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Trace element heterogeneity in molybdenite fingerprints stages of mineralization

journal contribution
posted on 2023-05-17, 21:00 authored by Ciobanu, CL, Cook, NJ, Kelson, CR, Guerin, R, Kalleske, N, Leonid Danyushevsky
Variations in molybdenite trace element chemistry represent a tool for discriminating discrete events in young magmatic-hydrothermal systems and constrain the role of granites in older greenstone belt-hosted gold systems. We show that besides Re and W (typical lattice-bound elements), molybdenite also concentrates chalcophile elements with chalcogenide affinity such as Bi, Pb, and Te (CEs). Elements from the latter group form nano- to micron-scale inclusions which also attract Au and Ag incorporation. High concentration of all elements is attributable to lattice-defects and coherent intergrowths between molybdenite and CE-minerals rather than polytypism. If both groups are used, trace element patterns are useful for interpreting superimposed ore-forming processes. We test the validity of this hypothesis by carrying out Laser-Ablation Inductively-Coupled Mass Spectroscopy spot analysis and element mapping on high-Re molybdenite from the Tertiary Au deposit at Hilltop (NV, USA) and the Archean Boddington Cu-Au deposit (Western Australia). Whereas W and CEs are affected by both deformation and interaction with subsequent fluids, Re is only affected by the latter. An epithermal overprint at Hilltop, recorded in a grain with a CE-rich halo surrounding a core with Re-W oscillatory zoning, upgrades Re content and is also traceable by measurable Au. At Boddington, granite-derived fluids dilute Re in precursor molybdenite, but both granite and orogenic deformation assist CE-mineral coarsening and Au release.

History

Publication title

Chemical Geology

Volume

347

Pagination

175-189

ISSN

0009-2541

Department/School

School of Natural Sciences

Publisher

Elsevier BV

Place of publication

Amsterdam, Netherlands

Rights statement

Copyright 2013 Elsevier B.V.

Repository Status

  • Restricted

Socio-economic Objectives

Mineral exploration not elsewhere classified

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