Skarn to Porphyry-Epithermal Transition in the Ouixane Fe District, Northeast Morocco: Interplay of Meteoric Water and Magmatic-Hydrothermal Fluids

Abstract

The Ouixane Fe skarn district in the northeastern Alpine Rifan belt is the highest grade iron district in Morocco with past production of 65 Mt of ore at >50 % Fe and estimated remaining reserves of 30 Mt grading 58 % Fe. Overall, the district consists of three major deposits, distributed in a 6 Â 6 km zone along the northeastern part of the Beni Bou Ifrour Massif. Mineralization occurs either within the 7.58 ± 0.03 Ma Ouixane post-collisional, hornblende-biotite quartz-diorite porphyry and related dike swarms, or more importantly at contacts of the porphyry with a *1,500-m-thick sequence of Upper Jurassic-Lower Cretaceous turbiditic and volcaniclastic sedimentary rocks. Igneous rocks have high-K, calc-alkaline to shoshonitic affinities and REE patterns that are consistent with emplacement in a typical arc setting. Concordance between the age of mineralization, which is thought to have occurred at 7.04 ± 0.47 Ma, and the 7.58 ± 0.03 Ma crystallization age of the Ouixane quartz-diorite porphyry constitutes strong evidence for a genetic relationship between Ouixane magnetite skarn mineralization and Late Neogene magmatism. Structural controls were important in focusing fluids and localizing the emplacement of late mineralizing phases. The ore zones have undergone strong post-ore displacement along steeply dipping, predominantly thrust

Origin of gem-quality barite at Jebel Ouichane district in Nador, Morocco: implications from integrated fluid inclusions, stable isotopes, and geochemistry

“…This conclusion stays in good agreement with fluid inclusions data obtained for other minerals representing a late retrograde stage of mineralization, i.e. quartz and calcite, which homogenize under a temperature range of 250 to 125˚C 13 .…”

“…The mineralization, mainly in the form of magnetite, hematite, limonite, pyrite, and rarely chalcopyrite and pyrrhotine, has likely resulted from the contact metamorphism of the Miocene quartz diorite porphyry intrusion to the country rocks built of Jurassic limestone 11 . As noted by Bouabdellah et al 13 , there is the concordance between the timing of mineralization (7.04 ± 0.47 Ma) and the crystallization age of the Ouichane quartz-diorite porphyry (7.58 ± 0.03 Ma), which provides strong evidence for a genetic relationship between ore mineralization and Late Neogene magmatism.…”

“…Quartz and plagioclase aplites, microdiorites, and porphyry micromonzonites are also abundant in this area 12,13 . The contact metamorphism of limestone and argillite is negligible, often limited to the recrystallization zone, i.e.…”

“…The Jebel Ouichane area, found near Nador city in the north of Morocco, is mainly built of Jurassic limestones with an admixture of clay sediments and subordinately igneous and metamorphic rocks (Fig. 1) 12,13 . On the slope of the Ouichane Mountain, there is a closed quarry complex hosting barite nodules, which was the important source of iron ore to many countries of western Europe during the first half of the 20 th century.…”

“…The stratification of that facies is quite complicated due to many sedimentary and tectonic processes recognized in this region, proved by the series of hollows, faults, micro-cracks, etc. 12,13 .…”