Bahatlar volkanitlerinin (Emet-Kütahya) petrografisi ve jeokimyası

Abstract

Batı Anadolu’da Eosen-Kuvaterner yaş aralığında volkanik kayaçlar yaygın olarak yüzlek vermektedir. Erken Miyosen volkanitleri Kütahya ve çevresinde andezit, dasit ve riyolitler şeklinde temsil edilmektedir. Bu çalışmada Emet Bor Havzası’nda yüzeyleyen riyolitlerden oluşan volkanik birimin tüm kayaç, Sr-Nd-Pb ve O izotop jeokimyası ile K-Ar jeokronolojisi çalışmaları yapılmıştır. Genel olarak vitrofirik porfirik dokuda gözlenen volkanitlerin bileşimini plajiyoklaz, biyotit, kuvars, sanidin ve amfibol mineralleri oluşturmaktadır. Kalkalkalen afinite gösteren ve yüksek-K içeren volkanitlerin, ana ve iz element değişimleri, kayaçların gelişiminde plajiyoklas, amfibol, biyotit ve alkali feldispat fraksiyonlaşmasının etkili olduğuna işaret etmektedir. Ayrıca yüksek LILE ve LREE ile düşük Nb, Zr, Y ve Ti içerikleri; bu volkanitlerin gelişiminde fraksiyonel kristallenme, kabuk katkısı ve/veya asimilasyonun kayaçların oluşumunda önemli bir rol oynadığını ve ana magmalarının zenginleşmiş bir kaynaktan türediğine işaret etmektedir. Tüm kayaç K-Ar yaşlandırma yöntemi ile, incelenen volkanitlere ait örneğin yaşının 21.4±0.6 My olduğunu göstermektedir. Elde edilen izotop sonuçlarına göre; (87Sr/86Sr)i oranı 0.708885, (143Nd/144Nd)i oranı 0,512347 206Pb/204Pb izotop oranı 19.04, 207Pb/204Pb izotop oranı 15,6790 ve 208Pb/204Pb izotop oranı 37.9130 ve δ18O oranı ise 11.3 ‰ olarak belirlenmiştir. Elde edilen jeokronolojik, jeokimyasal ve izotopik veriler incelenen volkanitlerin volkanik yay ortamında oluştuğunu ve oluşumunda fraksiyonel kristallenme ile beraber ayrıca kaynak manto bölgesinde zenginleşme ve kabuk kirliliğinin/asimilasyon (AFC) süreçlerinin etkisini taşıdığını işaret etmektedir.

Keywords

• Miyosen volkanitleri
• K-Ar jeokronolojisi
• Sr-NdPb ve O izotop jeokimyası
• Emet bor havzası
• Kütahya

Petrography and geochemistry of Bahatlar volcanites (Emet-Kütahya)

Abstract

In western Anatolia, volcanic rocks in the Eocene-Quaternary age range are widely outcropped. Early Miocene volcanites are represented as andesite, dacite and rhyolites in Kütahya and its surroundings. In this study, the whole rock, Sr-Nd-Pb and O isotope geochemistry and K-Ar geochronology data of the volcanic unit consisting of rhyolites outcropping in the Emet Borate Basin will be presented. Petrographic properties of the studied volcanites are generally observed in the porphyritic vitrophyric texture, and their composition consists of plagioclase, biotite, quartz, sanidine and amphibole minerals. The major and trace element variation of the volcanites, which have calc-alkaline affinity and contain high-K, indicate that plagioclase, amphibole, biotite and alkali feldspar fractionation is effective in the evolution of rocks. In addition, high LILE and LREE and low Nb, Zr, Y and Ti contents indicate that fractional crystallization, crustal contamination and/or assimilation play an important role in the evolution of volcanites and that their main magmas are derived from an enriched source. The whole rock K-Ar aging method shows that the age of the sample belonging to the studied volcanites is 21.4±0.6 Ma. According to the obtained isotope results, (87Sr/ 86Sr)i ratio is 0.708885, ( 143Nd/144Nd) i ratio is 0.512347206Pb/204Pb isotope ratio 19.04, 207Pb /204Pb isotope ratio is 15.6790 and 208Pb/204Pb isotope ratio is 37.9130 and δ18O ratio is 11.3 ‰. The obtained geochronological, geochemical, and isotopic data indicate that the investigated volcanites were formed in the volcanic arc environment and that fractional crystallization, as well as enrichment in the source mantle area and crustal pollution / assimilation (AFC) processes, have been influenced in their evolution.

Keywords

• Miocene volcanites
• K-Ar geochronology
• Sr-Nd-Pb and O isotope geochemistry
• Emet borate basin
• Kütahya.

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