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Alteration characteristics of the world-class archean orogenic Hutti gold deposit, southern India
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
J. Kolb, A. Rogers, F.M. Meyer
The most prominent alteration paragenesis in the reefs can be correlated to the D3 deformation event. The paragenesis includes chlorite, quartz, calcite, tourmaline, titanite, epidote/zoisite, sericite, pyrrhotite, chalcopyrite, sphalerite, and gold. Oxides are also present but with less abundance, they include ilmenite and rutile (Rogers et al. 2001). The chlorite forms platy crystals (50 µm) which replace the biotite crystals along cleavage planes. Quartz and calcite both increase in proportion within the matrix. The quartz varies in size from 40 µm to 1200 µm and is variously deformed, elongate crystals with flame structures as well as dynamically recrystallised crystals also displaying undulose extinction. The calcite crystals are slightly larger than that of quartz, frequently irregular and associated to altered plagioclase crystals.
Luzonite and associated Cu-excess tennantite from the Levant Sn–Cu deposit, Cornwall, England: Evidence for a high sulphidation hydrothermal event
Published in Applied Earth Science, 2021
Benjamin A. Grguric, Malcolm P. Roberts, Mark D. Raven, Kendal Martyn
A detailed structural and paragenetic study of the Levant Mine mineralisation was carried out by Jackson (1976). Primary hydrothermal Cu–Sn mineralisation at Levant is structurally-controlled in a series of veins and wall-rock alteration zones, with the hydrothermal fluids interpreted to have emanated from the Land’s End Pluton, a large body of Permian S-type granite (Chesley et al. 1993; Simons et al. 2016). Although the granite hosts some mineralisation at Levant, the bulk of the exploited ore was hosted in veins and replacements of wallrock metasediments and greenstones within the aureole of the granite. The mineralised zone exploited by the mine was a volume measuring approximately 2000 × 800 × 200 m with the ore shoots plunging 10–20° to the north-west, under the present-day seafloor (Figure 1). The main economic ore minerals were copper sulphides (chalcocite, chalcopyrite) and cassiterite in a complex paragenesis involving long-lived, multielement metasomatism over a wide temperature range, combined with supergene modifications in near-surface zones (Jackson 1976).
Economic byproducts in copper porphyries: Ag in the Ascutita Cu-porphyry, Romania
Published in Applied Earth Science, 2019
A. E. Eskdale, D. Smith, D. A. Holwell, M. Negulici
This chemical correlation has been obtained from 14 drill holes coordinated by Belevion, then analysed by assaying using an Aqua Regia Digestion and ME-ICP-AES. The unusual relationship between the Cu and Ag in this deposit is the focus of investigation in this study, with particular emphasis on vein paragenesis. Mineralogical analysis reveals that pyrite and chalcopyrite dominate the samples as the main sulphides with repeated replacement of a first-phase chalcopyrite by pyrite observed in reflected light. Chalcopyrite has also been replaced in some instances by other Cu sulphides such as covellite and potentially chalcocite. This relationship is present in all 20 samples collected from the drill holes and therefore indicates at least three phases of sulphides. SEM analyses will subsequently be used to verify the sulphide mineralogy of the samples before laser ablation ICP-MS work is conducted to determine the mineralogical form of the Ag and any spatial or temporal association it has with the Cu to explain the assay correlation.
Solstad, a Co-Se-bearing copper ore in the Västervik quartzites, Sweden
Published in GFF, 2022
Kjell Billström, Johan Söderhielm, Curt Broman, Krister Sundblad
The Solstad copper deposit was a significant producer of copper ore already during the seventeenth century. It is located ca. 20 km south of Västervik and is the southernmost occurrence of this sub-province, located close to the contact between the Västervik quartzites and the 1.8–1.6 Ga Transscandinavian Igneous Belt (TIB; Fig 1A). In spite of its historic importance and high Cu grades, the geological characteristics of the deposit are only briefly documented. The purpose of this contribution is to shed light on this deposit with respect to geological setting, ore mineral paragenesis, fluid inclusions and certain isotope aspects, in order to provide basic information on a key example of this poorly defined metallogenetic ore province.