Adolpho José Melfi

Continental Flood Volcanism From the Paraná Basin (Brazil)

In the past years study of the continental flood volcanism in the Parana basin had been mainly concentrated in the southern regions, where thick lava sequences are well exposed. Such research essentially concerned basic geology, petrography, radiometric dating and, subordinately, petrochemistry, isotope geochemistry and paleomagnetism (cf. Almeida, 1983; Amaral et al., 1966; Amaral and Crosta, 1983; Asmus and Baisch, 1983; Compston et al., 1968; Cordani et al., 1980; Creer et al., 1965; Ernesto, 1985; Ernesto et al., 1979; Fodor et al., 1985a, 1985b; Fulfaro et al., 1982; Halpern et al., 1974; Leinz et aL, 1966; McDougall and Ruegg, 1966; Mantovani et al., 1985a, 1985b; Marimon et al., 1983; Marques, 1983; Melfi, 1967; Minioli et al., 1971; Pacca and Hiodo, 1976; Pacca and Ernesto, 1982; Ruegg, 1976; Ruegg and Amaral, 1976; Sartori et al., 1975, 1982; Sartori and Gomes, 1980; Sartori and Filho, 1983; Souza, 1983).

Agricultural use of treated sewage effluents: agronomic and environmental implications and perspectives for Brazil

In many studies worldwide the use of treated sewage effluents (TSE) as water and nutrient sources in agricultural irrigation have been introduced as a viable alternative for wastewater destination in the environment. Considering agronomic and environmental aspects the objectives of this review were: (i) to present an overview of TSE irrigation on different agro-systems (annual crops, orchards, forests and forages); and (ii) to show the principal changes on chemical, physical and microbiological soil characteristics after TSE application. Various studies have revealed that the nutrient supply only by TSE irrigation was not sufficient to meet plant nutrient requirements resulting in yield decreases. The problem could be solved by an adapted effluent/fertilizer management. Moreover, TSE could generally substitute efficiently freshwater for irrigation. Regarding soil quality conditions, TSE irrigation affected mainly: (i) total soil carbon and nitrogen, and mineral nitrogen in soil solution; (ii) microbial activity, composition of microbial communities and their function; (iii) exchangeable calcium and magnesium; (iv) salinity, sodicity, clay dispersion and hydraulic conductivity. Other soil parameters considered in this review (e.g. heavy metals) did not present significant changes over short and medium terms. Due to the often observed accumulation of sodium and nitrogen losses (leaching, volatilization and denitrification) after TSE irrigation, the monitoring of these components is of crucial importance for a sustainable use. Finally, further studies on the technical-economical-environmental viability of TSE irrigation are required to establish reliable recommendations for TSE use particularly in Brazilian agro-systems.

Lower Cretaceous tholeiitic dyke swarms from the Ponta Grossa Arch (southeast Brazil): Petrology, Sr-Nd isotopes and genetic relationships with the Paraná flood volcanics

The Lower Cretaceous dykes of the Ponta Grossa Arch, the most important dyke swarms in Brazil, are associated with the flood basalts and rare acid flows of the northern Parana basin. The Ponta Grossa (PG) dykes are formed by two-pyroxene tholeiites and rare acid rocks. The basaltic dykes may be distinguished into two main groups: a dominant, high-TiO2 (> 2 wt.%; HTi) group and a subordinate, low-TiO2 (< 2 wt.%; LTi) group, characterized, for similar MgO content, by high and low incompatible-element contents, respectively. Most PG dykes do not show chemical and isotope evidence supporting important crustal contamination. PG dykes with (87Sr86Sr)0 < 0.7060 plot in the mantle array (ϵSr ≈ + 17 and ϵNd ≈ −3) and can be considered virtually uncontaminated. Intra-dyke chemical variations suggest that the normal or reverse differentiation trends may be related to pre-emplacement low-pressure differentiation processes. The important chemical differences between incompatible-element-poor and incompatible-element-rich basaltic dykes cannot be accounted for in terms of fractional crystallization, but are compatible with different melting degrees of a garnet peridotite mantle source, e.g. 9% and 20% melting for the HTi and LTi tholeiites, respectively. Field distribution of the magmatism, chemistry and Sr-Nd isotope compositions support that the PG dykes may be related to the flood volcanics of northern Parana, and not to those of the central and southern Parana. Paleomagnetic data indicate that PG dykes are younger than the Parana volcanics. All the results suggest that PG dykes were probably feeders of the stratoid volcanics erupted in northern Parana towards the continental margin and later eroded. Chemistry and isotopic data reveal that asthenospheric mantle components were not significant factors in the genesis of PG dykes. Dyke emplacement occurred during early phases of rifting and/or flexuring cutting flood volcanic suites.

Regional variations within the Paraná flood basalts (southern Brazil): Evidence for subcontinental mantle heterogeneity and crustal contamination

Abstract Continental flood volcanism of the Parana basin (Lower Cretaceous) is represented by two-pyroxene tholeiitic basalts (90 vol. %). The Northern Parana Province (NPP) is dominated by basalts high in TiO 2 and incompatible elements (HTiB), while the Southern Parana Province (SPP) is dominated by basalts low in TiO 2 and incompatible elements (LTiB). NPP basalts show relatively small variations of initial (120 Ma) 87 Sr 86 Sr ( R 0 ) and 143 Nd 144 Nd (Nd∗) ratios ( R 0 =0.7051−0.7062 and Nd ∗=0.5124−0.5125 , respectively) relative to those occurring in SPP ( R 0 =0.7046−0.7120 and Nd ∗=0.5122−0.5128 , respectively). The latter basalts show significant positive correlations between R 0 vs. SiO 2 , K 2 O, Rb and Ba, and negative correlations between R 0 vs. (Cr + Ni) and mg-value, believed to be due to crustal “granitic” contamination. In general, the effects of contamination are pronounced in SPP and tend to vanish towards NPP. δ 18 O-values range from +6.5 to +10.0‰ in the basalts from NPP and SPP and essentially reflect water-magma interactions. “Uncontaminated” LTiB and HTiB basalts from NPP are isotopically distinct from the “uncontaminated” analogues from SPP (LTiB) ( R 0 =0.7055 vs. 0.7046; Nd ∗=0.5124 vs. 0.5128, respectively). All chemical data consistently indicate distinct sources and a large-scale mantle heterogeneity. The NPP mantle source is expected to have relatively high content of “enriched” components, possibly related to small-volume melts and metasomatic fluids. Tentatively, the last stabilization age of the Parana mantle heterogeneity is 0.5–1.0 Ga old. The existence of high- and low-TiO 2 basalt suites in both Parana and Karoo provinces in Brazil and southern Africa, respectively, indicates a large-scale heterogeneity in the subcontinental mantle, and suggests that basalt generation occurred in the lithospheric mantle.

Behaviour of major and trace elements and fractionation of REE under tropical weathering of a typical apatite-rich carbonatite from Brazil

Abstract Detailed petrographical, mineralogical and geochemical studies have been carried out on a weathering profile developed on the phosphate-rich carbontite of Juquia(Brazil). Four weathering trends could be distinguished by means of the relationships between primary (apatites, dolomite, phlogopite, magnetite and barite) and secondary (apatites, gorceixite, wavellite, calcite and Fe Mn-oxyhydroxides) minerals. Local isovolumetric and isoelemental weathering processes allowed us to estimate chemical mass balances within some weathering trends. Except for Al in one profile, all the major and trace elements are mobile and transferred as a result of weathering of the primary minerals. The REE patterns of each primary/secondary mineral show that the weathering processes fractionate LREE and HREE. Relationships between REE content and the water/rock ratio may explain the various REE contents and distribution curves exhibited by the secondary minerals. Precipitation of secondary minerals in open microsystems (i.e., veins and fissures) appears to be associated with REE depletion and fractionation. In contrast, crystallization of secondary minerals within the intragranular micropores may result in a significant preservation of the REE content and distribution of the primary minerals being replaced. Moreover, poorly crystallized and flaky secondary minerals act as traps for REE.

Soils as an Important Sink for Mercury in the Amazon

This work focuses on the behaviour of mercury in lateritic soil profiles found in the Serra do Navio and Tartarugalzinhoareas of the State of Amapá in Northern Brazil. The Hg contents are high in the upper horizons of the soil profiles(100–300 μg kg-1), and decrease to less than 100 μg kg-1 at depths of 200 or 300 cm. The higher levels of Hg are associated with higher Fe concentrations, particularly in the ferruginous accumulations as mottles andnodules. For each horizon of the soil profile, balance calculations were used to distinguish the amount of mercury naturally accumulated from rocks through lateritic pedogenesis (lithogenic mercury) from the anthropogenic mercury introduced in the profile through atmospheric contamination. The results show that the anthropogenic contribution is significant in the upper horizons (up to 95%% of the total Hg), and decreases downward in the soil profile. Mercury burdens were calculated for soil profiles in both upslope (272 880 and 217 440 μg m-2 for the first 70 cm) and downslope positions (118 800 and 182 160 %μg m-2 for the first 70 cm). The loss of Hg in downslope profiles seems to be related to the natural evolution of iron duricrust into latossols, which has been brought about by climatic changes toward increasing humidityin the Amazon since the Tertiary.

Reclaimed wastewater: Impact on soil-plant system under tropical conditions

This study investigated the ionic speciation of reclaimed urban wastewater (RWW), and the impact of increasing RWW irrigation rates on soil properties and plant nutrition under field conditions. Most RWW elements (>66%) are readily available as NH(4)(+), Ca(2+), Mg(2+), K(+), SO(4)(2-), Cl(-), H(3)BO(3), Mn(2+) and Zn(2+), but in imbalanced proportion for plant nutrition. Lead, Cd, Cr and Al in RWW are mostly bounded with DOM or OH(-).(.)Irrigation with RWW decreased soil acidity, which is beneficial to the acidic tropical soil. Although RWW irrigation builds exchangeable Na(+) up, the excessive Na(+) was leached out of the soil profile after a rainy summer season (>400 mm). Benefits of the disposal of RWW to the soil under tropical conditions were discussed, however, the over irrigation with RWW (>100% of crop evapotranspiration) led to a nutritional imbalance, accumulating S and leading to a plant deficiency of P and K.

Potassium-argon ages for core samples of basaltic rocks from Southern Brazil☆

Abstract We present K-Ar ages for thirty-five basalt and diabase core samples, from drillings by Petrobras (Petroleo Brasileiro S.A.) in the Parana Basin. With one exception, where we separated and dated plagioclase from a coarser basalt, all samples were fine grained and wore dated by the whole-rock method. Microscopic examination, carried out in all cases prior to making the age determinations, showed that the core samples were essentially unaltered by weathering. The ages reported are susceptible to possible analytical error of about 2%. The results confirm ages for the Southern Brazil basaltic volcanism, previously reported from this laboratory but based principally upon surface samples. A histogram of the new ages shows a maximum near 130 m.y. Ages obtained for samples taken at different depths from the same drill hole did not show significant variations in age between successive lava flows, leading to the conclusion that in the same region, the lava flows were practically contemporaneous. However, significant variations in age, thought to be real, are found for different localities.

The Anari and Tapirapuã Jurassic formations, western Brazil: paleomagnetism, geochemistry and geochronology

The Anari and Tapirapua formations are very similar from the point of view of paleomagnetic, geochronological and geochemical results. They date from around 197 Ma and the flows are mainly tholeiitic basalts with a low TiO2 and incompatible element content. The magnetic carriers in rocks from these two formations were highly oxidized titanomagnetites, maghemites and, probably, titanomaghemites. Paleomagnetic analysis has shown that the magnetizations are all normal in polarity and virtual geomagnetic poles obtained for both formations are indistinguishable at the 95% confidence level. The calculated mean for these poles is 250.3°E, 65.5°S (N = 15; A95 = 3.6°; KSC = 1578). This pole is compatible with Jurassic poles which have been determined for South America or transposed from Africa.

Soil exchangeable cations, sugarcane production and nutrient uptake after wastewater irrigation

A irrigacao com aguas residuarias pode beneficiar as culturas agricolas com agua e nutrientes essenciais (especialmente nitrogenio), afetando tambem a quimica do solo. Os efeitos da irrigacao por 16 meses com efluente de esgoto na produtividade, extracao de nutrientes pelo colmo, e nos atributos quimicos do solo, foram estudados em um Latossolo cultivado com cana-de-acucar (Saccharum spp.), situado em Lins, Sao Paulo. As parcelas irrigadas receberam 50% do N mineral recomendado e 100, 125, 150 ou 200% da demanda hidrica da cultura, enquanto o controle nao recebeu N mineral e nem agua. As elevadas concentracoes de sodio do efluente ocasionaram um aporte de Na de ate 6,2 t ha-1, juntamente com ate 1497 kg N ha-1 e 628 kg K ha-1. Todas as parcelas irrigadas, com excecao do T125, apresentaram maior produtividade (ate 247 t ha-1) do que o controle (153 t ha-1). Quantidades expressivas de N (ate 597 kg ha-1) e de K (ate 546 kg ha-1) foram exportadas atraves da colheita da cultura. As adicoes de nutrientes e de Na via irrigacao nao foram compensadas pelo crescimento da planta, ocasionando uma baixa recuperacao de N, P, Ca e Na, evidenciando uma excessiva fertilizacao da planta (N). Alteracoes no solo de pH, H + Al, Ca, Mg e K, foram de pequena magnitude, enquanto houve acumulo de Na trocavel ao longo do tempo nos tratamentos irrigados. A irrigacao com aguas residuarias devera adquirir importância crescente, exigindo atencao detalhada ao balanco entre o aporte de nutrientes via irrigacao e as quantidades requeridas para a otimizacao da produtividade da cultura.A irrigacao com aguas residuarias pode beneficiar as culturas agricolas com agua e nutrientes essenciais (especialmente nitrogenio), afetando tambem a quimica do solo. Os efeitos da irrigacao por 16 meses com efluente de esgoto na produtividade, extracao de nutrientes pelo colmo, e nos atributos quimicos do solo, foram estudados em um Latossolo cultivado com cana-de-acucar (Saccharum spp.), situado em Lins, Sao Paulo. As parcelas irrigadas receberam 50% do N mineral recomendado e 100, 125, 150 ou 200% da demanda hidrica da cultura, enquanto o controle nao recebeu N mineral e nem agua. As elevadas concentracoes de sodio do efluente ocasionaram um aporte de Na de ate 6,2 t ha-1, juntamente com ate 1497 kg N ha-1 e 628 kg K ha-1. Todas as parcelas irrigadas, com excecao do T125, apresentaram maior produtividade (ate 247 t ha-1) do que o controle (153 t ha-1). Quantidades expressivas de N (ate 597 kg ha-1) e de K (ate 546 kg ha-1) foram exportadas atraves da colheita da cultura. As adicoes de nutrientes e de Na via irrigacao nao foram compensadas pelo crescimento da planta, ocasionando uma baixa recuperacao de N, P, Ca e Na, evidenciando uma excessiva fertilizacao da planta (N). Alteracoes no solo de pH, H + Al, Ca, Mg e K, foram de pequena magnitude, enquanto houve acumulo de Na trocavel ao longo do tempo nos tratamentos irrigados. A irrigacao com aguas residuarias devera adquirir importância crescente, exigindo atencao detalhada ao balanco entre o aporte de nutrientes via irrigacao e as quantidades requeridas para a otimizacao da produtividade da cultura.