GIS and ANN coupling model: an innovative approach to evaluate vulnerability of karst water inrush in coalmines of north China

Evaporites, including rock salt (halite) and gypsum (or anhydrite), are the most soluble among common rocks; they dissolve readily to form the same types of karst features that commonly are found in limestones and dolomites. Evaporites are present in 32 of the 48 contiguous states in USA, and they underlie about 40% of the land area. Typical evaporite-karst features observed in outcrops include sinkholes, caves, disappearing streams, and springs, whereas other evidence of active evaporite karst includes surface-collapse structures and saline springs or saline plumes that result from salt dissolution. Many evaporites also contain evidence of paleokarst, such as dissolution breccias, breccia pipes, slumped beds, and collapse structures. All these natural karst phenomena can be sources of engineering or environmental problems. Dangerous sinkholes and caves can form rapidly in evaporite rocks, or pre-existing karst features can be reactivated and open up (collapse) under certain hydrologic conditions or when the land is put to new uses. Many karst features also propagate upward through overlying surficial deposits. Human activities also have caused development of evaporite karst, primarily in salt deposits. Boreholes (petroleum tests or solution-mining operations) or underground mines may enable unsaturated water to flow through or against salt deposits, either intentionally or accidentally, thus allowing development of small to large dissolution cavities. If the dissolution cavity is large enough and shallow enough, successive roof failures can cause land subsidence and/or catastrophic collapse. Evaporite karst, natural and human-induced, is far more prevalent than is commonly believed.     

江苏地矿实验室生存发展新思路

1949年以来,江苏地矿实验室为江苏地矿事业的发展做出很大贡献。跟随国家机构改革的步伐,地矿实验室实现了属地化改造,隶属于国土资源系统。由于上级主管部门的缺失,江苏地矿实验室的生存与发展面临困境,本着立足江苏为出发点,提出了几点发展新思路。     

Evolution of the composition of seawater through geologic time, and its influence on the evolution of life

The redox state of the surface environment of the early Earth is still controversial, and a detailed and quantitative estimate is still lacking. We carried out in-situ analyses of major, trace, and rare-earth elements of carbonate minerals in rocks with primary sedimentary structures in shallow and deep sea-deposits, in order to eliminate secondary carbonate and contamination of detrital materials, and to estimate the redox condition of seawater through time. Based on the Ce content and anomalies of the carbonate minerals at given parameters of atmospheric CO₂ content (pCO₂) and Ca content of seawater, we calculated the oxygen contents of shallow and deep seawater, respectively. The results show that the oxygen content of the deep sea was low and constant until at least 1.9 Ga. The oxygen content of shallow seawater increased after 2.7 Ga, but fluctuated. It became quite high at 2.5 and 2.3 Ga, but eventually increased after the Phanerozoic. In addition, the calculation of a high pCO₂ condition shows that seawater was more oxic even in the Archean than at present, suggesting a relatively low pCO₂ through geologic time.Our detailed calculations from compositions of carbonate minerals in Three Gorge area, south China show a low oxygen content of seawater after the Snowball Earth until the late Ediacaran, an increase in the late Ediacaran, and a significant decrease around the Precambrian–Cambrian and Nemakit/Daldynian–Tommotian boundaries. These variations were possibly caused by global regression and dissolution of methane hydrates.     

Geothermal evolution of the Astrakhan Arch region of the Pricaspian basin

The Astrakhan Arch region contains one of the largest sub-salt structures of the Pricaspian basin, where perspectives for hydrocarbon generation and accumulation in the Devonian to Carboniferous deposits are considered to be high. The paper addresses the problem of structural and geothermal evolution of the region deformed by salt movements. Initially, we developed a model of the regional structural evolution along a geological profile using the volume-balancing and back-stripping methods and geological constraints on the sedimentation, erosion, and paleo-water depths. Then we developed geothermal models (along the study profile) associated with the regional structural evolution. The models were constrained by the temperatures measured in four deep boreholes along the profile. We show that the present temperatures and heat flux are influenced by the presence of salt diapirs. Since the Early Carboniferous and till Middle Permian times, the temperatures predicted by the models vary significantly due to the regional transgression and the presence of seawater. The temperature of Devonian–Carboniferous carbonates increases since the Late Permian (time of post-salt deposition) and attains its maximum values in the SW-part of the profile. If the model assumptions concerning the constant vertical and zero lateral heat fluxes are valid, we can conclude that hydrocarbons are most likely to be generated in the SW-part of the region for the post-Early Permian time.     

Provenance of Cretaceous clastics in the Subhercynian Basin: constraints to exhumation of the Harz Mountains and timing of inversion tectonics in Central Europe

The Harz Mountains and the adjacent Subhercynian Cretaceous Basin figure as the most prominent surface representative for Late Cretaceous inversion structures in Central Europe. Facies, depositional architecture and provenance of the basin fill reflect mechanisms and timing of the exhumation of the Harz. From Hauterivian to Early Santonian there is no evidence for detrital input from the nearby Harz area. Sediments are mature quartzarenites derived from Paleozoic basement rocks and/or recycled Permian to Mesozoic sedimentary rocks. This situation changed drastically in Middle to Late Santonian when freshly exhumed and eroded Mesozoic sedimentary cover rocks of the Harz were delivered into the basin. Feldspar and lithoclasts reflect erosion of Triassic and, in places, Jurassic to Turonian strata. Apatite and garnet in heavy mineral spectra are derived from largely unweathered Lower Triassic Buntsandstein as indicated by apatite and garnet chemistry. In Early Campanian, Paleozoic lithoclasts indicate erosion cutting down into the basement of the Harz. Simultaneous strong decrease of feldspar, garnet and apatite suggest an almost complete removal of the 2–3 km thick Mesozoic cover of the Harz within only 2–4 Myr. This translates into an exhumation rate of approximately 1 mm/a consistent with apatite fission track data from granitoid rocks of the Harz Mountains.     

水合盐相变储能材料研究

水合盐相变储能材料具有原料丰富、储热密度高、价格低等优点,在太阳能高效利用、工业余废热利用、跨季节储热采暖、智能温室、食品储存保鲜、轻纺行业等方面有着广阔的市场前景及经济效益。但是,在实际应用过程中会遇到过冷、相分离、非协调性熔解、热传效率低(热导率低)、体积变化、循环稳定性、结晶速率慢以及热化学稳定性等问题。针对这些问题,通过密度泛函理论、成核剂"协同效应"、纳米导热粒子、微纳核壳结构构筑等研究提升水合盐相变储能材料性能及应用范围,该研究思路对于水合盐相变储能材料的开发具有重要意义。     

南极普里兹湾主要碎屑矿物特征及物源分析

基于南极普里兹湾海域33个表层碎屑沉积物样品的碎屑矿物学分析,对该区的沉积环境与物质来源进行了分析。结果表明该区碎屑重矿物共17种,石榴子石、普通角闪石和磁铁矿为优势矿物,紫苏辉石和赤铁矿为特征矿物。根据矿物组合分布特征,普里兹湾可划分为4个矿物区:Ⅰ区为石榴子石含量占绝对优势、重矿物含量较高的弗拉姆浅滩矿物区;Ⅱ区为石榴子石、普通角闪石含量较高,磁铁矿为特征矿物的普里兹水道矿物区;Ⅲ区为紫苏辉石含量较突出的四女士浅滩矿物区;Ⅳ区为普通角闪石含量明显突出,石榴子石显著减少的深水陆坡矿物区。通过电子探针测试研究区石榴子石结果表明:碎屑石榴子石含有较高的Fe、Mg和较低的Ca、Mn,属主要来源于高级麻粒岩相副变质岩的A型石榴子石。普里兹湾海域的碎屑矿物分布特征是物质来源、海流系统以及冰川活动等多重因素综合作用的产物。     

The state of legislation and policy protecting Australia's mangrove and salt marsh and their ecosystem services

Saline coastal wetlands, such as mangrove and coastal salt marsh, provide many ecosystem services. In Australia, large areas have been lost since European colonization, particularly as a result of drainage, infilling and flood-mitigation works, often starting in the mid-19th century and aimed primarily towards converting land to agricultural, urban or industrial uses. These threats remain ongoing, and will be exacerbated by rapid population growth and climate change in the 21st century. Establishing the effect of wetland loss on the delivery of ecosystem services is confounded by the absence of a nationally consistent approach to mapping wetlands and defining the boundaries of different types of coastal wetland. In addition, climate change and its projected effect on mangrove and salt marsh distribution and ecosystem services is poorly, if at all, acknowledged in existing legislation and policy. Intensifying climate change means that there is little time to be complacent; indeed, there is an urgent need for proper valuation of ecosystem services and explicit recognition of ecosystem services within policy and legislation. Seven actions are identified that could improve protection of coastal wetlands and the ecosystem services they provide, including benchmarking and improving coastal wetland extent and health, reducing complexity and inconsistency in governance arrangements, and facilitating wetland adaptation and ecosystem service delivery using a range of relevant mechanisms. Actions that build upon the momentum to mitigate climate change by sequestering carbon – ‘blue carbon’ – could achieve multiple desirable objectives, including climate-change mitigation and adaptation, floodplain rehabilitation and habitat protection.     

Dissolution kinetics of selected natural minerals relevant to potential CO2-injection sites − Part 1: A review

This publication provides a literature review on experimental studies of dissolution kinetics of mainly carbonates and feldspar group minerals, i.e. most common minerals at potential CO₂-injection and/or storage sites. Geochemical interaction processes between injected CO₂ and coexisting phases, namely reservoir and cap rock minerals and formation fluids close to the CO₂-injection site can be simulated by flow-through or mixed flow reactors, while processes far from the injection site and long-term processes after termination actual CO₂-injection can be mimicked by batch reactors. At sufficient small stirring rates or fluid flow rates as well as low solute concentrations flow-through reactors are also able to simulate processes far from the injection site. The experimental parameter temperature not only intensifies the dissolution process, the dominant dissolution mechanisms are also influenced by temperature. The dissolution mechanisms change from incongruent and surface controlled mechanisms at lower temperatures to congruent and transport controlled mechanisms at higher temperatures. The CO₂ partial pressure has only a second order influence on dissolution behavior compared to the influence of pH-value and ionic strength of the CO₂-bearing brine. Minerals exposed to CO₂-bearing brines at elevated temperatures and pressures are subject of alteration, leading to severe changes of reactive surfaces and potential precipitation of secondary minerals.Computational simulations of mineral reactions at potential CO₂ storage sites have therefore to include not only the time-resolved changes of dissolution behavior and hence kinetics of mineral dissolution, but also the influence of secondary minerals on the interaction of the minerals with CO₂-enriched brines.     

Late Quaternary fluctuations of the Leeuwin Current and palaeoclimates on the adjacent land masses: Clay mineral evidence

Clay minerals eroded from soils by rivers and wind action become entrained in shallow‐ as well as deep‐water masses of the surrounding seas. Their pattern on the sea floor gives clues to their propagation by ocean currents. Clay mineral assemblages in sediment cores can be used as a useful proxy to decipher past changes in the intensity of ocean currents or in the nature of the palaeoclimatic processes on the adjacent landmasses. Three cores taken from beneath the path of the present‐day Leeuwin Current in the Timor Passage, from off the Australian North West Shelf and off the North West Cape of Western Australia are investigated. They provide a Late Quaternary record of environmental changes. Kaolinite and chlorite are transported into the Timor Passage today by the Indonesian Throughflow, while illite is provided locally from Timor. The Leeuwin Current leaves the Timor Passage with a characteristic clay mineral signature acquired in the Indonesian Archipelago (kaolinite, chlorite and illite). Uptake of clay minerals along its way through the Timor Sea, e.g. illite from the Kimberley area, changes this signature. South of North West Cape chlorite, injected by the rivers of the Pilbara region into the path of the Leeuwin Current, is prominent in surface sediments in less than 1000 m water depth and outlines the flow of the current today. During the last glacial period, the volume of the Indonesian Throughflow decreased and less kaolinite and chlorite reached the Timor Passage. Offshore from North West Cape, a reduction in chlorite during the last glacial may indicate a decrease or absence of the Leeuwin Current and/or a reduction in the input of chlorite due to drier conditions on land. A maximum of illite in recent sediments and the Holocene offshore from North West Cape results from the input of material from rivers periodically draining the adjacent hinterland. Again, a reduction in illite points to a drier climate in the area during the last glacial.