Concealed Mineral Deposits Research Articles

Metal nanoparticles in soil: Indicators of concealed mineral deposits

Metal nanoparticles in soil: Indicators of concealed mineral deposits

Subsurface Faults and Magma Controls on the Jinchuan Ni-Cu Sulfide Deposit: Constraints from Magnetotelluric Data

The Jinchuan Ni-Cu sulfide deposit in the Longshoushan terrane is among the world’s largest magmatic sulfide deposits. This study uses magnetotelluric (MT) survey data imaging combined with previous geophysical data to investigate Segment III of the deposit. The image of MT data reveals a significant low-resistivity anomaly ~200 m beneath Segment III, aligning with known ore bodies, and an additional anomaly to the north, indicating further exploration potential. These findings highlight the deep-seated intrusions and their connection to surface mineralization, emphasizing the critical role of ultramafic rock encapsulation and fault-controlled morphology in ore body formation. The newly identified northern anomaly, resembling the Segment III ore bodies, suggests a promising target for future exploration. Integrating MT surveys with other geophysical methods enhances the understanding of subsurface structures and mineralization, providing a robust framework for discovering concealed mineral deposits and improving exploration efficiency.

Geogas prospecting for igneous ore deposits covered by regolith: the Zijinshan high-sulfidation epithermal Cu–Au deposit in the Cathaysia Block

The mining industry faces a challenge due to the scarcity of outcrop or near-surface mineral deposits, necessitating the development of low-cost and efficient prospecting methods to explore through cover. Inductively coupled plasma mass spectrometry has been applied to geological sample analysis, and scientists have gradually improved the method of geogas prospecting. As a result, geogas prospecting has shown promising results in detecting underlying concealed Au, U and Cu–Ni deposits covered by Gobi sand and Quaternary sediments. To verify the effectiveness of this method for exploring underlying concealed mineral deposits developed in igneous covered areas, the Zijinshan high-sulfidation epithermal Cu–Au deposit, a concealed mineral deposit in southeastern China, was selected as the experimental field. Our experiments revealed nanoscale particles composed of Au, Cu–Fe and Cu–other elements in the geogas captured above the ore bodies of the deposit. Furthermore, Cu–nanoscale particles retain the isotopic composition of copper found in both the oxidation zone and deep copper ores. The geogas samples exhibited similar C1-chondrite normalized REE distributions, with REE patterns indicating significant enrichment of LREE relative to HREE and similar (La)N/(Sm)N and (Gd)N/(Yb)N ratios. These characteristics are similar to those of the gold ores, copper ores, altered rock and bedrock near the ore bodies. These findings suggest that deep-penetration geochemical methods using geogas can be a valuable tool for uncovering underlying concealed mineral deposits in igneous covered areas.

Single particle inductively coupled plasma mass spectrometry: A new method to detect geochemical anomalies in stream sediments

Single particle inductively coupled plasma mass spectrometry (spICP-MS) offers a new tool to explore for concealed mineral deposits. Through detection of metal nanoparticles (NPs) present in stream sediments, subtle geochemical anomalies may be identified farther from their source. Geochemical exploration with spICP-MS lowers the detection limit substantially from conventional ICP-MS for insoluble elements of interest. Analyzing only 197Au signal generated by individual NPs rather than an integrated signal, which can have a significant contribution from detector noise, resulted in a 53-fold reduction in detection limit compared to a digestion/quadrupole ICP-MS determination (21 ng∗L−1 to 0.39 ng∗L−1). Method development included analysis of dilute suspensions of manufactured 50 nm Au particles and three stream sediment samples (5–15 g sonicated in 20 mL 25 μM 11-mercaptoundeconoic acid). Au and Ag NPs were identified in the two sites downstream from a known area of mineralization, whereas none were detected in a background stream sediment site. Average particle numbers and masses of Au and Ag were highest in the sample closest to known mineralization. Additional results indicated that use of surfactant is an important contribution to the procedure. This pilot study of three sites provides a proof of concept in the analysis of spICP-MS for determination of Au and Ag in stream sediment samples, which could augment or improve current cyanide/acid dissolution/ICPMS methods for the ultra-trace concentration range.

Deep-penetration geochemical methods using geogas can uncover geological evidence of underlying concealed mineral deposits developed in volcanic rocks

Deep-penetration geochemical methods using geogas can uncover geological evidence of underlying concealed mineral deposits developed in volcanic rocks

Application of the fine-grained soil prospecting method in a loess-covered area of central China

Loess-covered landscapes occupy a large area of the globe and have substantially high potential for mineral exploration; however, as mineral information is obscured by loess cover, suitable prospecting techniques need to be applied. The fine-grained soil prospecting method—a deep-penetrating geochemical technology that can be used to identify concealed deposits—has been proven effective in some cases. In this study, we applied this method for mineral exploration in the loess-covered Luoning Basin in Central China. Our results revealed strong geochemical anomalies (e.g., Au, Ag, Pb, Zn, and Cu) over related and concealed ore deposits. Furthermore, a regional geochemical survey in the Luoning Basin revealed the spatial distribution and suites of elements that were consistent with the mineralization type. Moreover, higher geochemical anomalies of Au, Ag, Pb, and Zn were spatially related to an Au ore deposit and Ag–Pb–Zn polymetallic deposit, respectively. The results of a detailed geochemical survey in the Zhonghedi Ag–Pb–Zn polymetallic deposit further revealed that the distribution of surface element anomalies was associated with tectonic fractures throughout the exploration region, which are closely related to the distribution of orebodies. These results imply that the fine-grained soil prospecting method is suitable for anomaly delineation during detailed geochemical surveys as well as regional-scale surveys. Based on our results, we suggest that geochemical anomalies in the loess-covered surface in our study area are presumably the result of geogas dispersion processes; we provide a schematic model explaining how ore-forming and associated materials are brought to the surface by geogas flowing upwards along faults and fractures and, ultimately, accumulating in fine-grained loess soils. Overall, our research demonstrates that fine-grained soil prospecting can effectively aid the search for concealed mineral deposits in loess-covered landscapes.

Detection of Concealed Mineral Deposits using Magnetic Data in part of Osun State and its Environs, South-western Nigeria

Magnetic data of part of Osun State and its Environs, Southwestern Nigeria has been studied with the aim of identifying structures concealing mineral deposits through some enhancement techniques. These techniques are Analytic signal, Euler deconvolution, Center for exploration targeting and porphyry analysis. In this work we were have applied Analytic signal to identify edges and distribution of magnetic sources that are equivalent to concealed mineral deposits, Euler deconvolution was used to identify and estimate depth to various magnetic source geometries using prescribed structural indices of 0.0, 1.0 and 2.0 respectively and lastly, the center for exploration targeting and porphyry analysis was used to obtain magnetic lineaments and porphrytic intrusives that may serve as structures concealing mineral deposits. From this study, we were able to identify several volcanic intrusions which appeared beyond surface exposure and at the same time of Cenozoic era. These intrusions resulted from the high magnetic content which serves as a contributing factor for the presence of positive magnetic anomalies in the area. In conclusion, we have been able use magnetic data of Osun State and its environs to delineate structures concealing mineral deposits.

Three-Dimensional Mineral Potential Mapping for Reducing Multiplicity and Uncertainty: Kaerqueka Polymetallic Deposit, QingHai Province, China

This study focuses on the selection of a method combining simulations of mineralizing processes with three-dimensional (3D) mapping to quantitatively predict locations of concealed mineralization and to reduce uncertainty and multiplicity. The simulation of ore-forming processes for concealed mineralization requires the assessment of a region’s structural geology, ages of lithological units, degree of metamorphism, and role of magmatism in the genesis of mineralization. The evolution of various factors affecting the development of geological processes in space and time is discussed, including the assessment of models combining regional deformation-magmatic activity-mineralized hydrothermal fluid based on empirical knowledge. Given that metallogeny is a study of the genesis and regional distribution of mineral deposits and emphasizes their spatial and temporal relationships, this paper uses empirical knowledge to predict the locations of concealed mineral deposits. Furthermore, the analysis of 3D geological modeling of concealed orebodies is a process that contributes to understanding the metallogenesis of mineral deposits. In this study of the Kaerqueka skarn and porphyritic deposits, geological, geographic, remote sensing and geochemical data collected from this region are processed using computer modeling techniques available in the Surpac software to establish a digital representation of the mineral field. The “block mapping modeling” theory, geostatistical methods, simulations of ore-forming processes, and 3D mapping methods are then combined to predict the locations of the most promising areas for concealed mineral deposits around the Kaerqueka deposit. This research introduces a new method for predicting and evaluating the locations of concealed orebodies by reducing multiplicity and uncertainty.

Identification of metal sources in Geogas from the Wangjiazhuang copper deposit, Shandong, China: Evidence from lead isotopes

The Geogas survey has been confirmed to be a useful geochemical pathfinder in prospecting for mineral deposits concealed beneath various types and thicknesses of overburden. To understand the sources of metals in Geogas, the lead isotopes were chosen as tracers. The Pb isotope ratios in soil, host rocks and ores were determined following separation and purification by Nu Plasma HR Ionization Mass Spectrometer and those in Geogas samples were analyzed by HR-ICP-MS (High Resolution Inductively Coupled Plasma-Mass Spectronmetry) (Element 2) and iCAP Q-ICP-MS (Quadrupole Inductively Coupled Plasma-Mass Spectronmetry) with optimized operating parameters. The utilization of HR-ICP-MS and iCAP Q-ICP-MS can be effective in determining extremely low levels of Pb isotopes and make great progress in analytical precision and sensitivity to render the test data and experimental results more convincing. The results of this study of different samples collected at the Wangjiazhuang Cu deposit show that Pb isotope ratios of Geogas background samples are apparently different from those of various media (soil, host rocks and ores) in the vicinity of the ore bodies. The Pb isotope ratios in Geogas anomalous samples are quite distinct from those in Geogas background samples. The Pb isotope ratios of Geogas anomalous samples scatter close to ores. It is assumed that the anomalous Pb in Geogas samples came mainly from deeply concealed mineral deposits, this research provides much more reliable evidence for the explanation of Geogas anomalies and further demonstrates that the Geogas technique is a viable tool to identify deeply buried mineralization under exotic overburden.

Identifying geochemical anomalies associated with Cu mineralization in stream sediment samples in Gharachaman area, northwest of Iran

The aim of this paper was to delineate Cu anomalies in the eastern part of Gharachaman 1:100,000 sheet, which was located in Sahand–Bazman magmatic belt, northwest of Iran. The sample catchment basin (SCB) technique was applied on stream sediment data to prospect Cu and its related pathfinder at Gharachaman area; then the concentration–area (C–A) multifractal model was performed on positive Cu and Mo residuals to separate different population and mapping anomalies. The spatial distributions of residuals Cu and Mo, based on threshold values via C–A multifractal analysis, showed high anomaly in the northeast and southeast of the studied area, where intrusive rocks were underlain by the basaltic breccias. Furthermore, principle component analysis (PCA) was conducted on the results of SCB technique in order to determine multi-element geochemical signatures that reflected the presence of mineralization. As a result, four components were defined which could explain nearly 83% of the variability. Meanwhile, PC3 represented a Cu–Mo association and reflected a multi-element mineralization related to the hydrothermal Cu deposit occurrence. Finally, the C–A analysis was performed on positive scores of PC3. The PC3 scores map displayed less anomalous areas than uni-element of residual Cu map, probably due to the characteristic of PCA method that eliminated false anomalies. Studies proved that using this hybrid method (SCB and PCA) could be a useful technique to recognize the stream sediment anomalies in the preliminary stages of prospecting concealed mineral deposits.

Tracing the source of ‘Metals in Soil Gas’ with Pb isotope ratios at the Jiaolongzhang base metal deposit, north-western China

The ‘Metals in Soil Gas’ (MSG) survey has proven to be a useful tool for mineral exploration under exotic overburden. Tracing the source of these metals with Pb isotopes is helpful to understand the formation of MSG. Lead isotope ratios in MSG samples were determined by ICP-MS (Model HP4500); the Pb isotope ratios in loess, red soil, wall rocks and ores were measured following decomposition and separation using a VG-354 thermal ionization mass spectrometer (TIMS) for comparison. The results of the study of samples collected over the Jiaolongzhang base metal deposit show that the Pb isotope ratios of MSG background samples are markedly distinct from those ratios of any medium (loess, red soil layer, wall-rocks and ores) in the vicinity of the deposit. The Pb isotope ratios in the MSG anomalous samples ( 206 Pb/ 204 Pb = 18.34–18.56, 207 Pb/ 204 Pb = 15.622–15.809 and 208 Pb/ 204 Pb = 38.184–38.691) are totally different from those in the samples of background areas ( 206 Pb/ 204 Pb = 16.46–17.68, 207 Pb/ 204 Pb = 13.985–14.945 and 208 Pb/ 204 Pb = 34.199–36.884). The Pb isotope ratios of MSG anomalous samples scatter near the ratios of the mineralized wall-rocks ( 206 Pb/ 204 Pb = 18.554–18.874, 207 Pb/ 204 Pb = 15.618–15.755 and 208 Pb/ 204 Pb = 38.629–39.126) and sulphides ( 206 Pb/ 204 Pb = 18.130–18.251, 207 Pb/ 204 Pb = 15.671–15.767 and 208 Pb/ 204 Pb = 38.350–38.582). It can be concluded that some of the Pb in MSG anomalous samples originates from deep sulphide mineralization and Pb isotope ratios of MSG anomalous samples indicate that an MSG survey can detect the deeply concealed mineral deposits under exotic cover.

Further study on deep penetrating geochemistry over the Spence porphyry copper deposit, Chile

A study of deep penetrating geochemistry—the surface exploration techniques for finding concealed mineral deposits—was carried out over the Spence porphyry copper deposit in Chile by Australian, Canadian and Chinese laboratories using selective weak leach methods and is briefly reviewed here. Erratic and weak copper anomalies were obtained above the Spence deposit, which is concealed below a thick piedmont gravel cover. In the literature, such patterns are common in most of the weak selective leach studies carried out over known buried deposits. During exploration in unknown area, such weak leach techniques lead to some success and many dry holes. In this paper, stronger selective leaching methods are developed for oxides and sulfides, which may be the stable end products transformed and accumulated by a mobile precursor phase carried upward through the overburden by gas or water through long spans of geological time. The data obtained by the methods developed in this paper produced more significant and consistent anomalous data than previous efforts. Consequently, the leach approaches described here may increase the effectiveness of deep penetrating geochemistry in exploration for concealed ore deposits.

TEM observation of geogas-carried particles from the Changkeng concealed gold deposit, Guangdong Province, South China

Geogas prospecting is a relatively new technique in exploration for deep-seated and concealed mineral deposits. Now, the technique is to reveal the presence of concealed ore bodies by analyzing the element concentrations of substances that are transported by geogas from concealed ore bodies to the Earth's surface. However, the element concentrations provide us with limited information about the concealed ore bodies. In our work, to investigate the category, size, shape, chemical component of geogas particles, copper grids for transmission electron microscopy measurement were directly used to capture the geogas-carried solid particles in Quaternary sediments overlying the Changkeng concealed gold deposit, Guangdong Province, South China. In the samples, we found Au, PbSO 4, WO 3, Fe 2O 3, SiO 2, TiO 2, and Al 2O 3 particles, etc. using a transmission electron microscopy. Of which, gold particles, and Hg-, Zn-, Pb-, W-bearing particles may originate from concealed ore bodies and can provide more direct information than those provided by element concentrations.

Aeromagnetic data analysis for the identification of concealed uranium deposits: a case history from Singhbhum uranium province, India

Abstract Aeromagnetic data over a part of the Singhbhum uranium province, India, within the framework of ‘Operation Hard Rock’ have been analyzed. The aeromagnetic anomaly map, its analytic signal amplitude, the Euler solutions and apparent susceptibility map helped in identifying the nature and depth of the magnetic sources in the study region. The Singhbhum Shear Zone is clearly delineated. The location of the mined uranium deposits coincide with the shallow magnetic sources. The present study also identified distinctive magnetic sources between the Dalma Volcanics and the Chotanagpur Granitic Gneissic Complex that suggest the presence of a sub-surface shear. The magnetic sources in this newly identified shear zone lie at a depth of 200 m and depict a similar magnetic signature and susceptibility as those of the Singhbhum Shear Zone where uranium is being mined. This shear could be the subsurface contact between high-grade metamorphic rocks (amphibolite facies) to the north and the greenschist facies low-grade metamorphics to the south. This shear zone, also characterized by radiometric anomalies, possibly indicates a zone of concealed uranium deposit that can be explored in the future. The present analysis shows the importance of aeromagnetic surveys and its utility in exploration for concealed mineral deposits.

RESEARCH ADVANCE IN PREDICTION THEORY AND METHODS OF CONCEALED MINERAL DEPOSITS

Concealed mineral deposit prognostic is one important forward position problem of economical geology up to date. Geosciences have thoroughly done a vast amount of research work at different subjects and angles, and set up some new theories and methods, including model theory and method, theory of ore and petrology formation controlled by tectonics and structures methods, geochemistry theory and method, physical method, mathematics geology, petrologic and mineral methods, which have been used to prognostic and discover successfully some concealed mineral deposits. This paper has reviewed and summarized simply the advances in prediction theory and methods of concealed mineral deposits in recent twenty years, finally put forward that great science, great corporation and industrialization will be the main trends of research on prediction and methods of concealed mineral deposits.

Application of enhanced satellite-borne images to the relationships between fractures and mineralization in the nam Mae moei-nam Mae Ping area, northern Thailand

The study area is located in the Chiang Mai, Tak, and Mae Hong Son provinces of northern Thailand. Digitally enhanced Landsat TM5 and SPOT images and data on economic minerals deposits were used in the investigation. High-pass filtering and principal component analyses were determined to be the most appropriate enhancement methods. Space-borne image interpretation indicates two major faults: the north-trending Mae Hong Son and the northwest-trending Mae Ping. Both large-scale faults are inferred to be closely related to substantial, nearly parallel folds and thrusts. The four main sets of lineaments observed (north-south, northeast-southwest, northwest-southeast, and east-west) are considered to have an essential role in the occurrences of various mineral deposits. Mineral exploration has emphasized areas where several sets of lineaments cross-cut each other, since the possibility of finding concealed ore bodies or potential target areas is considered quite high. Some sets of lineaments probably control post-Triassic granitoid emplacements both directly and indirectly. Three major granitoid series are recognized in the study area: the Mae Lama (ca. 70 Ma), the Tae Song Yang (ca. 45 Ma), and the Mae Sariang (205–210 Ma) Granites. These peraluminous, S-type granites are closely related to tin, tungsten, and fluorite deposits. Fluorite, barite, manganese, and antimony deposits may be related to the northtrending lineaments. Stibnite deposits may be related to the northeast-trending lineaments. The tin/tungsten deposits are likely related to the east- and northwest-trending lineaments. Ovoid-shaped lineaments, found only at a few locations, are interpreted to indicate the granitoid emplacement and are thought to be important in the generation of concealed mineral deposits. We conclude that the existence of such lineaments is related to the post-Triassic abutment and collision of the Shan-Thai, Indochina, and Western Burma microcontinental blocks.

Preliminary studies of the CHIM electrogeochemical method at the Kokomo Mine, Russell Gulch, Colorado

Abstract The CHIM electrogeochemical exploration technique was developed in the former Soviet Union about 20 years ago and is claimed to be effective in exploration for concealed mineral deposits that are not detectable by other geochemical or geophysical techniques. The method involves providing a high-voltage direct current to an anode and an array of special collector cathodes. Cations mobile in the electric field are collected at the cathodes and their concentrations determined. The U.S. Geological Survey started a study of the CHIM method by conducting tests over a precious- and base-metal-bearing quartz vein covered with 3 m of colluvial soil and weathered bedrock near the Kokomo Mine, Colorado. The tests show that the CHIM method gives better definition of the vein than conventional soil geochemistry based on a total-dissolution technique. The CHIM technique gives reproducible geochemical anomaly patterns, but the absolute concentrations depend on local site variability as well as temporal variations. Weak partial dissolutions of soils at the Kokomo Mine by an enzyme leach, a dilute acetic acid leach, and a dilute hydrochloric acid leach show results comparable to those from the CHIM method. This supports the idea that the CHIM technique is essentially a weak in-situ partial extraction involving only ions able to move in a weak electric field.

Lead isotopes in iron and manganese oxide coatings and their use as an exploration guide for concealed mineralization

Lead isotopes from Fe and Mn oxides that coat stream pebbles from around the Mount Emmons porphyry molybdenum deposit in Colorado were studied to assess the feasibility of using Pb isotopes to detect concealed mineral deposits. The Fe/Mn oxide coatings were analyzed to determine their elemental concentrations using ICP-AES. The Pb isotope compositions of solutions from a selected suite of samples were measured, using both thermal ionization and ICP mass spectrometry, to compare results determined by the two analytical methods. Heavy mineral concentrates from the same sites were also analyzed to compare the Pb isotope compositions of the Fe/Mn coatings with those found in panned concentrates. The Fe/Mn and 206Pb/ 204Pb ratios of the oxide coatings are related to the lithology of the host rocks; Fe/Mn oxide coatings on pebbles of black shale have higher Fe/Mn values than do the coatings on either sandstone or igneous rocks. The shale host rocks have a more radiogenic signature (e.g. higher 206Pb/ 204Pb) than the sandstone or igneous host rocks. The Pb isotope data from sandstone and igneous hosts can detect concealed mineralized rock on both a regional and local scale, even though there are contributions from: (1) metals from the main-stage molybdenite ore deposit; (2) metals from the phyllic alteration zone which has a more radiogenic Pb isotope signature reflecting hydrothermal leaching of Pb from the Mancos Shale; (3) Pb-rich base metal veins with a highly variable Pb isotope signature; and (4) sedimentary country rocks which have a more radiogenic Pb isotope signature. An investigation of within-stream variation shows that the Pb isotope signature of the molybdenite ore zone is retained in the Fe/Mn oxide coatings and is not camouflaged by contributions from Pb-rich base-metal veins that crop out upstream. In another traverse, the Pb isotope data from Fe/Mn oxide coatings reflect a complex mixing of Pb from the molybdenite ore zone and its hornfels margin, Pb-rich base-metal veins, and sedimentary country rocks. Stream-sediment anomalies detected using oxalic acid leaches can be evaluated using Pb isotope analysesof selected geochemical anomalies. Such an evaluation procedure, given regional target Pb isotope signatures for concealed mineralization, can greatly reduce the cost of exploration for undiscovered ore deposits concealed beneath barren overburden. Lead isotope measurements on aliquots of the same solutions showed that ICP-MS determinations are of low precision and vary non-systematically when compared with the Pb isotope values of the higher precision thermal ionization method. These variations and lower precision of the ICP-MS measurements are attributed to matrix effects.

Multiple gas analyses using a mobile mass spectrometer

Abstract A truck-mounted mass-spectrometer gas analyzer is described and field examples of its use are given. This unit provides a gas analyzer that can be used in the field to rapidly analyze a large number of gases. It has enabled us to establish that gas anomalies occur over a variety of deposit types and in different environments. Gases may prove to be useful geochemical indicators in exploration for concealed mineral deposits.

Dispersion into pisolitic laterite from the greenbushes mineralized Sn-Ta pegmatite system, Western Australia

A study of dispersion into pisolitic laterite duricrust in the Archaean Greeenbushes mineralized pegmatite district reveals a geochemical anomaly that measures some 20 km by 12 km centred on the ore deposits that, prior to commencement of mining operations, were concealed. The anomaly is broadest for As, Sn, Be and Sb, all of which show well-defined centres over the swarm of mineralized pegmatites. Coincident highs of Nb, Ta and B also define the 5 km by 1 km anomaly centre. Over the strongest part of the multi-element anomaly, the following levels in ppm are reached in the pisolitic laterite: As 1150, Sb 75, Sn 4200, Nb 75, Ta 75, W 30, Li 100, B 500 and Be 60. The immediate source for the dispersion anomaly is the swarm of soft, weathered pegmatites and their wall rocks, most of which occur within a 5 km by 1 km area, elongated along strike. The source, as judged from past production plus soft pegmatite reserves, was a mass of some 30–40 million tonnes with an approximate average grade of 220 ppm Sn, 25 ppm Nb and 30 ppm Ta. The geochemical expression of the multi-element anomaly can conveniently be expressed in a map of pegmatite-associated elements. For example, the index PEG-4*X which uses an empirically derived weighted linear combination 0.09As + 1.33Sb + Sn + 0.6Nb + Ta (where values for each element are in ppm) gives a broad consistent anomaly. Investigation of dispersion processes shows that mechanical dispersion of cassiterite and columbo-tantalite took place for distances of at least 5 km during laterite formation along gradients ranging from 5 m to 20 m per km. The occurrence of anomalous As in the skins of pisolites indicates hydromorphic dispersion during laterite formation, but mechanical dispersion of goethitic material with scavenged As has also taken place. The size of the geochemical dispersion anomaly, together with its contrast and consistency, shows that it is feasible in the Australian environment to explore for concealed mineral deposits using low-density surface sampling. Sample spacings of 3 km are being tested in an extension of this approach to exploration.