A method for apatite Lu–Hf geochronology and elimination of the negative effects of phosphate inclusions on garnet Lu–Hf and Sm–Nd geochronology by chemical leaching
Apatite is a ubiquitous accessory mineral found in a wide variety of rocks. It has a highly variable chemical composition and contains sufficient isotopes for four radioactive dating systems with Lu–Hf being one of them. This means that apatite could be developed into an independent geochronometer p...
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| Other Authors: | , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
| Published: |
2019
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| Subjects: | |
| Online Access: | https://rex.libraries.wsu.edu/esploro/outputs/doctoral/A-method-for-apatite-LuHf-geochronology/99900581503301842 https://rex.libraries.wsu.edu/view/delivery/01ALLIANCE_WSU/12350010030001842/13350010020001842 |
| Summary: | Apatite is a ubiquitous accessory mineral found in a wide variety of rocks. It has a highly variable chemical composition and contains sufficient isotopes for four radioactive dating systems with Lu–Hf being one of them. This means that apatite could be developed into an independent geochronometer provides useful information, and when incorporated in another mineral, may, in turn, affect geochronologic information obtained from the hosting mineral. These manuscripts describe and discuss both roles of apatite in geochronology. Chapter one and two focus on apatite Lu–Hf geochronology. Chapter one reports a detailed chemical method and mass spectrometry analytical techniques for isotope dilution apatite Lu–Hf geochronology. The chemical separation method utilizes high-performance extraction chromatography columns to combat the naturally low Hf content in apatite. Chapter two extends the application of apatite Lu–Hf chronometer to apatite iron oxide (IOA) deposits, also known Kiruna type deposits, in the Coastal Cordillera of northern Chile and reports for the first time, age information on some of these deposits. The third chapter discusses the potentially detrimental effects of inclusions of apatite and another phosphate mineral, monazite, on garnet Lu–Hf and Sm–Nd geochronology and explores an optimized chemical partial dissolution method to address this problem. Overall, this research provides methods applicable to apatite Lu–Hf and garnet Lu–Hf and Sm–Nd geochronology. It also provides information useful for designing methods of mineral dissolution and chemical chromatography separation for unconventional minerals. |
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