Lower plate serpentinite diapirism in the Calabrian Arc subduction complex.

Mantle-derived serpentinites have been detected at magma-poor rifted margins and above subduction zones, where they are usually produced by fluids released from the slab to the mantle wedge. Here we show evidence of a new class of serpentinite diapirs within the external subduction system of the Calabrian Arc, derived directly from the lower plate. Mantle serpentinites rise through lithospheric faults caused by incipient rifting and the collapse of the accretionary wedge. Mantle-derived diapirism is not linked directly to subduction processes. The serpentinites, formed probably during Mesozoic Tethyan rifting, were carried below the subduction system by plate convergence; lithospheric faults driving margin segmentation act as windows through which inherited serpentinites rise to the sub-seafloor. The discovery of deep-seated seismogenic features coupled with inherited lower plate serpentinite diapirs, provides constraints on mechanisms exposing altered products of mantle peridotite at the seafloor long time after their formation.

Validation of the Italian version of the Spinal Cord Independence Measure (SCIM III) Self-Report.

STUDY DESIGN: Cross-sectional validation study. OBJECTIVES: To validate the Italian version of the Spinal Cord Independence Measure Self-Report (SCIM SR). SETTING: Two spinal cord injury (SCI) rehabilitation facilities in Italy. METHODS: The SCIM III comprises items on 19 daily tasks, grouped into three subscales: 'Self-care,' 'Respiration and sphincter management' and 'Mobility'. The total SCIM score ranges between 0 and 100. The Italian self-reported version (SCIM SR) was translated from the German tool. We studied 116 patients on their first hospitalization for rehabilitation after an SCI. At the time of discharge, patients were evaluated by the rehabilitation team using the SCIM III and self-assessed their independence with regard to activities of daily living using the SCIM SR. Pearson's correlation, Bland-Altman method, and stratified and regression analyses were used to examine the differences between evaluations. RESULTS: On the basis of Pearson's correlation, there was good agreement between the data from the SCIM III and SCIM SR (r=0.918 for 'Self-care,' 0.806 for 'Respiration and sphincter management,' 0.906 for 'Mobility' and 0.934 for total scores). By Bland-Altman analysis, patients rated their functioning nearly the same as professionals-the mean difference between SCIM III and SCIM SR scores was approximately 0 for all subscales and total scores. The stratified and regression analyses failed to identify any specific factor that was associated with differences between SCIM III and SCIM SR scores. CONCLUSIONS: These results support the validity of the Italian version of the SCIM SR, which can facilitate longer-term evaluations of the independence of individuals with SCIs.

Death and Transfiguration of a Triple Junction in the South Atlantic

Three major lithospheric plates-Antarctic, South American, and African-meet in the South Atlantic near Bouvet Island where the Mid-Atlantic Ridge (MAR), the Southwest Indian Ridge (SWIR), and the American Antarctic Ridge converge toward a fast evolving triple junction. A major magmatic pulse has recently built a new, swollen segment of the SWIR (Spiess Ridge) that is propagating toward the MAR at a rate of 4 to 5 centimeters per year, disrupting a former ridge-ridge-ridge (RRR) triple junction. A new triple junction will be established about 70 kilometers to the north when the propagating SWIR/Spiess segment will impact with the MAR, probably within the next 1 million years. The American Antarctic Ridge will take advantage of the MAR/SWIR duel by capturing an approximately 70-kilometer stretch of MAR, whereas the Antarctic plate will increase its size.

A Cold Suboceanic Mantle Belt at the Earth's Equator.

An exceptionally low degree of melting of the upper mantle in the equatorial part of the mid-Atlantic Ridge is indicated by the chemical composition of mantle-derived mid-ocean ridge peridotites and basalts. These data imply that mantle temperatures below the equatorial Atlantic are at least approximately 150 degrees C cooler than those below the normal mid-Atlantic Ridge, suggesting that isotherms are depressed and the mantle is downwelling in the equatorial Atlantic. An equatorial minimum of the zero-age crustal elevation of the East Pacific Rise suggests a similar situation in the Pacific. If so, an oceanic upper mantle cold equatorial belt separates hotter mantle regimes and perhaps distinct chemical and isotopic domains in the Northern and Southern hemispheres. Gravity data suggest the presence of high density material in the oceanic equatorial upper mantle, which is consistent with its inferred low temperature and undepleted composition. The equatorial distribution of cold, dense upper mantle may be ultimately an effect of the Earth's rotation.

Mantle uplifted block in the Western Indian ocean.

An anomalous topographic high located close to the intersection of the Owen Fracture Zone with the Mid-Indian Ridge exposes exclusively ultramafic rocks for a thickness of more than 2 kilometers. The rocks, consisting of partly serpentinized spinel lherzolites, with minor harzburgites and dunites, display protogranular to porphyroclastic fabrics, but no cumulate textures. The chemistry of olivine, ortho-and clinopyroxene, and spinel crystals suggests that the rocks originated at a depth of at least 25 kilometers in the oceanic lithosphere and were partially reequilibrated and recrystallized during subsequent upwelling. Thus, field, textural, and mineral chemistry data indicate the presence of an uplifted block of upper mantle. The considerable vertical uplift can be explained by a two-stage process: mantle upwelling in the axial zone of plate accretion, followed by vertical tectonic uplift along the fracture zone. The rate of uplift in the fracture zone was of the order of 1 millimeter per year.

Nonspreading crustal blocks at the mid-atlantic ridge.

Transverse ridges consisting of protrusions into crustal fractures of ultramafic bodies derived from the upper mantle exist at the intersection of the Mid-Atlantic Ridge with equatorial fracture zones. Shallow-water limestones containing detrital grains of quartz, microcline, and orthoclase 1 millimeter in diameter were found on the summit of one such transverse ultramafic body at the Vema Fracture Zone; these findings are explained on the assumption that the limestones were deposited within a narrow, shallow proto-Atlantic and were left behind during the further opening of the Atlantic. Transverse ultramafic bodies from the offset zones of the Mid-Atlantic Ridge behave as nonspreading blocks plastered between spreading crustal plates.

Final desiccation of the afar rift, ethiopia.

Stable and radioactive isotope studies of ancient corals and mollusks from a fossil atoll in the Afar Rift indicate that final separation of the Afar Depression from the Red Sea occurred not earlier than 32,000 years ago. Desiccation followed within a few thousand years. The events recorded in the Afar Rift illustrate the processes occurring in the incipient stages leading to the formation of an oceanic body by rifting of a continental block.

High-magnesian calcite: leaching of magnesium in the deep sea.

The high-magnesian calcite fraction of a shallow-water carbonate sand was converted to low-magnesian calcite after transport to the deep sea; strontium was also leached from the carbonate. Oxygen isotopic ratios indicate that loss of magnesium and strontium took place during recrystallization of the carbonate in the deep sea; this process did not alter textures of skeletal fragments. Previously, high-magnesian, calcite was thought only to dissolve in the deep sea.

Exposed guyot from the afar rift, ethiopia.

A series of originally submarine volcanoes has been found in the Afar Depression. Some of the volcanic structures are morphologically similar to oceanic guyots. One of them consists of strata of finely fragmented and pulverized basaltic glass. The fragmentation of the lava is probably the result of stream explosions taking place during the submarine eruption. The flat top of this guyot is considered to be a constructional feature; by analogy, it is suggested that not all oceanic guyots are necessarily the result of wave truncation of former volcanic islands.

Fissure basalts and ocean-floor spreading on the East pacific rise.

A basalt pavement outcrops almost continuously in a band along the crestal region of the East Pacific Rise from about 14 degrees S to 6 degrees S, that is, for more than 800 ikilometers; the outcrop may well extend beyond the above limits along the axis of the rise. The basalt band is generally between 40 and 60 kilometers wide and is replaced laterally by sediment. The lavas are fresh, "oceanic tholeiites" which were emplaced less than I million years ago by fissure eruptions. These findings, can be explained by the hypothesis of ocean-floor spreading; the basalts are the expression of material originating from the mantle and rising through fissures along the axis of the ridge. The absence of an axial rift valley on the East Pacific Rise may be explained by the fact that large volumes of lava are being outpoured along its crest.

Ages of pacific deep-sea basalts, and spreading of the sea floor.

Potassium-argon determinations of age from whole-rock samples of tholeiitic basalts, dredged from the crest of the East Pacific Rise and from the flanks of three seamounts at varying distances from the crest, show that the crest is younger than 1 million years and that age does not correlate with distance from the crest. Our data, however, do not necessarily oppose the general concept of spreading of the ocean floor.

Deep-sea iron deposit from the South pacific.

Along with specimens of manganese oxides and basalt, rocks containing more than 30 percent iron by weight and consisting mainly of poorly crystallized goethite have been dredged from the flanks of a seamount located on the East Pacific Rise. The Fe-Mn ratio varies widely among the various oxide rocks deposited at this locality and at another seamount in the same area. The deposit was probably formed by fractional precipitation of iron and manganese which had been introduced locally into the bottom water by hydrothermal solutions of volcanic origin, and by leaching from deep-sea basaltic lavas.

Deep-sea authigenic calcite and dolomite.

Crystals of calcite and, in one case, of dolomite up to 90 microm in size are dispersed in pelagic red clay at several sites on the floor of the South Pacific Ocean. They were analyzed by microscopic, x-ray diffraction, electron x-ray microprobe, and oxygen isotopic techniques. These carbonates are authigenic and were probably precipitated from hydrothermal solutions connected with deep-sea volcanic activity.