The effect of H<Subscript>2</Subscript>O on the olivine liquidus of basaltic melts: experiments and thermodynamic models

We designed and carried out experiments to investigate the effect of H₂O on the liquidus temperature of olivine-saturated primitive melts. The effect of H₂O was isolated from other influences by experimentally determining the liquidus temperatures of the same melt composition with various amounts of H₂O added. Experimental data indicate that the effect of H₂O does not depend on pressure or melt composition in the basaltic compositional range. The influence of H₂O on melting point lowering can be described as a polynomial function This expression can be used to account for the effect of H₂O on olivine-melt thermometers, and can be incorporated into fractionation models for primitive basalts. The non-linear effect of H₂O indicates that incorporation of H₂O in silicate melts is non-ideal, and involves interaction between H₂O and other melt components. The simple speciation approach that seems to account for the influence of H₂O in simple systems (albite-H₂O, diopside-H₂O) fails to describe the mixing behavior of H₂O in multi-component silicate melts. However, a non-ideal solution model that treats the effect of H₂O addition as a positive excess free energy can be fitted to describe the effect of melting point lowering.     

CODE’s five-system orbit and clock solution—the challenges of multi-GNSS data analysis

This article describes the processing strategy and the validation results of CODE’s MGEX (COM) orbit and satellite clock solution, including the satellite systems GPS, GLONASS, Galileo, BeiDou, and QZSS. The validation with orbit misclosures and SLR residuals shows that the orbits of the new systems Galileo, BeiDou, and QZSS are affected by modelling deficiencies with impact on the orbit scale (e.g., antenna calibration, Earth albedo, and transmitter antenna thrust). Another weakness is the attitude and solar radiation pressure (SRP) modelling of satellites moving in the orbit normal mode—which is not yet correctly considered in the COM solution. Due to these issues, we consider the current state COM solution as preliminary. We, however, use the long-time series of COM products for identifying the challenges and for the assessment of model-improvements. The latter is demonstrated on the example of the solar radiation pressure (SRP) model, which has been replaced by a more generalized model. The SLR validation shows that the new SRP model significantly improves the orbit determination of Galileo and QZSS satellites at times when the satellite’s attitude is maintained by yaw-steering. The impact of this orbit improvement is also visible in the estimated satellite clocks—demonstrating the potential use of the new generation satellite clocks for orbit validation. Finally, we point out further challenges and open issues affecting multi-GNSS data processing that deserves dedicated studies.     

Theoretical study of OH-defects in pure enstatite

The infrared spectroscopic properties of selected defects in orthoenstatite are investigated by first-principles calculations. The considered defects include doubly protonated Mg vacancies at M1 and M2 sites, fully protonated SiA and SiB vacancies (hydrogarnet defects), and doubly protonated SiA and SiB vacancies associated with interstitial Mg²⁺ cations. The bands observed at 3,070 and 3,360 cm^?1 in the spectrum of synthetic enstatite samples are ascribed to O2A–H and O2B–H groups, respectively, associated with M2 vacancies. The theoretical models suggest that bands observed at 3,590 and 3,690 cm^?1 in the spectrum of enstatite samples synthesized under low silica-activity conditions correspond to O2H and O1H groups associated with SiB vacancies partially compensated by interstitial Mg²⁺ cations in fivefold coordination. The theoretical relation between the integrated absorption coefficient of OH-defects and vibrational frequencies is consistent with previous observations indicating that the absorption coefficients of OH-defects are comparatively stronger in enstatite than in the olivine polymorphs.     

Modelling the formation of galaxy clusters in MOND

We present time-resolved spectroscopy and photometry of the cataclysmic variable (CV) SDSS J133941.11+484727.5 (SDSS 1339) which has been discovered in the Sloan Digital Sky Survey (SDSS) Data Release 4. The orbital period determined from radial velocity studies is 82.524(24) min, close to the observed period minimum. The optical spectrum of SDSS 1339 is dominated to 90 per cent by emission from the white dwarf (WD). The spectrum can be successfully reproduced by a three-component model (white dwarf, disc, secondary) with   T _WD=12 500 K  for a fixed  log   g = 8.0, d = 170 pc  , and a spectral type of the secondary later than M8. The mass-transfer rate corresponding to the optical luminosity of the accretion disc is very low,  ≃ 1.7 × 10⁻¹³ M_⊙ yr⁻¹  . Optical photometry reveals a coherent variability at 641 s with an amplitude of 0.025 mag, which we interpret as non-radial pulsations of the white dwarf. In addition, a long-period photometric variation with a period of either 320 or 344 min and an amplitude of 0.025 mag is detected, which bears no apparent relation with the orbital period of the system. Similar long-period photometric signals have been found in the CVs SDSS J123813.73−033933.0, SDSS J204817.85−061044.8, GW Lib and FS Aur, but so far no working model for this behaviour is available.     

Continuous supply of recycled Pacific oceanic materials in the source of Cenozoic basalts in SE China: the Zhejiang case

Various enriched recycled oceanic components in the source of Cenozoic intra-plate alkaline basalts from eastern China were identified by previous studies. Due to the existence of a stagnant subducted Pacific slab in the mantle transition zone beneath eastern China, it is logical to connect the stagnant slab to the recycled oceanic materials. However, the recycled oceanic materials could also result from ancient subduction events (e.g., Paleo-Tethyan, Paleo-Asian or Izanagi plate subduction) because enriched geochemical signatures of a recycled slab can be preserved in the mantle for longer than 1 Gyr. Investigating the temporal variations of the recycled oceanic materials in the mantle source is a useful way to trace the origin of the basalts. In this article, we have conducted a detailed geochemical study, including major and trace elements and Sr–Nd–Pb isotopes, on two alkaline basalt groups from Zhejiang, SE China, which erupted 26–17 Ma and after 11 Ma, respectively. In particular, we recovered the H₂O content of the initial magmas based on the H₂O content of the clinopyroxene (cpx) phenocrysts and the partition coefficients of H₂O between cpx and basaltic melts. The H₂O contents of the Zhejiang basalts range from 1.3 to 2.6 (wt.%), which fall within the range of back-arc basin or island arc basalts. The older basalts are more alkaline and have lower Si and Al contents; higher trace element concentrations; higher La/Yb, Ce/Pb and Nb/La ratios; lower H₂O/Ce and Ba/Th ratios; and stronger negative K, Pb, Hf and Ti anomalies than the younger ones. The co-relationships between Ba/La, H₂O/Ce, Nb/La, Ce/Pb and Ba/Th in the two groups of the Zhejiang basalts indicate that a recycled dehydrated oceanic alkaline basalt component is needed in the source of the older rocks, along with a depleted mantle component. Meanwhile, an additional recycled dehydrated sediment component was required in the source of the younger rocks. The temporal change in the recycled oceanic materials in the mantle sources of Zhejiang Cenozoic basalts demonstrates that the recycled components can only originate in the stagnant Pacific slab that is the only plate subducted since 100 Ma in this area.     

SPIRIT. SPOT 5 stereoscopic survey of Polar Ice: Reference Images and Topographies during the fourth International Polar Year (2007–2009)

Monitoring the evolution of polar glaciers, ice caps and ice streams is of utmost importance because they constitute a good indicator of global climate change and contribute significantly to ongoing sea level rise. Accurate topographic surveys are particularly relevant as they reflect the geometric evolution of ice masses. Unfortunately, the precision and/or spatial coverage of current satellite missions (radar altimetry, ICESat) or field surveys are generally insufficient. Improving our knowledge of the topography of Polar Regions is the goal of the SPIRIT (SPOT 5 stereoscopic survey of Polar Ice: Reference Images and Topographies) international polar year (IPY) project. SPIRIT will allow (1) the acquisition of a large archive of SPOT 5 stereoscopic images covering most polar ice masses and, (2) the delivery of digital terrain models (DTM) to the scientific community.Here, we present the architecture of this project and the coverage achieved over northern and southern polar areas during the first year of IPY (July 2007 to April 2008). We also provide the first accuracy assessments of the SPIRIT DTMs. Over Jakobshavn Isbrae (West Greenland), SPIRIT elevations are within ±6 m of ICESat elevations for 90% of the data. Some comparisons with ICESat profiles over Devon ice cap (Canada), St Elias Mountains (Alaska) and west Svalbard confirm the good overall quality of the SPIRIT DTMs although large errors are observed in the flat accumulation area of Devon ice cap. We then demonstrate the potential of SPIRIT DTMs for mapping glacier elevation changes. The comparison of summer-2007 SPIRIT DTMs with October-2003 ICESat profiles shows that the thinning of Jakobshavn Isbrae (by 30–40 m in 4 years) is restricted to the fast glacier trunk. The thinning of the coastal part of the ice stream (by over 100 m) and the retreat of its calving front (by up to 10 km) are clearly depicted by comparing the SPIRIT DTM to an ASTER April-2003 DTM.     

Age gap between the intrusion of gneissose granitoids and regional high‐temperature metamorphism in the Ryoke belt (Mikawa area), central Japan

The relationships between the intrusion of gneissose granitoids and the attainment of regional high‐T conditions recorded in metamorphic rocks from the Ryoke belt of the Mikawa area, central Japan, are explored. Seven gneissose granitoid samples (tonalite, granodiorite, granite) were collected from three distinct plutonic bodies that are mapped as the so‐called “Older Ryoke granitoids.” Based on bulk‐rock compositions and U–Pb zircon ages obtained by laser ablation inductively coupled plasma mass spectrometry, the analyzed granitoids can be separated into two groups. Gneissose granitoids from the northern part of the area give weighted mean ²⁰⁶Pb/²³⁸U ages of 99 ±1 Ma (two samples) and 95 ±1 Ma (one sample), whereas those from the southern part yield 81 ±1 Ma (two samples) and 78–77 ±1 Ma (two samples). Regional comparisons allow correlation of the northern granitoids (99–95 Ma) with the Kiyosaki granodiorite, and mostly with the Kamihara tonalite found to the east. The southern granitoids are tentatively renamed as “78–75 Ma (Hbl)?Bt granite” and “81–75 Ma Hbl?Bt tonalite” (Hbl, hornblende; Bt, biotite). and seem to be broadly coeval members of the same magmatic suite. With respect to available age data, no gneissose granitoid from the Mikawa area shows a U–Pb zircon age which matches that of high‐T metamorphism (ca 87 Ma). The southern gneissose granitoids (81–75 Ma), although they occur in the highest‐grade metamorphic zone, do not seem to represent the heat source which produced the metamorphic field gradient with a low dP/dT slope.     

Evolution of new regional development interventions in New Zealand: An analysis of the first year of the Provincial Growth Fund

Regional development has evolved in response to shifting local and global priorities. These shifts have transformed both the way we think about regions, their role and how that shapes the outcomes and benefits that might occur from engaging in regional development. Key debates centre around the ability (or desirability) of regional development interventions to unsettle path dependence and “lock‐in” created by past approaches and to create opportunities for alternative development futures and to provide choices between sectoral‐based investments to support economic activity in contrast to a more place‐based approach to regional development. This paper overviews the dynamic nature of regional development to offer reasons for its recent resurgence by highlighting the key debates about the purpose and function of regions and what regional development can or should do. We then discuss the New Zealand context specifically and use the first year of Provincial Growth Fund investments to reflect on how the processes, objectives and goals reflect particular interpretations of the meaning and purpose of regional development. We conclude that a strong adherence to a growth imperative has the potential to reinforce path dependencies at the expense of alternative development pathways.