TECTONICS AND COMPOSITIONAL INFLUENCE IN CONTROLLING CLEATS DEVELOPMENT IN THE LOW RANK COAL OF THE BARITO BASIN, SOUTH KALIMANTAN, INDONESIA
There are two main coal seams in the study area, Late Eocene and Lower to Middle Miocene with thickness ranging from 2 m up to 50 m. Coal rank are classified as Lignite - Sub Bituminous C with calorific values ranging 5000 – 8000 Cal/gr containing Ash content of 8%-17%. There are two methods of cleat and/or fracture measurements used in this study: scan-line and windows sampling (100 cm x 100 cm dimension). More than 20,000 cleats and/or fractures were measured from 60 scan-lines and 39 windows measurement locations.
Cleats distribution and orientation indicates three major orientations WNW-ESE, NNW-SSE, and NE-SW trending. This study summarizes relationship between cleats attributes and cleats density. They are: an inverse linear is the best fit data for the bed thickness-density relationship, an exponential relationship between average density and cleats height, a power-law relationship between average density and average spacing, and cleats density increases related to regional structural position where they increases towards main deformation zone. Cleats spacing varies with coal type and ash content. Relationship between cleats spacing and coal rank, spacing indicates decreasing from low to high rank coal. Relationship between cleats density with calorific value and ash contents showing general relationship where high calorific value with low ash content tends to have large density. This cleats origin might be subjected from several processes, where the cleats, which formed during coalification, can be superimposed by later processes such as hydrostatic pressure and tectonic stresses and also can be affected by the coal composition.