橄榄石集合体扭转大变形实验研究

对(Mg0.5,Fe0.5)2SiO4和(Mg0.7、Fe0.3)2SiO4橄榄石集合体进行了高温高压扭转大变形实验研究.试验在高精度和高分辨率Paterson气体介质变形试验机上进行,试验温度为1473K,围压为300MPa,应变率为10-4～10-5S-1,剪切应力为82～124MPa,剪切应变为～400%,将变形后试件沿轴向切开进行了显微结构分析,确定了不同纵截面上橄榄石的颗粒尺寸.由蠕变数据拟合出的流动律中,应力指数为与三轴压缩实验给出的应力指数吻合.利用EBSD方法分别对变形前后试件中橄榄石的晶格最优取向(LPO)进行了测定.在富铁橄榄石样品中观测到的最优晶格取向表明滑动属于(okl)[100]滑动系统.这个结果与Bystficky等人在Fo90种观测到的最优晶格取向特征是一致的.     

橄榄石集合体的简单剪切形变实验研究

本文利用高精度Paterson气体介质变形装置对富铁橄榄石集合体(Mg_(0.5),Fe_(0.5))_2SiO_4进行了高温简单剪切变形试验.试验在温度1473K和围压300MPa的条件下进行,差应力为64～153MPa,应变率为10~-5～10~-3s~-1.一共进行了三组试验,试件的剪切变形量分别为89%,131%和200%,通过对变形后试件的反射光学显微结构分析,得到富铁橄榄石集合体动态重结晶的微观机制,由结晶各向异性分析给出晶格最优取向和波速各向异性的分布及随应变的增加而表现出的演化特征.     

富铁橄榄石的高温变形实验研究

利用高精度Paterson气体介质变形装置对(Mg0.5,Fe0.5)2SiO4和(Mg0.7,Fe0.3)2SiO4橄榄石集合体进行了高温三轴压缩变形试验。首先用人工合成了纯铁橄榄石Fe2SiO4,然后用合成的纯铁橄榄石与天然圣卡罗橄榄石按一定比例混合烧结合成了含铁量分别为50％和30％的富铁橄榄石集合体Fo50和Fo70。三轴压缩蠕变变形试验在温度1223-1473 K和围压 300 MPa的条件下进行,差应力为10-300 MPa,应变率为10-7-10-4s-1,每个试件的最大变形量为20％．利用三维非线性方法对蠕变数据进行拟合,得出的流动律中,Fo50应力指数为4．1,活化能为499kJ／mol;Fo70应力指数为4．3,活化能为510kJ／ mol。将实验结果与Fo90圣卡罗橄榄石集合体的强度进行对比,发现含铁量的增加使橄榄石的强度明显下降,Fo50橄榄石集合体比Fo70的粘性低一个量级,Fo70比Fo90的粘性低一个量级。从而得到了含铁量对橄榄石的粘性(强度)影响的初步试验结果。     

铁橄榄石高温高压流变性的实验研究

通过高温高压实验研究了铁橄榄石集合体的流变性.首先,利用高精度的Paterson气体介质变形装置对铁橄榄石集合体Fe2SiO4进行了高温三轴压缩蠕变试验.变形试验条件为:温度1273～1423K,围压300MPa,差应力10～250MPa,应变率10-7～10-4s-1,试件的最大变形量不超过20%.利用三维非线性拟合方法对蠕变试验数据进行分析,得到铁橄榄石集合体的微观变形机制为扩散域和位错域,扩散域的应力指数为1左右.位错蠕变域中,干燥铁橄榄石集合体的应力指数为5.4.活化能为781kJ/mol;含水铁橄榄石集合体的应力指数为3.4,活化能为516kJ/mol.实验结果表明,含水时铁橄榄石的流变强度比干燥时小一个数量级.将实验结果与铁橄榄石单晶的强度进行对比,发现铁橄榄石集合体的流变强度比铁橄榄石单晶的强度高.从而得到了铁橄榄石集合体高温高压流变性(强度)的初步试验结果.     

含水对富铁橄榄石流变性的影响

橄榄石是下地壳上地幔最丰富的造岩矿物,橄榄石集合体的高温高压流变性对地幔动力学过程有着很大的影响。以往对橄榄石单晶和集合体进行过的流变性实验研究,涉及了温度、压力、氧逸度、含铁量以及含水等因素的影响,本文研究了含水对富铁橄榄石集合体流变性能的影响,首先,利用高精度 Paterson 气体介质变形装置对含水富铁橄榄石集合体(Mg_(0.9),Fe_(0.1))_2SiO_4、(Mg_(0.7),Fe_(0.3))_2SiO_4和(Mg_(0.5),Fe_(0.5))_2SiO_4进行了高温三轴压缩蠕变试验,变形试验条件为:温度1323～1473K,围压300MPa,差应力10～300MPa,应变率10~(-7)～10~(-4)s~(-1),每个试件的最大变形量为20%。利用三维非线性拟合方法对蠕变试验数据进行分析,结果表明,含水富铁橄榄石集合体的微观变形机制为扩散域和位错域,对三种铁含量,扩散域的应力指数为1。位错蠕变域中,Fo_(50)应力指教为3.8,活化能为444kJ/mol;Fo_(70)应力指数为3.7,活化能为479kJ/mol,Fo_(90)应力指数为3.6,活化能为514kJ/mol。将实验结果与不含水富铁橄榄石集合体的强度进行对比,发现含水使富铁橄榄石的强度明显下降,舍铁量相同时,含水橄榄石集合体的流变强度比干燥时小至少一个数量级。从而得到了含水对含铁量不同的橄榄石集合体粘性(强度)影响的初步试验结果。     

大变形橄榄石动态重结晶的实验观测研究

本文利用高温高压大变形扭转实验,对富铁橄榄石大变形情况下的动态重结晶和颗粒尺度变化的特点进行了实验观测分析.富铁橄榄石集合体由纯铁橄榄石Fa100和圣卡罗橄榄石Fa10混合物经人工合成得到,试件的几何形状为圆柱体,直径9.6mm,高度4.86mm.实验在常角速率条件下进行,温度为1473K,围压为300MPa,剪应力为72 ～ 99MPa,剪应变率为1.35×10-4～3.11×10-4s-1,累积剪应变为3.98.对变形后样品的微结构进行了光学和扫描电镜的观测分析,得到橄榄石颗粒随应变增加而产生动态重结晶的具体物理图像,由EBSD观测结果给出了晶格取向随外加应变增加而产生的变化过程,利用两种统计方法得到了颗粒尺寸随应变增加而变化的过程,探讨了橄榄石动态重结晶的微观机制.与已有三轴压缩、简单剪切以及圣卡罗橄榄石的扭转变形结果进行了对比分析,同时对实验结果在地球物理方面的应用进行了讨论.     

压力对橄榄石流变性的影响

本文给出细粒橄榄石集合体在位错蠕变域中压力效应的实验结果。对干燥、人工合成的橄榄石集合体进行了三轴压缩实验,试验在一台高分辨率的气体介质试验机上进行。典型的常载荷蠕变试验温度为1473K或1523K,围压为400MPa、200MPa、400MPa、200MPa。当差压力和温度给定时,试件在400MPa围压下,变形速度较200MPa围压下要慢。实验得出的细粒橄榄石集合体在位错蠕变域中的活化体积值为(23±3)×10~(-6)m~3/mol。最后,对实验结果在地幔动力学中的应用进行了讨论。     

MgO-SiO_2-Cr-O体系的亚固相相关系及有关含Cr~(2+)端员矿物的热力学特征

在t=1100-1500℃和P=0-2.88GPa条件下,实验确定了与金属Cr平衡的SiO_2-Cr-O及MgO-SiO_2-Cr-O体系中的亚固相相关系。结果显示,在SiO_2-Cr-O体系中,只发现绿铬矿-金属铬-石英(或鳞石英)组合;而在含MgO体系中,出现Mg-Cr~(2+)橄榄石、辉石及尖晶石固溶体。Cr~(3+)在橄榄石和辉石中的含量在可测定限度之下。当X_(Cr~(2+))=[Cr~(2+)/(Mg+Cr~(2+))]>0.2时,辉石的结构由斜方晶系转为单斜晶系;尖晶石的结构由立方变为四方。对实验数据进行热力学模拟,求得Mg-Cr~(2+)在橄榄石,辉石及尖晶石固溶体中的混合参数(W),以及铬橄榄石(Cr_2SiO_4)、铬辉石(Cr_2Si_2O_6)和铬尖晶石(Cr_3O_4)的形成自由能(△G°)与温度的关系。     

雅鲁藏布江蛇绿岩中橄榄石的位错构造及上地幔流变状态

本文通过对雅鲁藏布江蛇绿岩中橄榄石的透射电子显微分析（TEM）和变形参数测算,划分出3个应变带,即强应变带、过渡型应变带和弱应变带,并详细地研究了它们的岩石结构、位错构造、变形机制和流变状态。镁铁质糜棱岩组成的强应变带中橄榄石发育亚颗粒和位错网络,具有低自由位错密度(10⁷～10⁸cm^-2),是在温度为850～950℃、压力10～13kbar、差异应力2～3MPa、应变速率为10^-16～10^-17s^-1、粘度10²²～10²³Pa.s,大致相当于35～40km的岩石圈深部由位错机制控制的深层剪切流变作用形成的。     

贺根山豆荚状铬铁矿中硅酸盐包体及其地质意义

贺根山豆荚状铬铁矿是典型的高Al型铬铁矿(Cr#=47.8～54.9,Mg#=64.1～73.7),其中的包体以硅酸盐矿物为主(包括橄榄石、斜方辉石、单斜辉石、韭闪石、钠长石).根据包体形状、矿物组合及分布特征可将其划分为三类.第一类包体呈孤立单矿物相,主要包括橄榄石和单斜辉石,第二类包体由平衡共生的单斜辉石和斜方辉石构成,上述两类包体均具有被熔蚀的边,且零星分布在尖晶石中,属于捕虏晶成因.第三类包体属于熔融包体,具有多边形外形,包含复杂的矿物相并密集分布于尖晶石核部.利用尖晶石颗粒内部保存完好的单斜辉石以及单斜辉石和斜方辉石包体估算的温度(1148～1254℃)与压力(490～1290 MPa)表明,贺根山豆荚状铬铁矿矿床的形成深度为16～43 km.熔融包体中含大量钠长石和韭闪石,指示铬铁矿母熔体富集H2 O、Na和Si.与铬铁矿平衡母熔体的Al2 O3含量(15.4％～16.3％)、TiO2含量(0.3％～0.9％)和FeO/MgO比值(0.6～1.1)与低Ti拉斑玄武质熔体的类似.利用尖晶石和橄榄石包体计算获得铬铁矿原始熔体的Mg O含量为～19.8％.贺根山豆荚状铬铁矿经历了深部预富集和浅部成矿两个阶段,其中浅部成矿作用涉及熔体与方辉橄榄岩反应以及演化的熔体与原始熔体混合等过程.     

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