Mineralogy, Fluid Inclusions, and Oxygen Isotope Geochemistry Signature of Wolframite to Scheelite and Fe,Mn Chlorite Veins from the W, (Cu,Mo) Ore Deposit of Borralha, Portugal
Scheelitization of Mn-bearing wolframite, scheelite, quartz, and Fe,Mn-chlorite veins was identified in the W, (Cu,Mo) ore deposits of Borralha, by optical microscopy, electron-microprobe analysis, and stable isotope geochemistry. Fluid inclusions derived scheelite crystallization temperature was co...
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MDPI AG
2021-12-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/12/1/24 |
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| author | Iuliu Bobos Carlos Marques de Sá Fernando Noronha |
| author_facet | Iuliu Bobos Carlos Marques de Sá Fernando Noronha |
| author_sort | Iuliu Bobos |
| collection | DOAJ |
| description | Scheelitization of Mn-bearing wolframite, scheelite, quartz, and Fe,Mn-chlorite veins was identified in the W, (Cu,Mo) ore deposits of Borralha, by optical microscopy, electron-microprobe analysis, and stable isotope geochemistry. Fluid inclusions derived scheelite crystallization temperature was compared with the oxygen isotope temperature estimated. Scheelite was formed mainly during stage I from a low salinity aqueous-carbonic fluid dominated by CO<sub>2</sub>, where the homogenization temperature (<i>T<sub>h</sub></i>) decreased from 380 °C to 200 °C (average of 284 °C). As temperature decreased further, the aqueous-carbonic fluid became dominated by CH<sub>4</sub> (Stage II; (average <i>T<sub>h</sub></i> = 262 °C)). The final stage III corresponds to lower temperature mineralizing aqueous fluid (average <i>T<sub>h</sub></i> = 218 °C). In addition, salinity gradually decreased from 4.8 wt.% to 1.12 wt.%. The δ<sup>18</sup>O<sub>Fluid</sub> values calculated for quartz-water and wolframite-water fractionation fall within the calculated magmatic water range. The ∆<sub>quartz-scheelite</sub> fractionation occurred at about 350–400 °C. The ∆<sub>chlorite-water</sub> fractionation factor calculated is about +0.05‰ for 330 °C, dropping to −0.68‰ and −1.26‰ at 380 °C and 450 °C, respectively. Estimated crystallizing temperatures based on semi-empirical chlorite geothermometers range from 373 °C to 458 °C and 435 °C to 519 °C. A narrower temperature range of 375 °C to 410 °C was estimated for Fe,Mn-chlorite crystallization. |
| first_indexed | 2024-03-10T00:53:07Z |
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| last_indexed | 2024-03-10T00:53:07Z |
| publishDate | 2021-12-01 |
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| spelling | doaj.art-9d9dd690ffe14d37970f123040fb5e472023-11-23T14:49:05ZengMDPI AGMinerals2075-163X2021-12-011212410.3390/min12010024Mineralogy, Fluid Inclusions, and Oxygen Isotope Geochemistry Signature of Wolframite to Scheelite and Fe,Mn Chlorite Veins from the W, (Cu,Mo) Ore Deposit of Borralha, PortugalIuliu Bobos0Carlos Marques de Sá1Fernando Noronha2ICTerra-Porto, Faculdade de Ciências, Universidade do Porto, 4168-007 Porto, PortugalGrupo de Pesquisa em Recursos Minerais, Departamento de Geologia, Universidade Federal de Sergipe, Aracaju 49060-108, SE, BrazilICTerra-Porto, Faculdade de Ciências, Universidade do Porto, 4168-007 Porto, PortugalScheelitization of Mn-bearing wolframite, scheelite, quartz, and Fe,Mn-chlorite veins was identified in the W, (Cu,Mo) ore deposits of Borralha, by optical microscopy, electron-microprobe analysis, and stable isotope geochemistry. Fluid inclusions derived scheelite crystallization temperature was compared with the oxygen isotope temperature estimated. Scheelite was formed mainly during stage I from a low salinity aqueous-carbonic fluid dominated by CO<sub>2</sub>, where the homogenization temperature (<i>T<sub>h</sub></i>) decreased from 380 °C to 200 °C (average of 284 °C). As temperature decreased further, the aqueous-carbonic fluid became dominated by CH<sub>4</sub> (Stage II; (average <i>T<sub>h</sub></i> = 262 °C)). The final stage III corresponds to lower temperature mineralizing aqueous fluid (average <i>T<sub>h</sub></i> = 218 °C). In addition, salinity gradually decreased from 4.8 wt.% to 1.12 wt.%. The δ<sup>18</sup>O<sub>Fluid</sub> values calculated for quartz-water and wolframite-water fractionation fall within the calculated magmatic water range. The ∆<sub>quartz-scheelite</sub> fractionation occurred at about 350–400 °C. The ∆<sub>chlorite-water</sub> fractionation factor calculated is about +0.05‰ for 330 °C, dropping to −0.68‰ and −1.26‰ at 380 °C and 450 °C, respectively. Estimated crystallizing temperatures based on semi-empirical chlorite geothermometers range from 373 °C to 458 °C and 435 °C to 519 °C. A narrower temperature range of 375 °C to 410 °C was estimated for Fe,Mn-chlorite crystallization.https://www.mdpi.com/2075-163X/12/1/24wolframite scheelitizationFe,Mn-chloriteH<sub>2</sub>O-CO<sub>2</sub> (CH<sub>4</sub>) fluid inclusionstable isotope fractionationchlorite geothermometryBorralha |
| spellingShingle | Iuliu Bobos Carlos Marques de Sá Fernando Noronha Mineralogy, Fluid Inclusions, and Oxygen Isotope Geochemistry Signature of Wolframite to Scheelite and Fe,Mn Chlorite Veins from the W, (Cu,Mo) Ore Deposit of Borralha, Portugal Minerals wolframite scheelitization Fe,Mn-chlorite H<sub>2</sub>O-CO<sub>2</sub> (CH<sub>4</sub>) fluid inclusion stable isotope fractionation chlorite geothermometry Borralha |
| title | Mineralogy, Fluid Inclusions, and Oxygen Isotope Geochemistry Signature of Wolframite to Scheelite and Fe,Mn Chlorite Veins from the W, (Cu,Mo) Ore Deposit of Borralha, Portugal |
| title_full | Mineralogy, Fluid Inclusions, and Oxygen Isotope Geochemistry Signature of Wolframite to Scheelite and Fe,Mn Chlorite Veins from the W, (Cu,Mo) Ore Deposit of Borralha, Portugal |
| title_fullStr | Mineralogy, Fluid Inclusions, and Oxygen Isotope Geochemistry Signature of Wolframite to Scheelite and Fe,Mn Chlorite Veins from the W, (Cu,Mo) Ore Deposit of Borralha, Portugal |
| title_full_unstemmed | Mineralogy, Fluid Inclusions, and Oxygen Isotope Geochemistry Signature of Wolframite to Scheelite and Fe,Mn Chlorite Veins from the W, (Cu,Mo) Ore Deposit of Borralha, Portugal |
| title_short | Mineralogy, Fluid Inclusions, and Oxygen Isotope Geochemistry Signature of Wolframite to Scheelite and Fe,Mn Chlorite Veins from the W, (Cu,Mo) Ore Deposit of Borralha, Portugal |
| title_sort | mineralogy fluid inclusions and oxygen isotope geochemistry signature of wolframite to scheelite and fe mn chlorite veins from the w cu mo ore deposit of borralha portugal |
| topic | wolframite scheelitization Fe,Mn-chlorite H<sub>2</sub>O-CO<sub>2</sub> (CH<sub>4</sub>) fluid inclusion stable isotope fractionation chlorite geothermometry Borralha |
| url | https://www.mdpi.com/2075-163X/12/1/24 |
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