Origin and Economic Potential of Lithium-mineralized Granitic Pegmatites in Helgeland, North Norway
A comprehensive set of analytical techniques, encompassing geological, petrographic, mineralogical, and zircon U-Pb-Hf isotopic compositions, was employed to investigate a relatively poorly known pegmatite field located in Helgeland, North Norway. The Paleoproterozoic basement gneisses in the area h...
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UiT Norges arktiske universitet
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ftunivtroemsoe:oai:munin.uit.no:10037/31588 2023-11-12T04:17:05+01:00 Origin and Economic Potential of Lithium-mineralized Granitic Pegmatites in Helgeland, North Norway Lomotey, Reginald Mensah 2023-08-04 https://hdl.handle.net/10037/31588 eng eng UiT Norges arktiske universitet UiT The Arctic University of Norway https://hdl.handle.net/10037/31588 Copyright 2023 The Author(s) VDP::Mathematics and natural science: 400::Geosciences: 450 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450 GEO-3900 Mastergradsoppgave Master thesis 2023 ftunivtroemsoe 2023-10-25T23:07:51Z A comprehensive set of analytical techniques, encompassing geological, petrographic, mineralogical, and zircon U-Pb-Hf isotopic compositions, was employed to investigate a relatively poorly known pegmatite field located in Helgeland, North Norway. The Paleoproterozoic basement gneisses in the area have U-Pb zircon crystallization ages between 1870 ± 12 and 1811 ± 6 Ma, meaning that they belong to the Transscandinavian Igneous Belt (TIB) of the Fennoscandian Shield. The Paleoproterozoic basement in the study area has been overprinted by metamorphism during late stages of the Caledonian orogenic event. The U-Pb zircon age determinations for granitic pegmatite magma emplacement define two discrete pegmatite generations during the late stage of the Caledonian collisional event. An older generation of pegmatites, with ages between 422 ± 5 and 412 ± 5 Ma, that formed by partial melting related to collision and thrusting during the Caledonian orogenic event. The younger generation of pegmatites has ages between 403 ± 6 and 387 ± 6 Ma, and these magmas formed during decompression in the latest stages of the Caledonian orogeny. Using fractionation indicators such as K/Rb and Nb/Ta in micas, the study identified a correlation between the U-Pb ages of the Caledonian pegmatites and their degree of magmatic differentiation; the younger pegmatites are more evolved. The Helgeland pegmatites form a cluster of highly evolved and more primitive granitic magmas with some minor rare metal enrichment such as Li-Cs-Ta in the younger and more evolved pegmatites. Hafnium isotopic data for zircons reveal slightly subchondritic to firmly juvenile εHfi values between -3.3 and +5 for the Paleoproterozoic gneisses, whereas the Caledonian pegmatites show a spread between -32 and -8. For the pegmatites, significant within-sample variations of up to 24 epsilon-units are recorded, which indicates magma derivation from an isotopically heterogeneous crustal source region that may have contained metasedimentary rock packages. The zircon Hf ... Master Thesis Fennoscandian Helgeland North Norway University of Tromsø: Munin Open Research Archive Helgeland Norway |
institution |
Open Polar |
collection |
University of Tromsø: Munin Open Research Archive |
op_collection_id |
ftunivtroemsoe |
language |
English |
topic |
VDP::Mathematics and natural science: 400::Geosciences: 450 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450 GEO-3900 |
spellingShingle |
VDP::Mathematics and natural science: 400::Geosciences: 450 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450 GEO-3900 Lomotey, Reginald Mensah Origin and Economic Potential of Lithium-mineralized Granitic Pegmatites in Helgeland, North Norway |
topic_facet |
VDP::Mathematics and natural science: 400::Geosciences: 450 VDP::Matematikk og Naturvitenskap: 400::Geofag: 450 GEO-3900 |
description |
A comprehensive set of analytical techniques, encompassing geological, petrographic, mineralogical, and zircon U-Pb-Hf isotopic compositions, was employed to investigate a relatively poorly known pegmatite field located in Helgeland, North Norway. The Paleoproterozoic basement gneisses in the area have U-Pb zircon crystallization ages between 1870 ± 12 and 1811 ± 6 Ma, meaning that they belong to the Transscandinavian Igneous Belt (TIB) of the Fennoscandian Shield. The Paleoproterozoic basement in the study area has been overprinted by metamorphism during late stages of the Caledonian orogenic event. The U-Pb zircon age determinations for granitic pegmatite magma emplacement define two discrete pegmatite generations during the late stage of the Caledonian collisional event. An older generation of pegmatites, with ages between 422 ± 5 and 412 ± 5 Ma, that formed by partial melting related to collision and thrusting during the Caledonian orogenic event. The younger generation of pegmatites has ages between 403 ± 6 and 387 ± 6 Ma, and these magmas formed during decompression in the latest stages of the Caledonian orogeny. Using fractionation indicators such as K/Rb and Nb/Ta in micas, the study identified a correlation between the U-Pb ages of the Caledonian pegmatites and their degree of magmatic differentiation; the younger pegmatites are more evolved. The Helgeland pegmatites form a cluster of highly evolved and more primitive granitic magmas with some minor rare metal enrichment such as Li-Cs-Ta in the younger and more evolved pegmatites. Hafnium isotopic data for zircons reveal slightly subchondritic to firmly juvenile εHfi values between -3.3 and +5 for the Paleoproterozoic gneisses, whereas the Caledonian pegmatites show a spread between -32 and -8. For the pegmatites, significant within-sample variations of up to 24 epsilon-units are recorded, which indicates magma derivation from an isotopically heterogeneous crustal source region that may have contained metasedimentary rock packages. The zircon Hf ... |
format |
Master Thesis |
author |
Lomotey, Reginald Mensah |
author_facet |
Lomotey, Reginald Mensah |
author_sort |
Lomotey, Reginald Mensah |
title |
Origin and Economic Potential of Lithium-mineralized Granitic Pegmatites in Helgeland, North Norway |
title_short |
Origin and Economic Potential of Lithium-mineralized Granitic Pegmatites in Helgeland, North Norway |
title_full |
Origin and Economic Potential of Lithium-mineralized Granitic Pegmatites in Helgeland, North Norway |
title_fullStr |
Origin and Economic Potential of Lithium-mineralized Granitic Pegmatites in Helgeland, North Norway |
title_full_unstemmed |
Origin and Economic Potential of Lithium-mineralized Granitic Pegmatites in Helgeland, North Norway |
title_sort |
origin and economic potential of lithium-mineralized granitic pegmatites in helgeland, north norway |
publisher |
UiT Norges arktiske universitet |
publishDate |
2023 |
url |
https://hdl.handle.net/10037/31588 |
geographic |
Helgeland Norway |
geographic_facet |
Helgeland Norway |
genre |
Fennoscandian Helgeland North Norway |
genre_facet |
Fennoscandian Helgeland North Norway |
op_relation |
https://hdl.handle.net/10037/31588 |
op_rights |
Copyright 2023 The Author(s) |
_version_ |
1782334063906914304 |