Magma chamber processes and dynamics beneath northwestern Anatolia: Insights from mineral chemistry and crystal size distributions (CSDs) of the Kepsut volcanic complex (NW Turkey)

Ömer Kamacı*, Şafak Altunkaynak

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Özet

Mineral chemistry, petrography and crystal size distributions of Early Miocene mafic and intermediate lavas from the Kepsut Volcanic Complex (KVC) have been studied to decipher magma chamber processes and dynamics beneath northwestern Anatolia. KVC which is a part of the Western Anatolian Volcanic Province comprises lavas represented by various compositions ranging from basaltic andesite to rhyodacite and associated pyroclastics. Basaltic andesite and andesite lavas of the KVC, the focus of this study, present distinct petrographical features such as three plagioclase generations, patchy zoning, oscillatory reverse zoning, sieve textured crystals and clinopyroxene-mantled amphibole that are clear indicators of disequilibrium conditions in magma chamber(s). Petrography, mineral chemistry and crystal size distribution studies of andesite and basaltic andesite lavas of the KVC indicate that magma evolution occurred in four stages: (I) Near-Equilibrium Stage, (II) Mafic Input Stage, (III) Mixing/Mingling Stage and (IV) Pre-eruption Stage. Thermobarometry calculations indicate that crystallization of andesite and basaltic lavas occurred at similar pressure (mid-to-deep crustal depths, 5–7 kbar) but distinct temperature conditions (920–952 °C and 921–1069 °C, respectively) suggesting that KVC magmas evolved either in the same or different magma chambers at similar depths and experienced open-system processes. Both of these hypotheses are compatible with multistage evolution of the KVC. Combined petrography, mineral chemistry and geothermometry studies on KVC rocks indicate that mixing/mingling processes and subsequent decompression-driven crystallization were the principal mechanisms for the origin of the textural and mineralogical diversity that is characteristic of KVC lavas. Disequilibrium crystallization was probably caused by the influx of a hotter basaltic magma into crustal magma chambers during the first major period of north-south extension in western Anatolia.

Orijinal dilİngilizce
Makale numarası103889
DergiJournal of Asian Earth Sciences
Hacim181
DOI'lar
Yayın durumuYayınlandı - 1 Eyl 2019

Bibliyografik not

Publisher Copyright:
© 2019 Elsevier Ltd

Finansman

This study was supported by research grants from the Scientific & Technical Research Council of Turkey ( TUBITAK-CAYDAG-109Y082 and TUBITAK-2214-A International Doctorate Research Fellowship) and from Istanbul Technical University (Scientific Research Projects - BAP project 36010). Constructive reviews of A. Schmitt and an anonymous reviewer helped us improve the presentation and the scientific content of our paper. We are grateful to S. Yarar and A. Ünal for their help in the field.

FinansörlerFinansör numarası
Scientific & Technical Research Council of TurkeyTUBITAK-2214-A, TUBITAK-CAYDAG-109Y082
Istanbul Teknik Üniversitesi36010

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