A Proposed New Precambrian Skarn Deposits in the Arabian Shield

The bimodal hypsometry of the Arabian-Nubian Shield in the Neoproterozoic triggered the formation of post-amalgamation marine bains in the low-stand terranes of the Arabian shield (AS). The carbonate successions in the extraordinary marine basins in the AS are intruded by granite plutons of different causative types, with major shear zones pathways. Therefore, the conditions for the formation of skarn deposits are mature at the contact of the carbonate succession with the causative granite plutons. Multidisciplinary approaches including ASTER data, Magnetic data, and geochemical data have been applied to the Murdama basin to locate the promising areas for skarn deposits. The Murdama basin has contrasting magnetic anomalies of different intensity at the contact between the Murdama limestone and the post-Murdama causative batholiths; significant magnetic anomalies exist at the contact with the Idah causative magmas. Lineaments related to the Najd fault system (NFS) exist eastward, where calc-silicate alteration-related minerals were evolved, with no clues for penetrative effect for such alteration activity along pathways related to the fracture system or at contact with the Abanat suite. Different spectral mapping techniques, including Spectral Information Divergence (SID), Spectral Angle Mapper (SAM), and Constrained Energy Minimization (CEM) confirm that the Idah suite is the predominant causative magma in the study area with highly evolved calc-silicate alteration-related minerals, such as wollastonite, garnet, and pyroxene. Meanwhile, The Idah suite has been identified as the main causative magma for other reduced skarn localities that have been recorded from the Murdama basin, i.e. the Qitan and An Nimriyah South. Alteration related mineral zones of kaolinite, chlorite, muscovite, and hematite are evolved alongside with calc-silicate minerals at the contact bewteen Idah suite, and the Murdama carbonate member. The geochemical data suggests reducing effect for the Idah suite at the contact between the Murdama carbonate succession and Idah plutons. These preliminary results of this study need detailed field investigations and geochemical explorations for the proposed skarn deposits in the Neoproterozoic molasse basins of the AS.

کلیدواژه ها:

Neoproterozoic Skarn ، Murdama carbonate ، Causative plutons ، Arabian – Nubian shield ، Redox state of the magma