Evolution of K-rich magmas derived from a net veined lithospheric mantle in an ongoing extensional setting: Geochronology and geochemistry of Eocene and Miocene volcanic rocks from Eastern Pontides (Turkey) |
| |
| Institution: | 1. Department of Mining Engineering, Gümü?hane University, TR-29000 Gümü?hane, Turkey;2. Department of Geological Engineering, Karadeniz Technical University, TR-61080 Trabzon, Turkey;3. CNRS (CNRS/INSU) UMR 6118, Géosciences Rennes, Université de Rennes 1, F-35042 Rennes Cedex, France;4. Université de Rennes 1, Géosciences Rennes, F-35042 Rennes Cedex, France;1. Van Yüzüncü Y?l University, Faculty of Architecture and Engineering, Department of Mining Engineering, Zeve Campus, 65080 Van, Turkey;2. Istanbul University, Faculty of Engineering, Department of Geological Engineering, 34320 Avc?lar, Istanbul, Turkey;3. Russian Academy of Sciences, Institute of the Ore Deposits Geology, Petrology, Mineralogy and Geochemistry, Moscow, Russia;1. Çukurova University, Engineering Faculty, Geological Engineering Department, 01330, Adana, Turkey;2. University of Salzburg, Fachbereich für Geographie und Geologie, A-5020, Salzburg, Austria;3. University of Vienna, Department of Lithospheric Research, A-1090, Austria |
| |
| Abstract: | The Eocene and Miocene volcanic rocks between the cities of Trabzon and Giresun in the Eastern Pontides (NE Turkey) erupted as mildly and moderately alkaline magmas ranging from silica-saturated to silica-undersaturated types. 40Ar-39Ar dating and petrochemical data reveal that the studied volcanic rocks are discriminated in two: Lutetian (Middle Eocene) mildly alkaline, (basaltic rocks: 45.31 ± 0.18 to 43.86 ± 0.19 Ma; trachytic rocks: 44.87 ± 0.22 to 41.32 ± 0.12 Ma), and Messinian (Late Miocene) moderately alkaline volcanic rocks (tephrytic rocks: 6.05 ± 0.06 and 5.65 ± 0.06 Ma). The trace and the rare earth element systematic, characterised by moderate light earth element (LREE)/heavy rare earth element (HREE) ratios in the Eocene basaltic and trachytic rocks, high LREE/HREE ratios in the Miocene tephrytic rocks, and different degrees of depletion in Nb, Ta, Ti coupled with high Th/Yb ratios, show that the parental magmas of the volcanic rocks were derived from mantle sources previously enriched by slab-derived fluids and subducted sediments. The Sr, Nd and Pb isotopic composition of the Eocene and Miocene volcanic rocks support the presence of subduction-modified subcontinental lithospheric mantle. During the magma ascent in the crust, parental magmas of both the Eocene and Miocene volcanic rocks were mostly affected by fractional crystallisation rather than assimilation coupled with fractional crystallisation and mixing. The silica-undersaturated character of the Miocene tephrytic rocks could be attributed to assimilation of carbonate rocks within shallow-level magma chambers. The parental magmas of the Eocene volcanic rocks resulted from a relatively high melting degree of a net veined mantle and surrounding peridotites in the spinel stability field due to an increase in temperature, resulting from asthenospheric upwelling related to the extension of lithosphere subsequent to delamination. The parental magmas for the Miocene volcanic rocks resulted from a relatively low melting degree of a net veined mantle domain previously modified by metasomatic melts derived from a garnet peridotite source after decompression due to extensional tectonics, combined with strike-slip movement at a regional scale related to ongoing delamination. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
