Geochemistry and spatial distribution of Neoproterozoic dike swarms from the northwestern tip of the Arabian-Nubian Shield: Implications for crustal extension

Ediacaran dike swarms in the Arabian-Nubian Shield (ANS) provide key insights into post-collisional tectonics and magmatism. This study presents new chemical data, two Ar-40/Ar-39 ages, and spatial distribution analysis for dike swarms in the northernmost ANS exposures in SW Jordan. Hornblende from a lamprophyre sill intruding the Saramuj Conglomerate yielded a plateau age of similar to 592 +/- 3 Ma, interpreted as the crystallization age of the sill. Micro-cores of sericite-rich domains in altered plagioclase phenocrysts from a dolerite dike intruding similar to 586 Ma alkali granite produced ages of similar to 580-570 Ma, interpreted as hydrothermal alteration ages, constraining dike emplacement to 586-580 Ma. The geochemistry of investigated dikes varies from alkaline to subalkaline and crosscuts calc-alkaline magmatic rocks. This transition reflects a shift from compression to extension (similar to 610-590 Ma), lithospheric thinning, and changes in mantle sources. After 590 Ma, magmatism became exclusively alkaline, forming A-type granitoids and dolerites, marking a shift to extensional magmatism. Dikes predominantly follow NE-SW and E-W orientations, with rare N-S, NW-SE, and WNW-ESE trends, suggesting a major horizontal extension direction from NW-SE to N-S. Dike density ranges from 5 to 13 %, averaging similar to 9 %, with crustal extension estimates of 9-23 %, averaging 16 %. No correlation was found between dike composition, orientation, or order of emplacement, indicating consistent stress orientation during the final stage (605-580 Ma) of ANS evolution.