Day 2, Locality 4
4) Apliki, south of village; roadcut.
This section is in
the SDC, but shows much brecciation, although some dykes can be identified in
places upon close examination. Dark coloured areas ascending the section are
hydrothermal passageways and conduits. This is close to the base of the dyke
complex, and ridge crest axial shearing during extension has brecciated and
fractured the earlier formed crust, with fault breccias developed in parts of
the section. The section has also been permeated by hydrothermal circulatory
conduits, beneath black smoker vents. The hydrothermal fluids have enhanced the
brecciation of the dykes, and have altered and mineralised them to epidosites.
Quartz and epidote are the main alteration minerals, and many veins of these
minerals can be seen. Sulphides have also been precipitated from the solutions,
and in places chalcopyrite and pyrite mineralization is seen, again mainly in
veins. The location of Apliki is close to the axis of the Mitsero graben,
(figure 5) and here we are seeing the on-axis hydrothermal, black smoker
mineralization. Several kilometres further north, massive suphide deposits are
found, again close to the projected axis of the Mitsero graben, the result of
black smoker mineralisation as hydrothermal fluids circulated upwards during the
early stages of ridge-axis extension.
