Thermal transformations of akaganéite and lepidocrocite to hematite: assessment of possible precursors to Martian crystalline hematite

We examine the possibility that crystalline hematite (α-Fe₂O₃) deposits on Mars were derived from the precursor iron oxyhydroxide minerals akaganéite (β-FeOOH) or lepidocrocite (γ-FeOOH) and compare them to an earlier study of goethite (α-FeOOH) and magnetite (Fe₃O₄) precursors. Both the mid-infrared and visible/near infrared spectra of hematite are dependent upon the hematite precursor mineral and the temperature of transformation. Laboratory spectra are compared to spectra from the Mars Global Surveyor Thermal Emission Spectrometer (MGS-TES) and the Mars Exploration Rover (MER) Opportunity Mini-TES and Pancam experiments, allowing us to infer the formation environment of Martian crystalline hematite deposits. Akaganéite and lepidocrocite readily transform to hematite at temperatures of 300 and 500°C, respectively. The visible/near-infrared and mid-infrared spectra of akaganéite-derived hematite are poor matches to data returned from TES, Mini-TES, and Pancam. The spectra of lepidocrocite-derived hematite are slightly better fits, but previously published spectra of goethite-derived hematite still represent the best match to MGS and MER spectral data. The experiments demonstrate that hematite precursor mineralogy, temperature of formation, and crystal shape exert a strong control on the hematite spectra.     

Microbial control of mineral–groundwater equilibria:Macroscale to microscale

macroscale processes that perturb general groundwater chemistry and therefore mineral–water equilibria; and microscale interactions, where attached organisms locally perturb mineral–water equilibria, potentially releasing limiting trace nutrients from the dissolving mineral. In the contaminated unconfined glacio-fluvial aquifer near Bemidji, Minnesota, USA, carbonate chemistry is influenced primarily at the macroscale. Under oxic conditions, respiration by native aerobic heterotrophs produces excess carbon dioxide that promotes calcite and dolomite dissolution. Aerobic microorganisms do not colonize dolomite surfaces and few occur on calcite. Within the anoxic groundwater, calcite overgrowths form on uncolonized calcite cleavage surfaces, possibly due to the consumption of acidity by dissimilatory iron-reducing bacteria. As molecular oxygen concentration increases downgradient of the oil pool, aerobes again dominate and residual hydrocarbons and ferrous iron are oxidized, resulting in macroscale carbonate-mineral dissolution and iron precipitation. Feldspars, in contrast, weather exclusively at the microscale near attached microorganisms, principally in the anoxic region of the plume. Native organisms preferentially colonize feldspars that contain trace phosphorus as apatite inclusions, apparently as a consequence of the low P concentration in the groundwater. These feldspars weather rapidly, whereas nearby feldspars without trace P are uncolonized and unweathered. Feldspar dissolution is accompanied by the precipitation of secondary minerals, sometimes on the bacterial cell wall itself. These observations suggest a tightly linked biogeochemical system whereby microbial processes control mineral diagenesis at many scales of interaction, and the mineralogy and mineral chemistry influence microbial ecology. Only the macroscale interaction, however, is easily observable by standard geochemical methods, and documentation of the microscale interactions requires microscopic examination of microorganisms on mineral surfaces and the locally intense diagenetic reactions that result. Received, May 1999/Revised, October 1999/Accepted, October 1999     

The solidus of harzburgite to 3 GPa pressure: the compositions of primary abyssal tholeiite

Summary Abyssal tholeiite is generated by partial melting of the upper mantle. The mantle sections of ophiolite complexes show that partial melting leaves mantle residua that are lherzolitic or harzburgitic, harzburgite being the more depleted residuum. It is shown that some of the interstitial melt of partially molten harzburgite approximates a tholeiitic composition. Therefore, the solidus of harzburgite constitutes the maximum possible temperature for the generation of primary tholeiite. The MgO contents of primary tholeiites in equilibrium with harzburgite are determined to be about 21 and 23wt.% MgO at 2.0 and 3.0GPa, respectively. The possible MgO contents of primary abyssal tholeiite is suggested to range between 10 and 23wt.% MgO, with the MgO content increasing with increasing pressure.     

Assembly of Pampia to the SW Gondwana margin: A case of strike-slip docking?

Different hypotheses have been proposed to account for the geologic evolution of the southwestern margin of Gondwana in the Early Paleozoic, involving accretion and displacement of different terranes in a protracted convergent margin. In order to constrain and understand the kinematic and paleogeographic evolution of the Pampia terrane a paleomagnetic study was carried out in different Cambrian to Devonian units of the Eastern Cordillera (Cordillera Oriental) and the Interandean Zone (Interandino) of NW Argentina. Paleomagnetic poles from the Campanario Formation (Middle to Upper Cambrian): 1.5°N 1.9°E A₉₅ = 9.2° K = 37.46 N = 8; and Santa Rosita Formation (Lower Ordovician): 8.6°N 355.3°E A₉₅ = 10.1° K = 26.78 n = 9, representative of the Pampia terrane, are interpreted to indicate a Late Cambrian significant displacement with respect to the Río de la Plata and other Gondwana cratons. A model, compatible with several geological evidences that explains this displacement in the framework of the final stages of Gondwana assembly is presented. We propose a simple dextral strike-slip kinematic model in which Pampia and Antofalla (? Arequipa?) blocks moved during Late Cambrian times from a position at the present southern border of the Kalahari craton into its final position next to the Rio de la Plata craton by the Early Ordovician.     

From compassion to the will to improve: Elision of scripts? Philanthropy in post-tsunami Sri Lanka

The paper analyses how two private post-tsunami reconstruction initiatives in Sri Lanka mobilized well intended aid to support and assist tsunami affected families, drawing on narratives of compassion, which resulted in an inadvertent obtrusion of the moral imperatives of donors upon the lives of aid receivers. We trace the discursive terrain around goodness, kindness and compassion utilized to generate donations. This quickly slipped into the practical construction of village models that reflected individuals’ ideas and understandings of development, modernism, social consciousness and peaceful coexistence. This merging, we argue, quickly subverted intention for the ‘betterment of villagers lives’, and became a means through which donors made claims on villages and impressed their will upon recipients. Given that private donor involvement in post-tsunami Sri Lanka was a critical factor shaping conditions on the ground, we contend that it is important to unpack their (powerful) role in giving meaning to building back better.     

Erratum to: Solution of Kepler’s Equation with Machine Precision

Astronomy Reports - An Erratum to this paper has been published: https://doi.org/10.1134/S1063772921330015     

Equation of state of adamite up to 11 GPa: a synchrotron X-ray diffraction study

The compression behavior of natural adamite [Zn₂AsO₄OH] has been investigated up to 11.07 GPa at room temperature utilizing in situ angle-dispersive X-ray diffraction and a diamond anvil cell. No phase transition has been observed within the pressure range investigated. A third-order Birch–Murnaghan equation of state fitted to all of the data points yielded V ₀ = 430.1(4) Å³, K ₀ = 80(3) GPa, K′ ₀ = 1.9(5). The K ₀ was obtained as 69(1) GPa when K′ ₀ was fixed at 4. Analysis of axial compressible moduli shows the intense compression anisotropy of adamite: K _a0 = 37(3) GPa, K _b0 = 153(6) GPa, K _c0 = 168(8) GPa; hence, a axis is the most compressible and the compressibility of b and c axis is comparable. Furthermore, the comparisons among the compressional properties of adamite, libethenite (Cu₂PO₄OH, also belongs to olivenite group), and andalusite (Al₂SiO₄O has the similar structure with adamite) at high pressure were made.     

Biogeochemical cycling of nutrients in karstic catchments, southwestern China: Linkages to changes of eco-environments

In southwestern China, karst rocky desertification, a process of land degradation, takes place widely due to human impacts on the fragile karstic ecological systems, which includes soil erosion, extensive exposure of basement rocks, and drastic decrease i…     

Highway congestion during evacuation: examining the household’s choice of number of vehicles to evacuate

Hurricane evacuations in coastal counties have been reviewed and analyzed for the role of household preparedness and decisions before and during a disaster. However, one of the several emerging problems in the hurricane evacuation is transportation. Transportation issues have become more important in coastal evacuations as traffic problems impinge on people’s ability to get out of harm’s way and ultimately influence their decisions to evacuate. To add to the complexity, when families evacuate in multiple vehicles, it leads to additional vehicular traffic on roads and increased pressure on the transportation systems. However, little has been investigated on the characteristics that influence a household’s decision to evacuate in one or multiple vehicles. The outcome from such an analysis can help both the emergency managers and the transportation planners to targets groups that report taking more vehicles to develop policies that result in efficient evacuation. This study investigates the responses of evacuees surveyed after Hurricane Rita in the counties of Galveston, Brazoria and Harris County. The ordinary least square regression analysis revealed that access to transportation characteristics of a household such as number of registered vehicles in a household and number of eligible drivers was positively and significantly related to evacuating in more vehicles. Meanwhile, the risk of reaching destination safely was negatively related to taking more vehicles for evacuation even though both the risk index and deterrence index were positively significant. The time of decision and evacuation did not report any statistical significance.     

Remediation and restoration of metal-contaminated sites: Concepts and applications to mining areas

Metals, including heavy metals and metalloids, are a common group of environmental contaminants. Their sources in the environment are geogenic or anthropogenic. The growing trend in global industrialization ensures that more metals could be dispersed even…     

Ideas out of context and the contextualization of ideas: The transference of Jane Jacobs to São Paulo

The mobility and contextualization of urban policies between localities have received significant attention in recent literature. A number of mechanisms have been identified, including “best practices,” “policy tourism,” multinational firms, and conferences have been identified. This article identifies a new mechanism: the translation and publication of seminal theses into additional languages. Using citations analysis and interviews in São Paulo, this mechanism is confirmed as an additional mode of transference and identified as being responsible for the growth in interest in Jane Jacobs in São Paulo. However, this article finds that despite the increase in accessibility to her ideals, her emphasis on contextuality was overlooked in that case. This, in turn, calls attention to larger issues of the use of so-called ‘universally-good’ examples of urbanism.     

The demographic responses to famine: The case of China 1958–61

Pre-1949 China was The Sick Man of Asia, The Land of Famine. In 1949 Mao brought the communists to power and in the re-ordered world, all such problems were supposedly overcome — but not so. Thirty years ago China suffered one of the world's worst famines. Over the four years 1958–61, China suffered some 25–30 million more deaths and experienced some 30–35 million fewer births than might have been expected under normal conditions. Yet for almost a quarter of a century there would be few, outside of China, who were aware of the existence let alone the dimensions of the disaster. Access to Chinese census data since the mid-1980s has permitted a preliminary analysis of the demographic impact of the famine.Abbreviations JPRS-CEA-81-128 Joint Publications Research Service, China Economic Affairs Report 128, 1981 - JPRS-CPS-85-028 Joint Publications Research Service. China Report, Political, Sociological & Military Affairs 28, 1985     

Risk of water pollution due to ash–sludge mixtures: column trials

The purpose of this work was to study the risks of water pollution due to the use of mixtures containing wood ash and sewage sludge. Mixtures including sludge and ash may be recycled as fertilizers, and they are economical as they do not integrate commercial limes, but Escherichia coli counts may keep significantly high in such mixtures, because their pH is not alkaline enough. In view of that, it seems interesting to study the E. coli survival in lixiviate from ash?Csludge mixtures including limes rather than from ash?Csludge mixtures alone. Two kinds of experiments were performed using laboratory column trials under saturated flow conditions. The first experiment investigated the chemical leaching behaviour of a mixture of 70% timber-industry wood ashes and 30% urban sewage sludge (% dry weight) at doses equivalent to 10 and 30?Mg/ha. The second experiment studied the survival of E. coli in lixiviates generated from 30?Mg/ha of a mixture consisting in 75% wood ash, 20% sewage sludge and 5% quicklime (% dry weight). In the first experiment, admixture of the ash and sludge achieved a stabilization of elements such as aluminium, iron, magnesium, nickle, carbon monoxide, cadmium, chromium and molybdenum that reduced their solubility compared with that in the ash or sludge alone. Significant solubilisation of heavy metals was not observed, with overall minor risk of chemical water pollution. In the second experiment, although including quicklime E. coli counts were still detected in the lixiviate, indicating risk of water contamination.     

Analysis of human risks due to dam break floods—part 2: application to Tangjiashan landslide dam failure

The Tangjiashan landslide dam was formed during the Ms8.0 Wenchuan earthquake in 2008 and posed high risks to 1.2?million people downstream the dam. A human risk analysis model (HURAM) reported in the companion paper is applied to evaluate the human risk in the Tangjiashan landslide dam failure. The characteristics of this landslide dam are introduced first. The breaching parameters in two cases (i.e., the actual case and a high erodibility case) are predicted with a physically based model, and the flood routing processes in these two cases are simulated using numerical analysis. The population at risk downstream of the landslide dam is then obtained based on the results of the flood routing simulations. Subsequently, the human risks are analyzed with HURAM using Bayesian networks. Fourteen influence parameters and their interrelationships are considered in a systematic structure in the case study. A change in anyone of them may affect the other parameters and leads to loss of life. HURAM allows not only cause-to-result inference, but also result-to-cause inference by updating the Bayesian network with specific information from the study case. The uncertainties of the parameters and their relationships are studied both at the global level using multiple sources of information and at the local level by updating the prior probabilities.     

Unconformities of the auriferous,neoarchæan central rand group of South Africa: application to stratigraphy

In addition to their importance as stratigraphical levels of enhanced Au concentration, the unconformities of the Central Rand Group of South Africa also form natural lithostratigraphical formation boundaries. With a view to stimulating research of these unconformities, two hypotheses on the origins of two types of unconformities are reviewed in this paper and criteria for their distinction are proposed. Progressive unconformities are syntectonic and diachronous in nature, and develop in response to source-area orogeny. The result of such tectonism is a basinward shift of the locus of erosion and a progradation, manifested by a conformable coarsening-upward succession in distal, downstream areas of net aggradation. However, in proximal areas net erosion prevails, and parts of such coarsening-upward successions are truncated. Progressive unconformities typically result from localised source-area tectonism and will therefore be restricted to the proximal regions of a particular sub-basin. Some unconformities develop due to eustatic changes and form during relative sea level falls. Because of differential subsidence within different parts of the composite Witwatersrand Basin, some such unconformities would be restricted to certain sub-basins. Both types of unconformities discussed form natural local lithostratigraphical boundaries. However, long-range correlation of formation boundaries is a practice alien to lithostratigraphy.     

Geology and tectonics of Japanese islands: A review – The key to understanding the geology of Asia

The age of the major geological units in Japan ranges from Cambrian to Quaternary. Precambrian basement is, however, expected, as the provenance of by detrital clasts of conglomerate, detrital zircons of metamorphic and sedimentary rocks, and as metamorphic rocks intruded by 500 Ma granites. Although rocks of Paleozoic age are not widely distributed, rocks and formations of late Mesozoic to Cenozoic can be found easily throughout Japan. Rocks of Jurassic age occur mainly in the Jurassic accretionary complexes, which comprise the backbone of the Japanese archipelago. The western part of Japan is composed mainly of Cretaceous to Paleogene felsic volcanic and plutonic rocks and accretionary complexes. The eastern part of the country is covered extensively by Neogene sedimentary and volcanic rocks. During the Quaternary, volcanoes erupted in various parts of Japan, and alluvial plains were formed along the coastlines of the Japanese Islands. These geological units are divided by age and origin: i.e. Paleozoic continental margin; Paleozoic island arc; Paleozoic accretionary complexes; Mesozoic to Paleogene accretionary complexes and Cenozoic island arcs. These are further subdivided into the following tectonic units, e.g. Hida; Oki; Unazuki; Hida Gaien; Higo; Hitachi; Kurosegawa; South Kitakami; Nagato-Renge; Nedamo; Akiyoshi; Ultra-Tamba; Suo; Maizuru; Mino-Tamba; Chichibu; Chizu; Ryoke; Sanbagawa and Shimanto belts.The geological history of Japan commenced with the breakup of the Rodinia super continent, at about 750 Ma. At about 500 Ma, the Paleo-Pacific oceanic plate began to be subducted beneath the continental margin of the South China Block. Since then, Proto-Japan has been located on the convergent margin of East Asia for about 500 Ma. In this tectonic setting, the most significant tectonic events recorded in the geology of Japan are subduction–accretion, paired metamorphism, arc volcanism, back-arc spreading and arc–arc collision. The major accretionary complexes in the Japanese Islands are of Permian, Jurassic and Cretaceous–Paleogene age. These accretionary complexes became altered locally to low-temperature and high-pressure metamorphic, or high-temperature and low-pressure metamorphic rocks. Medium-pressure metamorphic rocks are limited to the Unazuki and Higo belts. Major plutonism occurred in Paleozoic, Mesozoic and Cenozoic time. Early Paleozoic Cambrian igneous activity is recorded as granites in the South Kitakami Belt. Late Paleozoic igneous activity is recognized in the Hida Belt. During Cretaceous to Paleogene time, extensive igneous activity occurred in Japan. The youngest granite in Japan is the Takidani Granite intruded at about 1–2 Ma. During Cenozoic time, the most important geologic events are back-arc opening and arc–arc collision. The major back-arc basins are the Sea of Japan and the Shikoku and Chishima basins. Arc–arc collision occurred between the Honshu and Izu-Bonin arcs, and the Honshu and Chishima arcs.     

Phase relations of carbonate-bearing eclogite assemblages from 2.5 to 5.5 GPa: implications for petrogenesis of carbonatites

We have experimentally investigated the phase and melting relations of garnet + clinopyroxene + carbonate assemblages at 2.5–5.5 GPa, to assess the feasibility of carbonated eclogite as a source for some crustally emplaced carbonatites. The solidus of our composition was at 1,125 °C at 2.5 GPa, 1,225 °C at 3.5 GPa and 1,310 °C at 5.0 GPa. Melts were sodic calcio-dolomitic carbonatites, and were markedly more calcic than the dolomitic melts produced by partial melting of carbonated peridotite. Na contents of the experimental carbonatites decreased with increasing pressure when compared at similar degrees of melting, and SiO₂ contents increased with degree of melting. Experiments on a second composition with enhanced Na₂O demonstrated its strong effect in lowering melting temperatures in carbonate eclogite. Natural carbonated eclogite bodies in the peridotitic upper mantle will have a range of solidus temperatures. In many cases, carbonate will be molten in the upper 250 km. Carbonate melt would segregate from its source eclogite at very low melt fractions and infiltrate surrounding peridotitic wall rock. This would result in metasomatic enrichment of the peridotitic wall rock, but its exact nature will depend on the relative P–T positions of the eclogite + CO₂ and peridotite + CO₂ solidii. As a result of these inevitable metasomatic interactions, it is considered unlikely that carbonatite melts derived from carbonated eclogite in the upper mantle could be emplaced into the crust unmodified. However, they may have a role in metasomatically enriching and carbonating parts of the upper mantle, producing sources suitable for subsequent production of silica undersaturated silicate liquids and carbonatites ultimately emplaced in the crust.Editorial responsibility: J. Hoefs     

Farmers’ response to agricultural drought in paddy field of southern China: a case study of temporal dimensions of resilience

Seasonal water scarcity in southern China has been an issue of concern for many years. The increased frequency of low precipitation in the growing season of rice created a flurry of discussions in the academic and policy arenas. These events severely disrupted the supply of irrigation water for agriculture in paddy field areas and posed a substantial threat to farmers’ livelihoods. Within a broader context of accessing farmers’ resilience to agricultural drought, this paper focuses on the response mechanisms and adaptive strategies adopted by farming households in three types of areas (Plain, Hill, Mountain) in Dingcheng, Hunan Province. With the increasing drought frequency and the pressure from the demand for livelihood improvement, farmers’ response mechanisms have evolved, expanding from short-term adjustments to long-term adaptations, and switching focus from securing reliable water sources to improving irrigation efficiency and diversifying both on- and off- farm productions. The three types of geographic units have different resilience profiles and have developed diverse patterns of adaptive processes that update the conceptual model of Disaster Resilience of “Loss-Response” of Location. It presents a temporal dimension to the study of resilience, which is largely missing from the current literature and provides insights into how to enhance farmers’ response capacities in the face of agricultural drought in southern China.