Compression Behaviour of Chlef Sand and Transition of Fines Content Using Pressure-Dependent Maximum Void Ratios of Sand

Geotechnical and Geological Engineering - This paper presents a study on Chlef sand to examine the effect of fines content (Fc), relative density (RD) and initial conditions on the compressibility...     

The Mineral Adsorption and The Application of a Metamorphic Felsic Rock as Aggregate in Asphalt Pavements

Geotechnical and Geological Engineering - The aggregates consist approximately 85% of the total volume in asphalts pavements, and their properties influence directly their behavior. Therefore, it...     

Source constraints for the young basaltic rocks from the northernmost end of Cappadocian region,Turkey: Melting evidence from peridotite and pyroxenite source domains

Widespread magmatic activity developed in the Middle Miocene in the Cappadocian Region of Central Anatolia in Turkey. Despite several previous studies that focus on the geochemical features of the magmatic rocks, the source components and development of melting conditions are still a matter of debate.Recent basaltic rocks from Karaburna and Gül?ehir (1228 and 96 Ka, respectively, Dogan, 2011) are considered as a part of the Central Anatolian Volcanic Province, situated at the northernmost end of the Cappadocian Region. These lavas have similar large ion lithophile (LIL) (except Rb) and high field strength (HFS) element abundances, however, Karaburna samples are more enriched in HFS elements, and both of the rocks suites reflect HFS depletions relative to the OIB signature.Karaburna and Gül?ehir basalts have low Nb/La (0.45–0.5; 0.35–0.5), Nb/Th (2.75–4.61; 1.26–2.85) values, respectively, suggesting contributions from crustal sources, whereas Zr/Ba ratios of these samples range between 0.32–0.93 and 0.4–0.88 and imply that these rocks appear to be derived from asthenospheric sources. These incompatible element ratios can be attributed to either different geochemical processes, or are related to melting from different source component(s).The ambient mantle source of the Cappadocian region appears to be consistent with spinel peridotite, but this domain is not solely satisfactory to represent the melting conditions in the light of new elemental data. Values of Tb/Yb(N) and Zn/Fe provide new constraints suggesting the magmas were generated from the asthenosphere. Tb/Yb(N) ratio separates garnet – spinel transition Tb/Yb_(N) (>1.8) and Zn/Fe ratio displays separation between the peridotite-derived (Zn/Fe <12) and pyroxenite-derived (13?20) melts.A melting model based on REE ratios and Zn/Fe, Co/Fe, Tb/Yb(N) values indicates that basaltic rocks were not derived from a single source component (peridotite). Instead, those values suggest substantial melting contributions from a pyroxenite source domain, which has not been discussed as a source component in previous studies. Melts, from both of the source domains, with the result of asthenospheric upwelling linked to the downgoing Aegean and Cyprean slabs, are distinct from the alkaline character frequently observed as the final products of recent volcanic activity in the Cappadocian region and also explains the different trace element variations observed in such a small scale.     

Zircon geochronology and geochemistry to constrain the youngest eruption events and magma evolution of the Mid-Miocene ignimbrite flare-up in the Pannonian Basin,eastern central Europe

A silicic ignimbrite flare-up episode occurred in the Pannonian Basin during the Miocene, coeval with the syn-extensional period in the region. It produced important correlation horizons in the regional stratigraphy; however, they lacked precise and accurate geochronology. Here, we used U–Pb (LA-ICP-MS and ID-TIMS) and (U–Th)/He dating of zircons to determine the eruption ages of the youngest stage of this volcanic activity and constrain the longevity of the magma storage in crustal reservoirs. Reliability of the U–Pb data is supported by (U–Th)/He zircon dating and magnetostratigraphic constraints. We distinguish four eruptive phases from 15.9 ± 0.3 to 14.1 ± 0.3 Ma, each of which possibly includes multiple eruptive events. Among these, at least two large volume eruptions (>10 km³) occurred at 14.8 ± 0.3 Ma (Demjén ignimbrite) and 14.1 ± 0.3 Ma (Harsány ignimbrite). The in situ U–Pb zircon dating shows wide age ranges (up to 700 kyr) in most of the crystal-poor pyroclastic units, containing few to no xenocrysts, which implies efficient recycling of antecrysts. We propose that long-lived silicic magma reservoirs, mostly kept as high-crystallinity mushes, have existed in the Pannonian Basin during the 16–14 Ma period. Small but significant differences in zircon, bulk rock and glass shard composition among units suggest the presence of spatially separated reservoirs, sometimes existing contemporaneously. Our results also better constrain the time frame of the main tectonic events that occurred in the Northern Pannonian Basin: We refined the upper temporal boundary (15 Ma) of the youngest counterclockwise block rotation and the beginning of a new deformation phase, which structurally characterized the onset of the youngest volcanic and sedimentary phase.     

Evaluation of the relative roles of global versus local sedimentary controls on Middle to Late Pleistocene formation of continental margin strata,Canterbury Basin,New Zealand

Determining the relative influence of eustasy versus local sedimentary processes on strata formation is a fundamental challenge in the study of continental margin stratigraphy. In this paper, the relative contribution of these factors on continental margin evolution during the Middle to Late Pleistocene is evaluated using samples from Integrated Ocean Drilling Program Expedition 317. Core‐logging, biostratigraphy and quantitative X‐ray diffraction mineralogy are used to delineate continental shelf sedimentary systems. Major lithological unconformities bound stratigraphic sequences that contain recurring compositional patterns and that resemble other examples of Middle to Upper Pleistocene sequences. However, a preliminary chronology suggests that sequence boundary formation cannot be linked ‘one to one’ with eustatic cycles and therefore these sequences can contain multiple ca 100 ka eustatic cycles. Smaller amplitude, higher frequency transitions in sediment composition are interpreted as stratigraphic sequences driven by more rapid perturbations in the interplay of accommodation and sediment supply; their stratigraphy is variable in time and across the shelf, suggesting a strong influence of local sedimentary forcing in their formation. Changes in sediment composition after the Middle Pleistocene Transition indicate that sediment transfer from onshore sources in the glaciated Southern Alps to the middle‐shelf occurred over a single 100 ka glacio‐eustatic cycle, with an additional 100 ka lag before the mineralogical signal was preserved on the outer‐shelf. This phenomenon is coincident with rapid shelf progradation in this basin, suggesting a causal relation between across‐shelf sediment transport and margin progradation. This is one of very few studies that provide insights at the core scale into the processes driving continental margin evolution during the Middle to Late Pleistocene. This work shows that compositional changes in mud‐dominated successions can lead to a sequence stratigraphic interpretation and the identification of high‐frequency sequences, which may not be possible using a conventional stratigraphic approach.