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B. Sc. Honours Thesis

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The effects of hydrothermal alteration and ore mineralization were studied in 34 basalt drill core samples from the Agrokipia Cretaceous seafloor hydrothermal system in Cyprus. Transmitted and reflected light microscope, X-ray diffraction and electron microprobe techniques were employed to determine the variation of secondary minerals and textures with depth. The depth intervals examined were the 24.00 m to 92.85 m interval in hole CY-2 and the 136.70 m to 406.85 m interval in hole CY-2A. These intervals represent the most altered sequences of the cores.

The four stable secondary mineral assemblages which occur in the samples studied are:

1. smectite + green chlorite + minor quartz + hematite in relatively fresh to partly altered basalt (in CY-2 samples and in CY-2A between 136.70 m and 150 m)
2. chlorite (green and brown) + smectite + pyrite + sphalerite + chalcopyrite in highly mineralized and partly to highly altered basalt (CY-2A 150 m to 170 m)
3. illite + quartz + sphene + pyrite + hematite in highly to pervasively mineralized and pervasively altered basalt (CY-2A 170 m to 300 m)
4. abundant green and brown chlorite + albite + epidote + minor pyrite + trace sphalerite in partly mineralized and highly to pervasively altered basalt (CY-2A 300 m to 406.85 m)

With the exception of the 30 m to 60 m interval, it appears that hole CY-2 did not penetrate any hydrothermally altered basalts while the 150 m to 300 m interval in hole CY-2A represents the most intense hydrothermal activity.

Microprobe analyses revealed the occurrence of Mn-rich chlorite and calcite with the highest Mn content in the chlorite of sample CY-2 92.85 and the calcite of sample CY-2A 153.25. The MnO values of the chlorites in hole CY-2A appear to increase with depth while those of calcite decrease with depth. In all cases, the vesicle chlorites contained higher levels of MnO than the matrix chlorites.

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Supervisor:聽 James Hall