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87Sr/86Sr in plagioclase, evidence for a crustal origin of the Hakefjorden Complex, SW Sweden

Glommé, Alexandra LU (2015) In Dissertations in Geology at Lund University GEOR02 20151
Department of Geology
Abstract
The studied intrusion, the Hakefjorden Complex on Älgön is a norite-anorthosite complex situated in the archipelago on the west coast of Sweden. The origin of the intrusion will be deduce through in situ Sr-isotope analysis by MC-ICP-MS (multiple collector- inductively coupled plasma- mass spectrometry) on plagioclase, together with petrographic description and chemical analysis. The examined plagioclase includes megacrysts and matrix crystals in the different rock units. Sr-isotopic results show that the magma is homogenous, with only small variations in the initial 87Sr/86Sr with an average of 0.7050 for the majority of rock units. The mafic enclave is the only one that distinguishes itself from the rest with higher values in the initial... (More)
The studied intrusion, the Hakefjorden Complex on Älgön is a norite-anorthosite complex situated in the archipelago on the west coast of Sweden. The origin of the intrusion will be deduce through in situ Sr-isotope analysis by MC-ICP-MS (multiple collector- inductively coupled plasma- mass spectrometry) on plagioclase, together with petrographic description and chemical analysis. The examined plagioclase includes megacrysts and matrix crystals in the different rock units. Sr-isotopic results show that the magma is homogenous, with only small variations in the initial 87Sr/86Sr with an average of 0.7050 for the majority of rock units. The mafic enclave is the only one that distinguishes itself from the rest with higher values in the initial 87Sr/86Sr, and a significantly more crustal signature. The anorthite (An) values shows more variation between the rock units and plagioclase types than the Sr. The An-variation indicates a crystallization sequence where the IRL-matrix plagioclase crystallizes first. Oscillatory variation of both initial Sr-ratio and An is seen in several of the plagioclase megacrysts. The Sr-ratio show that little contamination has occurred during crystallization and emplacement of the intrusion, and that the mafic enclave is not similar to the rest of the Hakefjorden Complex rock units. The combined results show that a polybaric evolution is most likely, with little contamination from crustal components or other magmas. (Less)
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author
Glommé, Alexandra LU
supervisor
organization
course
GEOR02 20151
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Plagioclase, Älgön, Sr-isotopes, Sweden, MC-ICP-MS, Hakefjorden complex, geochemistry, SEM
publication/series
Dissertations in Geology at Lund University
report number
453
language
English
id
7440056
date added to LUP
2015-06-23 14:29:33
date last changed
2017-06-23 04:11:12
@misc{7440056,
  abstract     = {The studied intrusion, the Hakefjorden Complex on Älgön is a norite-anorthosite complex situated in the archipelago on the west coast of Sweden. The origin of the intrusion will be deduce through in situ Sr-isotope analysis by MC-ICP-MS (multiple collector- inductively coupled plasma- mass spectrometry) on plagioclase, together with petrographic description and chemical analysis. The examined plagioclase includes megacrysts and matrix crystals in the different rock units. Sr-isotopic results show that the magma is homogenous, with only small variations in the initial 87Sr/86Sr with an average of 0.7050 for the majority of rock units. The mafic enclave is the only one that distinguishes itself from the rest with higher values in the initial 87Sr/86Sr, and a significantly more crustal signature. The anorthite (An) values shows more variation between the rock units and plagioclase types than the Sr. The An-variation indicates a crystallization sequence where the IRL-matrix plagioclase crystallizes first. Oscillatory variation of both initial Sr-ratio and An is seen in several of the plagioclase megacrysts. The Sr-ratio show that little contamination has occurred during crystallization and emplacement of the intrusion, and that the mafic enclave is not similar to the rest of the Hakefjorden Complex rock units. The combined results show that a polybaric evolution is most likely, with little contamination from crustal components or other magmas.},
  author       = {Glommé, Alexandra},
  keyword      = {Plagioclase,Älgön,Sr-isotopes,Sweden,MC-ICP-MS,Hakefjorden complex,geochemistry,SEM},
  language     = {eng},
  note         = {Student Paper},
  series       = {Dissertations in Geology at Lund University},
  title        = {[87]Sr/[86]Sr in plagioclase, evidence for a crustal origin of the Hakefjorden Complex, SW Sweden},
  year         = {2015},
}