonolitic involvement.
Publisher: Mineralogical Society
Date: 08-2003
Abstract: Rhönite occurs in lower crustal pyroxenite xenoliths erupted in phonolite from the Mount Sidley composite volcano, Marie Byrd Land, Antarctica, as a localized breakdown product, with plagioclase, clinopyroxene, ± olivine ± Ti-magnetite + melt, of kaersutite, and as microphenocrysts (with olivine, plagioclase, clinopyroxene) in pockets of basanitic melt. Rhö nite after kaersutite has a more NaSi-rich/ CaAl-poor composition, lower Ti, and formed at higher oxidation (∼NNO) conditions than rhönite occurring as microphenocrysts in basanite. Comparison with experimentally determined rhönite stability in understaturated alkali basalt and as a reaction product after Ti- hibole indicates that the Mount Sidley rhönite (and associated minerals) formed between 1090 and 1190°C at .5 kbar, presumably during temporary residence of the xenoliths in a shallow magma chamber below the volcanic edifice.
No related grants have been discovered for Paul William Owen Hoskin.