基于SAMCF法的攀西地区水系沉积物铂族元素异常提取   总被引：1，自引：0，他引：1  

任光明  李佑国  骆耀南  费光春  包凤琴  陈杰  徐静 《矿物岩石地球化学通报》2007,26(3):240-244

攀西地区是我国重要的铂族元素地球化学省,具良好的铂族元素(PGE)成矿地质条件;攀枝花-西昌一带有一个与峨眉山玄武岩分布范围基本吻合的Pt、Pd区域地球化学异常。本文根据不同地层单元水系沉积物中Pt、Pd元素地球化学特征,用子区中位数衬值滤波(SAMCF)法提取铂族元素异常,圈出多处Pt、Pd衬值异常区。结合有关铂族元素矿床地球化学特征,通过水系沉积物中Pt、Pd综合异常的筛选,初步优选出8个铂族元素异常找矿远景区和19个Ⅱ类异常区,为进一步开展铂族矿床找矿提供依据。  相似文献   

中国镍铜铂族岩浆矿床矿产地空间数据库建设及其开发应用     

焦建刚  ;汤中立  ;钱壮志  ;张振飞  ;刘瑞平 《西安地质学院学报》2007,(1):22-25

中国镍铜铂族岩浆硫化物矿床矿产资源方面，全国尚无统一的矿产地质数据库。经过大量资料收集、数据整理和建库，完成了中国镍铜铂族岩浆硫化物矿床矿产地数据库的建设。在此基础上，以MAPGIS为平台进行程序编程，建立了数据信息丰富、库结构合理、具有多项实用功能的矿产空间数据库软件。借助空间数据库软件对中国镍铜铂族岩浆硫化物矿床进行地质研究，总结了中国此类矿床的小岩体成矿特征和富集规律。  相似文献   

The source of platinum group elements in basalts of the ophiolite complex of the Kamchatsky Mys Peninsula (Eastern Kamchatka)     

D.P. Savelyev  S.V. Palesskii  M.V. Portnyagin 《Russian Geology and Geophysics》2018,59(12):1592-1602

Contents of platinum group elements (PGE—Os, Ir, Ru, Rh, Pt, and Pd) and rhenium in basalts of different geochemical types from the ophiolite complex of the Kamchatsky Mys Peninsula have been determined by the isotope dilution-mass spectrometry method. The total contents of PGE in different basalts are commensurate (1.4-3.6 ppb), but the element ratios vary considerably. A specific feature of the rocks is the low degree of PGE fractionation (Pd/Ir = 0.9-6.6, Pt/Pd = 1.0-7.3), which makes them similar to the Hawaiian tholeiitic basalts and picrites. The most fractionated PGE pattern is observed for alkali basalt (Pd/Ir = 6.6), and the least fractionated one, for E-MORB (Pd/Ir = 1.7). The similarity of the PGE patterns of basalts of different geochemical types suggests their similar mantle sources. We propose a model explaining the geochemical features of the basalts of the Kamchatsky Mys ophiolite complex by an impurity of the Earth’s core material in the plume source. The Ir/Pd-Ru/Pd and Pd/10-Ir-Ru discrimination diagrams can be used to identify enriched (plume) basalts based on their PGE content.  相似文献   

The feature and tectonic setting of Dongqiao podiform chromitite in the central segment of the Bangong Lake-Nujiang suture zone in TibetSCIEI北大核心CSCD     

曹楚奇  杨经绥  杨胜标  董玉飞  陈晓坚  熊发挥  卢雨潇 《岩石学报》2022,(11):3391-3410

早侏罗世东巧蛇绿岩位于班公湖-怒江缝合带(班怒带)东段,蕴含较为丰富的豆荚状铬铁矿资源。东巧地幔橄榄岩主体由方辉橄榄岩组成,铬铁矿赋存在其内部的纯橄岩脉中。方辉橄榄岩和纯橄岩均显示出弧前橄榄岩的特征。方辉橄榄岩中橄榄石的Fo值为89.8~92.2,斜方辉石的和单斜辉石的Mg^(#)值分别变化于89.7~92.0和92.7~95.1,铬尖晶石的Cr^(#)值(Cr^(#)=100×Cr/(Cr+Al))为60.8~75.9;纯橄岩中橄榄石的Fo值为91.7~92.5,斜方辉石Mg^(#)值变化于91.7~92.1,单斜辉石的Mg^(#)值变化于94.0~94.6,铬尖晶石的Cr^(#)值为69.0~83.1。铬铁矿主要呈致密块状和浸染状构造,其中铬尖晶石的矿物包裹体有橄榄石、斜方辉石、单斜辉石、角闪石和铂族矿物等。矿石中的铬尖晶石与橄榄岩中的铬尖晶石相比,具有较高的Cr^(#)值(72.5~86.9)和Mg^(#)值(52.8~70.5),较低的Al_(2)O_(3)(6.25%~13.6%)、TiO_(2)(0.06%~0.16%)和Zn(518×10^(-6)~714×10^(-6)),属于高铬型铬铁矿,平衡熔体与玻安质熔体有亲缘性。方辉橄榄岩中铂族元素(PGE)总含量(14.01×10^(-9)~32.81×10^(-9))近似于原始地幔,IPGE(Os、Ir和Ru)/PPGE(Rh、Pt和Pd)的比值均大于1;纯橄岩的PGE总量(13.36×10^(-9)~16.08×10^(-9))略低于原始地幔,IPGE和PPGE富集程度近似;铬铁矿的铂族元素总量(108.4×10^(-9)~645.7×10^(-9))远远高于原始地幔和地幔橄榄岩中PGE的含量,且IPGE以及Rh相对原始地幔富集,而Pt和Pd相对亏损,具明显右倾特征的配分模式,指示东巧地幔橄榄岩和铬铁矿形成过程经历了熔体抽取和交代作用。通过与全球典型豆荚状铬铁矿矿床的特征对比,认为班怒带的蛇绿岩应该有良好的铬铁矿成矿背景。  相似文献   

Filling the Bushveld Complex magma chamber: lateral expansion, roof and floor interaction, magmatic unconformities, and the formation of giant chromitite, PGE and Ti-V-magnetitite deposits   总被引：2，自引：0，他引：2  

F. Johan Kruger 《Mineralium Deposita》2005,40(5):451-472

“His mind was like a soup dish—wide and shallow; ...” - Irving Stone on William Jennings Bryan

A compilation of the Sr-isotopic stratigraphy of the Bushveld Complex, shows that the evolution of the magma chamber occurred in two major stages. During the lower open-system Integration Stage (Lower, Critical and Lower Main Zone), there were numerous influxes of magma of contrasting isotopic composition with concomitant mixing, crystallisation and deposition of cumulates. Larger influxes correspond to the boundaries of the zones and sub-zones and are marked by sustained isotopic shifts, major changes in mineral assemblages and development of unconformities. During the upper, closed system Differentiation Stage (Upper Main Zone and Upper Zone), there were no major magma additions (other than that which initiated the Upper Zone), and the thick magma layers evolved by fractional crystallisation. The Lower and Lower Critical Zones are restricted to a belt that runs from Steelpoort and Burgersfort in the northeast, to Rustenburg and Northam in the west and an outlier of the Lower and Lower Critical Zone, up to the LG4 chromitite layer, in the far western extension north of Zeerust. It is only in these areas that thick harzburgite and pyroxenite layers are developed and where chromitites of the Lower Critical Zone occur. These chromitites include the economically important c. 1 m thick LG6 and MG1 layers exposed around both the Eastern and Western lobes of the Bushveld Complex. The Upper Critical Zone has a greater lateral extent than the Lower Critical Zone and overlies but also onlaps the floor-rocks to the south of the Steelpoort area . The source of the magmas also appears to have been towards the south as the MG chromitite layers degrade and thin northward whereas the LG layers are very well represented in the North and degrade southward. Sr and Os isotope data indicate that the major chromitite layers including the LG6, MG1 and UG2 originated in a similar way. Extremely abrupt and stratigraphically restricted increases in the Sr isotope ratio imply that there was massive contamination of intruding melt which “hit the roof” of the chamber and incorporated floating granophyric liquid which forced the precipitation of chromite (Kruger 1999; Kinnaird et al. 2002). Therefore, each chromitite layer represents the point at which the magma chamber expanded and eroded and deformed its floor. Nevertheless, this was achieved by in situ contamination by roof-rock melt of the intruding Critical Zone liquids that had an orthopyroxenitic to noritic lineage. The Main Zone is present in the Eastern and Western lobes of the Bushveld Complex where it overlies the Critical Zone, and onlaps the floor-rocks to the south, and the north where it is also the basal zone in the Northern lobe. The new magma first intruded the Northern lobe north of the Thabazimbi–Murchison Lineament, interacted with the floor-rocks, incorporated sulphur and precipitated the “Platreef” along the floor-rock contact before flowing south into the main chamber. This exceptionally large influx of new magma then eroded an unconformity on the Critical Zone cumulate pile, and initiated the Main Zone in the main chamber by precipitating the Merensky Reef on the unconformity. The Upper Zone magma flowed into the chamber from the southern “Bethal” lobe as well as the TML. This gigantic influx eroded the Main Zone rocks and caused very large-scale unconformable relationships, clearly evident as the “Gap” areas in the Western Bushveld Complex. The base of this influx, which is also coincident with the Pyroxenite Marker and a troctolitic layer in the Northern lobe, is the petrological and stratigraphic base of the Upper Zone. Sr-isotope data show that all the PGE rich ores (including chromitites) are related to influxes of magma, and are thus related to the expansion and filling of the magma chamber dominantly by lateral expansion; with associated transgressive disconformities onto the floor-rocks coincident with major zone changes. These positions in the stratigraphy are marked by abrupt changes in lithology and erosional features over which succeeding lithologies are draped. The outcrop patterns and the concordance of geochemical, isotopic and mineralogical stratigraphy, indicate that during crystallisation, the Bushveld Complex was a wide and shallow, lobate, sill-like sheet, and the rock-strata and mineral deposits are quasi-continuous over the whole intrusion.

F. Johan KrugerEmail:

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PGE and Os-isotopic variations in lavas from Kohala Volcano, Hawaii: Constraints on PGE behavior and melt/crust interaction     

M. Jamais  J.C. Lassiter  G. Brügmann   《Chemical Geology》2008,250(1-4):16-28

We have examined Re, Platinum-Group Element (PGE) and Os-isotope variations in suites of variably fractionated lavas from Kohala Volcano, Hawaii, in order to evaluate the effects of melt/crust interaction on the mantle isotopic signature of these lavas. This study reveals that the behavior of Os and other PGEs changes during magma differentiation. The concentrations of all PGEs strongly decrease with increasing fractionation for melts with MgO < 8 wt.%. Fractionation trends indicate significantly higher bulk partition coefficients for PGEs in lavas with less than 8 wt.% MgO (D_PGE = 35–60) when compared to values for more primitive lavas with MgO > 8 wt.% (D_PGE ≤ 6). This sudden change in PGE behavior most likely reflects the onset of sulfur saturation and sulfide fractionation in Hawaiian magmas at about 8 wt.% MgO.

The Os-rich primitive lavas (≥ 8 wt.% MgO, > 0.1 ppb Os) display a narrow range of ¹⁸⁷Os/¹⁸⁸Os values (0.130–0.133), which are similar to values in high-MgO lavas from Mauna Kea and Haleakala Volcanoes and likely represent the mantle signature of Kohala lavas. However, Os-isotopic ratios become more radiogenic with decreasing MgO and Os content in evolved lavas, ranging from 0.130 to 0.196 in the shield-stage Pololu basalts and from 0.131 to 0.223 in the post-shield Hawi lavas. This reflects assimilation of local oceanic crust material during fractional crystallization of the magma at shallow level (AFC processes). AFC modeling suggests that assimilation of up to 10% upper oceanic crust could produce the most radiogenic Os-isotope ratios recorded in the Pololu lavas. This amount of upper crust assimilation has a negligible effect on the Sr and Nd-isotopic compositions of Kohala lavas. Thus, these isotopic compositions likely represent the composition of the mantle source of Kohala lavas.  相似文献   

河北高寺台杂岩体铂、钯地球化学分布和异常特征     

张兴超  王爱枝  袁德志  韩存强 《物探与化探》2008,32(3):261-266

在高寺台超镁铁杂岩体发现了2种铂族元素异常:一种异常分布在杂岩体纯橄榄岩或橄榄岩带的镁质超基性岩中,与已知的含铂族铬铁矿有关,与已知的铬、钴、镍等矿化主金属的强异常密切共生。在这种异常中,钯呈甚低的背景分布,w(Pt)/w(Pd)大;另一种铂族元素异常呈带状沿杂岩体透辉岩带及其中的剪切带分布,其异常特征是铂、钯异常密切共生,w(Pt)/w(Pd)近于1,并且,在这种异常中,不伴生铬、镍等元素的强异常。这是一种新的铂、钯等元素的地球化学富集和矿化。研究表明,采用岩石、土壤、水系沉积物铂、钯地球化学勘查技术,可以发现难识别的铂族矿化。  相似文献   

云南二叠纪白马寨铜镍硫化物矿床的成因:地壳混染与矿化的关系   总被引：6，自引：0，他引：6  

王焰 《矿物岩石地球化学通报》2008,27(4)

云南金平白马寨-营盘街-带的奥陶纪变砂岩和板岩中出露大量小型约260Ma的镁铁-超镁铁质岩体,其中白马寨地区三个岩体具明显铜-镍硫化物矿化：三号岩体有一个中型铜镍硫化物矿床,一号和二号岩体可见微弱矿化。一号岩体的Ni／Cu值为0．7～2．2,二号岩体的Ni／Cu值为1．4～4．0,与三号岩体的比值（Ni／Cu=-0．5～6．7）相近,说明他们的母岩浆成分接近,为富Mg的镁铁质或苦橄质岩浆。三个岩体遭受不同程度的地壳混染,表现为强烈的Nb（Ta）异常,很低的Nb／La值（O．5～O．7）和很负的￡。。（f）值（一5．1～一9．O）。根据全岩的Th／Yb和Nb／Th值估算,一号岩体的地壳混染程度为5％～20％,二号岩体的地壳混染程度为5％～10％,而三号岩体的地壳混染程度高达35％。三个岩体的地壳混染程度与岩体中硫化物的含量呈正相关关系,表明地壳混染是导致白马寨岩体硫化物饱和的主要因素。  相似文献   

四川木落稀土矿床方解石铂族元素地球化学特征     

朱志敏  郑荣才  周家云  罗丽萍 《地学前缘》2008,15(2):291-299

方解石作为木落稀土矿床常见的脉石矿物,其中的铂族元素(简称PGE)地球化学特征有可能记录了地质流体的性质。采用ICP-MS分析木落方解石中PGE的含量,并对铂族元素的分布、相关性、成因进行了探讨。木落方解石可以分为两类:I型方解石和Ⅱ型方解石。I型方解石中∑PGE(不含Os)0.62～1.33ng/g,具相对低的Pd/Pt、Pd/Rh、Pd/Ru、Pd/Ir比值,不太显著的Pt-Pd分配模式,为岩浆成因方解石,与成矿作用密切相关;Ⅱ型方解石中∑PGE(不含Os)1.85～2.97ng/g,具相对高的Pd/Pt、Pd/Rh、Pd/Ru、Pd/Ir比值和显著的Pt-Pd分配模式,为热液成因方解石,代表了成矿作用后的一期地质流体作用,与成矿关系不大,仅局部地区存在改造前次流体作用形成的稀土矿体。富CO2热液具有携带PGE的能力,并能够导致PGE的分异,与富CO2岩浆相比,富CO2热液对铂族元素具有一定程度的富集作用。  相似文献   

四川会理大岩子铂矿成矿地质特征及找矿标志   总被引：2，自引：0，他引：2  

杨大宏  刘俊思  曾祥贵 《四川地质学报》2005,25(4):208-214

四川会理大岩子铂矿床是新发现的我国第一个独立铂钯矿床.本文阐述了大岩子铂矿的成矿区域地质背景,总结了矿区地质特征并同诺里尔斯克铂矿床进行了对比,提出了找矿标志,开拓了地质找矿的新领域.  相似文献