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.

Highlights

  • Lead and zinc (Pb-Zn) are considered important economic ore minerals globally (Steve et al, 2018)

  • The Pb-Zn deposits have been formed through the processes of syngenetic or epigenetic and through replacement or fissure fillings observed at various places of Duddar, Gunga, and Surmai, in these areas the following types have found: i) stratiform, ii) strata bound-replacement type, iii) vein and cavity fillings

  • The abundant sediment-hosted Lead-zinc sulfides occurred as stratiform, strata bound and vein types found in the Indian passive margin of LasbelaKhuzdar belt of Balochistan, these sulfide mineralizations have been formed through the processes of syngenetic or epigenetic and through replacement or fissure fillings observed at various places of Duddar, Gunga and Surmai deposits and hosted by siliciclastics and carbonate sedimentary rocks of Mor range of Jurassic Ferozabad Group

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Summary

INTRODUCTION

Lead and zinc (Pb-Zn) are considered important economic ore minerals globally (Steve et al, 2018). The first sub-type is clastic-dominated (CD) Pb-Zn ores, which are hosted in shale, sandstone, siltstone, and mixed clastic rocks, which occur as carbonate replacement, within a CD sedimentary rock sequence. The second sub-type of sediment-hosted Pb-Zn deposits are the Mississippi Valley-type (MVT Pb-Zn) that occurs in platform carbonate sequences, typically in passive-margin tectonic settings (David, 2010). In other words, it can be discussed as the most important sediment-hosted Pb-Zn deposits; those are clastic rock-dominated sedimentary sequences traditionally called sedimentary exhalative (SEDEX) and those in carbonate-dominated sequences that are mainly of the Mississippi Valley-type (MVT), (Fig. 2). Aspiring to guide Pakistan's strategic work of Pb-Zn prospecting and a fundamental contribution of this research work is the compilation of basic mineral resource data on known deposits

SEDIMENT-HOSTED PB-ZN DEPOSITS IN BALOCHISTAN
Geological Background
Type of Mineralization
Important Pb-Zn Deposit in Balochistan
Duddar deposit
Gunga deposit The
Surmai
Overview of Tectonic evolution and Lead-zinc mineralization
Lead-Zinc Deposit Types
MVT deposit
SEDEX deposit
Proposed Models for Mineralization in the Jurassic Sedimentary Sequences
Findings
CONCLUSION
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