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

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Geological, mineralogical, and oxygen isotope studies of the Chandmani Uul iron oxide–copper–gold deposit in Dornogobi Province, Southeastern Mongolia
Resource Geology ( IF 1.1 ) Pub Date : 2020-03-17 , DOI: 10.1111/rge.12232
Luvsannyam Oyunjargal _{1,

2} , Ken‐ichiro Hayashi ₁ , Teruyuki Maruoka ₁

Affiliation

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.

中文翻译：

蒙古东南部多尔诺哥比省Chandmani Uul氧化铁-铜-金矿床的地质，矿物学和氧同位素研究

Chandmani Uul矿床位于蒙古东南部的Dornogovi省。铁氧化物存在于新元古代至下寒武纪的Shar Zeeg组的安山岩中。中-上-寒武纪的花岗岩岩体已经侵入了该矿床的西部和南部地区的宿主岩中。对铁氧化物矿体周围的围岩进行热液改造，形成钾质，埃迪奥铁矿和绢云母－亚氯酸盐蚀变带，方解石和石英脉脉在后期普遍存在。由于花岗质岩也经历了钾化蚀变，因此花岗质岩的活动必须与矿床具有遗传关系。矿石矿物组合以铁氧化物为主，例如具有同心和/或振荡带状纹理的穆什凯维铁矿，全金属磁铁矿，和花椰菜磁铁矿。少量的黄铜矿和黄铁矿伴随着氧化铁。在所有这些产品中，穆斯克维石占主导地位，并且分布在整个矿床中。同时，在沉积物中相对浅的水平上，有限数量的原液磁铁矿出现。相比之下，花椰菜磁铁矿局部出现在矿床的深部，并且与绿色的石榴石和方解石有关。硫化物矿物普遍与这些氧化铁缔合。氧同位素（δ 花椰菜磁铁矿局部出现在矿床的深处，并与绿色的石榴石和方解石有关。硫化物矿物普遍与这些氧化铁缔合。氧同位素（δ 花椰菜磁铁矿局部出现在矿床的深处，并与绿色的石榴石和方解石有关。硫化物矿物普遍与这些氧化铁缔合。氧同位素（δ发现所有类型的磁铁矿，石英和橄榄石的¹⁸ O）值分别为-5.9至-2.8‰，10.5至14.9‰和3.6至6.6‰。的δ ^18个石英磁铁矿对O值表明邻近300℃的平衡温度同位素。δ的计算值¹⁸ O代表负责磁铁矿的水为2〜10‰。在这项研究中获得的所有数据表明，钱德曼尼乌尔（Chandmani Uul）的氧化铁矿床是典型的氧化铁-铜-金矿床，并且该矿床是在氧化条件下形成中等深度的钾，绢云母-亚氯酸盐蚀变带形成的。赤铁矿稳定的环境。该δ ¹⁸估计的O范围暗示成矿流体是由结晶的粒二岩岩浆供应的，在深处溶解了大量的陨石水。

更新日期：2020-03-17

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