International audienceMicrogeochemical data and transmission electron microscope (TEM) imaging of S-rich monazite crystals demonstrate that S has been incorporated in the lattice of monazite as a clino-anhydrite component via the following exchange Ca2+ + S6+ = REE3+ + P5+, and that it is now partly exsolved in nanoclusters (5–10 nm) of CaSO4. The sample, an osumilite-bearing ultra-high-temperature granulite from Rogaland, Norway, is characterized by complexly patchy zoned monazite crystals. Three chemical domains are distinguished as (1) a sulphate-rich core (0.45–0.72 wt% SO2, Th incorporated as cheralite component), (2) secondary sulphate-bearing domains (SO2 >0.05 wt%, partly clouded with solid inclusions), and (3) late S-free, Y-rich domains (0.8–2.5 wt% Y2O3, Th accommodated as the huttonite component). These three domains yield distinct isotopic U–Pb ages of 1034 ± 6, 1005 ± 7, and 935 ± 7 Ma, respectively. Uranium–Th–Pb EPMA dating independently confirms these ages. This study illustrates that it is possible to discriminate different generations of monazite based on their S contents. From the petrological context, we propose that sulphate-rich monazite reflects high-temperature Fe–sulphide breakdown under oxidizing conditions, coeval with biotite dehydration melting. Monazite may therefore reveal the presence of S in anatectic melts from high-grade terrains at a specific point in time and date S mobilization from a reduced to an oxidized state. This property can be used to investigate the mineralization potential of a given geological event within a larger orogenic framework

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The Žulová Composite Pluton located at the north-eastern margin of the Bohemian Massif exposes undeformed coexisting mafic-felsic association typical of post-orogenic magmatism. The bulk of the pluton is made of biotite granite and granodiorites along with subordinate quartz monzodiorite. New LA-ICP-MS U-Pb zircon dating revealed a synchronous emplacement of the biotite granite (291 ± 5 Ma), granodiorite and quartz monzodiorite (292 ± 4 Ma). The whole-rock geochemistry and the Sr-Nd isotopic data indicate that a plausible source for the biotite granite and the granodiorite could have been a lithologically inhomogeneous pile of Devonian arc-derived, immature metagreywackes interbedded with volcaniclastics. Melting of this crustal material was probably triggered by the rise of hot basic (quartz monzodioritic) magma which could have been an enriched mantle-derived melt contaminated by the underlying Cadomian basement. The Žulová Composite Pluton is a part of a Late Carboniferous-Early Permian Sudetic Granite Belt, including in addition three large plutonic complexes distributed along major terrane boundaries: the Krkonoše-Jizera, the Strzegom-Sobótka and the Strzelin massifs. The genesis of this magmatic belt was likely induced by the rise of hot mantle-derived magma in the crust while their spatially and temporally discrete emplacement at shallow levels was probably related to the (extensional) reactivation of lithospheric discontinuities at terrane boundaries. Former orogenic wedges, resulting from the inversion of youthful plate margins, represent a feasible fertile source for such post-orogenic granitoids.

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In Rogaland, South Norway, a polycyclic granulite facies metamorphic domain surrounds the late‐Sveconorwegian anorthosite–mangerite–charnockite (AMC) plutonic complex. Integrated petrology, phase equilibria modelling, monazite microchemistry, Y‐in‐monazite thermometry, and monazite U–Th–Pb geochronology in eight samples, distributed across the apparent metamorphic field gradient, imply a sequence of two successive phases of ultrahigh temperature (UHT) metamorphism in the time window between 1,050 and 910 Ma. A first long‐lived metamorphic cycle (M1) between 1,045 ± 8 and 992 ± 11 Ma is recorded by monazite in all samples. This cycle is interpreted to represent prograde clockwise P–T path involving melt production in fertile protoliths and culminating in UHT conditions of ~6 kbar and 920°C. Y‐in‐monazite thermometry, in a residual garnet‐absent sapphirine–orthopyroxene granulite, provides critical evidence for average temperature of 931 and 917°C between 1,029 ± 9 and 1,006 ± 8 Ma. Metamorphism peaked after c. 20 Ma of crustal melting and melt extraction, probably supported by a protracted asthenospheric heat source following lithospheric mantle delamination. Between 990 and 940 Ma, slow conductive cooling to 750–800°C is characterized by monazite reactivity as opposed to silicate metastability. A second incursion (M2) to UHT conditions of ~3.5–5 kbar and 900–950°C, is recorded by Y‐rich monazite at 930 ± 6 Ma in an orthopyroxene–cordierite–hercynite gneiss and by an osumilite gneiss. This M2 metamorphism, typified by osumilite paragenesis, is related to the intrusion of the AMC plutonic complex at 931 ± 2 Ma. Thermal preconditioning of the crust during the first UHT metamorphism may explain the width of the aureole of contact metamorphism c. 75 Ma later, and also the rarity of osumilite‐bearing assemblages in general.

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