Trace element diffusivities in bone rule out simple diffusive uptake during fossilization but explain in vivo uptake...

Area of Science:

• Geochemistry
• Paleontology
• Biogeochemistry

Background:

• Understanding trace element diffusion in bone is crucial for interpreting paleontological and archeological records.
• Existing models for trace element alteration in phosphatic tissues lack precise kinetic data.

Purpose of the Study:

• To quantify diffusion rates of trace elements in bone at 20 °C.
• To compare experimental diffusion data with existing geochemical and radiotracer estimates.
• To elucidate the mechanisms controlling trace element profiles in fossils and archeological materials.

Main Methods:

• Laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to analyze experimentally induced diffusion profiles in bone.
• Diffusion experiments were conducted at a controlled temperature of 20 °C.

Main Results:

• Measured bone diffusivities are approximately one order of magnitude slower than geochemical estimates and 1.5 orders of magnitude faster than radiotracer estimates.
• Intrabone volume diffusion is too slow and element-independent to account for observed trace element profiles in young fossils.
• Element-specific diffusivity differences explain variations in strontium (Sr) vs. barium (Ba) and light vs. heavy rare earth element (REE) biokinetic washout.

Conclusions:

• Intrabone diffusion alone is insufficient to explain trace element profiles in young fossils; soil recrystallization and transport limitations are significant factors.
• The diffusion of trivalent cations, including REEs, in phosphatic tissues is likely governed by a common charge-compensating species, not ionic radii or partition coefficients.
• These findings refine biokinetic models and enhance understanding of trace element alteration in paleontological and archeological contexts.