Regolith Environment Research Articles

Effect of vermicompost on rhizobiome and the growth of wheat on Martian regolith simulant

As humanity embarks on the journey to establish permanent colonies on Mars, ensuring a reliable source of sustenance will be crucial. Therefore, detailed studies regarding crop cultivation using Martian simulants are of great importance. This study aimed to grow wheat on substrates based on soil and Martian simulants, with the addition of vermicompost, to investigate the differences in wheat development. Basic physical and chemical properties of substrates were examined, including determination of macro- and microelements as well as their microbiological properties. Plant growth parameters were also determined. The addition of vermicompost positively affected wheat grown on soil, but the effect on plants grown on substrate with Martian simulants was negligible. Comparing the microbiological and chemical components, it was observed that plants can defend themselves against the negative effects of growth on the Martian simulants, but their success depends on having the PGPR (Plant growth-promoting rhizobacteria) present, which can provide the plant with additional nitrogen. The presence of beneficial symbiotic microbiota will allow the wheat to wait out the negative growth time rather than adapt to the regolith environment.

A regolith lead isoscape of Australia

Abstract. We present the first national-scale lead (Pb) isotope maps of Australia based on surface regolith for five isotope ratios, 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb, 207Pb/206Pb, and 208Pb/206Pb, determined by single-collector sector field inductively coupled plasma mass spectrometry after an ammonium acetate leach followed by aqua regia digestion. The dataset is underpinned principally by the National Geochemical Survey of Australia (NGSA) archived floodplain sediment samples. We analysed 1219 samples (0–10 cm depth, <2 mm grain size), collected near the outlet of 1119 large catchments covering 5.647×106 km2 (∼75 % of Australia). The samples consist of mixtures of the dominant soils and rocks weathering in their respective catchments (and possibly those upstream) and are therefore assumed to form a reasonable representation of the average isotopic signature of those catchments. This assumption was tested in one of the NGSA catchments, within which 12 similar samples were also taken; results show that the Pb isotope ratios of the NGSA catchment outlet sediment sample are close to the average of the 12 upstream sub-catchment samples. National minimum, median, and maximum values were 15.56, 18.84, and 30.64 for 206Pb/204Pb; 14.36, 15.69, and 18.01 for 207Pb/204Pb; 33.56, 38.99, and 48.87 for 208Pb/204Pb; 0.5880, 0.8318, and 0.9847 for 207Pb/206Pb; and 1.4149, 2.0665, and 2.3002 for 208Pb/206Pb, respectively. The new dataset was compared with published bedrock and ore Pb isotope data, and it was found to dependably represent crustal elements of various ages from Archaean to Phanerozoic. This suggests that floodplain sediment samples are a suitable proxy for basement and basin geology at this scale, despite various degrees of transport, mixing, and weathering experienced in the regolith environment, locally over protracted periods of time. An example of atmospheric Pb contamination around Port Pirie, South Australia, where a Pb smelter has operated since the 1890s, is shown to illustrate potential environmental applications of this new dataset. Other applications may include elucidating details of Australian crustal evolution and mineralisation-related investigations. The new regolith Pb isotope dataset for Australia is publicly available (Desem et al., 2023; https://doi.org/10.26186/5ea8f6fd3de64).

Morphological and Spectral Characterization of Lunar Regolith Breakdown due to Water Ice

Remote sensing observations of the Moon suggest that the lunar polar regolith environment is affected by several natural processes that may cause the regolith in these regions to become more porous and fine particulate. One of these processes may be the mechanical breakdown of regolith particles through the interaction of water ice and regolith by frost wedging. We present morphological and spectral analyses of high-fidelity lunar regolith simulants LHS-1 (lunar highlands simulant-1) and LMS-1 (lunar mare simulant-1) that have been exposed to varying concentrations of water ice (1, 10, and 30 wt%) over extended periods of time (1, 3, and 6 months) to evaluate the extent at which lunar regolith may be weathered by ice-regolith interactions in the Moon’s polar regions. To characterize changes in regolith particle morphology, we explored grain size and shape parameters with the CILAS ExpertShape suite and characterized the abundance and evolution of clinging fines with scanning electron microscopy and energy dispersive X-ray spectroscopy. Reflectance spectra were taken from 1.0–22.5 μm (444.4–10,000 cm−1) to characterize any differences in spectral features that may occur as a result of regolith breakdown. Both the morphological and spectral investigations display trends that show simulant particle degradation as a function of composition, increasing water concentration, and freezing time. Our study demonstrates that the lunar regolith is susceptible to mechanical breakdown in the presence of water ice and that water ice is likely a contributor to the weathering environment within permanently shadowed regions on the lunar surface.

Recent trends in tribological performance of aerospace materials in lunar regolith environment – A critical review

Lunar exploration has emerged as an exciting area for the scientific community and aerospace industries. However, the lunar environment presents daunting challenges, including extreme temperatures, high vacuum conditions, and sharp abrasive lunar regolith. Past explorations have demonstrated that the lunar regolith is particularly difficult to contend with, as its abrasive and erosive nature damages equipment and rover due to wear. Herein, an assessment is made on the tribological performance of key structural and optical components used in space vehicles, rovers, and on-field equipment operating in the lunar regolith environment. The evolution of erosive and abrasive test equipment, its benefits, limitations, and simulant characteristics, such as particle morphology and size, are examined on different materials' impact and abrasive wear. Abrasive and erosive wear mechanisms are elucidated based on regolith particle impact velocity, impact angle (erosion), regolith morphology, and particle size (abrasion). The lack of research on how temperature affects the wear behavior of materials under lunar regolith represents a significant gap in current knowledge. By identifying these gaps and providing alternative pathways, this critique can guide researchers in developing effective dust mitigation strategies and advancing the testing and analysis of prospective space materials.

The formation and aqueous alteration of CM2 chondrites and their relationship to CO3 chondrites: A fresh isotopic (O, Cd, Cr, Si, Te, Ti, and Zn) perspective from the Winchcombe CM2 fall

AbstractAs part of an integrated consortium study, we have undertaken O, Cd, Cr, Si, Te, Ti, and Zn whole rock isotopic measurements of the Winchcombe CM2 meteorite. δ66Zn values determined for two Winchcombe aliquots are +0.29 ± 0.05‰ (2SD) and +0.45 ± 0.05‰ (2SD). The difference between these analyses likely reflects sample heterogeneity. Zn isotope compositions for Winchcombe show excellent agreement with published CM2 data. δ114Cd for a single Winchcombe aliquot is +0.29 ± 0.04‰ (2SD), which is close to a previous result for Murchison. δ130Te values for three aliquots gave indistinguishable results, with a mean value of +0.62 ± 0.01‰ (2SD) and are essentially identical to published values for CM2s. ε53Cr and ε54Cr for Winchcombe are 0.319 ± 0.029 (2SE) and 0.775 ± 0.067 (2SE), respectively. Based on its Cr isotopic composition, Winchcombe plots close to other CM2 chondrites. ε50Ti and ε46Ti values for Winchcombe are 3.21 ± 0.09 (2SE) and 0.46 ± 0.08 (2SE), respectively, and are in line with recently published data for CM2s. The δ30Si composition of Winchcombe is −0.50 ± 0.06‰ (2SD, n = 11) and is essentially indistinguishable from measurements obtained on other CM2 chondrites. In conformity with petrographic observations, oxygen isotope analyses of both bulk and micromilled fractions from Winchcombe clearly demonstrate that its parent body experienced extensive aqueous alteration. The style of alteration exhibited by Winchcombe is consistent with relatively closed system processes. Analysis of different fractions within Winchcombe broadly support the view that, while different lithologies within an individual CM2 meteorite can be highly variable, each meteorite is characterized by a predominant alteration type. Mixing of different lithologies within a regolith environment to form cataclastic matrix is supported by oxygen isotope analysis of micromilled fractions from Winchcombe. Previously unpublished bulk oxygen isotope data for 12 CM2 chondrites, when combined with published data, define a well‐constrained regression line with a slope of 0.77. Winchcombe analyses define a more limited linear trend at the isotopically heavy, more aqueously altered, end of the slope 0.77 CM2 array. The CM2 slope 0.77 array intersects the oxygen isotope field of CO3 falls, indicating that the unaltered precursor material to the CMs was essentially identical in oxygen isotope composition to the CO3 falls. Our data are consistent with earlier suggestions that the main differences between the CO3s and CM2s reflect differing amounts of water ice that co‐accreted into their respective parent bodies, being high in the case of CM2s and low in the case of CO3s. The small difference in Si isotope compositions between the CM and CO meteorites can be explained by different proportions of matrix versus refractory silicates. CMs and COs may also be indistinguishable with respect to Ti and Cr isotopes; however, further analysis is required to test this possibility. The close relationship between CO3 and CM2 chondrites revealed by our data supports the emerging view that the snow line within protoplanetary disks marks an important zone of planetesimal accretion.

Compositional and spectroscopic investigation of three ungrouped carbonaceous chondrites

AbstractUngrouped carbonaceous chondrites are not easily classified into one of the well‐established groups due to compositional/petrological differences and geochemical anomalies. Type 2 ungrouped carbonaceous chondrites represent a very small fraction of all carbonaceous chondrites. They can potentially represent different aspects of asteroids and their regolith material. By conducting a multitechnique investigation, we show that Queen Alexandra Range (QUE) 99038 and Elephant Moraine (EET) 83226 do not resemble type 2 carbonaceous chondrites. QUE 99038 exhibits coarse‐grained matrix, Fe‐rich rims on olivines, and an apparent lack of tochilinite, suggesting that QUE 99038 has been metamorphosed. Its polyaromatic organic matter structures closely resemble oxidized CV3 chondrites. EET 83226 exhibits a clastic texture with high porosity and shows similarities to CO3 chondrites. It consists of numerous large chondrules with fine‐grained rims that are often fragmented and discontinuous and set within matrix, suggesting a formation mechanism for the rims in a regolith environment. The kind of processes that can result in such chemical compositions as in QUE 99038 and EET 83226 is currently not fully known and clearly presents a conundrum. Tarda is a highly friable carbonaceous chondrite with close resemblance to Tagish Lake (ungrouped C2 chondrite). It comprises different types of chondrules (some with Fe‐rich rims), framboid magnetite, sulfides, carbonates, and phyllosilicate‐ and carbon‐rich matrix, and is consistent with being an ungrouped C2 chondrite.

Bacterial Utilisation of Aliphatic Organics: Is the Dwarf Planet Ceres Habitable?

The regolith environment and associated organic material on Ceres is analogous to environments that existed on Earth 3–4 billion years ago. This has implications not only for abiogenesis and the theory of transpermia, but it provides context for developing a framework to contrast the limits of Earth’s biosphere with extraterrestrial environments of interest. In this study, substrate utilisation by the ice-associated bacterium Colwellia hornerae was examined with respect to three aliphatic organic hydrocarbons that may be present on Ceres: dodecane, isobutyronitrile, and dioctyl-sulphide. Following inoculation into a phyllosilicate regolith spiked with a hydrocarbon (1% or 20% organic concentration wt%), cell density, electron transport activity, oxygen consumption, and the production of ATP, NADPH, and protein in C. hornerae was monitored for a period of 32 days. Microbial growth kinetics were correlated with changes in bioavailable carbon, nitrogen, and sulphur. We provide compelling evidence that C. hornerae can survive and grow by utilising isobutyronitrile and, in particular, dodecane. Cellular growth, electron transport activity, and oxygen consumption increased significantly in dodecane at 20 wt% compared to only minor growth at 1 wt%. Importantly, the reduction in total carbon, nitrogen, and sulphur observed at 20 wt% is attributed to biotic, rather than abiotic, processes. This study illustrates that short-term bacterial incubation studies using exotic substrates provide a useful indicator of habitability. We suggest that replicating the regolith environment of Ceres warrants further study and that this dwarf planet could be a valid target for future exploratory missions.

Influence of lunar regolith compressibility on sampling performance of thick wall spiral drills

A 2 m class robotic drill was sent to the Moon and successfully collected and returned regolith samples in late 2020 by China. It was a typical thick wall spiral drill (TWSD) with a hollow auger containing a complex coring system to retain subsurface regolith samples. Before the robotic drill was launched, a series of laboratory tests were carried out to investigate and predict the possible drilling loads it may encounter in the lunar environment. This work presents how the sampling performance of the TWSD is affected by the regolith compressibility. Experiments and analysis during the drilling and sampling process in a simulated lunar regolith environment were conducted. The compressibility of a typical lunar regolith simulant (LRS) was measured through uni-directional compression tests to study the relationship between its inner regolith stress and bulk density. A theoretical model was established to elucidate the cutting discharge behavior by auger flights based on the aforementioned relationship. Experiments were conducted with the LRS, and the results show that the sampling performance is greatly affected by the flux of the drilled cuttings into the spiral flight channels. This work helped in scheduling reasonable drilling parameters to promote the sampling performance of the robotic drill in the Chinese Chang'E 5 mission.

Robotic drilling tests in simulated lunar regolith environment

AbstractA deep extraterrestrial drilling mission potentially adds a new level of complexity, and it is crucial to understand the associated challenges. To cope with China's Chang'E 5 mission to return subsurface regolith samples from the Moon, a series of laboratory tests were performed to validate the lunar robotic drilling from 2015 to 2018. The tests took place in a simulated thermal‐vacuum regolith environment, a highly relevant lunar analog site. Force and temperature sensors were integrated into a 2‐m class dry auger coring drill to assess the mechanical and thermophysical status of the sampling process. The operation of the entire testing system was automated, covering regolith penetration and data collection and storage. The science team used sensing data to characterize the subsurface geologic strata, assess the conditions of the drilling robot, and direct the sampling strategy. This experiment represents an essential first step in understanding the technology and operational requirements for lunar drilling and sampling mission. Many laboratory tests have helped guide the design and implementation of the highly successful lunar regolith‐sampling task in the Chang'E 5 mission. This paper documents the experimental system design, highlighting some critical design criteria and design tradeoffs. It also discusses the results of laboratory testing and lists some of the key technological lessons learned.

The application of threshold gold values based on geochemical exploration in complex regolith terrains: A case study at Lawra Greenstone Belt of Northwest Ghana

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The technology of lunar regolith environment construction on Earth

Lunar regolith plays an extremely important role in the establishment of permanent human residence or robotic industries on the Moon. Lunar regolith environment construction may accelerate the progress of lunar engineering, biology, medicine, and agriculture for future colonization of the Moon. Although advances in investigating and simulating lunar regolith have achieved unprecedented progress, producing simulated lunar regolith environment on Earth with adequate fidelity remains challenging. Inspired by traditional Chinese tofu making process, we proposed a comprehensive methodology to construct lunar regolith environment on Earth, and developed theoretical models to illustrate gas and heat transfer behavior in this particulate and porous material. Our study, proven to be effective, reveals a complex but generic gas and heat transfer mechanism in granular lunar regolith simulant, and can be readily applied to construct experimental regolith environments for lunar scientific research.

The Forrestania and Nepean electromagnetic test ranges, Western Australia – a comparison of airborne systems

SummaryElectromagnetic (EM) systems are often described with varying technical specifications and standards, making it difficult to directly compare and assess their application to practical field examples. Exemplar case studies provided by contractors, whilst highlighting system capabilities, do not necessarily help to refine the suitability of the system across different geological targets and environments. Test ranges provide an opportunity for direct and consistent comparison of multiple systems for objective assessment.The Forrestania and Nepean EM test ranges in Western Australia consist of readily accessible land, openly available for testing by airborne, ground and downhole EM systems. Multiple conductors at varying depths beneath 10-20 Siemens (S) conductive overburden provide challenging, real-world conductive targets. Surveying using different EM systems allows for a direct comparison of system detection and resolution capabilities in a conductive regolith environment. The conductors have been well defined by drilling and provide a large range of metrics available for measurement, varying from 60-400 m in depth, 5,000-10,000 S in conductance, and with variable lateral profiles and depth extents.Multiple airborne, ground and downhole EM systems have utilised these test ranges, and several have made their data freely available for review. These include ground methods such as moving loop EM, fixed loop EM, SAMSON, downhole EM, and helicopter systems including HeliSAM FLEM, SkyTEM, VTEM, HELITEM, HeliGEOTEM, XTEM, HoistEM and AeroTEM. The SPECTREM, and Xcite airborne systems plan to fly the test range in the near future. Comparison of the airborne results, show that most of the post-2007 systems have been adequate to good at detecting the shallow IR2 conductor at Forrestania under conductive regolith. Only the hybrid grounded loop HeliSAM system has successfully detected the deep IR4 conductor at Forrestania.

The First Samples from Almahata Sitta Showing Contacts Between Ureilitic and Chondritic Lithologies: Implications for the Structure and Composition of Asteroid 2008 TC3.

Almahata Sitta (AhS), an anomalous polymict ureilite, is the first meteorite observed to originate from a spectrally classified asteroid (2008 TC3). However, correlating properties of the meteorite with those of the asteroid is not straightforward because the AhS stones are diverse types. Of those studied prior to this work, 70-80% are ureilites (achondrites) and 20-30% are various types of chondrites. Asteroid 2008 TC3 was a heterogeneous breccia that disintegrated in the atmosphere, with its clasts landing on Earth as individual stones and most of its mass lost. We describe AhS 91A and AhS 671, which are the first AhS stones to show contacts between ureilitic and chondritic materials and provide direct information about the structure and composition of asteroid 2008 TC3. AhS 91A and AhS 671 are friable breccias, consisting of a C1 lithology that encloses rounded to angular clasts (<10 μm to 3 mm) of olivine, pyroxenes, plagioclase, graphite, and metal-sulfide, as well as chondrules (~130-600 μm) and chondrule fragments. The C1 material consists of fine-grained phyllosilicates (serpentine and saponite) and amorphous material, magnetite, breunnerite, dolomite, fayalitic olivine (Fo 28-42), an unidentified Ca-rich silicate phase, Fe,Ni sulfides, and minor Ca-phosphate and ilmenite. It has similarities to CI1 but shows evidence of heterogeneous thermal metamorphism. Its bulk oxygen isotope composition (δ18O = 13.53‰, δ17O = 8.93‰) is unlike that of any known chondrite, but similar to compositions of several CC-like clasts in typical polymict ureilites. Its Cr isotope composition is unlike that of any known meteorite. The enclosed clasts and chondrules do not belong to the C1 lithology. The olivine (Fo 75-88), pyroxenes (pigeonite of Wo ~10 and orthopyroxene of Wo ~4.6), plagioclase, graphite, and some metal-sulfide are ureilitic, based on mineral compositions, textures, and oxygen isotope compositions, and represent at least six distinct ureilitic lithologies. The chondrules are probably derived from type 3 OC and/or CC, based on mineral and oxygen isotope compositions. Some of the metal-sulfide clasts are derived from EC. AhS 91A and AhS 671 are plausible representatives of the bulk of the asteroid that was lost. Reflectance spectra of AhS 91A are dark (reflectance ~0.04-0.05) and relatively featureless in VNIR, and have an ~2.7 μm absorption band due to OH- in phyllosilicates. Spectral modeling, using mixtures of laboratory VNIR reflectance spectra of AhS stones to fit the F-type spectrum of the asteroid, suggests that 2008 TC3 consisted mainly of ureilitic and AhS 91A-like materials, with as much as 40-70% of the latter, and <10% of OC, EC and other meteorite types. The bulk density of AhS 91A (2.35 ± 0.05 g/cm3) is lower than bulk densities of other AhS stones, and closer to estimates for the asteroid (~1.7-2.2 g/cm3). Its porosity (36%) is near the low end of estimates for the asteroid (33-50%), suggesting significant macroporosity. The textures of AhS 91A and AhS 671 (finely comminuted clasts of disparate materials intimately mixed) support formation of 2008 TC3 in a regolith environment. AhS 91A and AhS 671 could represent a volume of regolith formed when a CC-like body impacted into already well-gardened ureilitic + impactor-derived debris. AhS 91A bulk samples do not show a solar wind (SW) component, so they represent sub-surface layers. AhS 91A has a lower cosmic ray exposure (CRE) age (~5-9 Ma) than previously studied AhS stones (11-22 Ma). The spread in CRE ages argues for irradiation in a regolith environment. AhS 91A and AhS 671 show that ureilitic asteroids could have detectable ~2.7 μm absorption bands.

Supergene remobilization of Au in Au-bearing regolith related to orogenic deposits: A case study from Kazakhstan

Our study of the primary and supergene gold from the Suzdal and Raigorodok deposits in Kazakhstan confirms that during the formation of the regolith in both deposits, invisible and fine gold is released from the host sulfide minerals during their oxidation and destruction; and transported in the form of soluble thiosulfate complexes by near-surface solutions. Upon contact with a geochemical barrier, gold can be deposited as crystalline aggregates. In the deposition of this gold the role of geochemical barriers, such as variations of redox, pH and sorption are very important.Evidence of the past processes of dissolution, redistribution and aggregation of gold in the regolith in these deposits is provided by the following features: 1) The presence of dissolution and growth structures on the surface of newly formed gold; 2) The size of the gold grains increases and newly formed gold microcrystals appear on the surface of the grains; 3) Changes in the composition of native gold (e.g. decrease of silver content); 4) The accumulation of gold in subhorizontal localized layers within the regolith; 5) Gold association with supergene minerals (limonite, jarosite, goethite, Mn-hydroxides, opal, gypsum, calcite, clay minerals, etc.).This detailed study of the specific compositional and structural features of supergene gold and the physicochemical conditions of regolith environment allowed the recognition of the releasing, dissolution, transfer and aggregation processes of gold in the regolith.

Evacuation method and outgassing rate of a lunar regolith simulant for deep drilling tests

A novel method to evacuate large bins of lunar regolith simulant for deep drilling tests was proposed in the current work. This method can be used to simulate a vacuous lunar regolith environment to a maximum penetration depth of 2 m. An experimental apparatus was built and is composed of a vacuum chamber, a specially designed regolith container and a vacuum pumping system. A pressure on the order of 10 Pa could be reached with the 4.3 m3 vacuum chamber when compacted lunar regolith simulant with a volume of 0.4 m3 was loaded. A theoretical model to predict vacuum degree was proposed basing on the viscous flow theory. Evacuation experiments with or without lunar regolith simulant inside the chamber were performed and the outgassing properties of lunar regolith simulant was experimentally studied. The results show that the outgassing rate of the lunar regolith simulant was about 107 times to that of the electro-polished stainless-steel.

Ready functions for calculating the Martian radiation environment

It is extremely important to understand and model the Martian radiation environment in preparation for future human missions to Mars, especially during extreme and elevated conditions such as an intense solar energetic particle (SEP) event. Such events may enhance the radiation level drastically and should be forecasted as soon as possible to prevent severe damage to humans and equipment. Besides, the omnipresent galactic cosmic rays (GCRs) also contribute significantly to the radiation in space and on the surface of Mars and may cause long-term damages to current and future missions. Based on GEANT4 Monte Carlo simulations with the Martian atmospheric and regolith environment setup, we have calculated and obtained some ready-to-go functions which can be used to quickly convert any given SEP or GCR proton/helium ion spectra to the radiation dose on the surface of Mars and also at different depth of the atmosphere. We implement these functions to the RADMAREE tool under the Europlanet project which can be easily accessed by the public.

Thermal vacuum regolith environment simulator for China’s deep lunar drilling exploration

A thermal vacuum regolith environment simulator for China’s deep lunar drilling exploration was proposed and developed. The simulator can be used to provide not only a vacuum but also a high or low temperature environment for the lunar regolith simulant to a maximum depth of 2 m. It consisted of a vacuum system for simulating an airless condition, a regolith preparation system for compacting the regolith simulant with different bulking densities, and a thermal system for simulating the lunar regolith temperature distribution. Multi-layer stainless steel filters were used to filter regolith particles during the evacuation process. This method accelerated the dissipation of inner gas molecules and maintained the regolith simulant bulk density. The thermal system used iodine-tungsten lamps to heat the surface regolith and silicon oil to refrigerate the subsurface regolith. A rotating and locking mechanism inside the simulation chamber was proposed for multiple drillings within a single environment simulation.

Lack of Exploration Success in Northern Ghana: Problems and Solutions

The aim of this research is to investigate reasons for the lack of exploration success in the savannah regions of Northern Ghana and offer some remediation. The failure of exploration expedition could be traced from scores of unsuccessful and abandoned grassroots explorations programmes since 1935. More recently the discontinuous exploration activities in Northern Ghana, even in the midst of the gold boom and favorable commodity prices have been regrettable. Also, for about 78 years now that gold occurrence was reported in these northern Ghana, none had been developed to a prospective mine. The problem is attributed to the lack of understanding the regolith distribution and characteristics of gold deposits as well as poor exploration practices. Application of enhanced exploration methods such as the use of regolith mapping and characterization, remote sensing and study into landform modifications and variabilities in Northern Ghana could help reveal patchy and false anomalies. Again, resulting dispositional overburden as well as thick ferruginous enrichment which tend to mask anomalous signatures could be unraveled by enhanced exploration techniques. The solution to these unsuccessful exploration expeditions therefore require the understanding of the regolith environment, mineral hosts for gold and trace metals along with regolith map that aids in interpreting geochemical signatures could assist to unravel potential mineralization under cover.

Regolith Geochemistry and Mineralogy of the Mbalam Itabirite-Hosted Iron Ore District, South Eastern Cameroon

Mbalam is a major emerging iron ore district in Cameroon. The regolith over the Mbalam itabirite, consists of relict, erosion and depositional units. Itabirite rock fabric is preserved in the relict regolith, the erosion unit is marked by erosion of the carapace cap regolith, with the depositional unit dominated by canga (loose fragments of hematite and/or itabirite cemented by goethite) or loose scree. Fe concentration increases from average of 46.18 wt% in the depositional soil material to as much as 79.08 wt% in the relict regolith regime with variation due to supergene weathering. Fe is the least mobile of the major elements, and the Fe oxides become significant phases and control the distributions of many elements. Absorption of P by iron oxides or oxyhydroxides appears to be the major mechanism of P retention in the different regolith environment. Au dispersion in the weathering profile occurs by two possible mechanisms (mechanical and hydromorphic) and it distribution is sporadic. Zr maintains a positive correlation with Al and Ti indicating extensive chemical weathering in the source area and resulting in a relative concentration of those residual elements. The weathered material show relatively high ΣREE; this is due to upward remobilisation from the lower primary itabirite, and the downward leaching of the upper mineralisation horizons by the descending epigenetic solutions.

The petrology and geochemistry of Miller Range 05035: A new lunar gabbroic meteorite

Miller Range (MIL) 05035 is a lunar gabbroic meteorite. The mineralogy, Fe/Mn ratios in olivine and pyroxene, bulk-rock chemical composition and the bulk oxygen isotope values (δ 17O = 2.86–2.97‰ and δ 18O = 5.47–5.71‰) are similar to those of other mare basalts, and are taken as supporting evidence for a lunar origin for this meteorite. The sample is dominated by pyroxene grains (54–61% by area mode of thin section) along with large plagioclase feldspar (25–36% by mode) and accessory quartz, ilmenite, spinel, apatite and troilite. The bulk-rock major element composition of MIL 05035 indicates that the sample has a very low-Ti (VLT) to low-Ti lunar heritage (we measure bulk TiO 2 to be 0.9 Wt.%) and has low bulk incompatible trace element (ITE) concentrations, akin to samples from the VLT mare basalt suite. To account for these geochemical characteristics we hypothesize that MIL 05035’s parental melt was derived from a mantle region dominated by early cumulates of the magma ocean (comprised principally of olivine and orthopyroxene). MIL 05035 is likely launch paired with the Asuka-881757 and Yamato-793169 basaltic lunar meteorites and the basaltic regolith breccia MET 01210. This group of meteorites (Y/A/M/M) therefore may be a part of a stratigraphic column consisting of an upper regolith environment underlain by a coarsening downwards basalt lava flow.