Geothermometric Studies on the Attepe Iron Deposits
Total Page：16
File Type：pdf, Size：1020Kb
Mineral Res. Expl. Bul., 125, 1-11, 2002 GEOTHERMOMETRIC STUDIES ON THE ATTEPE IRON DEPOSITS Ali Rıza ÇOLAKOĞLU* and Gülay SEZERER KURU* ABSTRACT.- This study was carried out in the Attepe (Yahyalı) iron mineralization zone of Kayseri province. The main mineralization zone is 500 m long and lies approximately in the NNW/SSE direction. The study covers the geothermometric analyses which were carried out on the fluid inclusions of siderite, quartz and barites in relation within the iron mineralization. In this study samples were taken from five different rock groups observed in the field and were evaluated as a, b, c, d, e. Four different fluid inclusion types were determined in the siderite, quartz and barites of these rock groups (type I, type II, type III and type IV fluid inclusions). As a result of these studies three different formation processes were determined within the ore mineralization zone, namely (1) early stage, (2) late stage and (3) final late stage. Homogenization temperatures were 300-350°C in the early stage, 180-270°C in the late stage and 170-250°C in the final late stage. Early stage first group quartzes have in average 43 % NaCI in the early stage, the late stage guartzes of the first group on average have 35 % NaCI and the final stage barites have 3 % NaCI equivalent salinity. According to the macro observations in the mineralization area and the homog- enization temperature measurements made in laboratory whatever the origin of the fluids, the deposits were formed in the hydrothermal stage conditions and hypothermal, mesothermal and epithermal stages were active in these hydrothermal stages. INTRODUCTION and mineralization are also present (Ayhan The region within the Attepe iron mine and İplikçi, 1980; Metin 1983; Henden et al., which covers the study area is the second 1978; Henden and Önder, 1980; Önder and largest iron basin of Turkey. This deposit is Şahin, 1979, Şahin and Bakirdağ, 1985; Dağ- described firstly as Faras mine by Lucius in lıoğlu, 1990; Dağlıoğlu and Bançeci, 1992; the year 1972. In the region, The first comp- DağlıoğIu et al., 1998). This region is very im- rehensive studies on ore deposits were star- portant for steel-iron sector in our country that ted in the year 1967. After this period, studies ore production has been going on since have been corried out by various researchers 1969. and the region were investigated in detail in Mineralogical, petrographical and geoc- the terms of regional geology and ore depo- hemical studies have revealed that the iron sits. First geologic studies dealing with the ores in Attepe and its vicinity were present in chronostratigraphy were done by Blumenthal three different genetic types (Küpeli, 1986; (1944) and Abdüsselamoğlu (1958). Most de- 1991; Dağlıoğlu et al., 1998). In the region, tailed petrographical, geochemical, genetical mineralizations have been seen in the units and ore microscopy studies in the terms of which are of Mesozoic, Lower-Middle Cambri- mineralization were done by Küpeli, (1986, an, and Lower Cambrian ages (Dağlıoğlu et 1991 and 1999); Ayhan et al., (1992). Other al., 1998; Küpeli, 1999). These are sediman- detailed studies dealing with regional geology tary pyrite and hematite occurences (type, I), 2 Ali Rıza ÇOLAKOĞLU and Gülay SEZERER KURU hydrothermal siderite and hematite occuren- of these geothermometric measurement stu- ces (type, II), and karstic iron ores occuren- dies" were the determination of the homogeni- ces (type, III). Pyrite and hematite occurences sation temperatures of these minerals and the (type, I), in the Lower Cambrian aged bitumi- determination of the fluid inclusion types de- nous shale-phyllite and metaquartzites which veloped in connection with the mineralization are deposited in the sedimentary type are processes, attempts were also made to obta- firstly described by (Küpeli, 1986). The argu- in new data to support the previous data and ment that the ll'nd. type mineralization in the to determine the formation processes of the Lower-Middle Cambrian aged metacarbona- ore deposits. tes formed as a result of the hydrothermal processes are accepted by the all researc- GEOLOGICAL SETTING hers except Unlu and Stendal (1986). Based The Attepe iron ore deposits are boun- on the geochemical data Ünlü and Stendal ded by Geyikdağı unit, considered as otocton (1986) suggest a sedimantary model (Küpeli, by Özgül (1976), in the south, by Aladağ unit 1999). The ll'nd type mineralization were for- in the west, by Kireçliyayla melange in the med in the Paleocene-Lower Eocene time pe- north and by Göksun metamorphics in the riods on the other hand the lll'rd type minera- east. The oldest rocks of this region within this lization are formed at the beginning of Tertiary area are the Sicimindağ formation of Geyikda- epoch, by storage in endokarstic holes in the ğı unit. This formation contains Attepe mem- form of secondary ironhydroxide group of mi- ber on the top which is formed by alternating nerals within the framework of terrestrial mo- bituminous schist, phyllite and shales and vements and karstic processes of multiple Kandilcikdere member at the bottom compo- phases (Küpeli, 1991). The most important sed of schist and phyllite metquartzites (fig. 1). mineralizations in the region are classifed as On top of this formation lies the Çaltepe for- type II and type III ores. mation of Lower-Middle Cambrian age (Dean Mineralization have developed in tecto- and Monod, 1970). On top of these formati- nically controlled form and found as veins, ons lies the Seydişehir formation of Upper lenses and irregularly shaped masses. Pyri- Cambrian and Ordovician age containing El- te, tetrahedrite, chalcopyrite, marcasite, side- madağı ve Eğrisöğütdalı members and the rite, barite and little hematite and magnetite unit is composed of calcschist, phyllite, limes- are observed as ore minerals in all of these tone with nodules and metasandstones. On type mineralizations (Küpeli, 1999). In order top of these formations the Karakızoğlu for- to determine the conditions of the mineraliza- mation of Mesosoic age are present with an tion process and for the purpose of clarifying angular discordance. It is composed of schist, the previous observations and conclusions, phyllite calcschist and recrystallized limesto- geothermometric measurements were made nes. The mineralization is observed as lense on samples of five characters (a, b, c, d, e) in and vein shaped in all formations older than the field studies (fig. 1). In this study siderite, the Miocene age. The most important minera- quartz and barite in connection with the mine- lization are observed in metacarbonates of ralization zones are evaluated. The purpose Lower-Middle Cambrian age (fig. 1). GEOTHERMOMETRIC STUDIES ON THE ATTEPE IRON DEPOSITS 3 4 Ali Rıza ÇOLAKOĞLU and Gülay SEZERER KURU FLUID INCLUSION PETROGRAPHY Type II. fluid inclusions: three phases (li- Samples are taken from the quarry ope- quid + vapor + solid). rated by open-pit method for studies of fluid Type III. fluid inclusions: one phases (li- inclusion. These samples are, (a) siderite ve- quid). ins cutting through grey colored limestones, Type IV. fluid inclusins: one phase (va- (b) light brown-dark brown colored siderite por) transformed into iron-hydroxite group mine- As a result of the studies similar types of rals, (c) quartzes found in siderite and partly fluid inclusions were differentiated into pri- cutting through it, (d) quartzes in iron-hydro- mary and secondary origins however only the xite zone and (e) less observed barite seen data from the fluid inclusions of primary type in the mineralization zone. were evaluated. Fluid inclusions which are classifed into Dimensions of these fluid inclusions of four groups in are further subgrouped into five four types are generally within 2-18 microns. group samples (fig. 2). According to the com- They provide different fluid inclusion types position and fluid inclusions in the samples (a, with regular and irregular forms morphologi- b, c, d, e) are grouped into four different gro- es. For example in siderites fluid inclusions of ups (Roedder, 1984): type I and II, in quartzites types I, II, III and IV; Type I. fluid inclusions: two phases (liqu- and in barites only type I fluid inclusion is id + vapor). observed. GEOTHERMOMETRIC STUDIES ON THE ATTEPE IRON DEPOSITS 5 Geothermometric studies of the primary characteristics of the fluid inclu- Geothermometric measurements are sions by heat cold adhesives (entallan) is made according to the USGS fluid inclusion used and two sides are polished and 35 mic- systems. During the heating and freezing me- ron thick special fluid inclusion sections are asurements liquid and gaseous nitrogen is produced. Results of geothermometric me- used. The instrument is calibrated as ± 0,2°C asurements made on the fluid inclusions of si- for temperatures below 0 °C and as ± 2,0°C derite, quartz and barites taken from the mi- for higher temperatures. Synthetic fluid inclu- neral phases related to the ore are given in summary form (Table-1). sions containing CO2 and liquid phases are used in the calibration. To prevent the spoiling Siderites they have very few fluid inclusions. The se- Lenses of siderite are usually of 10-80 cond group of siderites have larger crystals cm thickness. In some locations siderites are (0.3 mm to 1 cm) and they contain few amo- in the form of crack fills. Siderites are divided unts of type I fluid inclusions of 6-10 microns into two groupes. First groups of siderite dimensions. Homogenization temperatures form siderite veins cross cutting to grey colo- obtained from the heating experiments made red limestones and schist rocks (a), second on these fluid inclusions indicate two sepera- group of siderites are of light dark brown colo- te phases. In the first stage the homogeneza- red. These are siderites (b) which show wide tion temperatures are in between 180-290°C.