Bulk precipitation and stream water chemistry data from 1993 to 2005 are used to analyze the relationship between Eurasian dust storms and nutrient deposition rates in the Kutsuki experimental forest (near Lake Biwa). From 2000 to 2005, atmospheric deposition, total nitrogen (TN), total phosphorus (TP) and dissolved silica (DSi) deposition rates increased by 26%, 132%, and 38%, respectively in the Kutsuki experimental forest. These TN and TP increases are associated with three seasonal factors: the increasing frequency and intensity of Eurasian spring dust events (March/April); the annual typhoon period (late August/September); and autumn/early winter (October to December) monsoons. The annual typhoon and monsoon winter periods are drivers for atmospheric TP and DSi deposition due to the correlation between the deposition and precipitation. In addition, increased spring dust deposition is a primarily driver for TN deposition changes. Increased emissions from urbanized areas in China (and likely Korea) affect the chemical properties of aerosols reaching downwind Japanese regions. Aerosol processes are responsible for increasing TN in aerosols, which are affected primarily by anthropogenic emissions. From 2000 to 2005, coal burning emissions from East Asia have contributed to an increase in TP (and possibly DSi) deposition rates. The observed increase in nutrient deposition did not noticeably impact short-term (5 year) stream water fluxes in the Kutsuki experimental forest. Due to plant uptake, the forest ecosystem retained atmospherically deposited N and P. Finally, the observed increases in nutrient deposition rates over the East China Sea and the Sea of Japan may significantly influence intra-annual net primary production. It is recommended that earth system modelling incorporate changes in atmospheric nutrient deposition rates and their impacts on the regional carbon cycle as well as aquatic and terrestrial ecosystems. 相似文献
Karst aquifers contribute substantially to freshwater supplies in many regions of the world, but are vulnerable to contamination and difficult to manage because of their unique hydrogeological characteristics. Many karst systems are hydraulically connected over wide areas and require transboundary exploration, protection and management. In order to obtain a better global overview of karst aquifers, to create a basis for sustainable international water-resources management, and to increase the awareness in the public and among decision makers, the World Karst Aquifer Mapping (WOKAM) project was established. The goal is to create a world map and database of karst aquifers, as a further development of earlier maps. This paper presents the basic concepts and the detailed mapping procedure, using France as an example to illustrate the step-by-step workflow, which includes generalization, differentiation of continuous and discontinuous carbonate and evaporite rock areas, and the identification of non-exposed karst aquifers. The map also shows selected caves and karst springs, which are collected in an associated global database. The draft karst aquifer map of Europe shows that 21.6% of the European land surface is characterized by the presence of (continuous or discontinuous) carbonate rocks; about 13.8% of the land surface is carbonate rock outcrop.
The sediment-hosted stratiform Cu–Co mineralization of the Luiswishi and Kamoto deposits in the Katangan Copperbelt is hosted
by the Neoproterozoic Mines Subgroup. Two main hypogene Cu–Co sulfide mineralization stages and associated gangue minerals
(dolomite and quartz) are distinguished. The first is an early diagenetic, typical stratiform mineralization with fine-grained
minerals, whereas the second is a multistage syn-orogenic stratiform to stratabound mineralization with coarse-grained minerals.
For both stages, the main hypogene Cu–Co sulfide minerals are chalcopyrite, bornite, carrollite, and chalcocite. These minerals
are in many places replaced by supergene sulfides (e.g., digenite and covellite), especially near the surface, and are completely
oxidized in the weathered superficial zone and in surface outcrops, with malachite, heterogenite, chrysocolla, and azurite
as the main oxidation products. The hypogene sulfides of the first Cu–Co stage display δ34S values (−10.3‰ to +3.1‰ Vienna Canyon Diablo Troilite (V-CDT)), which partly overlap with the δ34S signature of framboidal pyrites (−28.7‰ to 4.2‰ V-CDT) and have ∆34SSO4-Sulfides in the range of 14.4‰ to 27.8‰. This fractionation is consistent with bacterial sulfate reduction (BSR). The hypogene sulfides
of the second Cu–Co stage display δ34S signatures that are either similar (−13.1‰ to +5.2‰ V-CDT) to the δ34S values of the sulfides of the first Cu–Co stage or comparable (+18.6‰ to +21.0‰ V-CDT) to the δ34S of Neoproterozoic seawater. This indicates that the sulfides of the second stage obtained their sulfur by both remobilization
from early diagenetic sulfides and from thermochemical sulfate reduction (TSR). The carbon (−9.9‰ to −1.4‰ Vienna Pee Dee
Belemnite (V-PDB)) and oxygen (−14.3‰ to −7.7‰ V-PDB) isotope signatures of dolomites associated with the first Cu–Co stage
are in agreement with the interpretation that these dolomites are by-products of BSR. The carbon (−8.6‰ to +0.3‰ V-PDB) and
oxygen (−24.0‰ to −10.3‰ V-PDB) isotope signatures of dolomites associated with the second Cu–Co stage are mostly similar
to the δ13C (−7.1‰ to +1.3‰ V-PDB) and δ18O (−14.5‰ to −7.2‰ V-PDB) of the host rock and of the dolomites of the first Cu–Co stage. This indicates that the dolomites
of the second Cu–Co stage precipitated from a high-temperature, host rock-buffered fluid, possibly under the influence of
TSR. The dolomites associated with the first Cu–Co stage are characterized by significantly radiogenic Sr isotope signatures
(0.70987 to 0.73576) that show a good correspondence with the Sr isotope signatures of the granitic basement rocks at an age
of ca. 816 Ma. This indicates that the mineralizing fluid of the first Cu–Co stage has most likely leached radiogenic Sr and
Cu–Co metals by interaction with the underlying basement rocks and/or with arenitic sedimentary rocks derived from such a
basement. In contrast, the Sr isotope signatures (0.70883 to 0.71215) of the dolomites associated with the second stage show
a good correspondence with the 87Sr/86Sr ratios (0.70723 to 0.70927) of poorly mineralized/barren host rocks at ca. 590 Ma. This indicates that the fluid of the
second Cu–Co stage was likely a remobilizing fluid that significantly interacted with the country rocks and possibly did not
mobilize additional metals from the basement rocks. 相似文献
Zn- and Cu-rich massive sulfide ores of volcanogenic origin [volcanogenic massive sulfide (VMS) deposits] occur as stratiform/stratabound
lenses of variable size hosted by gneisses, amphibolites, and schists of the Areachap Group, in the Northern Cape Province
of South Africa. The Areachap Group represents the highly deformed and metamorphosed remnants of a Mesoproterozoic volcanic
arc that was accreted onto the western margin of the Kaapvaal Craton during the ∼1.0–1.2 Ga Namaquan Orogeny. Sulfur isotope
data (δ34S) are presented for 57 sulfide separates and one barite sample from five massive sulfide occurrences in the Areachap Group.
Although sulfides from each site have distinct sulfur isotope values, all δ34S values fall within a very limited range (3.0‰ to 8.5‰). Barite has a δ34S value of 18.5‰, very different from that of associated sulfides. At one of the studied sites (Kantienpan), a distinct increase
in δ34S of sulfides is observed from the massive sulfide lens into the disseminated sulfides associated with a distinct footwall
alteration zone. Sulfide–sulfide and sulfide–barite mineral pairs which recrystallized together during amphibolite- and lower
granulite facies metamorphism are not in isotopic equilibrium. Sulfur isotope characteristics of sulfides and sulfates of
the Zn–Cu ores in the Areachap Group are, however, very similar to base metal sulfide accumulations associated with modern
volcanic arcs and unsedimented mid-ocean ridges. It is thus concluded that profound recrystallization and textural reconstitution
associated with high-grade regional metamorphism of the massive sulfide ores of the Areachap Group did not result in extensive
sulfur isotopic homogenization. This is similar to observations in other metamorphosed VMS deposit districts and confirms
that massive sulfide ores remain effectively a closed system for sulfur isotopes for both sulfides and sulfates during metamorphism. 相似文献
A controlled field pilot has been developed in Bozeman, Montana, USA, to study near surface CO2 transport and detection technologies. A slotted horizontal well divided into six zones was installed in the shallow subsurface. The scale and CO2 release rates were chosen to be relevant to developing monitoring strategies for geological carbon storage. The field site was characterized before injection, and CO2 transport and concentrations in saturated soil and the vadose zone were modeled. Controlled releases of CO2 from the horizontal well were performed in the summers of 2007 and 2008, and collaborators from six national labs, three universities, and the U.S. Geological Survey investigated movement of CO2 through the soil, water, plants, and air with a wide range of near surface detection techniques. An overview of these results will be presented. 相似文献
A tsunami catalogue for Central America is compiledcontaining 49 tsunamis for the period 1539–1996,thirty seven of them are in the Pacific and twelve inthe Caribbean. The number of known tsunamis increaseddramatically after the middle of the nineteenth century,since 43 events occurred between 1850 and 1996. This isprobably a consequence of the lack of populationliving near the coast in earlier times.The preliminary regionalization of the earthquakessources related to reported tsunamis shows that, inthe Pacific, most events were generated by theCocos-Caribbean Subduction Zone (CO-CA). At theCaribbean side, 5 events are related with the NorthAmerican-Caribbean Plate Boundary (NA-CA) and 7 withthe North Panama Deformed Belt (NPDB).There are ten local tsunamis with a specific damagereport, seven in the Pacific and the rest in theCaribbean. The total number of casualties due to localtsunamis is less than 455 but this number could behigher. The damages reported range from coastal andship damage to destruction of small towns, and theredoes not exist a quantification of them.A preliminary empirical estimation of tsunami hazardindicates that 43% of the large earthquakes (Ms 7.0) along the Pacific Coast of Central America and100% along the Caribbean, generate tsunamis. On thePacific, the Guatemala–Nicaragua coastal segment hasa 32% probability of generating tsunamis after largeearthquakes while the probability is 67% for theCosta Rica–Panama segment. Sixty population centers onthe Pacific Coast and 44 on the Caribbean are exposedto the impact of tsunamis. This estimation alsosuggests that areas with higher tsunami potential inthe Pacific are the coasts from Nicaragua to Guatemalaand Central Costa Rica; on the Caribbean side, Golfode Honduras Zone and the coasts of Panama and CostaRica have major hazard. Earthquakes of magnitudelarger than 7 with epicenters offshore or onshore(close to the coastline) could trigger tsunamis thatwould impact those zones. 相似文献
The analysis of earthquake-related signals in hydrochemical time series is still a challenging task. Mostly it is unclear how the geometrical and energetic distribution of earthquakes is influencing variation in the hydrochemical composition of monitoring sites, e.g. located close to volcanoes. Past research showed that linear stress-release models alone are not capable to explain sufficiently observed variation in hydrochemical time series due to earthquake activity. A spring located at the base of Koryaksky Volcano, which has shown hydrochemical variation close to 5, major earthquakes, was chosen to analyse relation patterns between hydrochemical variation and seismicity. A possible mechanism, explaining observed hydrochemical variation, that seismic waves trigger an underground water pumping caused by nucleation of gas bubbles in magma was proposed. Consequences are an increase of discharge, gas content in water and changes in the mixing ratios of waters of different genesis. Based on functions of aggregated earthquake information (E) it is herein shown that seismotectonic-triggered processes have a significant influence on the variation of the hydrochemistry of the spring, lasting longer than two decades. At least seven categories of relation patterns between hydrochemical variation and seismotectonic activity E can be identified. A conducted spectral analysis shows that earthquake activity and hydrochemistry share spikes in frequencies. Results prove that the use of functions of transformed aggregated seismic observations is useful to represent the seismotectonic activity for analysing earthquake-related signals in hydrochemical time series. 相似文献
Fluid inclusions hosted in quartz and specular hematite from auriferous (jacutinga) and barren veins in the Quadrilátero Ferrífero (QF) have been studied using conventional and near infrared microscopy, respectively.
The mineralization consists of veins that cross-cut metamorphosed iron formation (itabirite) of the Paleoproterozoic Itabira
Group. The sample suite comprises hematite from veins from the low-strain domain in the W and SW of the study area, as well
as hematite samples from the eastern high-strain domain in the central and NE parts of the QF. Halogen ratios of fluid inclusions
in quartz and hematite from all studied deposits are consistent with a fluid evolved from dissolving and reprecipitating halite
that was subsequently diluted. Fluid inclusions hosted in quartz and hematite are characterized by consistent Na/K ratios
and considerable SO4 contents, and suggest similar formation conditions and, perhaps, fluid origin from a common source. Na/K and Na/Li fluid
mineral geothermometers indicate water–rock interaction at approximately 340±40°C. Hematites from the high-strain domain contain
fluid inclusion assemblages of high-temperature aqueous-carbonic and multiphase high-salinity, high-temperature aqueous inclusions
probably due to fluid immiscibility in the system H2O–NaCl–CO2. Fluid inclusions hosted in hematite from barren veins in the low-strain domain, as well as in hematite from jacutinga-type mineralization from the central part of the QF, only host multiphase aqueous fluid inclusions all showing narrow ranges
of salinity (7.2–11.7 wt.% NaCl equiv.) and homogenization temperatures (148 to 229°C). Lower homogenization temperatures
and the absence of CO2-rich inclusions in specular hematite from these occurrences are attributed to carbonate precipitation and/or CO2 escape due to cooling during fluid migration from the high- to the low-strain domain. Pb–Pb and U–Pb systematics of gold,
hematite and hematite-hosted fluid inclusions in combination with geochemical evidence indicate distinct sources for Pd, Au,
and Pb. The formation of specular hematite veins may be related to retrograde metamorphic fluids being released during the
Brazilian orogenic cycle (600–700 Ma). The Pb isotopic characteristics of all samples are readily reconciled in a simple model
that involves two different Paleoproterozoic or Archean source lithologies for lead and reflects contrasting depths of fluid
percolation during the Brasiliano orogeny. 相似文献
Stratiform and stratabound barite ± magnetite beds are intimately associated with the polymetallic Broken Hill-type (BHT)
massive sulfide deposits of the Aggeneys-Gamsberg Pb–Zn–Cu ± Ag–Ba district in the Northern Cape Province, South Africa. Barite
samples were collected and studied from four localities in the district. Although metamorphic water–rock interaction processes
have partially altered the chemical and to a lesser degree the isotopic composition of barite, samples identified as being
the least altered display distinctly different isotopic compositions that are thought to reflect different modes of origin.
All barite samples are marked by low concentrations of SrO (0.5 ± 0.2 wt%), highly radiogenic 87Sr/86Sr ratios, elevated δ34S and δ18O values compared to contemporaneous Mesoproterozoic seawater. Radiogenic 87Sr/86Sr signatures (0.7164 ± 0.0028) point to an evolved continental crustal source for Sr and Ba, while elevated δ34S values (27.3 ± 4.9‰) indicate that contemporaneous seawater sulfate, modified by bacterial sulfate reduction, was the single
most important sulfur reservoir for barite deposition. Most importantly, δ18O values suggest a lower temperature of formation for the Gamsberg deposit compared with the occurrences in the Aggeneys area,
i.e. Swartberg-Tank Hill and Big Syncline. The obvious differences in temperature of formation are in good agreement with
the Cu-rich, Ba-poor nature of the sulfide mineralization of the Aggeneys deposits vs the Cu-poor, Ba-rich character of the
Gamsberg deposit. In conjunction with this, isotopic and petrographic arguments favor a sub-seafloor replacement model for
the stratabound barite occurrences of the Aggeneys deposits, while at Gamsberg, deposition at the sediment–water interface
as a true sedimentary exhalite appears more likely. 相似文献