A Petrologic Study of the Hydrothermal Alteration and Ore Mineral Deposition in Drill Core Samples from Agrokipia, Cyprus.
Date
1983-03-15
Authors
Botros, Mona
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Abstract
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:
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)
chlorite (green and brown) + smectite + pyrite + sphalerite + chalcopyrite in highly mineralized and partly to highly altered basalt (CY-2A 150 m to 170 m)
illite + quartz + sphene + pyrite + hematite in highly to pervasively mineralized and pervasively altered basalt (CY-2A 170 m to 300 m)
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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Pages:121
Supervisor: James Hall