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The Troodos Ophiolite 

The Troodos Ophiolite consists of the following stratigraphic units, in ascending order: Plutonics (mantle sequence and cumulates); Intrusives; Volcanics; and, Chemical sediments.

 The mantle sequence is thus termed because the rocks that form this suite are considered to be the residuals after the partial melting of the upper mantle and the formation of basaltic magma, from which the remaining rocks of the ophiolite have been derived.  It is

 mainly composed of harzburgite and dunite with 50-80% of the original minerals altered to serpentine, and serpentinite (with or with-out concentrations of asbestos) where the alteration is almost complete. 

The cumulate rocks are the products of crystallisation and concentration of the crystals at the floor of the magma chamber, beneath the zones of sea floor spreading.  The main cumulate rocks (Fig. 3) include dunite with or without chromite concentrations, wehrlite, pyroxenite, gabbro and plagiogranites, which are observed in small, discontinued occurrences. 

The intrusive rocks (Sheeted Dyke Complex - Diabase) have a basaltic to doleritic composition and were formed by the solidification of the magma in the channels, through which it intruded from the magma chambers at the bottom of the oceanic crust, feeding at the same time the submarine extrusion of lava on the sea floor. 

The Sheeted Dyke Complex is followed by a suite of volcanic rocks that consist of two series of pillow lavas and lava flows, mainly of basaltic composition.  The pillow lavas (Fig. 4) have a characteristic spherical to ellipsoidal pillow shape, 30–70 cm in diameter, which were formed as a result of submarine volcanic activity.  Between the intrusive rocks and the pillow lavas a transitional zone known as the Basal Group occurs.  Dykes dominate the Basal Group while pillows are less common. 

The Perapedhi Formation is composed of umber (chemical sediment), radiolarites and radiolaritic shales.  These were the first sediments to be deposited over the ophiolite rocks as a result of hydrothermal activity (hot solutions rich in Fe and Mn) and sedimentation on the sea floor.

 

 

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