Most Phanerozoic oolites are marked by ooids with a diameter less than 2 mm. Observations on a Neoproterozoic oolite have resulted in a change of concept. The term "pisolite" that traditionally referred to oolites w...Most Phanerozoic oolites are marked by ooids with a diameter less than 2 mm. Observations on a Neoproterozoic oolite have resulted in a change of concept. The term "pisolite" that traditionally referred to oolites with a grain size of more than 2 ram, is now restricted to those coated carbonate grains formed by meteoritic freshwater diagenesis; oolites with a grain size of more than 2 mm are now defined as "giant". Particular unusual giant oolites within a set of oolitic-bank limestones with thicknesses of more than 40 m in the top part of the Lower Triassic (Induan) Daye (Ruiping) Formation at the Lichuan section in the western part of Hubei Province in South China, represent an important sedimentological phenomenon in both the specific geological period and the geological setting that is related to the end-Permian biological mass extinction. Like the giant oolites of the Neoproterozoic that represent deposits where oolites formed in a vast low-angle carbonate ramp at that special geological period, the Triassic Daye Formation at the study section are significant because they provide a comparative example to help understand the evolving carbonate world reflected by oolites, the origin of which is still uncertain, and they give insight into the sedimentation pattern of the desolate sea floor, which resulted from the mass extinction at the turn of the Permian into the Triassic.展开更多
The late Aptian(118-115 Ma) continental flood basalts of the Rajmahal Volcanic Province(RVP) are part of the Kerguelen Large Igneous Province,and constitute the uppermost part of the Gondwana Supergroup on the eas...The late Aptian(118-115 Ma) continental flood basalts of the Rajmahal Volcanic Province(RVP) are part of the Kerguelen Large Igneous Province,and constitute the uppermost part of the Gondwana Supergroup on the eastern Indian shield margin.The lower one-third of the Rajmahal volcanic succession contains thin layers of plant fossil-rich inter-trappean sedimentary rocks with pyroclasts,bentonite,grey and black shale/mudstone and oolite,whereas the upper two-thirds consist of sub-aerial fine-grained aphyric basalts with no inter-trappean material.At the eastern margin and the north-central sector of the RVP,the volcanics in the lower part include rhyolites and dacites overlain by enstatite-bearing basalts and enstatite-andesites.The pyroclastic rocks are largely felsic in composition,and comprise ignimbrite as well as coarse-grained tuff with lithic clasts,and tuff breccia with bombs,lapilli and ash that indicate explosive eruption of viscous rhyolitic magma.The rhyolites/dacites(〉68 wt.%) are separated from the andesites(〈 60 wt.%) by a gap in silica content indicating their formation through upper crustal anatexis with only heat supplied by the basaltic magma.On the other hand,partially melted siltstone xenoliths in enstatite-bearing basalts suggest that the enstatite-andesites originated through mixing of the upper crust with basaltic magma,crystallizing orthopyroxene at a pressure-temperature of ~3 kb/1150℃.In contrast,the northwestern sector of the RVP is devoid of felsic-intermediate rocks,and the volcaniclastic rocks are predominantly mafic(basaltic) in composition.Here,the presence of fine-grained tuffs,tuff breccia containing sideromelane shards and quenched texture,welded tuff breccia,peperite,shale/mudstone and oolite substantiates a subaqueous environment.Based on these observations,we conclude that the early phase of Rajmahal volcanism occurred under predominantly subaqueous conditions.The presence of grey and black shale/mudstone in the lower one-third of the succession across the entire Rajmahal basin provides unequivocal evidence of a shallow-marine continental shelf-type environment.Alignment of the Rajmahal eruptive centers with a major N—S mid-Neoproterozoic lineament and the presence of a gravity high on the RVP suggest a tectonic control for the eruption of melts associated with the Kerguelen plume that was active in a post-Gondwana rift between India and Australia-Antarctica.展开更多
Concavo-convex contacrs between oolites and quartz grains are observed in mixed siliciclastic-carbonate rocks of the lower part of number 1 of Shahejie Formation, beach area, Dagang. Thin sections observation shows th...Concavo-convex contacrs between oolites and quartz grains are observed in mixed siliciclastic-carbonate rocks of the lower part of number 1 of Shahejie Formation, beach area, Dagang. Thin sections observation shows that oolite is convex in quartz grain, and oolite is complete. A possible explanation for it is pressure dissolution under alkaline fluid.展开更多
High phosphorous oolitic hematite ore is one of typical intractable iron ores in China, and the conventional beneficiation methods are found to be impracticable to , remove phosphorus from the ore effectively. Better ...High phosphorous oolitic hematite ore is one of typical intractable iron ores in China, and the conventional beneficiation methods are found to be impracticable to , remove phosphorus from the ore effectively. Better beneficiation index were gotten by direct reduction roasting with dephosphorization agent followed by two stages of grinding and magnetic separation. P content decreases from 0.82% in the raw ore to 0.06% in the magnetic concentrate, and the total iron grade increases from 43.65% to 90.23%, the recovery of iron can reach 87%. Mechanisms of phosphorus removal in the beneficiation of high phosphorous oolitic hematite ore by direct reduction roasting with dephosphorization agent were studied using XRD, SEM and EPMA. The results showed that about 20% of the apatite in the raw ore transferred into phosphorus and volatilized with the gas in the process of reduction roasting, while the rest 80% apatite was not involved in the reaction of generation of phosphorus, and remained as apatite in the roasted products, which was removed to tailings by grinding and magnetic separation. A small amount of phosphorus existed in the magnetic concentrate as apatite. The oolitic texture of raw ore was partly changed during roasting, resulting in the formation of nepheline in the reaction between the dephosphorization agent, SiO2 and Al2O3 in the raw ore, which greatly improved the liberation degree of minerals in the roasted products, and it was beneficial to the subsequent grinding and magnetic separation.展开更多
Oolitic iron ore is one of the most important iron resources. This paper reports the recovery of iron from high phosphorus oolitic iron ore using coal-based reduction and magnetic separation. The influences of reducti...Oolitic iron ore is one of the most important iron resources. This paper reports the recovery of iron from high phosphorus oolitic iron ore using coal-based reduction and magnetic separation. The influences of reduction temperature, reduction time, C/O mole ratio, and CaO content on the metallization degree and iron recovery were investigated in detail. Experimental results show that reduced products with the metallization degree of 95.82% could be produced under the optimal conditions (i.e., reduction temperature, 1250℃; reduction time, 50 min; C/O mole ratio, 2.0; and CaO content, 10wt%). The magnetic concentrate containing 89.63wt% Fe with the iron recovery of 96.21% was obtained. According to the mineralogical and morphologic analysis, the iron minerals had been reduced and iron was mainly enriched into the metallic iron phase embedded in the slag matrix in the form of spherical particles. Apatite was also reduced to phosphorus, which partially migrated into the metallic iron phase.展开更多
Magnetizing roasting of oolitic hematite ore from western Hubei Province was investigated.The mechanism for reduction roasting of oolitic hematite ore was discussed and analyzed.It is found that flash magnetizing roas...Magnetizing roasting of oolitic hematite ore from western Hubei Province was investigated.The mechanism for reduction roasting of oolitic hematite ore was discussed and analyzed.It is found that flash magnetizing roasting-magnetic separation process is a promising approach for the processing of oolitic hematite ore from western Hubei Province.展开更多
To understand the migration mechanisms of phosphorus(P)during coal-based reduction,a high-phosphorus oolitic iron ore was reduced by coal under various experimental conditions.The migration characteristics and kinetic...To understand the migration mechanisms of phosphorus(P)during coal-based reduction,a high-phosphorus oolitic iron ore was reduced by coal under various experimental conditions.The migration characteristics and kinetics of P were investigated by a field-emission electron probe microanalyzer(FE-EPMA)and using the basic principle of solid phase mass transfer,respectively.Experimental results showed that the P transferred from the slag to the metallic phase during reduction,and the migration process could be divided into three stages:phosphorus diffusing from the slag to the metallic interface,the formation of Fe P compounds at the slag metal interface and P diffusing from the slag metal interface to the metallic interior.The reduction time and temperature significantly influenced the phosphorus content of the metallic and slag phases.The P content of the metallic phase increased with increasing reduction time and temperature,while that of the slag phase gradually decreased.The P diffusion constant and activation energy were determined and a migration kinetics model of P in coal-based reduction was proposed.P diffusion in the metallic phase was the controlling step of the P migration.展开更多
Suspension roasting followed by magnetic separation is a promising method to upgrade oolitic hematite ore.An oolitic hematite ore was roasted using suspension roasting technology at different temperatures.The phase tr...Suspension roasting followed by magnetic separation is a promising method to upgrade oolitic hematite ore.An oolitic hematite ore was roasted using suspension roasting technology at different temperatures.The phase transformation for iron minerals was investigated by XRD and Mossbauer spectrum,and the characteristics of roasted product were analyzed by VSM and SEM-EDS.Results indicate that the magnetic concentrate is of 58.73% Fe with iron recovery of 83.96% at 650 °C.The hematite is rapidly transformed into magnetite during the roasting with transformation ratio of 92.75% at 650 °C.Roasting temperature has a significant influence on the phase transformation of hematite to magnetite.The transformation ratio increases with increased temperature.After roasting,the magnetic susceptibility is significantly improved,while iron ore microstructure is not altered significantly.展开更多
The oolitic shoal reservoirs of the Lower Triassic Feixianguan Formation carbonates in the Sichuan Basin of southwest China are an important target for gas exploration in the basin.Their occurrence,like other cases wo...The oolitic shoal reservoirs of the Lower Triassic Feixianguan Formation carbonates in the Sichuan Basin of southwest China are an important target for gas exploration in the basin.Their occurrence,like other cases worldwide,can be divided into two locations in general,i.e.,platform interior and platform margin locations.Their differences of reservoir features and origins,however,have not been investigated comprehensively due to different exploration degrees.This issue is addressed in this paper,to provide basic data and information for the basin's hydrocarbon exploration and for the study of carbonate platform sedimentology and reservoir geology worldwide.We compared the features of these two types of reservoirs in detail,including the depositional and diagenetic features,pore types and petrophysical features.Based on the comparison,the origin of the reservoirs was further discussed.It is shown that the reservoirs in platform interior and platform margin locations differ significantly.The interior carbonates were deposited in moderate to high energy settings and the dominant lithologic type was limestone,which was weakly compacted and intensely cemented and has undergone meteoric dissolution.Pore types include intragranular dissolution and moldic pores,with low porosities(6%) and low permeabilities(0.1 mD).By contrast,the platform margin carbonates were deposited in relatively high energy settings and mainly consisted of dolostones with some limestones.The rocks were strongly compacted but incompletely cemented.As a result,some primary intergranular pores were preserved.Both meteoric solution and burial solution have taken place.There are various types of pore spaces including intergranular and intercrystalline solution pores and residual intergranular pores.This type of reservoir generally has better petrophysical properties(9% porosity and 0.1 mD permeability) and pore-throat structures than the interior reservoirs.These differences were influenced by both primary depositional features and secondary diagenesis.For the interior carbonate reservoirs,early meteoric dissolution,weak compaction and strong cementation are important controlling factors.By contrast,the factors controlling the formation of the margin carbonate reservoirs mainly include dolomitization,preservation of primary pores and burial dissolution.展开更多
A thermodynamic analysis of the carbothermic reduction of high-phosphorus oolitic iron ore(HPOIO) was conducted by the Fact Sage thermochemical software. The effects of temperature, C/O ratio, additive types, and do...A thermodynamic analysis of the carbothermic reduction of high-phosphorus oolitic iron ore(HPOIO) was conducted by the Fact Sage thermochemical software. The effects of temperature, C/O ratio, additive types, and dosages both on the reduction of fluorapatite and the formation of liquid slag were studied. The results show that the minimum thermodynamic reduction temperature of fluorapatite by carbon decreases to about 850°C, which is mainly ascribed to the presence of SiO_2, Al_2O_3, and Fe. The reduction rate of fluorapatite increases and the amount of liquid slag decreases with the rise of C/O ratio. The reduction of fluorapatite is hindered by the addition of CaO and Na_2CO_3, thereby allowing the selective reduction of iron oxides upon controlled C/O ratio. The thermodynamic results obtain in the present work are in good agreement with the experimental results available in the literatures.展开更多
The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in China.In this paper,the mechanism of high-temperatur...The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in China.In this paper,the mechanism of high-temperature pretreatment for enhancing the effect of iron enrichment and dephosphorization in the magnetization roasting–leaching process was studied by X-ray diffraction(XRD),vibration sample magnetometer(VSM),scanning electron microscopy and energy dispersive spectrometry(SEM–EDS).Compared with the process without high-temperature pretreatment,the iron grade of the magnetic separation concentrate after high-temperature pretreatment had increased by 0.98%,iron recovery rate had increased by 1.33%,and the phosphorus content in the leached residue had decreased by 0.12%.High-temperature pretreatment resulted in the dehydration and decomposition of hydroxyapatite,the dehydration of limonite and the thermal decomposition of siderite,which can produce pores and cracks and weaken the compactness of the ore,improve the magnetization characteristics of roasted ore,and strengthen the iron enrichment and dephosphorization during the magnetization roasting and leaching process.展开更多
Oolitic hematite is an iron ore resource with rich reserves,complex composition,low grade,fine disseminated particle sizes,and a unique oolitic structure.In this study,a microwave-assisted suspension magnetization roa...Oolitic hematite is an iron ore resource with rich reserves,complex composition,low grade,fine disseminated particle sizes,and a unique oolitic structure.In this study,a microwave-assisted suspension magnetization roasting technology was proposed to recover and utilize the ore.The results showed that under the conditions of microwave pretreatment temperature of 1050℃ for 2 min,a magnetic concentrate with an iron grade of 58.72%at a recovery of 89.32%was obtained by microwave suspension magnetization roasting and magnetic separation.Moreover,compared with the no microwave pretreatment case,the iron grade and recovery increased by 3.17%and 1.58%,respectively.Microwave pretreatment increased the saturation magnetization of the roasted products from 24.974 to 39.236(A∙m^(2))/kg and the saturation susceptibility from 0.179×10^(−3) m^(3)/kg to 0.283×10^(−3) m^(3)/kg.Microcracks were formed between the iron and gangue minerals,and they gradually extended to the core of oolite with the increase in the pretreatment time.The reducing gas diffused from outside to inside along the microcracks,which promoted the selective transformation of the weak magnetic hematite into the strong magnetic magnetite.展开更多
A large number of studies have shown that oolitic hematite is an iron ore that is extremely difficult to utilize because of its fine disseminated particle size, high harmful impurity content and oolitic structure.To r...A large number of studies have shown that oolitic hematite is an iron ore that is extremely difficult to utilize because of its fine disseminated particle size, high harmful impurity content and oolitic structure.To recover iron from oolitic hematite, we developed a novel multistage dynamic magnetizing roasting technology. Compared with traditional magnetizing roasting technologies, this novel technology has the following advantages: firstly, the oolitic hematite is dynamically reduced in a multi-stage roasting furnace, which shortens the reduction time and avoids ringing and over-reduction;secondly, the novel dynamic magnetizing roasting technology has strong raw material adaptability, and the size range of raw materials can be as wide as 0–15 mm;thirdly, the roasting furnace adopts a preheating-heating process, and the low-calorific value blast furnace gas can be used as the fuel and reductant, which greatly reduces the cost. The actual industrial production data showed that the energy consumption in the roasting process can be less than 35 kg of standard coal per ton of raw ore. The iron grade of the concentrate and iron recovery reached 65% and 90%, respectively.展开更多
The effect of coal levels on phosphorus removal from a high phosphorus oolitic hematite ore after direct reduction roasting have been investigated. Raw ore, coal, and a dephosphorizatiou agent were mixed and the mixtu...The effect of coal levels on phosphorus removal from a high phosphorus oolitic hematite ore after direct reduction roasting have been investigated. Raw ore, coal, and a dephosphorizatiou agent were mixed and the mixture was then roasted in a tunnel kiln. The roasted products were treated by two stages of grind- ing followed by magnetic separation. XRD and SEM-EDS examination of the products was used to analyze differences in the roasted products. The results show that coal is one of the most important factors affect- ing the direct reduction roasting process. When the inner coal levels increased from 0% to 15% the iron grade decreased linearly from 94.94%to 88.81% and the iron recovery increased from 55.94% to 92.94%. At the same time the phosphorus content increased from 0.045% to 0.231%. Increasing the inner coal levels also caused more hematite to be reduced to metallic iron but the oolitic structure of the roasted product was preserved in the presence of high coal loading. The phase of the phosphorus in raw ore was not changed after direct reduction roasting. The effect of coal on the phosphorus content in the H-concentrate arises from changes in the difficulty of mechanically liberating the metallic iron from the phosphorus bearing minerals.展开更多
The influence of microwave treatment on the liberation of iron ore from the high phosphorus oolitic iron ore from Aswan region, Egypt was studied. The effect of microwave power, exposure time and grain size on the lib...The influence of microwave treatment on the liberation of iron ore from the high phosphorus oolitic iron ore from Aswan region, Egypt was studied. The effect of microwave power, exposure time and grain size on the liberation of iron ore was investigated. The microfractures and cracks of the samples were characterized before and after microwave treatments. The heating rate of high phosphorus oolitic iron ore was studied. Crystallinity of hematite was characterized before and after microwave pretreatment. The results indicated that intergranular fractures formed between the gangues (fluorapatite and chamosite) and hematite after microwave treatment, leading to improved liberation of iron ore and a significant reduction in comminution energy. Percentages of fraction ≤ -0.125 mm increased from 46.6% to 59.76% with increased exposure time from 0 to 60 seconds. The heating rate of iron ore showed that microwave treatment was less efficient at smaller particle sizes for a fixed applied power density. Crystallinity of hematite increased with the microwave exposure time.展开更多
Based on comprehensive analyses of occurrence,petrological observation,pore structure and geochemistry,the different reservoir characteristics and reservoir evolutionary pathways between different oolitic shoal reserv...Based on comprehensive analyses of occurrence,petrological observation,pore structure and geochemistry,the different reservoir characteristics and reservoir evolutionary pathways between different oolitic shoal reservoir types of the Feixianguan Formation on the west side of the Kaijiang-Liangping Trough have been studied.There exist three stages of high-energy slope break belts in the Feixianguan period,the corresponding three stages of oolitic shoals gradually migrating in the direction of the trough.Three types of oolitic shoal reservoirs,namely,residual-oolitic dolomite,mold-oolitic dolomite and sparry oolitic limestone,were formed during sedimentary-diagenetic evolution,the pore types being intergranular dissolved pore,mold pore(or intragranular dissolved pore)and residual intergranular pore,respectively.The petrology,physical properties and pore structure of the different types of oolitic shoal reservoirs are quite different.Residual-oolitic dolomite reservoirs have the best quality,while sparry oolitic limestone reservoirs have the poorest.Combined with analyses of trace elements,rare earth elements and carbon-oxygen isotopes,it is suggested that the formation of residual-oolitic dolomite reservoirs is jointly controlled by penesaline seawater seepage-reflux dolomitization and hydrothermal dolomitization.Mold-pore oolitic dolomite reservoirs are controlled by penesaline seawater seepage-reflux dolomitization and meteoric water solution.The burial dissolution of organic acid not only further improves the reservoir qualities of previously formed oolitic dolomite reservoirs,but also preserves residual intergranular pores in the sparry oolitic limestone reservoirs.展开更多
In this study,direct reduction-magnetic separation process was applied to enrich phosphorus and iron to prepare Fe-P crude alloy from a high phosphorus oolitic hematite ore(HPOH).The results show that at lower tempera...In this study,direct reduction-magnetic separation process was applied to enrich phosphorus and iron to prepare Fe-P crude alloy from a high phosphorus oolitic hematite ore(HPOH).The results show that at lower temperatures and with absence of any of additives,Fe cannot be effectively recovered because of the oolitic structure is not destroyed.In contrast,under the conditions of 15%Na_(2)SO_(4)and reducing at 1050℃ for 120 min with a total C/Fe ratio(molar ratio)of 8.5,a final Fe-P alloy containing 92.40%Fe and 1.09%P can be obtained at an overall iron recovery of 95.43%and phosphorus recovery of 68.98%,respectively.This metallized Fe-P powder can be applied as the burden for production of weathering resistant steels.The developed process can provide an alternative for effective and green utilization of high phosphorus iron ore.展开更多
The main symptoms of root rot,anthracnose,blight and damping-off of Panax notoginseng( Burk) F. H. Chen are introduced in the paper,and the corresponding control measures are elaborated from the aspects of agricultura...The main symptoms of root rot,anthracnose,blight and damping-off of Panax notoginseng( Burk) F. H. Chen are introduced in the paper,and the corresponding control measures are elaborated from the aspects of agricultural management measures,seed disinfection,seedbed treatment and chemical control.展开更多
The present work is devoted to the determination of linear effective thermal conductivity of porous rocks characterized by an assemblage of grains(oolites) coated by a matrix. Two distinct classes of pores, i.e.microp...The present work is devoted to the determination of linear effective thermal conductivity of porous rocks characterized by an assemblage of grains(oolites) coated by a matrix. Two distinct classes of pores, i.e.micropores or intra oolitic pores(oolite porosity) and mesopores or inter oolitic pores(inter oolite porosity), are taken into account. The overall porosity is supposed to be connected and decomposed into oolite porosity and matrix porosity. Within the framework of Hashin composite sphere assemblage(CSA)models, a two-step homogenization method is developed. At the first homogenization step, pores are assembled into two layers by using self-consistent scheme(SCS). At the second step, the two porous layers constituting the oolites and the matrix are assembled by using generalized self-consistent scheme(GSCS) and referred to as three-phase model. Numerical results are presented for data representative of a porous oolitic limestone. It is shown that the influence of porosity on the overall thermal conductivity of such materials may be significant.展开更多
Iron was recovered from blast furnace dust and high-phosphorus oolitic hematite in the presence of Na2CO3 and CaCO3 additives. The functions of Na2CO3 and CaCO3 during the coreduction roasting process were investigate...Iron was recovered from blast furnace dust and high-phosphorus oolitic hematite in the presence of Na2CO3 and CaCO3 additives. The functions of Na2CO3 and CaCO3 during the coreduction roasting process were investigated by XRD and SEM-EDS analyses. Results indicate that these additives not only hinder the reduction of fluorapatite, CaCO3 also decreases the P content of direct reduced iron(DRI) by increasing the reduction alkalinity. P remains as fluorapatite in the slag, which can be removed by grinding and magnetic separation under optimal conditions. The Na2CO3 promotes hematite reduction and improves the iron recovery(εFe) by replacing the FeO from fayalite, which results in quick growth and aggregation of metallic iron and improvement of ε(Fe) in DRI. A DRI with 91.88 mass% Fe, and 0.065 mass% P can be achieved at a recovery of 87.86 mass% under the optimal condition.展开更多
基金funded by the Natural Sciences Foundation of China(Grant Nos.49802012,40472065)is a contribution to lUGS:UNESCO IGCP 572
文摘Most Phanerozoic oolites are marked by ooids with a diameter less than 2 mm. Observations on a Neoproterozoic oolite have resulted in a change of concept. The term "pisolite" that traditionally referred to oolites with a grain size of more than 2 ram, is now restricted to those coated carbonate grains formed by meteoritic freshwater diagenesis; oolites with a grain size of more than 2 mm are now defined as "giant". Particular unusual giant oolites within a set of oolitic-bank limestones with thicknesses of more than 40 m in the top part of the Lower Triassic (Induan) Daye (Ruiping) Formation at the Lichuan section in the western part of Hubei Province in South China, represent an important sedimentological phenomenon in both the specific geological period and the geological setting that is related to the end-Permian biological mass extinction. Like the giant oolites of the Neoproterozoic that represent deposits where oolites formed in a vast low-angle carbonate ramp at that special geological period, the Triassic Daye Formation at the study section are significant because they provide a comparative example to help understand the evolving carbonate world reflected by oolites, the origin of which is still uncertain, and they give insight into the sedimentation pattern of the desolate sea floor, which resulted from the mass extinction at the turn of the Permian into the Triassic.
文摘The late Aptian(118-115 Ma) continental flood basalts of the Rajmahal Volcanic Province(RVP) are part of the Kerguelen Large Igneous Province,and constitute the uppermost part of the Gondwana Supergroup on the eastern Indian shield margin.The lower one-third of the Rajmahal volcanic succession contains thin layers of plant fossil-rich inter-trappean sedimentary rocks with pyroclasts,bentonite,grey and black shale/mudstone and oolite,whereas the upper two-thirds consist of sub-aerial fine-grained aphyric basalts with no inter-trappean material.At the eastern margin and the north-central sector of the RVP,the volcanics in the lower part include rhyolites and dacites overlain by enstatite-bearing basalts and enstatite-andesites.The pyroclastic rocks are largely felsic in composition,and comprise ignimbrite as well as coarse-grained tuff with lithic clasts,and tuff breccia with bombs,lapilli and ash that indicate explosive eruption of viscous rhyolitic magma.The rhyolites/dacites(〉68 wt.%) are separated from the andesites(〈 60 wt.%) by a gap in silica content indicating their formation through upper crustal anatexis with only heat supplied by the basaltic magma.On the other hand,partially melted siltstone xenoliths in enstatite-bearing basalts suggest that the enstatite-andesites originated through mixing of the upper crust with basaltic magma,crystallizing orthopyroxene at a pressure-temperature of ~3 kb/1150℃.In contrast,the northwestern sector of the RVP is devoid of felsic-intermediate rocks,and the volcaniclastic rocks are predominantly mafic(basaltic) in composition.Here,the presence of fine-grained tuffs,tuff breccia containing sideromelane shards and quenched texture,welded tuff breccia,peperite,shale/mudstone and oolite substantiates a subaqueous environment.Based on these observations,we conclude that the early phase of Rajmahal volcanism occurred under predominantly subaqueous conditions.The presence of grey and black shale/mudstone in the lower one-third of the succession across the entire Rajmahal basin provides unequivocal evidence of a shallow-marine continental shelf-type environment.Alignment of the Rajmahal eruptive centers with a major N—S mid-Neoproterozoic lineament and the presence of a gravity high on the RVP suggest a tectonic control for the eruption of melts associated with the Kerguelen plume that was active in a post-Gondwana rift between India and Australia-Antarctica.
文摘Concavo-convex contacrs between oolites and quartz grains are observed in mixed siliciclastic-carbonate rocks of the lower part of number 1 of Shahejie Formation, beach area, Dagang. Thin sections observation shows that oolite is convex in quartz grain, and oolite is complete. A possible explanation for it is pressure dissolution under alkaline fluid.
基金Project (51074016) support by the National Natural Science Foundation of China
文摘High phosphorous oolitic hematite ore is one of typical intractable iron ores in China, and the conventional beneficiation methods are found to be impracticable to , remove phosphorus from the ore effectively. Better beneficiation index were gotten by direct reduction roasting with dephosphorization agent followed by two stages of grinding and magnetic separation. P content decreases from 0.82% in the raw ore to 0.06% in the magnetic concentrate, and the total iron grade increases from 43.65% to 90.23%, the recovery of iron can reach 87%. Mechanisms of phosphorus removal in the beneficiation of high phosphorous oolitic hematite ore by direct reduction roasting with dephosphorization agent were studied using XRD, SEM and EPMA. The results showed that about 20% of the apatite in the raw ore transferred into phosphorus and volatilized with the gas in the process of reduction roasting, while the rest 80% apatite was not involved in the reaction of generation of phosphorus, and remained as apatite in the roasted products, which was removed to tailings by grinding and magnetic separation. A small amount of phosphorus existed in the magnetic concentrate as apatite. The oolitic texture of raw ore was partly changed during roasting, resulting in the formation of nepheline in the reaction between the dephosphorization agent, SiO2 and Al2O3 in the raw ore, which greatly improved the liberation degree of minerals in the roasted products, and it was beneficial to the subsequent grinding and magnetic separation.
基金supported by the National Natural Science Foundation of China(Nos.51134002 and 51074036)
文摘Oolitic iron ore is one of the most important iron resources. This paper reports the recovery of iron from high phosphorus oolitic iron ore using coal-based reduction and magnetic separation. The influences of reduction temperature, reduction time, C/O mole ratio, and CaO content on the metallization degree and iron recovery were investigated in detail. Experimental results show that reduced products with the metallization degree of 95.82% could be produced under the optimal conditions (i.e., reduction temperature, 1250℃; reduction time, 50 min; C/O mole ratio, 2.0; and CaO content, 10wt%). The magnetic concentrate containing 89.63wt% Fe with the iron recovery of 96.21% was obtained. According to the mineralogical and morphologic analysis, the iron minerals had been reduced and iron was mainly enriched into the metallic iron phase embedded in the slag matrix in the form of spherical particles. Apatite was also reduced to phosphorus, which partially migrated into the metallic iron phase.
文摘Magnetizing roasting of oolitic hematite ore from western Hubei Province was investigated.The mechanism for reduction roasting of oolitic hematite ore was discussed and analyzed.It is found that flash magnetizing roasting-magnetic separation process is a promising approach for the processing of oolitic hematite ore from western Hubei Province.
基金financially supported by the National Natural Science Foundation of China (No.51604063)
文摘To understand the migration mechanisms of phosphorus(P)during coal-based reduction,a high-phosphorus oolitic iron ore was reduced by coal under various experimental conditions.The migration characteristics and kinetics of P were investigated by a field-emission electron probe microanalyzer(FE-EPMA)and using the basic principle of solid phase mass transfer,respectively.Experimental results showed that the P transferred from the slag to the metallic phase during reduction,and the migration process could be divided into three stages:phosphorus diffusing from the slag to the metallic interface,the formation of Fe P compounds at the slag metal interface and P diffusing from the slag metal interface to the metallic interior.The reduction time and temperature significantly influenced the phosphorus content of the metallic and slag phases.The P content of the metallic phase increased with increasing reduction time and temperature,while that of the slag phase gradually decreased.The P diffusion constant and activation energy were determined and a migration kinetics model of P in coal-based reduction was proposed.P diffusion in the metallic phase was the controlling step of the P migration.
基金Project([2011]01-69-07)supported by the China Geological Survey Project
文摘Suspension roasting followed by magnetic separation is a promising method to upgrade oolitic hematite ore.An oolitic hematite ore was roasted using suspension roasting technology at different temperatures.The phase transformation for iron minerals was investigated by XRD and Mossbauer spectrum,and the characteristics of roasted product were analyzed by VSM and SEM-EDS.Results indicate that the magnetic concentrate is of 58.73% Fe with iron recovery of 83.96% at 650 °C.The hematite is rapidly transformed into magnetite during the roasting with transformation ratio of 92.75% at 650 °C.Roasting temperature has a significant influence on the phase transformation of hematite to magnetite.The transformation ratio increases with increased temperature.After roasting,the magnetic susceptibility is significantly improved,while iron ore microstructure is not altered significantly.
基金funded by the National Basic Research Development Program(973 project, Grant No. 2012CB214803)PetroChina Youth Innovation Foundation (Grant No. 2011D-5006-0105)Key Subject Construction Project of Sichuan Province, China(Grant No. SZD 0414)
文摘The oolitic shoal reservoirs of the Lower Triassic Feixianguan Formation carbonates in the Sichuan Basin of southwest China are an important target for gas exploration in the basin.Their occurrence,like other cases worldwide,can be divided into two locations in general,i.e.,platform interior and platform margin locations.Their differences of reservoir features and origins,however,have not been investigated comprehensively due to different exploration degrees.This issue is addressed in this paper,to provide basic data and information for the basin's hydrocarbon exploration and for the study of carbonate platform sedimentology and reservoir geology worldwide.We compared the features of these two types of reservoirs in detail,including the depositional and diagenetic features,pore types and petrophysical features.Based on the comparison,the origin of the reservoirs was further discussed.It is shown that the reservoirs in platform interior and platform margin locations differ significantly.The interior carbonates were deposited in moderate to high energy settings and the dominant lithologic type was limestone,which was weakly compacted and intensely cemented and has undergone meteoric dissolution.Pore types include intragranular dissolution and moldic pores,with low porosities(6%) and low permeabilities(0.1 mD).By contrast,the platform margin carbonates were deposited in relatively high energy settings and mainly consisted of dolostones with some limestones.The rocks were strongly compacted but incompletely cemented.As a result,some primary intergranular pores were preserved.Both meteoric solution and burial solution have taken place.There are various types of pore spaces including intergranular and intercrystalline solution pores and residual intergranular pores.This type of reservoir generally has better petrophysical properties(9% porosity and 0.1 mD permeability) and pore-throat structures than the interior reservoirs.These differences were influenced by both primary depositional features and secondary diagenesis.For the interior carbonate reservoirs,early meteoric dissolution,weak compaction and strong cementation are important controlling factors.By contrast,the factors controlling the formation of the margin carbonate reservoirs mainly include dolomitization,preservation of primary pores and burial dissolution.
基金financially supported by the National Science Fund of China(No.51134002)the Foundation of Jiangxi Educational Committee,China(No.GJJ150624)the Doctoral Scientific Research Foundation of Jiangxi University of Science and Technology,China(No.JXXJBS16004)
文摘A thermodynamic analysis of the carbothermic reduction of high-phosphorus oolitic iron ore(HPOIO) was conducted by the Fact Sage thermochemical software. The effects of temperature, C/O ratio, additive types, and dosages both on the reduction of fluorapatite and the formation of liquid slag were studied. The results show that the minimum thermodynamic reduction temperature of fluorapatite by carbon decreases to about 850°C, which is mainly ascribed to the presence of SiO_2, Al_2O_3, and Fe. The reduction rate of fluorapatite increases and the amount of liquid slag decreases with the rise of C/O ratio. The reduction of fluorapatite is hindered by the addition of CaO and Na_2CO_3, thereby allowing the selective reduction of iron oxides upon controlled C/O ratio. The thermodynamic results obtain in the present work are in good agreement with the experimental results available in the literatures.
基金the National Natural Science Foundation of China(Nos.51734005,51874071,and 51604063)the Fok Ying Tung Education Foundation for Young Teachers in the Higher Education Institutions of China(No.161045)+1 种基金the Liao Ning Revitalization Talents Program(No.XLYC1807111)the Fundamental Research Funds for the Central Universities of China(No.N180105030).
文摘The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in China.In this paper,the mechanism of high-temperature pretreatment for enhancing the effect of iron enrichment and dephosphorization in the magnetization roasting–leaching process was studied by X-ray diffraction(XRD),vibration sample magnetometer(VSM),scanning electron microscopy and energy dispersive spectrometry(SEM–EDS).Compared with the process without high-temperature pretreatment,the iron grade of the magnetic separation concentrate after high-temperature pretreatment had increased by 0.98%,iron recovery rate had increased by 1.33%,and the phosphorus content in the leached residue had decreased by 0.12%.High-temperature pretreatment resulted in the dehydration and decomposition of hydroxyapatite,the dehydration of limonite and the thermal decomposition of siderite,which can produce pores and cracks and weaken the compactness of the ore,improve the magnetization characteristics of roasted ore,and strengthen the iron enrichment and dephosphorization during the magnetization roasting and leaching process.
基金Projects(51874071,51734005,52104257)supported by the National Natural Science Foundation of ChinaProject(161045)supported by the Fok Ying Tung Education Foundation for Yong Teachers in the Higher Education Institutions of China。
文摘Oolitic hematite is an iron ore resource with rich reserves,complex composition,low grade,fine disseminated particle sizes,and a unique oolitic structure.In this study,a microwave-assisted suspension magnetization roasting technology was proposed to recover and utilize the ore.The results showed that under the conditions of microwave pretreatment temperature of 1050℃ for 2 min,a magnetic concentrate with an iron grade of 58.72%at a recovery of 89.32%was obtained by microwave suspension magnetization roasting and magnetic separation.Moreover,compared with the no microwave pretreatment case,the iron grade and recovery increased by 3.17%and 1.58%,respectively.Microwave pretreatment increased the saturation magnetization of the roasted products from 24.974 to 39.236(A∙m^(2))/kg and the saturation susceptibility from 0.179×10^(−3) m^(3)/kg to 0.283×10^(−3) m^(3)/kg.Microcracks were formed between the iron and gangue minerals,and they gradually extended to the core of oolite with the increase in the pretreatment time.The reducing gas diffused from outside to inside along the microcracks,which promoted the selective transformation of the weak magnetic hematite into the strong magnetic magnetite.
基金National Natural Science Foundation of China (No. 51974204)。
文摘A large number of studies have shown that oolitic hematite is an iron ore that is extremely difficult to utilize because of its fine disseminated particle size, high harmful impurity content and oolitic structure.To recover iron from oolitic hematite, we developed a novel multistage dynamic magnetizing roasting technology. Compared with traditional magnetizing roasting technologies, this novel technology has the following advantages: firstly, the oolitic hematite is dynamically reduced in a multi-stage roasting furnace, which shortens the reduction time and avoids ringing and over-reduction;secondly, the novel dynamic magnetizing roasting technology has strong raw material adaptability, and the size range of raw materials can be as wide as 0–15 mm;thirdly, the roasting furnace adopts a preheating-heating process, and the low-calorific value blast furnace gas can be used as the fuel and reductant, which greatly reduces the cost. The actual industrial production data showed that the energy consumption in the roasting process can be less than 35 kg of standard coal per ton of raw ore. The iron grade of the concentrate and iron recovery reached 65% and 90%, respectively.
基金the National Natural Science Foundation of China (No. 51074016) for the financial support for this research
文摘The effect of coal levels on phosphorus removal from a high phosphorus oolitic hematite ore after direct reduction roasting have been investigated. Raw ore, coal, and a dephosphorizatiou agent were mixed and the mixture was then roasted in a tunnel kiln. The roasted products were treated by two stages of grind- ing followed by magnetic separation. XRD and SEM-EDS examination of the products was used to analyze differences in the roasted products. The results show that coal is one of the most important factors affect- ing the direct reduction roasting process. When the inner coal levels increased from 0% to 15% the iron grade decreased linearly from 94.94%to 88.81% and the iron recovery increased from 55.94% to 92.94%. At the same time the phosphorus content increased from 0.045% to 0.231%. Increasing the inner coal levels also caused more hematite to be reduced to metallic iron but the oolitic structure of the roasted product was preserved in the presence of high coal loading. The phase of the phosphorus in raw ore was not changed after direct reduction roasting. The effect of coal on the phosphorus content in the H-concentrate arises from changes in the difficulty of mechanically liberating the metallic iron from the phosphorus bearing minerals.
文摘The influence of microwave treatment on the liberation of iron ore from the high phosphorus oolitic iron ore from Aswan region, Egypt was studied. The effect of microwave power, exposure time and grain size on the liberation of iron ore was investigated. The microfractures and cracks of the samples were characterized before and after microwave treatments. The heating rate of high phosphorus oolitic iron ore was studied. Crystallinity of hematite was characterized before and after microwave pretreatment. The results indicated that intergranular fractures formed between the gangues (fluorapatite and chamosite) and hematite after microwave treatment, leading to improved liberation of iron ore and a significant reduction in comminution energy. Percentages of fraction ≤ -0.125 mm increased from 46.6% to 59.76% with increased exposure time from 0 to 60 seconds. The heating rate of iron ore showed that microwave treatment was less efficient at smaller particle sizes for a fixed applied power density. Crystallinity of hematite increased with the microwave exposure time.
基金This research was supported jointly by the National Natural Science Foundation of China(Grant No.41972165)National Science and Technology Major Project(Grant No.2017ZX05008-004-008)National Science and Technology Major Project(Grant No.2016E-0607).
文摘Based on comprehensive analyses of occurrence,petrological observation,pore structure and geochemistry,the different reservoir characteristics and reservoir evolutionary pathways between different oolitic shoal reservoir types of the Feixianguan Formation on the west side of the Kaijiang-Liangping Trough have been studied.There exist three stages of high-energy slope break belts in the Feixianguan period,the corresponding three stages of oolitic shoals gradually migrating in the direction of the trough.Three types of oolitic shoal reservoirs,namely,residual-oolitic dolomite,mold-oolitic dolomite and sparry oolitic limestone,were formed during sedimentary-diagenetic evolution,the pore types being intergranular dissolved pore,mold pore(or intragranular dissolved pore)and residual intergranular pore,respectively.The petrology,physical properties and pore structure of the different types of oolitic shoal reservoirs are quite different.Residual-oolitic dolomite reservoirs have the best quality,while sparry oolitic limestone reservoirs have the poorest.Combined with analyses of trace elements,rare earth elements and carbon-oxygen isotopes,it is suggested that the formation of residual-oolitic dolomite reservoirs is jointly controlled by penesaline seawater seepage-reflux dolomitization and hydrothermal dolomitization.Mold-pore oolitic dolomite reservoirs are controlled by penesaline seawater seepage-reflux dolomitization and meteoric water solution.The burial dissolution of organic acid not only further improves the reservoir qualities of previously formed oolitic dolomite reservoirs,but also preserves residual intergranular pores in the sparry oolitic limestone reservoirs.
基金Projects(AA18242003,AA148242003)supported by Innovation-driven Project of Guangxi Zhuang Autonomous Region,ChinaProject(51474161)supported by the National Natural Science Foundation of China。
文摘In this study,direct reduction-magnetic separation process was applied to enrich phosphorus and iron to prepare Fe-P crude alloy from a high phosphorus oolitic hematite ore(HPOH).The results show that at lower temperatures and with absence of any of additives,Fe cannot be effectively recovered because of the oolitic structure is not destroyed.In contrast,under the conditions of 15%Na_(2)SO_(4)and reducing at 1050℃ for 120 min with a total C/Fe ratio(molar ratio)of 8.5,a final Fe-P alloy containing 92.40%Fe and 1.09%P can be obtained at an overall iron recovery of 95.43%and phosphorus recovery of 68.98%,respectively.This metallized Fe-P powder can be applied as the burden for production of weathering resistant steels.The developed process can provide an alternative for effective and green utilization of high phosphorus iron ore.
文摘The main symptoms of root rot,anthracnose,blight and damping-off of Panax notoginseng( Burk) F. H. Chen are introduced in the paper,and the corresponding control measures are elaborated from the aspects of agricultural management measures,seed disinfection,seedbed treatment and chemical control.
基金support from TAMER (Trans-Atlantic Micromechanics Evolving Research) European Project (materials containing inhomogeneities of diverse physical properties, shapes and orientations)FP7 Project TAMER IRSES-GA2013-610547
文摘The present work is devoted to the determination of linear effective thermal conductivity of porous rocks characterized by an assemblage of grains(oolites) coated by a matrix. Two distinct classes of pores, i.e.micropores or intra oolitic pores(oolite porosity) and mesopores or inter oolitic pores(inter oolite porosity), are taken into account. The overall porosity is supposed to be connected and decomposed into oolite porosity and matrix porosity. Within the framework of Hashin composite sphere assemblage(CSA)models, a two-step homogenization method is developed. At the first homogenization step, pores are assembled into two layers by using self-consistent scheme(SCS). At the second step, the two porous layers constituting the oolites and the matrix are assembled by using generalized self-consistent scheme(GSCS) and referred to as three-phase model. Numerical results are presented for data representative of a porous oolitic limestone. It is shown that the influence of porosity on the overall thermal conductivity of such materials may be significant.
基金Funded by National Natural Science Foundation of China(No.51134002)
文摘Iron was recovered from blast furnace dust and high-phosphorus oolitic hematite in the presence of Na2CO3 and CaCO3 additives. The functions of Na2CO3 and CaCO3 during the coreduction roasting process were investigated by XRD and SEM-EDS analyses. Results indicate that these additives not only hinder the reduction of fluorapatite, CaCO3 also decreases the P content of direct reduced iron(DRI) by increasing the reduction alkalinity. P remains as fluorapatite in the slag, which can be removed by grinding and magnetic separation under optimal conditions. The Na2CO3 promotes hematite reduction and improves the iron recovery(εFe) by replacing the FeO from fayalite, which results in quick growth and aggregation of metallic iron and improvement of ε(Fe) in DRI. A DRI with 91.88 mass% Fe, and 0.065 mass% P can be achieved at a recovery of 87.86 mass% under the optimal condition.