Pétrographie des Roches Encaissantes du Gisement Cuprifère de Louvem

1973 ◽  
Vol 10 (5) ◽  
pp. 760-776 ◽  
Author(s):  
Guy Spitz ◽  
Richard Darling
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Copper Deposit ◽  
Wall Rock ◽  
Structural Features ◽  
Alteration Zone ◽  
Pyroclastic Rocks ◽  
Wall Rock Alteration ◽  
Host Rocks ◽  
Metamorphic Facies

The Louvem copper deposit, discovered by SOQUEM in 1968, is situated in the Precambrian volcanic belt that stretches between the mining districts of Noranda and Val d'Or. The ore deposit is in the upper part of the volcanic pile, near the base of the overlying silicic pyroclastic rocks, and it is conformable with surrounding rocks. Its host rocks are meta-rhyodacite and meta-dacite flows and silicic pyroclastic rocks including tuff, agglomerate, and breccia. The principal structural features are a well-developed shear zone along the original footwall of the deposit and a locally-developed, complexly folded zone that perhaps represents a zone of slumping along the original roof of the deposit. The rocks surrounding the deposit contain mineral assemblages characteristic of the greenschist metamorphic facies. Wall-rock alteration surrounding the deposit includes pyritization, chloritization, sericitization, and silicification. Pyrite and chlorite alteration is characteristic of rocks immediately surrounding the ore while sericite and secondary quartz are present in an outer alteration zone further from the deposit. Ore deposition took place in a zone of permeable pyroclastic rocks sandwiched between two massive bands of volcanic rocks.

Reactions between uranium veins and their host rocks in Vendée and Limousin (France)

1981 ◽  
Vol 44 (336) ◽  
pp. 417-423 ◽  
Author(s):  
M. Cathelineau ◽  
J. Leroy
Keyword(s):  
Structural Characteristics ◽  
Wall Rock ◽  
Structural Features ◽  
Gangue Mineral ◽  
List Type ◽  
Vein Formation ◽  
Wall Rock Alteration ◽  
Rock Alteration ◽  
Host Rocks ◽  
Basic Rocks

AbstractHydrothermal uranium veins, associated with the Hercynian leucogranites show important variations in their mineralogical, chemical and structural features in relation to the host rock lithology. These are described with particular reference to the Chardon deposit, Vendée where the veins cut granite, basic lithologies, and shales. The following features are described: 1Changes in the thickness of veins near to contact zones, particularly those between granites and basic lithologies, lamprophyres, and shales.2Changes in the gangue mineral assemblage with the preferential development of carbonate in veins cutting basic lithologies, and of silica in veins which cut granite.3Paragenetic zoning in the veins in passing from granites to their metamorphic aureoles.Comparisons between deposits of Vendée, Limousin, and Erzgebirge allow the following generalizations to be made: 1Open faults and subsequent mineralization are concentrated at boundaries between competent and more plastic lithologies.2Mineralizing fluids cause wall-rock alteration characterized by the removal of Si from granite and of Ca, Mg, Fe from metamorphic and basic rocks.3The chemical and structural characteristics of wallrocks are important controls on the mineralization but in acid lithologies the main controls on the pitchblende vein formation are the structural characteristics of the wallrock.

Ore Mineralogy of the Louvem Copper Deposit Val d'Or, Quebec

1972 ◽  
Vol 9 (12) ◽  
pp. 1596-1611 ◽  
Author(s):  
Jayanta Guha ◽  
Richard Darling
Keyword(s):  
Copper Deposit ◽  
Wall Rock ◽  
Textural Features ◽  
Ore Deposit ◽  
Ore Body ◽  
Ore Minerals ◽  
Wall Rock Alteration ◽  
Ore Mineralogy ◽  
Rock Alteration ◽  
Host Rocks

Microscopic study of samples from the Louvem copper deposit shows that the principal ore minerals are pyrite, chalcopyrite, and sphalerite and the accessory ore minerals are rutile, tetradymite, two unidentified tellurides, cobaltite, molybdenite, galena, and four optically distinct phases having compositions along the digenite–bornite tie line.The Louvem ore body is a pipe-shaped mass of mineralized rhyolitic tuff and agglomerate that is conformable with enclosing volcanic and pyroclastic rocks. The ore body is zoned, with a copper-rich core and pyrite-rich margins. Wall-rock alteration spatially related to the ore deposit suggests that it was formed by replacement of porous tuffaceous host rocks by a hydrothermal fluid. Textural features of the ore indicate that it was subjected to post-emplacement thermal metamorphism.

scholarly journals Geochemistry, Paragenesis, and Wall-Rock Alteration of the Qatruyeh Iron Deposits, Southwest of Iran: Implications for a Hydrothermal-Metasomatic Genetic Model

2014 ◽  
Vol 2014 ◽  
pp. 1-25 ◽  
Author(s):  
Sina Asadi ◽  
Mohammad Ali Rajabzadeh
Keyword(s):  
Genetic Model ◽  
Wall Rock ◽  
Hydrothermal Activity ◽  
Low Grade ◽  
Wall Rock Alteration ◽  
Propylitic Alteration ◽  
Iron Deposits ◽  
Geochemical Analyses ◽  
Southwest Of Iran ◽  
Host Rocks

The Qatruyeh iron deposits, located on the eastern border of the NW-SE trending Sanandaj-Sirjan metamorphic zone, southwest of Iran, are hosted by a late Proterozoic to early Paleozoic sequence dominated by metamorphosed carbonate rocks. The magnetite ores occurred as layered to massive bodies, with lesser amounts of disseminated magnetite and hematite-bearing veins. Textural evidences, along with geochemical analyses of the high field strengths (HFSEs), large ion lithophiles (LILEs), and rare earth elements (REEs), indicate that the main mineralization stage occurred as low-grade layered magnetite ores due to high-temperature hydrothermal fluids accompanied by Na-Ca alteration. Most of the main ore-stage minerals precipitated from an aqueous-carbonic fluid (3.5–15 wt.% NaCl equiv.) at temperatures ranging between 300° and 410°C during fluid mixing process, CO2 effervescence, cooling, and increasing of pH. Low-temperature hydrothermal activity subsequently produced hematite ores associated with propylitic alteration. The metacarbonate host rocks are LILE-depleted and HFSE-enriched due to metasomatic alteration.

The Deer Cove deposit, Baie Verte Peninsula, Newfoundland, a Paleozoic mesothermal lode-gold occurrence in the northern Appalachians

1993 ◽  
Vol 30 (7) ◽  
pp. 1532-1546 ◽  
Author(s):  
Karen S. Patey ◽  
Derek H. C. Wilton
Keyword(s):  
Volcanic Rocks ◽  
Wall Rock ◽  
Pure Gold ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Lode Gold ◽  
Basaltic Rocks ◽  
Gold Occurrence ◽  
Fracture Systems ◽  
Host Rocks

The Siluro-Devonian Deer Cove deposit, Baie Verte Peninsula, Newfoundland, is hosted by volcanic cover rocks of the Point Rousse Complex ophiolite. Mineralization consists of quartz vein lodes with gold, pyrite, lesser chalcopyrite, and minor arsenopyrite. Gold occurs as relatively pure gold intergrown with pyrite, and as solitary grains within the quartz gangue. Host rocks include basalt and gabbro at greenschist-facies metamorphic grade. The volcanic rocks have a general calcalkaline affinity, with (anhydrous) SiO2, TiO2, MgO, Al2O3, and Zr contents of 34–62%, 0.36–0.9%, 2.8–9%, 13.4–18.5%, and 28–48 ppm, respectively; Mg # ranges from 37 to 61. The host basaltic rocks were the products of island-arc or back-arc volcanism. Well-developed alteration haloes surround the quartz veins; the alteration grades from quartz–chlorite–carbonate in the veins, through sericitic wall rock, into propylitic (chlorite–epidote–carbonate–leucoxene) host rock. Trace-element geochemistry indicates that the ore fluids had large-ion lithophile element relationships similar to average crustal values. δ13C and δ18O values of carbonate separates range from −7 to −8‰ and 10 to 12‰, respectively. On the basis of geochemical, alteration, and isotopic data, the Deer Cove deposit should be classified as a typical mesothermal lode-gold occurrence. The veins apparently formed from mesothermal fluids with average crustal compositions that flowed along brittle fracture systems within the cover sequence during Siluro-Devonian Acadian deformation. As such the veins were unrelated to either sea-floor processes or Taconic ophiolite obduction. The vein systems apparently formed during transpressive tectonism which followed ocean closure and ophiolite obduction.

Isotopic studies of ore-leads of the circum-Kisseynew volcanic belt of Manitoba and Saskatchewan

1978 ◽  
Vol 15 (7) ◽  
pp. 1112-1121 ◽  
Author(s):  
D. F. Sangster
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Massive Sulfide ◽  
Good Evidence ◽  
Lake Area ◽  
Sulfide Deposits ◽  
North West ◽  
The North ◽  
Isotopic Abundances ◽  
Host Rocks

Volcanic rocks, distributed to the north, west, and south of the Kisseynew gneissic belt in Manitoba and Saskatchewan, define a crescent-shaped belt herein informally referred to as the 'circum-Kisseynew volcanic belt'. Field relationships lead to the conclusion that the flanking volcanics are correlative with, and grade basinward to, greywackes and shales.Nearly 30 volcanogenic massive sulfide deposits, interpreted as coeval with their host rocks, are distributed throughout the circum-Kisseynew volcanic belt. Lead isotopic abundances in a representative number of these deposits are, apart from 204-error, relatively homogeneous in composition and model lead ages determined from these isotopic ratios fall, for the most part, between 1700 and 1900 Ma. This is regarded as good evidence that the circum-Kisseynew volcanic belt, as well as its greywacke equivalent, is largely Aphebian in age.Model lead ages for sulfide deposits from the entire circum-Kisseynew volcanic belt, with one exception, agree well with recent Rb–Sr and U–Pb age determinations from the southern portion of the belt. Reasons for the exception, in the Hanson Lake area, are discussed in some detail.

The Touquoy Zone deposit: an example of "unusual" orogenic gold mineralisation in the Meguma Terrane, Nova Scotia, Canada

2003 ◽  
Vol 40 (3) ◽  
pp. 447-466 ◽  
Author(s):  
Frank P Bierlein ◽  
Paul K Smith
Keyword(s):  
Close Correlation ◽  
Wall Rock ◽  
Convincing Evidence ◽  
Structural Level ◽  
Vein Formation ◽  
Wall Rock Alteration ◽  
Base Metal Sulphides ◽  
Meguma Terrane ◽  
Rock Alteration ◽  
Host Rocks

The Touquoy Zone deposit is host to disseminated gold mineralisation in metasiltstones of lower Palaeozoic age. From the close correlation between ore grades and the intersection of favourable stratigraphy and bounding faults, it is apparent that mineralisation is controlled by both structural and lithological influences. Within the ore zone, disseminated gold, arsenopyrite, pyrite, and rare base-metal sulphides are associated with a network of widely spaced, millimetre-scale, quartz–carbonate veinlets. Quasi-pervasive fluid flow and prolonged interaction with the host rocks resulted in a diffuse, but pronounced halo of wall-rock alteration that is characterized by the breakdown of detrital feldspar and metamorphic chlorite and the development of hydrothermal carbonate phases, K-mica, and disseminated sulphides. These mineralogical changes are accompanied by enrichment in CO2, K, Au, As, and S and depletion in Na across the ore zone. Vein formation occurred at between 250° and 350°C and pressures of less than 1–2 kbar (1 kbar = 100 MPa), corresponding to an estimated depth of between <2.8 and 6 km. Mineralisation resulted from the unmixing of an overpressured (low-salinity, CO2-rich) fluid in response to decreasing pressure during its ascent and penetration into permeable host rocks. Geological and geochemical features of mineralisation in the Touquoy Zone deposit are seen as convincing evidence for a close genetic association between disseminated-style and lode gold mineralisation in orogenic terrains, with the resulting style of mineralisation largely controlled by the overall structural geometry of the mineralising site, rheological properties, permeability and chemical receptiveness of the host rock, and structural level of emplacement.

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.

A km-scale illite alteration zone in sedimentary wall rocks adjacent to a hydrothermal fluorite vein deposit

Clay Minerals ◽  
2005 ◽  
Vol 40 (2) ◽  
pp. 245-260 ◽  
Author(s):  
O. Brockamp ◽  
N. Clauer
Keyword(s):  
Hydrothermal Process ◽  
Wall Rock ◽  
Partial Substitution ◽  
Alteration Zone ◽  
Vein Deposit ◽  
The North ◽  
Wall Rock Alteration ◽  
Lower Temperature ◽  
Rock Alteration ◽  
Detrital Mineral

AbstractIn a study of wall-rock alteration in the 1.4 km long Würmtal adit at the Käfersteige hydrothermal vein deposit (northern Black Forest, Germany) illite was found to be the only clay mineral within the Bunter sandstone and intercalated claystone. Illite occurs mainly as a detrital mineral in the claystone, whereas it is hydrothermally neoformed in the sandstone, either in the pores or as an alteration product of K-feldspar. The extensive occurrence of authigenic illite along the entire 1.4 km long profile confirms that the fluids migrated far into the sandstone.The authigenic illite formed during a first pulse of high-temperature fluids (Th of ~220°C) with a low salinity (~1 wt.% NaCleq). These fluids also dissolved Sr and Rb from detrital illite of the claystones at the vein. A later hydrothermal pulse with a lower temperature (~70–150°C) and higher salinity (21–28 wt.% NaCleq) silicified the sandstone adjacent to the vein and caused partial substitution of OH- by F- in the structure of the detrital and neoformed illite along the profile.Within analytical error, the K-Ar dates for the neoformed illite of the <2 µm fraction are the same along the profile (~150 Ma). During this hydrothermal process, the age of the detrital illite within the claystone was reset from 310 to 190 Ma. The illite-rich <0.2 µm fractions yield ages of ~142 Ma (sandstone) indicating a Jurassic origin. The uniform age data for illite in the sandstone and in the claystone are probably due to extensive migration of hot fluids through the wall rocks.The hydrothermal fluids are attributed to recycled meteoric water and brines that ascended from the basement into the cover rocks during the opening of the North Atlantic and/or the nearby Tethys area.

The Kuh Toto volcanic-hosted copper deposit, Semnan Province, Iran: geochemical, fluid inclusion, and C and O isotopic studies

2021 ◽  
pp. geochem2021-018
Author(s):  
Omid Javariani ◽  
Farhad Ehya ◽  
Mohammad Ali Ali Abadi ◽  
Abbas Asgari ◽  
Mohammad Mehri
Keyword(s):  
Fluid Inclusion ◽  
Volcanic Rocks ◽  
Copper Deposit ◽  
Copper Ore ◽  
Copper Mineralization ◽  
Groundwater Environment ◽  
Oxygen Isotopic ◽  
Basic Volcanic ◽  
Host Rocks ◽  
Semnan Province

Supergene copper mineralization occurs at the Kuh Toto deposit, located 25 km to the west of Torud village in the Semnan Province, Iran. Mineralogical, fluid inclusion, and stable isotopic (C and O) studies, as well as rare earth element (REE) geochemistry of whole-rock and minerals are used to unravel the conditions under which the Cu ores formed. Malachite is the only copper ore mineral, and it is present as veinlets, coatings and small patches in Eocene volcanic rocks. Malachite is accompanied by minor calcite, manganese and iron oxides and oxyhydroxides, clay minerals, epidote, quartz, and chrysocolla. Argillic and, to a lesser extent, propylitic hydrothermal alteration partially affected the basic volcanic host rocks. The chondrite-normalized REE patterns of malachite and calcite are similar to those of the volcanic host rocks. They are enriched in LREEs. The volcanic host rocks are enriched in Cu (187 ppm on average). Fluid inclusions hosted in calcite reveal that calcite precipitated from hydrothermal fluids at low temperatures (69-150 °C) and low to moderate salinities (7.17-11.10 wt.% NaCl equivalent). The oxygen isotopic geothermometry yielded an average temperature of 41 °C for malachite formation. Geochemical and fluid inclusion evidence strongly support that mineral-forming elements, including Cu, originated from the associated volcanic rocks. Available data support the view that Cu was likely leached as mobile aqueous Cu2+ from the volcanic rocks by oxidizing surface waters. When Cu-enriched fluids entered the underlying groundwater environment, Cu was precipitated as malachite in fractures, via recombination with carbonate ions dissolved as CO2 in meteoric fluids.

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