Resumen de Aspectos químicos de la magnetita y clorita de las "ironstones" ordovicicas de Zamora (España).

Agustina Fernández Fernández, María Candelas Moro Benito

• The chemical characteristics of the magnetites and the chlorites from Ordovician ironstones of Zamora are described in this paper. The unusually Hig contents of Ti, V, Cr. Ba and Ni magnetite indicates, probably, the existence of a basic precursor in the sourceland and Co/Ni ratio< 1that suggests a sedimentary origin to itself. Also it shows a clear depletion in Eu anda light enrichment in Ce. The latter, together with the d18O value ranging from 3.6 to 8.61, also suggest a diagenetic or metamorphic origin to the magnetite. Starting from the major elements contents of the chamosite, the T. fO2 and fS2 have been estimated ranging from 234 to 312ºC, log fO2 from -36 to -31,4 and log fS2 from -11,9 to -9,8 respectively. These T are compatible with the metamorphism ones that affected this area during the Hercynian Orogeny, showing essentially a metamorphic origin to the chamosite.