Download - Coal Geology Introduction
By Abdi Suprayitno
Coal Geology
Chapter 1
Origin, age and occurrence of coal
Coal is a complex solid object, consisting of various elements representing many chemical components, most of them are derived from the remains of plants, consisting of various fibers which consists of multiple cells. By Thiessen (1947)
Coal is a solid object is composed by carbonaceous macerals. This definition include all the coal from various degrees of coal (coal rank) that begins from peat, lignite, sub-bituminous coal, bituminous coal, semi-anthracite, anthracite and meta-anthracite. By Spackman (1958)
Coal is a combustible sedimentary rock, formed by the remains of plants in varying levels of preservation, followed by the process of compacting and buried in the shallow basins. As soon as the barrier layer down constantly, the buried remain plant is influenced by temperature and pressure process. By The International Hand Book of Coal Petrography (1963)
Coal is a combustible sedimentary rock, derived from plants (mainly contain of carbon, hydrogen, and oxygen), brown to black, since depositional exposed to chemical and physical processes result the enrichment of carbon content. Wolf (1984)
Coal is sediment, organoclastic in nature, composed of lithified plant remains, which has distinction as combustible material. By Thomas (2002)
What Is Coal ?
Geotectonic PositionPaleotopografiGeographical PositionClimateFlora / PlantsDecompositionBasin SubsidenceGeological TimePost-Depositional ProcessOrganics Changing
Coal Forming Factors
Geotectonic PositionClimateBasin geometrySediment supplyAccommodation spaceFlora type
Coal Forming Factors
PaleotopografiBasin geometry Swampy area are formed
Geographical PositionClimateGroundwater surface Sea water abration
Coal Forming Factors
ClimatePlants growing
Tropical wet climate can build bright coalNeither in the pole earth
FloraSpecify the kind of flora/plants
DecompositionDetermine bacteria decompose the plants
Coal Forming Factors
Basin SubsidenceSubsidence and plant accumulation are in balance,
produce thick coalIf Subsidence < accumulation : plant will
decompose with airId Subsidence > accumulation : thin coal, plants
are not grown up well
Geological TimeProduce good coal, if buried with thick sedimentExcept coal is intruded by intrusions, high rank
coal
Coal Forming Factors
Post-Depositional ProcessEffect the quality of coal, such as structure,
intrusion, erotion
Organic ChangingBiochemistry Geochemistry
Coal Forming Factors
Biochemical ProcessPresent aerobe and anaerobe bacteria
Plants (cellulose) Glucose Gas and Water
Peatification
Aerobe bac.
Water
Aerobe bac.
Air
Peat
Anaerobe bac.
Deeper
Biochemical Process Vitrinisation Fusinitisation
Peatification
Peat characteristic :Brown to black> 75 % water content< 60 % carbon contentShown the origin plantsCan cut by a knifePorous like sponge
Peatification
Geochemical Process (physicochemical stage)Peat Lignite Bituminous AnthracitePressure + temperature + timePeat accumulation (coal 1 ft) :
Lignite : 160 yearsBituminous : 260 yearsAnthracite : 490 years
Temperature :200 deg C : > 10 million years150 deg C : > 50 million years100 deg C : > 200 million years50 – 60 deg C : Never be formed
Coalification
Coalification
Coal Rank control factors :Original coal rankIntrusion and structurePressureTemperatureDisturbing type and its period
Coalification
Autochthonous Coal (In situ)Seat earth presentRoot is perpendicular with
beds or seamClean coal (low ash)Steady swampWide spread coalHomogenous thicknessPresent fine grained
quartz sandstoneGood forming macerals
Allochthonous Coal (Drift)No seat earthNo perpendicular rootVary quality and thicknessDeltaic formationSharp contact with above
sedimentMarine environmentPresent Coal ballsSpotting coal spreadingHigh ashPresent macerals and
minerals
Depositional Basin
• Continental• Fluvial• Desert• Lacustrine • Glacial
• Marginal-marine / shoreline• beach / barrier island• estuarine / lagoonal• tidal flat
• Marine• neritic• oceanic
Depositional environment
Coal Depositional Basins
Lacustrine system
It can be formed by fault, rifting; landslide; crater explosion then collapse; fluvial activity.
Insitu and drift coal
River
Continental environment
Fluvial Flood Basin
River environment
Fluvial Flood Basin
River environment
Deltaic systemRiver enter the oceanSediment supply rapid than distribution to
basinInsitu and drift coal
Lagoonal and barrier island systemConsist of sandy barrier island; the lagoon;
channel crossed the barrier to the open seaInsitu and drift coal
Marginal-Marine / Shoreline environment
Deltaic System
Marginal-Marine / Shoreline environment
Regressive marine
Marine Environment
Coal Depositional Basins
TPI (Tissue Preservation Indices) & GI (Gelification)
TPI indicates where the peat was decomposed
GI indicates wetter condition
TPI – GI Vs Depositional Environment
Most of coal is formed in coastal area (Diessel, 1984)
Coal Environment
Refer to Horne (1978) in coastal area :
Back Barrier : thin coal, spread along the strike, layering, high S.
Lower delta plain : thin coal, vary in S content , along the channel, splitting
Transitional lower delta plain : thick coal, low S, splitting, washout
Upper delta plain - fluvial : thick coal, low S, pod shaped, splitting
Coal Environment
First period Lower Carbon to PermianNorth America and Europe
Second PeriodLower Cretaceous to TertiaryCoal
Third Period QuaternaryPeat
Coalification Period
PaleogeneOmbilin (West
Sumatera)Bayah (West java)Pasir (East
Kalimantan)Sebuku (South
Kalimantan)Melawai (West
Kalimantan)
NeogeneWarukin and Dohor
(South Kalimantan)Pamaluan,
Pulaubalang, Balikpapan dan Kampung Baru (East Kalimantan)
Coal Formation in Indonesia