Apatite U-Pb dating at UNAM laboratories: analytical protocols and examples of its application
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| Format: | Artículo científico |
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Universidad Nacional Autónoma de México
2019
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| author | Carlos Ortega-Obregón |
| author_facet | Carlos Ortega-Obregón |
| contents | Apatite U-Pb dating at UNAM laboratories: analytical protocols and examples of its application Carlos Ortega-Obregón Fanis Abdullin Luigi Solari Peter Schaaf Gabriela Solís-Pichardo Ciencias de la Tierra Mexico Apatite Pb dating laser ablation isotope dilution Apatite is the most common phosphate mineral in the Earth’s crust and can be found in practically all magmatic and metamorphic rocks, as well as in ancient and recent sediments and in certain ore deposits. Its effective closure temperature of 450–550 °C for the U-Pb system makes apatite an important natural medium-temperature thermochronometer that can be dated by both laser ablation inductively coupled plasma mass spectrometry (LA–ICP-MS) and isotope dilution thermal ionization mass spectrometry (ID–TIMS) techniques. Due to its low U content, coupled with high Pb contents incorporated during crystallization (also called common lead), apatite U-Pb dating is analytically challenging, and requires robust analytical protocols to achieve reliable ages. In this experimental study we obtained apatite U-Pb ages from six rock samples employing LA–ICP-MS (at Laboratorio de Estudios Isotópicos, Centro de Geociencias, UNAM), while one sample was also dated by ID–TIMS (at Laboratorio Universitario de Geoquímica Isotópica, UNAM). These samples have igneous emplacement or metamorphic ages broadly ranging from the Neoproterozoic to the Paleocene. The obtained apatite U-Pb ages agree well with other radioisotopic data (U-Pb on zircon and K-Ar or Ar-Ar on micas and hornblende) available for the same rock samples tested, or for the same geological units studied. These apatite U-Pb results, obtained for the first time at two main Mexican geochronology laboratories, are precise enough to be geologically meaningful and usually represent the cooling ages; though, in some cases they may also indicate the crystallization or the metamorphic age. Some advantages and disadvantages of LA–ICPMSand ID–TIMS-based methodologies were observed and outlined. Our results validate the analytical procedures used and will serve as an important trigger towards the development or improvement of medium-temperature thermochronology techniques in Mexico. 2019 artículo científico 1026-8774 https://www.redalyc.org/articulo.oa?id=57265242003 https://www.redalyc.org/journal/572/57265242003/ https://www.redalyc.org/journal/572/57265242003/html/ https://www.redalyc.org/journal/572/57265242003/57265242003.epub https://www.redalyc.org/journal/572/57265242003/movil https://doi.org/10.22201/cgeo.20072902e.2019.1.749 en http://www.redalyc.org/revista.oa?id=572 Revista Mexicana de Ciencias Geológicas application/pdf Universidad Nacional Autónoma de México Revista Mexicana de Ciencias Geológicas (México) Num.1 Vol.36 |
| format | Artículo científico |
| id | redalyc_57265242003 |
| institution | Redalyc |
| language | en |
| publishDate | 2019 |
| publisher | Universidad Nacional Autónoma de México |
| spellingShingle | Apatite U-Pb dating at UNAM laboratories: analytical protocols and examples of its application Carlos Ortega-Obregón Ciencias de la Tierra Mexico Apatite Pb dating laser ablation isotope dilution Apatite U-Pb dating at UNAM laboratories: analytical protocols and examples of its application Carlos Ortega-Obregón Fanis Abdullin Luigi Solari Peter Schaaf Gabriela Solís-Pichardo Ciencias de la Tierra Mexico Apatite Pb dating laser ablation isotope dilution Apatite is the most common phosphate mineral in the Earth’s crust and can be found in practically all magmatic and metamorphic rocks, as well as in ancient and recent sediments and in certain ore deposits. Its effective closure temperature of 450–550 °C for the U-Pb system makes apatite an important natural medium-temperature thermochronometer that can be dated by both laser ablation inductively coupled plasma mass spectrometry (LA–ICP-MS) and isotope dilution thermal ionization mass spectrometry (ID–TIMS) techniques. Due to its low U content, coupled with high Pb contents incorporated during crystallization (also called common lead), apatite U-Pb dating is analytically challenging, and requires robust analytical protocols to achieve reliable ages. In this experimental study we obtained apatite U-Pb ages from six rock samples employing LA–ICP-MS (at Laboratorio de Estudios Isotópicos, Centro de Geociencias, UNAM), while one sample was also dated by ID–TIMS (at Laboratorio Universitario de Geoquímica Isotópica, UNAM). These samples have igneous emplacement or metamorphic ages broadly ranging from the Neoproterozoic to the Paleocene. The obtained apatite U-Pb ages agree well with other radioisotopic data (U-Pb on zircon and K-Ar or Ar-Ar on micas and hornblende) available for the same rock samples tested, or for the same geological units studied. These apatite U-Pb results, obtained for the first time at two main Mexican geochronology laboratories, are precise enough to be geologically meaningful and usually represent the cooling ages; though, in some cases they may also indicate the crystallization or the metamorphic age. Some advantages and disadvantages of LA–ICPMSand ID–TIMS-based methodologies were observed and outlined. Our results validate the analytical procedures used and will serve as an important trigger towards the development or improvement of medium-temperature thermochronology techniques in Mexico. 2019 artículo científico 1026-8774 https://www.redalyc.org/articulo.oa?id=57265242003 https://www.redalyc.org/journal/572/57265242003/ https://www.redalyc.org/journal/572/57265242003/html/ https://www.redalyc.org/journal/572/57265242003/57265242003.epub https://www.redalyc.org/journal/572/57265242003/movil https://doi.org/10.22201/cgeo.20072902e.2019.1.749 en http://www.redalyc.org/revista.oa?id=572 Revista Mexicana de Ciencias Geológicas application/pdf Universidad Nacional Autónoma de México Revista Mexicana de Ciencias Geológicas (México) Num.1 Vol.36 |
| title | Apatite U-Pb dating at UNAM laboratories: analytical protocols and examples of its application |
| topic | Ciencias de la Tierra Mexico Apatite Pb dating laser ablation isotope dilution |
| url | https://www.redalyc.org/articulo.oa?id=57265242003 https://www.redalyc.org/journal/572/57265242003/ https://www.redalyc.org/journal/572/57265242003/html/ https://www.redalyc.org/journal/572/57265242003/57265242003.epub https://www.redalyc.org/journal/572/57265242003/movil https://doi.org/10.22201/cgeo.20072902e.2019.1.749 |