Chamalang coal resources and their depositional environments, Balochistan, Pakistan

Abstract

A good quality high calorific value coal has been found in and around Chamalang - Bala Dhaka, Lunda, Surghari, Nosham and Bahlol areas in Loralai, Barkhan and Kohlu districts of Balochistan. These deposits are parts of the eastern continuation of the Duki coal field deposits of Chamalang (Ghazij) group in the Sulaiman (Middle Indus) Basin and are another good addition to the coal fields of Balochistan. The rocks exposed in the coal bearing area are sedimentary rocks ranging in age from Jurassic to Pleistocene along with Subrecent and Recent surficial deposits. The oldest rocks exposed in the area are Spingwar and Loralai formations of Jurassic age and the youngest rocks are Dada and Sakhi Sarwar formations of Sakhi Sarwar group of Pleistocene-Holocene age and Subrecent and Recent surficial deposits. The coal bearing Chamalang Group of Early Eocene age is divided in to five units i.e. Shaheed Ghat formation (lower Chamalang/Ghazij), Toi formation (middle Chamalang/Ghazij), and Kingri, Drug and Baska formations (Upper Chamalang/Ghazij). The lower contact of Chamalang Group is conformable with the Dungan Formation of Paleocene age, while its upper contact is also conformable with the Habib Rahi Limestone of Kahan Group of Early-Middle Eocene age. The Chamalang group is generally comprised of thick sequence of shale/claystone, interbedded sandstone, limestone, marl, gypsum, with beds of coal. Coal is developed in the Middle Chamalang (Toi Formation) with more than 20 coal seams; however, the main coal seams are confined to 3 to 4 in number. The coal seams are generally lenticular and range in thickness from 1 to 6.5 feet. According to present investigation, the coals of these areas are generally medium to high in sulphur and ash contents. The sulphur content ranges from 3.44 to 6.93%, while ash in these coals ranges from 5.35 to 84.96%. The heating values of these coals are generally higher as compared to other coals of Balochistan which ranges from 1818 to 13569 BTU/lb. According to international ASTM classification, these coals could be ranked as lignite C to high volatile bituminous B coal. The present work has enhanced the proved reserves upto 5 million tons, and inferred reserves along with indicated and hypothetical reserves upto 25 million tons of 1foot and more than 1foot. The reserves (other resources) of more than 6 inches to less than 1 foot coal seams are estimated to be 70million tons. In this way total reserve of Chamalang coalfields are estimated to be 100 million tons. The depositional environments of coal bearing Toi Formation were deltaic.