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Timing of porphyry (Cu-Mo) and base metal (Zn-Pb-Ag-Cu) mineralisation in a magmatic-hydrothermal system—Morococha district, Peru

Catchpole, Honza ; Kouzmanov, Kalin ; Bendezú, Aldo ; Ovtcharova, Maria ; Spikings, Richard ; Stein, Holly ; Fontboté, Lluís

In: Mineralium Deposita, 2015, vol. 50, no. 8, p. 895-922

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    Titre
    • Timing of porphyry (Cu-Mo) and base metal (Zn-Pb-Ag-Cu) mineralisation in a magmatic-hydrothermal system—Morococha district, Peru
    Auteur
    • Catchpole, Honza. Department of Earth and Environmental Sciences, University of Geneva, Rue des Maraîchers 13, 1205, Geneva, Switzerland
    • Kouzmanov, Kalin. Department of Earth and Environmental Sciences, University of Geneva, Rue des Maraîchers 13, 1205, Geneva, Switzerland
    • Bendezú, Aldo. Department of Earth and Environmental Sciences, University of Geneva, Rue des Maraîchers 13, 1205, Geneva, Switzerland
    • Ovtcharova, Maria. Department of Earth and Environmental Sciences, University of Geneva, Rue des Maraîchers 13, 1205, Geneva, Switzerland
    • Spikings, Richard. Department of Earth and Environmental Sciences, University of Geneva, Rue des Maraîchers 13, 1205, Geneva, Switzerland
    • Stein, Holly. AIRIE Program, Department of Geosciences, Colorado State University, 80523-1482, Fort Collins, CO, USA
    • Fontboté, Lluís. Department of Earth and Environmental Sciences, University of Geneva, Rue des Maraîchers 13, 1205, Geneva, Switzerland
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • Mineralium Deposita, 2015, vol. 50, no. 8, p. 895-922. Springer Berlin Heidelberg
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:331265
    Summary
    The Morococha district in central Peru is characterised by economically important Cordilleran polymetallic (Zn-Pb-Ag-Cu) vein and replacement bodies and the large Toromocho porphyry Cu-Mo deposit in its centre. U-Pb, Re-Os, and 40Ar/39Ar geochronology data for various porphyry-related hydrothermal mineralisation styles record a 3.5-Ma multi-stage history of magmatic-hydrothermal activity in the district. In the late Miocene, three individual magmatic-hydrothermal centres were active: the Codiciada, Toromocho, and Ticlio centres, each separated in time and space. The Codiciada centre is the oldest magmatic-hydrothermal system in the district and consists of a composite porphyry stock associated with anhydrous skarn and quartz-molybdenite veins. The hydrothermal events are recorded by a titanite U-Pb age at 9.3 ± 0.2Ma and a molybdenite Re-Os age at 9.26 ± 0.03Ma. These ages are indistinguishable from zircon U-Pb ages for porphyry intrusions of the composite stock and indicate a time span of 0.2Ma for magmatic-hydrothermal activity. The small Ticlio magmatic-hydrothermal centre in the west of the district has a maximum duration of 0.3Ma, ranging from porphyry emplacement to porphyry mineralisation at 8.04 ± 0.14Ma (40Ar/39Ar muscovite cooling age). The Toromocho magmatic-hydrothermal centre has a minimum of five recorded porphyry intrusions that span a total of 1.3Ma and is responsible for the formation of the giant Toromocho Cu-Mo deposit. At least two hydrothermal pulses are identified. Post-dating a first pulse of molybdenite mineralisation, wide-spread hydrous skarn covers an area of over 6km2 and is recorded by five 40Ar/39Ar cooling ages at 7.2-6.8Ma. These ages mark the end of the slowly cooling and long-lived Toromocho magmatic-hydrothermal centre soon after last magmatic activity at 7.26 ± 0.02Ma. District-wide (50km2) Cordilleran base metal vein and replacement bodies post-date the youngest recorded porphyry mineralisation event at Toromocho by more than 0.5Ma. Polymetallic veins (5.78 ± 0.10 and 5.72 ± 0.18Ma; 40Ar/39Ar ages) and the Manto Italia polymetallic replacement bodies (6.23 ± 0.12 and 6.0 ± 0.2Ma; 40Ar/39Ar ages) are interpreted to have been formed by a single hydrothermal pulse. Hydrothermal activity ceased after the formation of the base metal vein and replacement bodies. Overlapping monazite U-Pb (8.26 ± 0.18Ma) and muscovite 40Ar/39Ar ages (8.1 ± 0.5Ma) from the early base metal stage of one Cordilleran vein sample in the Sulfurosa area provide evidence that a discrete hydrothermal pulse was responsible for polymetallic vein formation 2.6Ma prior to the district-wide polymetallic veins. These ages pre-date those of Toromocho porphyry Cu-Mo formation and show that Zn-Pb-Ag-Cu mineralisation formed during several discrete magmatic-hydrothermal pulses in the same district.