Upper Cretaceous volcano-sedimentary successions in the Central Pontides of Turkey, related to th... more Upper Cretaceous volcano-sedimentary successions in the Central Pontides of Turkey, related to the closure of the Tethys Ocean, include a variety of alkaline ultrapotassic igneous rocks that have been classified as leucititic, lamprophyric and trachytic based on their mineral paragenesis. Although the ultrapotassic rocks display a range of K 2 O contents (0Á9-8Á4 wt %) that may partly reflect alteration processes, they display subduction-related trace element signatures characterized by significant enrichment of large ion lithophile elements and light rare earth elements relative to high field strength elements and heavy rare earth elements and depletion of Nb and Ta. However, their initial Nd-Sr isotope compositions plot within the mantle array. The nature of the mantle source of their parental magmas is inferred to be highly complex, involving contributions from several different components based on contrasting geochemical and isotopic features: (1) a depleted mantle source, which is indicated by unradiogenic 87 Sr/ 86 Sr i (0Á70449-0Á70609) and radiogenic 143 Nd/ 144 Nd i (0Á51252-0Á51269); (2) an obvious requirement of mantle phlogopite to explain the high potassium contents; (3) slabderived fluids, which are indicated by ultra-low d 18 O cpx ratios regardless of the ultrapotassic rock type (2Á4-5ø), with high Ba/La and Nb/Ta, low Th/La and the most radiogenic 143 Nd/ 144 Nd i ; (4) a contribution from subducted sediments giving rise to low Ce/Pb ratios and high Th contents; (5) the introduction of convective mantle into the source region with an asthenospheric Pb isotope signature. Whereas the differentiation of silica-undersaturated leucititic and lamprophyric magmas was driven by heteromorphic reactions, owing to the absence of major and trace element variations between the resultant rock types, the formation of silica-saturated trachytic rocks was the result of assimilation-fractional crystallization processes. We propose that a complex sequence of subduction events, starting from at least the Middle Triassic, caused metasomatism of the depleted mantle source and the generation of the Late Cretaceous ultrapotassic parental magmas, facilitated by slab roll-back followed by slab tearing.
Petrology and geochemistry of late Cretaceous lamprophyric rocks from North Anatolian Ophiolitic Melange-Turkey
Subduction-related High-to Ultrahigh-Potassic Rocks of the Ankara-Erzincan Suture Belt of Turkey: a geochemical and isotopic approach to source and petrogenesis
A Late Cretaceous Volcano-sedimantary Succession (LCVS) trends parallel to Neo-Tethyan Suture in ... more A Late Cretaceous Volcano-sedimantary Succession (LCVS) trends parallel to Neo-Tethyan Suture in North Central Anatolia. Volcanic members of the LCVS consist mainy of coeval leucite phonolite/tephrites, trachytes, lamprophyres and andesitic rocks. Obtained Ar-Ar ages reveal that the volcanic activity occurred between 73.6±0.18 and 76.78±0.19 Ma, contemporaneous with the subduction of the Neo-Tethyan ocean beneath the Pontides. The volcanic rocks of LCVS are classified as alkaline, High-to ultrahigh-K, and silica-saturated and silica-unsaturated, geochemically. Rare calc-alkaline andesitic lavas are also occur within the volcanic sucession. Except the calc-alkaline samples, magmatic members of LCVS have similar major and trace element concentrations similar to the plagioleucitites or ultrapotassic rocks of the active orogenic zones (i.e. the Roman Province ultrapotassic series, Peccerillo, 2005). The multi element patterns on N-MORB-and Chondrite-normalized spider diagrams are characterized by significant LILE and LREE enrichments relative to HFSE and HREE, and display apparent Nb and Ta depletions, implying the subduction-related magmas. 87 Sr/ 86 Sr (i) (0.704493-0.706090) and 143 Nd/ 144 Nd (i) (0.512523-0.512680) isotope ratios are close to the mantle array, and are also in between the Aeolian Islands CA-Potassic rocks (Peccerillo, 2005), BSE and the circum-Mediterranean anorogenic Cenozoic igneous province (CiMACI, Lustrino&Wilson, 2007). Variable Mg# (33-60) evidences that these rocks are the products of evolved melts. The lead isotope values display a trend between EMI and DM, suggesting that the crustal involvement is more effective process during the generation of some lamprophyres relative to the other ultrapotassic rocks of LCVS. The results of clinopyroxene thermobarometry calculations reveal significant differences in depth of crys-tallization for the rock suites. Some trace element abundances and inter elemental ratios together with their co-variations show that the magmatic rock suites of LCVS had different crystallization history. REE melting modelings suggest a common mantle source, which contains variable amount of spinel lerzolite and garnet lerzolitic proportions. Considering the presence of some phlogopite-bearing clinopyroxenite xenolits in the lamprophyre and the leucite-bearing rocks, we propose that the LCVS ultrapotassic rocks were possibly derived from the low degree partial melting of veined SCLM.
Petrological characterization of the seismic low-velocity anomaly beneath the Eifel volcanic field (West Germany) using major and trace element compositions of olivine macrocrysts
Since the late 1970s, it has been increasingly recognized that the petrology and geochemistry of ... more Since the late 1970s, it has been increasingly recognized that the petrology and geochemistry of ophiolites predominantly resemble those of lithological units from intra-oceanic subduction zones, ranging from nascentand fore-to intra-or back-arcs, ruling out analogy with modern oceanic ridge lithosphere. This conclusion is
High-Mg ultrapotassic volcanic rock occurrences of lamproitic affinity are exposed in southwester... more High-Mg ultrapotassic volcanic rock occurrences of lamproitic affinity are exposed in southwestern Anatolia, mostly within the Menderes Massif. From north to south the lamproitic volcanism shows increasingly younger ages ranging from 20 to 4 Ma. Volcanism is contemporaneous with more voluminous shoshonitic, high-K calc-alkaline, and ultrapotassic magmatic activity in the Simav^Selendi, Us°ak, K|rka, Ko« ro! glu, Afyon and Isparta^Go« lcu« k areas. The southward decrease in the age of the volcanism correlates with changes in geochemical composition, particularly a decrease in 87 Sr/ 86 Sr, 207 Pb/
Lamproites are among the most enigmatic mantle generated melts, and are typically abundant in phl... more Lamproites are among the most enigmatic mantle generated melts, and are typically abundant in phlogopite. We investigated the major and trace element chemistry of phlogopite crystals from Mediterranean lamproite occurrences in Spain, Serbia and Turkey. The most primitive lamproite samples were selected in order to evaluate the generation of the different phlogopite populations in their distinct mantle setting(s). Phlogopite hosted in Mediterranean lamproites can be grouped into different compositional arrays on the basis of their major element chemistry using Al 2 O 3 , FeO T and TiO 2 concentrations. Contents of Cr, F and presumably Ti allow discrimination of the macrocrysts into phlogopite phenocrysts, which are liquidus and near-liquidus phases, and mantle xenocrysts. Further distinction among different populations of mantle-derived phlogopite can be achieved, considering trace element and isotopic ratios. The latter also distinguish between crustal and asthenospheric imprints on the source of the lamproitic parental melt.
Pb isotopes and geochronology of amphibole-and mica-bearing lamprophyres in northwestern Iran: Im... more Pb isotopes and geochronology of amphibole-and mica-bearing lamprophyres in northwestern Iran: Implications for mantle wedge heterogeneity in a paleo-subduction zone,
Afyon Zone, which was derived from the Anatolide-Tauride platform during closure of the Neo-Tethy... more Afyon Zone, which was derived from the Anatolide-Tauride platform during closure of the Neo-Tethys, is made up of pre-Mesozoic basement and unconformably overlying Triassic-Early Tertiary cover series. The Afyon Zone contains widespread metavolcanic rocks, which are dominated by rhyolite, dacite, and trachyandesite. They form a distinct volcanic succession, which is separated from the underlying Silurian-Lower Carboniferous metacarbonates and meta-siliciclastics by a regional unconformity. Trachyandesitic metavolcanics are made up of massive lava flows, pyroclastics and epiclastics, less frequently, domes and dikes, which were developed on a deeply eroded subaerial landmass. U/Pb and Pb/Pb zircon geochronology yielded Lower Triassic (*250 Ma) ages, which are interpreted as extrusion age of trachyandesitic volcanics. Based on the stratigraphic, geochronological, and geochemical data, we suggest that these Lower Triassic magmatic rocks represent an extensional tectonic setting on the northern active margin of the Gondwana, which led to the development of the northern branch of the Neo-Tethys.
Lamprophyres of different age showing distinctive mineralogy, geochemistry and isotopic ratios ar... more Lamprophyres of different age showing distinctive mineralogy, geochemistry and isotopic ratios are exposed in northwestern Iran. They can be divided into Late Cretaceous sannaite, Late Oligocene-Early Miocene camptonite (amphibole-bearing) and Late Miocene minette (mica-bearing) and spessartite (amphibole-bearing) lamprophyres.
Sannaites have high-Ti amphibole along with high-Ti and Al clinopyroxene, and they are characterised by homogeneous enrichment in incompatible trace elements with troughs at Pb. Spessartites have hornblende and low-Al and Ti clinopyroxene, and they are characterised by enriched incompatible trace element pattern with depletions of Nb, Ta, Pb, and Ti with respect to large ion lithophile elements. Minettes have high-Ti and Al brown mica and low-Al and Ti clinopyroxene, and similarly to spessartite, are characterised by fractionation of high field strength elements with respect to large ion lithophile elements, with troughs at Nb, Ta, and Ti and a peak at Pb. Minettes show high initial 87Sr/86Sr values up to 0.70760 and low initial 143Nd/144Nd down to 0.512463 with a negative correlation, consistent with the trace element distribution related with an enriched mantle source modified after sediment recycling during subduction and continental collision.
Cretaceous sannaites and Early Miocene spessartites show low initial 87Sr/86Sr approaching 0.70447 and high 143Nd/144Nd values up to 0.512667, which are consistent with a depleted within-plate mantle source. Minette and spessartite lamprophyres show high initial 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values, whereas sannaites have lower, but variable, initial 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values with respect to those of calc-alkaline lamprophyres. Minettes originated by partial melting of a metasomatised lithospheric mantle following siliciclastic sediment recycling by subduction. In contrast, sannaites were generated from the partial melting of a similar lithospheric mantle that was metasomatised by within-plate agents.
Uploads
Papers by Prelevic Dejan
Sannaites have high-Ti amphibole along with high-Ti and Al clinopyroxene, and they are characterised by homogeneous enrichment in incompatible trace elements with troughs at Pb. Spessartites have hornblende and low-Al and Ti clinopyroxene, and they are characterised by enriched incompatible trace element pattern with depletions of Nb, Ta, Pb, and Ti with respect to large ion lithophile elements. Minettes have high-Ti and Al brown mica and low-Al and Ti clinopyroxene, and similarly to spessartite, are characterised by fractionation of high field strength elements with respect to large ion lithophile elements, with troughs at Nb, Ta, and Ti and a peak at Pb. Minettes show high initial 87Sr/86Sr values up to 0.70760 and low initial 143Nd/144Nd down to 0.512463 with a negative correlation, consistent with the trace element distribution related with an enriched mantle source modified after sediment recycling during subduction and continental collision.
Cretaceous sannaites and Early Miocene spessartites show low initial 87Sr/86Sr approaching 0.70447 and high 143Nd/144Nd values up to 0.512667, which are consistent with a depleted within-plate mantle source. Minette and spessartite lamprophyres show high initial 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values, whereas sannaites have lower, but variable, initial 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values with respect to those of calc-alkaline lamprophyres. Minettes originated by partial melting of a metasomatised lithospheric mantle following siliciclastic sediment recycling by subduction. In contrast, sannaites were generated from the partial melting of a similar lithospheric mantle that was metasomatised by within-plate agents.