A komatiite component in Apollo 16 highland breccias: implications for the nickel-cobalt systematics and bulk composition of the moon

The lunar crust at the Apollo 16 landing site contains substantial amounts of a “primitive component” in which the ferromagnesian group of elements is concentrated. The composition of this component can be retrieved via an analysis of mixing relationships displayed by lunar breccias. It is found to be a komatiite which is compositionally similar to terrestrial komatiites both in major and minor elements. The komatiite component of the lunar crust is believed to have formed by extensive degrees of melting of the lunar interior at depths greater than were involved in the formation of the lunar magma ocean which was parental to the crust. After formation of the anorthositic crust, it was invaded by extensive flows and intrusions of komatiite magma from these deeper source regions. The komatiites became intimately mixed with the anorthosite by intensive meteoroid impacts about 4.5 b.y. ago, thereby accounting for the observed mixing relationships displayed by the crust. The compositional similarity between lunar and terrestrial komatiites strongly implies a corresponding similarity between the compositions of their source regions in the lunar interior and the Earth's upper mantle. The composition of the lunar interior can be modelled more specifically by combining the komatiite composition with its liquidus olivine composition (as determined experimentally) in proportions chosen so as to produce a cosmochemically acceptable range of Mg/Si ratios for the bulk Moon. Except for higher FeO and lower Na₂O, the range of compositions thereby obtained for the bulk moon is very similar to the composition of the Earth's upper mantle.The effects of meteoritic contamination on the abundances of cobalt and nickel in lunar highland breccias were subtracted on the assumption that the contaminating projectiles were chondritic. The cobalt and nickel residuals thereby obtained were found to correlate strongly with the (Mg + Fe) content of the breccias, demonstrating that the Co and Ni are associated with the ferromagnesian component of the breccias and are genuinely indigenous to the Moon. The lunar highland Co and Ni residuals also display striking Ni/Co versus Ni correlations which follow a similar trend to those displayed by terrestrial basalts, picrites and komatiites. The lunar trends provide further decisive evidence of the indigenous nature of the Co and Ni residuals and suggest the operation of extensive fractionation controlled by olivine-liquid equilibria in producing the primitive component of the lunar breccias. Indigenous nickel abundances at the Apollo 14, 15 and 17 sites are much lower than at the Apollo 16 site, although rocks from all sites follow the same Ni/Co versus Ni trends. It is suggested that the primitive component at the Apollo 14, 15 and 17 sites was generally of basaltic composition, in contrast to the komatiitic nature of the Apollo 16 primitive component.     

The Quadrennial Ozone Symposium 2016

<正>1.Overview The 2016 Quadrennial Ozone Symposium(QOS-2016)was held on 4–9 September 2016 in Edinburgh,UK.The Symposium was organized by the International Ozone Commission(IO3C),the NERC Centre for EcologyHydrology and the University of Edinburgh,and was co-sponsored by the International Union of Geodesy and Geophysics,the International Association of Meteorology and Atmospheric     

Global increase in record-breaking monthly-mean temperatures

The last decade has produced record-breaking heat waves in many parts of the world. At the same time, it was globally the warmest since sufficient measurements started in the 19th century. Here we show that, worldwide, the number of local record-breaking monthly temperature extremes is now on average five times larger than expected in a climate with no long-term warming. This implies that on average there is an 80 % chance that a new monthly heat record is due to climatic change. Large regional differences exist in the number of observed records. Summertime records, which are associated with prolonged heat waves, increased by more than a factor of ten in some continental regions including parts of Europe, Africa, southern Asia and Amazonia. Overall, these high record numbers are quantitatively consistent with those expected for the observed climatic warming trend with added stationary white noise. In addition, we find that the observed records cluster both in space and in time. Strong El Niño years see additional records superimposed on the expected long-term rise. Under a medium global warming scenario, by the 2040s we predict the number of monthly heat records globally to be more than 12 times as high as in a climate with no long-term warming.     

Optimal design of superelastic‐friction base isolators for seismic protection of highway bridges against near‐field earthquakes

The seismic response of a multi‐span continuous bridge isolated with novel superelastic‐friction base isolator (S‐FBI) is investigated under near‐field earthquakes. The isolation system consists of a flat steel‐Teflon sliding bearing and a superelastic NiTi shape memory alloy (SMA) device. The key design parameters of an S‐FBI system are the natural period of the isolated bridge, the yielding displacement of the SMA device, and the friction coefficient of the sliding bearings. The goal of this study is to obtain optimal values for each design parameter by performing sensitivity analysis of a bridge isolated by an S‐FBI system. First, a three‐span continuous bridge is modeled as two‐degrees‐of‐freedom with the S‐FBI system. A neuro‐fuzzy model is used to capture rate‐ and temperature‐dependent nonlinear behavior of the SMA device. Then, a set of nonlinear time history analyses of the isolated bridge is performed. The variation of the peak response quantities of interest is shown as a function of design parameters of the S‐FBI system and the optimal values for each parameter are evaluated. Next, in order to assess the effectiveness of the S‐FBI system, the response of the bridge isolated by the S‐FBI system is compared with the response of the non‐isolated bridge and the same bridge isolated by pure‐friction (P‐F) sliding isolation system. Finally, the influence of temperature variations on the performance of the S‐FBI system is evaluated. The results show that the optimum design of a bridge with the S‐FBI system can be achieved by a judicious specification of design parameters. Copyright © 2010 John Wiley & Sons, Ltd.