东南极拉斯曼丘陵富硼岩系中硅硼镁铝矿-柱晶石-电气石矿物的硼同位素组成及其意义

东南极拉斯曼丘陵地区麻粒岩相岩石中出露一套罕见的含硅硼镁铝矿-柱晶石-电气石矿物组合的富硼岩系.由于高级变质作用已使原岩的性质难以确定,变质原岩及其形成环境的恢复变得十分困难,而硼同位素组成则可以作为判定硼来源的有效示踪剂和指相标志.报道了东南极拉斯曼丘陵硅硼镁铝矿-柱晶石-电气石富硼岩系的硼同位素组成资料,其δ11B值变化范围为-12.0‰～-34.6‰,硼同位素的低比值和其他地质证据表明,其原岩为非海相蒸发硼酸盐岩.     

东南极拉斯曼丘陵硼硅酸盐矿物组合硅硼镁铝矿-硼柱晶石-电气石的形成过程及其岩石学意义

东南极拉斯曼丘陵长英质片麻岩中产出大量的电气石-硼柱晶石-硅硼镁铝矿之硼硅酸盐矿物组合,这些矿物(电气石除外)的形成晚于变质峰期一般的硅酸盐矿物。电气石可多次出现,硅硼镁铝矿之后形成硼柱晶石,很少见两种以上的硼硅酸盐矿物能够同时结晶,各种硼硅酸盐矿物在同一期、甚至同一阶段内呈递进关系。在硼硅酸盐矿物的结晶过程中,B₂O₃和Al₂O₃较为活动从而SiO₂的活度相对受到抑制,即存在组分的分异和活性波动,表明络阴离子SiO₄^4-、PO₄^3-、BO₃^3-活动高峰并非同步因而,挥发分组分对深熔作用的影响可能是有限的;同时,结晶的金属阳离子组分不断发生分异。不同的硼硅酸盐矿物形成的介质条件有所差异:电气石形成于富钙的弱酸性溶液,硅硼镁铝矿应为近中-碱性溶液介质,而硼柱晶石形成于含少量氟的偏碱性介质环境。除温压因素外,流体挥发分种类和介质条件也影响到硼硅酸矿物的多期次、多阶段的变化,从而造成矿物组合的复杂性。本区长英质岩石中硼(B)及其他挥发分组分的较高含量可由原岩成分决定,亦可经由变质-深熔作用引起,即深熔作用时熔体的整体优先吸收硼(硼的第一次富集)及随后熔体结晶阶段的局部残留和富集硼(硼的第二次富集)。Gdd-Prs-Trn硼硅酸盐矿物组合的存在,表明发生了以脱水为主的高级变质作用,同时伴随强烈的深熔作用。挥发分组分在露头尺度体系中可能属于开放性质,而在更大尺度和范围内则基本封闭;在深熔作用中,硼等挥发分的存在影响了熔体的组成使得岩浆熔点降低、熔融成分调整粘度有所降低,更容易运移;而且,熔体可以携带这些挥发分,当熔体结晶时挥发分析出、结晶局部富集而形成硼硅酸盐矿物,尤其是沿着一些构造有利部位发生显著的聚集。     

高压-超高压变质电气石研究的现状和进展

本文总结了近年来有关高压-超高压变质电气石的研究成果,并在此基础上指出未来该领域的重点研究方向.电气石是一种分布广泛的矿物.实验证明其稳定存在的温度大于850℃,压力大于4 GPa.由于较慢的空间扩散作用、复杂的成分替代关系和较高的环境敏感度,电气石可以保存完好的生长环带.这有助于我们分析同位素演化、变质流体成分、岩石变质历史等.高压-超高压电气石结构化学研究表明电气石结构中的某些元素含量(如Al和F含量)和矿物的形成温度具有很好的相关性.根据不同的硼同位素来源,高压-超高压变质电气石的生长模型可以分为A型电气石、B型电气石和C型电气石.通过分析出露在全球各地的代表性高压-超高压变质电气石,其特征总体表现为:①多为镁电气石;②X晶位具有很高的占位率(＞0.8 pfu);③化学结构中硼元素具有过量特征(3.2～3.3 pfu);④Ti、Mn、Li、Cl含量很低;⑤硼同位素成分的变化范围为:-16％ ＜δ11B＜+ 1‰.未来高压-超高压变质电气石的研究重点应该放在电气石晶体化学和变质p-t条件的关系、电气石-流体之间微量元素的分异作用以及含硼矿物组合的相平衡模拟等.     

麻山群孔兹岩系柱晶石特征及成因研究

文中所涉及的柱晶石产于我国黑龙江省东部麻山群变质沉积岩系中。作者对矿物的形态、物性、化学成分、结构特征及岩石矿物共生组合进行了系统研究,并与国外同类矿物的资料进行了对比。结合对麻山群变质地质的详细研究,本文还对柱晶石的成因及地质意义进行了探讨。     

澳大利亚布罗肯希尔地区电气石岩的成因和意义

在布罗肯希尔地区的早元古代维利亚马(Willyama)超群中,富电气石岩石是分布广而数量少的岩石。电气石集中产在层控和局部层状电气石岩、变质碎屑沉积岩、石英—锌尖晶石脉岩、层状 Pb-Zn-Ag 硫化物矿石、石榴石英岩、层控白钨矿矿床、石英-电气石结核、不整合石英脉和花岗伟晶岩内。大部分富电气石岩是产在赋主要 Pb-Zn-Ag的布罗肯希尔群内。在 Globe 矿山,沿主矿脉的西北端,电气石与 Pb-Zn-Ag 矿化紧密共生,在一些地方与富锰石榴石石英岩互层。在局部地方,方铅矿和其他矿石矿物是产在这些电气石岩中的重结晶电气石颗粒的核心,表明电气石和硫化物是在变形和高级变质作用之前已存在     

辽东裂谷带硫化物矿床内电气石系列矿物学与找矿关系

本文通过辽东裂谷硫化物矿床中不同产状电气石的研究，提示了不同环境内形成电气石矿物的标型、光性、成分、同位素组成、红外光谱与Ｘ衍射特征方面存在一定差异。不同物化条件下形成的电气石其演化系列表现在由近矿围岩到硫化物矿层电气石由富镁由富铁－镁过渡从层状矿体到热液改造矿体电气石由铁镁向富钙－镁过渡。研究表明，电气石的形成与元古代早期底火山喷发作用后引起的富硼热泉活动有关。     

与新英格兰块状硫化物矿床伴生的电气石

J.F.Slack进行的野外调查、文献研究和岩石学工作表明,电气石可能是变质贱金属块状硫化物矿床中一种常见副矿物.在产于近源沉积物的矿床中(不列颠哥伦比亚的沙利文矿山,滨海美茵的布莱克霍克矿山),以及在混有沉积岩和镁铁质火山岩环境中(佛蒙特铜矿带的伊利沙白矿山),电气石似乎特别丰富. 变质作用对电气石影响强烈,往往使之显著地重结晶和再活动.受变质而重结晶的电气石与铁-铜-锌矿床中最活动的硫化物——磁黄铁矿和黄铜矿呈定向互     

辽宁古元古代地体中富电气石岩石的成因：蒸发岩硼源的证据

辽宁东部古元古界底部地层(南辽河群)中赋存着大型的硼酸盐矿床，含矿层位中广泛分布含电气石的变粒岩和电英岩。空间上这些含电气石的岩石与硼酸盐有着密切的联系，电气石可以作为区域硼矿找矿的标志。已有研究结果表明，该地区的硼酸盐矿床是变质蒸发岩成因。本研究对该区不同产状的电气石和硼酸盐的地质特征，全岩和矿物成分、硼同位素组成进行了分析。本区的电气石包括层状和脉状两大类，而电气石的富集与硼酸盐关系密切，电英岩往往分布在硼酸盐矿体的上盘。而矿体的下盘一般不产出富电气石的岩石。当长英质脉体穿过硼酸盐矿体时，脉体中往往会富集电气石。含电气石岩石的全岩地球化学分析表明，它们的REE及其他微量元素特征以及相关性关系与周围不含电气石的同类岩石十分相似，反映出一种成因上的联系。本区电气石主要属于镁电气石一铁电气石系列，靠近硼矿体的电气石比远离硼矿体的电气石更加富镁，有着更高的Mg／Fe比值。电气石和硼酸盐的硼同位素成分分析显示出二者在同位素组成上的相似性，前者比后者的δ^11B稍低，这可能是由于热液活动过程中同位素分馏的结果。电气石的硼同位素组成在空间上显示出变化规律：远离硼酸盐矿体的电气石的δ^11B值(-5．2‰- 3．6‰)比矿体附近的电气石低(平均 10．5‰)。以上空间和成分上的关系表明硼酸盐可能是形成电气石主要的硼来源，电气石是在热液过程中通过淋滤下伏含硼蒸发岩中的硼形成含硼热液，在与上覆沉积物交代过程中形成含电气石岩石。电气石的条带是热液顺层选择交代的结果。本区电气石与硼酸盐的关系表明，层状电气石可以通过含硼热液交代的方式形成。变质地体中的层状电气石岩石的出现可能与变质蒸发岩有关。这一认识对区域硼矿勘查工作和变质地体的沉积环境分析有借鉴意义。     

澳大利亚与元三古代海底喷气矿床伴生的电气石岩

在绿片岩、角闪岩和麻粒岩和变质岩层中，电气石岩和富电气石的沉积物与喷气矿化伴生，它们遭受了中等到强烈的变形，呈连续层状分布于褶皱构造附近，显示出诸如层理、递变层理、交错层理、层内滑动等沉积构造和拉裂构造。在高级变质作用区，它们显示变质结构，通常被再活化而成的石英－电气石脉所穿切。富电气石岩出现在由海底喷气而形成的Pb－Zn－Ag、Cu－Co、Cu－Bi、W、Sn、Au和稀土元素矿化的下部、内部及矿化之上，且在横向上与矿化同期的地层中。在一些地方，电气石岩没有上述矿化现象，也不与花岗质岩石相伴生。电气石的成分是黑电气石－镁电气石，虽反映了其全岩成分，但不能作为矿化的标志。虽然电气石是与花岗岩、交代岩、角砾岩简伴生的普通矿物，但本文描述的富电气石层为山硅电气石前身的变质作用产生的富硼硅质铁建造。它们是一种常见的喷气岩类型，并且常常出现在早－中元古代厚层的泥质变沉积岩和蒸发岩层序中。这就说明硼是由含硼的粘土的淋滤作用或由含硼酸盐的蒸发岩的淋滤作用产生的。     

川西某地花岗伟晶岩接触变质特征及其找矿意义的初步研究

众所周知,侵入岩体围岩接触变质的研究,有着重要的理论和实际意义。有关花岗伟晶岩围岩接触变质带的研究,一般仅限于对花岗伟晶岩脉旁宽度不大的电气石云英岩化蚀变带进行一般性描述。本区的花岗伟晶岩,除电气石云英岩化蚀变带外,还发育有宽度很大,类型特殊的堇青石接触变质带。它的重要意义在于不但可以指示与该区花岗伟晶岩成因有关的隐伏矿体的存在,同时根据堇青石变质带本身的特征,还可以大致预测花岗伟晶岩的类型、产状、规模、埋藏深度及其主要矿化特征、矿化程度等。显然,它可以为区内发现隐伏花岗伟晶岩矿体,寻找与本区相类似地质特征的花岗伟晶岩矿床,提供极为宝贵和可靠的资料。     

Composition, mineral assemblages, and genesis of serendibite-bearing magnesian skarns

Variations in the composition and mineral assemblages of boronaluminosilciates (serendibite, grandidierite, kornerupine, and tourmaline) were studied in the abyssal and hypabyssal skarns of New York and California, United States, the Taezhnyi deposit of southern Yakutia, and deposits of the Pamirs, and compared to their occurrences around the world. The genesis of the boronaluminosilicates depends on the facies of the replaced skarns and the calcareous-skarn alteration of the primary composition of the host rocks. The substitution between Mg and Fe, as well as between Al, Si, and B, was studied in complex boronaluminosilciates and associated minerals. It was shown that f of serendibite is determined by that in the replaced skarn minerals (pyroxenes, spinel, sapphirine, and grandidierite) and is inherited in the replacing tourmaline and late silicates. Unlike serendibite, kornerupine is a typomorphic mineral of only bimetasomatic skarns of the abyssal facies. Serendibite, grandidierite, kornerupine, and tourmaline crystallized during the postmagmatic stage of the evolution of boron mineralization at skarn deposits of both the abyssal and the hypabyssal facies, at contact with magnesian carbonate sequences and desilicified aluminosilicate rocks.     

山西省中条山铜矿田电气石与电气石岩的研究

本文通过对中条山铜矿田电气石和电气石岩地质产状、岩相学和矿物学、矿物化学等特征的研究，指出本区有三种成因类型的电气石：（１）北峪酸性侵入体岩浆期后热液成因电气石；（２）中条群地层中变质热液形成的电气石；（３）赋矿岩石和近矿围岩中热液蚀变电气石。第（３）类电气石具有特征的产状、矿物化学和矿物共生组合标型，是重要的找矿标志     

Kornerupine-quartz symplectites in paragneiss, Lac Ste-Marie, Quebec, Canada: pseudomorphic replacement of a hexagonal phase, probably osumilite

Summary Kornerupine has been reported from several localities in the Grenville Province. It is most abundant and accessible within quartz - sillimanite - K-feldspar - tourmaline -Fe/Ti-oxides - garnet paragneiss, forming a 300m by 1500m lens in diopside- and chondrodite-bearing marble at Hinck's bridge along the Gatineau river near Lac Ste-Marie. Biotite-rich zones within the lens contain six-sided prisms, up to 7 cm in diameter and 30 cm long. These prisms consist of symmetrically zoned (coarse rim and finer grained centre) symplectitic intergrowths of kornerupine-quartz overgrowing the biotite foliation, with minor sillimanite (as fibrolitic inclusions in kornerupine), K-feldspar, and scattered trails of ilmenite.The kornerupine-quartz symplectite in the six-sided prism appears to be a replacement of an early single hexagonal phase. Habit and bulk composition of the prism point to osumilite as the precursor. Boron-bearing fluids during amphibolite- to granulite-grade metamorphism stabilised tourmaline-quartz intergrowths which crystallized by pseudomorphic replacement of osumilite. Numerous dark green tourmalines are found as relict inclusions in quartz (rare in kornerupine) in core and margin of a prism. In a later stage, kornerupine-quartz symplectites were formed by replacement of the tourmaline with loss of alkalis. On the margin of the prisms kornerupine is in turn partially in contact with (replaced by) fine-grained, light green, euhedral tourmaline. The inferred miner4l assemblages may reveal an early portion of the P-T-t path for the region. Kornerupine — quartz assemblages are not often described, whereas granite pegmatites commonly contain tourmaline — quartz symplectitic intergrowths.

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Kornerupine - Quarz Symplektite in Paragneis, Lac Ste-Marie, Quebec, Kanada: pseudomorpher Ersatz einer hexagonalen Phase, möglicherweise Osumilith

Zusammenfassung Kornerupin ist in der Grenville Province an mehreren Orten gefunden worden. An der Hinck's-Brücke am Gatineau Fluß, nahe dem Ste-Marie See, kommt Kornerupin in hoher Konzentration in einer 300 m x 1500 m Paragneis-Linse mit Quarz, Sillimanit, Kalifeldspat, Turmalin, Fe/Ti-Oxid und Granat vor, die von Diopsid- und Chondroditführendem Marmor eingeschlossen ist. In dieser Linse treten in Biotit-reichen Zonen sechseckige Prismen mit Durchmessern bis 7 cm und Längen bis 30 cm auf. Die Prismen sind symmetrisch vom Rand (grobkörnig) zum Zentrum (feinkörnig) zoniert und bestehen aus symplektitischen Kornerupin-Quarz Verwachsungen mit geringen Mengen an feinkörnigem Sillimanit (fibrolitische Einschlüsse in Kornerupin), Kalifeldspat und Ilmenit-Ketten.Die Kornerupin-Quarz-Verwachsung im sechseckigen Prisma ist an Stelle einer älteren hexagonalen Phase entstanden. Habitus und Gesamtchemismus des Prismas weist auf Osumilith als erste frühe Phase hin. Bor-führende Fluide stabilisierten während einer amphibolit- bis granulit-faziellen Metamorphose die Turmalin-Quarz-Verwachsung, die pseudomorph Osumilith ersetzte. Viele dunkelgrüne Turmaline sind als Relikteinschlüsse im Quarz und selten auch im Kornerupin im Zentrum und am Rand des Prismas zu finden. In einem späteren Stadium wurde Kornerupin-Quarz Symplektit durch Verdrängung von Turmalin mit Abgabe von Alkalien gebildet. Am Rand des Prismas ist Kornerupin teilweise in Kontakt mit (oder ersetzt durch) feinkörnigem, hellgrünen, idiomorphen Turmalin. Die abgeleiteten Mineralvergesellschaftungen entsprechen einem frühen Teil des P-T t Pfades für diese Region. Kornerupin-Quarz Paragenesen sind selten, wogegen in Granit-Pegmatiten Turmalin-Quarz Verwachsungen häufig auftreten.[/ p]

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With 4 Figures     

Kornerupine in Mg-Al-rich gneisses from Namaqualand,South Africa: mineralogy and evidence for late-metamorphic fluid activity

Three kornerupine occurrences are reported in distinctive SiO₂-poor, MgO- and Al₂O₃-rich paragneisses from the Namaqualand Metamorphic Complex in South Africa. Kornerupine coexists stably with phlogopite, cordierite, orthopyroxene, gedrite, sapphirine, sillimanite and plagioclase and, in sapphirine-free rocks, with spinel and corundum. Tourmaline of a texturally older generation than kornerupine is commonly present in the same samples.Ten analysed kornerupines show a variation in total Fe as FeO from 1.8 to 10.9 weight per cent. B₂O₃ contents are estimated from x-ray data and a few spectrochemical analyses to range from 0.9 to 3.5 weight per cent. There is a strong inverse correlation between B³⁺ and Al³⁺. Total iron content has a strong and systematic effect on refractive index, colour and dispersion. Fe and Mg are systematically partitioned with the other minerals, and Mg/(Mg+Fe) ratios increase as follows: spinel 相似文献   

Mineral chemistry of tourmaline from Mashak Pahar,South Purulia Shear Zone (SPSZ), eastern Indian Shield

The area of investigation at and around Mashak Pahar, Bankura district, West Bengal, India comprises a number of rock types namely: granite gneiss, migmatized quartz tourmaline gneiss, quartz pebble conglomerate, ferruginous quartzite, quartz tourmaline veins (as veins) and graphite schists. Interestingly, the study area lies in the region extending South Purulia Shear Zone (～Tamar–Porapahar Shear Zone) which marks the boundary between two contrasting tectonic blocks of eastern India, namely, the Chhotanagpur Gneissic Terrane (CGC) to the north and Singhbhum Group of rocks to the south. The rocks of the study area are poly-phasedly deformed by three phases of folding, namely, F₁, F₂ and F₃. All the tourmalines are classified to be of ‘Alkali Group’. Chemistry of tourmalines from migmatized quartz tourmaline gneiss and those from quartz tourmaline veins are in conformity with their relation to (earthquake induced) shear system evolution in this terrain. In general, the compositional evolution of tourmaline during prograde metamorphism (～400°–730°C) has been supported by both petrographic and chemical evidences. Assessment of mineral–chemical data of constituent tourmaline grains clearly suggests compositional variations across zonal boundaries within tourmaline that was controlled by changing metamorphic milieu in this terrane. Field and petrographic evidences clearly indicate activation of earlier and later shears in this region accompanied by infiltration of boron and formation of zoned tourmaline crystals.     

Reaction history of garnet-sapphirine granulites and conditions of Archaean high-pressure granulite-facies metamorphism in the Central Limpopo Mobile Belt, Zimbabwe

ABSTRACT Sequential reaction textures in Archaean garnet-corundum-sapphirine granulites from the Central Zone of the Limpopo Belt document a progression from early, coarse-grained, high-pressure (P > 9.5 kbar) granulite-facies assemblages (M1) to late, low-pressure (P <6 kbar) granulite-facies sub-assemblages (M2). The stable M1 assemblage was garnet (57% pyrope; Mg/(Mg + Fe) = 62) + sapphirine + corundum + gedrite + phlogopite + rutile. Late-M1 boron-free kornerupine grew at the expense of garnet and corundum, and coexisted with garnet, sapphirine and gedrite. Partial or complete breakdown of coarse garnet and kornerupine during M2 resulted in the development of pseudomorphs and coronas consisting of fine-grained symplectic intergrowths of cordierite, gedrite and sapphirine (later, spinel). The majority of reaction textures can be explained in terms of a stable reaction sequence, and a model time-sequence of mineral facies can be constructed. When compared with a qualitative petrogenetic grid of (Fe, Mg)-discontinuous reactions in the FMASH multisystem sapphirine-garnet-corundum-spinel-cordierite-gedrite-kornerupine, the facies-sequence indicates decompression at essentially constant T assuming constant a(H₂O). Exhumation of M1 corundum inclusions during M2 breakdown of kornerupine resulted in production of metastable spinel by a disequilibrium reaction with gedrite. A second disequilibrium reaction of the spinel with cordierite produced sapphirine. The operation of such reaction while pressure was decreasing (the opposite dP from that implied by the texture if assumed to be the product of an equilibrium reaction) has serious implications for the use of reaction textures in the construction of P-T vectors. Garnet-biotite thermometry on garnet interiors and phlogopite inclusions in corundum yields temperatures of ca. 850°C for the M1 stage. A minimum late-M1 pressure of ca. 7 kbar is indicated by the former association of kornerupine and corundum. Relict M1 kyanites reported by other workers indicate a minumum early-M1 pressure of 9.5 kbar, implying metamorphism at depths of at least 33 km (probably 38km). The high-pressure granulite-facies metamorphism was followed by an almost isothermal pressure decrease of > 5 kbar, indicative of rapid uplift. The P-T path is interpreted as the product of a single metamorphic cycle which probably took place in response to tectonic thickening of the crust. Such a process contrasts with the extensional origin recently proposed for isobarically cooled granulite-facies terranes.     

Tourmaline breakdown in the migmatite zone of the Ryoke metamorphic belt,SW Japan

A sharp line delimitating the distribution of tourmaline (termed as a ‘tourmaline‐out isograd’) is defined in the migmatite zone of the Ryoke metamorphic belt, Japan. The trend of the tourmaline‐out isograd closely matches that of the isograds formed through the regional metamorphism, suggesting that it represents the breakdown front of tourmaline during regional metamorphism. This is confirmed by the presence of the reaction textures of tourmaline to sillimanite and cordierite near the tourmaline‐out isograd. The breakdown of tourmaline would release boron into associated melts or fluids and be an important factor in controlling the behaviour of boron in tourmaline‐bearing high‐temperature metamorphic rocks. Near the tourmaline‐out isograd, large tourmaline crystals occur in the centre of interboudin partitions containing leucosome. In the melanosome of the intervening matrix, reaction textures involving tourmaline are locally observed. These observations imply that tourmaline breakdown is related to a melting reaction and that the boron in the leucosome is derived from the breakdown of tourmaline in the melanosome during prograde metamorphism. Boron released by tourmaline breakdown lowers both the solidus temperature of the rock and the viscosity of any associated melt. Considering that the tourmaline‐out isograd lies close to the schist–migmatite boundary, these effects might have enhanced melt generation and segregation in the migmatite zone of the Ryoke belt. The evidence for the breakdown of tourmaline and the almost complete absence of any borosilicates throughout the migmatite zone suggest that boron was effectively removed from this region by the movement of melt and/or fluid. This implies that the tourmaline‐out isograd can reflect a significant amount of mass transfer in the anatectic zones.     

高温-超高温变质作用成因研究——来自华北克拉通西部孔兹岩带和南非Kaapvaal克拉通西南部Namaqua活动带与Bushveld变质杂岩体的启示

超高温变质作用是在变质地质学领域,继超高压变质作用研究高峰之后的又一重要前缘课题,对于认识地壳构造-热演化具有重要意义。本文总结了华北克拉通西部孔兹岩带和南非Kaapvaal克拉通西南部Namaqua活动带与Bushveld变质杂岩体的高温-超高温麻粒岩的化学成分、矿物组合、变质演化特征,及其相应的变质事件与构造属性。我国的超高温变质作用带,包括华北克拉通西部的孔兹岩带——从内蒙西段的大青山到东段的集宁-凉城地区的超高温变质岩,皆为Al-Mg质和Al饱和体系的超高温变质岩石,常见假蓝宝石+石英、尖晶石+石英的典型超高温变质组合,以及含假蓝宝石±尖晶石、但缺少石英的非典型超高温变质组合。南非Namaqua活动带与Bushveld变质杂岩体分别发现有独特的Fe-Al饱和的铁尖晶石+石英+大隅石、刚玉+高温石英等超高温矿物组合,罕见的高温硼硅酸盐和硅硼铝镁石等超高温矿物组合;以及Ca-Mg质饱和的钙镁橄榄石+镁硅钙石镁黄长石+镁橄榄石等超高温矿物组合的麻粒岩。研究的核心问题是矿物和岩石在高温-超高温条件下的特殊行为方式,不同构造环境和岩石化学成分下的变质反应及其热动力学过程。由此提出超高温变质作用成因研究中的科学问题:包括不同类型和地质属性的高温-超高温麻粒岩的成因特征;麻粒岩的形成条件演化过程和构造背景;高温-超高温变质过程中部分熔融和重新水化过程中流体的作用以及岩体形变过程中的部分熔融;变质反应以及变质作用P-T-t轨迹、元素地球化学和熔体作用行为;岩石保留的可能的变质事件和年代学记录,定量评价高温-超高温过程中变质演化的时间跨度和演化速率。     

Prismatine含义的变化及其在南极中山站区的产出

本文对prismatine(Prs)名称的来历作了简要介绍,指出kornerupine(Krn)系列中一个四面体位置上的B含量可变化于0和1之间(在22(O,OH,F)的分子式中),并伴随成分、晶体结构及矿物组合的变化。以 B=0.5为界划分可出两种不同的矿物:若B<0.5,为Krnss,包括两种情形:B=0,为无B之Krnss,0相似文献   

Tourmaline in a low grade clastic metasedimentary rock: an example of the petrogenetic potential of tourmaline

Detrital tourmaline grains and their associated tourmaline overgrowths provide a means to unravel the provenance and petrogenetic history of low grade clastic metasedimentary rocks. Evidence derives from tourmaline grains found in a lithic wacke metamorphosed to chlorite zone conditions. The detrital tourmaline cores are diagnostic indicators of the source rocks of the sediment whereas the overgrowths record both diagenetic and metamorphic reactions in the rock. Tourmaline grains consist of a detrital core surrounded by asymmetric overgrowths comprised of inner and outer rims. Abrupt chemical discontinuities between each of these zones implies that volume diffusion within tourmaline was minor under the conditions of formation. Compositions of the detrital cores vary widely, yet can be correlated with source rock types that are consistent with lithic fragments recognizable in the metawacke. At either the analogous or antilogous pole, inner rim compositions proximal to the detrital cores converge, despite the substrate tourmaline composition, indicating an approach to chemical equilibrium. However, significant dufferences in Al and X-site vacancies at the expense of Mg, Na and Ti between the analogous and antilogous poles of the inner rims demonstrate the presence of significant amounts of compositional polarity. Outer rim compositions at either pole also converge but compositional polarity between the analogous and antilogous poles persists. The presence of the inner and outer rims separated by a compositional discontinuity suggests punctuated evolution of the overgrowth. This implies that boron was sporadically available during diagenesis and metamorphism. Based on boron contents of minerals, this may correspond to a mechanism such as boron release due to polytypic change of illite or consumption of illite and/or muscovite. As such, tourmaline growth stages may serve as a monitor of chemical reactions in low grade metamorphic rocks.