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Characteristics of Cu isotopes from chalcopyrite-rich black smoker chimneys at Brothers volcano, Kermadec arc, and Niuatahi volcano, Lau basin

Citation

Berkenbosch, HA and de Ronde, CEJ and Paul, BT and Gemmell, JB, Characteristics of Cu isotopes from chalcopyrite-rich black smoker chimneys at Brothers volcano, Kermadec arc, and Niuatahi volcano, Lau basin, Mineralium Deposita, 50, (7) pp. 811-824. ISSN 0026-4598 (2015) [Refereed Article]

Copyright Statement

Copyright 2015 Springer-Verlag Berlin Heidelberg

DOI: doi:10.1007/s00126-014-0571-y

Abstract

We analysed primary chalcopyrite from modern seafloor ‘black smoker’ chimneys to investigate high-temperature hydrothermal Cu isotope fractionation unaffected by metamorphism. Samples came from nine chimneys collected from Brothers volcano, Kermadec arc, and Niuatahi volcano, Lau backarc basin. This is the first known study of Cu isotopes from submarine intraoceanic arc/backarc volcanoes, with both volcanoes discharging significant amounts of magmatic volatiles. Our results (n = 22) range from δ65Cu = −0.03 to 1.44 ± 0.18 ‰ (2 sd), with the majority of samples between ∼0.00 and 0.50 ‰. We interpret this cluster (n = 17) of lower δ65Cu values as representing a mantle source for the chimney Cu, in agreement with δ65Cu values for mantle rocks. The few higher δ65Cu values (>0.90 ‰) occur (1) within the same chimneys as lower values, (2) randomly distributed within the chimneys (i.e. near the top and bottom, interior and exterior), and (3) within chalcopyrite of approximately the same age (<1 year). This suggests the higher δ65Cu values are not related to oxidation by mixing with ambient seawater, but to isotopic variation within the vent fluids over a relatively short time. Theoretical studies demonstrate significant isotopic fractionation can occur between aqueous and vapourous complexing species. When combined with evidence for periodic release of magmatic volatiles at Brothers, we believe vapour transport of Cu is responsible for the observed isotopic fractionation. When compared to global δ65Cu data for primary chalcopyrite, volcanic arc chimneys are most similar to porphyry copper deposits that also form from magmatic-hydrothermal processes in convergent tectonic settings.

Item Details

Item Type:Refereed Article
Keywords:copper isotopes, black smokers, Brothers volcano, Kermadec arc
Research Division:Earth Sciences
Research Group:Geology
Research Field:Ore Deposit Petrology
Objective Division:Mineral Resources (excl. Energy Resources)
Objective Group:Mineral Exploration
Objective Field:Copper Ore Exploration
Author:Berkenbosch, HA (Ms Heidi Berkenbosch)
Author:Gemmell, JB (Professor Bruce Gemmell)
ID Code:98442
Year Published:2015
Funding Support:Australian Research Council (CE0561595)
Web of Science® Times Cited:1
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2015-02-16
Last Modified:2017-10-24
Downloads:0

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