共查询到19条相似文献，搜索用时 125 毫秒
1.
给出云母化学成分比值FM=6(Fe+2+Mn)/(Fe2++Mn+Mg),用以表示Mg-Fe云母成分变化的基本趋势。根据291个云母的化学成分相对于FM值的异常变化,提出了天然Mg-Fe云母自然分类的新方案:把FM≌1.20(1.05-1.35)、4.80作为区分金云母、黑云母和铁叶云母的界线;FM>0.60的金云母称为铁金云母;以FM=2.70、3.60把黑云母再细分为富镁黑云母、镁铁黑云母和富铁黑云母。Mg-Fe云母自然分类的本质是各成员云母之间白云母置换方式和限度的潜在差异在不同的自然结晶条件下的反映。 相似文献
2.
云母:花岗岩-伟晶岩稀有金属成矿作用的重要标志矿物 总被引：4，自引：1，他引：3
云母是花岗岩、伟晶岩中的重要造岩矿物,不仅是整个岩浆阶段的结晶产物,而且也是热液过程的参与者。作为层状硅酸盐矿物,层间或八面体位置上可容纳锂、铷铯、锡、铌钽等稀有金属。本文结合前人研究积累和作者近年来的研究成果,阐述了云母作为一个重要的稀有金属成矿标志矿物的矿物学特征。铁锂云母-锂云母是稀有金属成矿作用中重要的锂矿物,同时云母中锂含量可以反映花岗岩的分异程度。铷、铯可以置换云母层间钾,在高演化花岗岩、伟晶岩中可以形成铷、铯为主的云母(既可以是锂云母系列,也可以是黑云母系列)。黑云母是稀有金属花岗岩中一个特殊的矿物。准铝质含锡花岗岩中黑云母锡含量可达100×10~(-6),其锡含量可以指示其锡成矿能力。稀有金属花岗岩中,常见的是铌钽氧化物矿物。但是最近研究发现,黑云母中铌可以超常富集(超过1000×10~(-6)),成为稀有金属花岗岩中最重要、甚至唯一的铌矿物,形成一种以富铌黑云母为特色的新类型稀有金属花岗岩,并可能代表了一种新型的潜在铌资源。基于云母在花岗岩中的重要性和结构的特殊性,今后要利用微区成分和结构分析技术,加强对云母中稀有金属晶体化学的研究,以及进一步揭示云母对稀有金属成矿的特殊重要意义。 相似文献
3.
利用增量方法对云母族矿物的氧同位素分馏进行了系统的理论计算。结果表明，不同化学成分和结构状态的云母之间存在一定的氧同位素分馏，其１８Ｏ富集顺序在热力学同位素平衡时为：多硅白云母＞钠云母＞锂云母＞白云母＝珍珠云母＞海绿石＞铁云母＞金云母＞黑云母。在４００℃以上的高温条件下，云母－水体系的氧同位素分馏与温度之间的相关性不明显，并且云母相对于水亏损１８Ｏ达１‰－２．５‰。石英－云母体系的氧同位素分馏与温度之间具有显著的负相关性，因此，能够作为灵敏的同位素地质温度计。不过，石英－黑云母对的氧同位素地质测温往往给出岩石冷却过程中的退化再平衡温度，而不是岩石形成温度。 相似文献
4.
Fe-Al云母及铝铁叶云母 总被引：2，自引：0，他引：2
黑云母花岗岩→二云母花岗岩→白云母花岗岩是华南花岗岩类中一种常见的岩石演化序列。岩石中存在贫Li富Fe、Al云母的矿物组合。例如:五里亭-101杂岩体云母组合为黑云母-铁白云母-白云母,湘千岩体为黑云母-锂铁叶云母-铁白云母-白云母,黄山岩体的云母组合包括锂黑云母-锂铁叶云母等。这些云母(表1)的分子式(按氧的原子数等于22计算)中,Li从小于0.4(白云母)到小于0.6(黑云母),低于八面体阳离子总数的10%。对这些富 相似文献
5.
6.
以小虎斯特91号伟晶岩脉中的不同结构带及蚀变围岩、交代岩、锂云母细脉中云母矿物为研究对象,通过电子探针(EMPA)和激光剥蚀等离子体质谱(LA-ICP-MS)对各结构带不同产状的云母进行主微量成分分析.研究表明,91号脉从围岩蚀变带、伟晶岩边缘带、外侧带、中间带到核部带,依次发育黑云母、白云母、富锂白云母和锂云母,伟晶岩中云母类矿物显示由白云母向锂云母演化趋势.Li在白云母和富锂云母(锂白云母和锂云母)中的置换机制不同,分别可能为2SiⅣ+ LiⅥ(←→)3A1Tot和Si+Li(←→)AlTot+Fe (Zn,Mn,Mg)(白云母)和3LiⅥ(←→)AlⅥ+ 2□Ⅵ(富锂云母,□代表空位).小虎斯特91号伟晶岩脉经历了岩浆-热液的演化过程,随着演化进行,云母中K/Rb、Mg/Li比值显著降低,Li、Rb、Cs、F含量显著增大,指示分离结晶作用是晚期熔体相Li、Rb、Cs、F富集的主要机制.但云母类矿物的主、微量元素特征显示小虎斯特91号脉岩浆-热液过渡阶段特征不明显,伟晶岩演化很快由正岩浆阶段转化为热液阶段. 相似文献
7.
位于南天山中段英买来岩体的主体由中粗粒似斑状黑云母钾长花岗岩组成,局部有粗粒似斑状二云母钾长花岗岩。二者全岩化学成分相似,但在矿物组成上表现出一定差异。前者不透明矿物为钛铁矿,而后者出现原生白云母,不透明矿物全部为磁铁矿。根据石原舜三(1977)的划分方案,黑云母钾长花岗岩全部符合钛铁矿系列特征,而二云母钾长花岗岩虽然表现出不透明矿物为磁铁矿、所含黑云母富镁等看似符合磁铁矿系列的特征,但所有的磁铁矿均和黑云母、钾长石共生,因此推测磁铁矿是由黑云母分解析出而成,并结合其同样具有全岩Fe3+/(Fe3++Fe2+)低、且出现钛铁矿系列的特征共生矿物白云母,亦判定其属于钛铁矿系列。另外,英买来岩体的矿物学和地球化学特征均符合S型花岗岩的特征,说明在本区钛铁矿系列和S型花岗岩相当。研究结果也表明南天山地区在早二叠世还没有完全进入板内演化阶段。 相似文献
8.
通过详细研究世界范围内1842—1993年他人76个及作者42个含Cr的且与白云母同结构的云母化学成分资料,确立了自然产出的云母族矿物结构层内八面体中Cr~(3+)与Al~(3+)的完全类质同象关系。重新核查了云母族矿物分类,强调了按云母族矿物结构层内,八面体位置上所占据的阳离子类型,及其类质同象程度进行亚族划分的原则,将过去的二八面体型Al系列即白云母亚族,扩充为Cr—Al系列即铬铝云母亚族 相似文献
9.
大别山榴辉岩富流体退变质阶段的白色云母 总被引：1，自引：0，他引：1
大别山榴辉岩的退变质过程可分为贫流体、弱流体和富流体3个阶段。贫流体阶段的主要作用是榴辉岩造岩矿物的重结晶、同质多象转变和固溶体出溶;弱流体阶段有少量流体参与,并且其压力、温度较高,形成的白色云母主要为多硅白云母;富流体阶段在大量流体参与下,形成大量的低压含水矿物,其中包括多种白色云母。富流体阶段早期的白色云母主要为多硅白云母,其Si原子数介于6．5pfu和7．2pfu之间;晚期白色云母成分复杂,包括钠云母、白云母和珍珠云母。黑云母是退变质作用最晚期形成的云母。退变质云母具环带结构,其内带为钠云母,中带为白云母和珍珠云母的交生体,外带为黑云母。 相似文献
10.
11.
Si+4 Content of natural phengites 总被引：2，自引：0，他引：2
B. Velde 《Contributions to Mineralogy and Petrology》1967,14(3):250-258
The chemical compositions of white micas separated from adjacent rocks of glaucophane and greenschist facies are compared with respect to their Si+4 content. The micas are predominantly phengitic, i.e. between muscovite, K[Al2Si3AlO10(OH)2] and celadonite, K[(R+2R+3)Si4O10(OH)2] in composition. Constancy of Si content in micas coming from rocks of different bulk chemical composition but closely similar physical conditions indicates that the silica content of a potassic dioctahedral mica can be used to indicate the pressure and temperature conditions of its formation. This conclusion is in part based upon previous experimental data obtained for synthetic phengites. 相似文献
12.
Mössbauer studies of micas on the polylithionite-side-rophyllite join show the existence of a relation between the quadrupole splitting (ΔE Q) values of Fe2+ high spin doublets and both cationic and anionic composition of micas. This linear relation is positive as Li2O content increases and negative as F content increases. In the lithium iron micas, the inner ferrous quadrupole doublet is assigned to the cis-site M(2), while the outer doublet is assigned to the trans-site M(1). A random distribution of Fe2+ is observed in fluorine-rich compositions, while slight enrichment of the M(1) site is noticed in hydroxyl compositions, perhaps due to a more sensitive oxidation in situ in M(2) than M(1) sites. The Mössbauer spectrum of siderophyllite K2(Fe 4 2+ Al2)(Si4Al4)O20(OH)4 shows the presence of only one ferrous doublet, which is assigned to M(2) sites. Hence from Mössbauer data we must consider a clintonite (“xanthophyllite”) structure for this mica. The ordered octahedral layer has two distorted ferrous cis-sites and one, more symmetrical, aluminum trans-site. 相似文献
13.
L. P. Ogorodova I. A. Kiseleva M. F. Vigasina L. V. Mel’chakova I. A. Bryzgalov D. A. Ksenofontov 《Geochemistry International》2017,55(9):814-821
The paper reports original thermochemical data on six natural amphibole samples of different composition. The data were obtained by high-temperature melt solution calorimetry in a Tian–Calvet microcalorometer and include the enthalpies of formation from elements for actinolite Ca1.95(Mg4.4Fe 0.5 2+ Al01)[Si8.0O22](OH)2(–12024 ± 13 kJ/mol) and Ca2.0(Mg2.9Fe 1.9 2+ Fe 0.2 3+ )[Si7.8Al0.2O22](OH)2, (–11462 ± 18 kJ/mol), and Na0.1Ca2.0(Mg3.2Fe 1.6 2+ Fe 0.2 3+ )[Si7.7Al0.3O22](OH)2 (–11588 ± 14 kJ/mol); for pargasite Na0.5K0.5Ca2.0-(Mg3.4Fe 1.8 2+ Al0.8)[Si6.2Al1.8O22](OH)2 (–12316 ± 10 kJ/mol) and Na0.8K0.2Ca2.0(Mg2.8Fe 1.3 3+ Al0.9) [Si6.1Al1.9O22](OH)2 (–12 223 ± 9 kJ/mol); and for hastingsite Na0.3K0.2Ca2.0(Mg0.4Fe 1.3 2+ Fe 0.9 3+ Al0.2) [Si6.4Al1.6O22](OH)2 (?10909 ± 11 kJ/mol). The standard entropy, enthalpy, and Gibbs free energy of formation are estimated for amphiboles of theoretical composition: end members and intermediate members of the isomorphic series tremolite–ferroactinolite, edenite–ferroedenite, pargasite–ferropargasite, and hastingsite. 相似文献
14.
N.C.N Stephenson 《Lithos》1977,10(1):9-27
The compositions of coexisting hornblendes and biotites from amphibolite and granulite facies gneisses from the south coast of Western Australia were controlled by host rock composition, paragenesis, metamophic grade, pressure, and oxygen fugacity. The Mg/(Mg + Fe2+) and Mn/Fe2+ ratios in both minerals and possibly the Alvi contents of the hornblendes are related to host rock compositions. Metamorphic grade appears to influence, perhaps only indirectly, the Ti, Mn, and Fe3+ contents of both minerals and possibly the hornblende Ca content. The higher Ti and lower Mn contents of the granulite facies hornblendes and biotites are attributed to their coexistence with pyroxenes, whereas their lower Fe3+/(Fe2+ + Fe3+) ratios are probably due to lower oxygen fugacity in the granulite facies environment. Grade-related colour variations in both minerals were controlled by their Ti/Fe2+ and Fe3+/(Fe2+ + Fe3+ ratios. The relatively low Alvi contents of the hornblendes suggest low- to moderate-pressure metamorphism.Variations in element distribution coefficients are related to variations in mineral compositions rather than metamorphic grade. Thus KD(Aliv ?Si) is related to the Aliv andedenite alkali contents of the hornblendes, KD(Fe2+ ?Mg) to the distributions of Aliv ?Si and Alvi + Ti + Fe3+, KD(Mn) to the Mn contents of both minerals, and KD(Alvi) to the Alvi contents of the biotites. 相似文献
15.
Stefano Pini Maria Franca Brigatti Marco Affronte Daniele Malferrari Augusto Marcelli 《Physics and Chemistry of Minerals》2012,39(8):665-674
This contribution is finalized at the discussion of the magnetic structure of two samples, belonging to phlogopite–annite [sample TK, chemical composition IV(Si2.76Al1.24) VI(Al0.64Mg0.72 $ {\text{Fe}}_{1.45}^{2 + } $ Mn0.03Ti0.15) (K0.96Na0.05) O10.67 (OH)1.31 Cl0.02] and polylithionite–siderophyllite joints [sample PPB, chemical composition IV(Si3.14Al0.86)VI(Al0.75Mg0.01 $ {\text{Fe}}_{1.03}^{2 + } $ $ {\text{Fe}}_{1.03}^{3 + } $ Mn0.01Ti0.01Li1.09) (K0.99Na0.01) O10.00 (OH)0.65F1.35]. Samples differ for Fe ordering in octahedral sites, Fe2+/(Fe2+?+?Fe3+) ratio, octahedral composition, defining a different environment around Fe cations, and layer symmetry. Spin-glass behavior was detected for both samples, as evidenced by the dependency of the temperature giving the peak in the susceptibility curve from the frequency of the applied alternating current magnetic field. The crystal chemical features are associated to the different temperature at which the maximum in magnetic susceptibility is observed: 6?K in TK, where Fe is disordered in all octahedral sites, and 8?K in PPB sample, showing a smaller and more regular coordination polyhedron for Fe, which is ordered in the trans-site and in one of the two cis-sites. 相似文献
16.
L. P. Ogorodova L. V. Mel’chakova M. F. Vigasina I. A. Kiseleva I. A. Bryzgalov 《Geochemistry International》2017,55(3):257-262
The thermochemical study of two natural trioctahedral Mg–Fe chlorites—clinochlores was carried out using high-temperature melt solution calorimetry with a Tian–Calvet microcalorimeter. The enthalpies of formation of clinochlores of compositions (Mg4.9Fe 0.3 2+ Al0.8)[Si3.2Al0.8O10](OH)8 (–8811 ± 12 kJ/mol) and (Mg4.3Fe 0.7 2+ Al1.0)[Si3.0Al1.0O10](OH)8 (–8696 ± 13 kJ/mol) from elements were determined. The values of the standard entropies and the Gibbs energies of formation of the studied natural minerals as well as thermodynamic properties of Mg–Fe chlorites of theoretical composition were estimated. 相似文献
17.
L. P. Ogorodova I. A. Kiseleva M. F. Vigasina L. V. Mel’chakova D. A. Ksenofontov I. A. Bryzgalov 《Geochemistry International》2017,55(7):669-673
The paper presents data on the thermochemical study (high-temperature melt calorimetry in a Tian–Calvet microcalorometer) of two natural Mg–Fe amphiboles: anthophyllite Mg2.0(Mg4.8Fe0.2 2+)[Si8.0O22](OH)2 from Kukh-i-Lal, southwestern Pamirs, Tajikistan, and gedrite Na0.4Mg2.0(Mg1.7Fe0.2 2+Al1.3)[Si6.3Al1.7O22](OH)2 from the Kola Peninsula, Russia. The enthalpy of formation from elements is obtained as–12021 ± 20 kJ/mol for anthophyllite and as–11545 ± 12 kJ/mol for gedrite. The standard entropy, enthalpy, and Gibbs energy of formation are evaluated for Mg–Fe amphiboles of theoretical composition. 相似文献
18.
Bruce Velde 《Contributions to Mineralogy and Petrology》1972,37(3):235-247
Phase relations for the bulk compositions of the celadonites between the MgAl, MgFe3+ and Fe2+Fe3+ types (celadonite = KR2+R3+ Si4O10 (OH)2) under magnetite-iron and nickel-nickel oxide solid-fluid buffers indicate the extent of solid solution possible in this potassic mica series at temperatures between 300° and 430° C at 2 Kb total pressure. Other possible combinations of Mg, Al, Fe ions in octahedrally coordinated sites did not produce single-phase mica products. The ferrous celadonite micas are stable only under oxygen fugacities where magnetite is the stable oxide—where both Fe2+ and Fe3+ can coexist. However the celadonite with the highest thermal stability at 2 Kb total pressure, nickel-nickel oxide buffer conditions is the KMgFe3+Si4O10(OH)2 phase which is stable up to 420°C, well into low grade metamorphic conditions. It is thus apparent that the presence of celadonite or glauconite mica will not be indicative of changing diagenetic conditions. 相似文献
19.
A series of alumina-free micas was synthesized hydrothermally in the potassium-poor portion of the system K2O-MgO-SiO2-H2O. One end member of this series has the composition KMg2.5[Si4O10](OH)2, which, because of its octahedral occupancy, is intermediate between the dioctahedral and trioctahedral micas.From this end member a series of mica solid solutions extends towards more Mg-rich compositions. Single phase micas were obtained along the substitution line 2Mg for Si which appears to involve incorporation of part of the Mg in tetrahedral sites. It leads to a theoretical end member with a structural formula KMg3[Si3.5Mg0.5O10](OH)2. Solid solutions containing up to 75 mole % of this theoretical end member could be synthesized. The observed densities, water contents, and a one-dimensional Fourier synthesis are consistent with the assumed substitution.At 1 kb fluid pressure and 620° C the Si-rich end member KMg2.5[Si4O10](OH)2 decomposes to a more Mg-rich mica, the roedderite phase K2Mg5Si12O30, liquid, and H2O-rich vapor. With increasing Mg-content the thermal stability of the mica solid solutions increases up to 860°C at a composition of about K2O·6.2MgO·7.4SiO2·2H2O, i.e. KMg2.8[Si3.7Mg0.3O10](OH)2. This mica disintegrates directly into forsterite + liquid + H2O-rich vapor. The mica phase richest in Mg with a composition of about K2O·6.5MgO·7.25SiO2·2H2O, i.e. KMg2.875 [Si3.625Mg0.375O10](OH)2, breaks down at 765° C into forsterite, a more Si-rich mica, liquid, and H2O-rich vapor.This binary series of alumina-free micas forms a complete series of ternary solid solutions with normal phlogopite, KMg3[Si3AlO10](OH)2. Analyses of some natural phlogopites showing Si in excess of 3.0 (up to 3.18) per formula unit can be explained through this ternary miscibility range. 相似文献