Geochemistry of tholeiitic to alkaline lavas from the east of Lake Van (Turkey): Implications for a late Cretaceous mature supra-subduction zone environment

Geochemistry of tholeiitic to alkaline lavas from the east of Lake Van (Turkey): Implications for a late Cretaceous mature supra-subduction zone environment

Accepted Manuscript Geochemistry of tholeiitic to alkaline lavas from the east of Lake Van (Turkey): Implications for a late Cretaceous mature supra s...

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Accepted Manuscript Geochemistry of tholeiitic to alkaline lavas from the east of Lake Van (Turkey): Implications for a late Cretaceous mature supra subduction zone environment Yavuz Özdemir PII:

S1464-343X(16)30134-0

DOI:

10.1016/j.jafrearsci.2016.04.018

Reference:

AES 2554

To appear in:

Journal of African Earth Sciences

Received Date: 31 January 2016 Revised Date:

13 April 2016

Accepted Date: 21 April 2016

Please cite this article as: Özdemir, Y., Geochemistry of tholeiitic to alkaline lavas from the east of Lake Van (Turkey): Implications for a late Cretaceous mature supra subduction zone environment, Journal of African Earth Sciences (2016), doi: 10.1016/j.jafrearsci.2016.04.018. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT

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GEOCHEMISTRY OF THOLEIITIC TO ALKALINE LAVAS FROM THE EAST OF

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LAKE VAN (TURKEY): IMPLICATIONS FOR A LATE CRETACEOUS MATURE

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SUPRA SUBDUCTION ZONE ENVIRONMENT

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Yavuz Özdemir

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Yüzüncü Yıl University, Department of Geological Engineering, Van, Turkey

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[email protected]

ABSTRACT

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Arc-related rocks of the Yüksekova Complex extend from Kahramanmaraş to Hakkari

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throughout the Southeast Anatolia representing the remnants of the Southern Branch of

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Neotethys. The volcanic members of this zone from the eastern parts of Lake Van suggest three

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different types of rock chemistry; tholeiitic (type I), calc-alkaline (type II) and alkaline (type III).

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Tholeiitic and calc-alkaline members suggest a subduction-related environment with their HFS

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and LIL element distributions. RE and trace element systematics and modelings indicate that i)

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the intermediate and the felsic calc-alkaline rocks are the result of fractional crystallization from

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a basic endmember, ii) alkaline members have originated from enriched mantle source relative to

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the tholeiitic and calc-alkaline lavas. Overall data from Yüksekova Complex suggest a mature

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supra-subduction zone environment within the southern Neotethyan Ocean during Upper

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Cretaceous time. The existence of Lutetian OIB like asthenospheric lavas at the upper parts of

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the ophiolitic assemblage in the eastern parts of Lake Van proposes the end of the normal

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ophiolite formation and the possible continuation of the magmatism with OIB like lavas during

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Middle Eocene.

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Keywords: Yüksekova Complex, Geochemistry, SSZ, Eastern Anatolia

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1. Introduction

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The southern Neotethyan oceanic basin was active along a period of Triassic to Eocene between

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the Tauride platform to the north and the Arabian platform to the south (e.g Şengör and Yılmaz,

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1981; Robertson and Dixon, 1984; Yılmaz, 1993; Robertson et al., 2007; Parlak et al., 2009).

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Southeast Anatolian ophiolites formed progressive elimination of this ocean above a north-

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dipping intra-oceanic subduction zone during Late Cretaceous (Parlak, 2009). Late Cretaceous

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arc-related rocks accompanying to the Southeast Anatolian ophiolites extend from the west

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(Göksun, Kahramanmaraş) to the east (Yüksekova, Hakkari) throughout Southeast Anatolia. The

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arc-related rocks are mainly basic to acidic extrusive and intrusive rocks (Parlak et al., 2009;

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Karaoğlan et al., 2013). Both extrusive and intrusive rocks were included within the Yüksekova

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Complex by Perinçek (1979). The geochemistry and geochronology of the Yüksekova Complex

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has been discussed in several studies (e.g. Perinçek, 1979; Aktaş and Robertson, 1984; Yazgan,

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1984; Yılmaz, 1993; Yılmaz et al., 1993; Elmas, 1994; Elmas and Yılmaz, 2003; Rızaoğlu et al.,

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2006; 2009; Robertson et al., 2007; Turan and Bingöl, 1989; Beyarslan and Bingöl, 2000;

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Karaoğlan, 2013; Çolakoğlu et al., 2011, 2014; Tekin et al., 2015; Ural et al., 2015). The

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extrusive rocks are interpreted as the upper part of a Late Cretaceous ophiolitic assemblage that

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includes basic, intermediate and silicic extrusive and dykes and all of them are interpreted as the

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upper part of the Late Cretaceous ophiolitic assemblage. Available data on the geochemistry of

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the volcanic rocks within the Yüksekova Complex indicate a supra-subduction zone type (SSZ)

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oceanic crust generation (e.g., Parlak et al., 2004; 2009). However, the tectonic setting of the

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volcanic rocks within the supra-subduction zone is not well presented due to the lack of data

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from the eastern parts of the zone.

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This paper presents new geochemical, isotopic and geochronological data on the oceanic arc-

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related volcanic rocks located to the east of Lake Van. The purpose of this study is to determine

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their tectonic setting(s) and magma source(s), and to evaluate changes in lava chemistry through

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time.

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2. Background geology

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Eastern parts of Lake Van are mainly composed of Eocene-Oligocene flysch, tectonic lenses of

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Yüksekova Complex and metamorphic rocks (Figure 1) (Acarlar et al., 1991; Ketin, 1977; Şenel

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and Ercan, 2002; Elmas, 1993; Çolakoğlu et al., 2011; 2014). The Yüksekova Complex

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comprises lithologies of ophiolitic succession, island arc and oceanic sediments (Perinçek, 1990;

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Yılmaz, 1993). The base of the complex consists of metavolcanics which are called Mordağ

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Metamorphics (Elmas and Yılmaz, 2003; Perinçek, 1990). The available fossil data from the

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oceanic sediments of Yüksekova Complex from the east of Lake Van suggest a Late Cretaceous-

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Early Paleocene depositional age (Elmas, 1992; Göncüoglu and Turhan, 1984; Perincek, 1990;

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Şenel et al., 1984; Çolakoğlu, et al., 2011; 2014). Volcano-sedimentary members of Yüksekova

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Complex are overlain by Upper Lutetian-Upper Oligocene sedimentary rocks of Erçek

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Formation consisting of sandstone, conglomerate, mudstone, marl, sandy limestone alternation

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and pelagic limestone layers (Elmas, 1992; Elmas and Yılmaz, 2003). Volcanic samples

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collected within the Yüksekova Complex are mainly from the Gövelek region (Figure 1). Some

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of the volcanics are intercalated with Erçek Formation within the study area.

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3. Methods

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Whole rock major element compositions were determined by ICP-Emission Spectrometry

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following a lithium metaborate/tetraborate fusion and dilute nitric acid digestion at ACME

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(Canada) analytical laboratories. Trace element contents were determined in the same laboratory

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by ICP Mass Spectrometry following a lithium metaborate/tetrabortate fusion and nitric acid

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digestion. Whole rock major element and trace element data is given in Table 1 together with

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geographical coordinates. Sr, Nd and Pb isotopic analysis of selected volcanics were performed

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at the Pacific Centre for Isotopic and Geochemical Research, Canada, using methods described

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by Weis et al. (2005, 2006) with Thermal Ionization Mass Spectrometer (TIMS). The Ar-Ar age

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dating of 3 samples was performed at the Isotope and Geochronology Laboratories of the

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University of Nevada. Samples analyzed by the furnace step heating method utilized a double

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vacuum resistance furnace similar to the Staudacher et al. (1978) design. Samples were run as

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conventional furnace step heating analyses on bulk mineral or volcanic rock groundmass

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separates. They were run more than once in an attempt to obtain better analytical data. There are

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no plateau or isochron ages defined by the data obtained from the furnace step heating analyses.

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Based on the report from Nevada Isotope and Geochronology Laboratories and the stratigraphic

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position of the samples, total gas ages are used for the interpretations (Table 2).

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4. Petrography

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Samples range in composition from basalt to rhyolite. All groups of samples have similar

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mineralogical compositions and are typically crystal-poor and porphyritic with hyalopilitic

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groundmass. Mafic rocks consist of olivine, clinopyroxene and plagioclase phenocrysts set in a

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groundmass comprising plagioclase, clinopyroxene Fe-Ti oxides, and glass. Intermediate

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members are mainly composed of plagioclase, clinopyroxene, hornblende and rarely K-feldspar

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and quartz. Pyroxene, plagioclase, K-Feldspar, quartz, biotite and hornblende minerals are the

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phenocryst assemblage of the acidic members. All the volcanic rocks have undergone low-grade

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metamorphism and/or alteration. The primary minerals and volcanic glass have been variably

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altered to clay minerals, sericite, chlorite, uralite, opacite and carbonate minerals.

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5. Geochemistry

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5.1. Major-trace and REE geochemistry

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LOI values of most of the samples are lower than 4 % wt, the other samples have values ranging

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between 4-14 wt %. The rocks from the Gövelek region have undergone low-grade

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metamorphism and a substantial degree of hydrothermal alteration. These processes have

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mobilized some major and trace elements in igneous rocks (e.g. Floyd & Winchester, 1976;

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Hastie et al., 2007; Neil et al., 2013). It is generally considered that most major and large ion

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lithophile elements (LILE) are mobilized, whereas Sc, Y, Co, Ni, Th, the REE and high field

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strength elements (HFSE) such as Ti, Nb, Ta, Zr, and Hf are immobile below amphibolite facies

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(e.g. Pearce, 1996; Neil et al., 2013). For testing the genetic relation between similar/different

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mantle rocks of Gövelek region some of the mobile elements have been excluded from the

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interpretations.

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A total of 25 samples were analyzed for whole rock compositions and are shown in Table 1.

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Volcanic units from Gövelek region cover a broad compositional spectrum from basalt to

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rhyolite (Figure 2). In Nb/Y-Zr/Ti diagram (Figure 2) the volcanics of the Gövelek region are

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subdivided into two groups as alkaline and subalkaline members. Alkaline members have higher

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Nb/Y ratios and their compositions range from basalt to trachyandesite. The SiO2, MgO and Mg#

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(100* MgO/(MgO+FeO) molar) of alkaline rocks are range between ~48-59 wt %, 0.91-3.34 wt

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% and 32-64 respectively. The subalkaline group has a different cluster area with different Nb/Y

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ratios in figure 2. The Co-Th diagram is appropriate to differentiate subalkaline altered volcanic

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arc and MOR rocks due to the immobile behavior of Co and Th under metamorphism and

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hydrothermal alteration (Figure 3) (Hastie et. al., 2007). Low Nb/Y (Figure 2) lavas of studied

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area have a tholeiitic character on Co-Th diagram. Calc-alkaline members are the lavas which

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reveal a broad compositional spectrum from basalt to rhyolite with moderate Nb/Y ratios

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compared to tholeiitic and alkaline members.

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Incompatible trace element characteristics are illustrated as MORB - normalized element

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diagrams in figure 4 and as chondrite-normalized rare earth element (REE) diagrams in figure 5.

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Three different groups (alkaline, calc-alkaline, tholeiitic) reveal completely different MORB-

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normalized trace element patterns. Alkaline lavas are enriched both in Large Ion lithophile (LIL)

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and HFS elements relative to MORB (Figure 4). Calc-alkaline group display enrichments of LIL

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relative to HFS elements with depletion of Sr, Ba, P and Ti increase from mafic to acidic

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members. The negative Nb and Ta troughs point to the presence of subduction component in the

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mantle source of calc-alkaline members. Tholeiitic members of Gövelek region have

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incompatible element patterns similar to MORB with slight depletion of Sr, K, Rb, Ti, Ta, and

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Nb (Figure 4). The negative Nb and Ta troughs point to the presence of a subduction component

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in the mantle source of the tholeiitic members. It is probable that the mantle source of tholeiitic

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members is MORB-like mantle source with a subduction component which is typically seen in

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supra-subduction zone environments.

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The chondrite-normalized REE patterns (Figure 5) reveal enrichment of Light Rare Earth

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Elements (LREE) over Heavy Rare Earth Elements (HREE) in alkaline and calc-alkaline

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members. The (La/Yb)N ratio of alkaline members ranges between 6-22 with slightly negative

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Eu anomaly (Eu/Eu* = 0.60-0.99, mean= 0.83). Calc-alkaline members have enriched LREE

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patterns with (La/Sm)N ratios between 1.70-4.37 and flat HREE patterns with (Gd/Yb)N ratios

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between 0.76-2.02. Negative Eu anomaly is more pronounced in this group of lavas and

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increasing mafic to acidic members (Eu/Eu* = 0.04-0.080, mean= 0.059). Tholeiitic members

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have flat patterns both in their LREE and HREE contents. (La/Yb)N ratios range between 0.6-

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1.5 with negative Eu anomaly (Eu/Eu* =0.049-0.073, mean = 0.060).

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5.2. Sr-Nd-Pb Isotope compositions

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Six samples from the Gövelek region were analyzed for their Sr, Nd and Pb isotope compositions

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and are reported in Table 2. Three of them are from calc-alkaline members, two of them are

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from tholeiitic and one of them from alkaline members. Isotopic ratios were back-calculated to

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their initial values at 44±0.3 Ma for alkaline rocks, 66.5±0.3 Ma for calc-alkaline rocks, 113±3

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Ma for tholeiitic rocks (Table 2).

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ranging between 0.705046 - 0.706714, 0.512834 - 0.512918, 37.8033-38.8194, 15.4468-15.5965,

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17.0879-18.8273 for tholeiitic members and 0.704686-0.707107,0.512735-0.512779,38.3619-

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38.5826,15.5242-15.6239,18.2607-18.5147 for calc-alkaline members respectively. The samples

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show moderate variations in Sr and Nd isotope composition (εSri alkaline = 29.7, εNdi alkaline= -0.7;

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εSri

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More radiogenic member belongs to the calc-alkaline members.

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Sr/86Sri,

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Nd/144Ndi,

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Pb/204Pbi,

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Pb/204Pbi and

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tholeiitic=

6.7-8.3; εSri

calc-alkaline

= 3.9-38.2, εNdi

calc-alkaline=

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6. Discussion

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6.1. Mantle source and slab components

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Volcanic samples from Gövelek region display three different geochemical affinities that can be

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clearly seen from the multi-element diagrams (Figures 4 and 5). The geochemical character of

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the lavas change from tholeiitic (GV11: 113±3 Ma, Table 2) to calc-alkaline within Uppermost

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Cretaceous (GV11: 66.5±0.3 Ma, Table 2). The youngest extrusive products of the Gövelek

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region are alkaline and probably originated from an enriched mantle source in Lutetian (GV12;

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44.1±0.3 Ma Table 2). These three different groups can be seen within the evolution life cycle of

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the SSZ from birth to death (Shervais, 2001). In order to discuss possible mantle source(s),

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Gövelek rocks are compared with extrusive and some subvolcanic products of Yüksekova

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Complex from Kahramanmaraş (Göksun-Afşin) (Parlak et al., 2002), Elazığ-Malatya (Ural et al.,

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2015) and Van region (Çolakoğlu et al., 2011;2014).

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Gövelek volcanics are characterized by three different mantle sources in Figure 6. Low Th/Yb,

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Nb/Yb, moderate Nb/Th, La/Nb (Figure 6 a-b) ratios represent a source with MORB affinity

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(mantle source I) slightly enriched by subduction components. These tholeiitic members are the

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older members of the Gövelek region and display similarities with the tholeiitic members of

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Elazığ-Malatya region. They have MORB-back arc affinities with their high V/Ti (20-50)

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(Figure 6c) contents and display shifts from N-MORB affinity to arc basalts in Figure 6d which

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correspond a subduction enriched MORB mantle for the source of these volcanics. Calc-alkaline

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members of Gövelek region have moderate to low Nb/Th, moderate Nb/Yb and La/Nb and high

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Th/Yb ratios and plot within the arc volcanics field (mantle source II) due to their high Th and

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various Zr contents (Figure 6). Calc-alkaline members are slightly overlapped with the volcanic

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rocks from Kahramanmaraş region. Alkaline members plotted within the OIB field (mantle

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source III) in Figure 6c have the highest Ti/V (>50) contents overlap with the Early-Late

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Cretaceous and Upper Most Cretaceous members of Yüksekova complex from the Van region.

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The most striking feature of the Gövelek volcanics is negative Nb, Ta anomalies in tholeiitic and

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calc-alkaline members which attributed to slab involvement to the mantle source. Slab

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involvement can be broadly classified as i) fluids from altered oceanic crust (Tatsumi et al.,

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1986; Hawkesworth et al., 1993, 1997; Turner et al., 1996; Turner, 2002; Guo et al., 2005) or

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subducted sediments (Ryan et al., 1995; Class et al., 2000; Elburg et al., 2002); (ii) partial melts

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from subducted sediments or the oceanic crust itself (e.g. Hawkesworth et al.,1993, 1997; Elliot

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et al.,1997; Elburg et al., 2002; Guo et al., 2005). It has been shown that some LILE (e.g. Rb,

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Ba, Sr, U) are mobile in aqueous fluids because these elements are water soluble; however, the

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REE and HFSE (e.g. Ce, Th, Nb, Zr and Ta) are less mobile or immobile in a fluid phase because

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they are relatively water insoluble trace elements (Sheppard &Taylor, 1992; Turner et al., 1997;

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Elburg et al., 2002; Turner, 2002). These characteristics lead to high concentrations of some

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water-soluble LILE and other fluid mobile elements (e.g. Rb, Ba), and very low contents of

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HFSE in the subduction - derived fluid. Thus, those volcanic rocks whose source was strongly

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metasomatized altered oceanic crust is likely to have higher Ba/Th (Figure 7a) (Hawkesworth et

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al., 1997), in contrast, arc volcanics with a strong imprint of a subduction-related subducted

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sediment in their source region have higher Th/Ce (Hawkesworth et al.,1997),

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Taylor, 1992). In Ba/Th vs. La/SmN diagram (Figure 7a) mantle source of the majority of the

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volcanic rocks from Yüksekova Complex seems enriched contributions from the subducted

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sediments. Hastie et al. (2009; 2013) used Th/La and (Ce/Ce*)Nd ratios to differentiate the

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different types of sediments that metasomatized the source region of the arc volcanoes (Figure

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Sr/86Sr,

Pb/204Pb (Hawkesworth et al., 1997; Guo et al., 2005, 2006) and La/SmN (Sheppard &

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7b). The negative Ce anomaly ((Ce/Ce*)Nd) in the diagram are associated with phosphate-rich

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phases in pelagic sediments and red clay sediments in oxidizing environments, and so the slab-

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related component has a negative Ce anomaly that subsequently imparts a negative Ce anomaly

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to the arc lavas (e.g., Ben Othman et al. 1989; McCulloch and Gamble 1991; Plank and

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Langmuir 1998; Elliott, 2003). Tholeiitic and a few calc-alkaline members of the Gövelek

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volcanism together with the lavas from Elazığ-Malatya and Van region are enriched in pelagic

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sediments and also arc-related volcanic detritus. Some intermediate and mafic members of calc-

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alkaline lavas seem to enrich in continental detritus which suggesting proximity to a continental

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margin.

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6.2. Fractional crystallization and origin of calc-alkaline felsic rocks

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The observed phenocryst phases and compositions of tholeiitic, calc-alkaline and alkaline groups

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indicate that olivine, clinopyroxene, and plagioclase minerals have controls on the geochemical

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evolution of the Gövelek volcanics. HFSE and REE ratios are unaffected by fractionation of

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pyroxenes, plagioclase, olivine and are thus commonly used to study the mantle component

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present in arc rocks (e.g. Pearce & Peate, 1995, Neil et al. 2013). However, the MREE are

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compatible in amphibole and Ti, Nb, and Ta may be moderately compatible depending upon the

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amphibole composition (Klein et al., 1997; Tiepolo et al., 2000, Neil et. al. 2013). Amphibole

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fractionation may thus alter HFSE and REE ratios in arc magmas. Amphibole is not recorded as

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phenocryst in primitive members of Gövelek volcanics, however, several studies (e.g. Davidson

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et al., 2007; Larocque and Canil, 2010; Maurice et al.,2012 Neil et al., 2013) point to the

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importance of amphibole in the differentiation of many island arc suites and the widespread

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cryptic amphibole fractionation in arc volcanic suites (Davidson et al., 2007). Cryptic amphibole

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and garnet fractionation in arc magmas can be determined by low MREE/HREE ratios and U-

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shaped REE profiles. However, the effect of these minerals on the evolution of arc magmas can

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be better depicted by a plot of Dy/Dy* vs Dy/Yb (Davidson et al., 2013) (Figure 9a). Lower

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Dy/Yb and Dy/Dy* ratios are associated with amphibole fractionation. The Dy/Yb ratio can be

236

used to differentiate the presence of any garnet in mantle source, or garnet fractionation, as the

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HREE are strongly compatible with garnet (e.g Neil et al., 2013). The calc-alkaline members of

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the Gövelek volcanics display a good correlation with the amphibole fractionation trend in

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Figure 8a however; higher Dy/Yb ratios of alkaline members appear to have originated from a

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residual garnet-bearing source.

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Calc-alkaline members of the Gövelek region have several intermediate and felsic members.

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Intermediate and felsic rocks of the calc-alkaline group have similar HFSE, LILE and REE

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patterns with the mafic end members pointing to similar mantle sources. Felsic magmas have

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been viewed as a minor component in oceanic arcs. However, recent studies reveal that they can

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be an important component of oceanic arcs (e.g. Hasse et al., 2006; Leat et al., 2006; Maurice et

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al., 2012; Barker et al., 2013). The origins of these lavas are attributed to fractional

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crystallization of basaltic magma or melting of lower to mid-crustal mafic or intermediate

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amphibolite (Brophy, 2008). The presence of high volumes of erupted felsic rocks in oceanic

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arcs has been attributed to amphibolite melting however; lower volumes have been associated

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with fractional crystallization of a mafic end member (e.g Pearce et al., 1995; Shukono., 2006;

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Maurice et al., 2012). Brophy (2008; 2009) has shown that a crystal fractionation origin for

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silicic magmas will generate positive trends between SiO2 and REE correlations whereas

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dehydration melting of amphibolite crust leads to negative SiO2-REE correlations. LREE (e.g.

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La)-SiO2 and HREE (e.g. Yb)-SiO2 variations for most of the Gövelek calc-alkaline volcanic

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rocks (Figure 8b-c) display steadily increasing La with increasing SiO2 and mostly higher Yb

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abundances relative to the mafic lavas. In order to test the effect of fractional crystallization on

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the felsic members of calc-alkaline lavas of Gövelek, a fractional crystallization model has been

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conducted using one of the mafic end members with an amphibole, clinopyroxene,

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orthopyroxene, olivine and plagioclase-bearing mineralogy. Fractional crystallization modeling

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covers most of the LREE enrichment or HREE depletion of intermediate and felsic rocks.

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However, this modeling cannot generate REE contents of some of the felsic rocks (are not

262

shown in Figure 8d). These REE patterns may be caused either by fractionation of another

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crystal phase not used in modeling or by extensive late-stage amphibole crystallization from the

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evolved melt, as LREEs have lower partition coefficients in amphiboles than MREEs or HREEs

265

in silicic magmas (Rollingson, 1993; Barker et al., 2013). Although REE contents and models

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support the origin of the felsic rocks as fractional crystallization, the possibility of amphibole

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melting cannot be ruled out.

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6.3. Melting

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The mantle wedge in many arc systems is assumed to be similar to the depleted MORB source

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mantle (Thirlwall et al., 1994). However, enriched mantle sources can also be involved in island

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arc volcanism (e.g. Hastie et al., 2010a, Neill et al., 2011; 2013). The Nb/Y vs Zr/Y diagram

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(Figure 9) (Fitton et al., 1997) separates MORB-source mantle from more enriched sources. In

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Figure 9 all tholeiitic and one calc-alkaline basaltic rocks of Gövelek, and together with island

275

arc tholeiites from Elazığ -Malatya regions plot below the lower tramline with low to moderate

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Zr/Y and Nb/Y ratios. That is to say, the source of the tholeiites of Yüksekova Complex is N-

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MORB type mantle. Two calc-alkaline members of Gövelek, together with rocks from Van

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(Çolakoğlu et al., 2011) and Elazığ-Malatya (Ural et al., 2015) regions with back-arc affinity,

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plot within the Icelandic array which implies plume-related material may have been involved in

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the petrogenesis these lavas. The alkaline rocks from Gövelek and Van region fall within the

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uppermost part of the Icelandic array with high Nb/Y vs. Zr/Y (Figure 9) ratios imply more

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enriched mantle source with respect to island arc tholeiites, back-arc lavas and calc-alkaline

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lavas from the Yüksekova Complex. Constraints on melting parameters of tholeiitic rocks from

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Gövelek, Elazığ- Malatya and calc-alkaline rocks from Gövelek regions are estimated from Nb-

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Yb covariations according to the approach of Pearce and Parkinson (1993) (Figure 10a). Use of

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Nb vs. Yb plot allows modeling of melts from both depleted and enriched sources. The model

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provides a convenient comparison between rocks that are derived from various arc systems

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generated in spinel peridotite sources. The melting grid on Nb-Yb plot results from melting

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curves both fertile MORB mantle (FMM) and residue of a %5 melt of FMM. The FMM melting

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curve further subdivides the field of peridotite into enriched and depleted portions. To perform

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the model, most mafic members were corrected for fractionation back to 9 % MgO using least-

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squares linear regression. The island arc tholeiites from Yüksekova Complex plot below the

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FMM melting vector (spinel peridotite mantle source), indicating that the source was depleted in

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the more incompatible components relative to FMM. However, the calc-alkaline lavas of the

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Gövelek region together with rocks with the back arc affinity from Van and Elazığ-Malatya

296

regions plot above the FMM melting vector consistent with generation from relatively enriched

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sources. Alkaline rocks are more enriched in LREE relative to HREE (Figure 5 and Figure 8a),

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implying the presence of garnet in the source region. Additionally, on a melting model using

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La/Yb-Yb ratios (Figure 10b) the enriched samples of the Gövelek and Van regions plot close to

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the garnet lherzolite melting curve implying an OIB like mantle source.

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6.4. Tectonic implications

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Samples from the Gövelek region reveal three different geochemical affinities. Tholeiitic and

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calc-alkaline members display geochemical characters of formation from a subduction modified

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mantle source. However, alkaline members have originated from enriched mantle source with no

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subduction component. The geochemical signatures of volcanics from Gövelek region represent

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a supra-subduction zone origin (SSZ). The SSZ origin of Yüksekova Complex has been accepted

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and reported by many researchers (e.g., Elmas; 1993; Yılmaz and Elmas 2003; Parlak et al.,

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2004;2009; 2013 Rızaoğlu et al., 2009; Robertson et al., 2007;Çolakoğlu et al., 2012;2014;

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Karaoğlan et al: 2013; Ural et al 2010;2015;Tekin et al., 2015). The available ages for the

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extrusive components of the Yüksekova complex are few. Recent isotope (e.g.Çolakoğlu 2012,

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Karaoğlan et al. 2013) and foraminiferal-radiolarian ages (e.g., Çolakoğlu et al., 2014; Tekin et

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al., 2015, Ural

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Cenomanian-Late Maastrichtian. The new Ar-Ar datings of this study reveal an age span

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between 113±3 Ma and 66.5±0.3 Ma for tholeiitic and calc-alkaline rocks respectively. However,

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an alkaline sample from the Gövelek region reveals a much younger age (44 ±0.3 Ma) which

316

corresponds to Lutetian. The three geochemical affinities described above correspond to the

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progressive stages in SSZ environments as defined by Shervais (2001). These include (1) birth-

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formation of incipient island arc crust above nascent subduction zone (e.g., Casey and Dewey,

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1984; Hawkins et al., 1984; Stern and Bloomer, 1992; Shervais et al., 2014). Rocks associated

320

with the ophiolite formation include the layered gabbros and some isotropic gabbros of the

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plutonic section. Volcanic rocks associated with this phase of SSZ environment are typically arc

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tholeiites (Shervais, 2001). These volcanic rocks resemble MORB in their overall geochemical

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character, however, they generally display distinct geochemical signatures from true MORB

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et al., 2015) yield an age span for Yüksekova extrusives between Late

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with their low Ti/V ratios minor enrichment in LILE and depletions especially in high field

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strength elements (Ti, Nb, Ta, Hf) relative to the LILE (Shervais, 2001). Ophiolites of the

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Yüksekova Complex include layered gabbros and isotropic gabbros within the İspendere,

327

Kömürhan and Göksun ophiolites (e.g. Parlak et al., 2004, 2009, Rızaoğlu et al., 2006; Robertson

328

et al., 2007; Karaoğlan et al., 2013) and also arc tholeiitic rocks with low Ti/V ratios (e.g. Parlak

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et al., 2004, 2009, Rızaoğlu et al., 2006; Robertson et al., 2007; Karaoğlan et al., 2013, Tekin et

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al., 2015, Ural et al., 2015, Özdemir-recent study). (2) Youth; Rocks associated with second

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phase of ophiolite formation include mafic and ultramafic rocks which are intrusive into the

332

older plutonic section and mainly boninitic volcanic rocks (Shervais, 2001). Wherlites,

333

plagioclase wherlites, diabasic and quartz microdioritic sheeted dykes (İspendere, Kömürhan,

334

Göksun ophiolites, e.g.Robertson et al., 2007, Parlak et al., 2009) are present within the

335

ophiolites of Yüksekova Complex, however, boninites are absent within Kahramanmaraş-

336

Hakkari zone of the southeast Anatolian ophiolites. (3) Maturity; Volcanic rocks associated with

337

this phase of SSZ ophiolite formation include typically calc-alkaline or transitional towards calc-

338

alkaline in composition. Plutonic rocks formed during this stage are plagiogranites (Shervais,

339

2001). Geochemically, plutonic rocks in mature stage represent a calc-alkaline intrusive suit that

340

corresponds to the volcanic members of this stage (Shervais, 2001). The existence of transitional

341

and calc-alkaline extrusives within the Yüksekova complex and plagiogranites are the main

342

magmatic rock groups in the mature stage. The Yüksekova Complex in southeast Anatolia

343

displays general features of an oceanic crust that formed during the mature stage of a supra

344

subduction zone life cycle (e.g. Parlak, 2002; Parlak et a., 2009; Karaoğlan et al., 2013).

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General geochemical character of the extrusive products turns tholeiitic to calc-alkaline within

346

Uppermost Cretaceous. Previous studies of the eastern parts of Lake Van reveal the presence of a

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young island-arc volcanic activity (e.g. Elmas, 1994; Elmas and Yılmaz, 2003) based on the

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calc-alkaline volcanics which are intercalated with upper Lutetian–Upper Oligocene sedimentary

349

rocks of the Erçek Formation. This volcanic activity is assumed as a continuation of Yüksekova

350

and Helete-island arcs (Elmas, 1994; Elmas and Yılmaz, 2003). However, Ar-Ar ages of current

351

study reveal Late Maastrichtian for calc-alkaline rocks and Middle Lutetian for alkaline volcanic

352

rocks from Gövelek region. The existence of younger alkaline OIB-like volcanic rocks within a

353

supra-subduction zone environment is accepted as the death of the ophiolite formation (Shervais,

354

2001), which may be the result of the collision of the ridgecrest/spreading center with the

355

subduction zone and the partial subduction of the spreading center (Shervais, 2001). Late

356

Cretaceous alkaline rocks within the Yüksekova Complex in the eastern parts of the Lake Van

357

region were also reported, however, these rocks are linked to the seamounts (Çolakoğlu et al.,

358

2011) which are common in the mature stage of the SSZ life cycle (Shervais, 2001).

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7. Conclusions

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Geochemical data presented in the current study suggest three different lava chemistry have been

362

generated from an intra-oceanic SSZ environment. The geochemical character of the Yüksekova

363

Complex seems to have changed from tholeiitic to calc-alkaline within the Uppermost

364

Cretaceous. Overall data from Yüksekova Complex suggest a mature SSZ environment within

365

the southern Neotethyan ocean during Late Cretaceous. The existence of Lutetian OIB-like

366

asthenospheric lavas at the upper parts of the ophiolitic assemblage in the area to the east of Lake

367

Van proposes the end of the normal ophiolite formation (layered gabbros, ultramafic intrusives,

368

calc-alkaline stocks) (Shervais, 2001) and the possible continuation of magmatism with leakage

369

of OIB-like lavas within Middle Eocene after the ridgecrest subduction and/or delamination of

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the subducted slab. Geochemical modelings also suggest that tholeiitic and calc-alkaline lavas

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from the Gövelek region originated from depleted sources relative to the alkaline members and

372

that acidic member of the calc-alkaline lavas are the result of fractionation from a basaltic

373

endmember.

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Acknowledgements

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The author would like to thank the anonymous reviewers and editor Damien Delvaux for their

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valuable comments and suggestions to improve the quality of paper. This work has been funded

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by both the Scientific and Technical Research Council of Turkey (TUBITAK, Project No

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112Y022) and Scientific Research Projects Office of Yüzüncü Yıl University (YYU-BAP,

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Project No 2012-HIZ-MİM004).

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Cycle of Supra-subduction Zone Ophiolites. International Geology Review, v. 46, 289-

571

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Staudacher, Th., Jessberger, E.K., Dorflinger, D and Kiko, J. (1978). A refined ultra-high

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576

Şengör, A.M.C., Yılmaz, Y. 1981. Tethyan evolution of Turkey: a plate tectonic approach, Tectonophysics, 75, 181–24.

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Tatsumi, Y., Hamilton, D. J. & Nesbitt, R.W. 1986. Chemical characterization of fluid phase

578

released from a subducted lithosphere and origin of arc magmas: Evidence from high-

579

pressure experiments and natural rocks. Journal of Volcanology and Geothermal

580

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TE D

577

Thirlwall, M. F., Upton, B. G. J. & Jenkins, C. 1994. Interaction between continental lithosphere

582

and the Iceland plume - Sr-Nd-Pb isotope geochemistry of Tertiary basalts, NE

583

Greenland. Journal of Petrology 35, 839-879.

EP

581

Tiepolo, M., Vannucci, R., Oberti, R., Foley, S., Bottazzi, P. & Zanetti, A. 2000. Nb and Ta

585

incorporation and fractionation in titanian pargasite and kaersutite: crystal-chemical

586 587

AC C

584

constraints and implications for natural systems. Earth and Planetary Science Letters 176, 185-201.

588

Tekin U.K., Ural M., Göncüoglu, M.C., Arslan M. and Kürüm S., 2015. Upper Cretaceous

589

Radiolarian ages from an arc-backarc within the Yüksekova Complex in the Southern

590

Neotethyan mélange, SE Turkey. C. R. Palevol., 14 (2): 73-84.

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591

Turan, M., Bingöl, A.F., 1989. Kovancılar–Baskil (Elazığ) arası bölgenin tektonostratigrafik

592

özellikleri. Ahmet Acar Jeoloji Sempozyumu, Bildiriler, Çukurova Üniversitesi, Adana,

593

pp. 213–227. Turner, S., Arnaud, N., Liu, J., Rogers, N., Hawkesworth, C., Harris, N., Kelley, S., van

595

Calsteren, P. & Deng, W. 1996. Post-collisional,shoshonitic volcanism on theTibetan

596

Plateau: implications for convective thinning of the lithosphere and the source of ocean

597

island basalts. Journal of Petrology 37, 45-71.

SC

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Turner, S., Hawkesworth, C., van Calsteren, P., Heath, E., Macdonald, R. & Black, S 1997. U-

599

series isotopes and destructive plate margin magma genesis in the Lesser Antilles. Earth

600

and Planetary Science Letters 142, 191-207.

601 602

M AN U

598

Turner, S. P 2002. On the time-scales of magmatism at island-arc volcanoes. Philosophical Transactions of the Royal Society of London, Series A 360, 2853-2871. Ural M., Arslan M., Göncüoglu, M.C., Tekin U.K., Kürüm S., 2015. Late Cretaceous arc and

604

back-arc formation within the southern Neotethys: whole-rock, trace element and Sr-Nd-

605

Pb isotopic data from basaltic rocks of the Yüksekova CompLex (Malatya- ELaziğ, SE

606

Turkey), Ofioliti 40(1), 52-72

EP

TE D

603

Weis, D., Kieffe, B., Maersschalk, C., Pretorius,W., Barling, J. (2005). High-precision Pb–Sr–

608

Nd–Hf isotopic characterization of USGS BHVO-1and BHVO-2 reference materials.

609

AC C

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Geochemistry Geophysics Geosystems 6, Q02002, doi:10.1029/2004GC 000852.

610

Weis, D., Kieffer, B., Maerschalk, C., Barling, J., de Jong, J., Williams, G.A., Hanano, D.,

611

Pretorius, W., Mattielli, N., Scoates, J.S., Goolaerts, A., Friedman, R.M. (2006).

612

Highprecision isotopic characterization of USGS reference materials by TIMS and MC–

613

ICP-MS. Geochemistry Geophysics Geosystems 7, doi:10.1029/2006GC001283.

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614

Winchester, J. A., Floyd, P. A. 1977. Geochemical discrimination of different magma series and

615

their differentiation products using immobile elements, Chemical Geology, 20 (4), p.

616

325-343. Wood, D.A., 1980. The application of a Th–Hf–Ta diagramto problems of tectonomagmatic

618

classification and to establishing the nature of crustal contamination of basaltic lavas of

619

the British Tertiary Volcanic Province. Earth and Planetary Science Letters 50, 11–30

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Yazgan, E., 1984. Geodynamic evolution of the eastern Taurus region (Malatya–Elazığ area,

621

Turkey). Proceedings of International Symposium, Geology of Taurus Belt, MTA,

622

Ankara, pp. 199–208

624

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SC

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Yılmaz, Y., 1993. New evidence and model on the evolution of the southeast Anatolian Orogen. Geological Society of America Bulletin 105, 251–271.

Yılmaz, Y., Yiğitbaş, E., & Genç, Ş. C. 1993. Ophiolitic and Metamorphic Assemblages of

626

Southeast Anatolia and their Significance in the geological evolution of the orogenic belt.

627

Tectonics, 12, 1280–1297.

630 631 632 633 634 635 636

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AC C

628

TE D

625

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Figure Captions

638

Figure 1.Simplified geological map of the eastern part of Lake Van (modified from MTA,2002).

639

Geographical coordinates are expressed in UTM projection, zone 38 S.

640

Figure 2. Classification of studied samples (Winchester and Floyd, 1977)

641

Figure 3. Th-Co classification of the lavas from Gövelek region (Hastie et. al. 2007). IAT, island

642

arc tholeiite; CA, calc-alkaline; H-K and SHO, high-K calc-alkaline and shoshonite; B, basalt;

643

BA/A, basaltic-andesite and andesite; D/R, dacite and rhyolite.

644

Figure 4. MORB normalized incompatible trace elements patterns of each group (Pearce, 1983)

645

Figure 5. Chondrite-normalized REE patterns of each group (Nakamura 1974)

646

Figure 6. (a) Nb/Th-La/Nb (Wood,1980), (b) Th/Yb-Nb/Yb (Pearce, 2008)

647

(Shervais, 1982), (d) Zr/117-Th-Nb/16 (Wood, 1980) diagrams for studied samples. Data source:

648

E-M; Elazığ-Malatya (Ural et al., 2015); K; Kahramanmaraş (Göksun-Afşin) (Parlak et al.,

649

2002), V-Vv; Van (Çolakoğlu et al., 2011;2014).

650

Figure 7. (a) Ba/Th-La/SmN, (b) (Ce/Ce*)Nd (Hastie et al., 2013) diagram for studied samples.

651

Symbols for volcanic areas same as Figure 6.

652

Figure 8. (a) Dy/Dy*-Dy/Yb (Davidson et al., 2013) diagram for all studied samples.

653

Dy/Dy*=DyN/LaN4/13 YbN9/13. DyN, LaN and YbN are the chondrite-normalized values of Dy, La

654

and Yb respectively. The normalization constants are from Nakamura (1974). (b-c) La-SiO2, Yb-

655

SiO2 diagrams for cac-alkaline members (d) Model REE patterns of calc-alkaline intermediate

656

and felsic members generation by fractionation of a basaltic calc-alkaline end member (GV-17,

657

Table 1) with a mineral composition of 0.2olivine + 0.1orthopyroxene + 0.2clinopyroxene + 0.1hornblende

658

+0.4plagioclase. Distrubition coefficients are from Rollingson, (1993). Green continuous lines

659

represent intermediate and felsic calc-alkaline members of Gövelek region. Black continuous

(c) V-Ti/1000

AC C

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637

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lines represent fractionation models. Red continuous line represent basaltic calc-alkaline end

661

member (GV-17).

662

Figure 9. Nb/ Y vs Zr/Y after Fitton et al. (1997) showing separation of MORB-source and

663

enriched, plume-like mantle sources. Symbols for volcanic areas same as Figure 6.

664

Figure 10. (a) Partial melting grid of Pearce & Parkinson (1993), (b) Yb vs La/Yb variation

665

diagram with peridotite vectors modified from Özdemir et al., 2014. Symbols for volcanic areas

666

same as Figure 6.

SC

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660

668

Table Captions

669

M AN U

667

Table 1. Major and trace element contents of volcanic rocks from Gövelek region. A-BA;

671

andesite and basaltic andesite, B; basalt, TA; trachy andesite, R-D; rhyolite and dacite, A;

672

alkaline, CA; calc-alkaline, T; tholeiitic

673

Table 2. Isotopic compositions and 40Ar-39Ar ages of selected Gövelek volcanics

676

EP

675

AC C

674

TE D

670

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GV9

379124

379110

379535

379736

379735

379735

380199

380199

377395

377395

377395

4269477

4269505

4270124

4269911

4269879

4269879

4269322

4269322

4265888

4265888

4265888

380693 UTM 4269081 Coordinates

SiO2 (%) Al2O3 Fe2O3 MgO CaO Na2O K2 O TiO2 P 2 O5 MnO Cr2O3 LOI TOTAL

R-D CA 66.17 14.34 5.90 1.31 2.20 4.88 1.77 0.70 0.19 0.10 0.003 2.3 99.87

R-D CA 75.86 11.69 2.66 0.28 0.60 3.05 4.35 0.23 0.05 0.04 <0.002 1.1 99.86

A-BA T 58.89 12.84 11.57 2.53 5.14 5.25 0.23 1.59 0.35 0.12 0.007 1.3 99.85

A-BA T 57.59 13.86 7.66 3.06 5.40 6.12 0.06 1.11 0.16 0.14 0.007 4.7 99.86

B A 50.54 16.57 9.73 3.34 4.35 5.42 2.26 1.92 1.11 0.14 0.002 4.3 99.71

TA A 48.28 14.43 3.88 0.91 12.61 6.63 0.70 0.94 0.36 0.14 0.003 10.8 99.65

TA A 58.92 4.66 2.22 1.98 15.71 0.68 0.89 0.26 0.10 0.12 0.021 14.3 99.88

B CA 48.36 16.16 9.79 4.25 5.96 3.00 4.79 1.04 0.53 0.17 0.003 5.6 99.61

R-D CA 73.92 11.91 2.81 1.02 0.84 3.06 4.38 0.33 0.08 0.03 <0.002 1.5 99.84

B CA 47.81 14.41 6.23 5.20 12.28 4.08 1.11 1.20 0.17 0.16 0.022 7.1 99.77

B CA 45.86 14.22 7.52 3.60 11.58 3.12 3.44 0.94 0.17 0.12 0.027 9.2 99.81

TA A 53.12 19.99 6.69 1.91 2.69 0.51 10.43 0.40 0.21 0.12 <0.002 3.2 99.25

Sc (ppm) Ba Co Cs Ga Hf Nb Rb Sr Ta Th U V W Zr Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Pb Zn Ni

10 173 9.2 0.6 17.9 7.6 10.1 42.0 86.6 0.8 7.7 2.6 54 1.0 326.5 48.8 21.6 45.8 6.09 25.9 6.30 1.51 7.62 1.28 8.28 1.65 5.39 0.84 5.48 0.86 5.7 83 3.8

7 348 3.2 0.6 14.1 10.5 14.3 94.4 51.3 0.7 13.3 3.0 30 <0.5 384.0 53.1 36.2 74.7 8.76 34.7 7.75 1.37 8.24 1.39 8.84 1.86 5.55 0.84 5.26 0.79 4.2 21 4.1

24 22 22.2 0.3 18.0 9.0 5.2 6.4 97.2 0.4 0.9 0.2 147 <0.5 283.8 86.3 11.0 30.1 5.23 25.7 8.76 2.67 13.27 2.21 15.50 3.00 9.75 1.34 9.67 1.31 <0.1 17 9.6

25 44 26.9 <0.1 15.7 3.2 2.6 0.7 66.2 0.2 0.3 0.4 220 <0.5 99.5 33.8 8.2 13.2 2.05 10.3 3.43 1.32 5.20 0.93 5.61 1.23 3.74 0.55 3.67 0.56 0.2 67 21.0

11 298 22.4 <0.1 26.4 12.2 69.1 14.6 440.8 3.7 8.4 2.1 83 <0.5 485.1 43.0 70.6 144.8 18.24 69.1 14.64 4.28 13.26 1.77 8.97 1.51 4.34 0.56 3.24 0.50 3.2 135 0.9

8 1728 7.4 0.8 10.9 6.5 43.6 32.2 442.6 2.5 6.6 2.1 56 0.8 252.8 38.2 37.9 73.8 8.72 36.3 7.07 1.87 7.16 1.09 6.45 1.31 4.11 0.55 4.18 0.57 2.6 64 8.9

5 165 5.4 1.1 6.4 1.8 26.6 26.3 202.1 1.8 4.5 1.1 50 0.7 103.0 15.5 22.4 35.6 4.35 14.3 3.25 0.64 3.14 0.42 2.50 0.52 1.47 0.21 0.98 0.22 3.2 37 30.3

20 1019 29.1 0.3 14.9 1.8 12.9 70.8 804.1 0.8 3.4 1.2 281 <0.5 91.8 20.6 25.1 47.8 5.98 25.1 5.14 1.47 4.96 0.70 3.83 0.76 2.63 0.32 1.87 0.30 4.5 79 9.0

5 347 2.6 1.5 12.4 6.1 10.0 103.4 346.5 0.6 8.9 2.4 34 0.6 273.8 24.1 22.5 43.6 5.11 21.5 4.41 0.76 4.47 0.65 4.01 0.89 2.86 0.36 2.70 0.40 10.2 30 3.6

30 117 27.4 0.8 14.0 3.2 4.7 25.9 473.8 0.2 1.0 0.9 220 <0.5 120.2 25.4 9.0 19.6 2.71 12.8 3.41 1.14 4.14 0.70 3.99 0.84 2.70 0.40 2.45 0.36 2.5 46 26.2

20 164 21.2 3.8 15.0 1.8 8.8 143.4 476.8 0.5 2.0 0.4 171 <0.5 88.3 14.6 8.4 17.0 2.24 9.6 2.31 0.91 3.08 0.45 2.65 0.55 2.04 0.23 1.21 0.23 1.2 28 60.0

2 4761 18.2 5.9 11.2 6.3 75.6 130.0 420.1 4.2 14.3 5.4 29 <0.5 323.9 23.8 106.0 162.3 15.72 51.7 6.66 1.92 4.88 0.66 3.83 0.80 2.58 0.45 3.24 0.47 4.6 53 3.6

GV16

GV17

GV19

Rock Type SiO2 (%) Al2O3 Fe2O3 MgO CaO Na2O K2 O TiO2 P 2 O5 MnO Cr2O3 LOI TOTAL

381516

GV24

GV27

GV28

GV29

GV30

GV34

GV35 GV39A GV39B GV46

GV50

GV51

381568

381712

381712

381712

377396

398931

398519

382757

382856

Sc (ppm) Ba Co Cs Ga Hf Nb Rb Sr Ta Th U V W Zr Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Pb Zn Ni

410368

410368

382496

4268898 4268934 4268993 4268993 4268993 4259935 4260081 4260600 4256820 4256820 4268571 4269243 4269245

A-BA CA 64.38 14.28 5.45 2.41 3.98 5.49 0.93 0.55 0.10 0.08 0.008 2.2 99.89

R-D CA 83.54 3.11 1.65 0.43 5.17 0.38 0.44 0.22 0.05 0.04 0.005 4.9 99.95

M AN U

GV15

TE D

GV14

EP

GV13

AC C

Rock Type

GV12

R-D CA 68.60 12.24 5.68 2.01 1.98 5.46 0.23 0.96 0.29 0.17 0.002 2.3 99.90

A-BA CA 58.77 15.60 7.83 2.77 4.42 5.63 1.58 0.81 0.15 0.10 0.002 2.2 99.85

A-BA T 54.81 11.29 9.62 3.79 7.50 3.86 0.06 1.53 0.17 0.10 0.004 7.1 99.85

A-BA CA 63.78 11.08 4.51 1.28 6.42 4.44 1.33 0.63 0.17 0.09 0.004 6.2 99.91

A-BA CA 72.48 10.09 3.26 0.59 4.04 4.89 0.54 0.47 0.20 0.06 0.003 3.3 99.92

R-D A-BA R-D CA CA CA 74.76 58.04 74.33 13.18 15.69 9.43 2.02 4.41 1.12 0.37 0.39 0.21 0.26 5.96 5.15 5.11 8.24 4.20 3.32 0.44 0.73 0.14 0.70 0.15 0.07 0.43 0.06 0.02 0.18 0.05 <0.002 <0.002 <0.002 0.6 4.4 4.4 99.89 98.91 99.81

A-BA T 61.88 15.21 7.25 2.66 1.61 7.20 0.20 0.86 0.34 0.10 0.003 2.6 99.86

R-D CA 69.53 12.75 3.11 0.76 3.74 5.61 0.79 0.36 0.10 0.08 <0.002 3.1 99.90

R-D CA 65.23 13.29 5.11 1.43 5.40 4.13 0.92 0.58 0.16 0.11 0.004 3.5 99.88

15 60 7.1 <0.1 15.1 5.6 12.5 2.1 61.0 0.8 5.4 1.4 44 <0.5 171.9 36.5 23.6 47.3 6.05 30.8 6.75 1.72 7.20 1.12 7.58 1.39 4.30 0.65 5.02 0.62 8.3 66 0.6

17 237 20.5 0.3 16.1 3.2 6.5 33.7 117.1 0.4 4.0 1.0 195 <0.5 112.4 19.8 12.5 24.3 2.97 11.9 3.11 0.77 3.22 0.56 3.26 0.79 2.25 0.33 2.51 0.32 1.8 42 8.4

27 21 24.5 <0.1 12.8 3.3 1.6 0.5 97.7 0.2 0.4 0.5 285 <0.5 115.7 41.5 4.2 13.5 2.17 10.7 4.20 1.20 6.01 1.12 7.45 1.50 4.83 0.66 4.76 0.70 2.4 65 11.3

11 149 6.5 0.3 13.9 4.8 9.5 27.8 50.2 0.6 4.9 1.6 43 1.1 160.5 28.0 20.2 39.0 4.92 21.8 4.56 1.24 4.87 0.76 5.31 0.89 2.73 0.44 2.98 0.45 10.9 73 4.3

13 50 5.5 0.3 5.5 2.4 3.0 11.5 268.0 0.2 2.3 0.9 106 <0.5 83.9 21.0 6.2 14.4 1.88 8.3 2.27 0.63 2.80 0.50 3.52 0.78 2.34 0.38 2.89 0.35 2.5 30 6.5

2 463 3.4 0.1 8.9 3.4 6.4 31.2 230.4 0.4 11.7 2.0 19 1.4 153.8 13.5 16.9 27.5 2.90 10.5 1.90 0.40 2.17 0.31 2.23 0.36 1.61 0.24 2.10 0.27 6.5 31 2.0

24 67 12.1 <0.1 16.4 2.0 1.7 1.6 344.2 0.2 0.4 0.2 105 <0.5 72.4 32.0 5.3 12.9 1.96 11.0 3.17 1.12 4.84 0.77 6.02 1.09 3.65 0.58 3.88 0.54 0.9 86 0.5

10 153 4.6 0.2 11.2 3.4 7.7 14.7 202.8 0.4 5.0 1.1 27 <0.5 153.5 25.3 16.6 34.6 4.13 17.4 3.96 0.93 4.13 0.69 4.41 0.93 2.63 0.43 3.21 0.46 10.0 53 6.1

14 190 6.9 0.3 15.3 4.5 11.8 20.5 202.3 0.8 6.1 1.7 64 0.9 163.9 27.6 21.9 42.9 5.26 21.7 4.80 1.15 4.97 0.82 5.86 1.04 3.31 0.44 3.23 0.44 11.9 70 10.8

RI PT

GV2

UTM Coordinates

GV11

Table 1 Continued GV20 Sample No GV21

GV1

SC

Table 1 Sample No

18 164 14.7 <0.1 14.1 3.5 3.7 21.4 78.5 0.3 2.9 1.0 122 <0.5 131.3 23.3 10.0 21.5 2.81 12.4 3.03 0.85 4.20 0.65 4.32 0.86 2.87 0.43 2.58 0.39 1.8 39 7.8

3 53 4.3 0.7 2.6 4.2 4.0 18.6 67.1 0.4 3.1 0.8 32 <0.5 132.9 10.1 11.2 23.2 2.73 12.9 1.92 0.39 1.88 0.25 1.95 0.33 1.02 0.12 0.97 0.13 5.9 19 16.0

17 8428 7.3 0.2 5.8 3.7 2.9 8.0 524.4 0.3 2.9 2.4 160 0.5 120.2 73.7 23.0 43.5 5.39 22.8 5.47 1.22 7.49 1.31 9.03 1.99 7.18 1.03 6.93 1.15 7.4 65 3.3

3 1254 1.9 0.2 4.9 2.5 2.2 9.8 338.8 0.2 2.3 0.6 18 0.6 97.5 17.5 8.0 14.8 1.90 6.0 1.80 0.41 2.07 0.36 2.65 0.51 1.94 0.28 2.17 0.33 1.6 8 3.0

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Sr/86Sri ԑ(Sr)i

Nd/144Ndi ԑ(Nd)i

Pb/204Pb

208

Pb/204Pbi 207Pb/204Pb

GV11

0.705051 0.705046

9.7

0.512983

0.512834

6.7

38.350

37.803

15.555

GV12

0.706542 0.706536

29.7

0.512582

0.512545

-0.7

39.121

38.749

15.603

GV15

0.704713 0.704688

3.8

0.512794

0.512740

3.7

38.540

38.378

GV17

0.704713 0.704698

3.9

0.512900

0.512830

5.4

38.677

GV19

0.707198 0.707116

38.3

0.512849

0.512786

4.6

GV48

0.706721 0.706714

33.4

0.513054

0.512918

8.3

143

208

Pb/204Pbi

206

Pb/204Pbi

40

Ar-39Ar Total Gas Age (Ma)

17.088

113 ± 3

15.590

18.076

17.793

44.1 ± 0.2

15.533

15.525

18.452

18.278

38.591

15.625

15.614

18.773

18.538

38.918

38.561

15.635

15.625

18.741

18.524

38.900

38.819

15.603

15.597

18.951

18.827

M AN U TE D EP

15.447

Pb/204Pb

206

19.316

GV27

AC C

207

RI PT

Nd/144Nd

143

87

SC

Sr/86Sr

87

Sample

66.5 ± 0.3

AC C

EP

TE D

M AN U

SC

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Highlights New geochemical data and 40Ar-39Ar ages from the Yüksekova Complex.



The volcanic members of the Yüksekova Complex from the eastern parts of Lake Van suggest three different types of rock chemistry.



HFS and LIL element distributions of tholeiitic and calc-alkaline members points a subduction-related environment.

SC

Alkaline members have originated from enriched mantle source relative to the tholeiitic

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and calc-alkaline ones.

AC C



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