kinematic reconstructions and magmatic evolution illuminating crustal and mantle dynamics of the eastern mediterranean region since the late cretaceous the relationship between subduction dynamics and crustal deformation in the mediterranean region has been recently studied using three dimensional 3d numerical models such models require however a detailed information concerning the past geological evolution we use stratigraphic petrologic metamorphic structural paleomagnetic and magmatic data to build new kinematic reconstructions of the eastern mediterranean region since the late cretaceous using the principle of non rigid domains the motions of the 56 deforming domains defined in this work are calculated based on published paleomagnetic rotations the directions and amounts of displacement on crustal scale shear zones and the burial and exhumation histories of the main metamorphic units extracted from these reconstructions paleotectonic maps and lithospheric scale cross sections illustrate that the present day subduction zone has been continuously retreating southward since the late cretaceous and has accreted several small continental domains in the process we find evidence for two back arc related extensional events 1 slow extension along the balkans and the pontides in the late cretaceous while the trench was long and linear and 2 faster extension in the rhodope aegean west anatolian region since the eocene oligocene rapid rotation of the hellenides between 15 and 8 ma probably indicates a slab tearing event below western anatolia that could have further accelerated this extensional kinematics spatial distribution and the geochemical signature of magmatic centers integrated in these reconstructions allow us to trace mantle related processes revealing the deep dynamics that controls both the magma genesis and the crustal deformation

tectono stratigraphy of the cankiri basin late cretaceous to early miocene evolution of the neotethyan suture zone in turkey the cankoro basin straddles the izmir ankara erzincan suture zone which demar cates the former position of the northern branch of the neotethys it includes more than 3 km of pre middle miocene in fill related to late cretaceous to pre middle miocene evolution of the region the basin has developed on the upper cretaceous subduction complex and arc related basins of the neotethys ocean the basin fill includes an upper cretaceous forearc sequence over lain by paleocene with a local unconformity the upper cretaceous configuration of the cankoro basin is interpreted as a part of a forearc basin the paleocene and younger history is interpreted as a foreland sequence dominated by progressively southwards migrated depocenters in front of southward migrating thrust faults upon which a series of piggy back basins were developed ter mination of the forearc setting and beginning of foreland basin conditions indicates complete sub duction of the neotethyan oceanic crust and onset of collision between the pontides laurasia and the taurides gondwana in the paleocene thrusting and related sedimentation continued until the aquitanian early miocene

new results and a palaeomagnetic overview of the pontides in northern turkey summary palaeomagnetic results are reported from 16 sites within volcanic and volcano sedimentary rocks of cretaceous and eocene age from the central pontides in northern turkey the sampled area is bounded by the north anatolian fault naf to the south and the black sea to the north the palaeomagnetic data collected demonstrate the presence of both non rotated and anticlockwise rotated regions i declination directions including lower upper cretaceous and eocene sites do not indicate any significant rotations north of where the naf exhibits an arcuate shape ii 20 anticlockwise rotation was observed in the sinop peninsula the northernmost extremity of the central pontides iii in the west of the central pontides two sites with normal and reversed antipodal directions indicate a 20 anticlockwise rotation and iv another region lies to the east of the study area and shows a rotation in an anticlockwise sense of about 5 30 the upper cretaceous and eocene directions reported in this paper and other palaeomagnetic studies show that there is not much difference between the inclination values of the upper cretaceous i 40 1 95 7 2 and the eocene sites i 39 6 95 8 1 furthermore the values of the inclination available from both sedimentary and volcanic upper jurassic lower cretaceous formations are shallower than the upper cretaceous ones this suggests that the entire pontides have undergone a northward drift of over 2000 km since the upper jurassic

volatile induced magma differentiation in the plumbing system of mt etna volcano italy evidence from glass in tephra of the 2001 eruption mount etna volcano was shaken during the summer 2001 by one of the most singular eruptive episodes of the last centuries for about 3 weeks several eruptive fractures developed emitting lava flows and tephra that significantly modified the landscape of the southern flank of the volcano this event stimulated the attention of the scientific community especially for the simultaneous emission of petrologically distinct magmas recognized as coming from different segments of the plumbing system a stratigraphically controlled sampling of tephra layers was performed at the most active vents of the eruption in particular at the 2 100 m cal and at the 2 550 m lag scoria cones detailed scanning electron microscope and energy dispersive x ray spectrometer sem eds analyses performed on glasses found in tephra and comparison with lava whole rock compositions indicate an anomalous increase in ti fe p and particularly of k and cl in the upper layers of the lag sequence mass balance and thermodynamic calculations have shown that this enrichment cannot be accounted for by classical differentiation processes such as crystal fractionation and magma mixing the analysis of petrological features of the magmas involved in the event integrated with the volcanological evolution has evidenced the role played by volatiles in controlling the magmatic evolution within the crustal portion of the plumbing system volatiles constituted of h2o co2 and cl complexes originated from a deeply seated magma body dbm their upward migration occurred through a fracture network possibly developed by the seismic swarms during the period preceding the event in the upper portion of the plumbing system a shallower residing magma body abt had chemical and physical conditions to receive migrating volatiles which hence dissolved the mobilized elements producing the observed selective enrichment this volatile induced differentiation involved exclusively the lowest erupted portion of the abt magma due to the low velocity of volatiles diffusion within a crystallizing magma body and or to the short time between volatiles migration and the onset of the eruption furthermore the increased amount of volatiles in this level of the chamber strongly affected the eruptive behavior in fact the emission of these products at the lag vent towards the end of the eruption modified the eruptive style from classical strombolian to strongly explosive

reductive diagenesis magnetite dissolution greigite growth and paleomagnetic smoothing in marine sediments a new view abstract in many anoxic sedimentary environments the onset of sulfate reduction and pyritization of detrital iron bearing minerals leads to a precipitous decline in magnetic mineral concentration during early diagenesis the usefulness of the surviving paleomagnetic record in such environments is usually argued to depend on how much of the primary detrital magnetic assemblage survives diagenetic dissolution detailed rock magnetic and electron microscope analyses of rapidly deposited 7 cm kyr latest pleistocene holocene sediments from the continental margins of oman 22 22 4 n 60 08 0 e and northern california 38 24 8 n 123 58 2 w demonstrate that pyritization during early diagenesis also leads to the progressive down core growth of the ferrimagnetic iron sulfide greigite greigite growth begins with nucleation of large concentrations of superparamagnetic sp nanoparticles at the inferred position of the sulfate methane transition which can explain the apparently paradoxical suggestion that diagenetically reduced sediments contain enhanced concentrations of sp particles looping of hysteresis parameters on a day plot records the dissolution of single domain sd titano magnetite and the formation of sp greigite which then slowly and progressively grows through its sd blocking volume and acquires a stable paleomagnetic signal this looping trend is also evident in data from several published records oregon margin korea strait japan sea niger fan argentine margin and the ontong java plateau indicating that these processes may be widespread in reducing environments our observations have profound implications for paleomagnetic records from sulfate reducing environments the paleomagnetic signal recorded by greigite is offset from the age of the surrounding sediments by 10 s of kyr and ongoing growth of greigite at depth results in smoothing of the recorded signal over intervals of 10 s to 100 s of kyr we therefore expect the presence of greigite to compromise paleomagnetic records in a wide range of settings that have undergone reductive diagenesis

volcanism and mantle crust evolution the etna case abstract mount etna is located in a particular region of convergence of african and eurasian plates where intense post collisional tectonics caused considerable uplift however we present arguments supporting the hypothesis that volcanism and associated seismic activity would result from a local mantle uprise leading to a horst probably linked to a deep rooted hot spot it ensued deformation and fracturing of the overlying crust with emission of aphyric tholeiitic basalts directly from their mantle source and subsequent development of a deep reservoir or complex of intrusions at the top of a mantle diapir near 30 km depth this is advocated by the appearance of porphyritic alkaline lavas whose mineral equilibria and differentiation processes are consistent with an 8 10 kbar pressure and by the development of central volcanoes the horst itself appears to have begun in the sw sector of the present volcanic area its uplift was greater westward as seen from the trend of the terraces along the simeto river and became later obvious toward the se these differential movements produced fractures and faults which are to day evident in the southern area of mt etna the growth of the horst then proceeded in a ne direction following the regional tectonic lines and with a greater intensity along the side facing se crossed by the regional nnw sse line aeolian maltese escarpment the seismicity and ground deformation registered over the last twenty years support the proposed model earthquakes are unfrequent in the lower southern and western areas of the volcano whereas they are numerous and stronger to the north east in the summit area above 1600 m a s l and in the eastern sector along the nw se faults and fractures finally a digital elevation model recently published reveals the existence of two tectonic domains the first one is associated with the horst and contains prevalently ne sw oriented faults whereas the second is mainly linked to regional tectonics with nnw sse and nw se faults and fractures

evolution of the triassic continental margin northwest anatolia abstract the northwest anatolian basement consists of two distinctly different metamorphic assemblages which were juxtaposed prior to the deposition of liassic cover sediments these include the lower and the upper associations the lower association is mainly represented by triassic metavolcanic and associated metasedimentary units together with a slice of ophiolite the upper association rests on the lower association with a low angle thrust fault and is composed of paleozoic or older schists gneisses and phyllites a transgressive succession begins above the basement with permo carboniferous neritic limestones these platform type carbonates were disrupted by rifting during the early triassic at the initial phase of rifting coarse clastics and associated rift type lavas were formed the rift then evolved into an ocean basin which closed at the end of the triassic the continental margin of the triassic basin underwent regional metamorphism initially high t low p it was followed later by a high p low t metamorphic phase during the metamorphism the continental margin units were multiply deformed by north directed compressive stress later on unmetamorphosed triassic successions of the continental margin were thrust northward onto the metamorphosed part of the same continental margin thus the triassic assemblages of northwest anatolia collectively display the dynamics and various structural affects of the deformation recorded in the continental margin and adjacent oceanic unit

persistently low asian paleolatitudes implications for the india asia collision history 1 paleomagnetism provides independent paleolatitude constraints on the india asia convergence however implied cenozoic latitudinal convergence within asia thousands of km largely exceeds geologic estimates of tectonic shortening hundreds of km this discrepancy may result from a notoriously low bias in paleomagnetically determined cenozoic paleolatitudes in asia we provide here new paleomagnetic data from cenozoic mongolian volcanic rocks and from chinese paleogene sediments corrected from the depositional bias of inclination shallowing these results combined with similar asian data sets confirm that paleolatitudes are still 5 10 lower than predicted by the paleomagnetic apparent polar wander path apwp for asia between 50 and 20 ma inclination shallowing being excluded from the selected data sets we investigate the likeliness of other proposed mechanisms for this discrepancy 1 more southerly positions of asia than expected by the apwp due to apwp inaccuracies rather than eurasian non rigidity or 2 non dipolar geomagnetic field contributions fully explaining this discrepancy by only one of these mechanisms would imply either unrealistically large 10 apwp inaccuracies or unrealistically large octupolar field contributions up to 16 a combination of these mechanisms is found more likely to have produced the observed latitudinal discrepancy but their respective contributions cannot be quantified given the still relatively low amount and poor quality of cenozoic paleomagnetic data from stable cratons of asia india and europe by allowing for reasonable time dependant non dipolar contributions and a slight 5 apwp bias the latitudinal discrepancy can be resolved and the excessive amounts of intra asian shortening decrease to values in line with tectonic shortening from structural studies

putative greigite magnetofossils from the pliocene epoch greigite crystals of bacterial origin are widespread in modern sedimentary environments but their occurrence in the fossil record remains controversial grains from romanian pliocene aged sediments have now been identified as bacterial in origin tentatively placing them among the oldest known greigite magnetofossils

dating the exhumation of a metamorphic dome geological evidence for pre eocene unroofing of the nigde massif central anatolia turkey the timing of exhumation of metamorphic rocks and granitoids of the nigde metamorphic dome at the southern tip of the central anatolian crystalline complex is a matter of debate according to some authors the metamorphic rocks are overlain nonconformably by a sedimentary sequence of late maastrichtian to late palaeocene age in contrast other authors recently argued that the nigde dome represents an extensional core complex of oligocene early miocene age finally unroofed during late miocene times on the one hand the results of our study contradict the latter interpretation a sedimentary sequence of earliest eocene to early middle eocene age nonconformably overlies the high grade rocks of the nigde dome on its southeastern flank pebbles from the metamorphic rocks are ubiquitous in the conglomerates of this sequence as a result the nigde metamorphic rocks must have reached the surface before eocene times or at the very beginning of the eocene at the latest the uckapili granite whose crystallization age has been inferred to be early miocene has intruded the metamorphic complex during exhumation the granite is also found as pebbles within the conglomerates of the eocene sedimentary sequence and thus is actually older than the eocene apatite fission track dates of 12 11 ma across the nigde dome do not indicate that the metamorphic rocks were still on their way to the surface at that time instead they must reflect a later event which is most probably heating during late neogene magmatism lastly there is no ductile then brittle extensional detachment in the two areas where it has been invoked that is on the western and southern flanks of the dome an extensional detachment nevertheless exists at the top of the nigde dome best documented in its northern part where the detachment fault superposes a superficial unit made up of massive ophiolitic rocks onto the high grade metamorphic sequence field evidence indicates that this detachment developed before eocene times on the other hand our observations do not confirm the nonconformity of the sedimentary sequence dated as late maastrichtian late palaeocene onto the nigde high grade rocks field relations show either a tectonic contact between the two or the direct nonconformity of the eocene sediments onto the metamorphic rocks the lack of coarse clasts originating from the nigde high grade rocks within the maastrichtian palaeocene sequence further suggests that the metamorphic dome did not reach the surface before late palaeocene times these results compare well with available data from the northwestern part of the central anatolian crystalline complex suggesting that exhumation has been broadly synchronous on the scale of the massif as a result of an episode of high magnitude extension that affected the region in campanian to palaeocene times

cenozoic evolution of the eastern black sea a test of depth dependent stretching models abstract subsidence analysis of the eastern black sea basin suggests that the stratigraphy of this deep extensional basin can be explained by a predominantly pure shear stretching history a strain rate inversion method that assumes pure shear extension obtains good fits between observed and predicted stratigraphy a relatively pure shear strain distribution is also obtained when a strain rate inversion algorithm is applied that allows extension to vary with depth without assuming its existence or form the timing of opening of the eastern black sea which occupied a back arc position during the closure of the tethys ocean has also been a subject of intense debate competing theories called for basin opening during the jurassic cretaceous or paleocene eocene our work suggests that extension likely continued into the early cenozoic in agreement with stratigraphic relationships onshore and with estimates for the timing of arc magmatism further basin deepening also appears to have occurred in the last 20 myr this anomalous subsidence event is focused in the northern part of the basin and reaches its peak at 15 10 ma we suggest that this comparatively localized shortening is associated with the northward movement of the arabian plate we also explore the effects of paleowater depth and elastic thickness on the results these parameters are controversial particularly for deep water basins and margins but their estimation is a necessary step in any analysis of the tectonic subsidence record stored in stratigraphy

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

magnetic fabric of clay sediments from the external northern apennines italy abstract we report on the anisotropy of magnetic susceptibility ams analyses of fine grained sediments deposited during the messinian in foredeep basins at the front of the northern apenninic chain the data refer to 32 sampling sites mostly distributed in the fine grained intervals of the laga and colombacci formations extending along the belt for a total length of about 300 km rock magnetism analyses indicate that the magnetic susceptibility and its anisotropy are in most cases dominated by the paramagnetic minerals of the clay matrix in order to delineate the contribution of the ferrimagnetic fraction to the overall susceptibility fabric the anisotropy of the anhysteretic remanent magnetisation was investigated at some representative sites the magnetic fabric of the studied sediments mostly reflects the effects of compaction showing a predominant magnetic foliation parallel to the bedding plane at all the sites a well distinct magnetic lineation was also found which is parallel to the fold axes and thrust fronts both at local and regional scales this feature is maintained in sequences that differ for sedimentological character and age implying that the magnetic lineation was produced by a mild tectonic overprint of the primary sedimentary compactional fabric the relationship between the magnetic lineation trends and the vertical axis rotations detected by speranza et al speranza f sagnotti l mattei m 1997 j geophys res 102 3153 3166 indicates that the magnetic lineation formed during the compressive phases of the messinian early pliocene when the apenninic front was almost rectilinear and oriented n320

a chemostratigraphic investigation of the prehistoric vavalaci lava sequence on mount etna simulating borehole drilling scientific drilling of volcanic successions has been suggested as a way of establishing stratigraphic sequences of unexposed lava flows on large complex volcanoes with the aim of in depth study of magmatic processes and source geochemistry of otherwise inaccessible lava sequences to simulate the core drilling of such sequences lava flows from the prehistoric vavalaci centre exposed in the south wall of the valle del bove mount etna sicily were sampled in four stratigraphic sections the fresh generally strongly porphyritic na alkaline trachybasalts and trachyandesites show diverging sub parallel trends of high and low alkali concentrations in total alkali versus silica tas diagrams whilst variations of other major and trace elements reveal two further distinct chemical groups enriched in k ree and ti which follow separate fractionation paths a set of control samples was used to establish geochemical variations within a single lava flow primitive mantle normalised incompatible element patterns demonstrate that the lavas have highly enriched oib signatures with a clear division in lree ba th nb and zr concentrations between the four different chemical groups comparison of data for the vavalaci lavas with the compositions of other prehistoric historic and recent eruptions of mt etna indicates a temporal trend towards more basic magma compositions the chemostratigraphy of the lavas was statistically analysed to give correlations between flows from different sections whilst a good number of geologically meaningful correlations were revealed we can demonstrate that only one set of lavas was actually sampled in all four sections whilst a number of unique lavas remain uncorrelated thus no individual section or simulated borehole core provided samples of the complete lava flow sequence without significant gaps in the stratigraphy the trends in lava compositions are also defined in the stratigraphy showing their evolution from low to high alkali lavas through the series which may be related to temporal decrease in degree of partial melting of the mantle rather than through simple fractionation processes or mixing of magmas

magnetic fabric of pleistocene clays from the tyrrhenian arc a magnetic lineation induced in the final stage of the middle pleistocene compressive event we present the results of an analysis of the anisotropy of magnetic susceptibility ams in early pleistocene clay sediments from the southern apennines and its foreland apulia measurements were performed on samples from different tectonic units the apulian unit the bradano unit and the apenninic belt the ams is characterized by a dominant magnetic foliation parallel to the bedding plane in all cases pointing to a primary sedimentary magnetic fabric no lineation is found in the clays from the apulian unit whereas the inner part of the bradano unit and the apenninic belt show a clear nw se trending magnetic lineation which is perpendicular to the main compressive stresses known for this area there is a very consistent wnw ese trending magnetic lineation for the clays from the southern apennines and the calabrian block to the south correction of this lineation with the established tectonic rotations shows that the lineation is clearly of postrotational origin and reflects the latest stages of deformation the lineation is linked to middle and late pleistocene tectonics its alignment occurred in the final stages of the compressive event affecting the tyrrhenian arc system for the sant arcangelo basin in the southern apennines anomalous trends of magnetic lineation compressive stress were established

assessing the link between mantle source and sub volcanic plumbing in the petrology of basalts from the 2001 and 2002 2003 eruptions of mount etna sicily evidence from geochemical and helium isotope data abstract the 2001 and 2002 2003 flank eruptions of mt etna consisted of near continuous explosive activity and sporadic lava flows previous studies have suggested that distinct magmas were simultaneously tapped by fissures in different parts of the volcano indicating a complex plumbing system from textural and chemical data it has been suggested that eccentric eruptions on the south flank were fed by a deep seated reservoir that is not related to the central conduit in contrast materials erupted above 2600 m and from the northeast flank represent partially degassed more fractionated magma typical of that residing within the central vents a concern is that etna has entered a new phase of activity with magma supply from a deep reservoir that is capable of generating recurrent flank eruptions posing significant hazard to populated areas and air travel we have investigated materials that erupted from different vents during both the 2001 and 2002 3 eruptive episodes by means of petrology whole rock chemistry and helium isotopic methods here we show from trace element chemistry and the 3he 4he isotope record of melt inclusions in olivine that the mantle source for both magma batches is identical furthermore this magmatic source has not changed over the past 0 5 ma as such our data support the premise that the petrological variability exhibited by products that erupted from different parts of the volcano reflects storage fractionation and degassing at different levels within the crust

palaeomagnetism and k ar dating of cretaceous basalts from mongolia we report a combined geochronology and palaeomagnetic study of cretaceous igneous rocks from shovon 44 4 n 103 8 e and arts bogd 44 3 n 102 2 e localities in the gobi desert south mongolia k ar dating based on seven rock samples with two independent measurements for each sample allows us to propose an age of 94 7 1 3 ma for shovon locality and a 98 2 1 4 to 118 3 1 7 ma age range for arts bogd stepwise thermal and af demagnetization generally isolated a high temperature component htc of magnetization for both shovon and arts bogds basalts eventually following a low temperature component ltc in some samples the htc directions display normal polarity consistent with the cretaceous long normal superchron rock magnetic analysis identifies fine grained pseudo single domain psd magnetite and titanomagnetite as primary carriers of the remanence mean htc palaeomagnetic direction is dm 8 2 im 63 7 n 18 flows k 41 1 95 5 5 for shovon and dm 12 1 im 66 4 n 27 flows k 53 0 95 3 9 for arts bogd because of their similar ages we combine data from shovon and data previously obtained from khurmen uul 92 0 4 0 ma recomputed in geographic coordinates and not in tilt corrected ones as in our previous interpretation at the shovon locality the combined final average palaeomagnetic direction for shovon khurmen uul is dm 7 4 im 62 7 n 23 flows k 41 4 95 4 8 the corresponding palaeopoles computed from these htc lie at 84 7 n 195 0 e dp dm 5 8 7 5 for shovon khurmen uul average age 93 4 2 6 ma and 80 5 n 159 0 e dp dm 5 2 6 3 for arts bogd average age 104 6 6 6 ma these poles are consistent with those from the european apparent polar wander path apwp at 90 100 and 110 ma and other published pole from the mongol okhotsk suture zone amuria and north china blocks this confirms the lack of a discernable latitudinal motion between amuria and siberia since their final accretion by the late jurassic early cretaceous and reinforces the idea that europe apwp can be used as a reference for siberia by the mid cretaceous we finally propose a mid cretaceous mean palaeomagnetic pole for the siberia amuria north china block assemblage which lies at 86 4 n 191 1 e n 10 k 74 9 a95 5 8

activity of mount etna preceding the february 1999 fissure eruption inferred mechanism from seismological and geochemical data abstract the february 1999 eruption of mt etna took place through a fissure on the sse flank of the cone of the summit se crater this event was preceded by continuous activity since 1995 sometimes accompanied by violent outbursts from one or more of the three other summit craters ne crater voragine or chasm and bocca nuova and finally by a series of 20 short lived eruptions from the se crater between september 1998 and january 1999 these phenomena could be accounted for by invoking gradual invasion of a shallow small reservoir by more primitive basic and gas rich magma coming from depth the shallow chamber is more likely to be a plexus of dikes which had developed during the previous years 1995 1997 following variations of the local stress field owing to enhanced magma generation and accumulation at the top of the mantle magma injection and mixing is evidenced through geochemistry whereas the state of stress of the volcanic pile and underlying crust is determined using earthquake distributions and focal mechanisms the behaviour of the seismic tremor amplitude appears to be a good indicator of the state of unrest of the volcano although not always directly linked to the relative energy of degassing phenomena

the contemporaneous emission of low k and high k trachybasalts and the role of the ne rift during the 2002 eruptive event mt etna italy mount etna volcano erupted almost simultaneously on its northeastern and southern flanks between october 27 and november 3 2002 the eruption on the northeastern flank lasted for 8 days while on the southern flank it continued for 3 months the northeastern flank eruption was characterized by the opening of a long eruptive fracture system between 2 900 and 1 900 m a s l a detailed survey indicates that the fractures direction shifted during the opening from n10w at the ne crater 2 900 m to n45e at its lowest portion 1 900 m and that distinct magma groups were erupted at distinct fracture segments based on their petrological features three distinct groups of rocks have been identified the first group high potassium porphyritic hkp is made up of porphyritic lavas with a porphyritic index p i of 20 32 and k2o content higher than 2 wt the second group is represented by lavas and tephra with low modal phenocryst abundance p i 20 named here oligo phyric low phyric and k2o content higher than 2 wt hko high potassium oligophyric the third group low potassium oligophyric lko consists of tephra with oligophyric texture p i 20 but k2o content 2 wt k rich magmas hkp and hko are similar to the magma erupted on the southern flank and geochemical variations within these groups can be accounted for by a variable degree of fractionation from a single parent magma the k poor magma lko erupted only in the upper segment of the fracture cannot be placed on the same liquid line of descent of the hk groups and it is similar to the magmas that fed the activity of etna volcano prior to the eruption of 1971 this is the first time since then that a magma of this composition has been documented at mt etna thus providing a strong indication for the existence of distinct batches of magma whose rise and differentiation are independent from the main conduit system the evolution of this eruption provides evidence that the ne rift plays a very active role in the activity of mt etna volcano and that its extensional tectonics allows the intrusion and residence of magma bodies at various depths which can therefore differentiate independently from the main open conduit system

magnetic properties of sedimentary greigite fe3s4 new data are presented here that document the previously poorly known magnetic characteristics of sedimentary greigite fe3s4 several diagnostic magnetic properties can be used in conjunction to rapidly screen sediments to detect the presence of greigite such discriminants are necessary because greigite displays a similar or higher range of coercivities compared to most ferrimagnetic minerals and the commonly used method of alternating field demagnetization cannot be used to distinguish between palaeomagnetic remanence components due to greigite and other ferrimagnetic minerals sedimentary greigite has high ratios of the saturation isothermal remanent magnetization to magnetic susceptibility mrs which are accompanied by hysteresis ratios of mrsms 0 5 and bcr bc 1 5 ms is the saturation magnetization bc is the coercive force and bcr is the coercivity of remanence greigite has no low temperature phase transition whereas the ferrimagnetic iron sulphide pyrrhotite undergoes a major phase transition at about 34 k and unoxidized magnetite displays the verwey transition at 118 k low temperature measurements may therefore prove valuable in distinguishing between magnetite pyrrhotite and greigite although the absence of a low temperature transition cannot be taken as definitive evidence for the presence of greigite greigite also displays characteristic high temperature behaviour with a major drop in magnetization between 270 and 350 c determination of the mrs ratio is an excellent means of rapidly screening sediments to identify stratigraphic intervals that may contain greigite subsequent low and high temperature analyses can then provide unambiguous identification of greigite and enable the evaluation of the presence of other magnetic minerals

late cretaceous to paleocene oroclinal bending in the central pontides turkey 1 the turkish pontide fold and thrust belt formed since the paleozoic and is an important element in the africa eurasia convergence and the resulting closure of the neo tethys ocean it has a peculiar arc shaped geometry in its central part along the black sea coast which may have resulted from oroclinal bending we have determined the vertical axis rotation history of this area using paleomagnetism on cretaceous to eocene rocks from 47 sites and critically analyzed previously published data we applied the same reliability criteria to all data our results show that late cretaceous sites have clockwise and counterclockwise rotations perpendicular to the structural trend in the central pontides in the eastern pontides they show only local rotations paleocene to eocene rocks in the central and eastern pontides show no rotation we conclude that the central pontide northward arc shaped geometry results from oroclinal bending in latest cretaceous to earliest paleocene times the timing and scale of geological processes that occurred in the region make it likely that orocline formation resulted from neo tethys closure between the pontides and the metamorphic promontory of the anatolide tauride block earlier studies on the southerly located cankiri basin reveal that clockwise and counterclockwise rotations occurred in eocene oligocene times this implies that the entire region underwent continuous deformation from late cretaceous to eocene caused by convergence of the pontides and the anatolide tauride block with a southward moving deformation front deformation was first localized in the northern part of the central pontides until the paleocene resulting in oroclinal bending and from at least eocene times it shifted toward the cankiri basin region

paleomagnetic reconstruction of the cenozoic evolution of the eastern mediterranean abstract a total of 113 paleomagnetic sites were sampled along an anatolian s n transect from the arabian platform the hatay region the eastern taurides the kirsehir block the sivas basin and the eastern pontides reliable characteristic remanent paleomagnetic directions were retrieved from 37 of these sites spanning in time from paleocene to miocene in a general way declinations are westerly deviated and inclinations are shallower than the geocentered dipole value at the present latitudes when combined with previously published results these data indicate that a large scale counterclockwise rotation of anatolia of some 25 has occurred since the miocene assuming that the pole of rotation of anatolia with respect to europe has remained constant in time at the location given by macclusky et al j geophys res 105 2000 5695 on the basis of the geodetic data this rotation implies that a large westward displacement 500 km at the average latitude of 40 has taken place assuming that the rotation was initiated by the arabia europe collision about 12 ma ago this corresponds to an average displacement of about 40 mm year together with previous results from the western part of the aegean arc these results indicate that the main trends of the cenozoic evolution of the eastern mediterranean appear to consist of two post early miocene rotations of opposite senses a clockwise rotation of the western part of the aegean tectonophysics 146 1988 183 around a pole situated in northern albania and a counterclockwise rotation around the pole given by mcclusky et al j geophys res 105 2000 5695 comparison with gps data suggest that both rotations are still active today

paleomagnetic results along the bitlis zagros suture zone in se anatolia turkey implications for the activation of the dead sea fault zone abstract the tectonic evolution of se anatolia is associated with the collision between the taurides and the arabian platform in the early cenozoic after the final closure of the southern branch of the neotethys ocean during late cretaceous to early eocene times the ongoing deformation was characterized by northward movement of arabia followed by westward extrusion of anatolia having been displaced along the northern and eastern anatolian transform faults the neotectonic deformation history between the anatolian plate and the arabian platform since the closure of the southern neotethyan oceanic basin from late cretaceous to present has not been studied in detail paleomagnetically therefore we carried out a paleomagnetic study of mesozoic and cenozoic rocks at 34 localities along the bitlis zagros suture zone in se anatolia located in the boundary region between the taurides and the arabian platform and delimited by the dead sea fault paleomagnetic results from the area show clockwise rotations of 35 6 14 1 and 26 7 8 0 with respect to the african plate from upper jurassic lower cretaceous and upper cretaceous limestones respectively the paleomagnetic results indicate also an earlier deformation opening due to the dead sea fault zone dsfz farther north on the tauride block counterclockwise rotation of 34 5 12 5 is recorded by upper cretaceous limestones in the se of the study area on the northern margin of arabia however smaller counterclockwise rotations of 12 3 8 3 and 2 5 10 0 in late cretaceous and 12 7 13 6 in middle eocene rocks show relative tectonic stability middle miocene rocks close to the suture zone show counterclockwise rotation by about 39 4 10 9 while farther away from the suture zone counterclockwise rotations of 21 9 9 9 and 7 5 5 8 are observed paleolatitudinal motion from south to north from the late jurassic to the present is in concordance with the apparent polar wander path of eurasia and africa

the evolution of yarlung tsangpo river constraints from the age and provenance of the gangdese conglomerates southern tibet abstract cenozoic conglomerates are exposed discontinuously along the length of the yarlung tsangpo suture zone on the southern margin of the gangdese arc these conglomerates the gangdese conglomerates herein record a crucial stage in the uplift and erosion histories of the southern tibet after the initial india asia collision in the mt kailas area the gangdese conglomerates strata consist of multiple sedimentary cycles and each cycle is a fining upward sequence that was deposited by alluvial fan braided river and delta systems whereas in the xigaze area the gangdese conglomerates strata comprise a coarsening upward sequence that was deposited by delta braided river and alluvial fan systems based on the detrital and igneous zircon u pb ages the depositional ages of the gangdese conglomerates are late oligocene to early pliocene ca 26 5 ma in the mt kailas area late oligocene to middle miocene ca 26 15 ma in the xigaze area and late oligocene to early miocene ca 26 19 ma in the zedong area paleocurrent measurements and provenance data i e conglomerate clast composition sandstone petrology and detrital zircon age indicate that the initial detritus of the gangdese conglomerates were entirely derived from the north mainly from the gangdese arc sediment resulting from denudation to the south the xigaze forearc basin the yarlung tsangpo suture zone and the northern margin of the indian plate first appeared by the early miocene ca 19 ma and subsequently increased in abundance gradually our new results together with previous data from the xigaze area reveal 3 major stages in the evolution of the yarlung tsangpo river system 1 the southward flowing stage ca 26 19 ma featured southward draining transverse rivers that transported materials from the gangdese arc southward southward paleocurrents in the gangdese conglomerates indicate a northern source 2 the westward flowing stage ca 19 15 ma developed due to the uplift of the suture zone and tethys himalaya to the south northward draining rivers began to develop and lakes resembling a string of beads formed and finally connected together initiating the westward flowing paleo yarlung tsangpo river westward paleoflows were recorded in the gangdese conglomerates 3 the eastward flowing stage ca 15 ma present resulted from differential uplift and denudation of the southern tibet which reversed the direction of the young yarlung tsangpo river by ca 15 ma the deposition of the gangdese conglomerates was controlled by eastward paleoflows at this point the modern eastward flowing yarlung tsangpo river system was established

palaeomagnetic evolution of the cankiri basin central anatolia turkey implications for oroclinal bending due to indentation p alaeomagnetic data in combination with palaeostress data and anisotropy of magnetic susceptibility orientations are utilized to develop a tectonic evolutionary model for the early tertiary part of the omega shaped ca nkiri basin turkey the results reveal clockwise rotations in the northeast and anticlockwise rotations in the west and southeastern corner of the basin the magnetic inclinations indicate a northward drift of the ca nkiri basin and support an indentation model for the kirsehir block it is proposed that the shape of the cankiri basin was the result of indentation of the kirsehir block into the sakarya continent during northwards migration accompanying closure of neotethys it appears that the indentation started prior to eocene and ended before middle miocene times

origin and assembly of the tethyside orogenic collage at the expense of gondwana land abstract the tethysides are a superorogenic complex flanking the eurasian continent to the south and consisting of the cimmerides and alpides products of palaeo and neo tethys respectively we here review their evolution mainly on the basis of new maps showing the distribution of sutures magmatic rocks certain palaeobiogeographically and palaeoclimatologically significant taxa and facies and fragments of pan african 900 450 ma orogenic system forming the basement of many tethyside blocks these are supplemented by palaeomagnetic data reported in the literature a fundamental tenet of this paper is that major sutures which contain ophiolite fragments represent tectonic sections between continental blocks where oceanic crust has been subducted palaeo tethys came into existence largely in late carboniferous time coevally it began to be consumed by both internal and peripheral subduction zones which continued into the permian some of these had been inherited from pre tethyan times in the later permian rifting subparallel with the northern margin of gondwana land began between the zagros and malaysia separating a cimmerian continent from n gondwana land and thus heralding the opening of neo tethys and other smaller oceans that were back arc basins of palaeo tethys this rifting possibly also extended farther west into crete and mainland greece however the north china block yangtze block huanan block the eastern moity of the qangtang block north tibet and annamia all originally pieces of the end proterozoic early palaeozoic gondwana land had already separated from it in pre late carboniferous times possibly during the devonian all of these blocks and the cimmerian continent were characterized by cathaysian floral elements in late palaeozoic time palaeomagnetic and palaeontological data showing the original gondwana land affinity of these continental blocks are supplemented by correlating late proterozoic early palaeozoic pan african sutures orogenic belts and sedimentary basin fragments across tethyside sutures late permian foraminiferal provinces are related to this palaeogeographical interpretation by triassic times most cimmeride subduction zones were already in existence the cimmerian continent accelerated its separation from gondwana land and locally in the late permian began disintegrating internally along the waser rushan pshart banggong co nu jiang mandalay ocean by late triassic time all of the chinese blocks except lhasa and annamia had collided with each other and with laurasia the resulting enormous orogenic collage had a soft cushion between itself and laurasia in the form of the enormous accretionary complex of the songpan ganzi this connection enabled laurasian land vertebrates to reach south east asia by late triassic time in late triassic to middle jurassic times most major cimmeride collisions were completed widespread aridity in central asia occurred in late jurassic time probably in the rain shadow of the newly formed cimmeride mountain wall neo tethyan subduction systems formed along the s margin of the cimmerides or within neo tethyan oceanic lithosphere during the jurassic most if not all were north or east dipping they continued the northerly migration of the tethyside blocks evolution of the tethysides influenced the distribution of marine and terrestrial organisms and affected sea level changes and patterns of atmospheric circulation during much of the mesozoic and cainozoic it is likely to have reflected the surface expression of a persistent trend in the large scale convective circulation in the mantle that continuously transported material northward into the tethyan domain

proterozoic ophiolites and mafic ultramafic complexes marginal to the istanbul block an exotic terrane of avalonian affinity in nw turkey abstract among the proterozoic inliers in the istanbul block the lowest structural levels are exposed in the sunnice massif north of bolu amphibolite facies mafic and subordinate ultramafic rocks of the cele meta ophiolite underlie the greenschist facies ediacaran calc alkaline yellice metavolcanics which are intruded by the 565 576 ma dirgine granitoids hornblende gneisses of the cele meta ophiolite comprise island arc meta tholeiites and transitional to calc alkaline metabasalts which together with minor serpentinite are disposed in a broadly antiformal structure the meta ophiolitic rocks are therefore the oldest ophiolites in nw turkey and are themselves thrust on to a putative pre existing continental margin now represented by the metasedimentary migmatites of the demirci gneisses which may thus be the oldest rocks of the complex the istanbul block is an exotic terrane unlike other western turkish terranes it lacks variscan metamorphism its different provenance indicated by its geological record faunal affinities and inherited mid proterozoic isotopic dates suggests a former link with avalonian basement in england nw europe and the maritime provinces of canada hence together with other terranes now situated further east than the avalonian terranes of nw europe the istanbul block may represent the easternmost extremities of avalonia which were detached during its end ordovician collision with the bruno silesian promontory on the sw margin of baltica subsequent migration of the istanbul block to its present location occurred by eastward displacement by sinistral transpression along the southern margin of baltica to a point east of the dobrogea and south of the scythian platform followed by collision with the sakarya block in the mesozoic and late cretaceous southward displacement with the opening of the black sea basin

cross sectional anatomy and geodynamic evolution of the central pontide orogenic belt northern turkey geophysical data allowed the construction of a 250 km long lithospheric scale balanced cross section of the southern black sea margin espurt et al in lithosphere 6 26 34 2014 in this paper we combine structural field data stratigraphic data and fault kinematics analyses with the 70 km long onshore part of the section to reconstruct the geodynamic evolution of the central pontide orogen these data reveal new aspects of the structural evolution of the pontides since the early cretaceous the central pontides is a doubly vergent orogenic wedge that results from the inversion of normal faults extensional subsidence occurred with an ene trend from aptian to paleocene we infer that the black sea back arc basin also opened during this period which was also the period of subduction of the tethys ocean below the pontides as in the western pontides the cretaceous paleocene subsidence was interrupted from latest albian to coniacian time by uplift and erosion that was probably related to a block collision and accretion in the subduction zone the restoration of the section to its pre shortening state paleocene shows that fault related subsidence locally reached 3600 m within the forearc basin structural inversion occurred from early eocene to mid miocene as a result of collision and indentation of the pontides by the kirsehir continental block to the south with 27 5 km 28 shortening along the section studied the inversion was characterized by nne trending shortening that predated the late neogene dextral escape of anatolia along the north anatolian fault and the modern stress field characterized by nw trending compression within the eocene boyabat basin

the tectonics of the strandja massif late variscan and mid mesozoic deformation and metamorphism in the northern aegean the strandja massif is a mid mesozoic orogenic belt in the balkans build on a late variscan basement of gneisses migmatites and granites new single zircon evaporation ages from the gneisses and granites indicate that the high grade metamorphism and plutonism is early permian in age 271 ma the late variscan basement was unconformably overlain by a continental to shallow marine sequence of early triassic mid jurassic age during the late jurassic early cretaceous oxfordian barremian the lower mesozoic cover and the basement were penetratively deformed and regionally metamorphosed in greenschist facies possibly due to a continental collision an rb sr biotite whole rock age from a metagranite dates the regional metamorphism as late jurassic 155 ma deformation involved north vergent thrust imbrication of the basement and the emplacement of allochthonous deep marine triassic series over the jurassic metasediments the metamorphic rocks of the strandja massif are unconformably overlain by the cenomanian shallow marine sandstones during the senonian the northern half of the strandja massif formed a basement to an intra arc basin and to a magmatic arc generated above the northward subducting tethyan oceanic lithosphere the srednogorie arc closed during the early tertiary through renewed northward thrusting of the strandja massif

2001 flank eruption of the alkali and volatile rich primitive basalt responsible for mount etna s evolution in the last three decades abstract since the early 1970s enhanced eruptive activity of mount etna has been accompanied by selective geochemical changes in erupted lavas among which a gradual increase of alkalis whose origin is still debated here we provide further insight into the origin of this recent evolution based on a detailed study of the chemistry and dissolved volatile content of melt inclusions trapped in olivine crystals of unusual plagioclase poor primitive basalt that was extruded during a highly explosive flank eruption in july august 2001 two types of lava were erupted simultaneously along a n s fracture system trachybasalts from the upper vents 2950 2700 m were simply drained out by fracturing of the central volcanic conduit they are identical to summit crater lavas and contain mg poor olivines fo 70 72 with evolved and volatile poor melt inclusions that represent late stage crystallisation during shallow open conduit degassing in contrast plagioclase poor basalt 80 of total extruded through the lower vents 2550 2100 m derived from lateral dyke intrusion of a more primitive and volatile rich magma across the sedimentary basement this primitive melt is best preserved in rare fo 82 4 80 5 skeletal olivines present in lapilli deposits from the most powerful activities at the 2550 m vent its high dissolved contents of h 2 o 3 4 wt co 2 0 11 to 0 41 wt s 0 32 wt cl 0 16 wt and f 0 094 wt point to its closed system ascent from 400 to 250 mpa 12 to 6 5 km depth b s l however the predominance of euhedral olivine phenocrysts with common reverse zoning cores fo 76 78 and rims fo 78 80 and decrepited inclusions shows that most of the erupted basalt derived from a slightly more evolved crystallizing body of the same magma that was invaded by the uprising primitive melt prior to erupting the few preserved inclusions in these olivines indicate pre eruptive storage of that magma body at about 5 km depth b s l in coherence with seismic data we propose that the 2001 flank eruption resulted from gradual overpressuring of etna s shallow plumbing system due to the influx of volatile rich primitive basalt that may have begun several months in advance we find that this basalt is much richer in alkalis 2 0 wt k 2 o and has higher s cl 2 0 but lower cl k and cl f ratios than all pre 1970s etnean lavas 1 4 wt k 2 o s cl 1 5 as further exemplified by melt inclusions in entrained olivine xenocrysts combining these new observations with previously published data we argue that the 2001 basalt represents a new alkali rich basic end member feeding mt etna only few amount of which had previously been extruded during a 1974 peripheral eruption and more recently during brief paroxysmal summit events over the last three decades this new magma has progressively mixed with and replaced the former k poorer trachybasalts filling the plumbing system leading to extrusion of gradually more primitive and alkali richer lavas its geochemical singularities cannot result from shallow crustal contaminations instead they suggest the involvement of an alkali richer but cl poorer arc type component during recent magma genesis beneath etna

intrusion age of pan african augen gneisses in the southern menderes massif and the age of cooling after alpine ductile extensional deformation

jurassic cretaceous paleomagnetism and paleogeography of the pontides turkey published paleomagnetic data from the pontides indicate anomalously low jurassic and early cretaceous paleolatitudes compatible with the southern neo tethyan african continental margin and significantly different from paleolatitudes predicted for the northern eurasian neo tethyan margin we present a new set of paleomagnetic data from 50 late cretaceous sites mainly from the western pontides and from the eastern pontides and 11 early jurassic sites mainly from the eastern pontides fold tests indicate that the characteristic magnetization components predate eocene folding late cretaceous site mean declinations are northerly in the eastern pontides and rotated to the west by a few tens of degrees in the western pontides late cretaceous site mean declinations are affected by local clockwise rotation in one sampling region close to the north anatolian fault the mean late cretaceous inclinations and resulting paleolatitudes are 41 1 23 5 n and 43 7 25 5 n for the western and eastern pontides respectively for the eastern pontides the early jurassic liassic mean inclination is 60 5 yielding a paleolatitude of 41 4 n considerably further north than previous paleolatitude estimates for the eastern pontides at this time the paleolatitude estimates for the western and eastern pontides are consistent with these units being close to the eurasian continental margin during liassic and late cretaceous time

degassing of so2 and co2 at mount etna sicily as an indicator of pre eruptive ascent and shallow emplacement of magma abstract we studied soil co 2 emissions together with crater so 2 fluxes from mt etna during the period july 1997 to march 1999 this period was characterized by high levels of volcanic activity and ended with the onset of a 10 month long sub terminal eruption on february 4 1999 soil co 2 degassing was measured at two sites p39 on the lower sw flank of etna and p78 on the e flank known for being connected to deep faults that allow the escape of magmatic gas site p39 is inferred to drain gas from a deep 15 km magma reservoir whereas site p78 is connected to a shallower 5 10 km reservoir based on the temporal variations of measured soil co 2 and crater so 2 data five intervals of anomalous degassing were recognized each of them is interpreted as due to massive gas release from a magma batch that is moving toward the surface the time lag between the occurrence of degassing anomalies of co 2 and those of so 2 agrees well with the different depth of exsolution of the two gases our data also indicate a step like migration of magma to the surface which bears on the existence of at least three different temporary storage levels within etna s feeder system lastly the observed anomalies preceded by months to weeks increases in the summit activity of mt etna including the february 4 1999 eruption comparison between the amounts of degassing magma during each interval of anomalous degassing based on so 2 fluxes and erupted volumes of lava during the same periods seems to indicate that the 1999 eruption was largely fed by magma that started entering the upper feeder system of etna about 1 year earlier

petrology and geochemistry of post collisional middle eocene volcanic units in north central turkey evidence for magma generation by slab breakoff following the closure of the northern neotethys ocean the eocene volcano sedimentary units of northern anatolia are confined into a narrow zone trending parallel to the intra pontide and izmir ankara erzincan sutures along which the northern branch of the neotethys ocean was closed during a period between late maastrichtian and paleocene the middle eocene formations overlie both the imbricated and highly deformed units of the suture zone which are paleocene or older in age as well as the formations of adjacent continental blocks with a regional disconformity therefore they can be regarded to be post collisional these units are composed of subaerial to shallow marine sedimentary beds i e the orencik formation at the base and a subaerial volcanic unit i e the hamamozu formation in the middle and at the top this sudden facies change from marine to subaerial environment in the middle eocene is a common phenomenon across northern turkey implying that a regional uplift event occurred possibly across the suture zone before the initiation of the volcanism during lutetian the middle eocene lavas span the whole compositional range from basalts to rhyolites and display a calc alkaline character except for alkaline to mildly alkaline lavas from the top of the sequence all lavas display a distinct subduction signature our geochemical data indicate that calc alkaline lavas were derived from a subduction modified source whereas alkaline to mildly alkaline lavas of the late stage were possibly sourced by an enriched mantle domain magmas evolved in magma chambers emplaced possibly at two different crustal levels magmas in deeper 13 km and possibly larger chambers fractionated hydrous mafic minerals e g amphibole and biotite two pyroxenes and plagioclase and assimilated a significant amount of crustal material intermediate to acid calc alkaline lavas and pyroclastics were derived from these chambers magmas in the shallower chambers on the other hand 12 km crystallized anhydrous mineral assemblages assimilated little or no crustal material and fed basic to intermediate lavas in the region both deep and shallow chambers were periodically replenished by mafic magmas we argue that a slab breakoff model explains better than any alternative model i why the volcanism during the middle eocene was confined into a rather narrow belt along the suture zone ii why it initiated almost contemporaneous with a regional uplift after the continental collision event iii why it postdated arc volcanism along the pontides in the north by 15 20 my iv why it assimilated significant amount of crustal material and v why alkalinity of lavas increased in time

palaeomagnetic study of block rotations in the niksar overlap region of the north anatolian fault zone central turkey abstract this palaeomagnetic study investigates crustal deformation within and adjacent to the niksar overlap area of the north anatolian fault zone nafz in central east turkey the studied rock formations comprise 1 red limestones of late cretaceous age 3 sites 2 mafic lavas of eocene age on the north side 13 sites and south side 9 sites of the nafz and 3 volcanic rocks of pliocene quaternary age from the niksar pull apart basin within the nafz 8 sites comparisons with reference palaeofield directions computed from apparent polar wander paths of the eurasian and afro arabian plates identify two scales of regional and local tectonic rotation 1 1 a pre tilting remanence in the eocene volcanic rocks south of the nafz d i 144 1 47 5 95 7 6 is interpreted to reflect counterclockwise rotation by 30 40 from the reference palaeofields contemporaneous volcanic rocks from the north side of the nafz have the same reverse polarity recorded in pre tilting magnetisations the remanence is also rotated counterclockwise d i 152 4 42 5 95 11 3 but by about 8 less than the volcanics on the south side of the nafz hence similar amounts of rotation are observed on both sides of the nafz and are interpreted to reflect motions during the pre middle miocene collisional history in this sector of the pontides no distributed clockwise rotations anticipated from subsequent dextral motion along the nafz intracontinental transform are observed the slightly larger anticlockwise rotation found on the south side of the nafz probably records relative rotation of en echelon wedges by continental escape during post middle miocene strike slip along the transform 2 2 within the narrow zone of intense deformation along the nafz cretaceous limestones appear to be rotated clockwise by dextral strike slip motion whilst plio quaternary lavas within a fault bounded block in the overlap region associated with the niksar pull apart basin have magnetisations consistently directed 240 270 e magnetic inclinations are not diagnostic of polarity but both polarity solutions identify rapid clockwise rotation at rates in excess of 50 m y a normal polarity solution is favoured and implies that a block ca 5 km across has undergone a strike slip displacement of around 12 km within the nafz during the last polarity chron cretaceous eocene palaeolatitudes are closer to those predicted from eurasia than afro arabia but a study of older rocks is required to resolve affinities of this sector of the anatolian block theoretical models of crustal deformation across intracontinental transforms obeying power law behaviour and treating the lithosphere as a viscous medium predict that distributed clockwise rotations should be observed about as broad across the nafz these rotations are not observed instead intense clockwise rotation is confined to a narrow zone close to the major fault break the concentration of historic seismic activity here also implies that the bulk of the dextral motion between the eurasian plate and the anatolian block is accommodated by slip along faults close and parallel to the main trace of the nafz

obduction subduction and collision as reflected in the upper cretaceous lower eocene sedimentary record of western turkey late cretaceous early eocene tethyan evolution of western turkey is characterized by ophiolite obduction high pressure low temperature metamorphism subduction arc magmatism and continent continent collision the imprints of these events in the upper cretaceous lower eocene sedimentary record of western anatolia are studied in thirty eight well described stratigraphic sections during the late cretaceous period western turkey consisted of two continents the pontides in the north and the anatolide taurides in the south these continental masses were separated by the izmir ankara neo tethyan ocean during the convergence the pontides formed the upper plate the anatolide taurides the lower plate the arc magmatism in the pontides along the black sea coast is biostratigraphically tightly constrained in time between the late turonian and latest campanian ophiolite obduction over the passive margin of the anatolide tauride block started in the santonian soon after the inception of subduction in the turonian as a result large areas of the anatolide tauride block subsided and became a region of pelagic carbonate sedimentation during the campanian the leading margin of the anatolide tauride block was buried deeply and was deformed and metamorphosed to blueschist facies during campanian times the campanian arc volcanic rocks in the pontides are conformably overlain by shaley limestone of maastrichtian palaeocene age however maastrichtian sedimentary sequences north of the tethyan suture are of fore arc type suggesting that although arc magmatism ceased by the end of the campanian age continent continent collision was delayed until palaeocene time when there was a change from marine to continental sedimentation in the fore arc basins the interval between the end of the arc magmatism and continent continent collision may have been related to a northward jump of the subduction zone at the end of campanian time or to continued obduction during the maastrichtian

metamorphism of the central anatolian crystalline complex turkey influence of orogen normal collision vs wrench dominated tectonics on p t t paths the central anatolian crystalline complex cacc is a microcontinent in the alpine himalayan belt it has previously been considered as a coherent structural entity but although the entire cacc is comprised of similar rocks primarily metasedimentary rocks and granitoids it consists of at least four tectonic blocks characterized by different p t t paths these blocks are the kirsehir north west akdag north east nigde south and aksaray west massifs the northern massifs experienced thrusting and folding during collision and were slowly exhumed by erosion metamorphic rocks are characterized by clockwise p t paths at moderate p t and local low p high t lp ht overprinting in the highest grade rocks apatite fission track ages are eocene to oligocene 47 32 ma the aksaray block represents the hot shallow mid crust of a late cretaceous early tertiary arc it is dominated by intrusions rare metapelitic rocks record low p 4 kbar regional metamorphism overprinted by lp ht contact metamorphism apatite fission track ages are 50 45 ma the nigde massif is different from the other cacc blocks because it evolved as a core complex in a wrench dominated setting it is characterized by clockwise p t paths at moderate p t followed by widespread lp ht metamorphism apatite fission track ages are miocene 12 9 ma significantly younger than those in the northern massifs nigde rocks resided in the mid crust at a time when the rest of the cacc was at or near the earth s surface variations in p t t and tectonic histories especially timing of exhumation between the northern and southern cacc reflect the difference between head on collision vs mid crustal wrenching

palaeomagnetic evidence for substantial rotation of the almacik flake within the north anatolian fault zone nw turkey summary palaeomagnetic data on eocene rocks from within the almacik flake bounded by two strands of the north anatolian right lateral fault indicate that the flake has undergone an apparent counterclockwise rotation of about 148 on average we interpret this as a real 212 clockwise rotation because the almacik flake is entirely delimited by the right lateral north anatolian fault strands the only dominant post eocene structure in the area and because areas surrounding the flake do not show the same rotation this rotation must have occurred since the north anatolian fault originated in the late medial miocene late serravallian 11 5 ma and if so may imply either a larger total slip along it than hitherto estimated or that the almacik flake is the surface expression of a flower structure rotating above a shear zone narrower than the present width of the flake

apatite fission track data from central anatolian granitoids turkey constraints on neo tethyan closure 1 apatite fission track age versus elevation profiles and temperature time path modeling indicate an early to middle paleocene 57 62 ma rapid exhumation of the middle to late cretaceous granitoids in central anatolia and an oligocene 28 30 ma rapid exhumation of the eocene kosedag batholith in the ne sivas region part of eastern central pontides the early to middle paleocene rapid exhumation is thought to result from a regional compressional regime following the collision of the eurasian plate and the tauride anatolide platform at the closure of the izmir ankara erzincan branch of the northern neo tethys the oligocene accelerated exhumation of the kosedag batholith is contemporaneous with the oligo miocene closure of the southern neo tethys which juxtaposed the amalgamated eurasian and tauride anatolide platform and the african arabian plate along the bitlis zagros suture in southeast anatolia the compressional regime due to this collision affected a large area between the greater caucasus in the north and northern african arabian plate in the south

the rotation of iberia during the aptian and the opening of the bay of biscay abstract the cretaceous rotation of the iberian plate in a geodynamical active setting between africa and europe is contemporaneous with the opening of the northern atlantic ocean and provides fundamental temporal and kinematical constraints on the evolution of the bay of biscay and the pyrenees here we report new paleomagnetic data from 50 sites 1109 drilled cores from marine sediments of the cretaceous organya basin in the southern pyrenees to constrain the timing and magnitude of the rotation of iberia berriasian to barremian directions in exclusively limestone lithology are remagnetised in agreement with previous organya basin studies the aptian to cenomanian marls and limestones in the organya basin however provide primary magnetisations asserted by rock magnetic experiments and positive fold tests our results constrain the rotation of iberia to be finished just before the albian paleomagnetic data cannot well constrain the onset of the rotation but sea floor anomaly studies restrict the onset of the rotation to anomaly m0 or the barremian aptian boundary this implies that the entire rotation of iberia happened in one single phase and is confined to the aptian this is in contrast to earlier studies that suggested a two phase rotation of iberia but we argue that the large errors in published ages are not in disagreement with our results in summary we constrain the 35 rotation of iberia to the aptian period which implies a rotation rate of 2 7 5 1 myr depending on the controversial duration of the aptian

middle eocene paleomagnetic data from the eastern sakarya zone and the central pontides implications for the tectonic evolution of north central anatolia 1 a paleomagnetic investigation has been carried out on middle eocene volcanic rocks at 23 sites in the eastern sakarya zone and the central pontides of north central anatolia in order to better understand the regional tectonic evolution of the main zones of northeastern anatolia in the middle eocene the results constrain the tectonic evolution of the area when evaluated in conjunction with earlier published paleomagnetic directions from 92 localities small counterclockwise rotations in the range of r r 1 3 1 4 to r r 17 2 16 8 with respect to eurasia are observed in the central pontides on the northern side of the north anatolian fault naf clockwise rotations ranging between r r 8 5 15 1 and r r 29 7 12 0 are observed between the naf and the sungurlu fault sf in the eastern sakarya zone counterclockwise rotations of r r 18 9 12 4 to r r 42 2 6 9 are observed to the south of the sf our findings combined with previous data support the indentation model of kaymakci et al 2000 2003a 2003b which postulates the collision and northeast directed indentation of the kirsehir block into the sakarya zone this model which was developed to explain the evolution of the cankiri basin can also explain the variable magnitudes of paleomagnetically determined rotations thrust directions and the curvature of the north anatolian ophiolite belt

rapid late miocene surface uplift of the central anatolian plateau margin abstract the central anatolian plateau cap turkey is bordered to its south by a steep mountain belt that emerged 8 7 ma ago from the mediterranean sea knowledge of the onset duration and rate of surface uplift and orographic barrier formation along the plateau margin is crucial for understanding the geodynamic drivers of plateau uplift we present a new comprehensive data set that includes 12 40ar 39ar ages and lacustrine carbonate 18 o data n 637 from 13 sections in upper oligocene to pliocene continental basins of the cap interior we aim at documenting the development of a rain shadow and therefore the surface uplift history of the cap and its southern margin tauride mts in the rain shadow of the tauride mts we observe a gradual 3 9 decrease of 18 o values of lacustrine carbonate between 11 and 5 ma that we interpret to originate from a similar change in 18 o values of precipitation owing to the late miocene development of an orographic barrier our stable isotope paleoaltimetry data show that by 5 ma the southern cap margin had reached similar to present elevations of 2 km surface uplift was coeval with ignimbritic magmatism forearc shortening and distributed compression we suggest that the removal of lithospheric mantle below anatolia led to surface uplift of the cap interior which was followed by surface uplift of the southern cap margin due to crustal thickening as a result of northward subduction of the african plate below central anatolia

carbonate sedimentation in an extensional active margin cretaceous history of the haymana region pontides the haymana region in central anatolia is located in the southern part of the pontides close to the izmir ankara suture during the cretaceous the region formed part of the south facing active margin of the eurasia the area preserves a nearly complete record of the cretaceous system shallow marine carbonates of earliest cretaceous age are overlain by a 700 m thick cretaceous sequence dominated by deep marine limestones three unconformity bounded pelagic carbonate sequences of berriasian albian cenomanian and turonian santonian ages are recognized each depositional sequence is preceded by a period of tilting and submarine erosion during the berriasian early albian and late cenomanian which corresponds to phases of local extension in the active continental margin carbonate breccias mark the base of the sequences and each carbonate sequence steps down on older units the deep marine carbonate deposition ended in the late santonian followed by tilting erosion and folding during the campanian deposition of thick siliciclastic turbidites started in the late campanian and continued into the tertiary unlike most forearc basins the haymana region was a site of deep marine carbonate deposition until the campanian this was because the pontide arc was extensional and the volcanic detritus was trapped in the intra arc basins and did not reach the forearc or the trench the extensional nature of the arc is also shown by the opening of the black sea as a backarc basin in the turonian santonian the carbonate sedimentation in an active margin is characterized by synsedimentary vertical displacements which results in submarine erosion carbonate breccias and in the lateral discontinuity of the sequences and differs from blanket like carbonate deposition in the passive margins

volatile rich magma injection into the feeding system during the 2001 eruption of mt etna italy its role on explosive activity and change in rheology of lavas the explosive behavior and the rheology of lavas in basaltic volcanoes usually driven by differentiation can also be significantly affected by the kinetics of magma degassing in the upper portion of the feeding system the complex eruption of 2001 at mt etna italy was marked by two crucial phenomena that occurred at the laghetto vent on the southern flank of the volcano 1 intense explosive activity and 2 at the end of the eruption emission of a lava flow with higher viscosity than flows previously emitted from the same vent here we investigate the hypothesis that these events were driven by the injection of volatile rich magma into the feeding system the input and mixing of this magma into a reservoir containing more evolved magma had the twofold effect of increasing 1 the overall concentration of volatiles and 2 their exsolution with consequent efficient vesiculation and degassing this led to an explosive stage of the eruption which produced a 75 m high cinder cone efficient volatile loss and the consequent increase of the liquidus temperature brought about the nucleation of fe oxides and other anhydrous crystalline phases which significantly increased the magma viscosity in the upper part of the conduit leading to the emission of a high viscosity lava flow that ended the eruption the 2001 eruption has offered the opportunity to investigate the important role that input of volatile rich magma may exert in controlling not only the geochemical features of erupted lavas but also the eruption dynamics these results present a new idea for interpreting similar eruptions in other basaltic volcanoes and explaining eruptions with uncommonly high explosivity when only basic magmas are involved

stratigraphic and structural development of the eastern pontides turkey this paper describes the stratigraphic and structural development of the eastern pontides north turkey based on section logging at eight localities construction of three structural profiles across the mountains and published literature the eastern pontides comprise a late carboniferous to miocene sequence resting on a basement of hercynian metamorphics late carboniferous to scythian sediments are continental clastics interpreted as having been deposited in an extensional half graben the middle triassic is limestone reflecting the development of a south facing passive margin in the late triassic the ocean palaeotethys began to close flysch was deposited in most places with minor shallow water limestones in the sinemurian above an inverted half graben all pre aalenian strata were deformed during the cimmerian orogeny after a phase of subduction related volcanism in the mid jurassic limestones were deposited during the late jurassic and early cretaceous mainly in shallow water the aptian and albian are absent due to doming in the western pontides prior to the opening of the western black sea but there is a thick sequence of upper cretaceous arc volcanic rocks and intervening turbidites the upper palaeocene is absent possibly due to rifting in the eastern black sea major compression affected the pontides from the eocene to the pliocene associated with the closure of the tethyan ocean oligocene and younger rocks are accordingly non marine

stratigraphic comparisons along the pontides turkey based on new nannoplankton age determinations in the eastern pontides geodynamic implications we compared the stratigraphic formations along the southern margin of the black sea using 196 nannoplankton ages determined in the western and central pontides and 112 new samples from the eastern pontides we inferred that the istanbul and sakarya zones were amalgamated prior to the early cretaceous extensional subsidence migrated eastwards along the pontides from the barremian to the palaeocene an eastwards younging of the cretaceous magmatism suggested that the eastern black sea basin is younger locally angular unconformities and a stratigraphic gap testify to the late albian uplift of the central pontides as the consequence of the collision of an oceanic edifice cretaceous oceanic red beds are marker beds of santonian age along the much of the pontides and are of mainly campanian age within the eastern pontides the middle campanian paleocene was a non volcanic period characterized by extensional subsidence mainly along the eastern black sea basin the end of cretaceous volcanism can be correlated with a southwards subduction jump syn compressional basins show that contraction started during the ypresian along the entire pontide belt eocene volcanism started earlier in the north lutetian than in the south bartonian of the eastern pontides this propagation of syn collisional volcanism could have resulted from slab steepening under the eastern pontides

map view restoration of aegean west anatolian accretion and extension since the eocene 1 the aegean region greece western turkey is one of the best studied continental extensional provinces here we provide the first detailed kinematic restoration of the aegean region since 35 ma the region consists of stacked upper crustal slices nappes that reflect a complex paleogeography these were decoupled from the subducting african adriatic lithospheric slab especially since 25 ma extensional detachments cut the nappe stack and exhumed its metamorphosed portions in metamorphic core complexes we reconstruct up to 400 km of trench perpendicular ne sw extension in two stages from 25 to 15 ma the aegean forearc rotated clockwise relative to the moesian platform around euler poles in northern greece accommodated by extensional detachments in the north and an inferred transfer fault se of the menderes massif the majority of extension occurred after 15 ma up to 290 km by opposite rotations of the western and eastern parts of the region simultaneously the aegean region underwent up to 650 km of post 25 ma trench parallel extension leading to dramatic crustal thinning on crete we restore a detachment configuration with the mid cycladic lineament representing a detachment that accommodated trench parallel extension in the central aegean region finally we demonstrate that the sakarya zone and cretaceous ophiolites of turkey cannot be traced far into the aegean region and are likely bounded by a pre 35 ma n s fault zone this fault became reactivated since 25 ma as an extensional detachment located west of lesbos island the paleogeographic units south of the izmir ankara sava suture however can be correlated from greece to turkey

tectonic configuration of the apuseni banat timok srednogorie belt balkans south carpathians constrained by high precision r e o s molybdenite ages the apuseni banat timok srednogorie magmatic metallogenic belt abts belt forms a substantial metallogenic province in the balkan south carpathian system in southeastern europe the belt hosts porphyry skarn and epithermal deposits mined since pre roman times generally the deposits prospects and occurrences within the belt are linked to magmatic centers of calc alkaline affinity fifty one rhenium osmium re os ages and re concentration data for molybdenites define systematic geochronologic trends and constrain the geochemical metallogenic evolution of the belt in space and time from these data and additional existing geologic geochemical data a general tectonic history for the belt is proposed mineralization ages in apuseni banat timok and panagyurishte the central district of the larger e w srednogorie zone range from 72 83 81 88 and 87 92 ma respectively and clearly document increasing age from the northwestern districts to the southeastern districts further re os ages suggest rapidly migrating pulses of late cretaceous magmatic hydrothermal activity with construction of deposits in 1 m y districts in 10 m y and the entire 1 500 km belt in 20 m y ages in both timok and panagyurishte show systematic younging while deposit ages in banat and apuseni are less systematic reflecting a restricted evolution of the tectonic system systematic differences are also observed for molybdenite re concentrations on the belt scale re concentrations generally range from hundreds to thousands of parts per million typical of subduction related cu au mo pge porphyry systems associated with the generation of juvenile crust the geochronologic and geochemical trends are compatible with proposed steepening of subducting oceanic slab and relaxation of upper continental plate compression resulting influx of sub continental mantle lithosphere scml and asthenosphere provide a fertile metal source and heat while the subducting slab contributes connate and mineral dehydration fluids which facilitate partial melting and metal leaching of scml and asthenosphere cu au mo pge porphyry deposits may develop where melts are trapped at shallow crustal levels often with associated volcanism and epithermal style deposits south banat timok and panagyurishte mo fe pb zn skarn deposits may develop where felsic melts are trapped adjacent to mesozoic limestones at moderate crustal levels north banat and apuseni systematic spatial variations in deposit style commodity enrichment re os ages and re concentrations support specific tectonic processes that led to ore formation in a post collisional setting subduction of vardar oceanic crust may have stalled causing slab steepening and rollback the slab rollback relaxes compression facilitating and enhancing orogenic collapse of previously thickened balkan south carpathian crust the progression of coupled rollback orogenic collapse is evidenced by the width of late cretaceous extensional basins and northward younging of re os ages from panagyurishte 60 km 92 87 ma to timok 20 km 88 81 ma to apuseni banat 5 km 83 72 ma generation of a well endowed mineral belt such as the abts requires a temporally and spatially restricted window of magmatic hydrothermal activity this window is quickly opened as upper plate compression relaxes thereby inducing melt generation and ingress of melt to higher crustal levels the window is just as quickly closed as upper plate compression is reinstated the transient tectonic state responsible for economic mineralization in the abts belt may be a paleo analogue to transient intervals in the present subduction tectonics of se asia where much mineral wealth has been created in the last few million years

the ductile shear zone in granitoid of the central anatolian crystalline complex turkey implications for the origins of the tuzgolu basin during the late cretaceous extensional deformation abstract the emizozu shear zone is the west northwest trending ductile shear zone within the agacoren granitoid in central turkey deformation that affected the granitoid along the emizozu shear zone resulted in mylonites with mylonitic foliation and stretching lineation the textural features of the deformed minerals suggest that mylonitization occurred under conditions of upper greenschist facies the shear indicators including asymmetric porphyroclasts oblique foliation and shear bands suggest a down dip top to the southwest displacement the orientation of stretching lineation as well as kinematic indicators indicates the extensional character of the emizozu shear zone although it is not precisely dated the available age constraints suggest that the zone formed at 78 71 ma according to field and micro structural data the agacoren granitoid was most likely emplaced during a regional deformation in central turkey and synchronously or shortly after was overprinted by the extensional emizozu shear zone the zone can also be correlated with the earlier stage development of the tuzgolu basin in central turkey

paleomagnetic constraints on the tectonic evolution of the sakarya continent northwestern anatolia comment abstract thirteen sites were sampled in northwestern anatolia in order to gather paleomagnetic information concerning the tectonic evolution of this region through jurassic to early tertiary time an interval encompassing much of the history of the neo tethys in this area specifically information concerning the history and behaviour of a crustal block the sakarya continent was sought in order to place some constraints on geologic models that have been proposed for the region four jurassic sites are believed to exhibit early magnetization signatures that yield similar paleolatitudes for all sites these results when compared with paleolatitude information for eurasia suggest that sakarya lay in close proximity to the southern eurasian margin at least during the jurassic part of its history significantly different declinations from the same four sites are interpreted to reflect the deformation of sakarya when it docked with eurasia during the early tertiary these rotations are not attributed to motions of the north anatolian fault since results from three paleocene sites in the same area show no evidence of significant rotation with respect to eurasia

timing of post obduction granitoids from intrusion through cooling to exhumation in central anatolia turkey abstract the middle to late cretaceous central anatolian granitoids intrude the supra subduction zone type central anatolian ophiolite and medium to high grade metasediments of central anatolian crystalline complex and are overlain by late palaeocene to early middle eocene sediments their single zircon 207 pb 206 pb evaporation ages define three clusters 1 cenomanian turonian weighted mean age 94 9 3 4 ma 2 turonian santonian 85 5 5 5 ma and 3 campanian 74 9 3 8 ma their hornblende and biotite 40 ar 39 ar and k ar cooling ages cluster around 80 65 ma the close hornblende and biotite ages reflect rapid exhumation of a mid crustal section during the campanian maastrichtian early to middle palaeocene 57 62 ma apatite fission track age clusters date the tail end of this exhumation episode it is proposed that the central anatolian granitoid melts were generated in a post collisional extensional setting following the docking of an oceanic island arc onto the tauride anatolide platform campanian maastrichtian to early middle palaeocene rapid exhumation event is considered to result from continent continent collisions between eurasian plate and the tauride anatolide platform along the izmir ankara erzincan suture zone

global plate motion frames toward a unified model 1 plate tectonics constitutes our primary framework for understanding how the earth works over geological timescales high resolution mapping of relative plate motions based on marine geophysical data has followed the discovery of geomagnetic reversals mid ocean ridges transform faults and seafloor spreading cementing the plate tectonic paradigm however so called absolute plate motions describing how the fragments of the outer shell of the earth have moved relative to a reference system such as the earth s mantle are still poorly understood accurate absolute plate motion models are essential surface boundary conditions for mantle convection models as well as for understanding past ocean circulation and climate as continent ocean distributions change with time a fundamental problem with deciphering absolute plate motions is that the earth s rotation axis and the averaged magnetic dipole axis are not necessarily fixed to the mantle reference system absolute plate motion models based on volcanic hot spot tracks are largely confined to the last 130 ma and ideally would require knowledge about the motions within the convecting mantle in contrast models based on paleomagnetic data reflect plate motion relative to the magnetic dipole axis for most of earth s history but cannot provide paleolongitudes because of the axial symmetry of the earth s magnetic dipole field we analyze four different reference frames paleomagnetic african fixed hot spot african moving hot spot and global moving hot spot discuss their uncertainties and develop a unifying approach for connecting a hot spot track system and a paleomagnetic absolute plate reference system into a hybrid model for the time period from the assembly of pangea 320 ma to the present for the last 100 ma we use a moving hot spot reference frame that takes mantle convection into account and we connect this to a pre 100 ma global paleomagnetic frame adjusted 5 in longitude to smooth the reference frame transition using plate driving force arguments and the mapping of reconstructed large igneous provinces to core mantle boundary topography we argue that continental paleolongitudes can be constrained with reasonable confidence

palaeomagnetically defined rotations of fault bounded continental blocks in the north anatolian shear zone north central anatolia abstract the 1200 km long north anatolian transform fault connects the east anatolian post collisional compressional regime in the east with the aegean back arc extensional regime to the west this active dextral fault system lies within a shear zone reaching up to 100 km in width and consists of southward splining branches these branches which have less frequent and smaller magnitude earthquake activity compare to the major transform cut and divide the shear zone into fault delimited blocks comparison of palaeomagnetic data from 46 sites in the eocene volcanics from different blocks indicate that each fault bounded block has been affected by vertical block rotations although clockwise rotations are dominant as expected from dextral fault bounded blocks anticlockwise rotations have also been documented these anticlockwise rotations are interpreted as due to anticlockwise rotation of the anatolian block as indicated by gps measurements and the effects of unmapped faults or pre north anatolian fault tectonic events

the origin and evolution of the menderes massif w turkey a rubidium strontium and oxygen isotope study the menderes massif located in the alpine orogen of western turkey has three litho structural units a basal gneiss core a schist mantle covering the gneiss core and an overlying marble mantle this study reports isotopic data from samples of metasediments and migmatites from the southern type a and of tonalitic to granitic metaigneous rocks from the northern menderes massif type b type a rocks define a rb sr whole rock isochron age of 502 10 ma and an initial87sr 86sr ratio of 0 71174 73 this is interpreted as the age of migmatization type b rocks give a rb sr whole rock isochron age of 471 9 ma with an initial87sr 86sr ratio of 0 70684 25 which we interpret as the intrusion age k white micas from rock type a give an average rb sr mineral age of 56 1 ma which can be interpreted as the formation age of the alpine mineral paragenesis k white micas from rock type b give rb sr mixed ages of 120 230 ma between alpine and pan african orogenies biotites from both rock types yield an average rb sr age of 37 1 ma which is interpreted as an alpine cooling age the oxygen isotope ratios of type a rocks range from 10 4 to 14 6 and of type b from 8 9 to 11 8 the oxygen and strontium isotopic compositions together clearly distinguish rocks of types a and b compositions of type a rocks suggest a crustal origin type b rocks have compositions transitional between those of crustal and mantle derived materials

s cl f degassing pattern of water rich alkali basalt modelling and relationship with eruption styles on mount etna volcano abstract our knowledge of the degassing pattern of sulphur chlorine and fluorine during ascent and eruption of basaltic magmas is still fragmental and mainly limited to water poor basalts here we model and discuss the pressure related degassing behaviour of s cl and f during ascent differentiation and extrusion of h2o co2 rich alkali basalt on mount etna sicily as a function of eruptive styles our modelling is based on published and new melt inclusion data for dissolved volatiles co2 h2o s cl f in quenched explosive products from both central conduit 1989 2001 and lateral dyke 2001 and 2002 eruptions pressures are obtained from the dissolved h2o and co2 concentrations and vapour melt partition coefficients of s cl and f are derived from best fitting of melt inclusion data for each step of magma evolution this allows us to compute the compositional evolution of the gas phase during either open or closed system degassing and to compare it with the measured composition of emitted gases we find that sulphur chlorine and fluorine begin to exsolve at respective pressures of 140 mpa 100 mpa and 10 mpa during etna basalt ascent and are respectively degassed at 95 22 55 and 15 upon eruption pure open system degassing fails to explain gas compositions measured during either lateral dyke or central conduit eruptions instead closed system ascent and eruption of the volatile rich basaltic melt well accounts for the time averaged gas composition measured during 2002 type lateral dyke eruptions s cl molar ratio of 5 1 35 bulk cl loss extensive magma fragmentation during the most energetic fountaining phases enhances cl release 55 and produces a lower s cl ratio of 3 7 as actually measured comparatively slower magma rise in the central conduits of etna favours both sulphide saturation of the melt and greater chlorine release 55 resulting in a distinct s cl evolution path and final ratio in eruptive gas in both eruption types any previous bubble melt separation at depth leads to increased s cl and s f ratios in emitted gas high s cl ratios measured during some discrete eruptive events can thus be explained by transitions from closed deep to open shallow system degassing with differential gas transfer extending down to 2 km depth below the vents this depth coincides with the base of the volcanic pile where structural discontinuities and the high magma vesicularity 60 may favour separate gas flow finally the excess s cl f gas discharge through etna summit craters during non eruptive periods requires a mixed supply from shallow magma degassing in the volcanic conduits and deeper derived so2 rich bubbles from the sub volcano plumbing system our modelling provides a useful reference framework for interpreting the monitored variations of s cl and f in mount etna gas emissions as a function of volcanic activity more broadly the observations made for s cl and f degassing on etna may apply to other basaltic volcanoes with water rich magmas such as in arcs

subduction like fluids in the genesis of mt etna magmas evidence from boron isotopes and fluid mobile elements abstract new whole rock b sr nd isotope ratios and 87sr 86sr on clinopyroxenes have been collected to study the enrichment of fluid mobile elements fmes observed in mt etna volcanics etna volcano one of the most active in the world is located in an extremely complex tectonic context at the boundary between colliding african and european plates the analytical work focuses on current 1974 1998 and historic 1851 1971 eruptive activity including some key prehistoric lavas in order to interpret the secular shift of its geochemical signature to more alkaline compositions boron is used as a tool to unravel the role of fluids in the genesis of magmas revealing far reaching consequences beyond the case study of mt etna small variations are observed in 11b 3 5 to 8 0 87sr 86sr 0 70323 0 70370 and 143nd 144nd 0 51293 0 51287 moreover temporal evolution to higher 11b and 87sr 86sr and to lower 143nd 144nd is observed in the current activity defining a regular trend sr isotopic equilibrium between whole rock and clinopyroxene pairs indicates the successive introduction of three distinct magma types into the etna plumbing system over time these are characterized by differing degrees of fme enrichment in addition certain lavas exhibit evidence for country rock assimilation magma fluid interaction or magma mixing in the shallow feeding system at times these processes apparently lowered magmatic 11b and or induced sr isotopic disequilibrium between whole rock and clinopyroxene the regular increase of 11b values is correlated with nb fme and 87sr 86sr ratios these correlations are consistent with simple mixing between the mantle source and aqueous fluids derived from nearby ionian slab the best fit of mt etna data is obtained using an enriched morb mantle source and a fluid phase with 11b of about 2 and 87sr 86sr of 0 708 we argue that the slab window generated by differential roll back of subducting ionian lithosphere with respect to sicily allows the upwelling of asthenosphere from below the subduction system and provides a suitable path of rise for subduction related fluids the increasing geochemical signature of fluid mobile elements enrichment to mt etna lavas is considered a consequence of the progressive opening of slab window through time

resolving the problem of shallow magnetizations of tertiary age in asia insights from paleomagnetic data from the qiangtang kunlun and qaidam blocks tibet china and a new hypothesis we present new paleomagnetic results obtained at 39 sampling sites from five sections of tertiary red bed formations two eocene formations from the qiangtang block of tibet xialaxiu locality 32 8 n 96 6 e and the xining basin of qaidam xining locality 36 5 n 102 0 e and three neogene formations from the xining basin jungong locality 34 7 n 100 7 e and the kunlun block tuoluo lake and west yushu localities 35 3 n 98 6 e and 33 2 n 96 7 e respectively thermal demagnetization of the rocks isolated a high temperature component that we interpret as the primary magnetization in four localities the paleopoles lie at 52 6 n 352 e dp dm 6 0 10 7 for xialaxiu 61 6 n 211 3 e dp dm 9 7 16 1 for xining 66 0 n 228 6 e dp dm 3 6 6 9 for jungong and 53 9 n 205 4 e dp dm 5 6 10 0 for west yushu as in previous studies of tertiary formations from asia the inclinations we obtained are shallower by 18 to 26 than the magnetic field computed from the eurasian apparent polar wander path apwp at 10 and 20 ma for neogene rocks and at 40 and 60 ma for eocene rocks on the basis of a compilation of eocene data from the south china block tibet central asia and kyrgyzstan we conclude that this inclination anomaly reflects erroneous predictions of positions of the siberian craton when based on the apwp of eurasia the main reason for this discrepancy might be nonrigid behavior of the eurasian plate in the tertiary combination of this with intracontinental shortening of asia under the penetration of india provides a full explanation for the anomaly verification of this new interpretation of the inclination anomaly will require new geologic and paleomagnetic data from the northern parts of these remote regions in mongolia and siberia

effects of weathering on single domain magnetite in early pliocene marine marls rock magnetic parameters are often used to recognize variations in the original magnetic mineralogy and for normalizing purposes in palaeointensity studies incipient weathering however is shown to have a profound but partly reversible influence on the rock magnetic properties of the marls of the early pliocene trubi formation in southern sicily italy the remanence in the marls resides in single domain sd magnetite grains but the remanent coercive force hcr shows a strong variation and most values observed are anomalously high hcr range 36 188 mt the enhanced coercivities are attributed to stress in the magnetite grains induced by surface oxidation at low temperature upon heating to 150 c a reduction of coercivities occurs that can be explained by a stress reduction as a result of a reduction of fe2 gradient due to a higher diffusion rate at elevated temperature after heating to 150 c coercivities are quite uniform throughout the outcrop and the values are characteristic of sd magnetite hcr range 30 38 mt the bulk susceptibility increases by 4 24 per cent and the isothermal remanent magnetization irm decreases by 5 11 per cent the increase in anhysteretic remanent magnetization arm is large 20 242 per cent the magnitude of the changes is related to the degree of weathering another effect of heating the marl samples to 150 c is a substantial reduction of the coercivities of the secondary overprint in the natural remanent magnetization after heating separation of the secondary and primary components by alternating field demagnetization is more efficient the usual difficulties of thermal demagnetization above 300 c may thus be avoided by a combination of moderate heating to 150 c and subsequent alternating field demagnetization

new tertiary paleomagnetic poles from mongolia and siberia at 40 30 20 and 13 ma clues on the inclination shallowing problem in central asia we report results of a paleomagnetic study of 490 cores from 59 sites corresponding to 52 distinct basaltic flows from mongolia and siberia khaton sudal 39 4 ma 44 5 n 101 4 e taatsyn gol 1 31 5 ma 45 4 n 101 3 e 2 28 0 ma 45 5 n 101 1 e ust bokson 19 9 ma 52 1 n 100 3 e and taatsyn gol 3 12 7 ma 45 5 n 101 0 e stepwise thermal and alternating field demagnetizations isolated a stable high temperature component htc of magnetization in most specimens which we interpret as the primary magnetization of these basaltic lava flows the four corresponding paleopoles appear consistent with coeval paleopoles from other asian effusive formations however except for the 12 7 ma paleopole the paleopoles are systematically far sided from the european apparent polar wander path apwp with respect to site locations corresponding to anomalously shallow inclinations in tertiary asian effusive formations in the hypothesis of a dipolar magnetic field in the tertiary this indicates a 1000 1500 km position of the siberia craton and amuria block farther south than expected at 40 and 30 ma tectonically this interpretation implies decoupling and relative rotations between the western and eastern parts of eurasia between the cretaceous and present we show that if siberia were located more to the south the 15 20 paleolatitude anomaly generally observed in sedimentary formations from central asia reduces to a more reasonable average value of 7 which could result from the superimposition of shallowing mechanisms due to sedimentary processes and northward motion of asian blocks under the effect of ongoing penetration of india into eurasia in the tertiary

petroleum geology of the black sea abstract the black sea comprises two extensional basins formed in a back arc setting above the northward subducting tethys ocean close to the southern margin of eurasia the two basins coalesced late in their post rift phases in the pliocene forming the present single depocentre the western black sea was initiated in the aptian when a part of the moesian platform now the western pontides of turkey began to rift and move away to the south east the eastern black sea probably formed by separation of the mid black sea high from the shatsky ridge during the palaeocene to eocene subsequent to rifting the basins were the sites of mainly deep water deposition only during the late miocene was there a major sea level fall leading to the development of a relatively shallow lake most of the margins of the black sea have been extensively modified by late eocene to recent compression associated with closure of the tethys ocean gas chromatography mass spectrometry and carbon isotope analysis of petroleum and rock extracts suggest that most petroleum occurrences around the black sea can be explained by generation from an oil prone source rock of most probably late eocene age although a wider age range is possible in the basin centres burial history modelling and source kitchen mapping indicate that this unit is currently generating both oil and gas in the post rift basin a palaeozoic source rock may have generated gas condensate in the gulf of odessa in bulgarian waters the main plays are associated with the development of an eocene foreland basin kamchia trough and in extensional structures related to western black sea rifting the latter continue into the romanian shelf where there is also potential in rollover anticlines due to gravity sliding of neogene sediments in the gulf of odessa gas condensate has been discovered in several compressional anticlines and there is potential in older extensional structures small gas and oil discoveries around the sea of azov point to further potential offshore around the central azov high in offshore russia and georgia there are large culminations on the shatsky ridge but these are mainly in deep water and may have poor reservoirs there are small compressional structures off the northern turkish coast related to the pontide deformation these may include eocene turbidite reservoirs the extensional fault blocks of the andrusov ridge mid black sea high are seen as having the best potential for large hydrocarbon volumes but in 2200 m of water

textural evolution and trace element chemistry of hydrothermal calcites from archean gold deposits in the hattu schist belt eastern finland indicators of the ore forming environment abstract orogenic style gold mineralizations in the archean hattu schist belt e finland are present in all major host rock lithologies including epiclastic sedimentary rocks volcanic rocks and felsic intrusives the gold deposits are related to extensive quartz dominated vein networks and the gold mineralization occurs as dissemination in altered wall rocks and within hydrothermal quartz veins the quartz dominated veins frequently contain calcite which is also present within the country rocks we analyze and compare the major and trace element chemistry of these calcites and test whether they carry the signatures of the origin of hydrothermal fluids associated with the gold deposits or record fluid interaction with the local wall rocks the calcites show textural growth and chemical zoning considerable chemical variations within samples and the chemical data do show some overlap between the samples all calcites contain dominantly ca with other elements being typically below 2 wt and they are accordingly classified as rather pure calcites amongst minor elements both mg and fe show larger variations than mn the concentrations of most trace elements analyzed are relatively low except for sr and y which can attain values up to 1 wt and 200 ppm respectively some of the trace elements or trace element ratios in hydrothermal calcite including sr y mn la lu n and ree show correlations with the respective host rock lithologies this indicates that interaction between hydrothermal fluids and adjacent and diverse host rocks has strongly affected the trace element chemistry of calcite chemically variable growth zones in large calcite crystals and distinct grain populations within individual samples cannot be readily explained by host rock control but instead they are interpreted to reflect changes in fluid composition over time the hydrothermal calcites have chondrite normalized ree patterns that are mostly hree enriched relative to lree with very few exceptions that show unfractionated flat or lree enriched relative to the hree patterns the ree patterns of the calcites are very different from those of their immediate host rocks suggesting that they are inherited from the hydrothermal fluid s from which they precipitated the hree enrichment relative to the lree visible in the patterns resembles the ree patterns of calcites from hydrothermal vein type deposits of metamorphic origin elsewhere and contrasts with the ree patterns of calcites from magmatic hydrothermal environments the ree patterns of the hydrothermal calcites in the hattu schist belt deposits would therefore be compatible with formation from a fluid system that is essentially derived from metamorphic sources in agreement with conclusions drawn from the fluid inclusion chemistry

coeval extensional shearing and lateral underflow during late cretaceous core complex development in the nigde massif central anatolia turkey 1 the nigde massif at the southern tip of the central anatolian crystalline complex consists of two structural units foliations in the lower unit define a dome cored by migmatites the contact between the two units bears all the elements of a ductile to brittle extensional detachment hence the nigde massif represents an extensional metamorphic core complex top to ne ene shearing at higher levels of the lower unit relates to displacement along the detachment deeper levels of the lower unit display high temperature top to ssw ductile shearing the two shearing deformations show a difference in the mean trend of stretching lineations of up to 58 new 40ar 39ar ages combined with previously published data enable us to infer that the two shears were contemporaneous in our favored interpretation oblique shearing in the core of the dome reflects lateral underflow i e horizontal flowing of the lower crust in a direction highly oblique to the direction of extension as a result of the interaction between lateral underflow and downdip shearing along the overlying detachment distinct structural domains are expected to exist within the migmatitic part of the core complex with observed counterparts in the nigde dome lateral underflow may reflect inward flow on the scale of the core complex regional scale channel flow is an alternative that would better account for the record of non coaxial deformation in the core of the dome more generally we suspect that the development of lateral underflow in a metamorphic core complex more likely reflects regional channel flow rather than local inward flow

insights from the talysh of azerbaijan into the paleogene evolution of the south caspian region the age and mode of formation of the south caspian basin are disputed an 10 km thick predominantly middle eocene clastic and volcanic succession is exposed in the talysh mountains of azerbaijan at its western margin here high k alkali basalts pass laterally to the east and southeast into volcanogenic sandstone dominated turbidity current and debris flow deposits these southeasterly directed depositional systems accumulated in water depths generally greater than 200 m and fed directly into the western south caspian basin new ar ar ages cluster around 39 ma with an upper 1400 m thick volcanic interval being deposited in 2 2 0 2 m y we interpret that this rapid deposition and magmatism records a major back arc extensional transtensional event in the talysh north of the north dipping neotethyan subduction zone this event is recognized across much of southwest asia and may indicate a period of significant basin formation within the adjacent south caspian basin a transition into upper eocene lower oligocene strata dominated by fine grained turbidity current and hemipelagic sediments with slope instability features is interpreted to mark the end of rifting and volcanism in the talysh and the start of the arabia eurasia collision overlying oligocene coarse clastic rocks are interpreted as the erosional products of localized topography created by the further propagation of compressional deformation into the talysh region

evolution of the etna volcano information from the southern wall of the valle del bove caldera abstract the greater part of etna can be regarded as a complex strato shield volcano constructed from the overlapping products of several centres of trachy basaltic activity the valle del bove is a horse shoe shaped caldera 8 km long and 5 km wide cut into the eastern flanks of etna the caldera is one of the few areas on the volcano where historic eruptions have not obscured the products of pre historic centres of activity and these are well exposed in the cliff walls surrounding the caldera examination of these older volcanics provides important information on the eruptive style and internal plumbing of the etna volcano during pre historic times and suggests that both were significantly different from the present day much of the southern wall of the valle del bove represents a surviving portion of the trifoglietto ii volcano the largest pre historic centre of activity a stratigraphy is constructed for the southern wall the trifoglietto ii lavas and pyroclastics rest unconformably upon the eroded remnants of an older centre and are themselves overlain by the products of younger centres all the lavas exposed in the southern wall are of alkalic affinity and comprise a trachybasaltic suite ranging from hawaiite to benmoreite variation in the chemistry of the lavas can be explained by their differentiation at high levels in the crust from a more basic magma of alkali olivine basalt hawaiite composition an anomalous trend in the tio 2 content of the trifoglietto ii lavas may be explained by the fractionation of kaersutite ti rich amphibole a study has been made of the numerous dykes exposed in the walls of the valle del bove the alignments of which parallel trends which are important on etna at the present time it is proposed that the initial opening of the valle del bove occurred sometime between 20 000 and 10 000 y b p as a result of a phreatic or phreato magmatic explosion near the base of the eastern flank of trifoglietto ii this is visualised as triggering a slope failure and resulting in the destruction of much of the centre by a catastrophic landslide this mechanism has much in common with the explosive eruptions which produced both the bandai san japan caldera in 1888 and the mount st helens caldera in may 1980