The Manso Glacier drainage system in the northern Patagonian Andes: an overview of its main hydrological characteristics

The Manso Glacier (~41°S, 72°W), in the northern Patagonian Andes of Argentina, is a regenerated glacier that, like many other glaciers in the region and elsewhere, has been showing a significant retreat. Glacial melt water feeds the Manso Superior River, which, before crossing the Andes to reach a Pacific outfall, flows through the Mascardi (a deep, oligotrophic and monomictic lake) and significantly smaller Hess and Steffen lakes. Harmonic analysis of Mascardi's lake level series suggests that the El Niño‐Southern Oscillation signal has been strong during the 1985–1995 decade but has grown weaker during the initial decade of the 21st century. Hydrological trend analyses applied in data recorded in the uppermost reaches show a monthly and annual decreasing trend in the Manso Superior River discharge series and Mascardi's lake level, which are connected with both, decreasing melt water discharge and (austral) wintertime atmospheric precipitation. Downstream, the decreasing signal initially looses statistical significance and then, when flowing through Steffen Lake, reverses the lake level trend that becomes significantly positive. This suggests that, on its way to the Pacific Ocean, the Manso River receives abundant Andean snow melt water and atmospheric precipitation, which are sufficient to obliterate the negative trend recorded in the uppermost reaches. The reason for this local phenomenon is that the Manso is an antecedent river (aka superposed stream), and hence, the valley crossing the Andes allows the incursion of Pacific humidity that modifies the hydrological regime several hundred kilometres inland. Copyright © 2012 John Wiley & Sons, Ltd.     

Magmatic and post-magmatic evolution of post-collisional rare-metal bearing granite: The Neoproterozoic Homrit Akarem Granitic Intrusion,south Eastern Desert of Egypt,Arabian-Nubian Shield

The Homrit Akarem granitic intrusion (HAGI) outcrops near the western edge of the south Eastern Desert basement exposure in Egypt. It is a composite of two cogenetic intrusive bodies: an early albite granite phase shallowly emplaced at the apex of a magmatic cupola, and a later subjacent pink granite phase with a marginal zone of muscovite granite and better preservation of magmatic features. Mineral chemistry of primary biotite and garnet, together with whole-rock chemistry, identify the HAGI as a highly fractionated A-type peraluminous intrusion. The chemistry of F-dominant, Li-bearing, Fe³⁺-rich primary magmatic mica in the pink granite resembles that typically found in highly evolved Nb-Y-F pegmatites. The HAGI is the evolved product of a primary magma generated by partial melting of juvenile crust of the Arabian-Nubian Shield (ANS), emplaced along a regional strike-slip fault system that promoted its ascent. The main emplacement mechanism and evolutionary sequence of the HAGI was magmatic, although secondary minerals and textures resulting from hydrothermal fluid interactions are observed, especially at its margins. Primary columbite-(Mn) crystallized from melt and was partly replaced by secondary fluorcalciomicrolite. The high fluorine content of magmatic fluids exsolved from the intrusion is indicated by quartz-fluorite veins, greisenization, albitization, and F-bearing secondary oxide minerals. The magmatic derivation of this fluid is demonstrated by the F-dominant primary mica, a siderophyllite-polylithionite solid solution commonly known as zinnwaldite. The chemistry of zinnwaldite constrains the F/OH activity ratio and oxygen fugacity of its parental melt and thereby resolves the ambiguity between pressure and the effects of F in controlling the normative quartz content of rare-metal granites. The HAGI is less mineralized than the post-collisional rare-metal granites found further east in the south Eastern Desert, replicating a trend observed previously in the central Eastern Desert and suggesting that east-west zoning in rare metal enrichment is a persistent feature across latitudes at the western edge of the ANS.     

Geology,petrology and geochemistry of the “Americano do Brasil” layered intrusion,central Brazil,and its Ni–Cu sulfide deposits

The “Americano do Brasil” Complex (ABC) is part of a cluster of coeval synorogenic mafic–ultramafic intrusions emplaced during the Brasiliano/Pan-African Orogenic Cycle in Brazil. The medium-sized ABC consists of interlayered dunite, peridotite, websterite, and gabbronorite. High Fo values of olivine (up to Fo₈₈) and the crystallization sequence of the ABC (Ol + Chr ≥ Ol + Opx + Chr ≥ Cpx + Opx ≥ Opx + Pl + Cpx ≥ Opx + Pl + Cpx + Ilm + Mag) suggest crystallization from tholeiitic high-MgO parental magmas. Light rare earth element (REE)-enriched mantle-normalized REE profiles and εNd(T) values of +2.4 for cumulate rocks from the ABC suggest a depleted mantle source for the parental magma. The ABC Ni–Cu sulfide deposit (3.1 Mt at 1.12 wt.% Ni and 1.02 wt.% Cu) consists of three distinctively different orebodies (S1, S2, and G2). The S2 orebody, an unusual occurrence of stratiform massive sulfide hosted by dunite and peridotite in the interior of a layered intrusion, results from sulfides accumulated at the transient base of the magma chamber following a new influx of parental magma. The G2 orebody has an irregular and roughly cylindrical shape, consisting mainly of net-textured sulfides. The G2 orebody is hosted by peridotite and pyroxenite and located stratigraphically below the S1 orebody. S2 and G2 orebodies are characterized by low Cu/Cu + Ni ratios (mainly below 0.4). The S1 orebody, hosted by websterite and gabbronorite in the more fractionated sequence of the ABC, is a cluster of several irregular discontinuous orebodies of Ni–Cu disseminated sulfides. The sulfides of the S1 orebody have high Cu/Cu + Ni ratios (mainly between 0.5 and 0.8) and are highly depleted in PGE. The S1 orebody is interpreted to result from a later event of sulfide segregation in the magma chamber, possibly following the event that originated the G2 orebody. The bulk of δ³⁴S values for sulfides of the ABC orebodies and their host rocks fall in the range of 0 ± 2‰. Higher δ³⁴S values (between 3‰ and 5‰) are restricted to pyrite from xenoliths of gneiss located close to the S1 orebody and sulfides from the S1 orebody. Crustal xenoliths and chemical data (lithogeochemistry and sulfur isotope composition) provide evidence of crustal contamination of the igneous rocks hosting the S1 orebody, suggesting that sulfur saturation was induced by contamination with sulfide-bearing crustal rocks. The ABC deposit is an example of Ni–Cu sulfide mineralization hosted by synorogenic mafic–ultramafic intrusions. The S2 orebody is the first documented example of an economic stratiform massive sulfide orebody located within layered intrusions, expanding the opportunities for exploration of Ni–Cu sulfides in orogenic regions worldwide.     

The Catalão I niobium deposit, central Brazil: Resources, geology and pyrochlore chemistry

The Catalão I alkaline–carbonatite–phoscorite complex contains both fresh rock and residual (weathering-related) niobium mineralization. The fresh rock niobium deposit consists of two plug-shaped orebodies named Mine II and East Area, respectively emplaced in carbonatite and phlogopitite. Together, these orebodies contain 29 Mt at 1.22 wt.% Nb₂O₅ (measured and indicated). In closer detail, the orebodies consist of dike swarms of pyrochlore-bearing, olivine-free phoscorite-series rocks (nelsonite) that can be either apatite-rich (P2 unit) or magnetite-rich (P3 unit). Dolomite carbonatite (DC) is intimately related with nelsonite. Natropyrochlore and calciopyrochlore are the most abundant niobium phases in the fresh rock deposit. Pyrochlore supergroup chemistry shows a compositional trend from Ca–Na dominant pyrochlores toward Ba-enriched kenopyrochlore in fresh rock and the dominance of Ba-rich kenopyrochlore in the residual deposit. Carbonates associated with Ba-, Sr-enriched pyrochlore show higher δ¹⁸O_SMOW than expected for carbonates crystallizing from mantle-derived magmas. We interpret both the δ¹⁸O_SMOW and pyrochlore chemistry variations from the original composition as evidence of interaction with low-temperature fluids which, albeit not responsible for the mineralization, modified its magmatic isotopic features. The origin of the Catalão I niobium deposit is related to carbonatite magmatism but the process that generated such niobium-rich rocks is still undetermined and might be related to crystal accumulation and/or emplacement of a phosphate–iron-oxide magma.     

Anthropogenic heat in the city of S?o Paulo, Brazil

The main goal of this work is to describe the anthropogenic energy flux (Q _F) in the city of S?o Paulo, Brazil. The hourly, monthly, and annual values of the anthropogenic energy flux are estimated using the inventory method, and the contributions of vehicular, stationary, and human metabolism sources from 2004 to 2007 are considered. The vehicular and stationary sources are evaluated using the primary consumption of energy based on fossil fuel, bio fuel, and electricity usage by the population. The diurnal evolution of the anthropogenic energy flux shows three relative maxima, with the largest maxima occurring early in the morning (??19.9 Wm^?2) and in the late afternoon (??20.3 Wm^?2). The relative maximum that occurs around noontime (??19.6 Wm^?2) reflects the diurnal pattern of vehicle traffic that seems to be specific to S?o Paulo. With respect to diurnal evolution, the energy flux released by vehicular sources (Q _FV) contributes approximately 50% of the total anthropogenic energy flux. Stationary sources (Q _FS) and human metabolism (Q _FM) represent about 41% and 9% of the anthropogenic energy flux, respectively. For 2007, the monthly values of Q _FV, Q _FS, Q _FM, and Q _F are, respectively, 16.8?±?0.25, 14.3?±?0.16, 3.5?±?0.03, and 34.6?±?0.41?MJ?m^?2?month^?1. The seasonal evolution monthly values of Q _FV, Q _FS, Q _FM, and Q _F show a relative minimum during the summer and winter vacations and a systematic and progressive increase associated with the seasonal evolution of the economic activity in S?o Paulo. The annual evolution of Q _F indicates that the city of S?o Paulo released 355.2?MJ?m^?2?year^?1 in 2004 and 415.5?MJ?m^?2?year^?1 in 2007 in association with an annual rate of increase of 19.6?MJ?m^?2?year^?1 (from 2004 to 2006) and 30.5?MJ?m^?2?year^?1 (from 2006 to 2007). The anthropogenic energy flux corresponds to about 9% of the net radiation at the surface in the summer and 15% in the winter. The amplitude of seasonal variation of the maximum hourly value of the diurnal variation increases exponentially with latitude.     

Recent climate variability and its impacts on soybean yields in Southern Brazil

Recent climate variability in rainfall, temperatures (maximum and minimum), and the diurnal temperature range is studied with emphasis on its influence over soybean yields in southern Brazil, during 1969 to 2002. The results showed that the soybean (Glycine max L. Merril) yields are more affected by changes in temperature during summer, while changes in rainfall are more important during the beginning of plantation and at its peak of development. Furthermore, soybean yields in Paraná are more sensitive to rainfall variations, while soybean yields in the Rio Grande do Sul are more sensitive to variations in temperature. Effects of interannual climatic variability on soybean yields are evaluated through three agro-meteorological models: additive Stewart, multiplicative Rao, and multiplicative Jensen. The Jensen model is able to reproduce the interannual behavior of soybean yield reasonably well.     

Long‐term morphological impacts of the opening of a new inlet on a multiple inlet system

In this study, the artificial opening of a new tidal inlet in an existing multiple inlet system is shown to significantly modify the adjacent nearshore and backbarrier morphology, as well as both updrift and downdrift shorelines. The study focuses on the dominant Faro‐Olhão and Armona inlets in the Ria Formosa barrier island system of southern Portugal. The equilibrium state and future evolution of the system are inferred using a range of morphological and hydrodynamic indicators, including the evolution of the inlet cross‐section, changes in tidal prism, and changes in the dimensions (length and area) of barrier islands. The results reveal how the morphology of an interconnected two‐inlet bay system and the adjacent coastlines has evolved following the artificial opening and stabilization of Faro‐Olhão inlet since 1929. A clear relationship between barrier island size, inlet cross‐section/width, and tidal prism is demonstrated. Decadal time‐scale changes in the tidal prism of the two interconnected inlets are shown to be the main mechanism responsible for morphological change, and have resulted in the remobilization of ebb‐tidal delta sediments deposited during previous hydraulic configurations. These changes, in turn, have contributed to a narrowing of Armona inlet and an increase in the size of Culatra Island. The work highlights the importance of ebb‐tidal deltas both as sand reservoirs and as conduits through which sand exchange between estuaries or lagoons and the open coast is regulated. It also shows the pivotal role of ebb‐tidal deltas in trapping longshore‐transported sediment and releasing it again during periods of increased wave activity. The findings have implications regarding the accurate assessment of the stability of multiple inlet systems. Copyright © 2011 John Wiley & Sons, Ltd.