Biomineral Reactivity: The Kinetics of the Replacement Reaction of Biological Aragonite to Apatite

Abstract

Abstract:We present results of bioaragonite to apatite conversion in bivalve, coral and cuttlebone skeletons, biological hard materials distinguished by specific microstructures, skeletal densities, original porosities and biopolymer contents. The most profound conversion occurs in the cuttlebone of the cephalopod Sepia officinalis, the least effect is observed for the nacreous shell portion of the bivalve Hyriopsis cumingii. The shell of the bivalve Arctica islandica consists of cross-lamellar aragonite, is dense at its innermost and porous at the seaward pointing shell layers. Increased porosity facilitates infiltration of the reaction fluid and renders large surface areas for the dissolution of aragonite and conversion to apatite. Skeletal microstructures of the coral Porites sp. and prismatic H. cumingii allow considerable conversion to apatite. Even though the surface area in Porites sp. is significantly larger in comparison to that of prismatic H. cumingii, the coral skeleton consists of clusters of dense, acicular aragonite. Conversion in the latter is sluggish at first as most apatite precipitates only onto its surface area. However, the process is accelerated when, in addition, fluids enter the hard tissue at centers of calcification. The prismatic shell portion of H. cumingii is readily transformed to apatite as we find here an increased porosity between prisms as well as within the membranes encasing the prisms. In conclusion, we observe distinct differences in bioaragonite to apatite conversion rates and kinetics depending on the feasibility of the reaction fluid to access aragonite crystallites. The latter is dependent on the content of biopolymers within the hard tissue, their feasibility to be decomposed, the extent of newly formed mineral surface area and the specific biogenic ultra-and microstructures.

Hydrothermal alteration of aragonitic biocarbonates: assessment of micro- and nanostructural dissolution–reprecipitation and constraints of diagenetic overprint from quantitative statistical grain-area analysis

“…shell parts that are next to the soft tissue of the animal, is mainly present in a crossedlamellar microstructural arrangement. Growth lines in A. islandica shells are frequent and are easily observed, as in this species biopolymer contents and mineral unit sizes are increased (Casella et al, 2017;Greiner et al, 2018). Even though the shell of A. islandica can be addressed as consisting of densely packed aragonite, it contains primary porosity.…”

“…Even though the shell of A. islandica can be addressed as consisting of densely packed aragonite, it contains primary porosity. The latter is unevenly distributed: along the seaward pointing shell portion, pores are abundant and large, while in shell parts that are closer to the soft tissue of the animal, pores are small and significantly less frequent (Greiner et al, 2018).…”

“…H. ovina) represent important archives for studies of palaeo-and present environmental change (Raffi, 1986;Richardson, 2001;Elliot et al, 2003;Wanamaker Jr. et al, 2008;Hippler et al, 2009;Schöne and Surge, 2012). The work of Hahn et al (2012Hahn et al ( , 2014 has shown that environmental reconstruction can be derived from microstructural information, as well as stable isotope and major element data (Jackson et al, 1988;Cartwright and Checa, 2007;Gries et al, 2009).…”

The Formation of Barite and Celestite through the Replacement of Gypsum

“…A further porosity contribution arises when the secondary phase is less soluble than the primary one [14][15][16]. Finally, factors like the solid to fluid volume ratio [17], the evolution of the composition of the fluid at the reaction front [18], the existence/absence of crystallographic relationships between the phases involved in the ICDP reaction [19], the presence of pre-existing cracks or other defects within the primary phase crystals [20] as well as the specific morphological and textural features of the secondary phase [21][22][23][24][25][26] can also contribute to modulate the volume of porosity generated during ICDP reactions and, more importantly, to define the spatial arrangement of the ICDP reaction-related porosity within the secondary phase [27][28][29]. The permeability and tortuosity of the thus-generated porosity network effectively define the degree of communication between the fluid phase and the reaction front.…”

Editorial for Special Issue “Mineral Surface Reactions at the Nanoscale”

“…Detailed micro-structural evidence is presented by Greiner et al [12] to introduce biomineral reactivity during the fluid-mediated replacement of biological aragonite (in bivalve, coral, and cuttlebone skeletons) to apatite (the mineral of bone material). This is a pseudomorphic replacement as a result of a tight interface-coupled dissolution-precipitation process.…”