Options
Controls on chemical evolution and rare element enrichment in crystallising albite-spodumene pegmatite and wallrocks: Constraints from mineral chemistry
Date Issued
2020-01
Date Available
2020-09-08T15:11:47Z
Abstract
Internal differentiation and consequent geochemical evolution in pegmatites are significant processes in the development of economically viable deposits of metal-bearing minerals. Albite-spodumene pegmatites, which represent important resources of Li and Ta worldwide, challenge the general rules of pegmatite petrogenesis as these are nearly homogeneous bodies with little or no intrusion-scale pegmatite zonation. Bulk intrusion concentrations of Li are in the uppermost range obtained by magmatic enrichment experiments, around 2 wt% Li2O, and extensive volumes of saccharoidal or platy albite are present. In Leinster, southeast Ireland, weakly zoned to homogeneous albitised spodumene pegmatites and their wallrocks were studied to compare mineral chemistry variations and understand the internal evolution of pegmatites, characteristics linked to the poor development of zonation, and links between internal evolution and pegmatite-wallrock interactions. Leinster pegmatites present mineralogical, textural and geochemical characteristics coherent with Li-saturation, and possibly supersaturation, prior to crystallisation. Weak border to centre zonation in the thickest bodies can be attributed to geochemically evolved initial melt, likely leading to nearly contemporaneous crystallisation throughout the intrusion and resulting in limited internal geochemical fractionation. Increased abundance of minerals bearing highly incompatible elements (e.g. columbite-group minerals and cassiterite) and network modifiers (e.g. phosphates) in albitite indicates it is a fractionation product from pegmatite crystallisation. Enrichment in incompatible elements B, Li, Rb, Cs and F in spodumene pegmatite exocontacts in different country rock types suggests unmixing of a hydrous fluid from the residual melt after the crystallisation of main pegmatitic assemblages, and that the H2O-rich component was mobilised into country rocks.
Sponsorship
European Commission - European Regional Development Fund
Science Foundation Ireland
Other Sponsorship
Coordenação de Aperfeiçoamento de Pessoal de NÃvel Superior (CAPES)
Type of Material
Journal Article
Publisher
Elsevier
Journal
Lithos
Volume
352–353
Start Page
1
End Page
19
Copyright (Published Version)
2019 Elsevier
Language
English
Status of Item
Peer reviewed
ISSN
0024-4937
This item is made available under a Creative Commons License
File(s)
Owning collection
Scopus© citations
38
Acquisition Date
Mar 28, 2024
Mar 28, 2024
Views
927
Last Month
2
2
Acquisition Date
Mar 28, 2024
Mar 28, 2024
Downloads
601
Last Week
4
4
Last Month
17
17
Acquisition Date
Mar 28, 2024
Mar 28, 2024