M. A. Gouveia

Behavior of REE and other trace and major elements during weathering of granitic rocks, Évora, Portugal☆

The distribution of elements within a weathering profile depends on several factors, including the relative stability of the mineral phases of the parent rock, redox and leaching conditions. Three main processes are involved in weathering: ( 1 ) the breakdown of the parent minerals; (2) the removal in solution of some of the released constituents; and (3) the formation of secondary phases with components from the atmosphere (water, oxygen and carbon dioxide), from the parent rock and from shallower levels, and transported by the percolating solutions (Fritz and Ragland, 1980; Nesbitt, 1980; Chesworth et al., 1981 ). The purpose of this work is to investigate how major and trace elements behave during the weathering of granitic rocks from l~vora, Portugal. The prevailing climatic characteristics of this region are: 700 mm annual rainfall; dry summers; and a mean annual temperature of 16°C.

Clay mineral assemblages in weathered basalt profiles from central and southern Portugal: climatic significance

Abstract Mineralogical and chemical changes during weathering of basalts from central and southern Portugal were studied. Both regions have a temperate Mediterranean type climate, the Algarve being more arid. The areas concerned are the Lisbon (72 Ma) and the Runa Volcanic Complexes (100–70 Ma), and Rio Maior (160–130 Ma) in central Portugal, and Budens (170–180 Ma) in the south. The basalts are generally rich in olivine phenocrysts. Clay minerals are in general well crystallised and comprise smectites, associated with 1:1 minerals (principally halloysite), illite and palygorskite. Kaolin minerals prevail in topographic highs, whilst smectites predominate in lower areas. Smectites were analysed from the

New Data on Sixteen Reference Materials Obtained by INAA

We report instrumental neutron activation analysis results for 15 elements (K, Fe, Sc, Cr, Co, Zn, As, Rb, Sb, Cs, Ba, Hf, Ta, Th, and U) in 16 geochemical reference samples, namely SDC-1, SCo-1, SGR-1, STM-1, RGM-1, BIR-1, MAG-1 and BHVO-1 from USGS (United States Geological Survey, Reston), Soil-5, Soil-7 and SL-1 from IAEA (International Atomic Energy Agency, Vienna), and GSS-1, GSS-4, GSS-7, GSR-2 and GSR-3 from IGGE Institute of Geophysical and Geochemical Prospecting, Peoples Republic of China), The results are compared with literature values. In general our results agree well with recommended or proposed values.

REE distribution of present-day and ancient surface environments of basaltic rocks (central Portugal)

Abstract Rare earth elements are mobilized, fractionated and precipitated during weathering processes of basaltic rocks of the Lisbon Volcanic Complex. In general there is an increase in the REE contents in the whole samples with increasing weathering and fractionation between LREE and HREE. Cerium is partially oxidized and Ce4+ is retained resulting in negative Ce anomalies in the whole samples of the base and middle profile zones. In the clay fraction there is an increase in the REE contents from the top to the bottom of the profiles, except for Ce, giving rise to positive Ce anomalies in the top and negative anomalies of this element in the middle and bottom of the profiles. Significant positive Ce anomalies occur in the finer fractions of palaeoweathered (Upper Cretaceous/ Lower Eocene) basalts associated with low REE contents relative to the whole samples indicating more intense leaching conditions in the Upper Cretaceous/Lower Eocene than at the present day. However, in both cases no positive Ce anomalies were found in the whole samples. There appears to be a negative correlation between the (La/Yb)ch ratio variation and the clay mineralogy/drainage conditions.

New data on the GSJ reference rocks JB-1a and JG-1a by instrumental neutron activation analysis

Two reference rocks of the Geological Survey of Japan have been analyzed for Na, K, Sc, Cr, Fe, Co, Zn, Rb, Cs, Ba, La, Ce, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Ta, Th and U, using instrumental neutron activation analysis. The results are reported and compared with consensus values proposed in the literature. In general, the agreement is good except for Cs.

Interference from uranium fission products in the determination of rare earths, zirconium and ruthenium by instrumental neutron activation analysis in rocks and minerals

A numerical procedure is given to correct for the interference of U in the determination of the light rare earths, Zr, and Ru. The corresponding interference factors were calculated and their values compared with experimental results. The agreement is favourable in most cases.

Factor for correcting the ruthenium interference in instrumental neutron activation analysis of barium in uraniferous samples

The fission spectral interference of ruthenium on the instrumental neutron activation analysis of barium in samples containing uranium is extensively discussed. In particular the dependence of the correction factor on the phi epi/phi th ratio is studied. An excellent agreement between experimental and calculated values is achieved. A procedure is suggested for the resolution of multiple interferences in the general case where uranium, barium and/or ruthenium are present in samples to be analysed.

ELEMENTAL CONCENTRATION DATA FOR USGS GEOCHEMICAL EXPLORATION REFERENCE MATERIALS GXR-1 TO GXR-4 AND GXR-6

Instrumental neutron activation analysis, atomic absorption spectrometry and conventional methods were used on five USGS Geochemical Exploration Reference Materials: GXR-1, 2, 3, 4 and 6. The concentrations of 35 elements are reported and compared with available literature values. In general the agreement is good.

ANALYSIS OF THE CCRMP REFERENCE ROCKS SY-2, SY-3 AND MRG-1 BY INSTRUMENTAL NEUTRON ACTIVATION

Three Canadian reference rocks, syenites SY-2 and SY-3, and gabbro MRG-1 have been analysed for Na, K, Sc, Cr, Fe, Co, Zn, As, Rb, Cs, Ba, La, Ce, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Ta and Th, by instrumental neutron activation analysis. The results are reported and compared with “usable” values. In general the agreement is good.

Determination of the REE in environmental samples near a coal power station based on k0-standardized NAA with counting in a LEPD

The Ree contents in lichens and plants determined by k0-standardized NAA with LEPD and HPGe are compared. We obtain similar values for Sm, Eu, Tb and Yb and better values for Ce and Nd by using LEPD Besides, LEPD allows the determination of Gd, Tm and Lu. The study of REE concentrations in the neighbourhood of two coal power stations show that: i) in the station under construction (C. T. Pego), the index of accumulation of each REE by the lichens and olive tree leaves is identical in two sampling loci where the soils have different REE concentration; and ii) in the station in operation (C. T. Sines), the REE contents in the soils is identical and the differences observed in the lichens and wild terrestrial plants are most probably due to the fly-ashes emmission from the station.