Gold Mineralization

Soil sampling is a useful tool for the assessment of large areas of land where low sulphidation epithermal vein mineralisation is known or suspected. It provides a quantitative means of mapping out the geometry of an epithermal system and identifying potentially economic gold concentrations. In this paper gold in soil geochemistry data from the La India gold mining district in Nicaragua is used to model the soil gold signature at different sample grid spacing over known gold resources. The most cost-effective or optimal soil sample grid spacing to explore for epithermal gold deposits in this tropical wet and dry environment is identified. La India gold mining district covers a 50 km² area of fault-fill gold-silver mineralized quartz-adularia veins in western Nicaragua. The distribution of gold veins is well understood with current estimates defining a mineral endowment of over 2.3 Moz gold. The exploration data includes full coverage of the district by a 200 m by 50 m soil survey of fine-fraction B-horizon soil with ultra-trace multi-element analysis. Soil close to the gold veins is enriched in gold at trace level. Gold resources and prospects can be effectively ranked using the soil data with the larger resources correlating to broader, higher-grade soil gold anomalies. The soil gold content can be used to map-out the geometry and distribution of the epithermal vein system. In this study the soil survey data is filtered to create simulated 200 m by 200 m and 400 m by 400 m soil grids. The simulated grids are assessed against the mapped veins, surface rock chip and trench results, and known mineral resources. It is concluded that a 200 m by 200 m soil grid is adequate to discover economic vein gold deposits in the soil type found in the tropical wet and dry zone of western Nicaragua. This grid spacing provides enough resolution to map out vein trends and the overall geometry of an epithermal vein system that is exposed at surface and provides sufficient resolution to rank the gold anomalies by size and grade with confidence that the ranking will broadly correlate with associated gold occurrences. A 400 m by 400 m spaced soil sampling does appear to detect the larger deposits but will miss smaller or partially hidden deeper-seated deposits, and the spacing is too wide to provide any useful information on epithermal vein orientation or network geometry.

La India gold mining district covers a 50 km² area of fault-fill gold-silver mineralized quartz-adularia veins on the western margin of a Tertiary volcanic arc in western Nicaragua. Historic mining records and modern mineral exploration data, which to-date has defined a mineral endowment of over 2.3 Moz gold, provide a wealth of geological information. This paper draws on these observations and data to describe and classify the gold-silver mineralisation at La India, identify the geological controls, and interpret the timing of mineralisation within the regional tectonic setting. The district-scale gold-silver mineralisation at La India occurs in two adjacent geological settings with distinct mineralization characteristics and exploration potential: (1) an upland area of strongly faulted felsic to andesitic volcanics where the historic mine workings are located, and (2) an adjacent downthrown graben, the Sebaco Graben, where a thick sequence of andesite is preserved overlying the felsic volcanic sequence. Gold mineralisation is classified as rift margin-type low-sulphidation epithermal gold-silver fault and fracture-fill vein mineralization. In the historic mining area erosion has exposed the top of the high-grade epithermal zone. Minimal erosion in the Sebaco Graben means that the epithermal system is fully preserved at depth, with localised hydrothermal sinter outcrops, sporadic low-grade mineralised veins and a phreatic breccia pipe exposed at surface. Apart from the one phreatic breccia, the gold-silver mineralisation occurs in quartz veins and breccias that filled brittle faults and associated fractures and fissures which developed in an extensional tectonic setting. The structures containing the gold-silver mineralisation were formed as normal and trans-tensional faults with orientations consistent with southwest-directed extension: (1) a predominant northwest to north-northwest set parallel to the subducting plate; (2) secondary but locally extensive east-west, and (3) tertiary shorter and narrower northeast and north-striking veins. A district-scale north-northwest orientated through-going structure linking the major gold-silver deposits in the historic mining area is interpreted as a deep crustal conduit for the gold-silver bearing hydrothermal fluids. Other, as yet unidentified basement feeder structures may have fed mineralised corridors in the east and west of the district. The gold-silver mineralisation is best developed where structures pass through competent felsic volcanics and welded tuffs in the historic mine area, and also in the overlying andesite flows in the Sebaco Graben. Gold-silver mineralisation is less well developed where the structure passes through less competent unwelded tuffs and volcanic agglomerates. Gold-silver mineralisation is interpreted as occurring shortly before or at 8-10 Ma at the end of a long period of slab-rollback induced extension and arc volcanism. Post-mineralisation block faulting split the La India district into the upthrown, and subsequently eroded historic mine area where epithermal mineralisation is largely exposed at surface, and the well-preserved downthrown blocks such as the Sebaco graben where much of the gold-silver mineralisation is still hidden several hundred metres below surface.

LOCATION

MRDS (2011) Location
11N 14E Sec. 09 SBM latitude: 35.05057 longitude: -115.49305

S1/2NE1/4 sec. 4, T. 11 N., R. 14 E. S.B.M., 0.2 mi outside of the study area and east of the Columbia Mine (Moyle and others, 1988:65).

Francis Copper Mine, comprising 8 claims, is located in the Kelso District, on the southwest slope of the Providence Mountains, 4 miles southeast of Ames, a station on the Union Pacific Railroad. Elevation 4350 feet (Tucker and Sampson, 1930:210).

There is another Francis mine in NW1/4, Section 9, T.11N, R.14E SBM. The relationship between these two deposits is unknown.

HISTORY

The deposit was discovered about 1900 and reopened in 1917 by the Francis Copper Mining Co. (Tucker, 1918a; 1921, p. 341). San Bernardino County records show the Cuyamaca and Woods Lodes located in 1911, the Western Star Lode located in 1916, the Fanny Nos. 1-3, the Amos No. l, the Ramona Lode, and the Monte Video Lode located in 1930. A claim map (Tucker, 1918a) shows the Francis and Confidence Copper properties as a continuous series of claims. The mines may have been developed together since Edward Bluett, superintendent of the Francis mine, was also the owner of the Confidence Copper mine. Considerable development work and some production occurred in 1918. Francis Copper Mining Co. located a millsite near the mine in 1925. C. Nichols and H. Martin optioned the property in 1943 and received a preliminary development loan from the Reconstruction Finance Corp. to dewater and retimber the mine (Tucker and Sampson, 1943, p. 434). Francis Copper Mining Co. held the mine for many years and filed assessment work with the BLM as recently as 1977 to 1979, but abandoned the property in 1982 (C. L. La Rue, personal communication, 1982) (Moyle and others, 1988:58).

GEOLOGY

Tucker and Sampson (1930, p. 310-312, 1931, p. 271-272) describe the [Francis mine] property as having three subparallel veins over an area 1,200-ft wide by 4,500-ft long. The main vein is referred to as the Cuyamaca vein or the Woods Dike No. 3. The conspicuously outcropping vein is 5 to 10 ft thick, strikes N. 600 to 700 E., and dips 650 to85° NW. in bleached, sheared, Precambrian granite gneiss. A Mesozoic granitic intrusion underlies the gneiss at shallow depth. The white to translucent gray, iron-oxide stained quartz contains pyrite, limonite pseudomorphs after pyrite, galena, chalcopyrite, sphalerite, fluorite, and possibly scheelite and/or wolframite. (Moyle and others, 1986:65).

DEVELOPMENT

Workings include six shafts from 40 to 140 ft deep, three adits from approximately 30 to 120 ft long, and three pits. Production was at least 200 tons (USBM statistical files) containing 2,377 oz silver (average 11.9 oz/ton) and 10,626 lb copper (average 2.7 pct). Tucker (1918b) reported 500 tons produced. (Goldfarb and others, 1988, Table 5, Deposit 22, p. D39).

  Orogenic gold deposits, though construed to focused fluid flow during orogenesis, commonly post-date the main accretionary events. Several lines of evidence indicate that orogenic gold formation in the Arabian–Nubian Shield continued through the orogen collapse stage and associated rapid exhumation and thermal re-equilibration. The Gidami gold deposit in the Eastern Desert of Egypt is associated with post-foliation, brittle-ductile shear zones that deformed a weakly foliated tonalite-trondhjemite massif dated as ~ 704 Ma (U–Pb zircon age). Gold-sulfide quartz veins exhibit textural features indicative of repeated mylonitization, recrystallization, and muscovite crystallization. New 40Ar/39Ar ages of muscovite flakes from the auriferous quartz veins and from the altered wallrock overlap within analytical uncertainty at ~ 583 Ma, which corresponds to the climax of extension-related wrenching and rapid exhumation in the region (~ 596 to 582 Ma). Laser ablation-inductively coupled pla...

Hydrofractures, or hydraulic fractures, are fractures where a significantly elevated fluid pressure played a role in their formation. Natural hydrofractures are abundant in rocks and are often preserved as magmatic dykes or sills, and mineral-filled fractures or mineral veins. However, we focus on the formation and evolution of non-igneous hydrofractures. Here we review the basic theory of the role of fluid pressure in rock failure, showing that both Terzaghi’s and Biot’s theories can be reconciled if the appropriate boundary conditions are considered. We next discuss the propagation of hydrofractures after initial failure, where networks of hydrofractures may form or hydrofractures may ascend through the crust as mobile hydrofractures. As fractures can form as a result of both tectonic stresses and an elevated fluid pressure, we address the question of how to ascertain whether a fracture is a hydrofracture. We argue that extensional or dilational fractures that formed below c. 2–3 ...

A regional study of gold from Otago Schist vein deposits from both Caples and Torlesse Terranes has revealed the presence of both Au-Ag and Au-Ag-Hg alloys in both terranes. Almost all Hg-bearing gold occurs in east Otago vein systems, and Hg-free gold occurs in central and northwest Otago vein systems, irrespective of host terrane. One Central Otago mineralised zone has up to 1.7 wt% Hg in the gold. Au-Ag alloy (3-8 wt% Ag) is typical for gold found in most Torlesse-hosted vein deposits, and Au-Ag-Hg alloys with 1-4 wt% Hg are found in vein material from the Torlesse-hosted Hyde-Macraes Shear Zone. Au-Ag-Hg alloy (3-8 wt% Ag, 2-8 wt% Hg) is found in many Caples-hosted vein deposits. There is no relationship between depth of vein emplacement and Hg content of gold, as both high and low Hg gold are found in shallow-formed (<2 km) and deep-formed (>6 km) deposits. There is no spatial relationship between Hg-bearing gold and cinnabar-bearing veins that occur in Caples Terrane rocks on the southern edge of the schist belt. Mercury-bearing placer gold in eastern Southland may have been derived from erosion of east Otago veins. The source of Hg-bearing placer gold in northern Southland is unknown as yet.

The Otago Schist in Central Otago has undergone complex late metamorphic and post-metamorphic deformation during uplift and exhumation. Two late metamorphic structural generations can be recognised and these may be genetically related. The earlier Manorburn Generation has been widely recognised and described previously. This generation has fold axes subparallel to a prominent syn-metamorphic quartz rodding lineation. A later generation, herein named Poolburn Generation, has folds which superficially resemble Manorburn Generation, but has fold axes that are at a high angle to the quartz rodding lineation. Both generations occur in mappable fold zones (kilometre-scale) that are generally not vergence boundaries, and some minor relative displacement may occur across fold zones. Fold zones occur within structurally and lithologically uniform schist domains. Abrupt changes in lithological sequences and orientations of structural elements such as Manorburn and Poolburn Generation fold axes and quartz rodding lineations occur at post-metamorphic faults which separate different schist domains. Central Otago schist can be subdivided on the regional scale (tens of kilometres) into at least nine schist domains whose structural and lithologic continuity is disrupted by fault discontinuities. The domains and bounding discontinuities developed during Late Jurassic and Early Cretaceous uplift. Syn-metamorphic compressive ductile deformation evolved to localised fold zones in the early stages of this uplift. Subsequently, regional extension caused juxtaposition of domains with different textural zones, and schists from slightly different structural levels. The Caples/Torlesse Terrane boundary is a composite feature, and different segments formed at different stages through the transition from ductile compression to brittle extensional deformation.

The Okpella region in southwestern Nigeria’s Precambrian Basement Complex holds significant gold (Au) mineralization potential but remains underexplored due to its complex lithostructural evolution. The terrain comprises diverse metasedimentary and granitoid rocks, including granite gneiss (GGN), garnet-biotite schist (GBS), calc-silicate gneiss (CGN), quartzite (Qs), banded iron formation (BIF), charnockite (Ch), granite (G), and minor pegmatite and basic dykes. This study presents a novel integration of geological, geochemical, and high-resolution aeromagnetic and radiometric data—including magnetic derivatives, optimized radiometric indices, potassium deviation analysis, Au prospectivity modeling, and magnetic depth-to-source estimations—to delineate lithological units, characterize hydrothermal alteration, identify Au-bearing zones, and estimate the depths of mineralized structures. The Ch-dominated southern domain shows low to moderate magneto-radiometric responses, while the central to northern zones (GGN, GBS, CGN, BIF, G) exhibit higher signals—with magnetic intensities reaching up to 105.6 nT—interspersed with localized lows. Enhanced magnetic derivatives, optimized radiometric indices, and Au prospectivity mapping refine auriferous targeting by highlighting structurally reactivated contacts, particularly GBS–G, CGN–G, GGN–CGN–G, and GBS–CGN–G, dominated by NE–SW and NW–SE structures. Three structurally controlled hydrothermal belts with exploitable depths from <37 to 125 m are delineated, while deeper magnetic models resolve reactivated crustal blocks down to ~3.5 km. The resulting framework provides a transferable exploration strategy, integrating geophysical, geochemical, and geological insights to support sustainable mineral development and national resource-based economic growth.

Réalisées dans le cadre des activités de l’Équipe d’Explorations Spéléologiques de Villefranche (EESV), les
recherches archéologiques sont soutenues depuis 2005 par la société Arkemine et par la DRAC Auvergne-Rhône-
Alpes. Y consacrant une grande partie de leur temps libre, des amateur(e)s et professionnel(le)s de l’archéologie,
des spéléologues et des naturalistes de l’EESV collaborent et interviennent sur le terrain. Passionnés, ces derniers
connaissent les cavités artificielles des monts du Lyonnais et du Beaujolais. Les recherches sur le terrain ont été
effectuées en collaboration avec d’autres associations et acteurs du patrimoine et de l’environnement (Patrimoine
en Haut Sornin, FRAPNA / FNE). Des laboratoires d’analyse sont aussi régulièrement sollicités pour des analyses
spécifiques (datations absolues, analyses de minerais...) en fonction des découvertes réalisées lors des fouilles
archéologiques. Les vestiges miniers se trouvent sur des terrains privés. Cet article est donc aussi l’occasion de
remercier les propriétaires qui ont autorisé la réalisation des fouilles archéologiques.
Au sein du Lyonnais et du Beaujolais, le patrimoine minier souterrain accessible concerne principalement les
gisements en contexte filonien. Toutefois, d’autres types de gisement ont été exploités, par exemple à Chessy et
Vaux-en-Beaujolais pour le cuivre et la pyrite où à Sainte- Paule pour la houille. La quasi-totalité des vestiges miniers
n’avait avant 2005 jamais fait l’objet d’une inspection à caractère archéologique. Beaucoup de vestiges sont liés à
des phases d’exploitation de la période contemporaine. C’est donc tout naturellement que les recherches se sont
aussi inscrites dans la diachronie en étudiant l’activité minière du Moyen-Âge à l’Ère industrielle. Toutefois, depuis
2020, nous développons nos recherches sur l’exploitation du cuivre associé à des amas stratiformes.
Les territoires des Monts du Lyonnais et du Beaujolais constituent un ensemble géologique dont le sous-sol est
principalement composé de roches métamorphiques et plutoniques. La mise en place des roches plutoniques, du
magma qui va cristalliser en granite après un refroidissement lent, favorise la circulation de fluides hydrothermaux
chargés en éléments chimiques, notamment en métaux. Ces fluides vont pénétrer dans les fracturations, créées par
l’orogénèse hercynienne et la mise en place des plutons, qui traversent les roches environnantes (www.geopark-
beaujolais.com/histoire-geologique.html). En remontant, ces fluides refroidissent et, la pression diminuant, les
éléments chimiques vont cristalliser sous la forme de composés minéraux en colmatant les fissures. Dans l’emprise du
Géoparc Beaujolais, les filons sont principalement constitués de quartz ainsi que de baryte et de fluorine (Mazenot,
1936, p.150). Ils intègrent des éléments plus rares, tels que des minerais métallifères sulfurés, en particulier de la galène,
un sulfure de plomb plus ou moins riche en argent, mais aussi plus rarement des minerais de cuivre et de l’antimoine.
Isolés ou formant des faisceaux, les filons subverticaux situés dans l’emprise du Géoparc Beaujolais ont été exploités
depuis la surface et en profondeur dès le Moyen-Âge. Ils ont ensuite été reconnus aux XVIIIe et début du XIXe siècles.
Après la période révolutionnaire, certains filons ont fait l’objet de permis de recherche et des concessions ont été
attribuées. De nombreuses sources historiques, archives et publications, permettent de documenter une activité
minière attestée dès la fin du Moyen Âge. Dans un premier temps, les filons ont été explorés pour trouver des métaux
non ferreux, en particulier de l’argent et du plomb. Durant l’ère industrielle, des minerais utilisés dans l’industrie
chimique ont principalement été exploités, tels que la baryte et la fluorine. Dans l’emprise du Géoparc Beaujolais
circonscrit au sein du département du Rhône, de nombreux vestiges témoignent donc des activités minières passées.

ISCHIA AND THE PHLEGREAN FIELDS. MISCELLANY OF GEOLOGY, MINING GEOGRAPHY, AND ENVIRONMENTAL GEOLOGY

The book brings together 15 articles on the history, on the volcanic and solfataric mineral products, and other geological and environmental pecularities of the island of Ischia and the Phlegraean Fields, including Posillipo Hill. It is the result of decades of observations and field investigations conducted with the help of classical authors, medieval documents, and modern literature, which have enabled the correction of long-held beliefs and the provision of new knowledge.

The sixteenth-century report of the presence of a gold mine in Campagnano of Ischia and the recent discovery of traces of epithermal gold and tiny grains of alluvial gold do not confirm the alleged and only report of Strabo, as geochemical investigations demonstrate that the gold is linked to the volcanic events of the years 1301-1302.  It is very likely, however, that Strabo had written about the presence, now confirmed, of ancient ceramic factories (chytreia) and that in the codices the word was altered to chryseia, meaning “goldsmiths” (transformed into “gold mines” in the Italian translations).

Sedimentary marine clay has historically been one of the most sought-after and used products on Ischia, but it's not true that this activity was continuous from prehistoric times to recent times. Archaeology and literature demonstrate that the activity ceased in Roman times and was resumed in the early 16th century for boulding uses. In the Casamicciola area, the widespread presence of clay lenses, disjointed and more or less hidden by surface soil, is the cause of periodic disastrous landslides.  In addition to sedimentary clay, often confused with it, a more or less kaolin and aluminous volcanic clay known as "bianchetto" is also present and has been mined. There is also evidence of the presence and prolonged historical exploitation of sulfur and other useful volcanic products, particularly alum, and in addition to the harvesting of natural efflorescences, "rock alum" was produced for centuries. The importance of the coastal magnetic sands has been exaggerated: although present and locally abundant, they were only mined in limited quantities between the 18th and 19th centuries, for export to the mainland ironworks. It is untrue that a recent ironworks ever existed, and as for the ancient furnaces recognized on the island, they have been shown to use ore imported from Elba island.

The Posillipo hill, which separates Naples from the Phlegraean Fields, was anciently perforated at two extreme points. The Cave named Sejano or Sillana (probable contraction of Posillipana) is the road tunnel that, as Strabo records, was built by Cocceius during the time of Agrippa, together with the one at Cumae. The two tunnels are completely similar, and the same characteristics are found in the smaller one that passes through the little island between Coroglio and Nisida, now half-submerged by the sea. Their construction was part of the general militarization of the Campanian coast directed by Agrippa on behalf of Octavian during the civil war against Sextus Pompey (38-36 BC). At the time, the coast was raised several meters above sea level, and the coastal road from Pozzuoli to Naples ran along it. Its most critical point was just below the Coroglio promontory, which was overcome by the tunnel above. At the same time, this and the coastal road were connected to the military port of Nisida by an artificial isthmus (and by the other short tunnel). Following the subsidence of the coast and the earthquake of the years 3-2 BC, the Coroglio tunnel remained isolated, as shown in the Peutinger Tablet; at the same time, it suffered internal collapses and, subsequently, its western exit was blocked by landslides from the hill above.  Forgotten for centuries, it ended up being confused with the other, more northern tunnel, known as the "Posillipo Cave".  However, this latter, excavated at the same time if not earlier, originally had no characteristics of a Roman road tunnel, and could not have had any due to the different structure of the hill: it was originally the service cuniculus for crossing the aqueduct (of the Serino), with which it is still connected at many points along the route. The narrow, dark, and dusty service cuniculus could be traversed on foot or on horseback, but with those inconveniences complained about by Seneca (mocked by Petronius).  It was made accessible to carriages only with the expansion and lighting works of the 15th and 16th centuries.

From the main aqueduct, two branches departed and ran along the two sides of the Posillipo hill: the first, from the Piedigrotta entrance, ran along the eastern slope and reached the Villa Pausilypon, supplying, along the way, the other Roman villas in the Neapolitan coast; the second, from the Fuorigrotta exit, ran along the western slope and, before the bradyseism and the earthquake, went to supply the port of Nisida passing, in its final stretch, over the artificial histo.

We describe the presence of Witwatersrand-type gold mineralization in Paleoproterozoic strata indicating this style of deposit is not confined to the Archean. The discovery of basal and intraformational conglomerate-hosted gold mineralization in the Huronian Supergroup's Mississagi Formation near Sudbury, Ontario, has indicated potential for Witwatersrand-type gold mineralization to occur also in early Paleoproterozoic basin fills on the Hearne, Wyoming and Karelian cratons. The Paleoproterozoic Hurwitz, Snowy Pass and Karelian supergroups, located on these cratons, are similar to the Huronian Supergroup on the Superior Craton, in terms of sequence and litho-stratigraphy, and maximum age of deposition. A review of the stratigraphy and past gold exploration from each supergroup has revealed each basin to contain similar fluvial poly-to oligomictic, pyritic conglomeratic strata with locally anomalous gold and/or uranium concentrations at stratigraphic levels that correlate to those of the Mississagi and Matinenda formations of the Huronian Supergroup. Examination of gold and gold-enriched pyrite from the Mississagi Formation conglomerates suggests that specific point sources existed for most of the gold therein. Each of the above basins forms part of a larger contiguous continental rift system prior to the breakup of the supercontinent Kenorland at around 2480 Ma. As each basin fill was displaced to different geographic positions following this continental breakup and then subjected to separate orogenic and metamorphic overprints, the gold and uranium mineralization in each of the basins is unlikely to be of a common, post-depositional hydrothermal origin, but in all likelihood of a paleoplacer origin. It is suggested that this period of gold-enrichment is the result of truncation and reworking of underlying stratigraphically older units and/or from former gold deposits/occurrences and gold-enriched greenstone-dominated hinterlands. The omnipresence of detrital and/or syn-depositional pyrite in conglomerates of each basin reinforces the idea that a lack of atmospheric oxygen at the time of Kenorland rifting existed during their deposition and prior to the ''great oxidation event". Our comparative analysis of Kenorland rift graben fills reveals that gold potential, which can be determined by the presence of detrital pyrite as observed at the Pardo project, should exist in all stratigraphic equivalents of the Mississagi and Matinenda formations where preferentially reworked fluvial conglomerates rest on an erosional unconformity and where a corresponding Au-enriched Archean hinterland existed.

The extraction and processing of naturally occurring phosphate deposits have significantly intensified the mobilization of potentially toxic elements (PTEs), resulting in their pervasive release into the environment. Accordingly, this study investigated the environmental impact of phosphate mining at Sebaiya East area (Egypt), analyzing 24 surface sediment samples for PTEs via ICP-OES, supported by statistical analysis (descriptive and multivariate), pollution indices (individual, composite, and ecological), and health risk assessments (carcinogenic and non-carcinogenic) to understand the release, distribution, accumulation, and geochemical behavior of contaminants. The median values of PTEs were lower than their maximum concentrations, highlighting localized hotspots. Cd’s average level consistently exceeded all geochemical reference values. The individual contamination grades, based on average Igeo and CF values, ranked as Cd > As > Cr > Ni > Zn > Cu > Pb. Samples showed overall contamination (mean PLI: 1.79, mean Cdeg: 20.45, mean PINemerow: 4.29), with 29.2% severely polluted (PLI > 2) and 37.5% highly contaminated (Cdeg ≥ 24), localized near mining activities. The mean RI value of 383.9 indicated a considerable ecological risk (300 < RI < 600) throughout the study area. Weak Pearson correlations observed for As and Cd with other PTEs indicated distinct geochemical behavior and anthropogenic origins. PCA revealed the mixed origin of Pb, Cu, Zn, As, and Ni in PC1 (weathering of local bedrock and diffuse deposition from mining activities) and the anthropogenic origin of Cd in PC2. Cr and As posed the highest carcinogenic (CR: 3.64E+02) and non-carcinogenic risks (HQ: 3.04E+05), respectively, exceeding safety thresholds.

Classical geographers-most prominently Claudius Ptolemy-refer to the Aurea Chersonesus ("Golden Peninsula"), long equated with the Malaya Peninsula. This study reexamines that consensus by triangulating Greco-Roman texts, Indic labels (Suvarṇabhūmi, Suvarṇadvīpa), resource geography, maritime routing, and toponymy. We argue that Ptolemy's χερσόνησος functions as a scale-normalized, bi-littoral construct: a gold-and tin-forward corridor spanning both shores of the Strait of Malacca. Read geometrically, Ptolemy Book 1, ch. 14 treats the first leg parallel to the equator and the second toward south-and-east, consistent with seasonally asymmetric monsoon routing. New contributions include: (i) a Sumatra-centered toponymic thread around Tanjung Emas ("Golden tanjung"-a projecting landform that may be marine or fluvial), accessible from the Bay of Berhala via the Batang Hari corridor and interpreted via metonymy (tanjung → regional chersonesos); and (ii) equator-ambiguous latitude tests combined with an alternative-inclusive crosswalk of Ptolemaic names. Results show that several Sumatra-Batang Hari alignments outperform canonical Malaya Peninsula placements on the latitude metric, and this advantage persists when multiple Malaya Peninsula alternatives are allowed. The framework preserves viable Malay identifications while motivating a Sumatra-focused component of the "Golden" label. It yields falsifiable predictions for archaeometallurgy (interior-to-estuary transects), toponymy audits (paired placements with winners), and sailing-time modeling (monsoon-aware residuals), providing a concrete agenda to confirm or revise the bi-littoral "Golden Corridor" model.

Nach biblischer Chronologie (vgl. Roger Liebi, Im Anfang schuf Gott) ereignete sich die Sintflut um etwa 2450 v. Chr.. In der Generation Pelegsrund 100 bis 200 Jahre später-heißt es, "teilte sich die Erde" (Gen 10,25). Damit wird im biblischen Text eine weltweite tektonische Umordnung in einen vergleichsweise kurzen Zeitraum eingeordnet. Während die heutige Geologie für die Kontinentaldrift Zeiträume von zig Millionen Jahren mit Spreizraten von wenigen cm pro Jahr annimmt, müsste sie im biblischen Rahmen auf tausende Kilometer in Jahrhunderten oder gar Jahrzehnten beschleunigt gewesen sein. Bereits bekannte Modelle wie Baumgardners Catastrophic Plate Tectonics (CPT) oder Browns Hydroplate Theory versuchen, dies zu erklären, stoßen aber vor allem bei der Wärme-und Energiebilanz an ihre Grenzen. Das Ziel des folgenden Entwurfs ist, innerhalb des biblischen Rahmens ein innovatives Szenario zu entwickeln, das diese Schwierigkeiten besser berücksichtigt und zugleich den biblischen Angaben treu bleibt. Einfache Zusammenfassung: Die Bibel berichtet, dass die Sintflut um 2450 v. Chr. stattfand und sich kurz darauf in Pelegs Zeit die Erde teilte. Peleg markiert nicht einfach einen Punkt, sondern eine Epoche:  Wahrscheinlich Beginn der Kontinentalteilung um seine Geburt herum,  mit einer Fortsetzung über sein Leben hinweg, und möglicherweise Abschluss am Ende seiner Generation.

An extraterrestrial origin for Earth's continental tectonic plates is based on the central insight of the remarkable similarity between Algoma-type banded iron formations (BIF) and gneiss/migmatite, with both exhibiting felsic-mafic banding and small-scale isoclinal folding. This physical similarity indicates formational similarity, with both BIF and gneiss/migmatite having formed by modulated sedimentation from hydrothermal plumes, where aphanitic (fine-grained) BIF formed on Earth and phaneritic (coarse-grained) gneiss/migmatite formed in the microgravity of hot-classical KBOs. Then hot-classical KBOs with sedimentary cores having a gneissic composition were perturbed into the inner solar system during the late heavy bombardment (LHB), circa 4.2–3.8 Ga.

The study area (South western part of Volta River Basin of Ghana), covering an area of 8570 km 2 , which is one-eleventh the area of the Volta River basin of Ghana, has been subjected to numerous academic research works but geophysical survey works because of virtual perceptive reasons. It is now believed to overly mineral-rich geological structures, hence, the use of magnetic and gravity survey methods to bring out these mineral-rich geological structures.Geographically, it (study area) is located at the south western part of the Voltaian basin at latitudes 07 o 00’ N and 08 o 00’ N and longitudes 02 o 00’ W and 01 o 00’ W respectively. Airborne gravity and magnetic survey methods were employed in the data collection. The field data correction and error reduction were applied to the two raw data on the field after which, Geosoft Oasis Montaj 7.01, Encom Profile Analysis (P.A) 11 and 13, Model Vision 12 and ArcGIS 10.0 were used to process, enhance (e.g. reduce to pole at low latitu...

The renewed interest in the reactivation of the defunct National Konongo Gold Mine located in the Ashanti Greenstone Belt, calls for a further probe into its geology and the associated mineral hosting structures to discover its mineralization potential. In order to achieve this, airborne magnetic, radiometric and electromagnetic datasets were interpreted to determine the potential gold hosting features in the studied area. The results show the area to consist of the metasediment, the metavolcanic, Tartwaian Formation and their associated granitoids. Results also show that the Tarkwaian sediments, observed largely in the north-eastern side of the site; widen out substantially and truncate in the south. The analysis of the structure lineaments using a rose diagram reveals three main tectonic structures trending in N-S, NNW-SSE, and third the structure trending in the NNE-SSW to NE-SW directions in the area. The dominant structures in the area, form 90% of all the delineated structures and trend in the NE-SW and NNE-SSW direction with the remaining 10% trending in the N-S and NNW-SSE. These structures are associated with the major shear and fracture zones located mainly at the contact between the basin sediments and volcanic belt and also associated with the Tarkwaian Formation. The mapped potential gold mineralization zones located mainly at the contact between the metasediment and the metavolcanic units of the Birimian Supergroup, as well as the Tarkwaian Formation, were mapped by integrating the structures, alteration zones as well as the complex dyke systems. This paper delineates the prominent geological structures with the potential of hosting economic gold mineralization in and around the Ko-

Airborne magnetic and radiometric datasets are used to interpret the geology and geological structural patterns which serve as potential gold mineralization zones in the Kyerano area located at south-western boundary of the prospective Sefwi Gold Belt and the Kumasi Basin in southwestern Ghana. The geophysical data processing approach adopted concentrated on mapping geological boundaries, geological structures and possible gold mineralization zones is link to hydrothermally altered zones. The application of the enhancement filtering algorithms such as the reduction to the pole and analytic signal to the magnetic data, as well as the ternary radiometric image aided in the mapping of the mafic metavolcanics, basin metasediments and the belt-type granitoid complexes. The first vertical derivative and tilt angle derivative filters helped to delineate fractures, folds, and the contact zones of the formations such as that of the metavolcanics-metasediments that host the main Bibiani Shear Zone. Lineament analysis of the structures using rose diagram, reveals two main tectonic episodes in the area. These are NE-SW and NNW-SSE trending regional structures which account for about 90% of the extracted structures and are associated with the D1 and D2 deformational episodes of the Birimian Formation respectively. These structures are major fracture systems and play a pivotal role in the localization of gold mineralization in the study area.

disseminations concordant with regional faults and shears. A gold-bearing fluid similar to that for the Birimian Supergroup-hosted quartz vein gold mineralisation, but with a larger H 2 O component, is proposed to have formed the granitoid-hosted gold mineralisation.

Mining beneficiation, the process of adding value to raw mineral resources through local processing and manufacturing, is increasingly recognised as a catalyst for socioeconomic empowerment in South Africa. This paper argues that beneficiation not only enhances economic growth but also creates shared value for communities most impacted by mining activities. By focusing on local employment, skills development, and community investment, beneficiation can transform historically disadvantaged communities into active participants in the mining sector. However, challenges such as capital investment, infrastructure, and skills development must be addressed to realize the full potential of beneficiation. This paper advocates for a comprehensive approach to mining beneficiation that prioritizes inclusivity and sustainability.

Matthews Bantsijang is a South African mining and energy expert and commentator involved with mining beneficiation, particularly in promoting its economic benefits and opportunities. He advocates for adding value to raw mineral resources through local processing and manufacturing, rather than exporting them in their raw form. His work also focuses on supporting SMMEs within the mining sector and community engagement through awareness programs.

The aim of this study of the spatial dispersion of tin, niobium and tantalum mineralization associated with the Mayo Darlé granitoids was to produce prospecting guides through predictive maps of Sn, Nb and Ta in the region. It was based on a database (in appendix) obtained after analysis of rock samples (greisens and quartz veins) collected in the field, using a portable X-ray fluorescence (XRF) spectrometer. Two approaches were used: 1) structural studies in the field using the directions of veins and fractures 2) the use of variographic maps, an essential element in geostatistics for determining directional anisotropies. A joint synthesis of the modelling results shows that tin, tantalum and niobium mineralization at Mayo Darlé is concentrated along strike intervals N315E to N320E, with mineralization also occurring along strike N35E for high-grade Sn, medium-grade Ta and low-grade Nb. In short, mineral concentrations disperse progressively in space: positively from east to west for tantalum and niobium, and inversely for tin.

Column flotation is a physical process where entrapped silica between bubbles is removed using bubble wash technology developed by Sivarao kshirasagara in INDIA at RD Mines, Rajasthan, for Zinc cleaning. The smelter rejected high-silica concentrates containing 8%. Technology helped to reduce it to 3%.
Technology is helpful to increase smelter capacity and reduce costs.

The Karasay site is located on the Apantepa-Karatagata square of Almalyk district in Republic of Uzbekistan. This area is located in the basin of the Karakiya River along the right tributaries – Karagatagatasay and Karasay. Three ore occurrences have been identified at this site: Karasay (the most studied and promising), Mazarsay and Apantepa. The method of studying ore minerals consisted in the study of polished grinds and briquettes
with pressed concentrates on a Carl Zeiss scanning electron microscope (SEM-EDX) which is located at Center for Advanced Technologies. Considering that gold in primary sulfide ores is a typical micro-nanomineral, nanomineralogical research methods were used

In the course of an areal and economic survey of the Bessemer quadrangle, Alabama, in 1910, the writer had the opportunity of examining a number of ore deposits, chief of which is the noted limonite deposit at Shelby, in Shelbj7County. There is another extensive deposit of brown ore southwest of Montevallo, and small deposits exist at other points. Stratified hematites also occur in the region*. The most important of these deposits have been described by Henry McCalley 1 and P. S. Smith.2

Fault stepovers are features where the main trace of a fault steps from one segment to the next in either an underlapping or overlapping manner. Stepovers exert a critical influence on crustal permeability and are known to control phenomena such as the migration of hydrocarbons and the location of geothermal fields. In the Kalgoorlie‐Ora Banda greenstone district, Western Australia, we demonstrate a spatial association between stepovers and gold deposits. It is shown that although underlapping stepover geometries are typically rare in fault systems, they are anomalously associated with gold deposits. Further, the along‐strike and across‐strike dimensions of both underlapping and overlapping fault stepovers fit, to a first‐order approximation, the same self‐similar trend. Boundary element modelling of Coulomb failure stress changes is used to explain these observations in terms of damage generated by rupture events on the bounding fault segments and associated aftershock sequences. O...

Airborne geophysical survey provides a most effective and cost efficient way of undertaking reconnaissance surveys over large areas. Detailed data is collected over localised areas. The data improves discovery of underground structures such as archaeological artefacts, extended geological boundaries and targeting of discovery of mineral deposits. Recent airborne geophysical survey (2013-2014) will help improve understanding of the geology of Malawi and speed up discovery of minerals deposits including oil and gas. The paper describes geophysical methods used and how interpretation of hidden treasures is made.

The assessment of fault activity is necessary to mitigate against damaging earthquakes. To adequately assess long-term fault activity, a new technique that complements chronological investigations is required. Here we examine the applicability of the slip tendency (ST) method, based on physical models, to assess fault activity in Japan. We computed the ST using a friction coefficient of 0.6 for the faults, a common friction coefficient for rocks, and the stress state estimated from earthquake focal mechanisms in northeastern Japan. Calculated ST values are high for the most active faults (e.g., the Senya segment) and are low for inactive fault (e.g., the Sakunami-Yashikidaira segment). Therefore, we propose that the ST method can be applied in assessments of fault activity. However, the ST method sometimes underestimates fault activity, and we have explored the necessary input parameters to obtain reliable results. To use the ST method, the determination of these parameters is critical for the robust assessment of fault activity based on physical models.

This paper describes a mine water tracer test in a flooded Germany underground limestone mine. Uranine was injected at two locations and the tracer concentration measured with an on-line fluorimeter. The breakthrough curve shows two peaks, relating to the two injection sites. Background values were reached after 24 months making this tracer test the longest mine water tracer test ever. Mean effective velocities range between 0.1 and 0.5md.¹ indicating a slow water circulation. The paper concludes that low effective velocities are an indication for mines with a simple geometry and that simple mine geometries facilitate stratification and a lower pollution potential.

The Okpella region, located in the eastern Igarra Schist Belt of southwestern Nigeria, is a Neoproterozoic metasedimentary-granitoid terrain known for its gold (Au) mineralization potential. Despite this, the complex interactions between litho-nuclide dynamics, hydrothermal alteration, and associated radiogenic and potentially toxic element (PTE) hazards have not been fully explored in the region. This study, the first to apply magnetic-assisted radiometric analysis combined with geochemical and PTE assessments in Nigerian geology, aims to address this gap. The results reveal significant geochemical heterogeneity, with elevated concentrations of K (up to 5.04%), eTh (up to 51.12 ppm), and eU (up to 13.42 ppm) predominantly found in garnet-biotite schist, calc-silicate gneiss, granite, and their contacts. These concentrations are attributed to hydrothermal fluid activity and fluid/melt-rock interactions. Conversely, charnockite in the southern region shows depleted radionuclide levels, reflecting limited alteration and the presence of K-poor minerals. Advanced mapping techniques have identified hydrothermal alteration zones and Au mineralization belts aligned with NE-SW and NW-SE structural trends. Magnetic depth-structure models suggest basement depths of ~ 0.3 to 3.5 km, with fractures acting as conduits for hydrothermal fluids, facilitating radionuclide redistribution near the surface. The study also highlights elevated radiogenic hazard indices, particularly in the central and northern regions, surpassing crustal limits. The PTE (mg/kg) trend in sediments (Hg > Cu > As > Pb > Zn > Co > Cr > Ni) indicates environmental and health risks, particularly from Hg contamination linked to artisanal Au mining. These findings underscore the need for controlled gold extraction, Hg-free processing, and continuous environmental monitoring. This study provides a scalable framework for balancing resource extraction with environmental sustainability, offering insights into best practices for mineralized terrains globally.

A Aerogeofísica tem colaborado significativamente no avanço do conhecimento geológico do Brasil, principalmente na pesquisa em grandes áreas, tendo destaque em áreas de acesso restrito ou cujo mapeamento e demais pesquisas de detalhe não foram realizados. Os métodos aerogeofísicos são magnetométrico, gamaespectrométrico, eletromagnético e gravimétrico, a altura e o espaçamento de linhas variam de acordo com o objetivo do levantamento (reconhecimento ou detalhe). Por meio de informações obtidas em levantamentos aerogeofísicos é possível complementar e extrapolar o que foi adquirido no mapeamento geológico de campo, gerando novas discussões e estimulando o desenvolvimento de pesquisas mais consistentes e detalhadas. No estado do Rio de Janeiro, a integração geológicaaerogeofísica ainda carece de aprofundamento. No mês de Junho de 2016 a CPRM inseriu em sua plataforma GEOBANK novos dados aerogeofísicos levantados em 2014, com linhas de voo de 500m de espaçamento. Neste trabalho, foi escolhida para correlação a folha Casimiro de Abreu, no norte Fluminense. Por meio da análise inicial desses dados, foi possível observar a existência de uma série de informações em aerolevantamento, ainda não existentes em mapeamento geológico realizado pelo projeto PRONAGEO, de 2007, também da CPRM, motivando o desenvolvimento deste trabalho. Especificamente, o trabalho objetiva identificar domínios possivelmente relacionados a enxames de diques não encontrados no mapa geológico de campo, bem como caracterizar a assinatura aerogeofísica da destacada Suíte Suruí, que, apesar de exibir contatos diferenciados, que não seguem a tendência de estruturação NE-SW, não apresentou inicialmente anomalias que permitissem diferenciá-la das rochas encaixantes.

A Aerogeofísica tem colaborado significativamente no avanço do conhecimento geológico do Brasil, principalmente na pesquisa em grandes áreas, tendo destaque em áreas de acesso restrito ou cujo mapeamento e demais pesquisas de detalhe não foram realizados. Os métodos aerogeofísicos são magnetométrico, gamaespectrométrico, eletromagnético e gravimétrico, a altura e o espaçamento de linhas variam de acordo com o objetivo do levantamento (reconhecimento ou detalhe). Por meio de informações obtidas em levantamentos aerogeofísicos é possível complementar e extrapolar o que foi adquirido no mapeamento geológico de campo, gerando novas discussões e estimulando o desenvolvimento de pesquisas mais consistentes e detalhadas. No estado do Rio de Janeiro, a integração geológicaaerogeofísica ainda carece de aprofundamento. No mês de Junho de 2016 a CPRM inseriu em sua plataforma GEOBANK novos dados aerogeofísicos levantados em 2014, com linhas de voo de 500m de espaçamento. Neste trabalho, foi escolhida para correlação a folha Casimiro de Abreu, no norte Fluminense. Por meio da análise inicial desses dados, foi possível observar a existência de uma série de informações em aerolevantamento, ainda não existentes em mapeamento geológico realizado pelo projeto PRONAGEO, de 2007, também da CPRM, motivando o desenvolvimento deste trabalho. Especificamente, o trabalho objetiva identificar domínios possivelmente relacionados a enxames de diques não encontrados no mapa geológico de campo, bem como caracterizar a assinatura aerogeofísica da destacada Suíte Suruí, que, apesar de exibir contatos diferenciados, que não seguem a tendência de estruturação NE-SW, não apresentou inicialmente anomalias que permitissem diferenciá-la das rochas encaixantes.

Dedico este trabalho a minha filha Nayumi. Agradeço primeiramente a Deus, por me abençoar com saúde e perseverança na busca de mais um objetivo. Por me conceder serenidade e sabedoria nos momentos mais conflituosos e difíceis de minha vida e por me dar coragem para seguir sempre em frente, mesmo diante das dificuldades. Edmilson e Júlia pela força, compreensão, paciência, incentivo e apoio demonstrados em mais essa etapa da minha vida. Ao meu irmão Henderson pela amizade e companheirismo. A minha companheira Mina, pelo incentivo e apoio nos momentos de desânimo e por fazer parte da minha vida. Ao meu orientador, Prof. Dr. Marcos Welby Correa Silva, pela oportunidade, paciência, dedicação, apoio e compreensão. Aos professores do Programa de Pós-Graduação em Geofísica, Cícero Roberto Teixeira Régis, por tornar os conhecimentos em Geofísica mais interessantes no decorrer de suas aulas, e Lúcia Maria da Costa e Silva, pela competência no ato de ensinar e pelas valiosas contribuições na minha formação. Aos arqueólogos Fernando Luiz Tavares Marques e Deusdédit Carneiro Leite Filho, pela oportunidade, amizade, troca de informações e sugestões para o desenvolvimento deste trabalho. Aos colegas da Pós-Graduação em Geofísica: Thiago Santa Rosa, Odinei Júnior, Marcelo Fernandes e Diego Miranda pelos momentos felizes que passamos e pelas horas de companheirismo durante nossa jornada acadêmica. A CAPES, pela concessão de bolsa de mestrado. A UFPA/CPGf, por ter proporcionado a continuidade da minha formação acadêmica e profissional dando toda estrutura e apoio logístico necessário à realização desta pesquisa. Às secretárias da pós-graduação, Benildes Lopes e Lucibela Soares, pela atenção, amizade, carinho, incentivo e presteza destinada aos alunos do curso. E por fim, a todos que de uma forma ou de outra contribuíram para realização deste trabalho. Esta pesquisa apresenta os resultados da aplicação de métodos geofísicos não invasivos, visando a indicação de possíveis locais de deposição de materiais, no levantamento arqueológicos em um sítio estuarino localizado no município de Penalva, no estado do Maranhão. Os métodos utilizados foram Magnetometria e Radar de Penetração no Solo (GPR). As medidas magnéticas foram utilizadas para indicar os locais para escavação. O GPR foi utilizado para confirmar as anomalias geradas pelo método magnético, proporcionando a diminuição de erros quando as anomalias magnéticas não são provenientes de feições arqueológicas. Foram realizados 14 perfis de GPR, utilizando uma antena de 400 MHz e 1664 medidas magnéticas, utilizando o magnetômetro. Durante o levantamento arqueológico realizado, baseando-se nas anomalias fornecidas pela geofísica, a equipe liderada pelos arqueólogos Deusdédit Carneiro Leite Filho e Fernando Luiz Tavares Marques realizou cinco escavações no sítio, o que lhes permitiu o resgate de várias peças cerâmicas. Os resultados apresentados nesta pesquisa permitiram verificar e avaliar a potencialidade da prospecção geofísica como método auxiliar em estudos arqueológicos. Palavras-chave: Geofísica. Magnetometria. GPR. Estudos Arqueológicos.

THIS WORK IS THE FIRST VOLUME of a greatly enlarged edition of a booklet published in 1979: Ghost Towns of the Central Mojave, by Alan Hensher. Here are the stories of about 35 vanished towns, large camps, and colonies in San Bernardino County's desert region. (A second volume will cover the deserts of Kern and Los Angeles counties.) All the settlements depended on mines, farms, railroads, or trade for their sustenance. With some reluctance, we have left out settlements that were meant to be temporary, such as military posts and most construction camps.

Although boom towns only rarely grew into cities, they were still more than ephemeral, limited‐purpose settlements or way stations. We define a town here as a fairly permanent settlement that provided goods and services to a trade area. Services could include culture and education, entertainment and recreation.

Our research has yielded a few surprises. First, the number of vanished towns and camps is astonishing‐‐several hundred in Southern California alone. Then, too, the larger settlements turned out to be family communities, noted more for romance than drunken brawls. Best of all, the stories of these communities and their people are available to everyone, in published diaries, government documents, and old newspapers and magazines.

The central portion of the Argus Range (Fig. 1) extends from
Water Canyon in the south, to Highway 190 in the north and is bounded
by China Lake Naval Weapons Center on the west. The northern end of
the area lies adjacent to the Darwin mining district, the southern
edge of the study area is about 20 miles north of Trona, the nearest
railhead. There is access to the range from the paved Trona-Wildrose
road in Panamint Valley via numerous unmaintained dirt roads, the
paved Westend Quarry haulage road, as well as maintained roads up
Water Canyon, to the Sinclair Mine, up Shepherd Canyon, to the mouth
of Bendire Canyon, up Knight Canyon, up Snow Canyon, and to the
Defense and Minnietta Mines. There is a landing strip east of the
Minnietta Mine and a power line connects the Westend Quarry to Trona.
Water was flowing during the fall of 1978 in Revenue Canyon and Knight
Canyons. Springs supply water in Water Canyon, Shepherd Canyon, south
of Bendire Canyon, north of Revenue Canyon and in Snow Canyon.

There has been past production gold, copper and semi-precious stone from the Turtle Mountains GEM Resource Area, and there is today small scale production of gold.

Substantial reserves of gold exist in the Turtle Mountains GEM Resource
Area, which should soon prove to make this an important gold producing
area. At the Desert Placer Claims, Marco Resources, Inc., expects to
process 700,000 tons of gold bearing sediment each year for the next 75 years. At the Grand Reef Claims there are 10 million tons of rock which
grades .05 oz. per ton gold and 2 million tons which grade .103 oz. per
ton gold and 1.87 oz. per ton silver.

Total contained gold is 706,000 oz. of gold worth $233,156,500 (at $330.25 per oz.) Total contained silver is 740,000 oz. worth $26,965,400 (at $7.21 per oz) .

Presently there is small scale production of gold from mines and prospects in the Carson's Wells area and in the southern part of the Mopah Range. There are 148 claims in the area. A Large variety of semi-precious stone is found associated with volcanic rock in the area. This material is collected by rock-hounds for recreation.

Convene at the Desert Studies Center. Make sure vehicles are packed with all your personal gear and have a full tank of gas. Check your spare tires. Carry water and snacks, plan your clothing for the conditions. Wear sturdy shoes. Bring hats and sunscreen. Watch for harmful plants and animals. Note that some stops are on Federal lands managed by the Bureau of Land Management and National Park Service. Respect the land and leave it as you found it: no rock or artifact collecting, digging, or harming plants and wildlife is allowed. Part of this day's route is within the Mojave National Preserve where special use permits are required for field trips with more than a limited number of vehicles or visitors. Carpooling is mandatory today. Make carpool arrangements at the symposium on Friday or Saturday. At one stop the trip requires high clearance -4WD due to soft sand. Please leave less road-worthy vehicles at Zzyzx. We will return to Zzyzx Sunday night.

In 1869, a prospecting expedition discovered copper and silver veins in the Clark Mountains. A supply center named Ivanpah arose at Ivanpah Spring, several miles from the silver deposits; the two main properties became the Beatrice and Lizzie Bullock. Mills were built at Ivanpah in the mid-1870s. The district reached its peak about 1879 and then declined rapidly during the early 1880s. The Copper World, the other major strike, was developed in 1898, when a smelter was built at nearby Rosalie Wells. Although the production was large at times, the operations were erratic, and the Copper World shut down about World War I. In 1879, gold and silver were found near Mountain Pass. This became the Mescal Mine. The property was developed in 1882 and remained active at least into 1887. The Mescal produced an estimated $250,000 in bullion.

Gold was reportedly discovered at Goldstone as early as the 1880s. Subse~uently there were two periods of activity, 1910-1916, and the 1930s. In May 1910, the Pacific Miner trumpeted: "Gold Stone is the name of a new camp, thirty-five miles north of Barstow, where some phenomenal ore has been found. Quite a stampede followed the discovery. Reports show that it is the richest locality in the Southwest"~ This "stampede" seems to have been touched off by the rich returns from the Drumm mine, which had reported that a ton of ore from the surface yielded $97 in gold and five ounces of silver at the Needles Smelter. In August, John Harper came into Barstow showing off some "picture rock" (rock typically shot through with native gold) from Goldstone which he said ran up to $180 per ton in gold. Others working properties at this time included jack Halford, Joe Goodrich,

So it was with great foresight that Eugene Garlock, the owner of a
mine near Tehachapi, saw an opportunity in the discovery of rich and
large deposits of gold ore in the Rand Mountains, northeast of Mojave.
The Yellow Aster claim, discovered in April, 1895, turned out to be
the most important mine.

But the Rand Mining District lacked a supply of readily available
water. In the beginning, all of it had to be hauled from Goler and
Cow Wells, about a dozen miles up a sandy road from the floor of
Fremont Valley. There, in the deep gravels lying below Cow Wells,
were heavily mineralized but abundant quantities of the "precious
fluid."

The first recorded mineral discovery in Clark Mountain, the Mescal
Range and the lvanpah Mountains was in 1868 at the Copper World
mine on the southwest slope of Clark Mountain. Earlier mining
occurred in 1863 at Rock Spring in the Providence Mountains, about
10 miles due south of the southern end of the lvanpah Mountains, and it
has been presumed that soldiers stationed at Marl Springs, between
1867 and 1868, first worked the small gold deposits there. Although the
Copper W odd mine was the first to be discovered, two mines
discovered in 1879, the Mescal and Bullion mines, were worked in the
1880s. The Mescal mine camp, though no more than a handfull of
buildings; briefly boasted mail service. The Copper World mine
languished until 1898 when it became one of the most significant
copper producers in the county. With a large payroll, this camp, known
as Rosalie, was also served by the U.S. Mails.

Until the coming of the Army in 1940, the central Mojave
Desert seems to be a place to pass through, to get somewhere
else, somewhat like the travelers on Interstate 15 today. But
on their way a few stopped, picked up some rocks and liked
what they saw.

The mining history of area of the central Mojave Desert
encompassed today by Fort Irwin is obscure, found scattered in
dozens of newspapers and mining periodicals, and hard to find
Federal and County documents. Mining began as early as 1850
just outside of the fort at Salt Springs, and flourished intensely
but briefly between 1904 and 1908. Towns were established,
stock was bought and sold but very little metal came from the
ground. This paper is not an exhaustive treatment of the
history of mining within Fort Irwin and on its borders, but it
hopefully brings to light some obscure aspects of mining
history here.

A large number of Variscan mesothermal gold deposits are located in the central part of the Bohemian Massif, close to the Central Bohemian Plutonic Complex. The Petra cÏ kova hora deposit has many features that distinguish it from other deposits in the region and suggest its mineralization is closely related to the late magmatic processes associated with the Petra cÏ kova hora granodiorite. The gold ores occur as sheeted arrays of quartz veins and veinlets hosted by the small Petra cÏ kova hora granodiorite stock. Gold is found mainly as free grains of >900 ®neness, and is accompanied by abundant pyrrhotite and chalcopyrite, and accessory pyrite, arsenopyrite, loellingite, and molybdenite. Molybdenite from the Petra cÏ kova hora deposit has been dated by the Re±Os method at 344.42.8 Ma. Hydrothermal alteration in the Petra cÏ kova hora deposit exhibits a distinct temporal paragenesis. Selectively pervasive, early K-alteration and silici®cation are the oldest hydrothermal phases. These were followed by early quartz veins (Q 1 to Q 4 ) that contain most of the gold mineralization. Late quartz veins (Q 5 ) and fracture-controlled silici®cation are gold-poor or barren. Barren calcite veins are the youngest hydrothermal product. Extensive low-temperature, meteoric-water dominated alteration, as is typical of classic porphyry deposits, is absent. However, the lower d 18 O whole rock values for Petra cÏ kova hora

The Ibala gold field, discovered by artisanal miners in 2018, is located east of Ibala town in Osun State, southwest Nigeria. As older mines are depleted and abandoned, miners are now investigating the source of the deposits, believed to be auriferous quartz veins. This study uses the mineral system approach to trace the origin of the alluvial gold in the Ibala area. The research is conducted in three phases: first, a detailed analysis of the region's structural patterns and rock distribution is undertaken to understand the area's tectonic history. Next, a 3D conceptual model is created using an integrated geological and geophysical modeeling techinque to identify exploration targets and map the mineral system components. Finally, onsite verification is performed to validate the findings. The study reveals that the gold originates from auriferous shear zones characterized by high conductivity and chargeability geophysical signatures. These zones were formed by auriferous fluids released during the metamorphic devolatilization of deep volcanic rocks. As the fluids migrated through shear zones, they interacted with host rocks, precipitating gold alongside pyrite. When weathered, the goldbearing material is transported via drainage channels, which miners now exploit. By using a mineral system approach, this research pinpoints the primary gold sources, supporting more efficient resource management and sustainable mining practices in the region.

La présente étude traite de l’activité d’orpaillage traditionnel. La recherche a été menée dans la portion malienne du haut Niger, précisément dans le cercle de Kangaba. Cette partie du fleuve Niger est devenue à partir de 2012 la destination pour des milliers d’individus qui, une fois sur place, s’adonnent de façon effrénée à un orpaillage mécanisé, avec pour seul objectif le profit économique. Dans le contexte actuel d’amenuisement des ressources du fleuve, de décentralisation et de fragilisation de l’autorité de l’Etat, il nous est paru opportun de mettre en exergue, d’une part les avantages d’une telle activité sur le plan socioéconomique, et d’autre part tous les risques en termes d’environnement et de tensions sociales autour du fleuve Niger et de ses ressources. L’étude a permis de caractériser l’orpaillage dans ses dimensions technique, démographique et socioéconomique ; d’identifier les principaux facteurs qui le favorisent ; de faire une analyse des acteurs et des enjeux. L’orpaillage à de nombreux impacts positifs, mais elle est aussi porteuse de nombreux risques en termes d’environnement et de tensions sociales. Enfin la recherche anticipe sur le dilemme que pose une telle activité pour un Etat politiquement et économiquement fragile comme le Mali à savoir quelle dimension privilégier entre l’économique et l’environnemental