Trace element behaviour in a LCT-pegmatite with rare-element mineralization : The Luolamäki pegmatite, a case study

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http://urn.fi/URN:NBN:fi:hulib-202101081105
Title: Trace element behaviour in a LCT-pegmatite with rare-element mineralization : The Luolamäki pegmatite, a case study
Author: Söderlund, Linda
Contributor: University of Helsinki, Faculty of Science
Publisher: Helsingin yliopisto
Date: 2020
URI: http://urn.fi/URN:NBN:fi:hulib-202101081105
http://hdl.handle.net/10138/324299
Thesis level: master's thesis
Abstract: In this modern world with its evolving technological applications the role of pegmatites has risen to an unexpected level. As pegmatites are hosts for rare-element mineralization’s they are mined extensively throughout the world. As a result of the transition to more ecological solutions in propulsions the need for large quantities of certain elements, elements such as lithium, for batteries are on the rise. Even though pegmatites have been studied extensively they have not yet yielded all their secrets to scientists. Even the classification of them is still under some debate before a final cohesion is found. Because of this, the study of pegmatites has also been far from systematic. The aim of this thesis is to map the trace element behaviour of the rare-elements of the Luolamäki pegmatite. This pegmatite was chosen due to the existing drill cores and its rare-element mineralization of pollucite, petalite and possibly rubicline.The drill cores were sampled and analysed with wave dispersive x-ray fluorescence (WD-XRF), electron probe microanalyzer (EPMA) and with laser ablation inductively coupled plasma mass spectrometry analysis (LA-ICP-MS). Quartz and three other salient rock-forming mineral groups, feldspars, micas and tourmalines were chosen for analysis. The Luumäki pegmatite is classified as belonging to the LCT-family and being of the petalite-subtype. The previous assumptions of the pegmatites asymmetric inner structure were confirmed with the notation of the reversed order of feldspars in the pegmatite dike with albitic feldspars on the hanging wall side and potassium feldspars on the foot wall side. This coupled with the trace element behaviour in the pegmatite it was confirmed that the pegmatite crystallized from the margins toward the centre instead from top to bottom, as is usual for pegmatitic dikes. The presence of rubicline was not verified, however. The results were then posed against existing research to test if the behaviours recorded are consistent. Some difference was found with the behaviour of the feldspars. The study area of Luolamäki brought up more questions to be answered as the pegmatite itself represents the end of pegmatitic fractioning in the area. It would be beneficial to study the other pegmatites in the area more thoroughly in an attempt to trace the origin for the Luolamäki pegmatite and to research if the enrichment of elements such as Li, Rb and Cs is traceable in the less fractionated pegmatites.
Subject: Pegmatite
trace element
rare-element
rare element mineralization
lithium
caesium
rubidium LCT
NYF
Discipline: Geologia


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