Isotopic and hydrochemical studies of groundwater flow and salinity in the Southern Upper Rhine Graben

In order to determine the origin and the propagation mechanisms of highly concentrated chloride brines within the Quaternary aquifer system in the southern part of the Upper Rhine Graben, a combined isotope (H, O, C) and hydrochemical analysis was carried out. Groundwater recharge in this area is a complex system, consisting of local precipitation, river bank filtration, lateral flow from the Graben borders and, to a minor extent, an old Pleistocene component. In some areas, groundwater consists of up to 90% of recent bank filtrate, reaching depths down to at least 100 m. The isotopic and hydrochemical results show, that the elevated chloride concentrations in the Quaternary aquifer mainly result from leaky settling basins charged by the French potash mines until the mid 1970s. Input of natural brines coming from tertiary salt diapirs is of only minor importance. While infiltrating, the anthropogenic brines were strongly diluted by local river bank filtrate of the Rhine. Nevertheless, maximum chloride concentrations nowadays still reach some 10,000 mg/l at the base of the aquifer at a depth of more than 100 m below surface. The main volume of the brines is stored in the less permeable lower part of the quaternary sediments (Breisgau-Formation) whereas only a minor part is transported northwards with the rapid convective groundwater flow. Brines undergoing only dilution preserve their hydrochemical characteristics (NaCl-type). In contrast, brines recirculated from the Breisgau-Formation show a northwards increasing alteration through ion exchange processes. Potassium and sodium may be fixed in the fine grained aquifer material while calcium is set free into the groundwater. After a flow distance of about 12 km, complex hydraulic interactions between groundwater and surface waters lead to the rise of strongly diluted and hydrochemically altered brines with chloride contents up to maximum 700 mg/l. The presented case study is an example for a detailed analysis of a multi-component groundwater mixing system using combined isotope and hydrochemical methods. Furthermore, cation exchange is shown as a major process affecting the hydrochemical evolution of the young groundwater in the southern Upper Rhine Graben which is locally strongly polluted by chloride as a consequence of former potash mining.     

Sedimentary-volcanic tufts formed during the early Middle Triassic volcanic event in Guizhou Province and their stratigraphic significance

The sedimentary-volcanic tuff （locally called ＂green-bean rock＂） formed during the early Middle Triassic volcanic event in Guizhou Province is characterized as being thin, stable, widespread, short in forming time and predominantly green in color. The green-bean rock is a perfect indicator for stratigraphic division. Its petrographic and geochemical features are unique, and it is composed mainly of glassy fragments and subordinately of crystal fragments and volcanic ash balls. Analysis of the major and trace elements and rare-earth elements （ REE）, as well as the related diagrams, permits us to believe that the green-bean rock is acidic volcanic material of the calc-alkaline series formed in the Indosinian orogenic belt on the Sino-Vietnam border, which was atmospherically transported to the tectonically stable areas and then deposited as sedimentary-volcanic rocks there. According to the age of green-bean rock, it is deduced that the boundary age of the Middle-Lower Triassic overlain by the sedimentary-volcanic tuff is about 247 Ma.     

西班牙南部Subbetic中带Río Fardes剖面Turonian-Coniacian大洋红层

Río Fardes剖面位于西班牙南部Granada东北,构造上属于深水环境的Subbetic中带。该剖面主要由白垩纪Fardes组第Ⅱ段和第Ⅲ段(半)远洋沉积构成,并出现浊流沉积和混杂沉积。本次研究在Fardes组浊流层序内首次发现两段红色沉积。钙质超微化石表明红层的时间从Turonian早期(UC7 带)到Coniacian中期—晚期界线(UC10/?UC11带)。红层由mm级红色泥岩夹灰色、杂色、偶尔黑色泥岩和钙质泥岩组成。沉积学研究表明新发现的Turonian Coniacian远洋红色泥岩沉积形成于CCD面之下深水盆地环境,浊流和碎屑流沉积强烈地影响着(半)远洋环境的背景泥岩相,并成为红色沉积结束的原因。     

Geochronology and Geochemistry of Late Triassic Intrusive Rocks in the Xiuyan Area,Liaodong Peninsula,Eastern North China Craton: Petrogenesis and Implications for Lithospheric Thinning

The timing and mechanisms of lithospheric thinning and destruction of the North China Craton (NCC) remain controversial, and the overall geodynamics of the process are poorly understood. This paper documents Late Triassic igneous rocks including monzogranite, gabbro, and diorite from the Xiuyan District on the Liaodong Peninsula in the eastern NCC, which have LA-ICP-MS zircon U-Pb ages of 229.0 ± 0.4 Ma, 216.2 ± 0.9 Ma, and 210.6 ± 2.0 Ma, respectively. Monzogranite shows high-SiO2 adakite affinity, negative εHf(t) values (?20.6 to ?17.9), and old TDM2 ages (3.53–3.29 Ga), suggesting that their parental magma was derived from thickened Paleoarchean mafic lower crust and minor mantle materials that were also involved their generation. Gabbro is ultrapotassic, strongly enriched in LREEs and LILEs, depleted in HFSEs, and has evolved zircon Hf isotopes with negative εHf of ?10.04 to ?5.85 and old TDM2 ages (2.59–2.22 Ga). These are diagnostic signatures of a crustal component, but their high contents of MgO, Cr, Co, Ni indicate that the primary magma originated from enriched mantle. Diorite is enriched in LILEs and LREEs, depleted in HFSEs (with negative Nb, Ta, and Ti anomalies), and contains negative εHf(t) values (?13.64 to ?11.01). Compared with the gabbro, the diorite is relatively enriched in Nb, Ta and HREEs, and also contains younger TDM2 ages (2.11–1.94 Ga), suggesting that the diorite was formed by mixing between ancient lower crust-derived felsic magmas and asthenospheric mantle-derived magmas. Field observations, geochronology, geochemistry, and zircon Lu-Hf isotopes indicate that Late Triassic magmatism and tectonic activity resulted from deep subduction of the Yangtze Craton beneath the NCC in the Xiuyan area. This phase of tectonic activity was completed in the eastern NCC by the Late Triassic (216 Ma), and was subsequently followed by lithospheric thinning that began in the Late Triassic.     

云南普朗斑岩铜矿晚三叠世构造控矿条件

普朗铜矿是义敦岛弧东多金属矿带的超大型斑岩型铜矿床.成矿带内岩浆构造活动频繁,裂隙构造叠加成矿-控矿作用显著,但研究程度薄弱.在对普朗铜矿区巷道进行构造岩相学综合调查研究的基础上,结合区域成矿构造背景,厘定矿区褶皱、断裂宏观特征,对典型中段进行节理（裂隙）测量分析.研究表明：1）古特提斯洋闭合过程斑岩铜矿成矿作用与晚三叠世构造演化、岩浆活动关系密切,普朗铜矿形成于俯冲造山阶段;2）区域深大断裂控制着矿区沉积建造和岩浆岩分布,矿床总体产于普朗背形核部,次级NEE及NE向断裂控制着含矿斑岩体和节理（裂隙）的发育,矿（化）体赋存于两组断裂交汇部位;3）矿区以张节理为主的复合型节理系统,为含矿热液的运移、扩散和富集提供导矿、储矿空间,裂隙发育程度与铜矿化呈正相关.通过对矿区岩浆侵入-构造裂隙系统特征与控矿规律的研究,认为热液脉状矿（化）体严格受控于构造-裂隙系统改造富集作用,裂隙构造发育部位是探寻富"脉状矿"的有利靶区.     

Pore Characteristics and Factors Controlling Lacustrine Shales from the Upper Cretaceous Qingshankou Formation of the Songliao Basin,Northeast China: A Study Combining SEM,Low-temperature Gas Adsorption and MICP Experiments

To investigate pore characteristics and the factors controlling lacustrine shales,geochemical,mineralogical and petrophysical experiments were performed on 23 shale samples from the Qingshankou Formation of the Songliao Basin,China.A comparison of mercury injection capillary pressure (MICP) and low-temperature N2 adsorption pore-size distribution showed that MICP has a higher pore-size distribution (PSD) line in its overlapping pore diameter range,which may be elevated by the higher pressure of MICP.Therefore,in the overlapping range,low-temperature N2 adsorption data were preferred in pore characterization.Negative correlations were observed between pore volumes and TOC content,indicating organic matter pores are not well-developed in the studied samples.This may be related to their low grade of maturity and type I kerogens.There existed negative relationships between pore volumes and S1,which illustrated that liquid hydrocarbons occupied some pore space.Micropore volume had a better correlation with S1 than mesopore and macropore volumes,which suggests that liquid hydrocarbons preferentially occur in micropores.No obvious relationships between pore volumes and quartz or feldspar were observed,while pore volumes increased with the increasing clay mineral content.These relationships indicate that intraparticle pores in clay minerals represent the principal pore type.     

松辽盆地西部斜坡区上二叠统林西组生烃潜力评价——来自吉白地2井的证据

对松辽盆地西部斜坡区中部吉白地2井上二叠统林西组的烃源岩发育特征及有机地球化学特征进行了系统研究.结果表明,该区上二叠统林西组暗色泥岩、板岩发育,单层最大厚度为29 m,累计厚度达138.42 m.有机碳含量为0.01％～2.10％,平均为0.62％,整体为中等烃源岩范畴,有机质丰度较高.应用干酪根碳同位素、干酪根元素...     

四川盆地下奥陶统桐梓组白云岩多元成因

四川盆地下奥陶统桐梓组白云岩的成因研究较少,模式存在多样性,尚未达成共识.通过系统的岩心观察、薄片鉴定、地球化学分析等方法,在四川盆地桐梓组识别出晶粒白云岩、颗粒白云岩和含石英白云岩及含白云质石英砂岩等与白云石相关的岩石类型.地球化学分析揭示不同类型白云岩具有不同的地球化学特征及白云石化机理,晶粒白云岩的MgO含量与C...     

宁夏红寺堡盆地地表沙漠化现状及其地质主控因素

以landsand-TM遥感影像资料提取为基础,详细解译了宁夏红寺堡盆地近30年来地表沙漠化的进程。进一步结合1:50000区域地质填图成果,系统建立了红寺堡盆地晚更新世区域地层对比格架,恢复了重要演化阶段的岩相古地理格局,地质与地球化学分析相结合,确立了区域沙漠化的物质来源。研究结果认为:1999年国家实施的西部生态移民战略使红寺堡盆地生态环境恶化得到了有效修复,区域沙漠化整体呈现出了稳中有降的变化趋势,但并未得到彻底的有效根治;地表沙丘沙脊的主体走向呈北西-南东向,与大罗山-牛首山构造带、烟筒山构造的主体走向基本一致,具有带状分布的格局;沙漠化物质来源主要受控于上更新统萨拉乌苏组三段湖退序列的疏松湖相砂,具有原地沙漠化的特征;地表风成沙与萨拉乌苏三段湖相砂在主量元素、微量元素和稀土元素特征上具有比较一致性的变化趋势,进一步说明了二者在成因上具有一定的亲源性。该研究成果对区域土地沙漠化的综合防治具有重要的现实指导意义。      

辽宁本溪中三叠世苏铁类密脉中国似查米亚

中国似查米亚属Sinozamites Sze是中国北方中、晚三叠世苏铁植物门Cycadophyta代表成分之一.自该属发现以来,该属在分类上属于苏铁目还是本内苏铁目一直不清楚.本文对产于辽宁本溪中三叠世林家组的密脉中国似查米亚S.myrioneurus表皮构造进行了研究.由于标本未保留角质层,故选择超景深显技术,发现该属气孔器属于单唇型,从而确立了该属植物属于苏铁目.研究过程中,既用盐酸又用硝酸来清除化石表面杂质.另根据已有的标本所显示的裂片和羽轴上下过渡关系,对该种羽片进行了部分重建.在此基础上,系统比较了类似的苏铁植物.