Summary:
The Pinargozu Property is located within the Horzum–Tufanbeyli Zinc Belt in the Eastern Tauride belt on the southern margin of the Anatolian block.
The style of zinc mineralisation in these districts, oxide and sulphide, is not well studied or understood. The deposits in the Zamanti and Tufanbeyli–Horzum districts have previously been described as Mississippi Valley-type (MVT) style, however the Horzum and Pinargozu deposits have been reinterpreted as Carbonate-Replacement Deposit (CRD) systems associated distally with magmatism, similar to those in the Keban district.
The Pinargozu mine is located within bedded grey limestone of the Degirmentas Formation that dips moderately to the southeast, with an interpreted basal thrust contact with clastic units. Mineralisation appears stratabound at a favourable level within the Degirmentas Formation, interpreted as a micritic unit overlain by muddier limestone providing an aquiclude. The footwall is bioclastic limestone with thin interbedded siltstone and mudstone horizons.
The Degirmentas Formation is locally dolomitised but there is no spatially association with mineralisation. All mineralisation is hosted in bleached recrystallised limestone that locally termed “marble” but that is interpreted to reflect hydrothermal alteration. It is characterised by small-scale brittle and vuggy dissolution veining and micro-brecciation, interpreted as fluid-escape features related to the main mineralised zone. The alteration extends up to 30 m from massive sulphide, and also appears stratabound.
Primary and secondary mineralisation form tabular stratabound bodies of variable thickness with subordinate narrower, often cross-cutting zones. Primary sulphide mineralisation is characterised by coarse massive sphalerite with subordinate pyrite. Massive galena locally cuts and replaces sphalerite with iron-carbonate gangue. Contacts of massive sulphide with bleached limestone are sharp, with minor disseminated and clotty sulphide in the limestone. Based on mining, the mineralisation is crudely stratabound within the central part of the Degirmentas Formation. Observations underground suggest that massive sulphide contacts are mainly stratabound, although steep cross-cutting galena-rich mineralisation was seen at Horzum.
Mining to date at Pinargozu has mainly been of secondary zinc mineralisation, formed through supergene oxidation of massive sulphide mineralisation. The secondary mineralisation largely formed by supergene direct-replacement of sulphide, but with substantial local remobilisation of zinc into karstic cavity systems. The secondary mineralisation includes high-grade rhythmic banded smithsonite-hemimorphite deposited as open-space fill, karstic sediments impregnated by zinc, and clay-rich karstic fill zones.
Primary massive sulphide mineralisation is becoming more dominant as the mine becomes deeper.
Sulphide Mineralisation
The primary mineralisation is characterised by coarse massive sphalerite-rich sulphide with subordinate pyrite. Massive galena also occurs and typically post-dates sphalerite, cutting and replacing sphalerite and associated with more abundant carbonate gangue. The carbonate weathers brown and is interpreted to be iron-rich and potentially manganoan. The absence of a black weathering patina suggests that manganese is subsidiary.
Contacts of massive sulphide with bleached limestone are sharp, with minor disseminated and clotty sulphide in the limestone. Based on mining, the mineralisation is crudely stratabound within the central part of the Degirmentas Formation. Observations underground suggest that massive sulphide contacts are mainly stratabound.
Secondary Zinc Mineralisation
During weathering of massive sulphide deposits in limestone, sulphide oxidation generates acid which readily transports Zn, and to a lesser extent Pb, until neutralised by carbonate wall rocks. Secondary zinc mineralisation can be direct replacement, where neutralisation is almost immediate and secondary minerals directly replace primary, or wall-rock replacement where zinc is transported out of the primary deposit and are precipitated by reaction with the wall rock, often in acid-enhanced karst cavity systems (Hitzman et al., 2003). Acid generation capacity is strongly related to pyrite content, which is low at Pinargozu.
The large-scale geometry of secondary mineralisation at Pinargozu and the mixed oxide-sulphide mineralisation (including more resistive galena within secondary zinc zones) indicates that the deposit is largely of direct-replacement type. However, on the smaller scale (probably metres, but not tens of metres), there has been substantial remobilisation of zinc into karstic cavity systems . The remobilised mineralisation is characterised by high-grades of Zn with little Pb.
The secondary mineralisation includes high-grade rhythmic banded smithsonite deposited as open-space fill, karstic sediments impregnated by Zn, and clay-rich karstic fill zones.
The tabular bodies of variable thickness are responsible for the bulk of the tonnage at Pinargozu and are largely of direct replacement origin including in-situ karst development. Wall-rock replacement zones are typically narrower, often with crosscutting non-sulphide mineralisation locally interconnected with open space fillings formed through remobilised of mineralised supergene fluids along fractures, breccias and joint planes. However primary mineralisation may also be partly controlled by fault and joint geometries and origin of secondary mineralisation cannot be determined by geometry alone.
Secondary zinc mineralisation at Pinargozu consists mainly of smithsonite, ZnCO3, and hemimorphite, Zn4Si2O7(OH)2·H2O, with minor amount of replacive hydrozincite, Zn5(CO3)2(OH)6. Secondary zinc mineralisation is associated with abundant (often friable) concentrations of Fe-oxides and hydroxides and cerussite, PbCO3, as well as remnant galena, sphalerite, and pyrite. Very high-grade zinc mineralisation (>40% Zn) is associated with banded smithsonite.
Mineralisation is accompanied by a general tenor of >50 g/t silver. Local pockets of high grade silver (>250 g/t) exist, most notably in the southern lodes where sulphide proportions are higher. Elevated lead concentrations (typically galena) are almost entirely restricted to these southern lodes where, as development has extended deeper, sulphide mineralisation has become more prevalent.
Structure
Structural mapping by Tripathi (2014) at 1/2,000 scale on the surface, and at 1:200 in underground workings, recognised five groups of structures at Pinargozu:
• 45°-69° to N138°dipping structures;
• East-west striking and 43°south to 78° north dipping shears;
• East-west striking and steep east-northeast dipping shears;
• The 43°/N184 dipping shears;
• The 78°/N004 dipping shears.