湖北铜绿山铜铁矿床成矿机制探讨

以铜绿山铜铁矿为例,探讨了浅成岩体冷却过程中夕卡岩及夕卡岩矿床在接触带上的形成过程及其耦合条件。在铜绿山矿区,矿体主要产出于石英二长闪长玢岩与下三叠统大冶群碳酸盐岩的半岛状 岛链状残留、捕虏体接触带中,矿体与夕卡岩密切共生。此次工作根据大量野外观察,结合对已有资料综合研究,提出成矿空间为冷缩低压区的概念,即夕卡岩及夕卡岩矿床形成的起因是在岩浆固结后的岩石冷凝收缩过程中,在接触带上形成了一个能使流体持续汇聚和长期驻留的低压区--冷缩低压区系统。这个系统与岩浆期后热液的耦合,在超临界流体、CO2气体和临界转换作用的配合下,满足了夕卡岩型矿床成矿的需求,形成了铜绿山矿床。     

青海祁漫塔格景忍—虎头崖矿田地质与找矿:岩浆—热力构造类型与构造—岩相填图

矿田是强调时间、空间、建造和构造成因上相紧密联系的一组矿床。矿田建造、构造和成矿作用标志及成矿动力学过程相关的综合研究是矿田地质研究的核心。前人对岩浆热力构造、类型划分和深部找矿预测的研究较少。岩浆热应力构造是指受岩浆热力作用影响或控制,与成矿期岩浆侵入或火山喷发活动有时空联系,形成于岩浆岩体中或围岩地层中或远程热力作用影响区的一系列与成矿有关的热力和热应力构造类型。文章在矿田地质学指导下,划分出五类岩浆热力构造类型,力图建立以岩浆热力构造为基础的构造研究、类型划分和深部找矿预测新方法。以近年实际调研工作为基础,选择青海祁漫塔格矿带景忍—虎头崖多金属矿田为例,建立印支期岩浆侵入成矿模式,厘定了岩浆热力构造的识别标志。在矿田建造与构造调研及构造岩相填图基础上,填制了该矿田岩浆热力构造类型分布图,以印支期中酸性侵入岩、花岗斑岩、夕卡岩带、大理岩带、古生代和新元古代碳酸盐岩有利岩性岩相层位和侵入接触带、断裂破碎带叠加热液蚀变带等构造发育地段为标志,圈定了该区成矿富集中心。研究剖析了该区花岗斑岩和夕卡岩型两类矿床特征,认为不同方向断裂控矿特征不同,近东西向和北西西向断裂控矿显著,晚三叠世岩浆侵入作用是该区多金属大规模成矿的主要内因,印支期岩浆侵入作用与各时代碳酸盐岩接触带形成了岩浆热液交代型矿田。目前海拔高度以夕卡岩型和热液型多金属矿床为主。中深部寻找斑岩型多金属矿床的潜力较大。此对该带矿田地质研究与找矿突破有引导推广价值。     

新疆磁海铁（钴）矿床次火山热液成矿学

磁海铁（钴）矿床颇具特色,以“石榴石－透辉石－磁铁矿”为基本矿石建造;成矿作用发生在早二叠世北山裂陷作用和火成活动晚期,以基性次火山岩浆期后富铁流体的（交代）充填为成矿方式,矿体产于辉绿岩体原生裂隙系统;成矿流体的化学演化具有典型（火山）岩浆期后热深演化特点,形成了一系列热液蚀变其中石榴石透辉石岩有别于传统理解的“夕卡岩”;成矿物质源于碱性玄武岩浆,基性次火山岩浆多次脉动式入侵是矿床形成的必要条件     

内蒙古赤峰山金-多金属矿床特征及找矿方向

赤峰山金．多金属矿位于北山多金属成矿带，区内共发现金．多金属矿脉114条，其中金和含金矿脉19条，均产于华力西晚期黑云二长花岗岩体和斑状花岗闪长岩株北接触带上的蓟县系平顶山群大理岩中，受接触带夕卡岩化带及近EW、NE、NW和NNW向断裂所控制。在空间上由内一外依次分布着高温热液接触交代夕卡岩型铜．铁矿床，中低温热液型金．铅．多金属矿床，明显地反映出岩浆热液型矿床自高一中一中低温的水平分带特征，呈现出与一般热液型矿床相一致的成矿序列。中酸性小岩株、岩枝与碳酸盐岩内外接触带的破碎带是赋矿的有利部位，夕卡岩化带以及地表遭受强烈氧化而形成的氧化铅及砷酸岩矿物是直接的找矿标志。     

黄岗梁夕卡岩型铁锡矿床萤石中流体一熔融包裹体及对矿床成因研究的意义

黄岗梁夕卡岩型铁锡矿床的主要成矿阶段一一含水夕卡岩阶段的萤石内,首次发现了含有多种子矿物的特殊的流体-熔融包裹体, 该种流体『熔融包裹体携带有较多Fe、Mg及Cr等深源组分,从原生至次生,其内熔体组分从以含Ca、F为主向以含Si为主的熔体演化, 由均句捕获向不均匀捕获演化,在此过程中熔体组分逐渐减少至消失,子矿物亦减少至消失.这显示了携带大量成矿元素的原始成矿熔体组分的演化、熔体相与流体相的分异是导致Fe、Sn等沉淀成矿重要因素,这一发现确定了黄岗梁夕卡岩型铁锡矿床的岩浆成因. 项工作填补了岩浆成因夕卡岩型矿床的研究空白,为该类型矿床矿流体和成矿作用研究提供了新的思路和方法手段,并进一步拓了流体包裹体的研究内容.     

岩浆热液型铅锌矿床生成条件的实验研究

岩浆热液型铅锌矿床是我国重要的矿床类型之一.它与中酸性浅成、超浅成小侵入体活动密切相关.矿体多产于岩浆岩与碳酸盐岩地层的接触带上及其附近,研究其形成条件,对铅锌矿床的找矿具有重要意义. 对岩浆热液型铅锌矿床进行较为系统的实验研究尚未见报道,但就这类矿床的各个侧面进行单项研究的却很多.我们在前人工作的基础上,对发育在断裂、破碎带中的岩浆热液夕卡岩型铅     

西藏谢通门县斯弄多大型叠加改造型铅锌矿床特征及找矿方向

斯弄多铅锌矿区位于冈底斯斑岩型矿床成矿带中。矿区花岗斑岩和闪长玢岩的地球化学特征表明,斯弄多铅锌矿与冈底斯斑岩型矿床为同一成矿体系,均形成于印—亚大陆主碰撞期和碰撞期后的构造体制转化阶段;岩浆来源于原岩以杂砂岩和泥质岩为主的前寒武纪念青唐古拉群变质结晶基底和下地壳基性岩类的部分熔融。成矿物质主要来源于雅鲁藏布江新特提斯洋对冈底斯弧俯冲板片的部分熔融并交代岛弧带上的基底岩系。矿床的形成分为3期:第一期为中石炭世,与碳酸盐岩沉积同时期的海底热水喷流沉积作用形成初始矿源层;第二期为构造活动成矿期,分2个成矿阶段:第一阶段为晚白垩世—始新世,即印-亚大陆主碰撞形成的早期与斑岩有关的岩浆热液型铅锌矿;第二阶段的铅锌矿化发生在主碰撞期后的伸展拉张阶段,由于花岗斑岩的侵位,使铅锌矿化进一步活化迁移、叠加、富集,与围岩接触部位形成夕卡岩型铅锌矿体,矿体的形成多受矿区内复杂的断裂构造控制,矿床类型主要为构造破碎带热液充填型和夕卡岩型;第三期为表生期,主要为原生硫化矿体的氧化流失和贫化。在I号矿带的深部、南部和北部异常区具有扩大矿床规模的远景。     

辽西杨家杖子-八家子钼多金属成矿带——典型钼矿床特征及找矿远景预测

辽西杨家杖子-八家子钼多金属矿成矿带钼矿床与燕山期中酸性岩体关系密切.产于花岗质岩类与碳酸盐岩地层接触带的钼矿床为夕卡岩型或斑岩-夕卡岩型钼矿床.产于花岗斑岩、长英质或中性火山岩内的钼矿床多为斑岩型钼矿床.不同类型钼矿床在成因、分布规律以及成矿元素的分带性上有着密切的时空关系.钼矿床的成矿物质来源于花岗岩,细粒花岗斑岩是主要成矿母岩.从成矿条件分析可确定,该钼多金属成矿带的找矿远景可观.     

云南普朗斑岩型铜矿田构造岩相成矿规律与控矿特征

云南西北部格咱岛弧是西南“三江”古特提斯阶段形成的重要地质构造单元,位于扬子西缘义敦岛弧带的南端。近年来新发现了包括普朗超大型斑岩型铜矿,红山-红牛、雪鸡坪大型和10余个中小型斑岩夕卡岩型铜矿床,成为斑岩型铜矿田和铜资源勘查开发基地。研究发现,矿田中矿床的形成与大地构造演化密切对应,不同阶段发育不同的矿床;对应于构造演化产生的区域北西向主干断裂控制岩带的展布,次级断裂及褶皱联合控制了岩体的形态和产状,斑岩型矿床主要产于背斜核部,其含矿斑岩侵位较浅,夕卡岩型铜矿主要产于向斜核部,含矿斑岩侵位相对较深;含矿斑岩多为复式岩体,顶部往往有火山岩岩盖,表明火山岩浆活动具有继承性的特征,普朗铜矿产于北西、北东东向两组断裂的交汇部位,形成岩体内斑岩铜(钼)矿、接触带夕卡岩铜矿和围岩中的大脉状铜矿“三位一体”的斑岩成矿系统,并在外带发育铅锌矿和浅成低温热液金(银)矿床。     

云南马厂箐矿田浅成低温热液-斑岩型Cu-Mo-Au多金属成矿系统

马厂箐Cu-Mo-Au多金属矿田位于西南三江复合造山带中段,是带内金多金属矿床的典型代表。矿田内矿化类型复杂,元素组合多样。围绕马厂箐富碱杂岩体矿化类型、元素组合、围岩蚀变呈明显的分带。在岩体中形成斑岩型铜-钼矿床;在岩体与地层内外接触带形成接触交代型(角岩型、夕卡岩型)铜-钼(铁)矿床;在岩体外围地层中形成浅成低温热液金-铅-锌矿床。对应的围岩蚀变表现为自岩体中心向外依次为强硅化带→石英钾长石化带→石英钾长石绢云母化带→夕卡岩化带→中低温热液蚀变。同位素测年结果表明3种类型的矿床成矿均发生于33.7～35.8Ma,金矿床略晚于铜-钼矿床,并与矿田内马厂箐杂岩体侵入时代(33～37Ma)一致。岩矿石的H、O、Pb、S同位素和流体包裹体系统研究表明,从斑岩型铜-钼矿床→接触交代型铜-钼(铁)矿床→浅成低温热液金-铅-锌矿床,矿石中流体包裹体均一温度、盐度和均一压力逐渐降低,成矿物质(矿质和流体)也逐渐从以深部岩浆源为主,演变为以围岩地层和大气降水为主。矿田内不同类型矿床间的时空及成因联系,反映它们是同源岩浆不同演化阶段成矿作用的产物,含矿热液的物化性质及时空迁移决定了它们在不同部位产出不同的矿床类型,构成与富碱斑岩有关的浅成低温热液-斑岩Cu-Mo-Au多金属成矿系统。     

江西省冷水坑银铅锌矿床铁锰碳酸盐角砾岩成因研究

江西省冷水坑银铅锌矿床的铁锰碳酸盐角砾岩层与顶底板侏罗系火山杂岩呈整合接触关系,填隙物内存在清晰可辨的火山凝灰物质。铁锰碳酸盐角砾岩的稀土元素配分型式属于轻稀土富集的右倾型,稀土组成特征有类似于正常湖相碳酸盐岩低的稀土总量,又类似于正长质岩浆岩的正Eu异常特征。碳氧同位素显示其形成环境属于陆相火山湖泊,陆相沉积岩与岩浆岩均为成岩提供了物质来源。通过顶底板火山杂岩锆石U-Pb年龄的限定,指示在155Ma左右,铁锰碳酸盐角砾岩经历了陆相火山湖泊沉积-火山喷发使之角砾化-正长质岩浆物质混入的成岩过程。     

应用奇异值分解与二维经验模型分解提取金矿化致矿重力异常

奇异值分解(singular value decomposition,SVD)和二维经验模型分解(bi-dimensional empirical mode decomposition,BEMD)2种方法用于鲁西铜石金矿田的金矿化致矿重力异常提取.通过对比研究得出如下结论:①基于重力数据,由BEMD和SVD 2种方法获...     

新疆雅满苏铁矿区碳酸盐岩地质地球化学特征及其对矿床成因的制约

新疆雅满苏铁矿床赋存于下石炭统雅满苏组中,矿区发育火山岩、碳酸盐岩及矽卡岩,因此,研究碳酸盐岩与矽卡岩及成矿的关系对厘定矿床成因类型和指导找矿勘查具有重要的理论和实际意义。文章在野外地质剖面测制和调查研究的基础上,对矿区及外围碳酸盐岩进行了岩相学、主量元素、稀土元素及微量元素分析,探讨了矿区碳酸盐岩的地质、地球化学特征。研究结果表明,雅满苏铁矿区的碳酸盐岩含有浅海相生物化石、鲕粒结构及内碎屑构造,与火山岩互层产出,指示沉积作用及火山喷发活动发生于浅海环境;矿区碳酸盐岩岩石类型包括微晶灰岩、细晶灰岩、大理岩、含凝灰质大理岩、糜棱岩化碳酸盐岩和方解石构造片岩,它们的主量元素含量差别不大,说明在变质变形和成矿作用过程中没有主量元素组分的明显带入带出;稀土、微量元素含量除方解石构造片岩稍有降低外,其余岩性均变化不大,也表明变质变形和成矿作用过程中没有外来物质的明显加入,包括成矿物质;与矿体毗邻的碳酸盐岩为方解石构造片岩,没有发生矽卡岩化,表明该碳酸盐岩在构造及成矿作用过程中只发生了构造片理化和热液重结晶,没有发生接触交代。因此,雅满苏铁矿床不是狭义的矽卡岩(接触交代)型铁矿床,而是海相火山岩型铁矿床。研究区的矽卡岩并非是接触交代的产物,而应是火山热液交代含碳酸盐的火山岩而成。是否有下部地层中的碳酸盐岩提供成岩成矿物质还需要进一步研究。     

Fluid metasomatic genesis of stratiform skarn in the Suoerkuduke Cu-Mo deposit,East Junggar,NW China

Stratiform skarns associated with ore deposits are widespread in the north of East Junggar, particularly in the Suoerkuduke Cu-Mo deposit. The Suoerkuduke stratiform and stratoid skarns are hosted by Devonian intermediate-mafic volcanic and pyroclastic rocks, mainly andesite, andesitic porphyry and tuffaceous sandstone, without carbonate or calcareous rocks. The skarns consist of dominant andradite-grossular, epidote, diopside-hedenbergite and minor actinolite, quartz, magnetite and metallic sulfides. The garnet and epidote composition, especially Fe^3 + and Al contents, is largely a function of the bulk composition and physicochemical environment (particularly fO₂) during crystallization. Such mineralogy indicates a relatively oxidizing environment and medium acidity of solution during skarnization.The Suoerkuduke skarns are distinct from typical contact metasomatic skarn in wall rock, as no carbonate or calcareous rocks were found, and differ in the distribution patterns of skarn zonation in that gradually weakened skarn zones are not quite symmetrically distributed on both sides of the alteration center (a garnet skarn). Abundant remnants of andesite, andesitic porphyry and tuffaceous sandstone in the weakened skarn zone indicate that the protolith of the skarn is andesite, andesitic porphyry and tuffaceous sandstone. Magmatic water, meteoric and seawater are involved in skarn alteration. Moyite and granitic porphyry are not coeval with skarn, and their emplacement resulted in the hornfelization of wall rock instead of skarnization, and themselves keep away from skarn alteration. Therefore, there was probably a huge batholith supplying magmatic fluid for skarn formation. Mass balance estimates suggest that hydrothermal fluid must contribute a portion of Ca and Fe to ensure sufficient supply for skarn formation in the absence of local carbonate and calcareous rocks. In conclusion, the stratiform skarns in the Suoerkuduke are products of intermediate-mafic volcanic and pyroclastic rocks metasomatised by hydrothermal fluid that probably leached calcareous wall rock during ascent.     

The large Bystrinskoe Cu–Au–Fe deposit (Eastern Trans-Baikal Region): Russia’s first example of a skarn–porphyry ore-forming system related to adakite

The Bystrinskoe skarn-porphyry Cu–Au–Fe deposit (Eastern Trans-Baikal Region) is confined to skarn zones, which were formed along the contact of granitoids referred to the Shakhtama intrusive complex (J_2–3), with terrigenous–carbonate sedimentary rocks. Commercial (Cu–Au–Fe ± W, Mo) mineralization was formed due to the regional postcollision development involving the intrusion of porphyritic granitoids, the derivatives of oxidized adakite highly magnesian magmas enriched in water, sulfur, and metals, which could develop under melting of garnet-bearing amphibolite in the mafic lower crustal arc.     

致矿侵入体的识别标志——以新疆阿尔夏提矽卡岩型铁铜矿床为例

致矿侵入体的识别是成矿学研究和资源勘查的关键环节之一,对于许多矿床类型来说也是一个难点.本文以新疆阿尔夏提矽卡岩型铁铜矿床为例,阐述了通过建立五种联系及其地质学、岩石学、矿物学、地球化学和成矿学标志的识别方法,进而提出推木尔特岩基为含矿流体屏蔽层的认识.推木尔特岩基与矽卡岩矿体具有紧密的空间联系,容易被误认为是致矿侵入体.然而,其成岩时间早于成矿时间,仅导致围岩的大理岩化和角岩化,因而不是成矿物质的来源.相反,矿区内分布的闪长质小岩体和各类岩墙不仅与矿体和矽卡岩存在紧密的空间联系,而且岩石中普遍见有造矿矿物与造岩矿物的共结关系,岩体(墙)本身及其围岩也经受了强烈的流体改造,是含矿流体的通道和真正的致矿侵入体.     

安徽沿江地区中生代原地和异地矽卡岩岩浆－热液成矿作用

在安徽沿江地区,既分布有大量接触交代成因和叠加复合成因的矽卡岩矿床,也分布有岩浆成因的矽卡岩矿床。本文给出了不同类型岩浆矽卡岩及其矿床的定义,论述了安徽沿江地区中生代岩浆矽卡岩及其矿床的特征,并在此基础上分析了区域中生代矽卡岩岩浆－热液成矿作用。根据矽卡岩岩浆就位位置的不同可将岩浆矽卡岩分成原地矽卡岩和异地矽卡岩两类,相应地将岩浆矽卡岩矿床分成原地矽卡岩矿床和异地矽卡岩矿床两大类。两类矽卡岩及其矿床具有明显不同的特征。在地质产状上,原地矽卡岩岩体常与壳幔同熔岩浆侵入体紧密伴生而分布在壳幔同熔岩浆侵入体与碳酸盐围岩的接触带上,在矽卡岩岩体边缘一般没有冷凝边和烘烤边,但常能见到因同化混染作用不彻底而留下的围岩残留体（多已变质成角岩或大理岩）。与此明显不同的是,异地矽卡岩岩体常分布在断裂带或地层虚脱带中,附近一般没有壳幔同熔岩浆侵入体与其紧密伴生,在矽卡岩岩体边缘一般有冷凝边和烘烤边,有时能见到气孔构造以及石榴石或透辉石堆积岩,但见不到围岩残留体。同时,原地矽卡岩和异地矽卡岩均具有明显的水平分带,但两者明显不同。原地矽卡岩的水平分带常表现为从侵入岩体经矽卡岩往碳酸盐围岩方向依次出现侵入岩→同化混染侵入岩→富铁矽卡岩→富钙矽卡岩→同化混染碳酸盐岩→碳酸盐岩,反映同化混染作用逐渐减弱,而异地矽卡岩的水平分带常表现为从矽卡岩体中央往两边依次出现中粗粒矽卡岩－中细粒矽卡岩,反映随降温速度逐渐增加结晶速度逐渐降低。在矿物组成上,原地矽卡岩中的石榴石包含钙铁榴石、钙铁铝榴石和钙铝榴石,辉石主要为透辉石和钙铁辉石,而异地矽卡岩中的石榴石几乎全是钙铁榴石,辉石全是钙铁辉石。在地球化学方面,相对于原地矽卡岩,异地矽卡岩明显富集W、F、Rb、Be、Fe,而亏损Al、Sr、Ba、Cu、Pb、Zn、Cr、Co、Ni等元素。在岩相学上,原地矽卡岩和异地矽卡岩大多具有自形等粒结构,其中大多能见到熔融包裹体,但原地矽卡岩中的石榴石和辉石更为自形且常发育良好环带,熔融包裹体的均一温度明显高于异地矽卡岩中熔融包裹体的均一温度。在矿床类型上,原地矽卡岩一般为铜矿床,矿石矿物主要是铜铁硫化物,而异地矽卡岩一般为铁矿床,矿石矿物主要是铁氧化物。通过综合分析,认为原地矽卡岩和异地矽卡岩是由矽卡岩岩浆在原地或异地发生冷却结晶作用形成的,而原地矽卡岩矿床和异地矽卡岩矿床是由原地矽卡岩岩浆和异地矽卡岩岩浆发生熔离作用和结晶分异作用,熔离出的矿浆和分异出的热液发生冷却结晶和交代蚀变作用形成的。     

The Vorontsovskoe Au-Hg-As ore deposit (Northern Urals,Russia): Geological setting,ore mineralogy,geochemistry, geochronology and genetic model

The large Vorontsovskoe Au-Hg-As deposit in the Urals is located in the exocontact of the Early Devonian Auerbah gabbro-diorite-granodiorite massif, which intrudes volcano-sedimentary rocks. The orebodies are confined to a tectonic contact of calcareous and tuffaceous rocks. They are composed of 6 types of disseminated ores, but the main reserves of gold are associated with the following ore types: gold-pyrite-arsenopyrite in altered tuffaceous rocks, pyrite-realgar ores in limestone breccia with a carbonate-volcanogenic cement, and gold-oxide-clay from regolith with residual gold. Early ore associations have been formed at 450–300 °C, whereas the late ores have been formed at lower temperature of 260–110 °C. We propose a model for the genesis of the Vorontsovskoe deposit based on synchronicity of mineralization with the formation of the Auerbah volcano-plutonic complex. The Ar-Ar age of hydromica from the gold-arsenopyrite association is 391.1 ± 4.9 Ma, which coincides with the age of igneous rocks of the Auerbah complex. The main sources of water and carbon dioxide were composed of the fluid derived from the magma chamber and the metamorphic water equilibrated with carbonate sedimentary rocks. Magmatic fluid dominated during the development of skarns, jasperoids and quartz veins, whereas metamorphic water was dominant during quartz-sericite alteration of volcano-sedimentary rocks and calcareous breccias. The bulk of the sulfur was supplied by a deep magma reservoir, however this source prevailed only during skarn ore formation. The mixing between deep-sourced sulfur and sedimentary or biogenic sulfur was established for other ore types. Gold and other ore components were possibly introduced during the volcanic and intrusive activity and also extracted from host sedimentary rocks.     

Geological, geochemical characteristics and isotope systematics of the Longqiao iron deposit in the Lu-Zong volcano-sedimentary basin, Middle-Lower Yangtze (Changjiang) River Valley, Eastern China

The Middle-Lower Yangtze (Changjiang) River Valley metallogenic belt is located on the northern margin of the Yangtze Craton of eastern China. Most polymetallic deposits in the Changjiang metallogenic belt are clustered in seven districts where magmatism of Mesozoic age (Yanshanian tectono-thermal event) is particularly extensive. From west to east these districts are: E-dong, Jiu-Rui, Anqing-Guichi, Lu-Zong, Tong-Ling, Ning-Wu and Ning-Zhen. World-class iron ore deposits occur in the Lu-Zong and Ning-Wu ore clusters, which are mainly located in continental fault-bound volcanic-sedimentary basins. One of these deposits is the Longqiao iron deposit, discovered in the northern part of the Lu-Zong Basin in 1985. This deposit consists of a single stratabound and stratiform orebody, hosted in sedimentary carbonate rocks of the Triassic Dongma'anshan Formation. A syenite pluton (Longqiao intrusion) is situated below the deposit. The iron ore is massive and disseminated and the ore minerals are mainly magnetite and minor pyrite. Wall rock alteration mostly consists of skarn minerals, such as diopside, garnet, potassic feldspar, quartz, chlorite, phlogopite and anhydrite. Thin sedimentary siderite beds of Triassic age occur as relict laminated ore at the top and the margin of the magnetite orebody. These sideritic laminae are part of Triassic evaporite-bearing carbonate deposits (Dongma'anshan Formation).Sulfur isotopic compositions show that the sulfur in the deposit was derived from a mixture of magmatic hydrothermal fluids and carbonate–evaporite host rocks. Similarly, the C and O isotopic compositions of limestones from the Dongma'anshan Formation indicate that these rocks interacted with magmatic hydrothermal fluids. The O isotopic compositions of the syenitic rocks and minerals from the deposit show that the hydrothermal magnetite and skarn minerals were formed from magmatic fluids. The Pb isotopic compositions of sulfides are similar to those of the Longqiao syenite. Phlogopite coexisting with magnetite in the magnetite ores yielded a plateau age of 130.5 ± 1.1 Ma (2σ), whereas the LA-ICP MS age of the syenite intrusion is 131.1 ± 1.5 Ma, which is slightly older than the age of phlogopite.The Longqiao syenite intrusion may have crystallized from a parental alkaline magma, generated by partial melting of lithospheric mantle, during extensional tectonics. The ore fluids were probably first derived from magma at depth, later emplaced in the sedimentary rocks of the Dongma'anshan Formation, where it interacted with siderite and evaporite-bearing carbonate strata, resulting in the formation of magnetite and skarn minerals. The Longqiao iron deposit is a skarn-type stratabound and stratiform mineral system, genetically and temporally related to the Longqiao syenite intrusion. The Longqiao syenite is part of the widespread Mesozoic intracontinental magmatism (Yanshanian event) in eastern China, which has been linked to lithospheric delamination and asthenospheric upwelling.