284-9 Structural Analysis of the Tectonic Control and Hercynian Deformation Influencing Sulfide Mineralization within the Kettara District, Central Jebilet, Morocco: Insights into Syntectonic Emplacement Hypotheses

Session: The Deformation-Metamorphism-Fluid Triplet Governing Plate Boundaries and Orogens

Presenting Author:

Authors:

Abstract:

The Kettara mining district (Central Jebilet, Morocco) hosts a stratiform pyrrhotite-rich massive sulfide lens embedded within a low-grade (epizonal) metamorphosed volcano-sedimentary Sarhlef sequence. This sequence is intruded by a bimodal magmatic suite dominated by mafic gabbros and a swarm of doleritic and microgranite dykes.

This study aims to clarify the structural context of the sulfide body and to determine whether its emplacement was pre- or syn-tectonic. A detailed structural analysis reveals, for the first time, a pronounced deformation gradient increasing towards the sulfide lens, with maximum deformation observed at its contact. This pattern suggests a syntectonic emplacement of the mineralization, although the possible remobilization of a pre-existing syngenetic orebody cannot be excluded.

Two main deformation phases have been identified:

D1, a coaxial compressive phase associated with regional metamorphism, is characterized by a layer-parallel foliation (S1) and tight anisopachous folds (P1) oriented N45. These structures affect both the host rocks and the sulfide lens.

D2, a non-coaxial ductile shear phase related to contact metamorphism, overprints D1 and produces a penetrative foliation (S2), isoclinal folds (P2) oriented N270–280, and stretching lineations shallowly plunging toward the SW–SSW. The P2 folds are often asymmetric, with long and short limbs, and display curved hinges, especially in highly deformed zones. This phase is accompanied by the development of shear zones within the gabbros, showing a deformation gradient increasing from undeformed gabbros to ultramylonites. Kinematic indicators reveal a dominant dextral shear, followed by reactivations along sinistral corridors, likely responsible for local chevron folds (P3, N190) and the reactivation of earlier structures. Within this framework, the doleritic and felsic dykes (N60), although slightly discordant to the foliation, are boudinaged and sheared, and are occasionally crosscut by late quartz and calcite veins associated with metric faults oriented N75, N95, and N110.

This evolution reflects a tectonic transition from an early coaxial compression (D1) to widespread dextral shearing (D2), followed by a late sinistral reactivation. The tight spatial correlation between deformation and ore localization, particularly the intensification of the deformation gradient at the ore-host contact, supports a syntectonic control on the emplacement or remobilization of the mineralization during D2, a hypothesis that remains to be confirmed through detailed petro-structural, geochemical, and geochronological analyses.

Keywords: syntectonic mineralization, deformation gradient, ductile shear zones, gabbro intrusions, Central Jebilet.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9790

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