Tracing mineralogy and alteration intensity using the spectral alteration index and depth ratios at the northwest zone of the Lemarchant volcanogenic massive sulfide deposit, Newfoundland, Canada
The use of hyperspectral reflectance in mineral exploration has been steadily increasing in recent decades. This study presents a novel approach that integrates geochemical and spectral proxies to delineate ore formation and alteration processes, which provide new spectral-based exploration paramete...
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Online Access: | https://doi.org/10.5382/econgeo.4723 http://ecite.utas.edu.au/142374 |
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ftunivtasecite:oai:ecite.utas.edu.au:142374 2023-05-15T17:22:03+02:00 Tracing mineralogy and alteration intensity using the spectral alteration index and depth ratios at the northwest zone of the Lemarchant volcanogenic massive sulfide deposit, Newfoundland, Canada Cloutier, J Piercey, SJ 2020 https://doi.org/10.5382/econgeo.4723 http://ecite.utas.edu.au/142374 en eng Economic Geology Publ Co http://dx.doi.org/10.5382/econgeo.4723 Cloutier, J and Piercey, SJ, Tracing mineralogy and alteration intensity using the spectral alteration index and depth ratios at the northwest zone of the Lemarchant volcanogenic massive sulfide deposit, Newfoundland, Canada, Economic Geology, 115, (5) pp. 1055-1078. ISSN 0361-0128 (2020) [Refereed Article] http://ecite.utas.edu.au/142374 Earth Sciences Geology Resource geoscience Refereed Article PeerReviewed 2020 ftunivtasecite https://doi.org/10.5382/econgeo.4723 2022-08-29T22:18:13Z The use of hyperspectral reflectance in mineral exploration has been steadily increasing in recent decades. This study presents a novel approach that integrates geochemical and spectral proxies to delineate ore formation and alteration processes, which provide new spectral-based exploration parameters that can be used in real time. The precious metal-bearing, bimodal-felsic Northwest zone of the Lemarchant volcanogenic massive sulfide (VMS) deposits, Newfoundland, Canada, is used as a case study. Alteration associated with the Northwest zone includes intense and localized sulfide (pyrite, chalcopyrite, sphalerite, and galena) and barite enrichment, as well as quartz, white mica, and chlorite alteration. Zones of elevated Zn (>5,000ppm) are associated with high chlorite carbonate pyrite index (CCPI), Ishikawa alteration index (AI), Ba/Sr, and low Na 2 O values and elevated SiO 2 and K 2 O, Fe 2 O 3 , Na 2 O, and BaO contents, similar to global alteration signatures in VMS deposits. Mineralized areas contain phengitic white micas with 2,200-nm absorption features longer than 2,215 nm and Mg-rich chlorites with 2,250-nm absorption features shorter than 2,252 nm. Together, these data are consistent with the Northwest zone having undergone intense hydrothermal alteration during the mineralization event. A new lithology-normalized spectral alteration index (SAI) for white mica and chlorite was developed in order to map and characterize the alteration intensity surrounding the deposit. In addition, depth ratio parameters (2200D/2340D vs. 2250D/2340D) were used to characterize mineralogical changes and zonation. Together, these features document a paleofluid pathway with Mg chlorite alteration extending to at least 300m away from the mineralization, outside the study area, within the andesitic and dacitic units. The use of hyperspectral reflectance coupled with geochemical alteration proxies permitted the identification of areas of intense alteration, the chemical affinities of the minerals, and their relationships ... Article in Journal/Newspaper Newfoundland eCite UTAS (University of Tasmania) Canada Economic Geology 115 5 1055 1078 |
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Earth Sciences Geology Resource geoscience |
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Earth Sciences Geology Resource geoscience Cloutier, J Piercey, SJ Tracing mineralogy and alteration intensity using the spectral alteration index and depth ratios at the northwest zone of the Lemarchant volcanogenic massive sulfide deposit, Newfoundland, Canada |
topic_facet |
Earth Sciences Geology Resource geoscience |
description |
The use of hyperspectral reflectance in mineral exploration has been steadily increasing in recent decades. This study presents a novel approach that integrates geochemical and spectral proxies to delineate ore formation and alteration processes, which provide new spectral-based exploration parameters that can be used in real time. The precious metal-bearing, bimodal-felsic Northwest zone of the Lemarchant volcanogenic massive sulfide (VMS) deposits, Newfoundland, Canada, is used as a case study. Alteration associated with the Northwest zone includes intense and localized sulfide (pyrite, chalcopyrite, sphalerite, and galena) and barite enrichment, as well as quartz, white mica, and chlorite alteration. Zones of elevated Zn (>5,000ppm) are associated with high chlorite carbonate pyrite index (CCPI), Ishikawa alteration index (AI), Ba/Sr, and low Na 2 O values and elevated SiO 2 and K 2 O, Fe 2 O 3 , Na 2 O, and BaO contents, similar to global alteration signatures in VMS deposits. Mineralized areas contain phengitic white micas with 2,200-nm absorption features longer than 2,215 nm and Mg-rich chlorites with 2,250-nm absorption features shorter than 2,252 nm. Together, these data are consistent with the Northwest zone having undergone intense hydrothermal alteration during the mineralization event. A new lithology-normalized spectral alteration index (SAI) for white mica and chlorite was developed in order to map and characterize the alteration intensity surrounding the deposit. In addition, depth ratio parameters (2200D/2340D vs. 2250D/2340D) were used to characterize mineralogical changes and zonation. Together, these features document a paleofluid pathway with Mg chlorite alteration extending to at least 300m away from the mineralization, outside the study area, within the andesitic and dacitic units. The use of hyperspectral reflectance coupled with geochemical alteration proxies permitted the identification of areas of intense alteration, the chemical affinities of the minerals, and their relationships ... |
format |
Article in Journal/Newspaper |
author |
Cloutier, J Piercey, SJ |
author_facet |
Cloutier, J Piercey, SJ |
author_sort |
Cloutier, J |
title |
Tracing mineralogy and alteration intensity using the spectral alteration index and depth ratios at the northwest zone of the Lemarchant volcanogenic massive sulfide deposit, Newfoundland, Canada |
title_short |
Tracing mineralogy and alteration intensity using the spectral alteration index and depth ratios at the northwest zone of the Lemarchant volcanogenic massive sulfide deposit, Newfoundland, Canada |
title_full |
Tracing mineralogy and alteration intensity using the spectral alteration index and depth ratios at the northwest zone of the Lemarchant volcanogenic massive sulfide deposit, Newfoundland, Canada |
title_fullStr |
Tracing mineralogy and alteration intensity using the spectral alteration index and depth ratios at the northwest zone of the Lemarchant volcanogenic massive sulfide deposit, Newfoundland, Canada |
title_full_unstemmed |
Tracing mineralogy and alteration intensity using the spectral alteration index and depth ratios at the northwest zone of the Lemarchant volcanogenic massive sulfide deposit, Newfoundland, Canada |
title_sort |
tracing mineralogy and alteration intensity using the spectral alteration index and depth ratios at the northwest zone of the lemarchant volcanogenic massive sulfide deposit, newfoundland, canada |
publisher |
Economic Geology Publ Co |
publishDate |
2020 |
url |
https://doi.org/10.5382/econgeo.4723 http://ecite.utas.edu.au/142374 |
geographic |
Canada |
geographic_facet |
Canada |
genre |
Newfoundland |
genre_facet |
Newfoundland |
op_relation |
http://dx.doi.org/10.5382/econgeo.4723 Cloutier, J and Piercey, SJ, Tracing mineralogy and alteration intensity using the spectral alteration index and depth ratios at the northwest zone of the Lemarchant volcanogenic massive sulfide deposit, Newfoundland, Canada, Economic Geology, 115, (5) pp. 1055-1078. ISSN 0361-0128 (2020) [Refereed Article] http://ecite.utas.edu.au/142374 |
op_doi |
https://doi.org/10.5382/econgeo.4723 |
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Economic Geology |
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115 |
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5 |
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1055 |
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1078 |
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1766108289712521216 |