Gravity topographic corrections computed from a square grid of height points

Summary Computation of terrain corrections from a map with a square grid of mean height points

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uu mnauu nna n am ¶rt;u m u¶rt; a¶rt;am mu m nm.

     

Interaction of mantle-derived magma with island crust? Trace element and oxygen isotope data from the Diego Hernandez Formation, Las Cañadas, Tenerife

The Quaternary Diego Hernandez Formation consists of interbedded phonolitic pyroclastics and basanite lavas and scoria beds. Most of the phonolites are mingled-magma units that contain a minor mafic component. The phonolites fall into two stratigraphically bounded groups, based on major and trace element abundances. Nb contents are especially distinctive, due to a varying role for titanite during petrogenesis. Nepheline syenite xenoliths, which are plentiful in some of the phonolitic ignimbrites, fall into the same two compositional groupings but are typically more strongly differentiated. Major and trace element variations during evolution of the phonolites can be modelled by fractional crystallization, by melting of syenite, or by some combination of the two such as AFC. Trace element variations among the basanites require the addition of a highly fractionated felsic component, either phonolitic magma or nepheline syenite. δ¹⁸O values of phonolites vary across twice the range of the basanites, inconsistent with an origin by pure fractional crystallization of a basanitic parent. We conclude that recycling of differentiated rocks within the Tenerife island edifice has played a significant role in Quaternary magmatism on Tenerife.     

Iterative Spherical Downward Continuation Applied to Magnetic and Gravitational Data from Satellite

In the last few decades, satellites have acquired various potential data sets hundreds of kilometers above the Earth’s surface. Conventionally, these global magnetic and gravitational data sets are approximated by using spherical harmonics that allow straightforward work with both fields outside the Earth’s mass. In this article, we present an alternative approach for working with potential data in mass-free space given over a regular coordinate grid on a spherical surface. The algorithm is based on an iterative scheme and the Poisson integral equation for the sphere. With help from the Fourier transform, global potential (magnetic or gravitational) data can efficiently be continued from a mean orbital sphere down to a reference surface without using the spherical harmonics. This is illustrated both with simulated magnetic field data and with real data from the satellite gradiometry mission GOCE. In the case of simulated magnetic data and the downward continuation for 450 km, we have achieved a root mean square at the level of 0.05 nT, while it was <1 E (eotvos) for real GOCE data continued for 250 km. The crucial point is to apply the algorithm twice as a large part of noise can be removed from the input data.     

TBT contamination identified in Antarctic marine sediments

We report for the first time butyltin contamination of near-shore sediments at six sites in the Ross Sea, Antarctica. A very high concentration of 2290 microg Sn kg(-1) sediment was recorded in one sample. The most likely source is abrasion of antifouling paint from the hulls of ice-breakers, but this pattern of contamination is also possible following ship groundings. Antifoulant biocides, such as TBT, have not been considered or detected in Antarctica previously and represent a new challenge to environmental managers and custodians.     

Variation in NbTa during differentiation of phonolitic magma,Tenerife, Canary Islands

Variation in $\text{Nb}\text{Ta}$ ratio through a suite of phonolitic volcanics is reported. Sphene, a phenocryst mineral, shows preferential incorporation of Ta relative to Mb, consistent with the bulk rock variation, where $\text{Nb}\text{Ta}$ increases with fractionation. Nb in these magmas may be partly present in the Nb³⁺ state.     

Precession-nutation torque in terms of the stokes constants

um nu-mau m nuuau u auumu m nm ma u. m mu u¶rt;uu¶rt;a m ma nuua u uu.     

The planetary system and solar-terrestrial phenomena

Summary The Sun moves at different distances round the barycentre of the Solar System with different velocities depending on the distribution of the planets. The mean period of the Sun's motion round the barycentre of 11.8627 years and its time variability were observed. A relation between the basic period of 178.4 years and other periods p_i in the Sun's motion (p_i=178.4/i; i=1, 2, ...) was found. The consistency of the periods in the Sun's motion round the barycentre with the periods of different solar-terrestrial phenomena was studied. It seems that the planetary system governs these phenomena.

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n¶rt; ¶rt;u nu¶rt; au a ama um (11,8627 m) u auauu. a a¶rt;a nuua ¶rt; m¶rt;u nu¶rt;au ¶rt;uu a (p_i=178,4/i). mu nu¶rt;a u nma nu¶rt; n¶rt; a - u. na¶rt;u nu¶rt; am, m a uma nam mu u.