... The crystal structure of a chromian pumpellyite of general formula VIIW8 VIX4 VIY8 IVZ12O56-n... more ... The crystal structure of a chromian pumpellyite of general formula VIIW8 VIX4 VIY8 IVZ12O56-n(OH)n from Sarani, Urals, Russia, was refined using X-ray single-crystal data to investigate the crystal-chemical behavior of Cr in pumpellyite. ...
ABSTRACT Raman spectroscopic and petrographic analyses were performed on samples collected from z... more ABSTRACT Raman spectroscopic and petrographic analyses were performed on samples collected from zones distal and proximal to the Macraes gold deposit in the Otago Schist of New Zealand to characterize the features and possible origins of Carbonaceous Material (CM) and to assess the potential role of CM in the formation of gold deposits. CM is a common component in meta-sedimentary orogenic gold deposits, and it has been proposed that CM contributes to gold mineralization processes, but the details of the mechanisms responsible are not fully understood. Documentation of the origins of the Otago schist CM will improve our understanding of the role of CM in gold deposits.
On-line flash pyrolysis, micro-scale sealed vessel (MSSV) pyrolysis and catalytic hydropyrolysis ... more On-line flash pyrolysis, micro-scale sealed vessel (MSSV) pyrolysis and catalytic hydropyrolysis (HyPy) were used to characterise the insoluble, macromolecular organic component of monosulfidic black oozes (MBO) which have accumulated within the contemporary eutrophic environment of the Peel–Harvey estuary system (Geographe Bay, Western Australia). Pyrolysates were analysed by gas chromatography–mass spectrometry (GC–MS) and the relative characterisation potential of the three pyrolysis techniques were evaluated with a particular interest in their sensitivity to organic sulfur compounds (OSCs). A similarity of results obtained from three different parts of the ~1 m cores sampled suggests a largely homogenous organic composition throughout the unit. The different pyrolysis techniques did, however, show several notable product differences, particularly the gaseous products detected by the on-line methods of flash- and MSSV-pyrolysis. The very high (i.e., ballistic) heating rate of flash-Py produced very high proportions of gaseous products (e.g., CO2, H2S and SO2). A strong terrestrially sourced product component was reflected in all three pyrolysates profiles: flash-Py showed relatively high concentrations of lignocellulose products, while MSSV-Py and HyPy produced an abundance of plant wax (>n-C20) n-alkanes. Additionally, quantitatively significant levels (7–14% of total GC product signal) of several higher plant derived terpenoids (e.g., cadalene, p-cymene and calamanene) were identified by MSSV-Py. MSSV-Py also produced far greater overall concentrations of GC-amenable products than flash-Py, including a 14-fold increase of OSCs, which comprised nearly 10% of the total sulfur signal (i.e., organic plus ‘inorganic’ sulfur; cf. 4% of flash pyrolysis). An extended series of alkyl (<C9) substituted thiophenes were the main OSCs. HyPy, in contrast, showed no evidence of OSCs – confirmed by GC-flame photometric detection (FPD). HyPy is renowned for its capacity to preserve primary structural units, so its failure to detect thiophenes and other OSCs abundant in the corresponding analysis, suggests these are not indigenous to the macromolecular fraction of the MBO. The detection of these products by MSSV-Py, and to a lesser extent flash-Py, suggests these pyrolysis methods initiate a restructuring of sulfur species towards more thermally stable secondary configurations. One explanation for the limited diagnostic S-speciation data obtained from the present analysis may be the existence of most of the S in the MBO as bridging units between covalently bound organic structures. These relatively weakly bound associations may form on the reaction of reduced sulfur species (from bacterial sulfate reduction) with highly functionalised organic compounds during the early stages of diagenesis.
Phosphorus (P) is often a limiting nutrient within freshwater and estuarine systems, thus excess ... more Phosphorus (P) is often a limiting nutrient within freshwater and estuarine systems, thus excess inputs of P from anthropogenic activities (dominantly agriculture) can induce eutrophication in receiving water bodies. The sequestration of P within estuarine sediments is controlled by sorption and precipitation processes, which are impacted by local redox conditions and burial environment. Despite the global spread of oxygen depletion in coastal marine systems, P burial under reducing conditions remains poorly understood. We investigated P cycling in relation to iron (Fe) redox chemistry in sediments from the eutrophic Peel-Harvey Estuary in Western Australia, using a combination of porewater analysis, sequential chemical P extractions, synchrotron-based micro-scale X-ray fluorescence mapping and Fe K-edge X-ray absorption spectroscopy, and PO4 3− sorption experiments. The sediments represented redox regimes varying from strongly reducing, organic-rich sediments with little or no reactive Fe(III) (oxyhydr)oxides to oxygenated sediments that were enriched in reactive Fe(III) phases. Organic P and Fe-associated P were the main P burial phases, and the latter was quantitatively important even in sediments with an overall strongly reducing character. We attribute this to adsorption of P onto micro-scale Fe(III) oxyhydroxide enrichments and/or Fe-bearing clay minerals. The organic-rich sediments showed a strong decline in P contents with depth; P was released from organic matter and Fe phases but apatite precipitation was apparently inhibited in these sediments. Despite greater and stronger PO4 3 − sorption capacity, the oxic sediments contained relatively little P due to a lack of the primary P source in marine sediments: organic matter. Our results provide detailed insight into P burial in dynamic estuarine sediments and show that micro-scale spectroscopic analyses greatly advance our understanding of P sequestration processes.
... The crystal structure of a chromian pumpellyite of general formula VIIW8 VIX4 VIY8 IVZ12O56-n... more ... The crystal structure of a chromian pumpellyite of general formula VIIW8 VIX4 VIY8 IVZ12O56-n(OH)n from Sarani, Urals, Russia, was refined using X-ray single-crystal data to investigate the crystal-chemical behavior of Cr in pumpellyite. ...
ABSTRACT Raman spectroscopic and petrographic analyses were performed on samples collected from z... more ABSTRACT Raman spectroscopic and petrographic analyses were performed on samples collected from zones distal and proximal to the Macraes gold deposit in the Otago Schist of New Zealand to characterize the features and possible origins of Carbonaceous Material (CM) and to assess the potential role of CM in the formation of gold deposits. CM is a common component in meta-sedimentary orogenic gold deposits, and it has been proposed that CM contributes to gold mineralization processes, but the details of the mechanisms responsible are not fully understood. Documentation of the origins of the Otago schist CM will improve our understanding of the role of CM in gold deposits.
On-line flash pyrolysis, micro-scale sealed vessel (MSSV) pyrolysis and catalytic hydropyrolysis ... more On-line flash pyrolysis, micro-scale sealed vessel (MSSV) pyrolysis and catalytic hydropyrolysis (HyPy) were used to characterise the insoluble, macromolecular organic component of monosulfidic black oozes (MBO) which have accumulated within the contemporary eutrophic environment of the Peel–Harvey estuary system (Geographe Bay, Western Australia). Pyrolysates were analysed by gas chromatography–mass spectrometry (GC–MS) and the relative characterisation potential of the three pyrolysis techniques were evaluated with a particular interest in their sensitivity to organic sulfur compounds (OSCs). A similarity of results obtained from three different parts of the ~1 m cores sampled suggests a largely homogenous organic composition throughout the unit. The different pyrolysis techniques did, however, show several notable product differences, particularly the gaseous products detected by the on-line methods of flash- and MSSV-pyrolysis. The very high (i.e., ballistic) heating rate of flash-Py produced very high proportions of gaseous products (e.g., CO2, H2S and SO2). A strong terrestrially sourced product component was reflected in all three pyrolysates profiles: flash-Py showed relatively high concentrations of lignocellulose products, while MSSV-Py and HyPy produced an abundance of plant wax (>n-C20) n-alkanes. Additionally, quantitatively significant levels (7–14% of total GC product signal) of several higher plant derived terpenoids (e.g., cadalene, p-cymene and calamanene) were identified by MSSV-Py. MSSV-Py also produced far greater overall concentrations of GC-amenable products than flash-Py, including a 14-fold increase of OSCs, which comprised nearly 10% of the total sulfur signal (i.e., organic plus ‘inorganic’ sulfur; cf. 4% of flash pyrolysis). An extended series of alkyl (<C9) substituted thiophenes were the main OSCs. HyPy, in contrast, showed no evidence of OSCs – confirmed by GC-flame photometric detection (FPD). HyPy is renowned for its capacity to preserve primary structural units, so its failure to detect thiophenes and other OSCs abundant in the corresponding analysis, suggests these are not indigenous to the macromolecular fraction of the MBO. The detection of these products by MSSV-Py, and to a lesser extent flash-Py, suggests these pyrolysis methods initiate a restructuring of sulfur species towards more thermally stable secondary configurations. One explanation for the limited diagnostic S-speciation data obtained from the present analysis may be the existence of most of the S in the MBO as bridging units between covalently bound organic structures. These relatively weakly bound associations may form on the reaction of reduced sulfur species (from bacterial sulfate reduction) with highly functionalised organic compounds during the early stages of diagenesis.
Phosphorus (P) is often a limiting nutrient within freshwater and estuarine systems, thus excess ... more Phosphorus (P) is often a limiting nutrient within freshwater and estuarine systems, thus excess inputs of P from anthropogenic activities (dominantly agriculture) can induce eutrophication in receiving water bodies. The sequestration of P within estuarine sediments is controlled by sorption and precipitation processes, which are impacted by local redox conditions and burial environment. Despite the global spread of oxygen depletion in coastal marine systems, P burial under reducing conditions remains poorly understood. We investigated P cycling in relation to iron (Fe) redox chemistry in sediments from the eutrophic Peel-Harvey Estuary in Western Australia, using a combination of porewater analysis, sequential chemical P extractions, synchrotron-based micro-scale X-ray fluorescence mapping and Fe K-edge X-ray absorption spectroscopy, and PO4 3− sorption experiments. The sediments represented redox regimes varying from strongly reducing, organic-rich sediments with little or no reactive Fe(III) (oxyhydr)oxides to oxygenated sediments that were enriched in reactive Fe(III) phases. Organic P and Fe-associated P were the main P burial phases, and the latter was quantitatively important even in sediments with an overall strongly reducing character. We attribute this to adsorption of P onto micro-scale Fe(III) oxyhydroxide enrichments and/or Fe-bearing clay minerals. The organic-rich sediments showed a strong decline in P contents with depth; P was released from organic matter and Fe phases but apatite precipitation was apparently inhibited in these sediments. Despite greater and stronger PO4 3 − sorption capacity, the oxic sediments contained relatively little P due to a lack of the primary P source in marine sediments: organic matter. Our results provide detailed insight into P burial in dynamic estuarine sediments and show that micro-scale spectroscopic analyses greatly advance our understanding of P sequestration processes.
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