The geochemistry of altered volcanic rocks at Matagami, Quebec: a geothermal model for massive sulphide genesis

1978 ◽  
Vol 15 (4) ◽  
pp. 551-570 ◽  
Author(s):  
P. J. MacGeehan

Volcanogenic exhalative massive sulphide deposits at Matagami are associated with a bimodal suite of tholeiitic basalt and rhyolite. However, these rocks now exhibit pseudo calc-alkaline alteration trends resulting from a hydrothermal alteration process in which footwall basalt was spilitized, and the host rhyolite was chloritized. These two alteration processes were contemporaneous events, which shared a common aqueous fluid, developed within cooling submarine volcanic rocks shortly after the extrusion of rhyolite, and terminated prior to extrusion of succeeding units.The geochemistry of the Garon Lake rhyolite and underlying basalt are examined in detail. Massive quantities of Fe, Mg and Ti, and over 10 ppm Zn and 5 ppm Cu were leached from basalt during spilitization, providing 30 000 t Zn and 15 000 t Cu, or approximately 1 Mt of ore grade material per km3 of basalt. Chlorite alteration zones and massive sulphide deposits in the overlying rhyolite were enriched in all those elements depleted from basalt. This evidence suggests a geothermal model for massive sulphide genesis, where Fe, Mg, Ti, Cu and Zn were leached from footwall rocks, flushed through a geothermal system, and then precipitated at the discharge point to form chlorite alteration zones in the overlying rhyolite and exhalite deposits at the sediment–seawater interface.

1992 ◽  
Vol 29 (7) ◽  
pp. 1375-1388 ◽  
Author(s):  
Yuanming Pan ◽  
Michael E. Fleet

Skarn-like calc-silicate rocks are reported in spatial association with the Archean Cu–Zn–Ag massive sulphide deposits at the Manitouwadge mining camp, Ontario. Calc-silicates in the footwall of the Willroy mine occur as matrix to breccia fragments of garnetiferous quartzo-feldspathic gneiss and as lenses within garnetiferous quartzo-feldspathic gneiss and are composed of clinopyroxene, garnet, calcic amphiboles, wollastonite, plagioclase, K-feldspar, epidote, quartz, calcite, magnetite, and minor sulphides. Calc-silicates within the main orebody of the Geco mine are characterized by clinopyroxene, calcic amphiboles (Cl–K-rich hastingsitic and ferro-edenitic hornblende, ferro-edenite (up to 4.7 wt.% Cl); and ferroactinolite (6.7 wt.% MnO)), garnet, epidote (including an epidote rich in rare-earth elements and Cl), calcite, quartz, and abundant sulphides. Calc-silicates within the basal 4/2 Copper Zone of the Geco mine contain garnet, gahnite, sphalerite, ferroactinolite (8.5 wt.% MnO), epidote, quartz, biotite, plagioclase, chlorite, muscovite, K-feldspar, and pyrosmalite (with Mn/(Mn + Fe) ratio ranging from 0.21 to 0.61, and up to 3.9 wt.% Cl). The calc-silicates probably represent metasomatic remobilization of dispersed Ca (and Cl) from sea-floor hydrothermal alteration of mafic to intermediate volcanic rocks and are only indirectly related to the hypothesized syngenetic ore-forming processes for the associated base metal sulphide deposits. The calc-silicates formed initially at about 600 °C and 3–5 kbar (1 kbar = 100 MPa) in a mildly reducing environment (from 1 log unit above to 1 log unit below the fayalite–magnetite–quartz buffer) during the upper-amphibolite- to granulite-facies regional metamorphism and were altered subsequently at lower temperatures (<500 °C).


2009 ◽  
Vol 46 (7) ◽  
pp. 509-527 ◽  
Author(s):  
Y. M. DeWolfe ◽  
H. L. Gibson ◽  
S. J. Piercey

A detailed study of the geochemical and isotopic characteristics of the volcanic rocks of the Hidden and Louis formations, which make up the hanging wall to the volcanogenic massive sulphide deposits at Flin Flon, Manitoba, was carried out on a stratigraphically controlled set of samples. The stratigraphy consists of the lowermost, dominantly basaltic, Hidden formation, and the overlying, dominantly basaltic, Louis formation. Of importance petrogenetically, is the 1920 unit a basaltic andesite with Nb/Thmn = 0.54–0.62, εNd(1.9Ga) = +3.6–+5.9, εHf(1.9Ga) = +8.5–+9.6, and 204Pb/206Pb = 23.9. The basaltic flows that dominate the Hidden formation have Nb/Thmn = 0.16–0.29, εNd(1.9Ga) = +1.7–+4.4, εHf(1.9Ga) = +7.0–+11.8 and 204Pb/206Pb = 16.9–18.6). The Carlisle Lake basaltic–andesite (top of Hidden formation) is characterized by Nb/Thmn = 0.16–0.14, and 204Pb/206Pb = 21.4. The rhyodacitic Tower member (bottom of Louis formation) has Nb/Thmn = 0.23, εNd1.9Ga = +4.6, εHf1.9Ga = +9.3, and 204Pb/206Pb = 22.2. The basaltic flows that dominate the Louis formation have Nb/Thmn = 0.18–0.25, εNd(1.9Ga) = +3.6–+4.2, εHf(1.9Ga) = +8.4–+11.3 and 204Pb/206Pb = 17.9. The Hidden and Louis formations show dominantly transitional arc tholeiite signatures, with the 1920 unit having arc tholeiite characteristics. It is interpreted to have formed through extensive fractional crystallization of differentiated magmas at shallow levels in oceanic crust. Given the geological, geochemical, and isotopic characteristics of the Hidden and Louis formations, they are interpreted to represent subducted slab metasomatism with minor contamination from subducted sediments.


2019 ◽  
Vol 61 (2) ◽  
pp. 3-22
Author(s):  
I. B. Seravkin ◽  
A. M. Kosarev

A comparative paleovolcanic and metallogenic analysis of two massive-sulphide-bearing regions, the Southern Urals and Ore Altai, located in different parts of the Ural-Mongolian folded belt, was performed. Comparison of the geodynamic evolution of these areas, the formation and facies composition of the ore-bearing strata and types of massive-sulphide deposits has led to the conclusion that the regions are similar only in the most general terms. Fundamental differences in the structure and composition of the crust of the regions led to differences in the profile of island-arc magmatism: basaltoid in the Southern Urals and rhyolitoid in Ore Altai. This, in its turn, determined the predominant composition of massive-sulphide mineralization: copper-zinc in the first of the regions and polymetallic — in the second. Opposite tendencies in the evolution of volcanism are also characteristic: homodromic in the Southern Urals and antidromic in the Ore Altai, which resulted in a different position of the types of massive-sulphide deposits in the ore districts: the bottom-up change of copper — massive-sulphide deposits by the massive-sulphide -polymetallic in the Southern Urals and barite polymetallic by massive-sulphide polymetallic and copper- massive-sulphide in the Ore Altai. Significant differences are also in the lateral distribution patterns of mineralization: a more pronounced control of mineralization by paleovolcanic structures of the central type in the Southern Urals and the frequent position of mineralization in intermediate and remote facies of volcanism in the Ore Altai, which is reflected in the prevalence of volcanic sections in the Urals and the majority of the volcanic sections and the larger majority of the volcanic rocks in the Ore Altai, which is reflected in the prevalence of volcanic rocks in the Urals and the majority of the volcanic sections and in the Ore Altai most of the volcanic minerals and the larger majority of the mineral rocks (20–80%) in the strata containing mineralization in the Ore Altai.


2019 ◽  
pp. 137-154
Author(s):  
Steven R. McCutcheon ◽  
James A. Walker

The Bathurst Mining Camp of northern New Brunswick is approximately 3800 km2 in area, encompassed by a circle of radius 35 km. It is known worldwide for its volcanogenic massive sulphide deposits, especially for the Brunswick No. 12 Mine, which was in production from 1964 to 2013. The camp was born in October of 1952, with the discovery of the Brunswick No. 6 deposit, and this sparked a staking rush with more hectares claimed in the province than at any time since.   In 1952, little was known about the geology of the Bathurst Mining Camp or the depositional settings of its mineral deposits, because access was poor and the area was largely forest covered. We have learned a lot since that time. The camp was glaciated during the last ice age and various ice-flow directions are reflected on the physiographic map of the area. Despite abundant glacial deposits, we now know that the camp comprises several groups of Ordovician predominantly volcanic rocks, belonging to the Dunnage Zone, which overlie older sedimentary rocks belonging to the Gander Zone. The volcanic rocks formed during rifting of a submarine volcanic arc on the continental margin of Ganderia, ultimately leading to the formation of a Sea of Japan-style basin that is referred to as the Tetagouche-Exploits back-arc basin. The massive sulphide deposits are mostly associated with early-stage, felsic volcanic rocks and formed during the Middle Ordovician upon or near the sea floor by precipitation from metalliferous fluids escaping from submarine hot springs.   The history of mineral exploration in the Bathurst Mining Camp can be divided into six periods: a) pre-1952, b) 1952-1958, c) 1959-1973, d) 1974-1988, and e) 1989-2000, over which time 45 massive sulphide deposits were discovered. Prior to 1952, only one deposit was known, but the efforts of three men, Patrick (Paddy) W. Meahan, Dr. William J. Wright, and Dr. Graham S. MacKenzie, focused attention on the mineral potential of northern New Brunswick, which led to the discovery of the Brunswick No. 6 deposit in October 1952. In the 1950s, 29 deposits were discovered, largely resulting from the application of airborne surveys, followed by ground geophysical methods. From 1959 to 1973, six deposits were discovered, mostly satellite bodies to known deposits. From 1974 to 1988, five deposits were found, largely because of the application of new low-cost analytical and geophysical techniques. From 1989 to 2000, four more deposits were discovered; three were deep drilling targets but one was at surface. RÉSUMÉLe camp minier de Bathurst, dans le nord du Nouveau-Brunswick, s’étend sur environ 3 800 km2 à l’intérieur d’un cercle de 35 km de rayon. Il est connu dans le monde entier pour ses gisements de sulfures massifs volcanogènes, en particulier pour la mine Brunswick n° 12, exploitée de 1964 à 2013. Le camp est né en octobre 1952 avec la découverte du gisement Brunswick n° 6 et a suscité une ruée au jalonnement sans précédent avec le plus d’hectares revendiqués dans la province qu’à présent.   En 1952, on savait peu de choses sur la géologie du camp minier de Bathurst ou sur les conditions de déposition de ses gisements minéraux, car l’accès était très limité et la zone était en grande partie recouverte de forêt. Nous avons beaucoup appris depuis cette période. Le camp était recouvert de glace au cours de la dernière période glaciaire et diverses directions d’écoulements glaciaires sont révélées sur la carte physiographique de la région. Malgré des dépôts glaciaires abondants, nous savons maintenant que le camp comprend plusieurs groupes de roches ordoviciennes à prédominance volcanique, appartenant à la zone Dunnage, qui recouvrent de plus vieilles roches sédimentaires de la zone Gander. Les roches volcaniques se sont formées lors du rifting d’un arc volcanique sous-marin sur la marge continentale de Ganderia, ce qui a finalement abouti à la formation d’un bassin de type mer du Japon, appelé bassin d’arrière-arc de Tetagouche-Exploits. Les gisements de sulfures massifs sont principalement associés aux roches volcaniques felsiques de stade précoce et se sont formés au cours de l’Ordovicien moyen sur ou proche du plancher océanique par la précipitation de fluides métallifères s’échappant de sources chaudes sous-marines.   L’histoire de l’exploration minière dans le camp minier de Bathurst peut être divisée en six périodes: a) antérieure à 1952, b) 1952-1958, c) 1959-1973, d) 1974-1988 et e) 1989-2000, au cours desquelles 45 dépôts de sulfures massifs ont été découverts. Avant 1952, un seul dépôt était connu, mais les efforts de trois hommes, Patrick (Paddy) W. Meahan, William J. Wright et Graham S. MacKenzie, ont attiré l’attention sur le potentiel minier du nord du Nouveau-Brunswick, ce qui a conduit à la découverte du gisement Brunswick n° 6 au mois d’octobre 1952. Dans les années 50, 29 gisements ont été découverts, résultant en grande partie de l’utilisation de levés aéroportés, suivis de campagnes géophysiques terrestres. De 1959 à 1973, six gisements ont été découverts. Ce sont essentiellement des formations satellites de gisements connus. De 1974 à 1988, cinq gisements ont été découverts, principalement grâce à l’utilisation de nouvelles techniques analytiques et géophysiques peu coûteuses. De 1989 à 2000, quatre autres gisements ont été découverts. Trois étaient des cibles de forage profondes, mais l’un était à la surface.


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