Massive sulfide deposits of the Noranda area, Quebec. IV. The Mobrun mine

1992 ◽  
Vol 29 (7) ◽  
pp. 1349-1374 ◽  
Author(s):  
T. J. Barrett ◽  
S. Cattalani ◽  
L. Hoy ◽  
J. Riopel ◽  
P.-J. Lafleur
Keyword(s):  
Hanging Wall ◽  
Volcanic Rocks ◽  
Massive Sulfide ◽  
Calc Alkaline ◽  
Sulfide Deposits ◽  
Calculated Mass ◽  
Higher Temperature ◽  
Felsic Volcanic ◽  
Clear Change

The Mobrun polymetallic deposit near Rouyn–Noranda comprises two complexes of massive sulfide lenses within mainly felsic volcanic rocks of the Archean Blake River Group. The Main lens contained 3.37 Mt of massive sulfides, with 1989 reserves of 0.95 Mt at 0.81% Cu, 2.44% Zn, 30.3 g/t Ag, and 2.2 g/t Au. The 1100 complex, located ~250 m to the southeast of the Main complex, contains estimated 1989 reserves of 10.4 Mt at 0.76% Cu, 5.43% Zn, 37.4 g/t Ag, and 1.35 g/t Au.Host volcanic rocks of the Main complex are mostly massive, brecciated, and tuffaceous rhyolites. The rhyolites are commonly strongly sheared parallel to lithological contacts, which are locally displaced by high-angle faults. Immobile-element plots such as Y–Zr and Nb–Zr show a separation of rhyolite data into two distinct alteration trends that generally correspond to massive and in situ brecciated rhyolite of the footwall, and tuffaceous rhyolite of the hanging wall. The hanging wall has tholeiitic Zr/Y ratios (3–5), whereas the footwall has mildly calc-alkaline Zr/Y ratios (7–9). Several immobile-element trends indicate that there was a subtle but clear change in rhyolite composition near the time of ore deposition. Identification of chemically distinct footwall and hanging wall rhyolites allows these units to be recognized and traced along strike, even where alteration is strong. Sericitization and silicification extend at least 100 m from the orebody, with local chloritic zones in the upper footwall. Calculated mass changes indicate that the footwall generally has lost silica mass relative to the hanging wall. Alteration zones associated with mineralization have mass gains in FeO + MgO and K2O gains, but mass loss in silica.The 1100 complex, located stratigraphically below the Main complex, is hosted by rhyolite, with one main andesite interval in the footwall. The footwall contains three chemically distinct rhyolite types, all tholeiitic. Hanging-wall rhyolites are, however, mildly calc-alkaline, and thus are chemically comparable to, and correlated with, the footwall of the Main complex. Rhyolites within ~100 m stratigraphically of the Main and 1100 complexes commonly have positively shifted δ18O whole-rock values of 11–13‰. These high values are interpreted as the result of an initial, widespread phase of low-temperature hydrothermal alteration that increased δ18O values by 3–5‰ relative to unaltered rhyolites. Some footwall rhyolites, however, are relatively depleted in 18O, strongly depleted in Ca–Na and depleted in Eu2+. Rhyolites with these chemical features have been overprinted by higher temperature alteration, presumably in localized feeder zones. All four rhyolite types near the 1100 complex are chemically recognizable despite contrasting alteration.The orebodies are interpreted as synvolcanic, based on their occurrence along distinctive volcanic contacts, and the presence of primary sulfide textures where deformation is minor. The chemostratigraphic framework defined for the host rhyolite sequence can be used to trace critical volcanic contacts through lithologically monotonous, strongly altered, and faulted stratigraphy.

Massive sulfide deposits of the Noranda area, Quebec. II. The Aldermac mine

1991 ◽  
Vol 28 (9) ◽  
pp. 1301-1327 ◽  
Author(s):  
T. J. Barrett ◽  
S. Cattalani ◽  
F. Chartrand ◽  
P. Jones
Keyword(s):  
Volcanic Rocks ◽  
Parental Magma ◽  
Mass Gain ◽  
Massive Sulfide ◽  
Sulfide Deposit ◽  
Calc Alkaline ◽  
Sulfide Deposits ◽  
Massive Sulfide Deposits ◽  
Fractionation Trend ◽  
Felsic Volcanic

The original Aldermac mine near Noranda contained several Cu–Zn massive sulfide lenses hosted by felsic to mafic volcanic rocks of the late Archean Blake River Group. The original Nos. 3–6 orebodies, which consisted of massive pyrite, with lesser magnetite, pyrrhotite, chalcopyrite, and sphalerite, contained 1.87 Mt of Cu–Zn ore that averaged 1.47% Cu (Zn was not recovered). The orebodies occurred within felsic breccias and tuffs up to 100 m thick that are stratigraphically overlain by an extensive dome of mainly massive rhyolite and rhyodacite (up to 250 m thick and at least 550 m across). Most of the volcanic rocks that laterally flank and overlie the felsic dome are dacitic to andesitic flows, breccia, and tuff, with minor rhyolites, and associated subvolcanic sills of quartz-feldspar porphyry and gabbro.The new massive sulfide deposit, discovered in 1988, lies 150–200 m east of the mined-out orebodies, at a similar stratigraphic level within altered felsic breccia and tuff. The sulfides are mainly in the No. 8 lens, which contains 1.0 Mt at an average grade of 1.54% Cu, 4.12% Zn, 31.2 g/t Ag, and 0.48 g/t Au. Pyrite forms porphyroblastic megacrysts in a groundmass of pyrrhotite, sphalerite, magnetite, and chalcopyrite. A funnel-shaped, chloritized stockwork zone underlies the No. 8 lens and contains Cu-stringer mineralization. The No. 8 lens appears to be zoned, with overall decreasing Cu:Zn ratios from the core to the fringes of the lens. Massive sulfides in this lens have high Ag, Cd, and Hg contents relative to other massive sulfide deposits near Noranda.Ti versus Zr trends for least-altered Aldermac volcanic rocks indicate a more or less continuous magmatic fractionation trend ranging from high-Ti andesite to andesite, dacite, rhyodacite, and two distinct rhyolites (A and B). Most volcanic rocks were derived from a common parental magma that was transitional between tholeiitic and calc-alkaline compositions, as indicated by Ti–Y–Zr–Nb data and rare-earth-element distributions.Ti versus Zr trends in altered volcanic rocks indicate that silicification (mass gain) has affected some of the andesitic to rhyodacitic rocks, whereas chloritization (mass loss) has affected many of the rhyolitic rocks. Intermediate to mafic volcanic rocks above and lateral to the felsic dome are commonly silicified, possibly the result of hydrothermally remobilized silica derived from underlying felsic volcanic rocks.The orebodies appear to have formed at an eruptive hiatus between mafic → felsic and felsic → mafic cycles, during explosive activity and accumulation of felsic breccia and tuff. Ore was deposited mainly within a felsic fragmental sequence (rhyolite A), but before emplacement of the dome of rhyolite B. In compositionally diverse volcanic terrains, the contact between successive mafic–felsic and felsic–mafic cycles may be a good exploration target, in particular specific geochemical contacts within the felsic stratigraphy.

Shock brecciation around the Kidd Creek deposit, Abitibi belt, Canada

2008 ◽  
Vol 45 (8) ◽  
pp. 871-878
Author(s):  
I. K. Pitcairn ◽  
N. T. Arndt
Keyword(s):  
Volcanic Rocks ◽  
Massive Sulfide ◽  
Chemical Compositions ◽  
Fine Grained ◽  
Volcanic Processes ◽  
The Matrix ◽  
Major Fault ◽  
Heavy Rare Earth Elements ◽  
Felsic Volcanic

The Kidd–Munro assemblage, Abitibi belt, Canada, is an ultramafic–mafic–felsic volcanic sequence that contains the giant Kidd Creek volcanic-hosted massive sulfide (VMS) deposit. The Kidd basin, 1.6 km northeast of the deposit, contains pervasively brecciated pillowed and massive basalts. The breccia is distinctly different from most breccias in volcanic rocks, which form through volcanic processes or during later deformation or alteration. The Kidd Creek breccia occurs pervasively through otherwise undeformed pillow interiors and margins, and also in localized corridors of particularly intense brecciation. Clasts are angular, up to 4 cm wide, hosted in a very fine-grained matrix, and commonly show jig-saw fit texture. The chemical compositions of the breccia fragments and matrix are generally similar, although the matrix is slightly enriched in high field-strength elements (HFSE) and heavy rare-earth elements (HREE) and depleted in some mobile elements, such as Rb and Ba. The breccia contains altered basaltic clasts and fragments of in-filled amygdales and is crosscut by late-stage quartz–carbonate–sulfide veins. The observations imply that the breccia was formed in-situ, with minimal transport of material, and developed after solidification of the volcanic rocks. In-situ breccias, such as these, are known to form proximal to major fault zones, but no such structure occurs in the vicinity of the Kidd Basin. We suggest the brecciation was caused by the propagation of shock waves from explosive volcanic eruption, perhaps related to the emplacement of felsic volcanic rocks observed in the Kidd Creek Mine. The breccia was subject to enhanced hydrothermal fluid flow, perhaps linked to the formation of the ore deposit.

Massive sulfide deposits of the Noranda area, Quebec. III. The Ansil mine

1991 ◽  
Vol 28 (11) ◽  
pp. 1699-1730 ◽  
Author(s):  
T. J. Barrett ◽  
W. H. MacLean ◽  
S. Cattalani ◽  
L. Hoy ◽  
G. Riverin
Keyword(s):  
Hanging Wall ◽  
Volcanic Rocks ◽  
Massive Sulfide ◽  
Hydrothermal Activity ◽  
Sulfide Deposit ◽  
Sulfide Deposits ◽  
Almost All ◽  
Host Rocks ◽  
Low K ◽  
General Range

The Ansil massive sulfide deposit occurs at the contact of the underlying Northwest Rhyolite and the overlying Rusty Ridge Andesite, in the lower part of the Central Mine sequence of the Blake River Group. The orebody, which is roughly ellipsoidal in outline and up to 200 m × 150 m across, contained reserves of 1.58 Mt of massive sulfide grading 7.2% Cu, 0.9% Zn, 1.6 g/t Au, and 26.5 g/t Ag. Production began in 1989. Least-altered host rocks are low-K basaltic andesites and low-K rhyolites. These rocks have Zr/Y ratios of ~5 and LaN/YbN ratios of ~2.3, typical of tholeiitic volcanic rocks, although their major-element chemistry is transitional between tholeiitic and calc-alkaline volcanic rocks.The Ansil deposit, which dips ~50° east, is a single orebody comprising two main massive sulfide lenses (up to ~35 m thick) connected laterally via a thinner blanket of massive sulfides, with thin discontinuous but conformable massive magnetite units at the base and top of the orebody. Sulfide ore consists of massive to banded pyrrhotite–chalcopyrite. In the downplunge lens, up to 10 m of massive magnetite are capped by up to 10 m of massive sulfide. Finely banded cherty tuff, with sphalerite–pyrite–chalcopyrite, forms a discontinuous fringe to the deposit.The two main lenses of massive sulfide have the highest contents of Cu, Ag, and Au and are thought to have formed in areas of major hydrothermal input. Altered feeder zones contain either chlorite + chalcopyrite + pyrrhotite ± magnetite, or chlorite + magnetite ± sulfides. Footwall mineralization forms semiconformable zones ~5–10 m thick that directly underlie the orebody and high-angle pipelike zones that extend at least 50 m into the footwall. Ti–Zr–Al plots indicate that almost all altered footwall rocks were derived from a homogeneous rhyolite precursor. Hanging-wall andesites were also altered. Despite some severe alteration, all initial volcanic rock compositions can be readily identified, and thus mass changes can be calculated. Silica has been both significantly added or removed from the footwall, whereas K has been added except in feeder pipes. Oxygen-isotope compositions up to at least 50 m into the hanging wall and footwall are typically depleted in δ18O by 2–6‰. These rocks have gained Fe + Mg and lost Si. Altered samples in general range from light-rare-earth-element (REE) depleted to light-REE enriched, although some samples exhibit little REE modification despite strong alkali depletion. Mineralized volcanic rocks immediately below the orebody are enriched in Eu (as are some Cu-rich sulfides in the orebody).Contact and petrographic relations generally suggest that the main zone of massive magnetite formed by replacement of cp–po-rich sulfides, although local relations are ambiguous. Magnetite formation may reflect waning hydrothermal activity, during which fluids mixed with seawater and became cooler and more oxidized. Cu-rich feeder pipes that cut magnetite-rich footwall indicate a renewal of Cu-sulfide mineralization after magnetite deposition. Chloritic zones with disseminated sulfides occur up to a few hundred metres above the orebody, attesting to continuing hydrothermal activity.

Geochemistry, U–Pb geochronology, and genesis of granitoid clasts in transported volcanogenic massive sulfide ore deposits, Buchans, Newfoundland

2013 ◽  
Vol 50 (11) ◽  
pp. 1116-1133 ◽  
Author(s):  
J.B. Whalen ◽  
A. Zagorevski ◽  
V.J. McNicoll ◽  
N. Rogers
Keyword(s):  
Volcanic Rocks ◽  
Massive Sulfide ◽  
Ore Deposits ◽  
Volcanogenic Massive Sulfide ◽  
Zircon Age ◽  
Felsic Volcanism ◽  
Mass Flows ◽  
Plutonic Rocks ◽  
Felsic Volcanic

The Buchans Group, central Newfoundland, represents an Ordovician continental bimodal calc-alkaline arc sequence that hosts numerous volcanogenic massive sulfide (VMS) occurrences, including both in situ and mechanically transported sulfide breccia–conglomerate orebodies. Diverse lithic clasts associated with transported deposits include rounded granitoid clasts. Earlier workers have suggested that Buchans Group VMS-hosting felsic extrusive units, small granodiorite intrusions (e.g., Wiley’s Brook), and granitoid cobbles associated with transported ore represent co-genetic products of the same magmatic system. The granitoid cobbles and small granodiorite intrusions are geochemically similar and closely resemble Buchans Group felsic volcanic units. U–Pb zircon age determinations show a (i) 466.7 ± 0.5 Ma crystallization age for the Wiley’s Brook granodiorite (WBG), (ii) 464 ± 4 Ma crystallization age for a granitoid cobble, and (iii) 466 ± 4 Ma maximum deposition age for a conglomerate–sandstone sequence associated with transported ore. Thus, Buchans Group felsic plutonic rocks are within experimental error of felsic volcanism and VMS deposition. Furthermore, εNd (T) (T, time of crystallization) values of four granitoid cobbles (–1.95 to –4.0) overlap values obtained from Buchans Group felsic volcanic units. Our results are compatible with plutonic and volcanic rocks being related through fractional crystallization or partial melting processes but do not support a petrogenetic link between VMS deposition and exposed felsic plutons. Comparisons to modern arc analogues favour exhumation of plutonic rocks by extension along caldera or rift walls and (or) subaerial erosion. Enigmatic rounding of Buchans granitoid clasts was likely accomplished in a subaerial or shallow marine environment, and the clasts transported into a VMS-active basin by mass flows.

Massive sulfide deposits of the Noranda area, Quebec. V. The Corbet mine

1993 ◽  
Vol 30 (9) ◽  
pp. 1934-1954 ◽  
Author(s):  
T. J. Barrett ◽  
W. H. MacLean ◽  
S. Cattalani ◽  
L. Hoy
Keyword(s):  
Volcanic Rocks ◽  
Massive Sulfide ◽  
Mass Change ◽  
Northwestern Part ◽  
Sulfide Deposits ◽  
Oxygen Isotope Ratios ◽  
Ore Body ◽  
Volcanic Formation ◽  
Calculated Mass ◽  
Volcanic Series

The Corbet deposit is located in the upper part of the Flavrian andesite, the lowest volcanic formation within cycle III of the Noranda Central Mine Sequence. The deposit consisted of one main lens of massive sulfides, and several smaller lenses, and contained 2.7 × 106 t of mineable ore at 2.92% Cu, 1.98% Zn, 20.6 g/t Ag, and 1.0 g/t Au. The orebody had a massive pyrrhotite–chalcopyrite core, which passed laterally into massive pyrite–sphalerite. The northwestern part of the ore-body is overlain by 50–100 m of Flavrian andesite, whereas the southeastern portion is overlain by Northwest rhyolite.Lavas within the Flavrian andesite and the lower Northwest rhyolite are low in K2O (<0.5%), and are partly of tholeiitic affinity, and partly of transitional affinity. The tholeiitic volcanic series has Zr/Y ratios of 2.8 to 4.5, whereas the transitional series has Zr/Y ratios of 4.5 to 7.1. The two series are also distinct in plots of Nb–Zr, Yb–Zr, Nb–Y, and the rare earth elements. These data indicate that two slightly different magma types existed in the chamber that fed this portion of the extrusive Central Mine Sequence.Alteration is most intense in the breccias of the upper Flavrian andesite, within ~50 m of the orebody, and is almost entirely chloritic. There is no zone of silicification, although moderate sericitization occurs lateral to and above the orebody. Mass-change calculations indicate that large amounts of SiO2 and CaO + Na2O were leached from the rocks by hydrothermal solutions, whereas large amounts of hydrothermal FeO and seawater MgO were added.Oxygen isotope depletions are among the largest in the Noranda area and extend laterally and vertically up to 300 m from the orebody. Within this volume, δ18O values of altered volcanic rocks have been decreased to values as low as 2 to −2‰. These depletions result from reactions with seawater at ~ 250–300 °C and from strong silica leaching, as indicated by mass-change calculations. The hydrothermal system at Corbet can be assessed using two lithogeochemical tools: calculated mass changes and oxygen isotope ratios, both of which are sensitive to water–rock ratio and temperature.

The Petrochemistry of Altered Volcanic Rocks Surrounding the Louvem Copper Deposit, Val d'Or, Quebec

1975 ◽  
Vol 12 (11) ◽  
pp. 1820-1849 ◽  
Author(s):  
Guy Spitz ◽  
Richard Darling
Keyword(s):  
Volcanic Rocks ◽  
Copper Deposit ◽  
Massive Sulfide ◽  
Original Compositions ◽  
Pyroclastic Rock ◽  
Calc Alkaline ◽  
Genetic Classification ◽  
Sulfide Deposits ◽  
Host Rocks

The Louvem copper deposit, a carrot-shaped body of mineralized silicic pyroclastic rock, appears generally conformable with surrounding, steeply dipping volcanic rocks, but otherwise closely resembles the cross-cutting feeder pipes that underlie many Archean stratiform volcanogenic massive sulfide deposits. It is, like many such deposits, associated with peraluminous and calc-alkaline rocks in the felsic upper portion of a volcanic sequence.Naming of the Louvem volcanic host rocks by means of their chemical composition is rendered difficult by intense local alteration which has changed their original compositions. Of the four classification schemes tried, that based on sample SiO2 content appears to provide results that are least affected by this alteration and which therefore reflect most clearly the original compositions of the rocks surrounding the ore deposit.The calc-alkaline nature of Louvem volcanic rocks is apparent even for very altered near-ore samples. This is revealed by Ol–Ne–Qz and AFM diagrams, which appear to be suitable for the genetic classification of such altered rocks.The chemical nature of the wallrock alteration in and around the deposit is revealed by certain petrologic diagrams. All rocks in the study area show magnesium enrichment, but no petrologic diagram illustrates this very clearly. Outside the orebody, the alteration consists mainly of Na and Ca depletion, and those diagrams which show such depletion are the most useful. Of these, the AKF, AFM, and ACF plots appear to be most practical.

Tectono-stratigraphic evolution of the Early Proterozoic Wisconsin magmatic terranes of the Penokean Orogen

1989 ◽  
Vol 26 (10) ◽  
pp. 2145-2158 ◽  
Author(s):  
P. K. Sims ◽  
W. R. Van Schmus ◽  
K. J. Schulz ◽  
Z. E. Peterman
Keyword(s):  
Subduction Zone ◽  
Continental Margin ◽  
Volcanic Rocks ◽  
Alkali Feldspar ◽  
Suture Zone ◽  
Island Arcs ◽  
Calc Alkaline ◽  
The South ◽  
Early Proterozoic ◽  
Felsic Volcanic

The Early Proterozoic Penokean Orogen developed along the southern margin of the Archean Superior craton. The orogen consists of a northern deformed continental margin prism overlying an Archean basement and a southern assemblage of oceanic arcs, the Wisconsin magmatic terranes. The south-dipping Niagara fault (suture) zone separates the south-facing continental margin from the accreted arc terranes. The suture zone contains a dismembered ophiolite.The Wisconsin magmatic terranes consist of two terranes that are distinguished on the basis of lithology and structure. The northern Pembine–Wausau terrane contains a major succession of tholeiitic and calc-alkaline volcanic rocks deposited in the interval 1860–1889 Ma and a more restricted succession of calc-alkaline volcanic rocks deposited about 1835 – 1845 Ma. Granitoid rocks ranging in age from about 1870 to 1760 Ma intrude the volcanic rocks. The older succession was generated as island arcs and (or) closed back-arc basins above the south-dipping subduction zone (Niagara fault zone), whereas the younger one developed as island arcs above a north-dipping subduction zone, the Eau Pleine shear zone. The northward subduction followed deformation related to arc–continent collision at the Niagara suture at about 1860 Ma. The southern Marshfield terrane contains remnants of mafic to felsic volcanic rocks about 1860 Ma that were deposited on Archean gneiss basement, foliated tonalite to granite bodies ranging in age from about 1890 to 1870 Ma, and younger undated granite plutons. Following amalgamation of the two arc terranes along the Eau Pleine suture at about 1840 Ma, intraplate magmatism (1835 Ma) produced rhyolite and anorogenic alkali-feldspar granite that straddled the internal suture.

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