Trace metals in surface seawaters and sediments from various habitats of the Red Sea coast of Yemen

The purpose of this study was to determine and assess the concentrations of trace metals in surface seawaters and sediments from different coastal habitats of the Red Sea coast of Yemen. Surface seawater and sediment samples were collected, treated and analyzed for cadmium, cobalt, manganese, chromium, lead, iron, nickel, copper, zinc and vanadium by the atomic absorption spectrometric analysis. The concentrations were high for cadmium, cobalt and lead and low or consistent with the natural background concentrations for the rest of the metals. However, the coastal habitats of the Red Sea coast of Yemen are still considered unpolluted, it is concluded that the cadmium cobalt and lead levels in surface seawaters are high and could have negative effects on marine life of the sites. Further studies are needed to characterize the sources fate, biogeochemical processes and impacts of these trace metals on coastal habitats and marine life of the region.     

Review of the tectonics of the Levant Rift system: the structural significance of oblique continental breakup

The Levant Rift system is an elongated series of structural basins that extends for more than 1000 km from the northern Red Sea to southern Anatolia. The system consists of three major segments, the Jordan Rift in the south, El Gharb–Kara-Su Rift in the north, and the Lebanese Fault splay in between. The rifted parts of this structural system are accompanied by intensively uplifted margins that mirror-image the basinal pattern, namely, the deeper the basin—the higher its margins, and vice versa. Uplifts also occur along the fault splay section. The Jordan Rift comprises axial basins that diminish in size from the south northwards, and are separated from each other by shallow threshold zones along the axis of the rift, where the margins are also subdued. The Lebanese Fault splay consists of five faults that emerge from the northern edge of the Jordan Rift and trend like a fan between the north and the northeast. One of these faults connects the Jordan and El Gharb–Kara-Su rifts. The Levant Rift and its uplifted margins started to develop in the middle-late Miocene, and most of the structural development occurred in the Plio-Pleistocene.The Levant Rift system is characterized by its oblique displacement, and evidence for both dip-slip and strike-slip displacement was measured on its faults. Earthquakes also indicate that same mixed pattern, some of them show strike-slip offset, and others normal. It is generally conceded that the amount of normal offset along the boundary faults of the Rift system reaches 8–10 km, but the lateral displacement is disputed, and offsets ranging from 11 to 107 km were suggested. Assessment of the available data led us to suggest that the sinistral offset along the Levant Rift system is approximately 10–20 km. The similarity between the vertical and the lateral displacements, the basin and threshold structural pattern of the Rift, model experiments in oblique rifting, as well as the significant tectonic resemblance to the Red Sea and the East African rifts, indicate that the Levant Rift is the product of continental breakup, and it is probably an emerging oceanic spreading center.     

Paleomagnetic and geochronological constraints on the post-collisional northward convergence of the southwest Tian Shan, NW China

A combined paleomagnetic and geochronological study is reported of Paleogene basalt lavas and an intercalated red bed succession, comprising a minimum of 14 basalt flows and 10 red bed horizons in the Tuoyun Basin of the southwest Tian Shan Range, China. Two basalt matrix samples yield ⁴⁰Ar / ³⁹Ar isochron ages of 58.5 ± 1.3 Ma (2σ, MSWD = 0.9) and 60.4 ± 1.3 Ma (2σ, MSWD = 1.7). These compare well with a previously published K–Ar dilution age of 61.7 ± 2.3 Ma for comparable Paleogene basalts and confirm that the younger pulse of magmatism in this basin is represented by both intrusive and extrusive activity. Demagnetization and component analysis identify a stable characteristic remanence (ChRM) with predominantly reversed polarity following removal of secondary remanence by peak demagnetization steps below 250–350 °C or 5 mT. Rock magnetic analysis identifies pseudo-single domain magnetite or titanomagnetite as carriers. The stable ChRM passes a fold test; it was probably acquired at the time of lava emplacement. Results from the bulk of the collection imply that paleomagnetic data from the upper and lower ( 115 Ma) basalt series in the Tuoyun Basin are not distinguishable at the 95% significance level and indicate that this tectonic domain remained essentially stationary with respect to the Earth's spin axis for 50 Ma prior to onset of the India/Asia collision in early Eocene times. It is therefore probable that no paleomagnetically detectable crustal shortening occurred in the southwest Tian Shan prior to collision. Paleomagnetic data sets from the Tuoyun Basin also show that little or no paleolatitude difference is present between the Tian Shan and the reference latitude of Eurasia at 60 Ma. This supports previous evidence suggesting that central Asian blocks in the vicinity of the Tian Shan are unlikely to have experienced appreciable northward convergence relative to Eurasia since onset of the India/Asia collision and initiation of the Himalaya.     

Large-Scale Dextral Strike-Slip Movement and Associated Tectonic Deformation Along the Red-River Fault Zone

INTRODUCTION TheRedRiverfaultinsouthwestChina,aboundaryfaultbetweentheIndochinaplateandthe Yangtzeplate,haslongbeenatopicofgeneralinterest.Manystudieshavebeendoneonthegenesis,evolutionandtectonicchangesinthehistoryoftheAilaoshan RedRivertectoniczoneinterm…     

中甸晚三叠世图姆沟组岩石化学与构造环境

本文对中甸东部晚三叠世图姆沟组深水浊积岩和弧火山岩、微量和稀土元素进行研究,投点多落入再旋回造山带物源区;微量和稀土元素与图解中多接近大陆岛弧区;常量元素分析与相关图解接近活动大陆边缘和大陆岛弧环境,与火山岩的大地构造环境具有相同的结论。图姆沟组为甘孜—理塘洋盆向西俯冲消减,中甸褶皱带东缘由被动大陆边缘转化为活动大陆边缘过程中形成的岛弧火山—沉积岩系。     

Salt and ice crystallisation in porous sandstones

Salt and ice crystallisation in the pore spaces causes major physical damage to natural building stones. The damaging effect of these processes can be traced back to physically induced stress inside of the rock while crystallizing. The increasing scientific research done during the past century has shown that there are numerous parameters that have an influence on the weathering resulting from these processes. However, the working mechanisms of the stress development within the rock and its material dependency are still subject to discussion. This article gives an overview of salt and ice weathering. Additionally, laboratory results of various sandstones examined are presented. Salt crystallisation tests and freeze/thaw tests were done to obtain information about how crystallisation weathering depends on material characteristics such as pore space, water transportation, and mechanical features. Simultaneous measuring of the length alternating during the salt and ice crystallisation has revealed detailed information on the development of crystal in the pore spaces as well as the development of stress. These findings can help to understand the damaging mechanisms.     

Utilization of red mud as a stabilization material for the preparation of clay liners

Red mud is a waste material generated by the Bayer Process widely used to produce alumina from bauxite throughout the world. Approximately, 35% to 40% per ton of bauxite treated using the Bayer Process ends up as red mud waste. Because of storing issues, the waste negatively affects the environment. To solve this problem, it is essential to investigate different uses for red mud waste. The potential use of red mud for the preparation of stabilization material is presented in this study. This study examines the effects of red mud on the unconfined compressive strength, hydraulic conductivity, and swelling percentage of compacted clay liners as a hydraulic barrier. The test results show that compacted clay samples containing red mud and cement–red mud additives have a high compressive strength and decreased the hydraulic conductivity and swelling percentage as compared to natural clay samples. Consequently, it is concluded that red mud and cement–red mud materials can be successfully used for the stabilization of clay liners in geotechnical applications.     

Distribution of diagenetic alterations in fluvial and paralic deposits within sequence stratigraphic framework: Evidence from the Petrohan Terrigenous Group and the Svidol Formation, Lower Triassic, NW Bulgaria

Elucidation of diagenetic alterations in the Petrohan Terrigenous Group (fluvial; highstand systems tract HST) sandstones and Svidol Formation (tide-dominated deltaic and tidal flat, transgressive systems tract TST and highstand systems tract HST, respectively) sandstones and calcarenite, Lower Triassic, NW Bulgaria was constrained within a sequence stratigraphic framework. Eogenetic alterations in the fluvial HST sandstones include (i) formation of grain-coating infiltrated clays as a result of percolation of mud-rich surface waters into underlying coarse-grained and permeable channel-fills and crevasse splay sandstones; (ii) formation of pseudomatrix by mechanical compaction of mud intraclasts that were incorporated into the coarse-grained channel sandstones during their lateral avulsion; and (iii) cementation by calcite (δ¹⁸O_VPDB = − 6.5‰ to − 3‰; δ¹³C_VPDB = − 5.1‰ to + 0.6‰) and dolomite (δ¹⁸O_VPDB = − 6.1‰ to − 0.3‰; δ¹³C_VPDB = − 7.2‰ to − 5.8‰) in the crevasse splay and floodplain sediments. Mesogenetic alterations that are encountered in the fluvial HST sandstones include (i) illitization of grain-coating clays, mud intraclasts, and mica, possibly because of simultaneous albitization of feldspars; (ii) cementation by calcite (δ¹⁸O_VPDB = − 14.5‰ to − 8.4‰; δ¹³C_VPDB = − 7.7‰ to + 0.6‰) and dolomite (δ¹⁸O_VPDB = − 15.8‰ to − 5‰; δ¹³C_VPDB = − 7.9‰ to + 1.5‰); and (iii) limited amounts of quartz overgrowths in the channel sandstones owing to occurrence of thick grain-coating clays.

Conversely, the tide-dominated deltaic TST sandstones and the tidal flat HST calcarenite were pervasively cemented by calcite (δ¹⁸O_VPDB = − 6.6‰ to − 3.1‰; δ¹³C_VPDB = − 5.1‰ to + 0.6‰) and siderite (δ¹⁸O_VPDB = − 7.2‰ to − 5.7‰; δ¹³C_VPDB = + 0.3‰ to + 0.9‰) particularly below marine and maximum flooding surfaces, due to the presence of abundant bioclasts and prolonged residence time of the sediments under certain geochemical conditions along these surfaces. The remaining open pores were cemented during mesodiagenesis by calcite (δ¹⁸O_VPDB = − 6.6‰ to − 3.1‰ and δ¹³C_VPDB = − 5.1‰ to + 0.6‰) and dolomite (δ¹⁸O_VPDB = − 6.6‰ to − 3.1‰ and δ¹³C_VPDB = − 5.1‰ to + 0.6‰).

This study shows that constructing a conceptual model for the distribution of diagenetic alterations is possible by integration of diagenesis with sequence stratigraphy. The model shows that tide-dominated deltaic TST sandstones and tidal flat HST calcarenite were pervasively cemented by carbonates during near-surface eodiagenesis, owing to the presence of abundant bioclasts. Conversely, fluvial LST sandstones remained poorly cemented during near-surface eodiagenesis due to the lack of bioclasts, but were cemented by mesogenetic calcite, dolomite and quartz overgrowths instead.     

Oligocene–Miocene formation of the Haifa basin: Qishon–Sirhan rifting coeval with the Red Sea–Suez rift system

During mid-Oligocene to early-Miocene times the northeastern Afro-Arabian plate underwent changes, from continental breakup along the Red Sea in the south, to continental collision with Eurasia in the north and formation of the N–S trending Dead Sea fault plate boundary. Concurrent uplift and erosion of the entire Levant area led to an incomplete sedimentary record, obscuring reconstructions of the transition between the two tectonic regimes. New well data, obtained on the continental shelf of the central Levant margin (Qishon Yam 1), revealed a uniquely undisturbed sedimentary sequence which covers this time period. Evaporitic facies found in this well have only one comparable location in the entire eastern Mediterranean area (onland and offshore) over the same time frame — the Red Sea–Suez rift system. Analysis of 4150 km of multi and single-channel seismic profiles, offshore central Levant, shows that the sequence was deposited in a narrow basin, restricted to the continental shelf. This basin (the Haifa Basin) evolved as a half graben along the NW trending Carmel fault, which at present is one of the main branches of the Dead Sea fault. Re-evaluation of geological data onland, in view of the new findings offshore, indicates that the Haifa basin is the northwestern-most of a larger series of basins, comprising a failed rift along the Qishon–Sirhan NW–SE trend. This failed rift evolved spatially parallel to the Red Sea–Suez rift system, and at the same time frame. The Carmel fault would therefore seem to be related to processes occurring several million years earlier than previously thought, before the formation of the Dead Sea fault. The development of a series of basins in conjunction with a young spreading center is a known phenomenon in other regions worldwide; however this is the only known example from across the Arabian plate.     

粤西地区红土光谱特性研究

土壤中水分、有机质和氧化铁的含量对其光谱特征有很大影响。本文对粤西红土的有机质光谱指标、水分、氧化铁含量与 野外光谱特征进行分析。研究表明，在短波红外波段，水分含量与野外红土反射光谱关系最密切； 在近红外波段，氧化铁含量与 野外红土反射光谱关系最密切； 在可见光波段，有机质对野外红土光谱影响最大。