The solubility and oxidation state of nickel in silicate melt at low oxygen fugacities: Results using a mechanically assisted equilibration technique

The solubility of Ni in a silicate melt has been measured using a new, mechanically assisted equilibration technique over a wide range of controlled ƒO2 values. The melt composition corresponds to the 1 atm eutectic in the system CaAl2Si2O8-CaMgSi2O6 + 10 wt% CaO. The experiments were performed at 1300°C and over an ƒO2 range of 10−8.5 to 10−13.75, and over a temperature range of 1270 to 1390°C at a constant gas mixing ratio ( ). The experiment consists of a sample of melt contained within a crucible of Ni metal and held in a 1 atm gas mixing furnace. A Ni spindle is entered into the sample from above and continuously rotated at a constant angular velocity using a viscometer head. The stirring of the sample serves to accelerate the approach to equilibrium between the liquid sample and the metal crucible (and spindle). This arrangement allows relatively rapid equilibration of Ni content following changes to higher or lower ƒO2 values. Samples of the melt may be taken at any time for analysis and thus the equilibrium solubility of Ni in the silicate melt may be determined from unambiguous experimental reversals. The Ni contents of samples, analysed both by INAA and by ICP-AES, range from 25 to 5300 ppm. The data presented in this paper indicate that the oxidation state of Ni in the investigated melt is Ni2+ over the entire range of ƒO2 investigated. This conclusion contrasts with recent reports in the literature of an inflection in the ƒO2 dependence of Ni solubility, which has been interpreted as solution of neutral Ni at low ƒO2 (Morse et al., 1991; Colson, 1992; Ehlers et al., 1992). We also present data for the temperature dependence of Ni solubility in the investigated melt. The solubility decreases with increasing temperature at constant ƒO2. The present results are in good agreement with the metal-loop-equilibration experiments reported by Holzheid et al. (1994)

An inherited duplication at the gene p21 protein-activated Kinase 7 (PAK7) is a risk factor for psychosis

FUNDING Funding for this study was provided by the Wellcome Trust Case Control Consortium 2 project (085475/B/08/Z and 085475/Z/08/Z), the Wellcome Trust (072894/Z/03/Z, 090532/Z/09/Z and 075491/Z/04/B), NIMH grants (MH 41953 and MH083094) and Science Foundation Ireland (08/IN.1/B1916). We acknowledge use of the Trinity Biobank sample from the Irish Blood Transfusion Service; the Trinity Centre for High Performance Computing; British 1958 Birth Cohort DNA collection funded by the Medical Research Council (G0000934) and the Wellcome Trust (068545/Z/02) and of the UK National Blood Service controls funded by the Wellcome Trust. Chris Spencer is supported by a Wellcome Trust Career Development Fellowship (097364/Z/11/Z). Funding to pay the Open Access publication charges for this article was provided by the Wellcome Trust. ACKNOWLEDGEMENTS The authors sincerely thank all patients who contributed to this study and all staff who facilitated their involvement. We thank W. Bodmer and B. Winney for use of the People of the British Isles DNA collection, which was funded by the Wellcome Trust. We thank Akira Sawa and Koko Ishzuki for advice on the PAK7–DISC1 interaction experiment and Jan Korbel for discussions on mechanism of structural variation.Peer reviewedPublisher PD

Contribution of copy number variants to schizophrenia from a genome-wide study of 41,321 subjects

Copy number variants (CNVs) have been strongly implicated in the genetic etiology of schizophrenia (SCZ). However, genome-wide investigation of the contribution of CNV to risk has been hampered by limited sample sizes. We sought to address this obstacle by applying a centralized analysis pipeline to a SCZ cohort of 21,094 cases and 20,227 controls. A global enrichment of CNV burden was observed in cases (OR=1.11, P=5.7×10−15), which persisted after excluding loci implicated in previous studies (OR=1.07, P=1.7 ×10−6). CNV burden was enriched for genes associated with synaptic function (OR = 1.68, P = 2.8 ×10−11) and neurobehavioral phenotypes in mouse (OR = 1.18, P= 7.3 ×10−5). Genome-wide significant evidence was obtained for eight loci, including 1q21.1, 2p16.3 (NRXN1), 3q29, 7q11.2, 15q13.3, distal 16p11.2, proximal 16p11.2 and 22q11.2. Suggestive support was found for eight additional candidate susceptibility and protective loci, which consisted predominantly of CNVs mediated by non-allelic homologous recombination

Genomic Dissection of Bipolar Disorder and Schizophrenia, Including 28 Subphenotypes

publisher: Elsevier articletitle: Genomic Dissection of Bipolar Disorder and Schizophrenia, Including 28 Subphenotypes journaltitle: Cell articlelink: https://doi.org/10.1016/j.cell.2018.05.046 content_type: article copyright: © 2018 Elsevier Inc

Schizophrenia-associated somatic copy-number variants from 12,834 cases reveal recurrent NRXN1 and ABCB11 disruptions

While germline copy-number variants (CNVs) contribute to schizophrenia (SCZ) risk, the contribution of somatic CNVs (sCNVs)—present in some but not all cells—remains unknown. We identified sCNVs using blood-derived genotype arrays from 12,834 SCZ cases and 11,648 controls, filtering sCNVs at loci recurrently mutated in clonal blood disorders. Likely early-developmental sCNVs were more common in cases (0.91%) than controls (0.51%, p = 2.68e−4), with recurrent somatic deletions of exons 1–5 of the NRXN1 gene in five SCZ cases. Hi-C maps revealed ectopic, allele-specific loops forming between a potential cryptic promoter and non-coding cis-regulatory elements upon 5′ deletions in NRXN1. We also observed recurrent intragenic deletions of ABCB11, encoding a transporter implicated in anti-psychotic response, in five treatment-resistant SCZ cases and showed that ABCB11 is specifically enriched in neurons forming mesocortical and mesolimbic dopaminergic projections. Our results indicate potential roles of sCNVs in SCZ risk

Causes of the Compositional Variability among Ocean Floor Basalts

The chemistry of ocean floor basalts (OFB) has been much studied for the insights that the compositions of their parental magmas may give into the thermal structure of the mantle, and its compositional heterogeneity. But as Mike O’Hara pointed out, OFBs are not primary magmas, and their extensive low-pressure differentiation ‘must be quantified before chemical features of lavas are ascribed to the nature of the underlying upper mantle’. O’Hara also emphasized that individual magmatic eruptions are products of complex magmatic systems. Volcanoes are not formed by isolated events, but are sites of long-term activity at which eruptions are caused by the arrival of replenishing magma that mixes with earlier magma through repeated cycles. In the intervals between replenishment events, part of the magma crystallizes, concentrating incompatible elements in the remaining magma. If the compositions of OFB are to be used to infer differences in the conditions of melting owing to mantle thermal structure, first it is necessary to disentangle the effects of this low-pressure evolution. It is a remarkable feature of OFB magmatism that these potentially complex replenish–mix–tap–crystallize (RMTX) cycles give rise to a simple pattern of chemical evolution when averaged at the global scale. Here we look at the deviations of 45 minor and trace element concentrations from these global average trends. The global trends are taken as the logarithms of the concentrations of the elements as a function of MgO concentration (log [M] vs [MgO]), and the deviations from these trends are defined as ‘variabilities’. An element’s variability is expected to result from a combination of source heterogeneity, partial melting in the mantle and melt extraction, and from the local variations in the RMTX process during crustal evolution. There is a strong correlation of an element’s variability with its slope in the global average trend, where the slope is a proxy for the element’s incompatibility (bulk partitioning) during global average RMTX. This correlation implies that the chemical controls on source heterogeneity and partial melting and melt extraction are similar to those during RMTX. Striking exceptions are the variabilities in plagioclase-hosted Na and Sr, indicating that a substantial part of the variability of Na in OFBs is due to variations in RMTX, rather than reflecting differences in extent of partial melting. If Iceland is excluded, there is no evidence from OFB chemistry to suppose that the distribution of potential temperatures in the sub-ridge mantle has a standard deviation, σ(Tp), larger than about 10°C, and if variability of the mantle source composition is allowed for, σ(Tp) could be even less. A principal component analysis of the variabilities reveals two more-or-less equally important principal components, suggesting that two distinct factors have affected incompatible trace element concentrations in global OFB. We suggest that these two factors are source heterogeneity and the RMTX process rather than the extent of partial melting or shape of the melting regime. An unexpected finding is the decoupling of the variabilities of very incompatible elements (VICE) such as Ba, Th and Nb, from those of the highly incompatible elements (HICE), such as La and the other light rare earth elements, Zr, P and Be

Liquidus temperatures of komatiites and the effect of cooling rate on element partitioning between olivine and komatiitic melt

Archean komatiites are the hottest magmas preserved on Earth and are thus unique probes of its thermal evolution. Estimating their eruption temperatures remains problematic, however, because the uppermost (A1, A2) zones of komatiite flows contain randomly oriented spinifex-textured olivines, indicative of rapid cooling and growth.This work was made possible by an Australian Postgraduate Award and ANU Vice Chancellor’s Scholarship to PAS and an Australian Research Council Discovery grant, DP130101355, to HO’N

Redox in magmas: comment on a recent treatment of the Kaiserstuhl Volcanics (Braunger et al., Journal of Petrology, 59, 1731–1762, 2018) and some other misconceptions

The recent contribution by Braunger et al. (2018) provides a thorough petrographic and geochemical description of peralkaline and carbonatitic igneous rocks from the Kaiserstuhl Volcanic Complex, SW Germany (KVC). These data are used to calculate several intensive variables: temperature (T), pressure (P), silica activity (aSiO2), and oxygen fugacity (fO2), which are then applied to constrain the petrogenesis of the different KVC magma series, including identifying features of their source with an emphasis on redox conditions. Using a variety of thermodynamic equilibria, Braunger et al. (2018) showed that the redox states of the various silicate KVC magmas in intensive-variable space follow..