Oceanic gabbros represent a voluminous part of oceanic crust and are to a large degree cumulative mineral assemblage composed of olivine-pyroxene-feldspar and iron oxides. As such, oceanic gabbros represent a large Fe isotope reservoir in the global Fe cycle. During recycling into the mantle, oceanic gabbros undergo metamorphic reactions but are often considered a small contributor to the subduction component in arcs (e.g., slab-derived fluids) due to their relatively dry and refractory nature. Instead, fluids released from serpentinite as a result of slab devolatisation are considered to be the main source of deep mantle wedge fluids and considerably contribute to arc-lava chemistry and the redox state of metasomatised mantle wedge. However, serpentinite-derived fluids will, by default, pass through overlying gabbroic sequences when ascending to the mantle wedge with a potentially considerable contribution to the Fe isotope budget of the mantle wedge and arc lavas. Here, we investigate the Fe isotopic signature of gabbroic rocks exposed on the seafloor along the Southwest Indian Ridge and collected during IODP scientific ocean drilling expedition leg 118 from the Atlantis Bank Gabbro Massif (IODP Site 735B). Site 735B is composed of intrusive lower crustal and upper mantle rock exhumed to the surface by detachment faulting. Iron was chemically leached, simulating passing fluids, with both leachate and residue analysed for their Fe isotope composition. Our samples display large variation in isotopic composition ranging from mantle to extreme values of δ57Fe = -0.07 to +0.68‰ (relative to IRMM-524a) for the leachate, and MORB-like δ57Fe = -0.1 to +0.21‰, for the residue, respectively. Our results imply that the leached isotopically heavier Fe from oceanic gabbros can be a significant contributor to the Fe isotope composition of the subduction component in arcs and counterbalance the light Fe isotopes derived from serpentinites. Considering the oxidation state of Fe in magnetite, this may further add to the oxidized nature of arc lavas. If such fluids remain in the mantle, they can potentially be a very heavy Fe isotope reservoir, which may explain some exotic signatures observed in ocean island lavas or transition zone diamond inclusions. Gabbroic residues deprived of any such leachate resembles Fe isotope signatures of the upper mantle and MORB and thus does not change the Fe isotope composition of the mantle significantly after subduction.

Abstract Different mineral clocks in granite can provide age information reflecting various aspects of rock formation, including cooling or post-emplacement fluid–rock interaction. However, the dating tool chosen can yield inconclusive age information due to differences in closure temperatures and susceptibility to fluid alteration among chronometers. This has led to an inferred superiority of U–Pb in zircon over U–Pb in monazite or Rb–Sr in mica. Here, we investigate age systematics using Rb–Sr biotite grains, U–Pb in monazite and zircon in a Devonian granite from Australia. Single-grain laser ablation ICP-MS/MS biotite analyses are combined with zircon–monazite U–Pb ages and trace element systematics. Textural and trace element evidence combined with age systematics reveals a Rb–Sr closure age of c. 360–330 Ma relative to a putative 364 Ma emplacement age, suggesting hydrothermal alteration of the granite. Trace element systematics and magnetic susceptibility in biotite grains reflect their partial chemical reset and fluid overprint in the granite. However, similar systematics are also observed for zircon and monazite. Our multiple chronometer dating approach, studied with modern laser-ablation methods, highlights the need for detailed investigation of isotope and trace element systematics in single grains and that individual ages should be used cautiously when dating altered granitoids.

The ancient cores of modern continents, cratons, are the oldest blocks of "stable" lithosphere on Earth. Their long-term survival relies on the resistance of their underlying thick, strong, and buoyant mantle keels to subsequent recycling. However, the effect of substantial geographical variations in keel thickness on the post-assembly behaviour and mass movement within these continental cores remains unknown. Here, we demonstrate that the spatial distribution of fluid-reset in-situ Rb-Sr ages for Paleo-Mesoarchean (3.6–2.8 billion years ago; Ga) granitoids of the Pilbara Craton, Australia shows remarkable correlation with independently-constrained lithospheric thickness models. Without craton-wide heating/magmatic events, these anomalously young Rb-Sr ages document episodes of fluid infiltration into granitoid complexes as a response to lithospheric reactivation by far-field stresses. This correlation implies that craton-wide fluid mobilization triggered by extra-cratonic Neoarchean to Mesoproterozoic (2.8–1.0 Ga) tectonic events is facilitated by variations in lithospheric strength and thickness. Compared to areas of older overprints, the two-thirds of the craton comprised of younger reset ages is underlain by comparatively thin lithosphere with higher susceptibility to reactivation-assisted fluid flow. We propose that even the strongest, most pristine cratons are less stable and impermeable than previously thought, as demonstrated by the role of granitoid complexes and cratons as selective lithospheric "sponges" in response to minor tectonic forces. Therefore, variations in lithospheric thickness, likely attained before cratonization, exert a crucial control on billions of years of fluid movement, elemental redistribution and mineralization within ancient continental nuclei.

Secular trends in plutonic whole-rock geochemistry pose critical, although non-unique, constraints to early Earth tectonics. Here, we present a large whole-rock geochemical (879 collated samples) dataset for granitoids from the Pilbara Craton, Western Australia, applying it to test the link between secular trends and proposed tectonic mechanisms. We show that the spatio-temporal distribution of granitoid trace element geochemistry is constrained within discrete lithotectonic blocks supporting the reconstruction of its tectonomagmatic evolution. Time-sliced geochemical contour mapping of key petrogenetic ratios indicates the craton underwent rifting similar to 3.2 Ga (billion years ago), marking a transition from predominantly sodic magmatism to a broader magmatic compositional spectrum. Our results demonstrate that rift-assisted breakup of proto-cratons is a viable craton growth mechanism. We identify a possible evolutionary sequence beginning with drips and upwellings below a Paleoarchean mafic plateau, which is subsequently dismembered by rifting. These plateau fragments form rigid blocks in the Mesoarchean, between which weaker, thinner crust accommodates minor convergence and divergence manifested as short-lived mobile lid-like features before stabilization. We conclude that these features do not require an active lid, plate tectonic regime.

Thermochemical convective instabilities in the mantle, often referred to as mantle plumes, cause mantle melting that give rise to ocean island basalts (OIB) in intraplate settings. The array of radiogenic isotope signatures in global intraplate OIB indicate that although plumes are individual entities, they share enriched components that resemble various parts of subducted crust and a hypothetical mantle matrix termed "focal zone" (FOZO). Each plume is expected to rise with an individual buoyancy flux, thereby producing variable volumes of melting with some OIB forming subaerial islands, whereas others produce submarine volcanoes.Here, we report the first radiogenic isotope data (Sr, Nd, Pb and Hf) for lavas of Lord Howe Island (LHI) in the Tasman Sea, the most prominent subaerial expression of the hypothesised Lord Howe mantle plume. Major element data are consistent with a moderate degree of partial melting, and heavy rare earth element depletion indicates melting occurred in the presence of garnet, consistent with other global plume lavas. Radiogenic Sr-Nd isotopic data are similar to those defining the relatively primitive FOZO component with no clear enriched mantle affinity. The nearby Tasmantid Seamounts are also sourced from a mantle plume, and have similar Sr-Nd character. However, combined208Pb/204Pb and 207Pb/204Pb vs 206Pb/204Pb ratios of LHI lavas are inconsistent with a FOZO-type source. Instead, Pb isotopes overlap with typical enriched mantle 1 (EM1) lavas (e.g., Pitcairn, Tristan da Cunha), trending slightly higher than the Northern Hemisphere Reference Line (NHRL). Hafnium isotopes follow trends observed in lavas of the archetypal EM1 Pitcairn-Gambier islands, and are partially decoupled from 143Nd/144Nd; this decoupling is rare among OIB. The combined element-isotope data indicate that LHI forms the most recent expression of a mantle plume track in the Tasman Sea. Albeit unique in its 208Pb*/206Pb* isotope code among global mantle plumes, the resemblance of LHI lavas with the spatially related and contemporaneous Taupo seamount of the parallel Tasmantid plume track in the Tasman sea supports a genetic relation of both plumes. The proposed common origin of the two parallel plume tracks requires a larger plume underpinning the Tasman sea with individual plume fingers rising towards the surface, possibly in a triple plume network considering the on-shore Cosgrove track in eastern Australia. The subaerial expression of LHI contrasts the submarine Tasmantid Seamounts; this expression is only possible due to the continental ribbon that forms the island's foundation, suggesting secondary plume fingers display similar low buoyancy fluxes.Plain language summary: Lord Howe Island is predominantly composed of basaltic rocks, which are created when mantle underneath the crust melts and the subsequent magma rises to the surface and erupts out of a volcano. The chemical composition of these volcanic rocks can provide us with valuable information about geologic processes. Moreover, we can compare the composition of islands like Lord Howe to better investigate and un-derstand volcanic networks that exist deep within the Earth. The composition of Lord Howe Island basalts was investigated for the first time using specialised instruments that can separate individual elements into different isotopes. The ratios of these different isotopes reflects the composition of the mantle source which can be enriched by the presence of subducted crustal rocks, oceanic rocks and sediments. Our data indicate the distinctive reservoir that Lord Howe Island samples were derived from is the same reservoir as that of the nearby Taupo Seamount volcano. We infer from this that a piece of ancient crust is stuck in the mantle, and the two volcanoes are sampling it. This study supports a theory of a large, linked volcanic network under the Tasman Sea, and adds to the growing body of research investigating 'double-chain' volcanism in the Pacific and Atlantic oceans.

The origin of volatile element depletion in terrestrial planets and meteorites relative to a solar composition represented by CI carbonaceous chondrites remains an unsolved problem. The isotope compositions of moderately volatile elements may offer the possibility to distinguish between the various processes that may have caused this depletion (e.g., partial condensation or partial evaporation). We report high precision Sn isotope measurements in carbonaceous chondrites and ordinary chondrites and the results are reported as delta Sn-124/116. Four carbonaceous chondrites (Orgueil CI, Murchison CM2, NWA 5240 CV3 and Allende CV3) show a limited range in delta Sn-124/116 (-0.02% to 0.11%) with an average value of 0.04 +/- 0.11% (2 s.d.) for a wide range of Sn concentrations (0.63 ppm to 1.57 ppm). The absence of Sn isotope fractionation among carbonaceous chondrites suggests that volatile depletion may have taken place under thermodynamic equilibrium conditions between solid and vapor in the Solar Nebula. Alternatively, the mixing of two components, a volatile-free component containing no or little Sn and a volatile-rich component could explain this trend. This latter hypothesis is consistent with the overall trace element pattern found in carbonaceous chondrites, showing a constant relative abundance when normalized to CI chondrites for the most volatile elements. In contrast with carbonaceous chondrites, ordinary chondrites exhibit a larger range of Sn isotope compositions (delta Sn-124/116 from -2.02% to 0.64%), but neither the degree of metamorphism (3-6) nor the group (H, L, LL) is correlated with Sn isotopic variations, or with the Sn contents (range 0.20 to 1.44 ppm). Nineteen out of twentyone ordinary chondrites are enriched in light Sn isotopes compared with carbonaceous chondrites and the bulk silicate Earth. The trace element patterns of volatile elements in ordinary chondrites suggest that equilibrated ordinary chondrites have been disturbed by parent body processes related to metamorphic or shock overprinting but also inherited isotope fractionation found in unequilibrated ordinary chondrites. Last, the isotope composition of the bulk silicate Earth (BSE) indicates that the volatile element depletion observed in the Earth took place in conditions perhaps similar to those of carbonaceous chondrites, as a simple model describing the effect of Earth's core formation on Sn isotopes shows that the Sn isotope composition of the bulk Earth is identical to that of the BSE and of carbonaceous chondrites. (C) 2021 Elsevier Ltd. All rights reserved.

Iron oxide grain coatings in red sandstones contain trace metals that are released upon dissolution of the coatings. Analyses by ICP-MS following acid leaching of the grain coatings show that the dissolved metals can constitute an ore-forming fluid, as hypothesized in models for sandstone-hosted ore deposits. Median compositions of 37 samples, mostly of Triassic to Devonian age, from across Britain and Ireland are 6.3 ppm copper, 2.4 ppm cobalt, 10.1 ppm vanadium, and 0.3 ppm uranium. These contents at the basin scale are adequate to form the observed range of ore deposits in red beds. The migration of hydrocarbons or brines can cause the dissolution of grain coatings and contributes to controlling the distribution of ore deposits. Future measurements should test red beds derived from uplifted, mineralized plate margins, in which sandstones may be preloaded with ore metals.

Pyritized burrows from three localities were analysed using LA-ICP-MS to determine their trace element content and assess their ability to sequester trace elements. Pyritic burrows from Hock Cliff (Jurassic), Wren's Nest (Silurian) and Southerham Grey Pit (Cretaceous) have anomalous levels of Se, Cu and Pb and are enriched relative to their host sediments. Sequestration rates were calculated using sedimentation rates from similar depositional environments. Results show that pyritic burrows, mediated by bacterial sulphate reduction, can sequester Se, Cu and Pb up to 3 orders of magnitude greater than the rate of Fe–Mn crusts, which are considered rich sources of trace elements, demonstrating that bioturbated marine sediments are significant sinks of trace elements.

The depletion in moderately volatile elements in the Moon relative to Earth and comparison of the isotope compositions of the Moon and Earth have placed important constraints on models of lunar formation. A liquid–vapour protolunar disk from a high-energy giant impact has been proposed to explain some of these constraints. Here we present high-precision tin isotope data for lunar rocks, measured by double-spike MC-ICP-MS (multicollector inductively coupled plasma mass spectrometry). The lunar rocks are enriched in light tin isotopes compared to the Earth (Δ 124/116 Sn Moon–Earth = −0.48 ± 0.15‰). On the basis of our data and constraints on tin speciation, we show that this tin isotope fractionation is inconsistent with volatile loss from a lunar magma ocean. Instead, we propose a scenario with vigorous mixing between the protolunar disk and the Earth in high-energy conditions during the impact, followed by liquid–vapour equilibration and phase separation at around 2,500 K while the disk was cooling. This scenario is consistent with the depletion in moderately volatile elements and isotope composition of the Moon.

Oil residues occur as solid bitumen in mineralized zones within the Devonian Weardale Granite of the northern Pennines, northern England. Comparable residues are present in the overlying Mississippian rocks and were probably derived from a Carboniferous source, i.e. during later mineralization of the granite. The bitumen was already solidified during fluorite mineralization, which does not contain oil inclusions. The residues do not show the high thermal maturity of organic matter in the region altered by the earliest Permian Whin Sill. Like the sulphide-fluorite mineralization, oil emplacement post-dated intrusion of the sill. Pyrite associated with the oil residues is enriched in trace elements including lead, silver, gold, selenium and tellurium, which suggests that mineralizing fluids at least shared pathways with migrating hydrocarbons and possibly also suggests undiscovered valuable metal resources.

Tin is a moderately volatile element whose isotope composition can be used to investigate Earth and planet differentiation and the early history of the Solar System. Although the Sn stable isotope composition of several geological and archaeological samples has been reported, there is currently scarce information about the effect of igneous processes on Sn isotopes. In this study, high-precision Sn isotope measurements of peridotites and basalts were obtained by MC-ICP-MS with a double-spike technique. The basalt samples display small variations in delta Sn-124/116 ranging from -0.01 +/- 0.11 to 0.27 +/- 0.11 parts per thousand (2 s.d.) relative to NIST SRM 3161a standard solution, while peridotites have more dispersed and more negative delta Sn-124 values ranging from -1.04 +/- 0.11 to -0.07 +/- 0.11 parts per thousand (2 s.d.). Overall, basalts are enriched in heavy Sn isotopes relative to peridotites. In addition, delta Sn-124 in peridotites become more negative with increasing degrees of melt depletion. These results can be explained by different partitioning behavior of Sn4+ and Sn2+ during partial melting. Sn4+ is overall more incompatible than Sn2+ during partial melting, resulting in Sn4+-rich silicate melt and Sn2+-rich residue. As Sn4+ has been shown experimentally to be enriched in heavy isotopes relative to Sn2+, the effect of melting is to enrich residual peridotites in relatively more compatible Sn2+, which results in isotopically lighter peridotites and isotopically heavier mantle-derived melts. This picture can be disturbed partly by the effect of refertilization. Similarly, the presence of enriched components such as recycled oceanic crust or sediments could explain part of the variations in Sn isotopes in oceanic basalts. The most primitive peridotite analyzed in this study was used for estimating the Sn isotope composition of the BSE, with delta Sn-124 = -0.08 +/- 0.11 parts per thousand (2 s.d.) relative to the Sn NIST SRM 3161a standard solution. Altogether, this suggests that Sn isotopes may be a powerful probe of redox processes in the mantle. (C) 2018 Elsevier Ltd. All rights reserved.

This study aimed at developing a new methodology for measuring tin isotope compositions in geological and cosmochemical materials.

The Earth formed in a swarm of Moon- to Mars-sized objects that collided together to build our planet. A large body of work has been dedicated to understanding the Earth's composition as being made of single groups or mixtures of chondrites, however, these models cannot account for the isotopic and elemental characteristics of the Earth. Here, we test mixtures of meteorites, including achondrites, analyzed for seven isotope systems (O, Cr, Ni, Ti, Mo, Ca and Sr), to reproduce the isotope compositions of the Earth and Mars. Our Monte Carlo inversion (a numerical method based on generation of random numbers used to invert multiparameter models) yields a new compositional model where Earth and Mars come almost entirely from the same source material. This finding is in striking agreement with recent planetary formation models in which Earth and Mars formed in a common narrow zone of the protoplanetary disk with Mars being ejected to its current position which prevented further accretion. An important outcome of the model is that a significant mass fraction of the Earth could have been made of volatile depleted and refractory enriched planetary bodies such as angrites (among the oldest known achondrites). This conclusion is also in agreement with new Si isotope data in angrites which suggest that a component of angrites would help explain the difference in δ30Si between the bulk silicate Earth and its building blocks. Our model matches all isotope compositions for both planets, reproduces the volatile element budget of Mars, and accounts for the enrichment in refractory elements of the Earth and Mars compared to chondrites.

This study is a first kinetic approach about the compost liquor treatment by activated sludge. This industrial wastewater is highly loaded in organic and nitrogen compounds (COD≈12,000 mg L(-1) and NH(4)(+)-N≈4,000 mg L(-1)). The possibility of its treatment in an urban WWTP is studied measuring ammonia oxidation rate with non-acclimated sludge to the industrial effluent. Compost liquor appears as an inhibitor substrate. The ammonia oxidation rate can be modelled by the Haldane model: U(MAX)=0.180 d(-1), K(S)=12.0 mgN.L(-1) and K(I)=26.0 mgN.L(-1). The ammonia oxidation rate also follows for a synthetic substrate which has the same pollutant load as the real substrate. In this case, the ammonia oxidation rate can be modelled by the Monod model: U(MAX)=0.073 d(-1) and K(S)=4.3 mgN.L(-1). This result confirms that the ammonia oxidising bacteria are inhibited by the real wastewater. The following-up of nitrate production shows also the inhibition of nitrite oxidising bacteria. The compost liquor treatment seems not possible in an urban WWTP (<50,000 p.e.). That's why a specific WWTP is recommended and an acclimation step of activated sludge is essential.