Solidification of the Earth’s core: The main energy source in the formation of trappean provinces and flood basalts

The discovery of a layer of increased density in the liquid core at the boundary with the solid core gives grounds to suggest that solidification of the solid core occurs with an increase in total core volume and is accompanied by an increase in internal pressure in the core. This makes it possible to suggest a translational mechanism of energy transfer from the core to the Earth’s surface. It is suggested that the restoration of lithostatic equilibrium occurs via rising of a column of mantle material, uplift as result of elastic mantle deformation of the boundary of the transition layer at a depth of 420 km, and the formation of rising at the surface.     

Morphotectonic study of two regions in the Centre-South Segment of Spain: Córdoba and Granada

The morphotectonics of Córdoba and Granada are differentiated using the Rantsman method [53]. Over 40 quantitative geomorphologic indicators are used in the systemic classification. Both areas are included in what are known as the macroblocks no. 1 (Southern) and no. 2 (Sub-Western 2A) of the Iberian Peninsula megablock. The qua ntities of the four lowest order Territorial Units defined for Córdoba/Granada are: mesoblocks (4/4), blocks (9/9), microblocks (15/35) and nanoblocks (64/83). The main lineaments/intersections determined in Córdoba total 16/1041 and in Granada 25/633, A series of seven morphostructural scarps is found in both areas, along with important modifications (inflections) in some river beds. Some of the structures described are seismicity-related. Córdoba displays less activity than Granada. Between the towns of Loja, Beas de Granada, and Lentejí a seismoactive sector (～820 km²) with blocks B2, B3, B5, and B6 forms the area where the deep earthquakes are concentrated.     

Bimodal magmatism of the Tucumã area,Carajás province: U-Pb geochronology,classification and processes

Geological mapping of the Tucumã area has enabled the identification of dike swarms intruded into an Archean basement. The disposition of these dikes is consistent with the well-defined NW-SE trending regional faults, and they can reach up to 20 km in length. They were divided into three main groups: (i) felsic dikes (70% of the dikes), composed exclusively of porphyritic rhyolite with euhedral phenocrysts of quartz and feldspars immersed in an aphyric felsite matrix; (ii) mafic dikes, with restricted occurrence, composed of basaltic andesite and subordinate basalt, with a mineralogical assembly consisting dominantly of plagioclase, clinopyroxene, orthopyroxene and olivine; and (iii) intermediate rocks, represented by andesite and dacite. Dacites are found in outcrops associated with felsic dikes, representing different degrees of hybridization or mixture of mafic and felsic magmas. This is evidenced by a large number of mafic enclaves in the felsic dikes and the frequent presence of embayment textures. SHRIMP U-Pb zircon dating of felsic dikes yielded an age of 1880.9 ± 3.3 Ma. The felsic dikes are peraluminous to slightly metaluminous and akin to A2, ferroan and reduced granites. The intermediate and mafic dikes are metaluminous and belong to the tholeiitic series. Geochemical modeling showed that mafic rocks evolved by pyroxene and plagioclase crystallization, while K-feldspar and biotite are the fractionate phases in felsic magma. A simple binary mixture model was used to determine the origin of intermediate rocks. It indicated that mixing 60% of rhyolite and 40% basaltic andesite melts could have generated the dacitic composition, while the andesite liquid could be produced by mixing of 60% and 40% basaltic andesite and rhyolite melts, respectively. The mixing of basaltic and andesitic magmas probably occurred during ascent and storage in the crust, where andesite dikes are likely produced by a more homogeneous mixture at high depths in the continental crust (mixing), while dacite dikes can be generated in the upper crust at a lower temperature, providing a less efficient mixing process (mingling). The affinities observed between the felsic to intermediate rocks of the Rio Maria and São Felix do Xingu areas and the bimodal magmatism of the Tucumã area reinforce the hypothesis that in the Paleoproterozoic the Carajás province was affected by processes involving thermal perturbations in the upper mantle, mafic underplating, and associated crustal extension or transtension. The 1.88 Ga fissure-controlled A-type magmatism of the Tucumã area was emplaced ∼1.0 to ∼0.65 Ga after stabilization of the Archean crust. Its origin is not related to subduction processes but to the disruption of the supercontinent at the end of the Paleoproterozoic.     

Magmatic–hydrothermal processes in Sangdong W–Mo deposit,Korea: Study of fluid inclusions and 39Ar–40Ar geochronology

The Sangdong scheelite–molybdenite deposit in northeast South Korea consists of strata-bound orebodies in intercalated carbonate-rich layers in the Cambrian Myobong slate formation. Among them, the M1 layer hosts the main orebody below which lie layers of F1–F4 host footwall orebodies. Each layer was first skarnized with the formation of a wollastonite + garnet + pyroxene assemblage hosting minor disseminated scheelite. The central parts of the layers were subsequently crosscut by two series of quartz veining events hosting minor scheelite and major scheelite–molybdenite ores, respectively. The former veins associate amphibole–magnetite (amphibole) alteration, whereas the latter veins host quartz–biotite–muscovite (mica) alteration. Deep quartz veins with molybdenite mineralization are hosted in the Cambrian Jangsan quartzite formation beneath the Myobong formation. In the Sunbawi area, which is in close proximity to the Sangdong deposit, quartz veins with scheelite mineralization are hosted in Precambrian metamorphic basement. Three muscovite ³⁹Ar–⁴⁰Ar ages between 86.6 ± 0.2 and 87.2 ± 0.3 Ma were obtained from M1 and F2 orebodies from the Sangdong deposit and Sunbawi quartz veins. The Upper Cretaceous age of the orebodies is concordant with the published ages of the hidden Sangdong granite, 87.5 ± 4.5 Ma. This strongly suggests that the intrusion is causative for the Sangdong W–Mo ores and Sunbawi veins.Fluid inclusions in the quartz veins from the M1 and F2 orebodies, the deep quartz-molybdenite veins, and the Sunbawi veins are commonly liquid-rich aqueous inclusions having bubble sizes of 10–30 vol%, apparent salinities of 2–8 wt% NaCl eqv., and homogenization temperatures of 180–350 °C. The densities of the aqueous inclusions are 0.70–0.94 g/cm³. No indication of fluid phase separation was observed in the vein. To constrain the formation depth in the Sangdong deposit, fluid isochores are combined with Ti–in–quartz geothermometry, which suggests that the M1 and F2 orebodies were formed at depths of 1–3 km and 5–6 km below the paleosurface, respectively. The similarity of the Cs (cesium) concentrations and Rb/Sr ratios in the fluid inclusions of the respective orebodies indicate an origin from source magmas having similar degrees of fractionation and enrichment of incompatible elements such as W and Mo. High S concentrations in the fluids and possibly organic C in the sedimentary source likely promoted molybdenite precipitation in the Sangdong orebodies, whereas the scheelite deposition in the deep quartz–molybdenite veins hosted in the quartzite is limited by a lack of Ca and Fe in the hydrothermal fluids. The molybdenite deposition in the Sunbawi quartz–molybdenite veins hosted in the Precambrian metamorphic basement rocks was possibly limited by a lack of reducing agents such as organic C.     

Assessment of microscale economic flood losses in urban and agricultural areas: case study of the Santa Bárbara River,Ecuador

Natural Hazards - To reduce and prevent significant economic flood losses, reliable tools are required to estimate potential river inundation effects. This paper focuses on the estimation of direct...     

The Mazarrón basin,SE Spain: a study of mineralization processes,evolving magmatic series,and geothermal activity

The Miocene to Present Mazarrón basin provides a window on the metallogenic role of an evolving magmatic series. High-K calc–alkaline magmas gave rise to an important cluster of Pb–Zn–Ag–Cu vein and stockwork deposits emplaced in dacitic to rhyodacitic domes, part of a complex volcanic–metallogenic province (Au, Hg, Pb–Zn–Cu–Ag, Sn) stretching for ～150 km along the Mediterranean coast of SE Spain. By Pliocene time the former magmatic series had been replaced by intraplate alkaline basaltic volcanism, thus becoming the southern branch of the Western/Central Europe alkaline province. In terms of base metal sulphide deposits, this European province is barren, although it triggered widespread, CO₂-rich geothermal activity. Modern geothermal activity at El Saladillo (Mazarrón) resulted in the deposition of carbonate sinter deposits and formation of microbial mats. Proximal facies consist of millimetric to centimetric multicoloured layers of microbial mats, including yellow-orange thin bands of calcified bacteria and mineral growths of aragonite and calcite; green layers of live thermophilic Lyngbya-type cyanobacteria; black, degraded organic matter; and pyrite as the sole sulphide phase. Except for arsenic (37–63 μg g^?1), all of the studied trace elements (Ag, Ba, Bi, Cd, Cu, Pb, Sb, Se, and Sn) appear in remarkably low concentrations in the geothermal sinters. This is consistent with compositional data for the El Saladillo waters, with no significant metal concentrations. We present the first conceptual model (Miocene to Present) for the ore-forming processes, magmatism, CO₂ degasification, and geothermal activity for this realm. We argue that the time- and space-limited character of this volcanism (small, scattered outcrops), the deep magma emplacement level, the metal sulphide behaviour in alkaline basaltic magmatic chambers, and the dry character of these magmas prevented any metallogenic interaction between the chambers and the much shallower meteoric waters that drove the El Saladillo geothermal system and others of the same kind in Spain and elsewhere in Europe.     

Petrology of two contrasting Mexican volcanoes,the Chiapanecan (El Chichón) and Central American (Tacaná) volcanic belts: the result of rift- versus subduction-related volcanism

The alkaline El Chichón and calc-alkaline Tacaná volcanoes, located in southern Mexico, form parts of the Chiapanecan Volcanic Belt and Central American Volcanic Arc, respectively. El Chichón has emitted potassium-, sulphur-, and phosphorus-rich trachyandesites and trachybasalts (as mafic enclaves), whereas Tacaná has erupted basalts to dacites with moderate potassium contents, and minor high-Ti magmas (1.5–1.8 wt.% TiO₂). The magmatic evolution in the two volcanoes has involved similar fractionating assemblages: Fe-Ti oxides, olivine, plagioclase, pyroxenes, amphibole, and apatite. K₂O/P₂O₅ ratios and isotopic signatures indicate that magmas from both El Chichón and Tacaná have undergone significant crustal contamination. The volcanism at both Tacaná and El Chichón was previously related to northeastward subduction of the Cocos Plate, representing the main arc and the backarc, respectively. Although such an origin is in accord with Tacaná occurring 100 km above the Cocos Benioff Zone, it is inconsistent with: (a) the absence of a calc-alkaline belt between El Chichón and the Middle America Trench; and (b) truncation of the subducted Cocos Plate by the southwesterly dipping Yucatan slab near the Middle America Trench (i.e. the Cocos Plate does not presently underlie El Chichón). On the other hand, El Chichón and the Chiapanecan Volcanic Belt are located on the sinistral Veracruz fault zone that forms the northern boundary of the Southern Mexico block, which has been migrating relatively to the east since ca. 5 Ma. In this context, the anomalous high potassium, sulphur, and phosphorus levels in the El Chichón magmas are explicable in terms of rifting in a pull-apart system with the weak subduction fingerprint inherited from the Yucatan slab.     

Spatial distribution of heavy metals and arsenic in soils of Aragón (northeast Spain): controlling factors and environmental implications

Legal regulation of heavy metal contents is an important issue in many European countries, where laws still do not exist establishing the heavy metal levels permitted in soils. As a first step to determine the reference levels of heavy metals, it is necessary to know their contents in soils under natural conditions. To achieve this goal in the Autonomous Community of Aragón, a total of 133 sites have been sampled. A balanced allotment of the sampling sites, according to soil spatial distribution in the region, has been carried out by selecting 9 soil types that represent 97.5% of its surface area. Fifteen elements (Cr, Cu, Ba, As, Sb, Hg, Sn, Mn, Fe, Al, Zn, Ni, Co, Cd and Pb) have been analysed by (ICP–AES) after a partial acid extraction. The content of analysed elements has been correlated to some soil parameters such as organic matter, pH, and granulometric fractions. Results of the statistical analyses have shown a large variety and complexity in some of these relationships. The main factors for variation in the heavy metal contents are both the soil type and the lithology. Gypsisols and Calcisols developed on sedimentary rocks have the lowest contents while Leptosols overlying metamorphic and igneous rocks have the highest contents. The spatial distribution of heavy metal contents shows a large variability with the highest contents in the mountain ranges (Iberian and Pyrenees) and the lowest in the plains of the central Ebro valley.     

Changes in carbon intensity of China’s energy-intensive industries: a combined decomposition and attribution analysis

There has been growing interest among researchers in factors influencing carbon emissions of energy-intensive industries in China due to the important roles they play. Such studies mainly focused on evaluating carbon emissions and identifying the contributing factors separately for each energy-intensive industry. Regarding energy-intensive industries as a whole and investigating the contribution of each industry to changes in carbon intensity have not yet been sufficiently addressed and quantified. In order to deeply understand this issue, this study employed the LMDI decomposition analysis to study driving forces (e.g., emission coefficient, energy intensity, and industrial structure) of carbon intensity of energy-intensive industries. Then, attribution analysis was further used to study the contribution of each energy-intensive industry to the percent change in carbon intensity through each impact factor. The results showed that the carbon intensity of energy-intensive industries dropped by 31.83% from 1996 to 2014. The energy intensity effect was largely responsible for this decrease, of which, five industries were the contributors except for the fuel-processing industry. The industrial structure effect also contributed to the decrease, and non-metallic industry and fuel-processing industry played important roles. However, the emission coefficient effect showed a slight impact on increasing carbon intensity, which principally due to chemical industry and power generation industry. The findings suggested that the adaptability and sensitivity of different energy-intensive industries to the implemented policies were various. Based on the results, differentiated and feasible policies related to energy intensity, industrial structure, and energy structure for energy-intensive industries were provided to further mitigate carbon intensity.     

Milankovic’s theory: multidimensional visualisation of the change of insolation and indicators of climatic change from 100000 before present to 100000 after present (in intervals of 1,000 years)

The deviation of the insolation on the earth’s surface from the past to the present and the present to the future for cloudless days is calculated in intervals of 1,000 years from 100000 years before present (BP) to 100000 years after present (AP), its basis being Milankovic’s theory. But the result are not the well-known Milankovic-curves, which are calculated for different latitudes and in which the x-axis represents years and the y-axis represents the insolation difference to present during the North-summer half-year. The calculations are made for each day of the selected years from the South Pole to the North Pole. Thus, two temporal dimensions are represented, that of a year and that of a day, furthermore the spatial dimension “latitude” and the dimension “energy” (insolation deviation). The performance of modern PCs allows the results of the calculations to be presented by a graphical animation. A determined deviation pattern of the insolation is obtained for each year. δ¹⁸O data, the mean global temperature and the additional ice volume on the continents are added to the graphic representations of those patterns for the period from 100000 years BP to the present. During that period insolation deviation patterns can be recognised which correlate with cool climates or climates getting cooler, and others which correlate with relatively warm climates or climates getting warmer. Correlations between the patterns are calculated and groups of similar patterns can be composed which can be associated in most cases with specific climatic conditions or specific climatic change. Comparison of patterns between 100000 years and present BP with patterns between present and 100000 years AP can help to estimate climatic change during the 100000 years ahead.     

Palaeozoic structures in the Xayacatlán area,Acatlán Complex,southern Mexico: transtensional rift‐ and subduction‐related deformation along the margin of Oaxaquia

The Xayacatlán area (eastern Mixteca terrane, southern Mexico) was previously inferred to preserve the Ordovician‐Silurian thrust contact between vestiges of the Iapetus Ocean and the para‐autochthon bordering Oaxaquia. Detailed remapping indicates that the rocks occur in four vertically‐bounded, NS fault blocks. The latter record the following tectonothermal events that post‐date Iapetus and occurred along the margins of the Rheic (1) and Pacific (2 and 3) oceans: (1) dextral transtension accompanying intrusion of an NS, tholeiitic dike swarm at ～442 Ma; (2) penetrative, greenschist‐facies deformation during the Mississippian related to extrusion of high‐pressure rocks; and (3) subgreenschist‐facies dextral transtension on NS faults during the generation of Middle Permian fabrics.     

Flood vulnerability and buildings’ flood exposure assessment in a densely urbanised city: comparative analysis of three scenarios using a neural network approach

Natural Hazards - Advances in the availability of multi-sensor, remote sensing-derived datasets, and machine learning algorithms can now provide an unprecedented possibility to predict flood events...     

Mafic forearc cumulates and associated rocks in the central high-pressure belt of the Acatlán Complex of southern México: geochemical constraints

The high-pressure (HP) Piaxtla Suite at Tehuitzingo contains peridotites, gabbros, and serpentinized peridotites, as well as granitoids and metasedimentary rocks. The HP mafic rocks are characterized by low SiO₂ (38–52 wt.%) and high Mg# (～48–70), Ni (100–470 ppm), and Cr (180–1750 ppm), typical of cumulate compositions. Trace elements and rare earth element (REE) primitive mantle-normalized patterns display generally flat profiles, indicative of derivation from a primitive mantle with two distinct patterns: (1) gabbroic patterns are characterized by a positive Eu anomaly, low REE abundances, and slightly depleted high REE (HREE) relative to low REE (LREE), typical of cumulus olivine, pyroxene, and plagioclase; and (2) mafic-intermediate gabbroic patterns exhibit very flat profiles characteristic of olivine and clinopyroxene as cumulus minerals. Their Nb/Y and Zr/TiO₂ ratios suggest a subalkaline character, whereas low Ti/V ratios indicate that the Tehuitzingo cumulates are island arc tholeiitic basalts that resemble modern, immature oceanic, forearc magmas. These cumulates have high values of ? _Nd(t) = 5.3–8.5 and ¹⁴⁷Sm/¹⁴⁴Nd = 0.18–0.23, which renders calculations of model ages meaningless. Our data are consistent with the Tehuitzingo arc rocks being part of a tectonically extruded Devonian–early Carboniferous arc developed along the west margin of Gondwana.     

A Carboniferous high-pressure klippe in the western Acatlán Complex of southern México: implications for the tectonothermal development and palaeogeography of Pangea

High-pressure (HP) rocks are critical for palinspastic restorations because they mark inferred subducted/extruded oceanic crust; knowledge of their geometric, geodynamic, and age relationships provide essential constraints on palaeogeographic reconstructions. The westernmost HP belt (Ixcamilpa) in the Acatlán Complex of southern Mexico has been inferred to be a mid-Late Ordovician backarc basin on the southern Iapetan margin that was subducted beneath eastern Laurentia and extruded up the subduction zone during the Early Silurian. Re-examination of Ixcamilpa HP rocks has revealed that they comprise lower Palaeozoic rift-passive margin protoliths and occur in a W-vergent klippe (not a suture) formed during polyphase deformation. Peak metamorphic mineral assemblages of blueschist-amphibole eclogite facies underwent retrogression through epidote amphibolite to greenschist facies. ⁴⁰Ar/³⁹Ar dating of various rocks yielded plateau ages of 344–339 Ma for calcic amphibole, 318 ± 4 Ma for glaucophane, and 329–325 ± 2 Ma for muscovite (excess argon), which clearly indicate a Carboniferous tectonothermal event. We interpret the 20 million years range in amphibole ages as reflecting progressive unroofing. The terminal stage of progressive thrusting placed the HP rocks above the middle Mississippian Zumpango Unit, during which a single penetrative sub-greenschist fabric was produced. Subsequent Permian or Laramide deformation refolded all the rocks about NE-trending upright folds. We postulate that the root zone of the HP nappe lies to the east in the median HP belt, which has a structure consistent with an extrusion zone. Inasmuch as similar units of the Acatlán Complex bound this HP root zone on either side, it is inferred to have been extruded into the upper plate above the subduction zone, and thus is not an oceanic suture. Our new data provide constraints for a Carboniferous palaeogeographic reconstruction, whereby subduction erosion of passive margin rocks took place along the western margin of Pangea and were subsequently extruded into the upper (Acatlán) plate.     

Manganese deposits: Communication 2. Major epochs and phases of manganese accumulation in the Earth’s history

Accumulation of manganiferous rocks in the history of the Earth’s lithosphere evolution began not later than the end of the Middle Archean. Primary manganese sediments were accumulated at that time in shallow-water sedimentation basins with the active participation of organic matter. The concentration of Mn in the primary sediments usually did not reach economic values. The formation of genuine manganese ores is related to later processes of the transformation of primary ores—diagenesis, catagenesis, metamorphism, and retrograde diagenesis. Types of basins of manganese ore sedimentation and character of processes of the formation of manganese sediments during the Earth’s shell evolution changed appreciably and correlated with the general evolution of paleocontinents. Major periods, epochs, and phases of manganese ore genesis are defined. At the early stages of lithosphere formation (Archean-Proterozoic), manganese was deposited in basins commonly confined to the central part of Western Gondwana and western part of Eastern Gondwana, as well as the western part of the Ur paleocontinent. Basins of manganese ore sedimentation were characterized by the ferruginous-siliceous, carbonaceous-clayey, and carbonaceous-carbonate-clayey composition. The Early-Middle Paleozoic epoch of manganiferous sediment accumulation was characterized by the presence of several small sedimentation basins with active manifestation of volcanic and hydrothermal activity. Since the formation of Pangea in the Late Paleozoic until its breakup, accumulation of Mn was closely associated with processes of diagenesis and active participation of the oxidized organic matter.     

Locational analysis of slums and the effects of slum dweller’s activities on the social,economic and ecological facets of the city: insights from Kumasi in Ghana

GeoJournal - Slum development has become a major urban planning and management problem due to the challenges they pose to the larger urban environment. Activities of slum dwellers are...