title: Na, K, Ca, Mg, and U-series in fossil bone and the proposal of a radial diffusion-adsorption model of uranium uptake.
abstract: Fossil bones are often the only materials available for chronological reconstruction of important archeological sites. However, since bone is an open system for uranium, it cannot be dated directly and therefore it is necessary to develop models for the U uptake. Hence, a radial diffusion-adsorption (RDA) model is described. Unlike the classic diffusion-adsorption (D-A) model, RDA uses a cylindrical geometry to describe the U uptake in fossil bones. The model was applied across a transverse section of a tibia of an extinct megamammal Macrauchenia patachonica from the La Paz Local Fauna, Montevideo State, Uruguay. Measurements of spatial distribution of Na, K, Ca, and Mg were also performed by neutron activation analysis (NAA). Gamma-ray spectrometric U-series dating was applied to determine the age of the bone sample. From U concentration profile, it was possible to observe the occurrence of a relatively slow and continuous uranium uptake under constant conditions that had not yet reached equilibrium, since the uranium distribution is a ∪-shaped closed-system. Predictions of the RDA model were obtained for a specific geochemical scenario, indicating that the effective diffusion coefficient D/R in this fossil bone is (2.4 ± 0.6)10(-12) cm(2)s(-1). Mean values of Na, K, Ca, and Mg contents along the radial line of the fossil tibia are consistent with the expected behavior for spatial distributions of these mineral elements across a modern bone section. This result indicates that the fossil tibia may have its mineral structure preserved.
authors: LARA - Laboratório de Radioecologia e Alterações Ambientais, Instituto de Física, Universidade Federal Fluminense, Av. Gal Milton Tavares de Souza, S/N, Gragoatá, 24210-346, Niterói, RJ, Brazil.
authors: A S
authors: AS
authors: Cid
authors: LARA - Laboratório de Radioecologia e Alterações Ambientais, Instituto de Física, Universidade Federal Fluminense, Av. Gal Milton Tavares de Souza, S/N, Gragoatá, 24210-346, Niterói, RJ, Brazil. Electronic address: meigikos@mail.if.uff.br.
authors: R M
authors: RM
authors: Anjos
authors: Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN), Centro do Reator de Pesquisa (CRPq), Av. Lineu Prestes 2242 - Cidade Universitária, 05508-000, São Paulo, SP, Brazil.
authors: C B
authors: CB
authors: Zamboni
authors: LARA - Laboratório de Radioecologia e Alterações Ambientais, Instituto de Física, Universidade Federal Fluminense, Av. Gal Milton Tavares de Souza, S/N, Gragoatá, 24210-346, Niterói, RJ, Brazil.
authors: R
authors: R
authors: Cardoso
authors: LARA - Laboratório de Radioecologia e Alterações Ambientais, Instituto de Física, Universidade Federal Fluminense, Av. Gal Milton Tavares de Souza, S/N, Gragoatá, 24210-346, Niterói, RJ, Brazil.
authors: M
authors: M
authors: Muniz
authors: Departamento de Evolución de Cuencas, Facultad de Ciencias, UDELAR, Iguá 4225, Montevideo 11400, Uruguay.
authors: A
authors: A
authors: Corona
authors: GEA - Instituto de Matemática Aplicada San Luis (IMASL), Universidad Nacional de San Luis, CCT-San Luis CONICET, Ej. de los Andes 950, D5700HHW, San Luis, Argentina.
authors: D L
authors: DL
authors: Valladares
authors: Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN), Centro do Reator de Pesquisa (CRPq), Av. Lineu Prestes 2242 - Cidade Universitária, 05508-000, São Paulo, SP, Brazil.
authors: L
authors: L
authors: Kovacs
authors: LARA - Laboratório de Radioecologia e Alterações Ambientais, Instituto de Física, Universidade Federal Fluminense, Av. Gal Milton Tavares de Souza, S/N, Gragoatá, 24210-346, Niterói, RJ, Brazil.
authors: K
authors: K
authors: Macario
authors: Departamento de Evolución de Cuencas, Facultad de Ciencias, UDELAR, Iguá 4225, Montevideo 11400, Uruguay.
authors: D
authors: D
authors: Perea
authors: Departamento de Evolución de Cuencas, Facultad de Ciencias, UDELAR, Iguá 4225, Montevideo 11400, Uruguay.
authors: C
authors: C
authors: Goso
authors: GEA - Instituto de Matemática Aplicada San Luis (IMASL), Universidad Nacional de San Luis, CCT-San Luis CONICET, Ej. de los Andes 950, D5700HHW, San Luis, Argentina.
authors: H
authors: H
authors: Velasco
mesh_terms: D000327:Adsorption; D000818:Animals; D001106:Archaeology / Q000379:methods*; D002118:Calcium / Q000737:chemistry; D004058:Diffusion; D005580:Fossils; D008322:Mammals; D019565:Metals, Light / Q000737:chemistry; D008962:Models, Theoretical; D009501:Neutron Activation Analysis; D010163:Paleontology / Q000379:methods*; D013051:Spectrometry, Gamma; D013977:Tibia / Q000737:chemistry*; D014501:Uranium / Q000032:analysis / Q000737:chemistry*
chemical_list: D019565:Metals, Light; D014501:Uranium; D002118:Calcium
keywords: Fossil bone; Gamma-ray spectrometric U-series dating; Neutron activation analysis; Radial diffusion–adsorption model; Uranium uptake