Molybdenite Mineralization and Re-Os Geochronology of the Escondida and Escondida Norte Porphyry Deposits, Northern Chile

Bárbara Romero, Shoji Kojima, Chilong Wong, Fernando Barra, Walter Véliz, Joaquin Ruiz

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

Molybdenum is an economically important subproduct of North Chilean porphyry-type deposits, and thus spatial and temporal distribution of molybdenite as the primary Mo-bearing mineral in the Escondida and Escondida Norte deposits were characterized using several mineralogical and chemical techniques and the Re-Os dating method. Molybdenum is distributed extensively in the two deposits, and high molybdenum concentrations (>500 ppm) are recognized particularly in the chlorite-sericite transitional zone between the potassic and sericitic zones. Two modes of occurrence of molybdenite are observed in the Escondida deposit: aggregates with Cu-Fe-sulfide minerals in fine veinlets (sulfide-veinlet type), and monomineralic microveinlets associated with NE-trending faults. The former and the latter yielded ages of 36.1 ± 0.2 Ma and 35.2 ± 0.2 Ma, respectively. Re-Os dating of Escondida Norte molybdenites also show two distinct episodes, at 37.7 ± 0.3 Ma and a younger episode at 36.6 ± 0.2 Ma. These data indicate that the Escondida Norte is older than the main Escondida deposit. The Re-Os age data combined with those of the porphyry emplacement suggest that the molybdenite mineralization in the Escondida district occurred as several short episodic pulses during the late-magmatic to hydrothermal transition, and that the Cu-Mo deposits were formed in a variable overall period spanning 1 to 5 m.y.

Original languageEnglish (US)
Pages (from-to)91-100
Number of pages10
JournalResource Geology
Volume61
Issue number1
DOIs
StatePublished - Jan 2011

Keywords

  • Chile
  • Escondida district
  • Molybdenite mineralization
  • Porphyry-type deposits
  • Re-Os geochronology

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

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