ABSTRACT Results from laboratory analyses of thermophysical properties and mineralogical composition of rocks belonging to the main geological formations of the Umbria-Marche stratigraphic succession are presented. We carried out measurements of thermal conductivity, porosity, and density. The samples were mineralogically characterized by means of powder X-ray diffraction and by calcimetry. Scanning electron microscope analyses were conducted to ascertain the absence of mineralized veins, which could have biased the mineralogical composition. A mixing model was also applied to infer the thermal conductivity. The results can be useful to characterize the behavior of shallow geothermal systems in the study region.

The iron oxidation state and coordination number have been determined by Fe K-edge X-ray absorption–near edge spectroscopy (XANES) for six tektites from the North American tektite strewn field (four bediasites and two georgiaites) and a tektite fragment from the Deep Sea Drilling Project (DSDP) Site 612, which is part of the North American tektite strewn field. All tektite samples display a pre-edge peak, the components of which are consistent with the presence of divalent Fe. Comparison of pre-edge peak data (integrated intensity and centroid energy) with those of Fe model compounds allows us to quantitatively determine the Fe oxidation state and coordination number. The Fe 3+ /(Fe 2+ + Fe 3+ ) ratio is close to 0.05 (±0.03), consistent with tektites from all the other strewn fields. The average Fe coordination number is intermediate between 4 and 5. Accurate determination of this value is hindered by the scatter of pre-edge peak intensity of all the Fe model compounds; [4] Fe/( [4] Fe + [5] Fe) is estimated to be 0.26 ± 0.15. In contrast to North American microtektites, for which iron oxidation state and coordination numbers display significant variations across the North American strewn field, no significant variations in the Fe oxidation state and coordination number were found between the georgiaites, bediasites, and the DSDP 612 tektite fragment. It is remarkable that the tektite fragment from the DSDP 612 site showed no sign of oxidation despite the long burial period in marine sediments.

We studied the oxidation state of Fe in silicate glasses produced during the first atomic bomb blast at the Trinity test site (New Mexico) by X-ray absorption–near edge spectroscopy (XANES). The sample consists of green glass resulting from melting of the quartz-bearing sand present at the test site; some relict unmelted sand is still fused to the bottom of the sample. Comparison of the pre-edge peak data with model compounds of known Fe oxidation state and coordination number shows that in the Trinity glass sample, Fe is in the divalent state and, on average, in a mixture of 4- and 5-fold coordination. XANES spectra collected at various heights of the sample, from the bottom of the sample up to the exposed surface, show no variation of the pre-edge peak and, thus, of the Fe oxidation state with the distance from the sand-glass interface. However, XANES analysis of a portion of the sand at the bottom of the sample shows Fe to be a mixture of Fe 2+ and Fe 3+ , with a Fe 3+ /(Fe 2+ + Fe 3+ ) ratio close to 0.5. This demonstrates that during the nuclear explosion, the ground rock was instantaneously reduced, transforming all the iron from mostly trivalent state to almost exclusively divalent. Pre-edge peak features (intensity and energy) are consistent with those of tektites from the Ivory Coast studied here and with literature data of tektites from all the other known strewn fields (Australasian, Central European, and North American). The reduction of Fe to divalent state during Trinity glass formation, the homogeneity of the Fe oxidation state within the glass, and the Fe structural role suggest that this glass represents a good analog of tektite glass.