Zone Ophiolites Research Articles

Discovery of Ordovician acritarchs in Buqingshan ophiolite complex, East Kunlun Mountains and its significance

This note reports the first discovery of Middle-Late Ordovician acritarchs from the Buqingshan ophiolite complex of the southern ophiolite zone of East Kunlun. The acritarch assemblage is dominated with acanthomorphids (approx. 32%) and sphaeromorphds (approx. 63%) and contains more characteristic forms, such asLophosphaeridium edenense, L. varum, Nothooidium sp.,?Buedingiisphaaeridium sp.,Visbysphaera sp.,Strophomorpha sp., etc. In addition, some tube-like fragments and tetrads, which are recognized as affinity to terrestrial plants and usual occurrence in Late Ordovician-Early Silurian strata, are preserved together with acritarchs. All the known fossil evidence indicates that the strata should be Middle-Late Ordovician in age. It not only provides paleontological proof for the existence of Ordovician ophiolite, but also challenges the usual ideas on strata composition of the studied area and the southern ophiolite zone of East Kunlun, and the models on tectonic framework and evolution of this area and the northern part of the Qinghai-Tibetan Plateau.

Birth, death, and resurrection: The life cycle of suprasubduction zone ophiolites

Suprasubduction zone (SSZ) ophiolites display a consistent sequence of events during their formation and evolution that suggests that they form in response to processes that are common to all such ophiolites. This sequence includes the following: (1) birth, which entails the formation of the ophiolite above a nascent or reconfigured subduction zone; this stage is typically characterized by the eruption of arc tholeiite lavas and the formation of layered gabbros and sheeted dike complex; (2) youth, during which is continued melting of refractory asthenosphere (depleted during birth) occurs in response to fluid flux from the subducting slab, with extensional deformation of the older plutonic suite, eruption of refractory lavas, and the intrusion of wehrlite‐pyroxenite; (3) maturity, with the onset of semistable arc volcanism, typically calc‐alkaline, as the subduction zone matures and stabilizes, and the intrusion of quartz diorite and eruption of silicic lavas; and (4) death, which is the sudden demise of active spreading and ophiolite‐related volcanism, which in many cases is linked to collision with an active spreading center and the onset of shallow underthrusting of the buoyant spreading axis; expressed as dikes and lavas with oceanic basalt compositions that crosscut or overlie rocks of the older suites; (5) resurrection, with emplacement by obduction onto a passive margin or accretionary uplift with continued subduction. The early stages (1–3) may be diachronous, and each stage may overlap in both time and space. The existence of this consistent progression implies that ophiolite formation is not a stochastic event but is a natural consequence of the SSZ tectonic setting.

La succession lithostratigraphique du bloc de Banda dans la region de Kolonodale (Sulawesi central, Indonesie)

Abstract Sulawesi island is the convergence area of the Eurasian, the Pacific and the Australian plates. Villeneuve et al. demonstrated, from both lithostratigraphic and tectonic studies, that east and southeast Sulawesi was composed of two major continental blocks. - The "Banda block", including also Buru, Seram and Sinta Ridge, collided with the Asian volcanic arc of west Sulawesi during Oligocene times, then was dismembered during the Late Neogene Banda sea opening. - The Banggai-Sula block which was drifted from Irian Jaya and collided with the Banda block during Mid-Late Pliocene times. One of the fragments of the Banda block is in East Sulawesi, corresponding to the ophiolitic zone. There, in the Kolonodale area, it is possible to reconstruct the sedimentary succession under the ophiolite, despite intensive deformations. Over several years the stratigraphic framework of this area was detailed, following general mapping, and it is now possible, by including unpublished data concerning Cainozoic rocks, to reconstruct the Mesozoic-Cainozoic succession. Reconstructing the succession was possible by joint structural, stratigraphic and palaeoenvironmental studies. An example of structural cross-sections around the Kolonodale gulf is given on figure 4, from which local successions were built. We can now propose the general succession.

Petrology of a supra-subduction zone ophiolite (Elaz1g, Turkey)

The Elaz1g region in eastern Taurus, Turkey, exposes Paleozoic-Tertiary metamorphic, magmatic, and sedimentary units. Contacts between the different units are mostly tectonic, but there are also primary sedimentary, and intrusive contacts. The metamorphic rocks of the Elaz1g region are the Bitlis-Pütürge and Keban-Malatya massifs, which are a single tectonostratigraphic unit that has been tectonically disrupted and fragmented during the Upper Cretaceous. Magmatic rocks in the region are represented by ophiolitic units, magmatic arc products, and young volcanic rocks. The sedimentary units are represented by Upper Cretaceous - Tertiary marine and lacustrine sedimentary rocks. In the study area, the metamorphic units are represented by the Paleozoic Pütürge metamorphic rocks composed of phyllite, slate, mica schist, quartz-muscovite schist, calc-schist, and low-grade metamorphite. The ophiolite that is described in this paper is composed of wehrlite-pyroxenite, gabbro, diabase dykes, and dykes cutting gabbro. These units are cut by the granitic rocks of the Upper Cretaceous Elaz1g magmatic suite. The lithological and geochemical data on the rocks of Kömürhan ophiolite indicate that these rocks were derived from crystallization of an enriched mid-ocean ridge basalt (MORB)-type magma. The Kömürhan ophiolite formed in a supra-subduction spreading zone during the Cretaceous; related to this event is the north-dipping subduction of the southern branch of Neo-Tethys ocean, which began spreading in the Late Triassic. The crust was thickened by the development of an island arc and by the thrusting of the Pütürge metamorphic rocks onto this island arc in response to north-south compression during the Late Cretaceous. The magma formed by partial melting of the subducted slab giving rise to granitic rocks that cut the upper parts of the ophiolite. The ophiolite and the Elaz1g magmatic suite attained their present position after the Middle Eocene.

Paleozoic accretionary terranes in Northern Tianslian, NW China

During the Paleozoic, the Northern Tianshan region of China in Central Asia consists of 7 allochthonous terranes which were situated in the ancient Sino-Mongolian Ocean as volcanic arcs and splitted continental fragments. The tectonic framework was similar to that of Southwest Pacific today. In the Late Paleozoic, these terranes started mutual amalgamation to cause strong thrusting. At the end of Carboniferous, the Sino-Mongolian ocean including several inter-terrane small sea basins closed and these terranes accreted on the margins of the Siberian and Tarim continents. The 6 ophiolitic zones among the terranes recorded this collision event.

Platinum-group element distribution in chromite ores from ophiolite complexes, western Turkey

Selected chromite mines in western Turkey (Fig. 1) were the focus for a study of platinum-group element (PGE) and Au concentrations in chromite ores and host rocks. Forty-six underground chromite mines were sampled in ten districts. The chromite is hosted in peridotite, dunite, serpentinized harzburgite and lherzolite rocks of late Jurassic to late Cretaceous age. A total of 113 ore and rock samples were collected and examined. High PGE concentrations are a feature of chromite-rich rocks worldwide in ultramafic complexes of Alpine type.1,6,8,23,29 Knowledge of the geology and geochemistry of these deposits is, therefore, critical to understanding of the mechanism of PGE mineralization and its genesis. The study area contains numerous chromite deposits in a complex, ENE-trending suture zone between the I . zmir–Ankara ophiolite zone in the north and the Taurides platform in the south. More than 200 chromite occurrences, prospects and mines are scattered throughout the peridotites, dunites and serpentinized lherzholite–harzburgites.10

Bela ophiolite zone of southern Pakistan: Tectonic setting and associated mineral deposits

Northwest of Karachi, the Bela ophiolite zone is the southernmost exposure in a string of three major ophiolitic occurrences in the Axial fold-thrust belt, which extends generally south and southwest from northern Pakistan to the Arabian Sea. Allochthonous and para-allochthonous Jurassic rock units are tectonically associated with this ophiolite zone. These units contain massive deposits of lead-zinc sulfides and barite, whereas the ophiolite zone hosts chromite, manganese, massive copper sulfide, and related mineral deposits. This study describes the regional tectonic setting and relationship to local geological features of the mineral deposits using gravity and aeromagnetic data. These geophysical studies provide a basis for interpreting the emplacement models and deformation history of the Bela ophiolite zone and associated Jurassic rocks. These models and their supporting geologic data suggest that hydrothermal solutions containing barite and massive sulfides rich in zinc and lead rose on the sea floor through crustal faults developed in areas of divergent tectonism and deposited these minerals in the Jurassic sedimentary sequence on the western margin of Indo-Pakistan subcontinental plate. The Cretaceous Neotethyan spreading center, however, gave rise to metallic mineralizations. The Tertiary convergence between the rifted western margin of the Indian subcontinent and the Neotethyan oceanic plate (a segment of the Arabian oceanic plate) obducted the Bela ophiolite zone (consisting of, e.g., chromite, manganese, massive copper sulfide) along the overriding edge of the subcontinental plate, which contained massive sulfides rich in zinc-lead and barite. These convergent phases through Paleocene to Pleistocene time intensely deformed the divergent products and created a geologically complex region.

Bela ophiolite zone of southern Pakistan: Tectonic setting and associated mineral deposits

Bela ophiolite zone of southern Pakistan: Tectonic setting and associated mineral deposits

Geodynamic cycles of subcontinental lithosphere in the Central Alps and the Arami enigma

Major masses of metamorphosed ultramafic rocks in the Central Alps, Western Alps and Liguria are former subcontinental lithospheric mantle. It occurs in two, tectonically distinct ophiolitic zones which paleogeographically correspond to the Jurassic, South Penninic, Piemontese ocean belt and to the more external, Cretaceous, North Penninic, Valais ocean belt, respectively. In both belts, the geodynamic cycle of pieces of subcontinental lithospheric mantle started with its exhumation during continental rifting and resulted in the exposure of denuded mantle in the Tethyan ocean basins. With the onset of oceanic closure, these mantle rocks were subducted and, after continental collision, integrated in the Alpine mountain chain and again exhumed. Combined evidence from two key areas of the Central Alps is presented. At Val Malenco, a stable continental crust-mantle transition (1.0–0.9 GPa; 800–600°C) welded by a 270 Ma gabbro intrusion existed into the Triassic. During Jurassic rifting, Malenco mantle with attached pieces of lower crust was rapidly exhumed and exposed in the Piemontese ocean basin near its Adriatic margin. There, an ‘Alpine type ophiolite suite’ developed, containing serpentinized ex-subcontinental mantle, rodingitized Permian gabbro, ophicarbonate rocks and MOR basalts. During Cretaceous convergence, the rifted margin of Val Malenco was only moderately subducted (∼450°C, 0.6 GPa) as it remained in a supra-subduction wedge. In the Western Alps and Liguria, rifted margins of the Piemontese belt were subducted to eclogite conditions (∼3 GPa, 650°C), but never beyond the stability of Antigorite. In the North-Penninic Adula-Cima Lunga nappe of the Central Alps, however, a suite analogous to Val Malenco was subducted to much higher metamorphic conditions (∼3 GPa, 830°C) during Eocene collision. Successive regional metamorphic prograde stages are proven by overgrowth textures in mafic rocks up to kyanite eclogite and in ultramafic rocks up to garnet peridotite. The inferred ultradeep garnet lherzolite of Alpe Arami forms part of the prograde Alpine suite of Adula-Cima Lunga. Ilmenite rods in olivine, as at Arami, invoked as ‘proof’ for an ultradeep origin, have been detected in over 10 localities. They have been shown to form from planar, Ti-bearing, (OH)-defects at conditions below 3 GPa. No direct evidence for an ultradeep origin for Alpe Arami has been presented so far.

GRAVITY MODEL FOR BELA OPHIOLITES AT WESTERN MARGIN OF THE INDO-PAKISTAN CONTINENTAL PLATE

The oroclinal axial fold-thrust mountain belt has notable features in the geology of Pakistan. The southern part of this belt is of particular importance because it includes the southern branch of the main Himalayan ophiolitic zone, the Bela ophiolites, and its continuation into the Arabian Sea. A number of geological models and hypotheses have been proposed for explanation of the tectonic setting of the area based on surface geological investigations. A gravity study was carried out to provide a model for the tectonic setting of the investigated area. The results of interactive gravity modeling point to the underthrusting of a narrow segment of the Arabian oceanic plate (Bela-Hingol micro-oceanic plate) under the western rifted margin of the Indo-Pakistan subcontinental plate, characterized by a well developed accretionary wedge, an ophiolite complex and a tectonically eroded green schist unit derived from the over-ridding continental plate.

Petrology of a supra-subduction zone ophiolite (Elaz1g, Turkey)

Petrology of a supra-subduction zone ophiolite (Elaz1g, Turkey)

Geochemical Character and Tectonic Environment of Neotethyan Ophiolitic Fragments and Metabasites in the Central Anatolian Crystalline Complex, Turkey

Abstract The Central Anatolian Crystalline Complex (CACC) or Kırşehir Block is part of the metamorphosed leading edge of the Tauride-Anatolide Carbonate Platform. It contains oceanic remnants derived from the Neotethys Ocean (İzmir-Ankara-Erzincan branch) which separate it from the Sakarya microcontinent. Two tectonic units are distinguished: an amphibolite facies Mesozoic ‘basement’, dominated by platform marbles, over which is thrust a younger fragmented Upper Cretaceous ophiolite sequence. Three metabasite horizons were sampled to reconstruct the development of the oceanic components: (1) fragmented Upper Cretaceous (90-85 Ma) stratiform ophiolitic members comprising gabbros, sheeted dykes, basalt lavas and pelagic sediments thrust over all other units; (2) a tectonised admixture of basite, ultramafic and felsic blocks in an ophiolitic mélange (Upper Cretaceous matrix) thrust over the basement metamorphic rocks; and (3) amphibolites concordant with ‘basement’ marbles and minor pelagics of the largely (?)Triassic Kaleboynu Formation in the lower part of the carbonate platform. Metabasalts and metagabbros from isolated fragments of the stratiform ophiolites form geochemically coherent groups and indicate the influence of a subduction component during their development. It is considered that the suprasubduction zone ophiolites record the association of a tholeiitic arc and an adjacent back-arc basin with more mid-ocean ridge basalt (MORB)-like compositions. Metabasite blocks within the tectonised ophiolitic mélange slice are MORB like, together with minor ocean island basalt (OIB) and island arc basalts, and may be tectonically related to ophiolitic units within the accretionary wedge of the Ankara Mélange. Concordant amphibolites of the Kaleboynu Formation are largely OIB types and reflect an early ensialic rifting stage of the Tauride-Anatolide Carbonate Platform. Small ocean basins also developed at this time, as recorded by the presence of MORB and associated pelagics. The CACC block, together with parts of the Ankara Mélange, are considered to represent oceanic lithosphere (comprising both early spreading centre and latter subduction-influenced crust) and continental carbonate platform that were subsequently ejected from an accretionary-subduction complex on collision with the Sakarya microcontinent.

Geochemistry of the ophiolite and island-Arc volcanic rocks in the Mianxian-Lueyang suture zone, southern Qinling and their tectonic significance

Ultrabasic rocks in the Mianxian-Lueyang ophiolitic melange zone include harzburgite and dunite which exhibit LREE depletion with remarkable positive Eu anomaly. The diabase dike swarm shows LREE enrichment but slightly negative Eu anomaly. Metamorphosed volcanic rocks can be divided into two groups in terms of their REE geochemistry and trace element ratios of Ti/V, Th/Ta, Th/Yb and Ta/Yb. One is the MORB-type basalt with LREE depletion, representing the fragments of oceanic crust and implying an association of the MORB-type ophiolite and an ancient ocean basin between theQinling and Yangtze plates during the Middle Paleozoic-Early Mesozoic era. The other comprises the island-arc volcanic rocks including tholeiitic basalt and a large amount of calc-alkaline intermediate-acid volcanic rock, which could not be the component of the ancient oceanic crust but the result of magmatism at the continental margin. This indicates that the Mianxian-Lueyang limited ocean basin had undergone a whole process of development, evolution and vanishing from Devonian-Cretaceous to Permian. And the Qinling area had become an independent lithospheric microplate, on the southern side of which there were exhibited the tectonic characteristics of active continental margins during the Late Paleozoic-Early Mesozoic. That is to say, the Qinling cannot be simply considered as a result of collision between the Yangtze and North China plates.

Geochemical evidence used to test alternative plate tectonic models for pre-Upper Jurassic (Palaeotethyan) units in the Central Pontides, N Turkey

East–west trending, inferred Palaeotethyan subduction–accretion complexes form much of the pre-Upper Jurassic basement of the Central Pontides. A number of specific tectonic units are present that include variably metamorphosed basic igneous rocks, as dismembered ophiolites, coherent stratigraphical successions, ordered thrust sheets, and blocks in melange. About 200 samples from a c. 200 km long N–S traverse were analysed by a high-precision X-ray fluorescence technique, supplemented by electron microprobe analysis. The basic igneous rocks have not experienced significant chemical mobility after formation and are thus useful for discrimination of tectonic settings of formation using well known binary and ternary plots and mid-ocean ridge basalt (MORB)-normalized ‘spidergrams’. From N to S the main results are that basalts of the Kure Complex were erupted in a subduction-influenced tectonic setting, favouring interpretation as a dismembered ophiolite formed in a marginal basin along the S Eurasian margin. Thick, mainly volcanic, successions of the Cangaldag Complex show a subduction-influenced calc-alkaline composition, above a basement varying from MORB/island arc tholeiite type to high-Mg (boninitic) type, with an inferred origin as an oceanic arc above forearc basement. Meta-basites from the adjacent Bayam Melange indicate a supra-subduction zone origin, possibly as a dismembered forearc ophiolite (possibly related to the Cangaldag). A large overriding thrust sheet of mainly ultramafic rocks, the Elekdag, is interpreted as a supra-subduction zone ophiolite, based on depleted chrome spinel composition (analysed by microprobe). Eclogitic blocks in structurally underlying melange are of mid-ocean ridge (MOR) type. Further south, a northward-dipping, inferred subduction–accretion complex, the Domuzdag–Saraycikdag Complex, includes MOR-type meta-basites in the north, and more ‘enriched’ compositions in the south, of within-plate origin. Lastly, the geochemistry of meta-basites in the south, within the Kargi Complex, suggests a plume-MOR to within-plate type eruptive setting, without continental crustal influence. The geochemical data mainly support a northward rather than southward subduction model for the Palaeotethyan assembly of the Central Pontides, particularly since the Kure ophiolitic basalts in the north exhibit a subduction-influenced chemical signature, in contrast to all the units in the south which lack any identifiable subduction component. Comparisons with published geochemical data from the Karakaya Complex in the SW Pontides reveal similar units, interpreted as accreted MORB lithosphere and oceanic seamounts, but emphasize that the Cangaldag arc is presently the only known Palaeotethyan subduction arc-related unit in Turkey. Copyright © 1999 John Wiley & Sons, Ltd.

Supra‐Subduction Zone Ophiolite Formed in an Extensional Forearc: Trinity Terrane, Klamath Mountains, California

The Paleozoic Trinity terrane is a massif of ultramafic rock and mafic intrusive complexes that forms the basement of eugeoclinal rocks in the eastern Klamath Mountains. The origin of the Trinity terrane has been particularly enigmatic and several mutually exclusive origin models have been proposed: (1) mantle diapir; (2) slice of obducted monogenetic oceanic lithosphere; (3) monogenetic backarc‐basin lithosphere; (4) forearc lithosphere; and (5) volcanic arc basement. We have compiled new and existing field, petrographic, geochronologic, isotopic, and whole‐rock chemical data for the Trinity terrane to evaluate these models and conclude that the Trinity terrane is an supra‐subduction zone ophiolite whose mafic intrusive complexes record subduction‐related magmatism and forearc extension that occurred during the inception of intraoceanic subduction. According to this extensional forearc model, all four terranes in the eastern Klamath Mountains evolved principally during the inception and evolution of a si...

Ophiolitic basement to a forearc basin and implications for continental growth: The Coast Range/Great Valley ophiolite, California

We present a compilation of 18 published models from the length of the Great Valley forearc basin, California, based on seismic reflection, borehole, seismic refraction, gravity, and aeromagnetic data to address long‐standing questions about the nature of the basement to the Great Valley, its origin, its tectonic history, and it's mechanism of incorporation into the North American continental margin. The geophysical models permit a 700‐km‐long, 70‐km‐wide, complete ophiolite sequence beneath the entire Great Valley. In the northern Great Valley, the ophiolite is overlain by ophiolitic breccia, the ophiolite crust is 7–8 km thick, and the mantle section is mostly unserpentinized. Beneath the southern Great Valley, there is no ophiolitic breccia, the crust may be up to 10 – 12 km thick, and the mantle section, if present at all, is serpentinized to such a degree that it cannot be distinguished from Sierran basement or mafic ophiolite members on the basis of velocity or density data. Geochemical, petrological, and paleomagnetic data support suprasubduction zone ophiolite formation at North American paleolatitudes, and geological data and geophysical models are consistent with ophiolite formation by back arc spreading behind an east facing arc. In the north, this was apparently followed by obduction of back arc crust onto older continental basement during the Late Jurassic Nevadan orogeny. In the south, the newly formed intraoceanic arc and back arc apparently collided with the continental margin during the Nevadan orogeny but were not obducted onto it. Instead, the arc and back arc “docked” with the continental margin leaving the arc itself to become the basement to the Great Valley basin. Cretaceous Sierran magmatism then intruded plutons beneath the docked ophiolite and mafic arc. Irrespective of the detailed accretionary history, our cross sections show a rapid pulse of continental growth by ophiolite accretion of more than 500 km³ km−1 in less than 10 Myr.

The Development of Croatian Geoscience as Reflected by the Study of Dinaridic Ophiolites

For approximately 120 years since the beginning of European geology up to Ihe present day. Croatian geoscience has included intensive geological research of the Dinaridc Ophiolite zone. Research results can be grouped into several periods depending on the basic predominant approaches of European and World geology. ( 1) During the flysch period, ophiolites were spatially connected with the flysch formations. (2) During the geosynclinal period ophiolites were classified into the Diabas-Hornstein Formation'. (3) During the transitional period, characterized by the elaboration or the Basic Geological Map, a voluminous data were collected which could not be incorporated in geosynclinal ideas. (4) The last period is charactcrized by modern geodynamic interpretations resulting from global tectonics.

Amphibolite tools of the Portuguese Copper Age (3000–2000 B.C.): A geoarchaeological approach to prehistoric economics and symbolism

One of the factors that may have contributed to the emergence of elites during the Copper Age (3000–2000 B.C.) of lowland Portugal was differential access to amphibolite. Amphibolite is a metamorphic rock found in the uplands of western Iberia and was used to make groundstone tools. In order to determine whether lowland communities had unequal access to amphibolite, source areas in western Iberia were analyzed, and groundstone artifacts from four Copper Age sites were studied. At the settlements, amphibolite was found to be the primary raw material used for groundstone tools. However, the proportion of tools made from amphibolite was significantly different among these sites, suggesting that the inhabitants of the sites did not enjoy equal access to amphibolite. Amphibolite tools were rarely found in burials, probably owing to their high value and/or use as heirlooms. Petrographic and geochemical analyses of amphibolites collected in the field demonstrate that the west Iberian source regions, specifically the Morais-Bragança Ophiolite Zone and the Ossa Morena Metavolcanic Zone, are distinctive. The artifacts analyzed were found to be most similar geochemically to the amphibolites collected in the Ossa Morena Zone, particularly from the areas of Arronches and Montemor-o-Novo. These areas were also significant ritual centers during the Neolithic and Copper Ages, suggesting that amphibolite had important symbolic meaning as well as economic value. © 1997 John Wiley & Sons, Inc.

Rodingite from Ailaoshan ophiolite zone, Yunnan Province, China.

Massive- and vein-type rodingites occurring in serpentinized peridotite of the Jinchan ultramafic body in the Ailaoshan ophiolite zone, S.W. China, have been investigated mineralogically and chemically. Rodingites of the massive-type consist of garnet, chlorite and diopside in rims, and garnet, diopside and subordinary chlorite in cores, while rodingites of the vein-type consist of garnet, chlorite and subordinary diopside. The garnet of the massive rodingites belongs essentially to the grandite-hydrograndite series, but extremely rich in TiO2: (Ca5.92Mg0.07)Σ5.99(Ti1.11Al0.44Fe1.112+Fe1.323+Cr0.02)Σ4.00(SiO4)5.78(O4H4)0.22. The petrography suggests that the rodingites were originally formed by metasomatism between titanium- and iron-rich and aluminum-poor rock and calcium-rich solution, and that they were deformed by the Ailaoshan metamorphism after the formation.

Supra-subduction zone ophiolites of Central Anatolia: geochemical evidence from the Sarikaraman Ophiolite, Aksaray, Turkey

AbstractThe Central Anatolian Crystalline Complex (CACC), situated between the northern and southern oceanic strands of Neotethys, contain a number of little-studied ophiolitic bodies of late Cretaceous age that have a bearing on the Mesozoic development of this region. The pillow lavas and sheeted dykes of the Sarikaraman Ophiolite were originally a comagmatic differentiated series of vesicular, aphyric and olivine-poor, plagioclase—clinopyroxene phyric tholeiites, but now exhibit greenschist facies assemblages. A set of late dolerite dykes cross-cutting the whole volcanic sequence are more chemically evolved and were probably derived from a different source. Relative to N-MORB the lavas and dykes are enriched in some LIL elements (K, Rb, Cs, U, Th and Sr) and depleted in HFS elements (Nb, Ta, Hf, Zr, Ti and Y) and light REE. In terms of immobile elements the ophiolitic basalts have the broad chemical characteristics of island are tholeiites that were formed in a supra-subduction zone setting, whereas the late dykes are more akin to N-MORB. In this respect the Sarikaraman Ophiolite is similar to other ophiolites found in the eastern Mediterranean region and emphasizes the preservation of this particular environment in the CACC. If all the Central Anatolian Ophiolites (of which the Sarikaraman Ophiolite is one example) were derived via southward thrusting from the Vardar-Izmir-Ankara-Erzincan Ocean branch to the north, age relationships suggest that this segment of ocean crust was relatively short-lived before obduction onto the CACC.