Thermal Analysis of Waste Heat Recovery Systems Using CFD

The project statement is to optimize the heat transfer in a compact heat recovery unit (Heat Recovery and Emission Control Equipment - HREC) using CFD with application in day to day life. In general, the outgoing exhaust gasses are released to atmosphere at over temperature of the dew point of water vapor in waste gases. Recovering a portion of the waste heat enhances the efficiency of the equipment and as well reduce the emissions providing energy savings and green environment. In this study, the potential of recovering waste heat emitted by any heat generation units in common day to day life and in industry is considered. The Heat Recovery and Emission Control Equipment (HREC) acts an intermediate unit at the exit of hot gas generation unit & feed water heating unit. As a result of the calculation, it was determined that recovery of the waste heat can be employed at many applications as like as a combustion air preheater by means of a recuperator.

Reassessing groundwater potentials and subsurface water hydrochemistry in a Tropical Anambra Basin, Southeastern Nigeria

This review presented a detailed re-assessment of the hydrogeology and hydrochemistry of the Tropical Anambra Basin. It identified and discussed the major geological formations and their groundwater potentials. The geological examination showed that the Ajali Formation is confined in places forming an artesian condition; the potentials of this aquifer decline in the western basin due to a decrease in thickness. The sandstone associates of the Nsukka Formation are aquiferous and have produced high-pressure artesian boreholes along the Oji River. The Imo Shale is characterized by permeability stability all over much of the intermediate unit. The Bende-Ameki aquifer has a lesser amount of groundwater when equated to other formations; the geologic characteristics do not produce favorable hydrogeological conditions for groundwater occurrence. The stratigraphical and structural framework suggested the presence of an efficient throughflow in the basin. Based on physical and chemical parameters of water quality, the basin holds water of acceptable quality. While there are considerable investigations on the hydrogeology and hydrochemistry, studies are short of analysis of the hydrogeochemical evolution of groundwater, water quality index, heavy metals pollution index as well as total hazard quotient. Suitability of groundwater based on agricultural water quality indices (e.g. SAR) is also salient. Therefore, future studies should address these owing to increasing dependence on groundwater.

Abandoned Mine Tailings Affecting Riverbed Sediments in the Cartagena–La Union District, Mediterranean Coastal Area (Spain)

This study presents the results of the geoenvironmental characterization of La Matildes riverbed, affected by mine tailings in the Cartagena–La Unión district, Murcia (southeast Spain). Soils and riverbeds in this area are highly polluted. Two Electrical Resistivity Imaging (ERI) profiles were carried out to obtain information about the thickness of the deposits and their internal structure. For the mine tailings deposits of La Murla, a tributary of the El Miedo riverbed, the geophysical method imaged two different units: the upper one characterized by low resistivity values and 5–8 m thickness, correlated with the mine tailings deposits; and the lower more resistive unit corresponding to the Paleozoic metasediments bedrock. The ERI profile transverse to the Las Matildes dry riverbed revealed the existence of three different units. The uppermost one has the lowest resistivity values and corresponds to the tailings deposits discharged to the riverbeds. An intermediate unit, with intermediate resistivity values, corresponds to the riverbed sediments before the mining operations. The lower unit is more resistive and corresponds to the bedrock. Significant amounts of pyrite, sphalerite, and galena were found both in tailings and riverbed sediments. The geochemical composition of borehole samples from the riverbed materials shows significantly high contents of As, Cd, Cu, Fe, Pb, and Zn being released to the environment. Mining works have modified the natural landscape near La Unión town. Surface extraction in three open-pit mines have changed the summits of Sierra de Cartagena–La Unión. Rock and metallurgical wastes have altered the drainage pattern and buried the headwaters of ephemeral channels. The environmental hazards require remediation to minimize the environmental impact on the Mar Menor coastal lagoon, one of the most touristic areas in SE Spain.

Pressure-temperature conditions and significance of Upper Devonian eclogite and amphibolite facies metamorphisms in southern French Massif central

The southwestern French Massif central in western Rouergue displays an inverted metamorphic sequence with eclogite and amphibolite facies units forming the top of the nappe stack. They are often grouped into the leptyno-amphibolite complex included, in this area, at the base of the Upper Gneiss Unit. We sampled garnet micaschists and amphibolites to investigate their metamorphic history with isochemical phase diagrams, thermobarometry and U-Pb zircon dating. Our results demonstrate that two different tectono-metamorphic units can be distinguished. The Najac unit consists of biotite-poor phengite-garnet micaschists, a basic-ultrabasic intrusion containing retrogressed eclogites and phengite orthogneisses. Pressure and temperature estimates on micaschists with syn-kinematic garnets yield a prograde with garnet growth starting at 380 °C/6–7 kbar, peak pressure at 16 kbar for 570 °C, followed by retrogression in the greenschist facies. The age of high pressure metamorphism has been constrained in a recent publication between ca. 383 and 369 Ma. The Laguépie unit comprises garnet-free and garnet-bearing amphibolites with isolated lenses, veins or dykes of leucotonalitic gneiss. Thermobarometry and phase diagram calculation on a garnet amphibolite yield suprasolidus peak P-T conditions at 710 °C, 10 kbar followed by retrogression and deformation under greenschist and amphibolite facies conditions. New U-Pb analyses obtained on igneous zircon rims from a leucotonalitic gneiss yield an age of 363 ± 3 Ma, interpreted as the timing of zircon crystallization after incipient partial melting of the host amphibolite. The eclogitic Najac unit records the subduction of a continental margin during Upper Devonian. It is tentatively correlated to a Middle Allochthon, sandwiched between the Lower Gneiss Unit and the Upper Gneiss Unit. Such an intermediate unit is still poorly defined in the French Massif central but it can be a lateral equivalent of the Groix blueschists in the south Armorican massif. The Uppermost Devonian, amphibolite facies Laguépie unit correlates in terms of P-T-t evolution to the Upper Gneiss Unit in the Western French Massif central. This Late Devonian metamorphism is contemporaneous with active margin magmatism and confirms that the French Massif central belonged to the continental upper plate of an ocean-continent subduction system just before the stacking of Mississippian nappes.

Stratigraphy and Toarcian marine fauna (ammonites and brachiopods) of the South Rifian Ridges, northern Morocco

The South Rifian Ridges (25 km north of Meknes) corresponds to several small to medium size massifs with Triassic to Middle Jurassic (Bojocian) deposits widely covered by upper Miocene marls. Faugères (1978) has distinguished in this area three lithostratigraphic units equivalent to three paleogeographic domains, which are from the periphery to the center of the Jurassic basin: Peripheral unit, consisting of two formations: red silty clays with evaporates of Triassic (100m) and Liassic neritic limestones (100m); Intermediate unit, more complete, showing in addition of the two previous formations, a thick series (300m) of Toarcian to Middle Bajocian, constituted of silty marl-limestones, sandstones and bioclastic or oolitic limestones, often with benthic fauna; and Central unit, corresponding to the axial zone of the South Rifian basin, showing pelagic deposits from the lower Pliensbachian to the Middle Bajocian. In this unit, particularly to the east and the west of Jbel Dehar En Nsour anticline, Faugères (1974, 1978), and Elmi and Faugères (1974) reported some Toarcian ammonite specimens. For its pelagic facies often rich in ammonites, we were interested in the study of the Toarcian sequence and faunal assemblages of this unit. More than ten outcrop sections were sampled bed-by-bed. The main collected ammonite species: Calliphylloceras nilssoni, Cleviceras aff. exaratum, Dactylioceras laticostatum, D. simplex, D. (Orthodactylites) semicelatum, Juraphyllites (Meneghiniceras) lariense, Lioceratoides serotinus, Maconiceras soloniacense, Neolioceratoides schopeni, Protogrammoceras paltum and Harpoceratinae indet., allowed characterizing the Mirabile and Semicelatum subzones of the Polymorphum Zone and have already been described and illustrated in Bardin et al. (2015). Belemnite specimens: Passaloteuthis bisulcata and P. zieteni of the same stratigraphic levels were also the subject of the article, Sanders al. (2013) and a palynological study on the same sections was realized by Chahidi et al. (2016). Recent investigations allowed to collect a new interesting paleontological material composed of lower Toarcian pyritic ammonites and middle to upper Toarcian brachiopods (Rhynchonellidae, Zelleridae, and Terebratulidae), currently under study.

Stratigraphy and Toarcian marine fauna (ammonites and brachiopods) of the South Rifian Ridges, northern Morocco

The South Rifian Ridges (25 km north of Meknes) corresponds to several small to medium size massifs with Triassic to Middle Jurassic (Bojocian) deposits widely covered by upper Miocene marls. Faugères (1978) has distinguished in this area three lithostratigraphic units equivalent to three paleogeographic domains, which are from the periphery to the center of the Jurassic basin: Peripheral unit, consisting of two formations: red silty clays with evaporates of Triassic (100m) and Liassic neritic limestones (100m); Intermediate unit, more complete, showing in addition of the two previous formations, a thick series (300m) of Toarcian to Middle Bajocian, constituted of silty marl-limestones, sandstones and bioclastic or oolitic limestones, often with benthic fauna; and Central unit, corresponding to the axial zone of the South Rifian basin, showing pelagic deposits from the lower Pliensbachian to the Middle Bajocian. In this unit, particularly to the east and the west of Jbel Dehar En Nsour anticline, Faugères (1974, 1978), and Elmi and Faugères (1974) reported some Toarcian ammonite specimens. For its pelagic facies often rich in ammonites, we were interested in the study of the Toarcian sequence and faunal assemblages of this unit. More than ten outcrop sections were sampled bed-by-bed. The main collected ammonite species: Calliphylloceras nilssoni, Cleviceras aff. exaratum, Dactylioceras laticostatum, D. simplex, D. (Orthodactylites) semicelatum, Juraphyllites (Meneghiniceras) lariense, Lioceratoides serotinus, Maconiceras soloniacense, Neolioceratoides schopeni, Protogrammoceras paltum and Harpoceratinae indet., allowed characterizing the Mirabile and Semicelatum subzones of the Polymorphum Zone and have already been described and illustrated in Bardin et al. (2015). Belemnite specimens: Passaloteuthis bisulcata and P. zieteni of the same stratigraphic levels were also the subject of the article, Sanders al. (2013) and a palynological study on the same sections was realized by Chahidi et al. (2016). Recent investigations allowed to collect a new interesting paleontological material composed of lower Toarcian pyritic ammonites and middle to upper Toarcian brachiopods (Rhynchonellidae, Zelleridae, and Terebratulidae), currently under study.

The Central Atlantic Magmatic Province (CAMP) in Morocco

The Central Atlantic Magmatic Province (CAMP) is a large igneous province (LIP) composed of basic dykes, sills, layered intrusions and lava flows emplaced before Pangea break-up and currently distributed on the four continents surrounding the Atlantic Ocean. One of the oldest, best preserved and most complete sub-provinces of the CAMP is located in Morocco. Geochemical, geochronologic, petrographic and magnetostratigraphic data obtained in previous studies allowed identification of four strato-chemical magmatic units, i.e. the Lower, Intermediate, Upper and Recurrent units. For this study, we completed a detailed sampling of the CAMP in Morocco, from the Anti Atlas in the south to the Meseta in the north. We provide a complete mineralogical, petrologic (major and trace elements on whole-rocks and minerals), geochronologic (40Ar/39Ar and U–Pb ages) and geochemical set of data (including Sr–Nd–Pb–Os isotope systematics) for basaltic and basaltic–andesitic lava flow piles and for their presumed feeder dykes and sills. Combined with field observations, these data suggest a very rapid (<0·3 Ma) emplacement of over 95% of the preserved magmatic rocks. In particular, new and previously published data for the Lower to Upper unit samples yielded indistinguishable 40Ar/39Ar (mean age = 201·2 ± 0·8 Ma) and U–Pb ages (201·57 ± 0·04 Ma), suggesting emplacement coincident with the main phase of the end-Triassic biotic turnover (c.201·5 to 201·3 Ma). Eruptions are suggested to have been pulsed with rates in excess of 10 km3/year during five main volcanic pulses, each pulse possibly lasting only a few centuries. Such high eruption rates reinforce the likelihood that CAMP magmatism triggered the end-Triassic climate change and mass extinction. Only the Recurrent unit may have been younger but by no more than 1 Ma. Whole-rock and mineral geochemistry constrain the petrogenesis of the CAMP basalts. The Moroccan magmas evolved in mid-crustal reservoirs (7–20 km deep) where most of the differentiation occurred. However, a previous stage of crystallization probably occurred at even greater depths. The four units cannot be linked by closed-system fractional crystallization processes, but require distinct parental magmas and/or distinct crustal assimilation processes. EC-AFC modeling shows that limited crustal assimilation (maximum c.5–8% assimilation of e.g. Eburnean or Pan-African granites) could explain some, but not all the observed geochemical variations. Intermediate unit magmas are apparently the most contaminated and may have been derived from parental magmas similar to the Upper basalts (as attested by indistinguishable trace element contents in the augites analysed for these units). Chemical differences between Central High Atlas and Middle Atlas samples in the Intermediate unit could be explained by distinct crustal contaminants (lower crustal rocks or Pan-African granites for the former and Eburnean granites for the latter). The CAMP units in Morocco are likely derived from 5–10% melting of enriched peridotite sources. The differences observed in REE ratios for the four units are attributed to variations in both source mineralogy and melting degree. In particular, the Lower basalts require a garnet peridotite source, while the Upper basalts were probably formed from a shallower melting region straddling the garnet–spinel transition. Recurrent basalts instead are relatively shallow-level melts generated mainly from spinel peridotites. Sr–Nd–Pb–Os isotopic ratios in the CAMP units from Morocco are similar to those of other CAMP sub-provinces and suggest a significant enrichment of the mantle-source regions by subducted crustal components. The enriched signature is attributed to involvement of about 5–10% recycled crustal materials introduced into an ambient depleted or PREMA-type mantle, while involvement of mantle-plume components like those sampled by present-day Central Atlantic Ocean Island Basalts (OIB, e.g. Cape Verde and Canary Islands) is not supported by the observed compositions. Only Recurrent basalts may possibly reflect a Central Atlantic plume-like signature similar to the Common or FOZO components.

Origin and evolution of lago Yehuin (Tierra del Fuego, Argentina): Results from a geophysical survey

Lago Yehuin, a WNW-ESE elongated basin located in the outer fold-and-thrust belt of the Fuegian Andes, occupies a compartmented structural depression originated along a segment of the left-lateral Lago Deseado fault system. This paper describes the first geophysical survey performed within the lake. New acquired high-resolution single-channel seismic data, integrated with geological information in the surroundings of the Lago Yehuin, allowed to: (i) produce a complete bathymetric map of the lake, (ii) reconstruct the basement surface of the lake, and (iii) analyze the geometry, distribution, and thickness of the sedimentary infill. Two sub-basins were recognized within Lago Yehuin: A western sub-basin, 7.5 km long, with a maximum depth of 118 m; an eastern sub-basin, 7.2 km long with a maximum depth of 80 m. Both sub-basins are limited by a set of normal faults which overprint NE-verging thrusts. Three seismo-stratigraphic units have been identified in the seismic records: (1) a lower unit with wedged geometry interpreted as a mass flow deposits; (2) a thick (up to 120 m) intermediate unit of glacio-lacustrine nature and irregularly distributed in the Yehuin basin; (3) a thin (generally

The Geon 14 arc-related mafic rocks from the central Grenville Province

The late Paleoproterozoic to Mesoproterozoic (ca. 1.7–1.2 Ga) evolution of the active southeastern margin of Laurentia terminated with the Grenvillian continental collision and the development of a large, hot, long-duration orogen at ca. 1.09–0.98 Ga. As a result, much of the hinterland of the Grenville Province consists of Paleoproterozoic and Mesoproterozoic rocks, mostly preserved as an imbricate stack of high-grade gneisses, that represent a potential repository of active-margin processes. This study presents geochronologic, geochemical, and isotopic analyses of two granulite-facies suites of ca. 1.45–1.40 Ga mafic tholeiites from the Canyon domain (Manicouagan area, central Grenville Province). One suite consists of 1439 +76/–68 Ma high-FeTi mafic sills with εNd values of –0.4 (TDM 2.57–2.72 Ga), indicate derivation from variably depleted to enriched MORB-type mantle sources, probably in an extensional back-arc setting, before intrusion in a ca. 1.5 Ga supracrustal metasedimentary sequence. The other, previously dated, 1410 ± 16 Ma Mafic to intermediate unit exhibits εNd values of 0.0 to +0.9 (TDM 2.02–2.25 Ga), and variably enriched MORB to arc geochemical signatures, for which formation in a transitional back-arc to arc setting is suggested. Integrated with published information, the new data support a model of a long-lived continental-margin arc and intermittent back-arc development on southeast Laurentia during the mid-Mesoproterozoic (ca. 1.5–1.4 Ga), in which repeated short periods of extension and crustal thinning in the back-arc or intra-arc regions were followed by compression and crustal thickening.