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1.
Re-Os dating of the Raobazhai ultra mafic massif in North Dabie 总被引:6,自引:2,他引:4
JIN Yongbin ZHI Xiachen MENG Qing GAO Tianshan & PENG ZichengSchool of Earth Space Sciences. University of Science Technology of China Hefei China 《科学通报(英文版)》2004,49(5):508-513
The ultramafic massif at Raobazhai in North Dabie is located in the suture zone between the Yangtze craton and North China eraton. The Re-Os isotope compositions of the massif are used to decipher the origin and tectonics of the ultramafic rocks involved in continental subduction and exhumation. Fifteen samples were collected from five drill holes along the main SE-NW axis of the Raobazhai massif. Major and trace element compositions of the samples show linear correlations between MgO, Yb and Al_2O_3. This suggests that the massif experienced partial melting with variable degrees and is from fertile to deplete in basaltic compositions. Nine selected samples were analyzed for Re-Os isotope compositions. Re contents range from 0.004 to 0.376 rig/g, Os contents from 0.695 to 3.761 ng/g, ~(187)Re/~(188)Os ratios from 0.022 to 2.564 and ~(187)Os/~(188)Os ratios from 0.1165 to 0.1306. These indicate that the massif is a piece of continental lithospheric mantle with variable depletion. Using the positive corre 相似文献
2.
Weidong Sun Xiachen Zhi Zicheng Peng Zhaorong Wang Ningjie Ge Xinhua Zhou 《科学通报(英文版)》1998,43(18):1575-1575
The osmium isotopic ratio of187Os/188Os ranging from 0.126 to 0.127 for the primitive upper mantle (PUM) is obtained according to the correlation between187Os/188Os and Al2O3 of mantle-derived xenoliths and orogenic peridotites, which consists with Allegre and Luck’s ALM value and similar to Yin’s
nuggets uniform reservoir (NUR) value. It shows that the Os isotope ratio is lower than enstatite or ondinary chondrites,
similar to carbonaceous chondrites (CV3). 相似文献
3.
YU ChunMei ZHENG JianPing GRIFFIN W L 《科学通报(英文版)》2007,52(20):2847-2853
In situ Re-Os isotopes of sulfides in peridotitic xenoliths from Cenozoic Hannuoba basalts were analyzed by LAM-MC-ICPMS. The suifides developed two types of occurrences including silicate-enclosed and interstitial. In the enclosed sulfides, 187Os/188Os vary from 0.1124 to 0.1362 and 187Re/188Os from 0.0026 to 1.8027. In the interstitial ones, 187Os/188Os have a range from 0.1174 to 0.1354 and 187Re/188Os from 0.0365 to 1.4469. The oldest age, calculated by TRD for the enclosed sulfides, is 2.1 Ga. An isochron age of 2.3±1.2 Ga is obtained by five grains of enclosed sulfides and primitive mantle. The sulfides used have lower Re-Os isotopic ratio than primitive mantle. Meanwhile, an isochron age of 645±225 Ma is given by all in- terstitial sulfides and the enclosed sulfides with higher Re-Os isotopic ratio due to Re addition after man- tle formation. In addition, the model age of 1.3 Ga recorded by one interstitial sulfide, having similar TDM and TRD, should be meaningful to deep thermal event. The coexistence of different ages, revealed by in situ Re-Os isotope, indicates frequently-occurring mantle events beneath Hannuoba area. 相似文献
4.
Re-Os isotopic constraint to the age of in komatiites in the Neoarchean Guyang greenstone belt, North China Craton 总被引:1,自引:0,他引:1
The 2.5 Ga Guyang greenstone belt is a major lithological unit in the northwestern part of the North China Craton. Komatiites have recently been identified to occur within the lower part of the meta-volcanic sedimentary sequence of the greenstone belt. The biggest komatiite near Guyang has been mapped out, which is 500 m long and 50 m wide lenticular block. Re-Os isotopic compositions of 9 samples were analyzed to date the komatiites. The Os contents are from 0.88 to 2.63 ppb, identical with typical komatiites, and slightly lower than the normal mantle. The 187Os/188Os ratios are from 0.1115 to 0.1197, which are lower enough to exclude the origin of Phanerozoic magma as widely developed in adjacent areas. The calculated Re depletion model ages (T RD) are from 1346 to 2454 Ma, among them the oldest age of 2454 Ma gives the minimum evaluation for the formation age of the Guyang komatiite. Therefore, the komatiites are a part of the Guyang greenstone belt, indicating high degree melting of mantle during ~2.5 Ga crustal growth event. 相似文献
5.
ZHI XiaChen QIN Xie SHI RenDeng HONG JiAn 《科学通报(英文版)》2007,52(16):2269-2274
Three Chinese ordinary chondrites,including Jilin (H5),Boxian (LL3.8) and Lujiang (LL6),have been studied for their Re and Os abundances and Os isotopic composition in whole-chondrite samples,separated magnetic and nonmagnetic fractions,and nodules. The results indicate that the Re and Os abundances of the whole-chondrite samples are in the ranges of corresponding H-and LL-Groups,respectively. The Re and Os abundances of magnetic fraction from Boxian and Lujiang are within the range of high-Os ⅡAB and ⅢAB irons,whereas those of nonmagnetic fractions of Boxian and Lujiang are lower than the whole-chondrite values. The Re and Os abundances of nodules in Jilin are in the range of the LL-Group. 187Re/188Os and 187Os/188Os ratios of the three whole chondrites are in the range of ordinary chondrites which locate around the isochron of ⅡAB ⅢAB irons. 187Re/188Os and 187Os/188Os ratios of the magnetic and nonmagnetic fractions from Boxian have a larger difference. The nonmag-netic fraction of Lujiang may contain a recent addition of Re,which causes deviation of the 187Re/188Os ratio from the irons isochron. The Re and Os abundances of nodules in Jilin are lower than those of the whole-chondrite,but their 187Os/188Os ratios are higher than that of the whole chondrite. 相似文献
6.
GuoLiang Zhang ShaoQing Jiang HeGen Ouyang DaiGeng Chen XueBo Yin XiaoYuan Wang XiaoMei Wang ZhiGang Zeng 《科学通报(英文版)》2010,55(16):1643-1656
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. 相似文献
7.
为了在高铝钢中得到最低的溶解氧含量,必须找到CaO-Al2O3-MgO体系中Al2O3活度最低点的位置。因此,利用炉渣结构的共存理论,结合CaO-Al2O3-MgO相图,利用Matlab软件计算了CaO-Al2O3-MgO体系中Al2O3活度。通过对不同模型计算出的CaO-Al2O3渣系中Al2O3活度值比较,表明其变化趋势基本相同。由共存理论对CaO-Al2O3-MgO体系中Al2O3活度进行计算得到,在一定的MgO含量下,随着CaO含量增加,炉渣中Al2O3活度降低;在一定的CaO含量下,随着MgO含量增加,炉渣中Al2O3活度降低,且Al2O3活度最低值在CaO和MgO均达饱和的区域。 相似文献
8.
Shang-hao Tong Yong Li Ming-wei Yan Peng Jiang Jia-jia Ma Dan-dan Yue 《矿物冶金与材料学报》2017,24(9):1061-1066
The Al-Al2O3-MgO composites with added aluminum contents of approximately 0wt%, 5wt%, and 10wt%, named as M1, M2, and M3, respectively, were prepared at 1700℃ for 5 h under a flowing N2 atmosphere using the reaction sintering method. After sintering, the Al-Al2O3-MgO composites were characterized and analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results show that specimen M1 was composed of MgO and MgAl2O4. Compared with specimen M1, specimens M2 and M3 possessed MgAlON, and its production increased with increasing aluminum addition. Under an N2 atmosphere, MgO, Al2O3, and Al in the matrix of specimens M2 and M3 reacted to form MgAlON and AlN-polytypoids, which combined the particles and the matrix together and imparted the Al-Al2O3-MgO composites with a dense structure. The mechanism of MgAlON synthesis is described as follows. Under an N2 atmosphere, the partial pressure of oxygen is quite low; thus, when the Al-Al2O3-MgO composites were soaked at 580℃ for an extended period, aluminum metal was transformed into AlN. With increasing temperature, Al2O3 diffused into AlN crystal lattices and formed AlN-polytypoids; however, MgO reacted with Al2O3 to form MgAl2O4. When the temperature was greater than (1640 ±10)℃, AlN diffused into Al2O3 and formed spinel-structured AlON. In situ MgAlON was acquired through a solid-solution reaction between AlON and MgAl2O4 at high temperatures because of their similar spinel structures. 相似文献
9.
Re-Os dating of auriferous pyrite from the Zhenyuan super-large gold deposit in Ailaoshan gold belt, Yunnan Province, Southwestern China 总被引:3,自引:0,他引:3
GuiYong Shi XiaoMing Sun WeiJian Pan BeiMing Hu WenJun Qu AnDao Du Chao Li 《科学通报(英文版)》2012,57(35):4578-4586
Zhenyuan gold deposit is the largest super large gold deposit in the Ailaoshan gold belt,but its precise mineralization age is still lack.Re-Os isotopic age of the auriferous pyrite from the Zhenyuan gold deposit was determined by using a high-resolution inductively coupled plasma mass spectrometry(HR-ICP-MS).The pyrite samples were decomposed in carius tubes,Os was separated by distillation and Re was extracted by acetone,respectively.The results show that the Re-Os isochron age is 229±38 Ma(MSWD=2.0,confidence level is 95%),with an initial 187 Os/188 Os value of 0.68±0.24 and a corresponding Os value of 442±91.The Re/Os ratios of the pyrite vary from 40.8 to 100.5.The data suggest that at least one important ore-forming event was occurred during Indosinian epoch,and the ore-forming materials probably derived from mixed sources of crustal and mantle,while the later dominated.The Ailaoshan composite orogen experienced complicated evolutional processes,including formation of Precambrian-Early Paleozoic basement,subduction and orogenesis of Late Paleozoic era,collisional orogenesis of Late Hercynian-Indosinain epoch,and extensional or striking orogenesis of Yanshainan-Cenozoic epoch.The polycycle tectonic evolution and magmatism in this area caused multi-stage and superposition metallization characteristics of the Zhenyuan gold deposit:the mineralization probably occur mainly during the Indosinian collisional orogeny,while the minor gold ores of altered granite-porphyry and altered lamprophyre may be formed in the late superposition metallization. 相似文献
10.
Xiao-xiong Luo Hai-tao Zhang Xing Han Shi-jie Guo Dan-dan Chen Jian-zhong Cui Hiromi Nagaumi 《矿物冶金与材料学报》2016,23(6):637-644
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. 相似文献
11.
Petrochemical characteristics of leucogranite and a case study of Bengbu leucogranites 总被引:1,自引:0,他引:1
Leucogranites have a relatively narrow variation in SiO2 content (70.5%-75.5%). Giving similar SiO2 content, leucogranites have relatively higher Al2O3 (〉13.5%) and lower TFeO + MgO (〈2.5%) contents than those of normal granites. These petrochemical characteristics suggest that leucogranites are de- rived from partial melting at relatively low temperature and are not significantly affected by fractional crystallization. In the present study, we propose that the Al2O3 vs SiO2 and TFeO + MgO vs SiO2 dia- grams can be used to distinguish leucogranites from normal granites. In addition, we report the major element compositions of the Jurassic granitic intrusions from Jingshan-Tushan-Mayishan in the Bengbu area, east-central China. Using the Al2O3 vs SiO2 and TFeO + MgO vs SiO2 diagrams and the comparison with the High Himalayan leucogranites in mineralogical and petrochemical characteristics, we suggest that the Jingshan-Tushan-Mayishan intrusions belong to a leucogranite belt. Similar to those of the High Himalayan leucogranites, the Bengbu leucogranites have low Mg# values, indicating that they resulted from low temperature dehydration partial melting of the subducted continental crust of the South China Block at the crustal depth. 相似文献
12.
XIA Qiongxia ZHI Xiachen LI Jianghai & HUANG Xiongnan . School of Earth Space Sciences University of Science Tech- nology of China Hefei China . Department of Geology Peking University Beijing China Correspondence should be addressed to Zhi Xiachen 《科学通报(英文版)》2004,49(23):2515-2520
The Os isotopic composition and evolution of con-vecting upper mantle (CUM) are an important and diffi-cult scientific issue related to the distributions of PGEs inearth’s interior and the accretion history of the earth. De-termination of 187Os/188Os of modern CUM has been at-tempted via analyses of abyssal peridotites, mid-oceanridge basalts (MORB), MORB glasses and sulfides. Abyssal peridotites, which are mantle samples re-covered from the ocean ridges, represent the upperm… 相似文献
13.
The compositional differences between mid-ocean-ridge and ocean-island basalts place important constraints on the form of mantle convection. Also, it is thought that the scale and nature of heterogeneities within plumes and the degree to which heterogeneous material endures within the mantle might be reflected in spatial variations of basalt composition observed at the Earth's surface. Here we report osmium isotope data on lavas from a transect across the Azores archipelago which vary in a symmetrical pattern across what is thought to be a mantle plume. Many of the lavas from the centre of the plume have lower 187Os/188Os ratios than most ocean-island basalts and some extend to subchondritic 187Os/188Os ratios-lower than any yet reported from ocean-island basalts. These low ratios require derivation from a depleted, harzburgitic mantle, consistent with the low-iron signature of the Azores plume. Rhenium-depletion model ages extend to 2.5 Gyr, and we infer that the osmium isotope signature is unlikely to be derived from Iberian subcontinental lithospheric mantle. Instead, we interpret the osmium isotope signature as having a deep origin and infer that it may be recycled, Archaean oceanic mantle lithosphere that has delaminated from its overlying oceanic crust. If correct, our data provide evidence for deep mantle subduction and storage of oceanic mantle lithosphere during the Archaean era. 相似文献
14.
为使莱钢高炉冶炼中具有合理渣系,保障高炉长期稳定运行,对其炉渣二元碱度及MgO、Al2O3、FeO含量对炉渣黏度的影响进行研究。结果表明,为保证较低的黏度,高炉渣保持二元碱度约为1.15、w(MgO)为8%~10%较适宜;当高炉渣Al2O3含量达到一定值时,其黏度会明显提高,高炉渣中Al2O3含量最好应控制在15%以内;高炉渣黏度随着FeO含量的增加而显著降低,初渣中较高FeO含量可改善其流动性能。 相似文献
15.
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. 相似文献
16.
Re-Os dating of gold-bearing arsenopyrite of the Maoling gold deposit,Liaoning Province,Northeast China and its geological significance 总被引:1,自引:0,他引:1
YU Gang YANG Gang CHEN Jiangfeng QU Wenjun DU Andao HE Wei 《科学通报(英文版)》2005,50(14):1509-1514
The Maoling gold deposit, one of the large gold deposits in eastern Liaoning Province, NE China, is an arsenopyrite-disseminated gold deposit with a resource of approximately 25 t Au and an average Au grade of 3.2 g/t. Six arsenopyrites closely related to Au mineralization of the Maoling gold deposit are dated by Re-Os technique and define a Re-Os isochron with an age of 2316±140 Ma, which suggests that the deposit was formed in the Paleoproterozoic era rather than in the Indosinian period as some early researchers suggested. High initial ^187Os/^188Os ratio of 1.32±0.48 indicates a crustal derivation of the ore-forming material of the deposit, which may be derived from rocks of the Gaixian formation of the Liaohe Group. Furthermore,the result also implies that the age of the Gaixian Formation in the Maoling district is older than 2316±140 Ma. 相似文献
17.
LIU YongChun LIU JunFeng HE Hong YU YunBo XUE Li 《科学通报(英文版)》2007,52(15):2063-2071
Heterogeneous oxidation of carbonyl sulfide (OCS) on mineral oxides including SiO2, Fe2O3, CaO, MgO, ZnO and TiO2, which are the main components of atmospheric particles, were investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), ion chromatography (IC), temperature-programmed desorption (TPD), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) methods. The main products and intermediates of the heterogeneous oxidation of OCS on these oxides were identified with in situ DRIFTS and IC. The reaction mechanism and kinetics were also discussed. It is found that the reaction mechanism on these mineral oxides is the same as that on Al2O3 for the same final products and the intermediates at room temperature. Namely, OCS can be catalytically oxidized to produce surface SO4^2- species and gaseous CO2 through the surface hydrogen thiocarbonate (HSCO2-) and HSO; species. The activity series for heterogeneous oxidation of OCS follows: Al2O3 ≈ CaO 〉 MgO 〉 TiO2 ≈ ZnO 〉 Fe2O3 〉 SiO2. The specific area, basic hydroxyl and surface basicity of these oxides have effect on the reactivity. This study suggests that heterogeneous reactions of OCS on mineral dust may be an unneglectable sink of OCS. 相似文献
18.
Effect of slag composition on the cleanliness of 28MnCr5 gear steel in the refining processes
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The equilibrium reaction between CaO—Al2O3—SiO2—MgO slag and 28MnCr5 molten steel was calculated to obtain the suitable slag composition which is effective for decreasing the oxygen content in molten steel. The dissolved oxygen content [O] in molten steel under different top slag conditions was calculated using a thermodynamic model and was measured using an electromotive force method in slag–steel equilibrium experiments at 1873 K. The relations among [O], the total oxygen content (T.O), and the composition of the slag were investigated. The experimental results show that both [O] and T.O decrease with decreasing SiO2 content of the slag and exhibit different trends with the changes in the CaO/Al2O3 mass ratio of the slag. Increasing the CaO/Al2O3 mass ratio results in a decrease in [O] and an increase in T.O. To ensure that T.O ≤ 20 ppm and [O] ≤ 10 ppm, the SiO2 content should be controlled to <5wt%, and the CaO/Al2O3 mass ratio should be in the range from 1.2 to 1.6. 相似文献
19.
Re-Os dating of Mo-bearing black shale of the Laoyaling deposit,Tongling, Anhui Province,China 总被引:3,自引:0,他引:3
YANG Gang CHEN Jiangfeng DU Andao QU Wenjun & YU Gang School of Earth Space Sciences University of Science Technology of China Hefei ChinaNational Research Center of Geoanalysis Beijing China 《科学通报(英文版)》2004,49(13):1396-1400
Laoyaling is a typical stratiform deposit in the Tongling district and the molybdenum orebody is hosted by black shale of the Dalong Formation of the Upper Permian system. Eight black shale samples from the Laoyaling Mo orebody were dated by Re-Os technique using ICP-MS, which give an isochron age of 234.2±7.3 Ma with an initial 187Os/188Os ratio of 1.37±0.39. The apparent Re-Os age is a few million years younger than the depositional age of the Late Permian. The young isochron age may be caused by the later hydrothermal disturbance or mass fractionation during ICP-MS measurement. However, the obtained isochron age is close to the depositional age and far earlier than those of the Late Yanshanian intrusions. It suggests that the Mo ore of the Laoyaling deposit is sedimentary in origin and not related to the Late Yanshanian magmatism. Black shales of the Upper Permian are distributed widely in the Mid-Lower Yangtze region, our result is important for understanding the ore-forming processes in the regio 相似文献
20.
To investigate the formation mechanism of calcium hexaluminate (CaAl12O19, CA6), the analytically pure alumina and calcia used as raw materials were mixed in CaO/Al2O3 ratio of 12.57:137.43 by mass. The raw materials were ball-milled and shaped into green specimens, and fired at 1300–1600°C. Then, the phase composition and microstructure evolution of the fired specimen were studied, and a first principle calculation was performed. The results show that in the reaction system of CaO and Al2O3, a small amount of CA6 forms at 1300°C, and greater amounts are formed at 1400°C and higher temperatures. The reaction is as follows: CaO·2Al2O3 (CA2) + 4Al2O3 → CA6. The diffusions of Ca2+ in CA2 towards Al2O3 and Al3+ in Al2O3 towards CA2 change the structures in different degrees of difficulty. Compared with the difficulty of structural change and the corresponding lattice energy change, it is deduced that the main formation mechanism is the diffusion of Ca2+ in CA2 towards Al2O3. 相似文献