Distribution of porphyry copper deposits along the western Tethyan and Andean subduction zones: Insights from a paleotectonic approach |
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| Affiliation: | 1. Geological Institute of Romania, Department of Regional and Economic Geology, 1 Caransebeş St., 01271 Bucharest, Romania;2. University of the Witwatersrand, School of Geosciences, 1 Ian Smuts St., Braamfontein 2000, Johannesburg, South Africa;3. State Key Lab of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;4. Rhodes University, Department of Geology, Artillery Road, 6140 Grahamstown, South Africa;1. State Key Laboratory of Geological Processes and Mineral Resources, and School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;2. State Key Laboratory of Geological Processes and Mineral Resources, and Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China;1. Department of Earth Sciences, University of Geneva, Rue des Maraîchers 13, 1205 Geneva, Switzerland;2. Institute of Geological Sciences, National Academy of the Republic of Armenia, Baghramyan Avenue 24, 0019 Yerevan, Armenia;3. Geological Department, Baku State University, Z. Khalilov St. 23, Az1145 Baku, Azerbaijan;4. Department of Earth Sciences, University of Durham, DH1 3LE United Kingdom;5. Institute of Earth Sciences, University of Lausanne, Géopolis, 1015 Lausanne, Switzerland;1. Department of Geology, Payame Noor University, Iran;2. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, People''s Republic of China |
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| Abstract: | Along the western Tethyan and Andean subduction zones the distribution of Cretaceous and Cenozoic porphyry Cu deposits is not random and shows that they were emplaced in distinct regional clusters. To understand the appearance of these clusters within their geodynamical contexts and identify kinematic features which would favor the genesis of porphyry-type ore bodies, we use a paleotectonic approach. Two clusters in the Aegean-Balkan-Carpathian area, which were emplaced in upper Cretaceous and Oligo-Miocene, and two others in the Andes, which were emplaced in late Eocene and Miocene, are sufficiently well constrained to be studied in detail. It appears that they are associated with a specific polyphased kinematic context related to the convergence of tectonic plates. This context is characterized by: 1) a relatively fast convergence rate shortly followed by 2) a drastic decrease of this rate. From these observations, and assuming that the major part of plate convergence is accommodated along subduction zones, we propose a two-phase geodynamic model favoring emplacement of porphyry Cu deposits: 1) a high melt production in the mantle wedge, followed by 2) an extensional regime (or at least relaxation of the compressional stress) in the upper plate, promoting ascension of fertile magmas to the upper crust. Melt production at depth and the following extensional regime, which would be related to variations in convergence rate, are thus associated with variations in plate and trench velocities, themselves being controlled by both plate kinematics at the surface and slab dynamics in the upper mantle. In particular, along-strike folding behavior of the subducting slab may strongly influence trench velocity changes and the location of porphyry Cu deposits. Metallogenic data suggest that periods of slab retreat, which would favor mineralization processes during ~ 40 Myrs, would be separated by barren periods lasting ~ 10 to 20 Myrs, corresponding to shorter episodes of trench advance, as observed in laboratory experiments. These results confirm the control of the geodynamic context, and especially subduction dynamics, on the genesis of porphyry Cu deposits. This study also shows that the paleotectonic approach is a promising tool that could help identify geodynamic and tectonic criteria favoring the genesis of various ore deposits. |
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