ORIGINAL PAPER Geochemical and organic petrographic characteristics of low-rank coals from Thar coalfield in the Sindh Province, Pakistan Abrar Ahmad & Mohammed Hail Hakimi & Muhammad Nawaz Chaudhry Received: 22 April 2014 /Accepted: 23 June 2014 # Saudi Society for Geosciences 2014 Abstract Pakistan’ s largest coal reserves are in the Sindh Province. The organic geochemical characteristics and petro- graphic characteristics of the Tertiary coals in the Thar coal- field, south-eastern Sindh Province, were investigated to their hydrocarbon generative potential and regional rank and to reconstruct the palaeoenvironment conditions during peat ac- cumulation. The Thar coals are lignite to subbituminous C rank, possessing huminite reflectance in the range of 0.26– 0.39 % and high moisture and volatile matter contents. The coals have total organic carbon (TOC) content in the range of 47–67 wt%, and hydrogen index values between 105 and 437 mg HC per gram TOC indicate that their organic matter type is dominated by type III and mixed types II–III kerogens, whereby the coals were derived from plant materials of terrig- enous origin. If subjected to appropriate burial and heating, the hydrocarbon potential of these coals would be considered to be mainly gas-prone with limited oil-generative capacity. Diagnostic macerals and petrographic facies show that the Thar coals are humic and characterised by predominant huminite with significant amounts of liptinite and low amounts of inertinite macerals, representing predominantly topogenous mires deposited under anaerobic conditions, with limited thermal and oxidative tissue destruction. The palaeoenvironment conditions of the coals are generally interpreted as a lower deltaic plain wet peat-swamp deposi- tional setting, which are generally characterised by low Tissue Preservation Index (TPI) and high Gelification Index (GI) values. These plotted on the marsh field of the Diessel’ s diagram, consistent with generate relatively high ash yield. The organic facies study also shows that the main coal seams of the Thar coalfields were deposited in limnic freshwater environment, generally wet limno-telmatic zone as supported by relatively low sulphur contents. Keywords Coal . Thar coalfield . Hydrocarbon generation . Palaeoenvironmental conditions . Pakistan Introduction Even though oil and gas resources are rare in Pakistan, there is a great potential of coal deposits (Fig. 1). These coal reserves are of an economic interest because Pakistan has recently experienced elevated electricity shortages, and despite being a coal-rich country, these resources have not been exploited. The bulk of Pakistan’ s indigenous coal resources lie in Sindh with largest reserve of lignite coal located in the Thar Desert where it has not yet been fully developed. A small amount of this coal reserve meets less than 10 % of the commercial energy needs of the country and accounts only for 1 % of power generation. The Thar coalfield is the largest in Pakistan (Fig. 1) that was discovered by the British Overseas Develop- ment Agency (ODA) in cooperation with the Sindh Arid Zone Development Authority. It is a giant coal field with 175,000 million-t resources that cover 9,000 km 2 with dimensions of 140 km (north-south) (Fasset and Durrani 1994; Ghaznavi 2002). The deposits have been dated as middle Palaeocene to early Eocene in age (Fasset and Durrani 1994). A maximum of 20 seams have been observed in individual boreholes; A. Ahmad Pakistan Petroleum Ltd, Exploration Department, PIDC House, PO Box 3942, Karachi, Pakistan M. H. Hakimi (*) Geology Department, Faculty of Applied Science, Taiz University, 6803 Taiz, Yemen e-mail: ibnalhakimi@yahoo.com M. N. Chaudhry College of Earth and Environmental Sciences, Punjab University, Lahore, Pakistan Arab J Geosci DOI 10.1007/s12517-014-1524-6