Late Alpine evolution of the central Menderes Massif, western Turkey

The central Menderes Massif (western Turkey) is characterized by an overall dome-shaped Alpine foliation pattern and a N-NNE-trending stretching lineation. A section through the southern flank of the central submassif along the northern margin of Büyük Menderes graben has been studied. There, asymmetric non-coaxial fabrics indicate that the submassif has experienced two distinct phases of Alpine deformation: a top-to-the N-NNE contractional phase and a top-to-the S-SSW extensional event. The former fabrics are coeval with a regional prograde Barrovian-type metamorphism at greenschist to upper-amphibolite facies conditions. This event, known as the main Menderes metamorphism, is thought to be the result of internal imbrication of the Menderes Massif rocks along south-verging thrust sheets during the collision of the Sakarya continent in the north and the Anatolide-Tauride platform in the south across the Gzmir-Ankara suture during the (?)Palaeocene-Eocene. Top-to-the S-SSW fabrics, represented by a well-developed ductile shear band foliation associated with inclined and/or curved foliation, asymmetric boudins, and cataclasites, were clearly superimposed on earlier contractional fabrics. These fabrics are interpreted to be related to a low-grade (greenschist?) retrogressive metamorphism and a continuum of deformation from ductile to brittle in the footwall rocks of a south-dipping, presently low-angle normal fault that accompanied Early Miocene orogenic collapse and continental extension in western Turkey. A similar tectono-metamorphic history has been documented for the northern flank of the dome along the southern margin of the Gediz graben with top-to-the N-NNE extensional fabrics. The exhumation of the central Menderes Massif can therefore be attributed to a model of symmetric gravity collapse of the previously thickened crust in the submassif area. The central submassif is thus interpreted as a piece of ductile lower-middle crust that was exhumed along two normal-sense shear zones with opposing vergence and may be regarded as a typical symmetrical metamorphic core complex. These relationships are consistent with previous models that the Miocene exhumation of the Menderes Massif and Cycladic Massif in the Aegean Sea was a result of bivergent extension.     

Material properties of the Menderes Massif Marbles from SW Turkey

Marbles are extensively quarried at four different stratigraphical levels from Permo-Carbonifereous to Paleogene in the southern flank of the Menderes Massif in SW Turkey. These marbles differ in color, texture and pattern depending on their stratigraphical levels and are well known in the international trade as the Mugla Black (Permo-Carbonifereous), Mugla White (Cretaceous), Milas Lemon, Lilac, Aubergine, Pearl, Veined and White (Triassic) and Aegean Bordeaux (Paleogene) marbles. The mineralogical, chemical, physical and mechanical properties of the representative marbles samples obtained from the quarries working in four major metamorphic carbonate horizons in the cover successions of the Menderes Massif's southern flank in SW Turkey are determined and the results of over 1700 tests carried out on the selected marble samples are presented. The mean test values of the physical and mechanical tests are in general, found to be above the threshold acceptance values suggested by the American and Turkish Standards for the use of marbles as a building stone and in the same order as the properties of Italian (Carrara) and Greek marbles reported in the literature. Additionally, the mean test values of the marbles have given high correlations with one another and the relations obtained between the index test results determined by simple techniques requiring minimal sample preparation effort and the mean values of the more elaborate engineering tests results are presented as tables and graphs for wider use.     

Complete Tertiary exhumation history of the Menderes massif, western Turkey: an alternative working hypothesis

The main exhumation of the Menderes massif, western Turkey, occurred along an originally N‐dipping Datça–Kale main breakaway fault that controlled depositions in the Kale and the Gökova basins during the Oligocene – Early Miocene interval. The isostatically controlled upward bending of the main breakaway fault brings the lower plate rocks to the surface. In the Early Miocene, E–W‐trending N‐ and S‐dipping graben‐bounding faults fragmented the exhumed, dome‐shaped massif. The development of half grabens by rolling master fault hinges has allowed further exhumation of the central Menderes massif. After the Pliocene, high‐angle normal faults cut all of the previous structures. This model suggests that the Menderes massif is a single large metamorphic core complex that has experienced a two‐stage exhumation process.     

Pan-African magmatism in the Menderes Massif: geochronological data from leucocratic tourmaline orthogneisses in western Turkey

The Menderes Massif, exposed in western Anatolia, is a metamorphic complex cropping out in the Alpine orogenic belt. The metamorphic rock succession of the Massif is made up of a Precambrian basement and overlying Paleozoic-early Tertiary cover series. The Pan-African basement is composed of late Proterozoic metasedimentary rocks consisting of partially migmatized paragneisses and conformably overlying medium- to high-grade mica schists, intruded by orthogneisses and metagabbros. Along the southern flank of the southern submassif, we recognized well-preserved primary contact relationship between biotite and leucocratic tourmaline orthogneisses and country rocks as the orthogneisses represent numerous large plutons, stocks and vein rocks intruded into a basement of garnet mica schists. Based on the radiometric data, the primary deposition age of the precursors of the country rocks, garnet mica schist, can be constrained between 600 and 550?Ma (latest Neoproterozoic). The North Africa–Arabian-Nubian Shield in the Mozambique Belt can be suggested as the possible provenance of these metaclastics. The intrusion ages of the leucocratic tourmaline orthogneisses and biotite orthogneisses were dated at 550–540?Ma (latest Neoproterozoic–earliest Cambrian) by zircon U/Pb and Pb/Pb geochronology. These granitoids represent the products of the widespread Pan-African acidic magmatic activity, which can be attributed to the closure of the Mozambique Ocean during the final collision of East and West Gondwana. Detrital zircon ages at about 550?Ma in the Paleozoic muscovite-quartz schists show that these Pan-African granitoids in the basement form the source rocks of the cover series of the Menderes Massif.     

Hydrogen and oxygen isotope evidence for fluid–rock interactions in the Menderes massif, western Turkey

The Menderes Massif comprises an inner crystalline core with gneissic rocks and an outer surrounding schist belt with predominantly metasedimentary rocks. Both units have a complex metamorphic history including a late Alpine overprint. Temperatures inferred from oxygen isotope compositions of coexisting minerals increase from 420 to 600°C from the rim to the center. More positive '¹⁸O values in all minerals from the schist belt may reflect a higher abundance of sedimentary precursor material, whereas biotites and muscovites in core and rim are indistinguishable in hydrogen isotope composition. 'D values of muscovites range from -35 to -60‰, whereas 'D values of biotites range from -65 to -125‰, indicating normal values for muscovite but anomalously negative values for some biotites. For muscovite the trend can be interpreted in terms of increasing loss of water with rising metamorphic temperature. For biotite the 'D values decrease with increasing H₂O content and decreasing Na₂O+K₂O content, which provides evidence for alteration processes or exchange of K and Na with water from interlayers of biotite forming hydro-biotite. The data suggest isotopic resetting of pre-Alpine characteristics during Alpine metamorphism. The hydrogen isotope composition of biotite was later disturbed, probably during extensional neotectonic movements in this region, as this allowed infiltration of and exchange with D-depleted meteoric water; however, the muscovites retained its Alpine characteristics.     

Pan-African deformations in the basement of the Negele area, southern Ethiopia

Polydeformed and metamorphosed Neoproterozoic rocks of the East African Orogen in the Negele area constituted three lithostructurally distinct and thrust-bounded terranes. These are, from west to east, the Kenticha, Alghe and Bulbul terranes. The Kenticha and Bulbul terranes are metavolcano-sedimentary and ultramafic sequences, representing parts of the Arabian-Nubian Shield (ANS), which are welded to the central Alghe gneissic terrane of the Mozambique Belt affinity along N-S-trending sheared thrust contacts. Structural data suggest that the Negele basement had evolved through three phases of deformation. During D1 (folding) deformation, north-south upright and inclined folds with north-trending axes were developed. East and west-verging thrusts, right-lateral shearing along the north-oriented Kenticha and Bulbul thrust contacts and related structural elements were developed during D2 (thrusting) deformation. The pervasive D1 event is interpreted to have occurred at 620-610 Ma and the D2 event ended prior to 554 Ma. Right-lateral strike-slips along thrust contacts are interpreted to have been initiated during late D2. During D3, left-lateral strike-slip along the Wadera Shear Zone and respective strike-slip movements along conjugate set of shear zones were developed in the Alghe terrane, and are interpreted to have occurred later than 557 Ma. The structural data suggest that eastward thrusting of the Kenticha and westward tectonic transport of the Bulbul sequences over the Alghe gneissic terrane of the Mozambique Belt, during D2, were accompanied by right-lateral strike-slip displacements along thrust contacts. Right-lateral strike-slip movements along the Kenticha thrust contact, further suggest northward movement of the Kenticha sequence during the Pan-African orogeny in the Neoproterozoic. Left-lateral strike-slip along the orogen-parallel NNE-SSW Wadera Shear Zone and strike-slip movements along a conjugate set of shear zones completed final terrane amalgamation between the Arabian-Nubian Shield and the Mozambique Belt in Neoproterozoic southern Ethiopia.     

Zn-rich högbomite formed from gahnite in the metabauxites of the Menderes Massif,SW Turkey

Gahnite, ZnAl₂O₄, present as an accessory mineral in regionally metamorphosed low-grade diasporites, has reacted in adjacent higher-grade, corundum-bearing metabauxite equivalents (emeries) to form Zn-rich högbomite, (Zn,Fe²⁺,Mg,Ni)_t-2x (Ti,Sn)_xAl₂O₄, of the 4H polytype. Commonly, the initial högbomite crystals grew epitactically along the octahedral faces of gahnite, which was subsequently dissolved, so that högbomite now forms spectacularly intergrown sets of eight crystals in perfect crystallographic orientation to each other. This indicates a metamorphic reaction, probably involving a fluid, transporting mainly the elements Zn and Al. Reactant Ti minerals in the diasporites were rutile and titanian hematite (10–15 mol% FeTiO₃). In the emeries högbomite coexists with still more Ti-rich hematites containing between 26 and 37 mol% FeTiO₃. The overall reaction relations involving partial reduction may be subdivided into the intial univariant reaction, gahnite+diaspore+Ti-hematite+rutile=högbomite+H₂O+O₂. This was followed, in the absence of gahnite, by compositional readjustments of högbomite and Ti-hematite and the appearance of magnetite. Core to rim zoning profiles indicate that, with continued growth, the högbomite crystals became poorer in Zn and Ti, but richer in Fe²⁺, while the Ti-contents of coexisting hematite increased. Högbomite formation at the expense of gahnite started at temperatures as low as about 400° C for an estimated pressure of 5–6 kbar.     

Geomorphological features and weathering of the Southern Submassif of the Menderes Massif (SW Turkey)

The Southern Submassif crops out in the SW of Turkey. This submassif consists of mostly large feldspar-bearing orthogneisses and to a lesser extent tourmaline-orthoclase-plagioclase-, quartz-, muscovite-, and biotite-bearing leucogranites. The orthogneiss forms domed bald hills. The leucogranites crop out (approximately 2 km²) in the southeastern lowland of the hill. Those units show various geomorphological features that are typically reported in granitoids. Many studies about the Menderes Massif are related with petrography and metamorphic history. The geomorphological features are not taken into consideration. Field observation, thin section analysis, joint set-foliation measurements, and Schmidt Hammer value determination were done in this study. The pillar structures (castellated and domed types) are among larger structures observed on flanks of the domed bald hill. Geomorphological features such as weathering pits, tafoni, honeycomb structures, polygonal cracks, flared slopes, exfoliation, and boulders are observed. The metamorphism causes mineral alignments that affect the strength of the rock. The studied rocks have high strength in perpendicular direction to foliation. The complex tectonic history caused developments of several joint sets. Differences in mineral strength (e.g., high in quartz, low in biotite and feldspar) increase weathering effect. Underground water percolation through the fractures weakens the rock and causes subsurface weathering. After exhumation, disintegrated materials are stripped off, and then flared slopes, polygonal cracks, and pillar structures are exposed. Surface weathering by wind and water increases the weathering effects and gives rise to a formation of rounded rock edges called spheroidal weathering. Contrary to other granitoid areas, the metamorphism promotes the formation of geomorphological features in the study area.     

Tectonic significance of deformation patterns in granitoid rocks of the Menderes nappes, Anatolide belt, southwest Turkey

Deformation fabrics in Proterozoic/Cambrian granitic rocks of the Çine nappe, and mid-Triassic granites of the Bozdag nappe constrain aspects of the tectonometamorphic evolution of the Menderes nappes of southwest Turkey. Based on intrusive contacts and structural criteria, the Proterozoic/Cambrian granitic rocks of the Çine nappe are subdivided into older orthogneisses and younger metagranites. The deformation history of the granitic rocks documents two major deformation events. An early, pre-Alpine deformation event (D_PA) during amphibolite-facies metamorphism affected only the orthogneisses and produced predominantly top-to-NE shear-sense indicators associated with a NE-trending stretching lineation. The younger metagranites are deformed both by isolated shear zones, and by a major shear zone along the southern boundary of the Çine submassif. We refer to this Alpine deformation event as D_A3. D_A3 shear zones are associated with a N-trending stretching lineation, which formed during greenschist-facies metamorphism. Kinematic indicators associated with this stretching lineation reveal a top-to-south sense of shear. The greenschist-facies shear zones cut the amphibolite-facies structures in the orthogneisses. ²⁰⁷Pb/²⁰⁶Pb dating of magmatic zircons from a metagranite, which crosscuts orthogneiss containing amphibolite-facies top-to-NE shear-sense indicators, shows that D_PA occurred before 547.2ǃ.0 Ma. Such an age is corroborated by the observation that mid-Triassic granites of the Çine and Bozdag nappes lack D_PA structures. The younger, top-to-south fabrics formed most likely as a result of top-to-south Alpine nappe stacking during the collision of the Sakarya continent with Anatolia in the Eocene.     

Late orogenic crustal extension in the northern Menderes massif (western Turkey): evidence for metamorphic core complex formation

The Simav metamorphic core complex of the northern Menderes massif, western Turkey, consists of a plutonic (Tertiary) and metamorphic (Precambrian) core (footwall) separated from an allochthonous cover sequence (hanging wall) by a low-angle, ductile-to-brittle, extensional fault zone (i.e. detachment fault). The core rocks below the detachment fault are converted into mylonites with a thickness of a few hundred metres. Two main deformation events have affected the core rocks. The first deformational event (D₁) was developed within the Precambrian metamorphic rocks. The second event (D₂), associated with the Tertiary crustal extension, includes two distinct stages. Stage one is the formation of a variably developed ductile (mylonitic) deformation (D_2d) in metamorphic and granitic core rocks under greenschist facies conditions. The majority of the mylonites in the study area have foliations that strike NNW to NNE and dip SW to SE. Stretched quartz and feldspar grains define the mineral lineation trending SW-NE direction and plunging gently to SW. The kinematic indicators indicate a top-to-NE sense of shear. Stage two formation of brittle deformation (D_2b) that affected all core and cover rocks. D_2b involves the development of cataclasites and high-angle normal faults. An overall top towards the north sense of shear for the ductile (mylonitic) fabrics in the core rocks is consistent with the N-S regional extension in western Turkey.     

Geological parameters affecting the marble production in the quarries along the southern flank of the Menderes Massif, in SW Turkey

The Mugla province is one of the major marble producing regions located in the southern flank of the Menderes Massif in SW Turkey. The Menderes Massif is a regionally metamorphosed massif with an old Pan-African core and cover successions from the Permo–Carboniferous to Paleocene. There are four major metamorphic carbonate horizons in the cover successions exploited for the marble production. These horizons are located within the Permo–Carboniferous, Triassic, Upper Cretaceous and Paleocene successions along the southern flank of the Menderes Massif. Here the world wide known marbles with names such as the Mugla Black, the Milas White, Veined, Pearl, Aubergine, Lilac and Lemony, the Mugla White and the Aegean Bordeaux are found.

Detailed geological studies were carried out in selected marble quarries representing the different stratigraphic levels to determine the geological parameters affecting the marble production in the southern flank of the Menderes Massif in SW Turkey. The geological parameters such as bedding, joints, schist interlayers and mica filled joints affecting the block production from the marble beds are considered to be primary features. The presence of dolomite bands and lenses, abnormal sized calcite crystals and emery minerals which affect the slab and the production qualities and appearances are considered to be secondary geological parameters. The primary and secondary geological parameters affecting the marble productions at different stratigraphical levels in SW Turkey, are determined and the practical aspects of these findings are discussed.     

Origin and Metamorphism of Corundum‐Rich Metabauxites at Mt. Ismail in the Southern Menderes Massif,SW Turkey

The corundum‐rich metabauxites, found at the northwest limb of an NE–SW‐trending isoclinal recumbent fold at Mt. Ismail, are enclosed in thick‐bedded platform‐type marbles of Late Cretaceous age, surrounding the polymetamorphic core series in the southern part of the Menderes Massif (SW Turkey). The metabauxite horizons observed as typically boudine‐like structure, extend laterally over c. 3 km and are 1 to 5 m thick. These rocks have dominant mineral assemblages of corundum (～50 modal %), chloritoid (～30 modal %), white mica (margarite, muscovite), diaspore, Fe–Ti‐Oxides (ilmenite, ilmenohematite, rutile), and goethite, limonite, pyrite, tourmaline (uvite, schorl) as minor phases. Chemical analyses of whole rock samples and the mineral assemblage indicate that coexisting minerals of metabauxites are highly aluminous. A number of minerals (e.g. chloritoid and margarite) display a large compositional variation reflecting the initial chemical inhomogenetiy of the karstbauxites. The field observations, trace‐element accumulation coefficients, concentration of elements such as Cr, Zr, Ga and Ni and low amounts of immobile elements all suggest that the studied corundum‐rich metabauxites can be classified as karstbauxites, and are more likely to be a product of weathering of intermediate igneous or argillaceous parental rocks, similar to the karstic Tauric bauxites in the Central Taurides (Seydi ?ehir region) and probably are similar in age (Cenomanian–Turonian). In respect of tectono‐metamorphic evolution, the studied corundum‐rich metabauxites were regionally metamorphosed at ～5–6 kbar pressure and 500–600°C as a consequence of the Barrovian metamorphism referred to as the ‘Main Menderes Metamorphism’ related to the ophiolitic obduction onto the Menderes platform from the Izmir–Ankara Suture during the Middle Eocene.     

Plagioclase relations in pelites, central Menderes Massif, Turkey. II. Perturbation of garnet-plagioclase geobarometers

Abstract Activity-composition relations in oligoclase near the peristerite gap are investigated in pelites from the Central Menderes Massif. The pressure of metamorphism is estimated independently, from garnet-rutile-ilmenite-kyanite-quartz, as being in the range 4–7 kbar. In the temperature range, 450–600°C approximately, both the Newton-Haselton calibration of the garnet-plagioclase-kyanite-quartz geobarometer and a related simple treatment of garnet-plagioclase-muscovite-biotite give a wide range of apparent pressures, correlated with plagioclase composition and ranging up to 11–12 kbar where the plagioclase is most sodic. This effect is attributed to failure of the activity model for plagioclase used in the Newton-Haselton treatment. It is inferred that, in the present area, γ^plag_An decreases with increasing X ^plag_An in the range An₁₅-An₂₅. The data can be interpreted in terms of high γ ^plag_An in the high-albite structure at these temperatures, modified to lower values by 'e'ordering in the more calcic oligoclases. The ordering appears to be independent of the peristerite gap, and the data do not support the interpretation of the gap as a solvus. Garnet-plagioclase assemblages are unreliable as geobarometers where the plagioclase is more sodic than approximately An₂₀ and T < 700°C, and should instead be used to investigate the γ -X behaviour of the plagioclase where independent geobarometry can be used as a constraint.     

Monazite ages and the evolution of the Menderes Massif, western Turkey

The Menderes Massif experienced polyphase deformation, but distinguishing Pan-African events from Alpine tectono-metamorphic evolution, and discriminating Eocene–Oligocene shortening from recent extension remain controversial. To address this, monazite in garnet-bearing rocks from the massifs Gordes, Central, and Cine sections were dated in thin section (in situ) using the Th–Pb ion microprobe method. Cambro–Ordovician monazite inclusions in Cine and Central Menderes Massif garnets are ~450 m.y. older than matrix grains. Monazites in reaction with allanite from the Kuzey Detachment, which bounds the northern edge of the Central Menderes Massif, are 17±5 Ma and 4.5±1.0 Ma. The Pliocene result shows that dating of monazite can record the time of extension. The Kuzey Detachment might have exhumed rocks a lateral distance of ~53 km at a rapid rate of ~12 mm/year assuming the present ~20° ramp dip, Pliocene monazite crystallization at ~450°C, and a geothermal gradient of ~25°C/km. Assuming an angle of 60°, the rate decreases to ~5 mm/year, with the detachment surface at ~21 km depth in the Pliocene. Two Gordes Massif monazites show a similar allanite–monazite reaction relationship and are 29.6±1.1 Ma and 27.9±1.0 Ma, suggesting that the Cenozoic extension in the Gordes Massif, and possibly the entire Menderes Massif, might have begun in the Late Oligocene.     

Exhumation Paths of High-Pressure-Low-Temperature Metamorphic Rocks from the Lycian Nappes and the Menderes Massif (SW Turkey): a Multi-Equilibrium Approach

The Menderes Massif and the overlying Lycian Nappes occupy anextensive area of SW Turkey where high-pressure–low-temperaturemetamorphic rocks occur. Precise retrograde P–T pathsreflecting the tectonic mechanisms responsible for the exhumationof these high-pressure–low-temperature rocks can be constrainedwith multi-equilibrium P–T estimates relying on localequilibria. Whereas a simple isothermal decompression is documentedfor the exhumation of high-pressure parageneses from the southernMenderes Massif, various P–T paths are observed in theoverlying Karaova Formation of the Lycian Nappes. In the uppermostlevels of this unit, far from the contact with the MenderesMassif, all P–T estimates depict cooling decompressionpaths. These high-pressure cooling paths are associated withtop-to-the-NNE movements related to the Akçakaya shearzone, located at the top of the Karaova Formation. This zoneof strain localization is a local intra-nappe contact that wasactive in the early stages of exhumation of the high-pressurerocks. In contrast, at the base of the Karaova Formation, alongthe contact with the Menderes Massif, P–T calculationsshow decompressional heating exhumation paths. These paths areassociated with severe deformation characterized by top-to-the-eastshearing related to a major shear zone (the Gerit shear zone)that reflects late exhumation of high-pressure parageneses underwarmer conditions. KEY WORDS: exhumation; high-pressure–low-temperature metamorphism; multi-equilibrium P–T estimates; Lycian Nappes; Menderes Massif     

Plagioclase relations in pelites, central Menderes Massif, Turkey. I. The peristerite gap with coexisting kyanite

Abstract In pelites of the central Menderes Massif, albite and oligoclase with only slight chemical zoning coexist in apparent textural equilibrium in the garnet zone, staurolite zone, and staurolite + kyanite transition zone. The metamorphic temperature range is estimated as approximately 440–550°C (from the Hodges-Spear calibration of the garnet-biotite geo-thermometer), or 440–500°C (Ganguly-Saxena calibration). While oligoclase composition at the peristerite gap changes from An₂₂ to An₁₄, albite also becomes more sodic (An_1,5–An_0.6). The slope of the albite limb is thus the reverse of that reported in other areas, and may not be a true equilibrium feature. Occurrence of kyanite, at temperatures below the crest of the gap, is due to low water activity in the presence of graphite: a H_2o is estimated at approximately 0.1–0.2 from the Na content of muscovite coexisting with albite + kyanite + quartz.     

Petrological and mineralogical studies of Pan-African serpentinites at Bir Al-Edeid area,central Eastern Desert,Egypt

The studied serpentinites occur as isolated masses, imbricate slices of variable thicknesses and as small blocks or lenses incorporated in the sedimentary matrix of the mélange. They are thrusted over the associated island arc calc-alkaline metavolcanics and replaced by talc-carbonates along shear zones. Lack of thermal effect of the serpentinites upon the enveloping country rocks, as well as their association with thrust faults indicates their tectonic emplacement as solid bodies. Petrographically, they are composed essentially of antigorite, chrysotile and lizardite with subordinate amounts of carbonates, chromite, magnetite, magnesite, talc, tremolite and chlorite. Chrysotile occurs as cross-fiber veinlets traversing the antigorite matrix, which indicate a late crystallization under static conditions. The predominance of antigorite over other serpentine minerals indicates that the serpentinites have undergone prograde metamorphism or the parent ultramafic rocks were serpentinized under higher pressure. The parent rocks of the studied serpentinites are mainly harzburgite and less commonly dunite and wehrlite due to the prevalence of mesh and bastite textures. The serpentinites have suffered regional metamorphism up to the greenschist facies, which occurred during the collisional stage or back-arc basin closure, followed by thrusting over a continental margin. The microprobe analyses of the serpentine minerals show wide variation in SiO₂, MgO, Al₂O₃, FeO and Cr₂O₃ due to different generations of serpentinization. The clinopyroxene relicts, from the partly serpentinized peridotite, are augite and similar to clinopyroxene in mantle-derived peridotites. The chromitite lenses associated with the serpentinites show common textures and structures typical of magmatic crystallization and podiform chromitites. The present data suggest that the serpentinites and associated chromitite lenses represent an ophiolitic mantle sequence from a supra-subduction zone, which were thrust over the continental margins during the collisional stage of back-arc basin.