Geostatistics Studies and Geochemical Modeling Based on Core Data,Sheytoor Iron Deposit,Iran

In general,the purpose of the mineralization modeling is the advancement of a mineral exploration project and ultimately,the extractive design of a deposit,which is one of the most important stages in mining engineering.Mineralization modeling is divided into two general categories,superficial and deep modeling.In surface modeling,the aim is finding abnormal locations in terms of mineralization at the study area,which is commonly used in the early stages of exploration as one of the means for locating exploratory boreholes.After drilling in the study area with the aim of identifying mineralization and reserve estimation it is necessary to obtain deep mineralization position and its geometric features,using statistical and modeling methods.Using mathematical,statistical and modeling methods,we can predict the position of iron mineralization in places where drilling is not done and eventually reach a three-dimensional model of the mineral materials underground.As a case study,the deep information about the boreholes of the sheytoor mining area in Yazd province of Iran was investigated.Iron mineralization was modeled as 2D cumulative model and 3D block model,and the results were presented.Finally the geochemical threshold and the anomalous limit of iron element are calculated by concentration-volume(C-V)fractal method in this deposit.Geochemical threshold and the anomalous limit for Fe in this deposit are 24.7%and 34.3%respectively.

The occurrences and geochemical characteristics of thorium in iron ore in the Bayan Obo deposit, Northern China

The Bayan Obo deposit in northern China is an ultra-large Fe–REE–Nb deposit.The occurrences,and geochemical characteristics of thorium in iron ores from the Bayan Obo Main Ore Body were examined using chemical analysis,field emission scanning electron microscopy,energy dispersive spectrometer,and automatic mineral analysis software.Results identified that 91.69%of ThO2 in the combined samples was mainly distributed in rare earth minerals(bastnaesite,huanghoite,monazite;56.43%abundance in the samples),iron minerals(magnetite,hematite,pyrite;20.97%),niobium minerals(aeschynite;14.29%),and gangue minerals(aegirine,riebeckite,mica,dolomite,apatite,fluorite;4.22%).An unidentified portion(4.09%)of ThO2 may occur in other niobium minerals(niobite,ilmenorutile,pyrochlore).Only a few independent minerals of thorium occur in the iron ore samples.Thorium mainly occurs in rare earth minerals in the form of isomorphic substitution.Analyses of the geochemical characteristics of the major elements indicate that thorium mineralization in the Main Ore Body was related to alkali metasomatism,which provided source material and favorable porosity for hydrothermal mineralization.Trace elements such as Sc,Nb,Zr,and Ta have higher correlation coefficients with thorium,which resulted from being related to the relevant minerals formed during thorium mineralization.In addition,correlation analysis of ThO2 and TFe,and REO and TFe in the six types of iron ore samples showed that ThO2 did not always account for the highest distribution rate in rare earth minerals,and the main occurrence minerals of ThO2 were closely related to iron ore types.

The Major Ore Clusters of Super-Large Iron Deposits in the World, Present Situation of Iron Resources in China, and Prospect

The metamorphosed sedimentary type of iron deposits（BIF） is the most important type of iron deposits in the world, and super-large iron ore clusters of this type include the Quadrilatero Ferrifero district and Carajas in Brazil, Hamersley in Australia, Kursk in Russia, Central Province of India and Anshan-Benxi in China. Subordinated types of iron deposits are magmatic, volcanic-hosted and sedimentary ones. This paper briefly introduces the geological characteristics of major super-large iron ore clusters in the world. The proven reserves of iron ores in China are relatively abundant, but they are mainly low-grade ores. Moreover, a considerate part of iron ores are difficult to utilize for their difficult ore dressing, deep burial or other reasons. Iron ore deposits are relatively concentrated in 11 metallogenic provinces（belts）, such as the Anshan-Benxi, eastern Hebei, Xichang-Central Yunnan Province and middle-lower reaches of Yangtze River. The main minerogenetic epoches vary widely from the Archean to Quaternary, and are mainly the Late Archean to Middle Proterozoic, Variscan, and Yanshanian periods. The main 7 genetic types of iron deposits in China are metamorphosed sedimentary type（BIF）, magmatic type, volcanic-hosted type, skarn type, hydrothermal type, sedimentary type and weathered leaching type. The iron-rich ores occur predominantly in the skarn and marine volcanic-hosted iron deposits, locally in the metamorphosed sedimentary type（BIF） as hydrothermal reformation products. The theory of minerogenetic series of mineral deposits and minerogenic models has applied in investigation and prospecting of iron ore deposits. A combination of deep analyses of aeromagnetic anomalies and geomagnetic anomalies, with gravity anomalies are an effective method to seeking large and deep-buried iron deposits. China has a relatively great oresearching potential of iron ores, especially for metamorphosed sedimentary, skarn, and marine volcanic-hosted iron deposits. For the lower guarantee degree of iron and steel industry, China should give a trading and open the foreign mining markets.

Investigation on the Geochemical Distribution of REE and Heavy Metals in Western Part of Jalal-Abad Iron Ore Deposit, Zarand, SE of Iran

The Jalal-Abad iron ore deposit, with a reserve of more than 200 Mt ore, is located in NW of Zarand region, southeastern Iran. The ore deposit occurs in the form of an elongated lens-shaped body incorporated in a folded structure of Rizu volcano-sedimentary unit. Mineralization occurred mainly in siltstones, acidic volcanic rocks and dolomitized limestones. The ore minerals include magnetite, hematite, pyrite, chalcopyrite, goethite, malachite and azurite. Chloritization and silicification are the two most widespread alteration types in the Jalal-Abad area. Cu and Ti are among the associated elements with iron in the ore samples. In comparison, the concentrations of Cu, Ti and REE are relatively low in the samples analyzed. The combined concentrations of Ce, La and Y show that geochemical background values for most areas have been measured. The Pearson correlation coefficient values and the results of cluster and principal component analyses indicate a strong correlation between REE, La, Ce, and Y with Sr in the same geochemical group suggesting a common source for these elements. A close association between Cu and Cl with metasomatic host rock and among Pb, Zn and Ba with carbonate host rocks is observed.

The Shilu Iron Ore Deposit in Hainan Province,South China:A Structurally and Hydrothermally Reworked and Re-Enriched Lake-Superior-Type BIF Iron Deposit

The Shilu iron ore deposit,located in the western Hainan Province,South China,is one of the most important iron-ore mining districts in China not only for its huge reserves of hematite-rich ores,but also for its potentially economic significance of associated metals of copper,cobalt,nickel,silver,lead and zinc,and of non-metals of dolomite,quartzite,barite,gypsum and sulfur.

Structural Origin of the Red-Ribbon Style Iron Ores in the Xinyu Iron Deposit,Central Jiangxi Province

The Xinyu iron deposit, located in central Jiangxi Province, is one of the most important BIF-type deposits in China. It is hosted in the Late Proterozoic volcanic- sedimentary rocks, which are composed of sericite- chlorite pyhllite, magnetite-bearing chlorite phyllite or schist, magnetite quartzite, and schist （Yu et al., 1989; Zeng et al., 2011）.

Quality Characteristics and Washability Treatment of Nickeliferous Iron Ore of Agios Athanasios Deposit (Kastoria, Greece)

The Agios Athanasios ore deposit is located within the wider area of Ieropigi in Kastoria, Greece. The specific ore deposit is developed in form of layers between ophiolites and Tertiary molassic conglomerates. The main mineralogical components are hematite, goethite, quartz, and secondarily, garnierite, lizardite, saponite, willemzeite and sepiolite, while scarcers are chromite, calcite and nepouite. Nickel is mainly found in garnierite, willemzeite and nepouite, which in coexistence with quartz are the main components in the binder material of the ore. For the mineral processing gravimetric and magnetic separations are used in the size of fractions -8 + 4 mm, -4 + 1 mm, -1 + 0.250 mm and -0.250 + 0.063 mm. The chemical and mineralogical analysis in combination with microscopic examination showed that mineral processing by gravimetric separation gave the most satisfactory results for the size fraction -1 + 0.250 mm.

Tectonic controls on ore deposit exhumation and preservation:A case study of the Handan-Xingtai iron-skarn district

Despite the growing concern regarding post-mineralization thermo-tectonic processes in recent years,the relative roles in exhuming and preserving ore deposits remain highly controversial.This study presents new apatite fission track and(U-Th)/He data from the Xishimen iron skarn deposit in the Handan-Xingtai district,central North China Craton.Apatite fission track dating yielded central ages ranging from 88±18 Ma to 125±9 Ma,with mean confined track lengths varying between 11.9±0.4μm and 13.3±0.2μm.Integrated apatite(U-Th)/He dating provided ages of 42.5±0.8 Ma to 48.1±3.3 Ma.Our new data,combined with previous zircon U-Pb and potassium-bearing mineral^(40)Ar/^(39)Ar ages,revealed three cooling episodes:very rapid cooling(100–140℃/Ma)at ca.130–120 Ma,a protracted slow cooling period(0.2–0.4℃/Ma)at ca.120–50 Ma,and moderate cooling(0.8–1.0℃/Ma)since ca.50 Ma.The initial rapid cooling phase was primarily attributed to post-magmatic thermal equilibration following the shallow emplacement of the Xishimen deposit.The subsequent cooling phases were controlled by uplift and exhumation processes.Our thermal models indicate an estimated total unroofing thickness of<3 km,which is shallower than the emplacement depth of the ore deposit(3–5 km).This suggests significant potential for mineral exploration.Furthermore,a comprehensive review of preservation mechanisms for various ore deposits underscores the significant role of tectonics in both exhuming and preserving ore bodies.

Geochemistry of Apatite from the Apatite-rich Iron Deposits in the Ningwu Region,East Central China

Four types of apatite have been identified in the Ningwu region. The first type of apatite is widely distributed in the middle dark colored zones （i.e. iron ores） of individual deposits. The assemblage includes magnetite, apatite and actinolite （or diopside）. The second type occurs within magnetite-apatite veins in the iron ores. The third type is seen in magnetite-apatite veins and （or） nodules in host rocks （i.e. gabbro-diorite porphyry or gabbro-diorite or pyroxene diorite）.The fourth type occurs within apatite-pyrite-quartz veins f＇dfing fractures in the Xiangshan Group. Rare earth elements （REE） geochemistry of apatite of the four occurrences in porphyry iron deposits is presented. The REE distribution patterns of apatite are generally similar to those of apatites in the Kiruna-type iron ores, nelsonites. They are enriched in fight REE, with pronounced negative Eu anomalies. The similarity of REE distribution patterns in apatites from various deposits in different locations in the world indicates a common process of formation for various ore types, e.g. immiscibility. Early magmatic apatites contain 3031.48-12080 ×10^-6 REE. Later hydrothermal apatite contains 1958 ×10^-6 REE, indicating that the later hydrothermal ore-forming solution contains lower REE. Although gabbro-diorite porphyry and apatite show similar REE patterns, gabbro-diorite porphyries have no europium anomalies or feeble positive or feeble negative europium anomalies, caused both by reduction environment of mantle source region and by fractionation and crystallization （immiscibility） under a high oxygen fugacity condition. Negative Eu anomalies of apatites were formed possibly due to acquisition of Eu^2＋ by earlier diopsite during ore magma cooling. The apatites in the Aoshan and Taishan iron deposits yield a narrow variation range of ^87Sr/^86Sr values from 0.7071 to 0.7073, similar to those of the volcanic and subvolcaulc rocks, indicating that apatites were formed by liquid immiscibility and differentiation of intermediate and basic magmas.

Ore Minerals and Genesis of Lala Copper Deposit,Sichuan Province

The Lala Cu deposit in Sichuan Province is one of the most important large deposits in SW China,both in terms of Cu and associated Au-Mo-Co-REE-Fe. Systematic ore petrology study shows that ore minerals are mainly composed of hydrothermal magnetite,chalcopyrite and molybdenite.The wall-rock alterations include biotitization,silicification, carbonatation,albitization,potash feldspathization, apatitation,actinolitation and fluoritation,et al. The Pyrite and magnetite have euhedral-subhedral crystalline grained texture and the chalcopyrite

Late Mesozoic Ore-forming Events in the Ningwu Ore District, Middle-Lower Yangtze River Polymetallic Ore Belt, East China: Evidence from Zircon U-Pb Geochronology and Hf Isotopic Compositions of the Granodioritic Stocks

Late Mesozoic volcanic-subvolcanic rocks and related iron deposits, known as porphyry iron deposits in China, are widespread in the Ningwu ore district （Cretaceous basin） of the middle-lower Yangtze River polymetallic ore belt, East China. Two types of Late Mesozoic magmatic rocks are exposed： one is dioritic rocks closely related to iron mineralization as the hosted rock, and the other one is granodioritic （-granitic） rocks that cut the ore bodies. To understand the age of the iron mineralization and the ore-forming event, detailed zircon U-Pb dating and Hf isotope measurement were performed on granodioritic stocks in the Washan, Gaocun-Nanshan, Dongshan and Heshangqiao iron deposits in the basin. Four emplacement and crystallization （typically for zircons） ages of granodioritic rocks were measured as 126.1±0.5 Ma, 126.8±0.5 Ma, 127.3±0.5 Ma and 126.3±0.4 Ma, respectively in these four deposits, with the LA-MC-ICP-MS zircon U-Pb method. Based on the above results combined with previous dating, it is inferred that the iron deposits in the Ningwu Cretaceous basin occurred in a very short period of 131-127 Ma. In situ zircon Hf compositions of εHf（t） of the granodiorite are mainly from -3 to -8 and their corresponding 176Hf/177Hf ratio are from 0.28245 to 0.28265, indicating similar characteristics of dioritic rocks in the basin. We infer that granodioritic rocks occurring in the Ningwu ore district have an original relationship with dioritic rocks. These new results provide significant evidence for further study of this ore district so as to understand the ore-forming event in the study area.

矿石中关键金属钴赋存状态研究方法流程的建立:以庐枞盆地龙桥富钴矽卡岩铁矿床为例

关键金属钴的赋存状态是研究关键金属成矿作用的核心问题之一。由于含钴矿物粒度较小,难以在矿床尺度查明关键金属矿物的种类、含量、粒度、分布特征以及与其他矿石矿物和脉石矿物的共生关系,因此亟需建立一套成本低且效率高的钴赋存状态研究流程。本次工作以龙桥铁矿床为例,建立了新的采样与制样流程,提高了样品的代表性,并大幅缩短了样品前处理与制样的时间。通过综合矿物分析技术(TIMA)分析,查明了不同钴含量的三类矿石样品中矿物的含量,在6个实验矿石样品中寻找到了辉砷钴矿、铁硫砷钴矿和硫铜钴矿三种钴矿物共753颗,并使用扫描电镜和能谱分析(SEM-EDS)对钴矿物进行了核验与半定量分析。最后,在同一个树脂靶上利用激光剥蚀-等离子体质谱仪(LA-ICP-MS)对磁铁矿和黄铁矿进行了原位点分析,进一步查明了样品中钴的赋存状态。本次研究建立了关键金属钴在矿石中赋存状态的研究方法和技术流程,具有制样简单便捷、分析时间短、分析费用低和分析精度高等诸多优点,为矿床尺度上关键金属空间分布规律和赋存状态研究提供了可靠的技术支撑。

Fossil bacteria in Xuanlong iron ore deposits of Hebei Province

Discovered in Early Proterozoic Xuanlong iron ore deposits are six genera of fossil iron bacteria, i. e. sphere (coenobium of) rod-shaped (monomer) Naumanniella, ellipsoid elliptical Ochrobium,sphere spherical Siderocapsa and chain spherical Siderococcus, chain rod-shaped Leptothrix and Lieskeella, and six genera of fossil blue bacteria, namely sphere spherical Gloeocapsa, Synechocystis and Globobacter, chain spherical Anabaena and Nostoc, and con-strictive septate tubular Nodularia. The biomineralized monomers and coenobia of the two cate-gories of bacteria, together with hematite plates made up the bacteria pelletal, bacteria silky, bacteria fibrous and clasty bacteria pelletal textural lamina. The bacteria pelletal laminae com-bined with other bacteria laminae to make up oncolite, stromatolite and laminate. The precipita-tion of iron oxide was accelerated due to iron and blue bacteria cohabiting on microbial film or mat. The Xuanlong iron ore deposits are microbial binding ore deposits of ocean source.

庐枞盆地龙桥铁矿床中菱铁矿的地质特征和成因意义

龙桥铁矿床是庐枞火山岩盆地中的一个大型的铁矿床,多年来对其矿床成因的认识存在较大的争论。文章在野外地质研究工作的基础上,通过对矿床中菱铁矿的岩矿分析鉴定和电子探针测试,确定了矿床纹层状矿石中的菱铁矿为沉积成因。通过对菱铁矿的产出特征分析,并结合龙桥铁矿床的部分地质地球化学研究成果,认为在该矿床形成过程中,早期沉积形成了纹层状的菱铁矿层,在燕山期的岩浆热事件中,部分沉积菱铁矿被交代形成了磁铁矿和具有残余骸晶结构等一系列矿石交代组构特征的矿物。纹层状矿石既具有沉积特征,也具有热液改造特征,证实了矿床的形成存在早期(三叠纪)的沉积成矿(菱铁矿)作用和晚期(燕山期)的热液成矿(磁铁矿)作用。菱铁矿的研究为进一步确定龙桥铁矿床的成因提供了新的佐证。

庐枞铁多金属矿集区龙桥铁矿反射地震初至波层析成像与隐伏矿床预测

为落实安徽庐枞地区北部的龙桥铁矿含矿层位在第二找矿深度的空间分布,本文应用小道距、长排列接收的地震反射初至波走时数据,运用层析成像方法,得到该地区近地表1000m以上的速度结构。研究结果显示,反射地震初至波携带了丰富的上地壳速度结构特征和界面变化的构造信息,精细的速度结构揭露出龙桥铁矿隐伏岩体顶界面深度与起伏形态,发现岩体顶面凸起及陡变化部位与矿体分布存在着明显的对应关系。长排列的深地震反射初至波走时层析成像方法能够为金属矿集区深部隐伏矿床的勘探与研究提供岩体的空间分布信息。

庐枞矿集区龙桥式铁矿床含矿层位地球化学特征及找矿意义

龙桥铁矿床是庐枞地区大型的铁矿床,矿床中含矿地层的归属长期存在争议。本文系统地调查了该矿床含矿层位的空间展布,分析了平面和剖面上矿体的构造样式,认为区内含矿地层为中侏罗世的罗岭组。同时,系统地研究了区内含矿地层的微量元素、稀土元素的地球化学特征。研究表明,硼元素含量与陆相沉积物接近。含矿地层中的碳酸盐岩具低∑REE、富集LREE的特征,且具弱Ce和弱Eu负异常,Y/Ho比值为34.8,与海相沉积物特征有一定差别,而与陆相湖泊沉积物稀土元素特征相似。含矿地层中矿化蚀变砂岩与中侏罗世的罗岭组砂岩也具有相似稀土元素特征。这也从地球化学上支持了野外调查得出的观点,即区内含矿地层为中侏罗世的罗岭组,为陆相沉积。在上述工作的基础上结合近期庐枞地区的勘查成果,指出庐枞南部是寻找沉积-叠加改造型矿床的有利地区。

长江中下游庐江-枞阳矿集区龙桥铁矿成矿时代研究

龙桥铁矿床是长江中下游地区隐伏的富铁矿床,位于庐江-枞阳火山岩矿集区的北缘,铁矿体主要赋存于下白垩统龙门院组火山岩之下和石英正长岩、二长岩之上的泥质粉砂岩和碳酸盐之中;本文分别采集了龙桥铁矿床井下370中段与黄铁矿矿体、方解石共生的黑云母样品(Lz370-1)和矿体围岩蚀变粗安岩中的黑云母样品(Lz370-2),进行Ar-Ar同位素测年,得到两个样品黑云母40Ar-39Ar坪年龄和等时线年龄分别为133.4±1.5Ma(2σ)、133.1±4.8Ma(MSWD=0.32)和135.4±1.4Ma(2σ)、135.5±1.8Ma(MSWD=1.3),它们代表了龙桥铁矿床的热液蚀变和矿化年龄。区域岩浆活动和典型矿床的成矿时代特征表明,长江中下游地区火山岩型铁矿床主要成矿时代在135Ma之后。

安徽庐江龙桥铁矿床金云母^(40)Ar/^(39)Ar定年:矿床成因的年代学证据

龙桥铁矿床是安徽庐枞盆地中的重要矿床,铁矿体主要赋存在中三叠统东马鞍山组。采集龙桥铁矿井下-355m中段矽卡岩矿体中与磁铁矿共生的金云母进行了40 Ar/39 Ar同位素年代学测试,得到坪年龄(147.13±1.45)Ma,代表了磁铁矿的形成时代。本区在中三叠世沉积了一套富含铁质的矿胚层;晚侏罗世-早白垩世,由于东部岩石圈伸展及郯庐断裂走滑热事件的影响,深部的成矿物质和热液开始上升并叠加改造含铁沉积矿胚层,热液叠加改造成矿作用从147Ma或更早就已经开始,此后矿床经历了区域火山喷发和正长岩体侵入等多次热事件的持续叠加改造成矿作用。龙桥铁矿矿床成因为沉积—热液叠加改造型。

安徽龙桥铁矿床辉长闪长岩的发现及其岩石学和年代学研究

龙桥铁矿床是长江中下游成矿带内的大型铁矿床,主矿体呈似层状赋存于三叠系东马鞍山组泥灰岩、角砾状灰岩和泥质粉砂岩中,单个矿体铁矿石资源量大于1亿吨,具有鲜明的成矿特色。前人研究认为,矿区内正长岩类侵入岩与成矿关系密切,龙桥矿床是成矿带内唯一与正长岩有关的大型铁矿床。随着生产勘探,在矿床中部井下巷道中发现辉长闪长岩侵入体,为矿床成因以及成矿模式提供了新的线索。文章在详细的野外地质工作基础上,开展了辉长闪长岩的岩石学、地球化学和年代学研究。辉长闪长岩岩体呈岩株状产出,被正长岩体穿切破坏,靠近矿体部位发育透辉石矽卡岩化蚀变。辉长闪长岩主要由拉长石(60%)、钾长石(10%)、普通辉石(10%)和角闪石(5%)组成;与正长岩相比,辉长闪长岩明显具有低硅、低钾、高镁铁特征。锆石LA ICP-MS定年结果表明其成岩时代为(133.5±0.8)Ma。在前人对龙桥矿床研究的基础上,笔者认为龙桥铁矿床辉长闪长岩与铁成矿作用关系更为密切,成岩成矿作用几乎同时发生,而正长岩为成矿期后破矿岩体。通过与庐枞矿集区和长江中下游成矿带内铁矿床对比表明,庐枞矿集区内大型铁矿床与正长岩无成因联系,而闪长质侵入岩则是庐枞矿集区内重要的成矿母岩。龙桥铁矿床与长江中下游成矿带庐枞、宁芜矿集区内玢岩型铁矿床以及鄂东南矿集区内矽卡岩型铁矿床在成岩成矿时代方面相近,属长江中下游第二期成岩成矿作用的产物。闪长质侵入岩是成矿带内矽卡岩型及玢岩型铁矿成矿的必要条件,而正长岩类侵入岩的形成大多晚于闪长岩,与铁成矿作用无直接关系。

基于3DSuffer的矿区深部关键界面特征

文中系统统计了庐江-枞阳矿集区龙桥铁矿区地表高程及深部矿体顶板、底板、火山岩底面、正长岩顶面矿石品位变化规律;以3DSuffer为基础,得到关键界面的3D图示。其中矿区地表高程变化明显反映了陆相火山岩边界和下伏侏罗系砂岩的接触界面;矿区深部矿体顶板、火山岩底、矿体底板和正长岩顶面的产状与地表出露的侏罗系砂岩不完全一致;矿石平均品位变化规律矿区南部高于北部。这些关键界面特征的获得为矿体开采、矿体深部构造特征及勘探提供了直观鲜明的数据信息。