Compressibility and structure behaviour of maruyamaite (K-tourmaline) from the Kokchetav massif at high pressure up to 20 GPa

Mineralogy and Petrology - The structural behaviour of maruyamaite (K-dominant tourmaline) X(K0.54Na0.28Ca0.19)Y(Mg1.3Al1.17Fe0.39Ti0.14)Z(Al5Mg)[Si5.95Al0.05O18](BO3)3V,W[O1.69(OH)2.31] from the...     

The First Find of Oxyborates in Rocks of the Norilsk-1 Intrusion (Northwestern Siberian Platform)

Doklady Earth Sciences - In the taxitic gabbro-dolerites of the upper contact zone of the Norilsk-1 intrusion, five boron minerals were found: kotoite Mg3(BO3)2, suanite Mg2B2O5, warwickite...     

东喜马拉雅构造结发现的富碳硼镁钛石:硼镁钛石的新亚种

在东喜马拉雅构造结火成碳酸岩脉中发现富碳硼镁钛石。晶体结构与化学成分分析表明,该矿物的分子式为(Mg_1.30,Ti_0.32,Fe_0.30,Al_0.10)_2.02[(B_0.51,C_0.42)_0.93O3]O。这提供了在[BO₃]原子团中B可被其它元素替换的第一个实例,暗示该矿物可能形成于高温高压的环境下。     

等离子体发射光谱法同时测定大洋富钴结壳中硅锰铁钙镁铝钛

大洋富钴结壳试样经ＨＣｌ＋ＨＮＯ３＋ＨＦ溶解,在０．２ｍｏｌ／ＬＨＦ和０．１３ｍｏｌ／ＬＨ３ＢＯ３介质中,用感耦等离子发射光谱法同时测定Ｓｉ、Ｍｎ、Ｆｅ、Ｃａ、Ｍｇ、Ａｌ、Ｔｉ元素的含量。方法经国家标准物质ＧＢＷ０７２４９大洋多金属结核验证,其结果与标准值相符,精密度ＲＳＤ〈３．２％（ｎ＝６）;已应用于太平洋富钴结壳中多元素分析。     

与遂安石共生的电气石矿物学特征及其地质意义

在对宽甸砖庙硼矿床的研究中发现了电气石与遂安石共生的现象,电气石为钙镁电气石,由电子探针分析结果计算的晶体化学式为:(Ca_0.59Na_0.355K_0.06)(Mg_2.557Fe_0.1512+Ti_0.013Cr_0.002Ni_0.006)(Al_5.416Fe_0.5642-（BO₃）₃Si _6.16 O₁₆（OH）₄,同围岩中的电气石相比:（1）淡绿色,多色性弱;（2）折射率为Ne=1.646,Ns=1.624;（3）成分上富Mg（MgO 11.47％）和Ca（CaO3.14％）;相对贫Na（Na₂O 1.09％）,Fe（FeO4.63％）和Al（Al₂O₃26.69％）（4）结构上d₁₀₁=3.393A,a₀=15.957±0.002,c₀=7.227±0.001;（5）红外光谱晶格Si-O₄四面体振动I₁₀₀₁>I₁₀₃₆。这些标型特征具有硼矿床的找矿指示意义。     

哀牢山─金沙江裂谷系岩石中镁铁云母成分特征及其岩石学意义

本区的Mg－Fe云母是富镁黑云母及金云母，MF＞1．35，［Mg／（Mg＋Fe3+＋Fe2+＋Mn）］＞0.65，［（Fe3+＋Fe2+）／（Fe3+＋Fe2+＋Mg）］＜0．4，属于富镁、富碱、高硅、贫铁类型云母。根据Mg－Fe云母的成分及形成的物化条件，表明其寄生岩石属于富碱，浅成一超浅成的幔源岩石。     

Revised magnesium abundances in galactic halo and disk stars

A differential analysis of the magnesium abundances in 61 F-K dwarfs and subgiants with metallicities ?2.6<[Fe/H]<+0.2 is performed based on published observational data. Fundamental parameters for 36 stars are determined: T _eff from V-K and V-R; logg from HIPPARCOS parallaxes, and [Fe/H] and ξ_t from Fe II lines. The computations allow for non-LTE effects in the formation of the Mg I lines. For most of the stars, the standard errors in the Mg abundances do not exceed 0.07 dex. The metallicity dependence of [Mg/Fe] is analyzed. Magnesium shows a constant overabundance relative to Fe of 0.46±0.06 dex for metallicities ?2.6<[Fe/H] $\overline {[Mg/Fe]} = + 0.22 dex$ ) compared to the [Mg/Fe] values for other stars with similar [Fe/H].     

Water soluble components of PM_(10) in Chongqing, China

1Introduction Particleswithanaerodynamicdiameterof< 10μmarerecognizedasinhalabaleparticlesandhave beenfoundtobewidelyassociatedwithhealthprob lems(Chapmanetal.,1997).Theywouldalsoinflu enceclimateandvisibilitythroughanumberofimpor tantatmosphericprocesses(Horvath,1993). Rapiddevelopmentofurbanconstructionandrap idgrowthofpopulationhaveexacerbatedChongqing’s pollution.Althoughsulfurdioxidehasbeenreducedby morethan60%incontrasttothevaluein1991,the concentrationsofparticulatematterarestil…     

微量萤石样品消解技术及其Sm-Nd同位素高精度热离子质谱法测试

Sm-Nd同位素被广泛地应用于萤石样品的定年和示踪。萤石样品Sm-Nd同位素测试的化学分离中,一般采用酸溶解样品,但氢氟酸和硝酸与萤石反应不完全,由于萤石(CaF_2)特殊化学结构导致氟离子会和稀土元素离子形成难溶稀土氟化物,易导致Sm-Nd亏损,因而对于Sm、Nd含量较低的萤石样品,Sm-Nd同位素测试需要较大样品用量(100~200 mg)。本研究建立了一种利用HNO_3+HClO_4+H_3BO_3溶解萤石样品的消解方法,在萤石溶解过程中加入H_3BO_3可有效提高Sm-Nd回收率。实验表明,利用5 mL浓硝酸和0.015 mL高氯酸溶解萤石样品过程中加入1 mL 0.49 mol/L H3BO3效果最佳,结合高灵敏度热电离质谱仪(Triton)可实现微量萤石样品高精度Sm-Nd同位素测试。较先前已有的溶解方法,本方法大大降低萤石样品用量。     

Garnet-clinopyroxene geothermometer

A garnet-clinopyroxene geothermometer based on the available experimental data on compositions of coexisting phases in the system MgO-FeO-MnO-Al₂O₃-Na₂O-SiO₂ is as follows: $$T({\text{}}K) = \frac{{8288 + 0.0276 P {\text{(bar)}} + Q1 - Q2}}{{1.987 \ln K_{\text{D}} + 2.4083}}$$ where P is pressure, and Q1, Q2, and K _D are given by the following equations $$Q1 = 2,710{\text{(}}X_{{\text{Fe}}} - X_{{\text{Mg}}} {\text{)}} + 3,150{\text{ }}X_{{\text{Ca}}} + 2,600{\text{ }}X_{{\text{Mn}}} $$ (mole fractions in garnet) $$\begin{gathered}Q2 = - 6,594[X_{{\text{Fe}}} {\text{(}}X_{{\text{Fe}}} - 2X_{{\text{Mg}}} {\text{)]}} \hfill \\{\text{ }} - 12762{\text{ [}}X_{{\text{Fe}}} - X_{{\text{Mg}}} (1 - X_{{\text{Fe}}} {\text{)]}} \hfill \\{\text{ }} - 11,281[X_{{\text{Ca}}} (1 - X_{{\text{Al}}} ) - 2X_{{\text{Mg}}} 2X_{{\text{Ca}}} ] \hfill \\{\text{ + 6137[}}X_{{\text{Ca}}} (2X_{{\text{Mg}}} + X_{{\text{Al}}} )] \hfill \\{\text{ + 35,791[}}X_{{\text{Al}}} (1 - 2X_{{\text{Mg}}} )] \hfill \\{\text{ + 25,409[(}}X_{{\text{Ca}}} )^2 ] - 55,137[X_{{\text{Ca}}} (X_{{\text{Mg}}} - X_{{\text{Fe}}} )] \hfill \\{\text{ }} - 11,338[X_{{\text{Al}}} (X_{{\text{Fe}}} - X_{{\text{Mg}}} )] \hfill \\\end{gathered} $$ [mole fractions in clinopyroxene Mg = MgSiO₃, Fe = FeSiO₃, Ca = CaSiO₃, Al = (Al₂O₃-Na₂O)] K _D = (Fe/Mg) in garnet/(Fe/Mg) in clinopyroxene. Mn and Cr in clinopyroxene, when present in small concentrations are added to Fe and Al respectively. Fe is total Fe²⁺+Fe³⁺.     

Tourmaline from deposits of the Birgil’da-Tomino ore cluster, South Urals

Tourmalines from the Kalinovka porphyry copper deposit with epithermal bismuth-gold-basemetal mineralization and the Michurino gold-silver-base-metal prospect have been studied in the South Urals. Tourmaline from the Kalinovka deposit occurs as pockets and veinlets in quartz-sericite metasomatic rock and propylite. The early schorl-“oxy-schorl” [Fe_tot/(Fe_tot + Mg) = 0.66?0.81] enriched in Fe³⁺ is characterized by the homovalent isomorphic substitution of Fe³⁺ for Al typical of propylites at porphyry copper deposits. The overgrowing tourmalines of the second and third generations from propylite and quartz-sericite metasomatic rock are intermediate members of the dravite-magnesio-foitite solid solution series [Fe_tot/(Fe_tot + Mg) = 0.05?0.46] with homovalent substitution of Mg for Fe²⁺ and coupled substitution of ^X _? + ^YAl for ^XNa + ^YMg. These substitutions differ from the coupled substitution of ^YAl + ^WO^2? for ^YFe²⁺ + ^WOH^? in tourmaline from quartz-sericite rocks at porphyry copper deposits. At the Michurino prospect, the tourmaline hosted in the chlorite-pyrite-quartz veins and veinlets with Ag-Au-Cu-Pb-Zn mineralization is an intermediate member of the dravite-magnesio-foitite solid solution series [Fe_tot/(Fe_tot + Mg) = 0.20?0.31] with homovalent substitution of Mg for Fe²⁺ and coupled substitutions of ^X _? + ^YAl for ^XNa + ^YMg identical to that of late tourmaline at the Kalinovka deposit. Thus, tourmalines of the porphyry and epithermal stages are different in isomorphic substitutions, which allow us to consider tourmaline as an indicator of super- or juxtaposed mineralization.     

Crystal chemical and geochemical features of genetically different paleozoic dolomites in the Volga–Ural region

The comparative analysis of primary sedimentary and secondary catagenetic dolomites revealed that they differ in many typomorphic properties. Sedimentary dolomites are characterized by the pelitomorphic and fine-grained structure, high stoichiometry, and presence of the electron-hole (p-n) centers [SO₂]^– and [SO₃]^– in the structure. Secondary dolomites have a fine- to medium-grained structure and distinguished by a lower degree of stoichiometry. Their crystal lattice shows isomorphous replacements Mg ? Fe and Mg ? Ca. They can be divided into two (massive and porous) varieties. The massive varieties are characterized by the conformal structure and xenomorphic habitus of the closely packed idiomorphic and hypidiomorphic grains. The Ca–Mg and Fe–Mg isomorphism in the massive dolomites is less expressed than in the porous varieties. These specific features of dolomite varieties are related to their different formation settings. The porous dolomites were formed in a free environment that fostered slow growth of the relatively large equant crystals with a high degree of isomorphism, whereas the massive dolomites were formed under “stringent constraints” during a faster growth of crystals.     

Interdiffusion of Mg–Fe in olivine at 1,400–1,600 °C and 1 atm total pressure

The interdiffusion coefficient of Mg–Fe in olivine (D _Mg–Fe) was obtained at 1,400–1,600 °C at the atmospheric pressure with the oxygen fugacity of 10^?3.5–10^?2 Pa using a diffusion couple technique. The D _Mg–Fe shows the anisotropy (largest along the [001] direction and smallest along the [100] direction), and its activation energy (280–320 kJ/mol) is ~80–120 kJ/mol higher than that estimated at lower temperatures. The D _Mg–Fe at temperatures of >1,400 °C can be explained by the cation-vacancy chemistry determined both by the Fe³⁺/Fe²⁺ equilibrium and by the intrinsic point defect formation with the formation enthalpy of 220–270 kJ/mol depending on the thermodynamical model for the Fe³⁺/Fe²⁺ equilibrium in olivine. The formation enthalpy of 220–270 kJ/mol for the point defect (cation vacancy) in olivine is consistent with that estimated from the Mg self-diffusion in Fe-free forsterite. The increase in the activation energy of D _Mg–Fe at >1,400 °C is thus interpreted as the result of the transition of diffusion mechanism from the transition metal extrinsic domain to the intrinsic domain at the atmospheric pressure.     

星叶石族矿物的晶体化学

星叶石是碱性岩中分布较广泛的副矿物,成分富含碱金属K、Na及Ti,随其产出的地球化学条件,类质同象代换情况较复杂,形成许多成分异种。本工作之前对其组成和性质都不十分清楚,前人虽进行了一般矿物学研究,但未能确定所属晶系,B.C.索波列夫曾推断星叶石中Ti呈四面体配位,并与硅氧四面体组成复杂构造。     

A depositional model for hydromagnesite–magnesite playas near Atlin,British Columbia,Canada

This study formulates a comprehensive depositional model for hydromagnesite–magnesite playas. Mineralogical, isotopic and hydrogeochemical data are coupled with electron microscopy and field observations of the hydromagnesite–magnesite playas near Atlin, British Columbia, Canada. Four surface environments are recognized: wetlands, grasslands, localized mounds (metre‐scale) and amalgamated mounds composed primarily of hydromagnesite [Mg₅(CO₃)₄(OH)₂·4H₂O], which are interpreted to represent stages in playa genesis. Water chemistry, precipitation kinetics and depositional environment are primary controls on sediment mineralogy. At depth (average ≈ 2 m), Ca–Mg‐carbonate sediments overlay early Holocene glaciolacustrine sediments indicating deposition within a lake post‐deglaciation. This mineralogical change corresponds to a shift from siliciclastic to chemical carbonate deposition as the supply of fresh surface water (for example, glacier meltwater) ceased and was replaced by alkaline groundwater. Weathering of ultramafic bedrock in the region produces Mg–HCO₃ groundwater that concentrates by evaporation upon discharging into closed basins, occupied by the playas. An uppermost unit of Mg‐carbonate sediments (hydromagnesite mounds) overlies the Ca–Mg‐carbonate sediments. This second mineralogical shift corresponds to a change in the depositional environment from subaqueous to subaerial, occurring once sediments ‘emerged’ from the water surface. Capillary action and evaporation draw Mg–HCO₃ water up towards the ground surface, precipitating Mg‐carbonate minerals. Evaporation at the water table causes precipitation of lansfordite [MgCO₃·5H₂O] which partially cements pre‐existing sediments forming a hardpan. As carbonate deposition continues, the weight of the overlying sediments causes compaction and minor lateral movement of the mounds leading to amalgamation of localized mounds. Radiocarbon dating of buried vegetation at the Ca–Mg‐carbonate boundary indicates that there has been ca 8000 years of continuous Mg‐carbonate deposition at a rate of 0·4 mm yr^?1. The depositional model accounts for the many sedimentological, mineralogical and geochemical processes that occur in the four surface environments; elucidating past and present carbonate deposition.     

Effects of seawater carbonate ion concentration and temperature on shell U, Mg, and Sr in cultured planktonic foraminifera

We investigate the sensitivity of U/Ca, Mg/Ca, and Sr/Ca to changes in seawater [CO₃²⁻] and temperature in calcite produced by the two planktonic foraminifera species, Orbulina universa and Globigerina bulloides, in laboratory culture experiments. Our results demonstrate that at constant temperature, U/Ca in O. universa decreases by 25 ± 7% per 100 μmol [CO₃²⁻] kg⁻¹, as seawater [CO₃²⁻] increases from 110 to 470 μmol kg⁻¹. Results from G. bulloides suggest a similar relationship, but U/Ca is consistently offset by ∼+40% at the same environmental [CO₃²⁻]. In O. universa, U/Ca is insensitive to temperature between 15°C and 25°C. Applying the O. universa relationship to three U/Ca records from a related species, Globigerinoides sacculifer, we estimate that Caribbean and tropical Atlantic [CO₃²⁻] was 110 ± 70 μmol kg⁻¹ and 80 ± 40 μmol kg⁻¹ higher, respectively, during the last glacial period relative to the Holocene. This result is consistent with estimates of the glacial-interglacial change in surface water [CO₃²⁻] based on both modeling and on boron isotope pH estimates. In settings where the addition of U by diagenetic processes is not a factor, down-core records of foraminiferal U/Ca have potential to provide information about changes in the ocean’s carbonate concentration.Below ambient pH (pH < 8.2), Mg/Ca decreased by 7 ± 5% (O. universa) to 16 ± 6% (G. bulloides) per 0.1 unit increase in pH. Above ambient pH, the change in Mg/Ca was not significant for either species. This result suggests that Mg/Ca-based paleotemperature estimates for the Quaternary, during which surface-ocean pH has been at or above modern levels, have not been biased by variations in surface-water pH. Sr/Ca increased linearly by 1.6 ± 0.4% per 0.1 unit increase in pH. Shell Mg/Ca increased exponentially with temperature in O. universa, where Mg/Ca = 0.85 exp (0.096*T), whereas the change in Sr/Ca with temperature was within the reproducibility of replicate measurements.     

硼在共存水蒸气-富硼熔体之间分配的实验研究及其地质意义

硼作为一种常用的地球化学指示剂和示踪剂,对研究俯冲带岩石学过程、岩浆-热液分异作用、火山活动以及稀有元素、铜、金的成矿机制具有重要意义。硼具有高水溶性和挥发性,它在气体中的分配、迁移能力和存在形式有助于理解含硼矿物的形成条件、流体化学组成的演化趋势、硼同位素的分馏效应和成矿金属的富集机理。本文在200-350℃、0.19-3.43 MPa条件下实验研究了B2O3-H2O体系中硼在共存水蒸气和富硼熔体（液体）之间的分配,平衡时气相中的B2O3含量为1.06%-32.35%。200℃、250℃、300℃和350℃时硼在气体-熔体之间的表观分配系数分别为0.035、0.042、0.20和0.33,即随温度上升,硼在含水气相中的分配和迁移能力增强。含水的富 B 熔体与硼酸稀溶液体系的气体-液体分配系数变化不大,表明B2O3-H2O±NaCl 体系中硼的气-液分配能力受液体或熔体中硼含量的影响较小,而主要与温度有关。经热力学分析,350℃、0.19-1.74 MPa条件下水蒸气中的气态硼物种可能为H3BO3和HBO2,可以预计随水蒸气压力的升高, H2O的配位数将会增大, H3BO3或其他可能的气态物种H3BO3·H2O会变得更为重要。某些火山活动区可见天然硼酸结壳（升华壳）的形成,灼热和干燥的火山岩石表面有利于硼酸从气相中凝析和沉淀。本实验结果表明,某些富硼酸的火山喷气孔气体的形成可能与地下高温火山岩浆（岩体）中存在因液态不混溶作用或晚期出溶作用产生的含水富硼的残余熔体或流体有关,熔体的去气作用或流体的减压相分离导致含水气相的产生,硼则随之大量分配至含水气体中并喷出地表。     

Influence of ignimbrite on the chemistry of river water in Shirasu plateau,Japan

River, rain and spring water samples from a region covered in “Shirasu” ignimbrite were collected on Kyushu Island, Japan. The analytical results were subjected to multivariate statistical analysis and stoichiometric calculation to understand the geographical distribution of chemical components in water and to extract geochemical underlying factors. The multivariate statistical analysis showed that the river-water chemistry is only slightly influenced by hot springs or polluted waters, but is highly controlled by weathering of ignimbrite. On the basis of the stoichiometric calculation based on water–rock interaction, the water chemistry was successfully estimated by a simple equation:\({\left[ {{\text{Si}}} \right]}{\text{ = 2}}{\left[ {{\text{Na}}^{{\text{ + }}} } \right]}{\text{ + }}{\left[ {{\text{Mg}}^{{{\text{2 + }}}} } \right]}\) in the upstream area, complemented by \({\left[ {{\text{Si}}} \right]}{\text{ = }}{\left[ {{\text{Na}}^{{\text{ + }}} } \right]}{\text{ - 3}}{\left[ {{\text{K}}^{{\text{ + }}} } \right]}{\text{ + }}{\left[ {{\text{Mg}}^{{{\text{2 + }}}} } \right]}{\text{ - 2}}{\left[ {{\text{Ca}}^{{{\text{2 + }}}} } \right]}\) in the downstream area.     

Late Holocene fire impact and post-fire regeneration from the Bereket basin, Taurus Mountains, southwest Turkey

The 800 cm long sequence from the Bereket provides the first detailed fire history in the western Taurus Mountains for the last three millennia. The main disturbances occurred during the Bey?ehir Occupation Phase (BO Phase), a period of intensive polyculture and dated at Bereket from ca. 2230 to 1550 cal yr BP. Four phases of local and extra-local fire periods have been recorded at 2320-2240, 1985-1970, 1865-1820 cal yr BP and post-AD 1950. The fire history established for the BO Phase is complex, with fire periods alternating with periods without local fires, as is the case for the late BO Phase from 1820 until 1550 cal yr BP. It is suggested that the past agricultural practices including fires cause a higher soil erodibility than agricultural practices without fires. A climatic shift towards aridity during Roman times may have triggered the observed change in fire regime but local processes, mainly human disturbances, appear to be the proximal cause of all recorded changes. In the Bereket surroundings, fires led to a simplification of the vegetation structure, favouring soil erosion, pastures and intensive cultivation.     

钙长石成分熔体粘滞度和自扩散系数压力效应的分子动力学研究

用分子动力学方法,研究了1999 K下,压力由23 MPa上升到15183 MPa的过程中,CaAl_2Si_2O_8成分熔体的微观结构、剪切粘滞度和粒子自扩散系数的压力效应。在此基础上,探讨压力对剪切粘滞度与粒子自扩散系数之间关系的影响,并将它同微观结构的变化联系起来。结果表明,粒子自扩散系数的压力效应与熔体结构有很强的相关性;压力的挤压效应阻碍了粒子的扩散,而Si-O和Al-O 5次配位体的形成又加速了扩散过程,两种相反的作用相互抵消,造成的结果是在0～5 GPa范围内,Si~(4 ),O~(2-)和Al~(3 )等网架形成粒子的自扩散系数随压力变化不明显;当压力继续增大时,挤压效应占了主导,导致自扩散系数值快速减小。Ca~(2 )作为网架修饰粒子,自扩散系数随压力升高单调下降。压力小于5 GPa时,粒子自扩散系数的大小关系是:D_(Ca)>D_(Al)>D_O>D_(Si)。系统粘滞度随压力的变化与熔体中BO的含量密切相关:BO含量小于域值时,一定范围内BO含量的变化不会对粘滞度产生很大的影响,超过域值,BO含量的微小增加会导致粘滞度值迅速增大。有效应用Eyring方程的关键是方程中粒子跳跃距离的确定,本研究发现,Si~(4 )和O~(2-)的跳跃距离可以通过系统中非桥氧的百分含量来获得。这一发现使得我们能够利用系统中NBO的含量,结合Eyring方程有效进行不同压