The Devonian Rudniy intrusion is a composite magmatic body comprising two gabbroid units. Located in the Tsagaan-Shuvuut ridge in NW Mongolia, it is the only one known to contain disseminated sulfide Ni-Cu-PGE minerals out of numerous gabbroid intrusions surrounding the Tuva depression. The ore occurs as disseminated sulfide globules made of pyrrhotite, pentlandite, chalcopyrite, and cubanite, confined to a narrow troctolitic layer at the margins of a melanogabbro, at the contact with a previously emplaced leucogabbro. Globules generally display mantle-dominated sulfur isotopic signatures but show variable metallogenic and mineralogical characteristics, as well as notably different sizes and morphologies reflecting variable cooling and crystallization regimes in different parts of the intrusion. Sulfides from the chilled margin of the melanogabbro are surrounded and intergrown with volatile-rich (i.e., CO₂-, H₂O-, F-, and Cl) phases such as calcite, chlorite, mica, amphibole, and apatite. Based on the mineralogical and textural relationships of volatile-rich phases with sulfides, we argue that this assemblage represents the product of the crystallization of volatile-rich carbonate melt immiscible with both silicate and sulfide liquids. We put forward the hypothesis that volatile-rich carbonate melt envelops sulfide droplets facilitating their transport in magmatic conduits and that this process may be more widespread than commonly thought. The smaller sulfide globules, which are interpreted to derive from the breakup of larger globules during transport and emplacement, do not display an association with volatile-rich phases, suggesting that the original carbonate melt could have been detached from them during the evolution of the magmatic system. Variable rates of crystallization may have been responsible for the observed disparities in the mineralogical and metallogenic characteristics of different sulfide globules entrained in the Rudniy intrusion.

泥盆纪 Rudniy 侵入体是由两个辉长岩单元组成的复合岩浆体。它位于蒙古西北部的 Tsagaan-Shuvuut 山脊，是图瓦凹陷周围众多辉长岩侵入体中唯一已知含有浸染状硫化物 Ni-Cu-PGE 矿物的地区。矿石以浸染状硫化物球的形式出现，由磁黄铁矿、镍黄铁矿、黄铜矿和立方石组成，局限于黑长辉长岩边缘的狭窄滑石层中，与先前就位的白辉长岩接触。球体通常显示出以地幔为主的硫同位素特征，但显示出不同的成矿和矿物学特征，以及明显不同的尺寸和形态，反映了侵入体不同部分的不同冷却和结晶状态。来自黑长岩冷边缘的硫化物被富含挥发物（即CO ₂ -、H ₂ O-、F-和Cl）相（例如方解石、绿泥石、云母、角闪石和磷灰石）包围并共生。基于富含挥发物相与硫化物的矿物学和结构关系，我们认为这种组合代表了与硅酸盐和硫化物液体不混溶的富含挥发物的碳酸盐熔体的结晶产物。我们提出了这样的假设：富含挥发物的碳酸盐熔体包裹着硫化物液滴，促进它们在岩浆通道中的传输，并且这个过程可能比通常认为的更广泛。较小的硫化物球体被解释为源自较大球体在运输和侵位过程中的破碎，它们并未表现出与富含挥发物相的关联，这表明原始碳酸盐熔体可能在岩浆演化过程中与它们分离。系统。不同的结晶速率可能是导致鲁德尼岩体中夹带的不同硫化物球体的矿物学和成矿特征差异的原因。