Elsevier

Journal of Asian Earth Sciences

Volume 27, Issue 4, 1 September 2006, Pages 512-522
Journal of Asian Earth Sciences

Geology and petrography of the Masatdagi diasporic bauxites, Alanya, Antalya, Turkey

https://doi.org/10.1016/j.jseaes.2005.07.001Get rights and content

Abstract

There are more than fifteen bauxite outcrops in the study area located in the southern part of the Central Taurides. The bauxites are developed in the Upper Permian Cebireis Formation (carbonate rocks interbedded with schist) and Lower Triassic Asmaca Formation (limestone, dolomite, quartzite and schist). The bauxite outcrops are observed as parts of two or three independent bauxite blocks that were broken apart by faulting and an erosional surface. Based on outcrop appearances, four ore types can be defined; black, earthy, clayey, and Fe- and Mn-bearing bauxites. Oolitic textures are common in all ore types, except the earthy ones. Bauxites are represented by a mixture of diaspore and clay in varying proportions. Diaspore, boehmite, gibbsite, corundum, hematite, goethite, amorphous iron hydroxide, magnetite, chamosite, pyrite, marcasite, psilomelane, rutile, kaolinite, illite, muscovite, hydro-muscovite, chlorite, chloritoid, rectorite, ephesite, albite, microcline, quartz, K–Mg–Al silicate, hydrated K–Al silicate, and dolomite are present in the ore paragenesis.

Bauxites, which are observed at or near the contact between the Cebireis and Asmaca formations, are thought to be fillings of cavities within and/or on Late Triassic—early Cretaceous carbonate rocks.

Introduction

The study area is located between Mahmutbey and Asmaca villages, 15 km northeast of Alanya, Turkey, and covers approximately 10 km2 (Fig. 1).

The purpose of this study is to collect data about the geological setting, ore geometry, mineral paragenesis, texture and structure of the diasporic bauxites, and to elucidate their depositional environment. During field work, previously drawn 1/25000 scaled geological maps were checked. Mineralogical and petrographical determinations were carried out on the samples randomly collected during outcrop measurements of ore bodies.

Bauxite deposits in the area were first studied by Barutoglu (1938) followed by Arni, 1940, Arni, 1941, Blumenthal, 1941, Blumenthal, 1951, Egger, 1959, Peyronnet, 1967, and Wippern (1962). In these previous studies, the units in the area were defined as a Paleozoic schist sequence, Permo-Carboniferous carbonate rocks, bauxite formation and Neogene sediments. Researchers such as Ozgul and Arpat, 1973, Monod, 1977, Sengun et al., 1978, Ozgul, 1984, Ozgul, 1984, and Kansun, 1993, Kansun, 2000 had done detailed studies, and defined these units in the formation rank. In all these studies, an unconformity surface was placed at the base of the Lower Triassic units and it was thought that the bauxites formed as continental deposits filling the karstic cavities developed during the Late Permian and Early Triassic. On the other hand, Temur et al. (2002) argued that the unconformity at the base of the Lower Triassic unit had not been proved and that the bauxite formed as a result of filling of terra rossa in the surface- and subsurface-karstic cavities in carbonate rock during Middle Triassic time. The geometries, reserve and formation of the bauxite deposits were interpreted by Etibank, 1976, Orhon, 1978. Using data collected from drilling in the study area. Orhon (1978) pointed out that bauxites were deposited on the surface of an angular unconformity developed between the Permian and Triassic units. It is interesting to see that bauxites always pinch out on cross sections prepared with the boreholes data. They were not cut by most boreholes, and the thickness of the cuttings are not as large as that of the outcrops (Fig. 2).

Section snippets

Geological Setting

In the study area, the Yumrudag Group comprises the upper part of the Alanya Unit. This group consists of the Upper Permian Cebireis Formation and the Lower Triassic Asmaca Formation. The Cebireis formation consists of a thick carbonate rocks (marble) with interbedded schist and quartzite. The Asmaca Formation is composed of calc-schist, muscovite-schist, chloritoid-schist and quartz-schist with metadolostone and quartzite interbeds. Bauxite deposits in the study area have been interpreted as

Distribution of ore deposits

There are many bauxite occurrences in the northern part of Alanya, and their distribution extends up to Gundogmus toward the north. These bauxites are not part of the Seydisehir-Akseki boehmitic bauxite belt. The Masatdagi ore deposit is part of the Alanya–Gundogmus diasporic bauxite belt.

There are more than fifteen bauxite outcrops in the study area. In fact, all these outcrops are parts of at most two or three single bauxite masses, which are broken apart by faulting and erosion. Bauxite

Ore geometry

The soil cover and heavy vegetation in the study area make it difficult to discern the three-dimensional trends of the ore bodies. Almost all of the observed bauxites are as talus (Fig. 4a and b) and/or as large blocks several meters in diameter (Fig. 4c and d) within the talus. These bauxite outcrops can be traced about 200–250 m.

The true thickness of these bauxite bodies with a 30–40 m outcrop width is estimated to be a maximum of 20 m. Peyronnet (1971b) reported vein thickness of 4–5 m and the

Ore petrography

Masatdagi bauxites contain diaspore, clay, iron oxides, clinochlore and chloritoid in varying amounts. Four types of bauxites were distinguished (Peyronnet, 1971b) and interpreted in the outcrops extending along the road cut near Asmaca junction on Kobatlar–Asmaca road, where the ore bodies can be seen best in two-dimensions (Fig. 5). The transition and distribution of the bauxites are irregular, therefore, an arrangement representing all ore deposits cannot be determined.

Discussion

The Lower Triassic Asmaca Formation rest conformably on the Upper Permian Cebireis Formation. This finding is contrary to previous works suggesting that the Upper Triassic Asmaca Formation rests unconformable on the older units. This is a very important and new perspective in evaluating the geology of the Central Taurus, especially the Alanya Unit. Therefore, the depositional age of the Masatdagi bauxite is between the Late Triassic—early Cretaceous, in contrast to previous interpretations of

Conclusions

The main bauxite ore bodies occur in the transition zone between the Cebireis Formation and Asmaca Formation. However, small-sized ore deposits such as karstic fillings are present within carbonate rocks of both formations. A probable progressive transitional zone between basement rocks and bauxites was not observed. Most of the bauxite ore bodies occur in carbonate rocks, but in some places quartzite is present as decomposition zones at the ceiling rock, which indicates a lateritic enrichment.

Acknowledgements

Authors thank to Dr Hukmu ORHAN (Selcuk Univ.) and Dr Ibrahim COPUROGLU (Nigde Univ.) from Turkey, for their help and advices. Furthermore, this paper is prepared benefit from the inventions of the project which supported by Seljuk Univ. Invest. Fund. Project number 2000/075.

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