Olivine basalt and trachyandesite peperites formed at the subsurface/surface interface of a semi-arid lake: An example from the Early Miocene Bigadiç basin,western Turkey |
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| Institution: | 1. University of Pittsburgh, 200 SRCC, Pittsburgh PA 15260, United States;2. University of South Wales, Pontypridd, RCT CF37 4BD, UK;3. The Open University in Scotland, 10 Drumsheugh Gardens, Edinburgh EH3 7QJ, UK;4. The University of Iceland, Askja, Sturlagata 7, 101 Reykjavik, Iceland;1. Department of Geological Sciences, The University of Texas at Austin, Jackson School of Geosciences, 1 University Station C1100, Austin, TX 78712, USA;2. Department of Geology, Dokuz Eylül University, Tinaztepe-Buca-35160, ?zmir, Turkey;3. Department of Geological Engineering, Dumlup?nar University, Main Campus, Tavþanlý Road 10 Mileage 43270 Kütahya, Turkey;1. Institute of Geodynamics, Romanian Academy, Jean-Louis Calderon 19-21, Bucharest 020032, Romania;2. Dokuz Eylül Üniversitesi, Mühendislik Fakültesi, Jeoloji Mühendisli?i Bölümü, TR-35160 ?zmir, Turkey;3. Institute of Nuclear Research, Hungarian Academy of Sciences, P.O. Box 51, Bem ter 18/c, H-4001, Debrecen, Hungary;1. Akdeniz University, Vocational School of Technical Sciences, Antalya, Turkey;2. Akdeniz University, Department of Geological Engineering, Antalya, Turkey;3. Dokuz Eylül University, Department of Geological Engineering, Buca-?zmir, Turkey;4. Karadeniz Technical University, Department of Geological Engineering, Trabzon, Turkey;5. Center for Earth Sciences, Department of Lithospheric Research UZA II, Vienna, Austria |
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| Abstract: | Miocene successions in western Turkey are dominated by lacustrine, fluvial and evaporitic sedimentary deposits. These deposits include considerable amounts of volcaniclastic detritus derived from numerous NE-trending volcanic centres in western Turkey as well as in the Bigadiç region. Early Miocene syn-depositional NE-trending olivine basalt and trachyandesite bodies that formed as intrusions and lava flows occur within the Bigadiç borate basin. Olivine basalts occur as partly emergent intrusions, and trachyandesite dykes fed extensive lava flows emplaced in a semi-arid lacustrine environment.Peperites associated with the olivine basalt and trachyandesites appear to display contrasting textural features, although all the localities include a large variety of clast morphologies from blocky to fluidal. Fluidal clasts, mainly globular, ameboidal and pillow-like varieties, are widespread in the peperite domains associated with olivine basalts, apparently due to large-volume sediment fluidisation. In contrast, fluidal clasts related to trachyandesites are restricted to narrow zones near the margins of the intrusions and have commonly elongate and polyhedral shapes with digitate margins, rather than globular and equant varieties. Blocky and fluidal clasts in the olivine basalt peperite display progressive disintegration, suggesting decreasing temperature and increasing viscosity during fragmentation. Abundance of blocky clasts with respect to fluidal clasts in the trachyandesite peperite indicates that the fluidal emplacement and low-volume sediment fluidisation in the early stages were immediately followed by quench fragmentation due to the high viscosity of the magma.Size, texture and abundance of the blocky and fluidal clasts in the olivine basalt and trachyandesite peperites were mainly controlled by sediment fluidisation, pulsatory magma injection and magma properties such as composition, viscosity, vesicularity, and size, abundance and orientation of phenocrysts. Variously combining these contrasting features to varying degrees may form diverse juvenile clast shapes in peperitic domains. |
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