Using white mica 40Ar/39Ar data as a tracer for fluid flow and permeability under high‐P conditions: Tauern Window,Eastern Alps

New single‐grain‐fusion muscovite and paragonite ⁴⁰Ar/³⁹Ar data from eclogite and blueschist units exposed in the Tauern Window, Eastern Alps yield a range of apparent ages from 90 to 23 Ma. These apparent ages are generally older than expected for ⁴⁰Ar/³⁹Ar cooling ages, given constraints from other geochronological systems such as Rb–Sr and U–Pb. Numerical Ar‐in‐muscovite diffusion models for Tauern Window nappe P–T paths in an open system suggest that ⁴⁰Ar/³⁹Ar ages should lie between 29 and 24 Ma, and that they should constrain cooling and decompression following the post‐high pressure Barrovian overprint. The measured ranges of apparent ⁴⁰Ar/³⁹Ar dates suggest that the assumption of open system behaviour is not valid for this region. The local and/or regional generation of fluid during exhumation promoted pervasive recrystallization of high pressure lithologies throughout the Tauern Window to greenschist and amphibolite facies assemblages. The old apparent ⁴⁰Ar/³⁹Ar white mica dates in all lithologies are therefore interpreted as being due to inefficient removal of grain boundary Ar by the grain boundary fluids during the Barrovian overprint, due to high Ar concentrations or limited connectivity or both. This caused spatially (mm‐scale) and temporally variable fluxes of Ar out of, and probably into, white mica in both metasedimentary and metabasic lithologies.     

Variations in composition and abundance of white mica in the hydrothermal alteration system at Hellyer,Tasmania, as revealed by infrared reflectance spectroscopy

Short-wave infrared (SWIR) spectral reflectance of hydrothermally altered volcanic rocks in the footwall of the Hellyer massive sulfide deposit was measured with a portable PIMA-II infrared spectrometer. The Al–OH band was used to derive information on the octahedral Al content and the abundance of white mica (sericite) in the hydrothermal alteration and mineralization system. The range of the Al–OH band wavelength from 2192 nm to 2222 nm corresponds to the number of octahedral Al (Al^vi) in white mica approximately from 3.9 to 3.0 (based on 4 octahedral cations per formula). This Al^vi range represents a significant compositional variation, covering most of the compositional region between muscovite (Al^vi = 4.0) and phengite (Al^vi = 3.0). Furthermore, the spectral reflectance data show that the compositional variation of white mica is spatially related to hydrothermal alteration zoning, such that phengitic white mica tends to occur in 1) main upflow fluid channel, 2) intensely altered volcanic rocks, and 3) Pb–Zn mineralization, whereas muscovitic white mica was formed preferentially distal to massive sulfide mineralization on the margin of the footwall alteration system. The results suggest that the Al–OH band wavelength, and therefore the octahedral Al content, of white mica can be used as vectors to mineralization to map the hydrothermal system at Hellyer.     

云母矿工业利用及发展现状探讨

云母工业产品分为云母片制品,云母纸,云母带,云母板（含云母零件）,云母介质电容器,云母粉（含珠光云母颜料）六大产品系列。本文介绍了其中重要产品一云母片、云母纸、云母带和云母板的原料、基材、加工工艺和用途,分析了云母制品的加工发展状况和前景。     

Neotectonics of Turkey – a synthesis

Abstract

Turkey forms one of the most actively deforming regions in the world and has a long history of devastating earthquakes. The belter understanding of its neotectonic features and active tectonics would provide insight, not only for the country but also for the entire Eastern Mediterranean region. Active tectonics of Turkey is the manifestation of collisional intracontinental convergence- and tectonic escape-related deformation since the Early Pliocene (~5 Ma). Three major structures govern the neotectonics of Turkey; they are dextral North Anatolian Fault Zone (NAFZ), sinistral East Anatolian Fault Zone (EAFZ) and the Aegean–Cyprean Arc. Also, sinistral Dead Sea Fault Zone has an important role. The Anatolian wedge between the NAFZ and EAFZ moves westward away from the eastern Anatolia, the collision zone between the Arabian and the Eurasian plates. Ongoing deformation along, and mutual interaction among them has resulted in four distinct neotectonic provinces, namely the East Anatolian contractional, the North Anatolian, the Central Anatolian ‘Ova’ and the West Anatolian extensional provinces. Each province is characterized by its unique structural elements, and forms an excellent laboratory to study active strike-slip, normal and reverse faulting and the associated basin formation. © 2001 Éditions scientifiques et médicales Elsevier SAS     

赣东北贵溪地区片岩中碎屑锆石的U-Pb年龄、Hf同位素及其地质意义

应用LA-ICP-MS U-Pb同位素原位微区定年方法及Hf同位素和微量元素分析方法,对华夏地块北部赣东北地区1个云母石英片岩中48个碎屑锆石进行了系统研究。这些锆石大部分具特征的振荡环带,Th/U比值较高(>0.4),稀土元素配分型式左倾(富集HREE),具明显正Ce和负Eu异常,属于特征的岩浆锆石。年代学研究显示,华夏北部新元古代变沉积岩主要在-775 Ma出现峰值并在-840 Ma出现次高峰,说明在此时期有两期大规模的岩浆活动。-840 Ma的峰值锆石对应的εHf(t)值明显分为两个区间,既有正值,也有负值,而在-775 Ma的峰值锆石对应测定的εHf(t)值均为负值。结合前人的Hf同位素测试结果,说明华夏地块新元古代中期岩浆活动主要表现为古老陆壳物质的再循环。形成于古元古代-1770 Ma的一个次高峰的年龄数据非常一致,单一的Hf同位素成分和较好的锆石晶形表明它们最可能捕获于深部的一个古元古代基底岩石。     

胶东金矿床围岩蚀变带内云母类矿物、矿物化学-多型系列及其找矿信息

对胶东15个金放床围岩蚀变带内30个云母类矿物的地质产状，空间分带，与矿化关系地质调查基础上，着重对各类型金矿床蚀变带内云母类矿物进行了单矿物提纯，矿物化学定量分析，物理性质鉴定，X光衍射分析，差热分析，红外吸收光谱分析，晶格常数计算，形成条件等方面的系统研究，确定了蚀变岩带内有9种云母类矿物，5个矿物化学－多型系列，新鉴定出5种云母类矿物，绿鳞石（Celadonite),铁绿鳞石（Ferian Celadonite)，铁铝绿磷石（Ferian-Alumino Celadonite)，铝绿鳞石（Alumino Celadonite)和伊利石（Illite)，总结了云母类矿物各系列的演化特征，查明了金矿床各蚀变－矿化带内所出现的云母类矿物晕，指出了各云母类矿物晕的找矿信息。     

The relation between grain size and Ar/Ar date for Alpine white mica from the Siviez-Mischabel Nappe, Switzerland

Variations in Alpine white mica ⁴⁰Ar/³⁹Ar dates from the cover units of the Siviez-Mischabel Nappe relate to regional variations in the thermal history of the nappe. We focus on three regions within the nappe: the central Siviez-Mischabel (CSM), the southern Siviez-Mischabel (SSM), and the eastern Siviez-Mischabel (ESM). Our approach weaves together observations of quartz and mica textures in thin section, the variation of ⁴⁰Ar/³⁹Ar date with grain size, considerations of the effective diffusion dimension (EDD) of argon in white mica, and a comparison of dates with diffusion model results. In the CSM, pressure solution of quartz and dislocation glide in mica accommodated Alpine deformation. Dates record mica growth during nappe emplacement from 40 to 36 Ma and do not vary with grain size. In the SSM and ESM, both mica and quartz show textures associated with dynamic recrystallization, and dates decrease with grain size. In the SSM, dates also agree with the timing of nappe emplacement, but in the ESM, dates significantly post-date the timing of nappe emplacement. A comparison of dates with diffusion model results supports inferences from rock fabrics that the SSM experienced higher peak temperatures than the CSM, even though dates from both units approximate the timing of mica growth. Dates obtained from the ESM, however, do not compare well with simple models, and the thermal evolution of this region of the nappe, in the neighborhood of the Simplon Fault Zone, is not well understood.     

云母族中白云母亚族扩展为铬铝云母亚族

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     

金伯利岩中的云母

我国金伯利岩中的云母主要为金云母。镁黑云母和铁黑云母较少见。根据金伯利岩中云母的光学性质,将其分为正吸收和反吸收云母。一般反吸收云母沿正吸收云母的解理面及边缘进行交代。反吸收金云母在四面体位置中,有相当多的Fe~(3+)。环带状云母的成分,从中心向边部不规则变化。富含金刚石的金伯利岩的基质云母含FeO,TiO_2低。云母加热至1100℃时,则变化为橄榄石和石榴石。     

从云母微量元素特征探讨华南花岗岩的成因和演化

云母中微量元素可分为浅源指示元素和深源指示元素。浅源指示元素Nb、Ta、Sn、Li、Rb在南岭系列云母中的含量高于长江系列,而深源指示元素Co、Ni的含量长江系列大于南岭系列。云母中Nb、Ta、Sn、Li、Rb变化特征是自身成矿演化的直接示踪剂,而Co、Ni变化特征是Fe、Cu、Au、Mo(W)、Pb、Zn成矿演化的重要示踪剂。云母中Cu、Zn、W、Mo、U、Th等元素呈波动性变化,不能灵敏指示花岗岩的成因与演化。微量元素在云母中的选择分布主要受岩浆物源化学背景的制约,同时也受岩浆侵位和分异演化程度高低以及结晶的物理化学条件变化等因素的影响。