Apatite U-Pb dating at UNAM laboratories: analytical protocols and examples of its application
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 importan...
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Universidad Nacional Autónoma de México
2019-03-01
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| Series: | Revista Mexicana de Ciencias Geológicas |
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| Online Access: | https://rmcg.unam.mx/index.php/rmcg/article/view/749 |
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| author | Carlos Ortega-Obregón Fanis Abdullin Luigi Solari Peter Schaaf Gabriela Solís-Pichardo |
| author_facet | Carlos Ortega-Obregón Fanis Abdullin Luigi Solari Peter Schaaf Gabriela Solís-Pichardo |
| author_sort | Carlos Ortega-Obregón |
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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–ICP-MS- and 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.
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| format | Article |
| id | doaj-art-8062d40fc498482fbae82d6aa1f68620 |
| institution | OA Journals |
| issn | 1026-8774 2007-2902 |
| language | English |
| publishDate | 2019-03-01 |
| publisher | Universidad Nacional Autónoma de México |
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| series | Revista Mexicana de Ciencias Geológicas |
| spelling | doaj-art-8062d40fc498482fbae82d6aa1f686202025-08-20T02:22:50ZengUniversidad Nacional Autónoma de MéxicoRevista Mexicana de Ciencias Geológicas1026-87742007-29022019-03-0136110.22201/cgeo.20072902e.2019.1.749Apatite U-Pb dating at UNAM laboratories: analytical protocols and examples of its applicationCarlos Ortega-Obregón0Fanis Abdullin1Luigi Solari2Peter Schaaf3Gabriela Solís-Pichardo4Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, 76230 Querétaro, Qro., Mexico.CONACyT – Universidad Nacional Autónoma de México, Campus Juriquilla, Centro de Geociencias, Boulevard Juriquilla No. 3001, C.P. 76230, Juriquilla, Querétaro, Mexico.Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, 76230 Querétaro, Qro., Mexico.Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510 Mexico City, Mexico.Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, Mexico City, Mexico. 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–ICP-MS- and 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. https://rmcg.unam.mx/index.php/rmcg/article/view/749apatitelaser ablationisotope dilutionU-Pb datingthermochronologyMexico |
| spellingShingle | Carlos Ortega-Obregón Fanis Abdullin Luigi Solari Peter Schaaf Gabriela Solís-Pichardo Apatite U-Pb dating at UNAM laboratories: analytical protocols and examples of its application Revista Mexicana de Ciencias Geológicas apatite laser ablation isotope dilution U-Pb dating thermochronology Mexico |
| title | Apatite U-Pb dating at UNAM laboratories: analytical protocols and examples of its application |
| title_full | Apatite U-Pb dating at UNAM laboratories: analytical protocols and examples of its application |
| title_fullStr | Apatite U-Pb dating at UNAM laboratories: analytical protocols and examples of its application |
| title_full_unstemmed | Apatite U-Pb dating at UNAM laboratories: analytical protocols and examples of its application |
| title_short | Apatite U-Pb dating at UNAM laboratories: analytical protocols and examples of its application |
| title_sort | apatite u pb dating at unam laboratories analytical protocols and examples of its application |
| topic | apatite laser ablation isotope dilution U-Pb dating thermochronology Mexico |
| url | https://rmcg.unam.mx/index.php/rmcg/article/view/749 |
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