Distribution of Sulfur and Pyrite in Coal Seams from Kutai Basin (East Kalimantan, Indonesia): Implications for Paleoenvironmental Conditions
Total Page：16
File Type：pdf, Size：1020Kb
International Journal of Coal Geology 81 (2010) 151–162 Contents lists available at ScienceDirect International Journal of Coal Geology journal homepage: www.elsevier.com/locate/ijcoalgeo Distribution of sulfur and pyrite in coal seams from Kutai Basin (East Kalimantan, Indonesia): Implications for paleoenvironmental conditions Sri Widodo a,⁎, Wolfgang Oschmann b, Achim Bechtel c, Reinhard F. Sachsenhofer c, Komang Anggayana d, Wilhelm Puettmann e a Department of Mining Engineering, Moslem University of Indonesia, Jln. Urip Sumoharjo, Makassar, Indonesia b Institute of Geosciece, J.W. Goethe-University, Altenhöferallee 1, D-60438 Frankfurt a.M., Germany c Department of Applied Geoscience and Geophysics,University of Leoben, Peter-Tunner-Str.5, A-8700 Leoben, Austria d Department of Mining Engineering, Bandung Institute of Technology, Jln. Ganesa 10, I-40132 Bandung, Indonesia e Institute of Atmospheric and Environmental Sciences, Dapartment of Analytical Enviromental Chemistry, J.W. Goethe-University, Altenhöferallee 1, D-60438 Frankfurt a.M., Germany article info abstract Article history: Thirteen Miocene coal samples from three active open pit and underground coal mines in the Kutai Basin Received 12 August 2009 (East Kalimantan, Indonesia) were collected. According to our microscopical and geochemical investigations, Received in revised form 29 November 2009 coal samples from Sebulu and Centra Busang coal mines yield high sulfur and pyrite contents as compared to Accepted 3 December 2009 the Embalut coal mine. The latter being characterized by very low sulfur (b1%) and pyrite contents. The ash, Available online 13 December 2009 mineral, total sulfur, iron (Fe) and pyrite contents of most of the coal samples from the Sebulu and Centra Busang coal mines are high and positively related in these samples. Low contents of ash, mineral, total sulfur, Keywords: Kutai Basin iron (Fe) and pyrite have been found only in sample TNT-32 from Centra Busang coal mine. Pyrite was the fl Pyrite only sulfur form that we could recognize under re ected light microscope (oil immersion). Pyrite occurred in Sulfur the coal as framboidal, euhedral, massive, anhedral and epigenetic pyrite in cleats/fractures. High Framboidal concentration of pyrite argues for the availability of iron (Fe) in the coal samples. Most coal samples from Ombrogenous the Embalut coal mine show lower sulfur (b1 wt.%) and pyrite contents as found within Centra Busang and Topogenous Sebulu coals. One exception is the coal sample KTD-38 from Embalut mine with total sulfur content of 1.41 wt.%. The rich ash, mineral, sulfur and pyrite contents of coals in the Kutai Basin (especially Centra Busang and Sebulu coals) can be related to the volcanic activity (Nyaan volcanic) during Tertiary whereby aeolian material was transported to the mire during or after the peatification process. Moreover, the adjacent early Tertiary deep marine sediment, mafic igneous rocks and melange in the center of Kalimantan Island might have provided mineral to the coal by uplift and erosion. The inorganic matter in the mire might also originate from the ground and surface water from the highland of central Kalimantan. © 2009 Elsevier B.V. All rights reserved. 1. Introduction ascending or descending solutions in cracks, fissures, or cavities or by alteration of primarily deposited minerals. Most of the inorganic matter in coal is present as minerals which The dominant mineral of coals is usually composed of sulfides, are dispersed throughout the coal macerals. Individual grains of clay, carbonates, and quartz and sometimes additional phosphates, minerals vary largely in size from less than one micrometre to tens or heavy minerals, and salts as minor contributions to inorganic matter hundreds of micrometres. Sometimes mineral-rich layers are even of coal. In most coals, sulfides are preferentially composed of pyrite thick enough to be visible on the coal surface (Taylor et al., 1998). and marcasite but pyrite is in general dominating by far (Balme, 1956; Mineral components in the coals were classified in three groups Mackowsky, 1943). according to their origin (Stach et al., 1975): (1) Mineral from the Sulfides can be categorized as either syngenetic (primary), early- original plants; (2) mineral that formed during the first stage of the diagenetic or epigenetic (secondary) in origin. During peatification, coalification process or which was introduced by water and wind into syngenetic or early-diagenetic fine-crystalline or fine-concretionary the later coal deposits; and (3) mineral deposited during the second pyrite appears, commonly in the form of framboids. Syngenetic pyrite phase of the coalification process, after consolidation of the coal, by formed during accumulation of the peat and/or during early (humification) processes, and is usually small in size, and intimately dispersed throughout the coal (Renton and Cecil, 1979; Reyes- Navarro and Davis, 1976). Occasionally, the cell walls of plant material ⁎ Corresponding author. Tel.: +62 411 454775; fax: +62 411 453009. have been replaced by pyrite (Taylor et al., 1998). Falcon and Snyman E-mail address: [email protected] (S. Widodo). (1986) suggest that the accumulation of pyrite in coal might also arise 0166-5162/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.coal.2009.12.003 152 S. Widodo et al. / International Journal of Coal Geology 81 (2010) 151–162 from the aeolian and fluviatile import of iron-rich mineral at the time The island of Kalimantan and in particular the Kutai Basin has of peat accumulation followed by in-situ precipitation. Epigenetic experienced a complex tectonic history from the Paleogene to the pyrite is incorporated in the coal after compaction or partial present day. The Kutai Basin was formed during early Tertiary times consolidation (Reyes-Navarro and Davis, 1976) and is generally and was filled-up with clastic sediments progressing from the much larger (coarse grained) and fills cracks, cleats, and cavities western to the eastern part of the basin. This basin was subdivided (Renton and Cecil, 1979). The formation of epigenetic pyrite is into the Upper Kutai Basin, consisting of Paleogene outcrops with dependent primarily on the availability of reduced sulfur, dissolved Cenozoic volcanics possessing a strong northwest–southeast struc- cation (ferrous iron) and a suitable site for formation i.e., cleat tural grain, and the Lower Kutai Basin with Miocene strata cropping (Casagrande et al., 1977; Spears and Caswell, 1986; Demchuk, 1992). out in a north–northeast-trending structure. The Meratus Mountains Moreover, epigenetic pyrite might be precipitated from water to the southwest and the Central Kalimantan Mountains to the north percolating into fractures, cavities and pores present in coal seams of the Kutai Basin have an ophiolitic basement together with long after accumulation of the peat (Falcon and Snyman, 1986). Paleogene strata striking dominantly in a north–northeast direction In general, coals deposited in paralic basins contain more pyrite (Clay et al., 2000). than those in limnic basins. Among the paralic deposits, coal seams The coal mining companies are located in the vicinity of the Mahakam which have been influenced by marine transgressions are consistently River, Kutai Basin, East Kalimantan Province (Fig. 2). The precise characterized by a particularly high content of pyrite and sometimes geographic position of Sebulu coal mine is S00°26′40.4″/E116°52′54.1″ also of organic sulfur, especially in the upper part of the seams (Balme, and Centra Busang coal mine is S00°44′22.2″/E116°89′16.6″,whereasthe 1956; Dai et al., 2002; Mackowsky, 1943). In sulfur-rich humic coals, Embalut coal mine is situated S00°33′34.9″/E117°12′15.5″.CentraBusang pyrite in the form of fine grains or fine concretions is particularly is located in the Busang village, East Kutai regency and Sebulu coal mine in common in microlithotypes containing a high proportion of vitrinite; the Sebulu village, Kutai Kertanegara regency, East Kalimantan province. these forms also tend to be common in sapropelic coals. In the absence The Embalut coal mine is located in Embalut village, Kutai Kertanegara of other criteria (such as marine fossils or coal balls), a relatively high regency, East Kalimantan province. Coal seams in the Centra Busang and proportion of synsedimentary or early-diagenetic pyrite can be useful Sebulu mines were found in the Pulau Balang Formation with Middle for seam correlation. Miocene age, and coal seams in the Embalut mine was found in the Pulau Many previous investigations (Anggayana et al., 2003; Baruah, 1995; Balang (Middle Miocene age) and Balikpapan Formation with Upper Dai et al., 2002, 2003, 2006, 2007, 2008; Dai and Chou, 2007; Elswick Miocene age (Fig. 3). et al., 2007; Frankie and Hower, 1987; Kortenski and Kostova, 1996; Previous studies of the sedimentary evolution of the Kutai Basin, Lόpez-Buendía et al., 2007; Querol et al., 1989; Renton and Bird, 1991; based on field survey and oil wells, have shown that the Tertiary Strauss and Schieber, 1989; Turner and Richardson, 2004; Wiese and sequences are broadly regressive in general with a (dominantly) Fyfe, 1986) have described the characteristics, type, morphology, offshore marine argillaceous sequence of Palaeocene age followed by genesis, and distribution of pyrite in coal seams from different deposits. a coal bearing deltaic and coastal plain succession of Miocene age. Our investigation deals with sulfur and pyrite occurrences in the Shoreline progradation was generally towards the east (Samuel and Miocene coal seams from Centra Busang, Sebulu and Embalut coal Muchsin, 1976; Rose and Hartono, 1978 in Land and Jones, 1987). mines, Kutai Basins, East Kalimantan, Indonesia. The primary purpose of According to Supriatna and Rustandi (1986) the Neogene the study is to explain why most Miocene coal seams from Kutai Basin succession in the Kutai Basin includes from bottom to top the have very low sulfur contents, whereas in some coal seams higher sulfur following formations: Pamaluan, Bebuluh, Pulau Balang, Balikpapan, contents are observed. The second purpose is to identify the types of Kampung Baru Formation and alluvial.