Distribution of δ~(34)S and δ~(18)O in SO_4~(2-) in Groundwater from the Ordos Cretaceous Groundwater Basin and Geological Implications     

YANG Yuncheng  SHEN Zhaoli  WEN Dongguang  HOU Guangcai  SHE Hongquan  ZHAO Zhenhong  WANG Dong  LI Jingwen 《《地质学报》英文版》2010,84(2):432-440

<正>The Ordos Cretaceous Groundwater Basin,located in an arid-semiarid area in northwestern China,is a large-style groundwater basin.SO_4~(2-) is one of the major harmful components in groundwater.Dissolved SO_4~(2-) concentrations,andδ~(34)S-SO_4~(2-) andδ~(18)O-SO_4~(2-) in groundwater from 14 boreholes and in gypsum from aquifer were analyzed.Results show that SO_4~(2-) in shallow groundwaters originates from precipitation,sulfide oxidation,and dissolution of stratum sulphate,with a big range ofδ~(34)S values,from-10.7‰to 9.2‰,and addition of SO_4~(2-) in deep groundwater results from dissolution of stratum sulphate,with biggerδ~(34)S values,from 7.8‰to 18.5‰,compared with those in shallow groundwater.This research also indicates that three types of sulphate are present in the strata,and characterized by highδ~(34)S values and highδ~(18)O values-style,highδ~(34)S values and middleδ~(18)O valuesstyle, middleδ~(34)S values and lowδ~(18)O values-style,respectively.Theδ~(34)S-SO_4~(2-) andδ~(18)O-SO_4~(2-) in groundwater have a good perspective for application in distinguishing different groundwater systems and determining groundwater circulation and evolution in this area.  相似文献   

Inhibition of dissolution within shallow water carbonate sediments: impacts of terrigenous sediment input on syn-depositional carbonate diagenesis   总被引：2，自引：0，他引：2  

CHRISTOPHER T. PERRY  KEVIN G. TAYLOR 《Sedimentology》2006,53(3):495-513

The early diagenetic chemical dissolution of skeletal carbonates has previously been documented as taking place within bioturbated, shallow water, tropical carbonate sediments. The diagenetic reactions operating within carbonate sediments that fall under the influence of iron‐rich (terrigenous) sediment input are less clearly understood. Such inputs should modify carbonate diagenetic reactions both by minimizing bacterial sulphate reduction in favour of bacterial iron reduction, and by the reaction of any pore‐water sulphide with iron oxides, thereby minimizing sulphide oxidation and associated acidity. To test this hypothesis sediment cores were taken from sites within Discovery Bay (north Jamaica), which exhibit varying levels of Fe‐rich bauxite sediment contamination. At non‐impacted sites sediments are dominated by CaCO₃ (up to 99% by weight). Pore waters from the upper few centimetres of cores show evidence for active sulphate reduction (reduced SO₄/Cl^? ratios) and minor CaCO₃ dissolution (increased Ca²⁺/Cl^? ratios). Petrographic observations of carbonate grains (specifically Halimeda and Amphiroa) show clear morphological evidence for dissolution throughout the sediment column. In contrast, at bauxite‐impacted sites, the sediment is composed of up to 15% non‐carbonate and contains up to 6000 μg g^?1 Fe. Pore waters show no evidence for sulphate reduction, but marked levels of Fe(II), suggesting that bacterial Fe(III) reduction is active. Carbonate grains show little evidence for dissolution, often exhibiting pristine surface morphologies. Samples from the deeper sections of these cores, which pre‐date bauxite influence, commonly exhibit morphological evidence for dissolution implying that this was a significant process prior to bauxite input. Previous studies have suggested that dissolution, driven by sulphate reduction and sulphide oxidation, can account for the loss of as much as 50% of primary carbonate production in localized platform environments. The finding that chemical dissolution is minor in a terrigenous‐impacted carbonate environment, therefore, has significant implications for carbonate budgets and cycling, and the preservation of carbonate grains in such sediment systems.  相似文献   

Presidential Address 2003: Why concrete cracks — geological factors in concrete failure     

William J. French 《Proceedings of the Geologists' Association. Geologists' Association》2005,116(2):89-105

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Deformation structures and an alteration zone linked to deposition of volcanogenic sulphate in an ancient playa (Oligocene of Nebraska, USA)     

DAVID B. LOOPE  JOSEPH A. MASON†  HUIMING BAO‡  RICHARD M. KETTLER  C. WILLIAM ZANNER¶ 《Sedimentology》2005,52(1):123-139

Historic, sulphur-rich volcanic eruptions have altered global climate for as much as five years, and much larger events are known from the geologic record. At Scotts Bluff, Nebraska, Early Oligocene strata of the lower Arikaree Group contain a tephra bed with abundant calcite pseudomorphs after gypsum. Previous work has shown sulphate from the pseudomorphs in this tephra bears a high ¹⁷O anomaly indicative of oxidation of sulphur gases by ozone or hydrogen peroxide in the atmosphere. Possible sources of the tephra were caldera eruptions at about 28 Ma in the San Juan volcanic field of south-western Colorado (∼500 km SW of the study site) and the eastern Great Basin (∼1000 km WSW). The present sedimentological study shows that tephra and volcanogenic sulphate were deposited and preserved within a small, surface-discharging playa that developed on the irregular upper surface of aeolian siltstones of the subjacent White River Group. Sulphate solutions (including perhaps sulphuric acid) percolated downward within the vadose zone, dissolving early formed smectite cement within underlying volcaniclastic sandstones, reddening these rocks along an irregular alteration front. Preserved fine-scale stratification within the sandstones precludes the possibility that reddening took place during pedogenesis. Displacive growth of gypsum at the playa centre folded tephra beds and forced tephra into underlying sandstones, forming elongate cones. The large mass fraction of gypsum (now replaced by calcite) in the playa sediments suggests a huge, long-distance delivery of sulphate aerosols. Some of the sulphate and tephra may have come from the same eruption, or the fine-grained tephra may simply have aided preservation of dry-fog sulphate derived from an unrelated, effusive eruption of lava.  相似文献   

Deep-water clastic evaporites deposition in the Messinian Adriatic foredeep (northern Apennines,Italy): did the Mediterranean ever dry out?   总被引：1，自引：0，他引：1  

VINICIO MANZI  STEFANO LUGLI†  FRANCO RICCI LUCCHI‡  MARCO ROVERI 《Sedimentology》2005,52(4):875-902

A new genetic facies model for deep-water clastic evaporites is presented, based on work carried out on the Messinian Gessoso-solfifera Formation of the northern Apennines during the last 15 years. This model is derived from the most recent siliciclastic turbidite models and describes the downcurrent transformations of a parent flow mainly composed of gypsum clasts. The model allows clearer comprehension of processes controlling the production and deposition of clastic evaporites, representing the most common evaporite facies of the northern Apennines, and the definition of the genetic and stratigraphic relationship with primary shallow-water evaporites formed and preserved in marginal settings. Due to the severe recrystallization processes usually affecting these deposits, petrographic and geochemical analyses are needed for a more accurate interpretation of the large spectrum of recognized gravity-driven deposits ranging from debrisflow to low-density turbidites. Almost all the laminar ‘balatino’ gypsum, previously considered a deep-water primary deposit, is here reinterpreted as the fine-grained product of high to low-density gravity flows. Facies associations permit the framing of the distribution of clastic evaporites into the complex tectonically controlled depositional settings of the Apennine foredeep basin. The Messinian Salinity Crisis occurred during an intense phase of geodynamic reorganization of the Mediterranean area that also produced the fragmentation of the former Miocene Apennine foredeep basin. In this area, primary shallow-water evaporites equivalent to the Mediterranean Lower Evaporites, apparently only formed in semi-closed thrust-top basins like the Vena del Gesso Basin. The subsequent uplift and subaerial exposure of such basins ended the evaporite precipitation and promoted a widespread phase of collapse leading to the resedimentation of the evaporites into deeper basins. Vertical facies sequences of clastic evaporites can be interpreted in terms of the complex interplay between the Messinian tectonic evolution of the Apennine thrust belt and related exhumation–erosional processes. The facies model here proposed could be helpful also for better comprehension of other different depositional and geodynamic contexts; the importance of clastic evaporites deposits has been overlooked in the study of other Mediterranean areas. Based on the Apennine basins experience, it is suggested here that evaporites diffused into the deeper portions of the Mediterranean basin may consist mainly of deep-water resedimented deposits rather than shallow-water to supratidal primary evaporites indicative of a complete basin desiccation.  相似文献   

硫酸盐岩溶蚀机理实验研究   总被引：6，自引：1，他引：6  

张凤娥  卢耀如 《水文地质工程地质》2001,28(5):12-16

在硫酸盐岩和碳酸盐岩混合建造地区，硫酸盐岩的溶蚀对岩溶的产生有着重要影响，对于某些岩溶现象和地质灾害的解释，必须考虑硫酸盐岩岩溶的影响，对硫酸盐岩的溶蚀机理及其影响因素的研究就显得尤为重要，本文采用室内实验模拟的方法，根据岩溶发育的影响因素，研究了硫酸盐岩的溶蚀机理。研究认为，硫酸盐岩溶蚀发育的条件不同于碳酸盐岩，即在水与硫酸盐岩体系内即使没有CO2的参与，水对硫酸盐岩仍具侵蚀性；硫酸盐岩溶蚀的发育不但与其本身的固有特性有关外，还与岩石所处的环境因素有关。  相似文献   

中国芒硝类矿产资源及硫酸钠产业状况   总被引：3，自引：0，他引：3       下载免费PDF全文

宣之强 《盐湖研究》1994,2(3):60-64

中国芒硝类矿产矿类齐全、资源丰富，硫酸钠资源居世界首位．硫酸钠产业起步于五十年代，八十年代得到迅速发展．至今，硫酸钠生产能力已跃居世界前列．改革开放和科技进步将为中国硫酸钠工矿业带来新的机遇．  相似文献   

化学成分和键价对矿物晶体结构形式的影响     

史红云 《地质科技情报》1992,11(4):41-45,50

本文从晶体化学观点出发,以硫酸盐矿物为例,探讨了影响矿物晶体结构形式的因素——化学成分因素(z/x比值)和原子键价(S)因素。它们直接制约着矿物的晶体结构形式。利用矿物的化学组成,原子的键价数据以及键价规则既可解释已有的结构,同时在某种程度上也可预测未知的矿物结构。  相似文献   

锌绿钾铁矾——一种硫酸盐新矿物     

李万茂  陈国英  孙淑荣 《矿物学报》1987,(4)

锌绿钾铁矾是一种含K、Zn、Fe和Al的硫酸盐新矿物。共生矿物为粒铁矾、水绿矾、石英和黄铁矿等。矿物呈分散的晶粒或粒状集合体产出,晶体一般1—2mm。单晶体常见,主要单形有o{111},c{100},d{110},n{211}。颜色绿黑到油绿色,灰绿色条痕。沥青到玻璃光泽,透明到微透明。硬度3.0,性脆,无解理,断口贝壳状。实测比重2.759g/cm~3,计算比重2.767g/cm~3。光性均质,N=1.605(3)。等轴晶系,空间群Fd3c,a=27.180,Z=16。粉末衍射图最强线为:5.54(48),4.26(28),3.53(67),3.39(100),3.13(39),3.03(28),2.84(32)。化学式为K_2Zn_5Fe_3~(3+)Al(SO_4)_(12)·18H_2O。差热分析显示,在249和702℃处有两个强吸收峰,在278和826℃处有两个弱吸收峰。红外吸收光谱曲线在3402—3065和1138—1004cm~(-1)处有两个主要吸收带,在1686—1637,625—590和442cm~(-1)处有三个次要吸收带。  相似文献   

Laboratory simulation of salt weathering processes in arid environments     

R. U. Cooke 《地球表面变化过程与地形》1979,4(4):347-359

The equipment and techniques being used at Bedford College, London to simulate salt weathering processes in deserts are described in the context of a general discussion of the nature of salt weathering processes and approaches to studying them. An experiment based on the equipment and techniques is described: it is designed to test the durability of three building stones in the presence of several different saline solutions under conditions of surface temperature and relative humidity that are considered typical of hot deserts. The experiment, the first of a series, shows that Na₂SO₄ is the most effective of the salts used, and that susceptibility of the rocks to weathering is related to such rock properties as porosity, microporosity and water absorption capacity.  相似文献