Proluvial Fan Research Articles

Role of seismogeological modeling in the attribute analysis of seismic data using the example of the forecast of the thickness of the Yu3t formation of the southwestern Kazakhatsan oil field

Relevance. The need to introduce the results of two-dimensional seismogeological modeling into seismic data attribute interpretation to identify signs of manifestation of the target object of the forecast in the wave field of seismic recording and assess the influence of interference of the host strata on it. Object. Highly productive terrigenous Upper Jurassic Yu3t formation of the Nizhnekumkol formation of the oil field of southwestern Kazakhstan, formed under conditions of a cone of liquid proluvial fan. Aim. To assess the impact of the interaction of the enclosing strata of the Upper Jurassic Yu3t formation on the seismogeological forecast of its capacities within the considered oil field. Methods. Two-dimensional seismogeological modeling based on the analysis of the frequency response and determination of the shape of the elementary pulse of seismic recording in the interval of the productive formation. Analysis of the thicknesses of geological inhomogeneities overlying the Yu3t formation in order to assess their effect on the wave characteristic of the time interval of research. Results. The performed two-dimensional seismogeological modeling showed that the amplitude characteristic of the negative phase of the wave packet of the target object, characterizing the power of the Yu3t formation, is affected to varying degrees by the overlapping thicknesses of the Yu3a formation and the inter-reservoir seal P1. Based on the modeling results, it was concluded that the basis for predicting the thickness of the Yu3t formation should be considered an attribute map of the difference in amplitudes of the upper positive (A) and average negative (B) phases of the considered wave packet A, B, C. At the same time, the correlation dependences of the obtained attribute with the values of the thickness of the Yu3t formation in drilled wells should be considered within the areas outside the zone the influence of other elements complicating the wave pattern of the target object (tectonic disturbances and erosive protrusions of the foundation).

Effects of desert plant communities on soil enzyme activities and soil organic carbon in the proluvial fan in the eastern foothills of the Helan Mountain in Ningxia, China

Effects of desert plant communities on soil enzyme activities and soil organic carbon in the proluvial fan in the eastern foothills of the Helan Mountain in Ningxia, China

Enhancing groundwater level prediction accuracy at a daily scale through combined machine learning and physics-based modeling

Study regionYongding River alluvial proluvial fan, a part of North China Plain with intense groundwater withdrawals. Study focusThe objective of this study is to enhance the accuracy of groundwater level (GWL) prediction at a daily scale by combining short-term memory (LSTM) and physics-based (PB) models. Two types of LSTM models were developed: LSTM-H-ORI, which predicts GWL, and LSTM-dH-ORI, which predicts simulated errors of the PB model. These models were subsequently refined into LSTM-H-IMP and LSTM-dH-IMP by incorporating the outputs from the PB model. To investigate the influence of groundwater flow processes, LSTM-H-IMP was further enhanced by considering the time lag properties of precipitation, referred to as LSTM-H-IMP-LAG. New hydrological insights for the regionSignificant improvements were found for LSTM-H-IMP when the performance of LSTM-H-ORI was poor (Nash–Sutcliffe Efficiency Coefficient, NSE<0) or the performance of PB model was not bad (NSE≥0). And the prediction accuracy was improved for over 67% of wells in this case. When the performance of PB model was medium and poor (NSE≤0.6), the improvement of LSTM-dH-IMP was more effective, leading to a prediction accuracy enhancement for over 77% of wells. Additionally, LSTM-H-IMP-LAG exhibited further improvement, with an average NSE increase of 0.1. This study provides scientific methods for accurate prediction of GWL at a daily time scale and the combined application of LSTM and PB models.

Spatial Distribution, Material Composition and Provenance of Loess in Xinjiang, China: Progress and Challenges

The loess in the arid area of Xinjiang is located at the eastern end of the Central Asia Loess Belt, and paleoclimate research about it is of great importance for understanding the mechanism of interaction of the Eurasian Westerly monsoon system and the aridity of Central Asia. This review focuses on recent progress concerning the spatial distribution, material composition and provenance of loess in Xinjiang and points out the shortcomings of and challenges to provenance and dust circulation. Field investigation and previous studies indicate that loess sediments have been mainly distributed on the river terraces and windward piedmont of the Tianshan Mountains and the Kunlun Mountains since the late Pliocene (mainly late Pleistocene). Grain size and age data show that Xinjiang loess deposits at some locations are rapid and discontinuous or sedimentary hiatus. The Siberian High system largely controlled dust mobilization and loess accumulation in northern Xinjiang but not southern Xinjiang. In southern Central Asia, the intensity of dust activity may be determined by the Caspian Sea–Hindu Kush Index (CasHKI) and local circulation. However, there is not enough evidence that the CasHKI index can affect the Tarim Basin area. Consequently, ascertaining the driving mechanism of mid-latitude Westerly winds and the dynamic process of loess deposition in Xinjiang is a specific suggestion for critical future research. Many indicators have shown that the loess dust sources in Xinjiang are composed of mainly proximal materials plus some remote materials. Alluvial plains and local proluvial fans contributed more to loess deposition, while Central Asian deserts comprise a small proportion of loess deposition in northern Xinjiang. In future provenance research, new technologies and new methods should be continuously tested to facilitate an objective understanding of the provenance of the loess in Xinjiang.

Reservoir characteristics and controlling factors of the Lower paleogene sandstones in the southeast part of Jiyang Sag, BohaiBay Basin, China

With the continuous improvement of exploration degree in Bohai Bay Basin, the red beds in Jiyang Sag has become a hot exploration spot in recent years, the red beds is buried deep, and the distribution of favorable reservoirs has become a key factor restricting oil and gas exploration. This paper combines logging, core and seismic data, mainly introduces the sandstone reservoir characteristics of red beds in the southeast of Jiyang depression, and analyzes the influence of sedimentary environment and diagenesis on its reservoir characteristics respectively. The results showed that the red bed sandstone is mainly composed of arkose, quartz-feldspar and feldspar-quartz graywackes, with good porosity and permeability. Under the control of the original sedimentary environment, three types of reservoir sand bodies are mainly developed in the study area: proluvial fan, fan delta and beach bar deposits, among them, fan delta deposits have better storage performance. The diagenetic environment was early alkaline and late acidic, compaction and cementation greatly reduced primary pores and a large number of secondary pores are produced due to minerals dissolution. Under the combined influence of sedimentary environment and diagenesis, the red-bed reservoirs have various types of reservoir spaces, with obvious differences in porosity and permeability.

Characteristics of groundwater in Northeast Qinghai-Tibet Plateau and its response to climate change and human activities: A case study of Delingha, Qaidam Basin

Delingha is located in the northeast margin of Qaidam Basin. Bayin River alluvial proluvial fan is the main aquifer of Delingha, in which groundwater generally flows from north to south. The hydrochemistry results showed that two different hydrochemical evolution paths formed along southeast and southwest directions, respectively. Cl-Na type groundwater was formed in front of Gahai Lake, and SO4·HCO3-Na·Ca type groundwater was formed in front of Keluke Lake. The results of deuterium (D) and 18O revealed that the groundwater mainly originated from the continuous accumulation of precipitation during geological history under cold and humid climate conditions. In addition, results of 14C indicated that the groundwater age was more than 1140 years, implying relatively poor renewal capability of regional groundwater. Moreover, our numerical modeling results showed that the regional groundwater level will continue to rise under the warm and humid climate conditions.© 2021 China Geology Editorial Office.

Evolution of the Barkol Basin, eastern Tian Shan, and its geodynamic background

The Barkol Basin (BB) is an intramontane basin in the easternmost Tian Shan, Northwest China. We reconstructed the tectonic evolution of the BB based on an investigation of its stratigraphy and faults, and we differentiated the basin infill into Quaternary sediments and the Oligocene–Miocene Taoshuyuanzi Formation by combining field observations and geophysical data with borehole data. We used detrital zircon U–Pb dating and palaeo-currents to decipher the provenance of the lower Jurassic Badaowan Formation, which contains the only Mesozoic sediments throughout the easternmost Tian Shan. The results demonstrate that the BB and Harlik Range constitute the main sources. Furthermore, we found that the Taoshuyuanzi Formation unconformably overlies the Palaeozoic basement in the basin, indicating that the BB formed during the Oligocene–Miocene. Based on Magnetotelluric (MT) and seismic profiles, this formation was deposited under the control of basin-bounded faults. According to the field investigation, the boundary faults of the basin were recognized as sinistral strike-slip normal faults. Additionally, remote sensing and electron spin resonance (ESR) data provided valuable information on the Quaternary proluvial fan divisions, which suggest a multi-stage tectonic evolution of the basin during the Quaternary. The Mesozoic–Cenozoic basin evolution in the easternmost Tian Shan was divided into four phases based on an integrated analysis of the stratigraphy and structures of the Santanghu Basin and the Turpan-Hami Basin: (1) from the Late Triassic to the Early-Middle Jurassic, tectonic subsidence dominated the Santanghu Basin and Turpan-Hami Basin; (2) during the Late Jurassic-Eocene, the episodic uplift of the Tian Shan Mountains constricted the Turpan-Hami Basin and the Santanghu Basin; (3) during the Oligocene–Miocene, the BB formed as a subsidence basin controlled by sinistral strike-slip normal faults, and the basins filled with thick layers of clastic rocks; and (4) during the Pliocene–Quaternary, the eastern BB uplifted, and the basins deformed. In conjunction with previous research, the dynamic background of the formation of the BB was presumably related to the clockwise rotation of the Tarim Block to the south and the strong left-lateral movement of the Gobi-Tian Shan fault system.

Spatial distribution of arsenic along groundwater flow path in Chaobai River alluvial–proluvial fan, North China Plain

The North China Plain has been identified as a potential high-arsenic (As) groundwater area; however, little is known about the As distribution along the groundwater flow path. In this study, 154 groundwater samples were collected from the alluvial–proluvial fan of the Chaobai River, which lies in the north of the North China Plain. The chemical compositions of the samples were analyzed to investigate the spatial distribution of groundwater As and to understand the hydrogeochemical processes that controls As mobilization. Results revealed that groundwater As concentrations were < 1 μg/L in the piedmont recharge zone (zone I) where groundwater flushing was strong, while high (< 1–73 μg/L) in the middle runoff zone (zone II), which features a moderate permeability and hydraulic gradient. In the downward plain zone (zone III) under stagnant hydraulic conditions, groundwater As concentrations reached 111 μg/L. Vertically, high-As groundwater mainly occurred in shallow aquifers (depths < 100 m) in zones II and III. In addition, iron (Fe), manganese (Mn), and NH4+ concentrations showed increasing trends similar to those of As along the groundwater flow path, whereas the NO3− concentrations and redox potential (Eh) showed decreasing trends, which implies a gradual change in the redox conditions. The systematic variation in the As concentrations along the groundwater flow path and the correlations between As and redox sensitive components suggest that groundwater As would occur via the reductive dissolution of Fe/Mn oxides and that slow groundwater flow is an important factor that promotes As enrichment in groundwater.

New evidence for the provenance and formation of loess deposits in the Ili River Basin, Arid Central Asia

Abstract Loess deposits are thick and widespread along the piedmonts of Arid Central Asia (ACA), however the source (provenance) and processes of formation of these fine-grained aeolian deposits are poorly understood. Here we investigate the provenance and possible distribution mechanisms for loess along the slopes of the Ili River basin, located in northwest China and southeastern Kazakhstan, using a grain-size mixture model and an elemental geochemistry-based source fingerprinting technique. Our results indicate that the Ili loess experiences low rates of sedimentary recycling downstream within the basin piedmont, and are strongly dependent on local geomorphic context. Loess deposits are dominated by proximal sources, indicating short-distance aeolian transport from the Ili River alluvial plains and local proluvial fans. Local sourcing dominated regardless of location within the catchment, although the proportion of fluvial input increases proportionally with increasing distance downstream. Our results suggest that the Central Asian deserts did not act as significant interim storage reservoirs for the loess deposits in the Ili River basin, which contrasts with the popular model for piedmont loess formation across Central Asia. Most likely the relatively enclosed and highly variable basin topography precluded transport from the open desert steppe into the upper Ili River valley. Our study provides the first clear evidence for a genetic link between the Asian high mountains and the loess of the adjacent piedmonts, based on geochemical and grain-size data, with the caveat that the high degree of topographic variability along the Tianshan piedmont likely results in a strongly localized influence on loess formation and accumulation.

Improving the Reliability of Numerical Groundwater Modeling in a Data-Sparse Region

In data-sparse areas, due to the lack of hydrogeological data, numerical groundwater models have some uncertainties. In this paper, a nested model and a multi-index calibration method are used to improve the reliability of a numerical groundwater model in a data-sparse region, the Nalinggele River catchment in the Qaidam Basin. Referencing this key study area, a regional three-dimensional groundwater flow model is developed in a relatively complete hydrogeological unit. A complex set of calibration indices, including groundwater fitting errors, dynamic groundwater trends, spring discharges, overflow zone location, and groundwater budget status, are proposed to calibrate the regional numerical groundwater model in the Nalinggele alluvial–proluvial fan. Constrained by regional groundwater modeling results, a local-scale groundwater model is developed, and the hydrogeological parameters are investigated to improve modeling accuracy and reliability in this data-sparse region.

Geochemistry and zircon U–Pb–Hf isotopic data for Permo-Carboniferous sediments in the Solonker Zone, Inner Mongolia, China: constraints on depositional age, provenance and tectonic setting

The Permo-Carboniferous tectonic setting of the SE Central Asian Orogenic Belt is poorly understood, especially with regard to the development of the Solonker (Suture) Zone. New stratigraphic, geochemical and detrital zircon analyses for Permo-Carboniferous sediments have been undertaken to resolve this problem. In the Mandula area, the Baotege Formation and former Amushan Formation were deposited in the early Permian. An unstable alluvial–proluvial fan to a stable shallow marine environment has been proposed. In the NE Sonid Youqi area, late Carboniferous to middle Permian carbonate–clastic rocks were deposited in a relatively stable shallow sea with a series of transgressions. Upper continental crust-like geochemical features, magmatic zircons and petrography show that the clastic rocks have a felsic source ranging from granites to tonalite–trondhjemite–granodiorite. Detrital zircons with prominent age groupings at c. 280–330 Ma, c. 350–370 Ma and/or c. 400–500 Ma with some Precambrian ages, together with zircon Hf isotopic data, indicate that the sediments were dominantly sourced from the orogenic belt itself and microcontinents. Basin analysis shows a transition from restricted basins in the late Carboniferous–early Permian to wider and deeper basins in the middle Permian. Accordingly, an extensional stage has been proposed, at least before the final closure of the Solonker Zone. Supplementary material: Detailed geochemical data, zircon Th/U ratios, U–Pb ages, Hf isotopic data and figures showing samples are available at https://doi.org/10.6084/m9.figshare.c.3948325

Preliminary study of the flooding characteristics on proluvial fan under different peak discharges

The changes of flooding area and surface morphology on a proluvial fan from typical middle-small scale gully in Southwest China were studied under different peak discharges based on large scale of field solid model experiments. The results showed that: in the model fan, 1) the changes of flooding area and surface morphology before and after floods increased with the increases of peak discharges. Most flooding occurred on the concave bank around top rush point, which also made the local surface morphology changed dramatically, i.e. the increases of width-depth ratio of river channel. 2) Buildings on the upper fan less than 20m away from the river bank could be affected seriously by the extreme floods, while the distance on the lower fan was 40m. On the middle part of model fan, buildings less than 10m away from the river bank would suffer disasters under small floods, and the distances were 30m and 80m under middle and extreme floods, respectively.

Analysis of the influence of different groundwater flow conditions on the thermal response test in Tangshan

Comprehensive thermal conductivity of the rock and soil is generally measured by thermal response test ignoring the effect on groundwater flow. However, the influence of the groundwater flow on thermal conductivity is drastic, so the design of ground heat exchangers with no consideration of groundwater flow is inaccurate. Tangshan is distributed in the river alluvial–proluvial fan of Luanhe River system and groundwater flow rapidly. Hence, analysis of thermal conductivity with thinking about groundwater flow is necessary. In this paper, the comprehensive thermal conductivity within depth of 100 m in Tangshan is measured by two methods: thermal response test and laboratory experiment. Pumping test and tracer test are implemented to simulate of groundwater flow field with different flow conditions. Test results show that: (1) Laboratory experiment results cannot truly represent the comprehensive thermal conductivity of layers. The average thermal conductivity of natural flow field is 23% higher than the laboratory experiment weighted results. (2) The comprehensive thermal conductivity increased 23% with the groundwater flow from the 1.026 to 4.176 m/d. Acceleration of groundwater flow is propitious to improve the thermal conductivity. (3) With the increase in groundwater flow, the initial temperature of ground decreases about 2.3 °C, the results of the stable thermal flow test and the stable operation condition test gradually rise slightly. So acceleration of groundwater flow is conducive to heat exchange. It is proved that the influence of groundwater flow cannot be ignored.

Iodine in groundwater of the Guanzhong Basin, China: sources and hydrogeochemical controls on its distribution

Groundwater sampling at 179 sites in the Guanzhong Basin, China, indicated iodine concentrations ranging from 2 to 28,620 μg/L. 7.3 % of the sites have iodine concentrations 300 μg/L and are defined as “iodine excess water.” Sites with low groundwater iodine concentrations are mainly distributed at the edge of a piedmont alluvial–proluvial fan containing bicarbonate-rich water with a low mineral content, near-neutral pH values and low fluorine concentrations. The piedmont fan is characterized by a fast groundwater flow and active leaching of iodine from the sediments. Conversely, high groundwater iodine concentrations are principally located in silty or clayey sedimentary zones having low groundwater flow rates, weakly alkaline to alkaline pH values, and water containing HCO3·SO4, SO4·Cl and Cl·SO4 hydrochemical types. Elevated iodine concentrations in shallow groundwater commonly occur in discharge areas where there is a high rate of solute evaporation; elevated iodine concentrations in deep groundwater are likely attributed to microbial decomposition of organic matter under anaerobic conditions. Processes of iodine enrichment lead to correlations between high iodine and high fluorine contents in shallow groundwater, and between high iodine and high arsenic concentrations in deep groundwater. Moreover, redox processes and active water recycling are important factors for groundwater iodine enrichment.

Groundwater evolution and recharge determination of the Quaternary aquifer in the Shule River basin, Northwest China

Groundwater recharge and evolution in the Shule River basin, Northwest China, was investigated by a combination of hydrogeochemical tracers, stable isotopes, and radiocarbon methods. Results showed the general chemistry of the groundwater is of SO4 2− type. Water–rock reactions of halite, Glauber’s salt, gypsum and celestite, and reverse ionic exchange dictated the groundwater chemistry evolution, increasing concentrations of Cl−, Na+, SO4 2−, Ca2+, Mg2+ and Sr2+ in the groundwater. The δ18O and δ2H values of groundwater ranged from −10.8 to −7.7 and −74.4 to −53.1 ‰, respectively. Modern groundwater was identified in the proluvial fan and the shallow aquifer of the fine soil plain, likely as a result of direct infiltration of rivers and irrigation returns. Deep groundwater was depleted in heavy isotopes with 14C ages ranging from 3,000 to 26,000 years, suggesting palaeowater that was recharged during the late Pleistocene and middle Holocene epochs under a cold climate. These results have important implications for groundwater management in the Shule River basin, since large amounts of groundwater are effectively being mined and a water-use strategy is urgently needed.

Active faults and dip slip rates along the northern margins of the Huashan Mountain and Weinan loess tableland in the southeastern Weihe Graben, central China

Two active faults, including the Huashan piedmont fault (HPF) along the northern margin of Huashan Mountain and the north margin fault of the Weinan loess tableland (NMF-WLT), were developed in the southeastern Weihe Graben, in central China. HPF, which is the most active fault in the Weihe Graben, is known throughout the world for the M81/4 great Guanzhong earthquake in 1556 AD. Through field investigation, AMS 14C, and OSL dating in this paper, in combination with previous studies, the following results are obtained: (i) Tectonic landforms, such as triangular fault facets, waterfalls and fault scraps of proluvial fans, were developed in the HPF, but these features were not developed in the NMF-WLT. (ii) HPF experienced three intensive seismic activities in 5920–7670Cal yr BP, 2215±95–3105±105Cal yr BP and 1556 AD during the Holocene, but there has only been one seismic event noted for the NMF-WLT since the Holocene (6865±80Cal yr BP). (iii) The dip-slip rate of the HPF was approximately 0.64mm/yr since the mid-Pleistocene and approximately 1.67–2.71mm/yr in the Holocene. In contrast, the dip-slip rate of NMF-WLT was approximately 0.32–0.42mm/yr since the early Pleistocene and was approximately 0.39–0.58mm/yr from the late Pleistocene to the Holocene. (iv) The seismic activity at the HPF has been more intense than at the NMF-WLT; the HPF was the triggering seismic fault of the M81/4 great Guanzhong earthquake in 1556 AD, whereas the NMF-WLT was not the seismogenic fault of this event. These results provide new information for the study of active tectonics of the Weihe Graben.

Microfossils and biofacies of the Vendian fossil biota in the southern Siberian Platform

Based on the study of the litho- and biofacies of the Vendian Nepa Horizon in the central area of the Siberian Platform inland, a paleoecological model for the Vendian microbiota has been developed. The sedimentation environments of the Katanga saddle have been reconstructed, and three sedimentary systems have been recognized: (1) lower continental, formed by the deposits of proluvial fans and riverbeds of temporary streams; (2) middle transgressive, made up of littoral sand facies in the lower part and of fine-clastic shelf strata in the upper part; and (3) upper, of sea highstand, composed of alternating sand bank facies and fine-clastic lagoon deposits. Four biofacies have been recognized in the fine-terrigenous deposits of the Nepa Horizon: (1) Appendisphaera, represented by a Doushantuo-Pertatataka acanthomorph assemblage; (2) Transitional, with a great diversity of plankton and benthic (including complex) taxa; (3) Vanavarataenia, dominated by Vanavarataenia complex benthic algae; and (4) Oscillatoriopsis, represented by taxonomically poor biotas with morphologically simple (mainly prokaryotic) remains. These biofacies are confined to the following sedimentation environments: Appendisphaera is widespread in the distal open-sea areas; the Transitional biofacies is localized in the distal environments of the semi-isolated inner basin; Vanavarataenia occurs in the proximal areas; and Oscillatoriopsis is typical of the shallow-water environments, both extended (corresponding to the highstand period) and local.

Geomorphology of the Dzungarian plain and its mountain frame

In the late Pliocene and Pleistocene onsite the Cretaceous-Paleogene peneplain peripherally the Dzungaria the high mountains occurred and the plain remained in the center as the territory of massive material accumulation which carried out of the mountains. Three main relief levels formed. Top level included high altitude, middle altitude stratum and intermountain basin stratum on the area of 146000 square kilometers. Middle and low levels formed Dzungarian plain on the area of 223,5 square kilometers. Its margin part (middle level) is represented low changed peneplain (28% of the area). Low level in central part organize the following geomorphological stratum: eolian (21%), lake (5%), alluvial-and-proluvial (21%) and stratal plain (11%), proluvial fans (10%) and front ranges – forbergs (less than 1%). Modern and ancient valleys of large streams occupied less than 3% of the plain area.

Hydrogeochemical contrasts between low and high arsenic groundwater and its implications for arsenic mobilization in shallow aquifers of the northern Yinchuan Basin, P.R. China

Summary Little is known about hydrogeochemical contrasts between low and high As groundwaters and their connection to As mobilization in the Yinchuan Basin. Investigations were carried out to evaluate As distribution and geochemical processes for As mobilization in three regions, including piedmont proluvial fans (PA), dry farmland (DF) and paddy farmland (PF). Ninety-two groundwater samples, 4 surface water samples, and 66 sediments samples were collected and analyzed for chemical and isotopic components. Results show that low As groundwater is generally found in PA. However, high As concentrations (up to 105 μg L−1) are mainly observed in groundwaters from DF and PF, which are associated with reducing conditions. High As groundwater is characterized by high concentrations of NH4+, dissolved Mn, dissolved Fe and Fe(II), and low concentrations of NO3− and SO42−. The intensive irrigation in PF recharges the aquifers by vertical infiltration of the diverted Yellow River water, and leads to the higher redox potentials and the lower dissolved As in comparison with those in DF. Environmental isotopes (δ18O and δD) show that evaporation due to the intensive irrigation plays a minor role in As enrichment. The positive correlation between As and dissolved Fe suggests that groundwater As would result from the reductive dissolution of Fe oxides. Besides, dissolved P may be involved in competing with As for binding sites on Fe oxide minerals. Sediment As ranges between 3.94 and 75.2 mg kg−1. HCl-leached As accounts for 60% of total As in the sediments, while H3PO4-leached As accounts for 5%. Depth-matched samples show a good correlation between dissolved As and H3PO4-leached As in sediments. Arsenic distribution coefficient (Kd), calculated from H3PO4-leached As and dissolved As, ranges between 5.08 and 17.3 cm3 g−1, which generally depends on groundwater redox potentials. In reducing conditions, low values are found with As being preferentially partitioned into groundwater.

The Strontium Isotopic Chemical Analysis of Geothermal Water in Guihu, Fuzhou

This paper takes Fuzhou Guihu geothermal field as the research object, analyzing its geothermal background of regional tectonic characteristics. With the increase of flow path, contents of carbonate and aluminosilicate minerals both raises, while 87Sr/86Sr goes down gradually. 87Sr/86Sr in discharge regions of geothermal water is the lowest. Analysis of the geothermal water chemistry and isotopic characteristics lead to the conclusion that the underground water circular depth of wells located on the alluvia and proluvial fans in front of mountains is relatively deep, which reaches 500-700m. Average of the mixed ratio is 0.14, which means that 14% cold water is mixed.