Alpine-Himalayan Orogeny Research Articles

Quaternary post-collisional high Nb-like basalts from Bijar-Qorveh, NW Iran: A metasomatized lithospheric mantle source

The Quaternary Bijar-Qorveh mafic volcanic rocks (BQMVR) occur in the Sanandaj-Sirjan Zone (SSZ) of Iran, a segment of the Alpine-Himalayan Orogeny with a Gondwana-affinity basement. Phases 1 and 2 of BQMVR are silica-undersaturated (basanite, tephrite, and phonotephrite) and form a highly alkaline or HA suite. The last phase, phase 3, of BQMVR is silica-saturated (alkali olivine basalt and hawaiite) and is called the mildly alkaline or MA suite. BQMVR share well-known subduction-related negative Nb Ta anomalies, and their Nb abundances are high enough to be classified as ‘high-Nb like basalts’. However, they do not show geochemical characteristics of typical high-Nb basalts. Trace element abundances and patterns of the MA suite mimic garnet-bearing spinel peridotite partial melts, whereas the HA suite is too rich in incompatible trace elements to match normal mantle partial melts. Enriched trace element patterns of the HA suite are akin to hornblendite experimental partial melts, and are likely derived from a garnet-amphibole peridotite source. Sr-Nd-Pb isotopic characteristics of the BQMVR indicate a subcontinental lithospheric mantle affinity. The HA suite tends toward the EM1 array, whereas the MA suite follows the EM2 array. The highly radiogenic Sr Nd isotopes of the MA suite indicate significant crustal contamination. Lithospheric delamination beneath the SSZ that followed Arabia-Eurasia collision, triggered garnet-amphibole peridotite partial melting that interacted with 10–30% of the asthenospheric component to have formed the HA suite. Mantle melting at shallower lithosphere depths followed and produced the MA suite. MELTS modeling shows the BQMVR underwent fractional crystallization of clinopyroxene ± olivine. Whole-rock thermobarometric calculations suggest derivation of the primary melts at a depth of ~97 km, however the Cpx-thermobarometer indicates that such melts equilibrated at lower crust depths at a depth of 45 km close to the Moho. The present Quaternary volcanostratigraphic study provides substantial clues for major post-collisional alkaline high-Nb mafic volcanism bearing signatures of two distinct magmatic stages; an early phase (phases 1 and 2) rooted in a deeper garnet amphibole peridotite followed by phase 3 rooted in a garnet-poor spinel peridotite. • Quaternary alkaline mafic volcanism in western Iran is post collisional. • Highly alkaline (HA) suite is derived from juvenile amphibole rich mantle. • Mildly alkaline (MA) suite is derived from shallower, ancient lithospheric mantle. • EM1 and EM2 affinities of the HA and MA suites respectively comply with the SCLM. • MELTS and isotopes revealed FC and AFC roles for HA and MA suites respectively.

Au-rich bimodal-mafic type volcanogenic massive sulphide deposit associated with Jurassic arc volcanism from the Central Pontide (Kastamonu, Turkey)

The central part of the Pontide Orogenic Belt, located in northern Anatolia, is a segment of the Alpine-Himalayan orogeny. Çangaldağ Metamorphic Complex (CMC) occurs within this segment which consists of ensimatic island arc volcanics and deep sea sediments which occasionally cut cross by mafic sills/dykes. They were exposed to metamorphism under the greenschist facies conditions and remain in tectonic contact with each other. The Say yayla mineralization is one of the recently discovered volcanogenic massive sulfide (VMS) deposits in the CMC with a remarkable Au content. The mafic and felsic metavolcanic rocks are the host-rocks of the Say Yayla mineralization and the ages determined by U-Pb zircon grains of these felsic volcanic rocks range from 170 Ma to 165 Ma indicating Middle Jurassic time.At the 0.1% cut-off grade, 7.5 million tons of resource has been calculated with 0.75 ppm Au, 0.65 wt% Cu, and 0.35 wt% Zn grades. The Say Yayla mineralization consists of massive and semi-massive sulfide minerals and a mineral assemblage represented by predominantly pyrite and chalcopyrite and trace amounts of sphalerite, tennantite and galena. Average base and precious metal grades of the zones occur with >1 wt% Cu are 2 wt% for Cu, 0.7 wt% for Zn, 0.04 wt% for Pb and 1.5 g/t for Au.The sulfur isotope values (δ34S VCDT) range from 4.9‰ to 6.7‰ for pyrite grains and 4.2‰ was obtained from the one sphalerite sample. δ18O values for the quartz from quartz-rich ore samples were 10.6 ‰ and 11.7‰ δ18O (VSMOW)qtz. δ18O (VSMOW)fluid values for the ore-forming fluids vary between 0‰ and 2.4‰. Lead isotope compositions of the pyrite minerals were 18.148–18.150 (206Pb/204Pb), 15.548–15.550 (207Pb/204Pb) and 38.078–38.083 (208Pb/204Pb)The geological, geochemical, and isotopic data of the ore and host-rocks reveal that the mineralization is a bimodal-mafic type (Noranda type), which is classified into Cu-Zn group of volcanogenic massive sulfides. Geochemical and geochronological data from the wall rocks further show that mineralization was developed within an ensimatic island arc environment during the Middle Jurassic.

Recent tectonic activity in Central Alborz Mountain, Iran: morphometric analysis and knickpoint identification

Alborz, as part of the Alpine-Himalayan orogeny belt, has been the result of the convergence of the Central Iranian and Eurasian plate since the late Triassic. The study area located in Central Alborz encompasses different Quaternary faults. Thus, the present study aimed to evaluate the effect of faults on river landforms through morphotectonic indices and the causes of knickpoints and knickzones in the Bedrock Rivers in part of Central Alborz. To this end, six morphometric indices such as longitudinal gradient (SL), hierarchical anomaly (Δa), the bifurcation index (R), hypsometric integral and hypsometric curve (Hi-Hc), relative relief (Bh), and basin shape (Bs) were calculated and analyzed in 38 sub-basins of the area. Finally, the area was divided into extremely high, high, medium, and low tectonic activity areas using the relative tectonic activity (IAT). Normalized steepness and concavity indices along with the longitudinal profiles of the streams were obtained using Matlab and Arc GIS software. Based on the findings, the existence of slope-break knickpoints at the mountain piedmont at the outlet of large rivers through active faults demonstrated that most of these landforms were created by movements along the main faults such as Khazar, Nusha, Soheil, Deylaman, Kashachal, representing high tectonic activity in the central and southern parts of the study area. However, the values of these indices were extremely low and indicated low tectonic activity in the northern parts located in the embayment part of the Caspian Sea. Finally, the findings revealed that these classes correspond well to the areas with landforms such as V-shaped and narrow valleys, gorges, deflected and offset streams, deformed Neogene, and Quaternary units that indicate the post-Neogene activity.

Late Cenozoic volcanism in the Almaludag region, Azerbaijan province, northwest Iran: Evidence for post-collisional extension

We discuss the geology, petrology, and major and trace element geochemistry of Late Cenozoic volcanic rocks in the Almaludag region in the Western Azerbaijan province, northwest Iran. Geology of this region evolved through the northward subduction of the Neotethyan oceanic lithosphere and subsequent collision of the Arabian and Eurasian plates during the Alpine-Himalayan orogeny. Two different Late Cenozoic periods of volcanic activity are recognized: Episode I produced pyroclastic deposits and trachydacitic lava (1.47 Ma, U-Pb dating) and Episode II generated mafic lava and scoria cones (including spatter/cinder). Geochemical data indicate that Episode I lavas have high-silica adakitic compositions, similar to the post-collisional and continental adakites, that formed from the partial melting of the thickened lower crust. Episode II lavas vary in composition and fall into two distinct geochemical groups. The first group includes picrobasalt-basanite and tephrite compared to the more evolved trachybasalt and basaltic trachyandesite of the second group. Both of these groups show alkaline to shoshonitic affinities.The binary geochemical plots of the Episode II samples display compositional trends that indicate magmatic processes such as fractional olivine ± clinopyroxene crystallization. The major and minor elemental variations of these samples reflect a mantle source heterogeneity and minor crustal contamination. The REE (rare earth elements) patterns and spider diagrams indicate enrichment of the large ion lithophile elements (LILE) and depletion of the high field strength elements (HFSE) relative to the heavy rare earth elements (HREE), and reveal an enriched lithospheric mantle source which was previously metasomatized by subduction components. The mantle source of the Episode II lavas was enriched by fluids and melts which were released from a subducted slab between Late Mesozoic and Early Cenozoic in northwest Iran. The Si-undersaturated lavas of the first group of Episode II probably originated in the garnet stability field in the lithospheric mantle with carbonate residue or veins, suggesting that the mantle source probably underwent carbonate metasomatism. Geochemistry of the SiO2 rich lavas of the second group of Episode II is consistent with a melt extracted from a peridotitic mantle source. The compositional variation from the rocks of the first group to those in the second group suggests a diminishing degree of metasomatic veins-wallrock interactions.The Late Cenozoic mafic rocks in the Almaludag region probably formed through extension in a post-collision, post-orogenic setting. The extension was likely the result of the delamination of the thickened subcontinental lithospheric mantle (SCLM) and ensuing asthenospheric upwelling after the collision of the Arabian and Eurasian plates.

Zircon U–Pb–Hf isotopes and whole rock geochemistry of magmatic rocks from the Posht-e-Badam Block: A key to tectonomagmatic evolution of Central Iran

The Posht-e-Badam Block in Central Iran likely formed part of the Neoproterozoic Arabian-Nubian Shield (ANS). However, its Phanerozoic history is not well constrained. Zircon UPb ages, Hf isotopic compositions and whole-rock geochemistry of igneous rocks from the Bafq district were determined to constrain their source and tectonomagmatic evolution. Two magmatic cycles are identified; early Paleozoic events associated with the Cadomian Orogeny resulting from Proto-Tethys subduction beneath the northern margin of Gondwana, and Cenozoic volcanism related to the Alpine-Himalayan Orogeny and closure of Neo-Tethys. The main plutonic and volcanic rocks record early Cambrian ages. The Zarigan, Narigan and Chahcholeh granitoids, volcanic rocks of the lower Cambrian volcano-sedimentary unit (CVSU) and the Zarigan gabbro have remarkably similar ages of 536 to 528 Ma. The Zarigan and Chahcholeh granitoids and volcanic rocks of the CVSU have positive εHf(t) values of 1.4 to 9.3, with Hf model ages (Hf-TDMc) of 715–1034 Ma. They are mostly A2-types, although some samples show affinity to A1- and I-types, suggesting an asthenospheric mantle source, modified by various amounts of crustal assimilation. The Narigan granite records εHf(t) values of −3.8 - 3.1, with Hf-TDMc of 970 to 1255 Ma and displays I-type characteristics, formed through mixing of mantle-derived melts with predominantly Neoproterozoic crust. All rocks were generated in a post-collisional setting. The Esfordy syenite and mafic dikes are younger and essentially coeval, with weighted mean ages of 457 ± 5 Ma and 451–448 Ma, respectively. The Esfordy syenite has A1-type characteristics, indicating possible derivation in an intraplate rift environment and was likely plume-related. The mafic dikes have OIB-like characteristics. Mafic rocks related to closure of Neo-Tethys include the ca. 23 Ma Bahabad diorite that records εHf(t) values of −16.8 to 10.1 (Hf-TDMc = 241–283 Ma) and an OIB-like signature, indicating assimilation of crustal material by asthenospheric mantle-derived melt.

Petrogenesis of the Snezhnoe Ruby Deposit, Central Pamir

The Snezhnoe ruby deposit is located in the Muzkol–Rangkul anticlinorium within the Cimmerian zone of the Central Pamir. On the local scale, the deposit occurs on discrete relict bedding planes of calcitic marbles belonging to the Sarydzhilgin suite. Four ruby-bearing mineral assemblages are present within the main parts of the deposit: (1) scapolite + phlogopite + muscovite + margarite; (2) plagioclase + muscovite + margarite; (3) muscovite + phlogopite + margarite; (4) calcite. The ruby + calcite association is the most economically important, whereas the association of plagioclase + scapolite + phlogopite + muscovite is typical for the ruby-free parts of the deposit. Mica group minerals with a distinctive green color due to enhanced Cr and V concentrations are the main prospecting indicators for the ruby mineralization. The oxygen isotopic composition of the rubies is +15.3‰, a common value for crustal metamorphic and sedimentary rocks. The ratios of indicative trace elements in the rubies are Ga/Mg < 8.2, Fe/Mg < 51.2, Cr/Ga > 6.9 and Fe/Ti < 31.6. These values are characteristic for metamorphic corundum. The bulk ruby-bearing rocks have an initial 87Sr/86Sr ratio of ~0.70791 and εNd of ~−9.6, also pointing to the crustal origin of the deposit in agreement with the geological data. Ancient Al-enriched sediments are suggested to be a possible protolith for the ruby-bearing rocks. The temperature of the metamorphic processes was estimated at 760 ± 30 °C using Zr-in-rutile geothermometry. Raman mapping of rutile inclusions trapped within the ruby crystal indicates that the minimum pressure of mineralization was about one kilobar. The age determined by the Rb–Sr thermal ionization mass spectrometry of phlogopite, plagioclase and bulk rock is 23 ± 1.6 Ma, corresponding to the timing of relaxation after peak metamorphism during the Alpine–Himalayan Orogeny.

Zircon U-Pb Ages and Magmatic History of the Kashan Plutons in the Central Urumieh-Dokhtar Magmatic Arc, Iran: Evidence for Neotethyan Subduction during Paleogene-Neogene

The Kashan plutons are situated in the central part of Urumieh-Dokhtar magmatic arc recording subduction-related magmatism within the Alpine-Himalayan orogeny in Iran. These rocks consist of different calc-alkaline plutonic rocks including gabbro, gabbroic diorite, microdiorite, monzodiorite, tonalite, granodiorite, and granite. The plutons were emplaced into the Jurassic sedimentary units (Shemshak Formation) and the Eocene calc-alkaline volcanic and pyroclastic rocks. New U-Pb zircon ages show that the Kashan plutons formed during two main periods at 35.20±0.71 Ma in the Late Eocene (Priabonian) and at 18.90±0.84, 19.26±0.83, 19.30±1.2, and 17.3±1.8 Ma in the Early Miocene (Burdigalian). The reported events in the Kashan plutons imply the final phases of subductionrelated magmatism before the collision which happened between the Arabian and Iranian plates in the Middle Miocene. The plutonic activity in the Kashan region occurred during the transition from Eocene subduction-related setting to Middle Miocene collisional setting.

SEISMIC ZONES AND SEISMICITY OF THE TERRITORY OF THE REPUBLIC OF NORTH MACEDONIA

According to all sources of data available to the Seismological Observatory the seismic activity in the Republic of North Macedonia is mainly tectonic, with the exception of weak collapse earthquakes. This seismic activity is caused by its affiliation to the Mediterranean area of the Alpine-Himalayan orogeny belt. Epicentral areas belong to the three main seismic zones, West-Macedonian seismic zone, Vardar seismic zone and East-Macedonian seismic zone. Three secondary seismic zones, transverse to the main seismic zones, are also defined. Each of these zones is characterized by а specific time and space distribution of earthquake locations, with frequent seismic microactivity, lot of minor to light earthquakes and very rare moderate to major earthquakes. Observed seismic activity on the territory of the Republic of North Macedonia has a main role for the evaluation of the seismic hazard of the specific territory.

Tectono-geomorphic development of intra-continental Cenozoic depressions within Cretaceous rocks of the Interior Homocline, Central Arabia

Intra-continental depressions occurred in Central Arabia, within the evaporite-bearing Sulaiy Formation, and extends for over 550 km along N-S arcuate belt, passing through eastern Ar Riyadh, Saudi Arabia. They mark Jurassic/Cretaceous contact within the Interior Homocline of Central Arabia, accommodating Neogene and Quaternary deposits. Two en echelon major depressional areas were discovered, the northern major depressional area and the southern major depressional area. The first depressional area occurs between Al Artawiyah and Ad Dilam towns, following the arcuate Jurassic/Cretaceous contact. It contains five depressions: N-S Al Artwaiyah depression; NW-SE Ath Thumamah depression, northeast of Riyadh; NW-SE Jinadriyah depression, east of Riyadh; E-W Al Kharj depression; and N-S Ad Dilam depression. All five depressions seems to be formed by tectonic and subsequent geomorphic events, except for Al Artawiyah and Jinadriyah depression, which developed mainly by tectonic events. Southern major depressional area steps over to southwest of Ad Dilam, and occurs from Hawtat bani tamim to Layla towns. This Hawtah-Layla major depression trends N-S, and Cretaceous units strike NNE, which is a slightly oblique relationship, suggesting expression of deep-seated structures. Tectonic features were part of the Alpine-Himalayan orogeny, developing during Eocene. They followed by a geomorphic event (karsts and subsequent collapse) that took place during Mid Pleistocene. Ad Dilam depression is a surface expression of three oil and gas fields, while the southern major depression between Hawtat Bani Tamim and Layla towns is a surface expression of four oil and gas fields. Yet, other several depressional areas are also accommodating Quaternary desert sediments, and they contain economic resources, which therefore, worth further detailed studies.

Alpine-Himalayan orogeny drove correlated morphological, molecular, and ecological diversification in the Persian dwarf snake (Squamata: Serpentes: Eirenis persicus)

Alpine-Himalayan orogeny drove correlated morphological, molecular, and ecological diversification in the Persian dwarf snake (Squamata: Serpentes: Eirenis persicus)

Synorogenic copper mineralization during the Alpine–Himalayan orogeny in the Zafarghand copper exploration district, Central Iran: petrogrography, geochemistry and alteration thermometry

AbstractThe Zafarghand porphyry copper exploration district is located in the NE of Isfahan (Central Iran), about 15 km SW of the city of Ardestan. This area consists of Eocene extrusive and Miocene intrusive rocks. The Eocene (ca. 56 Ma) units include andesites, dacites and rhyodacites spatially associated with pyroclastic materials (ignimbrites and pyroclastic tuff breccias), which are intruded by a Miocene (26–19 Ma) microgranular I‐type granodiorite. The entire igneous complex is intersected by NW–SE to E–W‐trending andesitic and dacitic dykes and N–S‐trending andesitic basalt dykes. Both the Miocene granodiorite and Eocene extrusives have undergone several hydrothermal alteration stages: (i) potassic, (ii) phyllic, (iii) argillic and (iv) propylitic alteration. The geochemical data of these formations are consistent with (i) the modal mineralogy derived from petrographic analysis of the samples and (ii) the regional tectonic setting of the samples having been emplaced in an active subduction‐related continental volcanic arc setting during the Zagros Orogeny. Copper mineralization in the Zafarghand area shows an average grade of 0.4% Cu, 200 ppm Mo, 0.2 ppm Ag and 0.01 g/t Au and a maximum age of 21 Ma, which implies that copper mineralization was synorogenic, coeval with the Alpine–Himalayan orogeny in this region. Copper mineralization occurs as chalcopyrite and bornite minerals as disseminated and stockwork mineralization associated with remobilized late epithermal vein mineralization. Chlorite geothermometry for the potassic and propylitic alteration zones yields a temperature range of 361–471 and 196–266 °C, respectively, which implies copper mineralization in a cooling synorogenic magmatic arc environment. Chlorite grains in these alteration zones indicate a classification of chlorites mainly as ripidolite, pycnochlorite, brunsvigite and diabantite. Copyright © 2016 John Wiley & Sons, Ltd.

Geochemical signature of Eocene Kuh-e Dom shoshonitic dikes in NE Ardestan, Central Iran: implications for melt evolution and tectonic setting

*Corr esponding author The Late Eocene Kuh-e Dom composite intrusion forms a segment of the Urumieh-Dokhtar magmatic arc, which recorded syn- to post-collisional magmatism during the Alpine–Himalayan orogeny in central Iran. Numerous acid and intermediate–basic dikes intrude the composite intrusive complex of the arc segment and its host-rock assemblage. The silicic dikes of porphyric microgranite, porphyric microgranodiorite and aplite consist of quartz, K-feldspar, plagioclase (albite), biotite and rare amphibole. The dikes are of subaluminous composition with shoshonitic affinity. Trace-element patterns exhibit pronounced negative anomalies of Nb, Ta, Ti, P and Sr together with positive anomalies of Cs, Th, U and La suggesting partial melting of a quartzo-feldspathic crustal source. The intermediate–basic dikes with phonolite, basanite and trachyandesite chemical compositions typically contain pyroxene (diopside–augite) and plagioclase phenocrysts (An 30–60 and An 98 ), calcic amphiboles (magnesiohornblende– magnesiohastingsite), magnesian biotites and alkali-feldspars (Or 95 ). The rocks show shoshonitic geochemical affinities. Low Ba/Rb ratios and high Rb/Sr ratios suggest that the primary dike melt originated by partial melting of a phlogopite-bearing lithospheric mantle, whereas LILE and LREE enrichment along with low Nb/Zr and Hf/Sm ratios and high Ba/ Nb and Rb/Nb ratios imply that these rocks formed at a convergent continental margin. The acidic dikes were emplaced in a transitional syn-collisional subduction setting whereas the intermediate–basic dikes have developed from remnant melt batches after cessation of active subduction, mostly in the post-collisional setting.

Magmatic and geodynamic evolution of Urumieh–Dokhtar basic volcanism, Central Iran: major, trace element, isotopic, and geochronologic implications

Basic volcanic rocks from the West Nain area of the Urumieh–Dokhtar Magmatic Assemblage demonstrate significant subduction-related geochemical characteristics; these along with the new age data obtained for the volcanic rocks shed new light on the geodynamic evolution of the Iranian segment of Alpine–Himalayan orogeny. The late Oligocene (26.5 Ma) high-Nb basic volcanic rocks are likely to represent a transient rather enriched asthenospheric mantle underlying the otherwise dominantly Eocene–early Oligocene West Nain island arc. Lithospheric mantle geochemical signatures of the low-Zr volcanic rocks (20.6 Ma) and high-Th volcanic rocks (19.7 Ma) imply replacement of the underlying mantle. The substitution of asthenospheric mantle by a lithospheric mantle wedge might have been associated with – or perhaps caused by – an increase in the subduction rate. Culmination of the West Nain magmatism into slab melting that produced the early Miocene (18.7 Ma) adakitic rocks is compatible with subsequent ascent that triggered slab decompression melting.

Attenuation of Ground-Motion Spectral Amplitudes and Its Variations across the Central Alborz Mountains

We selected 136 earthquakes recorded at stations of the Institute of Geo- physics of the University of Tehran (IGUT) during 1996-2007, in order to estimate the average attenuation parameters and variations of station corrections across the central Alborz mountains, the northern extension of the Alpine-Himalayan orogeny in wes- tern Asia. The selected events provide 1260 high signal-to-noise ratio (SNR) records with relatively good spatial coverage. We graphically find the distances at which the nature of geometrical spreading attenuation (R b ) changes significantly using a locally weighted scatterplot smoothing (LOWESS, local regression smoothing method) called robust LOWESS. A trilinear function with hinges at distances of about 80 and 160 km describes the geometric spreading attenuation with distance. By regressing to the hinged trilinear function, we found that b1 � −1:15 � 0:21, b2 � 0:09 � 0:31, and a fixed b3 � −0:5 minimize the average absolute value of the Fourier spectrum amplitude residuals. Using an anelastic attenuation coefficient at different frequencies, the direct quality factor Q in the central Alborz region is obtained as Q � 109 � 2f 0:64� 0:04 . The geographical distribution of station corrections at 1 Hz can be clearly separated along a dividing line connecting the North Tehran, Mosha, and Attari faults into two regions: the northern low-attenuating and the southern high attenuating regions. The stations with strong positive station corrections clearly align along the dividing line. This suggests the existence of a higher attenuation zone south of the dividing line. The presence of thick Tertiary-Quaternary sedimentary rocks with thick layers of salt in the southern region may explain the observed greater attenuation of seismic waves.

Crustal thickness variation across the northeast Iran continental collision zone from teleseismic converted waves

For the first time, we present the variation of crust–mantle boundary beneath the northeast Iran continental collision zone which is genetically part of the Alpine–Himalayan orogeny and beneath Central Iran which is a less-deformed tectonic block. The boundary was imaged by stacking teleseismic P–S converted phases and shows a strong variation of Moho from 27.5 km under Central Iran to 55.5 km beneath the Binalud foreland basin. The thickest crust is not located beneath the high topography of the Kopeh Dagh and Binalud mountain ranges suggesting that these mountain ranges are not supported by a crustal root. The simple gravity modeling of the Bouguer anomaly supports this idea.

Magmatism in the southeastern Anatolian orogenic belt: transition from arc to post-collisional setting in an evolving orogen

Abstract Late Cretaceous to Middle Eocene calc-alkaline to alkaline magmatic rocks emplaced within the southeastern Anatolian orogenic belt, the most extensive magmatic belt in Turkey, result from the complex collision between the Afro-Arabian and Eurasian plates and the subduction of the southern and northern Neotethyan oceanic basins beneath the Eurasian continental margin during the Alpine–Himalayan orogeny. In a transect in east-central Turkey extending from Baskil (Elazig) to Divrigi (Sivas) to the north, and from Copler (Erzincan) to Horozkoy (Nigde) to the SW, these magmatic rocks vary in time, spatial distribution, and composition. 40 Ar/ 39 Ar ages supplemented by a few U–Pb ages geochronology from major plutons demonstrate a general younging of magmatism in the transect from c . 83 Ma in the south (Baskil) to c . 69 Ma in the north (Divrigi-Keban), followed by a c . 44 Ma scattered magmatic complex now found along a NE trending arcuate belt between Copler and Horoz. In general, trace element and rare earth element (REE) geochemistry in the magmatic rocks suggest two main sources for the melts: (1) a mantle-wedge and subducted oceanic lithosphere producing arc-type magma; and (2) metasomatized lithospheric mantle modified by subduction producing magmatic rocks with more metasomatized mantle and within plate signatures. The combination of geochemical and geochronological data presented herein provides a basis to reconstruct the temporal and spatial transition from subduction-related to post-collision and to late-orogenic magmatism in the eastern Mediterranean region. Subduction-related magmatism is rooted to closure of the Neo-Tethyan Ocean whereas post-collision and late orogenic-within plate-related magmatism is driven by the collision of a northern promontory of the SE Anatolian orogenic belt with northerly derived ophiolitic rocks. The magmatic transition occurs regionally in northerly to northwesterly trending belts in the southeastern Anatolian orogenic belt. The magmatism exhibit a clear shift from deep seated arc-type to late-orogenic from south (Baskil) to more deeply eroded mid-crustal plutons at the north (Divrigi), then to magmatism related to incipient slab-rupture from northeast (Copler, Kabatas, Bizmisen-Calti) to SW (Karamadazi and Horoz). The age progression follows a south-to-north geochemical trend of decreasing crustal input into mantle-derived magmas, and is explained as a consequence of slab roll-back after the collision/obduction of northerly ophiolites followed by slab steepening and incipient rupture leading to transtensional block faulting and subsidence, and thus to the preservation of near-surface magmatic products along a NE trending belt.

Constraints on Miocene oceanography and climate in the Western and Central Paratethys: O-, Sr-, and Nd-isotope compositions of marine fish and mammal remains

The Paratethys evolved as a marginal sea during the Alpine–Himalayan orogeny in the Oligo-Miocene. Sediments from the northern Alpine Molasse Basin, the Vienna, and the Pannonian Basins located in the western and central part of the Paratethys thus provide unique information on regional changes in climate and oceanography during a period of active Alpine uplift. Oxygen isotope compositions of well-preserved phosphatic fossils recovered from the sediments support deposition under sub-tropical to warm-temperate climate with water temperatures of 14 to 28 °C for the Miocene. δ 18O values of fossil shark teeth are similar to those reported for other Miocene marine sections and, using the best available estimates of their biostratigraphic age, show a variation until the end of the Badenian similar to that reported for composite global record. The 87Sr/ 86Sr isotope ratios of the fossils follow the global Miocene seawater trend, albeit with a much larger scatter. The deviations of 87Sr/ 86Sr in the samples from the well-constrained seawater curve are interpreted as due to local input of terrestrially-derived Sr. Contribution of local sources is also reflected in the ε Nd values, consistent with input from ancient crystalline rocks (e.g., Bohemian Massif) and/or Mesozoic sediments with ε Nd < − 9. On the other hand, there is evidence for input from areas with Neogene volcanism as suggested by samples with elevated ε Nd values > − 7. Excluding samples showing local influence on the water column, an average ε Nd value of − 7.9 ± 0.5 may be inferred for the Miocene Paratethys. This value is indistinguishable from the ε Nd value of the contemporaneous Indian Ocean, supporting a dominant role of this ocean in the Western and Central Paratethys.

3: Geochronology and geodynamics of Late Cretaceous magmatism and Cu–Au mineralization in the Panagyurishte region of the Apuseni–Banat–Timok–Srednogorie belt, Bulgaria

The Apuseni–Banat–Timok–Srednogorie (ABTS) belt, Europe's most extensive belt of calc–alkaline magmatism and Cu–Au mineralization, is related to the subduction of the Tethys ocean beneath the European continental margin during the Late Cretaceous phase of the Alpine–Himalayan orogeny. Economic deposits are restricted to certain segments along the belt, and all major porphyry-style and high-sulphidation ore deposits in Bulgaria are aligned on the Panagyurishte corridor, a narrow zone obliquely crossing the ABTS belt. This paper reviews the geology, geochemistry and geochronology of igneous and hydrothermal events along this corridor, in a profile extending from the European continental basement in the north to the accretionary complex of the Rhodopes in the south. Extensive U–Pb dating of zircons from subvolcanic intrusions and major plutons, supplemented by published age data for magmatic rocks and hydrothermal ore deposits obtained by other methods, reveals a general younging of magmatism from ca. 92 Ma in the north (Elatsite) to ca. 78 Ma in the south (Capitan Dimitrievo). Cu–Au deposits are restricted to the northern and central parts of the profile (ranging in age from ∼92 to ∼86 Ma), while the southernmost part exposes more deeply eroded mid-crustal plutons devoid of economic mineralization. The age progression correlates with a north-to-south geochemical trend of decreasing crustal input into mantle-derived magmas. Magmatism and ore formation in individual magmatic–hydrothermal complexes along the profile is much shorter lived. For example, subvolcanic intrusions and porphyry Cu–Au mineralization at the Elatsite deposit and andesitic volcanism and high-sulphidation Au–As–Cu mineralization at Chelopech all occurred within a time span of about 1 million years. The age progression of calc–alkaline magmatism within the Panagyurishte region, Bulgaria, from north to south is explained as a consequence of slab retreat during oblique subduction. This led to transtensional block faulting and subsidence, and thus to the preservation of near-surface magmatic–hydrothermal products, including economic Cu–Au deposits. Accretion of continental fragments in the Rhodopes south of the ABTS belt led to greater uplift of the youngest Late Cretaceous intrusions. This removed any ore deposits that might have been formed in this area.

Reconstruction of the evolution of the Alpine-Himalayan orogen - an introduction

The Alpine-Himalayan belt is a young orogen suturing Gondwana-derived fragments with Eurasian continental crust. Its general structure, as a continuous belt of Mesozoic and Cenozoic deformation from Spain to Southeast Asia is described in the pioneering work of Argand (1924)(Figure 1). Further southeast, in the southwest Pacific, the orogenic belt is partly submerged but probably stretched as far as New Zealand (Figure 2). The advent of plate tectonics thirty-five years ago provided an explanation for the large-scale plate kinematics associated with Alpine-Himalayan orogeny. However, when it comes to details, plate tectonics has proved to be insufficient to reconstruct this complex system. In reality, the Alpine-Himalayan orogen has been subjected to numerous processes involving motions of smaller continental ribbons, retreating subduction systems, back-arc extension and accretion of magmatic arcs. In order to reconstruct the Alpine-Himalayan system, we need to analyse data derived from multidisciplinary sources and develop sets of spatio-temporal constraints. We can then test these constraints against a set of possible alternative reconstructions. Examples are the works of Dercourt et al. (1986; 1993; 2000) and Stampfli et al. (2001), which are extremely valuable to the reconstruction community. This volume includes ten contributions on the reconstruction of the tectonic evolution of the AlpineHimalayan orogen (see locations of study areas in Figure 3). The first paper by Martinez-Martinez & Azanon presents results of their study in the westernmost part of the Alpine-Himalayan orogen, the Gibraltar Arc. The authors provide evidence for two episodes of orthogonal extension in this region, and they discuss the significance of such events in terms of the regional kinematics and the evolution of the Alboran Sea. In the same region, Sanchez-Go mez et al. present structural and metamorphic analysis related to the emplacement of mantle peridotites within the Rif-Betic orogen. The authors argue that these peridotites were emplaced as a single slab during an Oligocene/Early Miocene suturing. Two contributions deal with the Pyrenean Mountains that formed a collisional plate boundary between Iberia and Europe until the Oligocene (Srivastava et al., 1990). Schellart presents results of a structural and sedimentological study of the western termination of the axial zone in the southern Pyrenees. These results provide the means for the construction of balanced cross sections and for crustal shortening calculations. Verge s et al. provide a comprehensive review of the tectonism in the Pyrenees since the Cretaceous. The authors analyse stratigraphical cross sections and lithospheric-scale transects, and discuss transitions between crustal shortening and extensional regimes. A plate reconstruction of western Tethys is presented by Stampfli et al., with an emphasis on orogeny in the western Alps. The latter is probably the most studied segment of the Alpine-Himalayan belt, but is still controversial as far as tectonic reconstruction is concerned.

Oxygen, strontium, and neodymium isotope composition of fossil shark teeth as a proxy for the palaeoceanography and palaeoclimatology of the Miocene northern Alpine Paratethys

The Upper Marine Molasse sediments of southern Germany were deposited during the Early to Middle Miocene, a period of significant change for the global Miocene palaeoceanography, palaeoclimate, and the regional palaeogeography because of the ongoing Alpine–Himalayan orogeny. To address the influence of the Alpine uplift on climate and oceanography of the northern Alpine molasse basin, a combined O-, Sr-, and Nd-isotope study was undertaken on fossil teeth from sharks ( Synodontaspis sp., Galeocerdo cf. aduncus, Chaenogaleus sp.), and button-like teeth from the bony fish of the Upper Marine Molasse ( Chrysophrys molassica). Average δ 18O values for hydroxyapatite of teeth from two sites are 20.3‰ (1 σ=0.6) and 21.2‰ (1 σ=0.5), while their average 87Sr/ 86Sr and 143Nd/ 144Nd ratios are 0.70850 (±0.00001, 2 σ) and 0.70882 (±0.00003, 2 σ), and 0.51220, and 0.51223 (both at ±0.00001, 2 σ), respectively. By comparison to the Sr-evolution curve for the global ocean, the Sr-isotope compositions suggest ages of about 22 and 17 Ma for the teeth. These ages are in good agreement with the depositional ages, which suggests open marine conditions. Open marine conditions are also compatible with (1) lower average δ 18O values and 87Sr/ 86Sr ratios for the one site compared to higher δ 18O values and higher 87Sr/ 86Sr ratios for the other site, (2) estimates for seawater temperatures which are similar to other estimates from deposits of similar latitude and age, (3) a comparison of seawater temperatures with average ambient air temperature estimates deduced from continental palaeoclimate indicators. Nd-isotope compositions are compatible with an influence of the North Atlantic on the Paratethys. Assuming constant salinity and seawater oxygen isotope composition, a 4°C cooling can be inferred from average δ 18O values of the teeth between 22 and 17 Ma. This is similar to trends observed for foraminiferal records from the Mediterranean Tethys, but different from foraminiferal and molluscan records of the North Atlantic and the North Sea during this period, and allows for the possibility that the Alpine orogeny had an influence on the regional, circum-Alpine climate.