Maldonite and Products of Its Replacement—Pure Native Gold, Jonassonite, and Bismuthic Aurostibite—in Gold Ores of the Darasun Deposit (Eastern Transbaikalia)
{"title":"Maldonite and Products of Its Replacement—Pure Native Gold, Jonassonite, and Bismuthic Aurostibite—in Gold Ores of the Darasun Deposit (Eastern Transbaikalia)","authors":"","doi":"10.1134/s1075701523070103","DOIUrl":null,"url":null,"abstract":"<span> <h3>Abstract</h3> <p>The Late Jurassic orogenic volcanogenic–plutonogenic Darasun gold deposit of the beresite–listvenite gold–sulfide–quartz formation is situated in the Mesozoids of the Eastern Transbaikalian segment of the Mongol–Okhotsk folded belt. The deposit includes Au–Bi–Te and the postgold Sb mineralization. Carbonate–quartz–sulfide veins in the Western block of the deposit composed of gabbroids, gabbro amphibolites, and, to a lesser extent, ultramafic rocks are surrounded by listvenite aureoles. Au-rich ores were formed under conditions of the low activity of sulfide sulfur; they are enriched in pyrrhotite and contain bismuthine and/or Pb–Bi sulfosalts and, locally, rare nests of native bismuth and ikunolite Bi<sub>4</sub>S<sub>3</sub>. The high-fineness gold (970–925) associates with bismuthinite and Pb–Bi sulfosalts. Instead of native gold, nests of native bismuth and ikunolite include abundant maldonite Au<sub>2</sub>Bi, an Ag-free mineral. Under conditions of the higher activity of sulfide sulfur, maldonite in gold-bearing hydrotherms is replaced by intergrowths of pure native gold and bismuth, and bismuthinite. The subsequent significant increase in activity of sulfur in gold-bearing hydrotherms led to mass replacement of maldonite by jonassonite. Thus, the direct replacement of maldonite by jonassonite is observed in Darasun ores probably as result of the following reaction: Au<sub>2</sub>Bi + 5Bi + 2Bi<sub>2</sub>S<sub>3</sub> + S<sub>2</sub> sol → 2AuBi<sub>5</sub>S<sub>4</sub>. The composition of jonassonite varies from pure AuBi<sub>5</sub>S<sub>4</sub>, which is most abundant in Darasun ores, to Au(Bi, Pb)<sub>5</sub>S<sub>4</sub> with 1–6 wt % Pb, in the case in which galena and bismutoplagionite occur among replaced minerals. Therefore, the jonassonite formula is AuBi<sub>5</sub>S<sub>4</sub>. Aurostibite pseudomorphs after gold minerals appeared in such ores due to superimposing Sb mineralization with native Sb. Apo-maldonite aurostibite pseudomorphs contain 4–10 wt % Bi. The probable aurostibite–maldonite replacement reaction is as follows: 2Au<sub>2</sub>Bi + 6Sb sol + Sb<sub>2</sub>S<sub>3</sub> sol → 4Au (Sb, Bi)<sub>2</sub> + (Bi, Sb)<sub>2</sub>S<sub>3</sub>. Aurostibite contains up to 18 wt % Bi within inner zones of pseudomorphs formed after maldonite decomposition products—pure native gold and bismuth.</p> </span>","PeriodicalId":12719,"journal":{"name":"Geology of Ore Deposits","volume":"64 1","pages":""},"PeriodicalIF":0.8000,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geology of Ore Deposits","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1134/s1075701523070103","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
The Late Jurassic orogenic volcanogenic–plutonogenic Darasun gold deposit of the beresite–listvenite gold–sulfide–quartz formation is situated in the Mesozoids of the Eastern Transbaikalian segment of the Mongol–Okhotsk folded belt. The deposit includes Au–Bi–Te and the postgold Sb mineralization. Carbonate–quartz–sulfide veins in the Western block of the deposit composed of gabbroids, gabbro amphibolites, and, to a lesser extent, ultramafic rocks are surrounded by listvenite aureoles. Au-rich ores were formed under conditions of the low activity of sulfide sulfur; they are enriched in pyrrhotite and contain bismuthine and/or Pb–Bi sulfosalts and, locally, rare nests of native bismuth and ikunolite Bi4S3. The high-fineness gold (970–925) associates with bismuthinite and Pb–Bi sulfosalts. Instead of native gold, nests of native bismuth and ikunolite include abundant maldonite Au2Bi, an Ag-free mineral. Under conditions of the higher activity of sulfide sulfur, maldonite in gold-bearing hydrotherms is replaced by intergrowths of pure native gold and bismuth, and bismuthinite. The subsequent significant increase in activity of sulfur in gold-bearing hydrotherms led to mass replacement of maldonite by jonassonite. Thus, the direct replacement of maldonite by jonassonite is observed in Darasun ores probably as result of the following reaction: Au2Bi + 5Bi + 2Bi2S3 + S2 sol → 2AuBi5S4. The composition of jonassonite varies from pure AuBi5S4, which is most abundant in Darasun ores, to Au(Bi, Pb)5S4 with 1–6 wt % Pb, in the case in which galena and bismutoplagionite occur among replaced minerals. Therefore, the jonassonite formula is AuBi5S4. Aurostibite pseudomorphs after gold minerals appeared in such ores due to superimposing Sb mineralization with native Sb. Apo-maldonite aurostibite pseudomorphs contain 4–10 wt % Bi. The probable aurostibite–maldonite replacement reaction is as follows: 2Au2Bi + 6Sb sol + Sb2S3 sol → 4Au (Sb, Bi)2 + (Bi, Sb)2S3. Aurostibite contains up to 18 wt % Bi within inner zones of pseudomorphs formed after maldonite decomposition products—pure native gold and bismuth.
期刊介绍：
Geology of Ore Deposits is a periodical covering the topic of metallic and nonmetallic mineral deposits, their formation conditions, and spatial and temporal distribution. The journal publishes original scientific articles and reviews on a wide range of problems in theoretical and applied geology. The journal focuses on the following problems: deep geological structure and geodynamic environment of ore formation; distribution pattern of metallogenic zones and mineral deposits; geology and formation environment of large and unique metallic and nonmetallic deposits; mineralogy of metallic and nonmetallic deposits; physicochemical and isotopic characteristics and geochemical environment of ore deposition; evolution of ore-forming systems; radiogeology and radioecology, economic problems in exploring, developing, and mining of ore commodities.
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号
