Abstract—

The Ushkatyn-III deposit is located in Central Kazakhstan, 300 km west of the city of Karaganda. The ore member consists of Upper Devonian carbonate rocks containing stratiform layers of hydrothermal–sedimentary iron–manganese and hydrothermal barite–lead ores. The study objects include barite–lead (barite–galena) ores localized within a reef limestone member. The major ore minerals are calcite, barite, and galena; characteristic minor minerals include quartz, hematite, sphalerite, pyrite, muscovite–phengite, chamosite, K-feldspar, albite, fluorite, dolomite, rhodochrosite, and siderite; and accessory minerals include native silver, rutile, ilmenite, chalcocite, acanthite, chalcopyrite, pyrargyrite, tetrahedrite, zircon, pyrophyllite, and apatite. Cerussite, pyromorphite, kaolinite, montmorillonite, and malachite are identified as supergene minerals. Cerussite is one of the main minerals in the oxidation zone. Three major ore varieties are distinguished in terms of texture. They are related by layered–banded, pocketlike–net, and massive spotted mutual transitions. The ore structure is indicative of the fact that barite and galena were mostly deposited in open pores and fractures of incompletely lithified carbonate deposits. Based on δ³⁴S_barite = 10.9–15.3‰, the barite formation involved isotopically heavy sulfur of the sulfate ion dissolved in seawater, whereas the δ³⁴S_{sulfides (galena)} values from –25.7 to –12.6‰ record ³²S-enriched (light isotope) hydrogen sulfide generated in the course of bacterial sulfate reduction. A formation model is proposed for the Ushkatyn-III deposit. According to this model, its barite–galena, iron, and manganese ores were products of a single hydrothermal system that developed within a thick sedimentary sequence. Barite–galena ores formed near the seabed surface with the discharge of hydrothermal solutions in internal zones of the still-forming reef. The ore material was deposited in the area where the hydrothermal solutions carrying Ba, Pb, Zn, Fe, Mn, and other elements were mixed with near-surface waters filling pores and fractures inside the reef, characterized by bacterial reduction of seawater sulfate ion to hydrogen sulfide. Penetrating through the reef, the fluids lost most of the Ba and Pb, deposited as barite and galena, but retained Zn, Fe, and Mn in dissolved form. Subsequently, Fe and Mn were deposited as oxides: Fe, on the reef surface or at some distance from it, and Mn, at a considerable distance. Zn dispersed in the surrounding space without forming any orebodies.

中文翻译：

---

哈萨克斯坦中部 Ushkatyn-III 矿床重晶石-方铅矿的成因：地质、矿物学和同位素（δ34S、δ13C、δ18O）数据分析

摘要-

Ushkatyn-III 矿床位于哈萨克斯坦中部，卡拉干达市以西 300 公里。该矿段由上泥盆统碳酸盐岩组成，含有热液-沉积铁-锰和热液重晶石-铅矿石的层状层。研究对象包括位于礁石灰岩构件内的重晶石-铅（重晶石-方铅矿）矿石。矿石矿物主要有方解石、重晶石和方铅矿；特征次要矿物包括石英、赤铁矿、闪锌矿、黄铁矿、白云母-辉长石、水辉石、钾长石、钠长石、萤石、白云石、菱锰矿和菱铁矿；副矿物包括天然银、金红石、钛铁矿、辉铜矿、尖晶石、黄铜矿、吡汞矿、四面体矿、锆石、叶蜡石和磷灰石。白铅矿、火山灰岩、高岭石、蒙脱石、孔雀石被确定为表生矿物。白铅矿是氧化带的主要矿物之一。三大矿石品种在质地方面有所区别。它们通过分层带状、口袋状网状和大量斑点状相互过渡相关联。矿石结构表明重晶石和方铅矿主要沉积在未完全石化的碳酸盐矿床的开孔和裂缝中。基于 δ³⁴ S_重晶石= 10.9-15.3‰，重晶石形成涉及溶解在海水中的硫酸根离子的同位素重硫，而 δ ³⁴ S_{硫化物（方铅矿）}值从 –25.7 到 –12.6‰ 记录³²细菌硫酸盐还原过程中产生的富硫（轻同位素）硫化氢。提出了 Ushkatyn-III 矿床的形成模型。根据该模型，其重晶石-方铅矿、铁和锰矿石是在厚沉积层序内发育的单一热液系统的产物。重晶石-方铅矿矿石在海床表面附近形成，在仍在形成的珊瑚礁内部区域排出热液溶液。矿石物质沉积在含有Ba、Pb、Zn、Fe、Mn等元素的热液与近地表水混合的区域，充填在礁体内的孔隙和裂缝中，其特征是海水硫酸根离子被细菌还原为硫化氢。穿透珊瑚礁的流体失去了大部分 Ba 和 Pb，沉积为重晶石和方铅矿，但保留溶解形式的 Zn、Fe 和 Mn。随后，Fe 和 Mn 以氧化物的形式沉积：Fe 沉积在珊瑚礁表面或距离珊瑚礁一定距离处，而 Mn 沉积在相当远的距离处。Zn分散在周围空间中，没有形成任何矿体。