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Zeolite cement is one of the main components of the Jurassic to Lower Cretaceous fluvial-aeolian succession in the Parnaiba Basin, northeastern Brazil. Core and outcrop-based stratigraphic analyses permitted the paleo-environmental and diagenetic interpretation of aeolian sandstone and showed the influence of the volcanic substrate in the origin of the zeolite cement. The substrate is represented by an extensive volcanic plain developed in the last stages of the Central Atlantic Magmatic Province (CAMP) in West Gondwana. The siliciclastic deposits consist of dune field, sand sheet and wadi deposit facies associations. The zeolite cement of the aeolian succession forms poikilotopic crystals with anomalous up to 50% modal content. X-ray diffraction and SEM/EDS/CL analyses showed laumontite and Ca-stilbite exhibiting, respectively, massive and radial textures. During eodiagenesis, the main processes included clay infiltration linked to water table fluctuations and flash flood events, producing clay coatings and displacive stilbite cementation. Massive laumontite cementation and smectite-chlorite conversion occurred in the mesodiagenesis, while in the final stages, the zeolite was partially replaced by calcite cement. Telodiagenesis is recorded by iron exsudation and the corrosion of clay films. Several processes can be inferred to explain the origin of the zeolite cement in the Jurassic-Lower Cretaceous sandstone of the Parnaiba Basin. After the first magmatic pulse (Triassic magmatism), the zeolite-bearing basalts were submitted to chemical weathering, causing cation leaching. Afterwards, the deposition of aeolian sands related to a wet desert system occurred above this weathered substrate. Fractured basaltic substrate favored the release of ions to the surface, with fluids enriched in sodium and calcium that percolated the permeable aeolian sandstone beds during the diagenesis. Furthermore, zeolite cement is geographically associated with the volcanic substrate in the western Parnaíba Basin. However, it is absent in the eastern part, where the aeolianites overlie sedimentary rocks. We suggest that the system was thermally reactivated by the last thermal CAMP phase, with basalt emplacement in the eastern Parnaiba Basin linked to the opening of the Equatorial Atlantic Ocean (Cretaceous magmatism). The progressive heating towards the western part of the basin triggered fluids convection, and the enrichment in ions such as Ca2+, Si4+, Na+, Al3+, HCO− 3 and SO 4 2−, promoting optimal conditions for zeolite crystal growth (100 °C–300 °C). Sandstone textural aspects, as well as extensional faults and fractures allowed fluids migration resulting in the massive poikilotopic zeolite cementation, characterizing one of the most singular features of the diagenetic history of the West Gondwana record. Unlabelled Image • Genesis of poikilotopic zeolite cement in aeolian sandstones is investigated. • Zeolites occur in anomalous content in aeolianites from Mesozoic of Parnaíba Basin. • Zeolite only occurs associated with a weathered volcanic substrate. • These deposits are influenced by heat propagation due to CAMP emplacement. [ABSTRACT FROM AUTHOR]

The opening of the Central Atlantic Ocean was accompanied by ascending plume zones that generated large igneous provinces (LIPs), such as the Central Atlantic Magmatic Province (CAMP), with voluminous lava flows and outpourings. One of the best records of the CAMP in the West Gondwana is the Jurassic volcanic-sedimentary succession exposed in the western Parnaíba Basin, northern Brazil. Diagenetic and hydrothermal processes are discussed, focusing on the lava-sediment interaction. The siliciclastic sediments called "intertrap deposits" record a wet desert system characterized by fluvial-aeolian and shallow lake deposits engulfed by lavas of the CAMP at approximately 200–202 Ma. The facies and petrographic studies, based on a drill core and outcrops, led to the interpretation of the palaeoenvironmental and diagenetic evolution of the intertrap deposits. The intertrap deposits are sandwiched by basalts and may be organized in seven sedimentary facies, grouped into two facies associations: 1) ephemeral braided river deposits (FA1), which consist of medium- to coarse-grained pebbly sandstone with poorly sorted angular to sub-rounded grains (basaltic fragments and quartz) and low-angle cross-bedding, even-parallel stratification, and trough cross-stratification, and 2) pond/shallow lake deposits (FA2) composed of tabular beds of sandstone/siltstone rhythmite and laminated mudstone. The main architectural elements of intertrap deposits are 1) channels on volcanic substrate, 2) sand sheets deposited over pre-existent lava topography, 3) tabular beds with laminated rhythmites, and 4) sand-filled fissures/fractures and clastic dykes. The intensification of magmatic processes due to the disruption of Pangaea promoted the formation of extensive volcanic plains, whereas wet desert settings were developed during the quiescent intervals between lava flow episodes. Fluvial channels with subaqueous dunes and sand sheets were incised into the basaltic substrate. The abandoned fluvial plains were affected by flash floods that promoted mechanical infiltration of clays, forming coatings over grains. The heat flow and hydrothermal activity of volcanic rocks increased the devitrification of glassy clasts, releasing silica and precipitating low-temperature authigenic mineral assemblages. The most common pore-filling process was the massive precipitation of early diagenetic-hydrothermal minerals, including smectite, chalcedony, poikilotopic zeolite, megaquartz, and haematite, which partially obliterated the primary porosity and permeability. These exceptional conditions of cementation triggered by basalt eruptions precluded the modification of a primary framework by late stages (post-Jurassic) burial diagenesis. The intertrap sandstones represent the last lava-sediment interaction related to the CAMP recorded in West Gondwana. • Pangaea breakup caused the installation of large volcanic plains in West Gondwana. • Wet desert settings developed during the quiescent intervals between lava flows. • The first description of CAMP-related lava-sediment interaction for the West Gondwana. • Basaltic hydrothermalism overtook the diagenetic history of the intertrap sandstone. • Heat flow-induced devitrification amplified silica release and authigenesis. [ABSTRACT FROM AUTHOR]