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K-Ar ages of illite-muscovite and fission track ages of zircon and apatite were determined from various lithotypes of the Bükkium, which forms the innermost segment of the Western Carpathians. The stratigraphic ages of these Dinaric type formations cover a wide range from the Late Ordovician up to the Late Jurassic. The grade of the orogenic dynamo-thermal metamorphism varies from the late diagenetic zone through the anchizone up to the epizone (chlorite, maximally biotite isograd of the greenschist facies). The K-Ar system of the illite-muscovite in the < 2 m grain-size fraction approached equilibrium only in epizonal and high-temperature anchizonal conditions. The orogenic metamorphism culminated between the eo-Hellenic (160-120 Ma) phase connected to the beginning of the subduction in the Dinarides, and the Austrian (100-95 Ma) phase characterized by compressional crustal thickening. No isotope geochronological evidence was found for proving any Hercynian recrystallization. The stability field of fission tracks in zircon was approached using the thermal histories of the different tectonic units. A temperature less than 250°C and effective heating time of 20–30 Ma had only negligible effects on the tracks, whereas total annealing was reached between 250 and 300°C. Apatite fission track ages from the Paleozoic and Mesozoic formations show that the uplift of the Bükk Mountains occurred only in the Tertiary (not earlier than ca. 40 Ma ago). Thermal modeling based on apatite fission track length spectra and preserved Paleogene sediment thickness data proved that the Late Neogene burial of the recently exhumed plateau of the Bükk Mountains exceeded 1 km. 相似文献
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《Quaternary Science Reviews》1999,18(4-5):549-554
The Gediz and the Büyük Menderes Graben basins, two of the most important structural elements of western Anatolia, markedly differ in their palaeogeographic evolution during the Holocene. On the basis of the study of the facies and the geomorphological characteristics of the youngest sedimentary fills it is suggested that the evolution of the Büyük Menderes basin has a simple progradational history while the Gediz River basin has shown a complex evolution mainly controlled by intense tectonic periods. Comparison between the palaeogeographic evolution of these basins points to the fact that tectonism has been more effective in the Gediz basin during the Holocene. 相似文献
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Based on the modified formalism of Dorogokupets and Oganov (2007), we calculated the equation of state for diamond, MgO, Ag, Al, Au, Cu, Mo, Nb, Pt, Ta, and W by simultaneous optimization of the data of shock-wave experiments and ultrasonic, X-ray diffraction, dilatometric, and thermochemical measurements in the temperature range from ~ 100 K to the melting points and pressures of up to several Mbar, depending on the material. The obtained room-temperature isotherms were adjusted with a shift of the R1 luminescence line of ruby, which was measured simultaneously with the unit cell parameters of metals in the helium and argon pressure media. The new ruby scale is expressed as P(GPa) = 1870?Δλ / λ0(1 + 6?Δλ / λ0). It can be used for correction of room-pressure isotherms of metals, diamond, and periclase. New simultaneous measurements of the volumes of Au, Pt, MgO, and B2-NaCl were used for interrelated test of obtained equations of state and calculation of the room-pressure isotherm for B2-NaCl. Therefore, the constructed equations of state for nine metals, diamond, periclase, and B2-NaCl can be considered self-consistent and consistent with the ruby scale and are close to a thermodynamic equilibrium. The calculated PVT relations can be used as self-consistent pressure scales in the study of the PVT properties of minerals using diamond anvil cell in a wide range of temperatures and pressures. 相似文献
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CAI Chunfang PENG Licai MEI Bowen XIAO Yingkai 《《地质学报》英文版》2006,80(4):550-556
In order to elucidate the origin and migration of basinal brines in the Bachu Bulge, Tarim Basin, we have carried out analyses on chemical composition, and boron, hydrogen and oxygen isotopes of formation waters together with the XRD of clay minerals from the Paleozoic strata. The waters show Ca, B, Li and Sr enrichment and SO4 depletion in the Carboniferous and Ordovician and K enrichment in part of the Ordovician relative to seawater. The relationship between δD and δ^18O shows that all the data of the waters decline towards the Global Meteoric Water Line with the intersection of them close to the present-day local meteoric water, suggesting that modern meteoric water has mixed with evaporated seawater. The ^87Sr/^86Sr ratios range from 0.7090 to 0.7011, significantly higher than those of the contemporary seawater. The δ^11B values range from ＋19.7 to ＋32.3‰, showing a decrease with the depth and B concentrations. The results suggest that isotopically distinct B and Sr were derived from external sources. However, since the percentages of illite are shown to increase with depth among clay minerals in the study area, i.e., illite is due to precipitation rather than leaching during deeper burial, it is unlikely for illite to have contributed a significant amount of B to the waters. Thus, B with low δ^11B values is interpreted to have been added mainly from thermal degradation of kerogen or the basalts in the Cambrian and Lower Ordovician. 相似文献
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《International Geology Review》2012,54(5):379-420
Variations in the abundances of Zn, Cu, and Pb are found to be useful in identifying tectonic regimes and separating oceanisland basalts into enriched- and depleted-source categories. The average Zn, Cu, and Pb contents of normal mid-ocean ridge basalts (N-MORB) are 84, 70, and 0.35 ppm, respectively. Differences in average Zn contents for various ridges reflect more the varying degrees of differentiation than variations of Zn content in the source rocks. At a Mg# of 70, or Mg#70, which is taken to represent primitive MORB, many MORB sequences converge at a Zn content of 58 ± 6 ppm, which is close to the value for primitive mantle (50 ppm) and ordinary chondrites (～55 ppm). Values of 0.1 to 0.15 ppm Pb in MORB at Mg#70, best defined at the superfast-spreading Southern East Pacific Rise, are similar to estimates of Pb in the primitive mantle (0.12 to 0.18 ppm). They also are near the lower end of the range for ordinary chondrites. The very slow spreading Southwest Indian Ocean Ridge has a sequence with higher Pb contents, in addition to a more normal sequence, which has a visual best value of 0.4 ppm Pb at Mg#70. With the exception of the Walvis Ridge, Zn and Cu appear to be little affected by proximity to hotspots (i.e., E-MORB); however, Pb contents are higher and average about 0.6 ppm. Both Zn and Pb in MORB are incompatible elements (i.e., favor the melt), but Cu is a compatible element. At Mg#70, there is the suggestion of a value of 100 ppm for Cu, with lower values possibly representing partial removal of sulfides and their associated Cu from the source. Nonetheless, Cu contents of primitive MORB tend to be much higher than even high estimates for the primitive mantle (28 ppm), and are closer to ordinary chondrites (～90 ppm). Therefore, Zn, Cu, and Pb all approximate chondritic values in the primitive MORB melt. Average contents of Zn, Cu, and Pb in oceanic island basalts (OIB) are 115, 62, and 3.2 ppm, respectively. At Mg#70, values of Zn and Cu are similar to the respective averages for OIB, with Zn higher and Cu lower than MORB. At a Mg# of ～40, however, OIB and MORB tend to have similar Zn contents. With further differentiation, OIB trachytes can contain >200 ppm Zn. Unlike MORB, OIB can differentiate to high Cu contents of 200 ppm at Mg#s of 40 to 60. In contrast to Zn and Cu, Pb regresses to a value of 0.83 ppm at Mg#70 for Hawaiian and Reunion volcanics, which is much less than the average value for Pb in OIB volcanics, but higher than for MORB. Average Zn, Cu, and Pb contents of magmatic-arc basalts are 77, 108, and 1.9 ppm, respectively. In basalts, Zn tends to be incompatible, but a dual incompatible and compatible behavior can occur at high SiO2 contents. Dacites may average near 55 ppm Zn, but peralkalic rhyolite can contain >300 ppm Zn. A dual compatible and incompatible nature occurs for Cu. Most common, particularly in submarine volcanics, is a compatible trend, with a Cu content of around 80 ppm at a Mg# of 60, which decreases to less than 40 ppm at a Mg# of 30. The incompatible trend of increasing Cu can achieve >200 ppm at a Mg# of 30, leaving a gap approaching 100 ppm at that Mg#. The gap is less obvious on a plot of Cu vs. SiO2, but is still there. The compatible trend is proposed to result from sulfur-saturated magmas, whereas the incompatible trend is believed to result from sulfur-deficient magmas. Support for this hypothesis is found in sparse sulfur-isotope data. Zn and Cu both can be incompatible over an extended range of Mg#s or silica content. When Zn and Cu are both compatible, Cu decreases more than twice as rapidly as Zn. Primitive magmas at Mg#70 average about 50 ppm Zn for submarine Mariana arc basalts and 58 ppm for forearc boninites, contents close to MORB values. Mariana arc basalts have a Zn content of ～45 ppm estimated at Mg#70. Cu varies more widely than Zn in primitive magmas, being about 50 ppm Cu for Mariana Islands volcanics and 120 ppm for Kermadec Islands volcanics, a range broadly around MORB values. Average Pb contents are 1.9 ppm for island-arc tholeiites, 5.6 ppm for high-Al basalt, and 3.2 ppm for alkali basalt with average boninite of approximately 1.8 ppm. Back-arc-basin basalts in the deepest parts of the Mariana trough have Pb contents of 0.45 ppm, but more shallow parts may exceed 1.0 ppm Pb. Although the lower contents are similar to MORB values, the 208Pb/204Pb values are greater than Pacific Ocean MORB. At Mg#70 for rocks from the Tonga and Kermadec island arcs, the Pb content is about 0.1 ppm, similar to MORB. 相似文献
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Joan Cabato Rainer Altherr Thomas Ludwig Hans-Peter Meyer 《Contributions to Mineralogy and Petrology》2013,165(6):1135-1154
Li, Be, B and δ7Li SIMS analyses of plagioclase phenocrysts from the 1040–1941 Niki dacite lava (Nea Kameni, Santorini, Greece) exhibit varied processes. From their anorthite contents alone, the crystals may be segregated into four main types: type-N shows the normal decline in An during crystallisation (An62–40); type-O has only oscillatory zoning accompanied by resorption surfaces (An58–39); type-C is complex with high-An cores (subtype C1: An64–58, subtype C2: An88–73) and normal rims (An55–42). Type-A plagioclase with high An content (An92–82) is found within mafic enclaves. On the basis of their Li concentrations, type-O crystals may be subdivided into subtype O1 with flat Li concentration profiles and subtype O2 with decreasing Li concentration from core to rim. The concentrations of Be and B of all four types show a negative correlation with anorthite content (An), but Li concentration profiles differ amongst the different plagioclase types. Types N and O1, and the cores of type-C, are equilibrated in Li concentration. Types O2 and A, and the mantles of type-C display an initial enrichment in Li, probably from volatile influx into the melt. Consistent with the propensity towards equilibrium with the melt, these crystals display dramatic rim-ward declines in Li concentration. All analysed plagioclase crystals, except for the xenocrystic type-A, have nearly the same Li, Be and B concentrations at their rims. These coincide with the composition of plagioclase microlites in the groundmass, thereby affording estimates of plagioclase-melt partitioning for the light elements: K Li = 0.19–0.28, K Be = 0.24–0.38 and K B = 0.007–0.009. δ7Li profiles in type-O2 and type-A phenocrysts manifest an unmistakable inverse relation to Li concentration, with variations of up to ~39 ‰, revealing preferential kinetic diffusion. This may have been driven by Li loss from the melt, most likely through degassing during decompression, perhaps in the course of magma ascent to subsequent eruption. Considering the rapid diffusion of Li in plagioclase, in situ phenocryst analyses may yield useful information about processes leading up to, or even causing, eruptions. 相似文献
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Dr. S. S. Augustithis 《Contributions to Mineralogy and Petrology》1962,8(6):491-498
True graphic quartz structures in pegmatites from Carrara/Giggiga and Harrar (town) districts of Ethiopia, are compared with the micrographic quartz textures in the Rapakiwi granite of Finland. Graphic-like textures of uraninite in microcline are also discussed and compared with these graphic structures.A quartz vein, about 1–2 meters in thickness, intersects a pegmatite in the Carrara/Giggiga district. This quartz vein extends into the microcline of the pegmatite as fine quartz veins which attain the form and character of graphic quartz. Also the graphic quartz of the Harrar pegmatites is observed to extend into and occupy cracks in the microcline.Comparable in origin to these graphic textures is the micrographic quartz in the Rapakiwi granite. Observations show micrographic quartz following the cleavage directions in the orthoclase as well as the interzonal spaces and the boundaries of inclusions in the K-feldspar.On the basis of the observed structures and textures these graphic and micrographic intergrowths are considered to be due to solutions penetrating or infiltrating into existing structures and not due to simultaneous crystallisation as conditions of eutectic crystallisation would require.In addition to the well known graphic structures there occur graphic or myrmekitic-like intergrowths of uraninite in microcline which, from a structural and physico-chemical point of view, cannot be considered to be due to eutectic crystallisation. 相似文献
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Edward Derbyshire 《中国地球化学学报》2006,25(B08):219-219
Fine atmospheric dust includes mineral particles and aggregates, fibrous minerals and fibrous organic material. Generation, dislodgement and transport （deflation） of natural dust with the finer （〈4 microns） components suspended as silt-size aggregates, is widespread in and adjacent to the world＇s drylands, as well as deriving from volcanic vents. Silica is a highly fibrogenic agent in lung tissue. Long-term inhaling of siliceous dusts can lead to a number of fibrotic lung diseases, including natural （non-occupational） pneumoconioses （notably silicosis, but including asbestosis and others）. Different polymorphs of silica show different levels of toxicity in interaction with lung tissue. Particles with highly active surfaces may release radicals, causing cell damage. Some types of inhaled particulates are degraded by macrophages, but many are highly resistant and persist in the lungs, some stimulating fibroblastic cells to deposit collagen. Silicosis is an inflammation of the lung commonly caused by silicate mineral particles, leading to fibrosis. Three types are recognized： nodular pulmonary fibrosis （simple or chronic silicosis）, acute silicosis, and accelerated silicosis. Generally, finer particulates have greater oxidative capacity than the coarser fractions. They contain more reactive oxygen species, their greater bioreactivity making them more toxic to pulmonary tissue. Nevertheless, inhalation of large dust particles （〉 10μm） may constitute a health risk if the mineralogy is toxic, regardless of where the grains lodge in the respiratory system. Dust may absorb harmful gases, disease-generating bacteria and carcinogenic hydrocarbon compounds. Silica-related respiratory disease may also an exacerbate cardiac problem, and epidemiology suggests a link with tuberculosis. Quantification of dust loading and exposure requires study of spatial and temporal patterns, supported by meteorological analysis, airflow modeling and satellite-borne imagery. Some acute, short-term health impacts have been assessed using atmospheric and health records both before and after a dust storm or by comparison of populations within and outside such events. Analysis of the size, shape, mineralogy and geochemistry of ambient dust particulates provides information on natural dust sources, dust concentrations, and potential particulate toxicity, as well as providing a datum for assessment of human exposure levels. 相似文献
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Asteroid impact spherule layers and tsunami deposits underlying banded iron-formations in the Fortescue and Hamersley Groups have been further investigated to test their potential stratigraphic relationships. This work has included new observations related to the ca 2.63 Ga Jeerinah Impact Layer (JIL) and impact spherules associated with the 4th Shale-Macroband of the Dales Gorge Iron Member (DGS4) of the Brockman Iron Formation. A unit of impact spherules (microkrystite) correlated with the ca 2.63 Ga JIL is observed within a >100 m-thick fragmental-intraclast breccia pile in drill cores near Roy Hill. The sequence represents significant thickening of the impact/tsunami unit relative to the JIL type section at Hesta, as well as relative to the 20–30 m-thick ca 2.63 Ga Carawine Dolomite spherule-bearing mega-breccia. The ca 2.48 Ga-old Dales Gorge Member of the Brockman Iron Formation is underlain by an ?0.5 m-thick rip-up clast breccia located at the top of the ca 2.50 Ga Mt McRae Shale, and is interpreted as a tsunami deposit. We suggest that the presence of impact ejecta and tsunami units stratigraphically beneath a number of banded iron-formations, and units of ferruginous shale in the Pilbara and South Africa may result from a genetic relationship. For example, it could be that under Archean atmospheric conditions, mafic volcanism triggered by large asteroid impacts enriched the oceans in soluble FeO. If so, seasonal microbial and/or photolytic oxidation to ferric oxide could have caused precipitation of Fe2O3 and silica. In view of the possible occurrence of depositional gaps and paraconformities between impact ejecta units and overlying ferruginous sediments, these relationships require further testing by isotopic age studies. 相似文献
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The characteristic structures of the Precambrian cherts from the Gusui section, Guangdong ,Chi-na, include bedded structure ,laminated structure ,massive structure and pseudobrecciated structure.The chert is characterized by consistently low abundance of TiO2,Al2O3 and most trace elements.Howevver ,it is enriched in Ba,As,Sb,Hg and Se.In Al-Fe-Mn ternary diagrams,it falls into the “hydrothermal field“ .Correspondence analysis and factor analysis show that many elements show up in the factor that represents the leaching of country rocks by hydrothermal solutions,and are the very characteristic element association fo the geochemically anomalous South China basement.Petrologic and geochemical evidence suggests a hydrothermal origin for the chert.The chert may have been formed in a Precambrian fift or an extension zone developed within the Yunkai marginal geosyncline, with a fault system linking it to an unknown heat source at depth. 相似文献
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Fred T. Mackenzie Andreas J. Andersson Rolf S. Arvidson Michael W. Guidry Abraham Lerman 《Applied Geochemistry》2011
Epochs of changing atmospheric CO2 and seawater CO2–carbonic acid system chemistry and acidification have occurred during the Phanerozoic at various time scales. On the longer geologic time scale, as sea level rose and fell and continental free board decreased and increased, respectively, the riverine fluxes of Ca, Mg, DIC, and total alkalinity to the coastal ocean varied and helped regulate the C chemistry of seawater, but nevertheless there were major epochs of ocean acidification (OA). On the shorter glacial–interglacial time scale from the Last Glacial Maximum (LGM) to late preindustrial time, riverine fluxes of DIC, total alkalinity, and N and P nutrients increased and along with rising sea level, atmospheric PCO2 and temperature led, among other changes, to a slightly deceasing pH of coastal and open ocean waters, and to increasing net ecosystem calcification and decreasing net heterotrophy in coastal ocean waters. From late preindustrial time to the present and projected into the 21st century, human activities, such as fossil fuel and land-use emissions of CO2 to the atmosphere, increasing application of N and P nutrient subsidies and combustion N to the landscape, and sewage discharges of C, N, P have led, and will continue to lead, to significant modifications of coastal ocean waters. The changes include a rapid decline in pH and carbonate saturation state (modern problem of ocean acidification), a shift toward dissolution of carbonate substrates exceeding production, potentially leading to the “demise” of the coral reefs, reversal of the direction of the sea-to-air flux of CO2 and enhanced biological production and burial of organic C, a small sink of anthropogenic CO2, accompanied by a continuous trend toward increasing autotrophy in coastal waters. 相似文献
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This study is aimed at determining the diffusion coefficient of net-work modifiers (mainly Na, K, and Ca) in a two-phase melt-NaCl
system, in which the melts are granitic and the system is NaCl-rich in composition. The diffusion coefficients of Na, K, and
Ca were measured at the temperatures of 750 – 1400°C, pressures of 0.001 × 108 – 2 × 108 Pa, and initial H2O contents of 0 wt% –6.9 wt% in the granitic melts. The diffusion coefficients of Fe and Mg were difficult to resolve. In
all experiments a NaCl melt was present as well. In the absence of H2O, the diffusion of net-work modifiers follows an Arrhanious equation at 1 × 105 Pa: lgDca=−3. 88−5140/T, lgDk =−3. 79−4040/T, and lgDNa, =−4.99−3350/T, where D is in cm2 /s andT is in K. The diffusion coefficients of Ca, Na, K, and Fe increase non-linearly with increasing H2O content in the melt. The presence of about 2 wt% H2O m the melt will lead to a dramatical increase in diffusivity, but higher H2O content has only a minor effect. This change is probably the result of a change in the melt structure when H2O is present. The diffusion coefficients measured in this study are significantly different from those in previous works.
This may be understood in terms of the “transient two-liquid equilibrium” theory. Element interdiffusion depends not only
on its concentration, but also on its activity co-efficient gradient, which is reflected by the distribution coefficient,
of the two contacting melts. 相似文献