Abstracts of selected papers






JOURNAL OF ASIAN EARTH SCIENCES,21: 365-376
Geology, mineralogy and fluid inclusion data of the Kızılcaören fluorite-barite-REE deposit, Eskisehir, Turkey.
Ali Haydar Gültekin, Yüksel Örgün, Fikret Suner Istanbul Teknik Üniversitesi, Maden Fakültesi, 80626 Maslak, Istanbul,TURKEY

Received 10 July 2001; accepted 2002 Abstract

The Kızılcaören fluorite-barite-Rare Earth Element (REE) deposit occurs as epithermal veins and breccia fillings in altered Triassic metasandstones and Oligocene-Miocene pyroclastics near to alkaline porphyritic trachyte and phonolites. The deposit is the only commercial REE and thorium source in Turkey.

The majority of the fluorite-barite-REE mineralisation at Kızılcaören has been formed by hydrothermal solutions, which are thought to be genetically associated with alkaline volcanism. The occurrence of the ore minerals in vuggy cavities and veins of massive and vuggy silica indicate that the ore stage clearly postdates hydrothermal alteration. The deposit contains evidence of at least three periods of hypogene mineralisation separated by two periods. The mineral assemblage of the deposit includes fluorite, barite, quartz, calcite, batnaesite, phlogopite, pyrolusite and hematite as well as minor amounts of plagioclase, feldspar, pyrite, psilomelane, braunite, monazite, fluocerite, brockite, goethite, and rutile.

Fluid inclusion microthermometry indicates that barite formed from low salinity (0.4 - 9.2 eq. wt. % NaCl) fluids at low-temperatures, between 105o and 246 oC, but fluorite from slightly higher salinity ( < 12.4 eq. wt. % NaCl) fluids at low- and moderate-temperatures, between 135 o - 354 oC. The depositional temperature of bastnaesite is between 143 oC - 386 oC. Local coexistence of liquid- and vapour-rich inclusions suggests the presence of boiling conditions. Many relatively low-salinity (about < 10.0 eq. wt. % NaCl), low- and moderate temperature (200 o - 300 oC) inclusions might be the results of episodic mixing of deep-saline brines with low-salinity meteoric fluids.

The narrow range of d34 S (barite and pyrite) values (2.89 to 6.92 %o suggests that the sulfur source of the hydrothermal fluids are the same and compatible with volcanogenic sulfate field, showing a magmatic sulphur source.



JOURNAL OF THE GEOLOGICAL SOCIETYOF INDIA 58 (3): 231-237 SEP2001 Significance of REE study for origin of sparry magnesite in Orhaneli Region, Turkey Suner F, Esenli F, Uz B, Esenli V, Gultekin AH

Abstract:


Pattern of REE distribution in various types of magnesite ore occurring within the Late Cretaceous ultramafics in Orhaneli Region (Western Anatolia) were studied to interpret their genetic significance. The samples were classified into three different groups viz. massive, lentiform and pignolite or stockwork. Individual groups exhibit distinctly different REE distribution pattern with variable Eu,Ce and Yb anomalies. Three types of REE distribution patterns arerecognizable with thefollowing characteristics: (1) high LREE/HREE ratios without having Ccand Eu anomalies, (2) similar LREE and HREE abundance with uncertain positive and negative Eu and Ce anomalies, and (3) low REE abundance with markedly positive Eu, negative Ce and slightly negative Yb anomalies. It is postulated that the redox conditions in the primary mineral formation system was subjected to change and as a result, subsequent mobilization followed by recrystallization took place in the formation of primary magnesite minerals. Although a low temperature environment is indicated for magnesite formation, it is possible that REE-poor solutions derived from the fluid-rock interaction had caused mobilization and later recrystallization of magnesite ore.

Author Keywords: geochemistry, magnesite, massive, lentiform, pignolite, stockwork, sparry, rare earth elements, Turkey




COMPUTERS AND GEOSCIENCES, 28: 1017-1036
CLASTOUR : A computer program for classification of the minerals of the tourmaline group

F. Yavuza,*, A. H. Gültekin*, M.Ç. Karakaya**
*İstanbul Teknik Üniversitesi, Maden Fakültesi, Maden Yatakları-Jeokimya Anabilim Dalı, 80670, Maslak, İstanbul, Turkey **Selçuk Üniversitesi, Mühendislik ve Mimarlık Fakültesi, Jeoloji Mühendisliği Bölümü, TR-42031, Konya, Turkey

Abstract

Tourmaline is the most important borosilicate mineral and a dominant carrier of boron, occurring in different geologic environments. Recently, many investigators have focused on the enhanced understanding of crystal chemistry of this complex mineral group. CLASTOUR is a program package for IBM-compatible personal computers that can be used for classification of the tourmaline group. The program classifies most of the currently valid tourmaline end-members together with other hypothetical end-members. Because it is difficult to establish OH- and O2- contents at the V- and W- sites without carrying out bond valance sum (BVS) calculations, CLASTOUR gives alternative names for some tourmalines including dominant O2- anion at their V- and W- sites. The program is developed to edit, to store and to calculate the tourmaline analyses obtained both from electron-microprobe and wet-chemical studies. It is designed to calculate entered tourmaline analyses into cation and molecular percentages, to share cation site-allocations at the different structural positions and to give mole percent of the end-members of alkali-, calcic-, and X-site vacant-group tourmalines. Thus, CLASTOUR makes it possible to plot various types of binary and ternary diagrams under the Grapher software. This program is a user-friendly software with pull-down menus, base-function keys, help menus, extensive error codes and mouse options. The compiled program together with the test data files and graphic files is approximately 1160 kilobyte.

Keywords : Tourmaline; Classification; End-member; Electron-microprobe; X-site vacant; Alkali; Calcic; Binary diagram; Ternary diagram




PROGRESS IN MINING AND OILFIELD CHEMISTRY, Vol. 1, pp. 239-248
Geochemistry of Andesite-Hosted, Vein-Type Mn-Ba Mineralizations, Bigadiç, Balıkesir,Turkey A. H. GÜLTEKİN, Y.ÖRGÜN Mining Faculty, Istanbul Technical University, Maslak, 80626, Turkey

Abstract

Numerous Early Miocene Mn oxide and Mn-Ba deposits are distributed in the Havran- Dursunbey metallogenic sub-province, eastern Balıkesir, Turkey. The Mn - Ba deposits usually cluster in the southeastern part of this province and occur as Mn oxide and barite veins and lenses formed along steeply dipping northeast-trending faults. The Yalakkaya Mn-Ba deposit constitutes one of the most important deposits of the Havran- Dursunbey metallogenic sub-province.

The Mn-Ba deposits in the Bigadiç area are associated with andesites. These rocks form a part of widespread post-Oligocene calc-alkaline volcanism which began during the Late Oligocene-Early Miocene in a compressional regime and display a large variations of K2O from approximately 2 % to 6 %. Si2O content ranges between 55 % and 63 %. These chemical results signify a high-K calc-alkaline spectrum. Another significant chemical characteristic of these rocks is enrichment in rare earth elements (REE). Absolute LREE abundances are close to the values shown by high-K calc-alkaline and anorogenic andesite. High field strength (HFS) elements are also in low-moderate concentration.

The Yalakkaya Mn-Ba mineralization has been formed by hydrothermal solutions which are thought to be genetically associated with calc-alcaline volcanism. In the deposit, early hydrothermal activity is responsible for the four types of hypogene alteration in decreasing intensity: silisification, hematization, argilic alteration and carbonatization. The ore stage clearly postdates hydrothermal alteration, as indicated by the occurrence of ore minerals in vuggy cavities and fractures in silica bodies. The mineral assemblage of the deposit includes pyrolusite, psilomelane, poliannite, barite, hematite, and quartz, as well as minor amounts of manganite, magnetite, manganocalcite, braunite, bixbyite, calcite, limonite, goethite, sphalerite, galena, calcopyrite and clay minerals. Generally, it was recognized three ore types as massive barite ore, pyrolusite + psilomelane + hematite+ barite ore and pyrolusite + psilomelane + poliannite ore. Massive barite ore, the only type of mineralization of economic interest (with estimated reserves of 0.5 million tons), contains an average of 71.2 percent barite, 2.7 percent Pb, 0.1 percent Zn. The Mn oxide ores are characterised by low Fe/Mn ratios and high trace element content and their rare earth element pattern are similar to those of hydrothermal Mn deposits. Alteration geochemistry indicates that the transition from fresh to altered andesite has little effect on most elemental levels.





FÖLDTANI KÖZLÖNY (BULLETIN OF THE HUNGARIAN GEOLOGICAL SOCIETY)128/4, PP: 1-22
Metallic and Non-metallic Mineral Resources in SE Anatolia
Ali Haydar GÜLTEKİN, Fikret SUNER and Yüksel ÖRGÜN Mining Faculty, İstanbul Technical University, Maslak 80626, İstanbul, Turkey

Abstract

The southeastern part of the Anatolian Peninsula comprises a large number of ore deposits showing the well-preserved sedimentary and magmatic textures connected with their origins. The whole region has undergone extensive deformations and corresponding high-grade metamorphism during the Alpin Orogeny. From oldest to youngest, the known metallic and non-metallic deposits are scattered to a large area of various rocks in the interior of the Eastern Taurus fold belt of southeastern Turkey. Most are essentially small deposits on a commercial scale and are of varying degrees of importance. The age of mineralization differs from place to place across the region and ranges from Paleozoic to Tertiary.

The metallic ore deposits of the region nearly always seem to be associated with the evolution of the Eastern Taurus fold belt, part of the Alpin tectonic system. This belt is dominated by upper Cretaceous-Oligocene eugeosynclinal lithologies and much ophiolite and blueschist, especially at its central part. The ultramafic and mafic members of the ophiolite suite contain the large chromite deposits and Cyprus-type massive sulphide deposits. The deposit at Guleman, Elazığ constitutes one of the most important chromite deposits of Turkey and has yielded roughly one-third of the country's total chrome production. All the deposits are of podiform type and are associated with ocean-floor spreading areas. The most important example of the massive sulphide deposits is that at Ergani, Elazığ. These are essentially sea-floor pyritic copper sulphides which occur within the ophiolite complexes. The Keban Pb-Zn deposits form other productive metallic deposits of the region and occurred as vein fillings, cavity fillings in brecias, and stockworks in the pneumo-hydrothermal stage of the intermediate and acidic magmas. Generally, the lead-zinc deposits are polymetallic vein systems developed in backarc environments. In addition to these deposits, replacement of the country rocks by high-temperature hydrothermal solution has given rise to some metallic orebodies emplaced especially within limestones.

The productive sedimentary deposits known in the region are the phospate deposits at Mazıdağ, Mardin and asphaltite seams at Şirnak. They are found in the various sedimentary formations ranging in the stratigraphical scale from Cambrian to Quaternary. These formations are metamorphosed in the greenschist or amphibolite facies in many places, as in the Avnik area, and convert to the metamorphic rocks such as gneiss, schist, phylitte, and marble. The phosphate deposits occur as beds in shallow marine environments and are associated with the segregation of phosphoric acid in the sea-water. The economic importance of metamorphic massifs is essentially restricted to some apatite -rich iron deposits and several epitermal veins formed along the main faults.

Key words : Chromite deposits, Massive sulphide deposits, Phosphate, Asphaltite seams, Eastern Taurus fold belt, Southeastern Anatolian thrust fault, Turkey.





JOURNAL OF ASIAN EARTH SCIENCES
Geology, mineralogy and fluid inclusion data from the Arapucan Pb-Zn-Cu-Ag deposit, Canakkale, Turkey.
Yüksel Örgün*, Ali Haydar Gültekin,*, Ayten Onal** *Istanbul Teknik Üniversitesi, Maden Fakültesi, 80626 Maslak, Istanbul,TURKEY **İnönü Üniversitesi, Mühendislik Fakültesi, Malatya, Turkey

Received 10 July 2001; accepted 2003 Abstract

The Arapucan Pb-Zn-Cu-Ag deposit occurs as hydrothermal veins in diabase and altered Triassic metasandstones adjacent to calc-alkaline intrusive igneous rocks. The deposit is an important commercial source of base metal in northwestern Turkey. Potential by-products are silver and gold.

The geology of the area features a Paleozoic metamorphic basement, Triassic sedimentary rocks including the carbonate blocks, Tertiary granitoids and Neogene volcanics. The mineral assemblage includes galena, quartz, calcite, sphalerite, chalcopyrite and pyrite as well as minor bismuthinite, tetrahedrite, pyrolusite, hematite, scheelite, malachite, magnetite, limonite and rutile. Silver is associated with tetrahedrite. Early hydrothermal activity was responsible for formation of three hypogene alteration types of decreasing intensity: silicification, sericitization and argillic alteration. These alteration styles show a rough spatial zonation. The ore stage clearly postdates hydrothermal alteration, as indicated by the occurrence of ore minerals in vuggy cavities and fractures in silica bodies. The deposit contains evidence of at least two periods of hypogene mineralization separated by a period of faulting.

In addition to Pb, Zn, Cu, Ag and Au, the ores contain substantial quantities of W, Bi, Sb and Te. Average ? 34S values for galena and pyrite are -3.95 and -2.24 o/oo, respectively, suggesting an igneous source for both the sulphur and metals. However, geologic and geochemical interpretations suggest that at least some of metals are leached from the metasandstones and diabases. Fluid inclusions in main-stage sphalerite homogenize at 229o to 384 oC with salinities ranging from 1.7 to 18.5 eq. wt % NaCl. The deposits formed during the interaction of two aqueous fluids: a higher-salinity fluid (probably magmatic) and a dilute meteoric fluid. The narrow range of ? 34S (galena and pyrite) values (- 5.2 to -1.2 o/oo CDT) suggests that the sulphur source of the hydrothermal fluids is the same during deposition of the metals.

Keywords: Ore, Alteration, magmatic fluid, Hydrothermal,. Epigenetic

* Corresponding author. E-mail: gultekin@itu.edu.tr





JOURNAL OF ASIAN EARTH SCIENCES, 24/ 1-9, 2004
Geochemical evidence for the tectonic setting of the Harmancık ophiolites, N.W. Turkey. H. Manav*, A.H. Gültekin**, B, Uz**
Department of Geology Engineering, University of Pamukkale, Denizli, Turkey
Mining Faculty, Istanbul Technical University, Maslak, 80626, Turkey Abstract

The ophiolites of NW Turkey are mainly represented by the Harmancık, Orhaneli and Tavşanlı ophiolites which are a remnant of oceanic lithosphere formed in the Mesozoic Neo-Tethys. These ophiolites constitute part of the İzmir-Ankara suture zone which the separates Pontides to the north from the Anatolides and Taurides to the south.

The Harmancık area includes a well-defined metamorphic basement, ophiolitic melange, peridotite (dunite, harzburgite), serpentinized peridotite, doleritic dykes and Neogene cover sediments. Metamorphic rocks of the Harmancık area are represented by clastic and recrystallised carbonates, indicating blueschist facies conditions and are tectonically overlain by the peridotites cut by basic dykes. Based on texture and mineralogy, the dykes are divided into three petrographic groups, coarse-grained, medium-grained and porphyritic dolerites. Their chemical composition is essentially similar in terms of major, trace and REE element contents. When plotted on basalt discrimination diagram the dykes plot on IAT field and indicate subduction zone magmatism. The chondrite-normalised REE patterns for the dykes are Eu-depleted, similar to patterns for the mean dolerite composition of the NE Anatolian ophiolite and are slightly LREE-enriched. Our results suggest that the Harmancık ophiolite is a supra-subduction zone ophiolite on which an arc sequence was built and that the doleritic dykes formed by the partial melting of a mantle section.

* Corresponding author. E-mail: gultekin@itu.edu.tr




Ana Sayfa