{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T01:31:26Z","timestamp":1760059886902,"version":"build-2065373602"},"reference-count":47,"publisher":"MDPI AG","issue":"14","license":[{"start":{"date-parts":[[2025,7,18]],"date-time":"2025-07-18T00:00:00Z","timestamp":1752796800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"national funds through FCT\u2014Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia, I.P.","award":["UID\/04683","UI\/BD\/154412\/2023"],"award-info":[{"award-number":["UID\/04683","UI\/BD\/154412\/2023"]}]},{"DOI":"10.13039\/501100001871","name":"Portuguese national funds through FCT","doi-asserted-by":"publisher","award":["UID\/04683","UI\/BD\/154412\/2023"],"award-info":[{"award-number":["UID\/04683","UI\/BD\/154412\/2023"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The increasing demand for critical raw materials, such as antimony\u2014a semimetal with strategic relevance in fire-retardant applications, electronic components, and national security\u2014has made the identification of European sources essential for the European Union\u2019s strategic autonomy. Remote sensing offers a valuable tool for detecting alteration minerals associated with subsurface gold and antimony deposits that reach the surface. However, the coarse spatial resolution of the most freely available satellite data remains a limiting factor. The PlanetScope satellite constellation presents a promising low-cost alternative for the academic community, providing 3 m spatial resolution and eight spectral bands. In this study, we evaluated PlanetScope\u2019s capacity to detect Fe3+-bearing iron oxides\u2014key indicators of hydrothermal alteration\u2014by applying targeted band ratios (BRs) in northern Portugal. A comparative analysis was conducted to validate its performance using established BRs from Sentinel-2, ASTER, and Landsat 9. The results were assessed through relative comparison methods, enabling both quantitative and qualitative evaluation of the spectral similarity among sensors. Spatial patterns were analyzed, and points of interest were identified and subsequently validated through fieldwork. Our findings demonstrate that PlanetScope is a viable option for mineral exploration applications, capable of detecting iron oxide anomalies associated with alteration zones while offering finer spatial detail than most freely accessible satellites.<\/jats:p>","DOI":"10.3390\/rs17142511","type":"journal-article","created":{"date-parts":[[2025,7,18]],"date-time":"2025-07-18T14:03:51Z","timestamp":1752847431000},"page":"2511","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Assessing the Potential of PlanetScope Imagery for Iron Oxide Detection in Antimony Exploration"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1529-1448","authenticated-orcid":false,"given":"Douglas","family":"Santos","sequence":"first","affiliation":[{"name":"Department of Geosciences, Environment and Spatial Planning, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal"},{"name":"Institute of Earth Sciences, FCUP Pole, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8265-3897","authenticated-orcid":false,"given":"Joana","family":"Cardoso-Fernandes","sequence":"additional","affiliation":[{"name":"Department of Geosciences, Environment and Spatial Planning, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal"},{"name":"Institute of Earth Sciences, FCUP Pole, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6598-5934","authenticated-orcid":false,"given":"Alexandre","family":"Lima","sequence":"additional","affiliation":[{"name":"Department of Geosciences, Environment and Spatial Planning, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal"},{"name":"Institute of Earth Sciences, FCUP Pole, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8043-6431","authenticated-orcid":false,"given":"Ana Cla\u00fadia","family":"Teodoro","sequence":"additional","affiliation":[{"name":"Department of Geosciences, Environment and Spatial Planning, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal"},{"name":"Institute of Earth Sciences, FCUP Pole, 4169-007 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,7,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Lewicka, E., Guzik, K., and Galos, K. (2021). On the Possibilities of Critical Raw Materials Production from the EU\u2019s Primary Sources. Resources, 10.","DOI":"10.3390\/resources10050050"},{"key":"ref_2","first-page":"691","article-title":"A Newly-Developed Multi-Algorithm Integration Technique for Mapping the Potentially Mineralized Alteration Zones","volume":"26","author":"Ali","year":"2023","journal-title":"Egypt. J. Remote Sens. Sp. Sci."},{"key":"ref_3","first-page":"653","article-title":"Mapping and Analysis of Structural Lineaments Using SRTM Radar Data and Landsat 8-OLI Images in Telouet-Tighza Area, Marrakech High Atlas-Morocco","volume":"60","author":"Ahmed","year":"2022","journal-title":"Res. Sq."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"591","DOI":"10.2113\/gsecongeo.78.4.591","article-title":"Remote Sensing for Porphyry Copper Deposits in Southern Arizona","volume":"78","author":"Abrams","year":"1983","journal-title":"Econ. Geol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"145","DOI":"10.1016\/0034-4257(93)90013-N","article-title":"The Spectral Image Processing System (SIPS)\u2014Interactive Visualization and Analysis of Imaging Spectrometer Data","volume":"44","author":"Kruse","year":"1993","journal-title":"Remote Sens. Environ."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"157","DOI":"10.1016\/S0169-1368(99)00007-4","article-title":"Remote Sensing for Mineral Exploration","volume":"14","author":"Sabins","year":"1999","journal-title":"Ore Geol. Rev."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"106347","DOI":"10.1016\/j.oregeorev.2024.106347","article-title":"Optimizing Exploration: Synergistic Approaches to Minimize False Positives in Pegmatite Prospecting\u2014A Comprehensive Guide for Remote Sensing and Mineral Exploration","volume":"175","author":"Santos","year":"2024","journal-title":"Ore Geol. Rev."},{"key":"ref_8","unstructured":"(2025, March 17). Planet Lab PlanetScope Overview. Available online: https:\/\/developers.planet.com\/docs\/data\/planetscope\/."},{"key":"ref_9","unstructured":"Park, C.F. (1986). The Geology of Ore Deposits, W.H. Freeman."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Wang, D., Chen, J., and Dai, X. (2024). Extracting Geological and Alteration Information and Predicting Antimony Ore Based on Multisource Remote Sensing Data in Huangyangling, Xinjiang. Front. Earth Sci., 12.","DOI":"10.3389\/feart.2024.1366727"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Rodriguez-Gomez, C., Kereszturi, G., Reeves, R., Mead, S., Pullanagari, R., Rae, A., and Jeyakumar, P. (October, January 26). Mapping Antimony Concentration over Geothermal Areas Using Hyperspectral and Thermal Remote Sensing. Proceedings of the IGARSS 2020-2020 IEEE International Geoscience and Remote Sensing Symposium, Waikoloa, HI, USA.","DOI":"10.1109\/IGARSS39084.2020.9323287"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Carvalho, M., Cardoso-Fernandes, J., Lima, A., and Teodoro, A.C. (2024). Convolutional Neural Networks Applied to Antimony Quantification via Soil Laboratory Reflectance Spectroscopy in Northern Portugal: Opportunities and Challenges. Remote Sens., 16.","DOI":"10.20944\/preprints202402.1438.v1"},{"key":"ref_13","unstructured":"Santos, D., Cardoso-Fernandes, J., Lima, A., and Teodoro, A.C. (2024, January 15\u201318). Application of Band Ratios to Map Hydrothermal Alteration Zones Related to Au-Sb Mineralization in Freixeda, Northern Portugal. Proceedings of the Earth Resources and Environmental Remote Sensing\/GIS Applications XV Location, Madrid, Spain."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Santos, D., Cardoso-Fernandes, J., Lima, A., M\u00fcller, A., Br\u00f6nner, M., and Teodoro, A.C. (2022). Spectral Analysis to Improve Inputs to Random Forest and Other Boosted Ensemble Tree-Based Algorithms for Detecting NYF Pegmatites in Tysfjord, Norway. Remote Sens., 14.","DOI":"10.3390\/rs14153532"},{"key":"ref_15","first-page":"101022","article-title":"Identification of Pegmatites Zones in Muiane and Naipa (Mozambique) from Sentinel-2 Images, Using Band Combinations, Band Ratios, PCA and Supervised Classification","volume":"32","author":"Gemusse","year":"2023","journal-title":"Remote Sens. Appl. Soc. Environ."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"105244","DOI":"10.1016\/j.oregeorev.2022.105244","article-title":"Mapping Hydrothermal and Supergene Alteration Zones Associated with Carbonate-Hosted Zn-Pb Deposits by Using PRISMA Satellite Imagery Supported by Field-Based Hyperspectral Data, Mineralogical and Geochemical Analysis","volume":"152","author":"Chirico","year":"2023","journal-title":"Ore Geol. Rev."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Sekandari, M., Masoumi, I., Beiranvand Pour, A., M Muslim, A., Rahmani, O., Hashim, M., Zoheir, B., Pradhan, B., Misra, A., and Aminpour, S.M. (2020). Application of Landsat-8, Sentinel-2, ASTER and WorldView-3 Spectral Imagery for Exploration of Carbonate-Hosted Pb-Zn Deposits in the Central Iranian Terrane (CIT). Remote Sens., 12.","DOI":"10.3390\/rs12081239"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1016\/j.jtusci.2014.11.008","article-title":"Hydrothermal Alteration Mapping from Landsat-8 Data, Sar Cheshmeh Copper Mining District, South-Eastern Islamic Republic of Iran","volume":"9","author":"Pour","year":"2015","journal-title":"J. Taibah Univ. Sci."},{"key":"ref_19","first-page":"217","article-title":"Identification of Hydrothermal Alteration Minerals for Exploring Porphyry Copper Deposit Using ASTER Data: A Case Study of Varzaghan Area, NW Iran","volume":"6","author":"Pazand","year":"2022","journal-title":"Geol. Ecol. Landsc."},{"key":"ref_20","unstructured":"Naftali Hawu Hede, A., Yahya Al Hakim, A., Fakhri Khairo, D., and Putri Rahmadica, S. (2020, January 26\u201327). Mapping of Small-Scale Gold Deposits Using Sentinel-2 and DEMNAS in Cineam, Fukuoka, Japan. Proceedings of the International Symposium on Earth Science Technology, Fukuoka, Japan."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"459","DOI":"10.1007\/s12517-021-06786-0","article-title":"Application of Remote Sensing Data in Gold Exploration: Targeting Hydrothermal Alteration Using Landsat 8 Imagery in Northern Portugal","volume":"14","author":"Frutuoso","year":"2021","journal-title":"Arab. J. Geosci."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"416","DOI":"10.1016\/S1002-0705(08)60075-8","article-title":"Extraction of Mineral Alteration Zone from ETM+ Data in Northwestern Yunnan, China","volume":"19","author":"Zhifang","year":"2008","journal-title":"J. China Univ. Geosci."},{"key":"ref_23","first-page":"417","article-title":"Exploring Mineralization Zones Using Remote Sensing and Aeromagnetic Data, West Allaqi Area, Eastern-Desert, Egypt","volume":"25","author":"ElGalladi","year":"2022","journal-title":"Egypt. J. Remote Sens. Space Sci."},{"key":"ref_24","first-page":"100306","article-title":"Mapping of Ferric (Fe3+) and Ferrous (Fe2+) Iron Oxides Distribution Using Band Ratio Techniques with ASTER Data and Geochemistry of Kanjamalai and Godumalai, Tamil Nadu, South India","volume":"18","author":"Gopinathan","year":"2020","journal-title":"Remote Sens. Appl. Soc. Environ."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Lima, A., Teodoro, A.C., and Casimiro, J.P. (2014, January 23\u201325). Evaluation of Remote Sensing Data Potential in the Geological Exploration of Freixeda Area (Mirandela, Portugal): A Preliminary Study. Proceedings of the Earth Resources and Environmental Remote Sensing\/GIS Applications V, Amsterdam, The Netherlands.","DOI":"10.1117\/12.2067183"},{"key":"ref_26","unstructured":"Montes, R., Gomes, M.E., Ferreira, A., and \u00c1vila, P. (2008). Geochemistry of Soils and Waters from the Abandoned Freixeda Gold Mine, Northeast Portugal, Sociedad Espa\u00f1ola de Mineralog\u00eda."},{"key":"ref_27","unstructured":"Marques, J.R.M.d.C. (2020). Caracteriza\u00e7\u00e3o Geol\u00f3gica E Metalog\u00e9nica Do Campo Filoniano Da Freixeda, Faculdade De Ciencias Da Universidade Do Porto, Reposit\u00f3rio Aberto da Universidade do Porto."},{"key":"ref_28","unstructured":"Costa, M.R., \u00c1vila, P., Ferreira, A., and Silva, E.F. (2013). \u201cReliable Mine Water Technology\u201d Availability of Trace Elements in the Abandoned Freixeda Gold Mine Area, NE Portugal. IMWA 2013-Reliable Mine Water Technology, 2013 Annual Conference, International Mine Water Association."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"331","DOI":"10.3406\/bulmi.1988.8056","article-title":"Fluid Associated with W and Ag-Au Deposits of the Mirandela Area, NE Portugal: An Example of Peri-Granitic Zoning","volume":"111","author":"Almeida","year":"1988","journal-title":"Bull. Min\u00e9ral."},{"key":"ref_30","unstructured":"(2024, October 02). Planet Understanding PlanetScope Instruments. Available online: https:\/\/developers.planet.com\/docs\/apis\/data\/sensors\/."},{"key":"ref_31","unstructured":"ESA (2024). E.S.A. User Guides: Sentinel-2, The European Space Agency."},{"key":"ref_32","unstructured":"(2024, November 11). ASTER: Mission, Available online: https:\/\/asterweb.jpl.nasa.gov\/mission.asp."},{"key":"ref_33","unstructured":"(2024, November 11). USGS Landsat 9, Available online: https:\/\/www.usgs.gov\/landsat-missions\/landsat-9."},{"key":"ref_34","unstructured":"(2024, November 11). Spectral Library of European Pegmatites, Pegmatite Minerals and Pegmatite Host-Rocks\u2014The GREENPEG Project Database. Available online: https:\/\/zenodo.org\/records\/6518319."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"3111","DOI":"10.5194\/essd-15-3111-2023","article-title":"Spectral Library of European Pegmatites, Pegmatite Minerals and Pegmatite Host-Rocks\u2014The GREENPEG Project Database","volume":"15","author":"Santos","year":"2023","journal-title":"Earth Syst. Sci. Data"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"111719","DOI":"10.1117\/1.OE.51.11.111719","article-title":"Quick Atmospheric Correction Code: Algorithm Description and Recent Upgrades","volume":"51","author":"Bernstein","year":"2012","journal-title":"Opt. Eng."},{"key":"ref_37","unstructured":"Wolfe, J.D., and Black, S.R. (2018). Hyperspectral Analytics in ENVI, NV5 Geospatial Solutions, Inc."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"105368","DOI":"10.1016\/j.jafrearsci.2024.105368","article-title":"Integrating Geochemical Insights and Remote Sensing for Enhanced Identification of Hydrothermal Alterations in the Igoudrane Region, Anti-Atlas, Morocco","volume":"218","author":"Baid","year":"2024","journal-title":"J. Afr. Earth Sci."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"39","DOI":"10.1016\/j.compag.2014.02.006","article-title":"A Fuzzy Logic-Based Spatial Suitability Model for Drought-Tolerant Switchgrass in the United States","volume":"103","author":"Lewis","year":"2014","journal-title":"Comput. Electron. Agric."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"149","DOI":"10.1515\/geo-2015-0012","article-title":"Regional Gold Potential Mapping in Kelantan (Malaysia) Using Probabilistic Based Models and GIS","volume":"7","author":"Yusoff","year":"2015","journal-title":"Open Geosci."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"e23334","DOI":"10.1016\/j.heliyon.2023.e23334","article-title":"Fuzzy-Logic Technique for Gold Mineralization Prospecting Using Landsat 9 OLI Processing and Fieldwork Data in the Bibemi Goldfield, North Cameroon","volume":"10","author":"Ousmanou","year":"2024","journal-title":"Heliyon"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1223","DOI":"10.1007\/s12524-024-01873-7","article-title":"Data Integration by Fuzzy Logic for Mineral Prospectivity Mapping in Ferdows\u2013Gonabad\u2013Bajestan Belt, Khorasan Razavi Province, Iran","volume":"52","author":"Honarmand","year":"2024","journal-title":"J. Indian Soc. Remote Sens."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"12653","DOI":"10.1029\/JB095iB08p12653","article-title":"High Spectral Resolution Reflectance Spectroscopy of Minerals","volume":"95","author":"Clark","year":"1990","journal-title":"J. Geophys. Res."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1613","DOI":"10.2113\/gsecongeo.74.7.1613","article-title":"Spectra of Altered Rocks in the Visible and Near Infrared","volume":"74","author":"Hunt","year":"1979","journal-title":"Econ. Geol."},{"key":"ref_45","first-page":"501","article-title":"Spectral signatures of particulate minerals in the visible and near infrared","volume":"42","author":"Hunt","year":"1977","journal-title":"Mol. Phys."},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Zagajewski, B., Kluczek, M., Zdunek, K.B., and Holland, D. (2024). Sentinel-2 versus PlanetScope Images for Goldenrod Invasive Plant Species Mapping. Remote Sens., 16.","DOI":"10.3390\/rs16040636"},{"key":"ref_47","first-page":"1902","article-title":"Cross comparison of ASTER and Landsat ETM+ multispectral measurements for NDVI and SAVI vegetation indices","volume":"31","author":"Xu","year":"2011","journal-title":"Guang Pu Xue Yu Guang Pu Fen Xi"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/17\/14\/2511\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T18:12:21Z","timestamp":1760033541000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/17\/14\/2511"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,7,18]]},"references-count":47,"journal-issue":{"issue":"14","published-online":{"date-parts":[[2025,7]]}},"alternative-id":["rs17142511"],"URL":"https:\/\/doi.org\/10.3390\/rs17142511","relation":{},"ISSN":["2072-4292"],"issn-type":[{"type":"electronic","value":"2072-4292"}],"subject":[],"published":{"date-parts":[[2025,7,18]]}}}