时变参数灰色模型背景值重构及实现

针对时变参数灰色模型PGM(1,1)的背景值重构收敛速度及稳定性问题,该文运用积分的方法综合序列在Δt内不同变化趋势,导出背景值模型的准确表达式。实现了反映序列对新老信息偏爱程度的最优权值介于(0,1)内,且非不能越过某一阈值;给出了背景值重构模型最优解准确求取的具体算法步骤。基于MATLAB语言的实验结果表明:改进模型预测精度高,易于实现;所研究的带权灰色模型GM(1,n)背景值模型的重构及计算方法验证了PGM(1,1)模型重构及计算实现方法的有效性和实用性。     

三重加权变形监测预测模型及应用

针对GM(1,1)建模过程存在背景值、时间因素和初始条件3方面的不足,该文提出三重加权TPGM(1,1)预测模型。通过对背景值进行加权生成新的背景值,建立PGM(1,1)模型;在PGM(1,1)基础上考虑到时间因素,在求解灰参数时进行第2次加权建立DPGM(1,1)模型;最后考虑到初始条件对预测模型的影响,在DPGM(1,1)基础上进行第3次加权,建立TPGM(1,1)模型。通过实例分析,比较GM(1,1)、PGM(1,1)、DPGM(1,1)、TPGM(1,1)4种模型在变形监测数据处理中的拟合和预测结果,表明三重加权TPGM(1,1)模型拟合效果更好、预测精度更高;该模型具有前3种模型的优点,同时弥补了传统GM(1,1)存在的不足。     

金川铜镍硫化物矿床中铂族矿物的主要类型和产出特征:热液蚀变过程中铂族元素的富集机理

金川铜镍硫化物矿床是我国最主要的铂族元素(PGE)资源产地,其矿石受热液蚀变作用影响明显,并产出多种铂族矿物(PGM)。岩浆演化和热液蚀变过程中PGE的迁移富集机制和PGM的成因,一直是研究PGE地球化学行为非常关注的问题。本文对金川铜镍硫化物矿床中PGM的研究发现,其主要类型包括含PGE的硫砷化物(硫砷铱矿)和砷化物(砷铂矿),Pd的铋化物、碲化物和硒化物,以及少量其他铂族矿物。其中,硫砷铱矿可包裹于各种贱金属硫化物(镍黄铁矿、磁黄铁矿和黄铜矿)中,表明硫砷铱矿可能结晶于早期的含As硫化物熔体,随后被包裹于硫化物熔体冷凝分异产生的单硫化物固溶体(MSS)和中间硫化物固溶体(ISS)中。硫化物熔体中的As可能主要通过地壳混染作用加入幔源岩浆。大量铋钯矿(PdBi)呈微细乳滴状包裹于黄铜矿中,为晚期ISS冷凝形成黄铜矿过程中出溶的产物。少量铋钯矿(PdBi_2)呈不规则状充填于矿物裂隙,与次生磁铁矿脉紧密共生,并随矿石的蚀变程度增加,铋钯矿的化学成分由PdBi逐渐向PdBi_2转变,表明这部分铋钯矿为后期热液蚀变产物。铋碲钯矿和钯的硒化物则主要产出于镍黄铁矿裂隙且与次生磁铁矿紧密共生,指示明显的热液成因。钯的硒化物的出现表明,岩浆期后酸性、高盐度、高氧逸度的富Cl~-流体对金川铜镍硫化物矿床中Pd的迁移和富集起到了关键控制作用。     

Platinum-Group Mineral Characterization in Concentrates from High-Grade PGE Al-rich Chromitites of Korydallos Area in the Pindos Ophiolite Complex (NW Greece)

The Pindos ophiolite complex, located in the north-western part of continental Greece, hosts various podiform chromite deposits generally characterized by low platinum-group element (PGE) grades. However, a few locally enriched in PPGE + Au (up to 29.3 ppm) chromitites of refractory type are also present, mainly in the area of Korydallos (south-eastern Pindos). The present data reveal that this enrichment is strongly dependant on chromian spinel chemistry and base metal sulfide and/or base metal alloy (BMS and BMA, respectively) content in chromitites. Consequently, we used super-panning to recover PGM from the Al-rich chromitites of the Korydallos area. The concentrate of the composite chromitite sample contained 159 PGM grains, including, in decreasing order of abundance, the following major PGM phases: Pd-Cu alloys (commonly non-stoichiometric, although a few Pd-Cu alloys respond to the chemical formula PdCu₄), Pd-bearing tetra-auricupride [(Au,Pd)Cu], nielsenite (PdCu₃), sperrylite (PtAs₂), skaergaardite (PdCu), Pd-bearing auricupride [(Au,Pd)Cu₃], Pt and Pd oxides, Pt-Fe-Ni alloys, hollingworthite (RhAsS) and Pt-Cu alloys. Isomertieite (Pd₁₁Sb₂As₂), zvyagintsevite (Pd₃Pb), native Au, keithconnite (Pd₂₀Te₇), naldrettite (Pd₂Sb) and Rh-bearing bismuthotelluride (RhBiTe, probably the Rh analogue of michenerite) constitute minor phases. The bulk of PGE-mineralization is dominated by PGM grains that range in size from 5 to 10 µm. The vast majority of the recovered PPGM are associated with secondary BMS and BMA, thus confirming that a sulphur-bearing melt played a very important role in scavenging the PGE + Au content of the silicate magma from which chromian spinel had already started to crystallize. The implemented technique has led to the recovery of more, as well as noble, PGM grains than the in situ mineralogical examination of single chromitite samples. Although, the majority of the PGM occur as free particles and in situ textural information is lost, single grain textural evidence is observed. In summary, this research provides information on the particles, grain size and associations of PGM, which are critical with respect to the petrogenesis and mineral processing.     

时变参数PGM（1,1）模型在变形监测中的应用研究

给出了时变参数PGM（1,1）模型的数值解法,比较了其与GM（1,1）、PGM（1,1）模型的预测精度,分析了灰区间作为预测结果的可靠性。     

西藏罗布莎铬铁矿中的原位铂族矿物研究:铬铁矿结晶环境的指示

本文对罗布莎三个矿区的铬铁矿进行了详细的原位PGM研究,发现罗布莎各个矿区的铬铁矿中PGM组合和显微结构不同,暗示PGM能够记录铬铁矿形成与演化过程。罗布莎矿区的PGM显微特征显示铬铁矿结晶于高温、低硫逸度的环境中,可能系岩石/熔体反应和结晶分异双重作用下的产物;康金拉矿区的原位PGM主要为组合型包裹体,有少量产于铬铁矿裂隙之间的贱金属硫化物和合金矿物,为不同来源的熔体混合作用的结果,并暗示铬铁矿成矿后还受到热液流体的改造;香卡山矿区的PGM表明铬铁矿成矿之后遭受到还原性流体的交代作用,铬铁矿中早期结晶出来的硫化物或者铂族矿物被还原改造,形成铁镍矿等次生矿物,保存于铬铁矿粒间或者铬铁矿的裂隙中,这个过程可能与蛇纹石化或者晚期构造流体改造作用有关。罗布莎原位PGM研究表明,PGM矿物贯穿于铬铁矿结晶成矿过程的始终,PGM的矿物及其组合能够记录铬铁矿结晶时母熔体的物理化学条件,甚至还能反映铬铁矿成矿后所经历的后期构造热液事件。因此,结合单矿物分选和原位调查两种方法,查明铬铁矿中PGM的赋存类型及微观结构,对全面理解铬铁矿的成矿过程有重要意义。     

Platinum-group Mineral (PGM) and Base-metal Sulphide (BMS) Inclusions in Chromitites of the Zedang Ophiolite, Southern Tibet, China and their Petrogenetic Significance

Voluminous platinum-group mineral(PGM) inclusions including erlichmanite(Os,Ru)S_2, laurite(Ru,Os)S_2, and irarsite(Ir,Os,Ru,Rh)As S, as well as native osmium Os(Ir) and inclusions of base metal sulphides(BMS), including millerite(NiS), heazlewoodite(Ni_3S_2), covellite(CuS) and digenite(Cu_3S_2), accompanied by native iron, have been identified in chromitites of the Zedang ophiolite, Tibet. The PGMs occur as both inclusions in magnesiochromite grains and as small interstitial granules between them; most are less than 10 μm in size and vary in shape from euhedral to anhedral. They occur either as single or composite(biphase or polyphase) grains composed solely of PGM, or PGM associated with silicate grains. Os-, Ir-, and Ru-rich PGMs are the common species and Pt-, Pd-, and Rh-rich varieties have not been identified. Sulfur fugacity and temperature appear to be the main factors that controlled the PGE mineralogy during crystallization of the host chromitite in the upper mantle. If the activity of chalcogenides(such as S, and As) is low, PGE clusters will remain suspended in the silicate melt until they can coalesce to form alloys. Under appropriate conditions of ?S_2 and ?O_2, PGE alloys might react with the melt to form sulfides-sulfarsenides. Thus, we suggest that the Os, Ir and Ru metallic clusters and alloys in the Zedang chromitites crystallized first under high temperature and low ?S_2, followed by crystallization of sulphides of the laurite-erlichmanite, solid-solution series as the magma cooled and ?S_2 increased. The abundance of primary BMS in the chromitites suggests that ?S_2 reached relatively high values during the final stages of magnesiochromite crystallization. The diversity of the PGE minerals, in combination with differences in the petrological characteristics of the magnesiochromites, suggest different degrees of partial melting, perhaps at different depths in the mantle. The estimated parental magma composition suggests formation in a suprasubduction zone environment, perhaps in a forearc.     

基于新陈代谢的PGM(1,1)模型在建筑物变形监测中的应用

针对目前灰色理论模型在变形监测中的应用,本文分析了PGM(1,1)模型中的参数及其求解的方法;对于建模时前期观测值对后期预测值的影响,引入新陈代谢理论,通过整体最小二乘求解得到模型的背景值。结合高层建筑物沉降监测的实例进行计算分析,结果表明,基于新陈代谢的PGM(1,1)模型相比于传统的GM(1,1)模型,在建筑物沉降预测方面具有较好的效果。     

时变参数PGM(1, 1)变形预测模型及其应用

在GM(1，1)模型的基础上，考虑参数随时间的变化，用多项式逼近模型参数，同时针对GM(1，1)模型背景值取值方法的不足，引入背景值最佳生成系数，建立了时变参数PGM(1，1)变形预测模型。多项式中的待定系数采用最小二乘法确定，背景值最佳生成系数采用搜索法确定。实例计算表明，时变参数PGM(1，1)变形预测模型具有较高的模拟精度和预测精度，适合用于变形体的变形预测。     

Platinum–Group Minerals in Podiform Chromitite from the Kamuikotan Zone, Hokkaido, Northern Japan

Abstract: Ru–Os–Ir alloys have been found in two podiform chromitites located at the Chiroro and Bankei mines in the Sarugawa peridotite complex in the Kamuikotan zone, Hokkaido, Japan. This is the first report on the occurrence of PGM (= platinum-group minerals) from chromitites in Japan. The Ru–Os–Ir alloys most typically form polyhedra associated with other minerals (Ni–Fe alloys and heazlewoodite) in chromian spinel. The PGM are possibly pseudomorphs after some primary PGM such as laurite and are chemically highly inhomogeneous, indicating a low-temperature alteration origin. This is consistent with intense alteration (formation of serpentine, uvarovite and kämmererite) imposed on the Kamuikotan chromitites. High-temperature primary PGE (platinum–group elements)–bearing sulfides were possibly recrystallized at low temperatures into a new assemblage of PGM, Ni-Fe alloys and sulfides. Placer PGM around the peridotite complexes are chemically different from the PGM in dunite and chromitite possibly due to the, as yet, incomplete search for the rock-hosted PGM. The PGE content in chromitites is distinctly higher in those in the Kamuikotan zone than in those in the Sangun zone of Southwest Japan, consistent with the more refractory nature (Cr# of spinel, up to 0.8) of the former than the latter (Cr# of spinel, 0.5).