地壳岩石在地幔压力下的变质作用的实验研究

近年来一些真正壳源变质岩石研究资料主要来自地中海碰撞带,其变质压力达到30kb,地热梯度极1氐(7℃/km)。在富镁铝变泥质岩中发现具有特殊意义的高压矿物和矿物组合,已有或正在进行一些实验研究。这些矿物与K_2O、MgO、Al_2O3、TiO_2、SiO_2、P_2O_5和H_2O模拟体系在高达50kb和1000℃条件的实验产物相吻合。本文将讨论以下的合成矿物相及其组合,同时特别强调其水压—温度范围(用括号表示)、反应关系及其在变质岩中已知的和可能的产状:铝绿泥石(0～12kb,150～380℃),出现于极低级的变质泥岩中;镁纤锰柱石(约7～45kb,约200～600℃),发现于斛冲带的变质铝土矿、变泥质岩和有关的石英脉中,镁硬绿泥石(18～45kb,400～760℃),自然界尚未发现纯的或近于纯的端元组分,它需要二氧化硅不足的环境;紫硅镁铝石在自然界中已知的仅有滑石—蓝晶石片岩一种地质产状。它的稳定范围很小(9～18kb,700～870℃,且不能和石英共生,但它以Fe存在时稳定;镁铝榴石(15—至少到50kb,700℃熔融),它引人注意地发现于石英岩,含有或不含有残留的柯石英包体;镁十字石(14—有的90kb,700～1000℃)最近被发现呈包体形式赋存干镁铝榴石之中,它需要二氧化硅不饱和的环境;镁镁铝—绿纤石是镁完全置换普通绿纤石中的钙的—新的合或相,由于它具有非常高的压力及低温度的稳定性(37—最小到55kb,<400～780℃),地球上不可能存在。Ellenbergerite(尚没有相应的中文名—译者注)—在镁铝榴石中呈包体形式的新高压矿物,Ti—ellenbergeritl的稳定与成分有关,且比含磷而不含钛的端元组分的形成压力更高(>20kb),纯的具有ellenbergerite结构的镁磷酸盐在10kb条件下即可形成。多硅白云母—广泛分布的Mg、Si置换的白云母,它需要增大高水压(直到20kb)来满足其较高的置换条件。但是铝绿磷石端元组分在任何条件下都是不稳定的。多硅白云母的成分及其有限的组合,如金云母、钾长石和一个SiO_2相是很好的地质压力计。普通的组合镁绿泥石+Al_2SiO_5(主要为蓝晶石)的稳定范围很广,从近于零到31kb和320～760℃。白片岩组合—滑石+蓝晶石(6～45kb,550～810℃)在碰撞带变质作用中起着非常重要的作用,它来自低级变质作用的绿片岩组合—绿泥石+石英,而在最高级变质作用中它又分解成镁铝榴石+柯石英组合,另一方面,滑石—多硅白云母组合(11—最小35kb,300—820℃)来自俯冲的变泥质岩。在15～20kb的压力,400～650℃条件下,非常富钾、镁的硅质流体由于钾长石和金云母(黑云母)矿物的相互反应的结果形成了,而钾长石和金云母矿物在包含芘岗岩的地壳岩石中是非常普通的矿物,这样的流体在邻近地幔岩石必然引起变质作用,直到以后温度的增高产生碰撞后的超钾质的钾镁煌斑岩的熔融体。     

钛粒硅镁石:冷俯冲带蛇纹岩超高压变质的特征变质矿物

蛇纹岩矿物组合简单,主要组成矿物蛇纹石的温压稳定范围很大,这导致确定蛇纹岩的变质温压条件存在困难。本文通过实验岩石学模拟的方法,确定了钛粒硅镁石是蛇纹岩经历超高压变质的特征变质矿物。根据实验观察,压力达到3.0~3.5 GPa条件下,600~700℃范围内均存在钛粒硅镁石的生成反应,说明钛粒硅镁石在压力大于3.0~3.5 GPa条件下才能稳定;温度高于750℃,钛粒硅镁石开始减少直至消失。至于钛粒硅镁石的压力上限,由于实验条件所限,本次实验并未得出。钛斜硅镁石先于钛粒硅镁石出现,晚于钛粒硅镁石消失,稳定的温压范围更大。对实验样品观察发现,普遍存在钛粒硅镁石、钛斜硅镁石和橄榄石互为核边、互相交生的现象,这些实验现象与自然界中观察到的现象一致。低温高压条件下,由于这3类矿物结构的相似性,钛斜硅镁石与橄榄石通常出现互为核边的现象;随着温度升高,钛斜硅镁石以斑块或者片晶出现在橄榄石中,直至最终分解消失。钛粒硅镁石的出现与否取决于温压条件：低温低压条件下,钛粒硅镁石不稳定,发生分解产生钛斜硅镁石,出现钛斜硅镁石包裹钛粒硅镁石的现象;低温高压条件下,钛粒硅镁石稳定生长,出现钛粒硅镁石发育于钛斜硅镁石边部的现象;高温条件下,钛粒硅镁石不稳定,以片晶形式存在于橄榄石或钛斜硅镁石中。研究表明,钛粒硅镁石稳定于低温高压条件,确定其为冷俯冲带蛇纹岩超高压变质的标志。同时详细的岩相学显示了钛硅镁石矿物在高压变质过程中的行为,从而为俯冲带超基性岩变质研究提供理论依据。     

大别山北部超高压变质大理岩及其地质意义

岩石学研究表明 ,大别山北部镁铁 超镁铁质岩带中白云质大理岩至少经历过三期变质阶段 :(1)榴辉岩相峰期变质阶段 ,矿物组合主要为方解石 +白云石 +金红石 +镁橄榄石 +钛 斜硅镁石 +富镁的钛铁矿±文石±石榴子石 ;(2 )麻粒岩相退变质阶段 ,矿物组合主要为方解石 +白云石 +金云母 +镁橄榄石 +透辉石 +钛铁矿 +尖晶石±斜方辉石等 ;(3)角闪岩相退变质阶段 ,主要矿物组合为方解石 +白云石 +磷灰石 +磁铁矿+榍石等。它的峰期变质矿物组合 ,类似于苏 鲁超高压大理岩 ,形成压力至少大于 2 .5GPa。这进一步证明 ,大别山北部大多数高级变质岩 (包括大理岩等 )都曾经过超高压变质作用 ,应属于印支期扬子俯冲陆壳的一部分。     

镁铁矿在镁夕卡岩Au(Fe、Cu)等矿床中的发现及镁铁矿—镁磁铁矿系列研究

镁铁矿是一种罕见的交代矿物,发现于安徽秦楼镁夕卡岩Au(Fe、Cu)矿床和陕西木龙沟镁夕卡岩 Fe(Mo、Cu)矿床,它在中国是首次发现。本文对镁铁矿及镁磁铁矿的产出地质条件、矿物共生组合、化学成分、物理性质、X—射线粉晶数据和红外吸收光谱等特征进行了较系统的研究,提供了一批新的数据。镁铁矿含MgO高达13.48％～17.66％,与其共生的矿物主要是斜硅镁石、粒硅镁石、蛇纹石、方解石和镁磁铁矿。镁铁矿的比重为4.537～4.720,反射率R=17.8～18.1,硬度838～900kg/mm~2,晶胞参数为0.8371～0.8379um。对镁铁矿—镁磁铁矿—磁铁矿系列的化学成分和物理性质、晶胞参     

湖南香花岭锡铍多金属矿区的含Li、Be条纹岩和有关交代岩

湖南香花岭锡铍多金属矿床的含Li、Be条纹岩和有关交代岩,在世界上独一无二,产于燕山期(155~154 Ma)富氟花岗岩接触带及岩体的围岩捕掳体中,围岩为中上泥盆统灰岩和白云质灰岩。按矿物共生组合特征,条纹岩可大致分为铁锂云母条纹岩、氟硼镁石条纹岩、金绿宝石条纹岩、粒硅镁石-磁铁矿条纹岩和金云母-绿泥石条纹岩5类。与条纹岩有关的交代岩生成稍晚,可大致分为香花石交代岩、金云母交代岩、粒硅镁石交代岩、符山石-磁铁矿交代岩、金云母-绿泥石交代岩和韭闪石交代岩6类。文章对条纹岩和有关交代岩的生成地质背景、矿物共生组合和岩石地球化学特征进行了探讨。     

国际地质学会推荐的深成岩野外分类法

矿物和矿物组 Q—石英;A—碱性长石(正长石、微斜长石、条纹长石、歪长石、钠长石An00～06);P—斜长石;An06～100、方柱石;F—似长石或似长石类(白榴石和假白榴石、霞石、方钠石、黝方石、兰方石、钙霞石、方沸石等);M—镁铁质和有关矿物(云母、内石、辉石、橄榄石、不透明矿物、付矿物(锆石、磷灰石、榍石等)、绿帘石、褐帘石、石榴石、黄长石、钙镁橄榄石、原生碳酸盐等] Q+A+P=100或A+P+F=100 M小于90％的岩石,主要按它们的淡色组分分类;M=90～100％的岩石,则按其镁铁质矿物分类。 M小于90％的岩石,是按它们在QAPF     

中国蓝闪片岩相的变质作用

本文论述了中国蓝闪片岩的分布、变质条件及其构造位置。中国的蓝闪片岩从中晚元古代开始,各变质期均有出现。根据矿物组合,可分为两类:第一类蓝闪片岩常含有高压矿物,如硬柱石、硬玉和文石以及蓝闪石、绿纤石、黑硬绿泥石、多硅白云母、红帘石等,属高压亚绿片岩相,称蓝闪—硬柱石片岩相,形成温度约250—350℃,压力大于500—800MPa,甚至可达1200MPa。此类蓝闪—硬柱石片岩相多代表海洋板块古消减带。第二类蓝闪片岩的常见矿物为蓝闪石、青铝闪石或镁钠闪石、黑硬绿泥石、红帘石和绿片岩相中的绿帘石、阳起石、绿泥石、白云母、有时还有黑云母、铁铝榴石和钠质辉石。形成温度约350—450℃,压力500—800MPa。此类蓝闪绿片岩相虽处于活动带,但与板块构造没有直接关系。我国西藏南部和内蒙温都尔庙属第一类,但大部分蓝闪片岩带属第二类。     

橄榄石-硅镁石型矿物的光学异向性

橄榄石型以及与其有密切关系的硅镁石型结构的矿物包括四个系列:1.硅酸盐橄榄石系列;2.磷酸盐橄榄石系列,即锂蓝铁矿系列;3.硅镁石系列;4.硅锰石系列。前两个系列是橄榄石型结构,后两个系列是硅镁石型结构。在这一类矿物中,氧离子都是六方最紧密堆积的,它们的平均折射率(N=(Ng Nm Np)/3)均严格服从最紧密堆积的折射率定律即     

玛湖凹陷风城组岩矿类型及其指示意义

正随着勘探的深入,深层二叠系风城组逐步成为准噶尔盆地玛湖凹陷重要的勘探层系,其发育一套非常特殊的含火山岩类的碱性矿物组合。通过岩芯观察、薄片鉴定、背散射成像、能谱及X-衍射分析,着重剖析了风城组岩类特征。通过研究,在玛湖凹陷风城组识别出天然碱、水硅钠石、碳酸钠钙石、氯碳钠镁石、丝硅镁石、磷钠镁石、碳钠镁石等碱性矿物及玄武岩等火山岩类矿物。纵向上,风城组二段碱性矿物最为发育。碱类岩矿的大量出现,指     

白云鄂博矿物岩石研究的新进展

本文论述了近年来白云鄂博矿区在旷物学、岩石学、地球化学和矿床成因研究方面的进展。在矿物学研究方面,除以往研究过的一百多种矿物外,八十年代中期以后,又相继发现并研究了含铌锐钛矿、含铌钙钛矿、锶铁钛石、水磷钙钍石、白云鄂博矿、未命名氟碳酸盐新种矿物、珀硅钛铈铁矿、硅钡镁石、带云母等矿物;发现了矿物间的共生和交代关系。在岩石学研究方面,找到了霓长岩,发现了霓长岩化作用,确定了火成碳酸岩岩石的存在。在地球化学和矿床成因方面,提出了稀土稀有金属矿化与火成碳酸岩岩浆活动有成因联系的见解。     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

Définition d'une limite multicritère ; stratigraphie du passage Campanien–Maastrichtien du site géologique de Tercis (Landes,SW France)Definition of a multi-criteria boundary; stratigraphy of the Campanian–Maastrichtian interval of the geological site at Tercis (Landes,SW France)

Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Late Wuchiapingian (Late Dzhulfian,early Late Permian) limestone olistolites within the Tertiary flysch of Glypia Unit (Mount Parnon,central–eastern Peloponnesus,Greece)

Some olistolites reworked in a Tertiary flysch of Mount Parnon (Peloponnesus, Greece) exhibit a Late Permian assemblage, dominated by Paradunbarula (Shindella) shindensis, Hemigordiopsis cf. luquensis and Colaniella aff. minima. This association corresponds to the Late Wuchiapingian (=Late Dzhulfian), a substage whose algae and foraminifera are generally little known. Contemporaneous limestones crop out in the middle part of the Episkopi Formation in Hydra, but they are rather commonly reworked in Mesozoic and Cainozoic sequences. The palaeobiogeographical affinities shared by the foraminiferal markers of Greece, southeastern Pamir, and southern China, are very strong (up to the specific level), and are congruent with the Pangea B reconstructions. To cite this article: E. Skourtsos et al., C. R. Geoscience 334 (2002) 925–931.     

PALEONTOLOGY

正20141596 Liu Yunhuan(School of Earth Sciences and Resources,Chang’an University,Xi’an 710054,China);Shao Tiequan Early Cambrian Quadrapyrgites Fossils of Xixiang Boita in Southern Shaanxi Province(Journal of Earth Sciences and Environment,ISSN1672-6561,CN61-1423/P,35(3),2013,p.39-43,3 illus.,20 refs.)     

GEOCHEMICAL EXPLORATION

正20141719 Chen Zhijun(State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China);Chen Jianguo Automated Batch Mapping Solution for Serial Maps:A Case Study of Exploration Geochemistry Maps(Journal of Geology,ISSN1674-3636,CN32-1796/P,37(3),2013,p.456-464,2 illus.,2 tables,10 refs.)     

MICROPALAEONTOLOGY

正20140962 Chen Fenning(Xi’an Institute of Geology and Mineral Resources,Xi’an710054,China);Chen Ruiming Late Miocene-Early Pleistocene Ostracoda Fauna of Gyirong Basin,Southern Tibet(Acta Geologica Sinica,ISSN0001-5717,CN11-1951/P,87(6),2013,p.872-886,6illus.,56refs.)     

PETROLOGY

正1.IGNEOUS PETROLOGY20142008Cai Jinhui(Wuhan Center,China Geological Survey,Wuhan 430205,China);Liu Wei Zircon U-Pb Geochronology and Mineralization Significance of Granodiorites from Fuzichong Pb-Zn Deposit,Guangxi,South China(Geology and Mineral Resources of South China,ISSN1007-3701,CN42-1417/P,29(4),2013,p.271-281,7illus.,     

ENVIRONMENTAL GEOLOGY

正20141205Cheng Weiming(State Key Laboratory of Resources and Environmental Information System,Institute of Geographic Sciences and Natural Resources Research,CAS,Beijing 100101,China);Xia Yao Regional Hazard Assessment of Disaster Environment for Debris Flows:Taking Jundu Mountain,Beijing as an