Hydrothermal alteration within the Brothers submarine arc volcano, Kermadec arc, New Zealand
Hydrothermal alteration within the Brothers submarine arc volcano, Kermadec arc, New Zealand
The hydrothermally active Brothers volcano on the Kermadec arc, New Zealand, hosts two geochemically distinct hydrothermal systems within a single caldera. At the NW Caldera, metal-sulfide–rich black smoker spires form on the caldera wall. In contrast, Fe-rich crusts and native sulfur-rich chimneys occur at the resurgent central Upper Cone. Previous studies have revealed that the contrasting styles of hydrothermalism relate to the variable contribution of magmatic volatiles between these sites, with the Upper Cone experiencing relatively higher amounts of magmatic volatile influx. We present results of a study of the hydrothermal alteration within Brothers volcano based on core samples to a depth of 453 meters below sea floor (mbsf) from both the Upper Cone (Site U5128) and NW Caldera sites (Site U1527 and U1530), drilled by the International Ocean Discovery Program. The dacitic to rhyolitic breccias that make up the volcano are variably altered to alteration mineral assemblages consisting of chlorite + quartz, illite + pyrophyllite, natroalunite + pyrophyllite, and smectite-rich assemblages. The distribution and textures of the alteration minerals within and between different sites at Brothers volcano reflect variations in temperature, fluid pH, and fluid flux. We find that natroalunite only occurs at the Upper Cone, while alteration at the NW Caldera is more diverse and is characterized by both chlorite and pyrophyllite-rich alteration, indicating that seawater-derived hydrothermal fluids overprinted earlier magmatic volatile-influenced alteration. Our data indicate that in magmatic volatile-dominated systems, the alteration mineralogy transitions from natroalunite to pyrophyllite-rich with increasing age or maturity. This is accompanied by a distinct change in sample texture from dominantly bleached selvages to a more massive, equigranular texture.
1657-1679
Martin, Andrew J.
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Jamieson, John W.
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de Ronde, Cornel E.j.
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Humphris, Susan E.
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Roberts, Stephen
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Macleod, Christopher J.
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Cai, Yuanfeng
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Zhang, Chao
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Schlicht, Lucy E.M.
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Nozaki, Tatsuo
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1 November 2023
Martin, Andrew J.
1ede8446-8618-42f3-85b1-21114c022785
Jamieson, John W.
53789c5f-d9ae-4389-9dfe-7ddfa9c90cb8
de Ronde, Cornel E.j.
b6e8fa3b-0dd8-43c1-a066-a9c603e52bde
Humphris, Susan E.
95e5c49e-1c3b-4e9d-9e9b-bc82419f2df0
Roberts, Stephen
f095c7ab-a37b-4064-8a41-ae4820832856
Macleod, Christopher J.
bee8897a-df69-460c-8a8f-21b753182f5b
Cai, Yuanfeng
25140220-8e25-4339-ad41-06cd0a3e343c
Zhang, Chao
275a6acd-9b7c-4c10-b894-2085af9ecd7c
Schlicht, Lucy E.M.
c0a1f7b5-c5f7-4d3b-89cc-cdc756885f18
Nozaki, Tatsuo
72088ad3-6a8e-44b5-8192-968b3530a545
Martin, Andrew J., Jamieson, John W., de Ronde, Cornel E.j., Humphris, Susan E., Roberts, Stephen, Macleod, Christopher J., Cai, Yuanfeng, Zhang, Chao, Schlicht, Lucy E.M. and Nozaki, Tatsuo
(2023)
Hydrothermal alteration within the Brothers submarine arc volcano, Kermadec arc, New Zealand.
Economic Geology, 118 (7), .
(doi:10.5382/econgeo.4962).
Abstract
The hydrothermally active Brothers volcano on the Kermadec arc, New Zealand, hosts two geochemically distinct hydrothermal systems within a single caldera. At the NW Caldera, metal-sulfide–rich black smoker spires form on the caldera wall. In contrast, Fe-rich crusts and native sulfur-rich chimneys occur at the resurgent central Upper Cone. Previous studies have revealed that the contrasting styles of hydrothermalism relate to the variable contribution of magmatic volatiles between these sites, with the Upper Cone experiencing relatively higher amounts of magmatic volatile influx. We present results of a study of the hydrothermal alteration within Brothers volcano based on core samples to a depth of 453 meters below sea floor (mbsf) from both the Upper Cone (Site U5128) and NW Caldera sites (Site U1527 and U1530), drilled by the International Ocean Discovery Program. The dacitic to rhyolitic breccias that make up the volcano are variably altered to alteration mineral assemblages consisting of chlorite + quartz, illite + pyrophyllite, natroalunite + pyrophyllite, and smectite-rich assemblages. The distribution and textures of the alteration minerals within and between different sites at Brothers volcano reflect variations in temperature, fluid pH, and fluid flux. We find that natroalunite only occurs at the Upper Cone, while alteration at the NW Caldera is more diverse and is characterized by both chlorite and pyrophyllite-rich alteration, indicating that seawater-derived hydrothermal fluids overprinted earlier magmatic volatile-influenced alteration. Our data indicate that in magmatic volatile-dominated systems, the alteration mineralogy transitions from natroalunite to pyrophyllite-rich with increasing age or maturity. This is accompanied by a distinct change in sample texture from dominantly bleached selvages to a more massive, equigranular texture.
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e-pub ahead of print date: 14 July 2022
Published date: 1 November 2023
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Funding Information:
This research used samples and data provided by the International Ocean Discovery Program (IODP). We thank the crew and technical staff aboard the D/V JOIDES Resolution during Expedition 376, “Brothers Arc Flux,” May–July 5th, 2018. A.J.M. and C.J.M. acknowledge the support of the National Environmental Research Council grant NE/ S006214/1. C.E.J. de Ronde acknowledges funding from the Ministry of Business, Innovation and Employment of the New Zealand Government. J.W.J. acknowledges the support of the Canadian Research Chair program. We thank Duncan Muir for his assistance during SEM analysis and Anthony Oldroyd for assistance during XRD analysis. We thank C.G.C. Patten, I. Pitcairn, and guest editor T.W. Höfig for their constructive reviews that helped to improve the quality of this manuscript.
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Local EPrints ID: 486068
URI: http://eprints.soton.ac.uk/id/eprint/486068
ISSN: 0361-0128
PURE UUID: e126eedb-b47c-46c7-bdb9-cf1faa21a78c
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Date deposited: 08 Jan 2024 17:41
Last modified: 18 Mar 2024 02:36
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Contributors
Author:
Andrew J. Martin
Author:
John W. Jamieson
Author:
Cornel E.j. de Ronde
Author:
Susan E. Humphris
Author:
Christopher J. Macleod
Author:
Yuanfeng Cai
Author:
Chao Zhang
Author:
Lucy E.M. Schlicht
Author:
Tatsuo Nozaki
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