Gördes çevresindeki neojen serilerin ve zeolitleşmenin jeolojik, mineralojik ve jeokimyasal incelenmesi

Abstract

Gördes yakın çevresinde, maksimum IDGDm.'yi bulan kalınlıktaki Ne'ojen çökel istifi, Menderes Masifi kris- talen kayaları ve İzmir-Ankara Zonunun kaya birimleri üzerinde uyumsuz olarak; altta kaba ve ince taneli, birbiriyle yanal ve düşey geçişli birimler ile bunların üzerinde volkanik ve klastiklerden oluşan gölsel birim¬ lerden ibaretdir. Alt kaba ve ince taneli birimler (bloktaşı, çakıltaşı,kumtaşı), başlangıçta yüksek ener¬ jili akarsu ortamının tipik alüvyal yelpazesi çökelleri daha sonra ise düşük enerjili akarsu ortamının başlıca kumtaşlarından oluşan, yersel alarak gölsel ortama ge¬ çişi ifade eden çamurtaşı-şeyl düzeyli çökellerdir. Üst volkanoklastikler ise altta ve üstte zeolitli iki tüf seviyesi ile bunların arasındaki kumlu, killi, kar¬ bonatlı ve tüf içerikli ardalanmalardan oluşmaktadır. Bu üst gölsel istif, volkanik cam ve smektitin havza kenarında, hoylandit-klinoptilolitlerin havza kenarı ve merkeze doğru, analsim ve K-feldspatında havza mer¬ kezinde bulunduğu özgün mineral fasiyes alanlarına haiz¬ dir. Alt ve üst tüf birimleri yüksek oranda hoylandit- klinoptilolit içeriklidir ve bu diyajenetik alterasyon ana kaya kimyasında, değişen oranlarda SiQ2, Na2Q ve K2Q kaybı, A1203, CaO, MgO ve H20 kazancını meydana ge¬ tirmiştir. Alt tüfler büyük oranda klinoptilolit,üst tüfler ise tümüyle hoylandit-2 tipinde grup mineralle¬ rine sahiptir. Bu tip farklılığı 400° ve 550° G -12' şer saat süreli ısıl kararlılıklar, birim hücre kimya¬ larına ait Si/Al ve Na+K/Mg+Ca oranları ve X-ışınları yansıma çizgilerine ait I(d=5.11A)/I(d=2.24fl) oranları ile ortaya konmuş olup, tüm bu parametreler özgün ayırt¬ man değerlere sahip olacak şekilde, klinoptilolitlerde hoylandit-2'lere göre daha yüksektir. Alt tüf birimi¬ ne ait, iki tip mineralinde beraberce bulunduğuna dair verilere sahip örnekler hariç tutulduğunda, Si/Al oranı 4.57'den Na+K/Mg+Ca oranı 0.42'den küçük hoylanditlerin 55aaC'deki ısıl kararlılıkları 0.20'den ve I(d=5.11A)/ I(d=5.24S) oranlarıda 1.00'den küçük bulunmuştur. Klinoptilolitlerde ise Si/Al oranı 4.61 'den, Na+K/Mg+Ca oranı 0.96'dan, ısıl kararlılıklar 0.44'den ve şiddet oranlarıda 1.28'den büyüktür.

This work aims to interpret the lithostratigraphic relations and petrographic characteristics of Neogene rock units and also areal and vertical variations of authigenic mineral facieses, mineralagical and chemical properties of zeolite minerals in the tuff and sedimentary units. This studied area covers 150 kmz, stretching from Salur and Dargil villages in the north to Deliler village and Kalabak hamlet in the south and from Softalar hamlet in the west to Sogeler and Kızıldam villages in the East. Negene sedimentary and volcano-sedimentary rocks disconf crmably overlie methamorphic rock units of Menderes massif in the eastand Mesozoic units of ophialits complex along the Izmir-Ankara zone in the north and northwest. These 1000 meter thick Neogene sequences mere observed and divided into five lithostratigraphic units. At the base, there is the lower coarse-grained unit made up of coarse conglomerate, conglomerate and pebbly sandstone having features typical of alluvial fans. These poorly consolidated, irregular deposits sedimented along the margins of the basement are 125 to 400 meters in thickness which is controlled largely by the basement topography and sedimentation rate. The lower coarse-grained unit gradually passes upwards to the lower fine-grained unit. This unit which is made up mainly of sandstone and pebbly sandstone was deposited in a relatively low-energy fluvial environment, Yellow, orange, gray and greenish, poorly consolidated Vll and massive sandstones comprise of widespread medium or well consolidated finely-bedded intercalations with cross bedding and sale marks. Carbonateous mudstone-shale unit is occured in the lower fine-grained unit with the thickness of 25D meters locally on the north and northwest of the studying area. This mudstone-shale sequence is approximately kü meters thick and mapable in this part of the area. Mudstones and shale generally show lamination and fissility in the shale horizons. This unit may be considered as a stage having changed from fluvial to lacustrine facies in the north and northwest of the area. Pyroclasts which came from the volcanic center, probably on the north or northeast, form lower tuff unit which constitutes the first volcanic sequence in the region. The maximum thickness of this tuff unit is 85 meters. The lower tuffs rest comformably on the lower fine-grained unit. Tuffs are made up of dust, ash and lapilli tuff regarding to the sizes of their elements and vitric and vitric-crystal tuff regarding to the type of their elements. The lower tuff unit has undergone diagenetic altertion and zeolites (heulandite, clinoptilolite, locally flipsite and chabazite), clay mineralsCsmectite, illite, celadonite). siliceous minerals(opal-CT, quartz), H-feldspar and carbonate minerals (calcite, rarely dolo mite) are authigenically formed. The outcrops of the lower tuff unit in the north of the boundary between Mahmudin hill-Yarendede hill show a fresh glass + smectite facies. Although this part of the unit was not affected by high degree alteration, there are some paragenetic zones which generally consist of heulandite-clinoptilolite 80% in the south of the boundary mentioned above. These facieces show zonation from the marginal basin to the deeper parts of the basin as ph and salinity change. H-feldspar and also quartz occurs in samples from the central of the area (around of Hıranköy Uillage). Clinoptilolite is the only heulandites group zeolite mineral of the lower tuff unit.- Clinoptitolites are formed in glass shard, cavities and along fibres within pumice fragments. These are 5-20 micron in length 3-8 Vlll micron in width and generally ahow irregular acnumalitiana. The lower tuff unit ia comf ormably overlain by the upper unit. Thia unit with maximum 2GD metera thickneas ia composed of aandstane, sandy-clayey limeatone, limestone, mudstone, shale, siliceous limestone, tuff, sandy tuff, carbonateous tuff which all appear to be of lacuatrine origin. Sandatonea at the bottom and top of the unit ahow relative thickening. Poorly conaolidated sandstones comprise of finely-bedded arenite intercala tions. Mudstones and shales consist of carbonate at the top and clay at the bottom zones. Tuff and limestones have frequently hibridic rock characteristics like aandy, siliceous carbonateous tuffa and sandy, siliceous, limestone. High content of analcime has been observed in the center of basin in tuff levels. The upper unit with maximum 70 meters thickness has a heulandite-2 with 77 % except the samples with K-feldspar. Rhyolithic and ryodacitic tuffs are glassy dust and ash typ in general. The upper tuff unit and the upper unit show zonation of facieces with heulandite- clinoptilolite, K-feldspar and analcime. Analcime and K-feldspar occurs in samples from the central of the area. Type of the group mineral of upper tuff unit is heulandite-2. There is not any sample having clino- ptilolite. Heulandite crystals giving regular accumali- tions of the upper tuff unit are less than 5 micron in length and 2.5 micron in width. Chemical comparisons between petrographically or mineralogically identified glass and its adjacent alteration products and unaltered and completely altered whole rocks from the same unit indicate that Si, Ca, Na, K, Mg, HpD and alao Al were mobile component. The gain of A12D37 MgO, CaD and H-O. and the lost of Si02,Na20, KpD are accomplished due to zeolltic alteration with heulandite and clinoptilolite of lower and upper tuff units. Heulandite group zeolites from Gardes basin are identified as heulandite-2 and clinoptilolite due to the results of the heat experiments and unit cell compositions. Twentynine samples from lower tuff unit were recognized as clinoptilolite. Four samples from same unit and all of the ten aamplea from upper tuff unit are heulandite-2. Descriptions of the heat experiments are done by following ALIETTI.C1972). IX Although polymorphism was observed in five heulan- dite-2 samples (A and I phases in one of the samples, A and B phases in two samples and A, I and B phases in the other samples) the other nine heulandite-2 samples do not show any polymorphism(they show only natural phase=A) depending on the position of d(020) spacing after a heat treatment for 12 hours at 400 C. d(D2D) spacings assumed three different values due to the existence of three phases, d(020):8.S3 8-9. 03A for A phase; d(02G)=8.63 H-8.7DH far I phase and d(020)=8.41A for B phase. Five heulandite samples, four of which show polymorphism, have been completely destroyed after a heat treatment for 12 hours at 55DDC. Differential thermal analyses of these samples show that at about 25D C, phase transformations start in heulandite and after 400 C heulandite becomes amorphous. The intensity of d(D20) peak taken from other nine heulandite-2 samples decreased by the percentage of 71-86 % Dn the Dther hand, the temperature of lattice destruction in all clinoptilo- lite sample is higher than 55D°C. The lost of the intensity of d(02D) peak taken from clinoptilolite samples is very small amount for 400 C but high percentage for 550 C in some samples. Thermal stability values calculated from the ratio of the intensity of d(020) peak far natural to the intensity of d(020) peak for 550°C are 0.DD-D.29 in heulandite-2 and D. 44-0.88 in clinoptilolite. There is a regular relation between chemical compositions and thermal stabilities of heulandite group minerals. This relation can be much better observed by the ratio of Na+K/Mg+Ca than Si/Al versus thermal stability. The relationship between thermal stability values and the ratio of Na+K/Mg+Ca can be established as a lineer line with correlation coefficient is 0.920 (Figure-1). The ratios of Si/Al in heulandite-2 and clinoptilolite samples are 4.22-5.04 and 4.S1-5.43 respectivetely. The ratio of Ma+H/Mg+Ca is 0.28-0.73 in heulandite samples and 0.9&-2.99 in clinoptilolite samples. a c- "5 c 0.8- 0.6 C o < O z: j= i-." ?.a o o 0.4 0.2- O 10 I 0.8 Na+K/ -i r- 1.6 Mg+Ca IN UNIT I 2.4 CELL 3.2 FIGURE: 1. The relationship between thermal stability and the ratio of Na+K/Mg+Ca Dn the Dther hand, the ratio of I(d=5. 1l8)/I(d=5,248) that is suggested firstly in this study is below 1.27 far heulandite-2 and above 1.28 for clinoptilolite samples. This ratio has a 1DD % certainty between the values given above. By the application of this ratio, it is possible to quess thermal stability and the ratio of alkaline/earth alkaline cations of the heulandite group minerals. XI The relationship between thermal stability and the ratio of I (d=5.1 1 A)/I (d=5. 24Â.) is shown in Figure The correlation coefficient of lineer line is 0.935. These intensity ratios are 1.14-1.27, 0.74-1.00 and 1.28-1.90 for heulandites-2 from lower tuffs, heulandites-2 from upper tuffs and clinoptilolites respectively. 1.00 n 0.80- 0.60- 0.40- = 0.20- aoo- 0.60 0.80 1 1 P 1.00 120 1A0 1.60 Hd=511Â) / I(d=524Â] zoo FIGURE:2. The Relationship Between Thermal Stability and the Ratio of I(d=5.11A)/I(d=5.24 A).