A sedimentary intrusion is a variably shaped, discordant body of sedimentary rock which disrupts coal-bearing strata (Pictures 1, 2, 3, and 4). Sedimentary intrusions can vary in lithology, have significantly different modes of emplacement, and in many cases resemble their igneous counterparts (Picture 5) (see Depositional Systems, Volume 1). For purposes of this report, sedimentary intrusions are categorized as follows: 1) sedimentary dikes, sills, and pipes which also are referred to as rock spars, clastic dikes, sandstone dikes, stone dikes and etc.; 2) clay veins which also are referred to as clay dikes, clay slips, horsebacks, mud slips, and etc.; and 3) sediment infilling of fractures. Because intrusions are often composed of hard rock and disrupt the coal seam, they can impact both coal mining and CBM production. In extreme cases, sedimentary intrusions can be so prolific that coal mining in those areas is not economical.
Figures & Tables
This volume of the “Atlas of Coal Geology” provides 393 images on various subject matters related to coal deposits and coal resource utilization. The supporting text provides an introductory overview of coal exploration, mining, and coalbed methane (CBM) development, followed by discussions on various megascopic aspects of coal geology (microscopic aspects are covered in Volume 2). Because of the vast subject matter, many generalities had to be made in the text. References are included to guide those interested to more detailed discussions. All citations within the document are linked to the detailed reference list for this volume. The overriding theme for this publication is that a picture is worth a thousand words.