Al-free di-trioctahedral substitution in chlorite and a ferri-sudoite end-member
نویسندگان
چکیده
A compilation of Fe-bearing chlorite analyses is used: (1) to investigate the Alfree di-trioctahedral (AFDT) substitution 2Fe +□ = 3(Mg,Fe) in chlorite; and (2) to estimate the composition of a ferri-sudoite end-member (Si3Al)[(Fe ,Mg)2Fe 3+ 2 □Al]O10(OH)8 within the chlorite solid-solution domain. According to our observations, up to two Fe cations might be allocated in the M2-M3 chlorite sites by the substitution AFDT, which does not involve Al. These unexpected observations were made possible by the development of μXANES techniques allowing in situ measurements of XFe (Fe/(Fe + Fe)) in heterogeneous chlorite. Although further studies are required to confirm the crystallographic position of Fe and refine its ionic/ magnetic behaviour in chlorite, this development creates opportunities for developing new geothermometers.
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