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Geochemistry of Porphyry Deposits

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posted on 2023-05-22, 15:39 authored by David CookeDavid Cooke, Hollings, P, Jamie Wilkinson, Tosdal, RM

Porphyry ore deposits typically form in convergent plate margin or postsubduction settings at depths of 1-6 km. Oxidized hydrous melts derived from the metasomatized mantle wedge transport Cu, Au, Mo, and other metals to upper-crustal magma chambers. Ponding and release of these magmas is promoted by transient compressional events that perturb steady-state subduction processes, such as the subduction of aseismic ridges or oceanic plateaus. Fractional crystallization leads to repeated cycles of volatile exsolution, vein stockwork formation, and hydrothermal brecciation within and above the mineralizing intrusions. Radiometric dating provides evidence for multiple mineralizing episodes over several million years in some deposits and durations of less than a few hundred thousand years for magmatism and mineralization in others.

Metals are transported by high-temperature brines, vapors, or vapor-like supercritical fluids, depending on local confining pressures. Ore deposition may occur due to decreasing temperature, decreasing pressure, sulfate reduction, water-rock interaction, SO2(g) disproportionation, condensation, or combinations thereof. Stable isotopic data indicate a predominance of magmatically derived sulfur, oxygen, deuterium, copper, iron, and molybdenum in the mineralized core of many porphyry deposits. Lead isotopes provide insights into crustal assimilation processes where there are significant differences in the isotopic compositions of local crustal and mantle sources of Pb.

Funding

Australian Research Council

AMIRA International Ltd

ARC C of E Industry Partner $ to be allocated

Anglo American Exploration Philippines Inc

AngloGold Ashanti Australia Limited

Australian National University

BHP Billiton Ltd

Barrick (Australia Pacific) PTY Limited

CSIRO Earth Science & Resource Engineering

Mineral Resources Tasmania

Minerals Council of Australia

Newcrest Mining Limited

Newmont Australia Ltd

Oz Minerals Australia Limited

Rio Tinto Exploration

St Barbara Limited

Teck Cominco Limited

University of Melbourne

University of Queensland

Zinifex Australia Ltd

History

Publication title

Treatise on Geochemistry

Volume

13

Edition

2nd

Editors

H Holland, K Turekian

Pagination

357-381

ISBN

978-0-08-098300-4

Department/School

School of Natural Sciences

Publisher

Elsevier

Place of publication

Italy

Extent

270

Rights statement

Copyright 2014 Elsevier Ltd.

Repository Status

  • Restricted

Socio-economic Objectives

Copper ore exploration

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