Intracrystalline Reaction-Induced Cracking in Olivine Evidenced by Hydration and Carbonation Experiments

Abstract

In order to better understand the microtextural changes associated with serpentinization reactions, natural millimeter-sized olivine grains were experimentally reacted with alkaline NaOH and NaHCO 3 solutions at a temperature of 200 • C and for durations of 3 to 12 months. During hydration experiments, dissolution and precipitation were intimately correlated in time and space, with reaction products growing in situ, either as layered veins or as nearly continuous surface cover. In contrast, carbonation experiments showed a strong decoupling between both processes leading to essentially delocalized precipitation of the reaction products away from dissolution sites. Textural analyses of the samples using scanning electron microscopy, Raman spectroscopy, and X-ray synchrotron microtomography provided experimental evidence for a cause-and-effect relationship between in situ precipitation and intracrystalline reaction-induced cracking in olivine. Juvenile cracks typically nucleated at the tip of dissolution notches or on diamond-shaped pores filled with reaction products, and propagated through the olivine crystal lattice during the course of the reaction. The occurrence of new cracks at the tip of diamond-shaped pores, but also of tiny subspherical pores lining up along microcracks, indicated that fracturation and porosity networks were mutually driven, making serpentinization an extremely efficient alteration process over time. Alternatively, our data suggested that some form of porosity also developed in absence of fracturation, thus further highlighting the remarkable efficiency and versatility of serpentinization processes.

Measurement of Volume Change and Mass Transfer During Serpentinization: Insights From the Oman Drilling Project

“…Displacement along cracks in the platelets indicates the generation of stresses sufficient for brittle deformation during serpentinization. This is consistent with the theoretical predictions and observations for reaction‐induced fracturing during serpentinization (Kelemen & Hirth, ; Lafay et al, ; Malvoisin et al, ). The measured changes in volume are between 59 ± 29% and 74 ± 36%, with average values that appear to be slightly higher than the 52% calculated for reaction in a closed system.…”

“…It leads to both decrease and increase in permeability through porosity filling by reaction products (Farough et al, ; Godard et al, ) and stress buildup leading to cracking (Evans, ; Jamtveit et al, ; Macdonald & Fyfe, ; O'Hanley, ), respectively. This latter process of reaction‐induced cracking is constrained with observations in natural systems (Coleman & Keith, ; Loney et al, ; Malvoisin et al, ; Plümper et al, ; Rouméjon & Cannat, ), thermodynamic theory (Kelemen & Hirth, ), thermodynamic models of water rock reaction in natural and simplified systems (de Obeso et al, ; Klein et al, ; Malvoisin, ), physical and numerical models (Evans et al, ; Malvoisin et al, ; Rudge et al, ; Shimizu & Okamoto, ; Ulven et al, ), and experiments (Lafay et al, ; Zhu et al, ; Zheng et al, ). Despite the key role of solid volume change during serpentinization, this parameter is not well constrained since it has not been measured in natural samples yet and it is closely related to mass transfer during reaction.…”

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.…”

Modeling Porosity Evolution Throughout Reaction‐Induced Fracturing in Rocks With Implications for Serpentinization

“…Reaction-induced fracturing is observed in many geodynamic and engineering contexts, from salt damage in concrete and rocks (Flatt, 2002;Noiriel et al, 2012;Steiger, 2005), formation of travertine deposits (Gratier et al, 2012), rock weathering (Røyne et al, 2008), and hydration reactions in the Earth's crust, including serpentinization and eclogitization transformations (Iyer et al, 2008;Jamtveit, Malthe-Sørenssen, & Kostenko, 2008;Kelemen & Hirth, 2012;Lafay et al, 2018;Lisabeth et al, 2017;Martin & Fyfe, 1970). Serpentinization occurs when mafic rocks originating from the Earth's mantle or crust, such as peridotites and volcanic rocks, are uplifted in the crust and meet meteoric or oceanic waters.…”

“…Several factors control the kinetics of serpentinization. The salinity of the fluid, the presence of CO 2 , the mineralogy of the reacting rock as well as the initial grain size of olivine all have influence on the serpentinization process (Lafay et al, ; Malvoisin et al, ; Martin & Fyfe, ). In situ stress state can also influence the reaction rate, as well as the generation of reaction‐induced fractures.…”