Buried Deposits Research Articles

Metal migration at the DeGrussa Cu-Au sulphide deposit, Western Australia: Soil, vegetation and groundwater studies

Transported overburden is a persistent problem for mineral exploration in Australia and elsewhere, with explorers not confident in the current understanding of where, when and how geochemical anomalies form (or don't form) in surficial materials and how to make the critical interpretive link to buried deposits. The recent discovery of the high-grade VHMS Cu-Au DeGrussa deposit on the margins of the Yilgarn Craton in the Bryah Basin of Western Australia highlights the value of effective exploration in these covered terrains. We investigated this deposit to understand the near surface geochemical signature from weathering and groundwater dispersion. Multiple sample media (soil, regolith, groundwater and vegetation) and analytical methods were used to examine metal migration. The DeGrussa (Cu-Au) ore body was successfully identified using organic soil, vegetation and groundwater with multi-element anomalies associated with the buried ore. Primarily, the anomalies are caused by weathering and vertical dispersion through thin (2 – 10 m) transported cover and vegetation cycling of Au and Cu located a few metres below the surface. Aqua regia extractions of soils and vegetation, and MMI-M extraction of soils were effective by providing strong, coherent multi-element anomalies at relatively close spacing (50 m). Conversely, portable XRF analysis was less effective at this site as the elemental concentrations were too low. Gold, As and Cu in groundwater were present in anomalous concentrations, but inconsistently so at larger sample spacing (100 s of metres). When compared to regional hydrogeochemistry (e.g. >1000 m spacing), Au, As, Cu, Pd and Pt element concentrations in the DeGrussa groundwater were elevated in a broad, general area along strike potentially identifying additional targets. Weathering, hydraulic lift by vegetation and hydromorphic dispersion are the mechanisms responsible for metal migration at the DeGrussa site.

Surficial geology of the Woodstock, IL 7.5 minute Quadrangle, Mchenry County, Illinois, scale 1:24,000

ABSTRACTThe surficial geology of the Woodstock 7.5-minute Quadrangle, which is located in the northwest part of the Chicago-Metropolitan Area, was mapped to better address natural resource issues and better understand local geologic history. In the study area, the population is dependent completely upon groundwater for water supplies, and groundwater withdrawals are expected to increase dramatically in coming decades. The landscape and surficial geologic materials in the Woodstock Quadrangle are a result of numerous glaciations during the Quaternary. Surficial sand and gravel deposits, along with buried outwash deposits from older glacial events, constitute important aquifer and aggregate resources for local residents and industry. The landscape within the Woodstock Quadrangle includes glacial moraines, ice-walled lake plains, kettles, incised valleys, and glacial lacustrine deposits. These landforms, coupled with the thick glacial sediments, record a complicated geologic history associated with glacial processes and paleoclimate change. The surficial geologic map of the Woodstock Quadrangle consists of seven lithostratigraphic units associated with the most recent Wisconsinan glaciations in North America. These geologic units include multiple till deposits, outwash sediments, lacustrine sediments, and modern alluvium and peat deposits. This map provides the base geologic knowledge for planners, decision-makers, and other scientists.

Pyrrhotite mineralization as a search criterion for sulfide deposits at sediment-covered spreading centers

Pyrrhotite ores forming the hydrothermal vents of the Hydrothermal Hills in the Southern Trough of the Guaymas depression were studied. A series of features pointing to the occurrence of surface and buried sulfide deposits of pyrrhotite mineralization was revealed: the presence of pyrrhotite associations to hydrocarbons of oil series; low concentrations of Cu, Zn, and Pb; the enrichment of sulfur of pyrrhotite and hydrogen sulfide of hydrothermal solutions in heavy 34S isotope by 5–7%; and the heavy isotope composition of carbon in naphthoid compounds. The results obtained allow one to suggest searching for large sulfide deposits at active rifts of high spreading and sedimentation rates, i.e., at near-continental rifts of the humid zone of avalanche sedimentation.

The discovery and geophysical response of the Atlántida Cu–Au porphyry deposit, Chile

The discovery of the Atlántida Cu–Au–Mo porphyry deposit, which is unconformably overlain by 25–80 m of gravels, is a recent example of exploration success under cover in a traditional mining jurisdiction. Early acquisition of geophysics was a key tool in the discovery, and in later guiding further exploration drilling throughout the life of the project. Detailed review of the geophysical response of the deposit, with respect to the distribution of lithologies and alteration, coupled with their petrophysical properties has allowed full characterisation, despite no exposure at the surface of host rock nor porphyry-style mineralisation. Data acquired over the project include induced polarisation, magnetotellurics, ground and airborne magnetics, ground-based gravimetry, and petrophysical sampling.The distribution of the key geological features of the deposit has been inferred via acquisition of petrophysical properties and interpretation of surface geophysical datasets. Magnetic susceptibility is influenced strongly by both alteration and primary lithology, whilst density variations are dominated by primary lithological control. Several studies have shown that electrical properties may map the footprint of the hydrothermal system and associated mineralisation, via a combination of chargeability and resistivity. These properties are observed in geophysical datasets acquired at surface and allow further targeting and sterilisation at the deposit and project scale.By understanding these geophysical characteristics in a geological context, these data can be used to infer distribution of lithological units, depth to exploration targets and the potential for high grade mineralisation. Future exploration will likely be increasingly reliant on the understanding of the surface manifestations of buried deposits in remotely acquired data. This review summarises the application and results of these principles at the Atlántida project of northern Chile. Geophysical data can be used to improve the chances of discovery beneath post-mineral cover, and also improve drilling results throughout the advanced exploration of the program. The process of data review against geological control information is essential.

The cause of arsenic contamination of groundwater in Cat Tien district, Lam Dong province

Five positions were drilled with the depth of 45 metres, in order to research the source of arsenic contamination in groundwater in Cat Tien district, Lam Dong province. In the Cat Tien district, high concentratring of arsenic are found in both of the Holocene (adQ) and Pleistocene (J2ln) aquifers. Reduction of FeOOH(As) and reduction of arsenic poverty ore types to release arsenic to solution, are main mechanisms to explain the arsenic pollutes groundwater in Cat Tien district. The high concentration of arsenic in the sediments of the Cat Tien delta and the occurrence of reducing conditions were essential conditions to explain the extreme degree and extent of arsenic pollution. Elevated arsenic pollution would be due to the biodegradation of buried peat deposits which caused the high reduction of FeOOH(As) and affored supplied high concentration of arsenic to the groundwater.

Water on the Moon

AbstractAfter years of thinking the Moon is dry, we now know there are three manifestations in which water appears on the Moon today: 1) Previously hypothesized buried deposits of volatiles at the lunar poles were found at Cabeus crater. There are questions about the origin of such volatiles (i.e., in-falling comets & meteorites, migration of recently formed surficial OH/H2O, and accumulated release from the interior), but there is no doubt the water is there. 2) Widespread, thinly-distributed, surficial OH (or H2O) has been clearly detected across all types of lunar terrain. The consensus is that the OH is derived from solar wind, but we do not know how quickly it forms, nor how mobile it is. 3) The amount of water present soon after the Moon formed is now documented in new analyses of lunar materials in volcanic glass beads, apatites and plagioclase feldspars. Apollo era sample analyses were not precise enough to distinguish between indigenous lunar water and terrestrial contamination. Measurements with modern equipment are more precise (both elemental and isotopic), and can better constrain a host of processes (e.g. diffusion, thermal cycling). Scientists around the world are studying lunar water. Ongoing analyses are informing a number of hypotheses and theories about the connection between the Earth and its wet Moon.

A new approach to isotope dating of buried organic-rich deposits with an example from the Kuryador section, upper Vychegda valley

A new approach to isotope dating of buried organic-rich deposits with an example from the Kuryador section, upper Vychegda valley

Pilot study of partial extraction geochemistry for base metal exploration in a thick loess-covered region

The Jiaolongzhang polymetallic deposit in Eastern Gansu is located under loess terrains with thicknesses ranging from <50m to >200m. The mineralization zones are completely covered by loess and by a red soil layer. A soil survey along Line 48 by using the total digestion technique at a depth of 30cm showed no responses for deposit-related elements Pb, Zn, Cu, and Ag. Different top soil leachants and leaching procedures were tested, and several elements were analyzed by using ICP–MS to decipher the leaching geochemistry in a loess terrain. Deionized water, NH4Cl, and HOAc did not detect any signals for the buried deposits, whereas 2% HCl leaching effectively detected buried deposits. Strong multi-point anomalies were found in many elements above the concealed ore bodies. The highest Cu, Pb, and Zn concentrations reached 800, 2000, and 8000ng/g in the anomalous samples, respectively, and reached 200, 70, and 400ng/g in the background samples, respectively. The elemental distribution patterns corresponded with the results of the metals-in-soil-gas survey. Most pH values of soil in background and anomalous samples were higher and lower than 8.45, respectively; thus, the pH values corresponded to a pattern of reduced chimneys.

Preservation of ancient ice at Pavonis and Arsia Mons: Tropical mountain glacier deposits on Mars

Large tropical mountain glacier (TMG) deposits on the northwest flanks of the Tharsis Montes and Olympus Mons volcanoes are interpreted to be the record of ancient climates characteristic of Mars several hundred million years ago when planetary spin-axis obliquity was ~45°. During this era, polar volatiles (predominantly H2O) were mobilized and transferred equatorward, undergoing adiabatic cooling on the Tharsis volcano flanks, and precipitating snow and ice to form cold-based tropical mountain glaciers up to several kilometers in thickness. Subsequent climate change resulted in retreat, sublimation and collapse of the tropical mountain glaciers, leaving the three typical facies observed today: (1) concentric ridges, the ridged facies, interpreted as drop moraines; (2) knobby facies, interpreted as debris-dominated sublimation residue; and (3) the smooth facies, interpreted as remnant alpine glacial deposits. Ring-mold craters (RMCs) are distinctive features formed by impacts into debris-covered ice. We describe a set of relatively fresh ring-mold craters superposed on the Arsia and Pavonis Mons TMG deposits; we interpret these to indicate that the impact events penetrated a veneer of sublimation lag and excavated buried remnant glacial ice, despite the lack of detection of buried ice by orbital radar instruments. The diameter distribution of the RMCs suggest that the remnant ice lies at a depth of at least 16m. The TMG deposit ages suggest that these ice deposits date from a period in the range of 125–220 million years before the present; the remnant ice may thus preserve records of the ancient atmospheric gas content and microbiota, as is common in terrestrial glacial ice. Preservation of this ice and the lack of any associated fluvial features suggest that the post-glacial climate has been cold, and related surface temperatures have not been sufficient to bring the buried deposits to the melting point of water.

Deep-penetrating geochemistry of the Tuwu copper deposit, northwestern China

Desert terrains in northern China are covered by widespread regolith sediments which mask geochemical signals from ore bodies and are major obstacles to mineral exploration. There is a critical need to study the vertical distribution of elements in this regolith and to establish optimum sampling and analytical methods. The aim of this study is to understand the dispersion and variation of elements throughout the cover in a vertical profile. The results demonstrate that the main elements show a distribution pattern of enrichment in clay layers in the vertical profile, i.e., most elements tend to be enriched in the most upper part of the profile above the orebodies except for some elements like Cu, Ca and Ag. Meanwhile, both fine (−160 mesh) and coarse (+20 mesh) fraction samples from clay-rich horizons are favorable samples and selective leaching of the elements absorbed on clays or oxide coatings is effective for localizing buried deposits. The distribution of active Cu and Mo is quite different because chalcopyrite is weathered into Cu sulfate and CuCO3, and is precipitated in alkaline environments in a layer below close to the surface. Mo is soluble in the alkaline environment so it can penetrate the caliche layer and be enriched on the surface of soil enriched with weakly cemented clay.

A Spatial Measurement and Statistics Method to Forecast Ore Deposits

This study used spatial measurement and statistics methods to investigate spatial relationship between ore deposits and fractures in Liaoning province of China. Firstly, bivariate J function found that the ore deposits have a clustering trend around the fractures. Secondly, a conditional intensity formula for ore deposits based on Poisson process was used to model the ore deposits spatial dependence on the fractures, and the formula of model was fitted in statistics software called R. Finally, the fitted model was used to predict high intensity areas of buried ore deposits based on locations of visible fractures, which could be used to guide ore deposit exploration.

Metal migration at the North Miitel Ni sulphide deposit in the southern Yilgarn Craton: Part 3, gas and overview

Gases provide a known mechanism of metal migration through cover and a potential sampling medium to explore through cover that is under-utilised and under-studied. Understanding how metals move through transported cover and their link to buried deposits is critical information for successful mineral exploration in many regions of the world including the well-endowed Yilgarn Craton of Western Australia. Here we employ metal and hydrocarbon soil gas collection methods to successfully predict the location of the underlying North Miitel Ni ore body. Laboratory experiments to replicate soil moisture, hypergeometric evaluation and variable spacing tests were used to verify the gaseous Ni signature. Soil gas hydrocarbon analysis also reported an unqualified, but positive result. Integrating this study with previous research on soil, regolith, groundwater and vegetation chemistry in the study area enabled a model of anomaly formation to be derived explaining the observed results and the contributions of weathering, hydromorphic, biotic, aeolian and gaseous dispersion mechanisms operating at the North Miitel site. Weathering and hydromorphic dispersion are responsible for lateral and minor vertical Ni migration at depth, aeolian Ni is dispersed laterally near the road, whereas vegetation is cycling Ni in the shallow soils only. Results indicate a gaseous migration of Ni is responsible for vertical migration through cover at this site and provides a viable target for exploration through 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.

The first case study of 230Th/U and 14C dating of mid-valdai organic deposits

From the viewpoint of precision and reliability of radioisotopic dating, deposits whose quantitative age can be determined through several methods of geochronometry are of special interest. The mutually conforming finite 14C and 230Th/U dates of buried Neopleistocene organic deposits, taken from the Tolokonka section by the North Dvina River (100 km downstream from the city of Kotlas), have been obtained for the first time in Russia. The stratigraphical reference of these results to those obtained via the optically induced luminescence for upper and lower bedding layers has been established. The presented geochronometric data have allowed us to consider the age of oxbow lake organic deposits completely reliable and refer the time of their formation to the Tyrbei warming within the MIS-3. The applicability of the new version of the 230Th/U method for dating of interglacial and interstadial deposits, for the purpose of solving the Middle and Late Neopleistocene chronostratigraphy issues, is confirmed.

Massive CO 2 Ice Deposits Sequestered in the South Polar Layered Deposits of Mars

Shallow Radar soundings from the Mars Reconnaissance Orbiter reveal a buried deposit of carbon dioxide (CO(2)) ice within the south polar layered deposits of Mars with a volume of 9500 to 12,500 cubic kilometers, about 30 times that previously estimated for the south pole residual cap. The deposit occurs within a stratigraphic unit that is uniquely marked by collapse features and other evidence of interior CO(2) volatile release. If released into the atmosphere at times of high obliquity, the CO(2) reservoir would increase the atmospheric mass by up to 80%, leading to more frequent and intense dust storms and to more regions where liquid water could persist without boiling.

瀬戸内海中部・出崎海岸（岡山県玉野市）における埋没泥炭層の再検討&amp;mdash;特に完新世中期の相対的海水準変動との関係について&amp;mdash;

瀬戸内海中部・出崎海岸（岡山県玉野市）における埋没泥炭層の再検討&amp;mdash;特に完新世中期の相対的海水準変動との関係について&amp;mdash;

Ecological Geochemical Investigations of the Contents of Heavy Metals in the Snow Cover in the Saint-Petersburg Region with Application of GIS Technologies

The present paper considers the results of ecological geochemical studies of the snow cover in the region of Saint- Petersburg. The studies have been conducted with application of GIS technologies: spatial distributions of concentrations of heavy metals in snow mantle have been estimated; values of the regional snow-chemical background are presented for a series of metallic elements; for each of the elements examined, the identified territories of snow-chemical anomalies are shown. Keyword: geoecology, heavy metals, snow-chemical anomalies, GIS Technologies, Saint-Petersburg Region. Discharges of poisonous substances to atmosphere in megalopolises amount to hundreds of thousands and millions tons per annum. The presence of correlations between the substances polluting the atmospheric air and their contents in snow cover allow us to use the latter type of depositing medium for fast geochemical estimation of the total level of pollution of urbanized territories (1). Snow-chemical anomalies, in essence, indicate the ecological and geochemical state of the atmosphere, summing up the effects of natural atmogeochemical (Earth degasification), natural and anthropogenic atmogeochemical (gaseous formations in buried deposits of pit etc.) and purely anthropogenic (industrial emissions), influencing the dynamics of the geochemical ecological function of the lithosphere in time (2). Snow cover mirrors the contours of the aerogenic pollution within the time-span of its formation, allowing us to make ideas on the dynamics of the processes occurring. The characteristics of anthropogenic anomalies in such depositing mediums as snow cover may be considered as indirect indicators of the pollution of the air basin, directly displaying the intensity of geochemical transformation of the surface section of the lithosphere. During the periods of snow melting, the toxicants present in the snow migrate to the surface waters, bottom deposits, soils and rock substrata, the area of their spread exceeding considerably the contours of the snow-chemical anomalies. The relative simplicity of snow-chemical surveys enables to conduct large-scale investigations of territories in order to estimate the spacial distribution of polluting substances, determine the geochemical background and to delineate the areas with anomalous values of the parameters under study. The utmost attention during ecological geochemical

About retardation of a physicochemical processes in overpressured sediments, South-Caspian basin, Azerbaijan

In paper the role of excess pressures in cata- genic processes of the South-Caspian basin (SCB) is considered. The results of the carried out researches taking into account world ex- perience on the given problem allow to con- clude, that SCB (mainly its deep-water part), as well as a number of other basins of the world with overpressures, is characterized by retarda- tion of processes cracking of kerogen and oil, and also reaction of transformation of clay minerals. Periodic intensification of these pro- cesses can provoke development of diapirs and mud volcanoes, which are the centers of pulse unloading of a hydrocarbon products from sys- tem. The conclusion about high prospects of revealing of hydrocarbon accumulations in deep buried deposits in overpressured basins is made.

Identification of Sediment routing process in Beach-Dune Systems with consideration of Sedimentary Environments

The sediment routing process in natural beach-dune systems plays an important role for sustaining the topography of sandy beach. Recent practices of coastal protection, however, tend to suppress sediment transfer between a coastal dune and the fronting sandy beach, reducing resilience of the beach subject to severe wave forcing. This study explores linkage between the beach and dune processes. The resistivity explorations and surface-wave prospecting performed on the coastal dune identified the sedimentary architecture of it, in conjunction with examination of existing borehole logs. Notably, there occurs a buried deposit of old sandy dune below the current beach surface. Furthermore, the examination of ten vibrocores retrieved from the seabed suggests that the deposit of well consolidated old dune extends out to the sea.

Terrigenous deposits in coastal marine habitats: influences on sediment geochemistry and behaviour of post-settlement bivalves

Dispersal of post-settlement juvenile macrofauna is widespread in the marine environ- ment, yet the cues used by these organisms to assess substrate suitability are poorly known. We investigated how deposition of fine terrestrial sediments (TS, 0.5 to 1.7 mm thick) affects both the solute concentrations at the sediment-water boundary and the burrowing behaviour of juvenile tellinid bivalves Macomona liliana. To elucidate previously observed gradual reduction in the strength of macrofaunal responses with increasing age of deposits, the effect of TS weathered in the field for 0, 7 and 14 d, and the influence of surface and buried TS layers, were also investigated. Bur- rowing was significantly reduced in 0 and 7 d old surface TS compared with controls, but there was no effect of buried deposits on M. liliana burrowing, irrespective of sediment age. Microelectrode measurements showed that thin surface TS layers reduced the supply of O2 to the underlying sedi- ment, raising the position of the vertical (O2) and pH gradients so that most of the gradient was located in the TS layer itself, rather than deeper in the sediment below it. Consequently, the likeli- hood of juveniles that are active in the near-surface layers being exposed to upward diffusing end products of microbial decomposition was increased. These results suggest a mechanism for the observed negative response of post-settlement M. liliana (and other macrofauna) to TS deposits asso- ciated with sedimentation events, and an avenue for further research into potential geochemical cues (especially pH and associated geochemical species).