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31.
Fluid and gas migration in the North German Basin: fluid inclusion and stable isotope constraints 总被引:1,自引:0,他引:1
Volker Lüders Christian Reutel Peer Hoth David A. Banks Birgit Mingram Thomas Pettke 《International Journal of Earth Sciences》2005,94(5-6):990-1009
Fluid inclusions have been studied in minerals infilling fissures (quartz, calcite, fluorite, anhydrite) hosted by Carboniferous
and Permian strata from wells in the central and eastern part of the North German Basin in order to decipher the fluid and
gas migration related to basin tectonics. The microthermometric data and the results of laser Raman spectroscopy reveal compelling
evidence for multiple events of fluid migration. The fluid systems evolved from a H2O–NaCl±KCl type during early stage of basin subsidence to a H2O–NaCl–CaCl2 type during further burial. Locally, fluid inclusions are enriched in K, Cs, Li, B, Rb and other cations indicating intensive
fluid–rock interaction of the saline brines with Lower Permian volcanic rocks or sediments. Fluid migration through Carboniferous
sediments was often accompanied by the migration of gases. Aqueous fluid inclusions in quartz from fissures in Carboniferous
sedimentary rocks are commonly associated with co-genetically trapped CH4–CO2 inclusions. P–T conditions estimated, via isochore construction, yield pressure conditions between 620 and 1,650 bar and temperatures between
170 and 300°C during fluid entrapment. The migration of CH4-rich gases within the Carboniferous rocks can be related to the main stage of basin subsidence and stages of basin uplift.
A different situation is recorded in fluid inclusions in fissure minerals hosted by Permian sandstones and carbonates: aqueous
fluid inclusions in calcite, quartz, fluorite and anhydrite are always H2O–NaCl–CaCl2-rich and show homogenization temperatures between 120 and 180°C. Co-genetically trapped gas inclusions are generally less
frequent. When present, they show variable N2–CH4 compositions but contain no CO2. P–T reconstructions indicate low-pressure conditions during fluid entrapment, always below 500 bar. The entrapment of N2–CH4 inclusions seems to be related to phases of tectonic uplift during the Upper Cretaceous. A potential source for nitrogen
in the inclusions and reservoirs is Corg-rich Carboniferous shales with high nitrogen content. Intensive interaction of brines with Carboniferous or even older shales
is proposed from fluid inclusion data (enrichment in Li, Ba, Pb, Zn, Mg) and sulfur isotopic compositions of abundant anhydrite
from fissures. The mainly light δ34S values of the fissure anhydrites suggest that sulfate is either derived through oxidation and re-deposition of biogenic
sulfur or through mixing of SO42−-rich formation waters with variable amounts of dissolved biogenic sulfide. An igneous source for nitrogen seems to be unlikely
since these rocks have low total nitrogen content and, furthermore, even extremely altered volcanic rocks from the study area
do not show a decrease in total nitrogen content. 相似文献
32.
A methodology to estimate seismic vulnerability of health facilities. Case study: Mexico City,Mexico
We developed a model to estimate seismic vulnerability of health facilities in Mexico City, Mexico, following these steps: (1) designing a theoretical framework (TF) to measure structural, non-structural, functional, and administrative-organizational vulnerabilities; (2) measurement of the vulnerability conditions of the analyzed facility by using the TF; and (3) estimation of the hospital’s seismic vulnerability by comparing the measured vulnerability to the TF’s vulnerability indicators by taking into account the optimal case. The TF was developed considering a scoring system and international standards for risk management in hospitals. The methodology establishes the degree of vulnerability of the analyzed institution as well as its interrelations with external infrastructure systems. This tool also identifies existing failures to estimate expected damage. The methodology was applied to the National Cardiology Hospital, the Children’s Hospital “Dr. Federico Gómez,” and the “Hospital de Jesus” of Mexico City. The vulnerability problems in these three hospitals are common within them, and some of the main causes of vulnerability found are: (1) the lack of technology to resistant seismic shaking; (2) the need to develop or update disaster response plans; (3) the need of periodic and proper maintenance to hospitals’ buildings; (4) the lack of sufficient financial resources for vulnerability reduction projects and autonomous operations of the hospital during 3–5 days after a disaster occurs. We believe that vulnerability in these health facilities can be reduced with low-cost procedures and that the methodology developed here will support the decision-making processes to reduce seismic risk in Mexico City. 相似文献
33.
José Alfredo Ramos-Leal Janete Morán-Ramírez José Teodoro Silva-García Rosa María Fuentes-Rivas Gustavo Cruz-Cárdenas Salvador Ochoa-Estrada Francisco Estrada-Godoy 《Arabian Journal of Geosciences》2018,11(15):422
The present study characterized the hydrogeochemical processes of the aquifer of Ciénega de Chapala in Michoacán, Mexico. The dominant water families contained bicarbonate magnesium and sodium. In the region, water infiltrates into a fractured volcanic environment exposed in the surrounding mountains and is transmitted to the volcano-sedimentary units of the ciénega, where silicate alteration and ion exchange processes occur in the clays of the subsoil. The Gibb diagrams confirm that the main evolutionary processes in the aquifer are rock-water interactions in the local flow and evaporation in the intermediate and regional flows. The molar ratios of HCO3/Na and Ca/Na are congruent with the type of volcano-sedimentary environment present in the area. Ternary mixing processes associated with three end members were also identified and were related to the flow systems in the area. The local flow contributes 77% of water to the system, and the intermediate and regional flows contribute 16% and 7%, respectively. 相似文献
34.
Fiddler crabs (Uca spp.) undergo the zoeal stage of development in open-ocean waters, where they experience stable salinity levels, low turbidity and reduced predation. The St Lucia estuarine system has undergone many geomorphological changes, both natural and anthropogenic, and the estuary mouth has been closed since the early 2000s. Despite recent attempts to improve marine connectivity, it remains limited, occurring primarily on the flood tide through channels connected to the adjacent Mfolozi River. Larval export from the St Lucia Estuary is therefore almost non-existent. A laboratory study was undertaken to examine the silt and salinity tolerance of Uca annulipes first stage zoeae, to investigate whether survival in the closed-estuary conditions would be possible. Salinity tolerance was narrow, with zoeae displaying 100% mortality at salinities <20 and >35 after five days. Zoeae were widely tolerant to silt loading and did not display a significant decrease in survival over a range of 0–1 000 NTU. A limited salinity tolerance is in accordance with the life-history strategy of fiddler crabs, and a high tolerance to turbid waters can be advantageous to small-bodied merozooplankton. Given the stenohaline nature of the zoeae, marine connectivity is therefore essential for the persistence of U. annulipes in this estuarine habitat. 相似文献