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Abstract. We obtain radiolarian fossils such as Follicucullus monacanthus, Pseudoalbaillella aff. globosa, Pseudoalbaillella cf fusiformis , and Pseudoalbaillella spp. belonging to the Pseudoalbaillella globosa and Follicucullus monacanthus Zones from manganese ore and associated red chert of the Ananai stratiform manganese deposit in the Northern Chichibu Belt, central Shikoku. The depositional age of the Ananai ore deposit is constrained as Guadalupian (Middle Permian) that is between 270.6 and 260.4 Ma in the updated geologic time scale. 相似文献
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Abstract. The radiolarian age of red chert from the Kunimiyama area of the Northern Chichibu Belt was determined in order to constrain the depositional age of the Kunimiyama deposit that is among the largest ferromanganese deposits in Japan. Pseudoalbaillella cf scalprata Holdsworth and Jones, Pseudoalbaillella cf longicornis Ishiga and Imoto and Pseudoalbaillella sp. belonging to the Ps. lomentaria Zone are found in the red chert, indicating an age of middle Early Permian (middle Wolfcampian). The red chert occurs immediately above the ferromanganese deposit, and the boundary between them is gradual. Based on their mode of occurrence and geochemical features, it is most likely that radiolarian chert and ferromanganese precipitate accumulated simultaneously to produce red chert during the waning stage of submarine hydrothermal activity that was responsible for the Kunimiyama deposit. Consequently, the age of Kunimiyama stratiform ferromanganese deposit is constrained as middle Early Permian (middle Wolfcampian). 相似文献
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Geological and Geochemical Investigation of Three Ophiolite‐Hosted Manganese Prospects,Southeast of Birjand,South Khorasan,East of Iran 
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下载免费PDF全文 Behnaz Barghi Ali Asghar Calagari Mohammad Hossein Zarrinkoub Vartan Simmonds 《Resource Geology》2017,67(4):414-425
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. 相似文献
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The gold deposits,occurring in the south subzone of western Qinling,are the only typical and important strata-bound gold deposits,which are associated with submarine exhalative sedimentation.The gold deposits include the La‘erma ore deposit,the Qiongmo ore deposit and the Yaxiang ore occurrence.They are hosted i the Cambrian silicalite formation composed of black chert and slate.The presence of typical chert offers important evidence to evaluate the possible submarine exhalative system and its role in the formation of the gold deposits,which are closely associated with peroclation and diffusion in the horizontal,vertical and axial directions,Element-assemblage zonation is clearly seen due to differences in element concentrations in different directions,Such a zonation makes gold.selenium,uranium,copper,stibium,molybdenum,mercury,etc,precipitate in the form of simple or composite orebodies.The establishent of the element-assemblage zonation is highly helpful for evaluating directly the metallogenesis of gold deposits. 相似文献
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Abstract. Inorganic chemical compositions are determined for a series of rocks crossing an Early Jurassic stratiform manganese ore deposit in a chert‐dominant sequence at Katsuyama, in the Mino Terrane of central Japan. The lithology in the vicinity of the manganese ore bed is classified into lower bedded chert, black shale, massive chert, manganese ore and upper bedded chert, in ascending order. The rocks surrounding the manganese deposit are anomalously high in certain elements: Pb (max. 29 ppm), Ni (1140) and Co (336) in the lower bedded chert, Mo (438), As (149), Tl (29) and U (12) in the black shales, V (210) and Cr (87) in the massive chert, and MnO and W (24) in the manganese ore. The aluminum‐normalized profiles reveal a distinct zonation of redox‐sensitive elements: Pb‐Zn, Ni‐Co‐Cu(‐Zn) and U‐Cr in the lower bedded chert, Mo‐As‐Tl in the black shale, V(‐Cr) in the massive chert, and Mn‐Fe‐Ba‐W in the manganese ore, in ascending order. The lower and upper bedded cherts and manganese ore generally exhibit flat rare earth element patterns with positive Ce anomalies, whereas the uppermost part of the lower bedded chert, the black shale and massive chert have flat patterns with weak or nonexistent negative Ce anomalies and weak positive Eu anomalies. The strong enrichment in Ni, Co, W, Tl and As detected in the Katsuyama section is not recognized in other sediments, including those of anoxic deposition origin, but is identified in modern ferromanganese nodules, suggesting that metal enrichment in the Katsuyama section is essentially due to the formation of ferromanganese nodules rather than to deposition in an anoxic environment. The observed elemental zonation is well explained by equilibrium calculations, reflecting early diagenetic formation and associated gradual reduction with depth. The concentration profiles in combination with litho‐ and biostratigraphical features suggest that formation of these bedded manganese deposits was triggered by an influx of warm, saline and oxic water into a stagnant deep ocean floor basin in Panthalassa at the end of the middle Early Jurassic. Paleoceanographic environmental controls thus appear to be important factors in the formation and preservation of this type of stratiform manganese deposit. 相似文献
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Masaharu NAKAGAWA 《地球学报》2012,33(S1):50-54
Bedded manganese ore deposits occur in many localities within the accretionary belts of the Shikoku region, SW Japan. The deposits occur mostly in bedded chert or its metamorphosed equivalent. These chert-hosted manganese deposits are considered to have been manganese nodule/crust-bearing siliceous sediments on deep-sea floor and have been converted to manganese ores by low-grade metamorphism through subduction-accretion process. The mineral assemblages of the ores reflect the metamorphic grade of the accretionary complexes. On the other hand, iron-manganese deposits and some manganese deposits occurring directly over basalt are considered to have been the hydrothermal precipitates associated with submarine volcanism. 相似文献
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Abstract. Chemistry and sulfur isotopes are analyzed for a series of rocks in the chert‐dominant sequence around the stratiform manganese ore deposit of the Noda‐Tamagawa mine in the northern Kitakami Terrane, northeast Japan. The sequence is litholog‐ically classified into six units in ascending order: lower bedded chert, lower black shale, massive chert, manganese ore, upper black shale, and upper bedded chert. The rocks around the manganese ore deposit exhibit anomalous enrichment in Ni (max. 337 ppm), Zn (102) and U (30) in the upper part of lower bedded chert, Mo (122), Tl (79) and Pb (33) in the lower black shale, MnO, Cu (786) and Co (62) in the manganese ore, and As (247) and Sb (17) in the upper black shale. The aluminum‐normalized profiles reveal zonal enrichment of redox‐sensitive elements around the manganese bed: Zn‐Ni‐Fe‐Mo‐U(‐Co), Tl‐Pb(‐Mo), Mn‐Fe‐Cu‐V‐Cr‐Co(‐Zn) and As‐Sb in ascending order. The uppermost part of the lower bedded chert and black shale exhibit negative Ce/Ce* values, whereas the massive chert, manganese ore and lower part of the upper bedded chert display positive values. The isotopic δ34S values are 0±6 % in the lower part of the lower bedded chert, ‐19 to ‐42 % in the upper part of the lower bedded chert, ‐36 to ‐42 % in the lower black shale, ‐28 to ‐35 % in the massive chert, manganese ore and upper black shale, and ‐23±5 % in the upper bedded chert. Thus, there is a marked negative shift in δ34S values in the lower bedded chert, and an upward‐increasing trend in δ34S through the manganese ore horizon. The present data provide evidence for a change in the paleoceanographic environmental resulting from inflow of oxic deepwater into the stagnant anoxic ocean floor below the manganese ore horizon. This event is likely to have triggered the precipitation of manganese oxyhydroxides. The redistribution of redox‐sensitive elements through the formation of metalliferous black shale and manganese carbonate ore may have occurred in association with bacterial decomposition of organic matter during early diagenesis of initial manganese oxyhydroxides. 相似文献
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Abstract: The southern segment of the Da Hinggan Mountains is a well‐known tin–polymetallic metallogenic belt of North China with Jurassic‐Cretaceous volcanic–plutonic rocks widespread. Principally because of this, most of the deposits are regarded as epigenetic hydrothermal deposits in genetic connection with the Mesozoic magmatism. But nearly 90 % of the deposits occur in Permian strata, and show concordant stratiform mineralization with a spatial distribution constrained by sedimentary facies of the Permian strata. A close association between mineralization and Permian strata is recognizable. The Huanggang Fe‐Sn deposit was regarded as a standard skarn‐type deposit formed by magmatic hydrothermal solutions in connection with Mesozoic granites. But there are abundant fabrics indicating submarine hydrothermal exhalation both in magnetite ores and in skarns, including bedding/lamination, soft–deformation, synsedimentary brecciation, and collo‐form fabrics. The magnetite orebodies and skarn‐bodies are predominantly concordant stratiform, and extend nearly 20 km along certain stratigraphic horizon, that is, the upper section of the Lower‐Permian submarine volcanic rocks. The Mesozoic granitic rocks crosscut the magnetite and skarn zone. Instead of skarnization, they show strong greisenization associated with cassiterite‐quartz veins, distinct from the magnetite skarn‐ore with disseminated tin in the Permian rocks. The Dajing Sn‐polymetallic deposit is generally regarded as subvolcanic‐hydrothermal origin, principally because of the close spatial association between ores and some of the Mesozoic subvolcanic dikes (called rhyolitic porphyry). Detailed geological, fabric, petrographical and mineralogical study demonstrates that this very kind of subvolcanic rocks is actually a new type of exhalites (called ‘siderite‐sericite chert’ according to its mineral assemblage), formed by hydrothermal sedimentation during the evolution of the Later‐Permian lacustrine basin. There are, however, indeed some rhyolitic porphyry dikes that crosscut orebod–ies. The orebodies and their associated exhalite predate, and thus have no genetic relation, to the Mesozoic magmatic process. We thus conclude that subaqueous exhalative mineralization did occur during the basin evolution at the Permian time in the southern segment of the Da Hinggan Mountains, which is ignored and poorly understood, but might be as important as the hydrothermal mineralization connected with the Mesozoic magmatism. 相似文献
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贵州及邻区二叠系锰矿地质特征及成矿作用探讨 总被引：11，自引：4，他引：7
本文在系统收集和分析了近年来贵州锰矿资源评价工作及以往锰矿工作资料的基础上,获得了对贵州及邻区二叠系锰矿更深入系统的认识。主要成果为：认为该区中二叠世茅口期含锰岩系可大致对比,可沿用遵义锰矿产出地区所使用的名称——中二叠统茅口组白泥塘层（P2m^b）;水城纳雍锰矿与宣威格学锰矿特征及成矿机制十分相似,均为第四纪氧化富集成矿,矿床类型属于风化矿床类的锰帽型锰矿床亚类,矿质来源于原始沉积的含锰岩系——白泥塘层,而白泥塘层的锰质来源于中二叠世茅口期峨眉山玄武岩喷发;将贵州及邻区二叠系各类型锰矿床的特征及含锰岩系、物质来源、成矿作用等方面作了有机联系和系统分析,并建立了统一的成矿模式。 相似文献
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拉尔玛-邛莫金矿床产于西秦岭南亚带寒武系硅岩建造中,受地层、岩性、构造控制十分明显.但与其它层控金矿床相比较,该矿床不仅含矿主岩特殊,而且矿石矿物和元素组合十分复杂.矿床中除Au外,Cu、U、Mo、Sb、V、Zn等元素在局部地段亦可圈出独立矿体.同时,矿床中存在铂族元素(PGE)、铟的高异常以及硒的矿化富集体,从而构成了Au-Cu-U-Mo-Se-PGE建造矿床.研究表明,金矿床的形成,至少经历了喷流沉积和地下水热液活动改造两个成矿期.前者表现为硅岩建造中出现了众多成矿元素的高异常和黄铁矿等条带状、层纹状构造的形成,显示出矿质的初步聚集;后者则促使矿质富集层中的成矿物质组分发生活化、迁移和再聚集,并最终导致工业矿床的形成.矿床属与海底喷流作用有关的喷流型层控金矿床. 相似文献
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沉积喷流型矿化的岩石学证据——以大兴安岭南段黄岗和大井矿床为例 总被引：21，自引：3，他引：21
沉积喷流型矿床往往有各种喷流岩（热水沉积岩）的共生，正确识别这些喷流岩经常能为认识矿床的成因提供关键证据。大兴安岭南段是我国北方著名的锡－多金属成矿区，燕山期火山－侵入岩广泛出露，因此认为区内矿床大都是与燕山期岩浆活动有关的热液矿床。但是，区内近90％的矿床却产在二叠纪地层中，显示了与二叠纪沉积地层的密切联系。本文以其中的黄岗铁－锡矿床和大井锡－多金属矿床为例，对与矿石密切共生的热水沉积岩开展了系统的地质学、岩相学、矿物学和组构学研究，并结合必要的地球化学数据，证明大兴安岭南段在二叠纪沉积盆地演化过程中可能普经有重要的水下热液沉积喷流成矿作用发生，尽管历来被人们所忽视，但其重要性可能并不亚于燕山期的岩浆热液成矿作用。黄岗矿床的层状矽卡岩与二叠纪海底火山活动关系密切，是一种很具特色的喷流岩；而被误认为是燕山期流纹斑岩的大井矿床菱铁织云硅质岩可能是一种产在陆相断陷盆地、与锡铜铅锌银多金属矿化有关的新类型热水沉积岩。显然，与热水沉积喷流矿床紧密共生的热水沉积岩是认识该类矿床至为重要的岩石学证据之一。 相似文献
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贵州遵义锰矿是我国二叠纪重要的锰矿床类型之一。近年来,遵义锰矿浅部资源日趋枯竭,找矿工作从浅部转向了深部,对隐伏锰矿的找矿迫在眉睫。在找寻隐伏锰矿中,原有的找矿勘查方法遇到了瓶颈,本文在结合大量地质研究的基础上,基于深部地层、构造、含矿岩系的电性差异,在研究区首次应用音频大地电磁法对隐伏锰矿体开展探索研究。研究发现,通过精细化的数据反演,该方法能够较好地反映研究区深部地层、构造及含矿岩系的展布特征,并部署钻探验证,所揭露的岩矿层位、构造特征和音频大地电磁法解译吻合程度较高。该方法可推广到研究区及其同类型区域的锰矿找矿勘查中,是锰矿找矿预测的有效方法之一。 相似文献
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桃江式锰矿成矿期岩相古地理及成矿预测 总被引：1，自引：0，他引：1
桃江式锰矿是优质锰矿。矿层产于中奥隐统磨刀溪组，矿体受海底扇控制，根据同层矿体沉积环境。钙屑浊积岩相，沉积层序和沉积构造，海底扇划分为内扇，中扇和外扇３个亚相。中扇是碳酸锰矿有利赋存部位。据此，进行了成矿预测，取得了较好的找矿效果。 相似文献
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The Vani manganese deposit is located in the rugged NW sector of Milos Island. It occurs within the Vani volcano-sedimentary basin, which is underlain by dacitic domes and flows of Upper Pliocene age (3.5–2.0 Ma). The end of the emplacement of the dacites was marked by the collapse of the magma chamber, which resulted in a huge pyroclastic episode and the deposition of a thick layer of pyroclastic material within a shallow submarine basin. This pyroclastic material subsequently compacted to form the volcaniclastic sandstone, which became the host for the manganese ore beds which were about 4 m thick in the two sections studied. Hydrothermal fluids penetrated these sandstone horizons via fractures and fissures to produce the manganese deposit. The permeable nature of the sandstone facilitated the retention of the hydrothermal fluids within these layers. This permitted the fluids to cool slowly and deposit the manganese oxides almost quantitatively. Formation of the hydrothermal manganese deposit took place fairly rapidly over a period of several tens of thousands of years at most. Strong tectonic activity resulted in rapid uplift of the area which elevated the deposit above sea level.Two generations of manganese oxides have been identified within this deposit; the first generation consists of pyrolusite and ramsdellite; the second generation of oxides of the isostructural series cryptomelane–hollandite–coronadite plus hydrohetaerolite characterized by high contents of K, Ba, Pb and Zn, respectively. This sequence is the result of a two-stage process of formation of the manganese-oxide minerals in which a second high-salinity hydrothermal fluid enriched in Ba, Pb and Zn as a result of the dissolution of sulphide minerals remineralized the original manganese-oxide assemblage. It is this two-stage process of formation, which was mainly responsible for the unique characteristics of this deposit. Although formed in a submarine setting, the deposit shows marked differences in mineralogy and composition from known submarine hydrothermal manganese deposits and is most analogous to the epithermal vein deposits of the southwestern United States. 相似文献
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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。 相似文献