新疆西天山智博铁矿床磁铁矿成分对其成矿机制的指示

智博铁矿床位于新疆西天山阿吾拉勒成矿带东段,主要赋矿围岩为石炭系大哈拉军山组安山岩、玄武质安山岩和火山碎屑岩.该矿床主要有东、中、西3个矿区,其中以东矿区为主矿区.矿体主要呈层状、似层状、厚板状和透镜状.金属矿物以磁铁矿为主,含有少量黄铁矿、赤铁矿和黄铜矿.矿石构造以块状和浸染状构造为主,此外还有角砾状构造、条带状构造、流纹状构造和脉状构造等.矿石结构有他形-半自形结构、板条状结构和海绵陨铁结构等.智博铁矿床蚀变矿物主要有透辉石、钠长石、阳起石、绿帘石、钾长石等,含有少量方解石、石英和绿泥石等.根据矿石和矿物共生关系,将智博铁矿床划分为岩浆期和热液期2个成矿期次.岩浆期可划分为钠长石-透辉石阶段和磁铁矿-阳起石阶段,热液期可划分为钾长石-绿帘石阶段和石英-硫化物阶段.根据智博磁铁矿的电子探针数据,各类磁铁矿矿石中除热液期含黄铁矿致密块状矿石w(FeOT)变化较大外,其他类型磁铁矿的w(FeOT)多集中在90％～95％,又以岩浆期块状矿石中w(FeOT)最高.对其氧化物进行相应的图解,电子探针数据中w(CaO)、w(Al2O3)、w(MnO)、w(K2O)、w(MgO)和w(SiO2)都和w(FeOT)有良好的负相关性,而NiO和TiO2则具有一定的正相关性,V2O3则在岩浆期块状和含磁铁矿脉矿石中含量明显高于其他类型矿石.根据磁铁矿TiO2-Al2O3-MgO成因图解和w(Ca+Al+Mn)-w(Ti+V)成因图解显示,智博铁矿床矿石兼具岩浆型成因特征和热液型成因特征,表明智博铁矿床的形成与岩浆作用和火山热液交代作用有关.     

Hydrothermal Mobilization and Enrichment of Iron in the Iron Deposits of the Middle—Lower Yangtze Valley District

There are two main types of iron deposits in the Middle-Lower Yangtze Valley district.Both of them underwent post-magmatic hydrothermal processes during ore formation.Iron in the hydrothermal ore bodies was derived largely through mobilization from substantially consolidated diroitic intrusives.Wall-roch alteration zonation indicates that iron-mobilizing hydrothermal fluids evolved in a trend of decreasing alkalinity,which is suggested by regularly distributed wall-rock alterations formed by iron-mobilizing hydrothermal fluids and is in contradiction with the current chloride,chloride complex and bicarbonate models for iron mobilization.The close association of carbonatization with iron ores and the high concentrations of reduced gases such as CO,CH4 and H2 in fluid inclusions suggest that iron is most probably transported in the form of iron carbonyls during post-magmatic hydrothermal processes. In the light of the iron carbonyl mobilization model,explanations are made of the constraints on ores of some geologic factors such as melanocratic alteration,carbonatization,carbonate strata,structural fractures,cyptoexplosive pipes and embryo ores.     

山东昌邑莲花山铁矿矿床地质与矿石稀土、微量元素特征

莲花山铁矿位于昌邑-安丘铁成矿带的中部,铁矿体赋存于古元古代粉子山群小宋组中。本文通过矿石地球化学特征及其与矽卡岩矿物组合和赋矿围岩结构特征的对比研究,证明了莲花山铁矿与条带状铁矿相似。莲花山铁矿矿石稀土元素含量较低,经页岩标准化的稀土元素配分模式呈现轻稀土元素亏损、重稀土元素富集的特征,具有明显的Eu、Y、La异常,为无明显Ce异常,Y/Ho比值反映了在其沉积时受到海水作用的影响,表明莲花山铁矿的稀土元素来源于火山热液和海水的混合溶液。微量元素中Ti、V、Co、Ni、Mn、Sr、Ba等含量较低,原始地幔标准化的微量元素配分曲线显示,U、La、Hf呈正异常,Ba、Nb、Ta、Sr呈负异常,SiO2/Al2O3、Ti/V、Ni/Co、和Sr/Ba的比值指示了莲花山铁矿成矿物质来源于火山物质的沉积。研究结果表明,莲花山铁矿成矿作用源于火山热液与海水的混合,成矿物质来自火山沉积物,其地质与地球化学特征与五台山铁矿一致,为火山沉积变质型铁矿床。     

High-grade iron ore at Windarling, Yilgarn Craton: a product of syn-orogenic deformation, hypogene hydrothermal alteration and supergene modification in an Archean BIF-basalt lithostratigraphy

Banded iron formation (BIF)-hosted iron ore deposits in the Windarling Range are located in the lower greenstone succession of the Marda–Diemals greenstone belt, Southern Cross domain, Yilgarn Craton and constitute a total hematite–martite–goethite ore resource of minimum 52 Mt at 60 wt.% Fe (0.07 P). Banded iron formation is interlayered with high-Mg basalts at Windarling and precipitated during episodes of volcanic quiescence. Trace element content and the rare earth element (REE) ratios Y/Ho (42 to 45), Sm/Yb (1.5), together with positive La and Gd anomalies in ‘least-altered’ hematite–magnetite–metachert–BIF indicate the precipitation from Archean seawater that was fertilised by hydrothermal vent fluids with a basaltic HREE-Y signature. Hypogene iron ore in sub-greenschist facies metamorphosed BIF formed during three distinct stages: ore stage 1 was a syn- to post-metamorphic, syn-D₁, Fe–Ca–Mg–Ni–Co–P–REE metasomatism that produced local Ni–REE-rich Fe–dolomite–magnetite alteration in BIF. Hydrothermal alteration was induced by hot fluid flow controlled by brittle–ductile reactivation of BIF-basalt margins and crosscutting D₁ faults. The Ni–Co-rich content of dolomite and a shift in REE ratios in carbonate-altered BIF towards Archean mafic rock signature (Y/Ho to 31 to 40, Sm/Yb to 1 to 2 and Gd/Gd* to 1.2 to 1.4) suggest that high-Mg basalts in the Windarling Range were the primary source of introduced metals. During ore stage 2, a syn-deformational and likely acidic and oxidised fluid flow along BIF-basalt margins and within D₁ faults leached carbonate and precipitated lepidoblastic and anhedral/granoblastic hematite. High-grade magnetite–hematite ore is formed during this stage. Ore stage 3 hydrothermal specular hematite (spcH)–Fe–dolomite–quartz alteration was controlled by a late-orogenic, brittle, compressional/transpressional stage (D₄; the regional-scale shear-zone-related D₃ is not preserved in Windarling). This minor event remobilised iron oxides, carbonate and quartz to form veins and breccia but did not generate significant volumes of iron ore. Ore stage 4 involved Mesozoic(?) to recent supergene oxidation and hydration in a weathering environment reaching down to depths of ～100 to maximum 200 m below surface. Supergene ore formation involved goethite replacement of dolomite and quartz as well as martitisation. Important ‘ground preparation’ for supergene modification and upgrade were mainly the formation of steep D₁ to D₄ structures, steep BIF/basalt margins and particularly the syn-D₁ to syn-D₂ carbonate alteration of BIF that is most susceptible to supergene dissolution. The Windarling deposits are structurally controlled, supergene-modified hydrothermal iron ore systems that share comparable physical, chemical and ore-forming characteristics to other iron ore deposits in the Yilgarn Craton (e.g. Koolyanobbing, Beebyn in the Weld Range, Mt. Gibson). However, the remarkable variety in pre-, syn- and post-deformational ore textures (relative to D₁ and D₂) has not been described elsewhere in the Yilgarn and are similar to the ore deposits in high-strain zones, such as of Brazil (Quadrilátero Ferrífero or Iron Quadrangle) and Nigeria. The overall similarity of alteration stages, i.e. the sequence of hydrothermal carbonate introduction and hypogene leaching, with other greenstone belt-hosted iron ore deposits supports the interpretation that syn-orogenic BIF alteration and upgrade was crucial in the formation of hypogene–supergene iron ore deposits in the Yilgarn Craton and possibly in other Archean/Paleoproterozoic greenstone belt settings worldwide.     

Formation mechanism of Gongchangling high-grade magnetite deposit hosted in Archean BIF,Anshan-Benxi area,Northeastern China

Banded iron-formations are main resources of global iron ore in which high-grade ore is mainly composed of martite–goethite and hematite. They are also the major resource of iron ore in China, mainly distributing in Liaoning and Hebei Province. In China, the iron ore with Fe greater than 50% is classified as high-grade iron ore. The high-grade iron ore mainly consists of magnetite and displays its unique characteristics. Gongchangling iron deposit is one typical BIF-iron deposit which contains 150 Mt of high-grade iron ore in China. The high-grade magnetite ore bodies mainly occur around magnetite quartzite, faults and the cores of folds and show positive relation to the development of the “altered rocks” in this deposit. This research shows that high-grade magnetite comes from magnetite quartzite and they are both formed, with little or no addition of aluminum-containing detrital material, by marine chemical deposition in reduced environment and they are closely related to seafloor hydrothermal activity.Muddy–silty rocks are original rocks of “altered rocks”, of which the primitive mantle normalized REE pattern, except Eu, is consistent with that of iron ore, reflecting that their formation is related to the formation of high-grade magnetite ore. Therefore, the formation mechanism of high-grade iron ore is proposed as following: the regional metamorphism provides storage space for the formation of high-grade magnetite ore and required temperature and pressure conditions for the mineral transformation; the regional metamorphic hydrothermal fluid leaches FeO out of magnetite quartzite when it passes by; and the FeO that leached out moves near faults or cores of folds together with the metamorphic hydrothermal fluid and aluminum-containing rocks, of which the original rocks are muddy–silty; in the formation of high-grade iron ore, aluminum-containing rock appears in the intervals of sedimentation of iron-containing rock series and consumes the silicon leached out of magnetite quartzite and forms garnet, chlorite, and biotite.     

山东莱芜张家洼铁矿平炉富矿和伴生的铜钴组分研究

山东莱芜张家洼铁矿赋存于矿山弧形背斜倾没端,已查明平炉富矿资源储量7 060×104t,伴生组分铜金属资源储量217 256.1t,钴金属资源储量48 548.3t。根据平炉富矿、伴生组分铜钴主要分布在假整合面及其复合部位,以及赋存在本溪组中的矿床（体）铁（铜）硫特高的特点,认为矿质与月门沟群本溪组中的山西式铁矿以及铁铝页岩层位中Fe,Cu,Co元素的高背景值有关。山西式铁矿和铁铝页岩层位或因热液作用就地改造叠加,在假整合面及附近形成复合矿体,并局部构成平炉富矿和伴生的铜、钴资源;或因构造沟通,被活化迁移至接触带与围岩中,产生双交代渗滤作用,形成接触带及附近的复合矿体,并构成少量平炉富矿与伴生的铜、钴资源。因此,山西式铁矿和本溪组铁铝页岩是平炉富矿和伴生组分铜、钴的重要物质来源。     

BIF微量稀土元素分析方法及其在冀东司家营铁矿中的应用

以硅铁条带交替出现为特征的条带状铁建造(BIF)是世界上最重要的铁矿资源类型,精确分析磁铁矿的化学组成具有重要意义。本文开展了磁铁矿样品不同溶样方法分析结果的比对,并详细分析和讨论了冀东司家营铁矿磁铁矿与燧石单条带的微量及REE元素分析的地球化学特征。分析结果表明,对于磁铁矿样品,常规HF+HNO₃溶样法与HBr+HNO₃组合溶样法具有一致的溶样效果;司家营BIF的Zr,Sc,Th含量极低,表明未受陆源碎屑的污染;铁质与硅质具有低LREE、高HREE、La和Y正异常的海水REE特征,同时具有Eu正异常的热液REE特征;Ce负异常的缺乏,说明当时的古海洋是一个缺氧的环境。研究发现富铁条带的稀土总量大于富硅条带的稀土总量,这可能与硅、铁沉积物的地球化学习性相关,铁质沉积物更易吸收稀土元素。富矿和普通矿石具有原生的热液与海水的混合来源,部分富矿受到后期流体的强烈扰动,甚至表现出热液流体的特征。     

Geochemical Fingerprint and Iron Ore Potential of the Siliceous Itabirite from Palaeoproterozoic Nyong Series,Zambi Area,Southwestern Cameroon

The study area forms part of an emerging iron ore province of southern Cameroon. Geochemistry analyses reveal that the siliceous itabirite has a very simple chemical composition, with Fe₂O₃ and SiO₂ representing more than 96 wt.% of the average composition; suggesting chemical precipitates of silica and iron. Low Al₂O₃ and TiO₂ concentrations and a weak positive correlation between them point to a minor detrital component in the precipitated marine sediments. The Si/Al ratio (average 52.7) indicates the hydrothermal origin of the studied itabirite. The Al–Si discrimination diagram supports this interpretation through the plot of all data in the hydrothermal field. The studied samples have low iron content (about 39.32% Fe), high gangue content (40.97% SiO₂ and 1.3 % Al₂O₃) and low concentration of the deleterious elements (0.16 % P and < 0.01% S). The main gangue mineral is silica which can be efficiently removed from iron ores during preparation of raw materials for the blast furnace process. According to commercial standards for crude iron ores, it may be concluded that the Zambi iron ores are a low‐grade magnetic ore that can be profitably exploited for the production of iron for steel production.     

安徽霍邱BIF铁矿地球化学特征及其成矿意义：以班台子和周油坊矿床为例

安徽霍邱铁矿田位于华北克拉通南缘,是一个大型BIF铁矿田.本文对霍邱矿田班台子矿区和周油坊矿区的铁矿石及其赋存的岩石共28件样品进行了详细的主微量元素地球化学分析.分析结果表明,班台子矿区的片麻岩和角闪岩的原岩属于一套亚碱性系列的岩石,具有大离子亲石元素(LILE)富集,高场强元素(HFSE)明显亏损的火山弧岩石的特征.班台子角闪岩具有低的K2O含量和Ti/V值,Ti/V=22.7 ～ 25.9,平均24.5,与岛弧拉斑玄武岩一致.弧后盆地玄武岩化学组成具有类似岛孤拉斑玄武岩的特征.BIFs的形成往往需要构造稳定的半深水-深水盆地,孤后盆地能够为BIFs韵律条带的产生提供稳定的沉积环境,因此霍邱BIFs铁矿的大量出现说明班台子矿区角闪岩形成于弧后盆地,代表了霍邱铁矿形成的构造环境.班台子矿区铁矿石的(Eu/Eu*)SN=1.57 ～1.82,与Superior型(简称S型)BIFs特征一致;而周油坊矿区假象镜铁矿的(Eu/Eu*)SN=1.93 ～3.41,与Algoma型(简称A型)BIFs特征比较吻合.正Eu异常的强弱反应了成矿位置距离海底火山热液喷气口的远近.因此,我们推断霍邱地区BIFs型铁矿形成位置与海底火山热液喷气口的距离比较特别,处于A型向S型过渡的位置.角闪岩和片麻岩及其赋存的铁矿石的Al2O3和TiO2良好的线性相关性说明铁矿石铁质部分来源于侵蚀的弧后盆地玄武岩.Y/Ho比值=31.05 ～56.67,平均为46.65,说明霍邱铁矿继承了海水与热液的混合特征,其中,海水的贡献更大一些.周油坊矿区的大理岩主要化学组成CaO为28.49％ ～29.10％,MgO为20.25％ ～ 21.22％以及少量的SiO2(2.45％～6.10％).与平均显生宙石灰岩相比,周油坊大理岩亏损LILE和HFSE;与后太古代平均澳大利亚页岩(PAAS)相比,周油坊假象镜铁矿稀土元素总量低,明显正Eu异常,Ce无明显异常,Y/Ho比值介于35.00～56.67,平均48.81.这些特征显示大理岩及其赋存的假象镜铁矿形成于缺氧的海洋环境,海水中的氧能使亚铁离子氧化成三价铁离子沉淀出Fe(OH)3,但不足以使Ce3+氧化成Ce4+.     

磷块岩形成过程中的生物作用

 对我国震旦纪、寒武纪磷块岩矿床的研究表明,参与成磷作用的生物主要是菌、藻类微生物。生物作用的标志表现为:P₂O₅主要富集在叠层石磷块岩中,富集在叠层石的柱体上,富集在柱体内部的富藻纹层中;而与磷块岩共生的白云石和黄铁矿的δ¹³C值和δ³⁴S值相对均较低,则是生物参与成磷作用的同位素标志特点。生物的成磷作用贯穿成磷过程的始终,但它随作用的相带、环境和阶段不同,生物的种属和作用方式也不同,因而矿石和矿床的质量也随之而异。     

Rare Earth Element Enrichment in Late Archean Manganese Deposits from the Iron Ore Group,East India

The major, trace and rare earth element (REE) composition of Late Archean manganese, ferromanganese and iron ores from the Iron Ore Group (IOG) in Orissa, east India, was examined. Manganese deposits, occurring above the iron formations of the IOG, display massive, rhythmically laminated or botryoidal textures. The ores are composed primarily of iron and manganese, and are low in other major and trace elements such as SiO₂, Al₂O₃, P₂O₅ and Zr. The total REE concentration is as high as 975 ppm in manganese ores, whereas concentrations as high as 345 ppm and 211 ppm are found in ferromanganese and iron ores, respectively. Heavy REE (HREE) enrichments, negative Ce anomalies and positive Eu anomalies were observed in post‐Archean average shale (PAAS)‐normalized REE patterns of the IOG manganese and ferromanganese ores. The stratiform or stratabound shapes of ore bodies within the shale horizon, and REE geochemistry, suggest that the manganese and ferromanganese ores of the IOG were formed by iron and/or manganese precipitation from a submarine, hydrothermal solution under oxic conditions that occurred as a result of mixing with oxic seawater. While HREE concentrations in the Late Archean manganese and ferromanganese ores in the IOG are slightly less than those of the Phanerozoic ferromanganese ores in Japan, HREE resources in the IOG manganese deposits appear to be two orders of magnitude higher because of the large size of the deposits. Although a reliable, economic concentration technique for HREE from manganese and ferromanganese ores has not yet been developed, those ores could be an important future source of HREE.     

凉山州富铁矿资源的分布及开发

凉山州境内的富铁矿按成因可分为火山型、热液型、沉积变质型、沉积型等类型,本文逐一对其分布、地质特征及规模等方面进行了叙述和总结;对主要富铁矿产地和储量作了统计,并介绍了主要矿区开发现状及经济效益。提出了今后矿山开发、资源保扩及寻找富铁矿的建议。     

华北陆块铁矿床地质特征和资源潜力展望

华北陆块是我国重要铁矿资源的分布区,铁矿石主要开采区,也是我国钢铁工业的重要分布区。区内保有铁矿资源储量299.48亿吨,占全国总资源储量51.94%。区内各省市的铁矿资源分布极不均匀,以辽宁、河北、山西三省铁矿资源最为集中,其资源储量达220.26亿吨,占全区总铁矿资源储量75.55%。区内矿床类型较为齐全,主要的有(火山)沉积变质型铁矿床、接触交代型铁矿床、岩浆型铁矿床、复合成矿作用型铁矿床、沉积型铁矿床、热液型铁矿床、海相火山岩型铁矿床等,其中以(火山)沉积变质型铁矿床最为重要,其资源储量占全区总资源储量84.02%;其次为邯邢式接触交代型铁矿床,资源储量占全区总资源储量6.19%。该区铁矿床从太古宙到新生代都有产出,但不同地质时期产出铁矿床类型和规模不尽相同,并与区内地壳演化的特征紧密相关。太古宙是区内最重要的地质时期,该时期形成铁矿资源储量占总资源储量79.87%,广泛分布在各古老结晶基底的变质岩系内。其次为元古宙和中生代,它们资源储量分别占总资源储量的12.6%和7.06%。该区铁矿资源寻找的主要类型是条带状铁建造型铁矿床,其次是邯邢式。除上述两个主要类型外,各省根据各自地质特征,对河北岩浆型大庙式,山东热液型朱崖式等其它铁矿类型,也需要进行地质找矿。该区资源潜力还是较大的。     

遵义松林地区下寒武统多金属磷块岩矿物组成及铀的存在形式

含铀磷块岩是中国非常规铀资源的重要类型之一,其铀的存在形式及赋存状态一直存在争议。笔者对贵州省遵义松林地区的多金属磷块岩进行了化学成分和微量元素分析,以及扫描电镜研究,结果表明:区内多金属磷块岩中Ba含量高达2339×10~(-6),Sr/Ba值为0.33~2.48,U/Th值为118~544;在Fe/Ti-Al/(Al+Fe+Mn)图中,投影点落在热水沉积区。这反映了多金属磷块岩成因上与热水沉积作用有联系。该类岩石中含有方硫镍矿、辉砷镍矿、针镍矿、辉钼矿、黄铁矿、闪锌矿、重晶石等热液成因矿物,以及鲕粒磷灰石、胶状磷灰石、重结晶磷灰石和晶质铀矿,也指示其受热水沉积作用的影响。由此认为,区内多金属磷块岩在沉积成岩过程中,携带矿质(Ni、Mo、As、Zn、Ba、U等)的热液随着温度、压力的降低,在磷块岩的微裂隙和微孔隙中共沉淀,并析出晶质铀矿和其他多金属矿物。存在于多金属磷块岩微裂隙和微孔隙中的独立铀矿物的发现,为该类型非常规铀资源的综合开发利用提供了有利依据。     

西天山智博铁矿床磁铁矿成分特征及其矿床成因意义

智博大型磁铁矿床位于新疆西天山阿吾拉勒成矿带东段,赋存于石炭系大哈拉军山组玄武质安山岩、安山岩及火山碎屑岩中。智博铁矿床包括东、中、西以及13号矿体4个矿段。矿体主要呈层状、似层状、透镜状。金属矿物以磁铁矿为主,含少量浸染状黄铁矿,局部可见细脉赤铁矿及零星状黄铜矿。矿石构造以块状和浸染状构造为主,角砾状次之,局部为条带状构造、脉状-网脉状构造;矿石结构包括半自形-他形粒状结构、交代残余结构、板条状结构。智博矿区的蚀变矿物组合以透辉石、钠长石、钾长石、绿帘石、阳起石为主,含有少量方解石、石英、绿泥石及榍石。根据矿物共生组合、矿石结构的观察以及矿物化学分析,识别出岩浆期和热液期2个成矿期,进一步细分为3个成矿阶段:磁铁矿-透辉石-绿帘石阶段(a1),磁铁矿-钾长石-绿帘石阶段(b1),石英-硫化物阶段(b2)。磁铁矿的电子探针成分分析显示,岩浆期矿石中FeOT含量较高,而Al2O3、CaO、MgO、SiO2等氧化物含量较低,热液期矿石则相反。角砾状和部分浸染状磁铁矿中V2O5含量相对较高,与火山岩中含量类似,暗示该矿化阶段的铁质部分来源于围岩;块状以及浸染状磁铁矿FeOT含量大部分在90%以上;角砾状、网脉状、树枝状矿石中磁铁矿的w(FeOT)分布相对比较集中,多数在90%~92%之间;纹层状矿石的w(FeOT)则变化于88%~92%之间,其CaO、SiO2等氧化物平均含量相对增加。TiO2-Al2O3-MgO图解和Ca+Al+Mn vs Ti+V图解均表明智博铁矿床的形成与火山活动和岩浆热液的交代作用有关。     

河南舞阳铁山庙式BIF铁矿的矿物学与地球化学特征及对矿床成因的指示

河南舞阳铁矿位于华北克拉通南缘.铁山庙式铁矿是舞阳铁矿的一部分,赋存于新太古界太华杂岩铁山庙组表壳岩中.本文根据铁山庙式铁矿中三种不同类型矿石(条带状石英-辉石-磁铁矿、块状辉石-磁铁矿、块状石英-磁铁矿)中磁铁矿的矿物成分、全岩/矿的主量元素及微量元素特征,探讨铁山庙式铁矿床的成因.磁铁矿单矿物成分分析表明,条带状石英-辉石-磁铁矿矿石中磁铁矿的FeOT含量90.6％ ～93.1％,平均91.8％;块状辉石-磁铁矿矿石中磁铁矿的FeOT含量90.7％～91.2％,平均91.0％;块状石英-磁铁矿矿石中磁铁矿的FeOT含量92.0％～93.0％,平均92.4％.上述平均值均与磁铁矿FeOT的理论值(93.1％)接近.三种类型矿石的其它元素如TiO2、MgO、MnO、CaO、Al2O3 Cr2O3 NiO等含量均＜0.1％,无明显区别,表明该区磁铁矿为含杂质极少的纯磁铁矿,表现出沉积变质成因磁铁矿的特征.矿石中斜方辉石-单斜辉石及近矿围岩紫苏辉石-长石-石英矿物组合,表明铁山庙式矿床经受了高级变质作用,石英、磁铁矿等矿物普遍发生变质重结晶,颗粒粗大,但仍保存原有的地球化学组成.元素地球化学分析显示,三种类型矿石中SiO2 、TiO2 Al2O3、P2O5的含量相近;块状辉石-磁铁矿较其它二者相对贫铁、富钙、镁,这是由于块状辉石-磁铁矿石中富含铁普通辉石和铁次透辉石所致;矿石中TiO2、Al2O3含量都极低,说明该区成岩成矿过程中未受到碎屑物质的混染.三种不同类型矿石的主量元素含量总体上都与世界典型BIF的相近.对于稀土元素,三种类型矿石均具有轻稀土亏损、重稀土富集((La/Yb)PAAS=0.29～0.995＜1),La、Eu、Y的正异常(La/La*=1.10～1.89;Eu/Eu* =1.30～2.23;Y/Y* =1.47～1.84),较高的Y/Ho比值(39.7 ～51.3),具有现代海水及高温热液混合特征.因此,我们认为铁山庙式铁矿三种不同类型的矿石是极少受到陆源碎屑混染的化学沉积成因,虽遭受后期变质作用,但仍属BIF型铁矿.     

贵州开阳以东震旦系陡山沱组磷矿富磷机制与“三位一体”预测找矿重大突破*

贵州开阳以东磷矿整装勘查区位处扬子陆块东南边缘,是中国富磷矿最集中分布区。通过对开阳磷矿沉积学、岩石学、地层学和古地理学综合研究认为,开阳地区磷矿成矿受黔中古陆长期剥蚀夷平形成的无障壁海岸的海滩环境控制,高品位磷块岩矿石岩相组合特征、矿物学特征和沉积规律指示了开阳磷矿动态“三阶段成矿作用”过程(即原始生物—化学成磷作用、波浪簸选(机械)成矿作用和暴露淋滤成矿作用),波浪簸选成矿作用是形成厚度大、品位高富磷矿床的主导因素。按照“三位一体”成矿地质理论,确定了以沿黔中古陆北缘开阔海滩相层状展布的磷矿体展布特征,建立了区域成矿模式和地质找矿预测模型,并圈定临滨带为富磷矿重点预测靶区,开展找矿预测。通过产—学—研联合攻关,实现了磷矿理论创新,突破了该区原有磷矿找矿理论瓶颈,成矿范围从250^km²增至1000^km²,预测资源量从0.9442×10⁸t增至13×10⁸t。通过部分区块的工程验证,获得估算磷矿资源量(推断量+预测量)5.4892×10⁸t,尤其新增富磷矿3.57×10⁸t,取得中国富磷矿找矿重大突破。     

云南澜沧县芒洪铁矿地质特征及找矿远景

云南澜沧县芒洪铁矿是近期开展1∶5万区域地质矿产调查新发现的铁矿床。芒洪铁矿为海相火山-沉积变质型矿床，矿体呈层状、似层状赋存于惠民增生杂岩中，铁矿体的分布受地层层位、岩性建造、火山-沉积旋回等因素联合控制；矿区的物化遥异常与已发现铁矿吻合较好，成矿条件有利，找矿标志明显，具有较好的找矿前景。     

Oxygen Isotope Study of Paleoproterozoic Banded Iron Formation, Hamersley Basin, Western Australia

A submillimeter‐scale variation of δ¹⁸O in quartz was identified in chert and Fe‐oxide mesobands of the Brockman Iron Formation, Western Australia, using an in situ CO₂‐laser fluorination technique. The total range of variation is 11.2–23.0‰, with >5‰ variations within a single mesoband of approximately 2 cm thickness. These data contradict most previous works, which have suggested that banded iron formations are isotopically homogeneous. The present sample was obtained outside of the iron mining area, and as such is considered to have been less altered by the hydrothermal event recently shown to be responsible for the formation of the iron ore. The data suggest that the largest Paleoproterozoic banded iron formations may have formed not in a stable, quiescent sea, but instead as a result of increased influx of iron‐ and silica‐rich solutions during periods of increased magmatism and submarine hydrothermal activity in a rift basin environment.     

对冀东司家营铁矿深部找矿问题的探讨

司家营铁矿是冀东最大的单体铁矿床，其资源量约占冀东铁矿资源总量的六分之一，具有重要的经济意义和资源战略地位。司家营铁矿自1914年发现至今已有100多年，有悠久的勘查和研究历史，取得了一系列重要研究进展：矿床的成矿时代为新太古代晚期；矿质初始来源于海底高温热液与海水混合；矿区内的褶皱和断裂构造对矿体的最终定位有控制作用；矿床的原始成矿地质背景可能为弧后盆地；矿区有原生沉积和热液改造贫矿而成的富铁矿，后期构造运动可以导致进一步的富集。通过对司家营铁矿的研究进展和存在问题综述，本文认为：滦县岩群的中上层是后续深部找矿的目标层位，而富铁矿应在厚大的贫矿体中找；辨别断裂的性质有助于推断深部矿体位置，褶皱的转折端和断裂的交汇处有助于赋存富铁矿；磁异常和重力异常是找大矿、找富矿的重要标志；混合岩化和热液蚀变作用发育的位置更利于找富铁矿；后续的找矿工作建议在矿区西侧矿体延深方向上开展；随着埋藏深度的加大，弱小的磁异常也值得高度重视。