Kevin Faure - Academia.edu (original) (raw)
Papers by Kevin Faure
Journal of Volcanology and Geothermal Research
American Mineralogist, 2002
Quick Search: All GSW Journals, GSW + GeoRef. advanced search. ...
Clays and Clay Minerals
ABSTRACT
Mineral Deposit Research: Meeting the Global Challenge, 2005
ABSTRACT
Irish Journal of Earth Sciences, 2006
ABSTRACT The results of fluid inclusion petrography and microthermometry of Oughterard Granite qu... more ABSTRACT The results of fluid inclusion petrography and microthermometry of Oughterard Granite quartz reveals the presence of a dominant and ubiquitous population of liquid rich (degree of fill ∼ 0.70-0.95) saline (<11 equivalent wt% NaCl) fluid inclusions. Temperature of homogenisation (to the liquid phase) ranges between 140°C and 380°C with the majority in the range 175°C to 250°C. These aqueous fluid inclusions invariably occur in annealed fractures that transverse the granite quartz. These represent evidence of saline hydrothermal fluid infiltration post crystallisation of granite quartz. Microthermometry also reveals that within this population rare CaCl2-bearing fluid inclusions occur. Oxygen isotope Δquartz-feldspar values are lower than 0.70, reflecting isotope disequilibrium. The isotope data supports the fluid inclusion evidence for the influx of post crystallisation hydrothermal fluids, possibly related to granite emplacement, or to a later incursion of relatively low temperature (<200°C) meteoric waters.
ABSTRACT Rock Garden, an uplifted ridge on the Hikurangi Margin offshore of New Zealand, appears ... more ABSTRACT Rock Garden, an uplifted ridge on the Hikurangi Margin offshore of New Zealand, appears to be eroded at ~ 600 m water depth. Pinchouts of bottom simulating reflections (BSRs) at the edges of its plateau-like crest and theoretical phase boundary considerations in combination with water temperature data suggest that most likely, erosion is linked to the top of gas hydrate stability in the ocean. We propose a combination of two mechanisms that may cause seafloor erosion during ridge uplift. An upward migrating base of gas hydrate stability with respect to the seafloor caused by depressurization during uplift may lead to overpressure and sliding. After sliding, water depth and hence, hydrate stability, increases again and the process may repeat itself during continued uplift. We present evidence from bathymetric and seismic data that support the presence of small slides on the edges of the plateau. However, for this mechanism to be efficient, the ridge crest must remain within the gas hydrate stability field, which seems to contradict the presence of BSR pinchouts. On the ridge crest, we predict gas hydrates close to the seafloor to repeatedly form and dissociate because of water temperature fluctuations and suggest that resulting pore volume contraction and expansion may cause a frost-heave-like weakening of the seafloor. We discuss the viability of both mechanisms. We also discuss the possibility that ridges like Rock Garden may focus methane transport from deeper sources towards the ridge crests where it may be released into the ocean, an effect that may increase the amount of methane released into intermediate-water depths.
New Zealand Journal of Geology and Geophysics, 2014
ABSTRACT A rhyolite dome complex at Maungaparerua, Ar/Ar dated at 3.7 ± 0.04 Ma (Early Pliocene),... more ABSTRACT A rhyolite dome complex at Maungaparerua, Ar/Ar dated at 3.7 ± 0.04 Ma (Early Pliocene), is bounded on the west by a sequence of hydrothermally altered basalt flows intercalated with several non-marine siltstone and rhyolitic tuff units. This basalt sequence and the rhyolite dome complex are overlain by younger unaltered basalt flows. Within the dome complex, several small pits have been worked in the past for china clays. Recent drilling has outlined a halloysite-rich ‘Southern Area’ extending to a depth of up to 24 m below the present-day erosion surface. Primary sanidine and plagioclase phenocrysts are completely leached in halloysite-rich rhyolite, but are only partially leached at greater depth. Halloysite-rich rhyolite is characterised by relative enrichment in loss on ignition (LOI; 5–9%) and Al2O3 (18–24%) and depletion in K2O (2O3 and 4.1% K2O in least-altered rhyolite. Oxygen and hydrogen isotope compositions of halloysite samples indicate that it is of supergene rather than hydrothermal origin. This is consistent with weathering type clay profiles in halloysite-rich zones. Although there is earlier hydrothermal alteration in the form of silicified rhyolite 800 m to the west of the Southern Area and kaolinite-pyrite alteration in the adjacent basalt, we conclude that the dominant process in the formation of the halloysite was deep weathering of sanidine rhyolite under water-saturated subtropical conditions.
Precambrian Research, 1991
Faure, K. and Harris, C., 1991. Oxygen and carbon isotope geochemistry of the 3.2 Ga Kaap Valley ... more Faure, K. and Harris, C., 1991. Oxygen and carbon isotope geochemistry of the 3.2 Ga Kaap Valley tonalite, Barberton greenstone belt, South Africa. Precambrian Res., 52:301-319.
Palaeogeography, Palaeoclimatology, Palaeoecology, 1999
Early Permian black pyritic shale units, i.e. the Whitehill, Irati and Huab formations and Black ... more Early Permian black pyritic shale units, i.e. the Whitehill, Irati and Huab formations and Black Rock Member, in southwestern Gondwana basins, have elevated δ 13 C values of total organic carbon up to 17‰ (PDB), hydrogen indices between 300 and 1000 mg CO 2 =g C and oxygen indices <30 mg CO 2 =g C. These data suggest a manifestation of a microbial bloom event. Values for δ 13 C (between 26 and 22‰, PDB), hydrogen (<100 mg CO 2 =g C) and oxygen indices of total organic carbon above and below these rock units are typical for Palaeozoic terrestrial (Type III) organic matter. Carbon-13 isotope stratigraphy concur with palaeontological evidence, that these formations are stratigraphical equivalents, and therefore, that the microbial blooms covered a vast area (¾5 million km 2 ), possibly Earth's most expansive microbial bloom. The palaeoenvironment of the rock units preceding and including the black shales was most likely lacustrine with fresh to brackish water, as shown by stable isotope (C, O, and S) evidence from organic matter, carbonates and pyrite. The implication is that a broad tectonic belt, which formed as a result of compressional tectonics during the Late Carboniferous to Early Permian from the palaeo-west, must have been sufficiently well developed to cut-off any contact with seawater, earlier than predicted (Late Permian) from previous stratigraphic and sedimentological studies. Stable isotope data, supported by mineralogical evidence, indicate that conditions, particularly in the upper portions of the lacustrine oil shales, were brackish and locally may have been evaporitic. We envisage that the microbial blooms (possibly Botryococcus) peaked in the upper half of the black shale units. Conditions rapidly became unfavourable for microbial blooms across the entire basin in the overlying formations, manifested by a change from oil shales (Type I organic matter) to organic-poor (Type III) shales. This may possibly have been a consequence of tectonic activity and interrelated causes. Stable isotope data of carbonates in the overlying sediments indicate that in the palaeo-north the basin became evaporitic (drying-up), and in the palaeo-southern part of the basin, high latitude=altitude water flooded the basin, and so brought to a close the microbial blooms.
New Zealand Journal of Geology and Geophysics, 2004
ABSTRACT
New Zealand Journal of Geology and Geophysics, 2014
ABSTRACT On the west side of Lee Bay on the northeast coast of Stewart Island, ventifact cobbles ... more ABSTRACT On the west side of Lee Bay on the northeast coast of Stewart Island, ventifact cobbles of pyrite-coated granite occur on the beach near the high tide mark and appear to be derived from a sand-cemented gravel deposit that forms a low bank at the back of the beach. The pyrite coat (up to 1 mm thick) completely covers the granitic cobbles and is zoned, with an inner zone of fine-grained colloform pyrite and an outer framboidal zone. Framboidal pyrite is typically formed in anoxic sedimentary environments. Subrounded grains of hematite, ilmenite with hematite blebs, magnetite, feldspar, biotite, quartz and zircon are present in the outer framboidal zone, with some ilmenite and hematite grains being partially replaced by pyrite. The assemblage of ilmenite-hematite-magnetite-biotite-zircon is similar both in mineralogy and size range to that found in heavy mineral beach sands. Sulphur isotope values of the pyrite coat are consistent with formation of the pyrite by microbial sulphate reduction of seawater sulphate. The framboidal texture together with the presence of grains of beach sand in the pyrite coating indicate that it was deposited in a low-temperature sedimentary environment.
Mineralium Deposita, 2012
ABSTRACT At the Matauri Bay halloysite deposit, economically valuable halloysite-rich clays are h... more ABSTRACT At the Matauri Bay halloysite deposit, economically valuable halloysite-rich clays are hosted by a sanidine rhyolite dome (Ar–Ar dated at 10.1 ± 0.03 Ma). The rhyolite dome intrudes an older basalt and is overlain by alluvial sediments and a younger basalt (4.0 ± 0.7 Ma). A blanket-like, halloysite-rich zone is restricted to depths of 10–30 m from the present day erosion surface. Primary sanidine and plagioclase phenocrysts in rhyolite are completely leached out in the halloysite-rich zone but are only partially leached out at greater depth. Halloysite was formed by hydrolysis and cation leaching of sanidine and plagioclase phenocrysts and groundmass glass in the rhyolite, resulting in loss of K, Ca, Na and Si and enrichment in OH (LOI 6–10%) and Al2O3 (20–30%) relative to least-altered rhyolite with 1.8% LOI and 14.5% Al2O3. Oxygen and hydrogen isotope data indicate the halloysite is supergene rather than hydrothermal in origin, which is consistent with the absence of pyrite, alunite and other acid-sulphate type hydrothermal minerals, and with the blanket-like alteration profile. The dominance of halloysite over kaolinite was favoured by water-saturated weathering conditions during the late Miocene-Pliocene subtropical weathering regime in Northland.
Mineralium Deposita, 2006
At Sams Creek, a gold-bearing, peralkaline granite porphyry dyke, which has a 7 km strike length ... more At Sams Creek, a gold-bearing, peralkaline granite porphyry dyke, which has a 7 km strike length and is up to 60 m in thickness, intrudes camptonite lamprophyre dykes and lower greenschist facies metapelites and quartzites of the Late Ordovician Wangapeka formation. The lamprophyre dykes occur as thin (< 3 m) slivers along the contacts of the granite dyke. d 18 O magma values (+5 to +8&, VSMOW) of the A-type granite suggest derivation from a primitive source, with an insignificant mature crustal contribution. Hydrothermal gold-sulphide mineralisation is confined to the granite and adjacent lamprophyre; metapelite country rocks have only weak hydrothermal alteration. Three stages of hydrothermal alteration have been identified in the granite: Stage I alteration (high fO 2 ) consisting of magnetite-siderite±biotite; Stage II consisting of thin quartz-pyrite veinlets; and Stage III (low fO 2 ) consisting of sulphides, quartz and siderite veins, and pervasive silicification. The lamprophyre is altered to an ankeritechlorite-sericite assemblage. Stage III sulphide veins are composed of arsenopyrite + pyrite ± galena ± sphalerite ± gold ± chalcopyrite ± pyrrhotite ± rutile ± graphite. Three phases of deformation have affected the area, and the mineralised veins and the granite and lamprophyre dykes have been deformed by two phases of folding, the youngest of which is Early Cretaceous. Locally preserved early-formed fluid inclusions are either carbonic, showing two-or three-phases at room temperature (liquid CO 2 -CH 4 + liquid H 2 O ± CO 2 vapour) or two-phase liquid-rich aqueous inclusions, some of which contain clathrates. Salinities of the aqueous inclusions are in the range of 1.4 to 7.6 wt% NaCl equiv. Final homogenisation temperatures (Th) of the carbonic inclusions indicate minimum trapping temperatures of 320 to 355°C, which are not too difduced granite Au-Bi deposits and alkaline intrusivehosted Au-Mo-Cu deposits.
Malaria Journal, 2011
Background: Plasmodium falciparum malaria remains a major public health problem. A vital componen... more Background: Plasmodium falciparum malaria remains a major public health problem. A vital component of malaria control rests on the availability of good quality artemisinin-derivative based combination therapy (ACT) at the correct dose. However, there are increasing reports of poor quality anti-malarials in Africa.
Journal of Volcanology and Geothermal Research
American Mineralogist, 2002
Quick Search: All GSW Journals, GSW + GeoRef. advanced search. ...
Clays and Clay Minerals
ABSTRACT
Mineral Deposit Research: Meeting the Global Challenge, 2005
ABSTRACT
Irish Journal of Earth Sciences, 2006
ABSTRACT The results of fluid inclusion petrography and microthermometry of Oughterard Granite qu... more ABSTRACT The results of fluid inclusion petrography and microthermometry of Oughterard Granite quartz reveals the presence of a dominant and ubiquitous population of liquid rich (degree of fill ∼ 0.70-0.95) saline (<11 equivalent wt% NaCl) fluid inclusions. Temperature of homogenisation (to the liquid phase) ranges between 140°C and 380°C with the majority in the range 175°C to 250°C. These aqueous fluid inclusions invariably occur in annealed fractures that transverse the granite quartz. These represent evidence of saline hydrothermal fluid infiltration post crystallisation of granite quartz. Microthermometry also reveals that within this population rare CaCl2-bearing fluid inclusions occur. Oxygen isotope Δquartz-feldspar values are lower than 0.70, reflecting isotope disequilibrium. The isotope data supports the fluid inclusion evidence for the influx of post crystallisation hydrothermal fluids, possibly related to granite emplacement, or to a later incursion of relatively low temperature (<200°C) meteoric waters.
ABSTRACT Rock Garden, an uplifted ridge on the Hikurangi Margin offshore of New Zealand, appears ... more ABSTRACT Rock Garden, an uplifted ridge on the Hikurangi Margin offshore of New Zealand, appears to be eroded at ~ 600 m water depth. Pinchouts of bottom simulating reflections (BSRs) at the edges of its plateau-like crest and theoretical phase boundary considerations in combination with water temperature data suggest that most likely, erosion is linked to the top of gas hydrate stability in the ocean. We propose a combination of two mechanisms that may cause seafloor erosion during ridge uplift. An upward migrating base of gas hydrate stability with respect to the seafloor caused by depressurization during uplift may lead to overpressure and sliding. After sliding, water depth and hence, hydrate stability, increases again and the process may repeat itself during continued uplift. We present evidence from bathymetric and seismic data that support the presence of small slides on the edges of the plateau. However, for this mechanism to be efficient, the ridge crest must remain within the gas hydrate stability field, which seems to contradict the presence of BSR pinchouts. On the ridge crest, we predict gas hydrates close to the seafloor to repeatedly form and dissociate because of water temperature fluctuations and suggest that resulting pore volume contraction and expansion may cause a frost-heave-like weakening of the seafloor. We discuss the viability of both mechanisms. We also discuss the possibility that ridges like Rock Garden may focus methane transport from deeper sources towards the ridge crests where it may be released into the ocean, an effect that may increase the amount of methane released into intermediate-water depths.
New Zealand Journal of Geology and Geophysics, 2014
ABSTRACT A rhyolite dome complex at Maungaparerua, Ar/Ar dated at 3.7 ± 0.04 Ma (Early Pliocene),... more ABSTRACT A rhyolite dome complex at Maungaparerua, Ar/Ar dated at 3.7 ± 0.04 Ma (Early Pliocene), is bounded on the west by a sequence of hydrothermally altered basalt flows intercalated with several non-marine siltstone and rhyolitic tuff units. This basalt sequence and the rhyolite dome complex are overlain by younger unaltered basalt flows. Within the dome complex, several small pits have been worked in the past for china clays. Recent drilling has outlined a halloysite-rich ‘Southern Area’ extending to a depth of up to 24 m below the present-day erosion surface. Primary sanidine and plagioclase phenocrysts are completely leached in halloysite-rich rhyolite, but are only partially leached at greater depth. Halloysite-rich rhyolite is characterised by relative enrichment in loss on ignition (LOI; 5–9%) and Al2O3 (18–24%) and depletion in K2O (2O3 and 4.1% K2O in least-altered rhyolite. Oxygen and hydrogen isotope compositions of halloysite samples indicate that it is of supergene rather than hydrothermal origin. This is consistent with weathering type clay profiles in halloysite-rich zones. Although there is earlier hydrothermal alteration in the form of silicified rhyolite 800 m to the west of the Southern Area and kaolinite-pyrite alteration in the adjacent basalt, we conclude that the dominant process in the formation of the halloysite was deep weathering of sanidine rhyolite under water-saturated subtropical conditions.
Precambrian Research, 1991
Faure, K. and Harris, C., 1991. Oxygen and carbon isotope geochemistry of the 3.2 Ga Kaap Valley ... more Faure, K. and Harris, C., 1991. Oxygen and carbon isotope geochemistry of the 3.2 Ga Kaap Valley tonalite, Barberton greenstone belt, South Africa. Precambrian Res., 52:301-319.
Palaeogeography, Palaeoclimatology, Palaeoecology, 1999
Early Permian black pyritic shale units, i.e. the Whitehill, Irati and Huab formations and Black ... more Early Permian black pyritic shale units, i.e. the Whitehill, Irati and Huab formations and Black Rock Member, in southwestern Gondwana basins, have elevated δ 13 C values of total organic carbon up to 17‰ (PDB), hydrogen indices between 300 and 1000 mg CO 2 =g C and oxygen indices <30 mg CO 2 =g C. These data suggest a manifestation of a microbial bloom event. Values for δ 13 C (between 26 and 22‰, PDB), hydrogen (<100 mg CO 2 =g C) and oxygen indices of total organic carbon above and below these rock units are typical for Palaeozoic terrestrial (Type III) organic matter. Carbon-13 isotope stratigraphy concur with palaeontological evidence, that these formations are stratigraphical equivalents, and therefore, that the microbial blooms covered a vast area (¾5 million km 2 ), possibly Earth's most expansive microbial bloom. The palaeoenvironment of the rock units preceding and including the black shales was most likely lacustrine with fresh to brackish water, as shown by stable isotope (C, O, and S) evidence from organic matter, carbonates and pyrite. The implication is that a broad tectonic belt, which formed as a result of compressional tectonics during the Late Carboniferous to Early Permian from the palaeo-west, must have been sufficiently well developed to cut-off any contact with seawater, earlier than predicted (Late Permian) from previous stratigraphic and sedimentological studies. Stable isotope data, supported by mineralogical evidence, indicate that conditions, particularly in the upper portions of the lacustrine oil shales, were brackish and locally may have been evaporitic. We envisage that the microbial blooms (possibly Botryococcus) peaked in the upper half of the black shale units. Conditions rapidly became unfavourable for microbial blooms across the entire basin in the overlying formations, manifested by a change from oil shales (Type I organic matter) to organic-poor (Type III) shales. This may possibly have been a consequence of tectonic activity and interrelated causes. Stable isotope data of carbonates in the overlying sediments indicate that in the palaeo-north the basin became evaporitic (drying-up), and in the palaeo-southern part of the basin, high latitude=altitude water flooded the basin, and so brought to a close the microbial blooms.
New Zealand Journal of Geology and Geophysics, 2004
ABSTRACT
New Zealand Journal of Geology and Geophysics, 2014
ABSTRACT On the west side of Lee Bay on the northeast coast of Stewart Island, ventifact cobbles ... more ABSTRACT On the west side of Lee Bay on the northeast coast of Stewart Island, ventifact cobbles of pyrite-coated granite occur on the beach near the high tide mark and appear to be derived from a sand-cemented gravel deposit that forms a low bank at the back of the beach. The pyrite coat (up to 1 mm thick) completely covers the granitic cobbles and is zoned, with an inner zone of fine-grained colloform pyrite and an outer framboidal zone. Framboidal pyrite is typically formed in anoxic sedimentary environments. Subrounded grains of hematite, ilmenite with hematite blebs, magnetite, feldspar, biotite, quartz and zircon are present in the outer framboidal zone, with some ilmenite and hematite grains being partially replaced by pyrite. The assemblage of ilmenite-hematite-magnetite-biotite-zircon is similar both in mineralogy and size range to that found in heavy mineral beach sands. Sulphur isotope values of the pyrite coat are consistent with formation of the pyrite by microbial sulphate reduction of seawater sulphate. The framboidal texture together with the presence of grains of beach sand in the pyrite coating indicate that it was deposited in a low-temperature sedimentary environment.
Mineralium Deposita, 2012
ABSTRACT At the Matauri Bay halloysite deposit, economically valuable halloysite-rich clays are h... more ABSTRACT At the Matauri Bay halloysite deposit, economically valuable halloysite-rich clays are hosted by a sanidine rhyolite dome (Ar–Ar dated at 10.1 ± 0.03 Ma). The rhyolite dome intrudes an older basalt and is overlain by alluvial sediments and a younger basalt (4.0 ± 0.7 Ma). A blanket-like, halloysite-rich zone is restricted to depths of 10–30 m from the present day erosion surface. Primary sanidine and plagioclase phenocrysts in rhyolite are completely leached out in the halloysite-rich zone but are only partially leached out at greater depth. Halloysite was formed by hydrolysis and cation leaching of sanidine and plagioclase phenocrysts and groundmass glass in the rhyolite, resulting in loss of K, Ca, Na and Si and enrichment in OH (LOI 6–10%) and Al2O3 (20–30%) relative to least-altered rhyolite with 1.8% LOI and 14.5% Al2O3. Oxygen and hydrogen isotope data indicate the halloysite is supergene rather than hydrothermal in origin, which is consistent with the absence of pyrite, alunite and other acid-sulphate type hydrothermal minerals, and with the blanket-like alteration profile. The dominance of halloysite over kaolinite was favoured by water-saturated weathering conditions during the late Miocene-Pliocene subtropical weathering regime in Northland.
Mineralium Deposita, 2006
At Sams Creek, a gold-bearing, peralkaline granite porphyry dyke, which has a 7 km strike length ... more At Sams Creek, a gold-bearing, peralkaline granite porphyry dyke, which has a 7 km strike length and is up to 60 m in thickness, intrudes camptonite lamprophyre dykes and lower greenschist facies metapelites and quartzites of the Late Ordovician Wangapeka formation. The lamprophyre dykes occur as thin (< 3 m) slivers along the contacts of the granite dyke. d 18 O magma values (+5 to +8&, VSMOW) of the A-type granite suggest derivation from a primitive source, with an insignificant mature crustal contribution. Hydrothermal gold-sulphide mineralisation is confined to the granite and adjacent lamprophyre; metapelite country rocks have only weak hydrothermal alteration. Three stages of hydrothermal alteration have been identified in the granite: Stage I alteration (high fO 2 ) consisting of magnetite-siderite±biotite; Stage II consisting of thin quartz-pyrite veinlets; and Stage III (low fO 2 ) consisting of sulphides, quartz and siderite veins, and pervasive silicification. The lamprophyre is altered to an ankeritechlorite-sericite assemblage. Stage III sulphide veins are composed of arsenopyrite + pyrite ± galena ± sphalerite ± gold ± chalcopyrite ± pyrrhotite ± rutile ± graphite. Three phases of deformation have affected the area, and the mineralised veins and the granite and lamprophyre dykes have been deformed by two phases of folding, the youngest of which is Early Cretaceous. Locally preserved early-formed fluid inclusions are either carbonic, showing two-or three-phases at room temperature (liquid CO 2 -CH 4 + liquid H 2 O ± CO 2 vapour) or two-phase liquid-rich aqueous inclusions, some of which contain clathrates. Salinities of the aqueous inclusions are in the range of 1.4 to 7.6 wt% NaCl equiv. Final homogenisation temperatures (Th) of the carbonic inclusions indicate minimum trapping temperatures of 320 to 355°C, which are not too difduced granite Au-Bi deposits and alkaline intrusivehosted Au-Mo-Cu deposits.
Malaria Journal, 2011
Background: Plasmodium falciparum malaria remains a major public health problem. A vital componen... more Background: Plasmodium falciparum malaria remains a major public health problem. A vital component of malaria control rests on the availability of good quality artemisinin-derivative based combination therapy (ACT) at the correct dose. However, there are increasing reports of poor quality anti-malarials in Africa.