Oxygen, hydrogen, and carbon isotopic studies of the Great Bear Lake silver deposits, Northwest Territories

1986 ◽  
Vol 23 (10) ◽  
pp. 1463-1469 ◽  
Author(s):  
A. Changkakoti ◽  
R. D. Morton ◽  
J. Gray ◽  
C. J. Yonge
Keyword(s):  
Meteoric Water ◽  
Carbon Isotopic ◽  
Bear Lake ◽  
Lake Region ◽  
Wide Range ◽  
Silver Deposits ◽  
Isotopic Studies ◽  
Native Silver ◽  
Host Rocks ◽  
Late Stages

The native-silver-bearing deposits of the Great Bear Lake region occur within two separate domains, namely the Echo Bay sector and the Camsell River sector. In all these deposits, native silver occurs in veins, associated with a wide range of Ni-, Co-, and Fe- arsenides, Cu-, Fe-, Ni-, and Co-sulfides, and pitchblende in gangues of quartz, calcite, dolomite, siderite, rhodochrosite, and fluorite. The host rocks of the veins are for the most part Aphebian volcano-sedimentary roof pendants within the Great Bear batholithic complex. The carbonates (calcite, dolomite, siderite, and rhodochrosite) show a wide range of δ18O (6.8 to 22.5‰, SMOW) and δ13C (−2.7 to −13.3‰, PDB) values. A single analysis of quartz gave a δ18O value of 16.54‰ (SMOW). The δD of water in fluid inclusions in quartz, dolomite, and calcite shows a range from −62.2 to −98.5‰ (SMOW). The δD of present-day meteoric waters from the region shows a range of −146.5 to −165.2‰ (SMOW). The δ18O of the hydrothermal fluids (0.47 to 9.12‰, SMOW) was calculated from the δ18O values of the quartz, calcite, and dolomite belonging to different paragenetic sequences. The δ13C of carbon (−2.8 to −8.6‰, PDB) in the hydrothermal fluid was calculated from the δ13C values of the calcites. The oxygen, carbon, and hydrogen isotopic values indicate that in the early stages of mineralization, magmatic water and carbon from a magmatic source were predominant. During the late stages of mineralization, the influence of meteoric water became more pronounced.

Electron microprobe analyses of native silver and associated arsenides from the Great Bear Lake silver deposits, Northwest Territories, Canada

1986 ◽  
Vol 23 (10) ◽  
pp. 1470-1479 ◽  
Author(s):  
A. Changkakoti ◽  
R. D. Morton
Keyword(s):  
Northwest Territories ◽  
Electron Microprobe ◽  
Hydrothermal Fluids ◽  
Bear Lake ◽  
Wide Range ◽  
Silver Deposits ◽  
Native Silver ◽  
Host Rocks

The Great Bear Lake silver deposits in the Northwest Territories of Canada occur within two separate domains, namely the Echo Bay sector and the Camsell River sector. In these deposits, native silver occurs in veins, associated with a wide range of Ni-, Co-, and Fe-arsenides, sulphides, and pitchblende in gangues of quartz, calcite, dolomite, rhodochrosite, and fluorite. The host rocks of the veins are for the most part Aphebian volcano-sedimentary roof pendants within the Great Bear batholithic complex. Native silver, nickeline (niccolite), maucherite, safflorite, rammelsbergite, pararammelsbergite, loellingite, skutterudite, cobaltite, gersdorffite, and arsenopyrite were analyzed on the electron microprobe to determine any local or regional chemical variations. Mercury and antimony were found to occur in significant quantities in the majority of the native-silver samples. The silver samples from the Camsell River sector were found to be generally more enriched in mercury than those of the Echo Bay sector. Nickeline, cobaltite, and gersdorffite were found to be enriched in arsenic in the ores of the Camsell River sector, versus those of the Echo Bay sector. Such variations are probably related to differing magmatic sources for the hydrothermal fluids or even to precursor metallo-organic associations and are not due to different rocks hosting the silver-bearing veins.

scholarly journals DIAMONDS OF UKRAINE: RESULTS AND GOALS

2021 ◽  
Vol 43 (3) ◽  
pp. 25-41
Author(s):  
V.M. Kvasnytsya
Keyword(s):  
Structural Characteristics ◽  
Carbon Isotopic Composition ◽  
Impurity Content ◽  
Geochemical Data ◽  
Future Research ◽  
Sedimentary Deposits ◽  
Carbon Isotopic ◽  
Wide Range ◽  
Nitrogen Concentrations ◽  
Host Rocks

Diamonds from Ukraine were studied in terms of their separation into their geological and genetic types, distribution and occurrence, the ages of their host rocks, and their nature in Proterozoic and Neogene age sediments. The diamonds are variable in morphology, internal structure, concentration and degree of aggregation of nitrogen centers, carbon isotopes and mineral inclusions. Placer diamonds, primarily from Neogene sands, are anomalous in many respects. They are mostly extremely small, polyhedral, and morphologically diverse showing octahedral, rhombic dodecahedral and cubic forms and they have various colors. In addition to the large heterogeneity in nitrogen concentrations, many diamonds are characterized by a low degree of aggregation of nitrogen centers, which indicates short mantle residence times. Depending on the nitrogen impurity content, the degree of aggregation of nitrogen centers and the possible temperatures of crystallization, several types of diamonds are distinguished in the studied sedimentary placers. According to new isotope-geochemical data, placer diamonds are characterized by a wide range of carbon isotopic composition. This may indicate isotopic inhomogeneity of diamond carbon, different modes of formation and chemical variability in their source regions. Impact diamonds from meteorite craters and Neogene sedimentary deposits of Ukraine are paramorphoses from graphite with similar morphological, isotopic and structural characteristics. The goals of future research of Ukrainian diamonds are discussed.

Silver deposits associated with the Proterozoic rocks of the Thunder Bay District, Ontario

1986 ◽  
Vol 23 (10) ◽  
pp. 1576-1591 ◽  
Author(s):  
J. M. Franklin ◽  
S. A. Kissin ◽  
M. C. Smyk ◽  
S. D. Scott
Keyword(s):  
Lake Superior ◽  
Normal Faults ◽  
Western Margin ◽  
Metasedimentary Rocks ◽  
Mafic Intrusions ◽  
Thunder Bay ◽  
Silver Deposits ◽  
Base Metal Sulphides ◽  
Native Silver ◽  
Host Rocks

The silver deposits to the immediate north and west of Lake Superior are divided into three groups. The Mainland veins, the largest group, occur along a zone of normal faults near the western margin of the Proterozoic rocks of the Southern Province. The most economically productive deposits, the Island group, arc in or very near a northeast-trending swarm of gabbro dykes lying immediately offshore the northwestern shore of Lake Superior. The third group occurs near the western margin of the Port Coldwell alkalic complex; these veins are in a shear zone that cuts both Archean metasedimentary rocks and a Proterozoic diabase dyke. The Mainland deposits occur in the Rove shale, immediately below the contact with Logan diabase sills. The veins locally extend upwards into the sills, but the silver-bearing portions, consisting of acanthite and native silver associated with base-metal sulphides, fluorite, barite, quartz, and calcite, are largely bounded by locally silicified shale. The Island veins, typified by the Silver Islet mine, are in fractures perpendicular to the gabbro-dyke host rocks. These veins contain both native silver and acanthite, associated with a Ni–Co sulpharsenide suite and the same mineral assemblage as the Mainland deposits. The veins near Coldwell are rich in sphalerite and galena.Lead-isotope data indicate that the Mainland and Island veins are genetically related and that the Mainland veins formed from an inhomogeneous fluid. Two-stage calculations indicate an early Proterozoic source rock, possibly the Rove shale. The Island veins are more isotopically homogeneous, and their metals may have been derived partially from the gabbro. The Coldwell veins contain lead that is less radiogenic than that of the other two groups and is possibly derived from the adjacent Archean rocks. All three groups of deposits have isotopic compositions that are much less uranogenic and more thorogenic than the nearby Pb–Zn–Ba veins of the Dorion area. Preliminary fluid-inclusion data from the Mainland veins indicate that deposition occurred from a fluid whose temperature varied from approximately 200 °C to more than 400 °C; deposition occurred during boiling induced by adiabatic expansion of the fluid at relatively shallow crustal depths. The Mainland veins developed in the shale (rather than the diabase), as its high fissility, and hence permeability, made it susceptible to intense fracturing by the expanding fluid. Both the Mainland and Island groups were deposited in structures formed dominantly by listric normal faulting during late stages of intracontinental rifting. Heat was supplied by abundant mafic intrusions that formed coincident with rifting. The ore fluid was probably formed as a result of metamorphic dewatering, with metals released to the fluid because of silicate and sulphide recrystallization.

scholarly journals Clinical and Forensic Aspects of the Different Subtypes of Argyria

2021 ◽  
Vol 10 (10) ◽  
pp. 2086
Author(s):  
Luís Mota ◽  
Ricardo Jorge Dinis-Oliveira
Keyword(s):  
Systemic Absorption ◽  
Histopathological Analysis ◽  
Wide Range ◽  
Silver Deposits ◽  
Specific Tissue ◽  
Eye Lesions ◽  
Dark Blue ◽  
Typical Skin ◽  
Viable Treatment

Argyria encompasses the different cosmetic alterations that can develop if enough silver particles deposit in a specific tissue, typically in the skin, ranging from localized dark-blue macules to a generalized slate-gray/bluish tinge following systemic absorption. This work aims to fully review the state of the art regarding pathophysiology, diagnosis, treatment, and relevant clinical and forensic features of argyria. Argyria has been diagnosed in a wide range of ages, both sexes and varied ethnicities, with no known individual predisposing factors. Ultraviolet radiation with subsequence increases of melanin production aggravates the discoloration due to a reduction in the silver deposits. Physical examination and silver exposure in the anamnesis can be highly suggestive of the diagnosis, but a histopathological analysis with Energy-Dispersive X-ray Spectroscopy is required to unequivocally determine the discoloration etiology. Safe and effective treatment has only been accomplished with laser techniques, though only a few cases have been reported and with limited follow-up time. In conclusion, argyria typically has an occupational or iatrogenic etiology. It should be suspected when a patient presents with typical skin or eye lesions. A seemingly viable treatment modality, with laser technology, is finally within the horizon.

Carbon Isotopic Studies of Organic Matter in Precambrian Rocks

Science ◽  
1972 ◽  
Vol 175 (4027) ◽  
pp. 1246-1248 ◽  
Author(s):  
D. Z. Oehler ◽  
J. W. Schopf ◽  
K. A. Kvenvolden
Keyword(s):  
Organic Matter ◽  
Precambrian Rocks ◽  
Carbon Isotopic ◽  
Isotopic Studies

Compositional variation in the chevkinite group: new data from igneous and metamorphic rocks

2009 ◽  
Vol 73 (5) ◽  
pp. 777-796 ◽  
Author(s):  
R. Macdonald ◽  
H. E. Belkin ◽  
F. Wall ◽  
B. Baginski
Keyword(s):  
Electron Microprobe ◽  
Host Rock ◽  
Metamorphic Rocks ◽  
Compositional Variation ◽  
Temperature Range ◽  
Wide Range ◽  
Host Rocks ◽  
Cation Sites ◽  
Dominant Cation

AbstractElectron microprobe analyses are presented of chevkinite-group minerals from Canada, USA, Guatemala, Norway, Scotland, Italy and India. The host rocks are metacarbonates, alkaline and subalkaline granitoids, quartz-bearing pegmatites, carbonatite and an inferred K-rich tuff. The analyses extend slightly the range of compositions in the chevkinite group, e.g. the most MgO-rich phases yet recorded, and we report two further examples where La is the dominant cation in the A site. Patchily- zoned crystals from Virginia and Guatemala contain both perrierite and chevkinite compositions. The new and published analyses are used to review compositional variation in minerals of the perrierite subgroup, which can form in a wide range of host rock compositions and over a substantial pressure- temperature range. The dominant substitutions in the various cation sites and a generalized substitution scheme are described.

Variation in kaolinite morphology with growth temperature in isotopically mixed pore-fluids, Brent Group, UK North Sea

Clay Minerals ◽  
1994 ◽  
Vol 29 (4) ◽  
pp. 591-608 ◽  
Author(s):  
M. Osborne ◽  
R. S. Haszeldine ◽  
A. E. Fallick
Keyword(s):  
Meteoric Water ◽  
Pore Space ◽  
Pore Waters ◽  
The West ◽  
Rock Interaction ◽  
Isotopic Studies ◽  
Reservoir Sandstones ◽  
Oxygen Isotopic ◽  
Low Degrees ◽  
Water Rock Interaction

AbstractDiagenetic kaolinite in reservoir sandstones of the Brent Group precipitated following the dissolution of detrial feldspar. Two distinct morphologies of kaolinite occur: (1) early diagenetic vermiform kaolinite which is often associated with expanded detrital micas; (2) later diagenetic ‘blocky’ kaolinite. Combined hydrogen and oxygen isotopic studies suggest that vermiform kaolinite precipitated at 25–50°C, and blocky kaolinite at 50–80°C, from pore-waters of a similar isotopic composition (δ18O = −6.5 to −3.5‰). These pore-waters are interpreted to be either a mixture of meteoric and compactional waters, or alternatively a meteoric water that had evolved isotopically due to water-rock interaction. Kaolinite precipitation occurred predominantly during the late Cretaceous to early Eocene. Influx of meteoric water into the Brent Group, probably occurred during the Palaeocene. Fluid flow across the entire basin was driven by a hydrostatic head on the East Shetland Platform palaeo-landmass to the west. The development of the two kaolinite morphologies is possibly related to the degree of supersaturation at the time of precipitation. At low degrees of supersaturation, vermiform kaolinite precipitated slowly upon detrital mica surfaces. Blocky kaolinite precipitated more rapidly into open pore-space at higher degrees of supersaturation. Precipitation of blocky kaolinite was perhaps triggered by the decay of oxalate.

Sign in / Sign up

Export Citation Format

Share Document