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The role of carbonate-fluoride melt immiscibility in shallow REE deposit evolution

Geoscience Frontiers 2019年第2期10卷 527-537页

作者： Jindrich Kynicky Martin P.Smith Wenlei Song Anton R.Chakhmouradian Cheng Xu Antonin Kopriva Michaela Vasinova Galiova Martin Brtnicky Mendel University in Brno Brno University of Technology University of Brighton University of Manitoba School of Earth and Space Sciences Peking University

The Lugiin Gol nepheline syenite intrusion, Mongolia, hosts a range of carbonatite dikes mineralized in rare-earth elements(REE). Both carbonatites and nepheline syenite-fluorite-calcite veinlets are host to a previously unreported macroscale texture involving pseudo-graphic intergrowths of fluorite and calcite. The inclusions within calcite occur as either pure fluorite, with associated REE minerals within the surrounding calcite, or as mixed calcite-fluorite inclusions, with associated zirconosilicate minerals. Consideration of the nature of the texture, and the proportions of fluorite and calcite present(～29 and 71 mol%,respectively), indicates that these textures most likely formed either through the immiscible separation of carbonate and fluoride melts, or from cotectic crystallization of a carbonatefluoride melt. Laser ablation ICP-MS analyses show the pure fluorite inclusions to be depleted in REE relative to the calcite. A model is proposed, in which a carbonate-fluoride melt phase enriched in Zr and the REE, separated from a phonolitic melt, and then either unmixed or underwent cotectic crystallization to generate an REE-rich carbonate melt and an REE-poor fluoride phase. The separation of the fluoride phase(either solid or melt) may have contributed to the enrichment of the carbonate melt in REE, and ultimately its saturation with REE minerals. Previous data have suggested that carbonate melts separated from silicate melts are relatively depleted in the REE, and thus melt immiscibility cannot result in the formation of REE-enriched carbonatites. The observations presented here provide a mechanism by which this could occur, as under either model the textures imply initial separation of a mixed carbonate-fluoride melt from a silicate magma. The separation of an REEenriched carbonate-fluoride melt from phonolitic magma is a hitherto unrecognized mechanism for REE-enrichment in carbonatites, and may play an important role in the formation of shallow magmatic R

关键词： Silicate-carbonate-fluoride melt immiscibility Carbonatite Alkaline syenite Shallow REE deposit Lugiin Gol Mongolia

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ESTIMATION OF SULFUR SOLUBILITY AND PREDICTION OF SULFIDE LIQUID immiscibility IN SILICATE MELTS

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Science China Chemistry 1989年第10期32卷 1262-1270页

作者：马鸿文 Institute of Geology Academia Sinica Beijing 100012 PRC

A set of 201 experimental data on solubility of sulfur in silicate melts was collectedfrom literature to formulate the changes of sulfur solubility as a function of bulk compo-sition of the melts and pressure, temperature, and the fugacity of oxygen and sulfur. Aregular solution model and a polynomial function have been put forward, from which sol-ubility of sulfur in natural silicate magmas can be estimated. Synthetic application of twomethods makes it possible to evaluate activity of FeS in a silicate melt, which will be po-tentially valuable for predicting immiscibility of sulfide liquid in magmatic processes.

关键词： magma thermodynamics sulfur solubility sulfide immiscibility

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Modelling of Sulfide immiscibility in Silicate Magmas

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Science China Chemistry 1994年第9期37卷 1138-1146页

作者：马鸿文 China University of Geosciences Beijing 100083 PRC

In dry silicate magmas equilibrated at or below FMQ buffer,sulfur is present mainly as S^(2-).The solution of sulfur can be represented by the reaction: FeO+(1/2)S_2=FeS+(1/2)O_2,assuming that activity of FeS in the coexisting sulfide liquid is close to unity,and that the activity of FeO in the silicate liquid fits the modified quasi-lattice melt model,a thermodynamical model for predicting solubility of sul- fur in dry silicate magmas has been established in this paper by fitting 147 experimentally determined sul- fur solubility data from *** following result is obtained:ΔH°=(158.718±3.970)J/mol, ΔS°=(33.361±2.682)J/K·mol,and ΔV°=(0.524±0.046)·10^(-5)J/Pa·*** model canbe used to predict solubility of sulfur,and to simulate sulfide liquid immiscibility in natural magmatic processes.

关键词： silicate magma sulfur solubility sulfide immiscibility orthomagmatic deposit

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Metastable phase separation and rapid solidification of undercooled Co_(40)Fe_(40)Cu_(20) alloy

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Chinese Physics B 2018年第11期27卷 305-309页

作者： Xiaojun Bai Yaocen Wang Chongde Cao Research and Development Institute of Norlhwestern Polytechnical University in Shenzhen Shenzhen 518057 China Department of Applied Physics Northwestern Polytechnical University Xi'an 710072 China

The metastable liquid phase separation and rapid solidification behaviors of Co_（40） Fe_（40） Cu_（20） alloy were investigated by using differential thermal analysis（DTA） in combination with glass fluxing and electromagnetic levitation（EML） techniques. The critical liquid phase separation undercooling for this alloy was determined by DTA to be 174 K. Macrosegregation morphologies are formed in the bulk samples processed by both DTA and EML. It is revealed that undercooling level, cooling rate, convection, and surface tension difference between the two separated phases play a dominant role in the coalescence and segregation of the separated phases. The growth velocity of the（Fe,Co） dendrite has been measured as a function of undercooling up to 275 K. The temperature rise resulting from recalescence increases linearly with the increase of undercooling because of the enhancement of recalescence. The slope change of the recalescence temperature rise versus undercooling at the critical undercooling also implies the occurrence of liquid demixing.

关键词： undercooling metastable phase separation rapid solidification immiscibility

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Microstructure Evolution of Cu-Pb Monotectic Alloys Processed in Drop Tube

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Journal of Materials Science & Technology 2002年第1期18卷 73-76页

作者： Cao, CD Wei, BB Northwestern Polytech Univ Dept Appl Phys Xian 710072 Peoples R China

Rapid solidification of Cu-Pb monotectic alloys has been accomplished during free fall in a 3 m drop tube. Both macrosegregated and uniformly dispersed structures are observed in Cu-40 wt pct Pb alloy droplets, whereas droplets of composition Cu-64 wt pct Pb exhibit only macrosegregation morphologies. The microstructures are strongly dependent on droplet size. The higher undercooling tends to facilitate liquid phase separation and results in more extensive macrosegregation in smaller droplets. There exists a pronounced tendency for the Pb-rich liquid to occupy the surface of the droplets of both compositions, resulting from the quite lower surface tension of the Pb-rich phase and causing a Pb-rich layer at the surface of the solidified droplet. The nucleation of monotectic cells in the Cu-40 wt pct Pb droplets with dispersed structures preferentially occurs at the droplet surface. A single nucleation event takes place more frequently as droplet size is reduced.

关键词： Rapid solidification Undercooling immiscibility Containerless processing Low-gravity Monotectic

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Phase separation and rapid solidification of liquid Cu_(60)Fe_(30)Co_(10) ternary peritectic alloy

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Science China(Physics,Mechanics & Astronomy) 2007年第4期50卷 509-518页

作者： DAI FuPing, CAO ChongDe & WEI BingBo Department of Applied Physics, Northwestern Polytechnical University, Xi’an 710072, China 1. Department of Applied Physics Northwestern Polytechnical University Xi’an 710072 China

The metastable liquid phase separation and rapid solidification of Cu60Fe30Co10 ternary peritectic alloy were investigated by using the drop tube technique and the differential scanning calorimetry method. It was found that the critical temperature of metastable liquid phase separation in this alloy is 1623.5 K, and the two sepa- rated liquid phases solidify as Cu(Fe,Co) and Fe(Cu,Co) solid solutions, respec- tively. The undercooling and cooling rate of droplets processed in the drop tube increase with the decrease of their diameters. During the drop tube processing, the structural morphologies of undercooled droplets are strongly dependent on the cooling rate. With the increase of the cooling rate, Fe(Cu,Co) spheres are refined greatly and become uniformly dispersed in the Cu-rich matrix. The calculations of Marangoni migration velocity (VM) and Stokes motion velocity (VS) of Fe(Cu,Co) droplets indicated that Marangoni migration contributes more to the coarsening and congregation of the minor phase during free fall. At the same undercooling, the VM/VS ratio increases drastically as Fe(Cu,Co) droplet size decreases. On the other hand, a larger undercooling tends to increase the VM/VS value for Fe(Cu,Co) drop- lets with the same size.

关键词： ternary peritectic alloy metastable immiscibility rapid solidification reduced gravity liquid phase separation

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

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Acta Geologica Sinica(English Edition) 2007年第4期81卷 637-648页

作者： YU Jinjie ZHANG Qi MAO Jingwen YAN Shenghao Institute of Mineral Resources Chinese Academy of Geological Scien~s Beijing 100037 Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029

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 an

关键词： iron deposit apatite rare earth elements strontium isotope immiscibility ore magma,Ningwu

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Experimental observation of deep crust fluid-NaCl aqueous solution at elevated temperatures and pressures and its significance

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Chinese Science Bulletin 1999年第7期44卷 654-660页

作者： Ronghua Zhang Shumin Hu Chinese Acad Geol Sci Open Res Lab Geochem Kinet Beijing 100037 Peoples R China

In order to reveal the nature of deep crust fluids, the phase relations of NaCI-saturated solution at high temperatures and pressures in a hydrothermal diamond anvil cell (HDAC)are investigated. Salinity of the solutions observed is about 35%—50%. The temperatures for the observation range from 25 to 850℃ and the pressures from 1 atm to about 1 GPa. A supercritical single phase, liquid phase (L), vapor phase (V), solid phase (H), L + H, H + V + L and the near-critical phases L + V can be observed. A two-phase (L + V) immiscibility field for the NaCI solution has been discovered to lie in a wide range of temperatures and pressures:from 250( ± 3) to 721℃. Within this field there are two parts, where the upper high temperature part of the two-phase regions is very unstable in character. It is possible to observe a 'critical phenomenon'. In some of our experiments an 'explosion' almost constantly occurred at the interface between the liquid and vapor phases, making the interface obscure, and a

关键词： two-phase immiscibility critical phenomenon solution structure.

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The Characteristics and Genetic Mechanism of Igneous Topazites in South China

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Acta Geologica Sinica(English Edition) 1996年第1期70卷 33-45,109页

作者： Liu Changshi, Shen Weizhou and Wang DeziDepartment of Earth Sciences, Nanjing U niversity, Nanjing, Jiang su Fei Zhenbi Department of Earth Sciences Nanjing U niversity Nanjing Jiangsu

Igneous topazites found recently in South China are closely associated with F-rich granites in time and space. They have a typical igneous porphyritic texture. The phenocrysts are topaz and quartz, while the groundmass consists mainly of prismatic or acicular topaz microlites and anhedral quartz. Compared with granites, topazites are rich in SiO2 (65.06%-81.12% ) and Al2O3 (13.01%-18.09%) but poor in MgO and Na2O and strongly peraluminous with A/NKC = 3.204-37.313. Geochemically, the rocks are evidently depleted in Sr and Ba, but enriched in Sn, W, Nb and F. The concentrations of Sn and partial W in the topazites are 1-2 orders of magnitude higher than the average of acid rocks. The F-riched granites related to the topazites in the area usually have much higher ISr (0.7103-0.7460) and δ18OQ‰ (9.5-14.24), but lower INdCT) (-4.8- 9.4). It suggests that the topazite is similar to S-type granites in genesis. Hydroxylated silicate melt inclusions, consisting of several grains of quartz and aqueous fluids, have been found in the quartz phenocrysts. The entrapment temperature of these inclusions is about 520℃.

关键词： topazite inclusion immiscibility

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Hydroxyl Group Modifies Aggregation Behavior of a Non-ionic Hydro-fluorocarbon Hybrid Surfactant by Disrupting Interfacial Water

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Chinese Journal of Chemical Physics 2020年第5期33卷 623-627,I0057-I0062,I0079页

作者： Ying-ying Peng Yi-fan Liao Wei Gan Qing-xiao Tong Qun-hui Yuan Flexible Printed Electronics Technology Center and School of ScienceHarbin Institute of Technology(Shenzhen)Shenzhen 518055China Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Material of Guangdong ProvinceShantou UniversityShantou 515063China State Key Laboratory of Advanced Welding and Joining and School of Materials Science and EngineeringHarbin Institute of Technology(Shenzhen)Shenzhen 518055China

Two non-ionic hydro-fluorocarbon hybrid surfactants with and without hydroxyl groups were synthesized and *** exhibited good thermal stability and superior surface *** was observed that the hydroxyl group had a profound effect on modifying the surface tension of their solutions and the morphology of the formed *** effect may be attributed to the rearranging of the alkane group from above the air/aqueous surface to below it and the disrupting of the interfacial water structure induced by the hydroxyl *** work provides a strategy to weaken the immiscibility between hydrocarbon and fluorocarbon chains by modifying their orientational structure at the interface,thus it is helpful for the design of surfactants with varied interfacial properties.

关键词： Hydro-fluorocarbon hybrid surfactant Surface activity immiscibility Micelle Water

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