The Rosh Pinah Mine is owned by Rosh Pinah Zinc Corporation (Pty) Ltd. (“RPZC”). Trevali owns a 90% interest in RPZC and is operationally responsible for the management of RPZC, with the remainder held by PE Minerals (Namibia) (Proprietary) Limited, Jaguar Investments Four (Proprietary) Limited and an Employee Empowerment Participation Scheme.
On June 27, 2023, Trevali Mining Corporation completed the sale of its 90% interest in the Rosh Pinah Mine located in Namibia to funds advised by Appian Capital Advisory LLP.
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Summary:
The Rosh Pinah deposit is hosted by the Rosh Pinah Formation (Hilda Subgroup of the Port Nolloth Group), forming part of the Neoproterozoic Gariep Terrane deposited onto a Palaeo-Mesoproterozoic basement of granite gneisses and supracrustals. The Gariep Terrane is divided into two distinct tectono-stratigraphic sub-terranes; the eastern, para-autochthonous Port Nolloth Group and the western, allochthonous Marmora Terrane.
The base metal sulphides (BMS) at Rosh Pinah are contained within the approximately 30 m thick mineralized horizon, which is locally termed the ore equivalent horizon (OEH). In the Property, the Rosh Pinah Formation has been shown to be at least 1,250 m thick.
The major mineralization types are:
• Microquartzite and argillite;
• Arkose / breccia;
• Carbonate.
The Rosh Pinah deposit is hosted by a thick package of turbidites comprising hinterland and contemporaneous volcanic clastics deposited in a Neo-Proterozoic rift basin during the early part of the evolution of the Gariep Terrane of southern Namibia. Metals scavenged from a primary argillite mineralization were concentrated by late hydrothermally driven carbonate alteration, providing a carbonate host. Basin inversion led to oblique continental collision and complex deformation of the deposit, resulting in two phases of disharmonic overfolding with associated faulting and shearing.
The deposit is consequently presented as a series of discrete carbonate and exhalite lenses located on second-phase fold hinges or steeply plunging fold limbs connected by a partially attenuated exhalite-dominated OEH.
The Rosh Pinah mine has been historically interpreted as being predominantly a reworked SEDEX type deposit comprising a primary banded sulphide exhalite, part of which was carbonatized with associated remobilization and enrichment of sulphides. The secondary carbonate mineralization carries the higher, economic, base-metal values.
The base-metal bearing brines were exhaled onto the sea floor from the present-day Western Fault bounding the Rosh Pinah Graben, during a period of sediment paucity and/or high sea-level. Exhalation was accompanied by silicification and hydraulic brecciation of the footwall. The primary
mineralization was deposited at, or below, the sediment/seawater interface as stratiform, inter- banded, massive sulphide and cherty argillite (micro quartzite). Time between exhalative pulses determined the variation in ratio of content, of chert-exhalite and background argillitic sediment.
At some stage following primary SEDEX style mineralization deposition, the hydrothermal fluid chemistry changed to carbonitic, either due to introduction of primary volcanogenic carbonate fluids or as the plumbing system tapped carbonate sediments elsewhere in the sedimentary package. Carbonatization of the more porous, arenitic hangingwall and footwall took preference. On-going base-metal exhalation was supplemented by remobilization of primary mineralization into the hydrothermal carbonate.
Microquartzite and argillite
The primary mineralization type is a silicified, grey to dark grey, fine-grained and laminated unit locally called microquartzite mineralization. It consists of alternating millimetre to centimetre wide bands of sulphides (sphalerite, pyrite and galena + minor chalcopyrite) and is believed to represent a classic sedimentary-exhalative (SEDEX) style although ongoing interpretations are supportive of a volcanogenic massive sulphide (VMS) origin similar to the nearby Gergarub and Skorpion deposits. The argillite mineralization would be similarly derived but diluted with background benthonic argillite.
Arkose / breccia
The mineralization occurs as breccia matrix and veins in silicified arenite lithologies (locally referred to as breccia mineralization) or as disseminated base-metal sulphides (locally referred to as arkose mineralization) and can reach economic grades. In places, the arkose / breccia mineralization gives indications of primary sulphide exhalations into an arenitic host. The breccia mineralization is commonly found in the immediate footwall to the ore equivalent horizon (OEH).
Carbonate
Carbonate mineralization is purely remobilized and provides the major economic component of the resource. Carbonate has replaced the arenites, both in the hangingwall and footwall of the mineralized horizon and a continuous range is observed from slightly carbonatic arenite (textures such as large, ghost feldspar grains occur) to pure carbonate, with all original textures lost. The carbonate has scavenged, concentrated, and remobilized BMS from the primary microquartzite mineralization. A near-total base metal enrichment of the carbonate mineralization gives rise to massive mineralization. When the carbonate has been leached out of the carbonate mineralization and the quartz grains and sulphides remain, the mineralization is locally referred to as sugary quartz ore.
Lens characterization
The deposit is hosted by a thick package of turbidites comprising hinterland and contemporaneous volcanic clastics deposited in a Neo-Proterozoic rift basin during the early part of the evolution of the Gariep Terrane of southern Namibia. Metals scavenged from a primary argillite mineralization were concentrated by late hydrothermally- driven carbonate alteration, providing a carbonate host to the economic deposit. Basin inversion led to oblique continental collision and complex deformation of the deposit, resulting in two phases of disharmonic overfolding with associated faulting and shearing.
The deposit is consequently presented as a series of discrete carbonate and exhalite lenses located on second-phase fold hinges or steeply plunging fold limbs connected by a partially attenuated exhalite-dominated OEH.