宁芜南部成矿模式及对深部找矿的思考

通过对长江中下游Fe-Cu-Au多金属重要成矿带的宁芜、大冶铁矿成矿模式和成矿地质背景的分析,按照成矿系列中缺位预测的原则,认为在宁芜盆地南段的岩体存在双层结构,与上层岩体有关的矿床为典型的"玢岩铁矿";深部下层岩体具有"大冶式"铁矿相似的成矿地质环境;在此基础上,提出了在宁芜玢岩铁矿下部有大冶式铁矿存在的认识,并构建了宁芜盆地南段"丰"字型成矿模式。认为采用"模式"类比、立体填图、综合物探方法进行综合探测将具有较好的找矿效果。     

长江中下游成矿带陆相火山岩型铁矿成矿规律

通过对长江中下游成矿带成矿地质背景、宁芜与庐枞火山盆地成矿对比等研究基础上,提出该区中生代陆相火山岩盆地及外围地区铁矿具有"双层结构控矿"的认识,上部为玢岩铁矿、下部类似于"大冶式"铁矿;同时,总结了区域铁矿成矿规律,提出了区内铁矿勘查的下步主要方向。     

宁芜盆地卧儿岗铁矿成矿地质特征及找矿方向探讨

[摘 要] 本文在分析研究卧儿岗铁矿成矿地质背景和矿床地质特征的基础上,探讨了宁芜盆地卧 儿岗铁矿的控矿因素和找矿方向。卧儿岗铁矿位于宁芜断陷盆地NW 向和NNE 向断裂的交汇部位,矿 体主要赋存在浅成、超浅成侵入的辉石闪长玢岩体顶部,严格受岩体制约,认为该矿床属于玢岩型铁矿。 指出在卧儿岗铁矿深部仍有较大找矿空间,在宁芜断陷盆地NW 向和NNE 向断裂构造交汇处,并且发 育有辉石闪长玢岩的部位是寻找玢岩铁矿的有利部位。     

宁芜盆地凹山铁矿床辉长闪长玢岩和花岗闪长斑岩的锆石U-Pb年龄及其地质意义

宁芜盆地是长江中下游多金属成矿带的重要矿集区之一,是玢岩型铁矿成矿模式建模的基地.玢岩型铁矿床成矿时代的约束对区域成岩成矿作用及成矿动力学背景研究具有重要的意义.凹山铁矿床是宁芜盆地玢岩型铁矿床的典型代表之一,本文选择矿区发育的两种与成矿作用关系密切的岩浆岩为研究对象,进行锆石LA-MC-ICP-MS U-Pb年代学研...     

宁芜盆地钟九铁矿地质特征及成因分析

钟九铁矿床位于宁芜盆地南段,其矿体呈似层状产于火山岩与三叠系中统黄马青组下段和三叠系中统周冲村组沉积岩的接触带附近.赋矿围岩蚀变强烈.矿床成因是岩浆热液交代围岩形成含矿热液,在适当的地质环境下形成矿床.矿床类型为白象山式钟九热液交代亚式的中型铁矿床.     

宁芜地区玢岩铁矿Pb同位素研究

本文对宁芜地区铁矿床中磷灰石和矿石进行了Pb同位素测定。磷灰石的208Pb-232Th等时线年龄为124Ma,与辉长闪长(玢)岩和钠长石岩的形成年龄均相吻合,为成矿时代与成岩时代相近提供了佐证。岩体长石Pb同位素显示,宁芜地区中生代火成岩的原始岩浆受到了大陆壳深部3.3Ga的古老岩系的混染。矿床中矿石铅主要来自赋矿母岩浆。成矿流体具有异常高的Th/U值,表明Th相对U的明显富集,这可能反映了流体中卤素为主要的矿物质迁移载体。     

宁芜盆地凹山铁矿床黄铁矿Re-Os同位素定年及其地质意义

宁芜盆地是长江中下游成矿带的7个矿集区之一,以中生代火山岩和玢岩铁矿的广泛发育为特征。凹山铁矿床位于盆地中部,是宁芜盆地玢岩型铁矿床的重要代表之一。本文首次利用成矿元素Fe的金属矿物对宁芜盆地凹山铁矿床的黄铁矿进行了Re-Os同位素测年,获得凹山铁矿床的黄铁矿Re-Os同位素等时线年龄为127.7±2.6Ma(n=5,MSWD=0.66),直接代表凹山铁矿床的成矿年龄。~(187)Os/~(188)Os初始比值为1.73±0.56,γ_(Os(t))值为527.18～535.93,介于地幔与地壳之间,结合已有研究成果,认为凹山铁矿床的成矿物质主要来源于富集地幔,少量来自地壳。     

安徽省陆相火山岩型铁矿成矿特征与成矿规律

安徽省陆相火山岩型铁矿主要产于中生代庐枞、宁芜火山岩盆地,盆地中发育一套中基性火山碎屑岩和火山熔岩,潜火山岩-辉长闪长岩、辉长闪长玢岩和辉石粗安玢岩,导致火山盆地内与潜火山岩有密切成因关系的铁矿床（点）星罗棋布,且绝大多数铁矿床的矿体全部或主要产于潜火山岩接触带及其内部,尤其是其顶部往往为成矿有利部位。庐枞和宁芜火山岩盆地是我国重要的铁铜矿产资源的生产基地,矿产资源开发利用历史悠久,也是我国“玢岩铁矿”（宁芜研究项目编写小组,1978）的发祥地,在国际成矿理论研究领域占有重要的一席之地。庐江泥河铁矿是在玢岩铁矿模式、大型矿集区成矿理论的指导下,利用钻探对磁异常进行验证于2007年发现的。文章对安徽省陆相火山岩型铁矿成矿特征与成矿规律进行总结,对于促进区域火山岩盆地成岩成矿作用的研究以及区内深部找矿均具有重要意义。     

宁芜和庐枞火山岩盆地玢岩铁矿矿床地球化学特征及其成矿动力学背景探讨

玢岩铁矿是我国铁矿的一个重要成矿类型,宁芜和庐枞火山岩盆地是长江中下游地区玢岩铁矿的主要矿集区.对宁芜和庐枞盆地的构造分析结果表明,NNE向断裂和NW向断裂控制了区内的岩浆活动,断裂的交汇部位往往是玢岩铁矿产出的有利空间.综合对比了宁芜和庐枞地区玢岩铁矿成矿岩体的主量元素、稀土元素以及铅同位素特征,表明其具有相似的地球化学特征和共同的物质来源.稀土元素特征表明两盆地玢岩铁矿的成矿物质主要来源于地幔或下地壳;Pb同位素特征则进一步说明其与EM-Ⅱ型富集地幔具有密切关系.宁芜和庐枞盆地在燕山期受太平洋板块俯冲作用的影响,成矿作用受岩浆活动所控制.两盆地玢岩铁矿成矿作用的差异,可能是由于其受地壳物质混染程度不同所致.     

宁芜盆地玢岩型铁矿床的成矿时代：金云母40Ar-39Ar同位素年代学研究

宁芜盆地是长江中下游成矿带的重要组成部分,盆地内广泛产出玢岩型铁矿床,但其精确的成矿时代及其形成构造背景研究仍十分薄弱.本文在详细野外地质工作的基础上,选择与磁铁矿密切共生的金云母为对象,利用40Ar-39Ar阶段加热同位素定年方法,对盆地内典型玢岩型铁矿床进行了成矿时代研究,确定了盆地内主要玢岩型铁矿床陶村、白象山和...     

弓长岭铁矿蚀变岩及富矿成因

弓长岭铁矿床是鞍山本溪地区最典型的BIF型铁矿床之一,而且是该地区最大的富铁矿产区。从野外产出关系来看,弓长岭矿区的富铁矿与蚀变岩密切相关,蚀变岩与富铁矿基本上是形影相随。蚀变岩具有分带性,由富铁矿向外依次为镁铁闪石岩石榴石岩绿泥石岩弱蚀变斜长角闪岩斜长角闪岩。弱蚀变岩保留了蚀变原岩的岩貌特征,矿物的蚀变并不完全,可见残余的原生矿物。强蚀变岩的蚀变较彻底,基本无原生矿物残留。将蚀变岩与斜长角闪岩、磁铁石英岩的地球化学特征进行对比可以发现弱蚀变岩、石榴石岩、绿泥石岩与斜长角闪岩的痕量元素特征基本一致,而镁铁闪石岩的痕量元素特征更接近磁铁石英岩。再结合镜下特征、野外接触关系、主量元素特征等证据,认为除了镁铁闪石岩是由磁铁石英岩蚀变形成,其余蚀变岩都是由斜长角闪岩蚀变形成。根据各类蚀变岩中主要矿物的(Fe+Mg)/Si值以及蚀变岩的SiO2和Fe2OT3含量变化规律可以发现,在蚀变岩和富矿形成过程中发生了Mg、Fe以及Si的迁移。对本次取样的样品进行原岩恢复和构造环境判别投图,投图结果表明,绿泥石岩和弱蚀变岩的最初原岩都是形成于弧后盆地的玄武岩。     

Ferric iron in tourmaline

Red Fe³⁺-rich and black Fe³⁺, Fe²⁺-rich tourmalines have been studied by optical and Mössbauer spectroscopies to determine the optical characteristics of Fe³⁺ in tourmaline. Prominent optical absorption features at 485 and 540 nm are assigned to transitions of multiple exchange-coupled Fe³⁺ pairs in several site combinations. These transitions are more intense than those of isolated Fe³⁺ and are polarized along the vector between the interacting ions, thus permitting site assignments. The 485 nm band occurs at an unusually low energy for Fe³⁺ in silicate minerals. Similar behavior has been observed in the spectrum of coalingite, Mg₁₀Fe ₂ ³⁺ (OH)₂₄CO₃·2H₂O, in which Fe³⁺ occurs in related pairs in edge-shared sheets. These lower energies are proposed to result from magnetic exchange in edge-shared geometries. Antiferromagnetic exchange has been confirmed by a variable temperature magnetic susceptibility study of a Kenyan dravite with 3.36 wt percent Fe. The Mössbauer spectrum of this sample is unusual in that it shows a pronounced decrease in width of component peaks from 298 K to 5 K.     

中国铁矿成矿规律及重点矿集区资源潜力分析

铁矿是中国重要的大宗金属矿产资源,对其进行成矿规律总结和潜力分析具有重要的理论和实际意义。本文总结了中国铁矿资源的禀赋特征;将中国铁矿床分为沉积变质型、岩浆型、接触交代-热液型、火山岩型、沉积型和风化淋滤型6种成因类型和40个矿床式,并建立了鞍山式沉积变质型、大庙式岩浆型、蒙库式海相火山岩型、大西沟式沉积型铁矿床的成矿模式;划分了36个中国铁矿成矿区带,编制了成矿区带图,总结了不同类型铁矿和不同时代铁矿的空间分布规律;总结了矿床类型、矿床规模和矿石类型的时间分布规律;最后,探讨了7个重点成矿区带的资源潜力。     

Retention of riverine iron in estuaries

Retention of Fe flocs, resulting from the mixing of river water and seawater, was examined in three Maine estuaries. Riverine Fe was found to remain fairly conservative with salinity, implying that the process of floccufation does not necessarily remove Fe from water parcels. Laboratory experiments corroborated the field data by demonstrating that neither gravity nor suspended sediment were very effective in removing flocculated Fe from suspension. However, input of a tannery effluent did appear to result in scavenging of Fe from estuarine waters. Flocculated riverine Fe was found to increase considerably the Fe concentrations of estuarine bottom sediments, with the amount of iron per sediment specific surface area dependent on mean river flow entering an estuary. While no long term retention efficiencies could be calculated for these estuaries, it seems likely that a significant portion of flocculated riverine Fe escapes to shelf waters.     

Water determination in iron oxyhydroxides and iron ores by Karl Fischer titration

Protohematite (Fe_2?x/3(OH) _x O_3?x 1 ≤ x < 0.5) and hydrohematite (Fe_2?x/3(OH) _x O_3?x 0.5 ≤ x < 0) are iron-defective phases containing hydroxyl groups in their structures. These species were described in prior studies mainly with the aid of X-ray diffraction and Infrared spectroscopy. The existence of these phases in soils might have influence in redox processes, and they were considered as a possible water reservoir in Martian soils. In this study, we have used for the first time the Karl Fischer titration method to determine the amount of water released after heating several synthetic samples of goethite, hematite and natural iron ores at 105, 400, 600 and 900 °C. It was found that heating at 105 °C did not remove all moisture from the samples, and higher temperatures were necessary to completely remove all the absorbed water. The water contents determined at 400, 600 and 900 °C were found to be the same within the experimental errors, suggesting the inexistence of both protohematite and hydrohematite in the investigated samples. Therefore, the above-mentioned effects of these phases in soils might have to be reevaluated.     

山东省东平—汶上铁矿带铁矿床地球化学特征分析

东平—汶上铁矿带是鲁西重要的鞍山式铁矿带,矿床赋存于新太古界泰山群山草峪组变质岩中,目前已经探明10余处大、中型铁矿床。铁矿体一般呈层状、似层状,长一般800m,厚度6m;矿石主要为磁铁石英岩,发育条带状构造。文章阐述了通过采集典型矿床矿石及围岩样品,测试其常量元素、稀土元素、微量元素,结果显示磁铁石英岩总体表现为高硅,低磷、低铝;矿石和围岩的稀土元素含量都较低(w(ΣREE)=23.74×10~(-6)~141.22×10~(-6)),相对富集轻稀土,亏损重稀土(w(LREE)/w(HREE)=4.10~5.42),Eu负异常(δEu=0.61~0.96,平均0.86),Ce不显异常(δCe=0.93~1.05,平均0.94);富集大离子亲石元素K、Rb、Ba、Th,高场强元素Ta、Nb、Zr、Hf、Ti等相对亏损。研究结果表明,东平—汶上铁矿成矿带的赋矿原岩形成于大陆边缘和火山岛弧构造环境;山草峪组变质岩原岩可能经历了多个完整的火山-沉积旋回,火山活动提供了成矿物质铁和硅;成矿期海水为缺氧的弱还原环境。     

Ferric iron in mantle-derived garnets

The oxidation state of a mantle assemblage may be defined by heterogeneous reactions between oxygen and iron-bearing minerals. In spinel lherzolites, the presence of Fe³⁺ in spinel allows use of the assemblage olivine-orthopyroxene-spinel to define f _{O 2} at fixed T and P. As a first step towards establishing an analogous reaction for garnet lherzolites, garnets from mantle-derived xenoliths from South Africa and the USSR have been analyzed with ⁵⁷Fe Mössbauer spectroscopy at 298 and 77K to determine Fe³⁺/Fe²⁺ and the coordination state of iron. Garnets from South African alkremites (pyrope+Mg-spinel) and eclogites, as well as garnet-spinel and low-temperature garnet lherzolites from both South Afica and the USSR, have Fe³⁺/Fe<0.07. In contrast, garnets from high-temperature garnet lherzolites from within the Kaapvaal craton of South Africa have Fe³⁺/Fe>0.10. Ferric iron is octahedrally coordinated, and ferrous iron is present in the dodecahedral site in all samples. The occurrence of significant Fe³⁺ in these garnets necessitates caution in the use of geothermometers and geobarometers that are applied to mantle samples. For example, the presence of 12% of the Fe as Fe³⁺ in garnets can increase temperatures calculated from existing Fe/Mg geothermometers by>200°C. The concomitant increase in pressures calculated from geobarometers that use the Al content in orthopyroxene coexisting with garnet are 10–15 kbar. Results of calculations based on heterogeneous equilibria between garnet, olivine, and pyroxene are consistent with the derivation of the peridotite samples from source regions that are relatively oxidized, between the f _{O 2} of the FMQ (quartz-fayalite-magnetite) buffer and that of the WM buffer. No samples yield values of f _{O 2} as reduced as IW (iron-wüstite buffer).     

中国磁性铁矿石全铁品位和磁性铁品位关系及其意义

中国铁矿以可磁选的低品位磁性铁矿石为主,但是圈定铁矿体多以全铁品位为依据。文章整理了矿产资源储量数据库中磁性铁矿石的全铁品位及其对应磁性铁品位数据,筛选出493组数据,建立了沉积变质型、岩浆型、火山岩型、矽卡岩-热液型铁矿床磁性铁矿石的全铁（TFe）品位与磁性铁（mFe）品位关系式,全部493组数据为mFe(%)=0.9077TFe(%)-3.1442,沉积变质型铁矿为mFe(%)=0.8605TFe(%)-1.8275,火山岩型铁矿为mFe(%)=0.6669TFe(%)+2.6842,矽卡岩-热液型铁矿为mFe(%)=0.9320TFe(%)-3.2442,岩浆型铁矿为mFe(%)=0.8799TFe(%)-3.0174。假定铁矿石的全铁品位为20%和25%时,根据这些关系式估算的磁性铁品位与地质行业规范的边界品位（w(TFe)≥20%,w(mFe)≥15%）和最低工业品位（w(TFe)≥25%,w(mFe)≥20%）十分一致。磁性铁品位的估算,对评价铁矿资源的可利用性、进行国际对比和研究保障程度具有重要参考价值。     

碱熔除铁氟化物置换容量法测定铁矿石中的三氧化二铝

试样经氢氧化钠碱熔,过滤分离铁等元素,将滤液酸化、DETA络合、氟化钠置换,再用硫酸铜标准溶液回滴释放出来的EDTA,从而实现对铝的测定,通过本方法对铁矿石标准物质及样品的测定,结果的相对标准偏差在0.93%~2.95%之间,且铁矿石标准物质测定值与认定值相符。