Review: Deep groundwater research with focus on Germany

While research focuses mainly on the intensively used shallower aquifers, only a little research has addressed groundwater movement in deeper aquifers. This is mainly because of the negligible relevance of deep groundwater for daily usage and the great efforts and high costs associated with its access. In the last few decades, the discussion about deep geological final repositories for radioactive waste has generated strong demand for the investigation and characterization of deep-lying aquifers. Other utilizations of the deeper underground have been added to the discussion: the use of geothermal energy, potential CO₂ storage, and sources of potable water as an alternative to the geogenic or anthropogenic contaminated shallow aquifers. As a consequence, the fast growing requirement for knowledge and understanding of these dynamic systems has spurred the research on deep groundwater systems and accordingly the development of suitable test methods, which currently show considerable limitations. This review provides an overview of the history of deep groundwater research. Deep groundwater flow and research in the main hydrogeological units is presented based on six projects and the methods used. The study focuses on Germany and two other locations in Europe.     

Analytical and numerical solutions on the response of pore pressure to cyclic atmospheric loading: with application to Horonobe underground research laboratory,Japan

During the long-term stability assessment of underground disposal repositories buried in sedimentary formations, one of crucial scientific problems is to determine parameters of site formations. The analysis of response of the pore pressure due to atmospheric loading provides a possible way of accurate estimation of formation parameters. In this paper, an analytical solution of response of the pore pressure to atmospheric loading was derived starting from the Biot’s poroelasticity, and its corresponding numerical solutions were developed by finite element methods for 1D and 2D situations. With comparison to the analytical solution, the experimental results show that the numerical schemes sound reasonable to implement the assessment of response of the pore pressure in horizontal multilayer sedimentary formations. In particular, it is effective for a 2D model over large area with consideration of background horizontal groundwater flow. A highlight of this work is to construct a reasonable approach to capture responses of the pore pressure to atmospheric loading, and at the same time to provide the feasibility of integrated analysis of well monitoring data of pore pressure variance in Horonobe Underground Research Laboratory (URL), Hokkaido, Japan.     

Episyenite formation in the Toki granite,central Japan

Episyenite is a quartz-depleted vuggy rock resulting from hydrothermal alteration of granitic rocks. This is the first report of its existence in an island arc, which is identified in a deep drill core of the Toki Cretaceous granite distributed in central Japan. In order to understand the petrographical features of the episyenite, neutron porosity measurement, geochemical analysis, microscopic observation, and X-ray computed tomography scanning were carried out. The results show remarkably high porosity (35.4 %) due to interconnecting vugs and the removal of quartz, plagioclase, and biotite. The Rb–Sr isotopic results and the paragenetic sequence of secondary minerals in the vugs suggest that the hydrothermal alteration process can be divided into an episyenitization stage and a later hydrothermal stage. At the episyenitization stage (70.6 ± 3.1 Ma) ca. 6 million years after the emplacement of the unaltered granite (76.3 ± 1.5 Ma), dissolution of quartz, biotite, and plagioclase occurred and was followed by the precipitation of albite, vermicular chlorite, and platy calcite. The episyenitization is considered as a local alteration of the Toki granite in an isotopically closed system. At the later hydrothermal stage, illite and secondary quartz precipitated from circulating meteoric-derived water in the dissolution vugs. Superimposing alteration at the later hydrothermal stage is limited, which results in the preservation of the episyenite in an almost primitive condition.     

Biogenic opal production changes during the Mid-Pleistocene Transition in the Bering Sea (IODP Expedition 323 Site U1343)

Biogenic opal content and mass accumulation rate (MAR) at IODP Expedition 323 Site U1343 were found to fluctuate consistently, generally being high under warm conditions and low under cold conditions during the last 2.4 Ma. Continuous wavelet transform analysis of the normalized biogenic opal content indicates that export production in the Bering Sea varied predominantly at 41-ka periodicity before 1.25 Ma, and shifted to 100-ka periodicity at the onset of the Mid-Pleistocene Transition (MPT; 1.25–0.7 Ma). The 100-ka cycles dominated until the Holocene. Export production in the Bering Sea decreased markedly in the Bering Sea two times during the MPT: the first occurred at the beginning of the MPT (1.25 Ma) and the second in the middle of the MPT (0.9 Ma). These decreases coincided with both increases in the relative abundance of sea-ice diatoms and decreases in the warm-water diatom species Neodenticula seminae, indicating that reductions in export production in the Bering Sea during the MPT were associated with climate cooling. Decreases in export production in the Bering Sea during the MPT were most likely associated with the increased influence of polar/Arctic domains on the high-latitude North Pacific.     

Changes in stream flow regime in headwater catchments of the Yellow River basin since the 1950s

The headwater catchments of the Yellow River basin generate over 35% of the basin's total stream flow and play a vital role in meeting downstream water resources requirements. In recent years the Yellow River has experienced significant changes in its hydrological regime, including an increased number of zero‐flow days. These changes have serious implications for water security and basin management. We investigated changes in stream flow regime of four headwater catchments since the 1950s. The rank‐based non‐parametric Mann–Kendall test was used to detect trends in annual stream flow. The results showed no significant trend for the period 1956 to 2000. However, change‐point analysis showed that a significant change in annual stream flow occurred around 1990, and hence the stream‐flow data can be divided into two periods: 1956–1990 and 1991–2000. There was a considerable difference in average annual stream flow between the two periods, with a maximum reduction of 51%. Wet‐season rainfall appears to be the main factor responsible for the decreasing trend in annual stream flow. Reductions in annual stream flow were associated with decreased interannual variability in stream flow. Seasonal stream flow distribution changed from bimodal to unimodal between the two periods, with winter stream flow showing a greater reduction than other seasons. Daily stream flow regime represented by flow duration curves showed that all percentile flows were decreased in the second period. The high flow index (Q₅/Q₅₀) reduced by up to 28%, whereas the reduction in the low flow index (Q₉₅/Q₅₀) is more dramatic, with up to 100% reduction. Copyright © 2006 John Wiley & Sons, Ltd.     

Upper Eocene travertine-lacustrine carbonate in the Jianchuan basin,southeastern Tibetan Plateau: Reappraisal of its origin and implication for the monsoon climate

The Asian monsoon is one of the largest climatic systems in the world, but age of its onset has been estimated differently ranging from the late Eocene to the Quaternary. We investigated the sedimentology and stable isotopic compositions of the upper Eocene Jiuziyan Formation, a terrestrial limestone unit in the Jianchuan basin, Yunnan Province in China. This limestone formation is restricted in several localities in the central part of the basin. Previously, this has been characterized as palustrine carbonate and the transition to the sublacustrine deposit of the overlying Shuanghe Formation was interpreted as the appearance of wetter climate during the late Eocene. Our observations of macro- and microfacies revealed sedimentary fabrics indicating rapid CaCO₃ precipitation, such as dendritic calcite and calcified reed stems, which are unlikely to develop in a simple lacustrine setting. High carbonate content (mostly >90 %) and restricted distribution of the Jiuziyan limestone indicate a depositional setting spatially limited and isolated from clastic influx. These findings, together with clearly higher δ¹³C values (−0.7 ‰ to +6.9 ‰) and lower δ¹⁸O values (−14.6 ‰ to −10.5 ‰) than those of the Shuanghe Formation, indicate that the limestone was mainly travertine, carbonate formed from endogenic spring water. The elevated δ¹³C resulted from a large amount of CO₂ degassing from spring water with high pCO₂. In addition, the occurrence of centimeter-scale lamination coupled with cyclic changes in δ¹³C and δ¹⁸O is almost identical with the modern annually-laminated travertine reported from Baishuitai in northern Yunnan Province, implying comparable amplitude of seasonal temperature and precipitation changes to the record of the modern travertine at Baishuitai. Our results do not contradict the previous interpretation of late Eocene wetting and additionally suggest the existence of the late Eocene monsoon climate in the Jianchuan basin.     

Multi-approach characterization of shallow-water carbonates off Minamitorishima and their depositional settings/history

Sedimentological, geochemical, and chronological analyses were carried out on 18 carbonate rock samples collected at depths of 938, 1085, and 3354 m on the western slope of Minamitorishima (Marcus Island), which is located near the western margin of the Pacific Plate. Four groups of carbonate rocks were distinguished: a mollusk-rich limestone, a coral-rich dolomite, a foraminiferal-nannofossil packstone, and a phosphatized mudstone/wackestone. The mollusk-rich limestone is characterized by the dominance of bivalves (including rudists) and gastropod shells. Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) and Mesorbitolina ex gr. texana (a large benthic foraminifer) indicate that the shallow-water carbonates were deposited during the late Aptian–early Albian (ca. 123–111 Ma). The coral-rich dolomite is characterized by abundant scleractinian corals and nongeniculate coralline algae associated with encrusting acervulinid foraminifers. The biotic composition is similar to that of the Oligocene–Pleistocene carbonates reported from other seamounts in the northwestern Pacific. Geochemical data show that the coral-rich carbonates were dolomitized at 9.5–6.8 Ma (Tortonian–Messinian) and that normal seawater was the most likely parent fluid. The foraminiferal-nannofossil packstone is a semi-consolidated foraminiferal-nannofossil ooze and was deposited during the Pleistocene (0.99–0.45 Ma). The phosphatized mudstone/wackestone is marked by the absence of macrofossils and the presence of traces of planktic foraminifers. Although its depositional age is not constrained, the Sr isotope ratios indicate that the phosphatization occurred at 33.2–28.9 Ma. After the deposition of the Cretaceous shallow-water carbonates, including the mollusk-rich limestone, Minamitorishima was drowned and its top was covered with a pelagic cap, represented by the mudstone/wackestone. The late Eocene–early Oligocene volcanism (40.2–33.2 Ma) caused episodic uplift and returned the top of Minamitorishima to a shallow-water environment. After the early Oligocene phosphatization of the pelagic cap, coral reefs flourished on the top of this island. The reef limestone was dolomitized during the Tortonian–Messinian.     

Study of polluted soil remediation based on freezing and thawing cycles

It is generally known that soil pollution poses a terrible hazard to the environment, but the present techniques of contaminated soil remediation cannot control this growing threat. This paper compares the pollutant extraction efficiency of traditional pumping and treating, which is a typical washing technology for the remediation of contaminated soils, with methods that utilize freeze-thaw cycles. In the soil freezing process, water shifts from unfrozen soils to the freezing front, and the permeability of soil will be enhanced under certain temperature gradients and water conditions. Therefore, this paper discusses the purification of contaminated soil through freeze-thaw action. We conducted a cleansing experiment on clay and silica sand infused with NaCl（simulation of heavy metals） and found that the efficiency of purification was enhanced remarkably in the latter by the freeze-thaw action. To assess the effective extraction of DNAPLs in soil, we conducted an experiment on suction by freezing, predicated on the different freezing points of moisture and pollutants. We found that the permeability coefficient was significantly increased by the freezing-thawing action, enabling the DNAPL contaminants to be extracted selectively and effectively.     

考虑系统柔度影响的水压致裂法测量深部岩石应力

为了有效测量水压致裂方法中的重张压力,必须使用具有足够小柔度的试验设备,否则无法从重张压力估计垂直钻孔平面的最大水平应力.仅通过替换水压致裂系统中的某一部件来大幅度降低系统柔度是很难的.但如果流量计尽可能安装在靠近跨接式封隔器隔离出的钻孔测试区.那么系统柔度就会大大降低.为此,我们研制出配有井下流量计的试验系统,并在野...     

Geochronological and geochemical constraints on the petrogenesis of high-K granite from the Suffi abad area, Sanandaj-Sirjan Zone, NW Iran

The Sanandaj-Sirjan Zone (SSZ) trends northwestward in western Iran on the Precambrian to Paleozoic basement and exposes abundant I-type granitoids and calc-alkaline volcanic rocks that were most active during the Late Jurassic to Upper Cretaceous. The petrogenesis of the granitoids and associated volcanic rocks has been widely related to Neotethyan subduction beneath the Iranian plate. We report a geochronological and geochemical study of the Suffi abad granite (SLG) body that crops outs southeast of Sanandaj within the SSZ and is mainly composed of K-feldspar + quartz + plagioclase ± hornblende. The SLG, which shows a high-K calc-alkaline affinity, has LA-ICPMS zircon U–Pb ages ranging between 149 ± 2 and 144 ± 3 Ma and initial ⁸⁷Sr/⁸⁶Sr of ∼0.7024–0.7069 and ¹⁴³Nd/¹⁴⁴Nd of ∼0.5125–0.5127. These value correspond to an ?_Nd (145 Ma) of +1.5 and +4.9, suggesting that the SLG originated from the juvenile crust or depleted mantle with a young T_DM (650–900 Ma) over the subduction zone beneath the SSZ. Zircon saturation temperatures suggest that crystallization of the zircons, or emplacement of the host magmas, occurred at 560–750 °C, consistent with an intergrowth texture of K-feldspar and quartz that implies crystallization around the K-feldspar-quartz eutectic at lower temperatures. Overall, geochemical data suggest that crystallization of the hornblende and plagioclase played a role in magma differentiation. These data allow us to conclude that the high-K SLG did not originate directly from the juvenile mantle source as do most I-type, calc-alkaline granitoids, but more likely was produced from the partial melting of pre-existing I-type granitoids in the upper continental crust under low pressure conditions.