282 Crustal Petrology, Part II

This session explores various igneous and metamorphic processes that have shaped Earth’s crust. We welcome contributions from the micro- to macroscale, from the deep to shallow crust, and from field- to laboratory- to modeling-based.

Wednesday, 22 October 2025
1:30 PM - 5:30 PM
HBGCC, 216AB

Modeling the effects of water, oxygen fugacity, and differentiation depth on magmatic vectors for porphyry-copper formation

Paper number: 282-10
Program: Technical Sessions
Time: 4:00 PM – 4:15 PM

Authors

Abstract

Porphyry copper deposits (PCDs) are Earth’s primary source of copper, and thus understanding their origin is essential for developing more effective exploration strategies to support the green energy transition. Here, we use phase-equilibrium and trace-element modeling to quantify the effects of H2O, oxygen fugacity (fO2), and differentiation depth on the formation of PCD-forming magmas. We explore how these factors control first-order compositional trends indicative of high PCD-forming potential (Sr/Y vs SiO2 and fO2) to test different models for the ideal amount of H2O and fO2 of PCD-forming magmas. Our findings suggest that initial oxidized conditions (i.e., magmas derived from an oxidized source) are necessary for PCD formation. We show that wet to super-wet magmatism (H2O >4 –8 wt.%) combined with an initially oxidized state better match the required conditions for PCD generation. Importantly, we show that garnet is not a necessary component for PCD formation; amphibole-bearing, garnet-free assemblages can also produce PCD-forming magmas.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412211

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