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The c. 2060 Ma Phalaborwa Igneous Complex forms an elongate intrusion into Archean granitic gneiss. The carbonatite within the central pyroxenite core of the complex (Loolekop) is well-mineralized in copper. Open pit mining operations started in 1965, followed by underground block caving in 2003. Although little attention has been paid to large-scale structures associated with intrusive phases and mineralization, ongoing infrastructure development and block caving, as part of the new Lift II Project, require far greater resolution of structural discontinuities. 3D modelling of these structures, from over 50 years of data, reveals that Loolekop occurs at the confluence of several major shears or fault zones. Of these, five major structures were pivotal in the emplacement of banded carbonatite, transgressive carbonatite and very late-stage, narrow, E-W trending, sulphide veinlets with short down-dip and along-strike extensions, which form the bulk of mineralization. Modelled structures typically have two or more segments, which are rotated with respect to one another, in turn suggesting repeated rotation or torsion of the entire intrusive volume, aided by cross-cutting structures. The oldest structure is the N-S trending Mica Fault Zone, which shows the same trend as the entire carbonatite complex and the nearby eastern edge of the Kaapvaal Craton and the Lebombo Lineament. The youngest structure is the Central Fault, which shows an E-W inflection that is co-incident with the carbonatite and the E-W, vein-hosted Cu mineralization trend. Based on cross-cutting relationships, sinistral movement along the Central Fault Zone and its localized E-W dilational jog is invoked as a mechanism for transgressive carbonatite emplacement and the introduction of late-stage Cu-rich fluids into numerous tensional veinlets. This shearing would have been caused by an E-W trending maximum principal stress orientation. In turn, this corresponds with the orientation of near-field, eastward-directed stress along the eastern lobe of the Bushveld Complex during its emplacement and subsequent deformation.

Palabora is a deep, hard rock, block cave in South Africa that has been in operation since 2002. After the open pit reached it maximum depth at 825 m, the mining method was changed from open pit to block caving. The first block cave lift (Lift I) was established 400 m below the open pit at a depth of 1,200 m and has been in production since 2002, with a capacity of 33,000 tonnes ore per day, hoisted through a production shaft to surface. The second block cave (Lift II) is currently being developed 450 m below Lift I. Over the next 3 years Lift I is expected to ramp down slowly while Lift II ramps up, to maintain 32,000 tonnes of ore per day during steady state production. During July 2018 an unfortunate conveyor fire incident took place that forced the suspension of all conveyance of material from underground to surface. Draw from the Lift I cave was suspended for approximately 10 months while the main (conveyor 5) ore conveying system was rebuilt. Lift II development continued during this period with development material trucked up to the Lift I extraction level, which was used as a stockpile area. Although Lift I is in its final stages of production there is sufficient copper remaining to justify its re-opening. There are multiple risks that needs to be taken in consideration during the process of restarting the cave. This includes but is not limited to; re-compaction, premature and/or accelerated convergence of accesses (crosscut drives), seismicity and the uncontrolled flow of material through drawpoints. Re-opening planning included assessing risks and identifying mitigation measures, which included the sequencing of draw and continuous monitoring through visual observations and convergence measurements. The objective of this paper is to give an account of the reopening process step by step , providing a record of the actual execution (implementation), including a description of the rock mass response, the challenges experienced and how these were addressed, as well as successes achieved throughout the process. These challenges also include, but are not limited to, the impact that the Lift I and Lift II cave activities have on each other.