ALBERT

Description: The Cu-triethylenetetramine-complex (Cutrien) is one of the commonly used index cations for CEC determination in clay science. Cutrien-exchanged smectites show basal spacings between 13.0 and 13.5A after correction for the Lorentz and polarization factors. The full width at half maximum (FWHM) of the d001 reflection is today related to the percentage of tetrahedral charge (beidellitic character) and/or to the Fe content of the smectites. The structural Fe content and the tetrahedral charge correlate, so their individual influence on d001 cannot be resolved. Nevertheless, the FWHM of Cutrien smectites should depend on the charge distribution rather than the Fe content. X-ray diffraction (XRD) and water uptake capacity measurements showed that the interlayer of Cutrien-exchanged smectites does not swell any more, but can take up a few water molecules. Accordingly, the water uptake capacity of the external surface area can be determined independently from the interlayer water uptake capacity. Adjusting the pH of Cutrien-bentonite dispersion to different values allows for the determination of the variable charge. In conclusion, Cutrien exchange of smectites appears to be suitable for the study of external surfaces area related phenomena (e.g. edge adsorption processes) without any influence of the interlayer region.

Description: A subseafloor replacement-style barite and sulfide occurrence was drilled in shallow waters at the Palinuro volcanic complex, the northernmost Aeolian arc volcano in the Tyrrhenian Sea, Italy. Using a lander-type drilling device, 11 successful drill holes yielded a total of 13.5 m of core from a sediment-filled depression located at a water depth of 630 to 650 m. The longest continuous drill core recovered consists of 4.84 m of massive to semimassive barite and sulfides with abundant late, native sulfur overprint. Seafloor observations suggest that the hydrothermal system associated with the formation of the subseafloor barite and sulfide ore zone is still active, although black smoker activity does not occur on the seafloor. The recovered drill core shows that the subseafloor deposit is zoned with depth. The top of the mineralized zone is comprised of a variably silicified vuggy barite-sulfide facies that shows notable polymetallic metal enrichment, while the deeper portion of the mineralized zone is dominated by massive pyrite having distinctly lower base and precious metal grades. Metal zonation of the barite and sulfide deposit is related to the evolution of the hydrothermal fluids in space and time. The barite cap and the massive pyrite present in the deeper portion of the mineralized zone appear to have formed early in the paragenesis. During the main stage of the mineralization, the barite cap was brecciated and cemented by a polymetallic assemblage of barite and pyrite with minor chalcopyrite and tetrahedrite, trace famatinite, and rare cinnabar. Lower temperature precipitates formed during the main stage of mineralization include sphalerite, galena, pyrite, opal-A, and barite, which are associated with traces of Pb-Sb-As sulfosalts such as bournonite-seligmannite, or semseyite. A distinct mineral assemblage of fine-grained anhedral enargite, hypogene covellite, chalcopyrite, and galena is commonly associated with colloform sphalerite, galena, and pyrite as a late phase of this main stage. Colloform pyrite and marcasite are the last sulfides formed in the paragenetic sequence. The deposit is interpreted to have formed from fluids having an intermediate-sulfidation state, although excursions to high- and very high sulfidation states are indicated by the presence of abundant enargite and hypogene covellite. Laser ablation and conventional sulfur isotope analyses show that pyrite formed close to the seafloor within the zone of polymetallic metal enrichment has a variable sulfur isotope composition ( 34 S = –39 to +3), whereas a more narrow range is observed in the massive pyrite at depth ( 34 S = –10 to 0). Similar variations were also documented for the late native sulfur overprint. Overall, the negative sulfur isotope ratios at depth, the intermediate- to very high sulfidation conditions during mineralization, and the abundance of native sulfur suggest contributions of magmatic volatiles to the mineralizing fluids from a degassing magma chamber at depth. Biological processes are interpreted to have played a major role during late stages of ore formation. The combination of a subseafloor replacement deposit with a massive to semimassive barite cap rock overlying massive pyrite, the intermediate- to high-sulfidation characteristics, and the strong biological influence on the late stages of mineralization are distinct from other modern seafloor massive sulfide deposits and represents a style of submarine mineralization not previously recognized in a modern volcanic arc environment. The barite and sulfide occurrence at Palinuro shares many characteristics with porphyry-related base metal veins and intermediate-sulfidation epithermal deposits, suggesting that metallogenic processes associated with arc-related magmatic-hydrothermal systems are not restricted to the subaerial environment.

Description: The Cu-triethylenetetramine-complex (Cutrien) is one of the commonly used index cations for CEC determination in clay science. Cutrien-exchanged smectites show basal spacings between 13.0 and 13.5A after correction for the Lorentz and polarization factors. The full width at half maximum (FWHM) of the d001 reflection is today related to the percentage of tetrahedral charge (beidellitic character) and/or to the Fe content of the smectites. The structural Fe content and the tetrahedral charge correlate, so their individual influence on d001 cannot be resolved. Nevertheless, the FWHM of Cutrien smectites should depend on the charge distribution rather than the Fe content. X-ray diffraction (XRD) and water uptake capacity measurements showed that the interlayer of Cutrien-exchanged smectites does not swell any more, but can take up a few water molecules. Accordingly, the water uptake capacity of the external surface area can be determined independently from the interlayer water uptake capacity. Adjusting the pH of Cutrien-bentonite dispersion to different values allows for the determination of the variable charge. In conclusion, Cutrien exchange of smectites appears to be suitable for the study of external surfaces area related phenomena (e.g. edge adsorption processes) without any influence of the interlayer region.

Description: X-ray diffraction patterns of oriented mounts of clay minerals are often used in clay mineralogy for qualitative and quantitative purposes. Fequently occurring stacking defects, in particular, can be characterized by this technique. Modeling of these diffraction profiles has become an important tool in obtaining structural information about the nature of stacking order. Manual matching of calculated and observed patterns is time consuming and user dependent. Automatic refinement procedures are, therefore, desirable. An improved approach for the treatment of disordered layer structures within a Rietveld refinement is presented here. The recursive calculation of structure factors, similar to that of the simulation program DIFFaX , was introduced in the Rietveld code BGMN . Complete implementation is formulated within the interpreter language of the Rietveld code and is transparent as well as flexible. Such a method has opened the application of Rietveld refinement to patterns of oriented mounts where only basal reflections of stacking disordered structures were recorded. The DIFFaX code was used to simulate basal reflections of illite-smectite mixed layers (I-S) with different ratios of illitic and smectitic layers and with different degrees of long-range ordering (Reichweite). Rietveld refinements with these simulated patterns were used to evaluate the application of this new approach. Several I-S with different degrees of ordering were also chosen as tests for the refinement of basal reflections. The samples were prepared as standard air-dried and ethylene glycol-solvated, oriented specimens. Realistic structural parameters were obtained for the composition and ordering of the I-S.

Description: X-ray diffraction (XRD) of powdered materials is one of the most common methods used for structural characterization as well as for the quantification of mineral contents in mixtures. The application of the Rietveld method for that purpose requires structure models for each phase. The recursive calculation of structure factors was applied here to the Rietveld refinement of XRD powder patterns of illite-smectite (I-S) minerals. This approach allowed implementation of stacking disorder in structural models. Models for disordered stacking of cis -vacant and trans -vacant dioctahedral 2:1 layers as well as rotational disorder were combined with models for mixed layering of illitic and smectitic layers. The DIFFaX code was used to simulate non-basal ( hk ) reflections of illites with different degrees of disorder. Rietveld refinements of these simulated patterns were used to evaluate the application of this new approach. A model describing rotational disorder ( n ·120° and n ·60° rotations) and mixed layering of cis -vacant and trans -vacant dioctahedral layers was tested. Different starting parameters led to identical results within the ranges of standard deviations and confirmed the stability of the automatic refinement procedure. The influence on the refinement result of an incorrect choice of fixed parameters was demonstrated. The hk model was combined with models describing the basal reflections of disordered I-S and tested on measured data. A glauconitic mineral (Urkut, Hungary), an ordered I-S (ISCz-1, a special clay in the Source Clays Repository of The Clay Minerals Society), and a dioctahedral I-S (F4, Füzérradvány, Hungary) were used as test substances. Parameters describing the mixed layering of illitic and smectitic layers were compared with the results from refinements of oriented mounts and showed good agreement. A pattern of a physical mixture of an I-S mineral and a turbostratically disordered smectite was analyzed in order to test the new approach for application in quantitative phase analysis. The quantitative Rietveld phase analysis results were found to be satisfactory.

Description: The Cu-triethylenetetramine-complex (Cutrien) is one of the commonly used index cations for CEC determination in clay science. Cutrien-exchanged smectites show basal spacings between 13.0 and 13.5 Å after correction for the Lorentz and polarization factors. The full width at half maximum (FWHM) of the d001 reflection is today related to the percentage of tetrahedral charge (beidellitic character) and/or to the Fe content of the smectites. The structural Fe content and the tetrahedral charge correlate, so their individual influence on d001 cannot be resolved. Nevertheless, the FWHM of Cutrien smectites should depend on the charge distribution rather than the Fe content.X-ray diffraction (XRD) and water uptake capacity measurements showed that the interlayer of Cutrien-exchanged smectites does not swell any more, but can take up a few water molecules. Accordingly, the water uptake capacity of the external surface area can be determined independently from the interlayer water uptake capacity. Adjusting the pH of Cutrien-bentonite dispersion to different values allows for the determination of the variable charge.In conclusion, Cutrien exchange of smectites appears to be suitable for the study of external surfaces area related phenomena (e.g. edge adsorption processes) without any influence of the interlayer region.

Description: A subseafloor replacement-style barite and sulfide occurrence was drilled in shallow waters at the Palinuro volcanic complex, the northernmost Aeolian arc volcano in the Tyrrhenian Sea, Italy. Using a lander-type drilling device, 11 successful drill holes yielded a total of 13.5 m of core from a sediment-filled depression located at a water depth of 630 to 650 m. The longest continuous drill core recovered consists of 4.84 m of massive to semimassive barite and sulfides with abundant late, native sulfur overprint. Seafloor observations suggest that the hydrothermal system associated with the formation of the subseafloor barite and sulfide ore zone is still active, although black smoker activity does not occur on the seafloor. The recovered drill core shows that the subseafloor deposit is zoned with depth. The top of the mineralized zone is comprised of a variably silicified vuggy barite-sulfide facies that shows notable polymetallic metal enrichment, while the deeper portion of the mineralized zone is dominated by massive pyrite having distinctly lower base and precious metal grades. Metal zonation of the barite and sulfide deposit is related to the evolution of the hydrothermal fluids in space and time. The barite cap and the massive pyrite present in the deeper portion of the mineralized zone appear to have formed early in the paragenesis. During the main stage of the mineralization, the barite cap was brecciated and cemented by a polymetallic assemblage of barite and pyrite with minor chalcopyrite and tetrahedrite, trace famatinite, and rare cinnabar. Lower temperature precipitates formed during the main stage of mineralization include sphalerite, galena, pyrite, opal-A, and barite, which are associated with traces of Pb-Sb-As sulfosalts such as bournonite-seligmannite, or semseyite. A distinct mineral assemblage of fine-grained anhedral enargite, hypogene covellite, chalcopyrite, and galena is commonly associated with colloform sphalerite, galena, and pyrite as a late phase of this main stage. Colloform pyrite and marcasite are the last sulfides formed in the paragenetic sequence. The deposit is interpreted to have formed from fluids having an intermediate-sulfidation state, although excursions to high- and very high sulfidation states are indicated by the presence of abundant enargite and hypogene covellite. Laser ablation and conventional sulfur isotope analyses show that pyrite formed close to the seafloor within the zone of polymetallic metal enrichment has a variable sulfur isotope composition (δ34S = −39 to +3‰), whereas a more narrow range is observed in the massive pyrite at depth (δ34S = −10 to 0‰). Similar variations were also documented for the late native sulfur overprint. Overall, the negative sulfur isotope ratios at depth, the intermediate- to very high sulfidation conditions during mineralization, and the abundance of native sulfur suggest contributions of magmatic volatiles to the mineralizing fluids from a degassing magma chamber at depth. Biological processes are interpreted to have played a major role during late stages of ore formation. The combination of a subseafloor replacement deposit with a massive to semimassive barite cap rock overlying massive pyrite, the intermediate- to high-sulfidation characteristics, and the strong biological influence on the late stages of mineralization are distinct from other modern seafloor massive sulfide deposits and represents a style of submarine mineralization not previously recognized in a modern volcanic arc environment. The barite and sulfide occurrence at Palinuro shares many characteristics with porphyry-related base metal veins and intermediate-sulfidation epithermal deposits, suggesting that metallogenic processes associated with arc-related magmatic-hydrothermal systems are not restricted to the subaerial environment.