The Kushk Zn-Pb ore deposit is located in the Posht e Badam block of the central Iranian tectono-magmatic zone, and 160 Km east of Yazd city. In this research, the role of structural factors specially faults on post-sulfide mineralization at the Kushk ore deposit is investigated. The dominant basement rocks of the Kushk volcano-sedimentary basin include the Tashk formation, volcanic units, shales and sandstones of the Rizu series and the Aqda limestone. The important structural factors in this research include post-mineralization fault systems. The pre-mineralization structures are thought to be related to a compressional structural regime coincide with the Pan African orogeny. Syn-mineralization structures, following the Pan African orogeny, and coinciding with an extensional tectonic regime, resulted in Zn-Pb sulfide mineralization. The post mineralization faults, following the formation of the Kushk ore deposit, resulted in fracturing the sulfide ore into three stages including: 1) a folding related faulting resulting in appearing the Kushk fault, 2) a dextral movement characterized by the new activation of the Kushk fault and also appearing the Zardu and Pahnu fault systems, and 3) a final sinistral movement evidenced by Konj fault system. The formation of some supergene minerals, including carbonates, sulfates, phosphates, clays, oxides, and silica, occurred along fault surfaces related to the reactivation of post-sulfide structural features.


Introduction
In this research, the role some post sulfide ore structural systems on the formation and development of some secondary ore formation features at the Kushk ore deposit is investigated. The relationships between structural factors and mineralization have been the subject of debate in the past (Kutina, 1983; Mirzababaei., 2011; Mirzababaei et al., 2016; Karimpour and Sadeghi., 2018; Karimpour et al., 2019). The Kushk Zn-Pb ore deposit, located in central Iranian tectono-magmatic zone, 160 Km east of Yazd city, is one of the world class base metals ore systems. There is a general consensus concerning the typology of the ore system generation, with the exception of some differences. With this framework, however, the structural framework of the Kushk ore deposit is still open to investigate. This research makes a case for re-examining the structural reactivations and importance of post mineralization structural factors in generation of some supergene mineral phases at the Kushk ore system in the context of regional tectonics through post-mineralization deformation history to formation of post mineralization secondary mineral phases.

Materials and methods
The geological report of the Rio Tinto company (RTZ, 1972) was the basic structural report of the Kushk area which is limited to the ore bodies. Since 2020, the stratigraphical and structural investigations were operated at the department of geology of the Kushk mine. The investigations discussed carried out on structural elements of the area as dip and strike measurements, continuity of fault systems, intersecting with stratigraphical units. The data interpretation was carried out in Arc GIS and Leapfrog software. Following the structural interpretations, selected samples from the newly formed mineralogical phases on fault surfaces were taken to laboratories. 19 Representative samples were taken to analyze by XRD at the Kansaran Binaloud research group. XRD methodology was carried out and the instrument was equipped with a voltage of 40 kv and a nickel filament. Similarly, 5 representative samples were selected to take SEM photomicrographs at the geological survey of Iran. SEM was performed using ZEISS system equipped with an accelerating voltage of 25 kv. Moreover, we also used some thin polished sections formerly prepared for investigation of the ore bodies occurrences in both layered and massive parts of the Kushk ore system.

Results and discussion
Structural analysis of the field-based investigation provides a method of assessing the structural significance in metallogeny. Structural features (all groups of pre-, syn-, and post-mineralization faults), in the Kushk Zn-Pb ore deposit in central Iran, have not been systematically investigated and the role of post-sulfide structural reactivation remains poorly understood. The main aims of this paper are to: 1) drawing a structural framework for the Kushk ore deposit; 2) investigate the role of post-sulfide structural factors in remobilization of elements from the hypogene ore to the structure bound supergene environment and 3) characterize the mineralogical features of the structurally controlled supergene mineral phases. In general, structural factors of the Kushk Zn-Pb ore deposit can be classifieds into three main categories: 1) faults formed prior to the development of the mineralization basin, 2) deep-rooted syn-mineralization fault systems, and 3) post sulfide mineralization fault systems. Except for a few cases (and just in theoretical models), almost all the structural factors debated in that Kushk Zn-Pb ore deposit, fall into the post mineralization category. The first structural groups are those coincided with the Pan African compressive tectonic regime. This orogeny was one of the most important tectonic processes affected the central Iranian litho-tectonic zone in the upper Neoproterozoic. On theoretical map of paleo-tectonics of Iran, Nadimi (2007), offers a tentative explanation of the large-scale geological processes responsible for the development of compressional environments. We believe, based on this research, that the pre-mineralization faults are connected to paleo-structural zones formed during the Pan African orogeny that lately, by contrast, ruptured and formed syn-mineralization faulted environment in younger tensional environments. The second group of faults, formed presumably, a fertile metallogenic environment for Zn-Pb sulfide mineralization in the Kushk ore deposit. Sulfide ore minerals in the Kushk ore deposit, volumetrically, include pyrite, sphalerite and galena. Theoretical modelling of these structures is given in Rajabi et al (2020). The third group of The third group comprises fault systems and faulted zones which are characterized by structural discontinuities within the layered to massive sulfide ore bodies in the mine blocks, structural displacement along the stratigraphic units hosting the ore bodies and in the overlying horizons, and the development of post-sulfide mineral phases, including carbonates, sulfates, phosphates, clays, oxides, and silica. The formation of these minerals is enhanced with CO₂ effervescence and degassing along the fault zones. Rarely, post-ore sulfide mineralization is also observed, represented by the formation of sphalerite hosted by phosphate minerals.

Conclusion
The mechanisms involved in appearing and formation of the post-mineralization faults in the Kushk ore deposit are investigated in the context of the regional structural geology of the study area. These structures mainly comprise fault systems that formed following the reactivation of stratigraphic blocks during the main post-mineralization phase of folding in the area. These structural forms resulted in remobilization of the former mineral mass along fault planes and the subsequent precipitation of newly formed post-sulfide mineral phases including carbonates, sulfates, phosphates, clays, oxides, silica and locally, post-ore sulfide mineralization, within low-pressure zones as veins, veinlets and open space fillings. The structural assessment and mineral chemistry of the newly formed minerals indicate that CO₂ effervescence and degassing within low-pressure zones along faults played a critical role in the formation of post-sulfide mineral phases.