26 October 2013 Alteration mineral mapping for iron prospecting using ETM+ data, Tonkolili iron field, northern Sierra Leone
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Proceedings Volume 8921, MIPPR 2013: Remote Sensing Image Processing, Geographic Information Systems, and Other Applications; 892102 (2013) https://doi.org/10.1117/12.2031506
Event: Eighth International Symposium on Multispectral Image Processing and Pattern Recognition, 2013, Wuhan, China
Abstract
The Tonkolili iron field in northern Sierra Leone has the largest known iron ore deposit in Africa. It occurs in a greenstone belt in an Achaean granitic basement. This study focused mainly on mapping areas with iron-oxide and hydroxyl bearing minerals, and identifying potential areas for haematite mineralization and banded iron formations (BIFs) in Tonkolili. The predominant mineral assemblage at the surface (laterite duricrust) of this iron field is haematitegoethite- limonite ±magnetite. The mineralization occurs in quartzitic banded ironstones, layered amphibolites, granites, schists and hornblendites. In this study, Crosta techniques were applied on Enhanced Thematic Mapper (ETM+) data to enhance areas with alteration minerals and target potential areas of haematite and BIF units in the Tonkolili iron field. Synthetic analysis shows that alteration zones mapped herein are consistent with the already discovered magnetite BIFs in Tonkolili. Based on the overlaps of the simplified geological map and the remote sensing-based alteration mineral maps obtained in this study, three new haematite prospects were inferred within, and one new haematite prospect was inferred outside the tenement boundary of the Tonkolili exploration license. As the primary iron mineral in Tonkolili is magnetite, the study concludes that, these haematite prospects could also be underlain by magnetite BIFs. This study also concludes that, the application of Crosta techniques on ETM+ data is effective not only in mapping iron-oxide and hydroxyl alterations but can also provide a basis for inferring areas of potential iron resources in Algoma-type banded iron formations (BIFs), such as those in the Tonkolili field.
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Lamin R. Mansaray, Lamin R. Mansaray, Lei Liu, Lei Liu, Jun Zhou, Jun Zhou, Zhimin Ma, Zhimin Ma, } "Alteration mineral mapping for iron prospecting using ETM+ data, Tonkolili iron field, northern Sierra Leone", Proc. SPIE 8921, MIPPR 2013: Remote Sensing Image Processing, Geographic Information Systems, and Other Applications, 892102 (26 October 2013); doi: 10.1117/12.2031506; https://doi.org/10.1117/12.2031506
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