Tectonic Evolution and Mineral Deposits of the Northern Appalachians in Southern New Brunswick

Geology of New Brunswick: field guide to excursions, 1973: Trip A-

Mineralogy and geochemistry of the Masa Valverde blind massive sulphide deposit, Iberian Pyrite Belt (Spain)

Masa Valverde is a blind, volcanic-hosted massive sulphide deposit recently discovered in the Spanish sector of the Iberian Pyrite Belt (IPB). The deposit is more than 1 km long and is located at depths between 400 and 850 m, in direct spatial association with a residual gravimetric anomaly. The ore body is concealed beneath Culm sedimentary rocks which cover the westem extension of a Hercynian age anticline, a few kilometers west of an area where older massive sulphide workings existed. The Masa Valverde deposit consists of two main ore bodies composed dominantly of massive and banded pyrite which are hosted by a volcano-sedimentary sequence made up of felsic tuffs interlayered with shale, siliceous exhalite and radiolarian chert. The abundance of sedimentary host rocks to the deposit is a feature shared by other large massive sulphide deposits in the eastem sector of the IPB and is interpreted as significant with respect to the origin of the deposit (a break in volcanic activity). The thickness of the upper massive sulphide orebody varies between a few meters and 70 m, and it consists of lenses and blankets of massive sulphides with interbedded tuff and shale and occasionally stockwork zones. The lower orebody is smaller and thinner than the upper one, but this may be due to incomplete drilling. Two types of stockwork occur beneath the massive sulphide bodies, the more common type consists of irregular and anastomosing sulphide veinlets and irregular blebs formed by replacement. Stockwork with cross-cutting, generally straight-sided, sulphide veins is, by contrast, suggestive of formation by hydraulic fracturing. The mineralogy and alteration processes of the ore and host rocks at Masa Valverde are analogous to those of other IPB massive sulphides

The inventory of geological heritage of the state of São Paulo, Brazil: Methodological basis, results and perspectives

An inventory of geological sites based on solid and clear criteria is a first step for any geoconservation strategy. This paper describes the method used in the geoheritage inventory of the State of São Paulo, Brazil, and presents its main results. This inventory developed by the geoscientific community aimed to identify geosites with scientific value in the whole state, using a systematic approach. All 142 geosites representative of 11 geological frameworks were characterised and quantitatively evaluated according to their scientific value and risk of degradation, in order to establish priorities for their future management. An online database of the inventory is under construction, which will be available to be easily consulted and updated by the geoscientific community. All data were made available to the State Geological Institute as the backbone for the implementation of a future state geoconservation strategy.The authors acknowledge the Science Without Borders Programme, Process 075/2012, which supported this study and the São Paulo Research Foundation (FAPESP), Process 2011/17261-6. We also thanks C. Mazoca for his help with maps and figures.info:eu-repo/semantics/acceptedVersio

Constraints on the Petrogenesis of a Proterozoic Talc Deposit in Southwestern Montana: A Petrological and Geochemical study

Talc, a magnesium phyllosilicate, is used in many products, including paints, rubber, ceramics, cosmetics, and plastics. Talc mineralization generally occurs in low-grade metamorphic conditions and requires a significant source of magnesium. Large amounts of Al, Ca, or K in the formational environment limit talc mineralization in favor of other minerals such as chlorite, tremolite, and biotite. Formation processes, such as metamorphism or hydrothermal events, of the talc bodies, control the inherent compositions and can dictate which impurities are present. This study focuses on a talc deposit near Alder, Montana, one of a series of high purity Precambrian deposits within this region. Petrographic results indicate that dolomitic marble was pseudomorphically replaced by talc. This implies that sufficient magnesium was supplied from the host rock and silica was supplied by the hydrothermal fluid. Relatively pure (>90% by XRD) talc samples have only trace amounts of Al, Ca, and K, and are very low in rare earth elements (REE), with generally flat chondrite-normalized REE patterns by XRF and ICP-MS. For these samples, the most common accessory mineral is clinochlore. Acetic acid leachates from carbonate-rich units yield light REE enriched patterns and higher REE concentrations than the pure talc samples. Rare earth element patterns and concentrations suggest that the talc inherited its REEs from the carbonate during recrystallization from carbonate to talc. Sm-Nd isotope data from the carbonate samples define a linear trend corresponding to an age of 1.42±0.07 Ga, which is consistent with the inferred age of the hydrothermal event responsible for the talc formation

Vectors to ore in replacive volcanogenic massive sulfide (VMS) deposits of the northern Iberian Pyrite Belt: Mineral zoning, whole rock geochemistry, and application of portable X-ray fluorescence

In this work we have performed a detailed study of vectors to ore to a representative volcanic-rock-hosted replacive volcanogenic massive sulfide (VMS) deposit located in the northern Iberian Pyrite Belt (Spain), the Aguas Teñidas deposit. The investigated vectors include the following: (1) mineralogical zoning, (2) host sequence characterization and mineralized unit identification based on whole rock geochemistry discrimination diagrams, (3) study of the characteristics and behaviour of whole rock geochemical anomalies around the ore (e.g. alteration-related compositional changes, characteristics and extent of geochemical halos of indicative elements such as Cu, Zn, Pb, Sb, Tl, and Ba around the deposit), and (4) application of portable X-ray fluorescence (p-XRF) analysis to the detection of the previous vectors

Geology Of The Ambler 4B Extension Of The Smucker Volcanogenic Massive Sulfide Deposit Ambler District, Alaska

Thesis (M.S.) University of Alaska Fairbanks, 198

Geology of New Brunswick: field guide to excursions, 1973

Geologic fieldtrips in New Bruswic

Study of the veins, alterations and mineralization of the Comtois gold deposit, Abitibi subprovince, Quebec, Canada

Le gîte de Comtois est situé dans le complexe volcanique archéen du Nord de la sous province de l'Abitibi. Les roches volcaniques hôtes sont de compositions mafiques, intermédiaires et felsiques. La séquence volcanique est verticalisée. Elle montre des textures massives et clastiques. Comtois se caractérise par ses nombreux dykes, des veines et des altérations hydrothermales. Cette étude vise à découvrir un lien entre la minéralogie des veines, les altérations hydrothermales et la minéralisation aurifère afin d'identifier le type de modèle génétique. L'étude des veines a permis d'établir quatre types sur la base de leur paragenènes et leur orientation. Les veines de type I sont composées de quartz gris d'orientation variable. Les veines de type II sont composées d'actinote + quartz ± épidote ± pyrite orientée 60°N et 100°N. Les veines de type III sont composées de pyrite ± chalcopyrite orientée 120°N. Les veines de type IV sont composées de quartz laiteux orienté 70°N. Les roches volcaniques ont subi plusieurs altérations hydrothermales. La cordiérite et andalousite sont trouvées de façon envahissante partout dans la zone d'étude. L'épidote et l'albite sont associées aux veines de type II. Une enveloppe d'altération à quartz est localement observée avec les veines de type III. La minéralisation en or est associée aux veines de types III dans l'enveloppe d'altération siliceuse. L'or se trouve en grain d'électrum dans la pyrite et ses fractures. Le ratio Au:Ag se situe entre 9:1 et 1:2. Des grains de BiTe sont aussi présents dans le même contexte. Le contexte géologique, les altérations hydrothermales et la composition des grains d'électrum sont consistants avec un modèle génétique de type sulfures massifs volcanogène. \ud ______________________________________________________________________________ \ud MOTS-CLÉS DE L’AUTEUR : Altération, Cordiérite, Andalousite, Veines, Sulfures Massif

Geological factors that influence the evaluation and exploitation of Canadian copper-zinc massive sulphide-, and Japanese polymetallic (kuroko) deposits

Volcanogenic massive sulphide deposits are important sources of base metals throughout the world. The Canadian Cu-Zn-(Au, Ag) deposits of Archaean age occur in greenstone terrains within the Canadian Shield. These deposits are closely associated with volcanic vents developed along zones of rifting within mobile belts. The vents are manifested by coarse felsic pyroclastics and/or rhyolitic domes. The Japanese Pb-Zn-Cu-Ba(Ag) deposits, generally known as Kuroko deposits, are of Miocene age, and although also associated with volcanic vents, are developed above zones of subduction. Mineralization in volcanogenic deposits is a result of submarine exhalation of metalliferous hydrothermal solutions derived from fractionation of predominantly calc-alkaline magmas. The deposits are characterized by certain geological features that result from the interaction of specific physical and chemical conditions during deposition. Primary features include massive and stringer sulphide bodies, alteration zones, mineralogical and metal zoning, and certain depositional textures and structures. These features are commonly modified by subsequent metamorphism and deformation which impart secondary ore textures and affect metal distribution and shape. The disparity in age between Canadian and Japanese deposits allows the entire spectrum of geological features to be studied; from the completely unaltered to the high deformed and recrystallized. The characteristic geological features are the prime factors which control the metal distribution and concentration, and the size and shape of the deposits, thereby influencing the viability of the respective ore bodies. A knowledge of these factors and the physico-chemical parameters which control them are thus fundamental in the "understanding" of these deposits. They ultimately control the geological interpretations and predictions made during ore body delineation, ore reserve estimation, mining and ore beneficiation