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Five varieties of Belgian black marbles are investigated in order to discriminate them. Their age ranges from Frasnian (Golzinne) to Visean (Dinant, Theux, Basècle, Lives). Three methods were used: petrography, magnetic susceptibility and geochemistry of major elements and Rare Earth Elements (REE). The petrographic analyze reveals 16 microfacies reflecting very quiet environments, sporadically perturbed by more energetic phenomena like turbidites or storms. These microfacies are integrated in two depositional models: a quiet offshore setting, below or close to the storm wave base (Salet, Basècles) and a shallow but very restricted zone, protected from waves and currents (Lives and Golzinne). The magnetic susceptibility results show that all the black marbles are characterized by very low, even slightly negative values, except the Golzinne one which shows higher values. Geochemical data allow to discriminate between the Theux black marble (low SiO2 content), and the Basècles samples (low Al2O3, K2O and REE contents). These methods could be useful to determine/refine the origin of archaeological stones, even if all these analyses are destructive. Two archeologic samples were investigated in order to identify their possible origin. [ABSTRACT FROM AUTHOR]

Manganese ore in the Cenomanian-Turonian dolostone of the Imini district (south of the High Atlas, Morocco) displays a high Mn content due to the occurrence of pyrolusite, cryptomelane, hollandite sensu stricto, coronadite, romanechite, and lithiophorite. The orebodies occur mainly as three stratabound layers along the ~25-km-long ore belt following a WSW-ENE direction. Using scanning electron microscopy (SEM-EDS) coupled with X-ray diffraction (XRD), we here refine the mineralogy and petrology of Mn oxides and oxyhydroxides in order to constrain the paragenetic sequence and define the main processes of ore formation. Deposition and concentration of Mn oxyhydroxides follow a two-step sequence after dolomitization: (1) replacement of dolomite fabric (dolomite micrite and dolomite rhombs) by hollandite group minerals leading to a textural conservation and then (2) neoformation of collomorphous aggregates in an opened and brecciated system. These observations are consistent with a multistage evolution including multiple reworking and brecciation. Pyrolusite is the main Mn oxide observed in the Imini district during both early and late stages. The superficial environment provides supergene conditions suitable for the deposition of only Mn oxyhydroxides. This supergene environment and the occurrence of multiple bands of hollandite group minerals indicate an external migration (allochthonous supply) of Mn and associated elements, contemporaneous to an in situ chemical and mechanical dissolution of the host dolostone. The lithological heterogeneities of dolostone and its chemical environment compared to less permeable surrounding rocks may have provided the conditions to concentrate Mn oxides and oxyhydroxides. [ABSTRACT FROM AUTHOR]

New carbon isotopic data from the Devonian of Ardennes (Belgium) and partly from the Holy Cross Mountains (Poland) highlight an abrupt and high-amplitude negative excursion in the punctata conodont Zone. Published information from Moravia and China suggests that this Middle Frasnian negative excursion, jointly with the preceding large-scale positive shift, should be used as a global chemostratigraphic marker. Causation scenarios for this negative 'punctata Event' are correlated neither with major biota turnover nor major sea-level changes, but may be related to: (1) the Alamo Impact Event, that led to (2) the massive dissociation of methane hydrates and (3) the rapid onset of global warming. [ABSTRACT FROM AUTHOR]

Illite Kübler index (KI) and oxygen isotope (brachiopods and micrites) investigations have been performed on more than 300 Frasnian limestones sampled in one borehole and numerous outcrops in the Dinant Synclinorium (Belgium, northern France) of the northern Variscan front. The illite Kübler index and δ18O data of a 3-km-thick, tectonically repeated Frasnian series from the Focant borehole are compared with their surrounding surface correspondents and document in-situ reheating induced by Variscan tectonic loading, which post-dated sedimentary burial alteration. The boundary between these two thermal processes (sedimentary burial and tectonic loading) on the Focant profile corresponds to an important location where the heat induced by the tectonic loading was equivalent to that Frasnian strata suffered during maximum sedimentary burial. Mainly based on this knowledge and on a former conodont colour alteration index study, the thickness of the eroded thrust sheet in the Focant area is estimated to be around 3,000 m. Oxygen isotopic exchange in these Frasnian closed carbonate systems, occurring under highest-grade diagenesis and anchimetamorphism, records two events. Brachiopods present a quite different and more homogeneous pattern, due to their higher resistance to heat alteration. These thermal events caused both δ18O records to become increasingly lighter than the presumed original seawater signature. The comparison between KI and δ18O profiles indicates that illite KI analysis is more appropriate than δ18O in highlighting the temperature variations in the burial metamorphism at the periphery of orogenic belts. [ABSTRACT FROM AUTHOR]

Describes a case regarding the removal of a knotted flow-directed catheter by a nonsurgical method. Medical profile of the patient; Background on catheter knotting; Description of the nonsurgical technique performed during the surgery.