Integration of Remote Sensing, Mineralogy, and Geochemistry to Delineate Petrogenesis and Mineralization of Post‐Collisional Neoproterozoic Granites From El‐Bakriya Ring Complex, Egypt

ABSTRACT

Late Neoproterozoic post‐collisional granites at El‐Bakriya area include calc‐alkaline granite (monzogranite) and A‐type granites (syenogranite and alkali feldspar granite). The post‐collisional A‐type granites form a ring complex that consists of an inner core of alkali feldspar granite and outer syenogranite with gradational contacts between them. Most of the mineralization in the El‐Bakriya area is concentrated in alteration zones such as albitization and greisenization, where many fluorite and baryte veins or stocks are found to be closely associated. PRISMA hyperspectral data distinguish among these post‐collisional granitoid types, utilizing various image processing techniques. Remote sensing analysis further highlights that the transitions between the granitic plutons are predominantly affected by hydrothermal alteration. A‐type granites contain a diverse array of accessory minerals including silicate minerals (garnet, zinnwaldite, muscovite, zircon, allanite, thorite, topaz, titanite, chlorite, and epidote) and non‐silicate minerals (columbite, pyrochlore, bastnäsite, monazite, apatite, fluorite, and Fe‐Ti oxides). Monzogranite has geochemical characteristics of post‐collisional calc‐alkaline granite, while syenogranite and alkali feldspar granite show characteristics of anorogenic granite. Compositional gaps and sharp intrusive contacts between the two phases suggest distinct magma sources. The post‐collisional calc‐alkaline monzogranite was evolved from a primary magma that was generated during the delamination process. This process induces extensive partial melting, generating mafic magmas that eventually evolved into monzogranite. The overall chemical characteristics of the A‐type granites are consistent with evolution from a single parental magma that was generated by partial melting of a juvenile crust, followed by extensive fractional crystallization and overprinting by late magmatic fluids. The alkali feldspar granite was formed at a shallower depth (5.5–9.3 km; av. 7.3 km) than syenogranite (6.3–9.9 km; av. 8.4 km). El‐Bakriya intrusion has mineralized zones associated with the apical and marginal parts of the alkali feldspar granite, where the hydrothermal solutions and the volatiles are concentrated in the upper part of the magma chamber before complete crystallization of granitic melts.