TY - JOUR
T1 - Porphyry Copper Deposit Formation
T2 - Identifying Garnet and Amphibole Fractionation With REE Pattern Curvature Modeling
AU - Tatnell, Lucas
AU - Anenburg, Michael
AU - Loucks, Robert
N1 - Funding Information:
This study was supported by Australian Research Council Linkage project LP190100785. We thank Nick Barber, Othmar Müntener, Osvaldo Rabbia, and an anonymous reviewer for their comments which allowed us to improve and focus this manuscript, and Quentin Williams for his editorial support. Open access publishing facilitated by Australian National University, as part of the Wiley ‐ Australian National University agreement via the Council of Australian University Librarians.
Funding Information:
This study was supported by Australian Research Council Linkage project LP190100785. We thank Nick Barber, Othmar Müntener, Osvaldo Rabbia, and an anonymous reviewer for their comments which allowed us to improve and focus this manuscript, and Quentin Williams for his editorial support. Open access publishing facilitated by Australian National University, as part of the Wiley - Australian National University agreement via the Council of Australian University Librarians.
Publisher Copyright:
© 2023. The Authors.
PY - 2023/7/28
Y1 - 2023/7/28
N2 - Porphyry copper ore-forming intrusions are distinguished from barren arc magmas by high oxidation state and “adakitic” high Sr/Y and La/Yb. Controversy over petrogenesis of adakites has centered on ambiguities in interpretation of their steep rare earth element (REE) patterns, and on whether garnet participates in their petrogenesis. Lambda (λ) coefficients deconvolute subtle differences in REE pattern curvature, providing a more quantitative method to explore mineral fractionation processes. Here, we use trace element and numerical λ coefficient modeling to assess the relative influence of amphibole, garnet, and plagioclase in the petrogenesis of porphyry ore-forming intrusions. We find that garnet-fractionation trends are not evident in REE patterns of many adakitic porphyry-forming intrusions. Instead, porphyry-forming intrusions in the western Pacific and Eocene porphyry-forming intrusions in northern Chile have REE patterns consistent with a garnet-free, amphibole-dominated cumulate. Traditional element ratios such at Dy/Dy*, LaN/YbN, and DyN/YbN are poor discriminants for garnet or amphibole fractionation.
AB - Porphyry copper ore-forming intrusions are distinguished from barren arc magmas by high oxidation state and “adakitic” high Sr/Y and La/Yb. Controversy over petrogenesis of adakites has centered on ambiguities in interpretation of their steep rare earth element (REE) patterns, and on whether garnet participates in their petrogenesis. Lambda (λ) coefficients deconvolute subtle differences in REE pattern curvature, providing a more quantitative method to explore mineral fractionation processes. Here, we use trace element and numerical λ coefficient modeling to assess the relative influence of amphibole, garnet, and plagioclase in the petrogenesis of porphyry ore-forming intrusions. We find that garnet-fractionation trends are not evident in REE patterns of many adakitic porphyry-forming intrusions. Instead, porphyry-forming intrusions in the western Pacific and Eocene porphyry-forming intrusions in northern Chile have REE patterns consistent with a garnet-free, amphibole-dominated cumulate. Traditional element ratios such at Dy/Dy*, LaN/YbN, and DyN/YbN are poor discriminants for garnet or amphibole fractionation.
UR - http://www.scopus.com/inward/record.url?scp=85165752844&partnerID=8YFLogxK
U2 - 10.1029/2023GL103525
DO - 10.1029/2023GL103525
M3 - Article
AN - SCOPUS:85165752844
SN - 0094-8276
VL - 50
JO - Geophysical Research Letters
JF - Geophysical Research Letters
IS - 14
M1 - e2023GL103525
ER -