2011 Spring Field Course Cyprus - Troodos Ophiolite 2011 Spring

Transcription

2011
2011 Spring
Spring Field
Field Course
Course
Cyprus
Cyprus - Troodos
Troodos Ophiolite
Ophiolite
UIUC Department of Geology
March 16-27, 2011
Itinerary
Wednesday, March 16: Leave NHB at noon from Matthews St.
Leave O’Hare Airport on BA flight 294 at 6:00 PM
Thursday, March 17: Arrive Heathrow Airport London at 6:30 AM
Leave Heathrow Airport at 8:35 AM on BA flight 662
Arrive Larnaca Airport Cyprus at 3:05 PM
Travel to Kakopetria - Ekali Hotel
Friday, March 18: Travel to Limmasol then take the A3 towards Pafos
1.1) Petra tou Rouminou - outcrop of Mamonia complex
1.2) Recent folding and faulting in sediments
1.3) Map and determine shear sense in recent faults
Explore Pafos - Roman mozaics, tombs, museums, beach
Saturday, March 19: Sediment - Lava contact and Extrusive series
2.1) Akaki River W of Arediou
2.2) Akaki River S of Klirou Bridge
2.3) Agia Koroni - Sheeted dikes
Sunday, March 20: Dikes and Dike- Gabbro transitions intrusive
3.1) Kannavia Canyon - near vertical dikes
3.2) Chandria - dike-gabbro relationships
3.3) Alona - plagiogranites
3.4) Askas - optional overlook of dike-gabbro transition
Monday, March 21: Dikes and Dike - Gabbro transition tectonized
4.1) Tilted Dikes near Gerakies
4.2) Lemithou Detachment
4.3) Pedhoulas - Gabbros
Tuesday, March 22: Gabbros and Ultramafic intrusives
5.1) complex intrusives NE of Prodromos
5.2) crust mantle transition
5.3) lower crustal and intrusives
Wednesday, March 23: Ultramafics and serpentinites
6.1) Troodos trail - ultramafic exposures
6.2) Chromite Mine Rd. - dunites and harzburgites
6.3) Asbestos Mine overlook
6.4) Contact between Serpentinite and Gabbro
Thursday, March 24: Mapping Project, Kakopetria
Friday, March 25: Mapping Project, Kakopetria - day 2
Saturday, March 26: Morning - final wrapup
Leave for airport ~noon
Leave Lanaca Airport at 4:15 PM on BA flight 663
Arrive Heathrow Airport at 7:25 PM
Stay at airport hotel
Sunday, March 27: Leave Heathrow Airport on BA flight 295 at 11:25 AM
Arrive O’Hare Airport at 2:15 PM
Drive back to Champaign-Urbana
1
Geology 415: Field Geology in Cyprus
Introduction
The Troodos ophiolite is a nearly intact mid-Cretaceous (91 million year old) slice of oceanic
crust, exposed over an area of 40 by 100 km in the Troodos mountains of Cyprus and the
foothills around them. Access by road to all parts of the ophiolite is straightforward. Troodos
was one of the first ophiolites to be studied in detail and has had a profound influence on
thinking about the ocean crust (see Cann 2003 and other papers from GSA Special Paper 373 in
the reference list below). For example, it was in Troodos that Ian Gass (Gass, 1968) first
recognized that the sheeted dike complex there was de facto evidence for seafloor spreading, and
that ophiolites thus represent on-land fragments of oceanic lithosphere.
The Troodos complex is particularly well known for its lava sequence, which lacks any late
metamorphic overprint, a superbly exposed sheeted dike complex (Varga 2003), hydrothermal
alteration including epidosites and a large number of small massive sulfide deposits.
The Troodos ophiolite was formed in a supra-subduction zone environment, as shown by lava
geochemistry (Pearce, 2003), in a small ocean basin within the complex Tethyan ocean domain
(Robertson et al., 1991). The spreading centre ran E-W at the time of crustal creation, but the
ophiolite was rotated 90° anticlockwise soon afterwards, at the end of the Cretaceous. Now the
general trend of the sheeted dikes runs N-S and the Arakapas Fault Belt, thought to be either a
discrete transform fault or the northern edge of a broad transform-related domain, trends E-W.
The low relief of the lava surface beneath the sedimentary cover (most of the fault scarps are less
than 20 meters high) suggests that the spreading rate may have been greater than 60 mm/yr full
rate, while the complexity of the gabbroic units suggests that the spreading rate was slow; an
intermediate spreading rate seems a good estimate.
Introduction
2
Introduction
3
The ophiolite can be divided into three regions:
1) The main Troodos Massif north of the Arakapas Fault Belt, which preserves a Penrose-type
ophiolitic stratigraphy, but with some complications as we shall see,
2) The east-west Arakapas Fault Belt, interpreted as the northern margin of a fossil transform
fault or as a discrete transform fault,
3) The Limassol Forest Complex, south of the Arakapas Fault Belt, in which similar lithologies
to those of the main Troodos Massif are seen, but in complex structural relationships with one
another, including low-angle extensional faults.
We will spend essentially all of the time in the main Troodos Massif, leaving the Limassol
Forest, Arakapas Fault Belt and other parts of the island for a personal visit.
Troodos Massif
The overall stratigraphy of the main Troodos massif is relatively simple. Submarine volcanics
overlie sheeted dikes that in turn overlie an upper plutonic unit composed principally of gabbros.
This in turn overlies a unit of mantle peridotite. Sulfide deposits occur within the lava section
and related deposits of umber overlie the lavas. The structure is dome-like so that the deepest
parts of the stratigraphy occupy the central, topographically highest area (Fig. 4)
The submarine volcanics show a wide range of volcanic products (Schmincke and Bednarz,
1990). These include pillow flows, sheet flows, breccias and hyaloclastites. Compositions range
from basalts through to andesites, dacites, and rhyolites, and include lavas allied to boninites
(distinctive high-magnesium andesites otherwise found in intraoceanic forearcs). Individual lava
flows can be identified and traced for several kilometers along strike. The lavas are cut by faults
that displace the ocean floor only by tens of meters, but are associated in places with rotation of
the dip of the lavas, which can be shown to have happened at the spreading axis. The thickness
of the lavas is variable, but is typically about 1000 m.
Over much of its thickness, the sheeted dike unit can be shown to be made up entirely of dikes
intruding one another, a graphic demonstration of ocean floor spreading. The dikes range in
width from narrow veins up to over ten meters, but the typical range of widths is from one to
about five meters. Though some dikes intrude high into the lavas, the main transition from lavas
to sheeted dikes happens over a vertical distance of only 100–200 m, as has been observed in
oceanic drill holes, indicating crustal construction from a narrow zone of dike injection (Kidd
and Cann, 1974). Over much of the Troodos massif, the dikes trend approximately north-south,
indicating the orientation of the spreading axis during crustal construction. The direction of
magma intrusion in the dikes varies from vertically upwards to horizontal, or sometimes even
downwards (Staudigel et al., 1999). The dike trend swings round to NE-SW and locally E-W
towards the Arakapas Fault Belt. Paleomagnetic data and cross-cutting dikes suggest that this is
the result of clockwise rotation, soon after the dikes were formed, induced by dextral shear along
the transform. The sheeted dike complex is extensively deformed by brittle fracturing and
generally metamorphosed in the greenschist facies.
Below the sheeted dikes, the upper plutonics are composed principally of layered and unlayered
gabbro, with some ultramafic layers and veins of plagiogranite, apparently the result of extreme
Introduction
4
fractionation of basaltic magma. The plagiogranites are in places highly altered to epidote-quartz
assemblages, apparently generated by magmatic fluids (Kelley and Malpas, 1992). The unit has a
complex structure, with multiple intrusive relationships that can be seen in the field (Malpas
1990).
At least three distinct relationships between dikes and gabbros have been described in the
Troodos Massif. At some localities the transition is gradual over a few hundred meters, with
vertical dikes separated by gabbro screens becoming thicker and coarser grained downwards,
while still showing chilled margins. Elsewhere there is a sharp boundary, with the gabbros
intruding and metamorphosing the dikes (Gillis and Coogan, 2002) (as described from ODP Hole
1256D). Finally there is an extensive area in the NW where dikes rotated to low angles are
separated from gabbros by a low-angle brittle fault, the Kakopetria detachment.
The lower plutonics are dominated by ultramafic and, to a lesser extent, gabbroic rocks, often
layered. They grade downward into pyroxenites and massive dunites that form a thick crustmantle transition zone.
The upper mantle, composed of partially serpentinized harzburgite, dunite and pyroxenite, is
exposed around the peak of Mount Olympus, and there are excellent localities showing evidence
of percolation of magma through mantle harzburgites. Chromite was mined from the mantle
section, and the relationships can be seen between chromite ore and host mantle. Peridotite
pervasively altered to serpentinite forms a ‘bullseye’-shaped unit at the east side of the mantle
massif. The formation of this unit is controversial. Its chromites have distinctly different
compositions to all other Troodos peridotites. The circular outcrop is underlain by a large
negative gravity anomaly, constraining the body to have a pipe-like form. It is conventionally
regarded as being the result of doming during uplift of the ophiolite during the Neogene,
probably linked to diapiric intrusion related to volume increase during hydration. However, it has
recently been suggested that the steep reverse fault that bounds the east side of the serpentinite
(the Amiandos Fault) was the steep part of an oceanic detachment fault formed during crustal
construction, possibly connecting with the shallow Kakopetria Detachment (see below) between
the dikes and the gabbros.
Introduction
5
During crustal construction, black smoker circulation was common. Pyrite-rich exhalative
sulfide deposits occur within the lavas at different levels and were mined for copper and/or
sulphur. Their exhalative nature can be demonstrated by associated sediments formed by seafloor
weathering of the sulfides, and by the presence of fossil worm tubes and gastropods within the
sulfides. We will get a view of the Skouriotissa sulfide deposit. Beneath the sulfide deposits are
alteration pipes that reach down to the top of the sheeted dike unit through which hydrothermal
solutions rose to the seafloor. Near the base of the sheeted dikes are extensive high-temperature
hydrothermal reaction zones marked by development of epidosites (epidote-quartz rocks) within
the dikes, and by depletion in Cu, Zn, and Mn (Richardson et al., 1987; Varga et al., 1999). The
black smoker circulation took place very close to the ancient spreading axis, as can be shown by
the burial of almost all of the sulfide deposits within the lava pile, by the close association of the
hydrothermal reaction zones with the dike-gabbro boundary, and by field evidence that dikes
were being intruded while hydrothermal circulation was proceeding.
Iron and manganese-rich hydrothermal sediments (umbers) occur in many places on top of the
lava sequence and occasionally within it. Within hollows or in half-grabens their thickness may
reach 35 meters, but most deposits are less than 10 meters thick. These sediments are interpreted
as fallout from black smoker plumes, formed by oxidation of the iron sulfide black smoke
particles in the water column and by adsorption of hydrothermal manganese from the diluted
hydrothermal solutions onto the newly formed iron oxides. They subsequently accumulated on
the seafloor and were preserved in hollows in the seabed. By analogy with modern systems,
accumulation rates of the umbers were probably fastest close to the vents, and just beyond the
limit reached by lava flows, though accumulation may have continued for several million years
at ever-decreasing rates as the crust spread away from the spreading centre.
Introduction
6
Low-temperature circulation continued for several tens of millions of years after crustal
construction. This has been documented by K/Ar dating of low-temperature alteration minerals
such as celadonite (Staudigel et al., 1986). In areas where the seafloor was not covered by
sediment for a long time, low-temperature circulation produced oxidative alteration of the basalts
with the development of orange palagonite and carbonates (Gillis and Robinson, 1990). Deeper
in the section in these same areas, alteration becomes more reducing and less pervasive, so that
fresh basaltic glass remains in pillow margins. As temperature of alteration increases with depth,
it can be difficult to distinguish later alteration from early black smoker alteration once the
sheeted dike complex is reached.
Several structural grabens have been identified in the main Troodos massif, mainly by the
rotation of dikes in the sheeted dike complex. The most marked one of these is the Solea Graben
that we will be visiting on the first day trip. On either side of this the dikes dip towards the
graben axis, implying rotation in the hanging wall ‘bookshelf’, probably listric, faulting above a
low-angle fault located at the gabbro-dike boundary (Varga 1991, Hurst et al., 1994). This lowangle structure has been termed the ‘Kakopetria Detachment’. The rotation is especially large
on the west side of the graben axis, where the dikes may dip at less than 30° towards the east.
This rotation can be shown to have happened very early in the history of the ophiolite, during the
construction of the oceanic crust, but after the epidotisation that happened very soon after dikes
were intruded. It is clear that this region has seen major extension, and an important question is
whether this extension is or is not related to detachment faulting of the type seen in the oceans.
The lack of displacement of the uppermost lavas by the faults within the grabens, and the lack of
significant mass wasting deposits in the lava sections, is hard to reconcile with the large rotations
of the dikes. These relationships are apparently at odds with observations from slow spreading
ridges, such as the Atlantic, where large fault-related rotations have been observed.
Arakapas Fault Belt
The Arakapas Fault Belt runs east-west along the southern edge of the Troodos massif. It forms a
prominent linear valley that is clearly visible today, on the ground or from space. The fault belt is
about 1 kilometer wide and was identified as a transform fault by Moores and Vine (1971). It
runs at right angles to the dike trend and is blanketed by overlying pelagic sediments, so was
clearly an ocean-floor structure.
Limassol Forest Complex
The Limassol Forest Complex lies south of the Arakapas Fault Belt. It contains the same
lithological units as the Troodos Massif, but without the simple layered stratigraphy seen there;
instead, the units are juxtaposed in a complex way, with very significant levels of brittle faulting.
In the eastern Limassol Forest a wide range of crustal units, ranging from lower crustal plutonics
up to sheeted dikes and lavas, is in direct contact with serpentinite with large parts of the crustal
section missing over much of the area. The relationships can be simplified into a basement unit
of serpentinised harzburgites and dunites overlain tectonically by overlapping, crustal blocks
bounded by gently SW-dipping normal faults. The boundary between the serpentinites and the
tilted crustal blocks is a low-angle extensional detachment fault, termed the Akapnou Forest
Décollement.
Introduction
7
Classification Schemes
8
9
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Day 1 Itinerary: Sediments and Neotectonics
Depart Kakopetria heading for Pafos.
Chalks

roadcuts along the A3 highway between Limassol and Pafos

Slow and view the Pakna Chalks and recent gravels cut by recent faulting and
intraformational slumping
Mamonia Complex – an enigmatic melange of rocks

Stop 1.1 At Petra tou Rominou
o Investigate dikes, pillows, chalks and their relationships

Continue on old road to Pafos
Chalks and Gravels

Stop 1.2 at Kouklia Fault
o Pakna Formation and top gravels overturned

Stop 1.3 near retaining dam and industrial park
o Investigate recent faulting in Pakna chalks.

go into Pafos – free time in afternoon – Roman mosaics, tombs, museums, beach

Head home to Kakopetria along the A3 then B9
Day 1
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Day 1 General Geology and Themes
We will travel Day 1 along the South coast of Cyprus to Pafos, a major resort city and
home to many archeological sites from prehistoric, through Roman to Byzantine times.
Along the trip on the A3 expressway look at the roadcuts, especially a series of 5
roadcuts about 16 km west of Limmasol for intraformational slumping, faulting and
slumping involving Pakna Chalk and recent gravels.
Our first stop (1.1) is at Petra tou Rominou. This is where myth has Aphrodite being
created from sea foam in the waves washing up on this beach. It is also an exposure of
the enigmatic Mamonia Complex, which is wildly variable in rock type, including
everything from sediments to ultramafic rocks. Here, look for rocks similar to the main
ophiolite composition including a pillow lava apparently intruded into massive chalk.
High chalk cliffs are in the background. Later stops will look at some of the sediments
and neotectonic evidence of faulting and folding that involves recent gravels.
Day 1
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Stop 1.1: Mamonia Complex at Petra tou Rominou
After parking, proceed down to the beach. There will be a group presentation/discussion
here after a short look around at the rocks.

1.1.1: Identify the rock types exposed along the beach for several hundred meters
and in the distance.

1.1.2: What are the contacts like between the volcanic rocks and adjoining
country rock?
Continue on the old Pafos road to an exit off the A3 near Kouklia, park at the end of the
exit road.
Stop 1.2: Folding and Faulting in recent sediments

Day 1
1.2.1: What does the deformation of the gravel layers say about the timing of the
faulting and folding?
14
Stop 1.3: Recent Faulting near Pafos Airport

Day 1
Sketch the outcrop from across the valley in the space below. Then go across the
valley and refine your sketch from close up. This out crop is faulted in several
places. What is the shear sense of the faulting? Mark this on your sketch.
15

What are the blocks bounded by faults called and how do they form?

What is the likely timing order of the faults?
Day 1
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Day 2 Itinerary: Traversing the upper crust
Depart Kakopetria heading for Akaki River near Arediou.
Sediment – lava contact

Stop 2.1 along the Akaki River west of Arediou
o Approximately 2 km southeast of Arediou on the E903, ~1 km northeast
of the junction with E905
o Here we will investigate lava morphologies and the sediment-lava contact.

Head South on the E903 to intersection with E905. Turn east on F962 toward
Klirou. Park just beyond the bridge over the river.
Upper-dike section transition to lavas

Stop 2.2 along the Akaki River Southwest of Klirou
o Investigate dike swarms intruding lavas and hyaloclastites

Continue south on E903 to roadcut just north of Agia Koroni ~ 2 km south of
turn-off to Agios Epifanios.

Stop 2.3 at Agia Koroni roadcut
o Investigate relationships between sheeted dikes and lava screens

If heading to Optional Stop X, return north on E903 to the intersection with 905.
Head west on 905 to the intersection with 906. Turn north on 906 and follow it to
the intersection with 907 ~1 km north of Kato Moni and park in the open space
opposite the intersection.

Optional Stop X at Kato Moni
o Investigate different lava morphologies and a fault

Return north on E903 (906 if from Stop X) working back to the B9. Head west on
the B9 toward Kakopetria. Exit left on the E908 toward Linou. Stop in the roadcut
~2.8 km west of the junction of E908 and B9.

Stop 2.4 in the transition from upper-dike section to lavas sequence
o Investigate dipping dikes and lavas as evidence for a rift valley graben

Day 2
Optional Stop XX or Head home to Kakopetria along the B9
18
Day 2 will be spent traversing the upper crustal section of the Troodos Ophiolite.
Field stops are located east of Kakopetria mostly along highway E903 running along the
Akaki River. We will begin a few kilometers southwest of Nicosia near Arediou, and
travel south throughout the day along E903 ending near Agia Koroni. Then we head
northwest on our return trip and into the Salea Graben.
Our first stop (2.1) is in the lava sections where you will see the lava-sediment
contact and different forms of lava morphology. We will continue down section as we
travel south, heading into the lava-dike transition (Stops 2.2 and 2.3). We then return
north and west toward Kakopetria making a stop in the dike-lava transition along the
flank of the Solea Graben. See the map for geologic setting of each location. We may
alter things a bit after Stop 2.2 or 2.3 and head west-northwest toward Kato Moni to see
multiple flow morphologies.
Day 2
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Stop 2.1: Top of the lava section in contact with sediments
After parking, proceed westwards down to the river along the winding track. Here you
will find lavas and overlying sediments. About 20 meters before the river you will come
across an outcropping. This is a good place to begin.

GPS coordinates: ________________

2.1.1: Identify and classify this rock. It is ~30 million years old (Oligocene).
Continue south along the track through the olive tree grove. The flat area is the site of the
Cyprus Crustal Study CY1 borehole drilled in the 1980s. Another ~50 m along the track
and you will see a steep outcropping.

2.1.2: Identify and classify the rock exposed here. This rock is upper Cretaceous
(~80 Ma).

What interesting rock structures do you see, and what does this indicate regarding
the environment in which this rock was emplaced?

Did you find evidence for the contact with the previous outcropping at 2.1.1?
What is the nature of the contact between these two rocks.
Day 2
20
Continue south around the corner about 30 m. Here you will find some huge phenocrysts!

2.1.3: Identify the phenocryst phase(s)

Investigate the distribution of phenocrysts within the lavas, and sketch what you
see. Explain how the phenocrysts come to be distributed in such a way(s) within
the flows.
Day 2
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Continue south for ~30 meters and notice a change in the lava morphology.

2.1.4: How would you characterize this new lava ‘morphology’ and how might
you interpret it?

2.1.5: Estimate the thickness of lavas you have traversed during this stop.

2.1.6: Did you notice any dikes during the transect?

2.1.7: Is your answer to 2.1.6 hard to rectify with this occurrence of lavas piled on
each other, each being erupted at the surface? Perhaps you should discuss this
with one of the Group 2 members.
Day 2
22
Gather-up for a discussion of what we’ve seen and a general discussion of lava
morphology, flow rates, and inflation led by Group 2: Stephanie Mager, Adam Angel ,
Stacy Dwyer , Lucas Gschwind , Tjames Poulos.
Day 2
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Day 2
24
Day 2
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Stop 2.2: The transition from the dike section to the lava section in Akaki Canyon
After parking on the south side of the bridge, proceed down the dirt road to the west and
follow the path off to the right leading to the highpoint overlooking the river. Across the
river valley you will see a classic geology locality with dike swarms cutting screens of
volcanic rocks.


2.2.1: Sketch the far hillside. Add Unit labels to your sketch after completing the
remainder of the stop. After completing your sketch, see a faculty member before
heading down to the river’s edge to investigate the hillside you just sketched.
Day 2
26

Day 2
2.2.1 continued
27

2.2.2: Investigating the rock units:
o Investigate the dike margins looking for vesicles, and amygdales
 What minerals might be filling these amygdales?

What is the origin of the minerals filling the amygdales?
o The vesicles and amygdales show evidence for magma transport. Find a
dike margin rich with vesicles and sketch it. Explain how the vesicles
illustrate the magma transport direction. Is transport vertical?
Day 2
28

2.2.3: climb over the dikes and look at the lava screen. Notice the lavas here are
not pillow form as they are higher up in the hillside. At this lower level, they are
fragments of glass (altered to clay). This is hyaloclastite and is presumed to be
formed by submarine fire-fountaining.
o Within the hyaloclastite are some pillow lavas. What is the relative
timing/relationship between the pillow lavas and the hyaloclastite and how
do you know?

2.2.4: If time permits, continue along the river ~30m to find a dike intruding
hyaloclastite and pillow lava.
o Notice the variation in dike width and width of its chill margins.
Speculate on the origins of these variations.
o A few more meters down stream and you’ll find pillow lavas with
bifurcated lobes indicating the direction of flow. What is that flow
direction?
Day 2
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Day 2
30
Stop 2.3: The transition from dikes to lavas 2. How to build a lava pile?
After exiting the vehicle, be careful of traffic while investigating this large roadcut. This
cut exposes dike swarms separated by screens of pillow lavas. The north end of the
roadcut is sheeted dikes and, as you proceed south, dikes decrease to ~70% of the
exposure.


2.3.1: Within the sheeted dikes of the north end,
o What is the attitude of these dikes?
o Can you find evidence for cross-cutting dikes? If so, what is the evidence?

2.3.2: Continue southward to investigate the relationship between the lava screens
and the sheeted dikes.
o Which way is ‘stratigraphic up’ and how do you know?
o Try to determine the relationship between dikes and lavas: (1) did the
dikes intrude the lavas, or (2) did the lavas flow into a fissure lined with
dikes?
Day 2
31
Exit the vehicles and safely address the roadcut exposing dike and lavas.
Stop 2.4: The transition from dikes to lavas 3. Is this evidence for a graben?


2.4.1: Which way is stratigraphic up? How do you know?

2.4.2: Is there a consistent attitude to the dikes and lavas? If so, measure the strike
and dip and report your results here.

2.4.3: Do the dikes intrude the lavas, or were the lavas erupted into dike-bounded
fissures? Explain and sketch your evidence.
Day 2
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
2.4.4: Notice the yellow and orange oxidized zones. What might have caused the
alteration?

2.4.5: Can you determine the timing of the alteration? What is your evidence and
what is the significance of this?

2.4.6: Make a conceptual sketch/drawing illustrating how the structure observed
here may indicate the direction to the rift axis.
Gather-up for a student-led discussion of the significance of stops 2.3 and 2.4. Group 2
will lead this discussion: Stephanie Mager, Adam Angel , Stacy Dwyer , Lucas
Gschwind, Tjames Poulos.
Let’s return to the vehicles and head home to Kakopetria (unless we have time for an
alternate stop…)
Day 2
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Optional stops
Exit the vehicles and safely cross the road to investigate the outcrops of multiple lava
morphologies, sills and a fault.
Alternate Stop X: Lava section continued at Kato Moni – multiple lava
morphologies


2.X.1: Find a sheet flow. How can you determine whether the flow is a sheet flow
later buried, or a sill intruded between pillows?

Day 2
2.X.2: Sketch where both types are in the outcrop
34

2.X.3: There is a major fault in the exposure. What is the dip and shear sense of
the fault? Sketch where the fault lies.

2.X.4: How does the volcanic expression change on either side of the fault

2.X.5: What is the alteration intensity of the rocks

2.X.6: What is the timing of the fault? Was it active on the seafloor, only after
uplift, or only recently?
Gather up for Student led discussion discussing the significance of today’s stops in light
of the difficulty in building a lava pile in spreading crust.
Day 2
35
Optional Stops
Optional Stop XX: Overlook of Memi Mine near Vizakiya,


2.XX.1: Measure the largest pillow that you can find

2.XX.2: Some dikes cut the pillows – measure the orientations, are they consistent
with east west trend.

2.XX.3: Try to extract glass from rims of pillows. Why is the glass preserved
when the interior of the pillows is altered?
Day 2
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37
Day 3: The Dike-Upper Gabbro transition in Eastern Troodos
Day 3 will be spent examining the dikes and upper gabbro section on the eastern side
of Troodos. Here the dikes are mostly vertical in orientation and the contact between the
dikes and gabbros appears to be magmatic. The observations of this day will then be
contrasted with our examination of a similar stratigraphic section (dikes to gabbro
transition) on Day 4 on the western side which the nature of the contact is more
complicated. We will be working along roads for several stops and there are hazards with
loose rock so please be careful—please PAY ATTENTION TO TRAFFIC (it comes from
the opposite direction as you think!). Also be wary of the hazards associated with falling
rocks at outcrops including being mindful of those below you.
Our first stop (3.1) will be in purely dikes at Kannavia. We will then move to the east
and examine relationships between gabbros and dikes along the road between Chandria
and Askas (3.2-3.4), including the perplexing problem of plagiogranite genesis. You will
observe several types of mafic intrusive rocks recording multiple intrusive events—
complicated relationships between these rocks and overlying dikes paints a picture of the
complexity of the process. Along the way, you are asked to identify a variety of rocks and
determine the relationships
of one to another. Key
questions to keep in your
mind are the relative timing
of the different rock types
and what is the nature of the
dike-gabbro boundary?
Day 3
38
Day 3 Itinerary: the eastern gabbro-dike transition
Depart Kakopetria to the southwest

Stop 3.1 near Kannavia
o Investigate sheeted dike complex
o Vertical sheeted dikes
o Look at chilled margins
 We are one canyon east from Kakopetria and east of the
Solea graben. The canyon you are in has steep walls of
sheeted dikes as you can see. Note the orientation of the
dikes. Examine the dikes for chilled margins, flow direction
markers, alteration, fracture patterns and cross cutting
relationships.

Stop 3.2 along F915 northern outskirts of Chandria—400 m section along road
o Investigate upper plutonic sequence
o Multiple magmatic injections producing upper gabbros
o Vertical sheeted dikes on hillsides above
o Exposure along road for ~400 m:
 First locality lies near roadsign (36499706E, 3866883N)
 Examine dark rocks for type, sequence of intrusion,
textures, relationship to each other
 Walk down road
 Start to see more leucocratic rocks

Stop 3.3 along F915 between Alona and Fterikoudi
o Investigate origin of plagiogranites
o Multiple magmatic injections
o Relationship to overlying dikes
 Collect spatial transect

Stop 3.4 (optional) along F915 near Askas
o Observe intrusion of gabbros into dikes
Day 3
39
Stop 3.1 in Sheeted Dike Complex near Kannavia
We are one canyon east from Kakopetria and east of the Solea graben. The canyon you
are in has steep walls of sheeted dikes as you can see. Note the orientation of the dikes.
Examine the dikes for chilled margins, flow direction markers, alteration, fracture
patterns and cross cutting relationships.

3.3.1 What is the average strike and dip of the dikes?

3.3.2 Of any crosscutting or anomalous dikes, what is the strike and dip?

3.3.1 What percentage of the dikes have 2 chilled margins?

3.3.1 What percentage of the dikes show epidosite alteration?
Day 3
40
Stop 3.2: Upper plutonic sequence near Chandria
along F915 northern outskirts of Chandria—400 m section along road
o Investigate upper plutonic sequence
o Multiple magmatic injections producing upper gabbros
o Vertical sheeted dikes on hillsides above
 First locality lies near roadsign (36499706E, 3866883N)

3.2.1: Start by drawing sketches of various areas along the road showing the
variety of rock types and their spatial relationships. Is this one big pluton? Does
it represents multiple injections—if so, why?

3.2.2 : perhaps you notice a change in the color index of the rocks as we
progress—how so? What is the type of rock that we are seeing more and more
of as we walk down the road?
Day 3
41
Day 3
42

3.2.3 Can you see any mafic dikes? If so, provide a sketch. What are the
margins of these dikes like? What is implied about relative temperatures of the
materials based on by textures you observe?

3.2.4 Find the plagiogranite outcrop shown in the fig. 2.13. b (above). Describe
the nature of this outcrop. Are there reaction rims on the plagiogranite? Walk
around the corner to find fig. 2.13. c above. What is the nature of the breccia?
Sketch and describe the nature of the materials and relative timing of formation.
Day 3
43
Stop 3.3 on F951 between Alona and Fteridoukis (Stop 2.11 in Edwards)
What is the origin of plagiogranite? What is the origin of granite for that matter? It is an
important question as we, as complex life forms, probably would not be around if it
weren’t for Earth’s bimodal crust. Plagiogranite genesis is doubly important because the
hot early earth likely produced just basaltic magma—thus making the early granites
(tonalites and tronjemites) had to occur in a basalt only setting.
Much of the current ideas on how silicic igneous rocks form, revolve around Tuttle and
Bowen’s (1958) classic experimental work on granitic systems. Their work showed that
there was a trough of minimum melting temperature where a melt coexisted with quartzfeldspar assemblages—the composition of the melt in equilibrium with quartz and two
feldspars closely resembled the average bulk composition of Earth’s granitoids (the bull’s
eye in the second ternary below). Thus they rightly concluded that granite was an igneous
rock that somehow reflected mineral-melt equilibrium. The next conclusion, that granites
therefore reflected either fractional crystallization or partial melting, remains an
interpretation because we cannot definitively observe what process is happening.
Is there an alternative to FC or PM to produce silicic igneous rocks? Maybe. Research at
Illinois shows that when wet silicate materials are placed in a big temperature gradient
(from 950 down to 350°C), they undergo a diffusion based differentiation process known
as thermal migration which results in a silicic granitic bulk composition material forming
at the cold end of the gradient. For instance, the figure below shows that andesite plus
water turns in a quartz-plag-kspar assemblage at 400°C.
Day 3
44
If you take a look at the Tuttle and Bowen figure above, you will see 4 squares on the
bull’s eye of igneous rocks diagram—the open square represents the starting material for
this experiment (andesite). The three filled squares represent the 3 lowermost samples
from the experiment; in other words, thermal migration takes a bulk composition not near
the bull’s eye and produces material at the cold end that hovers around the minimum melt
composition. Thus it is possible that this process could produce silicic igneous rocks.
Bowen (1921) made the ironclad argument that diffusion based processes in a
temperature gradient at the edge of a single magmatic intrusion could not be important.
This is because diffusion coefficient of heat (conduction) is roughly 4 orders of
magnitude greater than any mass diffusion coefficient—so any magma would cool faster
than mass could diffuse to change its composition. However, we now know that most
magmatic systems do not represent single injections of magma—rather, they reflect some
fairly continuous process of magma input which can lead to a sustained, nearly steady
state temperature gradient. A mid-ocean ridge magma lens might be one of the best
examples of a steady state temperature gradient—if so, maybe thermal migration can
differentiate the material at the sides of the magma lens to plagiogranite compositions.
You will help in a field test of this. The one thing that this alternative idea has going for it
is that there is a straightforward hypothesis test to be done. Temperature gradient driven
diffusion has a huge isotopic fractionation (apparently for all poly-isotopic elements yet
examined) so if thermal migration is occurring, we should see the signature in the rocks.
We are seeking to collect a spatial transect of samples from more mafic gabbros to
plagiogranite; back in Illinois we will dissolve up the rocks and analyze them for isotope
ratios in a variety of element systems (probably Fe, Mg, Si and Ca). The situation in the
field is vastly more complicated than the simple idea and there are many things to think
about when interpretations of the data are made.
Btw, I (CCL) am not asking anyone here to drink the kool-aid as MS says—critical
questions should be expected. Think about process and let your opinion be heard.
Day 3
45
At this stop, we will walk several hundred meters along the gravel track until we get to
outcrop. Group 3 will provide a presentation of work in this area on the thermal boundary
layer thought to exist between the gabbros and the sheeted dikes.

3.3.1: describe the rock types occurring in this locality. What is the mineralogy
of the two main rocks? Why is there so much iron staining? What is the
condition of the rocks in terms of alteration and weathering?

3.3.2: some of the rocks contain a green mineral that we discussed briefly in
class—what is it? What is its significance to the hydrothermal systems? What is
it about this mineral combined with quartz which leads to increasing
permeability for fluid flow? Is there a connection between formation of these
conduit rocks and plagiogranites? Maybe!

3.3.3 Walk back to parking area, then down hill to SE. What is the type of rock
here? What is its condition?
Day 3
46
Here is a figure from a recent paper by Stakes and Taylor on plagiogranites in the Semail
ophiolite in Oman. While the cartoon shows the differentiation sequence arranged
vertically (as opposed to the horizontal temperature gradient being hypothesized in our
thermal migration test), the cartoon based on observations in Semail does bring on some
further thought about the connections of systems at a MOR. For instance, plagiogranite
forms at the contact with the sheeted dikes and then has an epidote rind which, in some
cases, appears to lead into epidosites through the sheeted dikes. Further, these epidosites
appear to be tied to the umbers and hydrothermal deposits in the overlying volcanic
section. Could it be that the plagiogranites occur at the boundary with dikes where fluid
reaction and upflow begins?
Day 3
47
Optional Stop 3.4 Askas
Take a look at the cone shaped hill in the distance. What do you see in terms of the
spatial distribution of the rocks?
Let’s return to the vehicles and head home to Kakopetria
Day 3
48
49
Geology 415/515: Field Geology in Cyprus 2011
Day 4 Itinerary: Dikes to Gabbros
Depart Kakopetria to the Marathasa Valley and up the West side of Troodos.
Sheeted Dikes

Stop 4.1 between Gerakies and Kykko Monastery
o non-vertical dikes with some crosscutting dikes
Sheeted Dikes and the Dike –Gabbro contact

Stop 4.2 At Lemithou
o Investigate the relationship between tilted dikes and gabbro
Gabbros

Day 4
Stop 4.3 Gabbros on the road back to Kakopetria
o Investigate the complex intrusion and sheared nature of gabbros
50
This day is devoted mainly to the Sheeted Dike complex which makes up most of the
Troodos Ophiolite and the nature of its relationship to the underlying gabbros and
plagiogranites.
Kakopetria is partially situated on sheeted dikes on the central axis of the so-called
Solea Graben (by me, SDH, among others). So today we will drive north along the
graben axis and towards the Skouriotissa Mine at the northern end. At the turn to the west
from the main highway (B9) on the east side of the road is a rollover anticline in dikes
that is evidence for listric faulting in the sheeted dike section (including the Basal
Group). As we travel west we will pass several pillow mounds and roadcuts with dikes
and pillow screens of the Basal Group. Then, turning south again into the Marathasa
Valley (famous for cherries) we proceed into the main sheeted dike section that is also an
area of highly altered (epidotisized) dikes.
At an overlook near Pedhoulas we see the erosional outliers of sheeted dikes above
sheared gabbro. The contact between dikes and gabbro is gently dipping to the north over
a wide area here, cut by steep N-S trending faults.
Day 4
51
Our first stop (4.1) is in sheeted dikes between Gerakies and Kykko Monastery. 100%
sheeted dikes are exposed in road cuts all along this newly made road (to give better
access to the Monastery). Note that the dikes are not vertical. After looking at just dikes
for a while we will head to the geologically famous locality of Lemithou (4.2) to look at
the contact between dikes and gabbro close up. Then, on the way back to Kakopetria we
will stop at a roadcut (or two) to investigate aspects of the gabbro (4.3) underneath this
part of the sheeted dike complex.
Day 4
52
Stop 4.1: Sheeted Dike Complex
After parking, observe the sheeted dikes from across the road. Later approach for a close
up.

4.1.1: With your group you will do the chilled margin study of Kidd and Cann as
discussed in class earlier. This is an area they did not sample, we will see if it is
consistent with their results and also whether it might be consistent with the
identification of the Solea Graben as a deceased spreading center. So first with
your group identify a stretch of uninterupted dikes including at least 40-50 dikes
and sketch it, plausibly including every dike. Working together, identify chilled
margins on every possible dike and both mark them on your sketch and build a
tally of chilling directions. At the end of the stop, determine likely direction to the
spreading center indicated by the chilling statistics both from your group data
along and the combined data from the whole class.
Sketch below:
Day 4
53

Day 4
4.1.2: Meanwhile, also take strike and dip measurements on about 10 dike
margins where possible including anomalous and crosscutting dikes. Plot them on
the stereonet below. What is the average strike and dip of the dikes in this
outcrop? Are there any cross-cutting dikes with significantly different strike?
54
Stop 1.2: Dike – Gabbro contact exposed at Lemithou
This famous spot in Cyprus was on the cover of Geology once because of its excellent
photogenic juxtaposition of near horizontal (apparent dip) dikes over white gabbro. It is
an excellent display of the relationships between the dikes, the listric and low angle faults
and the deformation in the footwall.

Day 4
4.2.1: Sketch the outcrop below. What is the nature of the contact and its
orientation? Is the orientation the same everywhere?
55

Day 4
4.2.2: Measure the strike and dip of several dikes and plot below. What is the
average orientation of the dike? Measure the orientation of the faulted contact at
several places and plot? What is its orientation? Does a rotation axis in the fault
plane allow for the tilting of the dikes? In other works, can you plausibly rotate
the dikes back to vertical using a rotation axis that is also consistent with the fault
orientation?
56

4.2.3: Inspect the gabbro in the outcrop and describe the mineralogy. Are there
any veins or dikelets in the gabbro? What is their composition? What temperature
range do these mineral indicate the veins formed? Is that consistent with the
expected depth of the faulting here? Did this fault form at a spreading center?

4.2.4: The gabbro beneath the fault is highly sheared in some (all visible?)
locations probably due to the faulting. Identify some small striated surfaces in the
outcrop and measure the surface orientation and the orientation of the striae and
plot on the stereonet. Each group should try and measure at least 10 surfaces.
Day 4
57
These small slicks have been interpreted as Rydell shears, rather than typical
slickensides. Rydell shear slicks have a shear sense interpretation that is opposite to that
normally interpreted from traditional slickensides. What shear sense do these slicks give
generally for this outcrop? Therefore which way did the dikes rotate here (assuming they
rotated)? Is that consistent with extension at a spreading center in the Solea Graben?
Day 4
58
Stop 4.3: Gabbros along the Pedhoulas- Kakopetria road

4.3.1 Note the variety of gabbro exposures along this road. At the stop, is the
gabbro layered or isotropic? If layered, then what is the nature of the composition
changes among the layers? Are the layers horizontal? Take the strike and dip of
any layers.

Much of the gabbros along this road are highly fractured and in some places also
sheared. Are we near any major faults that might cause fracturing and shearing?

What is the composition of any dikes and veins that cut the gabbro? Are they
fractured and sheared in the same way as the gabbro – or do they appear to have
formed after most of the fracturing?
Day 4
59
60
Day 5 Itinerary: Traversing the Lower Crust and Upper Mantle
Depart Kakopetria to the southwest toward Prodromos on F936 stopping ~1.3 km before
the intersection with E908 at Prodromos.
Lower Intrusive layered gabbros

Stop 5.1 along F936 northeast of Prodromos
o Investigate lower plutonic sequence
o Two roadcuts ~700 m apart:
 First locality lies ~1.3 km northeast of the F936/E908 intersection.
Park on outside corner of bend in the road
 Begin section ~100 m to the southeast and continue back
up to the parking area
 Exposure of ~3 episodes of magmatic intrusion (peridotites,
pyroxenites and pegmatitic gabbro)
 Second locality is ~700 m further to southwest, and about 600 m
from the intersection of F936 and E908. Park on the right just
ahead of the sharp bend above Platania Restaurant.
 Exposure on outside of bend – Gabbros and ultramafic
intrusives.

Proceed southwest to the E908 and head south on the E908 toward Troodos. At
the intersection with the B8 in Troodos, head south toward Pano Platres stopping
~1.8 km southwest of Troodos. Park on the southwest side of B8 by the green
corrugated house.
Lower Crust – Mantle Transition (Moho?)

Stop 5.2 along the B8 ~1.8 km southwest of Troodos
o Investigate layered gabbro and lineated-foliated pyroxenites
o Two roadcuts ~800 m apart:
 First locality lies ~1.8 km from Troodos, park on the southeastern
side of B8 by green corrugated house.
 Section begins a bit to the southwest down the road.
 Exposure: gabbro and ultramafic rocks.
 Second locality is ~800 m walk down the road toward Pano Platres
at the arched bridge.
 Exposure of ultramafic rocks along the walk
 Stop ~35 m east of the old bridge on the old road and work
toward the bridge.

Proceed back toward Troodos on the B8. In Troodos, head north on the B9 toward
Kakopetria stopping after the sharp bend just east of Pano Amiantos. Park by the
small complex of old white buildings on the north side of the B9.
Day 5
61

Stop 5.3 along the B9 between Troodos and Kakopetria, east of Pano Amiantos
o Investigate banded and folded ultramafic intrusives
o Exposure in along a ridge that rises and runs southeast behind two old
white-walled buildings on the outside of the sharp bend in the B9.
Day 4 will be spent traversing the lower-crustal section and upper mantle section of
the Troodos Ophiolite. Field stops are located south of Kakopetria along highways F936,
E908, B8 and B9. We will begin a few kilometers southwest of Kakopetria near
Prodromos, and travel south on the E908 passing through Troodos and continuing south
on the B8 toward Pano Platres. We then return along the B8 passing through Troodos,
picking up the B9 heading through Pano Amiantos and returning to Kakopetria. Much of
our day is spent roadside, so please PAY ATTENTION TO TRAFFIC and be safe.
Our first stop (5.1) is in the lower crust where you will observe multiple types of
mafic and ultramafic intrusive rocks recording multiple intrusive events. We will
continue down section as we travel south, heading into the crust-mantle transition (Stop
5.2) crossing the Moho and then back up into the ultramafic intrusives of the lower crust
(Stop 5.3). See the map for geologic setting of each location.
Day 5
62
Stop 5.1: The Plutonic Rocks of the Lower Crustal Section
Be careful of traffic when exiting the vehicle and crossing the road. The section of
interest extends from beyond the bend by the leaning concrete telegraph pole to the
southeast ~100 m opposite the speed limit sign and warning sign. Spread out along the
roadcut working to cover the entire exposure; some may want to begin at the far end and
work back to the vehicle.


5.1.1: There are multiple rock types exposed along this roadcut. You should work
to identify as many as you can find. Yes, some are completely weathered – try to
determine what they used to be.
Rock 1 Name:
Mineralogy and volume %:
Rock 4 Name:
Textures:
Textures:
Rock 2 Name:
Rock 5 Name:
Textures:
Textures:
Rock 3 Name:
Rock 6 Name:
Textures:
Day 5
Textures:
63

5.1.2: How many episodes of intrusion can you find evidence for? Give the
evidence. This will be important for our discussion at the end of the day, so please
diligently record your observations.

5.1.3: Pay some attention to the layered rocks at the far end of the section by the
road signs. Look for a foliation within the layers. Is the foliation parallel to the
layering? Is the layering primary, igneous layering or is it produced by
deformation? Speculate on the origin of the layers.
Day 5
64
Proceed ~700 m down the road toward Prodromos (by vehicle or walk?). Stop and park
on the right just ahead of the sharp bend above Platania Restaurant. Investigate the
roadcuts on the outside bend of the curve. Be mindful of falling rocks. The section begins
northeast of the parking area and extends the first bend beyond the restaurant.

5.1.4: Three basic rock types are here: banded gabbro, poikilitic wehrlite, and
CPX-bearing dunite. See if you can work-out the intrusive relationships between
these rocks as you walk down toward the bridge/stream. Beyond the
bridge/stream things get more complicated.

5.1.5: Continue beyond the bridge/stream passing olivine-pyroxenite, pyroxenite,
gabbro and pegmatitic gabbro until you come to a large pyroxenite body in
contact with Wehrlite. Spend some time describing the contact between these two
bodies. Make a nice sketch of a contact.
Day 5
65
Proceed southwest to the E908 and head south an the E908 toward Troodos, following
the B8 past Troodos toward Pano Platres stopping ~1.8 km southwest of Troodos. Park
by the green corrugated house. Walk the short distance southeast to the continuous
exposure.
Stop 5.2: Transition Across the Moho


5.2.1: What is the main rock-type here (the
layered one)? Are we in the crust or mantle?

5.2.2: Notice the layering (1-40 cm thick layers). What defines the layering? Is the
layering primary or imposed by deformation?

5.2.3: Notice that some layers are folded, and perhaps the minerals show preferred
orientation. Speculate on the timing of this deformation relative to the formation
of the layers, and what might have caused this deformation.
Day 5
66
QuickTime™ and a
decompressor
are needed to see this picture.
Continue down the hill toward Pano Platres about 800 m and stop at the bridge on the
bend in the old road. Notice the changes in lithology of the rocks along your walk.

5.2.4: Examine the rocks ~35 m east of the bridge on the old road. Notice these
rocks are foliated harzburgite. Have you passed into the mantle? If so, why do you
think so? Did you cross a fault?

5.2.5: Continue toward the bridge and find the contact with the dunite body.
Investigate the contact between the dunite and harzburgite: which crosscuts the
other and how do you know?

5.2.6: See if you can find evidence for melt-harzburgite interactions. Sketch what
you find.
Day 5
67
Return to the vehicles and head back to Troodos, then northeast on the B9 toward
Kakopetria. Stop after the sharp bend just east of Pano Amiantos. Park by the small
complex of old white buildings on the north side of the B9. Exposure is along a ridge that
rises and runs southeast behind two old white-walled buildings on the outside of the sharp
bend in the B9. Views of the asbestos mine to the south.
Stop 5.3: The Lower Crust Again


5.3.1: The ridge exposes a variety of banded and folded ultramafic rocks, gabbro
and pegmatitic gabbro. Determine the field relationship between the gabbros and
the ultramafic rocks.

5.3.2: How many different kinds of xenoliths can you find in the gabbroic rocks?
List the rock-types you observed? Can you determine if these gabbros passed
through mantle rocks?

5.3.3: Look a little north of east from the ridge crest and you will see a roadcut
along the B9. The roadcut exposes a faulted contact between the mantle
pyroxenites and layered gabbros. Further down the road, you may see layered
gabbro cut by pegmatitic gabbro and chilled microgabbro dikes.
Day 5
68
Gather-up for a discussion of what we’ve seen and a general discussion of the plutonic
sequence and models of multiple injection and their implications for spreading models.
Group 1 will lead this discussion (Daniel Beach, Alison Bruegger, Norbert Gajos, Mary
Seid, Michael Walsworth).
Day 5
69
Brown and Musset, 1993
Walker et al., 1979
Stolper, 1990
Day 5
70
Let’s return to the vehicles and head home to Kakopetria (unless we have time for an
alternate stop…Perhaps the faulted mantle-lower crust contact up the road toward
Kakopetria)
Day 5
71
72
Day 6 will be spent examining the mantle section of Troodos, located in the center of
the ophiolite. We will learn about the types of rocks exposed in the upper mantle that
relate to processes of melting and melt extraction in the upwelling oceanic mantle
beneath a spreading center. The field stops are located near the highest point on the island
(Mt. Olympus), west of the town of Troodos. Much of our day will be spent walking
along dirt roads so traffic becomes less of an issue—nevertheless, remain vigilant about
traffic and be wary of the hazards associated with rotting ultramafic rocks at outcrops.
Our first stop (6.1) is at the top of Troodos examining and learning to identify the
types of ultramafic rocks you will see. We will then move down the road to hike along a
dirt road leading to the chromite mine (stop 6.2). Along the way, you will identify a
variety of mantle rocks, some in “vein” form, and determine the relationships of one to
another. Key questions will involve the relative timing of the different rock types and if
the rocks reflect an injection process of one into another or whether they reflect a
replacement process.
Day 6
73
Day 6 Itinerary: the mantle section of Troodos
08.30 a.m. Depart from Kakopetria. Drive to the car park near post office in Troodos.

Stop 6.1 Trailhead of Atlante nature trail around Mt. Olympus
o Familiarize yourself with basic mantle rock types
o Examine textures and relationships of “veins”
o Serpentine and Bastite
o Exposure along trail for ~400 m:
 Stop and introduce material at trail head
 Examine dark rocks for type, sequence of intrusion,
textures, relationship to each other
 Walk down trail to examine variety of rocks

Stop 6.2 beginning of dirt road to Chromite mine (Agios Nikolaos)
o Observe sequence of mantle rocks leading to chromite mine see the two
main types of mineralization associated with ophiolite peridotites: a
podiform chromite deposit and an asbestos deposit.
o Determine the temporal relationships of “veins”
o Injection or replacement origin of dunite?
o Walk ~4 km to mine RT
 As we walk down dirt road, we will examine the relationship
between harzburgite and variety of vein rocks
 Determine relative age and mechanism of emplacement
 Walk down road 4 km RT
 Examine chromite deposits and relationship to dunite.

Stop 6.3 overlook of asbestos mine
o Observe geology related to an asbestos deposit.
o Determine the temporal relationships of “veins”
o Discuss issues of asbestos hazard
o Walk short distance along trail and examine asbestos mineralization in
river deposits
Optional Stop 6.4) Fault contact between the highly serpentinized peridotite on the
eastern side of Troodos and gabbro.
Day 6
74
Stop 6.1 beginning of round Mt Olympus trail
The uppermost mantle is primarily composed of 4 minerals: Olivine ((Mg, Fe)2SiO4),
orthopyroxene ((Mg, Fe)2Si2O6), clinopyroxene (Ca(Mg, Fe)Si2O6), and spinel (Mg,
Fe)(Cr, Al)2O4). You should have been able to try to identify these minerals in an
unaltered peridotite (back in class in Illinois). Here the task is much more difficult
because these ultramafic rocks are significantly more battered than the mantle xenoliths
we were looking at in class. Much of the rock has been serpentinized (even the stuff we
call “harzburgite” here is significantly altered but not to the extent of the rock that we call
“serpentinite”). For your observational purposes, olivine becomes a smooth brown
serpentine when it is altered while the serpentine forming from orthopyroxene has a
platiness that sticks out and is referred to as bastite. Once the mantle cools to below
500°C or so, the common reaction is sepentinization. Typical reactions are:
2Mg2SiO4 +
olivine
3H2O =
water
Mg3Si2O5(OH)4 +
serpentine
Mg(OH)2
brucite
MgSiO3 +
othopyroxene
Mg2SiO4
olivine
+
Mg3Si2O5(OH)4
serpentine
2H2O
water
=
The harzburgite has a dominant fabric related to mid-ocean ridge dynamics, especially
the intense shearing that occurs as it undergoes corner flow when it changes from being
upwelling asthenosphere to a horizontally layered/stretched material that becomes part of
the lithospheric mantle. The rock can be called a mantle tectonite due to this fabric
reflecting the mechanical process of corner flow.
The mineralogy of the mantle tectonite on Mount Olympus is mainly harzburgite (olivine
+ orthopyroxene + chromite) with some dunite (olivine + chromite) and the product of
harzburgite and dunite alteration (serpentine). The rock shows brown weathering owing
to the oxidation of ferrous iron in the primary minerals to ferric oxides. If you look in
detail at the weathered surface, you may notice black specks (the chrome spinels),
bastites (platy serpentine pseudomorphs of orthopyroxene showing the original
cleavages) and a „smooth‟ serpentine (after olivine). If you look at a broken, unoxidised
surface, you may notice that the bastite is a bronze color and the serpentine after olivine
is black.
 6.1.1: What is the general orientation of the tectonite fabric in the harzburgite?
Day 6
75
The map below shows the general distribution of harzburgite and serpentinite in
Troodos.
Day 6
76

6.1.2: Examine the rock surface and identify the three minerals-sketch and label.
What are their approximate proportions? Given this mineralogy, what would you
guess about the degree of partial melting this rock has suffered?
The mantle contains various types of veins (we use the term vein generically in a sense to
avoid the use of dike which can imply an igneous injection interpretation), many of
which are tabular in shape. It is worth avoiding a genetic label as it is often not clear
whether these are forced injections or replacement by a reactive melt (textural
relationships can discriminate these). Most common are pyroxenite veins, both
orthopyroxenite and clinopyroxenite. The former is typically bronze-colored, the latter
pale green. Also present may be wehrlites (olivine + clinopyroxene) and websterites
(orthopyroxene and clinopyroxene), the former being green and black, the latter green
and brown. Dunites (>90% olivine) are common as irregular pods and lenses. You can
recognize these, if present, by the brown weathering and their smooth appearance due to
the absence of bastites. Dunites, as we talked about in class, often appear to be
replacement features where melt flowing through harzburgite has dissolved OPX and
precipitated out olivine (see figure from Kelemen et al., below).
Day 6
77
Gabbro veins, recognizable by the presence of white plagioclase feldspar may also
be present but are generally rarer.

Day 6
6.1.3: Make a sketch of a location where dunite and harzburgite are both found.
Give scale and show tectonite fabric on drawing. What is the relationship of the
dunite “vein” to the tectonite fabric? What does this tell you about the timing of
when the vein was created? Do you see any observations that are indicative of
replacement or magmatic injection?
78
Yes we know this figure was already in the guidebook in another location but we
petrologists love this one and it serves to remind you of our lecture connecting phase
petrology to the formation of dunite by reactive infiltration instability. The key take home
message from this diagram is that as pressure decreases, the field of olivine + liquid
expands meaning that ascending melts will want to dissolve OPX and precipitate olivine
from peridotite in order to remain multisaturated in the mantle assemblage. Because
olivine/dunite has better wetting behavior with melt, dunites have higher permeability
than harzburgite; this cause more melt to flow through them leading to more dissolution.
This positive feedback process is thought to lead to a “river-like” network of ascending
melt (Kelemen et al., 1997). To think about: why would this be a better explanation for
dunites than them being residues of high degrees of melting?
Day 6
79
Stop 6.2 Hike road to chromite mine
Start at parking lot with dirt road going to Agios Nikolaos. Descend down road through
densely wooded forest.

6.2.1: Keep an eye on the rock types—once out of the forest, you should observe
a change in the relative amounts of dunite and harzburgite—which is becoming
more prevalent?

6.2.2 Some of the dunites are more than simply dunites with a mineral border at
the contact with the harzburgites. Look around, find one and sketch it. What is
the mineral border? How do you suspect this forms?
Once at the mine, explore the slopes behind the main collection of old buildings that has
the old rusty water tank.

Day 6
Stop 6.2.3 What is the nature of the chromitite ore? Can you draw a grain scale
picture of what it looks like
80
The ore mineral in podiform chromite ores is chromite. Chromite has the composition
(Fe,Mg)(Cr,Al)2O4. There are two grades of chromite: metallurgical grade (Cr2O3>48wt.
%; Cr/Fe>2.8); and refractory grade (Cr2O3>30 wt.%; Cr2O3+ Al2O3>57wt.%; Fe<10
wt.%). Troodos chromite typically contains 48-55% Cr2O3 with Cr/Fe ratios of about 3.
The Kannoures podiform chromite mine started operation in 1939 and operated
sporadically since. It is small even by podiform chromite standards. It was estimated in
1979 that 4000 tonnes of ore had been extracted and that reserves stood at 8000 tonnes,
but the mining has since ceased. The ore zone is almost vertical, trending north-south
with an average thickness of about 5 metres.
Like other economic chromite deposits, the ore is restricted to the isolated pods and
layers of dunite in the harzburgite mantle sequence. The ores exhibit a variety of textures
from nodular to occluded silicate to chromite net-texture. Lineation in the chromite is
common: for example, nodules may be elongate in the nodular chromite. Cracks are
commonly filled with serpentine. Pull-apart textures are also common in the massive ore.
Both the chromite and the enclosing dunite are deformed together, concordant with the
fabric of the surrounding harzburgite.

Day 6
6.2.4 What is the texture of the chromite grains? Sketch an observed outcrop of
podiform chromite at a scale where harzburgite can be seen (maybe a few meters
across). Determine crosscutting relationships between dunite, harzburgites, and
chromite seams. Then, if possible, provide a larger scale sketch getting at the
bigger scale structure of the chromite deposits.
81
Room for second sketch…
Day 6
82
Stop 6.3 Asbestos mine
Group 5 presentation on the Serpentine diapir idea. Kato Amianos lies to the east of the
huge waste piles of the Amiantos mine. Walk westward up the dirt road keeping the river
on the left. Take a look at the rocks in the river bed and try to find some asbestos laden
samples.
Serpentinization of the mantle sequence on the Troodos Massif leads to production
“white” asbestos. Serpentine occurs as three polymorphs: the platy form, lizardite, which
forms the bastites and much of the fine grained serpentine after olivine that you have seen
so far; the fibrous form, chrysotile; and the platy or fibrous form, antigorite. Asbestos is
the mineral chrysotile, although lizardite is also present in the mine along with brucite
and magnetite and minor talc, hydrogarnet, tremolite and carbonates. This asbestos is
often called white asbestos and is demonstrably less hazardous than the much more
dangerous asbestiform minerals which are amphiboles (blue and brown asbestos). There
remains significant debate about how dangerous white asbestos is or is not and it is
important to realize that not all asbestos is the same.
In the Troodos Massif, chrysotile mineralization is confined to a 23 km2 area of faultbrecciated serpentinized harzburgite where it occurs as cross-fibres in veins of widths that
vary from hair-like stringers to up to 1.5 cm. The asbestos fibre is quite short, typically
less than 1 cm. The veins show no obvious regional pattern, being related to joints and
fractures of variable orientation. The asbestos was extracted from the Amiandos mine
(recently closed down following the collapse of the asbestos market as health risks
became apparent) that you will see from a distance at the next locality. This mine
extracted asbestos ore of just below 1 per cent grade and produced about 40,000 tons of
fibre per year.
Day 6
83

6.3.1: Record the different morphologies and colors of the serpentines you see
and list other minerals that are present

6.3.2: Can you find any evidence that might suggest that there were several
episodes of serpentinization? What is the likely origin of the fluids that cause
serpentinization? List the possible options.
Day 6
84
Optional Stop 6.4
Fault contact between the highly serpentinized peridotite on the eastern side of Troodos
and gabbro. Walk over to the high cliff outcrop by the spring. Be careful of traffic on the
road. Examine the rocks behind the spring and identify the rocks. Continue walking
downhill (to the north) paying attention to the rocks as you go. Within a few meters the
rock type will change.
6.4.1: What is the new rock type? Follow (with your now attuned eyes, or as a mountain
goat) the contact between the two rock types. What is the orientation (strike and dip)?
Can you find any shear sense indicators, and what shear sense do they indicate? Is this
the sense you expect? Given the orientation of the fault, is this a thrust, normal or strike
slip fault?
6.4.2: this fault is mapped (by Nuriel et al., Hurst et al., and others) to continue down
through Kakopetria and on to the massive sulfide mines of Apliki and Mavrovouni. Is
this fault likely to be a seafloor structure or not? Explain your thinking!
Day 6
85
32°55'
32°50'
Mavrovouni
Mine
Skouriotissa
Mine
Apliki Mine
35°00'
Evrykhou
Kalopanayiotis
Kakopetria
Pedhoulas
Alteration zones in the Solea Graben
Lemithou
0
1
Epidosite
K-Feldspar
Argillic
Greenschist,
Sub-Greenschist
2
Sample Sites
km
86
Towns
Mines
32°55'
32°50'
Skouriotissa
70
Mavrovouni
35°05'
35°05'
Apliki
50
70
60
Ayios Theodhoros
50
50
60
60
60
Evrykhou
50
40
70
Kaliana
40
35°00'
35°00'
Kalopanayiotis
Kakopetria
60
Kannavia
Moutoullas
32°55'
Spilia
Pedhoulas
Legend
50
Lemithou
Mt.
Olympus
Copper Mines
Contact
Towns
Normal Fault
Graben center
Low-angle Fault
N
Tres Elies
Areas with Dike Dips less than 50°
32°50'
0
km
Contoured Dike Dips in the
Solea Graben
87
5
Contour Interval 10°
0
32°55'
32°50'
Skouriotissa
Mavrovouni
0
35°05'
35°05'
Apliki
0
0
Ayios Theodhoros
Evrykhou
a
20
Kaliana
0
35°00'
Kalopanayiotis
Kakopetria
Moutoullas
Kannavia
Spilia
Pedhoulas
N
-20
0
-40
Lemithou
Tres Elies
32°50'
a'
32°55'
0
Residual Gravity Map of Solea graben area
(Bouguer Anomaly minus a 3rd order trend surface)
88
Contour interval 5 mgal
km
5
Schematic Cross-sections of Solea Graben from seafloor Spreading to present
89
0
W
a
kilometers
Kalopanayiotis
Detachment
Break-Away Zone
5
Ultramafic Rocks
Serpentinite
Gabbro
Kakopetria
Graben Axis
Sheeted Dikes
Detachment
Ductile shear zones or magmatic intrusions
Detachment
Graben Axis
Pillow Lavas & Flows
Plagiogranite
Gabbro Intrusions
E
a'

2011 Spring Field Course Cyprus - Troodos Ophiolite 2011 Spring

Transcription

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