A PRELIMINARY REVIEW ON THE METALLOGENY OF SEDIMENT-HOSTED PB-ZN DEPOSITS IN BALOCHISTAN, PAKISTAN

Abstract

Lead and Zinc deposits are very much important economic booster for the country all over the world. Economic geologists are engaged in the search of these economy booster minerals and rocks for three decades. Lead and zinc are profuse resources in the Lasbela-Khuzdar belt of Balochistan province of Pakistan, with reserves of about 50 million tons all over the country. In this paper, we have presented field observations of the Dudder mine area and summarised the work of earlier papers to provide the salient features of these ore mineralizations and deposits. The tectonic settings and important ore controls have been discussed based on field observations and previous work. The Pb-Zn dominantly occupied by exposures of rocks of the Ferozabad Group of Jurassic age in the Mor range, which is comprised of Lower-Middle-Upper Jurassic carbonates and deep-marine siliciclastics rock sequence. This group contains syngenetic and epigenetic Pb-Zn mineralization classified as a stratiform replacement, and vein-type fissure fillings observed at various places of Duddar, Gunga, and Surmai deposit areas. Generally, these deposits are hosted pyrites nuggets with fine-grained sphalerite matrix with galena in black shale, argillaceous limestone, and mudstone. We construct a Pb-Zn deposit predictive tectonic model that regards mineralization as the primary factor and the ore rock as secondary. The tectonics were more active when sedimentation of the Anjira Formation started in a disturbing third-order basin. The Hydrothermal solution comes into the basin along faults and gave rise to syngenetic mineralization of sulfides in the Anjira Formation, and epigenetic one in the underlying Spingwar and Loralai Formations. These deposits are considered as SEDEX deposits according to the distribution of Pb-Zn deposits, we concluded that a multi-period, multi-cycle orogenic environment is the most positive for lead-zinc deposit growth. With this, we analyze the association between tectonic evolution, geological mineralization, and Pb-Zn metallogenic epoch. The tectonic and mineralization mechanism models are expected to ease the detailed study on the geological and geochemical conditions of mineralization in the Ferozabad Group and economic assessment of the resources.