Porphyry copper formation driven by water-fluxed crustal melting during flat-slab subduction
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
The prevailing view of the formation of porphyry copper deposits along convergent plate boundaries involves deep crustal differentiation of metal-bearing juvenile magmas derived from the mantle wedge above a subduction zone. However, many major porphyry districts formed during periods of flat-slab subduction when the mantle wedge would have been reduced or absent, leaving the source of the ore-forming magmas unclear. Here we use geochronology and thermobarometry to investigate deep crustal processes during the genesis of the Late Cretaceous–Palaeocene Laramide Porphyry Province in Arizona, which formed during flat-slab subduction of the Farallon Plate beneath North America. We show that the isotopic signatures of Laramide granitic rocks are consistent with a Proterozoic crustal source that was potentially pre-enriched in copper. This source underwent water-fluxed melting between 73 and 60 Ma, coincident with the peak of granitic magmatism (78–50 Ma), porphyry genesis (73–56 Ma) and flat-slab subduction (70–40 Ma). To explain the formation of the Laramide Porphyry Province, we propose that volatiles derived from the leading edge of the Farallon flat slab promoted melting of both mafic and felsic pre-enriched lower crust, without requiring extensive magmatic or metallogenic input from the mantle wedge. Other convergent plate boundaries with flat-slab regimes may undergo a similar mechanism of volatile-mediated lower-crustal melting.
Date Issued
2024-12-01
Date Acceptance
2024-09-24
Citation
Nature Geoscience, 2024, 17 (12)
ISSN
1752-0894
Publisher
Nature Research
Journal / Book Title
Nature Geoscience
Volume
17
Issue
12
Copyright Statement
© The Author(s) 2024 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
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Subjects
ARIZONA INSIGHTS
FARALLON SLAB
Geology
Geosciences, Multidisciplinary
LARAMIDE OROGENY
MAFIC XENOLITHS
OROCOPIA SCHIST
Physical Sciences
RE-OS
Science & Technology
SULFIDE MINERALS
TECTONIC EVOLUTION
U-PB GEOCHRONOLOGY
WESTERN UNITED-STATES
Publication Status
Published
Date Publish Online
2024-11-04