Structural controls and timing of fault-hosted manganese at Woodie Woodie,East Pilbara,Western Australia

High-grade fault-hosted manganese deposits at the Woodie Woodie Mine, East Pilbara, are predominantly hydrothermal in origin with a late supergene overprint. The dominant manganese minerals are pyrolusite, braunite, and cryptomelane. The ore bodies are located on, or near the unconformities between the Neoarchean Carawine Dolomite and the Paleoproterozoic Pinjian Chert breccia (weathering product of Carawine Dolomite), and sedimentary units of the overlying ca 1300–1100 Ma Manganese Group. Stratabound manganese is typically located above or adjacent to steep fault-hosted manganese. The ore bodies range in size from 0.2 to 5.5 Mt with an average of 0.5 Mt. Historically, over 35 Mt of manganese has been mined at Woodie Woodie, and current ore resources are 29.94 Mt at 39.94% Mn, 6.96% Fe (resource and reserves statement, June 2011, Consolidated Minerals Pty Ltd).Manganese mineralization at Woodie Woodie is related to northwest–southeast directed extension and basin formation during the Mesoproterozoic. Basin architecture is generally well preserved and major manganese occurrences are localised along growth faults which down-throw the Pinjian Chert Breccia into local extensional basins. Manganese ore bodies are typically located on steep 2nd and 3rd order structures that extend off the major growth faults. Mineralized structures display a dominant northeast-trend reflecting the direction of maximum dilation during northwest–southeast extension.A paragenetic sequence is identified for the manganese ore at Woodie Woodie, with early hydrothermal braunite–pyrolusite–cryptomelane–todorokite–hausmannite, overprinted by late supergene oxides. Preliminary fluid inclusion studies in quartz crystals intergrown with pyrolusite and cryptomelane indicate that primary and pseudosecondary inclusions display a range of salinities from 1 to 18 eq. wt.% NaCl and trapping temperatures estimated to be from 220º to 290º at 1 kbar pressure.A lead–manganese oxide (coronadite) is common in manganese ores at Woodie Woodie, and Pb-isotope studies of 40 lead-rich ore samples from 16 pits indicate mineralization occurred within an age range of 955–1100 Ma. A mixed source is suggested for the lead, but was predominantly basalts and/or volcanogenic sedimentary units (e.g., Jeerinah Formation) of the ca 2700 Ma Fortescue Group. The typically high Mn:Fe ratios and enrichment in elements such as Pb, As, Cu, Mo, Zn are consistent with a dominantly hydrothermal origin for the manganese at Woodie Woodie. Supergene manganese is distinguished from hypogene manganese by a marked enrichment in REE in the supergene manganese.An early structural framework, established during Neoarchean rifting, provides a major structural control on manganese ore distribution. The Woodie Woodie mine corridor is located in a zone of oblique strike-slip extension on major northwest-trending transform faults and north-trending oblique normal faults. A major transform structure at the southern end of the Woodie Woodie mine corridor (Jewel-Southwest Fault Zone) likely acted as a major fluid conduit for manganese-bearing hydrothermal fluids and this would account for the concentration of significant manganese ore occurrences to the north and south of this structure.     

Proterozoic deformation in the east Pilbara Craton and tectonic setting of fault-hosted manganese at the Woodie Woodie mine

Neoarchean and Mesoproterozoic sequences in the Oakover Basin provide a record of deformation and sedimentation along the eastern edge of the Archean Pilbara Craton. The early extensional history of the Oakover Basin is overprinted by subsequent compressional events. Five distinct deformation events are recognised in the Woodie Woodie region; the Archean D₁ event, comprising west-northwest–east-southeast extension associated with formation of the Neoarchean Hamersley Basin; the Mesoproterozoic D_2a event, with northwest–southeast extension and basin formation associated with manganese mineralisation; the D_2b event, with renewed extension associated with intrusion of Davis Dolerite during the ca 1090–1050 Ma Warakurna event; the D₃ event, comprising northeast–southwest-directed compression attributed to the ca 900 Ma Edmundian Orogeny; the Neoproterozoic D₄ event, with east-northeast–west-southwest extension producing large D₄ grabens associated with the opening of the Officer Basin; and, the Neoproterozoic D₅ event comprising north–south-directed compression attributed to the ca 550 Ma Paterson Orogeny. Abundant manganese deposits are hosted by the Neoarchean and Mesoproterozoic sequences in the Oakover Basin, including the large high-grade manganese deposits at Woodie Woodie. The orebodies are predominantly hydrothermal in origin, with a late supergene overprint, and deposition of primary manganese mineralisation was synchronous with northwest–southeast Mesoproterozoic D_2a extension and basin formation. The manganese is associated with normal faults, and many of these represent growth faults related to basin formation. Stratabound manganese is found above or adjacent to fault-hosted manganese. An initial structural framework established during Archean rifting was reactivated in the D_2a event and provided a major structural control on manganese distribution. High-grade manganese deposits at Woodie Woodie mine appear to be located in a zone of oblique dextral extension on major north-northwest- to north-trending faults that mark the eastern ‘active’ or faulted margin of an early rift basin. These large north-northwest-trending normal faults are linked to a major northwest-trending transform fault zone (Jewel-Southwest Fault Zone) that separates the Oakover Basin into a northern and southern basin. The transform fault represents a major deep fluid conduit for hydrothermal fluids and most likely accounts for the concentration of significant manganese occurrences immediately to the north and south of this structure.     

湘中南华系大塘坡组锰矿地球化学特征及其意义

湘中湘潭盆地大塘坡组锰矿是湖南重要的锰矿基地。盆地内发育一组NNE向同沉积断裂,形成了一系列凹陷带（断陷槽）,控制了沉积岩相的分布,锰矿主要产于盆地凹陷带的黑色页岩夹碳酸锰矿微相内。矿石中Co、Zn、Pb、Mo和Ba等元素丰度较高,Co/Ni、SiO2/Al2O3、(Fe+Mn)/Ti、Al/(Fe+Mn+Al)比值以及Co/Zn-(Cu+Ni+Co)和Fe-Mn-(Cu+Ni+Co)图解都揭示锰矿成矿过程中有海底热水的参与;稀土元素分布模式、Ce、Eu异常表示锰矿形成于被动大陆边缘环境,并具有热水沉积特征;碳同位素结果显示出富集碳的轻同位素的特征,反映了湘中地区锰矿中碳同位素热水沉积的特征;氧同位素计算古温度为湘中地区锰矿的低温热水沉积成因提供了有利的佐证。     

非洲锰矿床成因类型、地质特征及表生富集作用

[研究目的]非洲锰矿资源丰富,储量3.1亿t、资源量6.6亿t排名在世界上均列第一,加强非洲锰矿床的研究和认识对推动锰矿找矿工作具有重要的指导意义.[研究方法]通过对重要成矿带典型矿床的解剖总结了非洲锰矿床的成因类型、地质特征.[研究结果]非洲锰矿成因类型主要有前寒武系条带状铁建造(BIF)型、海相沉积型、陆相(三角洲...     

上扬子东南缘民乐-古丈地区锰矿地质特征及找矿方向

湖南省民乐-古丈地区锰矿位于上扬子地块东南缘之武陵台陷的半局限浅海盆地中,为典型的海相沉积型锰矿床。区内主要有民乐和古丈2个锰矿产地,位于松桃成锰盆地的中东部,与贵州道坨锰矿、杨立掌锰矿处于同一断陷槽中,成矿地质条件较好,找矿潜力较大。通过对区内锰矿床（点）成矿地质特征、古构造、岩相古地理等综合分析,总结区域锰矿成矿规律和找矿方向,为上扬子地块东南缘南华系锰矿找矿突破提供依据。     

中国锰矿成矿规律初探-陈毓川院士八十华诞专辑

中国锰矿资源较丰富,资源量排名在世界上位列第5.中国锰矿种类多样,有海相沉积型、火山-沉积型、碳酸盐岩中热水沉积型(或“层控”型)、与岩浆作用有关的热液型、受变质型及表生型.其中,海相沉积型占资源量的71.4％,表生型占15.7％,是最主要的两种类型.中国锰矿广泛分布于“泛扬子区”、华北陆块的燕辽地区以及天山和祁连山部分地区,尤以“泛扬子区”为最,并具分布广泛又相对集中的总体特征.中国的成锰时代多,中—新元古代、早古生代(寒武纪、奥陶纪)、晚古生代—早中生代是中国锰矿形成的重要时代.中国锰矿时-空分布的主要特征是“北锰南迁”:中元古代锰矿主要产于华北陆块的燕辽裂谷带,新元古代—古生代锰矿主要产于“泛扬子区”的大陆边缘盆地或台内盆地中.大型、超大型锰矿床或锰矿田的形成,受控于非构造期盆地性质、古海洋结构、古海水性质及海平面升降等因素,其形成环境存在一定的相似性及同源性.     

湘中奥陶纪锰矿带成矿特征及资源前景

湘中奥陶纪沉积锰矿带位于湖南省安化县、桃江县、宁乡县境内,呈近EW向展布,矿带内锰矿以质量好而著称。该成矿带的成锰沉积盆地受控于加里东期张性断裂系统,为一断陷盆地。盆地内发育一组NW向同沉积断裂,形成了一系列断陷槽,控制了沉积岩相的分布。锰矿主要产于盆地中心亚相的黑色页岩夹碳酸锰矿微相内。据矿带中锰矿的地质和地球化学特征以及微量元素和碳、氧、锶同位素组成,笔者认为,该锰矿属于热水沉积成因。综合对比表明,该成矿带具有良好的成矿条件和值得注意的资源潜力,有可能发展为大型锰成矿带。     

新疆西天山莫托萨拉热水沉积型铁锰矿床矿物学与地球化学特征

莫托萨拉铁锰矿床位于西天山阿吾拉勒成矿带东端,研究程度相对薄弱,在矿床成因方面存在热水沉积、沉积-热液改造、胶体化学沉积等争论。本文详细研究了莫托萨拉最上层锰矿及其围岩的矿物组成、结构构造和地球化学特征,并综合前人资料对整个铁锰矿床的成因做了进一步探讨。本研究首次在矿区发现了热液长石岩,其主要由钠长石、钾长石以及少量重晶石、霓石、锌铁黄长石等矿物组成,类似于"白烟型"热水沉积岩。莫托萨拉最上层锰矿主要由锰橄榄石、褐锰矿、红硅锰矿、磁锰铁矿以及少量重晶石、方铁锰矿等矿物组成,发育有典型的热水内碎屑结构,指示其沉积于海底热液喷流口附近。该层锰矿的Al/(Al+Fe+Mn)值很低(0～0.02)、Si/Al值较高(7.9～10.9)、Fe/Ti值很高(428～1353),通过UCC标准化后发现明显富集Zn、Ba、Pb等元素,而Co、Ni、Cu等元素未见富集,以上地球化学特征与现代海底热液成因铁锰沉积物一致。在Fe/Ti-Al/(Al+Fe+Mn)、Si O2-Al2O3、10×(Co+Ni+Cu)-Fe-Mn、100×(Zr+Ce+Y)-15×(Cu+Ni)-(Fe+Mn)/4等判别图中,莫托萨拉的锰矿层和铁矿层样品均落在海底热液沉积区。锰矿层和铁矿层的稀土元素经PAAS标准化后具有明显的Ce负异常、Eu正异常和Y正异常,与现代海底热液成因铁锰沉积物的稀土配分模式非常相似。综合分析本次研究的矿物学、岩石学、地球化学特征以及前人资料,本文认为莫托萨拉铁锰矿床为海相热水沉积成因,成矿与同期海底火山的间歇性活动密切相关,海底热液的化学组分、温度高低和活动强弱都具有明显的脉动性。莫托萨拉矿区铁锰共存但各自独立成矿,且铁锰分离程度较高,这在显生宙沉积型锰矿中独具特色。鉴于前人曾报道莫托萨拉铁矿石中存在菌藻类微生物化石,我们推测,该矿床的铁锰分离过程除了受控于沉积环境的氧化还原条件变化外,微生物的选择性氧化沉淀可能也发挥了重要作用,值得开展深入研究。     

桂西南早-中三叠世东平-足荣大型锰矿床地球化学、年代学及成因研究

广西东平-足荣大型锰矿床位于桂西南锰矿带上,是广西重要的锰矿富集区。其含矿地层为三叠系北泗组,是一套以硅-泥-灰为主浅海台盆相含锰碳酸盐岩沉积,含锰矿物主要为钙菱锰矿、锰方解石和锰白云石。本文对矿区锰矿层顶部的沉凝灰岩及含锰岩系开展了详细的岩石学、岩石地球化学和锆石U-Pb年代学研究,进而对锰矿成矿时代、成因、沉积环境、沉凝灰岩源区和大地构造背景进行了探讨。锆石SHRIMP U-Pb定年结果显示,3件沉凝灰岩样品的锆石呈自形-半自形板柱状,发育良好的岩浆锆石振荡环带结构。~(206) Pb/~(238)U年龄加权平均值分别为250.8±2.1Ma(MSWD=0.98)、250.6±2.2Ma(MSWD=0.49)和243.6±2.3Ma(MSWD=0.44)。进一步限定了"东平"式锰矿的成矿时代为早-中三叠世(不晚于241～246Ma的范围内)。沉凝灰岩的构造环境判别图解及微量、稀土元素特征显示其岩浆可能形成于与俯冲消减作用相关的碰撞-弧相关或活动大陆边缘相关背景,推测东平-足荣锰矿的形成可能受到广西凭祥-东兴火山作用的影响。含锰岩系的U、V和Mo元素含量及U/Th、V/Cr、V/(V+Ni)、Ni/Co 比值显示东平-足荣锰矿形成于氧化-次氧化的沉积环境。logU-logTh、Fe/Ti-Al/(Al+Fe+Mn)图解及微量元素Ba含量、Ba/Sr值均指示成矿作用受到热水作用的影响。综合矿床地质研究,东平-足荣锰矿形成于弧后盆地拉张构造背景中,锰成矿受同期火山及海底热液作用影响,水体沉积环境为氧化-次氧化条件。     

广西东平地区碳酸锰矿床Ga含量高异常的发现及成因初探

Ga是一种典型的稀有分散元素,主要产于铝土矿、闪锌矿及煤矿之中。最近,在广西东平地区下三叠统北泗组碳酸锰矿床中发现Ga高异常含量,w(Ga)介于5.16×10~(-6)~82.80×10~(-6)之间,平均为33.76×10~(-6),达到了Ga工业品位标准;锰矿层和围岩中w(Ga)平均分别为46.40×10~(-6)、19.31×10~(-6),高于国内外已报道的大部分锰矿床。文中根据北泗组碳酸锰矿床地球化学特征,揭示了该锰矿床为热水沉积;同时,结合现代大洋铁锰沉积有关Ga的最新报道,提出北泗组碳酸锰矿床中Ga的赋存与含锰矿物密切相关,其来源与海底热液活动有关。最后,文中还利用Mn/Fe-Ga、Co-Ga关系图判别了古代铁锰沉积的成因类型。     

湖南桃江响涛源锰矿地球化学特征及其成因意义

湖南响涛源锰矿位于湘中桃江成锰盆地。盆地内发育一组NNW向同沉积断裂,形成了一系列断陷槽,控制了沉积岩相的分布,其中黑色页岩、含锰灰岩、碳酸锰矿为成矿最佳的岩性组合。矿石的化学组分多样,Co、Ni、Pb、Mo和Ba等丰度较高,Co/Ni、SiO2/Al2O3、(Fe+Mn)/Ti、Al/(Fe+Mn+Al)、Fe/Ti比值以及Co/Zn-(Cu+Ni+Co)和Fe-Mn-(Cu+Ni+Co)图解揭示锰矿成矿过程中有海底热水的参与;稀土元素配分模式、Ce、Eu异常表示锰矿形成于被动大陆边缘环境,并具有热水沉积特征;碳同位素结果显示出富集碳的轻同位素的特征,反映了响涛源锰矿成矿过程中深部热水沉积及生物作用的特征;氧同位素计算古温度为湘中响涛源锰矿床的低温热水沉积成因提供了有利的佐证。     

湘中地区中奥陶统“桃江式”锰矿的成矿作用研究

湘中地区“桃江式”锰矿产于中奥陶统磨刀溪组斜坡相-盆地边缘相沉积之中。发育锰矿层１～２层,锰矿层具有粒序层理、平行层理、斜纹层、水平纹层及角砾状等构造,夹于深水低能的暗色泥岩之中,是一种碳酸盐重力流沉积。其形成受区域构造、岩相古地理、沉积事件及水介质物理化学条件等的影响。其沉积学和地球化学特征显示锰质主要由海底热水补给,是一种热水成矿作用的产物。     

Sedimentary manganese metallogenesis in response to the evolution of the Earth system

The concentration of manganese in solution and its precipitation in inorganic systems are primarily redox-controlled, guided by several Earth processes most of which were tectonically induced. The Early Archean atmosphere-hydrosphere system was extremely O₂-deficient. Thus, the very high mantle heat flux producing superplumes, severe outgassing and high-temperature hydrothermal activity introduced substantial Mn²⁺ in anoxic oceans but prevented its precipitation. During the Late Archean, centered at ca. 2.75 Ga, the introduction of Photosystem II and decrease of the oxygen sinks led to a limited buildup of surface O₂-content locally, initiating modest deposition of manganese in shallow basin-margin oxygenated niches (e.g., deposits in India and Brazil). Rapid burial of organic matter, decline of reduced gases from a progressively oxygenated mantle and a net increase in photosynthetic oxygen marked the Archean-Proterozoic transition. Concurrently, a massive drawdown of atmospheric CO₂ owing to increased weathering rates on the tectonically expanded freeboard of the assembled supercontinents caused Paleoproterozoic glaciations (2.45-2.22 Ga). The spectacular sedimentary manganese deposits (at ca. 2.4 Ga) of Transvaal Supergroup, South Africa, were formed by oxidation of hydrothermally derived Mn²⁺ transferred from a stratified ocean to the continental shelf by transgression. Episodes of increased burial rate of organic matter during ca. 2.4 and 2.06 Ga are correlatable to ocean stratification and further rise of oxygen in the atmosphere. Black shale-hosted Mn carbonate deposits in the Birimian sequence (ca. 2.3-2.0 Ga), West Africa, its equivalents in South America and those in the Francevillian sequence (ca. 2.2-2.1 Ga), Gabon are correlatable to this period. Tectonically forced doming-up, attenuation and substantial increase in freeboard areas prompted increased silicate weathering and atmospheric CO₂ drawdown causing glaciation on the Neoproterozoic Rodinia supercontinent. Tectonic rifting and mantle outgassing led to deglaciation. Dissolved Mn²⁺ and Fe²⁺ concentrated earlier in highly saline stagnant seawater below the ice cover were exported to shallow shelves by transgression during deglaciation. During the Sturtian glacial-interglacial event (ca. 750-700 Ma), interstratified Mn oxide and BIF deposits of Damara sequence, Namibia, was formed. The Varangian (≡ Marinoan; ca. 600 Ma) cryogenic event produced Mn oxide and BIF deposits at Urucum, Jacadigo Group, Brazil. The Datangpo interglacial sequence, South China (Liantuo-Nantuo ≡ Varangian event) contains black shale-hosted Mn carbonate deposits. The Early Paleozoic witnessed several glacioeustatic sea level changes producing small Mn carbonate deposits of Tiantaishan (Early Cambrian) and Taojiang (Mid-Ordovician) in black shale sequences, China, and the major Mn oxide-carbonate deposits of Karadzhal-type, Central Kazakhstan (Late Devonian). The Mesozoic period of intense plate movements and volcanism produced greenhouse climate and stratified oceans. During the Early Jurassic OAE, organic-rich sediments host many Mn carbonate deposits in Europe (e.g., Úrkút, Hungary) in black shale sequences. The Late Jurassic giant Mn Carbonate deposit at Molango, Mexico, was also genetically related to sea level change. Mn carbonates were always derived from Mn oxyhydroxides during early diagenesis. Large Mn oxide deposits of Cretaceous age at Groote Eylandt, Australia and Imini-Tasdremt, Morocco, were also formed during transgression-regression in greenhouse climate. The Early Oligocene giant Mn oxide-carbonate deposit of Chiatura (Georgia) and Nikopol (Ukraine) were developed in a similar situation. Thereafter, manganese sedimentation was entirely shifted to the deep seafloor and since ca. 15 Ma B.P. was climatically controlled (glaciation-deglaciation) assisted by oxygenated polar bottom currents (AABW, NADW). The changes in climate and the sea level were mainly tectonically forced.     

锰矿主要类型、分布特点及开发现状

锰的用途非常广泛,世界上90％～95％的锰应用于冶金工业,其余应用于电池工业、陶瓷工业、化学工业等.根据成矿作用过程中的含矿岩系特征,将世界锰矿划分为海相沉积型、火山(热液)-沉积型、变质型、热液型和表生型5类,以海相沉积型、变质型和表生型为主.截至2019年,世界锰的储量达8.12亿t,但分布极不均匀,主要集中在南非...     

非洲锰矿床成矿规律、开发利用与勘查建议

锰矿是我国重要的战略矿产资源,需求量不断增长,长期依赖国外资源保障供需关系。本文总结分析了非洲锰矿资源的特点、矿床类型与成矿规律等地质特征与勘查开发利用及贸易现状。分析表明：非洲是全球探明锰矿储量和资源量最多的地区,具有分布集中,规模大、品位高、杂质少的特点;锰矿床类型主要有条带状含铁建造（BIF）型、海相沉积型、海相火山-沉积型、陆相（湖相三角洲）沉积型、岩浆热液型等五大类,普遍遭受表生风化淋滤（溶蚀）作用改造;主要分布在卡普瓦尔克拉通、刚果克拉通西北部的加蓬地块和西非克拉通南缘的马恩-莱奥地盾中;成矿时代主要集中于前寒武纪,尤其是2.2~2.0Ga;非洲锰矿资源的勘查开发程度较高,其中南非是非洲锰矿勘查程度最高的国家,中非、北非国家的勘查开发程度较低;南非是全球最大的锰矿石生产国和锰矿产品出口国,目前占全球出口量的68.19%以上,我国是非洲锰矿产的最大出口地,占其出口总量的70.19%。建议：我国在非洲的勘查应重点关注非洲中部的条带状含铁建造（BIF）型锰矿和海相火山-沉积型锰矿;在非洲已有的中企基础上,组建大型的集团公司,建立多元的锰矿资源供应体系。     

贵州省松桃杨家湾锰矿含锰岩系地质地球化学特征

贵州松桃南华系“大塘坡式”锰矿经过多年的勘查研究,浅部已形成以西溪堡、李家湾、杨家湾为主的全新“锰三角”格局。杨家湾锰矿是该“锰三角”中一个大型锰矿床。通过对该矿区含锰岩系的地质地球化学特征研究,发现该区含锰岩系中见凝灰质等火山物质,同时具有热水成因的黄铁矿、重晶石、锰方解石等矿物组合。该锰矿在Fe-Mn-(Ni+Co+Cu)×10及P₂O₅-Y图解上均落在热水沉积区内,As、Sb、Ga、Ag、Ba、Zn、Co、Bi、W及Pb的含量较正常沉积岩明显偏高,且Co/Ni、Y/Ho及Nb/Ta比值均与海底黑烟囱热流体特征类似,该锰矿床稀土含量总体偏高,轻重稀土分异明显,轻稀土相对较富集,稀土配分曲线平缓,略向右倾斜,δEu (0.49~0.71)、δCe(0.94~1.25)及Ce/La-La/Yb图解也均表明热水参与的特征。此外,该锰矿δ¹³C_PDB为-3.80‰~-4.17‰、δ¹⁸O_PDB为-6.95‰~-8.78‰,据此估算成矿温度为54.2~65.7 ℃,为中低温热水条件。杨家湾锰矿为海底热水沉积成因。     

Genesis for Rare Earth Elements Enrichment in the Permian Manganese Deposits in Zunyi,Guizhou Province,SW China

The Zunyi manganese deposits, which formed during the Middle to Late Permian period and are located in northern Guizhou and adjacent areas, are the core area of a series of large-medium scale manganese enrichment minerogenesis in the southern margin and interior of the Yangtze platform, Southern China. This study reports the universal enrichment of rare earth elements(REEs) in Zunyi manganese deposits and examines the enrichment characteristics, metallogenic environment and genesis of REEs. The manganese ore bodies present stratiform or stratoid in shape, hosted in the silicon–mud–limestones of the Late Permian Maokou Formation. The manganese ores generally present lamellar, massive, banded and brecciated structures, and mainly consist of rhodochrosite, ropperite, tetalite, capillitite, as well as contains paragenetic gangue minerals including pyrite, chalcopyrite, rutile, barite, tuffaceous clay rock, etc. The manganese ores have higher ΣREE contents range from 158 to 1138.9 ppm(average 509.54 ppm). In addition, the ΣREE contents of tuffaceous clay rock in ore beds vary from 1032.2 to 1824.5 ppm(average 1396.42 ppm). The REEs from manganese deposits are characterized by La, Ce, Nd and Y enriched, and existing in the form of independent minerals(e.g., monazite and xenotime), indicating Zunyi manganese deposits enriched in light rare earth elements(LREE). The Ce_(anom) ratios(average-0.13) and lithofacies and paleogeography characteristics indicate that Zunyi manganese deposits were formed in a weak oxidation-reduction environment. The(La/Yb)_(ch), Y/Ho,(La/Nd)_N,(Dy/Yb)_N, Ce/Ce* and Eu/Eu* values of samples from the Zunyi manganese deposits are 5.53–56.92, 18–39, 1.42–3.15, 0.55–2.20, 0.21–1.76 and 0.48–0.86, respectively, indicating a hydrothermal origin for the manganese mineralization and REEs enrichment. The δ~(13) C_(V-PDB)(-0.54 to-18.1‰) and δ~(18) O_(SMOW)(21.6 to 26.0‰) characteristics of manganese ores reveal a mixed source of magmatic and organic matter. Moreover, the manganese ore, tuffaceous clay rock and Emeishan basalt have extremely similar REE fractionation characteristic, suggesting REEs enrichment and manganese mineralization have been mainly origin from hydrothermal fluids.     

Geological and Geochemical Investigation of Three Ophiolite‐Hosted Manganese Prospects,Southeast of Birjand,South Khorasan,East of Iran

The studied ophiolite‐hosted manganese prospects are located in southeast of Birjand, South Khorasan, in the east of Iran. The manganese ores within the ophiolitic sequence in this region occur as small discrete patches, associated with radiolarian chert and shale. Manganese ores in the host rocks are recognizable as three distinct syngenetic, diagenetic, and epigenetic features. The syngenetic manganese ores occurred as bands associated with light‐red radiolarian chert. The diagenetic Mn ores occurred as lenses accompanied by dark‐red to brown radiolarian chert. The epigenetic Mn ores occurred as veins/veinlets within the green radiolarian shale. The major manganese ore minerals are pyrolusite, braunite, bixbyite, ramsdellite, and romanechite showing replacement, colloidal, and brecciated textures. The high mean values of Mn/Fe (15.32) and Si/Al (15.65), and the low mean concentration values of trace elements, such as Cu (85.9 ppm), Ni (249.9 ppm), and Zn (149 ppm), as well as the high concentration values of Si, Fe, Mn, Ba, Zn, Sr, and As in the studied manganese ores furnished sufficient evidence to postulate that the sea‐floor Mn‐rich hydrothermal exhalatives were chiefly responsible for the ore formation, and the hydrogenous processes had negligible role in generation of the ores. The further geological and geochemical evidence also revealed that the ores deposited on the upper parts of the ophiolitic sequence by submarine exhalatives. The intense hydrothermal activities caused leaching of elements such as Mn, Fe, Si, Ba, As and Sr from the basaltic lavas (spilites). After debouching of the sea‐floor exhalatives, these elements entered the sedimentary basin. The redox conditions were responsible for separation of Fe from Mn.     

贵州松桃西溪堡锰矿沉积地球化学特征

贵州黔东断裂坳陷带是贵州重要的锰矿成矿带,并发育新元古代大塘坡期的一套完整“黑色岩系”,锰矿主要赋存于该黑色岩系中。本文以松桃西溪堡锰矿床为例,通过岩石学、矿物学、地球化学等研究方法,探讨这类锰矿床的成矿物质来源及成因。研究表明矿石中的矿物组分复杂,结构构造类型多样,富集As、Sb、Ag、Co、Mo、W、Cs和Ba等元素,Fe／Ti、（Fe＋Mn）／Ti、A1／（AI＋Fe＋Mn）、Y／Ho、Nb／Ta比值,以及Cr．zr和Th．u图解均揭示成矿过程中有热水物质参与;V／（V＋Ni）、V／Cr比值表明锰矿形成于缺氧环境;稀土元素分布模式、Ce、Eu异常及La．Ce、La／Yb．EREE图解显示锰矿形成于被动大陆边缘环境,并具有热水沉积特征。因此,古被动大陆边缘是锰矿富集的理想场所,热水（液）活动为其提供了丰富的物质来源。这为锰矿的找矿拓展了新的思路。     

贵州遵义二叠系锰矿区硅质岩成因及成矿意义

贵州遵义二叠系锰矿底部发育一套特殊的硅质岩建造,该套硅质岩环绕锰矿富集区呈墙状产出,习称“白泥塘层”硅质岩或“城墙式”硅质岩,其与锰矿成矿作用之间有着紧密的成因联系。详细地野外地质调查发现,该套硅质岩具有条带状、角砾状和块状构造,其中钢灰色、黑色锰质细脉穿插于条带硅质岩之中,角砾状构造硅质岩多沿锰矿体周边分布。10 件硅质岩样品元素地球化学分析表明 ,硅质岩具有较高的 SiO₂（80.55% ～99.56%）和Fe₂O₃（0.47%～13.76 %）, 较低的Al₂O₃（0.05%～4.06%）和TiO₂（0～0.49%）, 指示其形成过程中陆源碎屑物质参与较少。（La/Ce）比值和Ce 异常值特征指示硅质岩形成于深水裂陷盆地中,环N 境条件为还原状态。Fe-Mn-Al 和SiO₂-Al₂O₃ 图解显示, 硅质岩主要落入热水沉积区内或其附近区域。硅质岩Al/（Al+Fe+Mn）均值为0.26、（La/Ce）_N 值为1.51～2.34、 Y/Ho 值为 30.64～43.91,Eu/Eu^* 值为0.96～1.67,且硅质岩稀土配分模式与热水沉积硅质岩类似,这些特征集中表明硅质岩成岩过程中有明显的热水物质参与,属于热水成因硅质岩,这为遵义二叠系锰矿床热水喷流沉积成因提供了新的佐证。