JOHANNESBURG (miningweekly.com) – Significant project value could be lost in Mozambique’s Tete coalfields if geological exploration was not conducted to an adequate standard, the Mineral Corporation senior technical adviser Gavin Andrews said on Wednesday.
The geology of the area was complex and, therefore, it was important for a project’s geological analysis to be correct, to prevent problems at a later project stage, he stated at the Fossil Fuel Foundation’s Mozambique Coal conference, held in Johannesburg.
“If money set aside for exploration is not used wisely, your project could, in fact, lose value during the exploration process.”
Andrews pointed out that the coal found in the Tete coalfields, which stretched over 400 km from Cahora Bassa Lake to the Malawi border, was not homogenous and that this had to be taken into account when a target area for a specific coal project was chosen.
“A structural understanding of the area is needed as faulted blocks may have been buried to different depths, affecting the nature of potential coal products, such as coking coal,” he explained.
Meanwhile, as a result of the variations in the area’s coal, selective sampling was not generally suitable for exploration in the Tete coalfields, he said.
“A coal resource tonnage must be reported with appropriate coal quality parameters. Therefore, the sampling and analytical programme must be well planned, comprehensive, consistent and suited to the nature of the targeted coal products,” he said, adding that a lack of suitable analytical data or the existence of abnormal trends could lead to a resource downgrade.
He further stated that continuity was key to the definition of a coal resource and that this had to be demonstrated through correlation. “If there is no convincing correlation, there can be no reportable resource.”
Geological features that affect coal seam distribution and continuity include the pre-Karoo topography, lateral variation, which included in-seam partings and seam splits, channel scours, faulting and intrusions.
“These features have to be taken into account as they affect your ability to correlate the coal zones or piles and, therefore, affect your ability to demonstrate continuity,” said Andrews.
Given the complexities of the Tete area, and the importance of accurate correlation and relevant sampling, the Mineral Corporation’s recommended resource definition strategy is to drill open boreholes over the target area, to geophysically log the boreholes and to then complete a comprehensive correlation and structural interpretation exercise.
After this is done, companies should identify the primary target area and decide on appropriate drill spacing for the desired resource category, after which targeted core drilling and sampling can be done.
Andrews did, however, point out that this strategy was costly and, therefore, it would not be suitable for junior miners.