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A combined study of rock-forming mineral and O isotope compositions, zircon U-Pb ages, trace element compositions, mineral inclusions and Hf-O isotopes was made on orogenic peridotites from North Qaidam in northern Tibet to provide insights into crustal metasomatism at the slab-mantle interface in a continental subduction channel. Rock-forming mineral O isotope analyses yield olivine δ18O values of 5.0-5.6% for lherzolites and 3.5-5.3% for dunites; orthopyroxene has δ18O values of 4.5-5.3% for lherzolites, 4.5-5.3% for dunites, and 7.8% for pyroxenites. It appears that the protolith of these ultramafic rocks underwent high-temperature metasomatism by both low- and high-δ18O fluids. The occurrence of zircon in thin section and the presence of olivine inclusions in zircon from these rocks explicitly indicates the growth of metasomatic zircon during continental subduction zone processes. Two distinct groups of zircon domains are distinguished. Intermediate- to highluminescent zircon domains have U-Pb ages of 417±4 to 426±3Ma, variable Th/U ratios, low rare earth element (REE) contents, flat heavy REE (HREE) patterns with a relative lack of negative Eu anomalies, and inclusions of olivine, clinopyroxene, orthopyroxene and graphite. These features are interpreted as zircon growth through metasomatic reaction by addition of fluids in the early exhumation stage of deeply subducted continental crust. The Hf-O isotope compositions of these zircon domains suggest the same origin for these fluids. In contrast, low-luminescent zircon rims mostly exhibit younger U-Pb ages of 404±3 to 405±8Ma, low Th/U ratios<0.1, high REE contents, and steep HREE patterns with negative Eu anomalies, and contain calcite inclusions as well as multiphase solid inclusions of Cal+Kfs and Qtz+Kfs+Pl. Such observations indicate their growth through metasomatic reaction by infiltration of hydrous silicate melts during the late exhumation stage. All the zircon domains have variable Hf isotope compositions with a large difference between samples, but a narrow δ18O range from 5.4 to 6.6%. Their Hf-O isotope compositions are similar to those of UHP metamorphic rocks in North Qaidam, suggesting that the metasomatic fluids originated from deeply subducted continental crust. Whereas the high-δ18O fluids originated from deeply subducted continental crust, the low-δ18O fluids were derived from dehydration of the subducting oceanic crust that preceded the subduction of continental crust. The orogenic peridotites thus record the metasomatic reaction of mantle wedge peridotite with fluids of different origins. [ABSTRACT FROM AUTHOR]

Until recently, most of the lower mantle was generally considered to be well-mixed with strong heterogeneity restricted to the lowermost several hundred kilometres above the core–mantle boundary, known as the D ″ layer. However several recent studies have started to hint at a potential change in Earth's structure at mid-mantle depths beneath the transition zone. Here we present a continental-wide search of Europe and the North Atlantic for mid-mantle P-to-s wave converted phases. Our data set consists of close to 50,000 high quality receiver functions. These are combined in slowness and depth stacks to identify seismic discontinuities in the range of 800–1400 km depth to determine at which depths and in which tectonic settings these features exist. Receiver functions are computed in different frequency bands to resolve the sharpness of the observed discontinuities. We find most seismic velocity jumps are observed between 975–1050 km depth, localised beneath western Europe and Iceland. The shear wave velocity jumps are roughly 1–2.5% velocity increase with depth occurring over less than 8 km in width. The most robust observations are coincident with areas of active upwelling (under Iceland) and an elongate lateral low velocity anomaly imaged in recent tomographic models which has been interpreted as diverted plume material at depth. The lack of any suggested phase change in a normal pyrolitic mantle composition at around 1000 km depth indicates the presence of regional chemical heterogeneity within the mid-mantle, potentially caused by diverted plume material. We hypothesise that our observations represent either a phase change within chemically distinct plume material itself, or are caused by small scale chemical heterogeneities entrained within the upwelling plume, either in the form of recycled basaltic material or deep sourced chemically distinct material from LLSVPs. Our observations, which cannot be directly linked to an area of either active or ancient subduction, along with observations in other hotspot regions, suggest that such mid-mantle seismic features are not unique to subduction zones despite the large number of observations that have previously been made in such settings. [ABSTRACT FROM AUTHOR]

Precision measurements of neutrino oscillation parameters have provided a tremendous boost to the search for sub-leading effects due to several beyond the Standard Model scenarios in neutrino oscillation experiments. Among these, two of the well-studied scenarios are Lorentz violation (LV) and non-standard interactions (NSI), both of which can affect neutrino oscillations significantly. We point out that, at a long-baseline experiment where the neutrino oscillation probabilities can be well-approximated by using the line-averaged constant matter density, the effects of these two scenarios can mimic each other. This would allow the limits obtained at such an experiment on one of the above scenarios to be directly translated to the limits on the other scenario. However, for the same reason, it would be difficult to distinguish between LV and NSI at a long-baseline experiment. We show that the observations of atmospheric neutrinos, which travel a wide range of baselines and may encounter sharp density changes at the core-mantle boundary, can break this degeneracy. We observe that identifying neutrinos and antineutrinos separately, as can be done at INO-ICAL, can enhance the capability of atmospheric neutrino experiments to discriminate between these two new-physics scenarios. [ABSTRACT FROM AUTHOR]

High alkali (Na 2 O + K 2 O) low SiO 2 lavas generally have highly fractionated trace element compositions and their petrogenesis is debated. Both pyroxene-rich (pyroxenite) and olivine-rich (peridotite) mantle sources have been proposed for such lavas. HIMU (high 238U/204Pb) lavas usually have such compositions and are often interpreted as being derived from garnet-pyroxenite (eclogite) residue of subducted recycled oceanic crust, possibly including a carbonate component. In some cases, an origin from a garnet peridotite source has also been considered. We present new Mg, Pb, Nd, and Sr isotopic data and elemental data for alkalic ultrabasic lavas (melilitites, nephelinites) from the Oslo Rift, Norway. The magmatic province of the Permo-Carboniferous Oslo Rift is interpreted as part of the much larger Skagerrak-Centered Large Igneous Province (SCLIP) which may be related to a mantle plume source originating from the African Large Low Shear Velocity Province (LLSVP) at the core-mantle boundary. The range of δ26Mg is narrow (−0.32 to −0.28) and is similar to typical mantle values, and therefore is inconsistent with a carbonated source as has been suggested for other similar lavas. The 206Pb/204Pb values of all the lavas are high, which identifies them as HIMU lavas. The ε Nd of +1 to +2 are substantially lower than for typical HIMU lavas, and in the ε Nd - ε Sr diagram they plot on the LoNd array between HIMU and EMI. The lavas are more like archetypal kimberlites (formerly, Group I kimberlites), as these also have ε Nd slightly higher than the chondritic value and Pb isotopes consistent with a HIMU source. The REE patterns of the lavas are also almost as fractionated as in Group I kimberlites. We used major and trace elements to infer the primary magma composition of these lavas. This primary magma composition is compared with experimental melts of both carbonated peridotite and carbonated eclogite source compositions and shows that their major element compositions are only consistent with either a very high degree of melting of eclogite or a very low degree melting of garnet peridotite. The strongly fractionated REE patterns of the lavas can only be made by low-degree melting of either eclogite or garnet peridotite, which therefore effectively rules out eclogite as a major component of the mantle source of these lavas. Further trace element modeling points to a mantle source composition with >97% garnet peridotite that was lightly carbonated (<0.5 wt% CO 2) and melted to a very low degree (∼0.4%) to produce these lavas. The modeled source trace element pattern was constrained by the Nd, Sr, and Pb isotopic compositions of the lavas. The measured high Ti contents of these lavas (3.8–6 wt%) are quantitatively shown to be the result of enrichment by both partial melting and fractional crystallization, using experimentally determined D Ti for melting of this type of source. We also show that a low degree of melting of a slightly carbonated source is sufficient to result in the likely very high CO 2 content (10–15 wt%) of the primary magma. The rather uniform Pb isotope composition of HIMU magmas suggests that the HIMU source is rather uniform in composition, but the Pb isotope composition requires this source to form late in Earth's history. The similarity of these lavas and kimberlites suggests a very deep source, possibly in the LLSVP that gave origin to the SCLIP. This means that LLSVPs do not represent some primordial layer around the core that escaped homogenization of the mantle by the Moon-forming giant impact. Instead, this layer must have formed late in Earth's history. The constraint that this source contains <3% of garnet-pyroxenite (eclogite) residue of recycled basaltic oceanic crust shows that this layer is primarily not a subducted slab graveyard. The process by which the LLSVPs formed, however, remains obscure. • Highly alkalic Oslo Rift lavas exhibit radiogenic, HIMU Pb isotope signatures. • The HIMU-like Olso Rift lavas are derived from a carbonated garnet peridotite source. • 206Pb/204Pb isotopes are not a tracer of a pyroxenite-source lithology. • HIMU-like Pb isotope signatures may have origins in the LLSVP. [ABSTRACT FROM AUTHOR]

• The historical geomagnetic field is characterized by stronger polar minima inside the northern TC than in the southern. • Tomographic dynamo models also exhibit stronger polar minima in the northern hemisphere. • This north/south dichotomy is explained in terms of the pattern of lowermost mantle seismic anomalies. The geomagnetic field on the core-mantle boundary (CMB) is characterized by weak or even reversed field in the polar regions and intense flux patches at the edges of the intersection of the inner-core tangent cylinder (TC) with the CMB. This high-latitude field morphology is in agreement with thermal wind theory inside the TC in which polar upwellings disperse magnetic field lines. Furthermore, inferences from the geomagnetic secular variation hint to the presence of a westward jet at high latitudes of the northern hemisphere, also in agreement with the TC dynamical theory, but not in the southern hemisphere. Here we study polar minima in an ensemble of geomagnetic field models that span the historical era and in a set of numerical dynamo simulations with a heterogeneous outer boundary heat flux inferred from a tomographic model of lowermost mantle seismic anomalies. We quantified the polar minima using a previously-proposed expression as well as a new measure which may better capture this phenomenon. We found that throughout the historical era the geomagnetic field is characterized by stronger polar minima and more reversed flux inside the northern TC than inside the southern TC. Likewise, almost all dynamo models exhibit on average stronger polar minima in the northern hemisphere. This north/south dichotomy is explained in terms of the pattern of lowermost mantle seismic anomalies, in particular the southern centers of the two Large Low Shear-wave Velocity Provinces below Africa and the Pacific. We also investigated polar minima in planets where magnetic field models at the top of the dynamo region are available. We speculate that the absence of polar minima in Mercury's field is likely due to the thick stratified layer at the top of its core, while the strong polar minima in Jupiter's field might have a different dynamical origin than the geomagnetic polar minima. [ABSTRACT FROM AUTHOR]

We use the tidal deformations of the Moon induced by the Earth and the Sun as a tool for studying the inner structure of our satellite. Based on measurements of the degree-two tidal Love numbers k 2 and h 2 and dissipation coefficients from the GRAIL mission, Lunar Laser Ranging and Laser Altimetry on board of the LRO spacecraft, we perform Monte Carlo samplings for 120,000 possible combinations of thicknesses and viscosities for two classes of the lunar models. The first one includes a uniform core, a low viscosity zone (LVZ) at the core–mantle boundary, a mantle and a crust. The second one has an additional inner core. All models are consistent with the lunar total mass as well as its moment of inertia. By comparing predicted and observed parameters for the tidal deformations we find that the existence of an inner core cannot be ruled out. Furthermore, by deducing temperature profiles for the LVZ and an Earth-like mantle, we obtain stringent constraints on the radius (500 ± 1) km, viscosity, (4. 5 ± 0. 8) × 1 0 16 Pa s and the density (3400 ± 10) kg/m 3 of the LVZ. We also infer the first estimation for the outer core viscosity, (2.07 ± 1.03) × 1017 Pa s, for two different possible structures: a Moon with a 70 km thick outer core and large inner core (290 km radius with a density of 6000 kg/m3), and a Moon with a thicker outer core (169 km thick) but a denser and smaller inner core (219 km radius for 8000 kg/m3). • Tidal deformations acting on the Moon as a tool for deciphering its internal structure. • The Moon low viscosity zone confirmed • First measurement of the lunar core viscosity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Emplacement ages of the diamondiferous rocks in South China have been constrained. • They were formed intermittently and eccentrically between 492 and 441 Ma. • They may be induced by the contribution of the upwelling of the lowest mantle. • The mantle evolution and the diamond potential have been reviewed. Mantle-derived magmas provide windows to the deep earth, and precise dating of the deep magmatic rocks such as kimberlite and related lithologies is crucial to attaining a better understanding of the mantle evolution and mantle-crust interaction in conjunction with global geodynamic cycle. Here we report a geochronology investigation of the diamondiferous kimberlite and related rocks from the southeastern side of the Yangtze Craton in China with the aim to constrain the deep mantle magma emplacement patterns and mantle evolution through time. Ultrabasic magmatic events occurred intermittently between 492 and 441 Ma, as inferred from apatite U-Pb dating and phlogopite 40Ar-39Ar dating. Combined with the previous data, two pulses of diamondiferous magmatism (ca. 488 Ma and ca. 450 Ma) are identified. The emplacement ages and patterns of these deep-seated diamondiferous magmas are unrelated to the reported Pan-African tectonothermal event (peak at ca. 522 Ma), Kwangsian Orogeny (peak at ca. 435 Ma), and Emeishan plume event (peak at ca. 260 Ma) in the South China Continent. Instead, we infer that the kimberlite and associated rocks in the South China Continent may be related to the upwellings from the edges of the Large Low Shear Velocity Province located at the core-mantle boundary at that time. The lack of magmatic event during 760 to 460 Ma and the existence of the thick lithosphere (>175 km) beneath the South China Continent are suitable for lithospheric diamond formation during the Early Paleozoic. These data suggest that future diamond exploration should be focused on the kimberlites emplaced during the Cambrian–Ordovician transition on the southeastern side of the former Yangzte Craton. [ABSTRACT FROM AUTHOR]

We approach this analysis of the inner-outer core boundary (IOCB) with antipodal waveform data in the distance range 179.0°–180° to test the hypothesis whether propagation at the base of the outer core is commensurate with diffraction and/or refraction. The propagation paths observed cover about two-thirds of the IOCB surface. Seismic data from seven diameters are examined—Tonga to Algeria (station code TAM), Sulawesi to Amazon (PTGA), northern Chile to Hainan Island (QIZ), two between central Chile and the mainland China (XAN, ENH), and two diameters from New Zealand to both Portugal (PTO) and Spain (ECAL). The adequacy of global Earth models—both 1-D and 1-D core +3D mantle—in fitting the antipodal observations is found to be deficient. Lateral heterogeneity among the propagation paths are mapped and projected to the Earth's surface for context. We stack data to increase signal-to-noise, and model waveform data via the 3D spectral element method on the EarthSimulator4. With the exception of one path to ENH China, none of the global Earth models match amplitudes of diffracted waves or the stacked amplitudes relative to PKIKP, which travels along the antipodal diameter. Energetic arrivals observed in the waveform data set are modeled as a combination of refraction within a low velocity zone (LVZ) at the base of the outer core, and diffraction around this structure. The observations at the base of the outer core may be further subdivided between paths with a thin low velocity zone (QIZ, XAN, PTGA), and those with a thicker, slower LVZ (TAM). The former paths are characterized by a thin LVZ (20–50 km thick, layer–gradient, respectively) with a velocity of approximately 10.0 km/s. The second group of paths shows large amplitude, complicated waveforms for TAM, corroborated by data from PTO and ECAL. TAM waveforms are modeled with a negative gradient from 100 to 50–75 km thickness above the IOCB, to a basal velocity of 8.8 km/s at IOCB. We also modeled the prospect of non-zero rigidity at the bottom of the outer core, but found no evidence of sensitivity in the core data. The structures fitting the data correlate across the inner–outer core boundary, with a velocity anomaly in PKPbc data juxtaposed immediately above the TAM path beneath SE Asia. More generally, the TAM IOCB path when projected up to the core-mantle boundary (CMB) apparently aligns with regions between the large low shear velocity provinces (LLSVP) at the CMB. Other paths with thinner or negligible LVZ at the IOCB partially underlie the LLSVP when projected to the CMB. [Display omitted] • Antipodal seismic observations of waves diffracting around 67% of the basal outer core. • Waveform data are modeled for diffraction plus refraction within a low velocity zone. • Two differing low velocity features are observed—one thin and another thicker, slower zone. • The structures fitting the data correlate across the inner–outer core boundary. • Basal outer core features bear a strong resemblance to seismological features at core-mantle boundary. [ABSTRACT FROM AUTHOR]

The Indian Ocean Geoid Low (IOGL) is one of the most prominent geoid anomalies on a global scale, located to the south of the Indian peninsula. It is a very long wavelength feature (> 15,000 km) and marks the lowest anomaly of −106 m in the Earth's geoid. Though various theories have been put forward to explain this negative geoid anomaly, a conclusive explanation remains elusive. This study provides a brief overview of the geophysical and geodynamic studies that have attempted to unravel the causes responsible for the IOGL. Studies on topics ranging from satellite geodesy to the advancement in seismology and theoretical geodynamics provide new insights into this classical problem. Studies that have investigated this problem suggest that its origin varies from shallow sources in the asthenosphere to mantle convection in the mid-mantle due to subducting slabs to depression in the core-mantle boundary (CMB) and the slab graveyards atop the CMB. The proposed model by utilizing previous studies indicates that the combined effect of low-density materials in the mantle transition zone (MTZ) and the high-density cold slab graves atop the CMB can explain this low geoid. [ABSTRACT FROM AUTHOR]

It is experimentally reported that the stratified layer atop Earth's outer core is hundreds of kilometers thick with a maximum sound velocity reduction of 0.3% relative to the preliminary reference Earth model. However, why the sound velocity atop the outer core is reduced remains theoretically unclear. In this paper, the Ni and vital light O in the outer core were both considered to have implications for the stratification of Earth's core, including the stratification thickness and the sound velocity profile. Ab initio molecular dynamics simulations were performed on the Fe-Ni-O fluid under the conditions of Earth's outer core, and the self-diffusion coefficients and ion-ion dynamic structure factors were calculated. The self-diffusion coefficient of O was calculated to be (19.56 ± 0.83) × 10−9 m2s−1 at the core-mantle boundary. Combining the diffusion equation with the time evolution of the O self-diffusion coefficient, the calculated stratification thickness at present is 194.7 km. The calculated ion-ion dynamic structural factors indicate that the sound velocity in the outmost outer core near the stratified layer is 7.86 km/s, which is lower than the preliminary reference Earth model values (∼8.05 km/s). These results show that Fe-Ni-O liquid atop the outer core featuring an appropriate thickness and a reduced sound velocity, thereby shedding light on the dynamic behavior of Earth's core. [Display omitted] • The self-diffusion coefficient of O is calculated to be (19.56 ± 0.83) × 10−9 m2s−1 at the core-mantle boundary. • The stratification thickness at present is 194.7 km. • The sound velocity of Fe-Ni-O liquid is 7.86 km/s at core-mantle boundary. [ABSTRACT FROM AUTHOR]

Iron hydride in Earth's interior can be formed by the reaction between hydrous minerals (water) and iron. Studying iron hydride improves our understanding of hydrogen transportation in Earth's interior. Our high-pressure experiments found that face-centered cubic (fcc) FeH x (x ≤ 1) is stable up to 165 GPa, and our ab initio molecular dynamics simulations predicted that fcc FeH x transforms to a superionic state under lower mantle conditions. In the superionic state, H-ions in fcc FeH become highly diffusive-like fluids with a high diffusion coefficient of ∼3.7 × 10 -4  cm 2  s -1 , which is comparable to that in the liquid Fe-H phase. The densities and melting temperatures of fcc FeH x were systematically calculated. Similar to superionic ice, the extra entropy of diffusive H-ions increases the melting temperature of fcc FeH. The wide stability field of fcc FeH enables hydrogen transport into the outer core to create a potential hydrogen reservoir in Earth's interior, leaving oxygen-rich patches (ORP) above the core mantle boundary (CMB)., Competing Interests: Conflict of interest The authors declare that they have no conflict of interest., (Copyright © 2023 Science China Press. Published by Elsevier B.V. All rights reserved.)

We use polarity reversal systematics from numerical dynamos to quantify the hypothesis that the modulation of geomagnetic reversal frequency, including geomagnetic superchrons, results from changes in core heat flux related to growth and collapse of lower mantle superplumes. We parameterize the reversal frequency sensitivity from numerical dynamos in terms of average core heat flux normalized by the difference between the present-day core heat flux and the core heat flux at geomagnetic superchron onset. A low-order polynomial fit to the 0-300 Ma Geomagnetic Polarity Time Scale (GPTS) reveals that a decrease in core heat flux relative to present-day of approximately 30% can account for the Cretaceous Normal Polarity and Kiaman Reverse Polarity Superchrons, whereas the hyper-reversing periods in the Jurassic require a core heat flux equal to or higher than present-day. Possible links between GPTS transitions, large igneous provinces (LIPs), and the two lower mantle superplumes are explored. Lower mantle superplume growth and collapse induce GPTS transitions by increasing and decreasing core heat flux, respectively. Age clusters of major LIPs postdate transitions from hyper-reversing to superchron geodynamo states by 30-60 Myr, suggesting that superchron onset may be contemporaneous with LIP-forming instabilities produced during collapses of lower mantle superplumes.

We have investigated a piece of the Netschaëvo IIE iron meteorite containing a silicate inclusion by means of electron microprobe analysis (EMPA) and transmission electron microscopy (TEM). Netschaëvo contains chondrule-bearing clasts and impact melt rock clasts were also recently found. The examined inclusion belongs to the latter and is characterized by a porphyritic texture dominated by clusters of coarse-grained olivine and pyroxene, set in a fine-grained groundmass that consists of new crystals of olivine and a hyaline matrix. This matrix material has a quasi-basaltic composition in the inner part of the inclusion, whereas the edge of the inclusion has a lower SiO 2 concentration and is enriched in MgO, P 2 O 5 , CaO, and FeO. Close to the metal host, the inclusion also contains euhedral Mg-chromite crystals and small (<2 μm), Si-rich globules. A TEM foil was cut from this glassy, silico-phosphate material. It shows that the material consists of elongated olivine crystallites containing up to 14 wt% P 2 O 5 , amorphous material, and interstitial Cl-apatite crystals. The Si-rich silicate glass globules show a second population of Fe-rich silicate glass droplets, indicating they formed by silicate liquid immiscibility. Together with the presence of phosphoran olivine and quenched Cl-apatite, these textures suggest rapid cooling and quenching as a consequence of an impact event. Moreover, the enrichment of phosphorus in the silicate inclusion close to the metal host (phosphoran olivine and Cl-apatite) indicates that phosphorus re-partitioned from the metal into the silicate phase upon cooling. This probably also took place in pallasite meteorites that contain late-crystallizing phases rich in phosphorus. Accordingly, our findings suggest that oxidation of phosphorus might be a general process in core–mantle environments, bearing on our understanding of planetesimal evolution. Thus, the Netschaëvo sample serves as a natural planetesimal core–mantle boundary experiment and based on our temperature estimates, the following sequence of events takes place: (i) precipitation of olivine (1400–1360 °C), (ii) re-partitioning of phosphorus from the metal into the silicate phase, and (iii) formation of immiscible melts (1230–1115 °C). [ABSTRACT FROM AUTHOR]

Models of inflation are instructive playgrounds for supersymmetry (SUSY) breaking in Supergravity and String Theory. In particular, combinations of branes and orientifolds that are not mutually BPS can lead to brane SUSY breaking, a phenomenon where nonlinear realizations are accompanied, in tachyon-free vacua, by the emergence of steep exponential potentials. When combined with milder terms, these exponentials can lead to slow-roll after a fast ascent and a turning point. This leaves behind distinctive patterns of scalar perturbations, where pre-inflationary peaks can lie well apart from an almost scale invariant profile. I review recent attempts to connect these power spectra to the low- cosmic microwave background (CMB), and a corresponding one-parameter extension of Lambda cold dark matter (CDM) with a low-frequency cut . A detailed likelihood analysis led to , at 99.4% confidence level, in an extended Galactic mask with , to be compared with a nearby value at 88.5% in the standard Planck 2015 mask with . In these scenarios, one would be confronted, in the CMB, with relics of an epoch of deceleration that preceded the onset of slow-roll. [ABSTRACT FROM AUTHOR]

The Aki-Utsu maximum likelihood method is widely used for estimation of the Gutenberg-Richter b-value, but not all authors are conscious of the method's limitations and implicit requirements. The Aki/Utsu method requires a representative estimate of the population mean magnitude; a requirement seldom satisfied in b-value studies, particularly in those that use data from small geographic and/or time windows, such as b-mapping and b-vs-time studies. Monte Carlo simulation methods are used to determine how large a sample is necessary to achieve representativity, particularly for rounded magnitudes. The size of a representative sample weakly depends on the actual b-value. It is shown that, for commonly used precisions, small samples give meaningless estimations of b. Our results give estimates on the probabilities of getting correct estimates of b for a given desired precision for samples of different sizes. We submit that all published studies reporting b-value estimations should include information about the size of the samples used. [ABSTRACT FROM AUTHOR]

Inflation with plateau potentials give the best fit to the CMB observables as they predict tensor to scalar ratio stringently bounded by the observations from Planck and BICEP2/Keck. In supergravity models it is possible to obtain plateau potentials for scalar fields in the Einstein frame which can serve as the inflation potential by considering higher dimensional Planck suppressed operators and by the choice of non-canonical Kähler potentials. We construct a plateau inflation model in MSSM where the inflation occurs along a sneutrino-Higgs flat direction. A hidden sector Polonyi field is used for the breaking of supersymmetry after the end of the inflation. The proper choice of superpotential leads to strong stabilization of the Polonyi field, m Z 2 ≫ m 3 / 2 2 , which is required to solve the cosmological moduli problem. Also, the SUSY breaking results in a TeV scale gravitino mass and scalar masses and gives rise to bilinear and trilinear couplings of scalars which can be tested at the LHC. The sneutrino inflation field can be observed at the LHC as a TeV scale diphoton resonance like the one reported by CMS and ATLAS. [ABSTRACT FROM AUTHOR]

We reviewed studies on aftershocks in Taiwan for the following topics: the spatial-temporal distributions and focal-plane solutions of aftershocks from of thirty larger earthquakes with magnitudes > 5; the correlations between the main shock and the largest aftershock based on dependence of the differences in magnitudes (ΔM), occurrence times (ΔT) epicenters (ΔH) and focal depths (ΔD) upon the main shock magnitude, Mm; magnitude-dependence of p-value of Omori's law of aftershocks; the correlation between the b-value of the Gutenberg-Richter's frequency-magnitude law and the p-value; application of the epidemic-type aftershock sequences (ETΔS) model to describe the aftershock sequence; the mechanisms of triggering aftershocks; and dynamic modeling of aftershocks. The main results are: (1) The spatial distribution of aftershocks for some earthquakes is consistent with the recognized fault; (2) Unlike Bath's law, ΔM slightly increases with Mm; (3) ΔT does not correlate with Mm; (4) ΔD does not correlate with Mm; (5) ΔT somewhat increases with ΔD; (6) The p-value slightly increases with Mm; (7) There is a negative correlation between the b- and p-values. (8) There was seismic quiescence over a broader region of Taiwan before the 1999 Chi-Chi earthquake; (9) Both the static and dynamic stress changes trigger aftershocks; and (10) Dynamic modeling shows that a decrease in elastic modulus is a significant factor in triggering aftershocks. [ABSTRACT FROM AUTHOR]

Observations of shear wave splitting provide unambiguous evidence of the presence of anisotropy in the Earth's lowermost mantle, a region known as D″. Much recent work has attempted to use these observations to place constraints on strain above the core-mantle boundary (CMB), as this may help map flow throughout the mantle. Previously, this interpretation has relied on the assumption that waves can be modelled as infinite-frequency rays, or that the Earth is radially symmetric. Due to computational constraints it has not been possible to test these approximations until now. We use fully 3-D, generally anisotropic simulations of ScS waves at the frequencies of the observations to show that ray methods are sometimes inadequate to interpret the signals seen. We test simple, uniform models, and for a D″ layer as thin as 50 km, significant splitting may be produced, and we find that recovered fast orientations usually reflect the imposed fast orientation above the CMB. Ray theory in these cases provides useful results, though there are occasional, notable differences between forwardmethods. Isotropic models do not generate apparent splitting. We also test more complex models, including ones based on our current understanding of mineral plasticity and elasticity in D″. The results show that variations of anisotropy over even several hundred kilometres cause the ray-theoretical and finite-frequency calculations to differ greatly. Importantly, models with extreme mineral alignment in D″ yield splitting times not dissimilar to observations (δt ≤ 3 s), suggesting that anisotropy in the lowermost mantle is probably much stronger than previously thought--potentially ~10 per cent shear wave anisotropy or more. We show that if the base of the mantle is as complicated as we believe, future studies of lowermost mantle anisotropy will have to incorporate finite-frequency effects to fully interpret observations of shear wave splitting. [ABSTRACT FROM AUTHOR]

Kevin Burke's original and thought-provoking contributions have been published steadily for the past 60 years, and more than a decade ago he set out to resolve how plate tectonics and mantle plumes interact by proposing a simple conceptual model, which we will refer to as the Burkian Earth. On the Burkian Earth, mantle plumes take us from the deepest mantle to sub-lithospheric depths, where partial melting occurs, and to the surface, where hotspot lavas erupt today, and where large igneous provinces and kimberlites have erupted episodically in the past. The arrival of a plume head contributes to continental break-up and punctuates plate tectonics by creating and modifying plate boundaries. Conversely, plate tectonics makes an essential contribution to the mantle through subduction. Slabs restore mass to the lowermost mantle and are the triggering mechanism for plumes that rise from the margins of the two large-scale low shear-wave velocity structures in the lowermost mantle, which Burke christened TUZO and JASON. Situated just above the core-mantle boundary, beneath Africa and the Pacific, these are stable and antipodal thermochemical piles, which Burke reasons represent the immediate after-effect of the moon-forming event and the final magma ocean crystallization. [ABSTRACT FROM AUTHOR]

Experimental research in the FeC-(Fe,Ni)S system was carried out. The objective of the investigation was to model the reactions of carbide-sulfide interaction related to graphite (diamond) formation in reduced lithosphere mantle domains. T ≤ 1200°C is the formation temperature of the Ni-cohenite + graphite assemblage coexisting with two immiscible melts such as sulfide (Fe-Ni-S) and metal-sulfide (Fe-Ni-S-C) containing dissolved carbon. Т ≥ 1300°C is the generation temperature of a unified melt such as (Fe-Ni-S-C) characterized by graphite crystallization and diamond growth. The extraction of carbide carbon during the interaction with the sulfide melt can be considered as one of the potential mechanisms of graphite and diamond formation in the reduced mantle. [ABSTRACT FROM AUTHOR]

This study investigates the metal–silicate partitioning of Ni, Co, V, Cr, Mn and Fe during core mantle differentiation of terrestrial planets under hydrous conditions. For this, we equilibrated a molten hydrous CI chondrite model composition with various Fe-rich alloys in the system Fe–C–Ni–Co–Si–S in a multi-anvil over a range of P, T, f O 2 and water content (5–20 GPa, 2073–2500 K, from 1 to 5 log units below the iron–wüstite (IW) buffer and for X H 2 O varying from 500 ppm to 1.5 wt%). By comparing the present experiments with the available data sets on dry systems, we observes that the effect of water on the partition coefficients of moderately siderophile elements is only moderate. For example, for iron we observed a decrease in the partition coefficient of Fe ( D met / sil Fe ) from 9.5 to 4.3, with increasing water content of the silicate melt, from 0 to 1.44 wt%, respectively. The evolution of metal–silicate partition coefficients of Ni, Co, V, Cr, Mn and Fe are modelled based on sets of empirical parameters. These empirical models are then used to refine the process of core segregation during accretion of Mars and the Earth. It appears that the likely presence of 3.5 wt% water on Mars during the core–mantle segregation could account for ∼74% of the FeO content of the Martian mantle. In contrast, water does not play such an important role for the Earth; only 4–6% of the FeO content of its mantle could be due to the water-induced Fe-oxidation, for a likely initial water concentration of 1.8 wt%. Thus, in order to reproduce the present-day FeO content of 8 wt% in the mantle, the Earth could initially have been accreted from a large fraction (between 85% and 90%) of reducing bodies (similar to EH chondrites), with 10–15% of the Earth’s mass likely made of more oxidized components that introduced the major part of water and FeO to the Earth. This high proportion of enstatite chondrites in the original constitution of the Earth is consistent with the 17 O, 48 Ca, 50 Ti, 62 Ni and 90 Mo isotopic study by Dauphas et al. (2014). If we assume that the CI-chondrite was oxidized during accretion, its intrinsically high water content suggests a maximum initial water concentration in the range of 1.2–1.8 wt% for the Earth, and 2.5–3.5 wt% for Mars. [ABSTRACT FROM AUTHOR]

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We study the implications of Planck data for models of dark energy (DE) and modified gravity (MG) beyond the standard cosmological constant scenario. We start with cases where the DE only directly affects the background evolution, considering Taylor expansions of the equation of state w(a), as well as principal component analysis and parameterizations related to the potential of a minimally coupled DE scalar field. When estimating the density of DE at early times, we significantly improve present constraints and find that it has to be below ~2% (at 95% confidence) of the critical density, even when forced to play a role for z < 50 only. We then move to general parameterizations of the DE or MG perturbations that encompass both effective field theories and the phenomenology of gravitational potentials in MG models. Lastly, we test a range of specific models, such as k-essence, ƒ(R) theories, and coupled DE. In addition to the latest Planck data, for our main analyses, we use background constraints from baryonic acoustic oscillations, type-Ia supernovae, and local measurements of the Hubble constant. We further show the impact of measurements of the cosmological perturbations, such as redshift-space distortions and weak gravitational lensing. These additional probes are important tools for testing MG models and for breaking degeneracies that are still present in the combination of Planck and background data sets. All results that include only background parameterizations (expansion of the equation of state, early DE, general potentials in minimally-coupled scalar fields or principal component analysis) are in agreement with ACDM. When testing models that also change perturbations (even when the background is fixed to ACDM), some tensions appear in a few scenarios: the maximum one found is ~σ for Planck TT+lowP when parameterizing observables related to the gravitational potentials with a chosen time dependence; the tension increases to, at most, 3σ when external data sets are included. It however disappears when including CMB lensing. [ABSTRACT FROM AUTHOR]

We conduct a numerical experiment to investigate potential bias in measurements of S-wave splitting (apparent differences between the arrival times of SH and SV phases) for waves propagating close to the core-mantle boundary (CMB) in the D layer. The bias is defined as the discrepancy between shear wave splitting measured from finite frequency synthetic seismograms ('apparent splitting') and the splitting predicted by ray theory, which is a highfrequency approximation. For simple isotropic models, we find biases which are typically between 0.5 and 4 s, depending on the model, the Q structure and the dominant period of the synthetics. The bias increases for lower frequencies or lower Q values. The epicentral distance at which the bias starts depends on the frequency and the Q structure. We also compute synthetics for models based on mineral physics (using the elastic constants under lower-mantle pressure and temperature conditions, taking into account the phase transition from Mg-perovskite to Mg-post-perovskite) and geodynamics (the thermal boundary layer) and find that the depth of the positive velocity jump associated with the phase transition and the depth range over which the velocity decreases (due to temperature increases) in the thermal boundary layer significantly influence the wavefield in the lowermost mantle. For example, in cold regions beneath subduction zones, wavefields for SH and SV differ greatly due to the steep velocity decrease close to the CMB. For complex models, apparent splitting can also arise from the possibility that low amplitude direct phases might be overlooked, and larger amplitude later phases might instead incorrectly be picked as the direct arrival. Biases of the type investigated in this study combine with other sources of uncertainty for splitting in D (e.g. the correction for upper-mantle anisotropy and the difference between SH and SV ray paths) to make a precise evaluation of the anisotropy in D difficult. [ABSTRACT FROM AUTHOR]

Tectonic plates are a key feature of Earth's structure, and their behavior and dynamics are fundamental drivers in a wide range of large-scale processes. The operation of plate tectonics, in general, depends intimately on the manner in which lithospheric plates couple to the convecting interior. Current debate centers on whether the transition from rigid lithosphere to flowing asthenosphere relates to increases in temperature or to changes in composition such as the presence of a small amount of melt or an increase in water content below a specified depth. Thus, the manner in which the rigid lithosphere couples to the flowing asthenosphere is currently unclear. Here we present results from laboratory-based torsion experiments on olivine aggregates with and without melt, yielding an improved database describing the crystallographic alignment of olivine grains. We combine this database with a flow model for oceanic upper mantle to predict the structure of the seismic anisotropy beneath ocean basins. Agreement between our model and seismological observations supports the view that the base of the lithosphere is thermally controlled. This model additionally supports the idea that discontinuities in velocity and anisotropy, often assumed to be the base of the lithosphere, are, instead, intralithospheric features reflecting a compositional boundary established at midocean ridges, not a rheological boundary. [ABSTRACT FROM AUTHOR]

Seismic observations reveal a patchwork of thin and dense structures, named UltraLow Velocity Zones (ULVZs) atop the Earth's core mantle boundary. The high width to height ratio of the ULVZs, their spatial correlation with the edges of Large Low Shear Velocity Provinces (LLSVPs), and their preservation as distinct structures in the convecting mantle remain an enigmatic problem. In this article, we carry out a series of numerical simulations using Fast Multipole Boundary Elements Method (FMBEM) to address these questions and study the internal deformation within the ULVZs. Our results demonstrate that coupled flow between dense, low viscosity ULVZ patches and the LLSVP accumulates the ULVZ into stable piles along LLSVP corners, while coalescence and gravitational drainage leads to thin and wide ULVZs away from the corners. Deformation of the matrix is localized within the weaker ULVZ and the LLSVP edges, while the strain in the interior of the LLSVP remains uniform and low, explaining the observed localized anisotropy near LLSVP edges. [ABSTRACT FROM AUTHOR]

We revisit the constraints on the deep lunar interior with a possible low-viscosity zone at the core-mantle boundary obtained from our previous forward modeling of the tidal response of the Moon, by comparing a numerical model with several tidal parameters (i.e., k 2 , k 3 , h 2 , and Q ) that have been improved or are newly determined by recent geodetic observations and analyses from GRAIL (gravity), LRO (shape), and LLR (rotation). Our results are in principle consistent with these data and suggest a low-viscosity layer (with an outer radius of about 540–560 km) which possibly extends inside the region where deep moonquakes occur. [ABSTRACT FROM AUTHOR]

Archaeomagnetic field models cover longer timescales than historical models and may therefore resolve the motion of geomagnetic features on the core-mantle boundary (CMB) in a more meaningful statistical sense. Here we perform a detailed appraisal of archaeomagnetic field models to infer some aspects of the physics of the outer core. We characterize and compare the identification and tracking of reversed flux patches (RFPs) in order to assess the RFPs robustness. We find similar behaviour within a family of models but differences among different families, suggesting that modelling strategy is more influential than data set. Similarities involve recurrent positions of RFPs, but no preferred direction of motion is found. The tracking of normal flux patches shows similar qualitative behaviour confirming that RFPs identification and tracking is not strongly biased by their relative weakness. We also compare the tracking of RFPs with that of the historical field model gufm1 and with seismic anomalies of the lowermost mantle to explore the possibility that RFPs have preferred locations prescribed by lower mantle lateral heterogeneity. The archaeomagnetic field model that most resembles the historical field is interpreted in terms of core dynamics and core-mantle thermal interactions. This model exhibits correlation between RFPs and low seismic shear velocity in co-latitude and a shift in longitude. These results shed light on core processes, in particular we infer toroidal field lines with azimuthal orientation below the CMB and large fluid upwelling structures with a width of about 80° (Africa) and 110° (Pacific) at the top of the core. Finally, similar preferred locations of RFPs in the past 9 and 3 kyr of the same archaeomagnetic field model suggest that a 3 kyr period is sufficiently long to reliably detect mantle control on core dynamics. This allows estimating an upper bound of 220-310 km for the magnetic boundary layer thickness below the CMB. [ABSTRACT FROM AUTHOR]

A fluid model for the formation of mantle plumes is proposed. During the emission of gas from the Earth’s core, it accumulates as lenses at the core-mantle boundary. Reaching a critical size, the lenses burst out into the mantle and migrate to the surface. A relatively stationary transmantle fluid flow from the core-mantle boundary arises, which heats the mantle and the layer interacting with it. The flow stops in the base of the hard lithosphere and spreads laterally, causing its melting accompanied by the formation of magma chambers, which, reaching critical sizes, massively intrude and flow out. [ABSTRACT FROM AUTHOR]

Direct S and Sdiff phases with anomalously low amplitudes are recorded for the earthquakes in Papua New Guinea by seismographs in northern America. According to the prediction by a standard 1D model, the amplitudes are the lowest at stations in southern California, at a distance and azimuth of around 95° and 55°, respectively, from the earthquake. The amplitude anomaly is more prominent at frequencies higher than 0.03 Hz. We checked and ruled out the possibility of the anomalies appearing because of the errors in the focal mechanism used in the reference synthetic waveform calculations. The observed anomaly distribution changes drastically with a relatively small shift in the location of the earthquake. The observations indicate that the amplitude reduction is likely due to the 3D shear velocity (Vs) structure, which deflects the wave energy away from the original ray paths. Moreover, some previous studies suggested that some of the S and Sdiff phases in our dataset are followed by a prominent postcursor and show a large travel time delay, which was explained by placing a large ultra-low velocity zone (ULVZ) located on the core-mantle boundary southwest of Hawaii. In this study, we evaluated the extent of amplitude anomalies that can be explained by the lower mantle structures in the existing models, including the previously proposed ULVZ. In addition, we modified and tested some models and searched for the possible causes of low amplitudes. Full 3D synthetic waveforms were calculated and compared with the observations. Our results show that while the existing models explain the trends of the observed amplitude anomalies, the size of such anomalies remain under-predicted especially at large distances. Adding a low velocity zone, which is spatially larger and has less Vs reduction than ULVZ, on the southwest side of ULVZ, contributes to explain the low amplitudes observed at distances larger than 100° from the earthquake. The newly proposed low velocity zone mostly overlaps with the northern part of the Pacific large low shear velocity province (LLSVP) revealed in tomographic models. Although the very low amplitudes observed at a distance of about 95° remain unexplained, our results indicate that the boundary of the Pacific LLSVP is sharp, and the amplitude of S waves at these large distances is lowered by strong vertical and/or lateral deflection at the boundary toward the interior of the low velocity province. [ABSTRACT FROM AUTHOR]

It is shown that the instability of turbulent flows with Ekman velocity profiles in the vicinity of the core-mantle boundary leads to the formation of horizontally oriented circulating roll structures. The geophysical implications of the presence of such structures in the liquid core are explored, namely, the formation of the hot zones with enhanced conductivity and their influence on geomagnetic reversals. [ABSTRACT FROM AUTHOR]

The temporal and spatial evolution characteristics of the geomagnetic secular acceleration (SA) are investigated, based on CHAOS-4 core field model during the period of 1997-2013. The SA evolution on a short time scale is associated with the phenomenon of the geomagnetic jerk. More details of the global extent and the occurrence time of the successive jerks (the 1999, 2003, 2007, and 2011 jerks) are obtained. The location, size and reversed polarity pattern for the 1999 jerk are similar to those for the 2003 jerk in the Asian-Indian sector. While the 2007 and 2011 jerks mainly take place in the Atlantic sector. The direction and speed of the shift for the four jerks are different, identified by the occurrence time of the jerks. The zonal motions of the SA patches exhibit an oscillation pattern in the Asian-Indian sector, whereas a purely westward drifting pattern is along the equator in the Atlantic sector. It is believed that the shift of the jerks is related to the motion of SA- B patches observed at the core-mantle boundary (CMB). [ABSTRACT FROM AUTHOR]

Anthropogenic seismicity (AS) is the undesired dynamic rockmass response to technological processes. AS environments are shallow hence their heterogeneities have important impact on AS. Moreover, AS is controlled by complex and changeable technological factors. This complicated origin of AS explains why models used in tectonic seismicity may be not suitable for AS. We study here four cases of AS, testing statistically whether the magnitudes follow the Gutenberg-Richter relation or not. The considered cases include the data from Mponeng gold mine in South Africa, the data observed during stimulation of geothermal well Basel 1 in Switzerland, the data from Acu water reservoir region in Brazil and the data from Song Tranh 2 hydropower plant region in Vietnam. The cases differ in inducing technologies, in the duration of periods in which they were recorded, and in the ranges of magnitudes. In all four cases the observed frequency-magnitude distributions statistically significantly differ from the Gutenberg-Richter relation. Although in all cases the Gutenberg-Richter b value changed in time, this factor turns out to be not responsible for the discovered deviations from the Gutenberg-Richter-born exponential distribution model. Though the deviations from Gutenberg-Richter law are not big, they substantially diminish the accuracy of assessment of seismic hazard parameters. It is demonstrated that the use of non-parametric kernel estimators of magnitude distribution functions improves significantly the accuracy of hazard estimates and, therefore, these estimators are recommended to be used in probabilistic analyses of seismic hazard caused by AS. [ABSTRACT FROM AUTHOR]

Tomographic images have shown that there are clear high-velocity heterogeneities to the north of the Pacific Anomaly near the core–mantle boundary (CMB), but the detailed structure and origin of these heterogeneities are poorly known. In this study, we analyze PKP precursors from earthquakes in the Aleutian Islands and Kamchatka Peninsula recorded by seismic arrays in Antarctica, and find that these heterogeneities extend ∼400 km above the CMB and are distributed between 30° and 45°N in latitude. The scatterers show the largest P-wave velocity perturbation of 1.0–1.2% in the center (160–180°E) and ∼0.5% to the west and east (140–160°E, 180–200°E). ScS–S differential travel-time residuals reveal similar features. We suggest that these seismic scatterers are the remnants of ancient subducted slab material. The lateral variations may be caused either by different slabs, or by variations in slab composition resulting from their segregation process. [ABSTRACT FROM AUTHOR]

Large peridotite massifs are scattered along the 1500 km length of the Yarlung-Zangbo Suture Zone (southern Tibet, China), the major suture between Asia and Greater India. Diamonds occur in the peridotites and chromitites of several massifs, together with an extensive suite of trace phases that indicate extremely low fO2 (SiC, nitrides, carbides, native elements) and/or ultrahigh pressures (UHP) (diamond, TiO2 II, coesite, possible stishovite). New physical and isotopic (C, N) studies of the diamonds indicate that they are natural, crystallized in a disequilibrium, high-T environment, and spent only a short time at mantle temperatures before exhumation and cooling. These constraints are difficult to reconcile with previous models for the history of the diamond-bearing rocks. Possible evidence for metamorphism in or near the upper part of the Transition Zone includes the following: (1) chromite (in disseminated, nodular and massive chromitites) containing exsolved pyroxenes and coesite, suggesting inversion from a high-P polymorph of chromite; (2) microstructural studies suggesting that the chromitites recrystallized from fine-grained, highly deformed mixtures of wadsleyite and an octahedral polymorph of chromite; (3) a new cubic Mg-silicate, with the space group of ringwoodite but an inverse-spinel structure (all Si in octahedral coordination); (4) harzburgites with coarsely vermicular symplectites of opx + Cr-Al spinel ± cpx; reconstructions suggest that these are the breakdown products of majoritic garnets, with estimated minimum pressures to > 13 GPa. Evidence for a shallow pre-metamorphic origin for the chromitites and peridotites includes the following: (1) trace-element data showing that the chromitites are typical of suprasubduction-zone (SSZ) chromitites formed by magma mixing or mingling, consistent with Hf-isotope data from magmatic (375 Ma) zircons in the chromitites; (2) the composition of the new cubic Mg-silicate, which suggests a low-P origin as antigorite, subsequently dehydrated; (3) the peridotites themselves, which carry the trace element signature of metasomatism in an SSZ environment, a signature that must have been imposed before the incorporation of the UHP and low-fO2 phases. A proposed P-T-t path involves the original formation of chromitites in mantle-wedge harzburgites, subduction of these harzburgites at c. 375 Ma, residence in the upper Transition Zone for >200 Myr, and rapid exhumation at c. 170-150 Ma or 130-120 Ma. Os-isotope data suggest that the subducted mantle consisted of previously depleted subcontinental lithosphere, dragged down by a subducting oceanic slab. Thermomechanical modeling shows that roll-back of a (much later) subducting slab would produce a high-velocity channelized upwelling that could exhume the buoyant harzburgites (and their chromitites) from the Transition Zone in < 10 Myr. This rapid upwelling, which may explain some characteristics of the diamonds, appears to have brought some massifs to the surface in forearc or back-arc basins, where they provided a basement for oceanic crust. This model can reconcile many apparently contradictory petrological and geological datasets. It also defines an important, previously unrecognized geodynamic process that may have operated along other large suture zones such as the Urals. [ABSTRACT FROM AUTHOR]

Alkali basalt hosted mantle xenoliths were sampled at four locations within the North Patagonian Massif, Argentina. The subcontinental lithospheric mantle (SCLM) beneath Comallo, Puesto Diaz and Cerro Chenque is mostly represented by spinel-harzburgites, whereas at Prahuaniyeu, spinelgarnetand garnet-peridotites occur next to spinel-peridotites. Partial melting estimates for the north Patagonian mantle xenoliths determined from clinopyroxene trace element abundances reveal up to 25% melt extraction. Whereas the SCLM beneath Puesto Diaz, Cerro Chenque and Comallo is exclusively represented by highly depleted mantle xenoliths, the Prahuaniyeu sample suite comprises both fertile lherzolites and depleted harzburgites. Elevated trace element contents in all the studied north Patagonian mantle samples indicate that melt-rock interaction took place after an initial melt depletion event. Variable primitive mantle normalized REE patterns of clinopyroxenes from within one sample locality suggest compositional changes attributed to melt percolation, which has not significantly affected the bulk-rock and mineral major element compositions. Melt percolation processes have also been detected in the isotopic compositions of the xenoliths, as well as in their highly siderophile element systematics. Hf isotopic compositions are decoupled from those of Nd and Sr and have been affected by variable degrees of enrichment. Platinum group element (PGE) abundances also reveal indications of melt-rock reaction. In some samples this is reflected in fractionation of the iridium-group PGE and/or enrichment in the palladium-group PGE and/or rhenium, which cannot result merely from partial melting processes. Rhenium depletion ages (TRD) determined from Os isotopic analyses reveal an at least late Paleoproterozoic (1.7 Ga) stabilization of the Prahuaniyeu SCLM. Mantle xenoliths sampled from beneath Comallo and Puesto Diaz-Cerro Chenque yield distinctly younger TRD of 1.3 Ga and 1.0 Ga, respectively. Distinct differences in the character of mantle xenoliths from Prahuaniyeu and from Puesto Diaz and Cerro Chenque (i.e. SCLM stabilization age and range of fertility) suggest that at least two SCLM domains exist below the North Patagonian Massif. [ABSTRACT FROM AUTHOR]

Recent studies proposing pre-orogenic mantle exhumation models have helped renew the interest of the geosciences community in the Pyrenees, which should be now interpreted as a hyper-extended passive margin before the convergence between Iberia and Eurasia occurred. Unresolved questions of the Pyrenean geology, as well as the understanding of the formation of hyper-extended passive margins, are how the crust was thinned, and when, where and how the crustal breakoff occurred. The study of the Variscan and pre-Variscan Pyrenean basement is thus critical to document and understand this Cretaceous crustal thinning. In order to specify the timing of Mesozoic metasomatism and the associated deformation in the pre-Mesozoic basement of the Pyrenees, we carried out a U-Th-Pb laser ablation ICP-MS study on a large panel of REE and titanium-rich minerals (titanite and rutile) from talc-chlorite ores from the eastern Pyrenees, with a special emphasis on the Trimouns deposit, the world's largest talc quarry. Our results suggest that the Trimouns talc formation was restricted to the upper Aptian-Cenomanian time, while the talc and chlorite formation in the eastern Pyrenees occurred during several distinct Permian, Jurassic and Cretaceous episodes. These results give strong constraints on the tectonic setting of the Pyrenean domain during the transition between the Variscan and Alpine orogenic cycles, and particularly on when and how the upper crust was thinned before the crustal breakoff and the final mantle exhumation. [ABSTRACT FROM AUTHOR]

Precise polarization measurements of the cosmic microwave background (CMB) require accurate knowledge of the instrument orientation relative to the sky frame used to define the cosmological Stokes parameters. Suitable celestial calibration sources that could be used to measure the polarimeter orientation angle are limited, so current experiments commonly 'self-calibrate.' The self-calibration method exploits the theoretical fact that the EB and TB cross-spectra of the CMB vanish in the standard cosmological model, so any detected EB and TB signals must be due to systematic errors. However, this assumption neglects the fact that polarized Galactic foregrounds in a given portion of the sky may have non-zero EB and TB cross-spectra. If these foreground signals remain in the observations, then they will bias the self-calibrated telescope polarization angle and produce a spurious B-mode signal. In this paper, we estimate the foreground-induced bias for various instrument configurations and then expand the self-calibration formalism to account for polarized foreground signals. Assuming the EB correlation signal for dust is in the range constrained by angular power spectrum measurements from Planck at 353 GHz (scaled down to 150 GHz), then the bias is negligible for high angular resolution experiments, which have access to CMB-dominated high l modes with which to self-calibrate. Low-resolution experiments observing particularly dusty sky patches can have a bias as large as 0°.5. A miscalibration of this magnitude generates a spurious BB signal corresponding to a tensor-to-scalar ratio of approximately r ~ 2 × 10-3, within the targeted range of planned experiments. [ABSTRACT FROM AUTHOR]

The geomagnetic westward drift and the inner core differential rotation relative to the mantle are two components of the Earth's core rotational dynamics. We present a systematic study of their long-term relationship in convective numerical simulations of the geodynamo. All models comprise gravitational coupling between the inner core and the mantle, in addition to electromagnetic coupling at the inner core and core–mantle boundaries. We show that the strength of these couplings has no influence on the global shear available in the fluid shell, the amount of which is entirely governed by the vigor of convection. This shear is distributed between the long-term westward drift and the long-term differential rotation of the inner core, in proportions controlled by the relative magnitudes of the electromagnetic and gravitational couplings. A present-day estimate of this available shear predicts a magnitude of the westward drift close to that observed on average during the last 400 yrs, which then implies a non-existent long-term inner core differential rotation. Assuming a lower mantle conductance of order 10 8 S , this in turn sets a constraint on the minimum stiffness of the inner core, the viscosity of which should be larger than 2 × 10 17 Pa s for the westward drift to dominate. [ABSTRACT FROM AUTHOR]

Ouyed et al. (Astrophys. J. 501:367, ) proposed Deuterium (DD) fusion at the core-mantle interface of giant planets as a mechanism to explain their observed heat excess. But rather high interior temperatures ( $\sim10^{5}~\mbox{K}$) and a stratified D layer are needed, making such a scenario unlikely. In this paper, we re-examine DD fusion, with the addition of screening effects pertinent to a deuterated core containing ice and some heavy elements. This alleviates the extreme temperature constraint and removes the requirement of a stratified D layer. As an application, we propose that, if their core temperatures are a few times $10^{4}~\mbox{K}$ and core composition is chemically inhomogeneous, the observed inflated size of some giant exoplanets ('hot Jupiters') may be linked to screened DD fusion occurring deep in the interior. Application of an analytic evolution model suggests that the amount of inflation from this effect can be important if there is sufficient rock-ice in the core, making DD fusion an effective extra internal energy source for radius inflation. The mechanism of screened DD fusion, operating in the above temperature range, is generally consistent with the trend in radius anomaly with planetary equilibrium temperature $T_{\mathrm{eq}}$, and also depends on planetary mass. Although we do not consider the effect of incident stellar flux, we expect that a minimum level of irradiation is necessary to trigger core erosion and subsequent DD fusion inside the planet. Since DD fusion is quite sensitive to the screening potential inferred from laboratory experiments, observations of inflated hot Jupiters may help constrain screening effects in the cores of giant planets. [ABSTRACT FROM AUTHOR]

Conductivity anisotropy of the lower mantle presumably caused by phase change of dielectric magnesiowustite at depths of 1500–2000 km is detectable from jerks. Jerks are induced by currents in the fluid outer core, propagate upward from the CMB through anisotropic conducting mantle, and appear on the Earth’s surface. The surface jerk patterns are studied theoretically from the potential of the geomagnetic field presented as a sum of magnetic and electric modes. Equations for the fields of both modes and their relationship in a weakly anisotropic earth are obtained by the perturbation method. The field potential is expanded into a series of spherical harmonics, and the equations are solved in the frequency and time domains. The surface jerk responses can be inverted to retrieve anisotropy parameters; the goal function in the inversion may correspond to misfit between the model and experimental values either along the horizontal or vertical components. [ABSTRACT FROM AUTHOR]

10.1007/s10712-021-09684-y 2 Koelemeijer P, Deuss A, Ritsema J. Density structure of Earth's lowermost mantle from Stoneley mode splitting observations. 10.1002/9781119528609 5 Lau HCP, Mitrovica JX, Davis JL, Tromp J, Yang HY, Al-Attar D. Tidal tomography constrains Earth's deep-mantle buoyancy. [Extracted from the article]