40Ar-39Ar Dating of Albite and Phlogopite from Porphyry Iron Deposits in the Ningwu Basin in East-Central China and Its Significance

40Ar-39Ar dating of albite from the Meishan and Taocun iron deposits yields plateau ages of 122.90±0.16 Ma and 124.89±0.30 Ma, and isochron ages of 122.60±0.16 Ma and 124.90±0.29 Ma, respectively. Phlogopite from the Zhongshan-Gushan ore field has a plateau age of 126.7±0.17 Ma and an isochron age of 127.21±1.63 Ma. Analysis of regional geodynamic evolution of the middle-lower Yangtze River region suggests that the porphyry iron deposits were formed as a result of large-scale lithosphere delamination and strong sinistral strike-slip movement of the Tancheng Lujiang fault zone. The copper, molybdenum and gold deposit system in the middle-lower Yangtze River region was formed during the stress transition period of the eastern China continent.

A synthesis of iron deposits in the eastern Tianshan,NW China

The northern Xinjiang region is one of the most significant iron metallogenic provinces in China.Iron deposits are found mainly within three regions:the Altay,western Tianshan,and eastern Tianshan orogenic belts.Previous studies have elaborated on the genesis of Fe deposits in the Altay orogenic belt and western Tianshan.However,the geological characteristics and mineralization history of iron deposits in the eastern Tianshan are still poorly understood.In this paper I describe the geological characteristics of iron deposits in the eastern Tianshan,and discuss their genetic types as well as metallogenic-tectonic settings,Iron deposits are preferentially distributed in central and southern parts of the eastern Tianshan.The known iron deposits in the eastern Tianshan show characteristics of magmatic Fe-Ti-V(e.g.,Weiya and Niumaoquan),sedimentary-metamorphic type(e.g.,Tianhu),and iron skarn(e.g.,Hongyuntan).In addition to the abovementioned iron deposits,many iron deposits in the eastern Tianshan are hosted in submarine volcanic rocks with well-developed skarn mineral assemblages.Their geological characteristics and magnetite compositions suggest that they may belong to distal skarns.SIMS zircon U-Pb analyses suggest that the Fe-Ti oxide ores from Niumaoquan and Weiya deposits were formed at 307.7±1.3 Ma and 242.7±1.9 Ma,respectively.Combined with available isotopic age data,the timing of Fe mineralization in the eastern Tianshan can be divided into four broad intervals:Early Ordovician-Early Silurian(476-438 Ma),Carboniferous(335-303 Ma),Early Permian(295-282 Ma),and Triassic(ca.243 Ma).Each of these episodes corresponds to a period of subduction,post-collision,and intraplate tectonics during the Paleozoic and Mesozoic time.

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.

Seasonal Variations in Dustfall and Its Iron Content over North China

Extensive dustfall collections were carried out from April 2001 to May 2002 in North China. The highest level of dustfall occurred in the Gobi deserts and at the margins of sandy deserts in the region. The iron content in dustfall in North China varied from 0.6% to 6.0% and there was significant seasonal variation, which indicates the dust sources differed during the year. Although the iron content in dustfall in North China is higher in the Loess Plateau and arable lands and lower in the Gobi and sandy deserts, the total iron deposition was higher in the Gobi desert regions. If the fine particles （PM10） in dustfall in North China are the major contributors of dust transport to eastern China and western parts of the North Pacific, then the annual deposition rates of iron may have been underestimated in previous studies. Our analysis indicates that iron deposition may reach 1.38 × 10^3 to 2.43 × 10^3 kg km^-2 and that most iron deposition occurs in spring and summer. If the more-coarse fractions （PM50） are considered, deposition rates may reach 2.75 × 10^3 and 6.80 × 10^3 kg km^-2, which would represent a large source of iron deposition in eastern China and the western North Pacific.

Occurrence of the Iron–rich Melt in the Heijianshan Iron Deposit, Eastern Tianshan, NW China: Insights into the Origin of Volcanic Rock–hosted Iron Deposits

Long-standing controversy persists over the presence and role of iron-rich melts in the formation of volcanic rock-hosted iron deposits. Conjugate iron-rich and silica-rich melt inclusions observed in thin-sections are considered as direct evidence for the presence of iron-rich melt, yet unequivocal outcrop-scale evidence of iron-rich melts are still lacking in volcanic rock-hosted iron deposits. Submarine volcanic rock-hosted iron deposits, which are mainly distributed in the western and eastern Tianshan Mountains in Xinjiang, are important resources of iron ores in China, but it remains unclear whether iron-rich melts have played a role in the mineralization of such iron ores. In this study, we observed abundant iron-rich agglomerates in the brecciated andesite lava of the Heijianshan submarine volcanic rock-hosted iron deposit, Eastern Tianshan, China. The iron-rich agglomerates occur as irregular and angular masses filling fractures of the host brecciated andesite lava. They show concentric potassic alteration with silicification or epidotization rims, indicative of their formation after the wall rocks. The iron-rich agglomerates have porphyritic and hyalopilitic textures, and locally display chilled margins in the contact zone with the host rocks. These features cannot be explained by hydrothermal replacement of wall rocks （brecciated andesite lava） which is free of vesicle and amygdale, rather they indicate direct crystallization of the iron-rich agglomerates from iron-rich melts. We propose that the iron-rich agglomerates were formed by open-space filling of volatile-rich iron-rich melt in fractures of the brecciated andesite lava. The iron-rich agglomerates are compositionally similar to the wall-rock brecciated andesite lava, but have much larger variation. Based on mineral assemblages, the iron-rich agglomerates are subdivided into five types, i.e., albite-magnetite type, albite-K-feldspar- magnetite type, K-feldspar-magnetite type, epidote-magnetite type and quartz-magnetite type, representing that products formed at different stages during the evolution of a magmatic-hydrothermal system. The albite-magnetite type represents the earliest crystallization product from a residual iron- rich melt; the albite-K-feldspar-magnetite and K-feldspar-magnetite types show features of magmatic- hydrothermal transition, whereas the epidote-magnetite and quartz-magnetite types represent products of hydrothermal alteration. The occurrence of iron-rich agglomerates provides macroscopic evidence for the presence of iron-rich melts in the mineralization of the Heijianshan iron deposit. It also indicates that iron mineralization of submarine volcanic rock-hosted iron deposits is genetically related to hydrothermal fluids derived from iron-rich melts.

Investigation on Positive Correlation of Increased Brain Iron Deposition with Cognitive Impairment in Alzheimer Disease by Using Quantitative MR R2' Mapping

Brain iron deposition has been proposed to play an important role in the pathophysiology of Alzheimer disease（AD）.The aim of this study was to investigate the correlation of brain iron accumulation with the severity of cognitive impairment in patients with AD by using quantitative MR relaxation rate R2＇ measurements.Fifteen patients with AD,15 age-and sex-matched healthy controls,and 30 healthy volunteers underwent 1.5T MR multi-echo T2 mapping and T2＊ mapping for the measurement of transverse relaxation rate R2＇（R2＇=R2＊-R2）.We statistically analyzed the R2＇ and iron concentrations of bilateral hippocampus（HP）,parietal cortex（PC）,frontal white matter（FWM）,putamen（PU）,caudate nucleus（CN）,thalamus（TH）,red nucleus（RN）,substantia nigra（SN）,and dentate nucleus（DN） of the cerebellum for the correlation with the severity of dementia.Two-tailed t-test,Student-Newman-Keuls test（ANOVA） and linear correlation test were used for statistical analysis.In 30 healthy volunteers,the R2＇ values of bilateral SN,RN,PU,CN,globus pallidus（GP）,TH,and FWM were measured.The correlation with the postmortem iron concentration in normal adults was analyzed in order to establish a formula on the relationship between regional R2＇ and brain iron concentration.The iron concentration of regions of interest（ROI） in AD patients and controls was calculated by this formula and its correlation with the severity of AD was analyzed.Regional R2＇ was positively correlated with regional brain iron concentration in normal adults（r=0.977,P0.01）.Iron concentrations in bilateral HP,PC,PU,CN,and DN of patients with AD were significantly higher than those of the controls（P0.05）;Moreover,the brain iron concentrations,especially in parietal cortex and hippocampus at the early stage of AD,were positively correlated with the severity of patients＇ cognitive impairment（P0.05）.The higher the R2＇ and iron concentrations were,the more severe the cognitive impairment was.Regional R2＇ and iron concentration in parietal cortex and hippocampus were positively correlated with the severity of AD patients＇ cognitive impairment,indicating that it may be used as a biomarker to evaluate the progression of AD.

Iron overload and HFE gene mutations in Polish patients with liver cirrhosis

BACKGROUND:Increased liver iron stores may contribute to the progression of liver injury and fibrosis,and are associated with a higher risk of hepatocellular carcinoma development.Pre-transplant symptoms of iron overload in patients with liver cirrhosis are associated with higher risk of infectious and malignant complications in liver transplant recipients.HFE gene mutations may be involved in the pathogenesis of liver iron overload and influence the progression of chronic liver diseases of different origins.This study was designed to determine the prevalence of iron overload in relation to HFE gene mutations among Polish patients with liver cirrhosis.METHODS:Sixty-one patients with liver cirrhosis included in the study were compared with a control group of 42 consecutive patients subjected to liver biopsy because of chronic liver diseases.Liver function tests and serum iron markers were assessed in both groups.All patients were screened for HFE mutations (C282Y,H63D,S65C).Thirty-six of 61 patients from the study group and all controls had liver biopsy performed with semiquantitative assessment of iron deposits in hepatocytes.RESULTS:The biochemical markers of iron overload and iron deposits in the liver were detected with a higher frequency (70% and 47% respectively) in patients with liver cirrhosis.There were no differences in the prevalence of all HFE mutations in both groups.In patients with a diagnosis of hepatocellular carcinoma,no significant associations with iron disorders and HFE gene mutations were found.CONCLUSIONS:Iron disorders were detected in patients with liver cirrhosis frequently but without significant association with HFE gene mutations.Only the homozygous C282Y mutation seems to occur more frequently in the selected population of patients with liver cirrhosis.As elevated biochemical iron indices accompanied liver iron deposits more frequently in liver cirrhosis compared to controls with chronic liver disease,there is a need for more extensive studies searching for the possible influence of non-HFE iron homeostasis regulators and their modulation on the course of chronic liver disease and liver cirrhosis.

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.

Zircon U-Pb-Hf isotopes and mineral chemistry of Early Cretaceous granodiorite in the Lunggar iron deposit in central Lhasa, Tibet Y, China

The Lunggar iron deposit belongs to the Bangong-Nujiang metallogenic belt and is located in central Lhasa on the Tibetan Plateau.In the Lunggar deposit,iron mineralization formed in the skarnization contact zone between the Early Cretaceous granodiorite and the late Permian Xiala Formation limestone.In this study,we achieved detailed zircon U-Pb-Hf isotopes and mineral chemistry for the Early Cretaceous granodiorite.Zircon U-Pb dating results indicate that the Early Cretaceous granodiorite emplaced at ca.119 Ma.Based on the trace elements in zircons and the mineral chemical composition of amphibole and biotite,the Early Cretaceous granodiorite was believed to form under condition of high temperature(>700°C),low pressure(100400 MPa),and relatively high oxygen fugacity(lgfO2)(13.6 to 13.9)and H2O content(4%8%).Zircon trace elements,Hf isotope and biotite chemistry collectively reveal that significant juvenile mantle-derived magmas contributed to the source of the granodiorite.The relatively high logfO2 and shallow magma chamber are beneficial for skarn iron mineralization,implying remarkable potential for further prospecting in the Lunggar iron deposit.

Chitosan—The Application of a Natural Polymer against Iron Hydroxide Deposition

As a consequence of mining, heavy metal ions can be exposed to the environment hence contaminate ground water and surface water amongst others. The natural polymer chitosan was proved to be an excellent adsorber material for the effective removal of iron and sulfate ions in batch as well as in column experiments. The adsorption behavior of iron ions, as well as sulfate ions was investigated by utilizing chitosan flakes as a natural adsorbent. The removal was studied using adsorbance measurements, SEM and SEM-EDX. The adsorption capacity of chitosan was determined at different times. The received adsorption capacities for iron ions were very promising with a maximum adsorption capacity of 85 mg/g and a rate of separation of 100%. The maximum adsorption capacity obtained for sulfate ions was 188.8 mg/g and a rate of 80%.

A preliminary study on ore-forming environments of Xianglushan-type iron deposit and the weathering mineralization of Emeishan basalt in Guizhou Province, China

Xianglushan-type iron deposits are one of the new types of iron deposits found in the Weining Area of Western Guizhou. The iron-bearing rock system is a paleo-weathered crustal sedimentary(or accumulating) stratum between the top of the Middle-Late Permian Emeishan basalt formation and the Late Permian Xuanwei formation. Iron ore is hosted in the Lower-Middle part of the rock system. In terms of the genesis of mineral deposit, this type of deposit should be a basalt paleo-weathering crustal redeposit type, very different from marine sedimentary iron deposits or continental weathering crust iron deposits. Based on field work and the analytical results of XRD Powder Diffraction, Electron Probe, Scanner Electron Microscope, etc., the geological setting of the ore-forming processes and the deposit features are illustrated in this paper. The ore-forming environment of the deposit and the Emeishan basalt weathering mineralization are also discussed in order to enhance the knowledge of the universality and diversity of mineralization of the Emeishan Large Igneous Province(ELIP), which may be a considerable reference to further research for ELIP metallogenic theories, and geological research for iron deposits in the paleo-weathering crust areas of the Emeishan basalt,Southwestern, China.

Geochemical characteristics and genesis of volcanic and sub-volcanic rocks from porphyrite-type iron deposits in Ningwu metallogenic province,eastern China:Constraints from elements

Ningwu porphyrite-type iron deposits are located in Ningwu Mesozoic volcanic basin,which belongs to the middle and lower reaches of the Yangtze River metallogenic province.The volcanic rocks can be divided into Longwangshan,Dawangshan,Gushan and Niangniangshan Formations from early to late.All these volcanic rocks are rich in alkali,and show the similar patterns in rare earth element(REE) distribution.However,some differences can be found in the trace elements and REE patterns.The study of petrology and REE geochemical characteristics shows that these rocks are derived from the underplating of the lithospheric mantle and are contaminated by crustal materials,undergo AFC process during the magmatic evolution.

Biomarkers (Alkanes )of the Xuanlong - Type Iron Deposits

The authors studied the biomarkers (alkanes) of eight iron ore samples from Nianpanshan and Dsbaodui of Pangjiabao and Longguan, Xuanhua, Hebei. These samples have higher nC15-nC20 contents, with main peaks at nC16, nC 17 and nC18, and contain abundant pristane and phytane. These results indicate that iron stromatolite and iron oncolites in orebodies are sedimentary structures of algal origin. Sedimentary iron accumulation mainly results from activity of blue algae. This study provides new valuable evidence for the origin of Xuanlong-type iron deposits.

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）.

Geological Features,Mineralization Types and Metallogenic Setting of the Phlaythong Large Iron Deposit,Southern Laos

The Phlaythong large iron deposit in Shampasak of southern Laos,is located in the Kon Tum microblock （Fig.1A）,central-southern part of the Indo-China block,and the geographic coordinate of the central mining area is 14°43′04″ N and 106°07′02″ E.

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.

Extraction of altered minerals from Aster remote sensing data in Gongchangling iron deposit of Liaoning, China

The precision of Aster data is higher than that of Landsat series of multispectral remote sensing data,which can more accurately reveal the distribution of altered minerals.It plays an important role in prospecting,but it is rarely used in areas with complex terrain and high vegetation coverage.Based on this purpose,this study used Aster remote sensing data,and took Gongchangling iron deposit as a case study.It combined the mineral spectrum theory and the basic geologic data of the study area,using the model of principal component analysis(PCA)and color synthesis to extract abnormal altered minerals.The results show that the distribution of identified anomalies is basically consistent with the existing geological data in this study area,which provides a reliable reference for the mineral resources ex-ploration and delineation of mining areas.

Geochronology of minerrlization and tectonic setting of Baishidong skaro-type iron deposit in Helony aree of Yanbian,Jilin Province,NE China

The Baishidong iron deposit is the only skarn-type iron deposit discovered in the study area.According to mineral assemblage and paragenesis,the mineralization can be divided into four metallogenic stages:early garnet-diopside skarn stage,late magnetite-tremolite-epidote skarn stage,early quartz-pyrite-chalcopyrite stage and late quartz-calcite-pyrite stage.Through LA-ICP-MS zircon U-Pb dating of diorite,which is closely related to mineralization,the results show that the weighted average age is 164.6±1.4 Ma,which limits the mineralization time of Baishidong iron deposit during or slightly later than Middle Jurassic.The diorite rocks are rich in sodium(Na_(2)O/K_(2)O=1.24-1.76),aluminium(Al_(2)O_(3)=17.41%-18.76%),LREE and large-ion lithophile elements(Ba,K and Sr),depleted in HREE and high-field-strength elements(Y,Nb,Ta,P and Ti),and show strongly fractionated patterns(LREE/HREE=6.58-9.93),no apparent Eu anomalies(δEu=0.91-1.13),which shows similar characteristics to island arc or active continental margin arc magma.The zirconεHf(t)values range from-22.6 to 5.9,and the age of the two-stage model(t_(DM2))is 836-2633 Ma.Above data combined with the geochemical characteristics,it is indicated that the magma was a mixture of multiple sources,composed of ancient materials and newly formed crust.During the process of evolution and ascending of magma,separation and crystallization occurred,and a large amount of continental crust material was mixed at the same time.Combined with regional tectonic evolution,the formation of this deposit may be related to the westward subduction of the Paleo-Pacific Plate to the Eurasian Plate.

The Shaytor Apatite-Magnetite Deposit in the Kashmar-Kerman Tectonic Zone (Central Iran): A Kiruna-Type Iron Deposit

The Shaytor apatite-rich iron deposit is located in the Kashmar-Kerman tectonic zone in the central of the Iranian plat, which is an important polymetallic belt in Iran. The ore bodies are interbedded with the upper inferacaamberian calc-alkaline igneous rocks that show well-preserved porphyritic and volcaniclastic textures. The iron ores have massive, disseminated, and brecciated structures. Magnetite from the Shaytor deposit is low in Ti (TiO2 = up to 0.70 wt.%) and different ore types show similar rare earth element (REE) and trace element-normalized patterns with weak-to-moderate enrichment in light REE and negative Eu anomalies, indicating a common source and genesis. The similar REE patterns for the magnetite and volcanic basaltic host rocks suggest their close genetic linkage and support a magmatic origin for the deposit. The Shaytor deposit shows the typical characteristics of Kiruna-type deposits with regard to the mineral assemblages, ore texture and structure, and the apatite and magnetite geochemistry. We propose that the Kiruna-type Shaytor apatite-rich iron deposit was derived from Fe-P-rich melt through liquid immiscibility and the activity of hydrothermal fluids.