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Arapucan

Turkey

Main commodities: Pb Zn Cu Au Ag
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The Arapucan Pb-Zn-Cu-Ag deposit is located in Canakkale province, northwestern Anatolia, Turkey, ~11 km NE of the town of Yenice, 75 km ESE of the city of Canakkale on the Bosphorous coast, and 200 km SW of Istanbul.

The mining history of the Arapucan deposit goes back to ancient time when the mine is believed to have supplied the first known lead products to nearby Troy (Agdemir et al., 1994). It is one of the many epigenetic Pb-Zn deposits in the Yenice-Kalkım mineral district of the Kazdag Massif the same mineral province as the Balya Mine, 40 km to the SE, which was the main producer of Pb and Ag in Turkey during the periods from 1839 to 1849 and 1892 to 1940. Mineralisation at Balya however, differs from that at Arapucan, in that it consists of Pb-Zn-Ag rich skarn and carbonate replacement zones, but also epithermal associations, and is hosted in limestones and dacites. Historic production at Balya amounted to ~4 Mt @ 10% Pb, 10% Zn, 0.75 g/t Au, and 250 g/t Ag which makes the two deposits comparable in size (see Arapucan reserves below).

The Arapucan deposit is located in the Sakarya Zone, one of four NE-SW trending tectonic zones of western Turkey, near the centre of the Kazdag Massif. The Kazdag massif is mainly composed of continental metamorphic rocks, dominantly medium-to coarse-grained felsic gneisses, banded amphibolites and quartzofeldspathic mica schists intercalated with marble, metamorphosed to amphibolite and granulite facies with local anatexis. The Sakarya Zone is a Hercynian continental fragment with Palaeo-Tethyan active-margin units. It comprises a complex, deformed Palaeozoic continental basement of metamorphic rocks and granitoids. During the late Triassic, the basement was overthrust from the south by a Permo-Triassic arc and related accretionary complexes of the Palaeo-Tethys, the Karakaya Formation (Okay, 1990; Okay and Tuysuz, 1999). These sequences are cut by late Cenozoic extensional faulting dividing them into elongate, roughly east-trending mountains.

The Permo-Triassic Karakaya Formation has been subdivided into:
• Lower unit - mainly of serpentinised ultrabasic lenses, metamafic and mafic tuffs, pyroclastic rocks and pillow lavas, interstratified with carbonate and shale bands;
• Upper unit - composed of two major clastic sequences; i). a quartzofeldspathic sandstone-shale sequence, with a continental granitic source, and ii). a greywacke-shale sequence containing also radiolarian chert, mafic volcanic rock and phyllite fragments.
These are unconformably overlain by a Jurassic sequence of conglomerate, sandstone, marl and limestones.

Rocks in and around the Arapucan area are from Palaeozoic to Tertiary in age, including Palaeozoic metamorphic rocks, Triassic conglomerate, and partly metamorphosed clastic rocks with carbonate blocks; Jurassic limestone and marl; Tertiary calc-alkaline granodiorite and Neogene conglomerate, sandstone, shale, marl and calc-alkaline volcanic rocks. The mainly arkose and greywacke clastic rocks, are considered to be equivalent to the Upper unit of Karakaya Formation and together with dolerites host the ore veins. The meta-arkose is light-grey to white and fine-to medium-grained with varying proportions of quartz, feldspar and mica, with shale interbeds. Greywackes comprise fine to medium, subangular particles, which are mainly mafic volcanic rocks and phyllite fragments, locally containing mudstone, dark green shale interbeds and hard, massive and partly metamorphosed limestone blocks of probable Permian age (Okay, 1990).

The volcanic rocks comprise andesite and brecciated dacite and are part of a dacite-andesite-trachyte-basalt sequence of regional extent. Andesites are dark yellow and brown, fine-to coarse-grained rocks, composed mostly of andesine and hornblende. Plagioclase occurs as phenocrysts. Dacites are fine grained to glassy rocks, mainly composed of quartz, albite or oligoclase. Dolerite occurs as large volume, medium-grained mafic dykes defined by plagioclase, pyroxene, biotite and chlorite. Pyroxene has been altered to amphibolite. On a regional scale, the granodiorite locally develops a contact aureole. These igneous rocks in the eastern and northeastern parts of the region are emplaced into metasediments with ages of from 29.2 ±1.6 to 20.1 ±1.1 Ma ( K/Ar; Delaloye and Bingol, 2000). Tertiary calc-alkaline magmatism in western Anatolia is associated with the closure of the Tethys Ocean (Ketin, 1966), considered to have been consumed by northward subduction below the Pontides during the latest Mesozoic to early Tertiary (Harris et al., 1994), with suturing of the Pontides and Anatolides and Taurides during the Eocene. This was accompanied by the emplacement of large ophiolite bodies over the Pontides to the north and the Anatolides to the south (Okay and Tuysuz, 1999). The granodiorites formed in a post-collisional environment, as a result of crustal thickening, although there is also some evidence of a subduction-related origin (Delaloye and Bingol, 2000). Mineralisation in the Arapucan district is interpreted to be coeval with the emplacement of the granodiorite (Anil, 1979), or formed shortly after the emplacement of granodiorite (Yucelay, 1971).

Closely spaced normal faults are found throughout the Arapucan district, with two fault systems defining the geometry of the Pb-Zn-Cu-Ag deposit. The first is an early, pre-mineralisation, regional NE-SW set which control the main sulphide ore veins. These faults cut both the metasandstones and the dolerite dykes, although late stage faults that cut the volcanic rocks are post-mineralisation. In some place, later faults offset the ore veins. The second fault system is also pre-mineralisation and essentially related to the emplacement and cooling of the granodiorites. These are characterised by radial and concentric fracturing, believed to be related to an unexposed cupola of a larger and deeper intrusive stock. A series of normal faults, which only separate the orebodies into blocks, indicates that the district was subjected to post-mineralisation faulting and fracturing.

Hydrothermal alteration resulted in silicification, sericitisation and argillisation of the meta-sandstone, dolerite and dacitic rocks. The meta-sandstones were altered by both hypogene hydrothermal and supergene processes, as well as the regional greenschist facies metamorphism, the affects of which are difficult to distinguish. However, it appears that the hydrothermal effects have been profound in the dolerite and dacitic rocks, affecting an area of about 1.5 km2 with a general zonal pattern. Silicification occurs as massive, vuggy silica bodies of microcrystalline quartz, derived from the recrystallisation of amorphous silica. This grades outward into sericitic alteration, which is widespread, both on the surface and at depth, and at Arapucan usually consists of sericite, quartz, chlorite and pyrite. These alteration products can be found as far as 10 m from massive ore. Argillic alteration led to the crystallisation of kaolinite and montmorrillonite and the bleaching of the rock. In general, argillisation is marked by the complete replacement of plagioclase by these clay minerals, while K-feldspar remains relatively fresh, with a greenish yellow colour due to presence of the sericite. Contact metasomatic (skarn) alteration and mineralisation occurs in places along the contacts between the granodiorite and the metasandstones. At the contact, these rocks have been locally metamorphosed to dense, hard, yellowish green hornfels, composed principally of actinolite-tremolite, epidote, chlorite and wollastonite. The contact metasomatic alteration is uncommon, unevenly distributed, and not associated directly with the Arapucan ore. At Arapucan, supergene alteration occurs as an oxidised and leached zone characterised by kaolinite, Fe and Mn-oxides (hematite, limonite and pyrolusite) and carbonates (malachite).

Two separate mineralised areas have been defined in the Arapucan district; Kor Maden, the most economically important in the north, comprising high-grade orebodies that are up to 200 m in length, hosted almost entirely in Triassic meta-sandsones; and Somas Maden in the south. In both areas, some of the mineralisation occurs in dolerite.

The Arapucan ore is composed primarily of galena, sphalerite, pyrite and chalcopyrite which constitute more than 90% of the total sulphide ore assemblage. The other minerals of the ore assemblage, in decreasing order of abundance, includes, in quartz, calcite, hematite, pyrolusite, tetrahedrite, bismuthinite, malachite, magnetite, limonite, scheelite and rutile. Galena, the most abundant sulphide, varies from 10 to ~65 wt.%, with bismuthinite and tetrahedrite inclusions. Sphalerite is mostly subhedral to anhedral grains adjacent to galena, locally occurring as massive fracture fill within sulphide grains and as isolated anhedral grains in calcite gangue. Chalcopyrite occurs as isolated anhedral grains in quartz-carbonate gangue, or adjacent to other sulphide grains, and is associated with high-grade ore veins. Tetrahedrite is the least common sulphide, mostly occurring in chalcopyrite-rich veins. Pyrite occurs as cubes and pyritohedra up to 5 mm across in vuggy sections, but is generally finer grained and granular, locally comprising >5% of the vein fill. Gangue minerals are mainly quartz and calcite. Pyrite crystals locally occur in fractures in the vuggy silica and massive silica bodies. Late quartz and calcite crystals line cavities, and are, in turn, coated with black, smooth, manganese oxide, plus small, euhedral crystals of scheelite. The Fe-Mn oxides and malachite are mainly associated with supergene alteration controlled by the present topographic surface, as mentioned above.

At least two periods of hypogene mineralisation are indicated within the Arapucan Pb-Zn-Cu-Ag ore veins, separated by a period of fracturing and at least two periods of brecciation. The early regional stage, Phase A involved large amounts of galena, sphalerite and chalcopyrite in pre-existing fractures and fault zones occurring in quartz-lined fractures, with galena and sphalerite deposition around etched chalcopyrite crystals and thin coatings of other crystals by Fe-and Mn-oxides. Minor amounts of magnetite, bismuthinite, tetrahedrite and scheelite were also deposited at this stage. The phase A fluids are partially responsible for the silicification, sericitisation and argillic alteration of the host rocks. The veins have a uniform structure, indicating no major movements on the vein-controlling faults since phase A, although a period of slight fracturing caused local dilatancies which were filled from phase B fluid. This phase is represented by narrow veinlets cutting earlier materials and filled mostly with galena, sphalerite and pyrite and lesser chalcopyrite.

The deposition of these assemblages varies through the deposit to form three main ore types:
Galena-dominated massive sulphide - which occurs as NNE-SSW trending, 40 to 50°ESE lenticular orebodies, with a vertical extents of at least 100 m. This ore type becomes more prominent toward the west and with depth, with variable thicknesses locally of up to 5.0 m. The ore to host rock contact is sharp. Mineral assemblages include galena (33 to 65 modal %), sphalerite (2.3 to 4.1 modal %), chalcopyrite (1.5 to 2.7 modal %), pyrite (1.3 to 2.3 modal %) with minor sericite, pyrolusite and Fe-oxides. Sphalerite and pyrite typically occur in the fractures of coarse-grained galena, where present. This ore constitutes up to 65 wt.% of the veins.
Sphalerite-galena-chalcopyrite massive sulphide mostly occurs in the southern part of the area, although variable amounts are present in all the veins. Mineralisation occurs in north and NE-trending veins that follow faults, dipping between 30 and 50°SE. Sphalerite is the most common sulphide, ranging from 13.6 to 55.0 wt.%. This ore mainly occurs as lenticular orebodies, varying from 0.2 to 1.0 m in width, locally grading laterally into disseminated chalcopyrite and pyrite. The ore bodies are zoned, with galena and sphalerite forming the outer portions, and chalcopyrite, quartz and calcite forming the cores of the veins.
Chalcopyrite-pyrite disseminated ore occurs as thin lenses along strike in both massive sulphide ores and is distinguished by the higher chalcopyrite content. The average amount of chalcopyrite is about 20 wt.%. Galena and sphalerite are also present.

The deposit was mined from 1972 to 1995 by the Turkish company Kor Madencilik A.S, during that time ~0.05 Mt of ore containing ~10.0% combined base metal were produced.

Remaining identified a geological reserves (Orgun et al., 2005) - 4.0 Mt @ 16.4% Pb, 12.1% Zn, 2.23% Cu. It also contains ~12 t of gold at an average of 4 g/t Au and 1050 t of silver at an average grade of 260 g/t Ag.

The most recent source geological information used to prepare this summary was dated: 2005.    
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:
Orgun, Y., Gultekin, A.H. and Onal, A.,  2005 - Geology, mineralogy and fluid inclusion data from the Arapucan Pb-Zn-Cu-Ag deposit, Canakkale, Turkey: in    J. of Asian Earth Sciences   v.25, pp. 629-642.


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, its employees and servants:   i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and   ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.

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