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SPIESS COMPLEX

The Spiess complex has an elliptical shape elongated in NW-SE direction. It is articulated in a central volcanic apparatus rising from 1200 m to 340 m and two main lateral reliefs. We did a detailed multibeam survey on the top, and morphological data revealed the existence of an elliptic caldera 2.8 x 2 Nm, 450 mt deep; the bottom is rough and some smaller cones appear. Magnetic data evidence an intense positive magnetic anomaly with a NW-SE trend. NW of the top we found the highest positive anomaly of the area ($>$ 2500 nT).

We occupied 6 stations (11,12,13,14,15,16): (a) around the main top and to the NW we recovered fresh vesicular aphyric and Cpx-Ol-Pl phyric basalts, with traces of post-eruptive oxidation, and (b) on the lateral reliefs we recovered Cpx-Ol-Pl phyric and aphyric basalts covered by Fe-Mn crusts fragments. We tried an heat-flow station (HF04) in the caldera, and recovered fresh glassy basalts from the corer. Figure 9 shows the investigated area.

figure

Figure 9: The Spiess Seamount bathymetry.
\begin{figure}\centerline{\epsfig{file=IMG/BVT96_SPIESS_GEO.eps,width=15cm}} \end{figure}

next up previous contents
Next: AREA SW SPIESS Up: INITIAL RESULTS Previous: CONRAD FZ   Contents
2008-01-01