International Journal of Geosciences, 2011, 2, 98-101
doi:10.4236/ijg.2011.22010 Published Online May 2011 (http://www.SciRP.org/journal/ijg)
Copyright © 2011 SciRes. IJG
Troodos: A Giant Serpentinite Diapir
Roelof Dirk Schuiling
Institute of Geosciences, Utrecht, The Netherlands
Received September 18, 2010; revised February 19, 2011; accepted April 1, 2011
Troodos is a classical ophiolite complex. It is proposed that the serpentinized harzburgites that now form the
top of the mountain and represent the originally lowest part of the ophiolite sequence rose as a diapir. This
diapiric rise is caused by the pervasive serpentinization of a suboceanic harzburgite, due to rock-sea water
interaction. The serpentinization caused a 44% expansion of the rocks. Contrary to salt diapirism, the driving
force for this diapiric rise is not so much the difference in density, but the volume increase asscociated with
the transformation of harzburgite into serpentinite. The overlying gabbros, sheeted dike complex and pillow
lavas were pierced by this serpentinite diapir but barely deformed. Their interaction with sea water was li-
mited to some pyroxenes in the gabbros being transformed to amphiboles, and epidotisation of some of the
dikes in the sheeted dike complex. The location of steep faults in the Troodos massif is determined by the
contrasting expansion behavior of different rock-types on both sides of the fault.
Keywords: Ophiolites, Seawater Interaction, Serpentinization, (Lack of) Deformation, Cyprus, Olympic Flame
Troodos is a classical ophiolite complex, representing a
slow spreading zone. Pillow lavas, sheeted dike complex,
gabbros, layered dunites and mantle rocks (serpentinized
harzburgites) are all represented. In its upper part there
are radiolarites and even some umbers, formed by sub-
marine exhalations, which also deposited the famous
copper deposits of Cyprus. The top of Troodos Mountain
is composed of pervasively serpentinized harzburgites,
which represent the lowest part of the ophiolite sequence.
It is well known that serpentinites can be easily duc-
tilely deformed under stress, like rock salt. In analogy to
salt diapirism, the serpentinized harzburgites around the
top of Troodos mountain on Cyprus are interpreted as a
serpentinite diapir. Serpentinite diapirism has been de-
scribed many times, often from fore-arc environments
[1,2]. The volume expansion associated with serpentini-
zation is considered to be the main driving force behind
the serpentinite diapirism. In future research on ophiolite
complexes this tectonic role of serpentinization should be
taken into account.
The harzburgites are pervasively serpentinized. Serpenti-
nization proceeds by
Mg2SiO4 + MgSiO3 + 2 H2O → Mg3Si2O5(OH)4
The molar volume of the serpentine on the right hand
side is 108.5 cm3, whereas the sum of the volumes of
olivine + enstatite is 75.3 cm3 . This means that a
harzburgite expands 44% during pervasive serpentiniza-
tion. Even if the ratio enstatite/olivine in the original
harzburgite was not exactly 1:1, once the conditions are
in the stability field of lizardite, slight amounts of either
magnesium or silica which are required for the formation
of monomineralic serpentine rock will be extracted from
the large volume of percolating seawater. This is com-
monly observed in the formation of monomineralic zones
during metasomatism. In case the iron becomes oxidized
to magnetite during serpentinization, one can write the
reactions as follows (there is a large variation range of
possible reactions, all leading to fairly similar results).
The olivine will have had a composition close to
Mg0.92Fe0.08SiO4, as is common in peridotites. During the
oxidation of FeO to magnetite, possibly with an interme-
diate stage of ferroan brucite , the silica associated
with the iron end-members of the olivine and enstatite
will be released. This silica will react with the abun-
dantly available magnesium in the percolating sea water
to form additional serpentine, according to
R. D. SCHUILING99
0.04 Fe2SiO4 + 0.04 FeSiO3 + 0.12 [Mg2+] + 0.01 CO2 +
0.22 H2O →0.04 Fe3O4 + 0.04 Mg3Si2O5(OH)4 + 0.01
CH4 + 0.24 H+
If we sum up the volume changes of the solid phases
in both reactions, we find that the volume change when a
harzburgite is serpentinized in a large volume of hot
seawater, and the iron is transformed into magnetite is
almost 50%. This is in agreement with the data presented
by Jamtveit and Austrheim  who state “Complete ser-
pentinization results in a solid volume increase of nearly
50% and causes a pronounced change in rheology”.
As there are many variations possible, we can con-
clude that the associated volume change is of the order of
40% to 50%. In the reaction the divalent iron is oxidized
by the simultaneous reduction of CO2 and water to me-
thane. Methane emanations are often associated with
actively ongoing serpentinization. A famous example is
the famous Yanartaşı (Turkish for “the rock that always
burns”) on the Turkish mainland, 250 km to the north-
west of the western tip of Cyprus, where methane flames
are permanently emerging from a dunite in the process of
The Yanartaşı has played an important role in classical
Greek history and mythology. Nearby was the ancient
Greek city of Olympos. On festive occasions the young
men of the town had to run to the mountain with a torch
in hand, to be lighted by the methane flames. The first
man to return to Olympos with a burning torch was the
winner. It is hard to believe that this is not the origin of
the Olympic flame.
It also plays a central role in the myth of Bellerophon
and his winged horse Pegasos. Bellerophon had to kill
the chimaera, a fire-breathing dragon that was ravaging
the country. After Bellerophon had spotted the dragon
from his flying horse, he dived into it and drove the dra-
gon into the ground. It is dead, but its flames are still
2.2. Absence of Deformation
Most rocks of the Troodos complex are undeformed,
without foliation or preferred orientation. The gabbros
are even explicitly designated as “isotropic gabbros”,
showing that their lack of tectonic imprint is obvious.
Their chemical transformation is limited to local amphi-
bolitization of their pyroxenes. The sheeted dikes and the
pillow lavas are equally undeformed, having preserved
even delicate glass selvages between the pillows (Figure
Figure 1. Pillow lavas with uncracked selvages of basaltic glass. Photo B.N.’tHart.
Copyright © 2011 SciRes. IJG
R. D. SCHUILING
Copyright © 2011 SciRes. IJG
The glass has remained unbroken throughout their geo-
logical history. Some of the dikes are tilted, but most are
(sub-) vertical. Dunites occasionally show igneous laye-
ring marked by chromite stringers, but are undeformed.
Some steep faults crosscut the complex, separating for
example the serpentinized harzburgites from gabbros.
We will assign no meaning to these faults, except that the
two rock masses must have moved with respect to each
3. Where Does This Lead Us?
After the spreading activity had stopped, very little
movement has affected the Troodos massif since, except
some tilting and occasional faulting. A similar observa-
tion is made by Gass , who states “The least deformed
ophiolites appear to be vertically uplifted pieces of ocean
floor that have not yet undergone much horizontal de-
formation. Two such sequences are … and the Troodos
massif in Cyprus”. .
Plate tectonic models for the region require large
movements, but the rocks tell a different story. They
show no sign of large-scale movement, and lack the in-
ternal fabric associated with tectonic transport. Yet,
Troodos rises to 1952 meter asl, although the rocks that
are now at the top of the mountain represent the deepest
part of the ophiolitic pile. They were part of a spreading
ridge at a sea depth of 2 to 3 km.
In the absence of large-scale horizontal displacements,
applying Occam’s razor, “the simplest explanation is
usually the best”, it is proposed that these serpentinites
rose vertically from the depth of the oceans to their pre-
Field evidence suggests that this vertical rise of the
center of the Troodos mountain was not only accompa-
nied by, but probably even caused by pervasive serpenti-
nization. To explain the total uplift of the Troodos Mt. by
serpentinization requires considerable seawater/rock in-
teraction. Serpentinites probably flow similar to salt,
particularly when heated to a certain extent by hydration
reactions , so in analogy to salt diapirs it is likely that
seawater/rock interaction first affected a broader area
than the diapir itself, but that the serpentinized were
squeezed upward through a narrower conduit. This is
analogous to what happens in salt diapirs, where the salt
in the diapir does not only derive from the salt that was
directly underneath, but also from salt that flowed side-
ways towards the diapir from a broader layer of salt. Salt
has a lower specific mass than the overlying sediments,
and likewise the serpentinized harzburgite is also con-
siderably lighter than the overlying ophiolitic rocks. The
serpentinized harzburgite has a specific mass of appr.
2.200 kg/m3, whereas the specific masses of the overly-
ing rock types (gabbros, dunites, diabase dikes and pil-
low lavas) range between 2.800 and 3.350 kg/m3. This
means that even without the enormous expansion there is
already a considerable force to set the diapiric movement
in motion. Yet, while in salt diapirism the density differ-
rence is the only driving force, in serpentinite diapirism
the expansion plays a more important role than the den-
When a rock expands, it must make room for itself. In
that sense it is more similar to the technology to raise
parts of the land by injecting sulfuric acid into subsurface
limestones. The resulting gypsum has twice the volume
of the original limestone, which causes the land to be
uplifted, making it safer for inundations . In Germany,
considerable damage to houses is associated with uplift
caused by the transformation of anhydrite into gypsum.
Since September 2007, numerous buildings in Staufen’s
Old Town have begun to exhibit large cracks that have
formed due to the uplift of the substrata. The extent of
the damage is considerable and there is no end to the
uplift process in sight. A geochemical process called
anhydrite swelling has been confirmed as the cause of
these uplifts .
The pushing together of serpentinites that derive from
different corners and slightly different thermal regimes in
the suboceanic harzburgite reservoir as it undergoes ser-
pentinization may offer an elegant solution to the re-
markable δD and δ18O gradients observed by Nuriel et al.
Intense seawater/rock interaction is also evident from
many dikes that have been transformed into undeformed
epidotites, from which the submarine exhalative copper
deposits derive for which Cyprus is famous.
Each dike of the sheeted dike complex represents an
extension equal to the thickness of that dike, but the un-
derlying mantle must simultaneously have undergone a
similar extension, providing easy access to seawater that
will react rapidly with the anhydrous mantle rocks,
helped by the fact that the hydration reaction is strongly
exothermic . The uneven thermal expansion that re-
sults may crack the rocks further, making them even
more accessible to seawater interaction.
A steep fault must separate gabbros from serpentinized
harzburgite, as one rock expands and rises 4 to 6 km,
whereas its neighbor does not move. Such steep faults
are typical of diapiric settings. The fact that the Amian-
thos Fault , separating the serpentinized harzburgites
from the adjoining gabbro dies out as soon as it leaves
the contact between these two rock-types with contrast-
ing expansion behavior is illustrative.
The diapiric rise of its central part has caused some
upward bending of the sediments around the Troodos
massif. Uplift continued at least to Miocene times, as
R. D. SCHUILING101
some Messinian gypsum layers are slightly tilted, sloping
away from the Troodos complex. Troodos may even still
be rising today, which could indicate that even now the
serpentinite has not yet reached its ultimate equilibrium
During its formation Troodos was probably similar to
the Atlantis sea mount that rises 3 km above the ocean
floor  and is also composed of serpentinized mantle
rocks and gabbros, and associated with white smokers.
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