Mineralogy and geochemistry of platinum-group elements in the Aguablanca Ni-Cu deposit (SW Spain)     

R. Piña  F. Gervilla  L. Ortega  R. Lunar 《Mineralogy and Petrology》2008,92(1-2):259-282

Summary The Aguablanca Ni-Cu-(PGE) magmatic sulphide deposit is associated with a magmatic breccia located in the northern part of the Aguablanca gabbro (SW, Iberia). Three types of ores are present: semi-massive, disseminated, and chalcopyrite-rich veined ore. The principal ore minerals are pyrrhotite, pentlandite and chalcopyrite. A relatively abundant platinum-group mineral (PGM) assemblage is present and includes merenskyite, melonite, michenerite, moncheite and sperrylite. Moreover, concentrations of base and precious metals and micro-PIXE analyses were obtained for the three ore-types. The mineralogy and the mantle-normalised chalcophile element profiles strongly suggest that semi-massive ore represents mss crystallisation, whereas the disseminated ore represents an unfractionated sulphide liquid and the chalcopyrite-rich veined ore a Cu-rich sulphide liquid. Palladium-bearing minerals occur commonly enclosed within sulphides, indicating a magmatic origin rather than hydrothermal. The occurrences and the composition of these minerals suggest that Pd was initially dissolved in the sulphides and subsequently exsolved at low temperatures to form bismutotellurides. Negative Pt and Au anomalies in the mantle-normalised chalcophile element profiles, a lack of Cu-S correlation and textural observations (such as sperrylite losing its euhedral shape when in contact with altered minerals) suggest partial remobilisation of Pt, Au and Cu by postmagmatic hydrothermal fluids after the sulphide crystallisation. Authors’ addresses: R. Pi?a, L. Ortega, R. Lunar, Departamento de Cristalografía y Mineralogía, Facultad de Geología, Universidad Complutense de Madrid, ES-28040 Madrid, Spain; F. Gervilla, Facultad de Ciencias, Instituto Andaluz de Ciencias de la Tierra, Universidad de Granada-CSIC, Avda. Fuentenueva, s/n, ES-18002 Granada, Spain  相似文献   

Gas hydrate disturbance fabrics of southern Hydrate Ridge sediments (ODP Leg 204): Relationship with texture and physical properties   总被引：1，自引：0，他引：1  

Elena Piñero  Eulàlia Gràcia  Francisca Martínez-Ruiz  Juan Cruz Larrasoaña  Alexis Vizcaino  Gemma Ercilla 《Geo-Marine Letters》2007,27(2-4):279-288

Soupy and mousse-like fabrics are disturbance sedimentary features that result from the dissociation of gas hydrate, a process that releases water. During the core retrieval process, soupy and mousse-like fabrics are produced in the gas hydrate-bearing sediments due to changes in pressure and temperature conditions. Therefore, the identification of soupy and mousse-like fabrics can be used as a proxy for the presence of gas hydrate in addition to other evidence, such as pore water freshening or anomalously cool temperature. We present here grain-size results, mineralogical composition and magnetic susceptibility data of soupy and mousse-like samples from the southern Hydrate Ridge (Cascadia accretionary complex) acquired during Leg 204 of the Ocean Drilling Program. In order to study the relationship between sedimentary texture and the presence of gas hydrates, we have compared these results with the main textural and compositional data available from the same area. Most of the disturbed analyzed samples from the summit and the western flank of southern Hydrate Ridge show a mean grain size coarser than the average mean grain size of the hemipelagic samples from the same area. The depositional features of the sediments are not recognised due to disturbance. However, their granulometric statistical parameters and distribution curves, and magnetic susceptibility logs indicate that they correspond to a turbidite facies. These results suggest that gas hydrates in the southern Hydrate Ridge could form preferentially in coarser grain-size layers that could act as conduits feeding gas from below the BSR. Two samples from the uppermost metres near the seafloor at the summit of the southern Hydrate Ridge show a finer mean grain-size value than the average of hemipelagic samples. They were located where the highest amount of gas hydrates was detected, suggesting that in this area the availability of methane gas was high enough to generate gas hydrates, even within low-permeability layers. The mineralogical composition of the soupy and mousse-like sediments does not show any specific characteristic with respect to the other samples from the southern Hydrate Ridge.  相似文献   

On the elliptic restricted three-body problem     

Jaume Llibre  Conxita Piñol 《Celestial Mechanics and Dynamical Astronomy》1990,48(4):319-345

The main goal of this paper is to show that the elliptic restricted three-body problem has ejection-collision orbits when the mass parameter µ is small enough. We make use of the blow up techniques. Moreover, we describe the global flow of the elliptic problem when µ = 0 taking into account the singularities due to collision and to infinity.  相似文献   

Periodic orbits of an electric charge in a magnetic dipole field     

Lidia Jiménez-Lara  Eduardo Piña 《Celestial Mechanics and Dynamical Astronomy》1990,49(4):327-345

Periodic orbits in the Stormer problem are studied using the symmetry lines of the Poincaré map introduced by De Vogelaere. Many known facts are explained by mean of these lines. The dynamics of four special symmetry lines when the Stormer parameter ₁ changes is presented, and we obtain a clear global view of the structure of the simple periodic orbits and their bifurcations, including the asymmetrical ones. New asymmetrical multiple periodic orbits are obtained.  相似文献   

库车坳陷下侏罗统沉积特征及砂体展布   总被引：6，自引：0，他引：6       下载免费PDF全文

张惠良  寿建峰  陈子料  王少依  杨晓宁  皮学军  蔡振忠 《古地理学报》2002,4(3):47-58

库车坳陷位于塔里木盆地北部，北缘是南天山山前断裂带，南缘是塔北隆起，呈NEE向展布，东西长250km，南北宽20－60km，面积约21170km^2。下侏罗统自下而上发育阿合组、阳霞组。对吐格尔明、克孜勒努尔、库车河剖面及依南2井岩芯观察发现，阿合组和阳霞组按其岩性特征均可以划分为5个岩性段，各个岩性段在全具有对比性。还可分出4类和17个亚类岩相。阿合组细砂岩以上的粗碎屑岩含量为80％以上；阳霞组细砂岩以上的碎屑岩含量为50％－60％。砂岩厚度占总地层厚度的50％－60％以上，是油气勘探的重要目的层系。以吐格尔明剖面为代表的依南2井以东地区的阿合组和阳霞组岩矿特征基本相似，以克孜勒努尔地区为代表的依南2井以西地区有较大差异，即阳霞组长石含量几乎为零。两区共同点是以岩屑砂岩为主，成分成熟度低，结构成熟度中等，岩屑含量较高。从岩性组合、沉积构造、微观岩石成分、结构和砂体形态等方面的综合分析认为，辫状三角洲沉积体系是该区阿合组和阳霞组的主要沉积体系。阿合组砂体纵向上以多个辫状三角洲平原上的辫状分流河道砂岩加积复合为主，横向上指状镶嵌叠置呈东西向展布。阳霞组第3岩性段砂体纵向上以多个辫状三角洲前缘上的水下辫状分流河道砂岩加积复合为主，横向上指状镶嵌叠置也呈东西向展布。第2、4、5岩性段砂体以河道滞流砂岩侧砂为主，横向叠瓦状叠置呈东西向展布。  相似文献   

用混合和扩散云室对大气冰核浓度的观测分析   总被引：3，自引：0，他引：3  

杨绍忠  王祥国  游来光  皮家雄 《气象》2004,30(12):39-43

继1963年用混合云室对春季冰核浓度观测之后，1994～1996年，在同季节、同地点用混合和静力扩散云室又做了同步观测。对取得的资料进行整理分析，得出了凝华核浓度在不同天气背景下占总冰核浓度的百分比，两种云室测值的对应关系；分析了扩散云室的容积效应及冰核浓度随气压、能见度等气象因子的变化。  相似文献   

Geological mapping for the urban area of Tarragona     

M. Vilà  D. Albalat  R. Pi 《Environmental Earth Sciences》2016,75(5):365

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Silver–bearing minerals in the Xinhua hydrothermal vein-type Pb-Zn deposit,South China     

Wang  Minfang  Zhang  Xubo  Guo  Xiaonan  Pi  Daohui  Yang  Meijun 《Mineralogy and Petrology》2018,112(1):85-103

Mineralogy and Petrology - Electron probe microanalysis (EPMA) results are reported for newly identified silver–bearing minerals from the Xinhua deposit, Yunkaidashan area, South China. The...  相似文献   

吉林浑江铅锌矿荒沟山区韧性剪切带特征及其控矿规律          下载免费PDF全文

张宝华  屈奋雄  张鹏程  刘如琦  徐英新  皮万有  张世民 《地质找矿论丛》1994,9(3):39-47

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Exfoliation of kaolinite by urea-intercalation precursor and microwave irradiation assistance process     

Pi Zhenbang  Liu Zhuoqin  Yang Chao  Tian Xike  Fei Jinbo  Zheng Jianhua 《Frontiers of Earth Science》2007,1(1):26-29

A type of exfoliated kaolinite was produced by urea-intercalation and original microwave irradiation assisted method. The product was investigated by Fourier transformation infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electronic microscopy (SEM), Brunauer-Emmett-Teller (BET) and laser particle analysis techniques. FT-IR spectra show that NHCO molecule exists in the intercalated kaolinite. XRD analyses indicate that the kaolinite sheet-like structure was disordered after microwave irradiation. The urea decomposition process and explosion effect between the sheet-like structures of kaolinite under microwave irradiation were discussed. The SEM and BET analyses reveal that the end product is exfoliated kaolinite with thin particles and increased surface area. Size and zeta potential analyses show that the particle size distribution is between 250 nm and 550 nm with normal distribution and the particle is negatively charged. In comparison with the conventional grind method, the process adopted appears to be economic and the exfoliated kaolinite end product may display a significantly enhanced performance in industrial applications.  相似文献