Comparison of Static,Kinematic and Dynamic Geodetic Deformation Models for Kutlugün Landslide in Northeastern Turkey

Being the cause of the loss of life and damaging property, landslide is an important natural hazard. Therefore, landslides have to be monitored and preventive measures taken accordingly. In Geodesy, landslides can be determined with static, kinematic and dynamic geodetic models. The aim of this study is to develop a dynamic geodetic model for landslides and compare it with static and kinematic geodetic models. A study area was selected in the Northeastern Black Sea Region of Turkey where landslides are the most effective natural hazard. Movements were determined with static, kinematic and dynamic geodetic models using geodetic, geologic and geophysical measurements made in the study area. Groundwater levels changes were regarded as causative forces in the formulation of the dynamic model. The dynamic model delivered more detailed information (direction, values, velocity, acceleration of movements) about landslide movements. It is possible to formulate more realistic strategies about prevention of landslides by using this information. As a result, it can be suggested that dynamic geodetic models are more useful in landslide studies.     

Evaluation of superficial settlements in low overburden tunnel TBM excavation: Numerical approaches

In this paper the problem of the superficial settlements related to tunnel mechanised excavation is analysed considering a low overburden application example. The excavation of tunnels in urban areas has actually important diffusion. This kind of work always implies to guarantee the safety and the stability of the existing superficial structures. The use of a tunnel boring machine (TBM) represents a good method in these conditions and the estimation of the induced settlement represents a difficult engineering problem. The study shows the differences between three different numerical approaches; the results, function of the same loss of volume, evidence from a quantitative point of view, the ground settlement.     

The 14-year Performance of a Compacted Clay Liner used as Part of a Composite Liner System for a Leachate Lagoon

The migration of contaminants through a 2.9 m thick compacted clay liner (CCL) for a landfill leachate lagoon is examined 14 years after construction. The clay liner formed the lower portion of the composite liner system but the geomembrane (GM) was found to have defects that had allowed leachate to migrate between the GM and CCL. Chloride, sodium, potassium, calcium and magnesium pore water profiles through the CCL are examined. It is shown that chloride migrated approximately 1.7 m into the CCL during the 14 years of the lagoon operation, sodium approximately 1.2 m, and potassium 0.7 m. Diffusion and sorption data from laboratory diffusion testing are utilized in combination with a finite layer contaminant transport model to predict field contaminant migration profiles through the composite liner system and to establish the time of ‘failure’ of the geomembrane at sometime between 0 and 6 years after installation. Relatively high sorptive uptake of potassium by the CCL soil is observed from batch testing and diffusion testing with field data suggesting an even larger amount of sorption. It is hypothesized that organic sludge matter at the base of the lagoon is responsible for potassium uptake from the leachate. This field case highlights the importance of the compacted clay liner as part of the composite liner system in acting as a diffusion barrier during the lifetime of the lagoon as well as using relatively non-conservative contaminants such as chloride and sodium to estimate geomembrane ‘failure’ times     

Experimental and geochemical evidence for derivation of the El Capitan Granite,California, by partial melting of hydrous gabbroic lower crust

Partial melting of mafic intrusions recently emplaced into the lower crust can produce voluminous silicic magmas with isotopic ratios similar to their mafic sources. Low-temperature (825 and 850°C) partial melts synthesized at 700 MPa in biotite-hornblende gabbros from the central Sierra Nevada batholith (Sisson et al. in Contrib Mineral Petrol 148:635–661, 2005) have major-element and modeled trace-element (REE, Rb, Ba, Sr, Th, U) compositions matching those of the Cretaceous El Capitan Granite, a prominent granite and silicic granodiorite pluton in the central part of the Sierra Nevada batholith (Yosemite, CA, USA) locally mingled with coeval, isotopically similar quartz diorite through gabbro intrusions (Ratajeski et al. in Geol Soc Am Bull 113:1486–1502, 2001). These results are evidence that the El Capitan Granite, and perhaps similar intrusions in the Sierra Nevada batholith with lithospheric-mantle-like isotopic values, were extracted from LILE-enriched, hydrous (hornblende-bearing) gabbroic rocks in the Sierran lower crust. Granitic partial melts derived by this process may also be silicic end members for mixing events leading to large-volume intermediate composition Sierran plutons such as the Cretaceous Lamarck Granodiorite. Voluminous gabbroic residues of partial melting may be lost to the mantle by their conversion to garnet-pyroxene assemblages during batholithic magmatic crustal thickening.     

Clay mineralogical,geochemical and isotopic tracing of the evolution of the Woodleigh impact structure,Southern Carnarvon Basin,Western Australia

Chaotically structured diamictite from the inner ring syncline surrounding the central uplift of the Woodleigh impact structure contains shocked metamorphic and impact melt-rock fragments, largely derived from Ordovician and Devonian target sandstones. Coarse illite fractions (<2 m) from the sandstones containing no K-feldspar yield K–Ar ages of around 400 Ma, whereas the K–Ar ages of authigenic clays of >0.2 m fractions from the diamictite without smectite and K-feldspar cluster around 360 Ma, consistent with Rb–Sr data. Crystallisation of newly formed illite in the impact melt rock clasts and recrystallisation of earlier formed illite in the sandstone clasts preserved in the diamictite, are attributed to impact-induced hydrothermal processes in the Late Devonian. The illitic clays from the diamictite and from the sandstones have very similar trace element compositions, with significantly enriched incompatible lithophile elements, which increase in concentrations correlatively with those of the compatible ferromagnesian elements. The unusual trace element associations in the clays may be due to the involvement of hot gravity-driven basinal fluids that interacted with rocks of the Precambrian craton to the east of the study area, or with such material transported and reworked in the studied sedimentary succession.     

Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS. Part 4: Plagioclase,orthopyroxene, clinopyroxene,glass geobarometer,and application to Mt. Ruapehu,New Zealand

A new phase equilibria geobarometer determines magmatic storage and crystallization conditions, including pressure, temperature, oxygen fugacity (\({f_{{{\text{o}}_2}}}\)), and the presence of a fluid phase for glass-bearing rocks containing the assemblage plagioclase?+?pyroxene(s). This newly developed geobarometer can better constrain crystallization conditions of shallow (<?500 MPa; <~?20 km), glass-bearing andesites to dacites. The geobarometer utilizes rhyolite-MELTS to determine crystallization conditions in natural pumice and scoria samples. The validity of the geobarometer is tested by comparing it to results from experiments. Uncertainties are assessed using Monte Carlo simulations. We apply the geobarometer to the plag?+?opx?+?cpx-bearing system of Mt. Ruapehu, in the southern Taupo Volcanic Zone, New Zealand. The samples from Mt. Ruapehu are tested from ~?5 to ~?400 MPa and from super-liquidus to 90% crystalline (~ 1200 to ~ 700 °C). Mt. Ruapehu serves as a methodological testing ground for the geobarometer, and results from our geobarometer agree with recent Mt. Ruapehu studies. Results show a distribution of crystallization pressures ranging from 50 to 150 MPa (~?2.0 to 5.9 km) for different eruptions, with modes of 110 MPa (~ 4.3 km) and 130 MPa (~ 5.1 km). These are consistent with field interpretations of different eruptive styles based on juvenile clast textures and previous knowledge of the magma plumbing system. Mt. Ruapehu magmas are fluid saturated, with \({f_{{{\text{o}}_2}}}\) of ΔQFM ~ + 1 (NNO).     

The accuracy of standard enthalpies and entropies for phases of petrological interest derived from density-functional calculations

The internal energies and entropies of 21 well-known minerals were calculated using the density functional theory (DFT), viz. kyanite, sillimanite, andalusite, albite, microcline, forsterite, fayalite, diopside, jadeite, hedenbergite, pyrope, grossular, talc, pyrophyllite, phlogopite, annite, muscovite, brucite, portlandite, tremolite, and CaTiO₃–perovskite. These thermodynamic quantities were then transformed into standard enthalpies of formation from the elements and standard entropies enabling a direct comparison with tabulated values. The deviations from reference enthalpy and entropy values are in the order of several kJ/mol and several J/mol/K, respectively, from which the former is more relevant. In the case of phase transitions, the DFT-computed thermodynamic data of involved phases turned out to be accurate and using them in phase diagram calculations yields reasonable results. This is shown for the Al₂SiO₅ polymorphs. The DFT-based phase boundaries are comparable to those derived from internally consistent thermodynamic data sets. They even suggest an improvement, because they agree with petrological observations concerning the coexistence of kyanite?+?quartz?+?corundum in high-grade metamorphic rocks, which are not reproduced correctly using internally consistent data sets. The DFT-derived thermodynamic data are also accurate enough for computing the P–T positions of reactions that are characterized by relatively large reaction enthalpies (>?100 kJ/mol), i.e., dehydration reactions. For reactions with small reaction enthalpies (a few kJ/mol), the DFT errors are too large. They, however, are still far better than enthalpy and entropy values obtained from estimation methods.     

Zoning and exsolution in alkali feldspars from Laacher See volcano (Western Germany): constraints on temperature history prior to eruption

Compositional zoning and exsolution patterns of alkali feldspars in carbonatite-bearing cognate syenites from the 6.3 km³ (D.R.E) phonolitic Laacher See Tephra (LST) deposit in western Germany (12.9 ka) are reported. These rocks represent the cooler outer portion and crystal-rich products of a cooling magma reservoir at upper crustal levels. Major and trace-element difference between cores and rims in sanidine crystals represent two generations of crystal growth separated by unmixing of a carbonate melt. Trace-element differences measured by LA–ICP–MS are in accordance with silicate–carbonate unmixing. Across the core–rim boundary, we extracted gray-scale profiles from multiple accumulations of back-scattered electron images. Gray scales directly represent K/Na ratios owing to low concentrations of Ba and Sr (<?30 ppm). Diffusion gradients are modeled to solve for temperature using known pre-eruptive U–Th zircon ages (0–20 ky) of each sample (Schmitt et al., J Petrol 51:1053–1085, 2010). Estimated temperatures range from 630 °C to 670 °C. For the exsolution boundaries, a diffusive homogenization model is constrained by the solvus temperature of ~ 712^_725 °C and gives short time scales of only 15–50 days. Based on our results, we present a model for the temperature–time history of these rocks. The model also constrains the thermal variation across the cooling crystal-rich carapace of the magma reservoir over 20 ka and suggests a thermal reactivation of cumulates, the cooling carapace, and probably the entire system only a few years prior to the explosive eruption of the remaining molten core of the phonolitic magma reservoir.     

Metasomatism and the crystallization of zircon megacrysts in Archaean peridotites from the Lewisian complex,NW Scotland

Zircon megacrysts are locally abundant in 1–40 cm-thick orthopyroxenite veins within peridotite host rocks in the Archaean Lewisian gneiss complex from NW Scotland. The veins formed by metasomatic interaction between the ultramafic host and Si-rich melts are derived from partial melting of the adjacent granulite-facies orthogneisses. The interaction produced abundant orthopyroxene and, within the thicker veins, phlogopite, pargasite and feldspathic bearing assemblages. Two generations of zircon are present with up to 1 cm megacrystic zircon and a later smaller equant population located around the megacryst margins. Patterns of zoning, rare earth element abundance and oxygen isotopic compositions indicate that the megacrysts crystallized from crustal melts, whereas the equant zircon represents new neocryst growth and partial replacement of the megacryst zircon within the ultramafic host. Both zircon types have U–Pb ages of ca. 2464 Ma, broadly contemporaneous with granulite-facies events in the adjacent gneisses. Zircon megacrysts locally form?>?10% of the assemblage and may be associated to zones of localized nucleation or physically concentrated during movement of the siliceous melts. Their unusual size is linked to the suppression of zircon nucleation and increased Zr solubility in the Si-undersaturated melts. The metasomatism between crustal melts and peridotite may represent an analog for processes in the mantle wedge above subducting slabs. As such, the crystallization of abundant zircon in ultramafic host rocks has implications for geochemistry of melts generated in the mantle and the widely reported depletion of high field strength elements in arc magmas.