Brucite-driven CO2 uptake in serpentinized dunites (Ligurian Ophiolites, Montecastelli, Tuscany)

Low Temperature Serpentinite Replacement by Carbonates during Seawater Influx in the Newfoundland Margin

“…The simulations predict the observation of calcite in the natural samples studied here, but they do also predict Ca-rich carbonates formation at temperatures above 100 • C, as is observed at the Lost City Hydrothermal Field. Due to missing compatible thermodynamic data, we do not include phases such as layered double hydroxides (coalingite-pyroaugite, LDHs), and hydrous Mg-carbonates (hydromagnesite and nesquehonite) (e.g., [82]).…”

“…It is important to note that carbonates are mostly calcites, and minor aragonite [2], never dolomite. Mineralogy of carbonates encountered in the Alpine Tethys ophicarbonates is mostly calcite, and minor dolomite (e.g., in Val Ventina, Alps, [82]; and in the Chenaillet, [13] and references therein). We compiled δ 18 O and δ 13 C measured in ophicarbonates from the literature in several locations in the Alpine Tethys.…”

Formation and loss of metastable brucite: does Fe(II)-bearing brucite support microbial activity in serpentinizing ecosystems?

“…A significant portion of the Fe in partially serpentinized rocks resides in brucite [3,5,6,[8][9][10][11]. The Mg# of brucite (where Mg# = Mg/(Mg + Fe) mole ratio) can often vary from 0.95 to much lower values such as 0.65 when there is a notable Fe(OH) 2 component [2,12,13] (figure 1). Anomalously ferroan brucite, with Mg#s as low as 0.4 have also been observed in highly reduced mineral assemblages in serpentinite [14].…”

“…[39]); the potential formation of stable MgCO 3 is of interest for carbon sequestration [40,41]. Boschi et al [12] show that the presence of brucite in serpentinites plays a notable role in the natural carbonation process, particularly in dunite lithologies that are brucite-rich.…”

“…However, the chemical behaviour of the Fe(OH) 2 component is not always investigated. When ferroan brucite reacts with CO 2 , Boschi et al [12] report that the brucite is replaced with Fe-Mg layered double hydroxides in the pyroaurite-coalingite solid solution of Mg 2+ -Fe 3+ carbonates. Similarly, Hostetler et al [1] invoke the conversion of ferroan brucite to pyroaurite-coalingite phases during reaction with CO 2 in groundwaters.…”