QEMSCAN mineral abundances from the 2021 Tajogaite eruption from La Palma, Canary Islands

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.

Date (Creation): 2024-10-07

Citation identifier: http://data.bgs.ac.uk/id/dataHolding/13608284

Point of contact

Organisation name	Individual name	Electronic mail address	Role
University of Liverpool	Katy Chamberlain	not available	Originator
British Geological Survey	Enquiries	not available	Distributor
British Geological Survey	Enquiries	not available	Point of contact

Maintenance and update frequency: notApplicable

GEMET - INSPIRE themes, version 1.0

Geology

BGS Thesaurus of Geosciences

Lavas
NGDC Deposited Data
Igneous petrology

dataCentre

NGDC Deposited Data

Keywords

NERC_DDC

Access constraints: Other restrictions

Other constraints: restricted

Other constraints: The dataset has been formally approved by BGS for access by external clients under a BGS Digital Data Licence, issued via BGS's IPR Section. The dataset must not be provided to, or be accessible by, an external client until the IPR Section confirms that signed licence documentation is in place. Refer to the IPR Section (DigitalLE@bgs.ac.) if further advice is required.. Constraint applies until 2025-10-31

Use constraints: Other restrictions

Other constraints: 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.

Other constraints: Either: (i) the dataset is made freely available, e.g. via the Internet, for a restricted category of use (e.g. educational use only); or (ii) the dataset has not been formally approved by BGS for access and use by external clients under licence, but its use may be permitted under alternative formal arrangements; or (iii) the dataset contains 3rd party data or information obtained by BGS under terms and conditions that must be consulted in order to determine the permitted usage of the dataset. Refer to the BGS staff member responsible for the creation of the dataset if further advice is required. He / she should be familiar with the composition of the dataset, particularly with regard to 3rd party IPR contained in it, and any resultant use restrictions. This staff member should revert to the IPR Section ( ipr@bgs.ac.uk) for advice, should the position not be clear.

Language: English

Topic category

Geoscientific information

Begin date: 2022-01-01

End date: 2022-12-31

Reference System Information

No information provided.

Distribution format

Name	Version
TIF file (.TIF)
Excel (xlsx)

Distributor contact

Organisation name	Individual name	Electronic mail address	Role
British Geological Survey	Enquiries	not available	Distributor

OnLine resource

Protocol	Linkage	Name
	https://webapps.bgs.ac.uk/services/ngdc/accessions/index.html#item186305	Data

Hierarchy level: Non geographic dataset

Other: non geographic dataset

Conformance result

Title: INSPIRE Implementing rules laying down technical arrangements for the interoperability and harmonisation of Geology

Date (Publication): 2011

Explanation: See the referenced specification

Pass: No

Conformance result

Title: 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

Date (Publication): 2010-12-08

Explanation: See http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2010:323:0011:0102:EN:PDF

Pass: No

Statement: 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).