Pits, outgrowths, and inclusions as coated grain kinetic instabilities

The development of outgrowths or pits of various shapes on coated grains is explained via a quantitative model of grain growth/dissolution kinetics coupled to evolving grain geometry (morphological dynamics). Grain-coating thinning or fracturing occurring due to nonplanar growth (and consequent grain surface area increase) is shown to underlie an instability to the formation of bumps, or in the case of undersaturated systems, to pitting. Examples of diagenetic outgrowth phenomena on clay-coated quartz are presented. A quantitative model of coupled quartz growth and coating dynamics is shown to imply many features observed in natural systems. Crystal growth anisotropy is shown to strongly influence the morphology of the outgrowths. The creation of inclusions is shown to be closely related to the present morphological instability. These morphological instability phenomena are interesting examples of geochemical self-organization.A steady-state model of the diffusion of solutes across the grain coating is shown to yield a novel nonlinear equation to be solved for the rate of growth of coated grains. This equation leads to a complex dependence of the growth/dissolution rate on saturation (or more generally on the composition of the fluid) in the medium surrounding the coated grain. The feedback between the dynamics of the coating thickness and morphology changes makes the phenomenon of interest here distinct from that arising from the coupling of grain growth and diffusion in the surrounding medium. This makes pits and needles possible even in a well-stirred surrounding medium, a fact of interest in interpreting the geologic record. For example, the present model can explain the development of spike, mushroom, and other outgrowths on clay-coated quartz grains in a sedimentary rock, whereas the classic Mullins and Sekerke diffusion model cannot, i.e., the time scale for eliminating concentration gradients in a pore is much shorter than that for grain growth. Predictions of the model are consistent with observations on quartz when typical values of diffusion, growth rate coefficients, and other parameters are used. In this paper, we emphasize that pitting can be closely related to outgrowth instabilities. If this be the case, then pitted dissolution of feldspars is a likely example. As feldspars dissolve, they commonly surround themselves with a clay coating, often leaving only a ghost remnant of the original growth.     

Studies on the effect of burden width on blast-induced vibration in open-pit mines

This study concerns the correlation between burden and blast-induced vibrations in open-pit mines. For this purpose, two different mines were studied. In these mines, the vibrations caused by explosions at burdens having widths ranging from 3 to 14 m were measured from various distances. From the results, it was found for these cases that burden width has a significant impact on vibrations. Consequently, it was proven that vibrations decrease as burden increases.     

Migration of giant planets in planetesimal discs

Planets orbiting a planetesimal circumstellar disc can migrate inward from their initial positions because of dynamical friction between planets and planetesimals. The migration rate depends on the disc mass and on its time evolution. Planets that are embedded in long-lived planetesimal discs, having total mass of 10⁻⁴– 0.01 M_⊙ , can migrate inward a large distance and can survive only if the inner disc is truncated or as a result of tidal interaction with the star. In this case the semimajor axis, a , of the planetary orbit is less than 0.1 au. Orbits with larger a are obtained for smaller values of the disc mass or for a rapid evolution (depletion) of the disc. This model may explain not only several of the orbital features of the giant planets that have been discovered in recent years orbiting nearby stars, but also the metallicity enhancement found in several stars associated with short-period planets.     

Gold and Silver Prospection Using Magnetic,Radiometry and Microgravity Methods in the Kışladağ Province of Western Turkey

The study area lies in the K??lada? province of western Turkey. The site has an approximate dimension of 1.5 to 2 km north‐south length and 3 km east‐west width. Combined methods from the fields of geology, geochemistry and geophysics were applied to elucidate the regional geologic framework and identify favorable environs for mineralization. There are a few volcanic hills in the center of the K??lada? caldera, which is actually a field of interest. Magnetics (M), Magnetic Total Field Gradient (Mg), Radiometry (Ra), Microgravity (MG) and Microgravity Gradient (MGG) methods were used to prospect the terrains and boundaries of gold and silver deposition in the area. The observed mineralized zones are characterized by low magnetization, low radiation, and high density contrast. Such zones appear to exist outside and beneath a magnetized cap rock. The locations of proposed drill holes were determined with varying depths. Following completion of geophysical and geochemical exploration, an open cut mine with a yearly production rate of about 5 to 6 tons of gold minerals at depths varying between 50 to 225 m has been operational.     

The Purpose and Age of Underwater Walls in the Bay of Elaia of Western Turkey: A Multidisciplinary Approach

Pergamum (modern: Bergama) was operating an important harbour used by military forces and merchants at the city of Elaia during Hellenistic and Roman Imperial times. Harbour‐related facilities such as warehouses, breakwaters and wharfs document the importance of this harbour site not only for the Pergamenians. This paper focuses on the purpose and age of six submerged wall structures situated approximately 1 km south of the ancient closed harbour basin of Elaia. Geoelectric cross‐sections and semi‐aquatic coring near these walls failed to detect any solid basement under the walls which excludes their possible use as breakwaters or wharfs. Instead, the walls were most likely delineating and separating evaporation ponds of salt works, which compares well with similar structures from other periods and places around the Mediterranean. Combined OSL and ¹⁴C‐dating determined the construction age of the installation between the 4th and 6th centuries A.D. Subsequent (re‐)uses are likely and are in agreement with findings from archaeological surveys.     

Time–space fractional governing equations of one‐dimensional unsteady open channel flow process: Numerical solution and exploration

Although fractional integration and differentiation have found many applications in various fields of science, such as physics, finance, bioengineering, continuum mechanics, and hydrology, their engineering applications, especially in the field of fluid flow processes, are rather limited. In this study, a finite difference numerical approach is proposed to solve the time–space fractional governing equations of 1‐dimensional unsteady/non‐uniform open channel flow process. By numerical simulations, results of the proposed fractional governing equations of the open channel flow process were compared with those of the standard Saint‐Venant equations. Numerical simulations showed that flow discharge and water depth can exhibit heavier tails in downstream locations as space and time fractional derivative powers decrease from 1. The fractional governing equations under consideration are generalizations of the well‐known Saint‐Venant equations, which are written in the integer differentiation framework. The new governing equations in the fractional‐order differentiation framework have the capability of modelling nonlocal flow processes both in time and in space by taking the global correlations into consideration. Furthermore, the generalized flow process may possibly shed light on understanding the theory of the anomalous transport processes and observed heavy‐tailed distributions of particle displacements in transport processes.     

Fission track dating obsidians in Central and Northern Anatolia

Twenty obsidian samples from Central and North Anatolia were dated by the fission track method. Split samples analyzed in two different laboratories give consistent results. Data presented refer to three volcanic fields and are summarized as follows: Orta-Sakaeli (Northern Anatolia) obsidians with ages from 21–23 Ma; Göllü Dagi dome complex near Çiftlik (Central anatolia) has given ages between 1.33–0.98 Ma; Acigöl caldera (Central Anatolia) shows three age groups: (1) Eruptions of precaldera (Bogazköy) obsidians with ages 0.18–0.15 Ma; (2) Formation of the large intracaldera dome Kocadag-Taskesiktepe at about 0.08 Ma (uncorrected apparent age of 0.075 Ma); and (3) Acigöl peripheral obsidian domes with plateau ages of 0.020 and 0.019 Ma, and an additional uncorrected age of 0.018 Ma form a distinct age group. This fission track parameters discriminate between the various obsidian sources of prehistoric obsidian artifacts.     

Temporal changes of warm-season pan evaporation in a semi-arid basin in Western Turkey

Warm-season (from May to September) pan evaporation series recorded at nine sites in semi-arid Büyük Menderes Basin in Western Turkey were analyzed for evidence of long-term changes using non-parametric Mann–Kendall test. Only two sites showed significant linear trends, one in decreasing direction and the other in increasing direction. Area-averaged normalized anomalies of pan evaporation stayed unchanged over the period 1975–2006. Based on correlation and multiple regression analysis with visual inspection of the time series plots, sunshine duration which is used as a proxy for global radiation was found to be the major factor explaining the change and variability of pan evaporation in warm-season in semi-arid Büyük Menderes Basin. Stepwise multiple regression analysis showed no significant effect of rainfall on pan evaporation, which means that the effect of complementary relationship is rather weak and even non-existent.