241c4430-bd35-2566-e063-0937940a2b65 English nonGeographicDataset non geographic dataset British Geological Survey +44 115 936 3100 Environmental Science Centre,Keyworth NOTTINGHAM NOTTINGHAMSHIRE NG12 5GG United Kingdom enquiries@bgs.ac.uk pointOfContact 2026-04-16 UK GEMINI 2.3 http://data.bgs.ac.uk/id/dataHolding/13608284 QEMSCAN mineral abundances from the 2021 Tajogaite eruption from La Palma, Canary Islands 2024-10-07 creation http://data.bgs.ac.uk/id/dataHolding/13608284 Quantitative Evaluation of Materials by Scanning Electron Microscopy (QEMSCAN®) analysis of thick sections of lava and tephra samples from the 2021 Tajogaite eruption from La Palma, Canary Islands. QEMSCAN® data were processed to produce a phase map and an olivine composition map per sample, in which each distinct phase/composition was assigned an 8-bit pixel intensity value. Olivine compositions were divided into 4 equal ranges of forsterite content (using the Fe-Mg ratio in the raw data) which were later calibrated using EPMA data. Pixels that did not fit the strict raw data requirements needed to be assigned a mineral phase were assigned to “Undifferentiated groundmass” , and instead reflect pixels containing glass or a combination of minerals ± glass below the pixel resolution. Isolated pixels of chemically complex phases such as amphibole may be the result of partial- or sub-volume interaction (i.e. between clinopyroxene, Ti-magnetite, plagioclase) and not a true representation of phase abundance. Isolated and small clusters of QEMSCAN® pixels of amphibole were shown by BSE data to be particularly prone to these effects, and so were added to the groundmass. Individual phase maps were extracted, labelled and analysed in Python using the pandas, numpy and skimage libraries. Pixel connectivity was determined by any of 4 neighbours, as opposed to 8 neighbours (any adjacent pixel including on the corners), which was more accurate in delineating groundmass crystals from each other. We chose an area of 10,000 microns2 to reflect the minimum size of phenocrysts, and assigned every region smaller than this limit to the groundmass. Phases that contributed =5% phenocrysts by area (normalised to solid rock area) in at least one sample were regarded as “major”, while the rest termed “minor”. Full details of the QEMSCAN® methodology is found in the accompanying Supplementary Data1_QEMSCAN spreadsheet. Katy Chamberlain University of Liverpool Department of Earth, Ocean & Environmental Sciences School of Environmental Sciences, Jane Herdman Laboratories Liverpool L69 3GP not available originator Enquiries British Geological Survey United Kingdom not available distributor Enquiries British Geological Survey United Kingdom not available pointOfContact notApplicable https://resources.bgs.ac.uk/images/geonetworkThumbs/241c4430-bd35-2566-e063-0937940a2b65.png Geology GEMET - INSPIRE themes, version 1.0 2008-06-01 publication Lavas Igneous petrology BGS Thesaurus of Geosciences 2022 revision NGDC Deposited Data dataCentre NERC_DDC otherRestrictions licenceOGL Available under the Open Government Licence subject to the following acknowledgement accompanying the reproduced NERC materials "Contains NERC materials ©NERC [year]" otherRestrictions The copyright of materials derived from the British Geological Survey's work is vested in the Natural Environment Research Council [NERC]. No part of this work may be reproduced or transmitted in any form or by any means, or stored in a retrieval system of any nature, without the prior permission of the copyright holder, via the BGS Intellectual Property Rights Manager. Use by customers of information provided by the BGS, is at the customer's own risk. In view of the disparate sources of information at BGS's disposal, including such material donated to BGS, that BGS accepts in good faith as being accurate, the Natural Environment Research Council (NERC) gives no warranty, expressed or implied, as to the quality or accuracy of the information supplied, or to the information's suitability for any use. NERC/BGS accepts no liability whatever in respect of loss, damage, injury or other occurence however caused. Available under the Open Government Licence subject to the following acknowledgement accompanying the reproduced NERC materials "Contains NERC materials ©NERC [year]" English geoscientificInformation 2022-01-01 2022-12-31 Image (TIFF) Microsoft Excel (XLSX) witheld Enquiries British Geological Survey United Kingdom not available distributor https://webapps.bgs.ac.uk/services/ngdc/accessions/index.html#item186305 WWW:DOWNLOAD-1.0-http--download Data download nonGeographicDataset non geographic dataset INSPIRE Implementing rules laying down technical arrangements for the interoperability and harmonisation of Geology 2011 publication See the referenced specification false Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services 2010-12-08 publication See http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2010:323:0011:0102:EN:PDF false Quantitative Evaluation of Materials by Scanning Electron Microscopy (QEMSCAN®) analysis of thick sections was undertaken at Camborne School of Mines, University of Exeter, UK using a QEMSCAN® 4300 (Gottlieb et al., 2000). iMeasure v4.2SR1 and iDiscover 4.2SR1 and 4.3 (Rollinson et al., 2011) were used for sample measurement and data processing. The QEMSCAN® operated at 25 kV, 5 nA, a 1000 X-ray count rate per pixel, a WD of around 22 mm under high vacuum and beam calibration every 30 minutes. Sample measurement used the fieldscan measurement mode (Pirrie and Rollinson, 2011) to analyze the samples at an X-ray resolution/pixel spacing of either 5 or 10 microns and a 1000 micron2 field size (x68 magnification).