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Difficulties in dating Mississippi Valley–type (MVT) mineral deposits and the often closely associated dolomitization have led to controversy regarding their origin. We report the first radiometric ages for the Gorno mining district in northern Italy, an example of the Alpine subclass of MVT deposits. U-Pb ages of hydrothermal carbonates pre- and postdating the ore-forming event show that base-metal mineralization occurred shortly after the deposition of the Carnian host rocks. This implies that the Gorno ore deposits formed at shallow burial depth prior to the Early Jurassic western Tethys rifting phase. Contemporaneous Triassic magmatism and extensional tectonics likely contributed to the high geothermal heat fluxes required to drive the mineralizing system. Our study reinforces the need for reliable geochronological data for metallogenic models and warns against a general application of classic North American MVT models to similar deposits worldwide.

In the Maritime Alps (NW Italy - SE France), the Middle Triassic-Berriasian platform carbonates of the Provençal Domain are locally affected by an intense hydrothermal dolomitization. This dolomitization resulted from a large-scale hydrothermal circulation related to deep-rooted faults, and is indirect evidence of a significant earliest Cretaceous fault activity in this part of the Alpine Tethys European palaeomargin. New carbonate U-Pb dating and geochemical (stable isotope and noble gases on inclusion-hosted water, 87Sr/86Sr, clumped isotopes) data allowed a better understanding of the timing and mechanisms of the hydrothermal circulation. Hydrothermal fluids probably originated from seawater, which was involved in a deep circulation within the underlying crystalline basement, undergoing heating to more than 200°C and substantial compositional modification by prolonged interaction with basement rocks. Thin cement rims rich in carbonaceous material, locally alternated with hydrothermal dolomite cements, are interpreted as remnants of ephemeral microbial communities that could colonize the upper part of hydrothermal conduits during periods of reduced hot fluid flow and contemporaneous downward seawater infiltration.

In the SW Alps, at the NE margin of the Argentera Massif, the occurrence of isolated bodies of silicate-bearing marbles (Valdieri Marble), laterally passing to non-metamorphic Mesozoic limestones of the Dauphinois succession, appears enigmatic, since their origin cannot be related to the regional metamorphism. The stratigraphic, geometric, petrographic, and geochemical features of the Valdieri Marble indicate that it originated from the upflow of hydrothermal fluids which deeply recrystallised the limestone and provoked the abundant neoblastesis of silicate minerals, at an estimated crystallisation temperature of ca. 350 °C. This paper provides for the first time an absolute U/Pb age, comprised between 30 and 31.6 Ma (early Oligocene), for the Valdieri Marble, which is affected by a syn-genetic shear foliation in turn crosscut by the main Alpine tectonic foliations. The hydrothermal fluids that formed the Valdieri Marble migrated along low-angle shear zones, mostly parallel to the sedimentary primary bedding, which were downward connected with high-angle master faults of the “Alpine SW transfer”, a main Oligocene–early Miocene transcurrent shear zone at the southern termination of the Western Alps. The localized heat flow sustaining the hydrothermal system could be related to the early Oligocene thermal event, well documented by magmatic activity in the Western and Central Alps.

The Graetz problem is a convection-diffusion equation in a pipe invariant along a direction. The contribution of the present work is to propose a mathematical analysis of the Neumann, Robin and periodic boundary condition on the boundary of a semi-infinite pipe. The solution in the 3D space of the original problem is reduced to eigenproblems in the 2D section of the pipe. The set of solutions is described, its structure depends on the type of boundary condition and of the sign of the total flow of the fluid. This analysis is the cornerstone of numerical methods to solve Graetz problem in finite pipes, semi infinite pipes and exchangers of arbitrary cross section. Numerical test-cases illustrate the capabilities of these methods to provide solutions in various configurations.

The Provençal and Dauphinois Mesozoic successions cropping out at the southeastern margin of the Argentera Massif (Maritime Alps, NW Italy) were deposited at the transition between the Provençal platform and the Dauphinois basin, marked in the study area by a partly preserved Mesozoic palaeoescarpment. These successions show important lateral variations occurring over relatively short distances, probably related to syndepositional tectonics. Different stratigraphic intervals of the pelagic-hemipelagic Dauphinois succession contain resedimented deposits, made up of both intra- and extrabasinal material, which provide a twofold evidence of syndepositional tectonics indicating both tectonically-triggered gravitational processes and a tectonically-driven evolution of the source areas. Two stages of syndepositional tectonics have been recognized: the first in the earliest Cretaceous, which is related to the deposition of carbonate breccias in the Dauphinois succession and to hydrothermal dolomitization of the Middle Triassic-Jurassic Provençal carbonates, and the second in the Late Cretaceous, which triggered the deposition of different detrital lithozones in the Upper Cretaceous Puriac Limestone. The cited evidence indicates that syndepositional tectonics continued to influence the evolution of the Alpine Tethys European passive margin long after the Late Triassic-Early Jurassic syn-rift stage, which caused the differentiation between the Dauphinois basin and the Provençal platform., Rivista Italiana di Paleontologia e Stratigrafia (Research In Paleontology and Stratigraphy), V. 123, N. 3 (2017)