Sudoite,a rock-forming mineral in Verrucano of the Northern Apennines (Italy) and the sudoite-chloritoid-pyrophyllite assemblage in prograde metamorphism

Sudoite, the di-trioctahedral chlorite with ideal composition (Mg₂Al)(Al₂)(Si₃Al)O₁₀(OH)₈ is a widespread rock-forming mineral in meta-siltstones and psammites of the Verrucano sequence of the Northern Apennines. Sub-ellipsoidal aggregates, probably derived from muscovite clasts, consisting of sudoite, pyrophyllite and muscovite, are common; sudoite may also occur as thin blades in the rock matrix. The co-existence of sudoite, Ferich chloritoid and pyrophyllite, reported here for the first time, has been observed in specimens from the M. Argentario and Monticiano-Roccastrada areas. This three-phase assemblage, diagnostic of a specific metamorphic facies, may be a tool for detailed zonation of low-grade terranes.     

Petrogenesis of Al–silicate-bearing trondhjemitic migmatites from NE Sardinia, Italy

The migmatites from Punta Sirenella (NE Sardinia) are layered rocks containing 3–5 vol.% of centimeter-sized stromatic leucosomes which are mainly trondhjemitic and only rarely granitic in composition. They underwent three deformation phases, from D₁ to D₃. The D₁ deformation shows a top to the NW shear component followed by a top to the NE/SE component along the XZ plane of the S₂ schistosity. Migmatization started early, during the compressional and crustal thickening stage of Variscan orogeny and was still in progress during the following extensional stage of unroofing and exhumation.

The trondhjemitic leucosomes, mainly consisting of quartz, plagioclase, biotite ± garnet ± kyanite ± fibrolite, retrograde muscovite and rare K-feldspar, are locally bordered by millimeter-sized biotite-rich melanosomes. The rare granitic leucosomes differ from trondhjemitic ones only in the increase in modal content of K-feldspar, up to 25%. Partial melting started in the kyanite field at about 700–720 °C and 0.8–0.9 GPa, and was followed by re-equilibration at 650–670 °C and 0.4–0.6 GPa, producing fibrolite–biotite intergrowth and coarse-grained muscovite.

The leucosomes have higher SiO₂, CaO, Na₂O, Sr and lower Al₂O₃, Fe₂O₃, MgO, TiO₂, K₂O, P₂O₅, Rb, Ba, Cr, V, Zr, Nb, Zn and REE content with respect to proximal hosts and pelitic metagreywackes. Sporadic anomalous high content of calcium and ferromagnesian elements in some leucosomes is due to entrainment of significant amounts of restitic plagioclase, biotite and accessory phases. The rare granitic leucosomes reveal peritectic K-feldspar produced by muscovite-dehydration melting. Most leucosomes show low REE content, moderately fractionated REE patterns and marked positive Eu anomaly. Proximal hosts and pelitic metagraywackes are characterized by higher REE content, more fractionated REE patterns and slightly negative Eu anomaly.

The trondhjemitic leucosomes were generated by H₂O-fluxed melting at 700 °C of a greywacke to pelitic–greywacke metasedimentary source-rock. The disequilibrium melting process is the most reliable melting model for Punta Sirenella leucosomes.     

Diesel oil and PCB-degrading psychrotrophic bacteria isolated from Antarctic seawaters (Terra Nova Bay, Ross Sea)

Fifty-seven Antarctic marine bacteria were examined for their ability to degrade commercial diesel oil as the sole organic substrate at both 4 °C and 20 °C. Based on the preliminary screening, two isolates (B11 and B15) with high capacity to degrade diesel oil were selected and their biodegradation efficiency was quantified by gas chromatographic analysis. As expected for psychrotrophs, diesel oil biodegradation was slower at 4 °C than at 20 °C. The two strains also mineralized the C₂₈ n-paraffin octacosane at 20 °C and polychlorinated biphenyls (PCBs) at 4 °C and 20 °C.