不同粒径的月球橄榄石二向性反射特征研究   总被引：1，自引：0，他引：1  

张渊智  黄朝君  周超  陈圣波 《地学前缘》2014,21(6):150-154

研究月表矿物组成和分布,对于探测月表地质构造以及月球的起源和演化具有重要的意义。因此,物质成分探测一直是月球研究的重点课题之一。尽管人类已经能够从月球采集样品进行实验室分析,但遥感技术仍然是研究月球的主要手段。文中主要目的是模拟不同粒径下橄榄石的二向性反射特征。为此,首先提出模拟不同粒径下反射特征的方法,然后利用Hapke模型和Mie散射理论对不同粒径下富铁和富镁橄榄石的二向性反射特征进行了模拟。模拟结果显示,富镁橄榄石的二向性反射率较富铁橄榄石的反射率高。最后,分析了反射率差值和等效粒径的相关性。该结论为选择探月传感器的波段组合、识别橄榄石镁铁含量提供了理论依据,也为应用遥感数据的橄榄石的判别奠定了基础。  相似文献   

橄榄石集合体的简单剪切形变实验研究   总被引：1，自引：1，他引：0  

赵永红  李小凡  M. Zimmerman  David L. Kohlstedt 《岩石学报》2009,25(10):2687-2693

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.  相似文献   

Major Element Chemical Heterogeneity in Geo2 Olivine Microbeam Reference Material: A Spatial Approach to Quantifying Heterogeneity in Primary Reference Materials          下载免费PDF全文

Matthew J. Pankhurst  Richard Walshaw  Daniel J. Morgan 《Geostandards and Geoanalytical Research》2017,41(1):85-91

A 270 spot‐analysis study was conducted across a large (ca. 1200 μm × 1200 μm) chip of Geo2 olivine from a commercially available GEO Mk2 block (P and H Developments 2016 , Standards for EPMA), which revealed an 8.7% relative range in FeO abundance. Interleaved and overlapping grids of different resolutions were measured sequentially to prove spatial patterns are not due to drift or other external sources of error. Results were mapped and interpolated using commercially available geographical information system software, such that composition could be predicted according to location with high accuracy. The simple, systematic zonation pattern observed demonstrates that useful‐sized regions of acceptable homogeneity do exist for some elements. This knowledge allows a user to target individual regions of a characterised chip for use as distinct measurement standards. As analysis times decrease and data sets grow, this approach may maximise laboratory efficiency by characterising large chips and extending time between conventional block repolish and coating, particularly in those cases where the avoidance of prior beam damage is a key concern.  相似文献   

江山-广丰地区早白垩世晚期玄武岩的岩石地球化学及其构造意义   总被引：17，自引：0，他引：17  

余心起  舒良树  颜铁增  俞云文  祖辅平  王彬 《地球化学》2004,33(5):465-476

江山-广丰地区所在的信江红色盆地与金衢红色盆地同属于NEE向赣杭断陷盆地带的组成部分.赣杭构造带自早白垩世晚期开始强烈拉张,红色盆地形成.红层下部夹有层状玄武岩,全岩K-Ar年龄为98～105 Ma,属早白垩世晚期.岩石地球化学特征表明研究区有两类玄武岩:江山陈塘坞一带的拉斑玄武岩,礼贤、广丰一带的碱性橄榄玄武岩.Nd、Sr同位素组成分析显示,拉斑玄武岩类(87Sr/86Sr)i值为0.705 4～0.707 0,εNd(t)值为1.69～0.70(接近于0),表明源区为基本未受壳源物质混染的原始地幔,在弧后陆缘环境下快速拉张而上升,呈熔岩被形式分布于信江盆地东部;碱性橄榄玄武岩(87Sr/86Sr)i值为0.707 6～0.708 0,而εNd(t)值偏低(-6.43～-5.18),表明来源于已受壳源物质混染的富集地幔,在拉张加剧、裂陷加深的构造背景下喷发,相对集中分布于盆地中部,范围小于拉斑玄武岩.二者的差别主要是地幔源区受到不均匀混染所致.研究表明,早白垩世晚期至晚白垩世期间,太平洋板块俯冲的角度由缓变陡以及向东南方向的后退作用,对弧后陆缘的快速拉张并形成赣杭带红色断陷盆地及其玄武岩起着关键性作用.  相似文献   

蛇绿岩型铬铁矿床包壳纯橄榄岩中的流体过程印记:来自西藏雅鲁藏布江缝合带罗布莎和泽当岩体的地质学、岩石学和橄榄石晶体化学证据   总被引：1，自引：0，他引：1  

罗照华  江秀敏  刘晓  李重  吴宗昌  井文超 《地学前缘》2019,26(1):272-285

岩浆型矿床一般认为是岩浆分异的产物,因为这类矿床通常缺乏强烈的近矿围岩蚀变。蛇绿岩中的豆荚状铬铁矿被认为是一种典型的岩浆型矿床,流行的成因模型包括岩浆通道模型和熔体-岩石反应模型。深部晶体群的大量发现,表明铬铁矿成矿系统不是一种理想系统,而是至少由两类子系统组成的复杂性动力系统。因此,流行模型不再适用,必须构建能够整合新证据的成因模型。这类矿床的典型地质特征是具有从方辉橄榄岩围岩经包壳纯橄榄岩到铬铁矿石的分带,且包壳纯橄榄岩与铬铁矿之间为渐变接触关系,包壳纯橄榄岩与方辉橄榄岩之间既可以为渐变接触关系,也可以为截然接触关系或侵入接触关系。因此,阐明纯橄榄岩的成因是理解豆荚状铬铁矿形成机制的关键。西藏雅鲁藏布江缝合带中罗布莎和泽当两个代表性超镁铁质杂岩体的新观察揭示:(1)包壳纯橄榄岩的出露宽度变化于厘米级到百米级,但岩石具有均匀的细粒结构,流行模型难以解释;(2)包壳纯橄榄岩可以划分为至少两种构造类型:块状纯橄榄岩和片理化纯橄榄岩,暗示了纯橄榄岩形成过程的多阶段特点;(3)包壳纯橄榄岩主要由变晶橄榄石组成,仅含有少量由熔体或流体析出的橄榄石晶体;(4)与方辉橄榄岩相比,包壳纯橄榄岩中的橄榄石具有高MgO、Cr2O3、CaO和低MnO、Al2O3的特点,展示了矛盾的晶体化学特征;(5)邻近铬铁矿体的纯橄榄岩中常见反豆状结构,类似于多相稀释流体流体制中紊流产生的中尺度结构。上述看似矛盾的证据表明包壳纯橄榄岩的形成过程有大量深部流体的参与,因而流体过程可以作为构建一个新的整合模型的基础。据此,文中提出一个熔体-流体流模型,其基本机制是溶解-沉淀反应Opx+Fluid→Ol±Sp±Cpx±Pl±SiO2(fluid),而基本前提则是深部还原流体的持续供给和熔体-流体流的快速上升。此外,文中还表明,依据火成岩地质学、岩石学和名义无水矿物晶体化学证据也可以再造岩浆系统的流体过程。  相似文献   

吉林省大石河橄榄石矿床的产出特征   总被引：1，自引：0，他引：1  

汪连成 《吉林大学学报(地球科学版)》1996,(1)

吉林省大石河玄武岩规模小，并受敦－密大断裂控制。玄武岩中构成宝石的橄榄石产于二辉橄榄岩包体中和少量的捕虏晶中。矿床为碱性玄武岩，以位于大断裂次级构造上为特征。  相似文献   

First-principles study of (MgH₂SiO₄)? n (Mg₂SiO₄) hydrous olivine structures. I. Crystal structure modelling of hydrous olivine Hy-2 a (MgH₂SiO₄) ? 3(Mg₂SiO₄)     

S. V. Churakov  N. R. Khisina  V. S. Urusov  R. Wirth 《Physics and Chemistry of Minerals》2003,30(1):1-11

 Recently, the Hy-2a hydrous olivine (MgH₂ SiO₄)·3(Mg₂SiO₄) occurring as nanometre-sized inclusions in mantle olivines has been found by TEM, and has been suggested to be a new DHMS phase (Khisina et al. 2001). A model of the crystal structure of Hy-2a has been proposed as a 2a-superstructure of olivine with one Me²⁺ -vacant octahedral layer in the (1 0 0) plane per Hy-2a unit cell (Khisina and Wirth 2002). In the present study the crystal structure of Hy-2a hydrous olivine is optimized by ab initio calculations. The aims of this study are: (1) verification of the suggested models of Hy-2a hydrous olivine structure; (2) calculation of the most stable configurations for Hy-2a structure with minimum static lattice energy, by assuming a possible formation of Me²⁺ vacancies in either M1 or M2 octahedral sites; (3) determination of the position of protons and hydrogen bonds in the Hy-2a structure. Several different possible configurations of the Hy-2a structure are optimized. The results support the idea of a stable olivine structure with ordered planar-segregated OH-bearing defects oriented parallel to (1 0 0). The data obtained indicate a preferred stability of the Hy-2a structure with the protons associated with M1 vacancies and bonded with O1 and O2 oxygen sites. The relative energy values of the optimized Hy-2a structure configurations correlate as a rule with the average shifts of atoms from their positions in pure forsterite structure. Received: 7 February 2002 / Accepted: 23 October 2002  相似文献   

Intensity and direction of lattice-preferred orientation of olivine: are electrical and seismic anisotropies of the Australian mantle reconcilable?     

Fiona Simpson 《Earth and Planetary Science Letters》2002,203(1):535-547

It has been hypothesised that seismic and electrical anisotropy at the base of the lithosphere are caused by strain-induced lattice-preferred orientation (LPO) of olivine [100] axes parallel to present-day plate motion. This would imply that seismic and electrical anisotropy observations can provide geodynamicists with fundamental information for characterising mantle flow. The qualitative agreement between the fast direction of SV-waves and direction of maximum electrical conductance modelled deeper than 150 km below the North Central craton of Australia appear to support a common alignment mechanism, and the observed, anisotropic electrical conductances can be generated by hydrogen diffusivity in a water-poor (<1000 ppm H/Si) olivine mantle. A quantitative test is proposed for the hypothesis that electrical anisotropy is generated by anisotropic hydrogen diffusion rates (D) in olivine. Electrical anisotropy factors are computed using random resistor network models assuming that D[100]≈20×D[010]≈40×D[001]. Electrical and seismic anisotropies calculated from olivine LPO angular distribution functions modelled for a range of shear strains under a simple shear deformation demonstrate that the intensity of olivine [100] alignments (and associated shear strains) that would be required to explain the electrical anisotropy in the mantle below central Australia are significantly greater than predicted by Rayleigh wave anisotropies. The poor agreement between the observed electrical anisotropies and the electrical anisotropies that would be predicted from the Rayleigh wave anisotropies indicates that either (i) electrical anisotropy in the upper mantle below central Australia is not generated by hydrogen diffusivity alone or (ii) the seismic anisotropy is underestimated. The orientation of the olivine [100] axes maxima is inferred to be ∼30° rotated relative to the direction of present-day absolute plate motion (APM) that is determined relative to the hotspot reference frame (HS2-NUVEL1). Both the APM direction that is determined relative to a reference frame defined by requiring no-net rotation of the lithosphere (NNR-NUVEL1) and GPS-derived plate motion vectors fit the geophysical observations of upper mantle anisotropy better. This may support the contention that hotspots are not stationary relative to the deep mantle.  相似文献   

Shear localisation in upper mantle peridotites     

Martyn R. Drury  Reinoud L. M. Vissers  Dirk Van der Wal  Eilard H. Hoogerduijn Strating 《Pure and Applied Geophysics》1991,137(4):439-460

Upper mantle peridotite bodies at the earth's surface contain relict structures and microstructures which provide direct information on the role and the mechanisms of shear localisation in the upper mantle. Deformation which occurred at high temperatures (T>950±50°C) is relatively homogeneous within domains ranging in scale from a few kilometres to a few tens of kilometres. Below 950±50°C strain is localised into centimetre to several hundred metre wide shear zones which commonly contain hydrated mylonitic peridotites. The microstructures developed in the peridotites suggest there is a correlation between the occurrence of shear localisation and the occurrence of strain softening and brittle deformation processes. The most important strain softening processes are inferred to be structural and reaction induced softening. Structural softening processes include dynamic recrystallisation and strain-induced transitions from dislocation creep to some form of grain-size-sensitive (GSS) creep. Reaction induced softening is related to the formation of fine grained polyphase reaction products which deform by GSS creep and the formation of weak sheet silicates such as phlogopite, chlorite, talc and antigorite. From experimental studies these softening processes and brittle deformation processes are inferred to occur mainly at temperatures less than about 910±160°C. This temperature range is inferred to be a significant rheological transition in the upper mantle. Below 910±160°C deformation during orogenesis may be accommodated by an anastomosing network of hydrated mylonitic shear zones with a distinct, perhaps weak, rheology. At higher temperatures strain is accommodated in much wider deformation zones.On the scale of the lithosphere the degree of localisation may be different to that determined at the scale of the periodotite massif. An anastomosing network of hundred metre wide mylonitic shear zones forming 0.05–0.3 by volume fraction of the mantle lithosphere atT<950°C could accommodate inhomogeneous or homogeneous bulk deformation depending on the spatial distribution and ordering of the mylonite zones. The higher temperature deformation at deeper levels in the mantle could be markedly inhomogeneous being concentrated in shear zones with widths in the range of 2–20 km, alternatively these zones may widen significantly during deformation, resulting in a decrease in the degree of localisation with increasing bulk strain.  相似文献   

山东金伯利岩中榄橄石的研究          下载免费PDF全文

董振信 《岩石矿物学杂志》1991,(4)

本文百次研究了山东金伯利岩中橄榄石的产状、含量、大小、世代、形态、颜色、环带、矿物包体、折光率、2V、化学成分、端员组分特征及红外光谱和穆斯堡尔谱特征,并分析研究了橄榄石的成因。指出了无色—浅绿色的、含MgO、Cr2O3、NiO高的橄榄石是找金刚石矿的指示性矿物。  相似文献