Magnesian siderite in carbonate concretions from argillaceous sediments in the Westphalian of Yorkshire
نویسنده
چکیده
Lattice parameters have been determined for two coexisting siderite phases in concretions of Westphalian age. Chemical evidence indicates that, for one concretion at least, the phase of smaller cell dimensions is a magnesian siderite with around 25 mole % MgCOa. Both abundances and compositions of the two phases vary between concretions whilst a single phase only is present in disseminated siderite. It is thought unlikely that the two phases represent an equilibrium assemblage and a mechanism is suggested by which magnesian siderite could have formed later.
منابع مشابه
Sideritic concretions from the Westphalian of Yorkshire: a chemical investigation of the carbonate phase
The carbonate phase of impure sideritic concretions from a sequence of argillaceous sediments from the Westphalian of Yorkshire has been analysed using an acid-dissolution technique and corrections allowing for the decomposition of non-carbonate minerals applied to obtain accurate compositional formulae. The siderites show considerable compositional variation, some containing Ca in excess of an...
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