Fluid Geochemistry as Indicator of Tectonically-Related,Deep Water Circulations in the Sardinian Rift-Campidano Graben (Italy): New Insights from Environmental Isotopes     

Elisa Sacchi  Gian Maria Zuppi  Luca Pizzino  Fedora Quattrocchi  Salvatore Lombardi 《Aquatic Geochemistry》2008,14(4):301-319

The EC funded Geochemical Seismic Zonation program (EEC GSZ Project 1996–1998) chose Sardinia as a low-seismicity site, in which the relationships between fluid geochemistry and seismo-tectonics had to be investigated and results compared with outcomes from other selected high-seismicity sites. A first article, examining the role of fault segmentation and seismic quiescence on the geochemical composition of groundwaters and gases, has already been presented (Angelone et al. 2005). This article deals with environmental isotopes which, together with selected hydrochemical data, give hints on tectonically-related fluid circulations. Four water-dominated hydrothermal systems were considered, all located along regional fault systems and discharging groundwaters belonging to the Na–HCO₃ and Na–Cl facies. In the considered systems, groundwater circulation takes place, principally, in the Palaeozoic Crystalline Basement (PCB), with the exception of the Logudoro system, where hydrological circuits develop in the Mesozoic Carbonate Platform (MCP). The high CO₂ contents, the non-attainment of fluid-rock equilibrium and the large lithological variability prevent the construction of a unique hydrogeological–geochemical conceptual model. In this case, stable isotopes provide a useful tool to describe the origin of fluids and their subterranean movements. Stable isotopes of water, integrated with hydrochemical data, indicate that fluids are derived from three main end members. The dominant component is a relatively recent local meteoric water; the second one is marine water; and the third one is a fossil freshwater, depleted in heavy isotopes with respect to modern rains. The latter end member entered the aquifer system in the past, when climatic conditions were greatly different from today. At least two circulation systems can be recognised, namely a shallow cold system and a deep hydrothermal system, as well as two distinct hydrological processes: (1) gravity-controlled descent of cold water towards greater depths and (2) convection linked to a thermal gradient, causing deep fluids to rise up from the hydrothermal reservoir towards the surface. The highly variable δ¹³C_TDIC values suggest the presence of two distinct CO₂ sources, namely, a biogenic one and a thermogenic one. The relation between the isotopic compositions of CO₂ and He indicates an increased mantle signature in uprising CO₂-rich fluids.  相似文献   

The Glueckstadt Graben of the North-German Basin: new insights into the structure from 3D and 2D gravity analyses   总被引：1，自引：0，他引：1  

Tamara Yegorova  Yuriy Maystrenko  Ulf Bayer  Magdalena Scheck-Wenderoth 《International Journal of Earth Sciences》2008,97(5):915-930

The structure of the Glueckstadt Graben has been investigated by use of 3D gravity backstripping technique and by 2D gravity and magnetic modelling. Subtracting the gravity effects of the Meso-Cenozoic sediments together with Permian salt reveals a positive residual anomaly within the Glueckstadt Graben. This anomaly includes two local maxima over the Westholstein and Eastholstein Troughs. The 2D gravity models point to the presence of a high-density body within the lower crust of the Glueckstadt Graben. In addition, the results of 2D magnetic modelling indicate that the central part of the high-density body is overlain by an area with high susceptibility. Most probable, the formation of this high-density body is a result of complex poly-phase tectonic history of the study area. Finally, the results of gravity modelling indicate that Permian salt is not homogeneous. 3D gravity analysis and, especially, 2D gravity modelling have distinguished the differences in degree of salt saturation in salt-rich bodies, and elucidate the proportion of Rotliegend salt.  相似文献   

Insight into the structure of the Upper Rhine Graben and its basement from a new compilation of Bouguer Gravity     

Y. Rotstein  J.-B. Edel  G. Gabriel  D. Boulanger  M. Schaming  M. Munschy 《Tectonophysics》2006,425(1-4):55-70

A compilation of gravity data from the Upper Rhine Graben (URG) is presented that includes all the main data sources from its German and French parts. This data is used to show that the URG consists of, at least, two arc-shaped and asymmetric rift units that tectonically are the basic building blocks of the graben. In this sense the URG does not differ from other continental rifts, such as the African rifts. This division should replace the now classical geomorphologic division of the URG into three segments, based on their different trends. Moreover, the gravity suggests that the faults in the central and southern segments are continuous and have the same trend, appearing to respond as a single kinematic unit. Changes in the gravity field in the graben are shown to reflect not only the structure of the graben, but also the highly variable composition of the basement. In this respect, the URG is quite different from some other Tertiary continental rifts, where possible changes in the composition of the basement are mostly masked in the gravity field by the effect of the overlying low-density sediments. This characteristic is used to study the extent of some of the main basement units that underlie the graben.  相似文献   

山西地堑系的最新水平运动   总被引：4，自引：0，他引：4  

王秀文  赵文星  杨国华 《山西地震》2004,(1):20-24

利用山西断裂带布设的GPS监测网的6期复测资料(1996—2001),分析了山西断陷带的水平运动特征。结果表明,整体呈现逆时针的差异活动,主压应力场的方位角为72°,断裂两侧不存在明显的走滑运动。2001年的运动显示,代县附近是差异活动的分界区段。  相似文献   

A pulsed extension model for the Neogene–Recent E–W-trending Alaşehir Graben and the NE–SW-trending Selendi and Gördes Basins, western Turkey     

Martin Purvis  Alastair Robertson   《Tectonophysics》2004,391(1-4):171

We have developed a significant body of new field-based evidence relating to the history of crustal extension in western Turkey. We establish that two of the NE–SW-trending basins in this region, the Gördes and Selendi Basins, whose sedimentary successions begin in the early Miocene, are unlikely to relate to late-stage Alpine compressional orogeny or to E–W extension of Tibetan-type grabens as previously suggested. We argue instead that these basins are the result of earlier (?) late Oligocene, low-angle normal faulting that created approximately N–S “scoop-shaped” depressions in which clastic to lacustine and later tuffaceous sediments accumulated during early–mid-Miocene time, separated by elongate structural highs. These basins were later cut by E–W-trending (?) Plio–Quaternary normal faults that post-date accumulation of the Neogene deposits. In addition, we interpret the Alaşehir (Gediz) Graben in terms of two phases of extension, an early phase lasting from the early Miocene to the (?) late Miocene and a young Plio–Quaternary phase that is still active. Taking into account our inferred earlier phase of regional extension, we thus propose a new three-phase “pulsed extension” model for western Turkey. We relate the first two phases to “roll-back” of the south Aegean subduction zone and the third phase to the westward “tectonic escape” of Anatolia.  相似文献   

Eocene-Pliocene time scale and stratigraphy of the Upper Rhine Graben (URG) and the Swiss Molasse Basin (SMB)     

Jean-Pierre Berger  Bettina Reichenbacher  Damien Becker  Matthias Grimm  Kirsten Grimm  Laurent Picot  Andrea Storni  Claudius Pirkenseer  Andreas Schaefer 《International Journal of Earth Sciences》2005,94(4):711-731

We present a general stratigraphic synthesis for the Upper Rhine Graben (URG) and the Swiss Molasse Basin (SMB) from Eocene to Pliocene times. The stratigraphic data were compiled both from literature and from research carried out by the authors during the past 6 years ; an index of the stratigraphically most important localitites is provided. We distinguish 14 geographical areas from the Helvetic domain in the South to the Hanau Basin in the North. For each geographical area, we give a synthesis of the biostratigraphy, lithofacies, and chronostratigraphic ranges. The relationships between this stratigraphic record and the global sea-level changes are generally disturbed by the geodynamic (e.g., subsidence) evolution of the basins. However, global sea-level changes probably affected the dynamic of transgression–regression in the URG (e.g., Middle Pechelbronn Beds and Serie Grise corresponding with sea-level rise between Ru1/Ru2 and Ru2/Ru3 sequences, respectively) as well as in the Molasse basin (regression of the UMM corresponding with the sea-level drop at the Ch1 sequence). The URGENT-project (Upper Rhine Graben evolution and neotectonics) provided an unique opportunity to carry out and present this synthesis. Discussions with scientists addressing sedimentology, tectonics, geophysics and geochemistry permitted the comparison of the sedimentary history and stratigraphy of the basin with processes controlling its geodynamic evolution. Data presented here back up the palaeogeographic reconstructions presented in a companion paper by the same authors (see Berger et al. in Int J Earth Sci 2005).  相似文献   

Intraplate deformation and 3D rheological structure of the Rhine Rift System and adjacent areas of the northern Alpine foreland   总被引：4，自引：0，他引：4  

S. Cloetingh  P. A. Ziegler  F. Beekman  P. A. M. Andriessen  N. Hardebol  P. Dèzes 《International Journal of Earth Sciences》2005,94(4):758-778

The lithosphere of the Northern Alpine foreland has undergone a polyphase evolution during which interacting stress-induced intraplate deformation and upper mantle thermal perturbations controlled folding of the thermally weakened lithosphere. In this paper we address relationships among deeper lithospheric processes, neotectonics and surface processes in the Northern Alpine foreland with special emphasis on tectonically induced topography. We focus on lithosphere memory and neotectonics, paying special attention to the thermo-mechanical structure of the Rhine Graben System and adjacent areas of the northern Alpine foreland lithosphere. We discuss implications for mechanisms of large-scale intraplate deformation and links with surface processes and topography evolution.  相似文献   

Control of Aptian palaeobathymetry on turbidite distribution in the Buchan Graben,Outer Moray Firth,Central North Sea     

T.E. Aas  J.A. Howell  M. Janocko  C.A.-L. Jackson 《Marine and Petroleum Geology》2010

It is widely recognised that palaeobathymetry is a key control on the distribution of turbidite deposits. Thus, the utilisation of palaeobathymetric surfaces as an input for numerical turbidity current modelling offers a potentially powerful method to predict the distribution of deep marine sands in ancient (subsurface or outcrop) successions. Such an approach has been tested on an Aptian turbidite deposit from the Buchan Graben, UK Central North Sea, where modelled sand distributions could be quality controlled against available well data.  相似文献   

On the detectability of a highly conductive layer in the upper mantle beneath the Black Forest crystalline using magnetotelluric methods     

Bülent Tezkan 《Geophysical Journal International》1994,118(1):185-200

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Plate tectonics,palaeoenvironments and limestone geomorphology in West-Central Britain     

Ian Douglas 《地球表面变化过程与地形》1987,12(5):481-495

The variety of active, exhumed, and buried limestone landforms of northern England, North Wales, and the Isle of Man arises in part from the way in which Dinantian (Lower Carboniferous) sedimentation was affected by a tilt-block basement structure evolved during the closure of the Iapetus Ocean suture to the north, and partly to subsequent plate tectonic movements associated with the closure of the proto-Tethys ocean, the opening of the Atlantic Ocean and the Alpine orogeny. Landforms created during the Dinantian now form important exhumed and buried landscape features. The Permian half-graben structures of the eastern Irish Sea-Cheshire-Worcester Basins account for many of the contrasts between the upland karsts of the Pennines and the lowland karsts of coastal areas.  相似文献