Helium solubility in olivine and implications for high ³He/⁴He in ocean island basalts

High 3He/4He ratios found in ocean island basalts are the main evidence for the existence of an undegassed mantle reservoir1, 2, 3. However, models of helium isotope evolution depend critically on the chemical behaviour of helium during mantle melting. It is generally assumed that helium is strongly enriched in mantle melts relative to uranium and thorium, yet estimates of helium partitioning in mantle minerals have produced conflicting results4, 5, 6. Here we present experimental measurements of helium solubility in olivine at atmospheric pressure. Natural and synthetic olivines were equilibrated with a 50% helium atmosphere and analysed by crushing in vacuo followed by melting, and yield a minimum olivine–melt partition coefficient of 0.0025 0.0005 (s.d.) and a maximum of 0.0060 0.0007 (s.d.). The results indicate that helium might be more compatible than uranium and thorium during mantle melting and that high 3He/4He ratios can be preserved in depleted residues of melting. A depleted source for high 3He/4He ocean island basalts would resolve the apparent discrepancy7 in the relative helium concentrations of ocean island and mid-ocean-ridge basalts

Social knowledge and social reasoning abilities in a neurotypical population and in children with Down syndrome.

Social knowledge refers to the ability to analyze and reason about social situations in relation to social rules which are essential to the development of social skills and social behavior. The present research aimed to assess these abilities with the "Social resolution task" in a neurotypical population of 351 children (4 to 12 years) and 39 young adults, and in 20 participants (10 to 18 years) with Down syndrome. Results showed that young children aged 4 to 6 were well able to distinguish between appropriate and inappropriate social behavior but they had significantly more difficulties in judging and identifying social cues for the transgression of conventional rules than for moral ones. Between age 4 and 8, their social reasoning was mainly based on factual answers, while older children showed significantly more social awareness, making more reference to emotional and social consequences for the "victims". The representation of a more universal applicability of social rules seemed to develop later in childhood, as of age 8. In contrast, participants with Down syndrome exhibited significantly more difficulties in judging, identifying and reasoning about transgression of social rules without social awareness. In conclusion, the results have shown that social reasoning abilities develop throughout childhood. Social awareness seems to have a long developmental course, which includes a sensibility about welfare and intersubjectivity, critical for the development of prosocial behavior. The clinical population with difficulties in social interaction and socio-emotional behavior could benefit from an early assessment and from learning social reasoning abilities to improve social skills

Geochemical evidence for melting of carbonated peridotite on Santa Maria Island, Azores

The islands of the Azores archipelago emerge from an oceanic plateau built on lithosphere increasing in age with distance from the Mid-Atlantic Ridge from 10 to 45 Ma. Here, we present the first comprehensive major and trace element and Sr-Nd-Pb isotope data from Santa Maria, the easternmost island of the archipelago, along with published data from the other Azores islands situated much closer to the Mid-Atlantic Ridge axis. We can show that the distinctively more variable and more enriched trace element ratios at Santa Maria combined with a relatively small range in Sr-Nd-Pb isotope ratios are the result of low degrees of partial melting of a common Azores mantle plume source underneath thicker lithosphere. This implies that melt extraction processes and melting dynamics may be able to better preserve the trace element mantle source variability underneath thicker lithosphere. These conclusions may apply widely for oceanic melts erupted on relatively thick lithosphere. In addition, lower Ti/Sm and K/La ratios and SiO2 contents of Santa Maria lavas imply melting of a carbonated peridotite source. Mixing of variable portions of deep small-degree carbonated peridotite melts and shallow volatile-free garnet peridotite could explain the geochemical variability underneath Santa Maria in agreement with the volatile-rich nature of the Azores mantle source. However, Santa Maria is the Azores island where the CO2-rich nature of the mantle source is more evident, reflecting a combination of a smaller extent of partial melting and the positioning at the edge of the tilted Azores mantle plume. © 2012 Springer-Verlag Berlin Heidelberg.0SCOPUS: ar.jSCOPUS: ar.jinfo:eu-repo/semantics/publishe