Stream Sediment Geochemical Survey Research Articles

Enhancing geochemical background estimation using rock weathering

The chemical composition of stream sediments is heavily influenced by weathering processes occurring in upstream lithological units. Despite their importance, these processes are frequently ignored in the examination of stream sediment geochemical data when identifying mineralized zones. Instead, existing geochemical background estimation procedures rely on the area size of upstream rocks as an indicator of their contribution to elemental concentrations of sediments. To address this limitation, a stream sediment geochemical survey was conducted in a pilot area in central Iran, and the physico-mechanical properties of upstream rock types, including elastic velocities, porosity, and Schmidt hammer rebound values, were evaluated. A new weathering index, “Wij,” was developed, utilizing proxies of rock weathering to estimate the geochemical background attributed to lithology at sediment sampling sites. The regression model was constructed by combining weathering proxies (Wij) with other independent variables, including the presence or absence of rocks in catchments, area size (Xij), and the weathering-corrected contributing factor (XijWij). The results suggested the significant capability of weathering proxies in explaining the geochemical variability of major elements such as Al, K, Fe, Ca, and Na. However, the regression model using weathering-corrected contributing factors delivered better overall accuracy than other independent variables. Nevertheless, our results also identified some limitations of the application of regression model in stream sediment data analysis.

Identifying high potential gold mineralization using geological and stream sediment geochemical data: A case study from western Dangreyongcuo area in the central Lhasa terrane, Tibet, China

Northern Tibet exhibits abundant placer gold deposits, with a longstanding history of mining activities. Despite the widespread placer gold occurrences, the reports on the primary rock gold deposits or occurrences remain scarce. The central Lhasa terrane in northern Tibet hosts well-developed Zenong Group volcanic rocks, indicating great potential for the exploration of porphyry-epithermal copper (gold) deposits. Here, we select the Dangreyongcuo area in this region to investigate its metallogenetic potentiality, through a comprehensive 1:50,000 stream sediment geochemical survey, analyzing 12 elements (Au, As, Sb, Ag, Te, Cu, Pb, Zn, W, Sn, Bi, and Mo), and a detailed geological mapping. We aim to identify gold-related mineralization anomalies and provide clues for further bedrock gold exploration in this region. Based on the stream sediment geochemical data, zones 1–4, have been delineated using single-element indicator Au and element association indicator Au + As + Sb, which was determined through robust principal component analysis (RPCA) and using the exploratory data analysis (EDA) method. Subsequent validation exercises evaluating these four delineated zones reveal that Zone 1, Xinlong-Langmeila area, is the most promising prospect due to its high element concentrations, large size, and marked coincidence of element assemblages (also referred to as high-large-coincidence anomalies; HLCAs) and its characteristics are in line with those of epithermal deposits. Notably, the Xinlong deposit represents the first documented epithermal gold deposit hosted within the Zenong Group volcanic rocks. The identification of this deposit offers valuable insights and strategic directions for the broader understanding of Zenong Group volcanic rocks across the central Lhasa terrane. Additionally, subsequent strategies have been proposed for mineral exploration at both Xinlong camp and regional scales.

Leucogranite mapping via convolutional recurrent neural networks and geochemical survey data in the Himalayan orogen

Geochemical survey data analysis is recognized as an implemented and feasible way for lithological mapping to assist mineral exploration. With respect to available approaches, recent methodological advances have focused on deep learning algorithms which provide access to learn and extract information directly from geochemical survey data through multi-level networks and outputting end-to-end classification. Accordingly, this study developed a lithological mapping framework with the joint application of a convolutional neural network (CNN) and a long short-term memory (LSTM). The CNN-LSTM model is dominant in correlation extraction from CNN layers and coupling interaction learning from LSTM layers. This hybrid approach was demonstrated by mapping leucogranites in the Himalayan orogen based on stream sediment geochemical survey data, where the targeted leucogranite was expected to be potential resources of rare metals such as Li, Be, and W mineralization. Three comparative case studies were carried out from both visual and quantitative perspectives to illustrate the superiority of the proposed model. A guided spatial distribution map of leucogranites in the Himalayan orogen, divided into high-, moderate-, and low-potential areas, was delineated by the success rate curve, which further improves the efficiency for identifying unmapped leucogranites through geological mapping. In light of these results, this study provides an alternative solution for lithologic mapping using geochemical survey data at a regional scale and reduces the risk for decision making associated with mineral exploration.

Geostatistics and inverse distance weighing (IDW) multivariate interpolation methods for regional geochemical stream sediment survey for base metal prospecting around Wapsa, Solukhumbu District, Nepal

A systematic regional geochemical stream sediment survey for base metals copper, lead, and zinc over an area of 200 sq.km was carried out around Wapsa in Solukhumbu District. 200 stream sediment samples were collected from active streams and analyzed them using atomic absorption spectrometry (AAS) method. All chemical analysis data were interpreted with geostatistical analysis and inverse distance weighing (IDW) multivariate interpolation method using the geographical information system (GIS). The results have shown consistency with geology, homogeneity, and mineralization in the area which is verified with significant copper anomaly over an old working area around Wapsa. The log10 transformed data of Cu, Pb, and Zn were used to estimate threshold and anomaly determination. The method is valid for regional geochemical stream sediment surveys for base metals prospecting.

Geochemical and Petrological Survey in Northern Ethiopia Basement Rocks for Investigation of Gold and Base Metal Mineralization in Finarwa Area and Its Surrounding Southeast Zone of Tigray, Ethiopia

The study is accompanied in northern Ethiopian basement rocks, Finarwa area and its surrounding areas, south eastern Tigray. The objective of the study is to amendment field geology, mineralogy, and geochemical characteristics to deliberate about the gold and base metal mineral potential investigations. From the field observations the geology of the area haven been described and mapped based on mineral composition, texture, structure and colour of both fresh and weather rocks.The ore mineral under microscope are commonly base metal sulphides pyrrhotite, Chalcopyrite, pentilandite occurring in variable proportions. Galena, chalcopyrite, pyrite and gold mineral are hosted in quartz vein. The base metal sulfides occur as disseminated, vein filling and replacement. Geochemical analyses result from inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS) indicates the threshold of geochemical anomalies is directly related to the identification of mineralization information. From samples stream sediment samples and the soil samples indicated that the most promising mineralization occur in the prospect area are gold(Au), copper (Cu) and zinc (Zn). This is also supported by the abundance of chalcopyrite and sphalerite in some highly altered samples. The stream sediment geochemical survey data shows relatively higher values for zinc compared to Pb and Cu. The moderate concentration of the base metals in some of the samples indicates availability base metal mineralization in the study area requiring further investigation. In addition the sulphide concentrations in the research area are related to different stages of mineralization and are controlled both by structures and lithology. They are well established in the slate-phyllite and metavolcanics along the shear zones and faults as disseminated and vein filling. The rock and soil geochemistry shows significant concentration of gold with maximum value of 0.33ppm and 0.97 ppm in the south western part of the study area.

Lithological Mapping Using a Convolutional Neural Network based on Stream Sediment Geochemical Survey Data

Lithological Mapping Using a Convolutional Neural Network based on Stream Sediment Geochemical Survey Data

The Relationship between Particle Size and Element Distribution in Stream Sediments from the Dongyuan W-Mo Deposit, Eastern China

Particle size exerts significant control on the concentration of elements in stream sediments and is therefore critical in stream sediment-based geochemical exploration, which has proved important in China’s National Geochemical Mapping Project. There are various geographical landscapes in China with different distribution characteristics of stream sediments. Therefore, we studied the relationship between particle size and element distribution in stream sediments, which is always a crucial but challenging issue in geochemical surveys. The distributions of minerals and elements in eight size fractions of stream sediments (2–0.84, 0.84–0.42, 0.42–0.25, 0.25–0.177, 0.177–0.125, 0.125–0.096, 0.096–0.074, and <0.074 mm) from the Dongyuan W-Mo deposit in eastern China were studied. The results show that the 2–0.25 mm particle size fraction of stream sediments is composed mainly of rock debris and various minerals from broken bedrock upstream, while the <0.25 mm fraction is composed mainly of clay, individual minerals, and organic matter. The pilot survey results prove that using 2–0.25 mm as the sampling particle size fraction is better than using <0.25 mm, especially in geochemical prospecting and geological body delineation. Sampling the 2–0.25 mm particle size fraction of stream sediments can help to delineate proven ore bodies, ore-related anomalies, and geological bodies more effectively and more credibly. The suggested sampling particle size fraction for a stream sediment geochemical survey in a humid to semi-humid low mountain landscape in eastern China is therefore 2–0.25 mm, rather than the particle size fraction of <0.25 mm that was used for sampling in this area before. This paper depicts a successful example for determining the optimal sampling particle size fraction for stream sediment-based geochemical exploration.

Stream Sediment Geochemical Survey of Rare Earth Elements in and Around Daringbadi, Kandhamal District, Odisha

Abstract There are number of Rare Earth Element (REE) bearing minerals, which get into the stream sediment by weathering of host rock.A chemical analysis of the stream sediment samples help to delineate the source rock, as they represent the composition of the drainage basin. So with main objective to identify new prospective areas for possible occurrences of mineral deposits on the basis these stream sediment samples, Geological Survey of India launched a national geochemical mapping programme in 2001. During the FS 2018-19 geochemical mapping was carried out in and around Daringbadi, Kandhamal district, Odisha in parts of toposheet no. 74A01. To study the distribution of REE group of elements in the stream sediment samples of the study area, 364 nos. of stream sediment/slope wash samples were collected on 1km x 1km grid interval constituting 91 nos. of composite samples.The collected samples were processed and analysed by inductively coupled plasma-mass spectrometer (ICP-MS) in GCM Lab, GSI, ER, Kolkata. Analytical results of composite and Soil samples shows that in the study area average value of ∑REE is 666.81 ppm and higher concentration is found in the central part of the study area near Daringbadi village over granite gneiss, khondalite and charnockite rocks. Elements such as Pb and Zr have average concentration 3 to 3.5 times higher than the average UCC value which may be due to the presence of charnockite.

Geochemical potential mapping of iron-oxide targets by Prediction-Area plot and Concentration-Number fractal model in Esfordi, Iran

This study serves the purpose of generating a geochemical Fe-bearing potential map. Stream sediment geochemical survey was employed by collecting 843 samples for analyzing 19 elements and oxides. Taking preprocessing of data (e.g. outlier correction and data normalization) into consideration, a Concentration–Number (C-N) fractal model was used to separate different geochemical populations of Fe2O3, TiO2, V and the main multi-element factor in close spatially association with the Fe targeting. A prediction-area (P-A) plot was drawn for each variable to determine the weight of each geochemical indicator. Results indicate that the main geochemical factor with an ore prediction rate of 73%, has occupied 27% of the Esfordi area as favorable zones for further mining propsectivity. The Esfordi as a favorable Fe-bearing zone is of special interest in the NE of the Bafq mining district that hosts important “Kiruna-type” Magnetite-Apatite deposits. In addition, a synthesized indicators map was prepared through implementing a data-driven multi-class index overlay in a similar fashion to the previous version of the method, upon which geochemical potential zones were mostly in the NE part of the Esfordi, intimately linked with intense fault density map. The significance of this study lies in localizing of the most geochemical favorable zones through simultaneous consideration of the C-N and P-A plots accompanied with the incorporation of known active mines and prospects to determine indicator weight. Of note is that the Mineral Potential Mapping (MPM) has higher efficiency over each geochemical indicator with an ore prediction rate of 78% and area occupation of 22%.

Signatures of Heavy Metal concentration over Laterites identified through Regional Stream Sediment Geochemical Survey in parts of Katni, Panna and Satna Districts of Madhya Pradesh, India

Abstract As a part of National Geochemical Mapping (NGCM) programme of GSI, regional geochemical mapping was carried out for an area of 705 sq km in parts of Katni, Panna and Satna districts of Madhya Pradesh covering toposheet number 64A/05 bounded by latitudes N23°45′00″ to N24°00′00″ and longitudes E80°15′00″ to E80°30′00″. Chemical analyses of 182 composite stream/slope sediments samples were carried out and baseline geochemical maps of oxides and elements were prepared. Data analyses has led to significant conclusions on environment hazard due to metal contamination and possible mineral potential due to REE enrichment. Study of the spatial distribution of individual variables showed Cr and Co have values higher than the permissible level in dry soils in some parts of the area which requires investigation by concerned agencies. Some samples over the laterites show higher than threshold values of REEs which are much higher than their crustal abundance. Factor analyses on the geochemical data with 46 oxides and elements has led to the identification of five factors accounting for 84% of the total variance of the data set and describing five physico-chemical processes controlling the spatial geochemical variation. The analyses points to the enrichment of the REEs in the lateritisation process. The laterites covering 171 sq km of the area need to be considered for investigation of REE potential.

Landsat-8 Lineament Analysis for Detection of Epigenetic Mineralization Zones in Parts of Igarra Schist Belt, Southwestern Nigeria

The study of lineaments derived from optical imagery provides insights to the location of mineral deposits as they reflect geologic structures. The present study employs lineament extraction from Landsat-8 Operational Land Imager (OLI) to identify possible areas of epigenetic mineralization in the rocks of Dagbala-Atte District. Fifty-one (51) geologically significant lineaments of varying lengths and directions were extracted. Lineament map revealed three promising zones of epigenetic mineralization. These zones are those in the northeastern, central, and southwestern parts of the district. Previous reconnaissance stream sediment geochemical survey in the larger region comprising the district had selected areas that correlate well with these zones as the more prospective for metallic mineralization. Also, pedogeochemical surveys in the district revealed plausible areas underlain by rocks most likely contain different metallic mineralizations that synchronize well with these promising zones. Geological mapping and preliminary lithogeochemical survey in these zones have unveiled uranium bearing pegmatite in the northeastern zone; gold bearing marble deposit and iron oxide-copper-gold-silver mineralized silicified sheared rock along the central zone; and lead-zinc mineralized metaconglomerate in the southwestern zone. Ample geological studies of these mineralized rocks are recommended.

Mineral prospectivity modelling using singularity mapping and multifractal analysis of stream sediment geochemical data from the auriferous Hutti-Maski schist belt, S. India

The regional stream sediment geochemical survey has become an all the more important exploration technique for delineating potential mineral zones to target exploration. However, the effective appraisal of pathfinder elements has remained a fundamental challenge in exploration geochemistry. In this regard, the singularity mapping technique based on modern nonlinear theory and fractal-multifractal geometry is a new efficient method to distinguish thresholds of anomalies based on stream sediment geochemical data. The auriferous Hutti-Maski schist belt in Eastern Dharwar Craton (EDC), S. India has been taken up for delineation future targets using local singularity analysis (LSA) of stream sediment geochemical data. Ordinary Singularity Mapping (OSM) and Spatially Weighted Singularity Mapping (SWSM) are employed for mapping singularity of gold pathfinder elements (Au, As, Ag, Hg, Sb, Se, Cu, and Zn). In SWSM, a distance-based fuzzy weighting method is used to estimate the spatial weighting factor with respect to ore controlling shear zones. The local isotropic singularity index and the local anisotropic singularity index are estimated for each of the eight elements. The Student’s t-statistics based on Weight of Evidence (WOE) model is used to determine the threshold singularity index value to separate geochemical anomaly from background. Principal Component Analysis (PCA) is applied to singularity maps of multiple elements derived using OSM and SWSM techniques. The first principal component (PC-1) scores estimated by the OSM-PCA and SWSM-PCA lead to comprehensive geochemical anomaly maps. Results of two different singularity mapping techniques are compared using Geochemical Mineralization Probability Index (GMPI), Concentration-Area (C-A) fractal analysis and Prediction-Area (P-A) plots. It is observed that the SWSM method results in a smaller target with higher predictive ability compared to OSM method that delineates a larger target area.

Stream sediment geochemical survey of rare elements in an arid region of the Hamadat area, central Eastern Desert, Egypt

The present work deals with the possibility of conducting orientated geochemical survey exploration in an arid area using stream sediments. These sediments were drained from the Neoproterozoic metavolcanic and granitic rocks of the Hamadat area, Egypt. The fine size fraction of <63 µm, which is most appropriate for the exploration in the arid desert conditions, has been considered. Fourty four samples, including 35 clay and silt fractions and three size fractions of three samples, were analyzed by ICP-MS for major and trace elements. The heavy mineral content was separated from the stream sediments and identified. Based on the geochemical and mineralogical features, the catchment area of the studied stream sediments is split into two primary domains: namely first and second. The first domain drains monzogranite and associated pegmatite and quartz veins, whereas the second domain drains a metasomatized riebeckite granite. The stream sediments of the first domain are enriched in LREE (and ΣREE), Th, Zr and Hf, whereas the second domain has a clear signature of Nb, Ta, Th, U, Y and HREE. These rare metals are predominantly accommodated in the structure of detrital minerals representative of the clastic aureole around the source rocks and are absorbed to a lesser extent. The obtained data are utilized for constructing high-resolution geochemical maps to show the distribution of different rare metals. The anomaly aureoles have been delineated for Y, Yb, Nb, Th and U on a base map of the catchment area. The distribution maps propose possible potential mineralization of rare metals, especially REE, Nb, Ta, Zr, and Hf, in the study area. The HREE + Y appear to be prospective in the second domain, whereas Th, Zr and LREE are possible resources in the first domain. Further studies to authenticate the potentiality of these resources are strongly recommended.

Geochemistry, fluid inclusions and sulfur isotopes of the Govin epithermal Cu-Au mineralization, Kerman province, SE Iran

Govin area is located southeast of the Urmieh-Dokhtar volcano- plutonic arc, which formed as the result of subduction of the Neo-tethyan oceanic crust beneath the central Iran continent. The arc hosts world-class Sar-Cheshmeh Cu porphyry deposit and many other Cu, Cu-Mo, Cu-Au porphyry, and Cu-Zn-Pb-Ag-Au skarn and epithermal deposits. The rock units in the Govin area include Eocene volcaniclastic rocks that intruded by post-Miocene hypabyssal quartz-monzonite, grano-diorite, diorite and quartz-diorite stocks. The stream sediment geochemical surveys display Cu, Au, Mo, Bi, Sb, Pb and As anomalies. The lithogeochemical prospecting in anomaly checking stage identified quartz veins with considerable abundances of Cu (2.98%) and Au (2.41 ppm). The ore-bearing quartz veins classify into quartz + iron oxides ± gold and quartz + sulfide ± gold. The dominant structural trend of vein systems is 60°–70° (NE-SW), with dips from 75° NW to vertical that cut altered andesite, porphyritic andesite, basaltic andesite and tuff. Mineral associations are quartz, adularia, chalcopyrite, pyrite, bornite, galena, sphalerite, as well as chalcocite, covellite, malachite, iron oxides and hydroxides in oxidized zones. Hydrothermal alteration is generally well-developed surrounding the ore-bearing systems. The main types of alterations in the area include propylitization, phyllic, and argillic associated with silicification. Fluid inclusions studies on quartz grains separated from mineralized veins exhibits the melting temperature of ice (Tm ice) values range from −12 to −1 °C corresponding to salinities of 2.5 to 37.04 wt% NaCl equiv. The superfluity LV fluid inclusions have salinity of 2.47 to 15.96 wt% NaCl equiv. The homogenization temperature of LV, VL and LVS fluid inclusions range from 146 to 366 °C, 405 to 425 °C and 236 to 270 °C, respectively. The fluid inclusions observations reveal that both dilution and boiling of fluids were important in the deposition of metals in the Govin. The δ34SCDT of pyrite and chalcopyrite grains associated with mineralized quartz veins range from −2.13‰ to −8.54‰ that indicate sulfur originated from host volcanic-sedimentary series in the area. The Cu-Au bearing quartz veins in the Govin area are classified as low-sulfidation epithermal system, located in closed association with the Sar-Cheshmeh and Darreh-Zar porphyry copper deposits.

Stream Sediment Geochemical Survey of Selected Element In Catchment Area Of Saguling Lake

Saguling Lake is one of the largest lakes in West Java Province that accommodates domestic and non-domestic wastes via the Citarum River as its main water source. This study aims to determine the geochemical background concentration (Cbg) in water catchment area of Saguling Lake. The knowledge of the Cbg of heavy metals is essential for defining pollution, identifying the source of contamination, and for establishing reliable environmental quality criteria for sediments. The value of Cbg will be used for assessment of the sediment quality in Saguling Lake. Assessment of sediment quality is very important to determine the actual condition of water in the lake and as the basis for management of waters environment in the future. The search was taken at 22 sampling points in the unpolluted water catchment area. Samples were collected and analyzed for Cd, Cr, Cu, and Pb. Each sample was digested in agua regia and analyzed by ICP-EOS. Results showed Cbg which are: Cd 0.34 ± 0.10 mg/kg, Cr 110.57 ± 28.61 mg/kg, Cu 49.93 ± 9.28 mg/kg, and Pb 18.62 ± 9.83 mg/kg. Based on the assessment result, it is concluded that the sediment quality in Saguling Lake is categorized as polluted by Cd, Cr, Cu, and Pb metals.

Big Data Analytics of Identifying Geochemical Anomalies Supported by Machine Learning Methods

Big data analytics brings a novel way for identifying geochemical anomalies in mineral exploration because it involves processing of the whole geochemical dataset to reveal statistical correlations between geochemical patterns and known mineralization. Traditional methods of processing exploration geochemical data mainly involve the identification of positive geochemical anomalies related to mineralization, but ignore negative geochemical anomalies. Therefore, the identified geochemical anomalies do not completely reflect the sought geochemical signature of mineralization, leading to uncertainty in geochemical prospecting. In this study, data for 39 geochemical variables from a regional stream sediment geochemical survey of southwest Fujian Province of China were subjected to big data analytics for identifying geochemical anomalies related to skarn-type Fe polymetallic mineralization through deep autoencoder network. The receiver operating characteristic (ROC) and areas under curve (AUC) were applied to evaluate the performance of big data analytics. The AUC of the anomaly map obtained using all the geochemical variables is larger than the AUC of the anomaly map obtained using only five selected elements known to be associated with the mineralization (i.e., Fe2O3, Cu, Pb, Zn, Mn). This indicates that big data analytics, with the support of machine learning methods, is a powerful tool for identifying multivariate geochemical anomalies related to mineralization.

Geochemical Stream Sediment Survey in the Wadi Umm Rilan Area, South Eastern Desert, Egypt: A New Occurrence for Gold Mineralization

Geochemical Stream Sediment Survey in the Wadi Umm Rilan Area, South Eastern Desert, Egypt: A New Occurrence for Gold Mineralization

Different spatial methods in regional geochemical mapping at high density sampling: An application on stream sediment of Romagna Apennines, Northern Italy

Geochemical mapping is a fundamental tool for environmental monitoring and land management. For this reason, regional-, national- and global-scale geochemical mapping projects have been carried out in various countries since the late 1960s. A high density regional stream sediment geochemical survey was carried out over an area of 4125km2 in the Romagna Apennines (Northern Apennines) by collecting 770 samples (1 sample per 5km2). The <0.180mm fraction was analysed for 30 elements by means of X-ray fluorescence spectrometry.The area has a complex geology dominated by sedimentary rocks, and characterised by various geological units, which belong to the Ligurian, Tosco-Umbrian and Padano-Adriatic palaeogeographical dominions. In the study area, the industrial sites and the largest towns are located on the plains, the agricultural areas are in the hills, and there is a wooded mountainous area in the upper reaches of the main streams.Various mapping techniques were used for presenting and interpreting the data: proportionally sized dots, Exploratory Data Analysis (EDA)-based symbols, Inverse Distance Weighted (IDW) interpolation and Sample Catchment Basin (SCB) mapping approach. Proportional dot maps indicate the lithological control of the geological units. EDA maps demonstrate that it might be easier to extract some information with relevant symbols and class divisions; moreover, the subdivision of a whole data set in separate populations, related to a specific grouping variable, highlights anomalous areas, which would not be visible in a general presentation. Finally, the comparison of IDW interpolation and SCB mapping techniques illustrates that significant anomalies related to geological and anthropogenic sources are better modelled when the geochemical landscape is represented as a discrete surface rather than a continuous surface. However, this study shows how the concentration of chemical elements cannot be presented properly with a standardised mapping technique in an area characterised by multiple factors. Indeed, the use of various mapping techniques highlights interesting features for understanding the effects of local geology or human impact.

Assessment of the potential occurrence of acid rock drainage through a geochemical stream sediment survey

During large constructions of roads or structures, unexpected acid rock drainage (ARD) can be caused by local mineralization containing sulfides in the geology. The potential of ARD occurrence of a certain area sometimes must be assessed before initiation of any engineering earth works. However, it is difficult to assess the entire area through collecting rock samples and predicting the potential by laboratory tests, such as the acid–base accounting method. In this study, a new prediction protocol using a geochemical exploration survey technique of stream sediment is proposed. Sediment samples were collected at the case study area where a large development is expected in the future, and the contents of some major and heavy metal elements were compared according to the major geologies of the sampling points. The modified geoaccumulation indices (Igeo) of Fe, Pb and As could indicate a possible zone of pyrophyllite mineralization, which may cause the occurrence of ARD at the study area. Using the enrichment index of the three elements relative to the median values of the area, a high potential zone of ARD could be designated, which was in agreement with the laboratory ARD prediction tests of the rock samples. In the other areas with different mineralization processes, other metallic elements can be selected as indicators of the ARD potential. Likewise, the potential of the occurrence of ARD at an area can be assessed by evaluating the geochemical distributions and drawing the indicator elements for ARD through a stream sediment survey.

Regional Geochemical Stream Sediment Survey for Gold Exploration in the Upper Lom Basin, Eastern Cameroon

Stream sediments are widely employed in reconnaissance exploration for gold especially in areas where outcrops are scarce and the overburden thick such as in the eastern Cameroon goldfields. In this study, 337 stream sediment samples were collected from the Lom river drainage basin. The study aims at identifying the main geological processes affecting the geochemical data from the sediments by considering the multi-elements relationships and spatial features of single elements. The samples were collected in duplicate. One set was panned, gold grains picked and weighed while the second set was wet sieved and the ≤100 microns size fraction retained. This fraction was eventually analyzed for gold by fire assay and a suite of elements by inductively coupled plasma mass spectrometry (ICP-MS). Single element maps were constructed using ArcGIS and the relationship between elements measured using Pearson correlation and principal component analysis (PCA). Gold concentrations in the samples are erratic, most below the detection limit and attain a high of 450 ppm. Five factors are derived from the PCA including single element factors for As and Au reflecting bedrock-hosted mineralization. The Cu-Zn-Y-Nb-Pb factor suggests sulphide mineralization perhaps related to felsic intrusions while the Sr-Ba-La-Ce-Zr factor is linked to lithologic control. These results demonstrate the usefulness of multi-element analysis and data interpretation using GIS tools in the exploration efforts for gold worldwide.