{"title":"Aurostibite, Silver-Bearing Gold, and Electrum As a Part of Post-Gold Antimony Mineralization in the Darasun Deposit (Eastern Transbaikalia)","authors":"","doi":"10.1134/s1075701523070115","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 and post-gold antimony mineralization. Carbonate–quartz–sulfide veins in the western part of the deposit, composed of gabbroids, gabbro amphibolites, and, to a lesser extent, ultramafic rocks are surrounded by listvenite aureoles. The Au-rich ores were formed under conditions of low activity of sulfide sulfur; they contain pyrrhotite, arsenopyrite, chalcopyrite, bismuthinite, and Pb–Bi sulfosalts associated with a high fineness gold (949–935‰). Aurostibite pseudomorphs after gold minerals have appeared there due to a superimposition of the antimony mineralization with native antimony on gold ores. This aurostibite contains 1.1–1.7 wt % Bi and 0.1–0.3 wt % As, isomorphically replacing Sb. Its composition is Au<sub>0.998–1.005</sub>(Sb<sub>1.947–1.965</sub>Bi<sub>0.024–0.036</sub>As<sub>0.009–0.017</sub>)<sub>1.995–2.002</sub>, and the average composition is Au<sub>1.001</sub>(Sb<sub>1.956</sub>Bi<sub>0.031</sub>As<sub>0.012</sub>)<sub>1.999</sub>. Aurostibite does not contain silver. Silver released during the replacement of native gold with aurostibite occurs near its metacrystals in the composition of heterogeneous reaction rims of newly formed gold minerals. They are represented by silver-bearing native gold (fineness 922–712, mostly 919–911) and electrum (fineness 693–584, mostly 625–604). The distribution of the gold fineness in the newly formed minerals of the gold–silver series, as a part of the antimony mineralization, in the volcanogenic–plutonogenic Darasun deposit is very heterogeneous and “irregular.”</p> </span>","PeriodicalId":12719,"journal":{"name":"Geology of Ore Deposits","volume":null,"pages":null},"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/s1075701523070115","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOLOGY","Score":null,"Total":0}
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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 and post-gold antimony mineralization. Carbonate–quartz–sulfide veins in the western part of the deposit, composed of gabbroids, gabbro amphibolites, and, to a lesser extent, ultramafic rocks are surrounded by listvenite aureoles. The Au-rich ores were formed under conditions of low activity of sulfide sulfur; they contain pyrrhotite, arsenopyrite, chalcopyrite, bismuthinite, and Pb–Bi sulfosalts associated with a high fineness gold (949–935‰). Aurostibite pseudomorphs after gold minerals have appeared there due to a superimposition of the antimony mineralization with native antimony on gold ores. This aurostibite contains 1.1–1.7 wt % Bi and 0.1–0.3 wt % As, isomorphically replacing Sb. Its composition is Au0.998–1.005(Sb1.947–1.965Bi0.024–0.036As0.009–0.017)1.995–2.002, and the average composition is Au1.001(Sb1.956Bi0.031As0.012)1.999. Aurostibite does not contain silver. Silver released during the replacement of native gold with aurostibite occurs near its metacrystals in the composition of heterogeneous reaction rims of newly formed gold minerals. They are represented by silver-bearing native gold (fineness 922–712, mostly 919–911) and electrum (fineness 693–584, mostly 625–604). The distribution of the gold fineness in the newly formed minerals of the gold–silver series, as a part of the antimony mineralization, in the volcanogenic–plutonogenic Darasun deposit is very heterogeneous and “irregular.”
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.
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