The hypothesis that basinal brines inherited their major ion chemistries and elevated salinities from evaporated paleoseawaters is tested by comparing the compositions of basinal brines in Silurian (Michigan basin, Illinois basin, Appalachian basin in eastern Ohio) and Jurassic/Cretaceous (Central Mississippi Salt Dome basin, Arkansas shelf, and south‐central Texas) host rocks, when the world oceans were ‘CaCl2seas’, with those from Permian and Pennsylvanian rocks (Palo Duro basin, Central Basin Platform, and Delaware basin, Texas and New Mexico) when the world oceans were ‘MgSO4seas’. Basinal brines examined are assumed to have originally formed from evaporation of the same seawaters that produced major evaporites. Sulfate, Mg and K levels in basinal brines are below the concentrations expected from evaporation of seawater of any type, which emphasizes the importance of diagenetic mineral–brine interactions in controlling basinal brine chemistry. There are no major differences in SO4, Mg and K concentrations between basinal brines hosted by rocks originally formed during ages when the world oceans were MgSO4seas versus CaCl2seas. Basinal brines in Pennsylvanian–Permian rocks are compositionally distinct (relatively high Na and low Ca) from basinal brines in Silurian, Jurassic and Cretaceous host rocks, which may reflect original differences in seawater chemistry. Basinal brines enriched in Ca and depleted in Na relative to evaporated seawater of any type have traditionally been interpreted to form by albitization of plagioclase feldspar. A new explanation for Ca enrichment and Na depletion of basinal brines is the mixing of evaporated CaCl2‐type seawater with more dilute water. Some basinal brines are similar in major ion composition to evaporated seawater of a particular age, for example basinal brines in the Cretaceous Edwards Group carbonates, Texas, where dolomitization is the only reaction required to convert evaporated Mesozoic CaCl2seawater into Edwards Group brine.

T. K. LOWENSTEIN

M. N. TIMOFEEFF

Geofluids

Secular variations in seawater chemistry as a control on the chemistry of basinal brines: test of the hypothesis

盆地卤水化学受海水化学长期变化的控制：假设检验

Formation water is produced during gas well production, which can seriously affect gas well productivity, especially in deep and ultradeep tight sandstone gas reservoirs. In this paper, we have studied the formation water production and geochemical properties of the ultradeep tight sandstone gas reservoir in the Cretaceous Bashijiqike Formation of the DK gas field in the Kuqa Depression. The results indicate that the formation water can be classified as condensate water, gas-water transition zone water, mixed water, and isolated formation water, all of which are acidic and of CaCl2 type, with increasing salinity or chloride ion content. Sodium/chloride ratio (ρNa+/ρCl-), metamorphic coefficient (ρ(Cl--Na+)/ρ(Mg2+)), desulfurization coefficient (100×ρSO42−/ρCl−), and trace elements concentration parameters show that the formation water was formed in a closed and reductive environment and experienced strong water-rock interaction. The formation water may have been influenced by early seawater, but it is not significant and is more likely to have been influenced by water seepage from the overlying gypsum strata. The Sr, H, and O isotopes reveal that the different types of formation water have good homology and are not affected by atmospheric precipitation, which is propitious to the preservation of natural gas.

Xiaobo Guo

Libin Zhao

Wei Han

Longfei Zhou

Zhilong Huang

Xiongwei Sun

Xuejun Yang

Tonghui Zhang

Chenglin Zhang

Geochemistry of Formation Water and Implications for Ultradeep Tight Sandstone of DK Gas Field in Kuqa Depression

Calcite veins in Paleoproterozoic granitoids on the Baltic Shield are the focus of this study. These veins are distinguished by their monomineralic character, unusual thickness and closeness to Neoproterozoic dolerite dykes and therefore have drawn attention. The aim of this study was to define the source of these veins and to unravel their isotopic and chemical nature by carrying out fine‐scale studies. Seven calcite veins covering a depth interval of 50–420 m below the ground surface and composed of breccias or crack‐sealed fillings typically expressing syntaxial growth were sampled and analysed for a variety of physicochemical variables: homogenization temperature (Th) and salinity of fluid inclusions, and stable isotopes (87Sr/86Sr,13C/12C,18O/16O), trace‐element concentrations (Fe, Mn, Mg, Sr, rare earth elements) and cathodoluminescence (CL) of the solid phase. The fluid‐inclusion data show that the calcites were precipitated mainly from relatively low‐temperature (Th= 73–106°C) brines (13.4–24.5 wt.% CaCl2), and the87Sr/86Sr is more radiogenic than expected for Rb‐poor minerals precipitated from Neoproterozoic fluids. These features, together with the distribution of δ13C and δ18O values, provide evidence that the calcite veins are not genetic with the nearby Neoproterozoic dolerite dykes, but are of Paleozoic age and were precipitated from warm brines expressing a rather large variability in salinity. Whereas the isotopic and chemical variables express rather constant average values among the individual veins, they vary considerably on fine‐scale across individual veins. This has implications for understanding processes causing calcite‐rich veins to form and capture trace metals in crystalline bedrock settings.

O. M. Maskenskaya

H. Drake

C. Broman

J. K. Hogmalm

G. Czuppon

M. E. Åström

Source and character of syntaxial hydrothermal calcite veins in Paleoproterozoic crystalline rocks revealed by fine‐scale investigations

通过精细尺度研究揭示的古元古代结晶岩中顺层热液方解石脉的来源与特征

Rainfall and reservoir level fluctuation are two of the main factors contributing to reservoir landslides. However, in China’s Three Gorges Reservoir Area, when the reservoir water level fluctuates significantly, it comes at a time of abundant rainfall, which makes it difficult to distinguish which factor dominates the deformation of the landslide. This study focuses on how rainfall and reservoir water level decline affect the seepage and displacement field of Baijiabao landslide spatially and temporally during drawdown of reservoir water level in the Three Gorges Reservoir Area, thus exploring its movement mechanism. The monitoring data of the landslide in the past 10 years were analyzed, and the correlation between rainfall, reservoir water level decline, and landslide displacement was clarified. By the numerical simulation method, the deformation evolution mechanism of this landslide during drawdown of reservoir water level was revealed, respectively, under three conditions, namely, rainfall, reservoir water level decline, and coupling of the above two conditions. The results showed that the deformation of the Baijiabao landslide was the coupling effect of rainfall and reservoir water level decline, while the latter effect is more pronounced.

Nenghao Zhao

Bin Hu

Qinglin Yi

Wenmin Yao

Chong Ma

The Coupling Effect of Rainfall and Reservoir Water Level Decline on the Baijiabao Landslide in the Three Gorges Reservoir Area, China

降雨与水库水位下降对三峡库区白家包滑坡的耦合效应

Abstract Salar Ignorado is a shallow acid saline lake hosted by a small intervolcanic basin high in the Andes Mountains of northern Chile. Modern surface waters have 3.3–4.1 pH , 0.5–3% total dissolved solids ( TDS ) and are actively precipitating gypsum crystals. The gypsum crystals trap the acid saline water as fluid inclusions, providing a record of recent surface water characteristics. Salar Ignorado gypsum contains three distinct types of primary fluid inclusions, which result from growth of the gypsum from surface waters. Petrography and microthermometry were performed on 27 gypsum crystals from Salar Ignorado to gain an understanding of recent water chemistry of the salar. One 18.3‐cm‐long gypsum crystal, hosting primary fluid inclusions along 28 successive growth bands, was the focus for fluid inclusion studies and allowed a record of high‐resolution chemical trends. This crystal showed a change in parent fluids during growth, from low salinity, to high salinity, back to low salinity. At the bottom of the crystal, the lowest six fluid inclusion assemblages have salinities of 1.7–5.1 eq. wt. % NaCl. The next nine fluid inclusion assemblages have significantly higher salinity (18.6–27.4 eq. wt. % NaCl) inclusions. The twelve fluid inclusion assemblages near the top of the crystal have low salinity (0.9–8.3 eq. wt. % NaCl) like those at the bottom of the crystal. The high‐salinity fluid inclusions in the middle of this gypsum crystal are interpreted to have formed during a pulse of magmatic/hydrothermal fluids to the surface, perhaps during local active volcanism. Secondary evidence of a magmatic influence on surface waters includes hydrogen sulfide and high molecular weight solid hydrocarbons within some fluid inclusions. This study is among the first detailed fluid inclusion studies of gypsum and suggests that fluid inclusions in gypsum can be paleo‐hydrogeologic proxies.

F. J. Karmanocky

K. C. Benison

A fluid inclusion record of magmatic/hydrothermal pulses in acid Salar Ignorado gypsum, northern Chile

智利北部酸性地热伊格诺拉多石膏中的流体包裹体记录的岩浆/热液脉冲

Composite aquiclude rock is an important part of the water barrier layer of coal seam floor, and its mechanical properties and failure characteristics have an important impact on the safety of coal seam mining. In order to explore the uniaxial compression failure characteristics and mechanical properties of composite aquiclude rocks, the mineral composition and microstructure of the composite cement rock were measured by XRD and SEM. Using a WAW‐1000D electrohydraulic servo universal test system, uniaxial compression tests were carried out on samples of four structural types, namely, mudstone/siltstone, mudstone/fine sandstone, fine sandstone/siltstone, and siltstone/mudstone/fine sandstone composites soaked in saline water with various immersion periods and pH values. The experimental results show that the failure of composite rock samples was mainly concentrated in the mudstone part. With the increased proportion of soft rock in the structure, the rock samples exhibited changes in tensile, X‐shaped conjugate inclined plane shear, and single inclined plane shear failure modes. The overall compressive strength of composite rock samples decreased with immersion time, and their failure mode shifted from shear to tensile with increasing immersion time. The strength‐weakening effect of high‐salinity water with different acidity and alkalinity on composite rock samples was significant. The increased pH promoted the tensile failure‐shear failure‐tensile failure evolution. The results of this study can provide important experimental data and theoretical basis for the stability control of composite aquiclude rock in coal mining.

Qiang Sun

Rui Zhao

Xiaolong Li

Hui Yuan

Experimental Study on Uniaxial Compression Failure Characteristics and Mechanical Properties of Composite Aquiclude Rock

复合隔水层岩石单轴压缩破坏特征及力学性能的实验研究

As one of the comprehensive exploration techniques for underground geological resources, surface geochemical methods could play an important role in geothermal exploration, which requires detailed and systematic investigations. In this study, we take the Shiba geothermal basin in Huizhou, China, as the research object and apply surface geochemical testing methods to analyze the intrinsic relationship between the geothermal system and the surface soil. The contents of soil gases and elements are mainly determined, among which hydrogen (H 2 ) and radon (Rn) show three obvious negative anomalies, corresponding to three positive anomalies of soil elements (Fe, U, Cr, V, Cu, and As) that are easy to migrate. The largest negative and positive anomalies correspond to the surface above the fault, which is related to the dominant channel from underground to the surface and is caused by the gas loss effect and the dissolution and migration of inorganic ions. However, the effects of the surface environment and organisms cannot be ignored. Only when the geothermal system has a significant impact on a certain geochemical parameter could the anomaly be manifested in the surface soil. Otherwise, most of the geothermal information, including thermal conduction, will be covered by surface factors. After surface geochemical anomalies related to the geothermal system have been identified, anomaly patterns (especially the top anomaly pattern) can be preliminarily established, which can be used for geothermal exploration. Furthermore, based on the empirical regional geothermal formula, the temperature and depth of the Shiba geothermal system are evaluated at 170°C and 4500 m, respectively, indicating that surface geochemical methods have a good practical prospect in the prediction of geothermal resources.

Yu Zou

Ce Wang

Guangzhi Li

Guojian Wang

Tao Jiang

Dongna Liu

Anomalous Characteristics of Surface Geochemistry Above the Basin Geothermal System: A Case Study of the Shiba Basin in Huizhou, China

盆地地热系统上方表层地球化学的异常特征：以中国惠州西湖盆地为例

There have been many M ≥ 3.0 earthquakes in and around the Jiangling Depression in history, and the stress variation can directly affect the preparation of surrounding earthquakes. This paper innovatively uses the variation characteristics of Jingzhou well water level and GNSS data to analyze the stress variation in the Jiangling Depression. The results show that (1) the long‐term decline trend of Jingzhou well water level has little correlation with rainfall and is mainly from deep source, which is different from the recharge source of the surrounding water system. The long‐term decline trend of Jingzhou well water level is mainly affected by the tension state of the region. (2) The strain rate in the northern part of the study area is relatively high, and the tension state in the NNW direction is dominant. The slope of HBJM‐HBJL stations baseline time series is positive, indicating that the NNW‐SSE is in a tension state as a whole, which is consistent with the trend of Jingzhou well water level. (3) Jingzhou well water level and GNSS baseline time series have good synchronization, which directly reflects that the stress field in and around Jiangling Depression is in a state of tension in recent years. There have been many ≥ 3.0 earthquakes in and around the Jiangling depression in history. In the future, it is worth noting when the stress–strain state of the study area changes.

Cheng Weng

Jiansheng Yu

Jie Wang

Pinji Lv

Xiaoxiao Song

Xiaocheng Zhou

Analysis of Stress Variation Characteristics of Jiangling Depression, Hubei, China, Based on Jingzhou Well Water Level and GNSS Data

基于荆州井水位和GNSS数据的湖北江陵凹陷应力变化特征分析

Aiming at the problems of safety production cost caused by the increase of mining face width and pressure mining in Xizhuo Coal Mine in Chenghe Mining area, a mechanical model of floor plastic slip failure is established based on the theory of plastic slip line, and the difference between it and the traditional floor failure model is analyzed. The damaged contour line of the support stress and lateral support stress on the bottom plate through the advancing direction of the working face is the intersection line of a straight line and an arc line. The failure of the floor caused by lateral supporting stress is the failure of the floor again on the basis of the failure of the floor in the advancing direction of the working face, and there is a superimposed failure area. The analysis of the failure form of the stope floor by this mechanical model is closer to the engineering practice. By using “ultrasonic detection method + stress monitoring inverse analysis method,” the measured data such as disturbance failure depth and distribution law of large mining width working face were obtained. The test method used in this paper is relatively rare in the monitoring of the depth of floor disturbance failure at home and abroad. Considering that the traditional pressure water test method has disadvantages such as easy collapse hole, long period, and large error in monitoring the failure rule of deep floor rock mass, the embedded stress monitoring and reverse analysis method and ultrasonic detection method are used to successfully collect and real‐time monitor the data of rock floor before, during and after mining in the lower part of wide mining face of Xizhuo Coal Mine for the first time, and several effective data are obtained, which solves the three‐part “spatial‐time” all‐round floor disturbance and failure law field measurement which cannot be realized by traditional testing technology. By comparing the results of theoretical analysis, field measurement, and numerical simulation, the law and depth of floor disturbance failure of a 240‐m wide mining face in the Chenghe mining area are obtained for the first time, which provides scientific guidance for floor water disaster induced by coal seam mining under similar conditions in the future and has an important reference role for the prevention and control of Ordovician ash water disaster in coal mining. It provides important technical parameters for the safe setting of the effective water barrier layer and the selection and timing of the grouting layer of the floor, which can bring considerable economic and social benefits. The research results have important popularization value.

Xipeng Cui

Shuancheng Gu

Jinhua Li

Jiahao Wen

Kailei Zhao

Xinlei Liu

Detection and Theoretical Numerical Simulation of the Failure Depth of the Bottom Plate in Belt Pressure Mining

带压开采底板破坏深度检测与理论数值模拟

This paper is aimed at introducing a method for the division of development units of thick carbonate reservoirs. This method consists of eight steps, ranked according to impact weight, each of which is independent but intrinsically linked. When there is a conflict between studies in different steps, the results of the previous step take precedence. (1) Pressure is the most important and reliable data. When the wells with an abnormal pressure gradient in the same interval account for more than 60%, further division of the reservoir is appropriate. (2) Baffles are the second most important and reliable basis. When there are continuous baffles or poor reservoirs that encounter more than 80% wells, it is appropriate to further divide reservoirs. (3) Without the two mentioned above, but with an unconformity surface or discontinuity surface between two sequences, it is appropriate to treat these two sequences as two development units. (4) Without the three mentioned above, if the permeability above and below the sequence boundary differs by 10 or more times, reservoirs above and below the sequence boundary are appropriate as distinct development units. (5) When the thickness, continuity, distribution pattern, and microstructure of two adjacent sequences are significantly different, it is appropriate to treat these two sequences as two development units. (6) If the development units are based on sequences, check for homogeneity within the stratigraphy. If depositional facies or physical property discontinuities are present, the sequence would be reconsidered for subdivision. (7) The reserves in each development unit should account for more than 20% of that of the whole reservoir. (8) When the division of the development units is complete, it needs to be examined to ensure that there is a consistent structure, fluid property, and free water level. If inconsistencies exist, then subdivision is considered. The method was successfully applied to A oilfield, Central Arabian Basin, in combination with the cores, cast thin sections, regular or special core analysis, wireline logging data from 450 wells, formation pressure from 63 wells, and more than 100 wells with a production logging test. The Mishrif reservoir was divided into four development units, in which different well patterns and well types were deployed. The improved development effect proves that the division of development units for thick bioclastic limestone reservoir is reasonable.

Fengfeng Li

Yong Li

Jiaheng Chen

Lei Li

Lixin Ren

Lei Meng

Wenyu Wang

Yang Wan

Yuedong Lu

Haowei Chen

Methods of Division of Development Unit for Thick Carbonate Reservoir—A Case Study of the Mishrif Formation, A Oilfield, Middle East

厚层碳酸盐岩储层开发单元划分方法——以中东A油田Mishrif组为例

GEOFLUIDS 是一份经过同行评审的开放获取期刊，为与流体在地壳的矿物学、化学和结构演化中的作用相关的原创研究和评论提供了一个论坛。其明确目标是在开展地流体研究的各个子学科范围内传播思想。为此，鼓励作者强调其研究的跨学科相关性和国际影响。还鼓励作者尽可能让其他子学科的读者能够访问他们的工作。GEOFLUIDS 强调整个地壳中地下流体的化学、微生物和物理方面。 GEOFLUIDS 涵盖地下水、陆地或海底地热流体、盆地盐水、石油、变质水或岩浆流体的研究。

GEOFLUIDS is a peer-reviewed open-access journal that provides a forum for original research and reviews related to the role of fluids in the mineralogy, chemistry, and structural evolution of the Earth's crust. Its explicit aim is to disseminate ideas across various sub-disciplines involved in geofluid research. Authors are encouraged to highlight the interdisciplinary relevance and international impact of their work, and to present their findings in a manner accessible to readers from other sub-disciplines. GEOFLUIDS emphasizes the chemical, microbial, and physical aspects of subsurface fluids throughout the crust, covering studies on groundwater, terrestrial or submarine geothermal fluids, basin brines, petroleum, metamorphic waters, and magmatic fluids.

GEOFLUIDS 是一本经过同行评审的开放获取期刊，专注于流体在地壳中的矿物学、化学和结构演化方面的原创研究和评论。期刊的目标是传播与地流体研究相关的各个子学科的思想，鼓励作者强调其研究的跨学科相关性和国际影响力。同时，作者也被鼓励以便于其他子学科的读者理解的方式呈现他们的工作。GEOFLUIDS 强调地下流体在整个地壳中的化学、微生物和物理特性，涵盖地下水、陆地或海底地热流体、盆地盐水、石油、变质水和岩浆流体等研究。

Journals	Geofluids
ISSN	1468-8115, 1468-8123
h-index	68
Journal Impact	1.08
Quartiles(Global)	GEOLOGY(Q2)
Quartiles(China)	地球科学(4区)地球科学地球化学与地球物理(4区)地球科学地质学(4区)