Origin of Silicic Magmatism at the Katla Volcano, South Iceland
Katla volcano, South Iceland, is a bimodal volcanic system hosting an unusual high number of silicic rocks within a basaltic rift setting. The petrogenesis of silica-rich rocks at Katla is controversial and two end-member hypotheses have been suggested. One model involves closed-system fractional cr...
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Uppsala universitet, Institutionen för geovetenskaper
2021
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ftuppsalauniv:oai:DiVA.org:uu-455651 2023-05-15T16:48:02+02:00 Origin of Silicic Magmatism at the Katla Volcano, South Iceland Ursprung för kiselrik magmatism vid vulkanen Katla, södra Island Svanholm, Caroline 2021 application/pdf http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-455651 eng eng Uppsala universitet, Institutionen för geovetenskaper http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-455651 info:eu-repo/semantics/openAccess Katla volcano Iceland high-silica rocks oxygen isotopes AFC processes Vulkanen Katla Island kiselrika bergarter syreisotoper AFC-processer Geology Geologi Student thesis info:eu-repo/semantics/bachelorThesis text 2021 ftuppsalauniv 2023-02-23T21:57:00Z Katla volcano, South Iceland, is a bimodal volcanic system hosting an unusual high number of silicic rocks within a basaltic rift setting. The petrogenesis of silica-rich rocks at Katla is controversial and two end-member hypotheses have been suggested. One model involves closed-system fractional crystallisation from a basaltic parental magma and the other emphasises partial melting of hydrothermally altered basaltic crust. To contribute to this debate, this study provides new δ18O data from a suite of high-silica eruptive rocks with complementary basaltic eruptive material from the Katla caldera complex. Petrographically, the rocks of this study display evidence of partial melting indicated by symplectites in xenoliths as well as variously extensive resorption features. The new δ18O data display a range of the basaltic suite between +4.3 and +8.5‰ (n=15), whereas the few intermediate samples range between +4.1 and +5.9‰ (n=3). The silicic xenoliths available in the study range between -4.9 and -2.3‰ (n=4) while the silicic eruptive material ranges between +2.7 and +6.4‰ (n=30). The dominant part of the high-silica eruptive material (97%) is considered as low-δ18O (≤5.0‰) and plots below typical MORB-type magmas (5.7‰ ±0.3). The wide range of δ18O values of the Katla silicic suite is not possible to explain by closed-system fractional crystallisation and to determine the origin of the high-silica Katla rocks, the new δ18O ratios were utilised in fractional crystallisation (FC) and assimilation and fractional crystallisation (AFC) modelling. The results indicate that a two-stage magma evolution process can explain the origin of the high-silica low-δ18O Katla rocks. The early-stage involves differentiation at deep- to mid-crustal levels by fractionation and assimilation processes involving both high and low δ18O crustal materials, allowing production of intermediate to felsic magmatic compositions. Following this deep differentiation, evolved magmas experience δ18O modification at shallow crustal levels by ... Bachelor Thesis Iceland Katla Uppsala University: Publications (DiVA) Katla ENVELOPE(-19.062,-19.062,63.631,63.631) |
institution |
Open Polar |
collection |
Uppsala University: Publications (DiVA) |
op_collection_id |
ftuppsalauniv |
language |
English |
topic |
Katla volcano Iceland high-silica rocks oxygen isotopes AFC processes Vulkanen Katla Island kiselrika bergarter syreisotoper AFC-processer Geology Geologi |
spellingShingle |
Katla volcano Iceland high-silica rocks oxygen isotopes AFC processes Vulkanen Katla Island kiselrika bergarter syreisotoper AFC-processer Geology Geologi Svanholm, Caroline Origin of Silicic Magmatism at the Katla Volcano, South Iceland |
topic_facet |
Katla volcano Iceland high-silica rocks oxygen isotopes AFC processes Vulkanen Katla Island kiselrika bergarter syreisotoper AFC-processer Geology Geologi |
description |
Katla volcano, South Iceland, is a bimodal volcanic system hosting an unusual high number of silicic rocks within a basaltic rift setting. The petrogenesis of silica-rich rocks at Katla is controversial and two end-member hypotheses have been suggested. One model involves closed-system fractional crystallisation from a basaltic parental magma and the other emphasises partial melting of hydrothermally altered basaltic crust. To contribute to this debate, this study provides new δ18O data from a suite of high-silica eruptive rocks with complementary basaltic eruptive material from the Katla caldera complex. Petrographically, the rocks of this study display evidence of partial melting indicated by symplectites in xenoliths as well as variously extensive resorption features. The new δ18O data display a range of the basaltic suite between +4.3 and +8.5‰ (n=15), whereas the few intermediate samples range between +4.1 and +5.9‰ (n=3). The silicic xenoliths available in the study range between -4.9 and -2.3‰ (n=4) while the silicic eruptive material ranges between +2.7 and +6.4‰ (n=30). The dominant part of the high-silica eruptive material (97%) is considered as low-δ18O (≤5.0‰) and plots below typical MORB-type magmas (5.7‰ ±0.3). The wide range of δ18O values of the Katla silicic suite is not possible to explain by closed-system fractional crystallisation and to determine the origin of the high-silica Katla rocks, the new δ18O ratios were utilised in fractional crystallisation (FC) and assimilation and fractional crystallisation (AFC) modelling. The results indicate that a two-stage magma evolution process can explain the origin of the high-silica low-δ18O Katla rocks. The early-stage involves differentiation at deep- to mid-crustal levels by fractionation and assimilation processes involving both high and low δ18O crustal materials, allowing production of intermediate to felsic magmatic compositions. Following this deep differentiation, evolved magmas experience δ18O modification at shallow crustal levels by ... |
format |
Bachelor Thesis |
author |
Svanholm, Caroline |
author_facet |
Svanholm, Caroline |
author_sort |
Svanholm, Caroline |
title |
Origin of Silicic Magmatism at the Katla Volcano, South Iceland |
title_short |
Origin of Silicic Magmatism at the Katla Volcano, South Iceland |
title_full |
Origin of Silicic Magmatism at the Katla Volcano, South Iceland |
title_fullStr |
Origin of Silicic Magmatism at the Katla Volcano, South Iceland |
title_full_unstemmed |
Origin of Silicic Magmatism at the Katla Volcano, South Iceland |
title_sort |
origin of silicic magmatism at the katla volcano, south iceland |
publisher |
Uppsala universitet, Institutionen för geovetenskaper |
publishDate |
2021 |
url |
http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-455651 |
long_lat |
ENVELOPE(-19.062,-19.062,63.631,63.631) |
geographic |
Katla |
geographic_facet |
Katla |
genre |
Iceland Katla |
genre_facet |
Iceland Katla |
op_relation |
http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-455651 |
op_rights |
info:eu-repo/semantics/openAccess |
_version_ |
1766038119668252672 |