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Spanning 2500 km along the western margin of North America are 780 Ma dykes, sills, and minor volcanic packages of the Gunbarrel Large Igneous Province. This study focuses on southern (northwestern United States) and central (northern British Columbia) Gunbarrel intrusions and metavolcanics rocks of the Irene and Huckleberry formation (Washington State). Southern Gunbarrel U--Pb ages range from 780 to 769 Ma and new U--Pb zircon dates for the Turah and Rogers Pass sills are 778.6 [+ or -] 0.7 and 778.7 [+ or -] 0.9 Ma, respectively. Southern Gunbarrel intrusions are medium- to coarse-grained diabases that are moderately evolved basaltic, continental tholeiites. Intrusions display negative Nb--Ta and positive Pb anomalies in normalized multielement plots, and [[epsilon].sub.Nd.sup.780] values vary from +3.6 to +1.5. The Irene and Huckleberry volcanic rocks are E-MORB in composition with higher [[epsilon].sub.Nd.sup.780] (+5 to +6) and likely represent partial melts of a mantle plume responsible for the Gunbarrel event. Assuming an Irene and Huckleberry parental magma, mixing models indicate that the southern Gunbarrel magmas were crustally contaminated, but local host rocks are not appropriate crustal contaminants. The modeling points to average upper crust as the crustal contaminant, with an [[epsilon].sub.Nd.sup.780] of approximately -2. This crustal contaminant likely resides on the craton impinged upon by the mantle plume. The remarkable geochemical homogeneity of Gunbarrel intrusions from the Yukon to Wyoming is best explained if primary, plume-derived E-MORB magmas were contaminated in large magma reservoirs near the plume centre and were then injected laterally into the crust 100s to 1000s of kilometres from the reservoir. Key words: Neoproterozoic, Gunbarrel Large Igneous Province, Large Igneous Province, geochemistry, isotopic composition, mantle sources. Répartis sur 2500 km le long de la bordure ouest de l'Amérique du Nord se trouvent des dykes, filons-couches et petits ensembles volcaniques de 780 Ma d'âge de la grande province ignée de Gunbarrel. L'étude porte sur les intrusions du sud (nord-ouest des États-Unis) et du centre (nord de la Colombie-Britannique) de la province de Gunbarrel et les roches métavolcaniques de la Formation d'Irene et Huckleberry (État de Washington). Les âges U--Pb pour le sud de la province de Gunbarrel vont de 780 à 769 Ma, et de nouveaux âges U--Pb sur zircons pour les filons-couches de Turah et Rogers Pass sont de 778,6 [+ or -] 0,7 et 778,7 [+ or -] 0,9 Ma, respectivement. Les intrusions du sud de la province de Gunbarrel sont des diabases à grains moyens à grossiers correspondant à des tholéites continentales basaltiques évoluées. Les intrusions présentent des anomalies négatives de Nb--Ta et positives de Pb dans des spectres multiéléments normalisés, et les valeurs de [[epsilon].sub.Nd.sup.780] vont de +3,6 à +1,5. Les roches volcaniques d'Irene et Huckleberry sont de type E-MORB, avec des valeurs de [[epsilon].sub.Nd.sup.780] plus élevées (+5 à +6) et représentent vraisemblablement des produits de la fusion partielle d'un panache mantellique à l'origine de l'épisode de Gunbarrel. Partant de l'hypothèse d'un magma parental d'Irene et Huckleberry, les modèles de mélange indiquent que les magmas du sud de la province de Gunbarrel ont fait l'objet d'une contamination crustale, bien que les roches encaissantes locales ne soient pas des contaminants crustaux convenables. La modélisation indiquerait qu'une croûte supérieure moyenne, présentant un [[epsilon].sub.Nd.sup.780] environs -2, serait la source de contamination crustale. Ce contaminant crustal se trouve vraisemblablement dans le craton sur lequel poussait le panache mantellique. L'homogénéité géochimique remarquable des intrusions de Gunbarrel du Yukon jusqu'au Wyoming s'explique le mieux par la contamination, dans de grands réservoirs de magma près du centre du panache, de magmas primaires de type E-MORB dérivés du panache, injectés ensuite latéralement dans la croûte à des centaines, voire des milliers de kilomètres du réservoir. [Traduit par la Rédaction] Mots-clés: Néoprotérozoïque, grande province ignée de Gunbarrel, grande province ignée, géochimie, composition isotopique, sources mantelliques., Introduction Spanning over 2500 km along the western margin of North America from the Yukon and Northwest Territories, Canada, to Montana, Wyoming, and Idaho, United States, are diabase dykes, sills, [...]

The many components of the Earth System are linked through complex feedbacks that can be revealed in large compilations of diverse geochemical proxy data for paleoclimate and ocean conditions. In those archives, for example, temporal and spatial trends can be visualized as topologies ('landscapes') defined by areas of high-density data, corresponding to steady states (= stability basins) maintained by negative feedbacks. The boundaries between those stability basins, representing low-density data areas (potential tipping points), are crossed when external drivers are involved, moving the system to a new steady state. These external drivers are often associated with positive feedbacks. As a proof of concept, we produced a stability 'landscape' using an extensive set of published carbon (δ13C) and oxygen (δ18O) isotope data from sedimentary carbonates spanning the last 2.5 billion years. The superimposed C-O isotopic pathways show a preference for particular regions of the 'landscape' at different times in Earth history. Major excursions reflect positive loops often set into motion by external inputs (drivers) that can overwhelm the system, such as major volcanic and tectonic events and human-induced climate effects. Our approach can be applied to other proxy datasets, and multivariate statistical treatments, including machine-learning approaches, can potentially yield a robust, high-resolution 'landscape' of the Earth System through time. [ABSTRACT FROM AUTHOR]