Zircon U-Pb Geochronology and Geochemical Characteristics of the Volcanic Host Rocks from the Tongyu VHMS Copper Deposit in the Western North Qinling Orogen and Their Geological Significance

Precise in situ zircon U-Pb dating and Lu–Hf isotopic measurement using an LA-ICP-MS system, whole-rock major and trace element geochemistry and Sr–Nd isotope geochemistry were conducted on the volcanic host rocks of the Tongyu copper deposit on the basis of further understanding of its geological characteristics. Three zircon samples from the volcanic host rocks yielded 206Pb/238 U weighted average ages ranging from 436±4 Ma to 440±5 Ma, which are statistically indistinguishable and coeval with the ca. 440 Ma northward subduction event of the Paleo-Qinling oceanic slab. The volcanic host rocks were products of magmatic differentiation that evolved from basalt to andesite to dacite to rhyolite, forming an integrated tholeiitic island arc volcanic rock suite. The primitive mantle-normalized trace element patterns for most samples show characteristics of island arc volcanic rocks, such as relative enrichment of LILE(e.g. Th, U, Pb and La) and depletion of HFSE(e.g. Nb, Ta, Ti, Zr and Hf). Discrimination diagrams of Ta/Yb vs Th/Yb, Ta vs Th, Yb vs Th/Ta, Ta/Hf vs Th/Hf, Hf/3 vs Th vs Nb/16, La vs La/Nb and Nb vs Nb/Th all suggest that both the volcanic host rocks from the Tongyu copper deposit and the volcanic rocks from the regional Xieyuguan Group were formed in an island arc environment related to subduction of an oceanic slab. Values of ISr(0.703457 to 0.708218) and εNd(t)(-2 to 5.8) indicate that the source materials of volcanic rocks from the Tongyu copper deposit and the Xieyuguan Group originated from the metasomatised mantle wedge with possible crustal material assimilation. Most of the volcanic rock samples show good agreement with the values of typical island arc volcanic rocks in the ISr-εNd(t) diagram. The involvement of crustal-derived material in the magma of the volcanic rocks from the Tongyu copper deposit was also reflected in the zircon εHf(t) values, which range from-3.08 to 10.7, and the existence of inherited ancient xenocrystic zircon cores(2616±39 Ma and 1297±22 Ma). The mineralization of the Tongyu copper deposit shows syn-volcanic characteristics such as layered orebodies interbedded with the volcanic rock strata, thus, the zircon U-Pb age of the volcanic host rocks can approximately represent the mineralization age of the Tongyu copper deposit. Both the Meigou pluton and the volcanic host rocks were formed during the ca. 440 Ma northward subduction of the Paleo-Qinling Ocean when high oxygen fugacity aqueous hydrothermal fluid released by dehydration of the slab and the overlying sediments fluxed into the mantle wedge, triggered partial melting of the mantle wedge, and activated and extracted Cu and other ore-forming elements. The magma and ore-bearing fluid upwelled and erupted, and consequently formed the island arc volcanic rock suite and the Tongyu VHMS-type copper deposit.     

Neo-deterministic seismic hazard assessment in North Africa

North Africa is one of the most earthquake-prone areas of the Mediterranean. Many devastating earthquakes, some of them tsunami-triggering, inflicted heavy loss of life and considerable economic damage to the region. In order to mitigate the destructive impact of the earthquakes, the regional seismic hazard in North Africa is assessed using the neo-deterministic, multi-scenario methodology (NDSHA) based on the computation of synthetic seismograms, using the modal summation technique, at a regular grid of 0.2?×?0.2°. This is the first study aimed at producing NDSHA maps of North Africa including five countries: Morocco, Algeria, Tunisia, Libya, and Egypt. The key input data for the NDSHA algorithm are earthquake sources, seismotectonic zonation, and structural models. In the preparation of the input data, it has been really important to go beyond the national borders and to adopt a coherent strategy all over the area. Thanks to the collaborative efforts of the teams involved, it has been possible to properly merge the earthquake catalogues available for each country to define with homogeneous criteria the seismogenic zones, the characteristic focal mechanism associated with each of them, and the structural models used to model wave propagation from the sources to the sites. As a result, reliable seismic hazard maps are produced in terms of maximum displacement (D _max), maximum velocity (V _max), and design ground acceleration.     

吉南地区万隆组燧石相微生物化石及其古环境意义

拉伸纪作为承接中元古代蓝菌时代以及成冰纪生物锐减的关键地质历史时期,是探索早期生命与环境演化最重要的时期之一。吉林南部地区地处华北板块东北缘,拉伸系发育完整、出露全,在燧石条带、燧石结核和泥页岩中富含微生物化石,是开展拉伸纪古生物学、生物地层学和古环境研究的理想地区。本次工作利用岩石切片法在吉林南部二道江地区万隆组顶部燧石中发现微生物化石6属9种,其中丝状蓝菌1属4种Siphonophycus robustum,S.typicum,S.kestron,S.solidum;球状蓝菌3属3种Eoentophysalis belcherensis,Gloeodiniopsis lamellosa,Scissilisphaera bistratosa;分类位置未定2属2种Glenobotrydion majorinum,Globophycus rugosum。这些微体化石的发现为开展万隆组古环境分析及生物地层对比研究提供了新的素材。研究显示,万隆组燧石相微生物组合以发育管鞘藻席(Siphonophycus mat)为主要特征,丝状蓝菌呈横向展布,长可达400μm以上,显示原地或近原地埋藏的特点...     

Hydrogeophysical investigation of groundwater potential in the El Bawiti, Northern Bahariya Oasis, Western Desert, Egypt

The future development of agriculture, industry, and civil activity planned to be in the Western Desert. This strategy need to the groundwater resource. Vertical electrical soundings (VES) and electromagnetic (TEM) measurements conducted in the El Bawiti, northern Bahariya Oasis. The measurements give detailed information about the geometry of the different hydrogeological layers in the aquifer system and depth to them. A total of 22 VES and TEM were carried out within El Bawiti area. Thirty-one sub soil samples were collected from eight sites to determine the chemical characteristics and address the effects of lithogenic source and anthropogenic activity on them. The geoelectrical measurements and borehole information indicate the presence of five geoelectrical units, from top to base; the surface cover, sand and shale, upper aquifer (Nubian sandstone), sand and shale, and lower aquifer (Nubian sandstone). Surface cover was equally distributed in thickness and composed of dry sand, gravel, and clay deposits. The regional resistivity of the upper aquifer increased in the southwestern part and decline in the northern, eastern, southern, and western parts. The decline in the resistivity reflects the high water yields and potentiality, as well as low salinity. The resistivity of the lower aquifer increased due the northwestern part and the southwestern part. The information collected during this research provides valuable data for estimating the fresh- to brackish-water resources and for development of a groundwater management plan. The integrated analyses carried out represent a significant and cost-effective method for delineating the main aquifer in this area. In turn, future well locations can be placed with more confidence than before, in accordance with the evaluation of the potentiality of the groundwater aquifers in the area. The electrical conductivity of the soil ranges from 302 to 8,490 μS/cm, increases in the western and central-northern parts. It is attributed to the location from the salt-affected soils (playa), the relatively lower elevation units (depressions) and the position in landscape in the Oasis. Sodium adsorption ratio ranges from 0.44 to 11 and the exchangeable sodium ratio ranges from 0.11 to 5. The estimated magnesium hazard fluctuated below 50%. The statistical analyses were accomplished in soil chemistry and discussed.     

Mapping the crustal thickness in southwest Japan using Moho-reflected waves

In this work we have tried to detect and collect later phases associated with the Moho discontinuity and use them to study the lateral variations of the crustal thickness in southwest (SW) Japan. We first compute synthetic seismograms for local earthquakes taking into account the focal mechanism solutions estimated from first motion polarity data. Then we compare the synthetics with the observed waveforms to detect the major later phases in seismograms of shallow crustal earthquakes in SW Japan. Taking the advantage of the high quality and great quantity of Hi-net waveform data now available throughout the entire Japan Islands, we have detected 1659 Moho-reflected phases (PmP and SmS) from shallow events in SW Japan. We estimated the crustal thickness in the study area using travel time differences between these later phases and the first P and S arrivals. Our results show that the Moho is deep in Chubu district and becomes shallower along the coastlines of the Japan Sea and the Pacific Ocean. A thinner crust appears in Osaka Bay and Awajii Island where the 1995 Kobe earthquake (M7.2) occurred.     

A new record and a new ichnospecies of Arachnostega from the Middle Miocene of Egypt

The ichnogenus Arachnostega Bertling, 1992 is recorded for the first time from a bioeroded, coral-rich, Middle Miocene limestone bed in the middle Siwa Escarpment Member (Marmarica Formation) at Siwa Oasis, northern Western Desert of Egypt. These burrowing traces are preserved on the surface of a few internal moulds of bivalves and gastropods. Until now, the ichnogenus Arachnostega included a single ichnospecies, A. gastrochaenae Bertling, 1992. In the material studied herein, two ichnospecies are identified, described, illustrated and compared with other, similar traces. One of these is a new ichnospecies of Arachnostega; this is here named A. siwaensis ichnosp. nov. It is distinguished from A. gastrochaenae in the possession of tunnels that usually branch in a V-pattern; intervals of ramification are longest in the main branch and decrease in second- and third-order branches. Arachnostega traces were produced in a warm, low-energy, shallow-marine (<10?m water depth) environment. Polychaetes are the most likely producers of marine Arachnostega, which are commonly occurred in the same studied bed. This new occurrence is significant in extending the known stratigraphical and geographical ranges of Arachnostega into the Middle Miocene of Egypt.     

Hydrochemical characterization and geospatial analysis of groundwater quality in Cap Bon region,northeastern Tunisia

The hydrogeochemical characteristics of shallow groundwater in the Grombalia region, northeastern Tunisia, were investigated to evaluate suitability for irrigation and other uses and to determine the main processes that control its chemical composition. A total of 21 groundwater samples were collected from existing wells in January–February 2015 and were analyzed for the major cations and anions concentrations. Conductivity, pH, T°, O₂ and salinity were also measured. Interrelationships between chemical parameters were determined by using the scatter matrix method. The suitability of groundwater for irrigation and other uses was assessed by determining the sodium adsorption ratio, soluble-sodium percentage, total dissolved solids, total hardness, Kelly’s index and permeability index values of water samples. The spatial distribution of key parameters was assessed using a GIS-based spatial gridding technique. This analysis indicated that the chemical composition of groundwater in the study area is of Cl–SO₄–Na–Ca mixed facies with concentrations of many chemical constituents exceeding known guideline values for irrigation. The salinity of groundwater is controlled by most dominant cation and anion (Na–Cl). A correlation analysis shows that Na⁺ is the dominant cation and that reverse ion exchange is a dominant process that controls the hydrogeochemical evolution of groundwater in the area. Geospatial mapping of hydrochemical parameters and indices analyzed with the USSL and Wilcox diagrams show distinctive areas of irrigation suitability. In contrast, 76.2% of samples fall in the highly doubtful to unsuitable category and indicate that the central and north-eastern parts of the study area are unsuitable for irrigation due to a high salinity and alkalinity.     

Adsorption of Congo red and crystal violet dyes onto cellulose extracted from Egyptian water hyacinth

Natural Hazards - The present investigation has highlighted the utility of floating aquatic Egyptian hyacinth, which is considered as a significant reason for environmental problems in Nile River,...     

SlugIn 1.0: A Free Tool for Automated Slug Test Analysis

The correct characterization of aquifer parameters is essential for water‐supply and water‐quality investigations. Slug tests are widely used for these purposes. While free software is available to interpret slug tests, some codes are not user‐friendly, or do not include a wide range of methods to interpret the results, or do not include automatic, inverse solutions to the test data. The private sector has also generated several good programs to interpret slug test data, but they are not free of charge. The computer program SlugIn 1.0 is available online for free download, and is demonstrated to aid in the analysis of slug tests to estimate hydraulic parameters. The program provides an easy‐to‐use Graphical User Interface. SlugIn 1.0 incorporates automated parameter estimation and facilitates the visualization of several interpretations of the same test. It incorporates solutions for confined and unconfined aquifers, partially penetrating wells, skin effects, shape factor, anisotropy, high hydraulic conductivity formations and the Mace test for large‐diameter wells. It is available in English and Spanish and can be downloaded from the web site of the Geological Survey of Spain. Two field examples are presented to illustrate how the software operates.