Major Geological Units Research Articles

Global Inversion of Lunar Surface Oxides by Adding Chang’e-5 Samples

The chemical distribution on the lunar surface results from the combined effects of both endogenic and exogenic geological processes. Exploring global maps of chemical composition helps to gain insights into the compositional variation among three major geological units, unraveling the geological evolution of the Moon. The existing oxide abundance maps were obtained from spectral images of remote sensing and geochemical data from samples returned by Apollo and Luna, missing the chemical characteristics of the Moon’s late critical period. In this study, by adding geochemical data from Chang’e (CE)-5 lunar samples, we construct inversion models between the Christiansen feature (CF) and oxide abundance of lunar samples using the particle swarm optimization–extreme gradient boosting (PSO-XGBoost) algorithm. Then, new global oxide maps (Al2O3, CaO, FeO, and MgO) and Mg# with the resolution of 32 pixels/degree (ppd) were produced, which reduced the space weathering effect to some extent. The PSO-XGBoost models were compared with partial least square regression (PLSR) models and four previous results, indicating that PSO-XGBoost models possess the capability to effectively describe nonlinear relationships between CF and oxide abundance. Furthermore, the average contents of our results and the Diviner results for 21 major maria demonstrate high correlations, with R2 of 0.95, 0.82, 0.95, and 0.86, respectively. In addition, a new Mg# map was generated, which reveals different magmatic evolutionary processes in the three geologic units.

Application of Remote Sensing and Spectroradiometry in Geological Mapping: a case study of Handeni (QDS 148) Block, Eastern Mozambique Belt, Tanzania

This study applies remote sensing (RS) as a geologic mapping aid tool , using Handeni Block of Tanzania as a case study. To achieve the objective of this study, we have utilized various RS processing and image enhancement techniques on multispectral data, including ASTER, Landsat 5, Landsat 8, and Sentinel 2A. The method proved successful whereby both Landsat-5-data with band combination (BC) 7:4:2 and 7:5:4 and band ratio (BR) 5/3:5/1:7/5 and Landsat-8 data with BCs 5:6:7 and 7:6:4 mapped out marble units. Sentinel 2A data (with BC 8:11:3, BRs 12/2:11/2:8/11; 12/4:11/3:11/2 and 12/4:12/2:11/3) together with image enhancement decorrelation stretch on BC 4:3:2 and BC 8:11:3 images succeeded to map other major geologic units. The findings were tested using another approach, an unsupervised classification (K-means algorithm) of Landsat 8 data and unsupervised and supervised classifications by IsoData and minimum distance algorithms, respectively. Similar results were obtained from the image classification whereby Sentinel 2A data produced classified images, which consistently delineate the same lithologies. Geologic structures (lineaments) have been mapped by ASTER DEM data. The result from supervised classification using end-member spectra of the collected representative rock samples also supports the remotely sensed lithologies, demonstrating the usefulness of RS in geologic mapping. The finding of this work have shown that the integration of RS and rock spectral analyses can be used as a robust aiding tool in geologic mapping. The method is more resource efficient than a purely conventional approach.

Crustal and Lithospheric Variations along the Western Passive Continental Margin of the Indian Peninsula

The western passive continental margin (WPCM) of the Indian Peninsula is one of the world's largest and most remarkable escarpments, signifying a boundary between oceanic and continental lithospheres. It traverses distinct lithological units, majorly the SGT, WDC, and DVP, each characterized by distinct geological structures, geochronological histories, and petro-physical properties. Despite numerous research efforts, the exact mechanisms governing the WPCM evolution and its developmental connections remain unclear due to limited data and significant uncertainties. In our study, we meticulously analyzed global and local models, focusing on the Western Ghats (WG), to examine crust and lithosphere thickness. Our analysis revealed significant uncertainties in crustal and lithospheric variations, with a maximum difference of 10.68% in crust thickness and 20.04% in lithospheric thickness across different major lithological formations in the WG. These differences can have a substantial impact on the geodynamic analysis of lithospheric structures and tectonic evolution. Additionally, we developed a 2-D lithospheric density model over the WG, crossing the major geological units, which delineates the crust and lithospheric structure between the eastern and western sides of the escarpment. Our results, in conjunction with geomorphological data, suggest that the WPCM’s thick lithosphere with elevated topography illustrates a continuous upwarp, supported by flexural compensation of uplifted terrain. The movement of the Indian plate, primarily in the N-S and NW-SE directions, subsequently modified the entire escarpment. This model offers insights into the evolution of the WPCM and potentially contributes to the formation of the NE-SW fault in the southern part of the South Indian Shield, with potential implications for the Palghat gap.

Small lunar crater identification and age estimation in Chang'e-5 landing area based on improved Faster R-CNN

The Chang'e-5 (CE-5) mission marks China's first lunar sample return endeavor, with its landing site (43.06°N, 51.92°W) situated in the Mons Rümker region of the northern Oceanus Procellarum on the Moon. This region hosts some of the youngest mare basalts of the Moon and contains a relatively youthful geologic unit characterized by crater's equilibrium diameters slightly over 100 m. By refining the Faster Region-based Convolutional Neural Network (Faster R-CNN) algorithm and leveraging high-resolution imagery to create training samples, accurate identification of lunar craters can be achieved. In this study, we enhance the algorithm in aspects such as anchor boxes and Region of Interest alignment. Additionally, we have utilized high-resolution images for training, and identify and statistics craters within the CE-5 landing area. Ultimately, our model attains a validation set Recall of 90%, Precision of 69%, and an Average Precision score of 0.83. Notably, in certain scales, such as for the crater larger than 400 m, recognition results reach Precision of 88% and Recall of 89%. The findings of this study are mapped into a crater catalog. Furthermore, we predict crater density and integrate it with geochronological functions to estimate the absolute model age of nine major geologic units within the CE-5 landing area. The results are generally in agreement with those of other studies who have used manual methods for crater counting, and verify the correctness of our automatic crater identification results.

Reconnaissance Basement Geology and Tectonics of North Zealandia

AbstractNew rock dredge samples supply key information to establish the tectonic and geological framework of the northern two‐thirds of the 95% submerged Zealandia continent. The R/V Investigator voyage IN2016T01 to the Fairway Ridge, Coral Sea, obtained poorly sorted poly‐lithologic pebbly to cobbly sandstones, well sorted fine grained sandstones, mudstones, bioclastic limestones, and basaltic lavas. Post‐cruise analytical work comprised petrography, whole rock geochemical and Sr and Nd isotopic analyses, and U‐Pb zircon, Rb‐Sr, and Ar‐Ar geochronology. A Fairway Ridge cobbly sandstone has a ∼95 Ma (early Late Cretaceous) depositional age; two biotite granite cobbles are 111 ± 1 and 128 ± 1 Ma in age, and some volcanic pebbles are also likely Early Cretaceous. Fairway Ridge basalts have intraplate alkaline chemistry and are of Late Eocene age (∼40–36 Ma). By analogy with South Zealandia, we interpret strong positive continental magnetic anomalies of North Zealandia to mainly result from Late Cretaceous to Cenozoic intraplate basalts, many of them rift‐related lavas. A new basement geological map of North Zealandia shows the position of the Mesozoic Gondwana magmatic arc axis (Median Batholith) and other major geological units. This study completes onland and offshore reconnaissance geological mapping of the entire 5 Mkm2 Zealandia continent.

Strong variation of near-surface seismic anisotropy in Taiwan and its geological implications

We report on the near-surface (< 500 m) seismic structure (Vp, Vs, and Vs anisotropy) of Taiwan using the empirical Green's functions of body waves between vertical station pairs at 60 borehole sites. The near-surface anisotropy in metamorphic rocks and Miocene or older sedimentary strata are mostly categorized as orogeny-parallel anisotropy (OPA), and sites exhibiting stress-aligned anisotropy (SAA) are located in areas with late Quaternary sedimentary deposits or in alluvial coastal plains. The results show that there is a significant variation of the anisotropy strength even within the same geological unit. Since all the major geological units of Taiwan are well sampled by borehole arrays, and drilling data for 52 sites are available, this provides a unique opportunity to investigate the geological implications of strong variations in near-surface anisotropy. The investigation indicates that (1) near-surface anisotropy caused by structural fabric is generally stronger than that resulting from the alignment of stress-induced open cracks, (2) SAA strength in sedimentary rocks, igneous rocks, and gravel sediments is generally higher than that in fine-grained sediments, and (3) the sites with the strongest OPA (> 30%) are located in mountain ranges and the mean OPA strength of these sites is significantly higher than that of foothills, suggesting that foliated metamorphic rocks lead to stronger OPA than do dipping sedimentary strata. The results also suggest that the fluid-saturation of micro-cracks is not a necessary condition for the occurrence of the SAA mechanism in the near-surface depth range.

A bioavailable strontium isoscape of Angola with implications for the archaeology of the transatlantic slave trade

The region of present-day Angola was one of the main areas from which millions of enslaved Africans were abducted and forced to migrate to the Americas during the transatlantic slave trade. Strontium isotope (87Sr/86Sr) analysis is a useful tool in reconstructing large-scale human movements across geologically distinct landscapes in archaeological and forensic contexts. However, the absence of environmental 87Sr/86Sr reference data from Angola hinders the use of 87Sr/86Sr analysis in provenance studies related to Angola, especially in identifying the geographic origin of enslaved people in the African Diaspora. Here, we measured 101 plant samples from most, yet not all, major geological units to draft the first bioavailable 87Sr/86Sr map (isoscape) for Angola using a machine learning framework. Our results suggest that the 87Sr/86Sr ratios in Angola span a large range from 0.70679 to 0.76815 between the different geological units. Specifically, the high average 87Sr/86Sr ratios of 0.74097 (±0.00938, 1 SD) found in the Angola Block of central Angola, are distinctly more radiogenic than any previously published bioavailable 87Sr/86Sr ratios for western Central and West Africa. However, these match the 87Sr/86Sr ratios previously published for human enamel samples from four historic slavery contexts in the Americas. We demonstrate that our strontium isoscape of Angola greatly improves the ability to assess the possible origins of enslaved African individuals discovered outside of Africa and encourage the future use of emerging African isoscapes in the study of life histories within the slave trade.

Geomorphic Analysis of Baghain River, Yamuna Basin, and its Implication for Drainage Characteristic and Tectonics using Remote Sensing and GIS Techniques

Abstract The present study aims to access the geomorphic analysis of the Baghain river basin and its implication on landscape evolution. Baghain river originates from the Panna hill, and flows through marginal and central Ganga plain. It empties itself in to Yamuna river near Chilla village, Banda district, Uttar Pradesh. The river basin comprises of three major geological units associated with this basin: Bundelkhand gneissic complex, Vindhyan Supergroup (hard rock terrain known as Panna hill) and Alluvial deposit (marginal Ganga plain and central Ganga plain). The current work focuses on study of morphometric parameters and geomorphic indices of Baghain river basin using digital elevation model (DEM) and topographic maps (1:50,000 scale). This basin exhibits four types of drainage patterns: dendritic, parallel, trellis and rectangular. Bifurcations ratio (4.82) of river basin suggest that the most part of the basin is not influenced by any geological structures. The elongation ratio (0.50) suggests that the basin is moderately elongated. The drainage density (0.62) and stream frequency (0.22) also suggest that the basin has moderate to high permeable and easily erodible alluvium terrain. The escarpment height is low in the proximal part (Panna Hill) and high in the middle and distal parts of the basin (marginal Ganga plain and central Ganga plain, respectively. Asymmetric factor (52) shows a leftward tilt of the basin. The region lies under marginal Ganga plain, and Bundelkhand plateau. The sharp bend present is probably due to the lithological variation. It reflects moderate gradient in the upper part (Panna hill), steep gradient in the lower part (Panna hill), and low gradient in the marginal to central Ganga plain.

Integrated geophysical methods and techniques for studying the perennial springs in Ikanje- Share, Kwara State, Nigeria

An integrated magnetic, self-potential (S.P.) and electrical resistivity survey involving magnetic profiling and 1D Vertical Electrical Sounding (VES) electrical imaging techniques were carried out in the transition environment between the Nupe Basin and Southwestern Nigeria Basement Complex at Ikanje-Share in Kwara State, Nigeria. The Ikanje-Share perennial springs started gaining a lot of attention after many travelers and tertiary institutions in Nigeria made it a good choice for their fieldwork exercise. The surveys were done in order to delineate the subsurface layers, determine the geoelectrical characteristics and identify geological structures (e.g., faults and fractures) that are responsible for the perennial spring formation. The magnetic profiling was used as reconnaissance technique to identify lineament features that are favourable to groundwater accumulation and transmission. Some magnetic lineaments were qualitatively inferred from some profiles in the study area. The fault locations coincide with inflection points in S.P. curves and occur as horizontal and consistent planes of discontinuities at depths of approximately 1.25, 4.25, 8.75, 13.15 and 21.25 m, respectively. The VES interpretation results indicated four to five major geologic units, which include: the topsoil/clay/lateritic layer, the lateritic layer, the weathered basement, the weathered/fractured basement and the fresh bedrock. The weathered and fractured basements constitute the main aquifer units and the overburden thickness varies from 5.0 to 16.8 m. The study has shown the usefulness of integrated geophysical methods and techniques in subsurface structural and groundwater development study over the perennial springs in the transition environment between the Nupe Basin and the Southwestern Nigeria Basement complex.

Anisotropy of Magnetic Susceptibility Reveals Late Miocene Tectonic Activity in the Western Qaidam Basin

The western Qaidam Basin on the northeastern Tibetan Plateau located at the intersection between the Altyn Tagh Fault and the Kunlun Fault/Qimen Tagh Fault holds significant potential to reveal the tectonic process of these two faults as well as the evolution of the Qaidam Basin. In this paper, we conducted detailed anisotropy of magnetic susceptibility (AMS) records from Late Cenozoic sediments at the Qigequan section in the western Qaidam Basin to shed new light on the tectonic processes in this region. Based on the distribution of three principal axes of magnetic fabrics as well as magnetic fabric parameters, the AMS records can be divided into three parts. The lower part (∼6.9–4.6 Ma), mainly made of fine-grained mudstone and siltstone, exhibits three well-grouped principal axes with a NE-SW elongated Kmin axis as the embryonic tectonic magnetic fabric, suggesting constant NE-SW compressional strain. The middle part (∼4.6–3.0 Ma), characterized by mudstone, siltstone and sandstone, shows three less grouped principal axes and suggests a relatively weak and stable tectonic environment. The three principal axes of the upper part (∼2.4–0.4 Ma) is composed of sandstone and conglomerate of the Qigequan Formation, similar to the middle part, which was primarily attributed to the coarse lithology and not sensitive to tectonics since ∼2.6 Ma. The NE-SW compressional strain in the western Qaidam Basin is consistent with that in the northeastern basin, both of which are parallel to the upper crust movements revealed by the GPS, suggesting the dominant NE-SW compressional strain in the western and northern basins in the late Cenozoic. The decreasing magnitude of tectonic activities during ∼6.9–4.6 Ma indicates that the major geological units released most of the compressional strain in the western Qaidam Basin during tectonic activity that initiated in the early-late Miocene.

Geological History of Southeastern Gorgonum Chaos, Mars: A Story of Water and Wind

AbstractGorgonum Chaos is part of the Eridania paleolake in Terra Sirenum and displays a number of prominent light‐toned morphological features that bear a record of the regional climatic conditions throughout most of Martian history. Based on an intergrated analysis of orbital data, we mapped a 1,500 km2 area in the southeast of Gorgonum Chaos. Morphologic, spectroscopic, and stratigraphic analyses were used to determine age and composition of the main geological units in the area. We identified four major geological units with decreasing content of hydrated minerals from the oldest to the youngest units, which were completely free of hydrated minerals. In the study area, phyllosilicate‐rich Noachian units compose the majority of the basin floor. Deposits enriched with evaporites were formed around the Noachian/Hesperian transition and erosion created prominent inverted morphologies. Loess‐like material without significant amounts of hydrated minerals was deposited until the late Hesperian. The youngest unit is an Amazonian layer free of hydrated minerals that originated from volcanic activities. This succession of minerals reflects the transition from more humid climatic conditions with the ability to sustain liquid water on the planet's surface during the Noachian to the hyper‐arid Amazonian environment we observe currently on Mars.

Hydrogeophysical Investigation and Aquifer Evaluation of the Formations in Nsukka Area, Southeastern Nigeria

The study targeted the aquiferous Ajali Sandstone and Nsukka Formations that underlies the Nsukka metropolis and its environs (within Latitudes 6 o 80 1 N and 6 o 89 1 N; Longitudes 7 o 21 1 E and 7 o 30 1 E), covering an area of about 210 square kilometres. Thirty four (34) cross array Vertical Electrical Sounding (using the Schlumberger electrode configuration) and records from four (4) selected boreholes have been used to investigate the subsurface distribution of electrical resistivity and to delineate hydraulic properties of aquifers in Nsukka area, Southeastern, Nigeria.The electrical surveys of the area show high values of permeability, ranging from 0.0075 to 0.015cm 2 , hydraulic conductivity, ranging from 8.29 to 16.64m/s, transmissivity, between 455.87 and 1002.48m 2 s -1 , and specific yield, ranging from 2.35 to 4.76m 3 . A tie with the results of borehole logs analysis reveals the presence of at least four layers of contrasting hydraulic conductivity. Analyses, however, suggests that the Nsukka Formation (which overlies the Ajali Sandstone) is thick and poorly conductive while the Ajali Sandstone unit is homogenous and anisotropic and has higher conductivity (especially beyond the depth of 100 m), suggesting a prolific water-bearing formation at such depth and beyond. The Ajali Sandstone aquifer in the area is thick and prolific. The distribution of major geological units, well log data, static water level data were shown to have influence on the groundwater occurrence and flow pattern in the area. Keywords: Ajali Sandstone Aquifer, Nsukka Metropolis, Resistivity measurements, Well data DOI: 10.7176/JEES/11-7-04 Publication date: July 31 st 2021

Delineating and Interpreting the Gold Veins Within Bida and Zungeru Area, Niger State Nigeria, Using Aeromagnetic and Radiometric Data

Abstract Both Airborne Magnetic and Radiometric datasets were employed to interpret the geology and geological structures that serve as host to gold and associated minerals within the Bida and Zungeru, Niger State, Nigeria. An area of 55 by 110km2, contained within the cretaceous sediments of Bida Basin and the meta-sediments of Zungeru-sarkin-pawa schist belt. Data interpretation involve the application of a mathematical algorithm for data enhancing such as, Reduce to the Equator, Analytical signal, First Vertical Derivative, and Centre for Exploration Targeting (CET) to the magnetic data, and Ternary imaging to the radiometric data, with a sole aim of mapping geological structures such as faults fracture folds joints and geological boundaries and possible gold mineralization veins that arise from hydrothermally altered zones. Two major geological units inhibit the study area, the cretaceous sediment, and the meta-sediments, major feature identifies within the Cretaceous sediment are the folds majority of which are located within the contacts. The result of the 1VD display is the vivid picture of the observed structural features such as faults fractures folds’ contacts labeled F1 to F8 both within the high region of magnetic susceptibility (in red) and low regions (in blue) geology contacts (yellow), folds (bold yellow) all across the field. Prominently at the North-Western corner of the study area are sets of linear structure that trend NE-SW, located within the contacts between the mylonites and the amphibolites and the belt-type meta-sediments located around Katakwo, Gindei, Kwange, Gabas and Akusu villages. Equallyworth mentioning are sets of lineament (in blue) trend E-W all across the mid-region of the study area, precisely at the Eastern corner within and below the Federal University of Technology Minna around Kata-eregi, Sabon-Dagan, Kakaki down Minkwoigi, Sunbwagi, Kakagi, Sabon dagga, and Bobo-shiri towns, where the majority of volcanic activities must have been recorded. The airborne radiometric show mobilization of the immobile thorium Th, concentration, and this also indicated hydrothermally altered zones. The increase in potassium concentration and decrease in K/Th relation observed from radiometric interpretation are very pinpointing of hydrothermal activities within the study area. The gold mineralisations are found within this vein and in the adjacent, highly deformed host rock located below the Federal University of Technology Minna Campus. The deformation seems to comprise principally of pebbly schist, amphibolites along fine-grained and magnetite.

Combining Site Characterization, Monitoring and Hydromechanical Modeling for Assessing Slope Stability

Rainfall-induced landslides are a disastrous natural hazard causing loss of life and significant damage to infrastructure, farmland and housing. Hydromechanical models are one way to assess the slope stability and to predict critical combinations of groundwater levels, soil water content and precipitation. However, hydromechanical models for slope stability evaluation require knowledge about mechanical and hydraulic parameters of the soils, lithostratigraphy and morphology. In this work, we present a multi-method approach of site characterization and investigation in combination with a hydromechanical model for a landslide-prone hillslope near Bonn, Germany. The field investigation was used to construct a three-dimensional slope model with major geological units derived from drilling and refraction seismic surveys. Mechanical and hydraulic soil parameters were obtained from previously published values for the study site based on laboratory analysis. Water dynamics were monitored through geoelectrical monitoring, a soil water content sensor network and groundwater stations. Historical data were used for calibration and validation of the hydromechanical model. The well-constrained model was then used to calculate potentially hazardous precipitation events to derive critical thresholds for monitored variables, such as soil water content and precipitation. This work introduces a potential workflow to improve numerical slope stability analysis through multiple data sources from field investigations and outlines the usage of such a system with respect to a site-specific early-warning system.

Sedimentary structure of the Sichuan Basin derived from seismic ambient noise tomography

SUMMARY Determining a detailed 3-D velocity model with high resolution for the sedimentary layer in the Sichuan Basin is potentially beneficial both to the industrial oil/gas exploration and earthquake hazards’ mitigation. In this study, we apply the ambient noise tomography method to construct a 3-D S-wave velocity model. This model focuses on the sedimentary layer of the Sichuan Basin, with a 0.3° × 0.3° grid precision. Dispersion curves of both group and phase velocities of Rayleigh wave at 4 to 40 s periods are utilized, which are extracted from 87 broad-band stations in the Sichuan Basin and the surrounding areas. The 3-D model reveals a thick sedimentary layer of the Sichuan Basin with S-wave velocity ranging from ∼2.0 to 3.4 km s−1. The sediment thickness in the margins of the Sichuan Basin is generally greater than the typical values of 6–10 km in the central areas due to surrounding orogenic activities, with a maximum depth of ∼13 km in the northwestern margin. Moreover, a prominent low S-wave velocity anomaly in the margins may be caused by the sediment accumulations from large-scale landslides and pronounced denudation of the surrounding orogenic belts. Major geologic units in the sedimentary layer are delineated in this study. The S-wave velocity values within each geologic unit and their bottom interfaces are obtained. Based on our model, we calculate synthetic ground motions for the 2013 Lushan earthquake and obtain the distribution of the peak ground acceleration from the earthquake epicentre to the western Sichuan Basin. The result clearly illustrates the basin amplification effect on the seismic waves.

INTERPRETATION OF MAJOR STRUCTURES WITHIN THE BASEMENT REGION OF BENUE-NIGER CONFLUENCE FROM AEROMAGNETIC AND RADIOMETRIC DATA KOGI STATE NIGERIA

Interpretation of Aeromagnetic and Radiometric Data covering the basement region of Benue-Niger confluence was executed to delineate major structures and other geologic frame works of mineral interest. The study area which hosts the Benue-Niger confluence also encloses two major geologic units which are basement complex and sedimentary basins. The Aeromagnetic data set comprising sheet 227 (Koton-Karfe), 247 (Lokoja) and 267 (Idah) was enhanced to reveal geologic structures while radiometric data was analysed to map lithology and zones affected by hydrothermal alterations. A set of mathematical algorithms was used to enhance the data for interpretation. First Vertical derivatives, Analytical Signal and Euler deconvolution filters were applied to the Aeromagnetic data while Ratio and Ternary images of the three radiogenic elements were obtained for the radiometric data. Magnetic signatures from the TMI showed a mixture of high and low susceptibility below koton-karfe due to intrusion of oolitic iron ore within the sedimentary formation. Lokoja regions recorded highest susceptibility of 165 nT due to magnetic signatures emanating from exposed basement rocks. The southern Idah regions recorded relatively low susceptibility. Result of First Vertical Derivative revealed near surface mineral potent structures labelled F1 – F8, cringing surface features B1, B2 and B3. Analytical signal revealed high amplitudes range of 0.174 to 0.579 cycles for magnetic sources majorly at the basement regions, while low amplitude range of 0.021 to 0.157 cycles were recorded around the sedimentary regions. Euler depth analysis revealed shallower depth to sources in the basement and deeper depth to sources in the sedimentary regions due to thick overburden. Radiometric signatures from the K/Th ratio map revealed portions around Latitude 8°00’ NW and 7°30’ SW shaded in pink colour and having values above known threshold of 0.2 %/ppm to be hydrothermally altered. Mapping of lithology from Ternary map revealed K-Feldspar mineral bearing rocks dominated the NW and SW regions, while sandstones, ironstones, mudstones, shale, alluvium and other fluvial sedimentary lithologies dominated the sedimentary North-east and South-Eastern regions. The western regions (NW and SW) hosted the major structures in form of magnetic lineaments trending NE-SW and E-W which also coincided with regions delineated to be hydrothermally altered and apparently represents the most prospective regions of mineralisation in the study area.

Metallogeny of critical metals in the SouthwesternYangtze Block

The Yangtze Block is one of the major geological units in China. Numerous and diverse mineralization are extensively distributed in this block, making the Yangtze Block be one of the well-known providers of mineral-resources worldwide. In the southwestern Yangtze Block, since Proterozoic, the diverse mineralization involves magmatic, magmatic-hydrothermal, low-temperature hydrothermal and weathering-sedimentary processes were extensively developed, of which critical metal mineralization (e.g., In, Ge, Ga, Cd, Re, W, Sn, Li, Nb, REE, and PGE) is generally present as by-products in some basic or precious deposits or as independent deposits. Previous studies have revealed ten types of critical metal mineralization in the region, specifically including the REE-rich phosphorite, PGE-Re-rich black shales, carbonate clay-type Li-Ga-REE, basalt weathering-type Nb-Ga-Zr-REE, In-rich cassiterite sulfide, REE-rich IOCG, Tl-rich low-temperature hydrothermal, Ge-rich Pb-Zn, Cu-Ni-PGE sulfides and carbonatite-related REE deposits. In the past decade, numerous studies have advanced our understanding of the mineralization styles, timing and ore genesis of these types of critical-metal mineralization, and are summarized in this paper. It was indicated that the Cu-Ni-PGE sulfide deposits are genetically related to the late Permian E’meishan mantle plume, whereas the carbonatite-related REE deposits are Cenozoic in age and have formed during post-collision between the Indian and Asian continents. Moreover, the REE-rich IOCG deposits were newly identified, constituting a Proterozoic IOCG metallogenic province that was first documented in China, and enrichments of REEs were suggested to be related to the chemical attributes of the late Cu mineralizing fluids; the In-rich sulfide deposits, distributed in a small area of the SW Yangtze Block, were suggested to be genetically related to late Yanshanian granites; the low-temperature hydrothermal mineralization, characterized mainly by the Pb-Zn and Au-As-Sb-Hg-Tl deposits that define one of the two world-largest low-temperature metallogenic provinces, was mainly formed at the Indosinian and Yanshanian periods during which granitic activities are relatively weak; numerous marine-facies sedimentary rocks particularly including the black shales and carbonate rocks are associated with the development of multi-episodes of sedimentary and/or weathering-sedimentary deposits that are uniquely enriched in Li, Nb, Zr, Ga. Re, REE and PGE. We also proposed some issues that are important but currently poorly addressed, including aspects of the evaluation of REE resource potential and mechanisms of REE concentrations in IOCG deposits, and key factors controlling the extreme enrichment of Ge, Ga, Cd and Tl in the Mesozoic low-temperature metallogenic province, with focuses on the background values of these elements in the region. Moreover, available studies show that In is extremely enriched in four giant cassiterite-rich, granite-related sulfide deposits distributed in the border area of Yunnan and Guangxi, making this area a unique In metallogenic province in the world. However, it is currently not clear why In is enriched in cassiterite-rich sulfide deposits and why In is enriched in the sphalerite as a function of “indium window” effect, which should be constrained through a combined study involving crust-mantle circulation, crystallization fractionation of magma, geochemical behaviors of metals and mineralogy. We also proposed that the weathering-sedimentary deposits, such as the clay-type Li-Ga-REE and basalt weathering-type Nb-Ga-Zr-REE ones, are likely brand-new types with huge potential of critical metal resources, and emphasized that in addition to ore genesis studies, researches on the distributions of metals and potential utilization of resources should also be paid more attention. We also highlight that current prospecting techniques and methods that are mostly used for exploration of some common basic or precious deposits are likely not applicable for the exploration of critical metal deposits. As such, new techniques and methods involving the integration of prospecting information, predication and locating of ore bodies and evaluation of resources should also be developed for critical metal deposits.

Baseline bioavailable strontium isotope values for the investigation of residential mobility and resource‐acquisition strategies in prehistoric Cambodia

Strontium (Sr) isotope ratios (87Sr/86Sr) measured in human skeletal material can increase one's understanding of the residential behaviour and resource‐acquisition strategies of past populations. The paper maps bioavailable 87Sr/86Sr variation in 183 plant and soil samples across Cambodia. Bioavailable 87Sr/86Sr, as measured in plants, differs significantly between four major geological units. The data set will support future investigations of skeletal material from Cambodian archaeological sites. Baseline 87Sr/86Sr data should be applied judiciously to skeletal populations, and in concert with other lines of evidence, to identify potential geographical outliers rather than to ascribe specific locations from which individuals may have moved.

Engineering Site Investigation and Shallow Foundation Design in Ore Area of Ondo State, Nigeria

Abstract The study integrates geophysical and geotechnical methods for subsoil evaluation and shallow foundation design. The study involved six vertical electrical sounding and geotechnical investigation involving cone penetration test and laboratory soil analysis. Three major geologic units were delineated; the topsoil, weathered layer and partly weathered/fractured/fresh bedrock. The overburden thickness is in between 15.2–32.9 m. Based on resistivity (16–890 ohm-m) and thickness (12.7–32 m) the weathered layer is competent to distribute structural load to underlying soil/rock. The groundwater level varies from 4.5 to 12.3 m. Therefore an average allowable bearing capacity of 200 kPa is recommended and would be appropriate for design of shallow foundation in the area, at a depth not less than 1.0 m with an expected settlement ranging from 9.03–48.20 mm. The ultimate bearing and allowable bearing capacity for depth levels of 1–3 m vary from 1403–2666 kPa and 468–889 kPa for strip footing while square footing varies in between 1956–3489 kPa and 652–1163 kPa respectively.

THE EVOLUTION OF THE ESTONIAN PRECAMBRIAN BASEMENT: GEOLOGICAL, GEOPHYSICAL AND GEOCHRONOLOGICAL CONSTRAINTS

The Estonian Precambrian crystalline basement that consists of Paleo- to Meso-Proterozoic metamorphic and igneous rocks is covered by a 100-780 m thick deposit of Paleozoic sedimentary rocks. Thus, the basement is unavailable for direct surficial observations and our present knowledge is based on information from cores of deep drillings and interpretation of potential - gravity and magnetic - fields. Accordingly, the basement of Estonia is subdivided into two major geological units – North Estonian amphibolite and South Estonian granulite complexes. Further division includes six structural - petrological zones such as Tallinn, Alutaguse, Johvi, West-Estonian, Tapa and South-Estonian zones. The present article provides an updated overview of the Estonian Precambrian basement, its rock types, geophysical fields, geochronology, metamorphism and metallogenesis.