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Modeling the behavior of trace elements during lunar magma ocean solidification is important to further our understanding of the chemical evolution of the Moon. Lunar magma ocean evolution models rely on consistent datasets on how trace elements partition between a lunar silicate melt and coexisting minerals at different pressures, temperatures, and redox conditions. Here we report new experimental trace element partition coefficients (D) between clinopyroxene (cpx), pigeonite, orthopyroxene, plagioclase, olivine (ol), and silicate melt at conditions relevant for the lunar magma ocean. The data include Dcpx−melt at ambient and high pressures (1.5 GPa and 1310 °C), and partition coefficients at ambient pressure for pig, opx, ol, and pl. Overall, clinopyroxene is a phase that may control the fractionation of key geochemical trace element ratios, such as Lu/Hf and Sm/Nd, during the evolution of the lunar magma ocean. We explore the impact of the new silicate Dmineral−melt on the trace element evolution of the lunar magma ocean and we find that accessory phosphate minerals, such as apatite or whitlockite are of critical importance to explain the observed trace element and isotopic signature of the KREEP reservoir on the Moon. The new partition coefficients were applied to calculate the trace element evolution of the residual melts of the crystallizing lunar magma ocean and we propose a new trace element composition for the urKREEP reservoir. The new data will be useful for future thermo-chemical models in order to adequately predict the duration of the lunar magma ocean and the age of the Moon. [ABSTRACT FROM AUTHOR]

Understanding calcite genesis in ultrahigh‐pressure crustal rocks is a key to the reconstruction of the evolution of ultrahigh‐pressure metacarbonate rocks. Here, we present new data and a new model on the genesis and the P–T conditions of the formation of calcite found in the ultrahigh‐pressure calc‐silicate rocks from the Kokchetav massif. In the studied sample aragonite inclusions coexist with Type A calcite inclusions (previously interpreted as mineral inclusions) and the inclusions of Type B calcite (previously interpreted as derived from the crystallization of carbonatitic melt) in cores of garnet porphyroblasts. The most Mg‐rich calcite from Type A inclusions coexisting with aragonite inclusions in one garnet growth zone shows XCa = 0.935 implying their crystallization during a retrograde metamorphic stage at P ~ 2.3 GPa and T ~ 870°C along the P–T path. Type A calcite and aragonite inclusions were also found coexisting in one growth zone with K‐bearing clinopyroxene inclusion (ω[K2O] = 0.5 wt.%). Such a high K2O‐content in clinopyroxene testify that the pressure of inclusion capture exceeded 3.5 GPa, which contradicts the P–T conditions estimated by XCa in magnesian calcite. Thus, Type A calcite inclusions were initially captured as an aggregate of aragonite+ magnesian calcite at ultrahigh pressure metamorphic stage (P ≥ 3.5 GPa, T = 900–1,000°C) and then re‐equilibrated at lower conditions (P ≤ 2.3 GPa and T ≤ 870°C). The trace element composition of aragonite and Type A and Type B calcite from inclusions was also studied to clarify calcite genesis in these inclusions. Aragonite shows high LREE (5–57 ppm) and Sr‐content (600–800 ppm). Calcite from Type A inclusions shows low LREE (2.9–19.8 ppm) and Sr‐content (490–670 ppm). Calcite from Type B inclusions forms two groups according to the LREE and Sr content distribution (Type B1 and Type B2). Trace element distribution in Type B1 calcite is identical to that of Type A calcite, while Type B2 calcite shows high LREE (6.8–64.9 ppm) concentrations along with low Sr‐content (180–340 ppm). Type A and Type B1 calcite is interpreted to have been re‐equilibrated. Type B2 calcite inclusions crystallized from the hydrous carbonatitic melt. [ABSTRACT FROM AUTHOR]

Trace elements provide crucial information about the origin and evolution of the Earth. One common issue regarding their analyses is the reduced analyte recovery during hot plate acid digestion for some geological samples. To overcome this, alkali fluxes (e.g., Lithium borate) have been used to produce an homogeneous synthetic glass that can be used then for both X-ray fluorescence (XRF) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In this sense, we developed a method for LA-ICP-MS whole rock trace element analyses in glasses prepared by mixing high-purity sodium tetraborate and rock powders at high-temperature. We selected six international reference materials including peridotite (JP-1), basalt (BRP-1), kimberlite (SARM-39), pyroxenite (NIM-P), diorite (DR-N) and andesite (JA-1). Glasses were produced in a fully automatic fusion machine with step heating. Run products analyses were carried out on a Thermo® Element2 SF-ICP-MS coupled to a New Wave Research® Nd:YAG (213 nm) laser ablation system and on a Thermo® Element XR ICP-MS coupled to an Analyte G2 (193 nm) LA system. Results show that glasses are homogeneous and there is good agreement (generally > 90%) between our data and literature values for most trace elements, including large ion lithophile elements (LILE), high-field strength elements (HFSE) and rare-earth elements (REE). [ABSTRACT FROM AUTHOR]

This study presents culture experiments of the cold water species Neogloboquadrina pachyderma (sinistral) and provides new insights into the incorporation of elements in foraminiferal calcite of common and newly established proxies for paleoenvironmental applications (shell Mg/Ca, Sr/Ca and Na/Ca). Specimens were collected from sea ice during the austral winter in the Antarctic Weddell Sea and subsequently cultured at different salinities and a constant temperature. Incorporation of the fluorescent dye calcein showed new chamber formation in the culture at salinities of 30, 31, and 69. Cultured foraminifers at salinities of 46 to 83 only revealed chamber wall thickening, indicated by the fluorescence of the whole shell. Signs of reproduction and the associated gametogenic calcite were not observed in any of the culture experiments. Trace element analyses were performed using an electron microprobe, which revealed increased shell Mg/Ca, Sr/Ca, and Na/Ca values at higher salinities, with Mg/Ca showing the lowest sensitivity to salinity changes. This study enhances the knowledge about unusually high element concentrations in foraminifera shells from high latitudes. Neogloboquadrina pachyderma appears to be able to calcify in the Antarctic sea ice within brine channels, which have low temperatures and exceptionally high salinities due to ongoing sea ice formation. [ABSTRACT FROM AUTHOR]

As a common constituent of metamorphic assemblages, rutile provides constraints on the timing and conditions of rock transformation at high resolution. However, very little is known about the links between trace element mobility and rutile microstructures that result from synmetamorphic deformation. To address this issue, here we combine in situ LA‐ICP‐MS and sensitive high‐resolution ion microprobe trace element data with electron back‐scatter diffraction microstructural analyses to investigate the links between rutile lattice distortions and Zr and U–Pb systematics. Furthermore, we apply this integrated approach to constrain further the temperature and timing of amphibolite facies metamorphism and deformation in the Bergen Arcs of southwestern Norway. In outcrop, the formation of porphyroblastic rutile in dynamically hydrated leucocratic domains of otherwise rutile‐poor statically hydrated amphibolite provides key contextual information on both the ambient conditions of hydration and deformation and the composition of the reactive fluid. Rutile in amphibolite recorded ambient metamorphic temperatures of ~590–730°C during static hydration of the granulitic precursor. By contrast, rutile from leucocratic domains in the directly adjacent shear zone indicates that deformation was accompanied by a localized increase in temperature. These higher temperatures are recorded in strain‐free rutile (~600–860°C) and by Zr concentration measurements on low‐angle boundaries and shear bands (620–820°C). In addition, we also observe slight depletions of Zr and U along rutile low‐angle boundaries relative to strain‐free areas in deformed grains from the shear zone. This indicates that crystal–plastic deformation facilitated the compositional re‐equilibration of rutile upon cooling to slightly below the peak temperature of deformation. Cessation of deformation at mid‐crustal conditions near ~600°C is recorded by late stage growth of small (<150 µm) rutile in the high‐strain zones. U–Pb age data obtained from the strain‐free and distorted rutile grains cluster in distinct populations of 437.4 ± 2.7 Ma and c. 405–410 Ma, respectively. These different ages are interpreted to reflect the difference in closure for thermally induced Pb diffusion between undeformed and deformed rutile during post‐deformation exhumation and cooling. Thus, our results provide a reconstruction of the thermochronological history of the amphibolite facies rocks of the Lindås Nappe and highlight the importance of integration of microstructural data during application of thermometers and geochronometers. [ABSTRACT FROM AUTHOR]

A new natural rutile reference material is presented, suitable for U‐Pb dating and Zr‐in‐rutile thermometry by microbeam methods. U‐Pb dating of rutile R632 using laser ablation ICP‐MS with both magnetic sector field and quadrupole instruments as well as isotope dilution‐thermal ionisation mass spectrometry yielded a concordia age of 496 ± 2 Ma. The high U content (> 300 μg g−1) enabled measurement of high‐precision U‐Pb ages despite its young age. The sample was found to have a Zr content of 4294 ± 196 μg g−1, which makes it an excellent complementary reference material for Zr‐in‐rutile thermometry. Individual rutile grains have homogeneous compositions of a number of other trace elements including V, Cr, Fe, Nb, Mo, Sn, Sb, Hf, Ta and W. This newly characterised material significantly expands the range of available rutile reference materials relevant for age and temperature determinations. [ABSTRACT FROM AUTHOR]

Most extraterrestrial samples feature the two accessory Ca-phosphates (apatite-group minerals and merrillite), which are important carrier phases of the rare earth elements (REE). The trace-element concentrations (REE, Sc, Ti, V, Cr, Mn, Co, As, Rb, Sr, Y, Zr, Nb, Ba, Hf, Ta, Pb, Th, and U) of selected grains were analyzed by LA-ICP-MS and/or SIMS (REE only). This systematic investigation includes 99 apatite and 149 merrillite analyses from meteorites deriving from various asteroidal bodies including 1 carbonaceous chondrite, 8 ordinary chondrites, 3 acapulcoites, 1 winonaite, 2 eucrites, 5 shergottites, 1 ureilitic trachyandesite, 2 mesosiderites, and 1 silicate-bearing IAB iron meteorite. Although Ca-phosphates predominantly form in metamorphic and/or metasomatic reactions, some are of igneous origin. As late-stage phases that often incorporate the vast majority of their host's bulk REE budget, the investigated Ca-phosphates have REE enrichments of up to two orders of magnitude compared to the host rock's bulk concentrations. Within a single sample, each phosphate species displays a uniform REE-pattern, and variations are mainly restricted to their enrichment, therefore indicating similar formation conditions. Exceptions are brecciated samples, i.e., the Adzhi-Bogdo (LL3-6) ordinary chondrite. Despite this uniformity within single samples, distinct meteorite groups do not necessarily have unique REE-patterns. Four basic shapes dominate the REE patterns of meteoritic Ca-phosphates: (1) flat patterns, smoothly decreasing from La-Lu with prominent negative Eu anomalies (acapulcoites, eucrites, apatite from the winonaite and the ureilitic trachyandesite, merrillite from ordinary chondrites); (2) unfractionated patterns, with only minor or no anomalies (mesosiderites, enriched shergottites, IAB-iron meteorite); (3) LREE-enriched patterns, with either positive or slightly negative Eu anomalies (chondritic apatite); and (4) strongly LREE-depleted patterns, with negative Eu anomalies (depleted shergottites). The patterns do not correlate with the grade of metamorphism (petrologic type), specific adjacent mineral assemblages or with Ca-phosphate grain size. Neither the proportions of different REE, nor particular REE patterns themselves are universally correlated to a specific formation mechanism yet Eu (i.e., magnitude of the Eu anomaly) is a sensitive indicator to evaluate the timing of plagioclase and phosphate crystallization. Based on our data, U and Th abundances in apatite increase (almost linearly) with the grade of metamorphism, as well as with the differentiation of their host rock. [ABSTRACT FROM AUTHOR]

natural, altered zircon crystal from an alkaline pegmatite from the Zomba-Malosa Complex of the Chilwa Alkaline Province in Malawi has been studied by a wide range of analytical techniques to understand the alteration process. The investigated zircon shows two texturally and chemically different domains. Whereas the central parts of the grain (zircon I) appear homogeneous in backscattered electron images and are characterised by high concentrations of trace elements, particularly Th, U, and Y, the outer regions (zircon II) contain significantly less trace elements, numerous pores, and inclusions of thorite, ytttrialite, and fergusonite. Zircon II contains very low or undetectable concentrations of non-formula elements such as Ca, Al, and Fe, which are commonly observed in high concentrations in altered radiation-damaged zircon. U-Pb dating of both zircon domains by LA-ICPMS and SHRIMP yielded statistically indistinguishable U-Pb weighted average ages of 119.3 ± 2.1 (2σ) and 118 ± 1.2 (2σ) Ma, respectively, demonstrating that the zircon had not accumulated a significant amount of self-irradiation damage at the time of the alteration event. Electron microprobe dating of thorite inclusions in zircon II yielded a Th-U-total Pb model age of 122 ± 5 (2σ) Ma, supporting the age relationship between both zircon domains. The hydrothermal solution responsible for the alteration of the investigated zircon was alkaline and rich in CO, as suggested by the occurrence of REE carbonates and CO-bearing fluid inclusions. The alteration of the crystalline, trace element-rich zircon is explained by an interface-coupled dissolution-reprecipitation mechanism. During such a process, the congruent dissolution of the trace element-rich parent zircon I was spatially and temporally coupled to the precipitation of the trace element-poor zircon II at an inward moving dissolution-precipitation front. The driving force for such a process was merely the difference between the solubility of the trace element-rich and -poor zircon in the hydrothermal solution. The replacement process and the occurrence of mineral inclusions and porosity in the product zircon II is explained by the thermodynamics of solid solution-aqueous solution systems. [ABSTRACT FROM AUTHOR]

Small amounts of felsic, evolved plutonic rocks, often called oceanic plagiogranites, always occur as veins or small stocks within the gabbroic section of the oceanic crust. Four major models are under debate to explain the formation of these rocks: (1) late-stage differentiation of a parental MORB melt, (2) partial melting of gabbroic rocks, (3) immiscibility in an evolved tholeiitic liquid, and (4) assimilation and partial melting of previously altered dikes. Recent experimental data in hydrous MORB-type systems are used to evaluate the petrogenesis of oceanic plagiogranites within the deep oceanic crust. Experiments show that TiO2 is a key parameter for the discrimination between different processes: TiO2 is relatively low in melts generated by anatexis of gabbros which is a consequence of the low TiO2 contents of the protolith, due to the depleted nature of typical cumulate gabbros formed in the oceanic crust. On the other hand, TiO2 is relatively high in those melts generated by MORB differentiation or liquid immiscibility. Since the TiO2 content of many oceanic plagiogranites is far below that expected in case of a generation by simple MORB differentiation or immiscibility, these rocks may be regarded as products of anatexis. This may indicate that partial melting processes triggered by water-rich fluids are more common in the deep oceanic crust than believed up to now. At slow-spreading ridges, seawater may be transported via high-temperature shear zones deeply into the crust and thus made available for melting processes. [ABSTRACT FROM AUTHOR]

The Konos Hill and Pagoni Rachi porphyry-epithermal prospects in northeastern Greece are characterized by abundant pyrite that displays important textural and geochemical variations between the various ore stages. It is commonly fine-grained and anhedral in the porphyry-related mineralization (M- and D-type veins), while it forms idiomorphic, medium- to coarse-grained crystals in the late, epithermal style veins (E-type). Porphyry-style pyrite from both prospects is characterized by an enrichment in Co, Se, Cu, and minor Zn, and a depletion in other trace elements, like Bi, Mo, Ag, etc. Pyrite in epithermal-style mineralization is mostly characterized by the presence of As, Bi, Pb, Ni, and Se. Gold in pyrite from all mineralization stages occurs as a non-stoichiometric substituting element, and its abundance correlates with As content. Arsenic in pyrite from Konos Hill records an increase from the porphyry stage to the epithermal stage (along with gold); however, at Pagoni Rachi, the highest Au and As contents are recorded in D-type pyrite and in the epithermal stage. The composition of the studied pyrite marks changes in the physico-chemical conditions of the ore-forming fluids and generally follows the geochemical trends from other porphyry-epithermal systems elsewhere. However, a notable enrichment of Se in the porphyry-style pyrite here is a prominent feature compared to other deposits and can be considered as an exploration tool towards Au-enriched mineralized areas. [ABSTRACT FROM AUTHOR]

We present experimentally determined trace element partition coefficients (D) between pyrochlore-group minerals (Ca2(Nb,Ta)2O6(O,F)), Ca fersmite (CaNb2O6), and silicate melts. Our data indicate that pyrochlores and fersmite are able to strongly fractionate trace elements during the evolution of SiO2-undersaturated magmas. Pyrochlore efficiently fractionates Zr and Hf from Nb and Ta, with DZr and DHf below or equal to unity, and DNb and DTa significantly above unity. We find that DTa pyrochlore-group mineral/silicate melt is always higher than DNb, which agrees with the HFSE partitioning of all other Ti–rich minerals such as perovskite, rutile, ilmenite or Fe-Ti spinel. Our experimental partition coefficients also show that, under oxidizing conditions, DTh is higher than corresponding DU and this implies that pyrochlore-group minerals may fractionate U and Th in silicate magmas. The rare earth element (REE) partition coefficients are around unity, only the light REE are compatible in pyrochlore-group minerals, which explains the high rare earth element concentrations in naturally occurring magmatic pyrochlores. [ABSTRACT FROM AUTHOR]

Magnetite is a common accessory phase in various types of ore deposits. Its trace element content has proven to have critical implications regarding petrogenesis and as guides in the exploration for ore deposits in general. In this study we use LA-ICP-MS (laser ablation-inductively coupled plasma-mass spectrometry) analyses of trace elements to chemically characterize magnetite from the Pagoni Rachi Cu–Mo–Re–Au porphyry-style prospect, Thrace, northern Greece. Igneous magnetite mostly occurs as euhedral grains, which are commonly replaced by hematite in fresh to propylitic-altered granodiorite porphyry, whereas, hydrothermal magnetite forms narrow veinlets or is disseminated in sodic/potassic-calcic altered (albite + K-feldspar + actinolite + biotite + chlorite) granodiorite porphyry. Magnetite is commonly associated with chalcopyrite and pyrite and locally exhibits martitization. Laser ablation ICP-MS analyses of hydrothermal magnetite yielded elevated concentrations in several trace elements (e.g., V, Pb, W, Mo, Ta, Zn, Cu, and Nb) whereas Ti, Cr, Ni, and Sn display higher concentration in its magmatic counterpart. A noteworthy enrichment in Mo, Pb, and Zn is an unusual feature of hydrothermal magnetite from Pagoni Rachi. High Si, Al, and Ca values in a few analyses of hydrothermal magnetite imply the presence of submicroscopic or nano-inclusions (e.g., chlorite, and titanite). The trace element patterns of the hydrothermal magnetite and especially the decrease in its Ti content reflect an evolution from the magmatic towards the hydrothermal conditions under decreasing temperatures, which is consistent with findings from analogous porphyry-style deposits elsewhere. [ABSTRACT FROM AUTHOR]

This study presents the results of high pressure and temperature experiments to investigate the mineral–melt trace element partitioning behaviour for minerals predicted to have formed during the crystallisation of the Lunar Magma Ocean (LMO). The focus of this work has been particularly on determining partition coefficients for parent–daughter pairs of radiogenic elements, for LMO-relevant temperatures, pressures and compositions. The new experimental data are compared with previous studies for the same minerals and elements in order to establish best estimates for the partition coefficient of each element for evolving compositions of minerals as predicted in recent studies modelling LMO crystallisation. These estimates are used to calculate evolving parent–daughter ratios in the LMO residual melt and crystallising minerals for the four main long-lived radiogenic isotope systems that have been studied in lunar samples (Rb–Sr, Sm–Nd, Lu–Hf and U–Pb). The calculated 87Rb/86Sr, 147Sm/144Nd, and 176Lu/177Hf ratios are consistent with predictions for the mantle sources of lunar basalts and evolved lithologies. In contrast, it is difficult to explain the wide range of 238U/204Pb source ratios predicted from the Pb isotopic compositions of basaltic lunar samples. Potential explanations for this observation are discussed, with the conclusion that the Moon most likely experienced a significant loss of volatiles (including Pb), towards the end of LMO crystallisation, resulting in the dramatic U–Pb fractionation evidenced by recent sample analyses. [ABSTRACT FROM AUTHOR]

• Five related meteorites define the Loongana (CL) group of carbonaceous chondrites. • Coolidge, Loongana 001, LoV 051, NWA 033, and NWA 13400 represent CL chondrites. • Strongest depletions of volatile elements in the CL group of carbonaceous chondrites. • Unique positions of carbonaceous chondrites of the CL group in a ε54Cr- ε50Ti diagram. • Enrichment of 16O in some CL chondrites compared to CO, CV, and CK chondrites. A coordinated study of the petrology, mineral chemistry, and bulk chemical and isotopic composition of the five ungrouped carbonaceous chondrites Coolidge, Loongana 001, Los Vientos (LoV) 051, Northwest Africa (NWA) 033, and NWA 13400 reveals that these meteorites have a similar set of properties that distinguishes them from the other carbonaceous chondrite groups and allows definition of the new Loongana (CL) group of carbonaceous chondrites. The basic characteristics of the investigated samples are: (1) Lithophile element ratios (e.g., Al/Mg, Si/Mg) are within the typical range of other carbonaceous chondrite groups. (2) Fe-Ni metal abundances are considerably higher than for CV, but similar to CR chondrites. (3) Chondrule size-frequency distributions are similar to CV, but dissimilar to CR chondrites. (4) The mean CAI abundance is ∼1.4 vol%, i.e., lower than in CV but much higher than in CR chondrites. (5) Very low amounts of matrix (17–21 vol%), the lowest among the main carbonaceous chondrite groups (CI, CM, CO, CV, CR, CK). (6) Olivine is nearly equilibrated, with mean fayalite (Fa) values between 12.5 mol% (Loongana 001) and 14.7 mol% (NWA 13400) as a metamorphic effect. (7) Lower Al 2 O 3 and higher MgO and Cr 2 O 3 concentrations in matrix, compared to matrix in CV, CK, and CR chondrites. (8) Volatile elements (Mn, Na, K, Rb, Cs, Zn, Se, Te, Pb, Tl) are considerably depleted compared to all other main carbonaceous chondrite groups, reflecting the low matrix abundance. (9) Bulk O isotope compositions plot along the CCAM line (Δ17O −3.96 to −5.47‰), partly overlapping with the CV and CK chondrite fields but including samples that are more 16O-rich. (10) Unique positions of CL values in the є54Cr-є50Ti isotope plot, with є54Cr values similar to CV, CK, and CO, but є50Ti values similar to CR chondrites. All CL chondrites studied here are of petrologic type 3.9 to 4, indicating that they have been thermally metamorphosed on the parent body. The diagnostic features of CL chondrites detailed here provide a basis for identifying CL members of lower petrologic types. Such samples will be important for determining the pristine state of these meteorites and their components. [ABSTRACT FROM AUTHOR]

Understanding the behavior of elements under highly reduced conditions is fundamental to explain the differentiation, crust formation, and volatile budget of Mercury. Here we report experiments on a synthetic composition representative of the bulk silicate Mercury (BSM), at pressure up to 3 GPa, temperature up to 1720 °C, and under highly reduced conditions (∼IW − 8 to ∼IW − 1, with IW the iron-wüstite oxygen fugacity buffer). We determined partition coefficients for >30 minor and trace elements between silicate melt, metal melt (Fe Si), sulfide melt (FeS), and MgS solid sulfides. Based on these results and published literature, we modeled the behavior of heat-producing elements (HPE: U, Th, and K) during Mercury's early differentiation and mantle partial melting and estimated their concentrations in the mantle and crust. We found that U, K and especially Th are principally concentrated in the BSM and did not partition into the core because they are not siderophile elements. Uranium is chalcophile under highly reduced conditions, and so our model suggests that an FeS layer at the core-mantle boundary formed during Mercury's primordial differentiation would likely have incorporated large amounts of U, significantly increasing the Th/U ratio of the BSM. However, this is inconsistent with the chondritic or slightly sub-chondritic Th/U ratios of Mercury's lavas. In addition, the likely presence of mantle sulfides, such as MgS, would have also fractionated U and Th, increasing the mantle Th/U. It is possible to have an FeS layer if Mercury formed under less reduced conditions, or if the building blocks of Mercury had Th/U ratios close to the lower end of chondritic data. If, as suggested by our model, no FeS layer formed during differentiation, it means that the majority of HPE are concentrated in Mercury's thin silicate part. Based on the compatibility of U, Th and K, we also show that surface K/Th and K/U ratios are respectively 2–4 times and 3–6 times lower than expected for initial K/Th and K/U ratios similar to enstatite chondrites, implying that the planet suffered an important volatile loss via mechanisms that remain undetermined. • FeS, metal and MgS/silicate partition coefficients for ∼30 minor and trace elements. • U, Th and K are largely concentrated in the silicate part of Mercury. • An FeS layer formed in equilibrium with the magma ocean is improbable. • Surface K/Th is lower than predicted, supporting bulk K loss for Mercury. [ABSTRACT FROM AUTHOR]

Trace element concentrations in quartz were determined from two major LCT pegmatite occurrences in Europe to test the applicability of quartz as a pathfinder mineral for Li mineralized pegmatites. The Wolfsberg spodumene pegmatite deposit and pegmatites throughout the wider Austroalpine Unit (Austria), and the Moylisha spodumene pegmatite deposit (SE Ireland), present two distinctly different geological histories. Spodumene pegmatites at Wolfsberg are associated with late Permian lithospheric extension that formed the Austroalpine Unit Pegmatite Province spanning the Eastern Alps. They were metamorphosed at up to eclogite-facies conditions during the Alpine orogeny. Contrastingly, the simple and spodumene pegmatites at Moylisha form a late Silurian to early Devonian NE-SW-striking pegmatite belt that intruded the East Carlow Deformation Zone along the SE margin of the late Caledonian S-type Leinster Batholith. All analyzed pegmatites contain assemblages including K-feldspar, albite, quartz, muscovite ± spodumene. LA-ICP-MS analysis shows quartz from spodumene pegmatites in both regions is distinguishable from that in simple pegmatites by higher concentrations of Al, Li, Ge and B, whereas simple pegmatite quartz contains higher Ti. Increasing concentrations of Al, Li and Ge and decreasing Ti in quartz from simple pegmatites (to leucogranites in the Austroalpine Unit) to spodumene pegmatites reflects increasing degree of fractionation, resulting from either magmatic differentiation or separately generated but increasingly fractionated melts. Chemical profiles through individual spodumene pegmatite bodies show relatively little chemical variation, consistent with Li saturation through most of their crystallization history. Principal component analysis of quartz data shows that high Ge, Be and B concentrations characterize quartz in pegmatites from the Austroalpine Unit whereas high Al and Li concentrations characterize quartz in pegmatites from Moylisha. Concentrations of >100 μgg−1 Al and >30 μgg−1 Li in pegmatite quartz represent an important threshold for potential spodumene mineralization, which may also be indicated by host rocks (e.g., mica schist) metasomatized by fluids expelled by pegmatites during emplacement and/or crystallization and generating a chemical halo. Retention of pegmatite chemical signatures at Wolfsberg supports the robustness of quartz as an effective pathfinder tool for Li mineralized pegmatites in regions that have been affected by high-pressure metamorphism. LA-ICP-MS of quartz in soil and stream sediments may also be a useful pathfinder in pegmatite provinces where Li-rich quartz is not too diluted by other quartz. • Quartz trace elements determined for LCT pegmatites at Wolfsberg and Moylisha. • Respective Ge-Be-B and Al-Li signatures in Wolfsberg and Moylisha pegmatite quartz. • Increasing Al, Li, Ge/decreasing Ti in quartz from simple to spodumene pegmatites. • >100 μgg−1 Al and > 30 μgg−1 Li in pegmatite quartz indicative of Li mineralization. [ABSTRACT FROM AUTHOR]

A suite of kimberlite-hosted mantle xenoliths from the Catalão region, southwestern margin of the São Francisco Craton (SFC), Brazil, consists of spinel lherzolites (type I and II) and garnet-phlogopite wehrlites. The chemical composition of these xenoliths provides evidence of enrichment and refertilization of the SFC lithosphere which were caused by distinct metasomatic agents. Garnet-phlogopite wehrlites have porphyroclastic textures and were equilibrated between 1005 and 1010 °C and 2.9–3.0 GPa (∼99 km). They record metasomatism caused by carbonatite and proto-kimberlite melts. Type I spinel lherzolite contains spinel-pyroxene symplectites indicating garnet destabilization due to variations of the P-T conditions. The minerals in this rock were equilibrated between 975 and 990 °C and their chemical compositions contain evidence for carbonatite metasomatism. High-Cr and low-Al clinopyroxene of garnet-phlogopite wehrlites and type I spinel lherzolite have high Mg#, Ca/Al, La/Yb N, Zr/Hf ratios, and high Sr contents, coupled with low to intermediate Ti/Eu and Ti/Nb, which also suggests that they were formed by carbonatite melt. These geochemical features, together with the presence of carbonate inclusions in the olivines, corroborate the interaction with carbonatite melt. The low-Ti-Cr phlogopite (Phl1), which is restricted to only the garnet-phlogopite wehrlites, was probably produced through the release of volatiles components from the carbonatite melt that reacted with garnet porphyroclasts. Furthermore, metasomatic reactions involving garnet-phlogopite wehrlites and a proto-kimberlite melt formed high-Ti-Cr phlogopite (Phl2), consuming the original phlogopite (Phl1). Phl2 occurs as rims around Phl1, as isolated flakes around garnets, and in the matrix of wehrlites. Therefore, we assume that the proto-kimberlite metasomatism responsible for generation of Phl2 occurred prior to the eruption of the host kimberlite magma. Conversely, type II spinel lherzolites (876–915 °C; ∼1.5 GPa) contain evidence of metasomatic reactions with silicate melts. These samples have high cpx/opx ratios (1.10–2.93) with low-Cr and high-Al clinopyroxene, and depleted incompatible trace element compositions. Some clinopyroxene crystals, however, show some enrichment in light rare earth elements (LREE), large ion lithophile elements (LILE), and Ti. Their low Ca/Al, La/Yb N , and Zr/Hf, low Sr contents, high Ti/Eu and Ti/Nb, and a strong positive correlation of Ti with the other high field strength elements (HFSE) and LREE, may indicate that these clinopyroxene crystals were formed by refertilization caused by a silicate melt that was depleted in incompatible elements. Overall, these metasomatic processes suggest a pervasive refertilization of the cratonic lithosphere where the typically depleted peridotites of cratonic regions were replaced by a pyroxene-rich lithology. • Mantle xenoliths from the SW margin of the SFC record pervasive metasomatism. • Wehrlites was formed by reaction of carbonatite melts with peridotite. • Low-Ti-Cr phlogopite records carbonatite metasomatism. • High-Ti-Cr phlogopite indicates proto-kimberlite melt metasomatism. • The shallow mantle (∼50 km) records refertilization caused by silicate melts. [ABSTRACT FROM AUTHOR]

Santorini volcano sits ~145 km above the Aegean Wadati-Benioff zone, where the African plate subducts northward beneath Eurasia. There are only a few localities in the whole Aegean where basaltic lavas primitive enough to constrain mantle processes beneath the Aegean arc can be found; in this work we analyzed one such locality, a basalt lava from the southern part of Santorini. We apply a suite of petrological tools (PRIMACALC2 and ABS5) in sequence to estimate magma chamber conditions, primary magma composition, mantle melting conditions, and slab dehydration conditions. Back-calculation modeling based on major-element chemistry yields shallow magma chamber conditions of P  = 0.02 GPa, fO 2  = QFM + 2, and ~1 wt% H 2 O in the primary magma. The estimated major element composition of this primary magma then leads to estimated mantle melting conditions of 2.1 GPa, 1353 °C, and F  = 8%; whereas a more precise estimate derived from trace element modeling implies 1.7 GPa, 1323 °C, and F  = 18%. Furthermore, the trace element model implies a slab flux derived from 4.6 GPa (~150 km slab depth). The estimated slab depth, magma segregation conditions, and magma chamber depth are all consistent with seismic observations, supporting slab dehydration in the seismically imaged steep slab interval and flux melting in a relatively hot mantle wedge. [ABSTRACT FROM AUTHOR]

Abstract: Zircon from quartzites in the contact aureole and wider environs of the Kadavur anorthosite complex, SE India, was studied by laser ablation ICP-MS to assess the response of the U–Pb isotope system and trace element concentrations to ultrahigh-temperature (UHT) contact metamorphism (≥1000°C). Combined cathodoluminescence imaging and LA-ICP-MS analyses show that zircon grains contain detrital cores, which yield ages between 3.4Ga and 1.8Ga and exhibit a large spread in REE concentrations. These cores are associated with one or two rims that provide concordant age populations at 955±16Ma and 810±7Ma (2σ) and relatively uniform REE patterns. The older ages of ca. 955Ma record the imprints of regional early Neoproterozoic metamorphism related to Rodinia assembly. The younger age is interpreted to date anorthosite emplacement and its associated contact metamorphism during a second regional metamorphic episode, coeval with the intrusion of A-type granites in the area. Zircon grains from the country rocks away from the anorthosite show additional rims yielding ages from 590 to 490Ma corresponding to regional Pan-African tectonometamorphism. The zircon rims are either newly grown domains or represent recrystallized and re-equilibrated parts of precursor zircon. Discordance is only observed in 25% of the detrital cores. These cores have relatively high U concentrations (>400ppm), which strongly suggests that Pb loss occurred under (U)HT conditions by partial recrystallization (annealing) of zircon that had become metamict. The preservation of old concordant ages and source REE characteristics by the low-U (i.e., weakly to non metamict) detrital cores shows that pristine zircon is extremely robust to thermal disturbance and that its U–Pb systematics can remain unaffected despite multiple (U)HT metamorphic episodes. These observations imply that U–Pb ages in zircon cannot be reset by volume diffusion under any crustal conditions. Disturbance of the U–Pb system in individual zircon crystals or parts thereof can only be achieved by recrystallization of radiation damaged zircon. [Copyright &y& Elsevier]

Many Cenozoic basaltic rocks in Eastern Australia exhibit an age-progressive trend from north to south, leading to the suggestion that one or more mantle plumes passed beneath the Australian plate. Trace element patterns indicate that the source regions have been metasomatised by infiltrating melts, but the source rock assemblages have never been closely identified. Here, trace element analyses of olivine and whole rock geochemistry for several occurrences in New South Wales (Dubbo, Ebor, Bingara/Inverell, and Barrington) are combined with samples from Buckland (Queensland) to characterize the mineralogy of the source and identify the nature of the melts that caused the metasomatic enrichment. According to Ni/Mg against Mn/Fe and Zn/Fe ratios in olivines, Zn/Fe and FC3MS (FeOT/CaO-3*MgO/SiO 2) parameters in whole rocks, tholeiite, alkali basalt, and basanite rich in olivine xenocrysts from Dubbo were derived from pyroxenite-dominated mixed source, mixed pyroxenite + peridotite source, and peridotite-dominated source, respectively. Similarly, basalts from Ebor and Bingara/Inverell are suggested to originate from a mixed pyroxenite + peridotite source based on their high FC3MS values. In contrast, the source of basanite and picrobasalt from Barrington was peridotite-dominated with less pyroxenite. High Li and Zn in olivines, high P 2 O 5 /TiO 2 and Zr/Hf at low Ti/Eu in whole rocks illustrate that the pyroxenite sources of basanites from Bingara/Inverell, Barrington, Dubbo and Buckland resulted from variable degrees of carbonatitic metasomatism. Partial melting of peridotite metasomatised by carbonatite melts at around the spinel-garnet peridotite transition depth produced basalts and basanites from Dubbo, Ebor, Bingara/Inverell, Barrington and Buckland. Carbonatitic metasomatism is widespread in the eastern Australian mantle lithosphere, concentrated on the ledge of the thick lithosphere beneath the Australian continent that stretches from Queensland, through New South Wales to Victoria. • Extensive Cenozoic basalts, basanites in eastern Australia are geochemically alike. • The sources of Cenozoic basalts and basanites are composed of 24–74% of pyroxenites. • Olivine phenocryst gives insight into carbonatite metasomatism. • The carbonatite metasomatism lies in the lithosphere base near the craton edge. [ABSTRACT FROM AUTHOR]

The Rosário-6 alnöite is an alkaline occurrence that belongs to the Rosário do Sul kimberlitic field, situated in the south-eastern edge of the Paraná Basin, in the South of Brazil, and erupted concomitant or just after the volcanism of the Paraná-Etendeka Large Igneous Province (LIP). Following recent published nomenclature, Rosário-6 was classified as a kimberlite from a deep mantle source with a distinctive inequigranular texture resulting from the presence of olivine macrocrysts set in a finer-grained matrix. Trace element compositions of olivine, monticellite, spinel, phlogopite, perovskite and apatite show an enrichment of Nb, Ce, Ta and U, which implies that the Rosário-6 mantle source was enriched by recycled oceanic crust. The positive anomalies of Rb, Ba and Sr, the enrichment in LREE, and the negative anomalies of HREE in the Rosário-6 minerals, are indicative of a metasomatic process in the mantle source that could be caused by fluids from recycled oceanic crust. Temperature, pressure and redox conditions (f O 2) of Rosário-6 crystallization are estimated from olivine, spinel, perovskite and monticellite compositions: Rosário-6 crystallization temperatures using olivine-spinel geothermobarometry were around 1390(±56)°C at a pressure of 2 GPa, and 1405(±56)°C at 3 GPa with ΔNNO = 2.8, at pressures constrained by the silica activity limited by the crystallization of monticellite. Using a perovskite oxybarometer, we obtained a larger range of ΔNNO (from −2.8 to 3.4), whereas the monticellite oxybarometer results in f O 2 of −2.6 to −0.8 ΔNNO units. The f O 2 indicate that the mantle source of Rosário-6 at the time of crystallization was possibly oxidized by materials from ancient subduction, which may be the cause for Rosário-6's low potential to carry and preserve diamonds. Horizontal tomographic images derived from P -wave velocity data constrain the thickness of the lithosphere in this region and the overall information indicates that mantle cooling at depths below 200 km may have resulted of an accumulation of oceanic plate slabs from old subduction. The geochemical data in conjunction with the geophysical characterizes the conditions of Rosário-6 mineral crystallization and also the mantle of this part of South America during Gondwana breakup. • P, T and f O 2 conditions of Rosário-6 alkaline occurrence crystallization are estimated. • Mineral trace elements and seismic tomography indicate mantle metasomatism by ancient slabs. • The slabs caused fertilization by melts derived from basaltic crust and subducted carbonates. [ABSTRACT FROM AUTHOR]

Laser ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOFMS) is a fast, relatively high-spatial resolution method which allows to measure and visualize major, minor and trace elements in fine-grained samples. Thus, it is a promising tool for the investigation of high-pressure, high-temperature (HP-HT) reaction experiments that typically produce small grain sizes. Here, we apply LA-ICP-TOFMS mapping to HP-HT reaction experiments by Gervasoni et al. 2017 between a) hydrous eclogite and fertile peridotite, which simulates metasomatism in subduction zones, and b) ultramafic silicate-carbonate melt and peridotite, which simulates metasomatism at the base of cratonic lithospheric mantle. A spatial resolution (i.e., laser spot size) of 5 μm and an acquisition rate of 20 multi-element pixels per second (i.e., laser repetition rate of 20 Hz) were used for mapping of the experimental samples. We demonstrate the applicability of LA-ICP-TOFMS by comparison of our results to maps created with electron probe micro-analysis (EPMA) and elemental concentrations measured by conventional (i.e., crater-drilling) LA-ICP-MS. Our new data suggest that metasomatism in subduction zones is expected to result in the formation of Al–Ti-rich amphiboles that strongly fractionate the rare earth elements (REE) and high-field strength elements (HFSE) from other trace elements. In contrast, metasomatism of the cratonic lithosphere involves fractionation in the light and middle REE, large ion lithophile elements (LILE) and HFSE, leaving Ni and heavy REE behind in olivine and garnet, respectively. The trace element enrichment patterns of the resulting melt bear a general resemblance to those of natural Group I kimberlites. • LA-ICP-TOFMS enables high-speed high-spatial resolution (e.g., 5 μm) imaging. • Here, multi-element mapping of HP-HT experimental samples at 20 pixels/second. • Experiments are reactions between a) hydrous eclogite and fertile peridotite and b) ultramafic silicate-carbonate melt and fertile peridotite. • Multi-element maps reveal different trace element fractionation within experiments. [ABSTRACT FROM AUTHOR]