Geological, mineralogical, and oxygen isotope studies of the Chandmani Uul iron oxide–copper–gold deposit in Dornogobi Province, Southeastern Mongolia

IF 1.1 4区 地球科学 Q3 GEOLOGY Resource Geology Pub Date : 2020-03-17 DOI:10.1111/rge.12232
Luvsannyam Oyunjargal, K. Hayashi, T. Maruoka
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引用次数: 4

Abstract

The Chandmani Uul deposit is located in Dornogovi province, Southeastern Mongolia. Iron oxide ores are hosted in the andesitic rocks of the Shar Zeeg Formation of Neoproterozoic to Lower‐Cambrian age. Middle‐ to Upper‐Cambrian bodies of granitic rocks have intruded into the host rocks in the western and southern regions of the deposit. The wall rocks around the iron oxide ore bodies were hydrothermally altered to form potassic, epidote, and sericite–chlorite alteration zones, and calcite and quartz veinlets are ubiquitous in the late stage. Since granitic rocks also underwent potassic alteration, the activity of the granitic rocks must have a genetic relation to the ore deposit. The ore mineral assemblage is dominated by iron oxides such as mushketovite, euhedral magnetite with concentric and/or oscillatory zoning textures, and cauliflower magnetite. Lesser amounts of chalcopyrite and pyrite accompany the iron oxides. Among all these products, mushketovite is dominant and is distributed throughout the deposit. Meanwhile, euhedral magnetite appears in limited amounts at relatively shallow levels in the deposit. By contrast, cauliflower magnetite appears locally in the deeper parts of the deposit, and is associated with green‐colored garnet and calcite. Sulfide minerals are ubiquitously associated with these iron oxides. The oxygen isotope (δ18O) values of all types of magnetite, quartz, and epidote were found to be −5.9 to −2.8‰, 10.5 to 14.9‰, and 3.6 to 6.6‰, respectively. The δ18O values of quartz–magnetite pairs suggest an equilibrium isotopic temperature near 300°C. The calculated values of δ18O for the water responsible for magnetite ranged from 2 to 10‰. All the data obtained in this study suggest that the iron oxide deposit at the Chandmani Uul is a typical iron oxide–copper–gold deposit, and that this deposit was formed at an intermediate depth with potassic and sericite–chlorite alteration zones under the oxidized conditions of a hematite‐stable environment. The δ18O range estimated implies that the ore‐forming fluid was supplied by a crystallizing granodioritic magma exsolving fluids at depth with a significant contribution of meteoric water.
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蒙古东南部多诺戈壁省Chandmani Uul氧化铁铜金矿床地质、矿物学及氧同位素研究
Chandmani Uul矿床位于蒙古东南部的Dornogovi省。氧化铁矿石赋存于新元古代至下寒武统沙河组安山岩中。在矿床西部和南部地区,中-上寒武统花岗岩侵入寄主岩。氧化铁矿体周围围岩发生热液蚀变,形成钾质、绿帘石、绢云母-绿泥石蚀变带,晚期方解石和石英细脉普遍存在。由于花岗质岩石也经历了钾蚀变,因此花岗质岩石的活动必然与矿床有成因关系。矿石矿物组合以含铁氧化物为主,如mushketovite、具有同心和/或振荡带结构的自面体磁铁矿和花椰菜磁铁矿。少量的黄铜矿和黄铁矿伴随着氧化铁。在所有这些产物中,木须石占主导地位,并分布于整个矿床。与此同时,自形磁铁矿在矿床中相对较浅的层次上少量出现。相比之下,花椰菜磁铁矿局部出现在矿床的较深部分,并与绿色石榴石和方解石相关联。硫化物矿物与这些氧化铁无处不在。各类磁铁矿、石英和绿帘石的氧同位素δ18O值分别为- 5.9 ~ - 2.8‰、10.5 ~ 14.9‰和3.6 ~ 6.6‰。石英-磁铁矿对的δ18O值表明平衡同位素温度接近300℃。磁铁矿成因水的δ18O计算值为2 ~ 10‰。研究结果表明,Chandmani Uul氧化铁矿床是典型的氧化铁-铜-金矿床,矿床形成于赤铁矿-稳定环境氧化条件下的含钾蚀变带和绢云母-绿泥石蚀变带的中深度。估算的δ18O范围表明成矿流体是由花岗闪长质岩浆在深部结晶溶出的流体提供的,其中有大气水的显著贡献。
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来源期刊
Resource Geology
Resource Geology 地学-地质学
CiteScore
2.30
自引率
14.30%
发文量
18
审稿时长
12 months
期刊介绍: Resource Geology is an international journal focusing on economic geology, geochemistry and environmental geology. Its purpose is to contribute to the promotion of earth sciences related to metallic and non-metallic mineral deposits mainly in Asia, Oceania and the Circum-Pacific region, although other parts of the world are also considered. Launched in 1998 by the Society for Resource Geology, the journal is published quarterly in English, making it more accessible to the international geological community. The journal publishes high quality papers of interest to those engaged in research and exploration of mineral deposits.
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