Abstract
The Jbel Rhals deposit, located in the Oriental High Atlas of Morocco, hosts a polymetallic Fe-Mn-Cu ore. Large metric veins of goethite and pyrolusite cut through Paleozoic schists that are overlaid by Permian-Triassic basalts and Triassic conglomerates. The genesis of this deposit is clearly polyphased, resulting from supergene processes superimposed over hydrothermal phases. The flow of Permian-Triassic basalts probably generated the circulation of hydrothermal fluids through the sedimentary series, the alteration of basalts and schists, and the formation of hydrothermal primary ore composed of carbonates (siderite) and Cu-Fe sulfides. Several episodes of uplift triggered the exhumation of ores and host rocks, generating their weathering and the precipitation of a supergene ore assemblage (goethite, pyrolusite, malachite and calcite). In the Paleozoic basement, Fe-Mn oxihydroxides are mostly observed as rhombohedral crystals that correspond to the pseudomorphose of a primary mineral thought to be siderite; goethite precipitated first, rapidly followed by pyrolusite and other Mn oxides. Malachite formed later, with calcite, in fine millimetric veins cutting through host-rock schists, conglomerates and Fe-Mn ores.
Highlights
The Jbel Rhals Fe-Mn-Cu deposit is located in the Moroccan Oriental High Atlas, 20 km south from Bou Arfa city (Figure 1)
We focus our investigation mainly on the supergene processes responsible for the current ore mineralogy, considering that the primary on the supergene processes responsible fororthe current mineralogy, considering that the primary mineralization is not exposed in outcrops pits, nor inore galleries, and that only the oxidation zone of mineralization is not exposed in outcrops or pits, nor in galleries, and that only the oxidation zone of the deposit is accessible
Most altered/weathered basalt is composed of a greenish clay-rich layer, a red-brown iron-rich layer and a white layer (Figure 3c,f)
Summary
The Jbel Rhals Fe-Mn-Cu deposit is located in the Moroccan Oriental High Atlas, 20 km south from Bou Arfa city (Figure 1). Several ore deposits in the Bou Arfa district were mined in the first half of the 20th century, and are recently (re)considered in several papers: Jbel Klakh (Cu) [1,2], Jbel Haouanit (Pb-Zn-Cu-V) [1,2], Hamarouet and Aïn Beida (Mn) [3]. The Jbel Rhals locality was known as a Cu deposit for centuries and has been shortly exploited during the 19th–20th centuries; some mining activities started up again in 2012. There is no mineralogical inventory of the Jbel Rhals deposit, and processes leading to the formation of the various mineral phases have not been investigated yet. This work presents a petrological, mineralogical, and geochemical synthesis of the Jbel Rhals deposit.
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