Deposits of Fe-Si-Mn oxyhydroxides are commonly found on the seafloor on seamounts and mid-ocean spreading centers. At Franklin Seamount located near the western extremity of Woodlark Basin, Papua New Guinea, Fe-Si-Mn oxyhydroxides are being precipitated as chimneys and mounds upon a substrate of mafic lava. Previous studies have shown that the vent fluids have a low temperature (20-30 uC) and are characterized by a total dissolved iron concentration of 0.038 mM kg 21 , neutral pH (6.26) and no measurable H 2 S. The chimneys have a yellowish appearance with mottled red-orange patches when observed in situ from a submersible, but collected samples become redder within a few hours of being removed from the sea. The amorphous iron oxyhydroxides, obtained from active and inactive vents, commonly possess filamentous textures similar in appearance to sheaths and stalks excreted by the iron-oxidizing bacteria Leptothrix and Gallionella; however, formless agglomerates are also common. Textural relationships between apparent bacterial and non-bacterial iron suggest that the filaments are coeval with and/or growing outwards from the agglomerates. The amorphous iron oxyhydroxides are suggested to precipitate hydrothermally as ferrosic hydroxide, a mixed-valence (Fe 2z -Fe 3z ) green-yellow iron hydroxide compound. Consideration of the thermodynamics and kinetics of iron in the vent fluid, suggest that the precipitation is largely pH controlled and that large amounts of amorphous iron oxyhydroxides are capable of being precipitated by a combination of abiotic hydrothermal processes. Some biologically induced precipitation of primary ferric oxyhydroxides (two-XRD-line ferrihydrite) may have occurred directly from the fluid, but most of the filamentous iron microtextures in the samples appear to have a diagenetic origin. They may have formed as a result of the interaction between the iron-oxidizing bacteria and the initially precipitated ferrosic hydroxide that provided a source of ferrous iron needed for their growth. The processes described at Franklin Seamount provide insight into the formation of other seafloor oxyhydroxide deposits and ancient oxide-facies iron formation.

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In 1994 a moving car and its driver, on a highway in southern Madrid (Getafe), were struck by a falling rock. Eighty-one additional fragments (total weight : 55.926 kg) were later recovered, which all pointed towards a meteorite fall. A study of the composition of this object revealed an ultrarefractory material displaying a most unusual chemical make-up which differs from any known meteorite class, and for some elements and minerals approaches the composition of CAÍ (Ca-Al-rich inclusions in chondrites). A study of some cosmic-ray-produced stable and radioactive nuclides indicates: a) space and terrestrial exposure ages which do not exceed 1,000 and 520,000 years, respectively; b) the presence of a small 22 Ne excess (1,100 °C fraction), which suggests either a nucleogenic contribution from the 19 F(a,n) 2 Ne reaction or a trapped Ne signature distinct from atmospheric Ne, and c) the existence of minor variations in the 3 Ar/ 36 Ar ratios also indicating a nucleogenic component or fractionation effects. 14 C data are consistent with "modern" carbón originated in the period 1955-1958 and not earlier or more recently. The possibility that the Getafe rock could have a man-made origin (i.e. ceramic and refractory tiles, industrial slag) is also considered. Keywords:Getafe rock. FalL Composition. Cosmic ray records. Meteorite. Slag. Madrid. Spain. La roca de Getafe: Caída, composición y registro de rayos cósmicos de un material inusual ultrarrefractario de escoriaResumen En 1994, una roca impactó, en trayectoria descendente, contra un coche que circulaba por la zona sur de Madrid (Getafe), dañando al conductor en el proceso de caída. Posteriormente, se recuperaron otros ochenta y un fragmentos adicionales, con un peso total de 55.926 kg, apuntando todo ello a que se trataba de una típica caída meteorítica. El estudio mineralógico y geoquímico de la roca de Getafe revela que se trata de un material ultrarrefractario, que muestra una composición muy inusual que difiere de los meteoritos conocidos y que, para algunos elementos y minerales, se aproxima a la composición de las CAÍ (inclusiones ricas en Ca-Al en condritas). El estudio de algunos núclidos estables y radiactivos producidos por los rayos cósmicos indica: a) edades de exposición en el espacio y terrestres que no sobrepasan los 1.000 y 520.000 años, respectivamente; b) la presencia de un pequeño exceso de 22