A Mineralogical, Geochemical, and Geochronological Study of ‘Valencianite’ from La Valenciana Mine, Guanajuato, Mexico
<i>Valencianite</i> has been described as a variety of K-feldspar (<i>adularia</i>) from La Valenciana mine, Guanajuato, Mexico, from which three samples were used for this study. We present new major and trace element analysis, X-ray powder diffraction with Rietveld refineme...
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MDPI AG
2021-07-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/11/7/741 |
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| author | Jesús Solé Teresa Pi-Puig Amabel Ortega-Rivera |
| author_facet | Jesús Solé Teresa Pi-Puig Amabel Ortega-Rivera |
| author_sort | Jesús Solé |
| collection | DOAJ |
| description | <i>Valencianite</i> has been described as a variety of K-feldspar (<i>adularia</i>) from La Valenciana mine, Guanajuato, Mexico, from which three samples were used for this study. We present new major and trace element analysis, X-ray powder diffraction with Rietveld refinement, and single-crystal <sup>40</sup>Ar/<sup>39</sup>Ar ages of this classical mineral. A detailed review of major works on feldspars and relevant papers from <i>adularia</i> shows that the structure of this mineral has monoclinic and triclinic domains with variable degrees of Al/Si order that we have been only able to model by powder X-ray diffraction assuming the presence of monoclinic (~50%) plus triclinic (~50%) K-feldspar. The literature data show some extreme structural states for <i>adularia</i> obtained in the pre-Rietveld refinement era; these data are dubious and need to be reanalyzed. A triangular diagram using the relative development of {110}, {010} and {001} faces is proposed. The temperature of formation, the Na/K ratio, and the growth kinetics seem to be the main factors controlling the morphological changes in K-feldspar crystals. The geochemistry of <i>valencianite</i> shows an almost pure orthoclase composition, as is common in most <i>adularia</i> crystals, although compositions up to Or<sub>90</sub>Ab<sub>10</sub> have been found. Measurement of thallium in <i>adularia</i> can be an exploration guide for ore deposits. The weighted mean of 15 <sup>40</sup>Ar/<sup>39</sup>Ar analyses of one <i>valencianite</i> from La Valenciana mine gave an age of 30.43 ± 0.27 Ma (2 standard deviations). It is discussed whether <i>valencianite</i> can be considered a new mineral. |
| first_indexed | 2024-03-10T09:31:19Z |
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| institution | Directory Open Access Journal |
| issn | 2075-163X |
| language | English |
| last_indexed | 2024-03-10T09:31:19Z |
| publishDate | 2021-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Minerals |
| spelling | doaj.art-3e81505ce9bc4b12ad5b967613e585782023-11-22T04:27:53ZengMDPI AGMinerals2075-163X2021-07-0111774110.3390/min11070741A Mineralogical, Geochemical, and Geochronological Study of ‘Valencianite’ from La Valenciana Mine, Guanajuato, MexicoJesús Solé0Teresa Pi-Puig1Amabel Ortega-Rivera2Laboratorio Nacional de Geoquímica y Mineralogía, Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán, Ciudad de México 04510, MexicoLaboratorio Nacional de Geoquímica y Mineralogía, Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán, Ciudad de México 04510, MexicoInstituto de Geología, Universidad Nacional Autónoma de México, Estación Regional del Noroeste, Apartado Postal 1039, Hermosillo, Sonora 83000, Mexico<i>Valencianite</i> has been described as a variety of K-feldspar (<i>adularia</i>) from La Valenciana mine, Guanajuato, Mexico, from which three samples were used for this study. We present new major and trace element analysis, X-ray powder diffraction with Rietveld refinement, and single-crystal <sup>40</sup>Ar/<sup>39</sup>Ar ages of this classical mineral. A detailed review of major works on feldspars and relevant papers from <i>adularia</i> shows that the structure of this mineral has monoclinic and triclinic domains with variable degrees of Al/Si order that we have been only able to model by powder X-ray diffraction assuming the presence of monoclinic (~50%) plus triclinic (~50%) K-feldspar. The literature data show some extreme structural states for <i>adularia</i> obtained in the pre-Rietveld refinement era; these data are dubious and need to be reanalyzed. A triangular diagram using the relative development of {110}, {010} and {001} faces is proposed. The temperature of formation, the Na/K ratio, and the growth kinetics seem to be the main factors controlling the morphological changes in K-feldspar crystals. The geochemistry of <i>valencianite</i> shows an almost pure orthoclase composition, as is common in most <i>adularia</i> crystals, although compositions up to Or<sub>90</sub>Ab<sub>10</sub> have been found. Measurement of thallium in <i>adularia</i> can be an exploration guide for ore deposits. The weighted mean of 15 <sup>40</sup>Ar/<sup>39</sup>Ar analyses of one <i>valencianite</i> from La Valenciana mine gave an age of 30.43 ± 0.27 Ma (2 standard deviations). It is discussed whether <i>valencianite</i> can be considered a new mineral.https://www.mdpi.com/2075-163X/11/7/741alkali-feldsparadulariaX-ray diffractionRietveld refinementmajor-elementstrace-elements |
| spellingShingle | Jesús Solé Teresa Pi-Puig Amabel Ortega-Rivera A Mineralogical, Geochemical, and Geochronological Study of ‘Valencianite’ from La Valenciana Mine, Guanajuato, Mexico Minerals alkali-feldspar adularia X-ray diffraction Rietveld refinement major-elements trace-elements |
| title | A Mineralogical, Geochemical, and Geochronological Study of ‘Valencianite’ from La Valenciana Mine, Guanajuato, Mexico |
| title_full | A Mineralogical, Geochemical, and Geochronological Study of ‘Valencianite’ from La Valenciana Mine, Guanajuato, Mexico |
| title_fullStr | A Mineralogical, Geochemical, and Geochronological Study of ‘Valencianite’ from La Valenciana Mine, Guanajuato, Mexico |
| title_full_unstemmed | A Mineralogical, Geochemical, and Geochronological Study of ‘Valencianite’ from La Valenciana Mine, Guanajuato, Mexico |
| title_short | A Mineralogical, Geochemical, and Geochronological Study of ‘Valencianite’ from La Valenciana Mine, Guanajuato, Mexico |
| title_sort | mineralogical geochemical and geochronological study of valencianite from la valenciana mine guanajuato mexico |
| topic | alkali-feldspar adularia X-ray diffraction Rietveld refinement major-elements trace-elements |
| url | https://www.mdpi.com/2075-163X/11/7/741 |
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