EXPLORATION AND MINING GEOLOGY JOURNAL

EMG
Volume 7, Nos. 4 (October, 1998)

Geology of the Owl Creek Gold Mine, Timmins, Ontario
P.R. Coad, D.I. Brisbin, R.J. Labine and R. Roussain

Radiometric Profiles of Uranium Dispersal Pattern Adjacent to Cretaceous Phosphatic Sediments in Wadi Qasser Al-Hallabat Basin, Central Syria
Y. Jubeli, M. Al-Hilal, G. Rajja and A. Al-Ali

Gamma-ray Spectrometric Applications to Volcanogenic Massive Sulfide Exploration
in the Heath Steele Mines Area, Bathurst Camp, New Brunswick
J.H. Rickard, D.R. Lentz, K.L. Ford and R.P. Taylor

Estimating the Geometry of Conjugate Veins
C. Roth and M. Armstrong

SEDEX Lead-zinc Deposits — Proposed Sub-types and Their Characteristics
D.F. Sangster and E.M. Hillary

Vanadium-bearing Magnetite from the Matagami and Chibougamau Mining Districts, Abitibi, Québec, Canada
M.F. Taner, T.S. Ercit and R.A. Gault

Mineralogical, Fluid Inclusion, and Stable Isotope Study of Wenyu-Dongchuang Gold Deposits in the Xiaoqinling Mt. Area, West Henan, China
J. Xu, Y. Xie, N. Jiang and F. Bie

Geology of the Owl Creek Gold Mine, Timmins, Ontario
P.R. COAD
Cameco Gold Inc.

D.I. BRISBIN
Cameco Corporation

R.J. LABINE
Battle Mountain Canada Limited, Holloway Mine

and
R. ROUSSAIN
Kinross Gold Corporation, Hoyle 2000
Received April 8, 1999; accepted September 16, 1999.

Abstract — The Owl Creek Mine is located near the west end of the Neo-archean Abitibi greenstone belt, 17 km northeast of Timmins, Ontario, and 4 km north of the Destor Porcupine fault. Gold occurs in epigenetic quartz veins and their pyritic wallrocks in two zones within a package of east striking, steeply north dipping, volcanic and sedimentary rocks. At the West Zone, 1 729 603 t of ore with a grade of 4.83 g/t Au (268 587 troy oz.) were produced from an open pit centered on a wedge-shaped unit of Tisdale Group basalt that occurs between two overturned, south facing units of Porcupine Group graywacke and argillite. Basalt/graywacke contacts are locally marked by graphitic-carbonaceous argillite, strike-parallel faults and massive quartz veins.

Deformed quartz+/-ankerite veins occur along the graphitic sedimentary/volcanic contacts and in gently to moderately dipping fractures in basalts, and, to a lesser extent, in graywackes. Veins also occur sub-parallel to steeply dipping 070° foliation. Altered host basalts are composed of iron carbonate, sericite, quartz, carbon, chlorite and disseminated pyrite. Gold occurs as inclusions in pyrite, and less commonly as free gold in fractures and along graphite-quartz grain boundaries in quartz veins.
Fractures preferentially developed in more competent basalts during pre- to syn-ore deformation are interpreted to have provided the permeability required for emplacement of mineralized quartz veins. Carbonaceous basalt/graywacke contacts further enhanced gold deposition by acting as chemical traps. The interaction of hydrothermal fluids with these carbonaceous sedimentary rocks led to the characteristic local darkening of host basalts due to carbon impregnation and chlorite development. © 2000 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.

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Radiometric Profiles of Uranium Dispersal Pattern Adjacent to Cretaceous Phosphatic Sediments in Wadi Qasser Al-Hallabat Basin, Central Syria
Y. JUBELI, M. AL-HILAL
Department of Geology and Nuclear Ores
G. RAJJA
Department of Radiation Protection and Safety
and
A. AL-ALI
Department of Geology and Nuclear Ores
Atomic Energy Commission, Damascus, Syria
Received June 10, 1998; accepted April 4, 2000.

Abstract — A radiometric survey was carried out over clastic sediments in the immediate vicinity of some phosphatic sediments of Cretaceous age in the Wadi Qasser Al-Hallabat basin of central Syria. The objective was to explore for uranium and to define its dispersion pattern. This was based on ground radiometric surveys and geological studies. All ground surveys (using radon emanometry, track etching, gamma-ray survey and geochemistry) gave similar results, outlining the locations of the radioactive phosphatic formations in the basin, and indicating the dispersion pattern of uranium in the clastic sediments in the surrounding area. The dispersal of uranium from upper Cretaceous phosphatic formation occurs by mechanical weathering and chemical leaching by oxidizing surface waters. A rough estimate is that about one-third of the original uranium content of the Cretaceous sediments has been dispersed. Mechanical erosion is responsible for the main part of this released uranium, which now occurs in Recent sediments. However, the occurrences of spotty secondary U mineralization indicates that another small part of the available uranium must have been chemically leached out by the prevailing oxidizing waters, forming minor surficial minerals.

© 2000 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.

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Gamma-ray Spectrometric Applications to Volcanogenic Massive Sulfide Exploration in the Heath Steele Mines Area, Bathurst Camp, New Brunswick
J.H. RICKARD
Department of Earth Sciences, Ottawa-Carleton Geoscience Centre, Carleton University

D.R. LENTZ
Department of Geology, University of New Brunswick

K.L. FORD
Geological Survey of Canada

R.P. TAYLOR
Department of Earth Sciences, Ottawa-Carleton Geoscience Centre, Carleton University
Received July 15, 1999; accepted April 17, 2000.

Abstract — Coupled gamma-ray spectrometric and lithogeochemical studies throughout the Heath Steele Mines area, Bathurst Camp, New Brunswick, indicate that primary and secondary geochemical differences exist between the stratigraphic footwall and hangingwall crystal tuff units which host the massive sulfide deposits. Of particular interest is Th, and to a lesser extent, Zr and Y, which are more concentrated in the hangingwall than the footwall crystal tuffs, whereas the opposite is true for TiO2. This expands on earlier lithogeochemical-chemostratigraphic results concentrated in the eastern part of the Heath Steele belt that led to revision of the local stratigraphy, and necessitated a structural re-interpretation of the area with implications for exploration. Although K depletion (decreased K and K/Th) is typical of chloritized footwall zones of chloritization, these features were not fully apparent here due to the recessive nature of these altered zones. In situ radiometric analysis using a portable gamma-ray spectrometer is a rapid, inexpensive analytical technique for chemostratigraphic characterization of rock units within volcanogenic massive sulfide deposit settings, provided there is a contrast in the distribution of natural radioelements, particularly Th and K.

© 2000 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.

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Estimating the Geometry of Conjugate Veins
Chris Roth and Margaret Armstrong
Centre de Géostatistique, Fontainebleau, France
Received January 30, 1998; accepted January 20, 1999.
Abstract —Estimating ore reserves for vein type deposits is a two-stage procedure: first, calculate the geometry of the vein system, and second, estimate the grades within this system. The grade estimation can only be consistently performed if the vein geometry — its size, shape and orientation — has been correctly characterized. Getting the size and shape of the different veins right means that the ore tonnages will not be artificially inflated, e.g., by falsely classifying host rock as veins. Similarly, correctly estimating their orientation and location helps mine management decide on the appropriate mining technique, selective or not. When applying geostatistics to estimate the vein geometry all available information needs to be used and not just the standard lithologic indicator of being or not being in a vein. © 2000 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.

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SEDEX Lead-zinc Deposits — Proposed Sub-types and Their Characteristics
D.F. SANGSTER* and E.M. HILLARY
Geological Survey of Canada
Ottawa, Canada, K1A 0E8
Received March 30, 2000; accepted May 2, 2000.

Abstract — As a contribution to the World Minerals Geoscience Database Project, an index-level database comprising information on 142 SEDEX Pb-Zn deposits and occurrences was constructed in Microsoft Access 95 format. Although consisting of only basic information, the compilation, with full referencing of all data, is possibly the largest non-corporate SEDEX Pb-Zn database in the world. It thus provides an opportunity to make geoscience queries of SEDEX Pb-Zn deposits on a scale not previously available. This report provides a summary of the results of a few such queries both as a contribution to a better understanding of SEDEX lead-zinc deposits and as a demonstration of what even such a simple database can offer.

During the compilation process, it became apparent that SEDEX Pb-Zn deposits could be assigned to one of the following three sub-types: Type 1 (53.5% of total) in which sulfide minerals are the only exhalative components; Type 2 (33.1%) in which the exhalative components are sulfides plus chert, siderite/ankerite, and/or barite; Type 3 (13.4%) which contains any components of Types 1 and 2 plus abundant iron-oxide minerals (commonly magnetite) and/or is associated with iron oxide-rich sedimentary rocks.
Highlights of systematic queries of the database reveal that:

• 1. a majority (84%) of the world’s SEDEX Pb-Zn deposits are not underlain by a discordant footwall feeder zone or vent complex;
• 2. 63.6% of deposits occur in Proterozoic strata followed by a second peak in the Devonian (16.8%). Of those in the Proterozoic, 83% of Type 3 deposits occur in the Gondwanaland supercontinent, whereas only 42% of Type 2 and 39% of Type 1 are located in this large paleo-landmass;
• 3. median (Pb+Zn) grades in Types 1 and 2 fall between 9% and 10% with a majority clustering within this range. Type 3 grades, however, range from ~1% to ~20% (Pb+Zn) with a median of 5%;
• 4. median size of Type 3 deposits is ~33 Mt, whereas Type 1 and 2 median sizes are ~7 Mt and ~8 Mt, respectively.
  The report concludes with a brief discussion of how an index-level database such as this can be used in conjunction with other, similar databases to reveal interesting and instructive relationships for guiding both research and exploration.

© 2000 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.

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Vanadium-bearing Magnetite from the Matagami and Chibougamau Mining Districts, Abitibi, Québec, Canada
MEHMET F. TANER, T. SCOTT ERCIT and ROBERT A. GAULT
Canadian Museum of Nature
Ottawa, Ontario, Canada, K1P 6P4
Received December 22, 1999; accepted April 20, 2000.

Abstract — Vanadium mineralization occurs in oxide-rich horizons within the layered gabbro zones of the upper parts of the Bell River Complex, Matagami, Québec and the Lac Doré Complex, Chibougamau, Québec. The vanadium-rich horizons are well defined on the ground and in aeromagnetic surveys by their high magnetic susceptibility; consequently, magnetic susceptibility can be an indicator of vanadium mineralization. The main oxide minerals are ilmenite and titanian magnetite, containing 20% to 70% of volume and the ratio of titanian magnetite to ilmenite is relatively constant, ranging from about 1:1 to 2:1. Their sizes are less than 5 µm to greater than 1 mm to 2 mm, occurring as coarse- to medium-grained subhedral crystals intergrown with cumulate silicate minerals (plagioclase, pyroxene, etc.). Electron microprobe analyses indicate that the ilmenite grains are mineralogically and compositionally homogeneous and have low V contents (average 0.18% equivalent V2O5). In contrast, the titanian magnetite grains are inhomogeneous, consisting of trellisworks of ilmenite lamellae in Ti-poor, V-rich magnetite [less than 2 wt% TiO2, and 1.41% equiv. V2O5 (1.16% V2O3) for 20 analyses]. Thus, the magnetite is the principal ore mineral of vanadium; it hosts vanadium in the form of V3+, not V5+, as is commonly and erroneously reported. We have also devised a flowchart for the beneficiation of vanadium-titanium ores. © 2000 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.

Sommaire — La minéralisation de vanadium se trouve dans des horizons riches en minéraux oxydés de la partie supérieure des zones de gabbros lités des Complexes de la Rivière Bell, Matagami, Québec et du Lac Doré, Chibougamau, Québec. Des horizons riches en vanadium ont été bien définis sur le terrain et dans les levés aéromagnétiques par leur susceptibilité magnétique élevée; conséquemment, la susceptibilité magnétique est l’indicateur directe du contenu en vanadium. Les principaux minéraux oxydés sont l’ilménite et la magnétite titanifère, contenant 20% à 70% du volume et le rapport de magnétite titanifère à ilménite est relativement constant, allant d’environ 1:1 à 2:1. Leur dimension varie de 5 µm à plus grande que 1 mm à 2 mm, apparaissant sous forme de cristaux subidiomorphes, de grains grossiers à médiums, intercroissant avec la gangue silicatée (plagioclase, pyroxène, etc.) de la texture de cumulat. Les analyses à la microsonde électronique montrent que les grains d’ilménite sont minéralogiquement et chimiquement homogènes avec un faible contenu en V (moyenne 0.18% équiv. V2O5 ). Contrairement, les grains de magnétite titanifère sont hétérogènes, contenant des lamelles d’ilménite en “trellisworks”; ces grains sont pauvres en Ti et riches en V pour la portion magnétite de la magnétite titanifère [surtout contenant moins de 2 wt. % TiO2, et en moyenne 1.41% équiv. (1.16% V2O3) pour 20 analyses]. Ainsi, la magnétite est le principal minerai de vanadium; elle renferme du vanadium sous forme de V3+ et non de V5+, tel qu’il a été communément et à tort rapporté. Nous avons aussi défini un “flowchart” pour la bénéficiation des minerais de vanadium-titanium.

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Mineralogical, Fluid Inclusion, and Stable Isotope Study of Wenyu-Dongchuang Gold Deposits in the Xiaoqinling Mt. Area, West Henan, China
JIUHUA XU, YULING XIE
Department of Geology, University of Science and Technology Beijing
Beijing 100083, China
NENG JIANG
Institute of Geology, Chinese Academy of Sciences, Beijing 100029, China
and
FENGLEI BIE
China University of Geosciences
Beijing 100083, China
Received August 31, 1999; accepted April 4, 2000.

Abstract — The Xiaoqingling Mt. area is one of the most productive gold districts in China. The gold-bearing quartz veins are controlled by a series of east-west shear zones within the Archean Taihua Group, and related to the late Yanshanian (Cretaceous) granite. The major metallic minerals are native gold, electrum, pyrite, galena, chalcopyrite and sphalerite, with gangue minerals dominated by quartz, sericite, ankerite, and calcite. The host rocks are mainly amphibolite, plagioclase gneiss, and migmatites. Principal alteration is sericitization, silicification, pyritization, and carbonization.

There are four generations of hydrothermal quartz in altered rocks of gold deposits. The earliest generation of quartz, (Q1), occurs in altered amphibolite gneiss and migmatite, and typically contains fluid inclusions with halite crystals (type A) and two phases, (L+V), of fluid inclusions (type B). The salinities of type A inclusions are 32 wt% to 52 wt%, with dissolution temperatures of halite crystals being from 155°C to 465°C. The second generation of quartz, (Q2), occurs as a fine-grained aggregate associated with sericite, and has small (less than 3 µm) type B inclusions. The third generation of quartz, (Q3), occurs in mylonitic, intensively altered rocks and specially beresite (a type of rock composed of quartz, sericite, and pyrite) near the veins, and contains large amounts of CO2-rich fluid inclusions (type C-fluid inclusions with liquid CO2 and type D-fluid inclusion with high density CO2). The CO2 contents of type C range from 72.6 to 87.4 mol% in gas phases, and 35.7 to 68.3 mol% in liquid phases, based on Laser Raman analysis. The homogenization temperatures of fluid inclusion type A and C are from 215°C to 380°C, and from 210°C to 325°C, respectively. The minimum trapping pressure of fluid inclusions is estimated as 80 MPa to 170 MPa for type A, and from 57 MPa to 190 MPa for type C, which approximate to those of fluid inclusions in vein quartz.

The d18O of quartz are from 10.4‰ to 11.0‰ for Q3 of altered rocks, and from 10.7‰ to 12.8‰ for stage I quartz. The calculated d18O of fluid inclusions varies from -1.3‰ to 6.0‰. The dD of fluid inclusions ranges from -67‰ to -59‰ and from -81‰ to -48 ‰, respectively. It is concluded that the water in the hydrothermal fluids both reacting with wallrocks and precipitating orebodies could have been mainly of magmatic and/or metamorphic nature. However, local meteoric water might have been important in late mineralization, because of a distinct oxygen-shift toward the meteoric water. The d34S values for pyrite of the ores range from -7.1‰ to +7.1‰, with an average of +2.9‰. Those of other sulfides (chalcopyrite, galena, and sphalerite, range from -12.5‰ to 8.3‰. The ratios of lead isotopes for galena of the ores are: 17.06 to 17.31 (206Pb/204Pb), 15.43 to 15.74 (207Pb/204Pb) and 37.58 to 38.45 (208Pb/204Pb). In summary, ore-forming fluids in the Wenyu-Dongchuang gold deposits may have originated from a mantle and/or lower crust source, and ore materials were derived from the Precambrian basement, the Taihua Group. © 2000 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.

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