Intracontinental Quaternary Volcanism in the Niksar Pull-Apart Basin, North Anatolian Fault Zone, Turkey

Orhan TATAR; Sema YURTMEN; Haluk TEMİZ; Halil GÜRSOY

Article Details

Intracontinental Quaternary Volcanism in the Niksar Pull-Apart Basin, North Anatolian Fault Zone, Turkey

Authors:

Orhan TATAR | Sema YURTMEN | Haluk TEMİZ | Halil GÜRSOY

Publisher:

TUBITAK

Main Topics:

Applied physics

Journal:

Turkish Journal of Earth Sciences 2007 Vol.16 Issue 4, pp.417-440

Document Type:

Article

Publication Date:

3/2007

Document Language:

English

Document ID (Org No.):

2000732572

Frequency:

Bimonthly

eISSN:

1303-619X

pISSN:

1300-0985

Abstract:

 

The Niksar Basin is sited along the eastern segment of the North Anatolian Fault Zone in Turkey. It is a young sigmoidal pull-apart basin bordered by two non-parallel master faults associated with earthquakes in 1939 and 1942. The fault geometry along the irregular ENE margin of the basin is complex where young Plio-Quaternary volcanic rocks reach the surface along pairs of steep strike-slip faults which cut the basin sediments. The volcanic rocks around the Niksar Basin have been dated by high precision K-Ar dating and the ages range between 542 ± 9 ka and 567 ± 9 ka. The lavas are mainly alkaline (sodium dominated) in nature and include basaltic trachandesite (mugearite) and trachyandesite (benmoreite) with minor sub-alkaline compositions of dacitic andesite, rhyodacite and rhyolite. Despite the large compositional gap between basaltic and felsic lavas, major and trace element distributions indicate that both the basaltic and felsic lavas are cogenetic. Abundances of major oxides and trace elements vary systematically through this compositional spectrum. Fractional crystallization of the observed phases accounts for the diversity of intermediate and evolved products. Amphibole fractionation in basalts at depth causes the trend towards silica saturation while alkali feldspar fractionation dominates the final stages of crystallization. Significant crustal contamination has occured in the evolved magmas but contamination is generally minimal or absent in their basaltic parents.  Alkaline basaltic rocks have OIB (ocean island basalt) like trace element patterns characterized by enrichment in LILE, HFSE, LREE and slight depletion in HREE relative to primitive mantle values. Overall geochemical variations indicate the combined effects of different degrees of partial melting, fractional crystallization and variable degrees of crustal contamination.

 

Kuzey Anadolu Fay Zonu’nun do¤u segmentleri üzerinde yer alan Niksar Havzas› 1939 ve 1942 depremleri ile iliflkili birbirine paralel olmayan iki ana fay ile s›n›rl›, genç sigmoidal bir çek-ay›r havzad›r. Fay geometrisi havzan›n düzensiz DKD kenar›nda karmafl›kt›r. Burada genç Pliyo–Kuvaterner yafll› volkanik kayaçlar havza sedimanlar›n› da kesen do¤rultu-at›ml› fay çiftleri boyunca yüzeye ç›kmaktad›r. Niksar havzas› civar›nda yüzeyleyen volkanik kayaçlar yüksek hassasiyetli K-Ar yötemiyle yaflland›r›lm›fl olup, yafllar 542 ± 9 ka ve 567 ± 9 ka aras›ndad›r. Lavlar ço¤unlukla alkalin (sodyumca zengin) özelliktedir ve bazaltik trakiandezit (Mujearit) and trakiandezit (benmorit) ile az oranda sub-alkalin bileflimli dasit, andezit, riyodasit ve riyolitten oluflmaktad›r. Bazaltik ve felsik lavlar aras›nda büyük bir bileflimsel boflluk olmas›na ra¤men, ana ve iz element da¤›l›mlar› hem bazaltik hem de felsik lavlar›n eflkökenli oldu¤unu gösterir. Ana oksitlerin ile iz elementlerin bollu¤u sistematik olarak bu bileflimsel da¤›l›m içinde çeflitlilik sunmaktad›r. Gözlenen fazlardaki fraksiyonel kristalleflme ortaç ve ileri derecede geliflmifl ürünlerdeki farkl›l›¤› ifade etmektedir. Derinde bazaltlardaki amfibol fraksiyonelleflmesi silikatca doygun bir yönelime neden olurken, alkali feldispat fraksiyonelleflmesi ise kristalleflmenin son evrelerini iflaret etmektedir. Belirgin kabuksal kirlenme geliflmifl magma içerisinde oluflmufltur, fakat kirlenme genellikle bunlar›n bazaltik ürünlerinde çok az yada hiç yoktur. Alkali bazaltik kayaçlar OIB (okyanus adas› bazaltlar) benzeri, LILE, HFSE, LRE zenginleflmesi ve az miktarda ilksel manto de¤erlerine nazaran azalma gösteren HREE de¤erleriyle karakterize edilen iz element da¤›l›mlar› sunmaktad›r. Tüm jeokimyasal da¤›l›mlar farkl› derecelerdeki k›smi ergime olay›n›n birleflik etkisini, fraksiyonel kristalleflmeyi ve de¤iflik derecelerde kabuksal kirlenmeyi göstermektedir.

Article Details

Intracontinental Quaternary Volcanism in the Niksar Pull-Apart Basin, North Anatolian Fault Zone, Turkey

Authors: Orhan TATAR | Sema YURTMEN | Haluk TEMİZ | Halil GÜRSOY

Publisher: TUBITAK

Main Topics: Applied physics

Journal: Turkish Journal of Earth Sciences 2007 Vol.16 Issue 4, pp.417-440

Document Type: Article

Publication Date: 3/2007

Document Language: English

Document ID (Org No.): 2000732572

Frequency: Bimonthly

eISSN: 1303-619X

pISSN: 1300-0985

Issues

Authors:

Orhan TATAR | Sema YURTMEN | Haluk TEMİZ | Halil GÜRSOY

Publisher:

TUBITAK

Main Topics:

Applied physics

Journal:

Turkish Journal of Earth Sciences 2007 Vol.16 Issue 4, pp.417-440

Document Type:

Article

Publication Date:

3/2007

Document Language:

English

Document ID (Org No.):

2000732572

Frequency:

Bimonthly

eISSN:

1303-619X

pISSN:

1300-0985