Geology of Ore Deposits最新文献

{"title":"Gold Rush as it Happens in Minas Gerais, Brazil: Geological Reconnaissance and Origin of Gold Nuggets","authors":"Alexandre Raphael Cabral, José Maria Leal, Rogerio Kwitko-Ribeiro","doi":"10.1134/s1075701524600087","DOIUrl":"https://doi.org/10.1134/s1075701524600087","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Gold nuggets, loose in talus material, triggered an ongoing gold rush in the southern Serra do Espinhaço, Minas Gerais, Brazil. The talus material has abundant fragments of vein quartz in a clay-rich matrix, resting on metagreywacke of the Neoproterozoic Macaúbas Group. Quartz lodes, which truncate the metamorphic foliation of the bedrock metagreywacke, are the source of the gold nuggets, which formed after the main tectonic and metamorphic overprint of the Ediacaran–Cambrian Brasiliano orogeny. The gold nuggets are hypogene in origin, but they have a minor component of supergene gold, which occurs as dendrites of bud-like gold particles, mostly &lt;1 µm across. Amongst the latter, apically branched hyphae of essentially pure gold are noteworthy and suggest pseudomorphism after fungi.</p>","PeriodicalId":12719,"journal":{"name":"Geology of Ore Deposits","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Genetic Classification of Bauxites of Futa Jallon-Mandingo Province (West Africa) by Textural and Structural Features","authors":"D. A. Vnuchkov, N. M. Boeva, M. A. Makarova, E. S. Shipilova, V. I. Mamedov, N. S. Bortnikov","doi":"10.1134/s107570152470020x","DOIUrl":"https://doi.org/10.1134/s107570152470020x","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>In the process of the formation of classical lateritic bauxites in the Futa Jallon-Mandingo province, due to a complex of two- to three-stage genesis, lithological and genetic types of bauxites were formed that differed in external characteristics, color, texture, and structure. The proposed genetic typification of bauxite based on textural and structural features of the rocks in fact is the basis for the geological and industrial classification of deposits of the region. Studying the textural and structural features of bauxites is the only way through which one can get an idea of the conditions of their formation. It is in the textures and structures of ores their genetic history is imprinted. The analysis shows that the deposits, within which deposits of sedimentary-lateritic and chemically transformed bauxites predominate, are distinguished not only by greater thicknesses of ore bodies and a significantly higher content of total alumina in the ores, but also by increased contents of monohydrate forms. This also determines various economic indicators of the operation and technology of metallurgical processing of bauxite.</p>","PeriodicalId":12719,"journal":{"name":"Geology of Ore Deposits","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chemical Mapping of Trace Elements in Pyrite Provides Insight into Mineralizing Processes: the Example of the Neoarchean Cu–Au Porphyry System of the Chibougamau Area, Canada","authors":"Lucie Mathieu, Dany Savard, Andrey Kulynych-Rinta","doi":"10.1134/s1075701524600051","DOIUrl":"https://doi.org/10.1134/s1075701524600051","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Archean porphyry-style mineralization is one of the sources of Au and Cu in greenstone belts. Archean porphyries have been modified by regional deformation and late fluid circulation, and questions remain on the timing of Au mineralization. Indeed, Au may have been introduced at the magmatic-hydrothermal (porphyry) stage, or by a post-magmatic hydrothermal fluid (overprinting orogenic gold system), or a combination of these two processes. Using the Cu–Au Corner Bay deposit as a case study and high-quality chemical mapping performed using laser ablation coupled to a time-of-flight mass spectrometer (LA-FF-ICP-ToF-MS), this study demonstrates that pyrite chemistry has the potential to reconstitute the metallogenic model for Archean porphyry systems. The Corner Bay deposit is associated with the ~2718–2715 Ma Chibougamau pluton, located in the northeastern corner of the gold-endowed Abitibi greenstone belt. Pyrite chemistry points to the following succession of events at Corner Bay: (1) an early porphyry stage that produced pyrite-mineralized quartz-anhydrite veins associated to chloritization and sericitization; (2) followed by a porphyry stage that includes brecciation in response to fluid overpressure and deposition of Cu-Au mineralization by magmatic-hydrothermal fluids with a multi-metal signature (Cu, Ag, Bi, Te, etc.); and (3) a post-porphyry deformation event(s) that induced parallel fracturing and minor carbonatization. This study proposes that, at Corner Bay, Au was introduced during the porphyry-stage of mineralization and was neither remobilized, nor further introduced, during the ~2700 Ma regional deformation stage that is coeval with most orogenic gold-style of mineralization in the southern part of the Abitibi greenstone belt.</p>","PeriodicalId":12719,"journal":{"name":"Geology of Ore Deposits","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detection and Interpretation of Central Type Structures within the Territory of Southeastern Transbaikalia for Prediction of Ore-Forming Systems","authors":"S. A. Ustinov, V. A. Petrov, V. A. Minaev, I. O. Nafigin, E. V. Yarovaya","doi":"10.1134/s107570152460018x","DOIUrl":"https://doi.org/10.1134/s107570152460018x","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Extremely little attention is paid to the issues of detecting and interpreting of central type structures (CTSs) when conducting remote structural-geological and structural-geomorphological studies. At the same time, in the 1970–1980s, it was proven that CTSs play an important role in the localization of deposits and ore fields. The position of these structures must necessarily be taken into account when solving problems of searching for and predicting mineral resources in the context of metallogenic analysis and reconstruction of the geological history of development of the studied areas. The almost complete absence of results of mass detection and interpreting of CTSs can be explained by the still poorly developed methodology for identifying and analyzing this type of structure. In the present study for the territory of Southeastern Transbaikalia, based on modern geoinformation technologies, the use of remote sensing data (radar topographic survey) of high resolution, the creation of a digital elevation model, and the application of an integrated structural-spatial analysis, an author’s approach to detection and interpretation of the CTSs is presented, including in connection with the localization of ore objects of various geological-industrial (geological-genetic) types within the framework of the concept of the formation of mineral systems. A statistical analysis of the CTSs identified in the area was carried out, which made it possible to establish a smooth increase in the number of structures with a decrease in their diameter. It is shown that the spatial maxima of ore mineralization extent within the territory are concentrated on the periphery of large CTSs and in their immediate vicinity. Most of the known large ore objects are confined to the internal areas of structures less than 10 km in diameter. Based on the approach of constructing model sections, it was possible to reconstruct the deep position of magma chambers associated with the identified CTSs, and, thereby, to determine the probable sources of metal-bearing fluids. A close spatial relationship between the identified magma chambers and deep faults has been established. To determine the most favorable sites for the deposition of ore mineralization, based on structural-spatial criteria, which include not only structural elements of the CTSs, but also segments of known fault structures, weight of evidence models of the territory have been created. The accuracy of the complex model is 89%. Thus, in accordance with the concept of mineral systems, the sources, migration pathways, and sites of the most probable deposition of ore mineralization have been reconstructed.</p>","PeriodicalId":12719,"journal":{"name":"Geology of Ore Deposits","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The First Results of a Study of Large Diamonds from Industrial Deposits of Yakutia","authors":"L. D. Bardukhinov, E. M. Sedykh, A. A. Evstratov, K. V. Garanin, N. N. Zinchuk","doi":"10.1134/s1075701524600166","DOIUrl":"https://doi.org/10.1134/s1075701524600166","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>A representative amount of diamonds larger than 10.8 carats extracted from deposits of Yakutia during separate ore processing of each kimberlite pipe has been studied for the first time. It is shown that, according to the diamond typomorphic characteristics of habit, nitrogen content, and aggregation, as well as hydrogen concentration in diamond, it is possible to carry out a preliminary evaluation of the deposit to predict the presence of large and giant diamonds. It has been established that large diamonds from the deposits of the Daldyn-Alakitsky area have wide variations of nitrogen impurity and its aggregations in comparison with diamonds from the Malobotuobinsky and Srednemarkhinsky areas. It is determined that the content of large diamonds in the pipes of Yakutia is inversely proportional to the number of rounded dodecahedroids. The most promising deposits for finding large diamonds are those in which the majority of diamonds belong to one population—average nitrogen low-aggregated diamonds that were formed at a temperature of ~1100°C. According to the study of geological collections of diamonds, it is shown that, in kimberlite pipes with an increased nitrogen content in diamonds, an increase in the proportion of large diamonds in the deposit is noted. On the contrary, according to the aggregation of nitrogen in diamonds, as a parameter of postgrowth history, there is a negative correlation with the content of large diamonds. An increased value of the concentrations of hydrogen in diamonds not only negatively affect the total diamond content of the deposit, but also generally control the decrease in the content of large diamonds.</p>","PeriodicalId":12719,"journal":{"name":"Geology of Ore Deposits","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Native Gold from Alluvial Sediments of the Kyvvozh Region and Its Possible Sources (Vol–Vym Uplift, Central Timan)","authors":"K. G. Parkhacheva, Yu. V. Glukhov, M. Yu. Sokerin, S. K. Kuznetsov, R. I. Shaibekov","doi":"10.1134/s1075701524600178","DOIUrl":"https://doi.org/10.1134/s1075701524600178","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The most possible genetic types of primary sources are determined on the basis of study of typomorphic features of gold from alluvial sediments of the Kyvvozh region of Central Timan, including economic placers. The size of gold particles widely varies, reaching small nuggets; there are rounded, weakly rounded, and nonrounded particles. Many of them underwent recurrent deformations in form of envelope curves, pits, and fractures. Most gold grains have high-fineness rims. Native gold always contains Ag and, locally, Cu, Pd, and Hg. There are frequent blocky gold particles with high-Ag veinlet zones. Native gold is intergrown with and contains inclusions of pyrite and galena and rarely minerals of the cobaltite–gersdorffite series, ankerite, galenobismuthite, native bismuth, and aurostibite, as well as sudovikovite PtSe₂, which is identified for the first time in the region. Three types of native gold are recognized: (1) homogenous Ag-bearing, (2) blocky with high-Ag veinlet zones, and (3) rare Ag-bearing with Cu and Pd. The morphology, composition, and structure of placer gold indicate its contribution from various (including proximal) sources. The NW-oriented zones of hydrothermal stringer-disseminated sulfide mineralization, which are partly exposed during placer exploitation, are most interesting. Native gold with Cu and Pd is most likely related to the derivatives of basic magmatism. The Vol–Vym, Tsil’ma, and Chetlas uplifts of Central Timan can be considered the promising for primary gold and deserve further study and searching works.</p>","PeriodicalId":12719,"journal":{"name":"Geology of Ore Deposits","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrothermal–Metasomatic and Metamorphic Formations of the Olympiada Gold-Ore Deposit (Yenisei Ridge): New Data on Their Composition and Mineralogical, Petrographic, and Geochemical Features","authors":"V. V. Shatov, S. V. Kashin, V. N. Belova, E. N. Afanasieva, V. A. Mikhailov","doi":"10.1134/s1075701524700223","DOIUrl":"https://doi.org/10.1134/s1075701524700223","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The article presents the results of mineralogical, petrographic, and geochemical studies of hydrothermally altered and metamorphic formations of the Olympiada deposit. It shows that the combination of beresitization-sericitization aureoles, which control the distribution of stratiform gold–sulfide mineralization in space with multiplicative positive geochemical anomalies of AuAsTeSbHg composition close to them in morphology, can be used as hydrothermal alteration and geochemical criteria for predicting gold–sulfide mineralization in the Olympiada ore field. The geological and genetic model of the formation of the Olympiada ore deposit is discussed, and recommendations on the use of this model for prospecting purposes are given.</p>","PeriodicalId":12719,"journal":{"name":"Geology of Ore Deposits","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142203866","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pyrite Re–Os Geochronology of the Erlian Uranium District: an Alternative Dating Method for Sandstone-type Uranium Deposits","authors":"C. Zhang, X. D. Li, C. H. Liu","doi":"10.1134/s1075701523600081","DOIUrl":"https://doi.org/10.1134/s1075701523600081","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Owing to the lack of precise and reliable mineralization ages, the origins of some sandstone-type U deposits (STUDs) are still debated. The unusual texture of U ore (commonly uraninite) and the difference between the chemical characteristics of U and its radiogenic daughter isotopes make U–Pb dating unsuitable for STUDs. However, STUDs are commonly rich in Re; therefore, Re–Os dating may be an alternative. Re–Os dating of two groups of pyrite samples from U ores in the Erlian sandstone-type U district yields two similar ages: 52.5 ± 4.7 and 53.3 ± 3.5 Ma. These ages are consistent with previous U–Pb ages (56.5 ± 7.5 and 63 ± 22 Ma) and demonstrate the reliability of sulfide Re–Os dating of STUDs. The pyrite Re–Os ages suggest that the Erlian STUDs formed at ~53 Ma, corresponding to the regional uplift of the Erlian basin during the Late Cretaceous–Early Eocene and the humid environment in the region during the Early Eocene Climatic Optimum.</p>","PeriodicalId":12719,"journal":{"name":"Geology of Ore Deposits","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141738137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unique Ore–Silicate Pegmatite of Monchepluton with High Contents of Ni, Cu, and PGE (Murmansk Region)","authors":"D. A. Orsoev, V. F. Smolkin, A. S. Mekhonoshin","doi":"10.1134/s1075701524700065","DOIUrl":"https://doi.org/10.1134/s1075701524700065","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>At the beginning of the 1960s, a large body of funnel-shaped ore pegmatite composed of Cu–Ni sulfide ores and a gabbronorite matrix was discovered at the Nittis–Kumuzhya–Travyanaya ore vein field of the Northern Chamber of Monchepluton (Kola Peninsula). In terms of its localization conditions, size, structure, and enrichment in sulfides and platinum-group elements (PGEs), it is a unique formation that has no analogues among other Paleoproterozoic layered complexes of the Fennoscandian Shield. Ore pegmatite occurs in the upper part of the layered zone of Mt. Nittis, which is composed of harzburgites and orthopyroxenites. Its horizontal size is 9 × 16 m, and the vertical one is 15 m. Three zones are distinguished in the structure of the body: I, a core of continuous sulfides; II, coarse- and giant-grained gabbronorites, enriched in interstitial sulfides; and III, a contact zone with sideronite sulfides with gradual transitions into host orthopyroxenites. Petro- and geochemical, mineralogical, and isotope studies of rocks and ores were performed using modern analysis methods. Ore pegmatite is most recent product in the processes of fractional crystallization of a magmatic melt, which derived as a large schlier with a sulfide core and a silicate matrix with a high concentration of fluids. The hypsometric level of the termination of the melt upwelling was determined by the equilibrium of the internal pressure of the volatiles and the external pressure of the overlying rocks. The δ¹⁸O values (+4.9…+6.1‰) are close to mantle marks (δ¹⁸O = +5.7‰) that correspond to basic igneous rocks. Early, late, and postmagmatic stages of mineral formation with a consistent increase in the role of fluid components (H₂O, CO₂, Cl, F) are distinguished in the formation history of the ore pegmatite. According to the results of calculations performed using various mineral geothermometers, the melt crystallization at the magmatic stage occurred in the range of ∼1100–900°C at a pressure of about 5 kbar. The separation (liquation) of the immiscible sulfide liquid began at temperatures of 1100–1000°C. As the temperature decreases, the main silicate minerals (clino- and orthopyroxenes, plagioclase) were first to crystallize. In the interstitial space between these minerals, residual melt and sulfide liquid enriched in PGEs, Au, Ag, and chalcophile elements (As, Sn, Sb, Te, Bi, Pb, Zn) accumulated. A late magmatic association (pargasite, magnesian hornblende and phlogopite) was formed from the residual melt. During the cooling of the sulfide liquid to a temperature of ∼1000°C and below, a copper-bearing monosulfide solid solution (<i>Mss</i>) is detached. As a result of its solid-phase transformations, pyrrhotite, pentlandite, and chalcopyrite were formed. An intermediate solid solution (<i>Iss</i>) was formed from the residual sulfide liquid, which was enriched with Cu and noble met","PeriodicalId":12719,"journal":{"name":"Geology of Ore Deposits","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141738139","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"LA-ICP-MS Zircon U-Pb Dating of Permian Manganese Ores in Zunyi, Guizhou Province and Mineralization Age","authors":"Minkai Du, Zhichen Liu, Wengchao Yu, Yang Wang, Deng Chen, Lin Xiao, Liang Xiao","doi":"10.1134/s1075701524700089","DOIUrl":"https://doi.org/10.1134/s1075701524700089","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The Middle Permian manganese deposit in Zunyi, northern Guizhou is one of the major manganese mining areas in South China. However, the age of this manganese deposit has not been accurately constrained. Previous studies have generally concluded that the formation of Zunyi manganese ores was linked with the early activities of the Emeishan Large Igneous Province (ELIP). In this study, we investigated the lithology and mineralization age of the Mn-bearing rocks in the study area and explored the connections between ELIP and the genesis of these rocks. Zircon samples from the Mn-bearing tuff in the Tuanxi section of Zunyi were used for zircon U-Pb chronological analysis by LA-ICP-MS method. The results constrain the deposition age of Mn-bearing rocks in Member 3 of the Maokou Formation was older than 266 ± 3 Ma, this age was closely related to the early stage of ELIP, but it was 5–10 Ma earlier than the main eruption of the Emeishan basalt. Combined with the regional paleogeography, we believe that the mantle plume activities prior to the main eruption of ELIP provided the tectonic stress, manganese source, and mineralization environment for manganese ore formation in the rift basin of the study area.</p>","PeriodicalId":12719,"journal":{"name":"Geology of Ore Deposits","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141738113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}