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
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.
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.
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
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.