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Losses of Radiogenic 40Ar in the Fine-Clay Size Fractions of Sediments
- Abraham Lerman, Norbert Clauer
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- Journal:
- Clays and Clay Minerals / Volume 53 / Issue 3 / June 2005
- Published online by Cambridge University Press:
- 01 January 2024, pp. 234-249
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The common observation that smaller particle-size fractions of sedimentary rocks yield younger K-Ar apparent ages than the larger particle-size fractions of the same stratigraphic age was analyzed with the aid of the 40Ar/40K ratio from 14 stratigraphically and regionally different sections. Estimation of the loss of radiogenic 40Ar from varied clay-rich size fractions was based on two models: a relationship between particle size and the 40Ar/40K ratio, and a theoretical diffusional loss from spherical particles. The differences between the two models and reconciliation of their results are discussed. For the smallest fractions (up to <0.5 μm), percent-wise losses of 40Ar from the spherical particles model increase from Upper Carboniferous and Permian (38±10%), to Late Triassic (47±10%), and to Miocene and Late Neogene (65±8%). This trend suggests that escape of 40Ar from the smaller particles in older sediments decreased or even stopped after deposition of the sedimentary sections.
The large 40Ar losses derived from small 40Ar/40K ratios in the younger Tertiary sediments, indicate that addition of K to the small fractions is, at least in part, responsible for the young K-Ar apparent ages in geologically different settings. In several 102–103 m thick sections, authigenic illite in the <0.1 to <2 μm fractions yields young K-Ar apparent ages resulting from simultaneous 40Ar production and release during clay authigenesis. In a production and loss model, a first-order escape-rate parameter (e) was estimated at 0.2 × 10−8 to 4 × 10−8 y−1, depending on the K-Ar apparent age of the size fractions and the stratigraphic age of the section. The limitations and uncertainties of the methods of evaluating diagenetic 40Ar losses from fine clay particles are discussed.
Contributors
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- By Shamsuddin Akhtar, Greg Albert, Sidney Allison, Muhammad Anwar, Haruo Arita, Amanda Barker, Mary Hanna Bekhit, Jeanna Blitz, Tyson Bolinske, David Burbulys, Asokumar Buvanendran, Gregory Cain, Keith A. Candiotti, Daniel B. Carr, Derek Chalmers, John Charney, Rex Cheng, Roger Chou, Keun Sam Chung, Anna Clebone, Frederick Conlin, Susan Dabu-Bondoc, Tiffany Denepitiya-Balicki, Jeanette Derdemezi, Anahat Kaur Dhillon, Ho Dzung, Juan Jose Egas, Stephen M. Eskaros, Zhuang T. Fang, Claudia R. Fernandez Robles, Victor A. Filadora, Ellen Flanagan, Dan Froicu, Allison Gandey, Nehal Gatha, Boris Gelman, Christopher Gharibo, Muhammad K. Ghori, Brian Ginsberg, Michael E. Goldberg, Jeff Gudin, Thomas Halaszynski, Martin Hale, Dorothea Hall, Craig T. Hartrick, Justin Hata, Lars E. Helgeson, Joe C. Hong, Richard W. Hong, Balazs Horvath, Eric S. Hsu, Gabriel Jacobs, Jonathan S. Jahr, Rongjie Jaing, Inderjeet Singh Julka, Zeev N. Kain, Clinton Kakazu, Kianusch Kiai, Mary Keyes, Michael M. Kim, Peter G. Lacouture, Ryan Lanier, Vivian K. Lee, Mark J. Lema, Oscar A. de Leon-Casasola, Imanuel Lerman, Philip Levin, Steven Levin, JinLei Li, Eric C. Lin, Sharon Lin, David A. Lindley, Ana M. Lobo, Marisa Lomanto, Mirjana Lovrincevic, Brenda C. McClain, Tariq Malik, Jure Marijic, Joseph Marino, Laura Mechtler, Alan Miller, Carly Miller, Amit Mirchandani, Sukanya Mitra, Fleurise Montecillo, James M. Moore, Debra E. Morrison, Philip F. Morway, Carsten Nadjat-Haiem, Hamid Nourmand, Dana Oprea, Sunil J. Panchal, Edward J. Park, Kathleen Ji Park, Kellie Park, Parisa Partownavid, Akta Patel, Bijal Patel, Komal D. Patel, Neesa Patel, Swati Patel, Paul M. Peloso, Danielle Perret, Anthony DePlato, Marjorie Podraza Stiegler, Despina Psillides, Mamatha Punjala, Johan Raeder, Siamak Rahman, Aziz M. Razzuk, Maggy G. Riad, Kristin L. Richards, R. Todd Rinnier, Ian W. Rodger, Joseph Rosa, Abraham Rosenbaum, Alireza Sadoughi, Veena Salgar, Leslie Schechter, Michael Seneca, Yasser F. Shaheen, James H. Shull, Elizabeth Sinatra, Raymond S. Sinatra, Neil Singla, Neil Sinha, Denis V. Snegovskikh, Dmitri Souzdalnitski, Julie Sramcik, Zoreh Steffens, Alexander Timchenko, Vadim Tokhner, Marc C. Torjman, Co T. Truong, Nalini Vadivelu, Ashley Vaughn, Anjali Vira, Eugene R. Viscusi, Dajie Wang, Shu-ming Wang, J. Michael Watkins-Pitchford, Steven J. Weisman, Ira Whitten, Bryan S. Williams, Jeremy M. Wong, Thomas Wong, Christopher Wray, Yaw Wu, Anthony T. Yarussi, Laurie Yonemoto, Bita H. Zadeh, Jill Zafar, Martha Zegarra, Keren Ziv
- Edited by Raymond S. Sinatra, Jonathan S. Jahr, University of California, Los Angeles, School of Medicine, J. Michael Watkins-Pitchford
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- Book:
- The Essence of Analgesia and Analgesics
- Published online:
- 06 December 2010
- Print publication:
- 14 October 2010, pp xi-xviii
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