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  • 1
    Electronic Resource
    Electronic Resource
    Discussion for the manuscript of J. A. Noble: “Metallogenic provinces of the Cordillera of Western North and South America” Mineralium Deposita, volume 11, p. 219–233 (1976) (1977)
    Springer
    Mineralium deposita 12 (1977), S. 239-240 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206030
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  • 2
    Electronic Resource
    Electronic Resource
    The Milluachaqui epithermal silver district of northern Peru (1977)
    Springer
    Mineralium deposita 12 (1977), S. 235-238 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The mines in the Milluachaqui district, located near Salpo in the northern part of Peru, show a vertically zoned, epithermal silver-gold mineralization. Colonial production was obtained from oxidized, high-grade ores, consisting mostly of native silver and cerargyrite. More modern development exposed, from the top of ore shoots to their base, the "bonanza" ores (the pyrargyrite-polybasite-acanthite zone), silver-copper ores (the tetrahedrite zone), silver-lead ores (the galena-sphalerite zone), and the basal zone ores (the sphalerite zone). The ratio of gold to silver in the "bonanza" ores was about 1 to 100, by weight. Interpretation of mineralogical textures and the composition of minerals in the sulfide zone suggests that supergene movement and enrichment of silver at Milluachaqui was not a significant factor. Silver tended to be fixed in place during weathering as the chloride and native mineral. The "bonanza" ores are interpreted to be hypogene sulfide accumulations. These findings contrast to hypotheses proposed for some epithermal districts in the U.S. which assume supergene activity to have been significant in the accumulation of high grade, near-surface silver ores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206029
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  • 3
    Electronic Resource
    Electronic Resource
    The North Fork porphyry copper deposit of the Washington Cascades (1978)
    Springer
    Mineralium deposita 13 (1978), S. 191-199 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The North Fork porphyry copper deposit in the Cascade volcanic arc of Washington displays copper mineralization confined to the potassic (biotite) and phyllic (sericite) alteration zones. No secondary potassium feldspars have been found in either alteration zone; moreover, chemical analyses indicate the potassic alteration zone contains a low K2O content. Argillic and propylitic zones are also recognized, but these are barren of hypogene copper mineralization. Biotite-chalcopyrite intergrowths in the deposit have been given a 9.9 K-Ar age. Thus it is not only one of the youngest deposits dated in the western Cordillera, but it is associated with a volcanic arc which has no current Benioff zone seismic array or accompanying trench. The deposit appears to have developed during the period when coupling of the North American and Juan de Fuca plates probably inhibited subduction under the Cascade volcanic arc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204642
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  • 4
    Electronic Resource
    Electronic Resource
    The porphyry molybdenum deposit of Compaccha, Peru, and its geologic setting (1975)
    Springer
    Mineralium deposita 10 (1975), S. 141-151 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Compaccha, in Peru, is a zoned molybdenum, copper, zinc, lead, antimonyarsenic district which has historically been important because of tungsten production derived from all zones. Wolframite, the principal tungsten mineral, is zoned compatibly with the sulfides. Manganese tungstate occurs in the molybdenum zone, while iron replaces the manganese increasingly importantly as distance is gained away from this zone. The alteration zoning in and around the molybdenum zone is typical of that of a porphyry copper deposit, in that fluorite, topaz or other fluorine rich silicates are not common. The molybdenum zone does include a porphyry molybdenum deposit, however, and this is characterized by intense silicification and quartz veining (stockworks). Within the area of the deposit, east of the coastal batholith, no Mesozoic arc type or basic volcanics can be inferred. A cratonic setting is postulated for the deposit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206529
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  • 5
    Electronic Resource
    Electronic Resource
    The michiquillay porphyry copper deposit (1974)
    Springer
    Mineralium deposita 9 (1974), S. 261-269 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Michiquillay is a mineralized intrusive quartz monzonite porphyry displaying typical porphyry copper alteration zones as found in metallized intrusives of that composition. From the interior outward these are the phyllic, argillic and propylitic zones. The potassic zone is not exposed at the surface. The intrusion and the center of mineralization coincide with the intersection of a major transverse fault and a cross fault. Mineralization appears dominantly to occur in fractures which may be related to each of these major structures, and is ascribed in origin to simultaneous movement on each fault during the period of hydrothermal activity. The stockwork developed at the fault intersection, and which is the locus of the ore body, fades as distance is gained away from its center. Coincidentally, intensity of mineralization also weakens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204000
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  • 6
    Electronic Resource
    Electronic Resource
    Structural control and hydrothermal alteration pattern of Chaucha Porphyry Copper, Ecuador (1973)
    Springer
    Mineralium deposita 8 (1973), S. 321-331 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé L'activité ignée, la zonalité de l'altération hydrothermale et la minéralisation du type Porphyry Copper à Chaucha sont controllées d'une façon évidente par l'intersection de deux failles importantes: la «faille de Chaucha» et la «faille Cordillera». Le developpement des fractures et de la foliation dans les roches intrusives ainsi que dans les roches intrudées obéissent au même control tectonique. Le jeu des failles affecte la diorite et la granodiorite mais pas la minéralisation ni l'intrusion de monzonite quartzifère. La texture et la nature des roches aussi bien que l'environnement géologique suggérent une origine volcanique pour ce gisement. Se basant sur les relations tectoniques et d'autres arguments géologiques, l'origine du gisement (roches et minéralisation) est interpretée, d'une façon préliminaire, à la lumiere de la tectonique des plaques.
    Notes: Abstract The intrusives and associated volcanic activity, the hydrothermal alteration pattern, and mineralization of the Chaucha porphyry copper deposit appear to be strongly controlled by the intersection of two major structures: the Chaucha fault and the Cordillera fault. Stockwork development and dynamic foliation of the intrusives and surrounding rocks respond to the same control. The fault movements affect the diorite and granodiorite intrusions and largely predate the mineralization and the quartz monzonite intrusion. The lithologies and peculiar geological setting favor a volcanic origin of the Chaucha porphyry copper. Using structural relations and other geological criteria, the Chaucha porphyry copper is tentatively placed in the plate tectonic model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00207515
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  • 7
    Electronic Resource
    Electronic Resource
    Relationship between low-grade gold disseminations and high-grade veins in the Quartz Mountain district, Oregon (1993)
    Springer
    Natural resources research 2 (1993), S. 284-291 
    Details
    ISSN: 1573-8981
    Keywords: Gold and mercury mineralization ; Epithermal veins ; Mineral exploration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Gold and mercury mineralization related to epithermal hot springs occurs spatially associated with rhyolite dome complexes in the Quartz Mountain district, Lake County, Oregon. Drilling of over 800 holes from 1983 to 1991, mostly by Quartz Mountain Gold Corp., has resulted in a mineral inventory of at least 100,000,000 tons, averaging 0.0255 ounce gold per ton in two near-surface, disseminated gold ore bodies, Quartz Butte and Crone Hill. Extensive gold disseminations are underlain by and include rare, higher-grade veins that could be feeders for the near-surface, quasi-horizontal, pervasively mineralized gold dissemination. The veins contain about 2,000,000 tons of ore, aver-aging 0.29 ounce gold per ton. Approximately 750,000 tons of this underlie Quartz Butte, and the remainder is included in the Crone Hill low-grade dissemination. With a mineral inventory of about 3,000,000 ounces, Quartz Mountain is currently the largest known gold deposit in Oregon. As now known, the veins seem too few in number and too sporadically positioned to account for the volume of near-surface gold disseminations. We offer hypotheses to explain the apparent anomaly between the volume of disseminated gold ore and the paucity of feeders. Quartz Mountain has numerous alteration and mineralization similarities with the well-studied Steamboat Springs district (White and others, 1964). Coincidences between the two districts are noted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02257539
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  • 8
    Electronic Resource
    Electronic Resource
    Geology of epithermal silver-gold bulk-mining targets, bodie district, Mono County, California (1995)
    Springer
    Natural resources research 4 (1995), S. 129-137 
    Details
    ISSN: 1573-8981
    Keywords: Gold ; Silver ; Electrum ; Quartz ; Adularia ; Epithermal ; Bulk mining
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Bodie mining district in Mono County, California, is zoned with a core polymetallic-quartz vein system and silver- and gold-bearing quartz-adularia veins north and south of the core. The veins formed as a result of repeated normal faulting during doming shortly after extrusion of felsic flows and tuffs, and the magmatic-hydrothermal event seems to span at least 2 Ma. Epithermal mineralization accompanied repeated movement of the normal faults, resulting in vein development in the planes of the faults. The veins occur in a very large area of argillic alteration. Individual mineralized structures commonly formed new fracture planes during separate fault movements, with resulting broad zones of veinlets growing in the walls of the major vein-faults. The veinlet swarms have been found to constitute a target estimated at 75,000,000 tons, averaging 0.037 ounce gold per ton. The target is amenable to bulkmining exploitation. The epithermal mineralogy is simple, with electrum being the most important precious metal mineral. The host veins are typical low-sulfide banded epithermal quartz and adularia structures that filled voids created by the faulting. Historical data show that beneficiation of the simple vein mineralogy is very efficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02259036
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