Fluid inclusions hidden in coesite-bearing zircons in ultrahigh-pressure metamorphic rocks from southwestern Sulu terrane in eastern China

Fluidinclusionstudiesarepowerfultoolsfordeci-pheringthefluidevolutionandfluid-rockinteractionin-volvingultrahigh-pressure(UHP)metamorphismofcrustalrocksatmantledepths.Thecompositionandprop-ertiesoffluidinclusionscanreflectthephysico-chemicalconditionsofthefluidsduringplatesubduction,UHPmetamorphismandexhumation.However,UHPmeta-morphicrockscommonlyexperiencedconsiderablede-compressionrelatedtotherapidexhumationprocess.Thishascausedtheinternalpressureoftheinclusionstrappedinthemetamorphicmin…     

Pure CO2 fluids in the Sarekoubu gold deposit at southern margin of Altai Mountains in Xinjiang, West China

Sarekoubu gold deposit occurs in metamorphosed acid volcanic rocks and volcaniclastic rocks of Devonian Kangbutiebao Formation along the southern margin of Altai Mountains in Xinjiang, West China. Pyritization, silicification and carbonatization are developed in wallrocks, and main gold mineralization stages are pyrite-quartz stage (Ⅱ)and polymetallic sulfide stage (Ⅲ). Primary fluid inclusions are often seen in main gold mineralization stages, which are almost pure CO2 liquid inclusions (Lco2) under room temperature with high densities of 0.85--1.07 g/cm^3. CO2-rich inclusions (Lco2-LH2O) and H2O-rich inclusions (LH2O-LCo2)are subordinate. Fluid inclusions in stage Ⅰ (polymetallic sulfide stage) are more complex than in stage Ⅱ, containing CO2-CH4 system with -78.1-61.9℃ of solid CO2 melting temperatures and -33.7-17.7℃ of partial homogenization temperatures. The trapping pressures of high densities are estimated to be 150-350 MPa. Laser Raman microprobe was used to confirm the composition of pure CO2 liquid inclusions. δ^13C values of CO2 inclusions range from -10.73‰ to -21.15‰, which are similar to some of fluids in the mantle-derived minerals that contain surface organic carbon by subduction recycling. These characteristics differ from many hydrothermal gold deposits. CO2 fluids have a regional source related to post-collisional orogeny.     

High density methane inclusions in Puguang Gasfield: Discovery and a T-P genetic study

Based on measurement of homogenization temperature of inclusions and Raman spectral analysis, high density methane inclusions were discovered in the Triassic reservoirs of Puguang Gasfield. The methane inclusions show a homogenization temperature Th = -117.5― -118.1℃, a corresponding density of 0.3455―0.3477 g/cm3, and a Raman scatter peak v1 shift varying between 2911―2910 cm-1, which signifies a very high density of methane inclusions. The salt water inclusions paragenetic with methane inclusions show a homogenization temperature Th=170―180℃. Based on the composition of methane inclusions as determined by Raman spectra, PVTsim software was used to simulate the trapping pressure for high density methane inclusions in geologic history, and the trapping pressure was found to be as high as 153―160 MPa. Even though Puguang Gasfield is currently a gas pool of normal pressure, and the fluid pressure for the gas pool ranges between 56―65 MPa. However, data from this study indicates that remarkable overpressure may be generated at the stage of mass production of gas cracked from oils in Cretaceous, as high density methane inclusions constitute key evidence for overpressure in gas pool in geologic history. Meanwhile, discovery of small amounts of H2S, CO2 or heavy hydrocarbon in part of the high density methane inclusions indicates that the geochemical environment for trapping of inclusions may be related to formation of H2S. Therefore, the observation results can help to explore the thermochemical sulfate reduction （TSR） conditions for oil cracking and H2S formation.     

In situ cryogenic Raman spectroscopic studies on the synthetic fluid inclusions in the systems H2O and NaCl-H2O

Fluid inclusions of the H2O-salt systems constitute the major fluid inclusion types preserved in the nature. The salts commonly present in the fluid inclusions are NaCl, KCl, CaCl2 and MgCl2[1,2]; among them NaCl is the dominant species. The most powerful…     

Ch4-rich fluid inclusions in the Yushigou mantle peridotite and their implications, North Qilian Mountains, China

Studies were carried out on the early phase of fluid inclusions which occur in residual olivines in harzburgite from the Yushigou ophiolitic mantle peridotite, the North Qilian Mountains. Components of these inclusions, analyzed by micro laser Raman spectroscopy, are dominantly CH, (70%–95%) with minor H₂, N₂, H₂S, CO₂,C₂H₄, C₂H₆, and C₃H₆ but there are no H₂O,CO and SO₂. The highly CH₄-rich fluid was probably derived from an ancient deep mantle. This discovery plays an important role in all-round understanding of the fluid property of the upper mantle, especially the ancient oceanic upper mantle.     

Characteristics of inclusions in high-Al steel during electroslag remelting process

The characteristics of inclusions in high-Al steel refined by electroslag remelting (ESR) were investigated by image analysis, scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). The results show that the size of almost all the inclusions observed in ESR ingots is less than 5 μm. Inclusions smaller than 3 μm take nearly 75% of the total inclusions observed in each ingot. Inclusions observed in ESR ingots are pure AlN as dominating precipitates and some fine spherical Al₂O₃ inclusions with a size of 1 μm or less. It is also found that protective gas operation and slag deoxidation treatment during ESR process have significant effects on the number of inclusions smaller than 2 μm but little effects on that of inclusions larger than 2 μm. Thermodynamic calculations show that AlN inclusions are unable to precipitate in the liquid metal pool under the present experimental conditions, while the precipitation of AlN inclusions could take place at the solidifying front due to the microsegregation of Al and N in liquid steel during solidification.     

Isothermal Kinetics of the Pentlandite Exsolution from mss/Pyrrhotite Using Model-Free Method

Introduction Pyrrhotite(Fe,Ni)1?xS and pentlandite(Fe,Ni)9S8areimportant constituents of primary nickel sulfide oredeposits.Pentlandite is invariably associated with pyr-rhotite.At high temperatures(above610℃)(Fe,Ni)1?xS has the NiAs structure and is kno…     

Modification of MgO·Al<Subscript>2</Subscript>O<Subscript>3</Subscript> spinel inclusions in Al-killed steel by Ca-treatment

The modification of MgO·Al₂O₃ spinel inclusions in Al-killed steel by Ca-treatment has been studied by industrial trials and thermodynamic calculations. In the industrial trials, samples were taken systematically during the refining process in which the molten steel was treated by calcium, and the characters of the inclusions were analyzed using scanning electron microscopy (SEM) and energy dispersive spectra (EDS). The effects of Ca-treatment were evaluated by tracking the compositions of the inclusions. The results show that the modification of MgO·Al₂O₃ spinel inclusions by Ca-treatment is effective and the transformation sequence of the inclusions during the refining is Al₂O₃→MgO·Al₂O₃→liquid complex inclusions. The modification of spinel inclusions by Ca-treatment was calculated by FactSage6.0 utilizing its free-energy minimization routines. The results of thermodynamic calculations indicate that spinel inclusions are easier to be modified than Al₂O₃ inclusions and the spinel inclusions in 30CrMo steel would transform to liquid complex inclusions when the content of dissolved Ca in the molten steel exceeds 1×10⁻⁶. Also, the results show that adding more calcium into the molten steel would lower the contents of Al₂O₃ and MgO and increase the CaO content of the inclusions, while the change in SiO₂ content is little.     

The fluid inclusions in jadeitite from Pharkant area, Myanmar

A lot of liquid-gas and liquid-gas-solid inclusions were found in Pharkant jadeitites, northwestern Myanmar and their characteristics, geological setting and porphyroclastic jadeites with inclusions in them were described in detail. The results analyzed by Raman spectrometer showed that the component of liquid-gas phase and solid phase (daughter minerals) in fluid inclusions is H₂O + CH₄ and jadeite separately. The results indicated that Pharkant jadeitites were crystallized from H₂O + CH₄ bearing jadeitic melt which may originate from mantle. The P-T conditions in which the jadeitites were crystallized were speculated to be T ＞650℃, P ＞1.5 GPa.     

Magma mixing in upper mantle: Evidence from high Mg<Superscript>#</Superscript> olivine hosted melt inclusions in MORBs near East Pacific Rise 13°N

Early formed high-Mg^# olivine phenocrysts during evolution of MORB magmas usually host melt inclusions, which record im-portant information about the early-stage evolution of magma. Five MORB samples from near East Pacific Rise (EPR) 13°N vary little in K/Ti (0.07–0.12), Tb/Lu (1.72–1.84) and Sm/Nd (0.310–0.332) and have similar REEs patterns, indicating that depleted upper mantle has similar mineral composition. Sixty-five initial melt inclusions derived by correcting olivine fractionation and “FeO-Loss” show averagely higher MgO contents than their host rocks. Melt inclusions have higher CaO/Al₂O₃ ratios than their host rocks, and these CaO/Al₂O₃ ratios are positively and negatively correlated with MgO and Na₂O respectively, suggesting that these magmas have experienced high pressure crystallization of clinopyroxene. Average crystallization pressure, which is calculated based on the pressure dependence of clinopyroxene crystallization, is 0.83–0.25 GPa, and implys that these melt inclusions are averagely trapped in mantle depth of ~24 km. These melt inclusions show negative correlations of Ca₈/Al₈ and Na₈ with Fe₈, and wider ranges of Ca₈/Al₈, Na₈, Fe₈ and K/Ti than their host rocks, suggesting that these melt inclusions formed by mixing magmas of different melting degrees and depths. According to the average value and ranges of Ca₈/Al₈, Na₈, Fe₈ and K/Ti, these magmas would necessitate other mixing ends in shallow crust except in upper mantle. The compositional diversity of melt inclusions in MORBs phenocrysts cannot always be used to indicate magma mixing and crystallization in shallow crust, and melt inclusions in high Mg^# olivine formed under mantle pressure must be excluded in study of the magma process at crustal level. This study shows that, in EPR, MORBs have experienced mixing of magmas formed by different melting degrees and depths in the mantle.     

Fluid inclusions evidence for differential exhumation of ultrahigh pressure metamorphic rocks in the Sulu terrane

Since the discovery of coesite and diamond inclusions in eclogites from the Dabie-Sulu orogen, east-central China[1―3], this largest ultrahigh pressure (UHP) metamor- phic terrane in the world has attracted extensive scientific interests. A number of hydrous minerals such as zoisite, phengite, magnesite and talc have been found in the UHP rocks, showing that fluids have played an important role in this type of extreme metamorphic evolution[4―8]. Sev-eral techniques have been applied to th…     

Inclusion variations and calcium treatment optimization in pipeline steel production

SiCa line and SiCaBaFe alloy were injected into liquid pipeline steel at the end of LF refining as calcium treatment, and samples were taken from the ladles, mould, and slabs. Analysis of Ca content and inclusions shows that Ca content in steel decreases obviously in the following process after calcium treatment; the compositions, morphology, and sizes of inclusions also vary much in the production; primary inclusions in the ladles prior to calcium treatment are mainly Al₂O₃ inclusions, but they turn to fine irregular CaS-CaO-Al₂O₃ compound inclusions after the treatment, then become fine globular CaO-Al₂O₃ inclusions in the mould, and finally change to a few larger irregular CaS-CaO-Al₂O₃ complex inclusions in the slabs. Thermodynamic study reveals that inclusion variations are related with the preferential reactions among Ca, Al₂O₃, and S and the precipitation of S in CaO-Al₂O₃ inclusions with high sulfur capacity. New evaluation standards for calcium treatment in high-grade pipeline steel were put forward according to the inclusion variations and requirements of pipeline steel on inclusion controlling, and the calcium process was studied and optimized.     

Zn release from fluid inclusions in a natural sphalerite

The type, size, and compositions of fluid inclusions in a natural sphalerite were investigated and the total concentration of Zn released from the fluid inclusions was measured. To compare the total concentration of Zn released from the fluid inclusions with that dissolved from the sphalerite itself, dissolution experiments and theoretical calculations for the dissolution equilibrium of the sphalerite were also performed. The results indicate that large numbers of fluid inclusions with various sizes exist in the sphalerite, which can be divided into four types, i.e., pure gaseous inclusions, pure liquid inclusions, gas-liquid inclusions, and gas-liquid inclusions containing solid minerals. These inclusions were broken open during the grinding process, and their compositions were released to the solution. The total concentration of Zn released from these inclusions reaches 18.35×10?6 mol/L, which is much higher than that of Zn dissolved from the sphalerite itself (1.93×10?6 mol/L) and the theoretical calculation value (2.73×10?8 mol/L).     

Top slag refining for inclusion composition transform control in tire cord steel

Controlling conditions for inclusion plasticization were calculated by FactSage, and the steel/slag reaction equilibration time was determined by pre-equilibrium experiments. Laboratory experiments with different top slags were carried out in 90 min, and industrial tests were performed based on the results of calculation and laboratory experiments. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used to determine the morphology and composition of inclusions in tire cord steel. It is found that the shape of inclusions can be controlled well, and the composition of inclusions varies in the industrial test as the following transformation route:MnO-Al₂O₃-SiO₂→CaO-Al₂O₃-SiO₂→MnO-Al₂O₃-SiO₂. Inclusion plasticization can be achieved by controlling the binary basicity of top slag (CaO/SiO₂ by mass) around 1.0 and the (Al₂O₃) content in top slag below 10wt%. Under these controlling conditions in the industrial test, almost all of inclusions in the wire rods achieve plastic deformation.     

Development of inclusions in 3104 alloy melt during heating and holding treatments

Developments in the contents of different typical inclusions in 3104 alloy melt were described during heating and holding processing. The settling process of inclusion particles was investigated by measuring the contents of inclusions in the surface, center, and bottom layers of the molten metal. In the results, main inclusions observed and determined by Prefil and PoDFA methods are MgO, Al₂O₃, spinel (MgAl₂O₄), and TiB₂ particles or thin films. It is found that some small particles of Al₂O₃ and MgO are transformed into spinel particles, and the formation rate increases as the temperature and the holding period of melt increase. The content of inclusions increases from 3.37 mm2·kg-1 to 7.54 mm2·kg-1 and then decreases to 3.08 mm2·kg-1 after holding for 90 min. This is attributed to a settling phenomenon and a significant increase in settling velocity after holding for 60 min. The content of inclusion particles decreases by means of settlement and flotation in liquid aluminum with an increase in holding time. The theoretical analysis and experiment results are in essential agreement with those from industrial production.     

Clogging behavior of submerged entry nozzles for Ti-bearing IF steel

The nozzle clogging behavior of Ti-bearing IF steel was studied by metallographic analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). According to the experimental results, nozzle clogging primarily appears three layers. There are a lot of large-sized iron particles in the inner layer and mainly slag phase in the middle and outer layers. The principal clog constituents of the inner layer are loose alumina cluster inclusions and granular shaped alumina inclusions, containing iron particles. The clog constituents of the middle layer are mainly dendrite alumina inclusions. The primary phases existing in nozzle clogging are FeO·TiO₂ and FeO·Al₂O₃ besides α-Al₂O₃ and α-Fe. The FeO·TiO₂ phases among the deposits adhere the deposits together firmly enough to lead to the inferior castability of Ti-bearing ultra low carbon steel compared with that of Ti-free low carbon Al-killed steel.     

滇西富碱斑岩型多金属矿稀有气体同位素组成特征及地质意义*

通过对滇西富碱斑岩型多金属矿区稀有气体同位素组成的研究表明,黄铁矿和石英脉等流体包裹体中3He/4He值主要为0.160 8~3.470 0 Ra,远高于地壳特征值,而整体略低于地幔特征值;20Ne/22Ne和21Ne/22Ne平均值分别为11.271和0.032 2,接近地幔同位素组成;40Ar/36Ar和38Ar/36Ar平均值分别为395.51和0.197 6,均高于大气比值,而低于MORB比值;128~136Xe/130Xe值与大气相比均表现出过剩的特征。综合研究表明,滇西多金属矿区包裹体中稀有气体同位素组成在显示含矿流体的幔源特征的同时,又表现出强烈的地壳特征;成矿流体主要源于深部地幔,在参与交代蚀变过程中,其性质由熔浆向热液过渡,同时引发壳幔物质叠加混染,正是这种流体作用构成了滇西新生代富碱斑岩多金属成矿的内在统一制约因素。     

Glass melt inclusion in clinopyroxene from Linqu Cenozoic basalt, Shandong Province, China

Melt inclusions or glasses usually occur in spinel- facies peridotitic xenoliths entrained in the global ba- salts[1―4], and olivine phenocrysts and/or xenocrysts carried in the intermediate-mafic volcanic rocks (such as basalts, basaltic andesites and h…     

Acidithiobacillus ferrooxidans对黄铜矿和镍黄铁矿的浸出

以黄铜矿和镍黄铁矿为研究对象,初步探讨了Acidithiobacillus ferrooxidans对黄铜矿和镍黄铁矿的浸出.结果表明:有细菌参与下,黄铜矿的浸出率是无菌体系浸出率的2.41倍;镍黄铁矿的浸出率是无菌体系浸出率的1.91倍,细菌在矿物的浸出过程中起到了很好的促进作用.浸出过程中会有黄色的黄钾铁矾(K[Fe3(SO4)2(OH)6])沉淀产生,黄钾铁矾附着在矿体表面,产生"钝化现象",严重阻碍矿物的氧化.     

LF精炼过程中SAE8620钢所含MgO复合夹杂物分析

采用非水溶液电解的方法,萃取分离出SAE8620齿轮钢中含MgO复合夹杂物,利用扫描电镜、能谱分析仪对夹杂物的组成、类型和形貌特征进行分析。结果表明,SAE8620齿轮钢在LF精炼过程中,含MgO复合夹杂物中MgO、CaO含量逐渐增加,SiO2含量逐渐减少,Al2O3含量呈先上升后下降的趋势;夹杂物的形貌多不规则,呈块状且棱角分明;夹杂物类型主要为SiO2-Al2O3-MgO、SiO2-MgO、SiO2-Al2O3-CaO-MgO等,此类夹杂物的尺寸较大、熔点较高,直接影响钢材的质量和使用性能。