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1.
晋蒙边界富铝片麻岩的矿物演化序列及动力学意义   总被引：1，自引：0，他引：1  
华北地台北缘早前寒武纪孔兹岩系的变质反应结构及矿物组合演化序列在晋蒙边界地区代表性岩石；夕线石榴黑云钾长（二长）片麻岩（Ａ）和石榴（紫苏）黑云斜长片麻岩（Ｂ）中保存的最为完整，以岩相学及显微组构特征为依据，可将其划分四个世代的矿物组合；（１）峰前以含蓝晶石残晶和包裹于平衡镶嵌，出现典型的麻粒岩相矿物组合；Ｋｙ±Ｇｔ＋Ｋｆ±ｐｌ＋Ｑｚ（Ａ），Ｂｉ±Ｇｔ＋Ｐｌ＋Ｑｚ（Ｂ）；（２）峰期以基质矿物平衡镶嵌  相似文献   

2.
蓝晶石族矿物包括蓝晶石、矽线石和红柱石,因其具有耐高温、抗腐蚀和煅燃后体积膨胀等特性而为人们所瞩目,成为钢铁工业的娇子,世界蓝晶石族矿产量的50%用于钢铁工业;由于近年钢铁工业的不断发展,对它的需求量更以每年10%的速度递增.我国的蓝晶石族矿各地均有发现,其中河北、辽宁、河南、新疆、山西、内蒙、广东、浙江、陕西等省  相似文献   

3.
四川丹巴地区基性，超基性岩型Cu-Ni-Pt族元素矿床中，含有多种Pt族元素矿物，主要有：（1）碲化物及碲铋化物，碲锑化物类，（2）锑化物类，（3）砷化石类，（4）自然元素类，通过显微镜下的观察鉴定和成分电子探针分析结果，分别计算了矿床中主要矿石矿物的结晶化学式，结果表明，矿床中有7种已知的Pt族元素矿物和6种可能是Pt族元素新矿物或新变种矿物。  相似文献   

4.
喜马拉雅造山带内广泛分布着淡色花岗岩，近期研究表明多个岩体与稀有金属成矿作用密切相关。喜马拉雅东部拉隆岩体中花岗质伟晶岩发育有铌钽成矿作用，主要赋存在铌铁矿族矿物中。本次研究考察了该岩体的伟晶岩，观察了这些铌铁矿族矿物的产状，并对它们的主量、微量元素成分进行了分析。根据岩相学特征的差异，拉隆伟晶岩被分为边部带、过渡带和核部带。铌铁矿族矿物大多出现在过渡带中，具有明显的核边结构，根据产状和Ta#[Ta/(Ta+Nb)]可将铌铁矿族矿物分为两类，第一类矿物成分均一，自形程度好，晶体内部缺少内部结构。第二类矿物自形程度差，分布于第一类矿物的边部、填充于第一类矿物的裂隙或交代其核部，并发育有一系列的亚显微结构（包括韵律环带结构、交代结构、溶蚀孔洞结构和裂隙填充结构）。第一类铌铁矿族矿物是Ta#较低（0.08～0.34）的铌铁矿，而第二类为Ta#相对较高（0.45～0.60）的铌铁矿和钽铁矿。这两类铌铁矿族矿物的稀土配分模式相近，Eu呈强烈的负异常，δEu的范围为0.001～0.020。配分曲线总体呈海鸥型，四分组效应不明显；LREE/HREE值范围为0.016～0.044，反映出重稀土元素富集...  相似文献   

5.
本文对山西五台山地区与超镁铁质岩密切共生的含蓝晶石的各类片岩进行了研究。研究发现，在蓝晶石铝直闪石片岩中存在一种特殊的冠状体结构，即蓝晶石和铝直闪石被它们之间内圈的十字石十刚玉十绿泥石和外圈的堇青石所包绕。这种特殊的反应边结构，说明岩石曾处于较高的压力条件下（０．９～１．４ＧＰａ），然后经历了明显的近等温的减压过程。其它类型的含蓝晶石片岩，也包含了高压变质矿物组合，并经历了同样的变质演化过程。这种演化历史与该区经历了古洋壳俯冲，消减，弧陆碰撞和伴随的迅速折返和抬升是密切有关的。  相似文献   

6.
萤石颜色与自由基关系的电子自族共振（ESR）研究   总被引：1，自引：0，他引：1  
萤石颜色与自由基关系的电子自族共振（ＥＳＲ）研究唐荣炳，温桂兰（中国科学院地球化学研究所，贵阳５５０００２）（中国科学院广州地球化学研究所，广州５１０６４０）关键词萤石，顺磁离子，自由基长期以来，对矿物颜色的研究，先是定性观察和分类，再是应用光的吸收...  相似文献   

7.
李思泉 《江西地质》1995,9(4):319-326
本文就蓝晶石类矿物的基本特征，用途及国内外对蓝晶石类矿物资源利用现状作了介绍，并结合本省成矿地质条件，提出了具体找矿方向。  相似文献   

8.
一、岩石的物质组份及主要矿物特征蓝晶石产于蓝晶石岩、蓝儡石白云母石英片岩及含蓝晶石白云母石英片岩三个类型的岩石中。其中蓝晶石岩含蓝晶石50—90%,次要矿物为绢云母、褐铁矿、刚玉、金红石、榍石等。蓝晶石白云母石英片岩含蓝晶石10—30%,主要矿物为石英、白云母,少量矿物有赤铁矿、金红石、黄铁矿等,蓝晶石与白云母呈反消长关系。含蓝晶石白云母石英片岩中,蓝晶  相似文献   

9.
白云鄂博矿床氟金云母的矿物学研究   总被引：2，自引：1，他引：2  
徐金沙  沈敢富 《矿物学报》2005,25(3):213-216
内蒙白云鄂博REE-Nb-Fe矿床广泛分布的“金云母”，以F含量〉〉H2O^＋含量为其鲜明特色。按∑（O＋F）=12计算的金云母化学式表明，其附加阴离子中，绝大多数F〉OH。根据国际矿物协会（IMA）新矿物及矿物命名委员会（CNMMN）的规定，F〉OH（离子摩尔数）的金云母，应称氟金云母，属云母族的独立矿物种。检索IMA CNMMN公布的已知矿物种名录，均无氟金云母条目。为此，按新矿物要求，对该矿物作了详尽而系统的矿物学研究；同时还对金云母组的矿物作了分类。  相似文献   

10.
角闪石族和辉石族矿物的系统矿物学分类命名   总被引：1，自引：0，他引：1  
角闪石族和辉石族矿物是链状硅酸盐矿物的重要组成部分,它们中的许多矿物种属于造岩矿物和/或工业矿物,具有重要的成因矿物研究意义和工业应用开发价值。国内学者对它们的分类命名和基本系统认识主要源自于王璞等(1984)编著的《系统矿物学》。随着科学技术发展和矿物学研究的不断深入,原有的矿物基础资料和分类命名都在不断更新与完善,迄今已有专业学术机构和学者在不同年代陆续发表了不同版本对该两类矿物的修订或修改意见,但一直没有统一整合,导致在涉及该两类矿物的应用研究中,在分类命名上与国际标准不统一。根据本课题组在国家公益性行业科研专项项目(新编《系统矿物学》)所承担的研究任务和当前国内外研究进展,本文系统归纳、梳理并综述了角闪石族和辉石族矿物的分类方案和命名原则,使分类命名统一标准、原则和认识并与国际接轨,这有利于该两类矿物的理论研究与开发应用,更好地支撑地质学及相关学科的研究与发展。  相似文献   

11.
The distribution and textural features of staurolite–Al2SiO5 mineral assemblages do not agree with predictions of current equilibrium phase diagrams. In contrast to abundant examples of Barrovian staurolite–kyanite–sillimanite sequences and Buchan‐type staurolite–andalusite–sillimanite sequences, there are few examples of staurolite–sillimanite sequences with neither kyanite nor andalusite anywhere in the sequence, despite the wide (~2.5 kbar) pressure interval in which they are predicted. Textural features of staurolite–kyanite or staurolite–andalusite mineral assemblages commonly imply no reaction relationship between the two minerals, at odds with the predicted first development (in a prograde sense) of kyanite or andalusite at the expense of staurolite in current phase diagrams. In a number of prograde sequences, the incoming of staurolite and either kyanite, in Barrovian sequences, or andalusite, in Buchan‐type sequences, is coincident or nearly so, rather than kyanite or andalusite developing upgrade of a significant staurolite zone as predicted. The width of zones of coexisting staurolite and either kyanite, in Barrovian sequences, or andalusite, in Buchan‐type sequences, is much wider than predicted in equilibrium phase diagrams, and staurolite commonly persists upgrade until its demise in the sillimanite zone. We argue that disequilibrium processes provide the best explanation for these mismatches. We suggest that kyanite (or andalusite) may develop independently and approximately contemporaneously with staurolite by metastable chlorite‐consuming reactions that occur at lower P–T conditions than the thermodynamically predicted staurolite‐to‐kyanite/andalusite reaction, a process that involves only modest overstepping (<15°C) of the stable chlorite‐to‐staurolite reaction and which is favoured, in the case of kyanite, by advantageous nucleation kinetics. If so, the pressure difference between Barrovian kyanite‐bearing sequences and Buchan andalusite‐bearing sequences could be ~1 kbar or less, in better agreement with the natural record. The unusual width of coexistence of staurolite and Al2SiO5 minerals, in particular kyanite and andalusite, can be accounted for by a combination of lack of thermodynamic driving force for conversion of staurolite to kyanite or andalusite, sluggish dissolution of staurolite, and possibly the absence of a fluid phase to catalyse reaction. This study represents an example of how kinetic controls on metamorphic mineral assemblage development have to be considered in regional as well as contact metamorphism.  相似文献   

12.
Quartz‐rich veins in metapelitic schists of the Sanandaj‐Sirjan belt, Hamadan region, Iran, commonly contain two Al2SiO5 polymorphs, and, more rarely, three coexisting Al2SiO5 polymorphs. In most andalusite and sillimanite schists, the types of polymorphs in veins correlate with Al2SiO5 polymorph(s) in the host rocks, although vein polymorphs are texturally and compositionally distinct from those in adjacent host rocks; e.g. vein andalusite is enriched in Fe2O3 relative to host rock andalusite. Low‐grade rocks contain andalusite + quartz veins, medium‐grade rocks contain andalusite + sillimanite + quartz ± plagioclase veins, and high‐grade rocks contain sillimanite + quartz + plagioclase veins/leucosomes. Although most andalusite and sillimanite‐bearing veins occur in host rocks that also contain Al2SiO5, kyanite‐quartz veins crosscut rocks that lack Al2SiO5 (e.g. staurolite schist, granite). A quartz vein containing andalusite + kyanite + sillimanite + staurolite + muscovite occurs in andalusite–sillimanite host rocks. Textural relationships in this vein indicate the crystallization sequence andalusite to kyanite to sillimanite. This crystallization sequence conflicts with the observation that kyanite‐quartz veins post‐date andalusite–sillimanite veins and at least one intrusive phase of a granite that produced a low‐pressure–high‐temperature contact aureole; these relationships imply a sequence of andalusite to sillimanite to kyanite. Varying crystallization sequences for rocks in a largely coherent metamorphic belt can be explained by P–T paths of different rocks passing near (slightly above, slightly below) the Al2SiO5 triple point, and by overprinting of multiple metamorphic events in a terrane that evolved from a continental arc to a collisional orogen.  相似文献   

13.
Oxygen‐isotope compositions of kyanite, andalusite, prismatic sillimanite and fibrolite from the Proterozoic terrane in the Truchas Mountains, New Mexico differ from one another, suggesting that these minerals did not grow in equilibrium at the Al2SiO5 (AS) polymorph‐invariant point as previously suggested. Instead, oxygen‐isotope temperature estimates indicate that growth of kyanite, andalusite and prismatic sillimanite occurred at c. 575, 615 and 640 °C respectively. Temperature estimates reported in this paper are interpreted as those of growth for the different AS polymorphs, which are not necessarily the same as peak metamorphic temperatures for this terrane. Two distinct temperature estimates of c. 580 °C and c. 700 °C are calculated for most fibrolite samples, with two samples yielding clear evidence of quartz‐fibrolite oxygen‐isotope disequilibrium. These data indicate that locally, and potentially regionally, oxygen‐isotope disequilibrium between quartz and fibrolite may have resulted from rapid fibrolite nucleation. Pressures of mineral growth that were extrapolated from oxygen‐isotope thermometry results and calculated using petrological constraints suggest that kyanite and one generation of fibrolite grew during M1 at 5 kbar, and that andalusite, prismatic sillimanite and a second generation of fibrolite grew during M2 at 3.5 kbar. M1 and M2 therefore represent two distinct metamorphic events that occurred at different crustal levels. The ability of the AS polymorphs to retain δ18O values of crystallization make these minerals ideal to model prograde‐growth histories of mineral assemblages in metamorphic terranes and to understand more clearly the pressure–temperature histories of multiple metamorphic events.  相似文献   

14.
Torsion experiments were performed on the Al2SiO5 polymorphs in the sillimanite stability field to determine basic rheological characteristics and the effect of deformation on polymorphic transformation. The experiments resulted in extensive transformation of andalusite and kyanite to sillimanite. No transformation occurred during the hot-press (no deformation) stage of sample preparation, which was carried out at similar P–T conditions and duration as the torsion experiments. Experiments were conducted on fine-grained (< 15 µm) aggregates of natural andalusite, kyanite and sillimanite at 1250 °C, 300 MPa, and a constant shear strain rate of 2 × 10− 4/s to a maximum shear strain of 400%. Electron back-scattered diffraction (EBSD) analysis of the experiments revealed development of lattice-preferred orientations, with alignment of sillimanite and andalusite [001] slightly oblique to the shear plane. The kyanite experiment could not be analyzed using EBSD because of near complete transformation to sillimanite. Very little strain ( 30%) is required to produce widespread transformation in kyanite and andalusite. Polymorphic transformation in andalusite and kyanite experiments occurred primarily along 500 µm wide shear bands oriented slightly oblique and antithetic to the shear plane and dominated by sub-µm (100–150 nm) fibrolitic sillimanite. Shear bands are observed across the entire strain field preserved in the torsion samples. Scanning transmission electron microscope imaging shows evidence for transformation away from shear bands; e.g. fibrolitic rims on relict andalusite or kyanite. Relict grains typically have an asymmetry that is consistent with shear direction. These experimental results show that sillimanite is by far the weakest of the polymorphs, but no distinction can yet be made on the relative strengths of kyanite and andalusite. These observations also suggest that attaining high bulk strain energy in strong materials such as the Al2SiO5 polymorphs is not necessary for triggering transformation. Strain energy is concentrated along grain boundaries, and transformation occurs by a dynamic recrystallization type process. These experiments also illustrate the importance of grain-size sensitive creep at high strains in a system with simultaneous reaction and deformation.  相似文献   

15.
Kyanite replaces andalusite in a belt of Ordovician and Silurian pelitic rocks that form a narrow synform pinched between high-grade antiforms in NW Variscan Iberia. Kyanite occurs across the belt in Al-rich, black pelites in assemblages I: kyanite–chloritoid–chlorite–muscovite and II: kyanite–staurolite– chlorite–muscovite. In I, kyanite occurs in the matrix and in kyanite–muscovite aggregates that pseudomorph earlier andalusite porphyroblasts. The aggregates are found across the belt and can still be recognized in assemblage II and even in III: andalusite–staurolite–biotite–muscovite, this latter being a hornfelsic Silurian schist where kyanite is relic and staurolite occurs in the matrix, and is resorbed inside new massive pleochroic andalusite. KFMASH and MnKFMASH pseudosections have been constructed using Thermocalc for Al-rich and Al-poorer compositions from the belt. Chloritoid zoning in Al-rich rocks containing assemblage I, plus chloritoid–chlorite thermometry complemented with garnet–chlorite thermometry in Al-poorer lithologies, mean that the path is one of increasing pressure and temperature. Conditions prior to assemblage I, with earlier andalusite stable, are those of the andalusite–chloritoid– chlorite field as testified by chloritoid enclosed in andalusite porphyroblast rims. The passage from assemblage I to II implies a prograde path within the kyanite field. Assemblage III represents peak conditions, indicating a prograde staurolite-consuming reaction across a KFMASH field, leading eventually to a locally found andalusite–biotite–muscovite hornfels. The lowest pressure stages are recorded by cordierite–biotite in Al-poor pelites. Garnet-bearing MnKFMASH assemblages in Al-poorer pelites record conditions similar to assemblages II and III. The replacement of andalusite by kyanite in assemblage I is attributed to downdragging of andalusite-bearing rocks into a synform as testified by the strained andalusite porphyroblasts affected by a subvertical crenulation cleavage. Prograde metamorphism in the eastern contact of the belt is due to heat transferred to the belt from the ascending high grade antiform across the Vivero fault.  相似文献   

16.
The aureoles of the Donegal granites frequently contain combinationsof the following minerals: kyanite, andalusite, fibrolite, sillimanite.Textural and spatial evidence suggests these minerals did notgrow simultaneously but sequentially in the order above, asthe temperature increased in the aureoles. Reactions are notcomplete and overstepping is common. Early porphyroblast phasesdo not take part in later reactions, they remain closed systems.Later reactions take place essentially from the groundmass layeredminerals. Polymorphic change from one aluminium silicate toanother is rare. The presence of more than one polymorph ina rock is therefore due to the metastable persistence of thelower temperature phase(s) which grew stably. Kyanite is confined to rocks with values of MgO/(MgO/FeO) (molecularratios) greater than about 0-50, so that its absence in someaureoles is due to a lack of rocks of the appropriate compositionrather than inadequate pressure during crystallization. Sillimanite,fibrolite, and andalusite show no restriction to rocks of agiven composition. The aureoles in Donegal were probably formedover a relatively narrow pressure band and a wide temperaturerange.  相似文献   

17.
Hydrothermal experiments utilizing the seeding technique show conclusively that the lower temperature stability limit of Mg cordierite so far accepted (Schreyer and Yoder, 1964) represents metastable equilibria throughout the pressure range 1–7 kb. The stable equilibrium curve generally lies at somewhat higher temperatures and is not subdivided by an invariant point involving the phase pyrophyllite within this pressure range. Instead of pyrophyllite+andalusite+chlorite, hitherto assumed to be the breakdown assemblage of cordierite below 5 kb water pressure, the paragenesis Al silicate+chlorite+quartz was found to be stable over the entire pressure range investigated. The andalusite/kyanite transition, as determined by Richardson et al. (1969), is confirmed by a minor change of slope of the cordierite breakdown curve. Direct breakdown of cordierite into pyrophyllite-bearing assemblages must be limited to conditions below about 1 kb and 450° C. This gives indirect support to Kerrick's (1968) stability data on pyrophyllite, as opposed to those of Althaus (1969) and others. These new results offer an explanation for the common assemblage chlorite+andalusite (or kyanite)+quartz occuring in spotted slates, greenschists, and also as retrograde alteration products of natural cordierites.We thank Dr. K. Langer, Bochum, for partial analyses of some of the natural starting materials. Financial support of this work by Deutsche Forschungsgemeinschaft, Bad Godesberg, is gratefully acknowledged.  相似文献   

18.
The raw-material base of the Russian aluminum industry is considered. The raw materials include common (bauxites, nepheline syenites) and uncommon (nepheline ores, synnyrites, anorthosites, power-and-heating plant ashes, kaolines) types of ores. With regard to many criteria (reserves and quality of ores, technology of their processing, etc.), the problem of alumina deficit can be solved by mining sillimanite group minerals Al2SiO5 (wt.%: Al2O3 = 62.9, SiO2 = 37.1), namely, andalusite, sillimanite, and kyanite. Their proved reserves converted to the final product (aluminum) exceed 400 mln tons. This will be enough for more than a hundred years provided that aluminum is produced in the present-day output (4 mln tons in 2008). Almost all deposits can be explored by strip mining, with application of the gravitation, flotation, and electromagnetic separation methods for ore dressing. The alumina content in concentrates reaches 60–62 wt.%. Only high-grade bauxites and the above concentration methods can ensure such a high yield of Al2O3. Sillimanite group minerals can be processed together with nepheline ores by sintering or be used for the direct electrothermal production of silumin and aluminum, excluding the alumina production stage. The latter method is the most promising in Russia.  相似文献   

19.
Aluminum silicate triple-point occurrences are common in metamorphicrocks of northern New Mexico. The three polymorphs show extensivesolid solution, with Fe and Mn substituting for Al. Mineraltextures, the spatial distribution of phases, and the systematicpartitioning of Fe and Mn indicate that the kyanite-andalusite-sillimaniteassemblages crystallized in equilibrium. The compositions ofminerals in the three-phase assemblage vary across the studyarea, recording regional variations in the pressures and temperaturesof metamorphism. The highest-pressure rocks, exposed at RioMora, contain kyanite at higher elevations and sillimanite atlower elevations. A sub-horizontal isograd separates the twominerals. Kyanite and sillimanite have nearly identical Fe contentwhich varies systematically with XFe2O3 in hematite or ilmenite.Andalusite occurs only along a single manganiferous layer, incrystals rich in MnAlSiO5 and saturated in FeAlSiO5. Triple-pointassemblages can be found wherever the folded manganiferous layercrosses the unfolded kyanite-sillimanite isograd. The TruchasRange, preserving slightly lower pressures of metamorphism,shows kyanite-andalusite-sillimanite in rocks with titaniferoushematite. Andalusite is enriched in Fe relative to kyanite andsillimanite, but no polymorphs contain Mn. Rocks with lowerXFe2O3 in hematite have kyanite and sillimanite without andalusite,whereas rocks with pure hematite contain only andalusite. Theshallowest erosional levels are preserved in the western PicurisRange where the three polymorphs occur as pure minerals in ilmenite-bearingrocks. Hematitic samples contain only andalusite which showsextensive solid solution of both Fe and Mn. The assemblage kyanite-andalusite-sillimanite is not invariant.Iron and manganese both add degrees of freedom. These transitionmetals have stabilized the three-phase assemblage, in apparentchemical equilibrium, across a P-T interval of 500-540 ?C, 3?8-4?6kb in rocks from New Mexico. The saturation level of FeAlSiO5in andalusite does not vary with Mn content but does vary withpressure and temperature. Calculations indicate that a 2-3 kbdecrease in pressure or a 25-50 ?C increase in temperature resultsin a 1 mole per cent increase in XFeAlSiO5 in iron-saturatedandalusite.  相似文献   

20.
The sequential growth of biotite, garnet, staurolite, kyanite, andalusite, cordierite and fibrolitic sillimanite, their microstructural relationships, foliation intersection axes preserved in porphyroblasts (FIAs), geochronology, P–T pseudosection (MnNCKFMASH system) modelling and geothermobarometry provide evidence for a P–T–t–D path that changes from clockwise to anticlockwise with time for the Balcooma Metamorphic Group. Growth of garnet at ～530 °C and 4.6 kbar during the N–S‐shortening event that formed FIA 1 was followed by staurolite, plagioclase and kyanite growth. The inclusions of garnet in staurolite porphyroblasts that formed during the development of FIAs 2 and 3 plus kyanite growth during FIA 3 reflect continuous crustal thickening from c. 443 to 425 Ma during an Early Silurian Benambran Orogenic event. The temperature and pressure increased during this time from ～530 °C and 4.6 kbar to ～630 °C and 6.2 kbar. The overprinting of garnet‐, staurolite‐ and kyanite‐bearing mineral assemblages by low‐pressure andalusite and cordierite assemblages implies ～4‐kbar decompression during Early Devonian exhumation of the Greenvale Province.  相似文献   

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