4.2
Hydrogeological setting
The following sections describe the hydrogeological setting of the Mount Morgan area, and the hydrogeological conceptualisation developed for UMG TSF. The development of this section and the hydrogeological model builds upon that information described in Section 4, and incorporates new site specific information, including recent investigations completed within and adjacent to the proposed TSF footprint, to refine the understanding of groundwater occurrence, flow mechanisms, and seepage pathways. This information is used to develop a site specific hydrogeological conceptual and supports evaluation of potential interactions between the TSF, groundwater system, and downstream receiving environments.
4.2.1
Geology
Review of the geological map 1:250,000 geological map for the Rockhampton sheet SF5613 [6], indicates that:
— The mine site is underlain by Paleozoic (Devonian-Carboniferous) volcanic, volcaniclastic, and intrusive rocks of the Calliope Inlier, comprising mainly felsic to intermediate volcanic units (e.g. tuffs, breccias, volcaniclastic sediments) that are variably altered, fractured, and weathered, and which form the regional geological basement and principal host to groundwater flow at depth. — These units are unconformably overlain in elevated areas by Jurassic Razorback Beds, consisting predominantly of sandstone, siltstone, and minor conglomerate, which are preserved discontinuously along ridge crests and topographic highs surrounding the mine site and are largely absent from gullies and valley floors due to erosion. — Quaternary sediments occur as thin to locally thick accumulations of colluvium and alluvium within gullies, drainage lines, and low‑lying areas (including Upper Mundic Gully), comprising heterogeneous mixtures of clay, silt, sand, gravel, and locally reworked mine materials, with a spatial distribution strongly controlled by topography and historic mining disturbance. — Several faults have been mapped throughout the Mount Morgan mine; multiple concealed faults cut across the OCP in a northeast-southwest direction and terminate on other faults which run perpendicular in a northwest-southeast direction. — Several mine landforms, including waste rock, spoil dumps and TSFs occur across the mining lease and consist of a range of geological material, excavated from the pit and deposited as tailings from the ore processing.
— An extract of the geological map is presented in Figure 4.3.
Project No PS213278 Mount Morgan Mine - Upper Mundic Gully TSF Seepage Management Plan Heritage Minerals
WSP May 2026 Page 11
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