Alteration, mineralization, and metamorphism in the area of the East South "C" ore zone, 24th level of the Dickenson mine, Red Lake, northwestern Ontario

1984 ◽  
Vol 21 (1) ◽  
pp. 35-52 ◽  
Author(s):  
Neil A. Mathieson ◽  
C. Jay Hodgson
Keyword(s):  
Volcanic Rocks ◽  
Fluid Pressure ◽  
Chemical Effect ◽  
Iron Formation ◽  
Mesoscopic Scale ◽  
Red Lake ◽  
Northwestern Ontario ◽  
Mineral Associations ◽  
Mineral Assemblages ◽  
Volcaniclastic Rocks

The area of the East South "C" (ESC) orebody of the Dickenson mine, Red Lake, consists of variably altered and mineralized basalt, basaltic volcaniclastic rocks, minor sulphidic iron formation, and a series of mainly postdeformation dykes. Except for the dykes, the rocks are in general well foliated. The macroscopic structural geometry of the stratiform rocks has been determined to a large extent by movement on schistosity-parallel faults.Three broad types of mineralization or alteration are recognized: an Na–Ca–Mg depletion with associated Fe–Mn enrichment controlled by primary permeable structures in basalt; a series of carbonate and quartz or "chert" veins emplaced into fissures; and auriferous silicified and sulphidized zones controlled by vein-filled fractures. The last is the main mineralization type in the ESC orebody on the 24th level of the mine, which was the focus of this study. Although all mineralization types occur within the mine, they are not directly associated either temporally or spatially on a mesoscopic scale. All, however, appear to have been overprinted by or formed synchronously with the amphibolite-facies metamorphism.A rich variety of metamorphic mineral assemblages occurs in the volcanic rocks because of the chemical effect of pre- or synmetamorphic hydrothermal alteration. These assemblages and the composition and mineral associations of arsenopyrite in the ESC orebody closely constrain the conditions of metamorphism to 520–540 °C and 3.8–4.2 kbar (380–420 MPa) fluid pressure.

ARCHAEAN SEDIMENTARY ROCKS OF NORTH SPIRIT LAKE AREA, NORTHWESTERN ONTARIO

1965 ◽  
Vol 2 (6) ◽  
pp. 622-647 ◽  
Author(s):  
J. A. Donaldson ◽  
G. D. Jackson
Keyword(s):  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Sole Source ◽  
Lake Area ◽  
Red Lake ◽  
Sedimentary Sequences ◽  
The North ◽  
Northwestern Ontario ◽  
History Of ◽  
Granitoid Rocks

Archaean sedimentary rocks of the North Spirit Lake area show little evidence of having been derived predominantly from associated Archaean volcanic rocks. Instead, compositions of the sediments reflect significant sedimentary and (or) granitoid provenance. A remarkably high content of clastic quartz in thick units of sandstone and conglomerate suggests either reworking of older quartzose sediments, or reduction of the labile constituents in quartz-rich granitoid rocks through prolonged weathering and rigorous transport. Observations for other sedimentary sequences in the region between Red Lake and Lansdowne House suggest that the North Spirit sediments are not unique in the Superior Province. Quartzose sandstones commonly are regarded as atypical of the Archaean, but such rocks arc abundant in northwestern Ontario. Frameworks of many Archaean greywackes actually are richer in quartz than typical greywackes from numerous Proterozoic and Phanerozoic sequences.The concept of rapidly rising volcanic arcs as the sole source of Archaean sedimentary detritus is rejected for the North Spirit area. The volcanies, rather than representing relicts of protocontinents, probably record events removed from initial volcanism in the history of the earth by one or more orogenic cycles. Major unconformities may therefore exist not only between sedimentary and volcanic units, but also between these units and older granitoid rocks.

The hyper-agpaitic stage in the evolution of the Ilímaussaq alkaline complex, South Greenland

2001 ◽  
pp. 83-94 ◽  
Author(s):  
Henning Sørensen ◽  
Lotte Melchior Larsen
Keyword(s):  
Oxygen Fugacity ◽  
Volcanic Rocks ◽  
Alkaline Complex ◽  
Mineral Association ◽  
Original Series ◽  
Pressure Oxygen ◽  
Mineral Associations ◽  
Mineral Assemblages ◽  
Hydrothermal Veins ◽  
Highly Evolved

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Sørensen , H., & Melchior Larsen, L. (2001). The hyper-agpaitic stage in the evolution of the Ilímaussaq alkaline complex, South Greenland. Geology of Greenland Survey Bulletin, 190, 83-94. https://doi.org/10.34194/ggub.v190.5177 _______________ The term hyper-agpaitic covers mineral associations characterised by a wealth of Na-rich minerals such as natrosilite, zirsinalite, ussingite, vuonnemite, vitusite and lomonosovite. This mineral association clearly indicates a higher degree of alkalinity than for agpaitic rocks in general. In the Ilímaussaq complex hyper-agpaitic mineral associations occur not only in pegmatites and hydrothermal veins as in the Kola complexes, Khibina and Lovozero, but also in highly evolved lujavrites and in the fenitised volcanic rocks in the roof of the complex. This paper reviews the occurrences of hyper-agpaitic mineral associations in the Ilímaussaq complex. The mineral assemblages are determined by an interplay of temperature, pressure, oxygen fugacity, alkalinity, especially the concentration of Na, and contents of elements such as Zr, Ti, Nb, REE, Fe, Mn, U, Th, P, F, Cl and H2O. Increasing and decreasing stages of alkalinity may be distinguished. At increasing alkalinity nepheline is for instance substituted by naujakasite, while at decreasing alkalinity and temperature naujakasite is substituted by analcime.

U–Pb zircon ages for magmatism in the Red Lake greenstone belt, northwestern Ontario

1986 ◽  
Vol 23 (1) ◽  
pp. 27-42 ◽  
Author(s):  
F. Corfu ◽  
H. Wallace
Keyword(s):  
Greenstone Belt ◽  
Volcanic Rocks ◽  
Gold Deposits ◽  
Calc Alkaline ◽  
Red Lake ◽  
Northwestern Ontario ◽  
Igneous Activity ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks ◽  
Chemical Sediments

U–Pb dating was carried out on nine volcanic rocks and two felsic intrusions from the Red Lake greenstone belt in order to establish an absolute time framework for the magmatic evolution of the area and yield first indications on the time of deformation and gold mineralization.The data indicate a protracted period of igneous activity spanning at least 270 Ma. Felsic volcanic rocks near the top of the tholeiitic to komatiitic sequence in the eastern part of the belt yield ages of [Formula: see text] and [Formula: see text]. A third unit, dated at [Formula: see text], contains inherited zircons older than 2982 Ma, which casts some uncertainty on the validity of the inferred intercept age. Rocks in the western part of the belt, previously believed to form a relatively young calc-alkalic sequence but now known to be dominantly tholeiitic, are shown to be relatively old, with ages of [Formula: see text] and [Formula: see text]. These two dates also bracket the age of stromatolites occurring in chemical sediments that are under and overlain by the dated units.Another volcanic horizon in the centre of the belt is dated at 2830 ± 15 Ma, and calc-alkaline volcanic sequences on the southern and northern flanks of the belt yield ages of 2739.0 ± 3.0 and [Formula: see text], respectively. An age of [Formula: see text] was determined for tholeiitic pyroclastic rocks near the base of the predominantly calc-alkaline Heyson sequence.The major gold deposits of the Red Lake belt appear to be present dominantly within older supracrustal sequences. On the other hand, they are also associated with late deformation zones that postdate the intrusion of the Dome Stock dated at 2718.2 ± 1.1 Ma ago. The time of an earlier folding event is bracketed by this age and by the age of [Formula: see text] for an isoclinally folded felsic dike.

A new volcanic province: evidence from glacial erratics in western North Greenland

2000 ◽  
pp. 35-41 ◽  
Author(s):  
Peter R. Dawes ◽  
Bjørn Thomassen ◽  
T.I. Hauge Andersson
Keyword(s):  
Volcanic Rocks ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Common Component ◽  
Volcanic Province ◽  
North West ◽  
North East ◽  
The North ◽  
Surficial Deposits ◽  
North Greenland

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Dawes, P. R., Thomassen, B., & Andersson, T. H. (2000). A new volcanic province: evidence from glacial erratics in western North Greenland. Geology of Greenland Survey Bulletin, 186, 35-41. https://doi.org/10.34194/ggub.v186.5213 _______________ Mapping and regional geological studies in northern Greenland were carried out during the project Kane Basin 1999 (see Dawes et al. 2000, this volume). During ore geological studies in Washington Land by one of us (B.T.), finds of erratics of banded iron formation (BIF) directed special attention to the till, glaciofluvial and fluvial sediments. This led to the discovery that in certain parts of Daugaard-Jensen Land and Washington Land volcanic rocks form a common component of the surficial deposits, with particularly colourful, red porphyries catching the eye. The presence of BIF is interesting but not altogether unexpected since BIF erratics have been reported from southern Hall Land just to the north-east (Kelly & Bennike 1992) and such rocks crop out in the Precambrian shield of North-West Greenland to the south (Fig. 1; Dawes 1991). On the other hand, the presence of volcanic erratics was unexpected and stimulated the work reported on here.

scholarly journals Stratigraphy and lithogeochemistry of the Goldenville horizon and associated rocks, Baie Verte Peninsula, Newfoundland

2021 ◽  
Author(s):  
C Mueller ◽  
S J Piercey ◽  
M G Babechuk ◽  
D Copeland
Keyword(s):  
Gold Mineralization ◽  
Iron Formation ◽  
Fine Grained ◽  
Hydrothermal Sediment ◽  
Post Archean Australian Shale ◽  
Oxygenated Water ◽  
Volcaniclastic Rocks ◽  
Laurentian Margin ◽  
Mn Oxides ◽  
Hydrothermal Venting

The Goldenville horizon in the Baie Verte Peninsula is an important stratigraphic horizon that hosts primary (Cambrian to Ordovician) exhalative magnetite and pyrite and was a chemical trap for younger (Silurian to Devonian) orogenic gold mineralization. The horizon is overlain by basaltic flows and volcaniclastic rocks, is intercalated with variably coloured argillites and cherts, and underlain by mafic volcaniclastic rocks; the entire stratigraphy is cut by younger fine-grained mafic dykes and coarser gabbro. Lithogeochemical signatures of the Goldenville horizon allow it to be divided into high-Fe iron formation (HIF; >50% Fe2O3), low-Fe iron formation (LIF; 15-50% Fe2O3), and argillite with iron minerals (AIF; <15% Fe2O3). These variably Fe-rich rocks have Fe-Ti-Mn-Al systematics consistent with element derivation from varying mineral contributions from hydrothermal venting and ambient detrital sedimentation. Post-Archean Australian Shale (PAAS)-normalized rare earth element (REE) signatures for the HIF samples have negative Ce anomalies and patterns similar to modern hydrothermal sediment deposited under oxygenated ocean conditions. The PAAS-normalized REE signatures of LIF samples have positive Ce anomalies, similar to hydrothermal sediment deposited under anoxic to sub-oxic conditions. The paradoxical Ce behaviour is potentially explained by the Mn geochemistry of the LIF samples. The LIF have elevated MnO contents (2.0-7.5 weight %), suggesting that Mn from hydrothermal fluids was oxidized in an oxygenated water column during hydrothermal venting, Mn-oxides then scavenged Ce from seawater, and these Mn-oxides were subsequently deposited in the hydrothermal sediment. The Mn-rich LIF samples with positive Ce anomalies are intercalated with HIF with negative Ce anomalies, both regionally and on a metre scale within drill holes. Thus, the LIF positive Ce anomaly signature may record extended and particle-specific scavenging rather than sub-oxic/redox-stratified marine conditions. Collectively, results suggest that the Cambro-Ordovician Taconic seaway along the Laurentian margin may have been completely or near-completely oxygenated at the time of Goldenville horizon deposition.

Seismic wave attenuation due to fluid pressure diffusion at the mesoscopic scale: an experimental and numerical study

2021 ◽  
Author(s):  
Samuel Chapman ◽  
Jan V. M. Borgomano ◽  
Beatriz Quintal ◽  
Sally M. Benson ◽  
Jerome Fortin
Keyword(s):  
Seismic Wave ◽  
Seismic Waves ◽  
Wave Attenuation ◽  
Fluid Pressure ◽  
Fluid Distribution ◽  
Mesoscopic Scale ◽  
Seismic Wave Attenuation ◽  
X Ray ◽  
Pressure Diffusion ◽  
Attenuation And Dispersion

<p>Monitoring of the subsurface with seismic methods can be improved by better understanding the attenuation of seismic waves due to fluid pressure diffusion (FPD). In porous rocks saturated with multiple fluid phases the attenuation of seismic waves by FPD is sensitive to the mesoscopic scale distribution of the respective fluids. The relationship between fluid distribution and seismic wave attenuation could be used, for example, to assess the effectiveness of residual trapping of carbon dioxide (CO2) in the subsurface. Determining such relationships requires validating models of FPD with accurate laboratory measurements of seismic wave attenuation and modulus dispersion over a broad frequency range, and, in addition, characterising the fluid distribution during experiments. To address this challenge, experiments were performed on a Berea sandstone sample in which the exsolution of CO2 from water in the pore space of the sample was induced by a reduction in pore pressure. The fluid distribution was determined with X-ray computed tomography (CT) in a first set of experiments. The CO2 exosolved predominantly near the outlet, resulting in a heterogeneous fluid distribution along the sample length. In a second set of experiments, at similar pressure and temperature conditions, the forced oscillation method was used to measure the attenuation and modulus dispersion in the partially saturated sample over a broad frequency range (0.1 - 1000 Hz). Significant P-wave attenuation and dispersion was observed, while S-wave attenuation and dispersion were negligible. These observations suggest that the dominant mechanism of attenuation and dispersion was FPD. The attenuation and dispersion by FPD was subsequently modelled by solving Biot’s quasi-static equations of poroelasticity with the finite element method. The fluid saturation distribution determined from the X-ray CT was used in combination with a Reuss average to define a single phase effective fluid bulk modulus. The numerical solutions agree well with the attenuation and modulus dispersion measured in the laboratory, supporting the interpretation that attenuation and dispersion was due to FPD occurring in the heterogenous distribution of the coexisting fluids. The numerical simulations have the advantage that the models can easily be improved by including sub-core scale porosity and permeability distributions, which can also be determined using X-ray CT. In the future this could allow for conducting experiments on heterogenous samples.</p>

A detailed gravity profile across the English River Subprovince, northwestern Ontario

1984 ◽  
Vol 21 (2) ◽  
pp. 145-151 ◽  
Author(s):  
V. K. Gupta ◽  
R. B. Barlow
Keyword(s):  
Seismic Data ◽  
Bouguer Anomaly ◽  
Density Data ◽  
Density Measurements ◽  
Anomaly Field ◽  
Red Lake ◽  
Northwestern Ontario ◽  
Crustal Model ◽  
Regional Gravity ◽  
Gravity Profile

This paper presents the results of a detailed gravity profile measured across the two lithotectonic domains of the English River Subprovince from Vermilion Bay to Red Lake, a distance of 190 km, in northwestern Ontario. Along the profile 283 fresh rock samples were collected for density measurements. The density data clearly suggest that there is a measurable and significant density difference between the migmatized metasediments and plutonic rocks.A crustal model based on the seismic data, along the profile, has been used for computing a regional gravity field, which in turn has been used in isolating the residual anomalies from the Bouguer anomaly field. A strong correlation has been found to exist between the residual anomalies, the rock densities, and the surface lithologies. The Northern Supracrustal Domain, which is at its widest (60 km) along the profile, is dominated by a pronounced 15 mGal (150 μm s−2) positive residual anomaly believed to be caused by outcropping, anomalously dense metasediments extending to a modelled depth of approximately 10 km. In the Southern Plutonic Domain the residual anomalies along the profile are small (less than 5 mGal (50 μm s−2)) and limited in depth. The Mystery Lake dome extends to a modelled depth of approximately 2.5 km.

Sign in / Sign up

Export Citation Format

Share Document