Geology, Mineralogy and Genesis of Yenidoğan (Sivrihisar) Sepiolite Deposit

Yıl 1992, Cilt: 114 Sayı: 114, 51 - 64, 01.07.1992

Mefail Yeniyol

Öz

 In addition to the lump sepiolite known as the meerschaum, it has been known that there also exist some
layered sepiolite deposits in the Eskişehir Neogene basin since 1960's. Sepiolite deposit, which is found nearby the Yenidoğan
village, southern Sivrihisar is one of the most important one among them. Here, sepiolite occurs as two separate beds in the
upper part of the Pliocene sequence, which is made up of the alternation of dolomites and dolomitic marls. The lower sepiolite
bed is up to 3 m. thick and consists of sepiolite clay and dolomitic sepiolite. The upper one has maximum thickness of 10m.
and it regularly extends over 750 000 square meters. It is made up of the alternation of sepiolite clay and sepiolite-rich layers
and lenses. Sepiolite clay consists of over 90 % sepiolite mineral and also organic material in varying proportions but not exceeding
10 %. It may also contain quartz, feldspar, illite, dolomite and pumice grains less than 5 %. Dolomitic sepiolite is the
most abundant sepiolite-rich material in the upper bed. Its dolomite content is less than 50 %, and in some cases, illite and
quartz grains may also be found in trace amounts. Sepiolite has been deposited at the shallow margins of alkaline lake, shortliving
ponds and marshlands. Si4+
and Mg
2+-rich solutions with 8-8.5 pH values have probably favoured sepiolite formation. Under
these conditions, sepiolite was formed by direct crystallization and precipitation from the lake water. It was also formed from
the solutions circulating through the intergranular space and along the desiccation cracks during and after diagenesis.

Anahtar Kelimeler

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Kaynakça

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