80 JITENDRA VAISH AND S. K. PAL SPEC.PUBL.GEOL.SOC.INDIA, NO.4, 2016 DOI: 10.17491/cgsi/2016/95899 Subsurface Coal Fire Mapping in Patherdih Colliery, a Part of the Jharia Coal Field, India JITENDRA VAISH and S. K. PAL * Department of App. Geophysics, Indian School of Mines, Dhanbad – 826 004, India *Email: sanjitism@gmail.com Abstract: Coal fires are a universal problem in worldwide coal mining areas. They burn out precious coal resources, hinder mining activities and pose a danger to man and machine, besides leading to environmental pollution and land subsidence problems. In this context, high resolution magnetic survey offers a powerful tool for the detection, delineation and monitoring of coalfires. The Jharia coalfield in India is known for its high grade coal and associated coal fires. The valuable coal reserves are destroyed in the subsurface due to fire, before their exploitation. The present study deals with the mapping and understanding of subsurface coal fire on the basis of magnetic properties of materials and their changes with temperatures above or below the Curie temperature. The coal burning heat rising above Curie temperature results in a loss of natural magnetism in nearby area. Small regions, called domains, within the crystal structure reorient themselves which upon cooling; align themselves more or less in the direction of the ambient magnetic field. This remanent magnetism may be several orders of magnitude greater than the natural magnetism. The minerals which are formed and their respective magnetic strengths depend on the temperatures reached and the amount of oxygen available. Magnetic data acquisition has been carried out using high resolution GSM-19T proton precession magnetometer in gradient mode. The acquired magnetic data have been processed and analyzed using Geosoft Oasis Montaj software to study magnetic field anomaly of Patherdih Colliery in Jharia coal field, India for mapping and understanding of subsurface coal fire. The processed data provide a clear indication of location of active coal fire affected area. This repeated study could help for characterization of dynamics of coal fire of the region. Keywords: Coal fire mapping, Proton Precession Magnetometer, Residual Magnetic anomaly, Patherdih Colliery. INTRODUCTION The Jharia coalfield, India is known for its high grade coal and associated coal fires (Vaish and Pal, 2015a; Bharti et al. 2016; Srivardhan et al. 2016). The valuable coal reserves are destroyed in the subsurface due to coal fire, before their exploitation. Coal fires result in the loss of valuable economic resources, emission of greenhouse gases, toxic gases and vegetation deterioration that affect the global climate and increase the global mean surface temperature (Bell et al. 2001). Coal ash, smoke and hot wind blow pollute local areas. Wide spread cracking and land subsidence are very common in coal fire affected areas, which lead to extensive damage to the infrastructure such as agricultural land, buildings, roads, railways etc (Singh et al. 2007; Bharti et al. 2016; Singh et al. 2015). The severity and extent of coal fires in Jharia coalfield is quite alarming. The combination of underground fire and resulting subsidence has destroyed vast areas of the Jharia coalfield. Coal fire is a dynamic phenomenon; its location and extent change with time. The coal fire and associated subsidence have endangered the environment safety of the Jharia coalfield. Therefore, the status of the subsurface coal fires must be assessed periodically to control the same. Coal fire in the Jharia coalfield was first noticed in 1916. Most of the coal fires are caused by spontaneous combustion resulting from poor mining practices, the nature of the coal deposits and the apparent susceptibility of the coal to self combustion. The Jharia coalfield was nationalized in 1970 and over the past decades the coal fires spread in many areas. Most coal fires in the Jharia coalfield were ignited by spontaneous combustion of coal, subsequent to opencast and underground mining. Unplanned coal exploitation without fire-prevention arrangements prior to the nationalization was responsible for the start of these coal fires (Vaish and Pal, 2015a; Bharti et al. 2016; Srivardhan et al. 2016). The first indication of subsurface coal fire in Patherdih colliery was noticed in IX/X seam quarry in 1968. The surface and subsurface mine fire study is carried out with different techniques like borehole temperature measurement, thermo-compositional analysis, thermo-graphic measurement, airborne remote sensing and space-borne remote sensing techniques (Bhattacharya et al. 1991; Saraf et al. 1995; Prakash and Gupta, 1998, 1999; Ghose and Majee, 2002; SPECIAL PUBLICATION OF THE GEOLOGICAL SOCIETY OF INDIA No.4, 2016, pp.80-85