河北武安玉泉岭铁矿床流体包裹体地球化学特征     

夏浩东 《地质与勘探》2013,49(5):855-860

本文在系统总结前人关于玉泉岭铁矿床地质特征及矿床特征的基础上,开展了石榴石和方解石流体包裹体均一法测温,并对磁铁矿、黄铁矿和方解石样品进行了气液相成分测试。结果表明,流体包裹体气相的主要成分为H2O和CO2,液相成分以K+、Ca2+、Na+、Mg2+、Cl-、F-、SO2-4为主。流体包裹体均一温度变化于100～560℃,主要集中于140～540℃,盐度变化于1.91%～21.19%,主要集中于4.50%～18.00%。综合以上流体包裹体特征,表明成矿流体可能主要来源于岩浆水,部分来自大气降水。  相似文献   

Opaque mineralogy and magnetic properties of selected banded iron‐formations,Hamersley Basin,Western Australia     

L. A. Tompkins  D. R. Cowan 《Australian Journal of Earth Sciences》2013,60(3):427-437

The oxide mineralogy and rock magnetic properties of unmineralised banded iron‐formations in selected portions of four drillholes in the Hamersley Basin, Western Australia are reviewed. In all four drillholes, petrographic studies indicate that primary euhedral to subhedral hematite is partially replaced by magnetite as a result of subsolidus reduction. All drillholes show partial recrystallisation of the secondary magnetite, suggesting that early subsolidus reduction was probably a regional event occurring during prograde metamorphism. Incomplete replacement of primary hematite by magnetite within and between sedimentary band structures indicates that equilibration in the magnetite stability field was not reached even at the mesoband scale. Subsequent subsolidus oxidation of magnetite and the formation of a second‐generation hematite are documented in only two of the drillholes. Goethite‐filled veins and thick selvages of goethite around some veins reflect movement of circulating oxidising fluids. The absence of goethite and second‐generation hematite in two of the drillholes indicates that subsolidus oxidation is not a regional event, but very much localised. Rapid changes in down‐hole susceptibility measurements correlate directly with detailed petrographic results as susceptibility readings change with the hematite/magnetite ratio on a mesoband scale. Acquisition of the main remanence correlates with the formation of hematite as the primary oxide phase followed by partial replacement by magnetite as a result of subsolidus reduction, supporting regional models requiring pre‐folding remanence. The strong orientation of the primary hematite parent parallel to band structures in the banded iron‐formations has influenced the direction of crystallisation remanent magnetisation during subsolidus reduction to the magnetite daughter. The strong planar alignment has also produced a planar magnetic fabric and marked anisotropy of magnetic susceptibility. A natural remanent magnetisation overprint and reduction in anisotropy of magnetic susceptibility are only recorded in samples that have undergone subsolidus oxidation and the recognition of localised post‐metamorphic oxidation overprinting can also explain ore deposit models requiring post‐folding remanence. The relative timing of and between oxidising fluid events is not known, but both petrographic and rock magnetic evidence to date suggests that there was at least one and probably two post‐folding oxidising events in the area of study.  相似文献   

Inliers of banded iron‐formation in the Proterozoic Wyloo Group sediments near Paraburdoo,Western Australia     

Desmond F. Lascelles 《Australian Journal of Earth Sciences》2013,60(1-2):161-165

Two inliers with a total outcrop length of 3000 m and a maximum width of 200 m, consisting of a sedimentary klippe (olistolith) and an olistostrome (both composed of banded iron‐formation and shale belonging to the Hamersley Group) occur within the Mininer Turbidite Member of the Wyloo Group, south of Paraburdoo, W.A., 2500 m from the top of the Hamersley Group proper. The olistostrome is a typical debris slide produced by slumping of unconsolidated material. The klippe was rafted into position as a solid block by a turbidity current.

The pattern of mineralisation within the banded iron‐formation part of the klippe, which is identified as being from the Brockman Iron Formation, together with evidence from the basal conglomerate of the Wyloo Group, shows that the formation of the Hamersley iron ore deposits commenced prior to the deposition of the Wyloo Group sediments.  相似文献   

Genesis of the channel iron deposits (CID) of the Pilbara region,Western Australia     

R. C. Morris  E. R. Ramanaidou 《Australian Journal of Earth Sciences》2013,60(5):733-756

Miocene fluvial goethite/hematite channel iron deposits (CID) are part of the Cenozoic Detritals 2 (CzD2), of the Western Australian Pilbara region. They range from gravelly mudstones through granular rocks to intraformational pebble, cobble and rare boulder conglomerates, as infill in numerous meandering palaeochannels in a mature surface that includes Precambrian granitoids, volcanics, metasediments, BIF and ferruginous Palaeogene valley fill. In the Hamersley Province of the Pilbara, the consolidated fine gravels and subordinate interbedded conglomerates, with their leached equivalents, are a major source of export iron ore. This granular ore typically comprises pedogenically derived pelletoids comprising hematite nuclei and goethite cortices (ooids and lesser pisoids), with abundant coarser goethitised wood/charcoal fragments and goethitic peloids, minor clay, and generally minimal porous goethitic matrix, with late-stage episodic solution and partial infill by secondary goethite, silica and siderite (now oxidised) in places. Clay horizons and non-ore polymictic basal and marginal conglomerates are also present. The accretionary pedogenic pelletoids were mostly derived from stripping of a mature ferruginous but apparently well-vegetated surface, developed in the Early to Middle Miocene on a wide variety of susceptible rock types including BIF, basic intrusives and sediments. This deep ferruginisation effectively destroyed most remnants of the original rock textures producing a unique surface, very different to those that produced the underlying CzD1 (Palaeogene) and the overlying CzD3 (Pliocene – Quaternary). The peloids were derived both intraformationally from fragmentation and reworking of desiccated goethite-rich muds, and from the regolith. Tiny wood/charcoal fragments replaced in soil by goethite, and dehydrated to hematite, formed nuclei for many pelletoids. Additionally, abundant small (≤10 mm) fragments of wood/charcoal, now goethite, were probably replaced in situ within the consolidating CID. This profusion of fossil wood, both as pelletoid nuclei and as discrete fragments, suggests major episodic wild fires in heavily vegetated catchments, a point supported by the abundance of kenomagnetite – maghemite developed from goethite in the pelletoids, but less commonly in the peloids. The matrix to the heterogeneous colluvial and intraformational components is essentially goethite, primarily derived from modified chemically precipitated iron hydroxyoxides, resulting from leaching of iron-rich soils in an organic environment, together with goethitic soil-derived alluvial material. Major variations in the granular ore CID after deposition have resulted from intermittent groundwater flow in the channels causing dissolution and reprecipitation of goethite and silica, particularly in the basal CID zones, with surface weathering of eroded exposures playing a role in masking some of these effects. However, significant variations in rock types in both the general CID and the granular ore CID have also resulted from the effects of varied provenance.  相似文献   

Nature and origins of granitic regolith in bauxite mine floors in the Darling Range,Western Australia     

G. A. Kew  R. J. Gilkes  C. I. Mathison 《Australian Journal of Earth Sciences》2013,60(4):473-492

Chemical and physical weathering of primary minerals during the formation of laterite profiles in the Darling Range has formed distinct secondary mineral and morphological zones in the regolith. Erosion and human activity such as mining have exposed large areas of lateritic regolith, and its classification is important for land management, especially for mine rehabilitation. Preserved rock fabrics within regolith may enable the identification of parent rock type and degree of weathering, thus providing explanations for variations in important physical properties such as the strength and water retention of regolith. Feldspar, quartz, biotite and muscovite in porphyritic and fine-grained monzogranite in lateritic profiles have weathered via a series of gradational changes to form saprolite and pedolith consisting of kaolin, quartz, iron oxides, muscovite and gibbsite. Local reorganisation in the upper regolith or pedoplasmation zone has included illuviation of kaolin, which may be iron oxide-stained and which has disrupted the preserved rock fabric of saprock and saprolite. Quartz grain- or matrix-supported fabrics have developed, with greater pedoplasmation resulting in a quartz-grain-supported fabric. The recognition of these processes enables the use of gibbsite grainsize and distribution in regolith to infer original feldspar grainsize. Muscovite-rich or muscovite-deficient kaolin matrix indicates where plagioclase or alkali feldspar, respectively, was present in the parent rock. In some regolith, cementing by iron oxides has faithfully preserved rock fabric. The recognition of these various regolith types provides a basis for identifying the parent materials of lateritic regolith developed from granitic and doleritic rocks. Rock fabric is sometimes preserved in iron oxide-cemented bauxite mine floor regolith (Zh) due to the pseudomorphic gibbsite grains and iron oxide cement which forms a porous, rigid fabric. Plagioclase-rich granitoid is more likely to have weathered to dense clay-rich regolith (Zp), whereas albite and alkali feldspar have weathered to quartz-rich regolith (Zm) with the random orientation of quartz grains indicating that substantial reorganisation of rock fabric has occurred. It is possible to predict the response of regolith materials exposed in mine floors to management practices including ripping and re-vegetation, thus allowing targeted use of deep-ripping and planting density based on regolith type.  相似文献   

Coupled asteroid impacts and banded iron-formations,Fortescue and Hamersley Groups,Pilbara, Western Australia     

A.Y. Glikson  A.H. Hickman 《Australian Journal of Earth Sciences》2013,60(5):689-701

Asteroid impact spherule layers and tsunami deposits underlying banded iron-formations in the Fortescue and Hamersley Groups have been further investigated to test their potential stratigraphic relationships. This work has included new observations related to the ca 2.63 Ga Jeerinah Impact Layer (JIL) and impact spherules associated with the 4th Shale-Macroband of the Dales Gorge Iron Member (DGS4) of the Brockman Iron Formation. A unit of impact spherules (microkrystite) correlated with the ca 2.63 Ga JIL is observed within a >100 m-thick fragmental-intraclast breccia pile in drill cores near Roy Hill. The sequence represents significant thickening of the impact/tsunami unit relative to the JIL type section at Hesta, as well as relative to the 20–30 m-thick ca 2.63 Ga Carawine Dolomite spherule-bearing mega-breccia. The ca 2.48 Ga-old Dales Gorge Member of the Brockman Iron Formation is underlain by an ?0.5 m-thick rip-up clast breccia located at the top of the ca 2.50 Ga Mt McRae Shale, and is interpreted as a tsunami deposit. We suggest that the presence of impact ejecta and tsunami units stratigraphically beneath a number of banded iron-formations, and units of ferruginous shale in the Pilbara and South Africa may result from a genetic relationship. For example, it could be that under Archean atmospheric conditions, mafic volcanism triggered by large asteroid impacts enriched the oceans in soluble FeO. If so, seasonal microbial and/or photolytic oxidation to ferric oxide could have caused precipitation of Fe₂O₃ and silica. In view of the possible occurrence of depositional gaps and paraconformities between impact ejecta units and overlying ferruginous sediments, these relationships require further testing by isotopic age studies.  相似文献   

鞍山陈台沟铁矿地质地球物理找矿模型   总被引：1，自引：0，他引：1       下载免费PDF全文

于仕祥  姚良德  李厚民  赵洪振  洪学宽  杨志辽 《地质找矿论丛》2013,28(3):361-365

陈台沟铁矿床为新太古代时期形成的鞍山式沉积变质型铁矿床,是近年来在鞍山地区将地质与物探相结合,寻找深部贫铁矿床最为成功的典型范例。文章分析了陈台沟铁矿床的控矿地质条件及磁异常特征,建立了地质-地球物理找矿模型,对深部铁矿赋存部位进行了预测,并实施了钻探验证,以期为类似条件下寻找深部隐伏铁矿提供参考。  相似文献   

吉林省白山市二岔铁矿地质特征及矿床成因探讨     

王唯存  王守兴  王向丽  左雷  林野 《吉林地质》2013,(4):83-87

吉林省白山市二岔铁矿位于中朝准地台、辽东台隆、铁岭—靖宇台拱、龙岗断块中南部边缘,太古宙早期区域内发生幅度较大的拗陷,接受广泛巨厚的一套粘土质、砂质碎屑岩类沉积,其间夹有硅铁质沉积并伴有火山（基性）岩浆喷溢活动,太古宙末期强烈造山运动使这些沉积岩层发生强烈挤压,形成褶皱构造及区域性断裂。伴随强烈造山运动致使太古宙地体发生中、深度区域变质作用与混合岩化作用。区域变质作用和混合岩化作用,对本区火山沉积变质铁矿的形成具有重要意义。二岔铁矿已探明基础储量（122b）30.26万吨、资源量（333）11.44万吨  相似文献   

深海溶解态锰和铁的原位分析技术研究进展     

潘安阳  杨群慧  周怀阳  王虎  季福武 《地球科学进展》2013,28(4):420-428

溶解态的锰和铁是海洋中重要的生物营养元素,也是探查海底热液活动及其演化的重要示踪剂.由于海底热液活动研究的迫切需求,以及AUV,ROV和HOV等水下运载支撑平台的迅速发展,20世纪80年代以来深海溶解态锰铁原位分析技术得到了快速发展.早期研发的Scanner和SUAVE,可对热液羽流中高含量的锰铁元素实现联合测定,但存在元素之间相互干扰等问题,因此针对锰、铁元素单独测量的原位分析仪应运而生.锰原位分析仪中,ZAPS虽然具有较低的检测限,但是无法在深海高压环境下进行原位校正;GAMOS系列具有原位校正功能,且能耗较低,可长期运行,但是检测限偏高,因此只能应用于热液环境中含量相对高的锰监测.铁原位分析仪中,改进的ALCHIMIST可实现热液喷口异常高含量铁和正常海域水体中低含量铁的检测,但由于能耗较高而难以应用于长期观测中;低能耗的Fe-Osmo-Analyzer和CHEMINI则在长期运行方面有着明显的优势.随着AUV/ROV/HOV等水下移动平台应用的日渐广泛以及海底观测网技术的迅速发展,发展原位分析仪进行长期的自主观测将成为一种必然趋势.  相似文献   

新疆契列克其铁矿床地质特征及找矿标志          下载免费PDF全文

晋红展 《江苏地质》2013,37(2):308-312

新疆契列克其铁矿位于阿克陶县.目前,矿区内发现2个矿体、12个铁矿矿脉,赋矿地层为奥陶—志留统下组(未分)的第一、第二岩性段.矿床成因类型为沉积变质碳酸盐型菱铁矿.通过对矿区成矿地质背景、矿体特征、找矿标志的研究、分析,阐述了矿区地质、矿床、矿石特征和矿体找矿标志,为矿区及其外围进一步找矿提供参考.  相似文献