The Lakeh Siah iron oxide-apatite deposit occurs within the Cambrian succession of volcanic tuffs and rhyolitic rocks intercalated with dolomites, dolomitic limestones, and evaporites. Magnetite is the dominant ore mineral, accompanied by apatite, amphibole, diopside, calcite, and andradite garnet. Apatite, allanite, and titanite are the main rare earth element (REE)-bearing minerals. Concentrations of minor elements in magnetite and apatite are consistent with those in the magmatic Kiruna-type IOA deposits. The magmatic stage in the Lakeh Siah deposit is recorded in magnetite-rutile symplectites pseudomorphozing pseudobrookite and replaced by titanite-rutile ± ilmenite ± magnetite, titanite + rutile, and finally REE-rich titanite. The pseudobrookite with 28–42 mol% FeTi₂O₅ was either a primary magmatic mineral or a product of hemoilmenite breakdown at temperatures higher than 810 °C. The titanite-rutile-ilmenite-magnetite symplectites originated between 475 and 700 °C and oxygen fugacities 1.6–1.9 logfO₂ units below the hematite-magnetite buffer. Fluorotremolite associated with diopside and fluorapatite crystallized at temperatures between 710 and 780 °C, and high oxygen fugacities, up to 6 logfO₂ units above NNO buffer. The oxidizing conditions are reflected in increased ferric iron contents (Fe³⁺/Fe²⁺ molar ratios > 1.7) in tremolite, contrasting with the negligible Fe³⁺ in superimposed actinolite. Hydrothermal alteration of the primary magmatic, REE-bearing fluorapatite resulted in the reprecipitation of REE-depleted fluorapatite, monazite-(Ce), and arsenian xenotime. Epidote-ferriepidote and allanite-ferriallanite with up to 26 wt% REE (0.98 apfu) were also replaced by an unidentified Y–Ce–Nd–concentrating Ca,Fe,REE-hydrosilicate, containing up to 39 wt% Y + REE. Low yttrium contents in the neoformed monazite (< 0.02 apfu) indicate crystallization temperatures below 200 °C, but the monazite-xenotime thermometer based on Gd partitioning returns up to 700 °C. Breakdown textures in magnetite and apatite, increased sulfate contents in monazite (up to 1.5 wt% SO₃), and the presence of anhydrite-, calcite-, hematite-, and halite-bearing aqueous inclusions with variable phase ratios in the neoformed apatite reveal metasomatism induced by the interaction with heterogeneous, chloride-sulfate-carbonate brines capable of transporting rare earth elements. The brines were probably mobilized from evaporite-bearing sedimentary strata during the Cambrian volcanism and possibly also during superimposed intrusive episodes coincidental with Silurian and Triassic extension-related magmatism.

Lakeh Siah 氧化铁-磷灰石矿床发生在火山凝灰岩和流纹岩的寒武纪序列中，夹有白云岩、白云质灰岩和蒸发岩。磁铁矿是主要的矿石矿物，伴有磷灰石、闪石、透辉石、方解石和石榴石。磷灰石、褐沸石和钛石是主要的含稀土元素 (REE) 的矿物。磁铁矿和磷灰石中微量元素的浓度与岩浆基律纳型 IOA 矿床中的浓度一致。Lakeh Siah 矿床的岩浆阶段记录在磁铁矿-金红石复合岩假晶化假板钛矿中，并被钛铁矿-金红石±钛铁矿±磁铁矿、钛铁矿+金红石和最后富含稀土的钛铁矿所取代。含有 28–42 mol% FeTi ₂ O _{5的假板钛矿}要么是原生岩浆矿物，要么是在高于 810 °C 的温度下氧化硅铁矿分解的产物。钛铁矿-金红石-钛铁矿-磁铁矿合晶起源于 475 到 700 °C，氧逸度在赤铁矿-磁铁矿缓冲层以下1.6-1.9 log f O 2_单位。与透辉石和氟磷灰石相关的氟透闪石在 710 到 780 °C 的温度下结晶，氧逸度高，比NNO 缓冲液高 6 log f O _2单位。氧化条件反映在透闪石中增加的三价铁含量（Fe ³⁺ /Fe ^{2+摩尔比 > 1.7），与可忽略不计的 Fe 3+形成对比}在叠加的阳起石中。原生岩浆、含稀土元素的氟磷灰石的热液蚀变导致贫稀土元素的氟磷灰石、独居石-(Ce) 和砷磷灰石的再沉淀。含有高达 26 wt% REE (0.98 apfu) 的 Epidote-ferriepidote 和 allanite-ferriallanite 也被含有高达 39 wt% Y + REE 的未鉴定的 Y-Ce-Nd-浓缩 Ca,Fe,REE-氢硅酸盐所取代。新形成的独居石中的低钇含量 (< 0.02 apfu) 表明结晶温度低于 200 °C，但基于 Gd 分配的独居石-磷钇矿温度计返回高达 700 °C。磁铁矿和磷灰石中的分解结构，独居石中硫酸盐含量增加（高达 1.5 wt% SO ₃), 以及新形成的磷灰石中具有可变相比的硬石膏、方解石、赤铁矿和岩盐含水包裹体的存在揭示了与能够输送稀土元素的异质氯化物-硫酸盐-碳酸盐盐水相互作用引起的交代作用. 卤水可能是在寒武纪火山活动期间从含蒸发岩的沉积地层中移动出来的，也可能是在与志留纪和三叠纪伸展相关岩浆作用同时发生的叠加侵入事件期间动员起来的。