Finely preserved fossil assemblages (lagerstätten) provide crucial insights into evolutionary innovations in deep time. We report an exceptionally preserved Early Triassic fossil assemblage, the Guiyang Biota, from the Daye Formation near Guiyang, South China. High-precision uranium-lead dating shows that the age of the Guiyang Biota is 250.83 +0.07/–0.06 million years ago. This is only 1.08 ± 0.08 million years after the severe Permian-Triassic mass extinction, and this assemblage therefore represents the oldest known Mesozoic lagerstätte found so far. The Guiyang Biota comprises at least 12 classes and 19 orders, including diverse fish fauna and malacostracans, revealing a trophically complex marine ecosystem. Therefore, this assemblage demonstrates the rapid rise of modern-type marine ecosystems after the Permian-Triassic mass extinction.

In the Quebec Appalachians, the Laurentian continental margin (Humber Zone) and adjacent oceanic domain (Dunnage Zone) were amalgamated during the Ordovician Taconian orogeny. The Dunnage Zone includes ophiolites and overlying synorogenic deposits of both the Saint-Daniel Mélange and Magog Group. The latter consists of a ∼3 km-thick pile of sandstone, felsic volcaniclastic rocks and graphitic slate at the base (Frontière, Etchemin and Beauceville formations) overlain by a ∼7 km-thick turbiditic flysch sequence, constituting the Saint-Victor Formation. The maximum upper age limit of the Magog Group was considered to be Darriwilian based on graptolite fauna. This was proven consistent with a 462⁺⁵/₋₄ Ma (U-Pb ID-TIMS) from a felsic tuff of the Beauceville Formation, but contradicts a detrital zircon U-Pb age of 424 ± 6 Ma recently measured in the Saint-Victor Formation. A new detrital zircon U-Pb geochronology study (HR-LA-ICP-MS and ID-TIMS), focused on the Saint-Victor Formation, yields young detrital populations that suggest that the Saint-Victor Formation is not exclusively Ordovician and extends into the Silurian, as indicated by a maximum age of sedimentation around 430 Ma. Detrital zircon U-Pb geochronology associated with fossil age constraints and stratigraphic correlations in adjacent areas attest that the Saint-Victor Formation should be considered as an upper Magog Group sequence that is separated from lower units (the Frontière-Etchemin-Beauceville formations) by an unconformity corresponding to a sedimentary hiatus of ≤ 10 m.y. Regional tectonic considerations imply that the Magog Group evolved from a syn-Taconian forearc basin in Middle-Late Ordovician time to a syn-Salinic peri-continental basin in early Silurian time. Several NW and SE erosional sources are invoked for the sedimentation of the Magog Group, evolving from the erosion of both the southern Quebec ophiolites and adjacent sedimentary rocks of the Laurentia margin to the NW, and volcanic arc rocks of the Ascot Complex, Shelbourne Falls and Bronson Hill massifs to the SE. Potential sources for ca. 430 Ma zircons found towards the top of the Saint-Victor sequence are the Silurian Frontenac Formation and the East Inlet granitic pluton, both located in the vicinity of the Quebec-Maine border.

The Imourkhssen porphyry Cu±Mo±Au±Ag deposit is located at the Ouzellagh-Siroua Salient (OSS) straddling the boundary between the central Anti-Atlas and the central High Atlas. It is characterized by a typical porphyry-style mineralization. The volcanic rocks are intruded by numerous magmatic rocks of the Ouarzazate Group (580–539 Ma), referred to as the Late Ediacaran magmatic suites (LEMS). Of these, the Askaoun, Imourkhssen, and Imourgane granites are the most significant as they are related to the porphyry mineralization. The entire set is intruded by the Zaghar mafic dyke swarms. Zircon U-Pb dating of the Imourkhssen granite and the ore-bearing granite porphyry shows that these intrusive rocks were emplaced at 558 ± 1 and 550 ± 2 Ma, respectively. Moreover, the whole-rock major and trace element geochemistry reveal a high-K calc-alkaline I-type composition, consistent with an emplacement in a post-collisional setting under a trans-tensional tectonic regime. Ore bodies are hosted by the Askaoun granodiorite as well as the Imourgane granite. The mineralization occurs as fine-grained dissemination and infills of hydrothermally altered NNE–SSW to N–S trending veins and veinlets. Ore-related hydrothermal alteration consists of potassic, chlorite-sericite, serecitic, and propylitic mineral assemblages along with pervasive silicification and pyritization, providing a porphyry-style alteration pattern. The ore periods comprise supergene and magmatic-hydrothermal periods. The latter includes primary dissemination and secondary NNE–SSW to N–S ore-bearing system stages. The occurrence of molybdenite is either restricted to the potassic and chlorite-sericite alteration zones of the ore-bearing granite as fine disseminations or alternatively as veinlet infills within the propylitic halos. The molybdenite occurrences along with pyrite, chalcopyrite, galena, and tennantite dissemination are assigned to the primary ore stage, while the NNE–SSW to N–S ore-bearing system is related to the secondary ore stage. It consists of pyrite, chalcopyrite, bornite, covellite, diagenite, sphalerite, hematite, galena, gold, and chenguodaite. The predominance of cockade and crack-and-seal textures suggest multiple episodes of ore-forming fluid circulations under epithermal conditions. The supergene stage is achieved by subordinate malachite, azurite, barite, hematite, epsomite, and chrysocolla. From the descriptions above, we argue that the Imourkhssen Cu±Mo±Au±Ag mineralization shares many mineralogical and paragenetic attributes of porphyry-copper deposits.