dc.contributor |
Háskóli Íslands |
dc.contributor |
University of Iceland |
dc.contributor.author |
Nikkola, Paavo |
dc.contributor.author |
Thordarson, Thorvaldur |
dc.contributor.author |
Rämö, O. Tapani |
dc.contributor.author |
Heikkilä, Pasi |
dc.date.accessioned |
2020-02-10T11:41:29Z |
dc.date.available |
2020-02-10T11:41:29Z |
dc.date.issued |
2019-11-25 |
dc.identifier.citation |
Nikkola, P., Thordarson, T., Rämö, O.T. et al. Formation of segregation structures in Hafnarhraun pāhoehoe lobe, SW Iceland: a window into crystal–melt separation in basaltic magma. Bull Volcanol 81, 70 (2019). https://doi.org/10.1007/s00445-019-1330-9 |
dc.identifier.issn |
0258-8900 |
dc.identifier.issn |
1432-0819 (eISSN) |
dc.identifier.uri |
https://hdl.handle.net/20.500.11815/1520 |
dc.description |
Publisher's version (útgefin grein). |
dc.description.abstract |
To gain insights into crystal–melt separation processes during basalt differentiation, we have studied an 8-m-thick
pāhoehoe lava lobe from the Hafnarhraun lava flow field in SW Iceland. The lobe has abundant melt segregations,
porous cylindrical and sheet-like structures, generally interpreted as separated residual melts of a lava lobe. We
divide these melt segregations into three types based on morphology and composition: vesicle cylinders (VC), type 1
horizontal vesicle sheets (HVS1), and type 2 horizontal vesicle sheets (HVS2). Remarkably, the studied VC are not
simple residual melts generated by fractional crystallization, but their composition points to removal of plagioclase
from the parental lava. HVS1 resemble VC, but have fractionated more olivine (ol) + plagioclase (plg) ± augite and
have lost most, if not all, of their olivine phenocrysts. HVS2 are Fe-rich and evolved, corresponding to residual
melts after 50–60% fractional crystallization of the lobe. We suggest that the Hafnarhraun VC formed in a two-stage
process. Firstly, VC forming residual melt and vapor detached as rising diapirs from ol+plg+melt+vapor mush near
the lava base, and later, these VC diapirs accumulated ol phenocrysts and minor plg microphenocrysts in the lava
core. HVS1 represent accumulations of VC to the viscous base of the solidifying upper crust of the lobe, and HVS2
formed as evolved vapor-saturated residual melts seeped into voids within the upper crust. Such vapor-aided differentiation, here documented for the Hafnarhraun lava, may also apply to shallow crustal magma storage zones,
contributing to the formation of evolved basalts. |
dc.description.sponsorship |
The Nordic Volcanological Center funded this work
2015–2017. We thank Robert A. Askew and Leó Kristjánsson for the aid
in sampling, Atli Hjartarson and Guðmundur H. Guðfinnsson for the help
in sample preparation and microprobe analyses, and Richard J. Brown for
the editorial handling. Comments from Kaisa Nikkilä, Scott Rowland,
and anonymous reviewer significantly improved the manuscript.
Funding information: Open access funding provided by University of
Helsinki including Helsinki University Central Hospital. |
dc.format.extent |
70 |
dc.language.iso |
en |
dc.publisher |
Springer Science and Business Media LLC |
dc.relation.ispartofseries |
Bulletin of Volcanology;81(12) |
dc.rights |
info:eu-repo/semantics/openAccess |
dc.subject |
Lava flow |
dc.subject |
Basalt |
dc.subject |
Fractional crystallization |
dc.subject |
Melt segregations |
dc.subject |
Magmatic differentiation |
dc.subject |
Hraunrennsli |
dc.subject |
Hraun |
dc.title |
Formation of segregation structures in Hafnarhraun pāhoehoe lobe, SW Iceland: a window into crystal–melt separation in basaltic magma |
dc.type |
info:eu-repo/semantics/article |
dcterms.license |
Open Access. This article is distributed under the terms of the Creative
Commons Attribution 4.0 International License (http://
creativecommons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided you give
appropriate credit to the original author(s) and the source, provide a link
to the Creative Commons license, and indicate if changes were made. |
dc.description.version |
Peer Reviewed |
dc.identifier.journal |
Bulletin of Volcanology |
dc.identifier.doi |
10.1007/s00445-019-1330-9 |
dc.contributor.department |
Jarðvísindadeild (HÍ) |
dc.contributor.department |
Faculty of Earth Sciences (UI) |
dc.contributor.department |
Institute of Earth Sciences (UI) |
dc.contributor.department |
Jarðvísindastofnun (HÍ) |
dc.contributor.school |
School of Engineering and Natural Sciences (UI) |
dc.contributor.school |
Verkfræði- og náttúruvísindasvið (HÍ) |