142-7 Final Stitches of a Supercontinent: Neoproterozoic Dikes in South Jordan

Session: Undergraduate and Graduate Geoscience Student Lightning Talk Showcase (Posters)

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The northern margin of the Arabian-Nubian Shield in southern Jordan exposes a plethora of cross-cutting mafic to intermediate dikes that intrude late Neoproterozoic granitoids and metavolcanic units. While the absolute timing and significance of these different generations of dikes remain poorly constrained, they have been hypothesized to represent the final magmatic events associated with East and West Gondwana suturing during the East African orogeny. However, systematic variations in dike composition and spatial orientation, the lack of robust geochronological dike emplacement age constraints, prevent a differentiation of syn-collisional and post-collisional/extensional magmatism and hamper a more detailed geodynamic attribution of the different dike generations. This project presents new field observations, petrographic characterization, U-Pb zircon geochronology, and novel in-situ LA-ICP-MS apatite U-Pb geochronology to constrain the timing and potential geodynamic drivers of dike emplacement in the northern Arabian Shield in southern Jordan. In-situ apatite U-Pb geochronology by LA-ICP-MS offers a powerful and efficient means to directly date mafic to intermediate dikes that lack zircon and/or have undergone alteration of the aphanitic groundmass. For this, apatite was identified through elemental SEM-EDA mapping prior to LA-ICP-MS analysis. In this study, we document multiple dike orientations and cross-cutting relationships, suggesting an evolving stress regime during the late stages of the East African Orogeny and a transition to more bimodal dike compositions, reflecting the transition to post-collisional magmatism within the Arabian Shield. In-situ apatite U-Pb ages for mafic to intermediate dikes range in age from Ediacaran 568±14 Ma, only marginally postdating syn-collisional regional magmatism in the northern Arabian shield, to earliest Cambrian 542±10 Ma, intruding syn-extensional deposits and barely pre-dating the basal Cambrian unconformity. In particular, new apatite U-Pb ages from ~570–540 Ma mafic dike swarms in southern Jordan constrain the post-orogenic stages of the Arabian Shield and provide critical insight into the transition to post-orogenic extension. Overall, our new data provide critical new insights into the late-to-post-orogenic tectonic evolution and sedimentary basin development in the northern reaches of the Arabian Shield in Jordan. The results also demonstrate the potential to explore abundant dike swarms in other portions of the Arabian-Nubian Shield to explore the late orogenic stitching and collapse of the East African orogenic system, suturing East and West Gondwana.

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

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