Continental ca 1.7 – 1.69 Ga Fe-rich metatholeiites in the Curnamona Province,Australia: a record of melting of a heterogeneous,subduction-modified lithospheric mantle

Mg-rich and Fe-rich metatholeiites intruded the Willyama Supergroup of the southern Australian Curnamona Province in the Late Palaeoproterozoic at ca 1700 Ma and 1685 Ma, respectively. Intrusion of the Fe-rich metatholeiites occurred during a period of punctuated extension in the Willyama basin. Major-element concentrations are variable (SiO₂ 45.4 – 56.5 wt%; Fe₂O₃? 8.5 – 20.7; TiO₂ 0.46 – 2.52 wt%; Mg# 70.5 – 29.1) and, in conjunction with trace-element data, support near-closed-system fractionation of a mantle-derived melt with little or no replenishment. Fractionation produced progressively Fe-rich derivative melts. Crystallising phases were dominated by clinopyroxene and olivine, whereas Fe – (Ti) oxide crystallisation was hindered. Primitive mantle-normalised immobile trace elements are characterised by variable Th, Nb, Sr, P and Ti anomalies. Chondrite-normalised rare-earth element patterns for the most primitive, Mg-rich samples from the western Broken Hill Domain have La_N/Sm_N < 1, whereas the most evolved Fe-rich samples from the Olary Domain have ratios of La_N/Sm_N > 1. Initial εNd values range between – 2.2 and + 2.7 for the majority of the samples, with the isotopic compositions showing no correlation with differentiation or assimilation. The combined geochemical and isotopic data suggest that the southern Curnamona Province metatholeiites were extracted from a depleted mantle in the western Broken Hill Domain, and a variably enriched, heterogeneous subcontinental lithospheric mantle in the Olary Domain. Magmatism most likely occurred in a backarc basin or intracontinental setting. It is speculated that the geochemically enriched mantle component was derived from subduction-related processes, probably related to pre-Willyama basin accretionary processes along the southern and eastern margins of the North Australian Craton.     

Origin of a late Neoproterozoic (605 ± 13 Ma) intrusive carbonate–albitite complex in Southern Sinai, Egypt

New geochemical, isotopic, and geochronological data and interpretations are presented for late Neoproterozoic intrusive carbonates and related rocks of southern Sinai, Egypt (northernmost Arabian–Nubian Shield). The Tarr carbonates are coarsely crystalline and related to explosive emplacement of hypabyssal and volcanic albitite at 605 ± 13 Ma. The carbonates associated with the albitites are divisible into two types: primary dolomitite and secondary breunneritite (Fe-rich magnesite). The dolomitite was clearly intrusive but differs from classic igneous carbonatites, containing much lower abundances of incompatible elements, such as REE, U, Th, Rb, Nb, Y, P, Sr, Zr, Ba, and total alkalies. The breunneritite is a secondary replacement of dolomitite, probably marking the roots of a vigorous hydrothermal system. Albitites show pristine abundances of major and trace elements and were not subjected to a major metamorphic overprint. They are relatively more fractionated, alkaline and related to within-plate A-type magmas, were emplaced in an extensional or non-compressive tectonic regime in the cupola of high-level A-type granite. Tarr albitites may represent residual magma remaining after near-total crystallization of an A-type granite pluton at depth, forcibly emplaced into the roof above the cooling pluton. The intrusive dolomitite exsolved from highly differentiated albitite melt, in the apical regions of a still-buried alkaline “A-type” granite pluton that was rich in CO₂; these volatiles migrated upwards and towards the cooler margins of the magma body. Late NNE-SSW extension allowed a shallow-level cupola to form, into which albitite melts and carbonate fluids migrated, culminating in explosive emplacement of albitite breccia and intrusive carbonate. Isotopic compositions of Tarr dolomitite and albitite indicate these are consanguineous and ultimately of mantle origin. Magmatic volatiles fenitized the wall rock, while submarine hydrothermal activity transformed some of the dolomitite into breunneritite. Recognition of Tarr-type should encourage similar hypabyssal complex intrusions to be sought for in association with A-type granitic plutons elsewhere.     

Optimal Interpolation of Gravity Maps Using a Modified Neural Network

This paper proposes an interpolation method based on a modified Kohonen artificial neural network, and is used to interpolate marine gravity data on a regular grid. This method combines accuracy comparable to that of kriging with a much shorter computing time than kriging. It is particularly efficient when both the size of the grid and the quantity of available data are large. Under some hypotheses similar to those of kriging with a trend, the unbiasedness and optimality of the method can be demonstrated. Comparison with kriging with a trend using marine gravity data shows similar results. Although neural interpolation is slightly less efficient, it is more robust outside of the marine data area.     

Modelling Syntectonic Sedimentation: Combining a Discrete Element Model of Tectonic Deformation and a Process-based Sedimentary Model in 3D

This paper presents a new numerical program able to model syntectonic sedimentation. The new model combines a discrete element model of the tectonic deformation of a sedimentary cover and a process-based model of sedimentation in a single framework. The integration of these two methods allows us to include the simulation of both sedimentation and deformation processes in a single and more effective model. The paper describes briefly the antecedents of the program, Simsafadim-Clastic and a discrete element model, in order to introduce the methodology used to merge both programs to create the new code. To illustrate the operation and application of the program, analysis of the evolution of syntectonic geometries in an extensional environment and also associated with thrust fault propagation is undertaken. Using the new code, much more complex and realistic depositional structures can be simulated together with a more complex analysis of the evolution of the deformation within the sedimentary cover, which is seen to be affected by the presence of the new syntectonic sediments.     

Assessment of flood mitigation through riparian detention in response to a changing climate – a case study

Considering that urban areas may suffer more substantial losses than riparian farmlands during floods, diverting floodwater into riparian areas for temporal detention is expected to mitigate flood damage in downstream urban areas. In this study, an assessment has been conducted to evaluate the effect of flood mitigation through riparian detention in response to a changing climate in the Tou-Chien River basin of Taiwan. An integrated 1D–2D flow model was used to simulate the movement of flood wave in the main stream and the overbank flow inundating into the nearby lowlands. Based on the numerical simulation results, the flooding extents in the basin corresponding to different return periods of flood using existing flood prevention infrastructures were investigated. A detention strategy by lowering the levee along the riparian farmlands was proposed to avoid severe flooding in the densely populated urban areas of the basin. Research findings showed that the proposed detention measure can completely protect the downstream areas from overbank flooding when a flood having 20-yr period occurs, and can effectively alleviate the downstream flooding area from 27.4 to \(7.6\,\hbox {km}^{2}\) for a flood possessing 200-yr period.     

Discrimination of pore fluid and lithology of a well in X Field,Niger Delta,Nigeria

Quantitative rock physics analyses were used to determine the lithology and pore fluid of a reservoir in the Niger Delta. Inaccurate prediction of lithology and pore fluid results in the inaccurate determination of other petrophysical properties and parameters such as porosity, permeability, and net pay. This research is to predict lithology and pore fluid using rock physics analysis. However, reservoir zones were also predicted. Density, compressional wave velocity, and shear wave velocity logs were used as input to calculate elastic parameters such as velocity ratio, Poisson’s ratio, and bulk modulus. The calculated velocity ratio log was used to differentiate between sand and shale. Poisson’s ratio and velocity ratio using Goodway interpretation template were carried out and used to delineate pore fluid content, gas sand, oil sand, and sandstone formation from crossplot analysis.     

The Oeschinensee rock avalanche,Bernese Alps,Switzerland: a co-seismic failure 2300 years ago?

Landslide deposits dam Lake Oeschinen (Oeschinensee), located above Kandersteg, Switzerland. However, past confusion differentiating deposits of multiple landslide events has confounded efforts to quantify the volume, age, and failure dynamics of the Oeschinensee rock avalanche. Here we combine field and remote mapping, topographic reconstruction, cosmogenic surface exposure dating, and numerical runout modeling to quantify salient parameters of the event. Differences in boulder lithology and deposit morphology reveal that the landslide body damming Oeschinensee consists of debris from both an older rock avalanche, possibly Kandertal, as well as the Oeschinensee rock avalanche. We distinguish a source volume for the Oeschinensee event of 37 Mm³, resulting in an estimated deposit volume of 46 Mm³, smaller than previous estimates that included portions of the Kandertal mass. Runout modeling revealed peak and average rock avalanche velocities of 65 and 45 m/s, respectively, and support a single-event failure scenario. ³⁶Cl surface exposure dating of deposited boulders indicates a mean age for the rock avalanche of 2.3 ± 0.2 kyr. This age coincides with the timing of a paleo-seismic event identified from lacustrine sediments in Swiss lakes, suggesting an earthquake trigger. Our results help clarify the hazard and geomorphic effects of rare, large rock avalanches in alpine settings.     

Biomediated Precipitation of Calcium Carbonate in a Slightly Acidic Hot Spring, Yunnan Province

A slightly acidic hot spring named "Female Tower"(t=73.5°C, pH=6.64) is located in the Jifei Geothermal Field, Yunnan Province, southwestern China. The precipitates in the hot spring are composed of large amounts of calcite, aragonite and sulfur. Scanning electron microscopy(SEM) analyses reveal that the microbial mats were formed from various coccoid or rod-shaped filamentous microbes. Transmission electron microscopy(TEM) shows that the intracellular sulfur granules are commonly associated with these microbes. A culture-independent molecular phylogenetic analysis demonstrates that the majority of the bacteria in the spring are sulfur-oxidizing bacteria. In the spring water, H_2S concentration is up to 60 ppm, while SO_4~(2-) concentration is only about 10 ppm. We speculate that H_2S might derive from sulfur-oxidizing bacteria in this hot spring water, leading to the intracellular formation of sulfur granules. Meanwhile, this reaction increased the p H in the micronscale microdomains, which fosters the precipitation of calcium carbonate in the microbial mats. The results of this study indicate that the sulfur-oxidizing bacteria might play an important role in calcium carbonate precipitation in slightly acidic hot spring environments.     

Palaeoproterozoic (1.83 Ga) zircons in a Bajocian (169 Ma) granite within a Middle Jurassic ophiolite (Rubiku,central Albania): a challenge for geodynamic models

Two distinct zircon populations, 1,827 ± 17 and 169 ± 2 Ma in age, have been found in the Rubiku granite dyke in the Middle Jurassic Mirdita ophiolite in central Albania. The old inherited zircons represent a homogeneous population formed during a discrete Palaeoproterozoic, likely magmatic, zircon crystallization event. These older zircons were likely incorporated, in large part, into the granite magma that crystallized broadly at the time of the ophiolite emplacement (around 169 Ma). The limited data available do not allow for the construction of an unequivocal petrogenetic model, though several palaeotectonic scenarios are discussed as possible settings for the granite formation. The models refer to recent findings of old inherited zircons in rocks at recent mid-ocean ridge settings, but also consider likely contributions of crustal materials to primary basic ophiolitic magmas within supra-subduction settings and subsequent accretion/collision circumstances. The presence of old zircons in much younger rocks within ophiolite successions runs counter to geodynamic models of interaction between the oceanic lithosphere and continental crust, but constraining their genesis would require further systematic studies on these old inherited zircons, both in mafic (if present) and in felsic rocks of the ophiolites.     

U-Pb Ages of the Late Early Cretaceous Magmatic Rocks in the Zhalantun Area of Inner Mongolia

A great deal of early-to-mid Early Cretaceous magmatic activities have been recorded in the Zhalantun area of Inner Mongolia,while the late Early to Late Cretaceous magmatic rocks have been barely reported(Guo et al.,2018;Zhang Xiangxin et al.,2017).At present,only a few Late Cretaceous magmatic activities were reported in the Arongqi area,such as volcanic rocks of the Gushanzhen Formation.However,the Gushanzhen Formation lacks accurate isotopic age,and contemporaneous intrusive rocks has not been reported yet.In this work,we collected the volcanic rocks from the Gushanzhen Formation and contemporaneous intrusive rocks in the Zhanlantun and nearby,and aim to figure out the formation ages of volcanic rocks of the Gushanzhen Formation and accompanied intrusive rocks by analyzing zircon U-Pb isotopes(Fig.1).     

PAHs contamination in groundwater from a part of metropolitan city,India: a study based on sampling over a 10-year period

Presence of polycyclic aromatic hydrocarbons (PAHs) in the soil and water is of serious environmental concern as they are carcinogenic in nature. The present study was carried out with an aim to identify the presence of PAHs in groundwater of Chennai, Tamil Nadu, India. This is an industrialised area where petrochemical storage tanks are located. Groundwater sampling was carried out in the years 2001, 2011 and 2012 to understand the variation in PAHs content in this area. Concentration of major ions, pH and EC were measured during the year 2001. Of the 24 groundwater samples collected in the year 2001, most of them were alkaline and 62.5 % were not permissible for drinking based on pH and EC, respectively. Influence of seawater was the major reason for the Na–Cl dominant nature of groundwater. TPH and PAHs analysis of groundwater carried out in 2001 and 2011, and physical examination of groundwater in 2012 indicate the increased level of contamination in the eastern part of the study area. The contamination in the eastern part persists because of the fact that groundwater is flowing towards the east and also due to the presence of petrochemical storage tanks near the coast. Thus this area is affected by PAHs pollution which has endured over the past 50 years. An underground storage tank that was functioning in this area was closed about 50 years ago and leakage of PAHs from this tank was reported in the year 1993. However, the present study indicates the decrease in the area of zone of pollution, possibly due to natural flushing of groundwater zone.     

Reconstructing the event stratigraphy from the complex structural – stratigraphic architecture of an Archaean volcanic – intrusive – sedimentary succession: the Boorara Domain,Eastern Goldfields Superterrane,Western Australia

Two main deformational phases are recognised in the Archaean Boorara Domain of the Kalgoorlie Terrane, Eastern Goldfields Superterrane, Yilgarn Craton, Western Australia, primarily involving south-over-north thrust faulting that repeated and thickened the stratigraphy, followed by east-northeast – west-southwest shortening that resulted in macroscale folding of the greenstone lithologies. The domain preserves mid-greenschist facies metamorphic grade, with an increase to lower amphibolite metamorphic grade towards the north of the region. As a result of the deformation and metamorphism, individual stratigraphic horizons are difficult to trace continuously throughout the entire domain. Volcanological and sedimentological textures and structures, primary lithological contacts, petrography and geochemistry have been used to correlate lithofacies between fault-bounded structural blocks. The correlated stratigraphic sequence for the Boorara Domain comprises quartzo-feldspathic turbidite packages, overlain by high-Mg tholeiitic basalt (lower basalt), coherent and clastic dacite facies, intrusive and extrusive komatiite units, an overlying komatiitic basalt unit (upper basalt), and at the stratigraphic top of the sequence, volcaniclastic quartz-rich turbidites. Reconstruction of the stratigraphy and consideration of emplacement dynamics has allowed reconstruction of the emplacement history and setting of the preserved sequence. This involves a felsic, mafic and ultramafic magmatic system emplaced as high-level intrusions, with localised emergent volcanic centres, into a submarine basin in which active sedimentation was occurring.     

Apatite recrystallisation during prograde metamorphism,Cooma, southeast Australia: implications for using an apatite – graphite association as a biotracer in ancient metasedimentary rocks

The major patterns in the evolution of life during the Phanerozoic are reviewed. Critical transitions in the evolution of life that reflect increases in ecological complexity are the Cambrian radiation; the Ordovician biodiversification and its subsequent diversification and transition into the Modern Marine Fauna following the Permo-Triassic mass extinction; the colonisation of land, and its subsequent diversification; and the biological colonisation of the atmosphere. This increase in ecological diversity and complexity was often accompanied by increases in morphological complexity, arising, in part, from elaboration of the developmental program. However, it was additionally fuelled by increases in diversification and disparity arising also from morphological simplification in some lineages as developmental program became reduced.     

Directional Wavelets and a Wavelet Variogram for Two-Dimensional Data

This paper describes two new approaches that can be used to compute the two-dimensional experimental wavelet variogram. They are based on an extension from earlier work in one dimension. The methods are powerful 2D generalizations of the 1D variogram that use one- and two-dimensional filters to remove different types of trend present in the data and to provide information on the underlying variation simultaneously. In particular, the two-dimensional filtering method is effective in removing polynomial trend with filters having a simple structure. These methods are tested with simulated fields and microrelief data, and generate results similar to those of the ordinary method of moments variogram. Furthermore, from a filtering point of view, the variogram can be viewed in terms of a convolution of the data with a filter, which is computed fast in O(NLogN) number of operations in the frequency domain. We can also generate images of the filtered data corresponding to the nugget effect, sill and range of the variogram. This in turn provides additional tools to analyze the data further.     

Log-Ratio Analysis Is a Limiting Case of Correspondence Analysis

It is common practice in compositional data analysis to perform the log-ratio transformation in order to preserve sub-compositional coherence in the analysis. Correspondence analysis is an alternative approach to analyzing ratio-scale data and is often contrasted with log-ratio analysis. It turns out that if one introduces a power transformation into the correspondence analysis algorithm, then the limit of the power-transformed correspondence analysis, as the power parameter tends to zero, is exactly the log-ratio analysis. Depending on how the power transformation is applied, we can obtain as limiting cases either Aitchison’s unweighted log-ratio analysis or the weighted form called “spectral mapping”. The upshot of this is that one can come as close as one likes to the log-ratio analysis, weighted or unweighted, using correspondence analysis.     

Intra-oceanic production of continental crust in a Th-depleted ca. 3.0 Ga arc complex,western Superior Province,Canada

The English Lake magmatic complex in the western Superior Province of Canada represents a fragment of early (3.0 Ga) continental crust exposed in oblique cross section through tonalitic upper levels and subjacent quartz diorite, diorite and gabbro, which are cut by late gabbro, anorthosite and hornblendite dykes. Massive, foliated and gneissic units of tonalitic to gabbroic composition, crystallized over a 10 to 18 m.y. period, bear common geochemical attributes, including negative Th, U and Nb anomalies, and only slight LREE and LILE enrichment on NMORB-normalized trace-element profiles. Epsilon Nd values (+0.1 to +1.7) and ¹⁸O (+6.7 to +8.0 ) do not co-vary with silica or other crustal contamination indices. High Mg#'s and Ni contents suggest derivation from, or interaction with mantle, and large positive anomalies for Ba, Sr and Pb, as well as high U/Th, suggest metasomatism by hydrous fluids. Trace-element profiles resemble those of primitive intra-oceanic island arc magmas except for the negative Th-U anomaly, which precludes the involvement of either oceanic (sedimentary or basaltic) or continental crust in the petrogenesis of English Lake magmas. In order to account for the unusual geochemical character of the suite, we postulate that water-rich fluids derived from subducted, sea-floor-altered serpentinite provided the flux for melting a depleted mantle wedge. Contemporaneous, proximal high Th/Nb tonalites suggest that the zone of serpentinite subduction occurred within a restricted arc segment possibly due to subduction of either: (a) a seamount chain oriented broadly perpendicular to an arc, or (b) a similarly oriented serpentinite-enclosed oceanic fracture zone or fault.Electronic Supplementary Material Supplementary material is available in the online version of this article at .Editorial responsibility: T.L. Grove     

Geotechnical,Geological, and Hydrologic Characterization of a 52 km Electrical Power Transmission Line Alignment Route in Southeastern Nigeria

A 132 kVA electrical transmission line has been proposed to connect the towns of Eket and Ikot Abasi in the eastern Niger delta in Nigeria. A geotechnical and hydrological study was performed to geotechnically characterize the route alignment and to provide data for design of the foundations for the transmission towers. In this paper, we introduce the study location and its geological, topographical and physiological characteristics, present the hydrological and geotechnical investigations and their results, and make recomendations for the design of the transmission tower foundations. Hydrological inspection of the power line alignment revealed that the route is traversed by numerous tributaries of the Qua-Iboe and Imo Rivers, the two major rivers that control the drainage of the study area. In-situ geotechnical tests consisted of cone penetration tests (CPTs), vane shear tests, test pit sampling (0–2.0 m depth) and lithologic boreholes (20 and 50 m deep). Laboratory tests included grain size analysis, pH determination and Atterberg Limits. Based on the CPT log pattern, no of stratum, and refusal depths, the soils along the transmission alignment were classified into twelve structural domains having common geotechnical properties. Because of the elevated water levels, and the nature of the soils, deep pile foundations were recommended for the towers. Software from the Louisiana Transportation Research Center, was employed to estimate skin friction, end bearing, and ultimate bearing capacities for assumed 225 mm square shaped reinforced concrete pile in each of the different zones of the alignment.     

New U-Pb Geochronological Constraints on Formation and Evolution of the Susong Complex Zone in the Dabie Orogen

<正>Objective The Susong complex zone(SCZ)is a relatively lowgrade metamorphic unit mostly with an epidoteamphibolite facies,located in the southernmost part of the Dabie orogen.However,its rock compositions,ages,metamorphic processes and petrogenesis are still