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Avnik - Murdere, Miskel, Haylandere, Gomic Tepe, Kelme Tepe, Kilhaz, Villik, Harabe, Hamek, Kasiman

Turkey

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The Avnik apatite rich iron deposits are located some 30 km south-east of the city of Bingol in southeastern Turkey, approximately 800 km ESE of Ankara.

The deposits lie in the western part of the Bitlis Massif, a large block of Palaeozoic metamorphic rocks within the East Taurus Fold Belt of southeastern Turkey. The ore deposits are hosted by calc-alkaline meta-volcanics of intermediate to felsic composition which range from greenschist to amphibolite metamorphic facies.

The host rocks are divided into: i). an Upper Series, comprising 1250 m of garnet-biotite-mica schist, unconformably overlain by 600 m of Permian marble, 500 m of marble with schistose intercalations and 700 m of predominantly marble. These units unconformably overlie ii). a Lower Series of intermediate to felsic calc-alkaline metamorphics dated at 454 ±13 Ma, with interbedded banded and massive apatite rich iron deposits, which are intruded by the Avnik granitoid and the 347 ±52 Ma Yayla granite.

The lower series has been subdivided into: a). The lowermost quartz-feldspar gneiss, which is approximately 1100 m thick, is composed predominantly of quartz and feldspar with variable amphibole, muscovite, magnetite and secondary chlorite after biotite. It alternates with amphibole rich gneiss to amphibolite and has been interpreted to represent a strongly foliated, recrystallised and albitised felsic meta-volcanic. Along the contact with the Avnik granitoid it is migmatised. b). Overlying amphibolite rich gneisses, composed of amphibole (actinolite, rarely hornblende and crossite) with diopside, albite, epidote, apatite, magnetite, biotite, muscovite and minor quartz, talc, chlorite, calcite, sphene abd hematite. The amphibole rich gneisses are predominantly intermediate in composition and are interpreted to represent meta-volcanic to meta-tuff protoliths. The felsic gneisses become more abundant towards the top of the 400 m thick unit. c). Meta-volcanics and meta-agglomerates which, although very variable, are dominantly felsic in character with 1 to 5 mm quartz and K-feldspar megacrysts in a fine matrix with iregular microsctructures and rare relict spherulitic textures. Thin lenses of meta-agglomerates comprising volcanic debris in a fine grained schistose matrix occur within the unit and commonly display cataclastic textures. d). Avnik Granitoid (or Albitite), is foliated and recrystallised on its margins and is transitional with the surrounding, partially assimilated meta-volcanics. It is composed of quartz, albite, K-feldspar and amphibole with minor muscovite, biotite, chlorite, zircon, sphene, magnetite and hematite and has a porphyritic to granoblastic texture on its margins. e). The Yayla Granite which is coarse grained and equigranular with 4 to 5 mm quartz, orthoclase, microcline, perthite, amphibole and biotite, intruded by abundant aplite and pegmatite dyke and veins. The angular unconfrmity at the base of the Upper Series truncates both the Avnik Granitoid and the Yayla Granite.

Ore occurs in three types, as follows:

Massive and banded ores - found as generally concordant lenses, ranging in thickness from 5 to 10 cm up to 2 to 5 m of usually fine grained (0.06 to 5 mm), internally laminated, magnetite, apatite and commonly actinolite. Individual laminations are 1 to 2 mm, up to a few cm thick.

Disseminated ores - which are widespread in the gneisses and metavolcanics, usually adjacent to the massive ores, although in some examples it is the dominant mineralisation style. Disseminated magnetite, as euhedral crystals up to 1 cm across, is fairly homogenously distributed, accounting for up to 20 to 30% of the host rock. Inclusions of apatite, actinolite and rarely crossite are found within the magnetite grains.

Stockwork ores - which are represented by irregular, crosscutting networks veins of magnetite and apatite cutting other iron rich rocks and the metavolcanics. These veins vary from a few mm to 5 m in thickness and contain large magnetite, apatite and actinolite crystals from 2 to 15 cm across. They and are found where the Avnik Granite has cut developments of massive and stockwork magnetite

The ores are generally stratigraphically controlled, occuring in the gradtional interval between the gneisses and meta-volcanics. In the Avnik district the metamorphics are localised in a large anticline which is overturned to the south. The Murdere and Miskel deposits occur in the NW plunging nose of the anticline, while the Haylandere, Gomic Tepe, Kelme Tepe and Kilhaz deposits are on the SW overturned limb of the anticline. The Villik and Harabe deposits are on the north-eastern upright limb. The Hamek and Kasiman deposits are in imbricate thrusts in the northern part of the zone.

Proven ore reserves in the Avnik district in 1984 amounted to 104 Mt @ 14 to 58% Fe.

The most recent source geological information used to prepare this summary was dated: 1984.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.


  References & Additional Information
   Selected References:
Helvaci C  1984 - Apatite-rich iron deposits of the Avnik (Bingol) Region, southeastern Turkey: in    Econ. Geol.   v79 pp 354-371


Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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