Abstract
The genesis of the base-metal massive sulfide deposits hosted within the Moroccan Hercynian Jebilet and Guemassa Massifs is still under debate. No consensus currently exists between the two models that have been proposed to explain the deposits, i.e., (1) syngenetic volcanogenic massive sulfide mineralization, and (2) synmetamorphic tectonic fluid-assisted epigenetic mineralization. Conversely, researchers agree that all Hercynian massive sulfide deposits in Morocco are deformed, even though 3D structural mapping at the deposit scale is still lacking. Therefore, while avoiding the use of a model-driven approach, the main aim of this contribution is to establish a first-order structural pattern and the controls of the Hajjar base metal deposit. We used a classical structural geology toolbox in surface and subsurface mining work to image finite strain at different levels. Our data demonstrate that: i) the Hajjar area is affected by a single foliation plane (not two) which developed during a single tectonic event encompassing a HT metamorphism. This syn-metamorphic deformation is not restricted to the Hajjar area, as it is widespread at the western Meseta scale, and it occurred during Late Carboniferous times; ii) the Hajjar ore deposit is hosted within a regional transpressive right-lateral NE-trending shear zone in which syn- to post-metamorphic ductile to brittle shear planes are responsible for significant inflexion (or virgation) of the foliation yielding an anastomosing pattern within the Hajjar shear zone. Again, this feature is not an exception, as various Late Carboniferous-Permian regional scale wrenching shear zones are recognized throughout the Hercynian Meseta orogenic segment. Finally, we present several lines of evidence emphasizing the role of deformation in terms of mechanical and fluid-assisted ore concentrations.
Highlights
Most Volcanogenic Massive Sulfide Deposits (VMSDs) are assumed to form within extensional and subsiding basins during both divergent and convergent plate tectonic settings (e.g., [1])
In spite of recent advances in modern textural and opaque mineral strain characterization (e.g., [7,8,9,10]), it still remains difficult for economic geologists dealing with deformed VMSD to decipher the respective parts of primary syngenetic vs. epigenetic mineralizing processes
Toward an Integrated Tectono-Metamorphic Model for the massive sulfide deposits (MSD)-Bearing Jebilet and Guemassa Massifs. These interpretations must be discussed in terms of the ages and tectono-metamorphic evolutions established for the Guemassa and Jebilet Massifs; both of these Massifs bear the major MSD in Morocco
Summary
Most Volcanogenic Massive Sulfide Deposits (VMSDs) are assumed to form within extensional and subsiding basins during both divergent and convergent plate tectonic settings (e.g., [1]). Minerals 2018, 8, 435 in convergent settings leading to continental collision for instance, many VMSDs underwent deformation, burial, and metamorphism During these transformations, syngenetic massive sulfide bodies (e.g., stratoid lenses, chimneys and stockwerks) were reworked, and primary metallic bearing mineral assemblages may have been remobilized (e.g., either depleted or enriched). Syngenetic massive sulfide bodies (e.g., stratoid lenses, chimneys and stockwerks) were reworked, and primary metallic bearing mineral assemblages may have been remobilized (e.g., either depleted or enriched) For this reason, the deformation and (re)mobilization of the primary sulfide concentration is a fundamental and economic matter which has been recognized and studied for a long time (e.g., [2,3,4,5,6]). Metallogenic models of very large base metal concentrations all over the world are still ambiguous and under debate
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