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

Abstract: 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 ore-searching 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.     

桂西岩溶堆积型铝土矿床成矿作用及控矿因素

桂西岩溶堆积型铝土矿赋存于岩溶洼地中的红土层中，具有矿床规模大、矿石质量优的特点。成矿物质来源于上二叠统底部的古风化壳型铝土矿层，成矿时代为早更新世，矿床成因与岩溶作用、红土化作用有关。成矿受矿源层、地层岩性、气候、构造、地貌等因素控制。     

西藏班公湖-怒江成矿带及邻区铋矿化带的发现与意义

铋是一种稀有金属, 在世界分布很不均匀, 全世界铋资源绝大部分赋存在中国, 我国的铋资源主要集中在湖南的柿竹园。本文通过系统的野外调查与样品采集、室内ICP-MS与扫描电镜及电镜能谱方法分析, 确定班公湖-怒江成矿带12个矿床(点)单件样品铋含量达到边界品位的要求, 9个矿床(点)单件样品达到工业品位的要求, 最高达到9575×10?6。铋含量高的地质体东西向呈带状展布, 为一铋的成矿带。确定材玛矽卡岩型铁矿、尕尔穷矽卡岩型铜矿、舍索矽卡岩型铜铅锌多金属矿-社样多金属矿-更乃矽卡岩型铜铁矿、拉屋矽卡岩型铜矿-尤卡浪脉状铅矿共4个铋矿找矿远景区。铋矿物种类为硫铜铋矿、自然铋、硫铋铜铅矿、硫铋银矿共4种。铋含量较高的样品主要分布于矽卡岩型矿床中, 斑岩型矿床的铋含量较低。班公湖-怒江成矿带铋的矿化时代应为燕山期,为班公湖-怒江向南(即冈底斯地块)俯冲使之闭合后碰撞阶段所形成的。拉屋多金属矿床正在开采, 其矿石含有较高的铋含量, 由于铋的单位价值远远大于正在开采的铜与铅锌等资源, 因此, 该矿床开采时需加强铋资源的评价, 以提高其资源的综合利用价值。     

矽卡岩型铁矿的铁质来源与迁移富集机理探讨

矽卡岩型铁矿是我国最重要的富铁矿类型,其铁质来源及迁移富集机理是目前最核心、也最具争议的问题之一。本文在矽卡岩矿床复杂性和多成因性研究的基础上,对浅部铁质活化、迁移和富集机理进行整理归纳,建立了流程图;分别探讨了不同类矽卡岩型铁矿铁质的最大可能来源,认为与中酸性侵入体有关的该类铁矿,铁质主要源于浅部侵入岩;与酸性侵入体有关的该类铁矿,矿床附近的原始赋铁层位可能提供了大量铁质。但并非所有与酸性岩有关的此类铁床附近都存在赋铁地层,故本文对铁质深部来源的可能性进行了探讨,结合"岩浆矽卡岩-富碱侵入岩对"的概念,提出了全新的深部铁质活化、运移和富集的可能模式,即深部岩浆同化钙质岩石融离出的富铁矿浆上升并运移到浅部侵入岩与碳酸盐岩的接触带附近,与该系统中的热液相遇并反应,热液吸收矿浆中的铁质生成富铁的复合热液,后复合热液在接触带因物理化学条件的剧变而沉淀成矿。     

中国矽卡岩矿床找矿新进展和时空分布规律

近年来,中国矽卡岩矿床找矿取得了很大的新进展:西藏冈底斯成矿带和班公湖-怒江成矿带发现和探明了十余个大中型矽卡岩铜、金多金属矿床;在青海西部祁漫塔格成矿带发现和探明了不少铁多金属矽卡岩矿床;在东部地区发现和探明了一批大型隐伏的矽卡岩矿床,如河北白涧铁矿床、江西朱溪钨多金属矿床、湖南锡田锡钨矿床、福建上房钨矿床等。在新疆西天山发现和探明了一批大(中)型与火山-侵入活动有关的矽卡岩铁矿床。另外,在新疆发现白干湖、沙沟等大型钨矿床,在甘肃也发现和探明了大型钨矿床。学者们对上述矿床进行了较详细的研究。中国主要矽卡岩矿床最新同位素测年资料表明,矽卡岩矿床的生成时代从元古宙、古生代、中生代到新生代都有,但最重要的成岩成矿期是中生代的燕山期。在空间分布上,赵一鸣等(1990)曾划分出14个重要的矽卡岩成矿带,通过广大地质工作者的努力,在西藏、新疆和青海等省(区)找矿工作的重大进展,又新增4个矽卡岩成矿带,即西藏冈底斯成矿带、班公湖-怒江成矿带、青海祁漫塔格成矿带和新疆西天山成矿带。     

Metallogenic mechanism of cobalt in the Zhuchong cobalt -rich skarn iron deposit in the Middle -Lower Yangtze River Valley Metallogenic Belt: Constrained by in -situ sulfur isotopes and zircon U-Pb datingSCIEI北大核心CSCD

Cobalt, being a vital strategic rare and precious metal, is primarily produced within diverse deposit types through co association. The cobalt -rich skarn iron deposit is a key deposit type with considerable development potential. However, the source and enrichment mechanism of cobalt in skarn iron deposit remain unclear. The Zhuchong cobalt -rich skarn iron deposit is located in the Anqing-Guichi district of the Middle -Lower Yangtze River Valley Metallogenic Belt ( MLYB). It is the first large-scale skarn iron -rich deposit discovered in the metallogenic belt in recent years. Its associated cobalt resources have reached a medium scale. Meanwhile, the cobalt grade in the Zhuchong cobalt -rich skarn iron deposit is the highest among similar deposits in the MLYB, reaching 190g/t. In this study, the zircon U-Pb dating of the ore -forming intrusions and the spatial variation of pyrite in -situ sulfur isotopes in the vertical direction ( drilling section) of the Zhuchong cobalt -rich skarn iron deposit were carried out. The results indicate that the U-Pb ages of the two deep concealed magmatic rock samples are 139. 6 +/- 1. 0Ma and 138. 9 +/- 0. 6Ma, respectively, which occurred during the Early Cretaceous. Vertically, the overall range of pyrite sulfur isotope is +5. 3%similar to + 13. 9%o, and delta S-34 varies greatly from top to bottom, and shows strong heterogeneity, which is obviously different from the sulfur isotope compositions of Anqing skarn Cu -Fe deposit. The pyrite delta S-34 in the cobalt -rich magnetite ore body in the bottom -up mineralization -alteration zone of the Zhuchong deposit ranges from 5. 3%o to 10. 0%o. In the diopside skarn belt near the ore, the delta S-34 range of the vein pyrite spans from 12. 1%o to 13. 9%o. Within the altered diorite, the delta S-34 values of vein pyrite vary from 7. 1%o to 10. 8%o. In the outer skarn, the delta S-34 range of vein pyrite ranges fall between 6. 8%o and 7. 6%o. Within the siltstone of the Yueshan Formation, located in the gypsum -bearing salt layer, the delta S-34 values of pyrite range from 12. 0%o to 12. 7%o. Similarly, the uppermost siltstone vein pyrite of the Tongtoujian Formation exhibits a delta S-34 range of 6. 1%o to 7. 8%o. The sulfur isotope composition of pyrite within the Zhuchong cobalt -rich magnetite ore exhibits an intermediate range between that of the Yueshan pluton and the gypsum -salt layer of the Yueshan Formation. This suggests that the sulfur isotope signature within the ore reflects a mixture of two distinct end members. Statistical analysis of scale and grade within the MLYB cobalt -rich skarn deposits ( Fe -Cu -Co) indicates no apparent correlation between cobalt mineralization and the type of Fe -Cu skarn deposits. Furthermore, the involvement of sulfur through the gypsum -salt layer in the ore -forming hydrothermal fluid does not exhibit a discernible     

西藏甲马铜多金属矿床夕卡岩的喷流成因

夕卡岩为西藏甲马铜多金属矿床的主要容矿岩石 ,具有独特的喷流沉积和喷流交代成因。研究表明该夕卡岩的主要特征为 :(1)呈层状、似层状赋存于碳酸盐岩和细碎屑岩接触带 ,产状与地层一致 ;(2 )被后期脉岩穿切 ,成因上与岩浆岩无关 ;(3)喷流交代夕卡岩具交代残余结构和假角砾状构造 ,而喷流沉积夕卡岩具微粒状结构、雏晶结构和层纹、条纹、条带状构造 ,反映了二者不同的喷流成因 ;(4)发育典型的低温夕卡岩矿物组合 ,其形成温度小于30 0℃ ;(5 )夕卡岩的稀土配分型式与围岩的一致。甲马铜多金属矿床的夕卡岩是同生断裂系统、海底热流体 +深部烃碱流体与碳酸盐岩 +细碎屑岩耦合的产物 ,其成岩和成矿作用密不可分。     

论中国斑岩、矽卡岩型铜、钼矿床的形成与地壳演化的关系

根据中国120个斑岩、矽卡岩型铜、钼矿床的研究表明:中国斑岩、矽卡岩钢、钼矿床形成于地壳发展的一定阶段,一定构造单元。即形成于吕梁期之后的地槽褶皱区和印支期之后的地洼区,特别是后者,它是中国斑岩、矽卡岩铜、钼矿床发育最盛时期。它们分别占中国该类铜、钼矿床总量的84.7％,96.6％斑岩、矽卡岩铜、钼矿床的形成主要是由于地洼或地槽褶皱时期构造、岩浆活动改造或活化、迁移、富集原地层中的成矿物质或矿源层、层状铜(钼)矿的结果。     

新疆琼河坝地区铁矿床类型及其成矿特征

新疆琼河坝位于准噶尔成矿带东段,是一个潜在的以铁、铜、金为主的矿集区。区内铁矿床(点)众多,以往的找矿和研究工作大多聚焦于矽卡岩型富铁矿,对其他类型的铁矿床缺乏足够的重视。为了拓宽琼河坝地区铁矿床勘查思路,需要对区内铁矿床的类型和成矿特征进行系统归纳。文章在野外调查和室内测试分析的基础上,依据矿床(点)的产出地质环境、矿体及矿石矿物成分特征,结合铁矿石主要矿物的主量、微量及稀土元素特征,将琼河坝地区铁矿床划分为矽卡岩型、火山岩型、岩浆分异型、火山间歇期沉积型和湖相沉积型5种类型。矽卡岩型、火山岩型、岩浆分异型和火山间歇期沉积型铁矿赋存在晚古生代泥盆纪—石炭纪火山岩中,湖相沉积型铁矿床赋存于中侏罗统湖沼相含煤碎屑沉积岩中。火山间歇期沉积型铁矿床是在琼河坝地区首次发现的新类型,矿体赋存部位、矿石颗粒磨圆度及胶结成分特征均显示了该类铁矿成矿作用的特殊性。从找矿角度分析,目前主攻方向为矽卡岩型铁矿,而火山岩型铁矿是下一步找矿研究的重点。     

Genetic Types and Metallogenic Model for the Polymetallic Copper–Gold Deposits in the Tongling Ore District,Anhui Province,Eastern China

The Tongling ore district is one of the most economically important ore areas in the Middle–Lower Yangtze River Metallogenic Belt, eastern China. It contains hundreds of polymetallic copper–gold deposits and occurrences. Those deposits are mainly clustered(from west to east) within the Tongguanshan, Shizishan, Xinqiao, Fenghuangshan, and Shatanjiao orefields. Until recently, the majority of these deposits were thought to be skarn-or porphyry–skarn-type deposits; however there have been recent discoveries of numerous vein-type Au, Ag, and Pb-Zn deposits that do not fall into either of these categories. This indicates that there is some uncertainty over this classification. Here, we present the results of several systematic geological studies of representative deposits in the Tongling ore district. From investigation of the ore-controlling structures, lithology of the host rock, mineral assemblages, and the characteristics of the mineralization and alteration within these deposits, three genetic types of deposits(skarn-, porphyry-, and vein-type deposits) have been identified. The spatial and temporal relationships between the orebodies and Yanshanian intrusions combined with the sources of the ore-forming fluids and metals, as well as the geodynamic setting of this ore district, indicate that all three deposit types are genetically related each other and constitute a magmatic–hydrothermal system. This study outlines a model that relates the polymetallic copper–gold porphyry-, skarn-, and vein-type deposits within the Tongling ore district. This model provides a theoretical basis to guide exploration for deep-seated and concealed porphyry-type Cu(–Mo, –Au) deposits as well as shallow vein-type Au, Ag, and Pb–Zn deposits in this area and elsewhere.     

Geology and geochemistry of bauxite deposits in Lushoto District, Usambara Mountains, Tanzania

Bauxite deposits in the Usambara Mountains of north eastern Tanzania occur as remnants of residual deposits on two geomorphologically related plateaus of Mabughai-Mlomboza and Kidundai at Magamba in Lushoto, Usambara Mountains. The parent rocks for the deposits are mainly granulites and feldspathic gneisses of Neoproterozoic Mozambique belt. The plateaus represent a preserved Late Cretaceous–Lower Tertiary old land surface (African surface). Other parts of the Usambara Mountains and the neighbouring Pare Mountains are covered mostly by red–brown lateritic soils and impure reddish-brown kaolinitic clays. The bauxite deposits contain mainly Al₂O₃ (40–69 wt.%), Fe₂O₃ (3–10 wt.%), SiO₂ (0.16–7 wt.%) and other elements occur in quantities not substantial to affect the quality or processing of the bauxite, and are attributed to the presence of relic minerals. Gibbsite makes up to 98 vol.% of the bauxite ore in special cases. Gibbsite is accompanied by goethite in the ore. Boehmite occurs in small amounts and is usually accompanied by hematite. Impurities include goethite, hematite, kaolinite, and minor relic quartz and microcline. Kaolinite is the sole clay mineral encountered in the bauxite ore, suggesting mature soil profiles and a development of the bauxite deposits on a well-drained peneplanation. Ore reserve estimates from the drilling data and surface geological mapping of the deposits yielded bauxite reserves of about 37 million tonnes.     

岩浆成因矽卡岩的某些特征及形成机制初探

在矽卡岩型矿床中有两种矽卡岩,一是由渗滤-扩散交代作用形成的矽卡岩,另一种是由充填作用形成的脉状矽卡岩。脉状矽卡岩具有以下特点,表明属岩浆成因:1)呈脉状产出,与围岩界线清楚截然,在易于交代的大理岩中也一样;2)脉状矽卡岩中可含有类似花岗岩的矿物组合,并可出现伟晶岩囊,有时可见脉状矽卡岩与脉岩过渡;3)存在粗晶矽卡岩矿物的囊状体;4)发育气孔状构造和豆状构造;5)有流动构造;6)自身熔离现象十分普遍;7)在矽卡岩脉中常见由重力分异和挥发组分向上集中而形成的垂直分带现象;8)脉状矽卡岩常与矿浆成因的铁、铜矿体和由富含挥发分的硅浆成因的含钨石英脉相共生或过渡;9)脉状矽卡岩中已发现熔融包裹体。     

新疆西天山查岗诺尔铁矿床矿物学特征及其地质意义

查岗诺尔大型磁铁矿床位于西天山阿吾拉勒东段,矿体赋存于下石炭统大哈拉军山组安山质火山碎屑岩或凝灰岩中,主要呈层状、似层状、透镜状,受NW、NWW、NE断裂及环形断裂构造控制。矿区发育石榴石、透辉石、方柱石、阳起石、钾长石、绿帘石、绿泥石、方解石等蚀变矿物,矿石矿物主要为磁铁矿和赤铁矿,伴生的金属矿物以黄铁矿和黄铜矿为主。电子探针分析结果表明,石榴石和辉石分别为钙铁榴石-钙铝榴石系列和透辉石-钙铁辉石系列,其化学组成可表示为Adr37.97~97.89Grs0.19~57.21(Alm+Sps)0.84~4.38和Di28.68~87.46Hd10.46~70.13Jo0.24~5.53,与典型的矽卡岩型铁矿中石榴石和辉石的端员组分相似。在磁铁矿和赤铁矿的Ca+Al+Mn-Ti+V图解中,多数样品落入矽卡岩型铁矿的区域;在磁铁矿的TiO2-Al2O3-MgO图解中,多数样品落入或趋近于沉积变质-接触交代磁铁矿区域。结合矿床地质特征和矿物学研究,认为该矿床的形成与矽卡岩化紧密相关,矽卡岩化对铁成矿有重要的贡献。     

Sn, B and Pb-Zn Skarn, Vein and Disseminated Deposits in the East Sikhote–Alin, Russia

Abstract: Sn, B and Pb-Zn skarn, vein and disseminated deposits occur in the eastern part of Sikhote-Alin fold system associated with the late Cretaceous-earliest Paleogene volcano-plutonic complexes, which are products of a continental margin-type subduction along the East Sikhote-Alin belt. There are two metallogenic zones where the ore deposits are concentrated. The Taukha metallogenic zone combining B and Pb-Zn skarn, vein and disseminated deposits occurs on the main volcanic chain along the Japan Sea coast. Late Cretaceous-earliest Paleogene calc-alkaline plutonic and volcanic rocks of magnetite series predominate here. Volcanic rocks overlie on the lower Cretaceous Taukha terrane which consists of abundant olistostromes with numerous olistoliths of Triassic limestones. During the middle-late Cretaceous time, an ignimbrite erupted and formed a huge borosilicate skarn deposit. A later subduction related volcanism of the late Cretaceous-earliest Paleogene stage (70–55 Ma) was predominated by andesites and rhyodacites. Many Pb-Zn skarn and vein deposits were formed. Sulfur isotope compositions of galena in the B and Pb-Zn deposits of the Taukha metallogenic zone vary from –1. 3 to +2. 0%, averaging 0% in the δ³⁴S.     

陆相火山-侵入岩有关的铁多金属矿成矿作用及矿床模型——以长江中下游为例

在长江中下游地区,与白垩纪陆相火山-侵入岩有关的铁多金属矿床在空间上绝大多数发育于白垩纪火山盆地,仅程潮和金山店出现于隆起区;成矿时间上分为两个时代,即133~130Ma和127~125Ma。按照成矿物质来源和成矿过程,鉴别出4个成矿系统:即在隆起区与石英闪长岩有关的矽卡岩铁矿(系统1);在火山盆地内,与大王山(或砖桥)旋回火山-次火山活动有关的铁多金属矿床(包括,磷灰石-磁铁矿型铁矿、类矽卡岩型铁矿、矿浆型铁矿、热液型硫铜金矿、热液型铅锌矿)(系统2)和与二长-正长岩有关的矽卡岩型铁矿(系统3);与娘娘山(或浮山)旋回火山-次火山活动有关的铜(金)矿和金铀矿(系统4)。盆地内和隆起区的矽卡岩型铁矿形成时间基本一致,略晚于与辉石闪长玢岩有关的铁多金属矿床(系统2), 但早于铜金铀为主的成矿系统4。前人以系统2中的磷灰石-磁铁矿型铁矿、类矽卡岩型铁矿和矿浆型铁矿为主,结合其他一些少见或不具工业意义的铁矿类型,提出一个具有广泛影响的玢岩铁矿成矿模式。此文以玢岩铁矿成矿模式为基础,结合4个成矿系统的基本特点,提出了白垩纪陆相火山-侵入岩有关的铁多金属矿床模型。以上这些具有成因联系的矿床系统和类型及其分带互为找矿标志。     

铁矿储量-品位统计分布及其地质意义

通过对比各类铁矿储量－品位统计分布曲线，详细分析了其分布模式特点，认为不同类型铁矿品位分布模式同各类铁矿的成矿地质地球化学背景的复杂程度和成矿作用机制特征有关，段和多种成矿作用的同位叠加成矿总体趋势和各类铁矿成矿富集能力上的差异，指出了多期次，多阶段和多种成矿作用的同位叠加对矿床及工业富矿形成的重大意义。     

安徽月山矿田铜、金矿床氢氧同位素地球化学及成矿流体输运-化学反应成矿动力学

本文基于氢氧同位素的地球化学研究，论述了安徽月山矿田两类铜、金矿床成矿流体的来源、演化及成矿流体输运扣化学反应扣成矿作用动力学过程。结论认为。月山矿田金属矿床成矿流体为具复杂演化历史的岩浆水或多成因水的混合，主要成矿阶段成矿热液均以岩浆水占绝对优势，两类矿床是同源岩浆热液系统在不同的地质、地球化学环境下演化的产物，是成矿流体的等温输运反应及温度梯度输运反应等综合作用的结果。     

Mesozoic molybdenum deposits in the east Qinling–Dabie orogenic belt: Characteristics and tectonic settings

The East Qinling–Dabie orogenic belt accommodates the largest Mo ore district in the world. It contains 8.43 Mt of proven Mo metal reserves which accounts for 66% of the total proven Chinese Mo reserves. The Mo ore district includes 24 deposits and 12 occurrences, with four major types of Mo mineral systems, i.e., porphyry, porphyry-skarn, skarn and hydrothermal veins. The latter can be further subdivided into quartz vein and carbonatite vein types. Although Mo mineralization in the belt began in the Paleoproterozoic (1680 ± 24 to 2044 ± 14 Ma), all economically significant deposits were formed during the Mesozoic. Re/Os dating of molybdenite has shown that there are three episodes of Mo mineralization, i.e., Late Triassic (233–221 Ma), Late Jurassic to Early Cretaceous (148–138 Ma) and Early to middle Cretaceous (131–112 Ma).Late Triassic Mo deposits developed as molybdenite–quartz veins and carbonatite vein types. Stable isotope systematics (C, O, S) and high contents of Re and Sr indicate that the carbonatite Mo veins are mantle-derived. Porphyry and porphyry–skarn Mo mineral deposits were formed in the Late Jurassic to Early Cretaceous and Early to middle Cretaceous. The Late Jurassic to Early Cretaceous granite porphyries that are associated with the Mo deposits usually occupy less than 1.5 km² at the surface and are situated in the East Qinling area, far west of China's continental margin. On the other hand, the Early to middle Cretaceous batholiths and granite porphyries, , with associated Mo deposits are located in the Dabieshan area and eastern part of the East Qinling area. The Late Jurassic to Early Creataceous granitoids and related Mo deposits possibly formed in a back-arc extensional setting of the Eurasian continental margin, which was probably triggered by the oblique subduction of the Izanagi plate. The Early to middle Cretaceous batholiths and granite porphyries are linked to the tectonic regime of lithospheric thinning, asthenospheric upwelling and partial melting of the crust, induced by a change in Izanagi Plate motion parallel to the continent margin.In the East Qinling–Dabie belt there are vein type Pb–Zn–Ag deposits surrounding porphyry and/or porphyry–skarn Mo (W) deposits, forming well defined ore clusters. The same spatial arrangement (i.e., porphyry Mo stockworks and outlying Pb–Zn–Ag ore veins) is also observed at the deposit scale. Thus, Mo porphyry stockworks and distal polymetallic veins belong to the same ore system and may reflect an outward temperature decrease from the highly fractionated granite plutons. Both, porphyry stockworks and polymetallic veins, can be used as vectors for further prospecting.     

安徽铜陵狮子山铜矿田地球化学特征综述

安徽铜陵狮子山矿田是铜陵矿集区内储量最大的铜（金）矿田。矿田内矿床类型多样,成矿作用复杂,分布有东狮子山、西狮子山、大团山、老鸦岭、冬瓜山和花树坡等铜（金）矿床。这些矿床均围绕岩体产出,多数为隐伏矿,赋存于上石炭统一中三叠统的不同层位,在空间上具有明显的分带特征,由下向上依次为层控夕卡岩型、夕卡岩型和热液脉型矿床。其中...     

Mineralogy,fluid inclusions,and isotopes of the Cihai iron deposit,eastern Tianshan,NW China: Implication for hydrothermal evolution and genesis of subvolcanic rocks-hosted skarn-type deposits

Most skarn deposits are closely related to granitoids that intruded into carbonate rocks. The Cihai (>100 Mt at 45% Fe) is a deposit with mineral assemblages and hydrothermal features similar to many other typical skarn deposits of the world. However, the iron orebodies of Cihai are mainly hosted within the diabase and not in contact with carbonate rocks. In addition, some magnetite grains exhibit unusual relatively high TiO₂ content. These features are not consistent with the typical skarn iron deposit. Different hydrothermal and/or magmatic processes are being actively investigated for its origin. Because of a lack of systematic studies of geology, mineral compositions, fluid inclusions, and isotopes, the genetic type, ore genesis, and hydrothermal evolution of this deposit are still poorly understood and remain controversial.The skarn mineral assemblages are the alteration products of diabase. Three main paragenetic stages of skarn formation and ore deposition have been recognized based on petrographic observations, which show a prograde skarn stage (garnet-clinopyroxene-disseminated magnetite), a retrograde skarn stage (main iron ore stage, massive magnetite-amphibole-epidote ± ilvaite), and a quartz-sulfide stage (quartz-calcite-pyrite-pyrrhotite-cobaltite).Overall, the compositions of garnet, clinpyroxene, and amphibole are consistent with those of typical skarn Fe deposits worldwide. In the disseminated ores, some magnetite grains exhibit relatively high TiO₂ content (>1 wt.%), which may be inherited from the diabase protoliths. Some distinct chemical zoning in magnetite grains were observed in this study, wherein cores are enriched in Ti, and magnetite rims show a pronounced depletion in Ti. The textural and compositional data of magnetite confirm that the Cihai Fe deposit is of hydrothermal origin, rather than associated with iron rich melts as previously suggested.Fluid inclusions study reveal that, the prograde skarn (garnet and pyroxene) formed from high temperature (520–600 °C), moderate- to high-salinity (8.1–23.1 wt.% NaCl equiv, and >46 wt.% NaCl equiv) fluids. Massive iron ore and retrograde skarn assemblages (amphibole-epidote ± ilvaite) formed under hydrostatic condition after the fracturing of early skarn. Fluids in this stage had lower temperature (220°–456 °C) and salinity (8.4–16.3 wt.% NaCl equiv). Fluid inclusions in quartz-sulfide stage quartz and calcite also record similar conditions, with temperature range from 128° to 367 °C and salinity range from 0.2 to 22.9 wt.% NaCl equiv. Oxygen and hydrogen isotopic data of garnet and quartz suggest that mixing and dilution of early magmatic fluids with external fluids (e.g., meteoric waters) caused a decrease in fluid temperature and salinity in the later stages of the skarn formation and massive iron precipitation. The δ¹⁸O values of magnetite from iron ores vary between 4.1 and 8.5‰, which are similar to values reported in other skarn Fe deposits. Such values are distinct from those of other iron ore deposits such as Kiruna-type and magmatic Fe-Ti-V deposits worldwide. Taken together, these geologic, geochemical, and isotopic data confirm that Cihai is a diabase-hosted skarn deposit related to the granitoids at depth.