Local relaxations around Fe3+ and Cr3+ in Al sites in minerals

Second-order zero-field splitting (ZFS) parameters from the literature for Fe³⁺ in twelve and for Cr³⁺ in seven minerals substituting for Al were evaluated by application of the superposition model. For Fe³⁺ in monoclinic site symmetries a fair agreement of the observed splitting patterns with those calculated from the crystal structure data was observed in most cases, but the distortions for Fe³⁺ appear to be usually larger than those of the unrelaxed Al sites. In cases of not too large local relaxation the unknown sign of the axialZFS parameterb ₀ ² could be predicted, in two cases a different sign than that reported was postulated. In cordierite and scolecite the reportedEPR spectra could thus be assigned to the sites with larger average bond distances. For Fe³⁺ in beryl the relaxation of the axial site can be deduced within narrow limits. For Cr³⁺ significantly larger differences between observed and calculatedZFS patterns are found suggesting additional relaxations due to the non-spherical electron distribution in the ground state of this ion.     

硅灰石矿物发光材料的人工合成研究

对硅灰石矿物发光材料进行了人工合成研究，在合成试样中，分别掺入少量Ｅｕ＾３＋，Ｇｄ＾３＋，Ｐｂ＾２＋，Ｍｎ＾２＋等激活剂，于１０００℃或１１８０℃条件下分别通入Ｈ２Ｓ（ｇ），Ｈ２Ｏ（ｇ）以及用ＮＨ３，Ｈ２Ｏ吸收ＣＯ２（ｇ）等方法进行合成低温ＴＣ型三斜硅灰石和高温型假硅灰石，合成产物通过扫描电镜、Ｘ射线衍射和红外光谱实验，对合成过程中温度高低，时间长短、冷却快慢、降低温度合成高温型假硅灰石的方法进行     

Time-resolved luminescence of Fe3+ and Mn2+ ions in hydrous volcanic glasses

 Time-resolved luminescence spectra of natural and synthetic hydrous volcanic glasses with different colors and different Fe, Mn, and H₂O content were measured, and the implications for the glass structure are discussed. Three luminescence ranges are observed at about 380–460, 500–560, and 700–760 nm. The very short-living (lifetimes less than 40 ns) blue band (380–460 nm) is most probably due to the ⁴T₂(⁴D) →⁶A₁(⁶S) and ⁴A₁(⁴G) →⁶A₁(⁶S) ligand field transitions of Fe³⁺. The green luminescence (500–560 nm) arises from the Mn²⁺ transition ⁴T₁(⁴G) →⁶A₁(⁶S). It shows weak vibronic structure, short lifetimes less than 250 μs, and indicates that Mn²⁺ is tetrahedrally coordinated, occupying sites with similar distortions and ion–oxygen interactions in all samples studied. The red luminescence (700–760 nm) arising from the ⁴T₁(⁴G) →⁶A₁(⁶S) transition of Fe³⁺ has much longer lifetimes of the order of several ms, and indicates that ferric iron is also mainly tetrahedrally coordinated. Increasing the total water content of the glasses leads to quenching of the red luminescence and decrease of the distortions of the Fe³⁺ polyhedra. Received: 30 July 2001 / Accepted: 15 November 2001     

Malanite——A New Cupric Platinum (Pt~(3+)) and Iridium (Ir~(3+)) Sulphide

Malanite was first found in veinlets of disseminated copper-nickel ores inZunhua County, Hebei Province, and then in platinum-bearing chromite ores in ShuangfengVillage, Yanshan. In the former case, malanite appears as octahedrons or dodecahedrons asso-ciated with pyrrhotite, pentlandite, sperrylite and cooperite; while in the latter case, it is massiveor present in anhedral glomerocrysts, filling in cracks of iridisite and associated with osmiride,ferrian platinum and iridisite. Malanite is steel-grey in colour, opaque with metallic lustre andblack streaks and brittle with no magnetism. H_M=5.0, VHN_(20)=417kg/mm~2, cleavage {111}sometimes observed. The calculated density is 7.57g/cm~3. The reflective colour is white with alight green tint. Internal reflections are not observed. This mineral is isotropic, showing nobireflection or reflection pleochroism in air. By means of electron microprobe analysis, the em-pirical formula (based on 7 atoms) is expressed as (Cu_(0.93)Fe_(0.06))_(∑0.99)(Pt_(1.03)Ir_(0.66)Rh_(0.04)Pd_(0.03)Co_(0.20)Ni_(0.03))_(1.99)S_(4.03) or (Cu_(0.95)Fe_(0.07))_(∑1.02)(Pt_(1.37)Ir_(0.45)Co_(0.11)Rh_(0.08))_(∑2.01)S_(3.97). Five strongestlines (hkl, d, I) of X-ray powder diffraction data of malanite are 311,2.98(6); 400,2.48(5);333, 1.90(7); 440, 1.75(10); 731, 1.29(5). It was known on the basis of X-ray powder diffractiondata that malanite is cubic, and the space group is Fd3m with α=0.9940nm, V=0.9821(3)nm~3 and Z=4. The type material of malanite is deposited at the Geological Museum of China(GMC)s     

Evidence for absorption by exchange-coupled Fe2+-Fe3+ pairs in the near infra-red spectra of minerals

Reduction of Fe³⁺ to Fe²⁺ by heating in hydrogen reduces the absorbance of the bands at 9,000 and 13,800 cm^?1 in the E ⊥ c spectrum of tourmaline, and the 9,000 and 11,000 cm^?1 bands in the E ∥ (001) spectrum of biotite. This behaviour is consistent with the presumed d-d origin of these bands (which seems well established) only if they gain much of their intensity from exchange-coupling with neighbouring Fe³⁺ ions. Intensification of spin-forbidden bands in sapphire by Fe³⁺-Fe³⁺ exchange-coupling was recognized by Ferguson and Fielding (1971, 1972), but exchange-coupling has not previously been thought to intensify spin-allowed d-d bands. Spin-allowed exchange-coupled bands resulting from Fe²⁺-Fe³⁺ pairs have features in common with both normal single ion d-d bands, which they resemble in energy, width and pressure dependence, and Fe²⁺+Fe³⁺→Fe³⁺+Fe²⁺ charge transfer bands, which they resemble in temperature-, heat treatment-, composition-, and polarization-dependence. Distinction between normal d-d, charge transfer, and pair d-d absorptions is thus complicated, and criteria for assigning these bands are discussed. Spin-allowed exchange-coupled pair bands should be sought in the spectra of transition metal clusters (trimers and polymers as well as pairs may be involved) whenever geometry favours their origin. It is possible that the bands near 10,000 and 11,500 cm^?1 in blue sapphire, and at about 5,000 cm^?1 in titanian garnets are of this type, but many other examples are likely to occur. Exchange-coupling may involve ions other than Fe³⁺ (e.g., Mn²⁺, also d ⁵), although Fe²⁺-Fe²⁺ coupling is unlikely to be important at laboratory temperatures.     

白云鄂博矿床稀土矿物稳定同位素特征及其意义

稀土元素是白云鄂博矿床最有特色的矿产。本文在详细讨论了稀土矿物氧、碳同位素制样方法的基础上，对矿床中晚期脉、白云石型矿石、萤石型矿石中的主要稀土矿物进行了系统的氧、碳同位素分析。其中，晚期脉中的氟碳酸盐矿物的碳、氧同位素值较低，具有幔源热液结晶的特点；白云岩型矿石中氟碳铈矿δ１３Ｃ在－１．１‰～－３．４‰，δ１８Ｏ在８．６‰～１２．０‰；独居石δ１８Ｏ在５．７‰～１１．４‰，磷灰石δ１８Ｏ在６．３‰～９．４‰；萤石型矿石中氟碳铈矿δ１３Ｃ在－５．２‰～－５．８‰，δ１８Ｏ在３．６‰～５．５‰；独居石δ１８Ｏ在３．５‰～４．５‰。结合矿床地质特征分析，矿区萤石型矿石和晚期脉的形成可能与深源热液有关；而白云岩中的稀土矿化作用则表现出多源多期次的特点     

NdSr isotope and REE geochemistry of alkali basalts from the Massif Central,France

Nd and Sr isotopic compositions as well as trace element concentrations have been determined on a suite of alkali basalts from the Massif Central, in France. Samples show a typical enrichment in incompatible elements. In particular, the REE patterns exhibit a strong fractionation characterized by a ($\text{La}\text{Yb}\text{)}{}_{\mathrm{<mtext>N</mtext>}}$ ratio of about 20. The Yb_N content is about 10 times chondrite. The $\text{143}\text{Nd}\text{144}\text{Nd}$ ratios exhibit a range from 0.512775 to 0.512989, values quite comparable to those from oceanic island basalts. The $\text{87}\text{Sr}\text{86}\text{Sr}$ ratios vary between 0.70338 and 0.70458 and are anti-correlated with the Nd isotopic ratio.The isotopic and the trace element (in particular REE) data have been used in order to quantitatively model the genesis of the alkali basalts. Among the several types of models tested here, the most likely one appears to be the model of mantle metasomatism. A semi-quantitative approach shows that the source of alkali basalts from the Massif Central was metasomatized prior to melting. In such a model, the basalts could be produced by rather high degrees of partial melting (such as 10 or 15%) of the metasomatically enriched mantle.     

REE Geochemical Characteristics of Tungsten Minerals as a Discriminant Indicator of Genetic Types of Ore Deposits

Tungsten minerals (scheelite and wolframite) from two genetic types of granitoids show significant differences in REE distribution, probably due to different material sources and origins. Tungsten minerals in granite porphyry of the crust-mantle source are relatively high in ΣREE(1884ppm on average). Σ Ce is rich relative to Σ Y and Σ Ce/ΣY is relatively high (>1). The chondrite-normalized REE distribution patterns are characterized by a group of rightward-inclined curves. Tungsten minerals in quartz veins intruding the granites of crust origin have lower ΣREE (335 ppm on average). ΣY is rich relative to ΣCe and ΣCe/ΣY is relatively low (<1). The chondrite-normalized REE distribution patterns are characterized by a group of leftward-inclined curves. So the REE distribution patterns can be used to discriminate the sources of rock-and ore-forming materials and the genetic types of W deposits so as to provide clues to ore prospecting.     

Discovery of the REE minerals and its geological significance in the Quyang bauxite deposit,West Guangxi,China

Most of the karstic bauxite deposits in China are enriched in REE, and the REE has commonly been considered to be adsorbed on the surface of clay or diaspore minerals as ion state. However, occurrence of REE minerals in the bauxite deposits has not been reported by far. In the Quyang bauxite deposit from Guangxi province, we find REE minerals. The minerals are parisite and churchite. Parisite is widely distributed in the ooids and matrix, inducing positive Ce anomaly of the ores; whereas, churchite is rare and occurred in the core of ooid. The compositions of the REE minerals show the Eu anomaly can change gently during the weathering, and the Eu anomaly analyses suggest that the REE in the ores are mostly derived from the underlying carbonates. The parisite is formed in an alkaline condition, while churchite in an acidic situation; the co-existence of the two minerals in the ores suggests the Permian environment for bauxite formation is complex with great change of pH value. Moreover, parisite is inferred to be formed earlier than the churchite.     

Compression moduli of Cr3+-centered octahedra in a variety of oxygen-based rock-forming minerals

High-pressure electronic absorption spectra at room temperature and at pressures 10^?4<P[GPa]<8 were measured in the spectral range 380<λ[nm] <780(26218>ν?[cm^?1]>12820) on analysed single crystal slabs, about 20?μm thick, of Cr³⁺-bearing spinel (I), kyanite (II), corundum (III), pyrope (IV) and uvarovite (V) using DAC-cell techniques in combination with single-beam microscopespectrometry. Ligand field theoretical evaluation of the spectra yielded following results: (i)?the octahedral crystal field parameter, 10Dq_Cr3+[6], linearly shifts on increasing pressure to higher energies with slopes, (δ10Dq_Cr3+[6]/δP), of 103.1 (I), 99.5 (II), 104.0 (III), 111.7 (IV) and 110.3?[cm^?1/GPa] (V) (reliability parameters r≥0.92), (ii)?The Racah-parameter B_Cr3+[6], reflecting the covalency of the Cr–O bonds, does not significantly change with pressure up to 8?GPa, in those cases where it could be evaluated from the spectra (III, IV, V). This result is contrary to the behaviour of B_Cr3+[6] with increasing temperature (Taran et?al. 1994) and shows that P and T are not inversely correlated parameters with respect to B_Cr3+[6], a decrease of which reflects an increase in covalency. (iii)?This result enabled to extract octahedral compression moduli, k_Cr3+[6], from the pressure slopes of 10Dq_Cr3+[6]: 312+48 (I), 297+70 (II), 298+44 (III), 275+35 (IV), 257+32?GPa (V). Quotients k_cr3+[6]/k_bulk,phase are nearly the same (ca. 1.6) for I, II, IV and V but significantly lower (ca. 1.1) for III. Deviations between spectroscopically determined k_Cr3+[6] and published k_Al[6], obtained by HP-XRD on ruby and pyrope, are interpreted by lattice strain induced by [Cr³⁺,?Al3+?1]^[6] substitution.     

汉诺坝玄武岩中地幔岩捕掳体REE和Sr,Nd同位素地球化学

本文报道汉诺坝玄武岩中地幔岩捕掳体的ＲＥＥ丰度和Ｓｒ、Ｎｄ同位素组成。不同岩石类型的ＲＥＥ配分模式和同位素组成反映地幔部分熔融程度和交代作用过程。二辉橄榄岩亏损轻稀土,是原始地幔经不同程度部分熔融的残留体。方辉橄榄岩具Ｕ型ＲＥＥ配分模式,是强烈亏损的地幔岩被熔体非化学平衡交代的结果。二辉岩脉状体富轻、中稀土,它同与脉状体接触的二辉橄榄岩可达化学平衡或近于化学平衡,而二辉岩脉状体的形成与玄武岩岩浆无成因关系。据对二辉岩脉状体和不含脉状体橄榄岩的Ｓｍ－Ｎｄ同位素定年,这种脉状体形成于３００Ｍａ左右。     

影响咸淡水界面水敏性的几个因素

文章通过砂柱的水击试验,对水流速度、盐浓度、pH值对咸淡水界面水敏性的影响进行了研究.试验结果表明,咸淡水界面上存在临界盐浓度值和临界流速值,当入流溶液浓度达到临界盐浓度和流速达到临界流速时,都会产生颗粒释放现象,导致砂柱的渗透率下降,水敏性发生.在相同的盐浓度和进水流速条件下,进水的pH值越低,颗粒释放的速度越慢,释放总量越少;进水的pH值越高,颗粒释放的速度越快,释放总量越多.     

南极三块（L3）陨石球粒结构类型及其矿物学物征

我国第16次南极考察队回收到6块稀少种类陨石-13型,GRV99001,GRV99019,GRV99020,GRV99021,GRV99022,GRV99026。本文对其中3块陨石进行研究,研究它们的球粒结构和矿物化学成分．它们虽然部属于非平衡普通球粒陨石（L3）,但它们的亚类不同,GRV99001为13．4,GRV99026为L3．5,GRV99019为L3．6．它们的球粒结构和球粒内的矿物晶体完整性和矿物组合变化比较大．橄榄石和辉石以高镁为特征．这三块陨石的球粒结构种类比较多．有班状的、炉条状的、扇形的和隐晶质的等．在GRV99001陨石中班状结构的球粒内能见到一个或两个以上完整的单晶橄榄石构成的球粒,也能见到多个细小的或是破碎橄榄石,被包襄在辉石晶体内．而在GRV99019和GRV99026陨石中只能见到多个细小单晶体或是破碎的橄榄石晶体．GRV99001陨石的炉条状结构,好象是由一条带状长石矿物,穿插在单个橄榄石晶体中构成．扇形和伞形结构的球粒,以一个点为中心,向外放射呈扇形．如GRV99019陨石中扇形结构球粒,它们是以辉石为主,陨硫铁充填在低钙辉石缝隙中,形成扇形．另一种是以多个点为中心,如GRV99001陨石,它们是由橄榄石、低钙辉石和长石质的玻璃．构成多个小伞形,形状类似三维立体的球,裂缝中也充填有金属矿物．隐晶质的球粒在GRV99026陨石中有两种,一种是在一厘米等于100un时呈现隐晶质矿物,而放大到一厘米等于5un时,就可以清楚看到两种低钙辉石矿物,在低钙辉石中还有金属矿物．另一种隐晶质结构球粒由极细小破碎的橄榄石和辉石矿物构成．这三块陨石中的橄榄石和辉石都以高镁为特征．班状结构球粒,在GRV99001陨石中橄榄石的MgO～33．37～51．21,辉石为35．9～36．61;GRV99019陨石中橄榄石23．33～56．58．辉石21.38-33.07,GRV99026陨石中榄橄榄石45.91-52.63,辉石34.48-37.35,扇形结构球粒,在GRV99001陨石中橄榄石29.94-46.22,辉石28.17-30.36;GRV99019陨石中橄榄石29.17-34.38,辉石23.11-27.79,炉条状结构的球粒,在GRV99001陨石中橄榄石51.84-56.03,隐晶质结构球粒,在GRV99026陨石中辉石20.17-21.54,橄榄石30.84-32.66,由此看出矿物晶体完整性越好镁的含量越高。     

The first discovery of abnormal (Y+REE)-enriched zircons in rocks of the Baltic shield

Zircons with an anomalously high content of Y and REEs in rims were first found in rocks of the Baltic shield (in a pegmatite vein in the Gridino eclogite-bearing melange and in quartz syenites of the North-Karelian greenstone belt); the total content reaching 17 wt %. The presence of such an amount of nonformula elements is caused by the isomorphic occurrence of them in zircon and is not associated with microinclusions of accessory minerals. The age of formation of these rims was determined as the Svecofennian, although the direct dating yields underestimated values of the age, which are void of geological sense.     

H~+对Cu~(2+)—Me~(2+)二元体系吸附的影响规律研究

土壤对重金属离子的吸附容量严格受H~+浓度的控制。本文通过试验探讨了H~+ 对Cu~(2+)——Pb~(2+),Cn~(2+)——Zu~(2+),Cu~(2+)——Hg~(2+)系统中Cu~(2+)吸附量的影响规律。当pHpH时,Cu~(2+)吸附量随pH值增大而减小。对于酸性土,pH=6.5(初始值)或7.0(平衡值),对碱性土,pH=5.5(初始值)或7.8(平衡值)。在pHpH_(ZPC)时,吸附模式具有完全不同的形式。     

岩石暴露年龄释光测定的若干影响因素研究

近年来,光释光测年技术已被成功应用于岩石暴露年龄的测定,在地质、地貌、气候和考古等研究领域显示出广泛的应用前景。该技术能否准确并广泛应用于经历各种地质活动而暴露的基岩、砾石定年,了解影响其表层光释光信号晒退速率的因素至关重要。文章采用红褐色长石石英砂岩、灰白色黑云母花岗岩和表面附着有岩石漆的花岗角砾岩,针对样品岩性、采样面朝向、表面覆盖物（岩石漆）3个因素对红外释光（IRSL）50度测量信号的影响程度进行了晒退实验。实验结果显示：岩石表层一定深度IRSL信号可被太阳光快速晒退,且随着曝光时间增长,砂岩和花岗岩释光信号的晒退深度均逐渐增大,与深色砂岩相比,浅色的花岗岩有更快的晒退速率;在阳光下曝光约5114 h后,花岗岩朝上一面的信号晒退深度大于朝北一面,表现为拟合朝上一面的晒退曲线所获值和曲线拐点深度值皆大于朝北一面,揭示在该暴露时间内（如约5114 h）不同采样面朝向对信号晒退有一定程度的影响;阳光下暴露相对较短的时间（如40 h）,样品表面覆盖物（岩石漆）可能因对光线的屏蔽作用而使光释光信号晒退速率减小,无岩石漆覆盖的岩块具有更深的信号晒退深度,但随着暴露时间的延长（如约2416 h）,这种影响程度渐趋减弱。该研究为准确获得岩石样品定年所需的光晒退速率和光透系数μ这两个重要参数奠定了基础,也为了解不同岩性岩石的光释光信号晒退速率、测年对象的合理选择以及岩石样品采集等提供了实验数据支持。     

Pb、Sr和REE在矿物中的扩散补偿关系及其对扩散系数的预测

对现有实验扩散数据的检查发现，不仅Pb、Sr和REE元素在不同矿物中存在着扩散补偿关系，不同元素在同一矿物或同族矿物中也满足扩散补偿关系。阴离子孔隙度作为矿物内部离子堆积密度的一种量度，它与Pb和REE扩散活化能之间存在负的线性相关性，在固定温度下与Sr扩散系数（lnDT)之间呈正的线性相关，因而可以用于预测元素在矿物中的扩散系数。本文分别采用离子孔隙度法和双补偿法预测了Pb、Sr和REE在不同矿物中的扩散系数，这些结果与已有的实验数据在实验误差范围内是一致的，因此可以应用到与扩散有关的地球化学动力学研究中。