Giant Porphyry Copper Deposits Caused by a Slab Jamming in the Mantle Transition Zone

Nipaporn Nakrong; Marnie Forster; Wim Spakman; Hielke Jelsma; Francois Gaboury; Gordon Lister

doi:10.1111/ter.70018

Giant Porphyry Copper Deposits Caused by a Slab Jamming in the Mantle Transition Zone

Nipaporn Nakrong^*, Marnie Forster, Wim Spakman, Hielke Jelsma, Francois Gaboury, Gordon Lister

^*Corresponding author for this work

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

Two giant porphyry copper deposits in the Southern Central Andes formed during the Miocene–Pliocene transition when a bend in the subducting Juan de Fernández hotspot chain jammed in the mantle transition zone, causing mega-scale slab-kinking. This geometry implies mechanical resistance that caused East–West compression and eventually a thrust-mode failure in a now flattened slab segment at depth. The geometric incompatibility of the kinking zone, compared to the subducting slab adjacent, caused transverse, down-dip slab tears parallel to (but not coincident with) the Juan de Fernández Ridge. One torn flat slab segment acted as a trapdoor, which opened, gaped, and then detached. The largest copper deposits formed along the prolongation of the trapdoor tear, where it intersected tears at the southern edge of the flat slab kink segment. Fluid rising from the sinking slablet beneath escaped for only a limited period before the slab gape was over-ridden by ongoing subduction.

Original language	English
Journal	Terra Nova
DOIs	https://doi.org/10.1111/ter.70018
Publication status	E-pub ahead of print - 31 Oct 2025

Bibliographical note

Publisher Copyright:
© 2025 The Author(s). Terra Nova published by John Wiley & Sons Ltd.

Funding

This research resulted from the TEAR project funded by Anglo American and AngloGold Ashanti, initially at the Australian National University (ANU). Nipaporn Nakrong was supported by a Royal Thai Government Scholarship and a supplementary scholarship from ANU. We are indebted to additional support provided by Anglo American during the pandemic, and to Gem Midgley for her help with the Geoscience ANALYST software. Fangqin Chen contributed to the concept of slab jamming during the earlier stages of her PhD research. Anonymous reviewers are thanked for constructive suggestions. Carlo Doglioni and Vincenzo Stagno handled the manuscript.

Funders
Anglo American
AngloGold Ashanti, initially at the Australian National University (ANU)
Royal Thai Government Scholarship
ANU

Keywords

3D+time tectonic reconstruction
flat slab subduction
porphyry copper deposits
slab jamming

Access to Document

10.1111/ter.70018Licence: CC BY-NC

Cite this

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abstract = "Two giant porphyry copper deposits in the Southern Central Andes formed during the Miocene–Pliocene transition when a bend in the subducting Juan de Fern{\'a}ndez hotspot chain jammed in the mantle transition zone, causing mega-scale slab-kinking. This geometry implies mechanical resistance that caused East–West compression and eventually a thrust-mode failure in a now flattened slab segment at depth. The geometric incompatibility of the kinking zone, compared to the subducting slab adjacent, caused transverse, down-dip slab tears parallel to (but not coincident with) the Juan de Fern{\'a}ndez Ridge. One torn flat slab segment acted as a trapdoor, which opened, gaped, and then detached. The largest copper deposits formed along the prolongation of the trapdoor tear, where it intersected tears at the southern edge of the flat slab kink segment. Fluid rising from the sinking slablet beneath escaped for only a limited period before the slab gape was over-ridden by ongoing subduction.",

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AU - Jelsma, Hielke

AU - Gaboury, Francois

AU - Lister, Gordon

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N2 - Two giant porphyry copper deposits in the Southern Central Andes formed during the Miocene–Pliocene transition when a bend in the subducting Juan de Fernández hotspot chain jammed in the mantle transition zone, causing mega-scale slab-kinking. This geometry implies mechanical resistance that caused East–West compression and eventually a thrust-mode failure in a now flattened slab segment at depth. The geometric incompatibility of the kinking zone, compared to the subducting slab adjacent, caused transverse, down-dip slab tears parallel to (but not coincident with) the Juan de Fernández Ridge. One torn flat slab segment acted as a trapdoor, which opened, gaped, and then detached. The largest copper deposits formed along the prolongation of the trapdoor tear, where it intersected tears at the southern edge of the flat slab kink segment. Fluid rising from the sinking slablet beneath escaped for only a limited period before the slab gape was over-ridden by ongoing subduction.

AB - Two giant porphyry copper deposits in the Southern Central Andes formed during the Miocene–Pliocene transition when a bend in the subducting Juan de Fernández hotspot chain jammed in the mantle transition zone, causing mega-scale slab-kinking. This geometry implies mechanical resistance that caused East–West compression and eventually a thrust-mode failure in a now flattened slab segment at depth. The geometric incompatibility of the kinking zone, compared to the subducting slab adjacent, caused transverse, down-dip slab tears parallel to (but not coincident with) the Juan de Fernández Ridge. One torn flat slab segment acted as a trapdoor, which opened, gaped, and then detached. The largest copper deposits formed along the prolongation of the trapdoor tear, where it intersected tears at the southern edge of the flat slab kink segment. Fluid rising from the sinking slablet beneath escaped for only a limited period before the slab gape was over-ridden by ongoing subduction.

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Giant Porphyry Copper Deposits Caused by a Slab Jamming in the Mantle Transition Zone

Abstract

Bibliographical note

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Keywords

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