Application and Significance of Geological, Geochemical, and Geophysical Methods in the Nanpo Gold Field in Laos

As the main part of the Indosinian metallogenic province in the eastern part of the Tethys metallogenic domain, Southeast Asia has experienced multiple stages of tectonic magnetic activities accompanied by the formation of rich mineral resources. However, due to the undeveloped economy, low degree of geological work, dense vegetation cover, and lack of obvious prospecting marks, traditional geological prospecting work in the area is not optimal. Consequently, the combination of high-precision geophysics and geochemistry has become an important method of looking for ore bodies deep underground in this area. The Nanpo gold deposit is a hydrothermal gold deposit that occurs in the Indosinian felsic volcanic rock body, and its mineralization is closely related to felsic magmatism. This study carried out comprehensive geophysical and geochemical exploration methods of soil geochemical survey, induced polarization (IP) survey, and audio-frequency magnetotelluric (AMT) survey. Based on the characteristics of geophysical and geochemical anomalies, geological inference, and interpretation, the integrated geophysical and geochemical prospecting criteria of the ore area have been determined: The large-scale and overlapping Au-Ag-Cu anomaly area in the host felsic magmatic rocks (mainly diorite, monzodiorite and granodiorite) is a favorable metallogenic area. Two anomalies, P1–H1 and P3–H6, with the best metallogenetic conditions and the deepest extensions of the known ore bodies, were further selected as engineering verification targets. After the study of the drill core, gold (mineralized) bodies consistent with the anomalies were found, indicating that the combined method is suitable for the exploration of mineral resources in this area, and the prospecting effect is good. At the same time, the metallogenic prediction shows that the deep part of the mining area still has great metallogenic prospects and prospecting potential. The characteristics of geophysical and geochemical anomalies and prospecting experience in the study area can provide references for the prospecting of hydrothermal gold deposits in the Luang Prabang–Loei structural belt.

Construction and applications of knowledge graph of porphyry copper deposits

A knowledge graph is becoming popular due to its ability to describe the real world by using a graph language that can be understood by both humans and machines using computer technologies. A case study to construct the knowledge graph of porphyry copper deposits is presented in this paper. First of all, the raw text data is collected and integrated from selected porphyry copper deposits and porphyry-skarn copper deposits in the Qinzhou Bay – Hangzhou Bay metallogenic belt, South China. Second, the text's entities, relations, and attributes are labeled and extracted with reference to the conceptual model of porphyry copper deposits in the study area. The third, a knowledge graph of porphyry copper deposits, was constructed using Neo4j 4.3. The resulted knowledge graph of porphyry copper deposit has the basic functions of an application. Furthermore, as part of a planned integrated knowledge graph from a single deposit, through an upper-geared metallogenic series, to a high-top metallogenic province, the understanding from the present study may be extended to mineral resource prospectivity and assessment beyond today. The interrelationship between the earth system, the metallogenic system, the exploration system, and the prospectivity and assessment (ES-MS-ES-PS) should be completely understood, and a knowledge graph system for ES-MS-ES-PS is needed. The key scientific and technological problems for achieving the ES-MS-ES-PS knowledge graph system are included in the progressively relative system of the domain ontology and knowledge graph of ES-MS-ES-PS, the automatic construction technology of complicated ESMS-ES-PS domain ontology and knowledge graph, the self-evolution and complementary techniques for multi-modal correlation data embedding in the ES-MS-ES-PS knowledge graph, and the knowledge graph, big data mining and artificial intelligence based on ES-resource prospectivity, and assessment theory, and methods.

Indices De Minéralisations En Or Dans La Province Panafricaine Du Sud Maradi (Sud Niger)

Le socle du Sud Maradi (Sud Niger) correspond à l’extrémité Nord du bouclier Bénino-Nigérian, appartenant à la zone mobile panafricaine à l’Est du Craton Ouest-Africain. Cette étude apporte une modeste contribution dans la caractérisation géochimique des minéralisations aurifères de cette province métallogénique panafricaine. A cet effet, l’approche méthodologique mise en oeuvre associe le dosage géochimique de l’or par absorption atomique (Au Fire Assay/AA) pour les roches saines, et la séparation des pépites d’or par l’utilisation de la table à secousse pour les altérites du socle et les sédiments (placers et paléoplacers). Les analyses géochimiques ont mis en évidence l’existence de deux types de minéralisations: primaires et secondaires. Les minéralisations primaires de l’or sont à l’état disséminé (faibles teneurs de 0.005 à 0.017 g/t) mais des teneurs relativement plus élevées (0.006 à 0.017 g/t) ont été enregistrées au voisinage des zones de cisaillement du socle. Tandis que la minéralisation secondaire, mise en évidence dans les altérites du socle, dans les alluvions (placers) et dans les grès du Crétacé (paléoplacers) présentent des teneurs en or plus élevées (5 à 30 g/t), dépassant largement les teneurs des minéralisations primaires observées dans les roches saines du socle. Ce grand écart de teneurs s’explique par un fort lessivage du socle, qui aurait permis une reconcentration de l’or dans les sédiments. The South Maradi (South Niger) basement corresponds to the northeastern part of the Benin-Nigerian Shield, belonging to the Pan-African mobile zone, which is located to the east of the West African Craton. This study brings a modest contribution to the geochemical characterization of gold mineralization in this Pan-African metallogenic province. For this purpose, the methodological approach implemented combines the geochemical determination of gold contents by atomic absorption (Au Fire Assay/AA) for basement rocks and physical separation of gold specks by using the vibrating table process for basement alterites and sediments (placers and paleoplacers). The obtained results showed two types of gold mineralization: primary and secondary. Primary gold mineralization is in a disseminated state (low contents of 0.005 to 0.017 g / t) but relatively the higher values (0.006 to 0.017 g / t) were recorded near the basement shear zones. While the secondary gold mineralization, highlighted in basement alterites, alluvium (placers) and Cretaceous sandstones (paleoplacers) present higher gold contents (5 to 30 g / t) than primary gold contents observed in basement rocks. This large difference in values can be explained by a strong alteration of the basement, which would have allowed a reconcentration of the gold in the sediments.

Granitoid-hosted gold mineralization in Ikibzyaksky ore field: a new milestone in Baikal-Patom metallogenic province gold potential study

New data is provided on gold mineralization in the southern Baikal-Patom metallogenic province, Ikibzyakskoye ore field, located in Pravo-Mamakansky deep fault zone separating Patom fold area from Baikal-Vitim volcanic-plutonic belt. For the first time, the metallogenic province was found to comprise granitoid-hosted ore vein-stringer zones with high-grade economic gold sulfide-quartz mineralization. This mineralization is localized within fault shistosity zones manifesting intense beresitization and listvenitization (in metabasite xenoliths).

The Features of Native Gold in Ore-Bearing Breccias with Realgar-Orpiment Cement of the Vorontsovskoe Deposit (Northern Urals, Russia)

This paper describes native gold in ore-bearing breccias with realgar-orpiment cement from the Vorontsovskoe gold deposit (Northern Urals, Russia). Particular attention is paid to the morphological features of native gold and its relation to other minerals. The latter include both common (orpiment, barite, pyrite, prehnite, realgar) and rare species (Tl and Hg sulfosalts, such as boscardinite, dalnegroite, écrinsite, gillulyite, parapierrotite, routhierite, sicherite, vrbaite, etc.). The general geological and geochemical patterns of the Turyinsk-Auerbakh metallogenic province, including the presence of small non-economic copper porphyry deposits and general trend in change of the composition of native gold (an increase in the fineness of gold from high-temperature skarns to low-temperature realgar-orpiment breccias) confirm that the Vorontsovskoe deposit is an integral part of a large ore-magmatic system genetically associated with the formation of the Auerbakh intrusion.

Gold fingerprint of the SCLM beneath a metallogenic province

<p>Magmatic-hydrothermal gold deposits form clusters in the Earth’s crust and are heterogeneously distributed within lithospheric blocks. A global assessment of whole-rock gold abundances in mantle lithologies worldwide indicates that Au concentrations increase with increasing fertility of mantle peridotites, with median Au contents ranging from 0.50 ppb in dunites, 1.00 ppb in harzburgites, and up to 1.26 ppb in lherzolites. Of particular interest are those volumes of fertile Subcontinental Lithospheric Mantle (SCLM) veined by pyroxenites and wehrlites, usually the Au-richest lithologies in the mantle as they have 2.05 ppb median Au concentrations. Partial melting of SCLM domains endowed in gold seems to play a key role in the genesis of gold-enriched magmas parental to magmatic-hydrothermal gold deposits in continental arc settings. The mineralogical expressions of gold inventory in such fertile mantle rocks are accessory Ni-Fe-Cu sulfides and discrete micron-to-nano-sized Au mineral particles that control the extraction and transport of gold in the mantle. Mantle xenoliths from the Neogene Volcanic Province (NVP) of southeast Spain represent an excellent example of SCLM refertilized by gold-sulfide-rich silicate melts underlying a gold metallogenic province. Here we present mineralogical and compositional data of sulfides in mantle xenoliths from this area (Tallante volcanic center), which are anomalously rich in gold (up to 46 ppm) compared to sulfides from SCLM not associated with Au-metallogenic provinces. We propose that these gold-rich, fertile mantle sources may have melted during the Cenozoic evolution of the westernmost Mediterranean subduction system and fed the ore-productive volcanic activity in southeast Spain.</p>

LA-ICP-MS U-Pb geochronology of carbonates from Ag-Bi-Co-Ni-As±U veins in the Erzgebirge (Germany and Czech Republic): New insights into the timing of mineralization

<p>Hydrothermal Ag-Bi-Co-Ni-As±U (five-element) veins are particularly prevalent across Central Europe, where this type of mineralization has been mined throughout the ages for its high-grade resources of Ag, Co, Ni, and U. The timing and the detailed geodynamic setting in which this style of mineralization formed remains, however, insufficiently understood due to the limited amount of geochronological data. In this contribution, we report the results of innovative LA-ICP-MS U-Pb geochronology on the carbonate gangue of Ag-Bi-Co-Ni-As±U mineralization from six districts in the Erzgebirge/Krušné Hory metallogenic province of Germany and the Czech Republic, with the goal to constrain the timing of ore formation in the context of Central Europe's geodynamic framework.</p><p><em>In-situ</em> U-Pb ages of twelve samples, including dolomite-ankerite, calcite, and siderite cogenetic with Co-Ni-Fe-arsenides, range from 129.4 ± 8.2 to 85.93 ± 3.4 Ma. The ages of Ag-Bi-Co-Ni-As±U and fluorite-barite-Pb-Zn veins from the same occurrence (Annaberg-Buchholz district) overlap each other, suggesting that these two styles of mineralization are genetically related and may form coevally. The compilation of geochronological data from other Ag-Bi-Co-Ni-As±U occurrences in Europe suggests that the origin of this style of mineralization in Central Europe can be related to continental rifting associated with the Mesozoic opening of the Atlantic and/or the Alpine Tethys (200-100 Ma). This provides for the first time evidence for the formation of Ag-Bi-Co-Ni-As±U vein mineralization across Central Europe in response to continental rifting.</p>

The Geology, Geochemistry, and Origin of the Porphyry Cu-Au-(Mo) System at Vathi, Serbo-Macedonian Massif, Greece

The Vathi porphyry Cu-Au ± Mo mineralization is located in the Serbo-Macedonian metallogenic province of the Western Tethyan Metallogenic Belt. It is mainly hosted by a latite and is genetically associated with a quartz monzonite intrusion, which intruded the basement rocks of the Vertiskos Unit and the latite, 18 to 17 Ma ago. A phreatic breccia crosscuts the latite. The quartz monzonite was affected by potassic alteration, whereas the latite was subjected to local propylitic alteration. Both styles of alteration were subsequently overprinted by intense sericitic alteration. M-type and A-type veins are spatially associated with potassic alteration, whereas D-type veins are related to the sericitic alteration. Three ore assemblages are associated with the porphyry stage: (1) pyrite + chalcopyrite + bornite + molybdenite + magnetite associated with potassic alteration; (2) pyrite + chalcopyrite related to propylitic alteration; and (3) pyrite + chalcopyrite + native gold ± tetradymite associated with sericitic alteration. A fourth assemblage consisting of sphalerite + galena + arsenopyrite + pyrrhotite + pyrite ± stibnite ± tennantite is related to an epithermal overprint. Fluid inclusion data indicate that the A-type veins and related porphyry-style mineralization formed at 390–540 °C and pressures of up to 646 bars (<2.6 km depth) from boiling hydrothermal fluids. A later condensation of vapor-rich inclusions resulted in a moderately saline fluid (8.4–11.2 wt % NaCl equiv) at temperatures between 311 and 392 °C, which were related to sericitic alteration, D-type veins, and associated metallic mineralization. Subsequent dilution of the moderately saline fluid at lower temperatures (205–259 °C) produced a less saline (1.4–2.9 wt % NaCl equiv.) fluid, which is likely associated with the late epithermal overprint.