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<jats:p> The Western Indonesia Bauxite Province in Kalimantan forms a lateritic bauxite region with a complex history and poorly known sustainable metal contents within the bauxite residue. Bauxite residue produced using the Bayer process contains notable scandium. We present new geochemistry, mineralogical, and geological data from the lateritic bauxite and red mud from the active mine and deposit, which aims to investigate the behavior of critical elements during weathering. The geochemical analysis and translated isocon results have shown that the content of scandium in red mud is higher than the average concentration of crustal rocks and is concentrated in the ferrite layer and bauxite residue. A positive correlation between the existence of iron oxyhydroxide mineral in residual iron-rich layer and red muds with the rare earth elements (REE) and scandium concentrations may be interpreted as a scavenging effect of mobile REE. The weathering and leaching processes in bauxite allows the adsorption of the trivalent scandium cation (Sc <jats:sup>3+</jats:sup> ) on goethite and are followed by the ionic substitution with other trivalent cations in the crystal of hematite. The study illustrates the importance of understanding processes during weathering and laterization for geochemical processes and rare earth elements exploration in tropical areas. </jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Geochemical processes related to mined, milled, or natural metal deposits collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/geochemical-processes-related-to-mined-milled-or-natural-metal-deposits">https://www.lyellcollection.org/topic/collections/geochemical-processes-related-to-mined-milled-or-natural-metal-deposits</jats:ext-link> </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" specific-use="dataset is-supplemented-by" xlink:href="https://doi.org/10.6084/m9.figshare.c.6689139">https://doi.org/10.6084/m9.figshare.c.6689139</jats:ext-link> </jats:p>

<jats:p>Significant progress in the classification, definition, and understanding of the main Au deposit types could significantly aid improvements in Au exploration. Because of the wide occurrence of Au in the central part of the Tethyan Eurasian Metallogenic Belt, Iranian structures composed of more than seventeen zones (arcs and blocks) are considered as having one of the largest Au reserves in the Middle East. Without attempts at understanding the tectono-magmatic evolution of Iran and the geodynamic settings of Au deposition, the establishment of a reliable predictive exploration model for Au-type deposits in Iran and other parts of the world will be unsuccessful. By considering, a total number of 33 Au deposits and prospects in Iran, a mineralization sequence is revealed from VMS, orogenic, Carlin-type, epithermal/ porphyry Cu-Au/ skarn, epithermal/ and IOCG, respectively. The trend of deposition gradually changes in the SW-NE axis to intrusion-related, epithermal, and porphyry Cu-Au deposits at UDMA and post-arc magmatism. Orogenic and volcanogenic massive sulfide (VMS) deposits occur adjacent to the northeast Zagros Fold and Thrust Belt, at the SSZ. The Zagros Orogeny and associated post-collisional magmatism at Urumieh-Dokhtar Magmatic Arc (UDMA) host many porphyry, epithermal, and intrusion-related Au deposits, with a major magmatism peak in the Miocene. The finding of the manuscript reveals that orogenic and Carlin-type Au mineralization are linked genetically. After each associated subduction for paleo-tethys (286-215 Ma) and Neo-tethys (210-68 Ma) in Iran, VMS and orogenic Au-deposits are formed in the border of the subduction (±obduction) zone. The porphyry, intrusion-related, epithermal, and IOCG mineralization are emplaced in appropriate formations and structures during collision and post-collision processes.</jats:p>

<jats:p>Stream sediment surveys support early-stage reconnaissance mineral exploration and regional assessment programs, enhanced by recent improvements in analytical method detection limits, continuously improving mineral chemistry, and new approaches to the interpretation of geochemical data. Sediment surveys may be used to predict catchment basin lithology, mineralization type based on pathfinder geochemistry, and geological features based on indicator mineral chemistry. Sediment surveys that target a finer fraction sediment sample led to discovery of the La Colosa gold deposit, Colombia. The Batu Hijau porphyry Cu-Au deposit in Indonesia was discovered based on an anomalous clay-sized fraction sample 12 km downstream. In an arid region with poorly developed drainages and minor topographic relief, the Ag-base-metal Navidad District in Argentina was discovered with clay-fraction sediment geochemistry. Heavy mineral concentrate sediment surveys (HMC) that include mineral chemistry determinations have led to global diamond discoveries. HMC surveys contributed to discovery of the Ring of Fire Ni-Cu-PGE and chromite district, Ontario Canada. Discoveries and geochemical mapping can assist advancement of the application of stream sediment geochemistry in those global areas for which lithologies and deposits are exposed. Stream sediment surveys continue to be one of the most cost-effective geochemical methods for covering large areas for mineral exploration.</jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Reviews in Exploration Geochemistry collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/reviews-in-exploration-geochemistry">https://www.lyellcollection.org/topic/collections/reviews-in-exploration-geochemistry</jats:ext-link> </jats:p>

<jats:p>Breccia pipe deposits of the Grand Canyon region contain ore grade copper and uranium. Horn Creek is located near the Orphan Mine mineralized breccia pipe deposit and groundwater emerging from the bedrock in the headwaters of Horn Creek has the highest uranium concentrations in the region. Uranium decreases an order of magnitude between the groundwater at the top of the watershed and the groundwater emerging from the alluvial material lower in the watershed. Horn Creek water has low sulfur and uranium isotopic ratios which may suggest interaction with sulfide and uranium minerals found in mineralized breccia pipe deposits. Per- and polyfluoroalkyl substances (PFBA and PFBS) were found in low concentrations in groundwater from the bedrock and may be related to mining process materials or other anthropogenic activities. PHREEQC modeling suggests that water that is elevated in uranium emerging from the bedrock in the upper watershed may mix with other groundwater and atmospheric precipitation infiltrated into the alluvial material in the lower watershed. Tritium is elevated in Horn Creek groundwaters suggesting a component of modern water, some of which may have interacted with Orphan Mine workings. Additional studies could build on this understanding of chemistry changes in waters of Horn Creek to provide more direct evidence of contribution of water moving through the Orphan Mine.</jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Geochemical processes related to mined, milled, or natural metal deposits collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/geochemical-processes-related-to-mined-milled-or-natural-metal-deposits">https://www.lyellcollection.org/topic/collections/geochemical-processes-related-to-mined-milled-or-natural-metal-deposits</jats:ext-link> </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" specific-use="dataset is-supplemented-by" xlink:href="https://doi.org/10.6084/m9.figshare.c.6747638">https://doi.org/10.6084/m9.figshare.c.6747638</jats:ext-link> </jats:p>

<jats:p>The Lower Devonian plant-bearing Rhynie Chert, Aberdeenshire, UK, consists of sinters deposited by a hot spring system. Like many modern hot springs, the Rhynie geothermal system was lithium-rich, and its silica deposits are richer in lithium than other current or fossil sinters. Twenty samples of Rhynie sinter have a mean content of 255 ppm lithium. The high values imply exceptional lithium contents in the spring waters. Together with pegmatites and granites in the same region, the chert is related to a lithium-rich Late Caledonian magmatic suite, of which it is a surface expression. The measurements suggest that ancient hot spring deposits could provide valuable data during the exploration for lithium.</jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" specific-use="dataset is-supplemented-by" xlink:href="https://doi.org/10.6084/m9.figshare.c.6756506">https://doi.org/10.6084/m9.figshare.c.6756506</jats:ext-link> </jats:p>

<jats:p> We applied the Backward Elimination (BE) method as a criterion-based iterative stepwise method to estimate the concentration of Au from the variables Ag, Cu, Pb, and Zn. We optimized the quadratic polynomial model (QPM) on various boreholes and trenches. The results indicate that the vertical zonation of Au is associated with Ag and Cu, along with their respective elemental functions Ag×Cu, Pb <jats:sup>2</jats:sup> , Pb×Zn, and Zn <jats:sup>2</jats:sup> . On the other hand, the lateral dispersion of Au is determined by Pb and Zn, along with the essential functions Ag×Zn and Pb×Zn. Zonation is in-depth and is indicated primarily by Zn rather than Cu and minor Pb, with Cu-Pb-Zn gradually extending upward at the upper levels. The vertical zonation trend describes the Ag&lt;Au&lt;Cu&lt;Pb&lt;Zn sequence from proximal to distal veins, with the near-surface zone exhibiting enrichment in Zn. At the Glojeh site, the host rock value, Ag×Cu, Zn <jats:sup>2</jats:sup> , and Pb×Zn, were identified as strong indicators of the vertical occurrence of Au in the upper host rock, whereas Pb <jats:sup>2</jats:sup> proved more suitable for the deeper boreholes. Cu→Pb→Zn demonstrates the enrichment trend from depth to the surface. The lateral kriging surface estimation confirms the dispersion pattern of elements revealed in-depth at Glojeh. Our aims with this approach were to reduce the cost of fire-assay analysis due to high precision estimation by associated variables and determine elemental interactions and the lateral or vertical dependencies of elements. </jats:p>

<jats:p>The central section of China's South-to-North Water Diversion Project (SNWD) has been designated as a national water conservation area, and the soil ecological security in its associated watersheds is of great importance. A total of 204 soil samples (0-20 cm) were obtained from the Laoguanhe River Basin. The concentrations of seven elements (Cd, Cr, Cu, Ni, Zn, Pb and Hg) were determined by ICP-MS and AFS following a near-total acid dissolution. Data analyses (including potential ecological risk, principal component analysis, geostatistical analysis and positive matrix factorization model) were applied to evaluate the contamination of soil heavy metals and to identify their sources. The research results demonstrated that the mean contents of these seven elements exceeded background values for Henan Province, China, indicating human disturbance. Ecological risk evaluation revealed that Cd was the most frequently detected and highly polluted heavy metal., Principal component analysis indicated that Cr, Ni and Cu stem from natural sources, while Zn and Cd are predominantly influenced by agricultural activities. Additionally, industrial activities and atmospheric deposition were responsible for the excess presence of Pb and Hg. The study suggests taking measures to control Cd sources in agricultural areas, reducing heavy metals input to the river, and providing scientific support for managing water quality.</jats:p>

<jats:p>Since the 1970s, till geochemical and indicator mineral methods for mineral exploration, provenance studies and environmental research in glaciated terrain have been developed, tested, and refined. This paper summarizes these methods, focussing on field and laboratory methods for till geochemical, indicator mineral, and boulder surveys. This review of protocols is meant to be a guide for the mineral exploration industry and publicly funded agencies. The paper summarizes till as a sample medium, describes the formation of glacial dispersal trains, and methods for till sample collection, sample processing, matrix geochemistry, indicator mineral analyses, quality assurance/quality control (QA/QC) procedures, and data reporting and interpretation. The methods described here can be used to conduct reconnaissance- to deposit-scale till sampling surveys to assess mineral resource potential and establish environmental baselines.</jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Reviews in Exploration Geochemistry collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/reviews-in-exploration-geochemistry">https://www.lyellcollection.org/topic/collections/reviews-in-exploration-geochemistry</jats:ext-link> </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" specific-use="dataset is-supplemented-by" xlink:href="https://doi.org/10.6084/m9.figshare.c.6786087">https://doi.org/10.6084/m9.figshare.c.6786087</jats:ext-link> </jats:p>

<jats:p> A novel method of estimating the silica (SiO <jats:sub>2</jats:sub> ) and loss-on-ignition (LOI) concentrations for the North American Soil Geochemical Landscapes (NASGL) project datasets is proposed. Combining the precision of the geochemical determinations with the completeness of the mineralogical NASGL data, we suggest a ‘reverse normative’ or inversion approach to first calculate the minimum SiO <jats:sub>2</jats:sub> , water (H <jats:sub>2</jats:sub> O) and carbon dioxide (CO <jats:sub>2</jats:sub> ) concentrations in weight percent (wt%) in these samples. These can be used in a first step to compute minimum and maximum estimates for SiO <jats:sub>2</jats:sub> . In a recursive step, a ‘consensus’ SiO <jats:sub>2</jats:sub> is then established as the average between the two aforementioned SiO <jats:sub>2</jats:sub> estimates, trimmed as necessary to yield a total composition (major oxides converted from reported Al, Ca, Fe, K, Mg, Mn, Na, P, S, and Ti elemental concentrations + ‘consensus’ SiO <jats:sub>2</jats:sub> + reported trace element concentrations converted to wt% + ‘normative’ H <jats:sub>2</jats:sub> O + ‘normative’ CO <jats:sub>2</jats:sub> ) of no more than 100 wt%. Any remaining compositional gap between 100 wt% and this sum is considered ‘other’ LOI and likely includes H <jats:sub>2</jats:sub> O and CO <jats:sub>2</jats:sub> from the reported ‘amorphous’ phase (of unknown geochemical or mineralogical composition) as well as other volatile components present in soil. We validate the technique against a separate dataset from Australia where geochemical (including all major oxides) and mineralogical data exist on the same samples. The correlation between predicted and observed SiO <jats:sub>2</jats:sub> is linear, strong (R <jats:sup>2</jats:sup> = 0.91) and homoscedastic. We also compare the estimated NASGL SiO <jats:sub>2</jats:sub> concentrations with a sparser, publicly available continental-scale survey over the conterminous USA, the ‘Shacklette and Boerngen’ dataset. This comparison shows the new data to be a reasonable representation of SiO <jats:sub>2</jats:sub> values measured on the ground over the conterminous USA. We recommend the approach of combining geochemical and mineralogical information to estimate missing SiO <jats:sub>2</jats:sub> and LOI by the recursive inversion approach in datasets elsewhere, with the caveat to always validate results. </jats:p>

<jats:p>The Nowa Sól deposit is a part of the newly discovered Northern Copper Belt and is situated some 30 km north-west of the Lubin-Sieroszowice Mining District (so called New Copper District) in SW Poland. The ore horizon spans across the upper part of the Lower Permian (Rotliegend) terrestrial redbeds and the lower part of the Upper Permian (Zechstein) marine rocks and comprises three lithotypes: sandstone, shale and carbonate.</jats:p> <jats:p>The high-grade shale ore has polymetallic characteristics and is a crucial host for by-product metals such as silver, cobalt, and nickel (studied in this paper), but also molybdenum, vanadium, and rhenium. The results of bulk-rock and electron microprobe as well as mineralogical (optical and scanning electron microscope) data of the mineralized, organic-rich shale ore from the Nowa Sól deposit are presented. This thin stratigraphic horizon, ranging from 0.06 m to 0.59 m, shows notable concentrations of critical metals, including on average 15.9 wt. % copper, 715 g/t silver, 318 g/t cobalt, and 345 g/t nickel. It constitutes less than 10% of the total ore mass, but accounts for 36% of the silver, 40% of the nickel, and 42% of the cobalt found within the deposit.</jats:p> <jats:p>The ore sulfides in the mineralized shale in the Nowa Sól deposit include chalcocite, djurleite, bornite, accompanied by digenite, covellite, tennantite, galena, sphalerite, and pyrite. The silver content within the copper sulfides exhibits a linear decrease: chalcocite &gt; djurleite &gt; bornite. Three primary silver minerals are identified within the shale ore, namely native silver, silver amalgam, and stromeyerite. Two types of silver amalgam are observed: Hg-rich and Hg-poor. Cobaltite and gersdorffite represent the primary cobalt and nickel minerals, occurring as micrometer-sized inclusions within chalcocite and djurleite. Textural observations suggest that the silver, cobalt, and nickel mineralization postdates the major phase of copper sulfide precipitation. It is shown that in the Nowa Sól deposit, the Kupferschiefer horizon has acted as a geochemical barrier for abovementioned metals during protracted time – from early, syndepositional to late, epigenetic stage of basin evolution.</jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" specific-use="dataset is-supplemented-by" xlink:href="https://doi.org/10.6084/m9.figshare.c.6873631">https://doi.org/10.6084/m9.figshare.c.6873631</jats:ext-link> </jats:p>