Successive geothermal, volcanic-hydrothermal and contact-metasomatic events in Cenozoic volcanic-arc basalts, South Shetland Islands, Antarctica
Hydrothermal alteration in volcanic arcs occurs in many settings and may involve magmatic, marine, lacustrine or groundwaters, driven by magmatic, tectonic or thermal events. King George Island, part of the South Shetland Island Cenozoic volcanic arc, contains an 80 km long zone of propylitized volc...
Published in: | Geological Magazine |
---|---|
Main Authors: | , |
Format: | Article in Journal/Newspaper |
Language: | unknown |
Published: |
Cambridge University Press
2002
|
Subjects: | |
Online Access: | http://nora.nerc.ac.uk/id/eprint/17518/ http://journals.cambridge.org/action/displayFulltext?type=1&fid=113762&jid=GEO&volumeId=139&issueId=02&aid=113761 |
id |
ftnerc:oai:nora.nerc.ac.uk:17518 |
---|---|
record_format |
openpolar |
spelling |
ftnerc:oai:nora.nerc.ac.uk:17518 2023-05-15T13:45:12+02:00 Successive geothermal, volcanic-hydrothermal and contact-metasomatic events in Cenozoic volcanic-arc basalts, South Shetland Islands, Antarctica Willan, Robert C.R. Armstrong, Debbie C. 2002 http://nora.nerc.ac.uk/id/eprint/17518/ http://journals.cambridge.org/action/displayFulltext?type=1&fid=113762&jid=GEO&volumeId=139&issueId=02&aid=113761 unknown Cambridge University Press Willan, Robert C.R.; Armstrong, Debbie C. 2002 Successive geothermal, volcanic-hydrothermal and contact-metasomatic events in Cenozoic volcanic-arc basalts, South Shetland Islands, Antarctica. Geological Magazine, 139 (2). 209231. https://doi.org/10.1017/S0016756802006301 <https://doi.org/10.1017/S0016756802006301> Publication - Article PeerReviewed 2002 ftnerc https://doi.org/10.1017/S0016756802006301 2023-02-04T19:31:09Z Hydrothermal alteration in volcanic arcs occurs in many settings and may involve magmatic, marine, lacustrine or groundwaters, driven by magmatic, tectonic or thermal events. King George Island, part of the South Shetland Island Cenozoic volcanic arc, contains an 80 km long zone of propylitized volcanic rocks, with numerous occurrences of quartz veining, silicic, sericitic, argillic and advanced-argillic alteration. On Barton Peninsula, a basaltic lava sequence (49–44 Ma) intruded by a small, high-level granodiorite pluton (~ 42 Ma), contains these alteration types, previously interpreted as a single porphyry-copper system. In this study, we report three, possibly four, distinct fossil hydrothermal episodes. (1) Banded chalcedonic quartz, quartz-sericite and propylitic alteration occurs along ESE faults and as reworked clasts in nearby tuffs. Drusy quartz + calcite veins with silicic/sericitic, argillic and propylitic wallrocks may represent feeders to the near-surface silicification. These characteristics, and anomalous Ag + Pb + Sb + Au plus Te + Se + Zn + As, suggest a neutralpH geothermal system that was active during volcanism. (2) The lavas and banded-quartz rocks were brecciated, veined and replaced by alunite + native sulphur + pyrite, and pyrophyllite + quartz + pyrite + zunyite + diaspore assemblages with anomalous Hg + Se + As + Bi + Au + Tl + Sb + Cu. Such advanced-argillic alteration is diagnostic of degassing of a felsic magma into shallow (< 500 m) meteoric groundwaters. Rhyolite tuffs, previously not reported on King George Island, may represent leakage of this magma to the surface. (3) Subsequent burial to ~ 3 km was followed by emplacement of a granodiorite pluton and formation of a silicic contact-metasomatic aureole containing muscovite, biotite, actinolite, magnetite, K-feldspar and tourmaline. Disseminated andalusite + corundum also formed in areas previously affected by the advanced-argillic alteration. Iron/copper-sulphide veinlets are locally abundant, but a porphyry-style geochemical ... Article in Journal/Newspaper Antarc* Antarctica King George Island South Shetland Islands Natural Environment Research Council: NERC Open Research Archive Barton ENVELOPE(-58.733,-58.733,-62.233,-62.233) Barton Peninsula ENVELOPE(-58.741,-58.741,-62.227,-62.227) King George Island South Shetland Islands Geological Magazine 139 2 209 231 |
institution |
Open Polar |
collection |
Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
unknown |
description |
Hydrothermal alteration in volcanic arcs occurs in many settings and may involve magmatic, marine, lacustrine or groundwaters, driven by magmatic, tectonic or thermal events. King George Island, part of the South Shetland Island Cenozoic volcanic arc, contains an 80 km long zone of propylitized volcanic rocks, with numerous occurrences of quartz veining, silicic, sericitic, argillic and advanced-argillic alteration. On Barton Peninsula, a basaltic lava sequence (49–44 Ma) intruded by a small, high-level granodiorite pluton (~ 42 Ma), contains these alteration types, previously interpreted as a single porphyry-copper system. In this study, we report three, possibly four, distinct fossil hydrothermal episodes. (1) Banded chalcedonic quartz, quartz-sericite and propylitic alteration occurs along ESE faults and as reworked clasts in nearby tuffs. Drusy quartz + calcite veins with silicic/sericitic, argillic and propylitic wallrocks may represent feeders to the near-surface silicification. These characteristics, and anomalous Ag + Pb + Sb + Au plus Te + Se + Zn + As, suggest a neutralpH geothermal system that was active during volcanism. (2) The lavas and banded-quartz rocks were brecciated, veined and replaced by alunite + native sulphur + pyrite, and pyrophyllite + quartz + pyrite + zunyite + diaspore assemblages with anomalous Hg + Se + As + Bi + Au + Tl + Sb + Cu. Such advanced-argillic alteration is diagnostic of degassing of a felsic magma into shallow (< 500 m) meteoric groundwaters. Rhyolite tuffs, previously not reported on King George Island, may represent leakage of this magma to the surface. (3) Subsequent burial to ~ 3 km was followed by emplacement of a granodiorite pluton and formation of a silicic contact-metasomatic aureole containing muscovite, biotite, actinolite, magnetite, K-feldspar and tourmaline. Disseminated andalusite + corundum also formed in areas previously affected by the advanced-argillic alteration. Iron/copper-sulphide veinlets are locally abundant, but a porphyry-style geochemical ... |
format |
Article in Journal/Newspaper |
author |
Willan, Robert C.R. Armstrong, Debbie C. |
spellingShingle |
Willan, Robert C.R. Armstrong, Debbie C. Successive geothermal, volcanic-hydrothermal and contact-metasomatic events in Cenozoic volcanic-arc basalts, South Shetland Islands, Antarctica |
author_facet |
Willan, Robert C.R. Armstrong, Debbie C. |
author_sort |
Willan, Robert C.R. |
title |
Successive geothermal, volcanic-hydrothermal and contact-metasomatic events in Cenozoic volcanic-arc basalts, South Shetland Islands, Antarctica |
title_short |
Successive geothermal, volcanic-hydrothermal and contact-metasomatic events in Cenozoic volcanic-arc basalts, South Shetland Islands, Antarctica |
title_full |
Successive geothermal, volcanic-hydrothermal and contact-metasomatic events in Cenozoic volcanic-arc basalts, South Shetland Islands, Antarctica |
title_fullStr |
Successive geothermal, volcanic-hydrothermal and contact-metasomatic events in Cenozoic volcanic-arc basalts, South Shetland Islands, Antarctica |
title_full_unstemmed |
Successive geothermal, volcanic-hydrothermal and contact-metasomatic events in Cenozoic volcanic-arc basalts, South Shetland Islands, Antarctica |
title_sort |
successive geothermal, volcanic-hydrothermal and contact-metasomatic events in cenozoic volcanic-arc basalts, south shetland islands, antarctica |
publisher |
Cambridge University Press |
publishDate |
2002 |
url |
http://nora.nerc.ac.uk/id/eprint/17518/ http://journals.cambridge.org/action/displayFulltext?type=1&fid=113762&jid=GEO&volumeId=139&issueId=02&aid=113761 |
long_lat |
ENVELOPE(-58.733,-58.733,-62.233,-62.233) ENVELOPE(-58.741,-58.741,-62.227,-62.227) |
geographic |
Barton Barton Peninsula King George Island South Shetland Islands |
geographic_facet |
Barton Barton Peninsula King George Island South Shetland Islands |
genre |
Antarc* Antarctica King George Island South Shetland Islands |
genre_facet |
Antarc* Antarctica King George Island South Shetland Islands |
op_relation |
Willan, Robert C.R.; Armstrong, Debbie C. 2002 Successive geothermal, volcanic-hydrothermal and contact-metasomatic events in Cenozoic volcanic-arc basalts, South Shetland Islands, Antarctica. Geological Magazine, 139 (2). 209231. https://doi.org/10.1017/S0016756802006301 <https://doi.org/10.1017/S0016756802006301> |
op_doi |
https://doi.org/10.1017/S0016756802006301 |
container_title |
Geological Magazine |
container_volume |
139 |
container_issue |
2 |
container_start_page |
209 |
op_container_end_page |
231 |
_version_ |
1766216353501413376 |