GEOLOGY AND GEOCHEMİSTRY OF THE KARADAĞ VOLCANİC succession , POLİOCENE - QUATERNARY, CENTRAL 2INATOLIA, TURKEY

The Karadağ volcanic succession of Pliocene and Oualernaiy represents typical Continen ­ tal volcanisms of central Anatolia. It consists of nıainîy lava flows and pyroclastic depositş. Overall, they Avere produced by magmato-phreatic e.Kplosions in four periods throiıgh the plioce ­ ne and Çuaternay times. The product of each period can be easiîy distinguished by vvcathering surfaces and localiy erodcd surfaces. Petrographical and geochemical analysis show that they are mostly andcsitic and dacitic roeks, originated from partial rnelting of Continental crust.


INTRODUCTION
The volcanic activity, developed in Anatolia (Turkey) during Neogene and Quaternary periods represents one of the most outstanding esamples of arc volcanism, related to Continental collisioıı (Pasquare et al., 1988), and it has heen investigated in several previoûs works, mainly dealing with its petrographical characteristics (e-g- Jung and Keller, 1972;Innocenti et al., 1975;Keller et al., 1977;Baseng et al., 1977;Baş, 1985;Tankut, 1985).In few studies, this volcanism from .stratigraphical and tectonical points of view were discussed (Savaşçın, 1982;Ercan, 1983;Pasquare et al., 1968).The main diffieulty to explain the volcanic evolution of Anatolia is the lack of a complete volcanic succession developed during Neogene and Quaternary.Volcanic fields are qnite away from each other.Additionally, characteristics and produets of volcanism differ from arca to arca.Tliere is only one locality in Ana- tolia, where volcanism of Neogene and Quaternary were supeıimposedly developed; Karadağ volcanic succession, which is described in this paper.It provides a unique axemple in oıder to examine the complete volcanic activities of tirese times.Generally, it is thought that The Karadağ volcanic succession forms an important topographic relief in the large Konya-Karaman plain.The elevations are 1100 m at the plain and 2288 m at the highest point.Deep recent valleys, incised the succession radially, provide good cross-sections.Overall, the Kara dağ volcanic succession consists of four volcanic sequences each of which represents separate volcanic periods (Fig. 1 and 2).The volcanic seguences are distinguished from cadı other by plaeosoiTlayers and/or intensely weatherecl surfaces.Erosive surfaces are locally developed.111 general, the volcanic següences are two-partite, comprising volcaniclastic and lava units.They described lıcloAv separately.are Volcanic Sequence 1 (Mercik Sequence): This is the basal sequence which is situated in Mercik area, some 3 km for away from the volcanic body.It has a core-like geometry and represents monogenic volcanic çenter.This sequence consists of mainly lava flows and subordinate pyroclastics.Units of lava flows are 1 to 3 m thick.Microscopically, they comprise some phenocrists of plagioclase, biotitc and hornblende in a porphyric texture.According to radiometric dating of Besaiıg et al., (1977)  V (kı?ı!dââ'    tallıkdağ and Kızıldağ areas.Volcanic sequence is composcd of at 2 least three monogenic centers which havı; two subsequences as volcaniclastics in its Iower seetion and iawa flows in its upper scetion.

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Stratigraphically, the lovvernıost part of the first snbsequence is composed of pumice-rich deposits, which indioates sediuıentary struetures of bare surge deposits.Puniice layers are also inciuded.There, relatively finer-grained layers are overlain by very thick, up to 100 ııı.block-andash flow deposit.s...Lverage size of blocks is 45 cm.Welding is locally present.Ali pyroclastics are superinıposcd and/or interfingered by retvorked pyroclastic deposits, such a.s lahars and volcanic mudflow8.Thicknesses of the rev'orked pyıoclastic units inerease relativciy towards the flanks of the VS2.
The second subsequeııcc of VS2 is lava flotvs with assymetric dome-like geometries.Lnits of the subsequence.
to 3 m thick, are inclined towards the south, probably due to origiııal topograplıy.Ijnit thicknesses decrease also sn the same direction dating indicates tlıat they emplaced within 2.05-1.95Ma ago (Besang et al., 1977).Petrographically, lava flow units types of andesite.
are composed of augitehornblende-biotite 1 V olcanic Sequejıce 3 (Merkez Sequence): Pıock.s of this sequence form the main body of the succession, emplacing in the Central areas, particularly around Bahar Tepe and Bozdağ.Rock facies and their stratigraphical pattern are similar to VS2 hotvever, volcaniclastic-s are much ınore spreaded than A S2's. Pyroclas- tic surge deposits are typical at the base of the sequence, and they pass laterally and vertically into pyroclastic flow deposits.Pumice-rich and ignimbritic layers are interbedded with coarse-grained, pıobably blockand-ash fîow units.Non-erosional to erosional bases of coarse-grained beds and irregularities in bed geometries suggest that block-and-ash flow units had been deposited as mass flows.
Vertically, pyroclastic units grade up to the flow breccias in addition to lava flows.Lawa flow thicknes ses reach occasionally up to 5.8 m.Breccias are very coarse-grained and ınean size of individual grains is 35 em in diameter.Lava flow units are in homogene tevture, however, flowage struetures are locally observed.Radiometric dating of Besang et al., (1977) indicated they occurreil 1.1 Ma ago.
A'olcanic Sequence 4 (Degle Sequence): This is the youngest sequence of the Karadağ volcanic succession, mostly situated in SW of A^S3, around Bozdağ and Değle dağ.It incîudes somc dome-like relief, suggesting moııogenic volcanic centers.
Pyroclastic units of the sequence are clominantly fine-grained.and localiy welded.They are covered bv flow brecciâs and lava flows.The lava units have radiaî distribution with inclination sometimes up to 45°.\ S4 is not only the youngest scquence, but also the highest level of the Karadağ volcanic succession, creating pictoresque morphology due to modern erosion.iAccording to stratigraphic position, lava lows of the sequence (SS4) emplaced at the end of Pleistoceııe time.
Overall, the four volcanic sequences seem to have heen formed by magmatophreatic eruptions, containing abundantly coarse grained pyro clastics.Block, cobbie and pehble size fragments are volumetrically dominated with the seguences, Neogene volcaniclastics of central Anatolia, tvhich occurred near and /or in lacustrine environments are relatively finer-grained resulted by phreatic explosions.as tuff or igrimbrites of Ürgütp-Göreme area.Consequently, this type of volcanism might to be related to Neogene pleogeography of Central Anatolia.

GEOCHEMİSTRY
Petrographically, the roeks of the Karadağ volcanic succession have rather homogeneous composition.In particular, autoclastics and lava flow units of the four sequence8 are composed of andesite and dacite.Totalîy 21 rock saınples (Tab.1), collected from the lava units and flow brecciâs, were analyzed and their C.I.P.W. ııorms was FejOj/FeO 0,15 and the results were checked and interpreted by various methods.
As it is seen in Tabîe 2, the roeks of the succession are generally silisium-rich volcanics and their SİO2 contents are between 59-66 %.According to Pecerillo and Taylor (1975) The charges in total alcaline content of the rocks against SİO2 content are illustrated in Figüre 5. Kuro (1966) classifies the rocks into 3 groups as pigeonitic (tholeitic) hiperstenic (high Al)and alcaline rocks by using the above mentioned changes.Except one sample of Ka radağ volcanics, ali the others are in calcalcaline fields (Fig, 5).The same results are also obtained hy using McDonald (1968); and Irwinand Baragar (19"l)'s criteria (Fig. 5).[After Kuno, 1966].
No rock samples of the succession, vvhich are found in subalcaline field of Figüre 5, show any increase in the content and bence they are in calcalcaline fields in AFM diagram (Fig. 6).The correlation of normative color index (NCI) and normative plagioglase composi tion (NPC) [the diagram of Irwin and Baagar (1971)] indicates that the studied samples are grouped on the line of andesite-dacite and particularly 11 samples are referrcd as dacite and 10 samples on andesite field (Fig. 7).Here, in the Ab'-An-Or triangle diagram, conciuded from CIPW norınes, ali rocks are seen mostly potassic composition (Fig. 8).According to Irwin and Baragar (1911)'s classification based tive plagioclase composition and AI2O2 contents, the samples in calc-alcaline area (Fig. 9).

on normaare mostly
The T values (t =-APO, -Na,0 /TİO2) of rocks are generally greater than 10, hence, they indicate sialic origin (Rittman, 1968).What is more ,the same results is emphazised bv the lo (Fig. 10).Line 2: Skaergaard Intrusion area [Wager, 1960).From geochemical point of view, the roeks of Karadağ succession have an intermediate acidic calc-alcaline characteristics and they sialic origin.Adiditionally, some of them are andesite and some are are dacite in petrographical definitions.Similar results are also reported by some previoûs works on the different volcanic areas of Turkey (e.g.Keller and Villari, 1972;Baş, 1979;Ercan, 1983;Terzioğlu, 1986).Acidic volcanics may be originated by various ways, for example, by the contamination of bacis magma with crustal material (Kuno, 1950) or by differentiation of basic magma (Kuno, 1968), or by anatexis of crustal material (Wiııkler, 1974), or also by partly melting of upper mantle components in high-water phase (Kuso, 9170).Origin of the Karadağ volcanic rocks seem to be rather complex.Both their minera- logical and geochemical compositions match to crustal rocks (granite, granodiorite).Consequently, this concordancc may suggest partial melting of Continental crust.On the other hand, presence of lamprophirized Ti-augite minerals within the studied rocks may also indicate a magmatic contamination .However, no basic magmatic rock is observed in hybridisation in the study area.Their presence in the crust may have been masked by the complex tectonic regime, at least since Late Miocene.So far, hybridisation was mentioned for volcanics empîaced in northern part of Central Anatolia (Tankut, 1985;Terzioğlu, 1986).Further systematic studies on thin sections are necessary to clarify the view.b) Volcanic evolution: On the hasis of stratigraphy of the Karadağ volcanic sucession, four main periods can be distinguished in the Pliocene and Quaternary The second period has occurred about 2,05 to 1,95 Ma ago (Besang et al. 1977).It has mostly evplosive characteristics.At least three monogenic centers cleveloped representing present Kartallık dağ, Sızak dağ and Kızıldağ elevations (dağ. in Turkish nıeans bili, mountain) The third period (1,1 Ma ago) w as probably the greatest volcanic activity, giving a caldera 2 km long and 1,5 km wide in the Merkez area (Fig, 1).Th'S monogenic çenter produced mainly pyroclastic deposits (Fig. 2).The last period (late Pleistocene) is represeuted by the formation of Bozdağ and Değledağ volcanics which inciude very thick unit.s of lava flows and flow breccias.The volcanics of this period were produced bv at least two monogenic centers at the northern side of the sucession (Fig-!)• Begginning of the volcanic activity in Konya ~ Karaman region should be related to geological setting of the Central Anatolia, possibly collisioıı of Afro-Arabian plate and Âuatolian plate (Pasquare et al, 1988).However, its evolution varies locally.The characteristics of the Karadağ volcanic succession is the presence of large lava flow units (Fig. 2).During each period, pyroclastic deposits were predominantly produced by explosive activities, and then lava empîaced.This sequeutial development suggests that volcanic activity of each period has been extinguished in time and resumed in the next period.We sug gest that this two~partite stratigraphy and/or extinction of voîcanism might be related to not only regional tectonics, but also to paleogeograplıy.In areas of Central Anatolia where pyroclastics are common deposits, syncronous lacustine deposits are also widespread and volcanism seems to have been influenced by large Neogene lakes.The lack of Plio-quatemary lacustine environment aroıınd the study area (Fig. 1).suggests effusive magmatophreatic eruptions giving thick lava units.
lavaş emplaced 3, 2 Ma ago.Probably, it cOcurred ■with effusive explosions.The other volcanic centers might be capped by later explosions.Volcanic Sequence 2 (Sızak Sequence): This is one of the main sequence8 of the Karadağ volcanic succes sion.It emplaced largely in NE side of the sucession, around Sızak, Kar-

Fig 1 .
Fig 1. Geological map of the Karadağ area.