The NE–SW trending Tiddas Souk Es-Sebt des Ait Ikko (TSESDAI) basin, located at 110 km southeast of Rabat, in the region of Khmesset between the village of Tiddas and Souk Es-Sebt des Ait Ikko, is the third largest late Palaeozoic continental trough in the northern Central Moroccan Meseta. It is a ~20 km long and ~2–3 km wide basin, comprising mainly mixed volcano-sedimentary reddish-purple continental Permian rocks laying with an angular unconformity on Visean deep marine siliciclastic sediments and unconformably overlain by the Triassic and Cenozoic formations. In this study we aim to better determine the age of Permian volcanics and their chemical and mineralogical characteristics, as well as assess the provenance of inherited zircons, thus contributing to the understanding of the late stages of the Variscan orogeny in Morocco. The standard volcanic succession includes the following terms: (i) andesites, lapilli tuffs and andesitic ash deposits; (ii) accumulations of rhyolitic lavas; (iii) lapilli tuffs and rhyolitic ash (formation F1); (iv) flows and breccias of dacites; (v) andesite flows; and (vi) basaltic flows. The various volcanic and subvolcanic studied rocks display calc-alkaline-series characteristics with high contents of SiO₂, Al₂O₃, CaO, MgO, and relatively abundant alkalis, and low contents of MnO. In the classification diagram, the studied facies occupy the fields of andesites, trachy-basalts, dacites, trachydacites, and rhyolites and display a sub-alkaline behavior. These lavas would be derived from a parental mafic magma (basalts) produced by partial fusion of the upper mantle. Specific chemical analyses that were carried out on the mineralogical phases (biotite and pyroxene) revealed that the examined biotites can be classified as magnesian and share similarities with the calc-alkaline association-field, while the clinopyroxenes are mainly augites and plot on the calc-alkaline orogenic basalt field. Andesites and dacites of TSESDAI show similarities with the rocks of the calc-alkaline series not linked to active subduction and which involve a continental crust in their genesis. The existence of enclaves in the lavas of the TSESDAI massif; the abnormally high contents of Rb, Ba, Th, and La; and the systematic anomalies in TiO₂ and P₂O₅ indicate also a crustal contamination mechanism. Three magmatic episodes are distinguished with two episodes that correspond to an eruptive cycle of calc-alkaline andesites and rhyolites followed by a basaltic episode. The SHRIMP U–Pb geochronologic data of zircons recovered from the rhyolite dome of Ari El Mahsar in TSESDAI basin show a Concordia age of 286.4 ± 4.7 Ma interpreted to date the magmatic crystallization of this dome. Thus, the rhyolite likely belongs to the third magmatic episodes of TSESDAI.

The Ouarzazate Group in the Anti-Atlas Belt of southern Morocco, part of the West African Craton (WAC), is a significant Proterozoic lithostratigraphic unit formed during the late Ediacaran period. It includes extensive volcanic rocks associated with the early stages of Iapetus Ocean opening. Zircon U-Pb dating and geochemical analyses of the Oued Dar’a Caldera (ODC) volcanic succession in the Saghro Massif reveal two major eruptive cycles corresponding to the lower and upper Ouarzazate Group. The 1st cycle (588–563 Ma) includes pre- and syn-caldera volcanic succession characterized by basaltic andesite to rhyolitic rocks, formed in a volcanic arc setting through lithospheric mantle-derived mafic magmatism and crustal melting. A major caldera-forming eruption occurred approximately 571–562 Ma, with associated rhyolitic dyke swarms indicating a larger caldera extent than previously known. The 2nd cycle (561–543 Ma) features post-caldera bimodal volcanism, with tholeiitic basalts and intraplate felsic magmas, signaling a shift to continental flood basalts and silicic volcanic systems. The entire volcanic activity spans approximately 23–40 million years. This succession is linked to late Ediacaran intracontinental super-eruptions tied to orogenic collapse and continental extension, likely in association with the Central Iapetus Magmatic Province (CIMP), marking a significant transition in the geodynamic evolution of the WAC.

Post-collisional volcanism provides valuable insights into mantle dynamics, crustal processes, and mechanisms driving orogen uplift and collapse. This study presents geological, geochemical, and geochronological data for Ediacaran effusive and pyroclastic units from the Taghdout Volcanic Field (TVF) in the Siroua Window, Anti-Atlas Belt. Two eruptive cycles are identified based on volcanological and geochemical signatures. The first cycle comprises a diverse volcanic succession of basalts, basaltic andesites, andesites, dacites, and rhyolitic crystal-rich tuffs and ignimbrites, exhibiting arc calc-alkaline affinities. These mafic magmas were derived from a lithospheric mantle metasomatized by subduction-related fluids and are associated with the gravitational collapse of the Pan-African Orogen. The second cycle is marked by bimodal volcanism, featuring tholeiitic basalts sourced from the asthenospheric mantle and felsic intraplate magmas. These units display volcanological characteristics typical of facies models for continental basaltsuccessions and continental felsic volcanoes. Precise CA-ID-TIMS U-Pb zircon dating constrains the volcanic activity to 575–557 Ma, reflecting an 18-million-year period of lithospheric thinning, delamination, and asthenospheric upwelling. This progression marks the transition from orogen collapse to continental rifting, culminating in the breakup of the Rodinia supercontinent and the opening of the Iapetus Ocean. The TVF exemplifies the dynamic interplay between lithospheric and asthenospheric processes during post-collisional tectonic evolution.

Nott Corona is within Isabella Quadrangle (V-50), located 3000 km south of Atla Regio, east of Aditi Dorsa, southwest of Wawalag Planitia, and north of Nsomeka Planitia. Nott Corona has a central depression with dimensions of 110 x 80 km and a depth of about 250 m. Nott Corona has been described in the initial reconnaissance mapping of Quadrangle V-50 (e.g., [1-2]), and briefly discussed in [3]. Isabella (175 km diameter) is the second-largest impact crater on Venus and has been previously characterized in detail [4]. The region has abundant magmatic features in addition to Nott Corona: Epon Corona, Libby Patera, Tursa Tholus, as well as graben-fissure systems. We have selected the Nott corona region for detailed (1:500,000 scale) geological mapping to produce a geological history that integrates the volcanic features (lava flows and magmatic centres) along with graben fissure systems interpreted to overlie dyke swarms (c.f. [5]). The focus of this abstract is our detailed mapping of the radiating graben-fissure systems in the region, and grouping of these into different swarms. Our mapping reveals the impressive radiating swarm associated with Nott corona and additional centres, and also circumferential swarms associated with Libby Patera and Epona corona, as well as additional linear swarms whose source is not yet identified, but could belong to giant radiating swarms fed from distal magmatic centres outside the study area. Future mapping in this area will focus on detailed mapping (1:500,000 scale) of the flows to determine their history and identify their magmatic sources, whether fissure-fed from dykes (circumferential or radial) or fed from inferred small magma chambers marked by surface collapse features [6], or fed from circular fractures associated with caldera collapse [6, 7].   References: [1] Bleamaster L.F. (2006) 37th LPSC, Abstract # 2233. [2] Bleamaster L.F. (2008) Abstr. Ann. Mtg. Planet. Geol. Mappers.  [3] Basilevsky A.T., et al. (2009) 40th LPSC, Abstract # 1827. [4] Miyamoto H., Sasaki, S. (2000) Icarus, 145, 533-545. [5] Buchan K.L. and Ernst R.E. (2021). Gond. Res., 100, 25-43.  [6] MacLellan L.M., et al. (2021). Earth-Sci. Rev., 220. 103619. [7] El Bilali H., et al. (2021). 52nd LPSC, Abstract No. 2529.