Calibrating a Handheld LIBS for Li Exploration in the Barroso–Alvão Aplite-Pegmatite Field, Northern Portugal: Textural Precautions and Procedures When Analyzing Spodumene and Petalite
Author:
Dias Filipa12ORCID, Ribeiro Ricardo12ORCID, Gonçalves Filipe12, Lima Alexandre12ORCID, Roda-Robles Encarnación3ORCID, Martins Tânia4
Affiliation:
1. Department of Geosciences, Environment and Land Planning, Faculty of Sciences, University of Porto, Rua Campo Alegre, 687, 4169-007 Porto, Portugal 2. Institute of Earth Sciences, ICT, Pole of University of Porto, 4169-007 Porto, Portugal 3. Department of Geology, University of País Vasco (UPV/EHU), Barrio Sarriena s/n, 48940 Leioa, Spain 4. Manitoba Geological Survey, 360-1395 Ellice Avenue, Winnipeg, MB R3G 3P2, Canada
Abstract
In pegmatites containing abundant petalite and spodumene, such as those from the Barroso–Alvão (BA) aplite-pegmatite field, calibrating a portable laser-induced breakdown spectroscopy (pLIBS) equipment to identify and analyze these minerals may be challenging. Forty-nine samples of spodumene, petalite and spodumene + quartz were collected from 22 aplite-pegmatites from the BA field and sent for inductively coupled plasma-mass spectroscopy analysis. One calibration for both spodumene and petalite has been proven to be impossible since almost all the LIBS intensity ratios, including for Li, overlapped on both minerals. Thus, three calibrations were developed: one qualitative to distinguish both minerals and two more quantitative, specifically made for each mineral. The first LIBS calibration only has Fe since it is the sole element with intensity ratios different enough to distinguish both minerals. Eleven calibration lines were created: Li, Al, Si, Be, Na, P, K, Mn, Fe, Rb and Cs; however, only the Li, Al, and Si have consistent errors below 20%. Thin sections were produced and observed with optical microscopy and cathodoluminescence (CL) to control the purity and mineral paragenesis of the samples. The petalite pellets were also controlled with cold CL since petalite crystals often present fine spodumene and quartz inclusions.
Funder
European Commission’s Horizon 2020 innovation programme CAVALI—Cadeia de Valor do Lítio INOVMINERAL 4.0—Tecnologias Avançadas e Software para os recursos Minerais ICT project national funds from MCTES through FCT European Social Fund
Subject
Geology,Geotechnical Engineering and Engineering Geology
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