Synthesis and Structure of Tochilinite: A Layered Metal Hydroxide/Sulfide Composite

Hydrothermal alteration experiments of enstatite: Implications for aqueous alteration of carbonaceous chondrites

“…Hydrothermal experiments (Kakos et al 1994;Kozerenko et al 1996) showed that tochilinite can be produced from Fe sulfide/hydroxide at pH 7.8-11.5. Our interpretation that aqueous alteration in CM chondrites occurred under neutral to moderately alkaline conditions and at lower temperatures relative to CV and CI chondrites (see below) is consistent with these interpretations and results.…”

“…However, it should be noted that the aqueous alteration in CM chondrites may be related to not only pH/temperature but also other parameters such as oxygen fugacity and precursor mineralogy. For example, tochilinite is known to form under low oxygen fugacity (Kakos et al 1994;Kozerenko et al 1996), suggesting that aqueous alteration in CM chondrites occurred under reducing conditions. In CM chondrites, not only enstatite but also a variety of Mg-Fe-rich minerals such as Mg-Fe olivine, Fe-Ni metal, and Fe sulfide have been involved in extensive aqueous alteration (e.g., Tomeoka and Buseck 1985;Hanowski and Brearley 2001).…”

Hydrothermal preparation of analogous matrix minerals of CM carbonaceous chondrites from metal alloy particles

“…In addition, the successful preparation of tochilinite and TCI may, to some extent, also show that Harder's viewpoint is correct, but the structures of tochilinite and TCI indicate that the Fe(OH) 2 or Fe(OH) 2 -like layers can also be stabilized by mackinawite-like Fe 1−x S layers in aqueous solution (Kakos et al, 1994;Kozerenko et al, 1996Kozerenko et al, , 2001Peng et al, 2007Peng et al, , 2009). …”

“…1a and 1b shows typical XRD patterns of the synthetic mineral assemblage, which can be viewed mainly as a superposition of serpentine minerals (e.g., cronstedtite, Joint Committee on Powder (Kakos et al, 1994;Peng et al, 2007;Nakamura and Nakamuta, 1996). For the readers to see the evolution of the mineral assemblage with reaction time, addition XRD patterns are presented in Fig.…”

“…Contrary to the above simulated hydrothermal experiments, the successful syntheses of tochilinite and TCI have been carried out in strictly O 2 -free and reducing environment (Kakos et al, 1994;Kozerenko et al, 1996Kozerenko et al, , 2001Peng et al, 2007Peng et al, , 2009. Theoretical study on tochilinite indicated that tochilinite must be prepared in a reducing environment (log(oxygen fugacity) or log( f O 2 (g) ) < −85 or Eh < −0.45 V at standard temperature and pressure (STP, 25 • C and 10 5 Pa); Zolensky, 1984;Browning and Bourcier, 1996).…”