XRPD (Rietveld method),TG, DTG and DTA investigation of SAFOD cuttings ( ) Federico Zorzi 1, Fabio Ferri 1 and Giulio Di Toro 1,2 1, Dipartimento di Geoscienze, Università di Padova, Italy 2, Istituto Nazionale di Geofisica e Vulcanologia, Roma, Italy.

plagioclase pyrite microcline calcite quartz mixed smectite-illite The mineral composition of the cuttings was determined from XRPD data. The low angle broad peaks evidence the presence of illlite + mixed layer smectite-illite + chlorite which cannot be resolved. XRPD – SAFOD cuttings

The quantitaive determination of the phases was performed with Rietveld analysis on XRPD data. Since it was not possible to enrich and separate the clayey fraction, in the refinement strategy all the clays were treated as amorphous material and 10 % wt of corundum was added as inner standard. Quartz57.2% Plagioclase14.1% Calcite2.8% K-feldspar6.5% Pyrite1% Chlorite4.4% Clays 14% observed calculated illite structure inadequate to fit the low angle data RIETVELD ANALYSIS

1.5 %wt loss due to illite-smectite decomposition The thermal analysis suggest that clay amount in the cuttings is around 10-15% wt which is in agreement with data obtained from the Rietveld refinement THERMAL GRAVIMENTRY (TG), DIFFERENTIAL THERMAL GRAVIMETRY (DTG), DIFFERENTIAL THERMAL ANALYSIS (DTA)