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1.
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2.
Elemental mobility based on major element geochemistry from 58 horizons related to six paleosols profiles in a typical Miocene — Pliocene Siwalik fluvial sequence in the NW Himalaya has been reported here. The paleosols developed over felsic parent material of fine to medium grained sandstone indicate notable enrichment of sesquioxides (Al2O3 = 29 % and Fe2O3 = 54 %) depicting significant leaching and dissolution. The depletion of base cations (mean wt% of Na2O = 0.24; CaO = 0.51) and SiO2 (mean wt% = 63.6) in the pedogenic layers and its enrichment in the parental material (mean wt% of Na2O = 0.44; CaO = 1.3; SiO2 = 70.1) shows a good gradient of elemental mobility due to pedogenesis. Bivariate plots of the base ratios (Na2O/K2O, CaO/K2O, and MgO/K2O) vs. Al2O3 reveal independent distribution for parent material, pedogenic horizons and the incipient zone indicating the gradual addition/removal of immobile/mobile elements with varying pedogenesis. Discontinuous and segmented pattern of the geochemical parameters enables discrimination of multiple pedogenic episodes and recognition of soil welding processes in the multistorey composite paleosols. We also test the applicability of the geochemical climofunctions: the Mean Annual Precipitation (MAP) and Mean Annual Temperature (MAT); that demands more data for calibration in the Siwalik paleosols.  相似文献   

3.
The ambient pressure elastic properties of a natural clinopyroxene (C2/c symmetry) from Kilbourne Hole, NM have been determined. In terms of end-members, diopside (CaMgSi2O6), hedenbergite (CaFeSi2O6), jadeite (NaAlSi2O6), cosmochlor (NaCrSi2O6), and Mg-Tschermak (MgAl(AlSi)O6), its composition is Di72He9Jd3Cr3Ts12. The analytic density, based on chemistry and cell parameters is 3.327 (0.003) g/cm3. The elastic constants [c11, c12, c13, c15, c22, c23, c25, c33, c35, c44, c46, c55, c66] are [273.8 (0.9), 83.5 (1.3), 80.0 (1.1), 9.0 (0.6), 183.6 (0.9), 59.9 (1.6), 9.5 (1.0), 229.5 (0.9), 48.1 (0.6), 76.5 (0.9), 8.4 (0.8), 73.0 (0.4), 81.6 (1.0)] GPa where uncertainties are reported at the 95% confidence level. The aggregate (mean of Hashin-Strikman bounds) adiabatic bulk modulus is 117.2 (0.7) GPa, and the shear modulus is 72.2 (0.2) GPa. Although measured moduli are broadly consistent with trends in elasticity versus atomic volume, deviations from the systematics would produce significant (percent level) changes in calculated velocities for candidate mantle mineral assemblages. The compositional dependence of elasticity for several clinopyroxenes is explored on the basis of just the Di+He and Jd+Ts mole fractions. The bulk modulus lies within experimental uncertainties of the linear mixture of end-member properties while the shear modulus deviates by 3%. Received: 29 September 1997 / Revised, accepted: 4 March 1998  相似文献   

4.
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5.
Minor element abundances in olivines of the Sharps (H-3) chondrite   总被引：2，自引：0，他引：2  
Olivine crystals in 21 chondrules from the Sharps (H-3) chondrite were analyzed for CaO, Al2O3, Cr2O3, MnO, TiO2, NiO, and Na2O. The chondrules studied include representatives of all major types found in Sharps, and the mean fayalite contents of their olivine range from 1 to 28 %. Those olivines which contain less than 18 mol.% fayalite typically contain or occur with metallic nickel-iron; the others are metal-free.Na2O is below detectability (0.01 wt.%) in all cases, and the abundances of Al2O3, NiO and TiO2 are also typically very low. MnO varies simply and directly with FeO.Cr2O3 varies widely (0.03–0.21%) and several lines of evidence suggest that Cr is dominantly trivalent. It is concluded that FO 2 was rarely less than 10–11 atm. during the crystallization of the chondrules in Sharps.  相似文献   

6.
Tropospheric ozone (O3) acts as greenhouse gas and air pollutant. Over the last 100 years, tropospheric O3 levels increased above background by factor 2.5 in the northern hemisphere and by factor 3–4 across Europe. The gas poses a potential risk to forest ecosystems in many mountain areas. There, O3 concentrations result from long-range transport and are influenced by removal processes (dry deposition, gas phase and cloud removal, reduction on wet aerosols). Most trend studies analyzed annual-mean concentrations. We focus on winter O3 trends at high altitudes in the German/Czech Erzgebirge (period 1981–2020) to avoid major noise from photochemical reactions and to better explain recent O3 behavior in Central Europe. Hourly air quality and meteorological data from four stations (Carlsfeld, CAR; Fichtelberg, FIB; Schwartenberg, SWB; Zinnwald, ZIW) were used to analyze O3 trends. The data can explain the complex O3 formation and removal behavior.Three distinct periods of O3-concentration trends can be discerned: i) Until the late 1980s, characterized by relatively low O3 concentrations. ii) Dramatic transformation in the 1990s with changing air pollution in Central Europe. Strong O3-concentration increase at FIB is corroborated by data from CAR and ZIW. iii) Stabilization as of 1997/98, when O3 concentrations remained at the same level for all four stations, despite general regional air pollution decrease. Key results are:a) Winter O3 trends mainly depend on O3 concentration of air masses transported to the stations and on the O3-removal potential (ORP) of clouds, not on local formation processes.b) ORP differs between clouds and fog, depending on droplet chemical composition. Fog from the North Bohemian Basin showed the highest ORP due to reaction with liquid phase S(IV). However, O3 reactions with O2− in fog droplets showed high ORP, too, depending on cloud-water pH values and NOx concentrations.c) So-called “Bohemian fog” decreased, and with it related ORP, while that of clouds from westerly and northwesterly air masses remained nearly unchanged since 1997/98.d) Decreasing ORP in clouds and fog (= higher O3 concentration) oppose decreasing O3 concentrations in westerly air masses. Both effects lead to unchanged O3 levels in the Erzgebirge since 1997/98.  相似文献   

7.
The supposedly second finding of rare arsenosilicate cervandonite-(Ce) in the world is characterized. The mineral was recognized in the ore-bearing metasomatic rocks of the Berezitovoe gold-base metal deposit (Upper Priamurye, Russian Far East) in association with quartz, biotite, muscovite, orthoclase, garnet (almandine-spessartine), tourmaline, basic plagioclase, and sulfides. The cervandonite is represented by optically homogeneous and heterogeneous aggregates with visible crystals from 10 fum to 0.1–0.3 mm in size. Based on the microprobe analysis, the average chemical composition of the homogeneous cervandonite-(Ce) aggregates is as follows (wt %): Ce2O3 - 13.00, La2O3 - 5.70, Nd2O3 - 5.20, Pr2O3 - 1.41, Y2O3 - 0.77, Sm2O3 - 0.77, Eu2O3 - 0.23, Gd2O3 - 0.54, Dy2O3 - 0.31, ThO2 - 1.12, UO2 - 0.30, TiO2 - 12.86, Al2O3 - 9.24, Fe2O3 - 8.93, FeO - 2.68, CaO - 0.14, SiO2 - 19.98, As2O3 - 16.19. The comparative study of the cervandonite-(Ce) from the Berezitovoe deposit and the analogous minerals from the Alpine mica gneiss of Mt. Pizzo Cervandone (Central Alps) showed that the former mineral can be assigned to a new variety of cervandonite-(Ce) in terms of its compositional features. This variety is characterized by an ordered stoichiometric composition corresponding to the simpler theoretical formula (Ce,Nd,La)(Fe3+, Fe2+, Ti4+, Al)3 (Si2As3+)3O12.  相似文献   

8.
王頔 《岩矿测试》2021,(5):783-792
应用碱熔-磷钒钼黄光度法以检测波长420nm分析产铀矿石硅酸盐中P2O5时,样品中共存元素铁与钒钼酸铵显色剂发生络合反应,显现与磷钒钼黄相同的黄色而同时被检测,产生正干扰使P2O5测定结果偏高。本文对碱熔-磷钒钼黄光度法测定产铀矿石硅酸盐P2O5的检测波长进行波长校正消除铁干扰。以Fe2O3作为硅酸盐全分析中铁的考核量,变换检测波长从400nm到480nm,考察Fe2O3不同添加量（0.00~0.70mg/mL）分别对0.20μg/mL、2.00μg/mL和8.00μg/mL P2O5吸光值的影响。实验表明：①当P2O5检测波长从国家标准方法420nm变换到450nm,校正了产铀矿石中铁对P2O5分析结果产生的正干扰。以产铀岩石国家标准物质GBW04117~GBW04122为验证样品,样品中Fe2O3和P2O5的含量均在校正范围内。②在450nm下对产铀岩石、玄武岩、泥质灰岩国家标准物质P2O5进行分析,其结果符合误差要求,方法精密度（RSD）在1.1%~15.7%之间。可以满足硅酸盐样品、产铀矿石等相似基体样品P2O5检测要求。③此波长校正方法操作简单易行,为碱熔-磷钒钼黄光度法测定产铀矿石硅酸盐P2O5提供了方法补充。  相似文献   

9.
Enthalpy of formation and third law entropy for andradite (Ca3Fe2Si3O12) and hedenbergite (CaFeSi2O6) at standard state have been retrieved from experimental P-T-f(O2) data on the stability relations of these phases. The data for hedenbergite were combined with the thermodynamic data for related phases (Berman 1988) to formulate the geobarometers based on the reactions CaFeSi2O6+2CaAl2Si2O8+2FeTiO3= Ca3Al2Si3O12+Fe3Al2Si3O12+2TiO2 (CPG-IR), 3CaFeSi2O6+3CaAl2Si2O8+3FeTiO3=Ca3Al2Si3O12 +2Fe3Al2Si3O12+3CaTiSiO5 (CPG-IS) and 3CaFeSi2O6+3CaAl2Si2O8=2Ca3Al2Si3O12+ Fe3Al2Si3O12+3SiO2 (CPG-O). The geobarometers involving rutile and sphene are proposed for the first time. In several granulite terranes, pressures have been estimated from the three geobarometers for basic granulites and charnockitic suite of rocks containing the above assemblages. In clinopyroxene-garnet-plagioclase-quartz-ilmenite-rutile assemblages, pressures obtained from CPG-IR are within ±500 bars of pressures calculated from the CPG-Q barometer. However, if rutile is absent, the pressures computed from the CPG-IR barometer are 300 to 1,200 bars higher than those calculated from the CPG-Q barometer. For maximum differences in pressures obtained from the two equilibria TiO2 activity [a(TiO2)] in the rocks is calculated to be 0.8. The sphene-bearing geobarometer (CPG-IS) also registers pressures comparable (<±500 bars) to those obtained from the CPG-Q barometer. The close agreement in pressure values obtained from the CPG-IR and the CPG-IS equilibria with those registered by the CPG-Q geobarometer in assemblages containing quartz implies that the rutile- and sphene-bearing geobarometers which do not involve quartz, can also be applied to estimate pressures from quartz-absent assemblages-assemblages which are not amenable to quantitative geobarometry using existing formulations.  相似文献   

10.
The National Centre for Compositional Characterisation of Materials (NCCCM) / Bhabha Atomic Research Centre (BARC) and National Aluminium Company Limited (NALCO), India have produced an Indian origin bauxite certified reference material (CRM), referred to as BARC-B1201, certified for major (Al2O3, Fe2O3, SiO2, TiO2, loss on ignition - LOI) and trace contents (V2O5, MnO, Cr2O3, MgO). Characterisation was undertaken by strict adherence to ISO Guides. A method previously developed and validated in our laboratory, using single step bauxite dissolution and subsequent quantitation (of Al2O3, Fe2O3, SiO2, TiO2, V2O5, MnO, Cr2O3 and MgO) by ICP-AES (SSBD ICP-AES) was used for homogeneity studies and an inter-laboratory comparison exercise (ILCE) of the candidate CRM. LOI was determined by thermo-gravimetric analysis. Property values were assigned after an ILCE with participation from seventeen reputed government and private sector laboratories in India. The CRM was certified for nine property values: Al2O3, Fe2O3, SiO2, TiO2, V2O5, MnO, Cr2O3, MgO and LOI, which are traceable to SI units.  相似文献   

11.
Geochemical and geochronological studies were conducted on basalts and laterites from the Bolaven Plateau in southern Laos in order to evaluate the mobility and mineralization of REE, Y and Sc during laterization. The basalts are classified into three categories: (i) small volumetric alkali basalt (eruption age: 15.7 Ma), large volumetric olivine tholeiite (1.2 Ma) and quartz tholeiite with olivine tholeiite (younger than 0.5 ± 0.2 Ma). Formation of REE minerals during laterization result in mobilization and fractionation of REE and Y in laterite profiles. Occurrence of florencite‐(Ce) in a laterite profile derived from alkali basalt immobilizes REE (particularly LREE) and this leads the laterites to be enriched in LREE relative to the parent basalt. Few positive Ce anomalies in this profile suggest that florencite‐(Ce) [(Ce)Al3(PO4)2(OH)2] formation was followed by CeO2 precipitation due to the change of redox condition. In tholeiite‐derived laterite profiles, florencite is not recognized and REE and Y tend to be depleted relative to the parent basalts with positive Ce anomalies. This is interpreted as scavenging REE3+ except for Ce4+ from the laterite profile in oxidizing conditions. Sc behaves similarly to Fe during laterization and it is more abundant in the tholeiitic laterite than that in the alkali basaltic laterite. Results of sequential extraction indicate that REE of the alkali basaltic laterite are contained in residual phase, which is dominantly florencite‐(Ce), but they are rarely present in ion‐adsorption phase. It is concluded that basaltic laterites have a low potential of REE resource in terms of low REE contents and a difficulty in REE extraction.  相似文献   

12.
The Neoproterozoic evolution of the Jiangnan Orogen is important for understanding the tectonic history of South China. As a volcanic-sedimentary sequence developed in the Nanhua rift, the Banxi Group preserves the records of important magmatic and tectonic events linked to the assembly and breakup of the Rodinia supercontinent. In this study, we report the results from whole-rock major-and trace-element concentrations, with zircon LA-(MC)-ICP-MS U-Pb ages, trace elements and Lu-Hf isotopic comp...  相似文献   

13.
A strongly reduced native iron-bearing andesite breccia from Disko contains graphite-rich modified shale xenoliths with magnesian spinels. These spinels are free from or very poor in ferric iron and vary considerably within the MgO-FeO-Cr2O3-Al2O3 compositional space. Through a simple substitution of the type 3 (Mg, Fe)2+ ⇆ 2(Al, Cr)3++□vacancy, the spinels vary from stoichiometric (Mg, Fe)2+ (Al, Cr)3+ 2O4 towards (Al, Cr)2O3. The simple substitution of Cr for Al suggests that Cr was accepted into the spinel structure as Cr3+, despite the reduced nature of the enclosing andesite. The most magnesian spinels are cation deficient spinelss in the synthetic systems MgO-Al2O3 and MgO-Al2O3-Cr2O3. The absence of exolved (Al, Cr)2O3-component is probable due to rapid quenching.  相似文献   

14.
 Quantum-mechanical solid-state calculations have been performed on the highest-pressure polymorph of magnesium aluminate (CaTi2O4-type structure, Cmcm space group), as well as on the low-pressure (Fd3ˉm) spinel phase and on MgO and Al2O3. An ab initio all-electron periodic scheme with localized basis functions (Gaussian-type atomic orbitals) has been used, employing density-functional-theory Hamiltonians based on LDA and B3LYP functionals. Least-enthalpy structure optimizations in the pressure range 0 to 60 GPa have allowed us to predict: (1) the full crystal structure, the pV equation of state and the compressibility of Cmcm-MgAl2O4 as a function of pressure; (2) the phase diagram of the MgO–Al2O3–MgAl2O4 system (with exclusion of CaFe2O4-type Pmcn-MgAl2O4), and the equilibrium pressures for the reactions of formation/decomposition of the Fd3ˉm and Cmcm polymorphs of MgAl2O4 from the MgO + Al2O3 assemblage. Cmcm-MgAl2O4 is predicted to form at 39 and 57 GPa by LDA and B3LYP calculations, with K 0=248 (K′=3.3) and 222 GPa (K′=3.8), respectively. Results are compared to experimental data, where available, and the performance of different DFT functionals is discussed. Received: 31 January 2001 / Accepted: 16 May 2001  相似文献   

15.
The paper presents data on accessory rutile in Cr–V-rich metamorphic rocks of the Slyudyanka crystalline (granulite) complex in the southern Baikal region. The geochemical features of the studied rutile are unique in combining isomorphic admixtures typical of the mineral from either mafic (Cr) or felsic igneous and associated metasomatic rocks (W), as well as the Nb and V contents, which are abnormally high for metamorphic rocks. The highest concentrations of these elements are as follows, wt %: 15.38 V2O3, 4.33 Cr2O3, 11.09 Nb2O5, 12.36 WO3. These high W and V contents have never been measured in natural rutile. The studied rutile is compared to that from other Cr–V-bearing rocks in the world and various genetic types. The optimal isomorphic substitutions and probable conditions of their realization are discussed.  相似文献   

16.
The techniques of electron paramagnetic resonance (EPR) were used to measure the concentration ratio of Eu2+ to Eu3+ in quenched CaMgSi2O6, Ca3Si3O12, and CaAl2Si2O8 liquids as functions of partial pressure of oxygen and temperature. The redox equilibrium of the Eu ions was described by the reaction 4Eu3+ + 202? = 4Eu2+ + O2. The reduction of Eu3+ to Eu2+ was endothermic, and for CaMgSi2O6 and Ca3Al2Si3O12 liquids the mean value of ΔH0 and the standard deviation from that mean were 25 ± 7 kcal/mole.The magnitude of the Eu anomaly in the distribution coefficients is discussed in terms of the compositions of the solid and liquid phases.  相似文献   

17.
陕西华阳川铀稀有多金属矿床伴生大量的稀土资源,其矿石类型独特、组分复杂,系统的稀土矿物学工作将揭示矿石主要稀土矿物类型、稀土元素赋存状态,进而对矿床开发中稀土元素综合利用及选冶技术提供重要参考.本文在岩相学基础上,利用电子探针、扫描电镜对陕西华阳川铀稀有多金属矿床矿石中的稀土独立矿物与含稀土矿物进行系统研究,在矿石中发...  相似文献   

18.
The best known cause for colors in insulating minerals is due to transition metal ions as impurities. As an example, Cr3+ is responsible for the red color of ruby (α-Al2O3:Cr3+) and the green color of eskolaite (α-Cr2O3). Using X-ray absorption measurements, we connect the colors of the Cr x Al2−x O3 series with the structural and electronic local environment around Cr. UV–VIS electronic parameters, such as the crystal field and the Racah parameter B, are related to those deduced from the analysis of the isotropic and XMCD spectra at the Cr L2,3-edges in Cr0.07Al1.93O3 and eskolaite. The Cr–O bond lengths are extracted by EXAFS at the Cr K-edge in the whole Cr x Al2−x O3 (0.07≤x< 2) solid solution series. The variation of the mean Cr–O distance between Cr0.07Al1.93O3 and α-Cr2O3 is evaluated to be 0.015 Å (≈1%). The variation of the crystal field in the Cr x Al2−x O3 series is discussed in relation with the variation of the averaged Cr–O distances.  相似文献   

19.
Three new crystalline phases differing in Si/Al ratio have been synthesized from compositions along the join NiAl2O4-Ni2SiO4. Four reversible univariant equilibria involving these new phases plus Ni2SiO4 (olivine) have been located within the P-T region studied (1 atm–40 kb, 1000–1700° C); an invariant point occurs near 22 kb, 1150°C.All three new phases are orthorhombic. Precession photographs and electron microprobe analyses yield the following information:Phase I: 5NiO·3Al2O3·SiO2 = 3NiAl2O4·Ni2SiO4, Pmma, a=5.67, b=11.51, c=8.10 (Å)Phase II: 7NiO·3Al2O3·2SiO2 = 3NiAl2O4· 2Ni2SiO4, Imma, a=5.66, b=17.32, c=8.11Phase III: 3NiO· Al2O3· SiO2 = NiAl2O4·Ni2SiO4, Imma, a=5.68, b=11.49, c=8.12Comparison with known structures suggests that these three phases plus NiAl2O4 spinel and high pressure Ni2SiO4 spinel belong to a homologous series based on a cubic close oxygen packing of the formula: M2n O n}-1 (T n O3n+1) where M and T are octahedrally and tetrahedrally coordinated cations, respectively. When n=1 the formula for spinel is obtained; n = 2 for phase I and phase III, both similar to the beta-phase of orthosilicates; and n = 3 for phase II which is related to the manganostibite structure.Similar phase equilibria and structural relations may occur on other joins of the aluminateorthosilicate type. Furthermore, the occurrence of such structural modifications between the spinel (aluminate) and olivine (orthosilicate) compositions suggests that there could be a corresponding polymorphic series between the olivine and spinel forms of orthosilicates.  相似文献   

20.
石家庄城市土壤重金属空间分布特征及源解析   总被引：9，自引：1，他引：8       下载免费PDF全文
文章对石家庄市土壤重金属含量水平进行了研究,通过采集的220个城市土壤样品,分析了Al2O3、As、Cd、Cr、Cu、Ni、Pb、Zn等8个元素。结果表明,与土壤背景值相比,石家庄市土壤中除As和Al2O3外的重金属含量总体明显升高。采用相关分析和主成分分析,对土壤重金属元素来源进行解析,认为有3种主要来源:一是Cu、Zn、Pb与人类的工业生产、汽车尾气排放有关。二是Ni、Cr、Cd除与工业生产有关外,还与燃煤活动排放有关。三是As、Al2O3主要与土壤母质有关(自然来源)。石家庄城市土壤的重金属含量高值区与工业区域、交通分布相吻合。  相似文献   

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