Hydrogeochemistry and pollution assessment of quaternary–tertiary aquifer in the Liwa area,United Arab Emirates

This study presents the data on the hydrochemical characteristics and isotope chemistry of Liwa aquifer, which could be useful to clarify the hydrochemical facies and hydrogeological regime in the study area. Electric conductivity and total dissolved solid values show that the investigated water is slightly brackish, due to the effect of evaporation and the occurrences of evaporite rocks in the adjacent Sabkhas of Abu Dhabi. Major cations and anions arranged according to their decreasing concentrations are: Na⁺ > Ca⁺² > K⁺ > Mg⁺² and Cl⁻ > HCO₃ ⁻ > SO₄⁻², respectively. As sodium is the dominate cation and chloride is the prevailing anion, hydrochemically the groundwater of Liwa can be classified as Na–Cl rich, predominantly chloridic. Ion concentrations increase towards the northeast and presumably coincide with the lithological sources of ions. Factors affecting the hydrochemistry of the groundwater of the investigated area include the effect of weathering of soil and rocks, evaporation and agricultural activities. Stable isotopes of oxygen and hydrogen show that the shallow aquifers contain a single water type that originated in a distinct climatic regime. This water type deviates from the local meteoric water line, as well as from the Eastern Mediterranean Meteoric Water Line, suggesting potential evaporation of recharged water prior to infiltration. The waters are poor in tritium, and thus can be considered generally as indication for recharge prior to 1952. The degradation of groundwater quality can be attributed to evaporation and agricultural practices in most cases.     

Diagenesis of the Triassic Yanchang Formation Tight Sandstone Reservoir in the Xifeng–Ansai Area of Ordos Basin and its Porosity Evolution

This work aims to reveal the evolution of the porosity in the Triassic Yanchang Formation tight sandstone reservoir of the Xifeng–Ansai area of Ordos Basin. Based on destructive diagenesis(compaction and cementation) and constructive diagenesis(dissolution) of sandstone reservoirs, this study analyzed the diagenesis characteristics of the tight sandstone reservoirs in this area, and discussed the relationship between sandstone diagenesis and porosity evolution in combination with present porosity profile characteristics of sandstone reservoir. The effect simulation principle was employed for the mathematical derivation and simulation of the evolution of porosity in the Yanchang Formation tight sandstone reservoirs. The result shows that compaction always occurs in tight sandstone reservoirs in the Yanchang Formation, and cementation occurs when the burial depth increases to a certain value and remains ever since. Dissolution occurs only at a certain stage of the evolution with window features. In the corresponding present porosity profile, diagenesis is characterized by segmentation. From the shallow to the deep, compaction, compaction, cementation and dissolution, compaction and cementation occur successively. Therefore, the evolution of sandstone porosity can be divided into normal compaction section, acidification and incremental porosity section, and normal compaction section after dissolution. The results show that the evolution of sandstone porosity can be decomposed into porosity reduction model and porosity increase model. The superposition of the two models at the same depth in the three stages or in the same geological time can constitute the evolution simulation of the total porosity in sandstone reservoirs. By simulating the evolution of sandstone reservoir porosity of the eighth member in Xifeng area and the sixth member in Ansai area, it shows that they are similar in the evolution process and trend. The difference is caused by the regional uplift or subsidence and burial depth.     

Semial ophiolite veins of United Arab Emirates―A fluid inclusions study

Calcite and quartz veins in the gabbroic and dunite rocks of the Semial ophiolite (UAE) were selected for fluid inclusion analysis. The inclusions contain both aqueous low-salinity and hydrocarbon-dominated fluids. Mi-crothermometry data indicate that the aqueous fluids contain 0.22 to 1.45 equivalent wt% NaCl and occasionally contain traces of hydrocarbons. Homogenization to liquid occurred between 91 and 152℃. Modeling based on these fluid inclusion observations indicates that the trapping conditions of t...     

Semial ophiolite veins of United Arab Emirates—A fluid inclusions study

Calcite and quartz veins in the gabbroic and dunite rocks of the Semial ophiolite (UAE) were selected for fluid inclusion analysis. The inclusions contain both aqueous low-salinity and hydrocarbon-dominated fluids. Mi-crothermometry data indicate that the aqueous fluids contain 0.22 to 1.45 equivalent wt% NaCl and occasionally contain traces of hydrocarbons. Homogenization to liquid occurred between 91 and 152℃. Modeling based on these fluid inclusion observations indicates that the trapping conditions of the studied rocks were subjected to temperatures of 162 and 172℃, occasional pressures of 610-710 Pa and the sequence percolation of aqueous and hydrocarbon fluids.     

Remnants of late Permian–Middle Triassic ocean islands in northern Tibet: Implications for the late-stage evolution of the Paleo-Tethys Ocean

In this paper we present new data for the Tianquan (TQ) and Dabure (DB) ocean islands in the western segment of the Longmuco–Shuanghu–Lancangjiang suture zone, northern Tibet, including the results of major and trace element analyses, zircon U–Pb dating, and Hf isotope analyses. Our aim was to assess the genesis of these ocean islands and to consider the implications for the tectonic evolution of the region as a whole. Both TQ and DB retain an ocean-island-type double-layered structure comprising a volcanic basement (basalt and andesite) and an oceanic sedimentary cover sequence (conglomerate, limestone, and chert). The basalts and andesites in the TQ and DB are enriched in light rare earth elements and high field strength elements (Nb, Ta, Zr, Hf, and Ti), yielding chondrite-normalized REE patterns and primitive-mantle-normalized trace element patterns that are similar to those of ocean island basalts. Given the small and generally positive ε_Hf(t) values of the TQ andesites (+ 4.25 to + 6.22) and DB andesites (− 0.59 to + 1.97, mostly > 0), we conclude that the basalts were derived from the partial melting of garnet peridotite in the mantle and that the andesites were formed by fractional crystallization of the mafic parent magma derived from the garnet peridotite mantle. The ascending magmas underwent varying degrees of fractional crystallization but were not contaminated by crustal material. These features indicate that both TQ and DB are typical ocean islands that formed in an ocean basin. Geochemical analyses of cherts from TQ and DB show that they contain terrigenous material, indicating the proximity of a continental margin. The andesites of TQ contain zircons that yield two U–Pb ages of 251 Ma. Given that ages of 246, 247, and 254 Ma had been reported previously, we conclude that TQ formed during the late Permian–Early Triassic. The andesites of DB contain zircons that yield U–Pb ages of 242 and 246 Ma. Taking into account the youngest age of 244 Ma from the DB basalt, we conclude that DB formed during the Middle Triassic. These data, combined with the geological history of the region, indicate that the development of the Longmuco–Shuanghu–Lancangjiang Paleo-Tethys Ocean continued after the early Permian and that the closure of this ocean was diachronous from east to west. The eastern segment of the ocean closed during the Early Triassic; however, the western segment remained at least partially open until the Middle Triassic, although the ocean was relatively small at this time. The ocean finally closed in the Late Triassic.     

Structural Connections between the Urals and Western Siberia: A Common Stage of Formation at the Permian–Triassic Boundary

Doklady Earth Sciences - The 40Ar–39Ar dating of mica from schists and blastomylonites, sampled within the limits of a fault that separates the Eastern zone of the Middle Urals, sinking...     

Application of a 3D photorealistic model for the geological analysis of the Permian carbonates (Khuff Formation) in Saudi Arabia

Three dimensional (3D) photorealistic models of geological outcrops have the potential to enhance the teaching of earth sciences by providing scale models in a virtual reality environment. These models can be run on low-cost desktop computers. Photorealistic models for geological outcrops are a digital illustration of outcrop photographs with either a point cloud representation or Triangular Irregular Network (TIN) mesh of the outcrop surface. The level of detail for these models is dependent on the target resolutions (physical and optical) that were used during data acquisition. In addition, the technique in which the data is rendered as a digital model affects the level of detail that can be observed by the geologists. A colored point cloud representation is suitable for large-scale features, but fine details are lost when the geologist zooms in to view the model close up. In contrast, a photorealistic model that is constructed from photographs draped onto a triangle mesh surface derived from Light Detection and Ranging (LiDAR) point clouds provides a level of detail that is restricted only by the resolution of the photographs.     

Facies analysis of the Semanggol Formation,South Kedah,Malaysia: A possible Permian–Triassic boundary section

Although the Permian–Triassic Semanggol Formation is widely distributed in northwestern Peninsula Malaysia and is made of various lithofacies, its sedimentology and possible relation with the Permian–Triassic boundary (PTB) were not considered before. In this study, detailed facies analysis was conducted for two sections of the Semanggol Formation at the Bukit Kukus and Baling areas, South Kedah to clarify its sedimentology and relation to the PTB. Four facies from the Permian part of the Semanggol Formation that were identified at the Bukit Kukus section include laminated black mudstone, interbedded mudstone and sandstone, volcanogenic sediments, and bedded chert. In Baling area, the Triassic part of the formation is classified into three members. The lower member comprises of claystone and bedded chert facies, while the middle member is composed of sandstone and claystone interbeds (rhythmite). On the other hand, the upper member is grouped into two main units. The lower unit is mainly claystone and includes two facies: the varve-like laminated silt and clay and massive black claystone. The upper unit is composed of various sandstone lithofacies ranging from hummocky cross stratified (HCS) sandstone to thinly laminated sandstone to burrowed sandstone facies. The HCS sandstones occur as two units of fine-grained poorly sorted sandstone with clay lenses as flaser structure and are separated by a hard iron crust. They also show coarse grains of lag deposits at their bases. The laminated black mudstone at the lowermost part of the Semanggol Formation represents a reducing and quite conditions, which is most probably below the fairweather wave base in offshore environment that changed upwards into a fining upward sequence of tide environment. Abundance of chert beds in the volcanogenic sediments suggests the deposition of tuffs and volcanic ashes in deep marine setting which continues to form the Permian pelagic bedded chert and claystone. The bedded chert in the lower member of the Triassic section suggests its formation in deep marine conditions. The rhythmic sandstone and claystone interbeds of the middle member are suggestive for its formation as a distal fan of a turbidite sequence. Lithology and primary sedimentary structure of the upper member suggest its deposition in environments range from deep marine represented by the varve-like laminated silt and clay to subtidal environment corresponds to the massive black claystone to coastal environment represented by the hummocky sandstone units and reaches the maximum regression at the hiatus surface. Another cycle of transgression can be indicated from the second hummocky unit with transgressive lag deposits that develops to relatively deeper conditions as indicated from the formation of relatively thick laminated sandstone and bioturbated massive sandstone facies that represent tidal and subtidal environment, respectively. Late Permian lithological variation from the radiolarian chert into early Triassic claystone probably resulted from a decrease in productivity of radiolarians and might represent a PTB in the Semanggol Formation. Volcanogenic sediments in the studied section can be used as an evidence for volcanic activities at the end of the Permian, which is probably connected to the nearby volcanic ash layers in the eastern China, the ultimate cause of the PTB in this area. Black mudstone in the Permian part of the studied section may be interrelated to the Latest Permian Anoxia that started to build in the deep ocean well before the event on shallow shelves.     

Tectono–sedimentary Evolution of the Late Triassic Xujiahe Formation in the Sichuan Basin

The early stage of Sichuan Basin formation was controlled by the convergence of three major Chinese continental blocks during the Indosinian orogeny that include South China,North China,and Qiangtang blocks.Although the Late Triassic Xujiahe Formation is assumed to represent the commencement of continental deposition in the Sichuan Basin,little research is available on the details of this particular stratum.Sequence stratigraphic analysis reveals that the Xujiahe Formation comprises four third-order depositional sequences.Moreover,two tectono-sedimentary evolution stages,deposition and denudation,have been identified.Typical wedge-shaped geometry revealed in a cross section of the southern Sichuan Basin normal to the Longmen Shan fold-thrust belt is displayed for the entire Xujiahe Formation.The depositional extent did not cover the Luzhou paleohigh during the LST1 to LST2 （LST,TST and HST mean Iowstand,transgressive and highstand systems tracts,1,2,3 and 4 represent depositional sequence 1,2,3 and 4）,deltaic and fluvial systems fed sediments from the Longmen Shan belt,Luzhou paleohigh,Hannan dome,and Daba Shan paleohigh into a foreland basin with a centrally located lake.The forebulge of the western Sichuan foreland basin was located southeast of the Luzhou paleohigh after LST2.According to the principle of nonmarine sequence stratigraphy and the lithology of the Xujiahe Formation,four thrusting events in the Longmen Shan fold-thrust belt were distinguished,corresponding to the basal boundaries of sequences 1,2,3,and 4.The northern Sichuan Basin was tilted after the deposition of sequence 3,inducing intensive erosion of sequences 3 and 4,and formation of wedge-shaped deposition geometry in sequence 4 from south to north.The tilting probably resulted from small-scale subduction and exhumation of the western South China block during the South and North China block collision.     

Deposition and deformation of fluvial–lacustrine sediments of the Upper Triassic–Lower Jurassic Whitmore Point Member,Moenave Formation,northern Arizona

The stratigraphic section of the Upper Triassic–Lower Jurassic Whitmore Point Member of the Moenave Formation at Potter Canyon, Arizona, comprises c. 26 m of gray to black shales and red mudstones interbedded with mainly sheet-like siltstones and sandstones. These strata represent deposition from suspension and sheetflow processes in shallow, perennial meromictic to ephemeral lakes, and on dry mudflats of the terminal floodout of the northward-flowing Moenave stream system. The lakes were small, as indicated by the lack of shoreline features and limited evidence for deltas. Changes in base level, likely forced by climate change, drove the variations between mudflat and perennial lacustrine conditions. Lenticular sandstones that occur across the outcrop face in the same stratigraphic interval in the lower part of the sequence represent the bedload fill of channels incised into a coarsening-upward lacustrine sequence following a fall in base level. These sandstones are distinctive for the common presence of over-steepened bedding, dewatering structures, and less commonly, folding. Deformation of these sandstones is interpreted as aseismic due to the lack of features typically associated with seismicity, such as fault-graded bedding, diapirs, brecciated fabrics and clastic dikes. Rapid deposition of the sands on a fluid-rich substrate produced a reverse density gradient that destabilized, and potentially fluidized the underlying, finer-grained sediments. This destabilization allowed synsedimentary subsidence of most of the channel sands, accompanied by longitudinal rotation and/or ductile deformation of the sand bodies.     

Teaching GIS in the Gulf Co-operation Council Universities – With a case study of the geography department, University of the United Arab Emirates

Within universities there has developed a clear theoretical convergence between Geographical Information Systems (GIS) and geography (Antenuccl, 1991). Studies have revealed that one of the qualified departments to teach GIS within universities is the geography department. This study focuses on: the importance of establishing GIS as a major curriculum element within universities. In geography departments, economic geography students require a strong statistical/mathematical background to allow them to work with major databases. They should know how to design a specific database for economic activities, such as agriculture and manufacturing, and tertiary industry and how to relate this database to a map, so that changes can be monitored more accurately. In any aspect of geography spatial location is a key factor and GIS allows spatial patterns to be interpreted with great facility. Therefore it is important that students have a good knowledge not only of computers and related software on economic geography, but also on GIS systems (Burrough, 1993). The work of geography students from the United Arab Emirates (UAE) and other Gulf Co-operation Council (GCC) geography departments is examined to evaluate the importance of training in GIS technology. This paper evaluates the effects of implementing GIS as a tool in teaching economic geography. At present there are 15 geography departments in the GCC which offer economic geography. Of those 15 departments, only 3 provide GIS courses within their curriculum, and 4 have basic equipment, although 6 additional departments are to introduce GIS in the near future. This revised version was published online in July 2006 with corrections to the Cover Date.     

Depositional environment and provenance of the upper Permian–Lower Triassic Tianquanshan Formation,northern Tibet: implications for the Palaeozoic evolution of the Southern Qiangtang,Lhasa, and Himalayan terranes in the Tibetan Plateau

Abstract

This article reports the depositional environment and provenance for the Tianquanshan Formation in the Longmuco–Shuanghu–Lancangjiang suture zone, and uses these to better understand the tectonic evolution of this region. Zircons in the andesite of the Tianquanshan Formation yielded concordia ages of 246, 247, and 254 Ma, indicating that the Tianquanshan Formation formed during the late Permian–Early Triassic. The Tianquanshan Formation consists of flysch and ocean island rock assemblages, indicating that the Longmuco–Shuanghu–Lancangjiang Palaeo-Tethys Ocean continued to exist as a mature ocean in the late Permian–Early Triassic. The detrital zircons in the greywackes of the Tianquanshan Formation yielded peak ages of 470–620, 710–830, 910–1080, 1450–1660, and 2400–2650 Ma, indicating the provenance of the Tianquanshan Formation was either Indian Gondwana or terranes that have an affinity with Indian Gondwana in the Tibetan Plateau (i.e. the Southern Qiangtang, Lhasa, and Himalayan terranes). The Ordovician quartzites, Carboniferous sandstones, Carboniferous–Permian diamictites, and the Upper Permian–Lower Triassic greywackes in the Southern Qiangtang, Lhasa, and Himalayan terranes all contain detrital zircons with youngest ages of ca. 470 Ma, indicating their source areas have been in a stable tectonic environment since the Ordovician, and this inference is supported by the continuous deposition in a littoral–neritic passive margin in these regions from the Ordovician to the lower Permian. Combining the present results with regional geological data, we infer that the Southern Qiangtang, Lhasa, and Himalayan terranes were all in a stable passive continental margin along the northern part of Indian Gondwana during the long period from the Ordovician to the early Permian. At early Permian, because of the opening of the Neo-Tethys Ocean, the tectonic framework of this region underwent a marked change to a rifting and active environment.     

Palynology of Triassic–Jurassic boundary sections in northern Switzerland

A first palynostratigraphic scheme of Upper Triassic deposits in northern Switzerland was established based on spore-pollen associations and dinoflagellate cyst records from the upper part of the Upper Triassic Klettgau Formation and the lower part of the Lower Jurassic Staffelegg Formation. Drill cores from the Adlerberg region (Basel Tabular Jura) and from Weiach (northern part of Canton Zurich) as well as from an outcrop at the Chilchzimmersattel (Basel Folded Jura) were studied and five informal palynological associations are distinguished. These palynological associations correlate with palynological association of the Central European Epicontinental Basin and the Tethyan realm and provide a stratigraphic framework for the uppermost Triassic sediments in northern Switzerland. Throughout the uppermost Triassic to Jurassic palynological succession a remarkable prominence of Classopollis spp. is observed. Besides Classopollis spp. the three Rhaetian palynological associations A to C from the Upper Triassic Belchen Member include typical Rhaetian spore-pollen and dinoflagellate taxa (e.g., Rhaetipollis germanicus, Geopollis zwolinskae, Rhaetogonyaulax rhaetica, and Dapcodinium priscum). Association B differs from association A in a higher relative abundance of the sporomorph taxa Perinopollenites spp. and the consistent occurrence of Granuloperculatipollis rudis and Ricciisporites tuberculatus. Spore diversity is highest in the late Rhaetian palynological association C and includes Polypodiisporites polymicroforatus. A Rhaetian age for the Belchen Member is confirmed by palynological associations A–C, but there is no record of the latest Rhaetian and the earliest Jurassic. In contrast to the Rhaetian palynological associations the Early Jurassic associations W and D include Pinuspollenites spp., Trachysporites fuscus (in association W), and Ischyosporites variegatus. In the view of the end-Triassic mass extinction and contemporaneous environmental changes the described palynofloral succession represents the pre-extinction phase (associations A and B) including a distinct transgression, the extinction phase (association C) associated with a regression, and the post-extinction phase (association W).     

Formation of the Huoqiu Banded Iron Formation (BIF), Western Anhui Province

Please refer to the attachment(s) for more details.     

Re–Os and U–Pb geochronology of the Shazigou Mo polymetallic ore field,Inner Mongolia: Implications for Permian–Triassic mineralization at the northern margin of the North China Craton

The recently discovered polymetallic Shazigou Mo–W–Pb–Zn ore field is located at the northern margin of the North China Craton. This integrated metallogenic system is comprised of quartz vein mineralization in three deposits: Shazigou Mo–W, Jindouzishan Pb–Zn and Mantougou Pb–Zn. The total reserves are estimated to be 50 kt Mo, 626 t WO₃, 244 kt Pb and 150 kt Zn. Molybdenite Re–Os dating of five quartz vein-type ores yielded a mean model age of 243.8 ± 1.6 Ma (MSWD = 0.81) and hydrothermal zircons yielded a concordant U–Pb age of 245 ± 2.6 Ma (MSWD = 0.65). These results suggest that the mineralization was formed in the early Triassic and could be related to Paleo-Asian Ocean subduction. Microthermometry and quartz fluid inclusion compositions indicate that fluids related to the Mo–W mineralization were mainly derived from magmatic sources and precipitated under relatively high temperature (280–340 °C) and salinity conditions (6–9 wt% NaCl equiv.), whereas subsequent Pb–Zn mineralization-related fluids may have been modified by metamorphic and meteoric waters. The discovery of the Shazigou ore field suggests conditions may be favourable for more extensive mineralization in the western Xilamulun Mo metallogenic belt at the northern margin of the North China Craton.     

Origin of two contrasting latest Permian–Triassic volcanic rock suites in the northern North China Craton: implications for early Mesozoic lithosphere thinning

New geological, geochronological, and geochemical results on volcanic rocks and cobbles from early Mesozoic sedimentary rocks identify two contrasting latest Permian–Triassic volcanic rock suites in the northern North China Craton (NCC). The early rock suite erupted during the latest Permian–Early Triassic at ca. 255–245 Ma and was probably widely distributed in the northern NCC prior to the Early Jurassic. It comprises rhyolitic welded tuff, rhyolite, and tuffaceous sandstone and is characterized by high contents of SiO₂ and K₂O, moderate initial ⁸⁷Sr/⁸⁶Sr, low negative ε_Nd(t) and ε_Hf(t) values, and old Nd-Hf isotopic model ages. It was likely produced by fractional crystallization of lower crustal-derived magmas due to underplating by lithospheric mantle-derived magmas near the crust–mantle boundary in syncollisional to post-collisional/post-orogenic tectonic settings. The late rock suite, erupted during the Middle–Late Triassic at ca. 238–228 Ma, displays adakitic geochemical signatures and consists of intermediate volcanic rocks such as andesite, trachyandesite, and autoclastic trachyandesite breccia, with minor felsic rocks. This suite is characterized by high Al₂O₃, MgO, Sr, Ba, Cr, V, and Ni concentrations; high Mg# values; low Y and Yb concentrations and high Sr/Y ratios; low initial ⁸⁷Sr/⁸⁶Sr; high negative ε_Nd(t) and ε_Hf(t) values; and young Nd-Hf isotopic model ages. The younger suite was generated by mixing of magmas derived from melting of upwelling asthenosphere, with melts of ancient lower crust induced by underplating of basaltic magmas in an intraplate extensional setting. Strong upwelling of asthenospheric mantle and significant involvement of the asthenospheric mantle materials indicate that the lithospheric mantle beneath the northern NCC was partially delaminated during Middle–Late Triassic time, representing the initial destruction and lithospheric thinning of the northern NCC. Lithospheric thinning and delamination are likely the most important reasons for the Triassic tectonic transition and change of magmatism and deformation patterns in the northern NCC.     

Triassic–Jurassic granites on the Lord Howe Rise,northern Zealandia

We present U–Pb zircon ages from a phosphate-cemented pebbly sandstone dredged from the central Lord Howe Rise and a 97 Ma rhyolite drilled on the southern Lord Howe Rise. Four granitoid pebbles from the sandstone give U–Pb ages in the range 216–183 Ma. Most detrital zircons in the bulk sandstone are also Late Triassic–Early Jurassic, but subordinate populations of Late Cretaceous and Precambrian zircons are present. The pebbly sandstone's highly restricted Late Triassic–Early Jurassic zircon population indicates the nearby occurrence of underlying basement plutons that are the same age as parts of the I-type Darran Suite, Median Batholith of New Zealand and supports a continuation of the Early Mesozoic magmatic arc northwest from New Zealand. Zircon cores from the southern Lord Howe Rise rhyolite do not yield ages older than 97 Ma and thus provide no information about older basement.     

The Apparent Polar Wander Path for South America during the Permian–Triassic

Many of the controversies that arise in global reconstructions for Permian–Triassic time could be resolved by taking into account the large latitudinal and counter-clockwise movement of Gondwana during that interval of time. The proper trace of the apparent polar wander curve should differentiate one position for the Early Permian, another position for the Late Permian and yet another for the Triassic. By doing so and comparing the Apparent Polar Wander Paths (APWP) of South America and Africa it is easy to see that both curves have the same shape, therefore it is possible to arrive at a good fit between them, which previous analyses were unable to achieve. This new proposed Permian–Triassic track of the APWP reveals a hook not hitherto recognized that should be accounted for in global reconstructions.