Granitic weathering: a Brazilian study

Chemical and mineral studies were carried out on weathered materials from six profiles developed on granites located in different areas of Brazil. Quartz and K-feldspar are the most abundant minerals overall. Kaolinite is the most common secondary mineral and is principally a feldspar weathering product. Mica breakdown is associated with smectite formation in semi-arid regions. In more humid regions mica weathering products include interlayered mica-vermiculite, vermiculite and kaolinite. Changes in the concentrations of Si, Al and K reflect the weathering behaviour of quartz, kaolinite, K-feldspar respectively, although K mobilities sometimes appear to be governed by processes related to the formation of secondary minerals. Ca and Mg are the first elements to exhibit depletion and their removal rates are very fast relative to K. P is also among the most mobile elements. Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba and Pb concentrations were measured. The first row transition metals are the most depleted. Rb and Sr are retained relative to Na, Mg, and Ca, and Ba accumulates as weathering proceeds. Y, Zr, Nb and Pb concentrations show little variation. The conclusion is that the factors controlling deep leaching are complex and the common notion that weathering rates are higher at lower latitudes should be reassessed.     

Effect of natural organic soil solutes on weathering rates of soil minerals

The rate at which minerals in the soil weather is affected by pH and concentration of organic solutes (DOC). The rates of release of Al, Ca, Fe, K, Mg, Na, P and Si from a mineral soil sample to solutions of natural organic solutes and HCI (control) were determined at pH 3 and 4 for up to 17 weeks. Soil solutions were collected by centrifuging materials of O horizons from various soil types under four tree species (spruce, birch, oak, beech) and passed through a cation-exchange resin to yield H⁺-saturated organic solutes. The acceleration of the elements' release by the organic solutes was shown directly by the relative ligand effect (RLE), that is, the release rate in the organic solute solution divided by the release rate in the HCI solution (control) at the same pH. The RLE was greater at pH 4 than at pH 3, and it decreased for the elements in the order Fe > Ca > Mg > Al ≈ Si > K ≈ Na. This indicates that natural organic solutes are more important weathering agents at higher than lower pH and for weathering of mafic minerals rich in Ca, Fe and Mg than of felsic minerals such as K- and Na-feldspars. For all elements and at both pHs, RLE was strongly correlated with the concentration of DOC, which was also closely correlated with titratable acidity of the organic solutes. The important effect of soil type and tree species in producing weathering-promoting organic solutes therefore seems to be expressed through the concentration and not the composition of the organic soil solutes.     

Evaluation of the Impacts of Marine Salts and Asian Dust on the Forested Yakushima Island Ecosystem, a World Natural Heritage Site in Japan

To elucidate the influence of airborne materials on the ecosystem of Japan??s Yakushima Island, we determined the elemental compositions and Sr and Nd isotope ratios in streamwater, soils, vegetation, and rocks. Streamwater had high Na and Cl contents, low Ca and HCO₃ contents, and Na/Cl and Mg/Cl ratios close to those of seawater, but it had low pH (5.4 to 7.1), a higher Ca/Cl ratio than seawater, and distinct ⁸⁷Sr/⁸⁶Sr ratios that depended on the bedrock type. The proportions of rain-derived cations in streamwater, estimated by assuming that Cl was derived from sea salt aerosols, averaged 81?% for Na, 83?% for Mg, 36?% for K, 32?% for Ca, and 33?% for Sr. The Sr value was comparable to the 28?% estimated by comparing Sr isotope ratios between rain and granite bedrock. The soils are depleted in Ca, Na, P, and Sr compared with the parent materials. At Yotsuse in the northwestern side, plants and the soil pool have ⁸⁷Sr/⁸⁶Sr ratios similar to that of rainwater with a high sea salt component. In contrast, the Sr and Nd isotope ratios of soil minerals in the A and B horizons approach those of silicate minerals in northern China??s loess soils. The soil Ca and P depletion results largely from chemical weathering of plagioclase and of small amounts of apatite and calcite in granitic rocks. This suggests that Yakushima??s ecosystem is affected by large amounts of acidic precipitation with a high sea salt component, which leaches Ca and its proxy (Sr) from bedrock into streams, and by Asian dust-derived apatite, which is an important source of P in base cation-depleted soils.     

Rates and processes of mineral weathering in soils developed on greywackes and shales in the Southern Uplands of Scotland

Critical loads of acid deposition are exceeded in parts of the Southern Uplands of Scotland where base saturation in the topmost mineral horizons in many soils developed on greywackes and shales is <10%. Long-term weathering rates calculated by the elemental depletion method from nine soil profiles across a 200 km transect indicate losses of base cations in the range 4–31 meq m^?2a^?1. In every profile the most depleted base cation is Mg which is directly related to the weathering of chlorite which is often present at the 20–40% level in basal horizons but is often completely weathered out in E horizons. The second most depleted base cation is usually K, and this is clearly related to the weathering of mica to a vermiculitic mineral which, in the clay fractions, contains polymeric hydroxyaluminium in the interlamellar space if the soil pH is >4.3. The base cation least depleted is Ca and this is in sharp contrast to current weathering rates calculated from input-output budgets where Ca is the main base cation being exported. This discrepancy may be due to a contribution to the output from easily soluble Ca-bearing minerals (e.g. calcite) in narrow veins and fractures in the bedrock.     

Nitrogen and mineral composition of autumn‐grazed pasture

Abstract

Grazing management in autumn can influence the botanical composition and productivity of a sward. Cycling of nutrients as a result of grazing livestock activity and variable canopy growth rates may influence mineral nutrient supply and demand in a dynamic canopy. An experiment was conducted to determine the influence of autumn grazing practices on the growth and composition, including minerals in terms of ruminant requirements, of a grass/legume sward. Paddocks were established and three replicates grazed by growing lambs for 30‐, 60‐, or 90‐d intervals beginning in late summer. Herbage samples were collected at the beginning of the grazing interval and at the end of each interval (closing date). Herbage mass, and nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), and sulfur (S), as well as copper (Cu) and zinc (Zn) were examined in terms of the influence of sampling date, closing date, year, and the interaction of these factors from stockpiled and grazed canopies. Soil mineral composition was determined as well. Concentrations of all minerals declined with increasing soil depth and P, Na, Mg, and Ca increased in soil over the course of the experiment. Soil N concentration was reflected in the pattern of herbage growth in autumn. In general, closing date had no influence on herbage mineral composition and concentrations were within the recommended levels for a range of livestock. Phosphorus was the exception and concentrations in herbage were low in terms of requirements for high producing livestock such as lactating dairy cattle. Uptake or mineral reallocation within the plant remained constant during the autumn growth interval, since mineral yields were stable as growth rates declined in 1991 and increased when growth rates were stable in 1992. Mineral related nutritional problems in grazed mixed‐species pasture, would most likely be a function of mineral bioavailability or interactions, rather than low concentrations in the herbage.     

Changes caused by Norway spruce in an ochreous brown earth, assessed by the isoquartz method

Previous investigations had shown that about 80 years of Norway spruce monoculture on an ochreous brown earth of the Belgian Ardennes were sufficient to accentuate the weak podzolization process already present in the climax beechwood soil and to increase the weathering of several minerals, e.g. 2:2 clay minerals. In order to evaluate more accurately mineral weathering and spruce-induced losses of nutrient elements, an isoquartz assessment method has been applied to a pair of soil profiles, one developed under beech, the other under spruce.
Results show a clear decrease of several weatherable minerals in the soil of the spruce stand which was more marked than in the beechwood, especially for chloritic minerals: losses reach about 30% of the initial chlorite content in the cambic horizon and regularly increase up to 70% in the humic layer. There were severe spruce-induced losses of Mg and Na: 27% of the initial Mg reserve was removed from the whole soil and the losses reached 60% in the upper 20 cm.
It is concluded that 86 years of Norway spruce monoculture have appreciably increased weathering processes and removal of elements.     

Soil,forage, and serum nutrient changes as affected by deposition of volcanic sediments in northwestern nicaragua

Abstract

A study was carried out to determine the mineral status of grazing cattle as affected by the eruption of the Cerro Negro Volcano in northwestern Nicaragua. A total of 14 composite soil and forage samples and 30 blood samples were collected at each collection period, before (August 1991) and after (August 1992) the volcanic eruption. Higher soil levels of calcium (Ca), sodium (Na), manganese (Mn) (P<0.01), zinc (Zn) (P<0.05), and lower organic matter (OM) (P<0.01) were found after the volcanic eruption. Phosphorus (P) was the only macromineral found deficient with 93 and 71% of the samples below a critical level before and after volcanic eruption, respectively. Forage Ca, potassium (K), magnesium (Mg), P, Zn, copper (Cu), and selenium (Se) concentrations did not vary between collections. Forage crude protein (CP), in vitro organic matter digestibility [(IVOMD) P<0.05], cobalt (Co), Mn, and Na (P<0.01) were lower after the eruption. Iron (Fe) was the only mineral in forages that increased (P<0.01) after the volcanic eruption. Of the six minerals evaluated in serum only Ca and Mg concentrations were higher (P<0.05) after the volcanic eruption. The macrominerals more likely to be deficient in this area are P and Mg. Trace elements most likely to limit cattle productivity are Zn, Mn, Cu, Se, and Co. Special attention should be given to supplementation of Cu, since both plant and animal tissue samples reflected a deficiency of this mineral.     

Inductively coupled plasma optical emission spectrometric determination of minerals in thyme honeys and their contribution to geographical discrimination

Twenty-four Spanish thyme honey samples were analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES). Twenty-four minerals were quantified for each honey. The elements Al, As, Ba, Ca, Cr, Cu, Fe, K, Li, Mg, Mn, Na, P, Pb, S, Se, Si, Sr, and Zn were detected in all samples; seven elements are very abundant (Ca, K, Mg, Na, P, S, and Si), and six are not abundant (Al, Cu, Fe, Li, Mn, and Zn). Eleven of them are trace elements (As, Ba, Cd, Co, Cr, Ni, Mo, Pb, Se, Sr, and V) at <1 mg kg(-)(1). Classification of thyme honeys according to their origin (coast, mountains) was achieved by pattern recognition techniques on the mineral data. By means of principal component analysis, a good separation by geographical origin is obtained when scores for the two first principal components are plotted. Classification functions of 11 metals (Al, As, Cr, Cu, K, Li, Mg, Na, P, S, and V) were obtained using stepwise discriminant analysis and applied to classify correctly approximately 100% of the honey samples.     

Correlation analysis of mineral element contents and quality traits in milled rice (Oryza stavia L.)

The relationships among potassium (K), calcium (Ca), sodium (Na), magnesium (Mg), iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn) contents in milled rice (Oryza stavia L.) of 274 genotypes and the relationships between these mineral element contents and other rice quality traits including 3 cooking quality traits, 17 amino acid contents, and protein content were investigated. The results showed that there were significant correlations among most of mineral element contents. Mg, Fe, and Mn contents were significantly correlated with most of the other mineral element contents, while Cu content had significantly negative associations with the K and Mg contents of rice. The relationships between mineral element contents and cooking quality traits showed that gel consistency (GC) was significantly correlated with K, Cu, and Mn contents of rice. Amylose content (AC) was significantly associated with K, Na, Mg, Cu, and Mn contents. The alkali spreading value (ASV) had closely positive relationships with Ca, Mg, and Mn contents. In addition, 8 mineral element contents had obvious correlations with different amino acid contents. Mg, Ca, and Zn contents were significantly correlated with most of the 17 amino acid contents, but Na content did not correlate with amino acid contents except aspartic acid of rice. Furthermore, significant associations were found between protein content and Na, Mg, Zn, Cu, or Mn content. Six principal components were extracted to explain 84.50% of the total variances and contained the information provided by the original 29 variables according to the principal component analysis.     

Ca Depletion in the Soil Column on a Granite Substrate on the Island of Yakushima, a World Natural Heritage Site

We investigated the vertical profile of element distributions in the soil column on a granite substrate at three sites on the island of Yakushima, a world natural heritage site in southwestern Japan, where stream acidification due to acid rain is of increasing concern. Statistical analysis shows that the elements in the granitic soil can be classified into three groups according to their mineralogical derivations: Group 1 (K, Mg, Mn, Rb, and Nb), group 2 (Fe, Ti, Zr, Cr, and Pb), and group 3 (Ca, Na, Sr, and P), which are related to the presence of K-feldspar and K-mica, Fe-Ti oxides, and plagioclase and apatite, respectively. The pattern of distribution of group-1 elements in the soil column differs slightly among the sites because of differences in the proportions of K-feldspar and K-mica, The organic surface soil is enriched in group-2 elements and shows a strong magnetic susceptibility, indicating the presence of biogenetic magnetite. At all sites, Ca and Sr are intensely depleted due to the selective dissolution of plagioclase. Ca depletion compared to the original granite reaches more than 90 % in the C horizon, resulting in a decreasing capacity for the neutralization of acid rain and an increasing contribution of atmospheric Ca to the surface soil and vegetation.     

冬枣果实发育期结果枝叶与营养枝叶矿质元素动态变化的比较

对比研究冬枣果实发育期内结果枝叶和营养枝叶片矿质元素动态变化的差异性,可为制定冬枣不同类型叶片的营养诊断标准提供理论依据。以沾化冬枣为试验材料,比较研究了沾化冬枣不同果实发育阶段（始花期、盛花期、末花期、硬核期、完熟期）结果枝叶和营养枝叶中矿质元素N、P、K、Ca、Mg、Na的含量动态变化及其差异性。结果表明,冬枣果实发育过程中,自始花期至完熟期叶片N、P含量呈下降趋势,K含量呈逐渐增高趋势,而Ca及Mg含量则呈先增高后降低的变化趋势,叶片Na含量在果实发育过程中变化较小,只有在完熟期呈现突然增高现象。在上述各生长发育阶段内,结果枝叶K含量多大于营养枝叶,而N、P、Ca、Mg、Na含量则呈相反的变化规律。方差分析表明,在盛花期至末花期内,两种类型叶片Ca、Mg含量的差异均达到显著水平（P<0.05）,N含量只有在盛花期存在显著差异,而两种类型叶片K和Na含量在各果实发育阶段内均无显著差异。叶片元素含量比值分析表明,冬枣叶片N/P在盛花期至完熟期逐渐增高,其值均大于16,可知该阶段冬枣叶片生长主要受P元素限制;K/Na、Ca/Na、Mg/Na在果实发育期内的变化规律与K、Ca、Mg元素变化规律基本类似,在完熟期这3个比值均较前期明显降低。相关分析结果表明,冬枣叶片中N/P主要由P含量决定,Ca/Na、Mg/Na分别由Ca与Na、Mg与Na共同决定,而在营养枝叶中K/Na主要由Na含量决定。综上,盛花期至末花期（6—7月）是冬枣矿质元素相对稳定时期,可作为冬枣结果枝叶和营养枝叶营养诊断的适宜时期,同时冬枣结果枝叶该时期可适当施加适量Ca、Mg肥料,从而保证冬枣的果实品质和产量。     

Selection of cowpea genotypes based on grain mineral and total protein content

Grain legumes, including cowpea, are the cheapest sources of minerals and protein to enhance human nutrition. Cultivar development and deployment of cowpea with increased grain mineral content and protein composition rely on selection of genetically unique and complementary breeding lines. The objective of this study was to assess the grain minerals and protein composition of diverse cowpea collections of eastern, southern and western Africa to select promising parents to develop a breeding population. Twenty-two genetically diverse cowpea genotypes were field evaluated using a randomised complete block design with three replications in two locations in South Africa. The dried grain mineral contents were determined using an Atomic Absorption Spectrophotometre, while the protein content was determined by the combustion method. Analyses of variance showed significant (P?<?0.05) effects of genotypes, locations and their interactions. The test genotypes showed considerable variation for the following nine mineral contents: calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), phosphorus (P), and zinc (Zn) varying from 0.07 to 0.12?mg?kg^?1; 4.46 to 7.81?mg?kg^?1; 0.06 to 0.11?g; 11.82 to 14.45?g; 1.86 to 2.27?g; 9.24 to 13.30?mg?kg^?1; 0.26 to 0.80?g; 4.63 to 5.92?g and 0.03.00 to 0.05?g, respectively. Further, the total protein content varied from 23.16 to 28.13%. Significant correlations were detected among some mineral elements and total protein content, suggesting the possibility of simultaneous selection for these traits. The principal component analysis (PCA) identified four principal components (PCs) contributing to 70.93% of the total explained variation amongst genotypes. Overall the following genotypes with desirable grain mineral and protein attributes were selected: IT90K-59 (Ca), 98K-5301 (Ca and protein), ITOOK-1060 (Cu), ITOOK-1217 and IT845-2246 (Fe), Bensogla (K, Na, and P), TVU11424 and ITOOK-1217 (Mg), CH14 (Mn and Na), TVU12637 (Mn) and Glenda and Vuli (Zn). The selected cowpea genotypes are useful genetic resources for population and cultivar development for grain nutrients composition.     

Mineral imbalance in hevea brasiliensis micro‐cuttings: Relation with in vitro multiplication and acclimatization

The mineral composition of Hevea brasiliensis shoots was analyzed at different stages of the microcutting procedure from mother plants grown in greenhouses to rooted microcuttings at the acclimatization stage. Compared to the mineral status of the mother plants, a mineral imbalance was noticed in shoots right from the in vitro establishment phase. Phosphorus (P), potassium (K), sodium (Na), chloride (Cl), and zinc (Zn) contents increased, while calcium (Ca), magnesium (Mg), iron (Fe), and copper (Cu) diminished, resulting in a substantial modification to the mineral balance. The N: P, N: K, Mg: P and K: Na ratios were very low, whereas the K: Mg, K: P, and K: Ca ratios were very high. During the multiplication phase, the N: P ratio returned virtually to its initial value but the other ratios remained modified. A mineral analysis of shoots after three years multiplication in vitro revealed a very low N: P ratio, a very high K: Ca ratio and a normal K: Na ratio. The same results were obtained right from the initial culture cycles on shoots developed in vitro from mother plants with a high multiplication potential. These results are discussed and lead us to consider the N: P, K: Ca, and K: Na ratios as potential markers of Hevea brasiliensis multiplication ability in vitro. During the rooting phase, the Mg: P and K: Ca ratios returned to their normal values, whereas the other ratios returned to normal values on formation of the second leaf flush ex‐vitro.     

The Transfer of Chemical Elements within a Heath-Ecosystem (Calluna vulgaris) in Northwest Germany

The purpose of this investigation was to describe the element budget of a heathland area in Northwest Germany by measuring the fluxes of elements within the ecosystem. The following fluxes were considered: input by precipitation, canopy-drip, mineralisation, ion uptake, litterfall, output with seepage water. The elements H, Na, K, Ca, Mg, Mn, Fe, Al, S, P, CI, NO, NH, N_org were analysed, the period of investigation was one year. The results demonstrate the high importance of deposited nutrients like N (especially No3), Ca and Mg for the element budget and the stability of a heath-ecosystem. The internal turnover of K, Ca, Mg and Mn within the ecosystem mainly took place by leaching. No leaching was found for N, P, AI, Fe, S, CI, Na. For these elements litterfall was the dominant internal way of cycling. The humus layer was a sink for total-N, NO, Ca, Mg, Mn, Fe and S. NO, Ca, Mg, Mn and S were removed from the percolating solution, while for Fe and especially N and Mn an inhibition of mineralisation was found. The element balance for the mineral soil showed that this part is a sink for Hand a source mainly for Al, Ca and Mg, less for K and Na. From the cation/anion balance of the storage changes in mineral soil the ecosystem-internal H ion production was calculated as 0.4 keq per ha and year. It may be traced back to an uptake of NH, and dissociation of fulvic acids in the mineral soil. The results are discussed with respect to the development, stability and management of heath-ecosystems.     

Identification of introgression lines of Oryza glaberrima Steud. with high mineral content in grains

Mineral concentrations in cereals are crucial for human health, especially for people who consume cereals as a subsistence diet. Although rice (Oryza sativa L.) is one of most important staple crops in the world, starch constitutes a large portion of its grains, and mineral concentrations are lower than in other staple crops. One solution is the improvement of mineral concentrations in rice grains through biofortification, and this approach requires investigation of genetic resources that confer high mineral concentrations to rice grains. In the present study, we performed 2 years of field experiments, in 2012 and 2013, and determined sodium (Na), magnesium (Mg), phosphorus (P), potassium (K), calcium (Ca), boron (B), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn) and molybdenum (Mo) concentrations in the rice grains of 40 introgression lines derived from a cross between a japonica cultivar, Taichung 65 (T65), and African rice, Oryza glaberrima Steud. Substantial variation in mineral concentrations was observed among the 40 introgression lines. We selected several elite lines that had significantly higher concentrations of minerals, including Fe, Cu, Zn, Mo, Mg, P and Ca than the cultivated rice T65. These lines could be novel potential materials for breeding programs for biofortification and provide us with positional information for the candidate loci in the O. glaberrima genome responsible for high mineral concentrations in rice grains.     

Influence of Nitrogen and Saline Water on the Growth and Partitioning of Mineral Content in Maize

ABSTRACT

Saline irrigation water has a tremendous impact on the yield potential of crops. Distribution of mineral elements in the parts of maize plant in response to saline water and nitrogen (N) nutrition was studied in a pot experiment for six weeks. Plants were irrigated either with tap water or saline water (ECw: 3.2 dSm^?1). Nitrogen was applied at the rate of 0, 50, 100 and 200-kg ha^?1 denoted as N0, N1, N2, and N3, respectively. Plants were separated into leaf, stem and root and analyzed for N, calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K) concentrations. Dry matter production of leaf, stem and root was significantly reduced with saline water. The partitioning of elements in plants was the function of nitrogen and saline water. The N concentration of plant parts varied in the order of leaf > stem > root. A significant decrease in the N content was noted in plants under saline water. The root contained the highest Na content, Ca and Mg were higher in the leaf, whereas K was highest in the stem under saline water. Sodium was highest in the root and the remainder elements were greatest in the stem under tap water. Potassium and Cl were significantly reduced by N level whereas the reverse was true for Ca, Mg and Na content. The Na/K, Na/Ca, and Na/Mg ratios were also higher in salt stressed plant parts due to higher accumulation of Na ion. Among N-fertilizer treatments the Na/Ca and Na/Mg ratios were highest in control whereas Na/K increased with the addition of N. This study indicated that interaction of saline water and nitrogen has mixed effects on the partitioning of mineral elements in maize.     

Maturity effects on mineral concentration and uptake in Solanum nigrum L.

The revitalisation of wild vegetables by consuming and cultivating them in home gardens is one of the strategies that agriculturalists have recently identified to combat food insecurity. However, data on mineral uptake with maturity are not available for a larger majority of wild vegetables. S. nigrum, one of the popular wild vegetables consumed in the Eastern Cape Province of South Africa, was cultivated both on the field and glasshouse to gain a better understanding of the uptake of some macrominerals as the plant matures. Five treatments (control; 100 kg N/ha; 8.13 t manure/ha; 100 kg N/ha + 8.13 t manure/ha and 50 kg N/ha + 4.07 t manure/ha) were set up in a Randomised Complete Block Design in both trials. The data were subjected to analysis of variance using MINITAB statistical software package. K (%) ranged between 3.11–6.98 in the glasshouse and 3.88–6.98 on the field; Ca (%) between 1.23–3.72 in the glasshouse and 1.39–3.98 on the field; Mg (%) between 0.31–0.93 in the glasshouse and 0.48–0.82 on the field; P (mg/kg) between 0.23–0.80 in the glasshouse and 0.29–0.77 on the field and Na (mg/kg) ranged between 749–3070 in the glasshouse and 187–3070 on the field. The application of 50 kg N/ha + 4.07 t manure/ha increased the uptake of a majority of the minerals. K, P and Na decreased with maturity while Ca increased and Mg varied. Although the current results indicate that for K, P and Na nutritional interventions, the leaves of S. nigrum are best harvested during the early phase of growth and the final phase for Ca, the concentration of these minerals has the potential to supply sufficient quantities of the minerals in human physiology at all stages of the plant's growth. This wild vegetable is therefore recommended for both consumption and cultivation.     

Differential weathering of granitic stocks and landscape effects in a Mediterranean climate,Southern Iberian Massif (Spain)

Mineralogical and structural features control the weathering processes and landform development of two different crystalline stocks in the Iberian Massif, Spain (the Santa Elena and Linares stocks). The Santa Elena stock shows irregular saprolite profiles and boulder landforms whereas the Linares stock develops broad and plain landscapes with uniform saprolites and less boulder forms. The Santa Elena stock is more closely jointed and fractured than the Linares body. The main secondary minerals are kaolinite, and illite; illite/smectite interstratification was only observed in deep samples from the Linares profile. The Linares profile is feldspar-enriched whereas in Santa Elena plagioclase is almost absent and clay mineral content, especially kaolinite, is higher. Feldspars show dissolution channels developed along cleavage planes filled by clay minerals. Biotite–kaolinite intergrowths have fanned-out textures of epitaxial disposition. Weathered materials are enriched in Al and H₂O and Fe, and depleted in Ca, Na, Mg, Ti, P. The Santa Elena weathered materials are richer in H₂O than those from Linares and have lower Si/Al ratios. Mineralogical and geochemical evidence indicate the Santa Elena materials are more intensely weathered. High fracturation and high Ca-richer plagioclase contents are key factors producing the pervasive Santa Elena stock weathering. Fluvial erosion removed the alteration products in incised tectonically controlled streams resulting in boulder accumulation.     

Verwitterungsverhalten silikatischer Gesteinsmehle unter Laborbedingungen

Artificial weathering of silicate rock powders The weathering properties of rock powders of different geological origin were investigated under laboratory conditions. Extraction media were water and hydrochloric acid (1N). The parameters measured were pH-value and (under the point of view of plant nutrition) the macro elements Ca, Mg, K and Na as well as the trace elements Fe, Mn, Cu and Zn. Of the tested rocks, basalt, diabas, phonolite, lava and granite, the basic origins are characterized by a high release of Ca, Mg and Fe, phonolite by a noticeable release of Na, and lava by a significant mobility of K. Mn was extracted to greater extent than Cu and Zn. The price level of some rock powders is shown and discussed with special reference to the presented data of nutrient release.