三次贝塞尔曲线拼接模型的折线式等值线曲线化应用

本文通过对曾广鸿等人[1]提出的利用三次Bezier曲线拼接模型实现满足拓扑关系的折线武等值线曲线化的理论方法进行编程实践后,发现仅仅根据文中的方法不能完全正确地实现等值线的绘制,为此作者通过编程实践对该方法进行了补充与完善,文中详细完整地介绍了能完全满足拓扑关系的折线式等值线全参数曲线化的具体实现方法.     

Quartz and calcite microfabric transitions in a pressure and temperature gradient,Sivrihisar, Turkey

Interlayered quartzite and marble in the southern Sivrihisar Massif, Turkey, record metamorphic conditions ranging from high-pressure/low-temperature through a Barrovian overprint from chlorite- to sillimanite-zone conditions. This sequence was exhumed under transtension, producing macroscopic constrictional fabrics (L-tectonites) during crustal thinning. Quartz microstructures consist of dynamically recrystallized aggregates in the dislocation creep regime dominated by grain boundary migration. Quartz microstructures are relatively constant across the high metamorphic gradient, and crystallographic fabric patterns transition from plane strain to constriction strain. Calcite fabrics are characterized by progressive overprinting of a columnar texture inherited from the high-pressure polymorph aragonite. In the low-temperature Barrovian domain (<400?°C), shearing of calcite rods produced a very strong c-axis point maximum. At moderate temperature, calcite rods were partially to totally recrystallized and the strong preferred orientation maintained. At temperature >500?°C and high constriction strain, marble has no crystallographic fabric, likely reflecting a transition from dislocation creep to diffusion creep. Phengite in high-pressure/low-temperature marble and quartzite yields relatively simple age spectra with Late Cretaceous (88–82 Ma) ⁴⁰Ar/³⁹Ar ages. Barrovian muscovite records significantly younger ages (63–55 Ma). The transtension system and associated metamorphism may have occurred above a subduction zone in Paleocene–Eocene time as a precursor to intrusion of Eocene (~53 Ma) arc plutons.     

辉锑矿-硒锑矿系列的实验研究

合成Sb-S-Se体系中硫、硒代换的实验研究显示,辉锑矿-硒锑矿系列是由于硫-硒代换形成的二元固溶体系列。该系列的两个端元成分分别是Sb2S3与Sb2Se3。在该二元固溶体系列中,硒含量的变化是完全连续的,显示出硒对硫的取代,是以无序取代和完全混溶的方式进行的。故其为一个完全混溶的二元固溶体系列。同时,随硒含量的增加,该二元固溶体系列的矿物结晶学参数有规律性的变化。即晶胞参数a,b,c值与晶胞体积V值、矿物密度D值,均随硒含量的增加而增大。     

The Bingham Distribution of Quaternions and Its Spherical Radon Transform in Texture Analysis

Spherical geometry of quaternions is employed to characterize the Bingham distribution on the 3-dimensional sphere as being uniquely composed of a bipolar, a circular and a spherical component. A new parametrization of its dispersion parameters provides a classification of patterns of crystallographic preferred orientations (CPO, or textures). It is shown that the Bingham distribution can represent most types of ideal CPO patterns; in particular single component, fiber and surface textures are represented by rotationally invariant bipolar, circular and spherical distributions, respectively. Pole figures of given crystal directions are derived by the spherical Radon transform of the Bingham probability density function of rotations, which are displayed for general and special cases.     

Oriented growth of garnet by topotactic reactions and epitaxy in high‐pressure,mafic garnet granulite formed by dehydration melting of metastable hornblende‐gabbronorite (Jijal Complex,Kohistan Complex,north Pakistan)

Garnet growth in high‐pressure, mafic garnet granulites formed by dehydration melting of hornblende‐gabbronorite protoliths in the Jijal complex (Kohistan palaeo‐island arc complex, north Pakistan) was investigated through a microstructural EBSD‐SEM and HRTEM study. Composite samples preserve a sharp transition in which the low‐pressure precursor is replaced by garnet through a millimetre‐sized reaction front. A magmatic foliation in the gabbronorite is defined by mafic‐rich layering, with an associated magmatic lineation defined by the shape‐preferred orientation (SPO) of mafic clusters composed of orthopyroxene (Opx), clinopyroxene (Cpx), amphibole (Amp) and oxides. The shape of the reaction front is convoluted and oblique to the magmatic layering. Opx, Amp and, to a lesser extent, Cpx show a strong lattice‐preferred orientation (LPO) characterized by an alignment of [001] axes parallel to the magmatic lineation in the precursor hornblende‐gabbronorite. Product garnet (Grt) also displays a strong LPO. Two of the four 〈111〉 axes are within the magmatic foliation plane and the density maximum is subparallel to the precursor magmatic lineation. The crystallographic relationship 〈111〉_Grt // [001]_Opx,Cpx,Amp deduced from the LPO was confirmed by TEM observations. The sharp and discontinuous modal and compositional variations observed at the reaction front attest to the kinetic inhibition of prograde solid‐state reactions predicted by equilibrium‐phase diagrams. The P–T field for the equilibration of Jijal garnet granulites shows that the reaction affinities are 5–10 kJ mol.^?1 for the Grt‐in reaction and 0–5 kJ mol.^?1 for the Opx‐out reaction. Petrographic and textural observations indicate that garnet first nucleated on amphibole at the rims of mafic clusters; this topotactic replacement resulted in a strong LPO of garnet. Once the amphibole was consumed in the reaction, the parallelism of [001] axes of the mafic‐phase reactants favoured the growth of garnet crystals with similar orientations over a pyroxene substrate. These aggregates eventually sintered into single‐crystal garnet. In the absence of deformation, the orientation of mafic precursor phases conditioned the nucleation site and the crystallographic orientation of garnet because of topotaxial transformation reactions and homoepitaxial growth of garnet during the formation of high‐pressure, mafic garnet‐granulite after low‐pressure mafic protoliths.     

石英结晶学优选与应用

石英集合体的结晶学优选可由位错滑移、双晶滑移、定向成核与生长等形成,其中位错滑移是塑性变形岩石中石英结晶学优选产生的最重要的机制。影响变形石英结晶学优选的因素有温度、应变速率、应变、差应力、水、复矿物岩石中各种矿物间的相互作用、初始结晶学方向等。系统总结了石英晶体变形与滑移系,结晶学优选的测量与表达,多种条件下石英的结晶学优选,以及在判断剪切方向、计算运动学涡度、判定变形温度、分析变形历史等方面的应用,并认为应用石英组构作运动学和动力学解析时需与其它微观、宏观现象相结合。     

金属硫化物矿石中同沉积组构的成因鉴别

同沉积组构是特定地质环境的产物，在矿化地层中有一定的空间分布特点。对组构进行成因鉴别时，必须注意野外地质产状的调查。在室内，既要对组构中硫化物颗粒的形态特征、排布形式及其与胶结物的关系进行放大观察，还要对一些可能是多解性的组构形态进一步进行测试研究。电子探针可以对其中的矿物颗粒进行成分对比分析，Ｘ光岩组可以测定硫化物晶体的定向特征及其与层理的方位关系。     

赣南淘锡坑锡矿床中锡石晶体形态学和地球化学研究

本文对淘锡坑锡矿床的含矿石英脉中的锡石晶体开展了晶体形态学和地球化学的系统研究。按晶面组合特征,淘锡坑锡矿床中的锡石可分为三种类型:由{111}锥面+{110}柱面共2个单形构成的A型锡石、由{111}锥面+{110}柱面+{100}柱面共3个单形构成的B型锡石和由{111}锥面+{101}锥面+{110}柱面+{100}柱面共4个单形构成的C型锡石。综合各种锡石晶型与结晶条件的资料分析,本文推测A型、B型锡石的结晶温度高于C型锡石的。本文首次利用电子探针分析仪对锡石进行阴极发光（CL）成像观测,发现淘锡坑锡矿床中的锡石经历了两期结晶作用:早期锡石以CL荧光亮度较小（黑色——暗灰色）为特征,边缘有明显的溶蚀痕迹,常见典型的韵律振荡构造和砂钟构造,其晶面组合特征显示了早期锡石属于A型或B型锡石;晚期锡石以CL荧光亮度较大（白色——浅灰色）为特征,往往沿着早期锡石的溶蚀边界面充填生长,一般不显示韵律振荡构造和砂钟构造,其晶面组合特征显示了晚期锡石属于C型锡石。电子探针分析显示,淘锡坑锡矿床中锡石的FeO、Ta₂O₅含量较高,指示其形成于高温热液环境;HfO₂含量较高,Zr/Hf比值较低,说明成矿热液来源于高度分异的花岗质岩浆。两期锡石的FeO含量和In₂O₃含量的对比结果显示,早期锡石相对富FeO而贫In₂O₃,反映了早期锡石的结晶温度和压力均高于晚期锡石的,故两期锡石的结晶作用分别与淘锡坑矿床的两期岩浆热液成矿作用相关。     

玛瑙的结构、水含量和成因机制

玛瑙是一种隐晶质硅质岩石,主要由玉髓以及少量蛋白石、斜硅石和微晶石英等组成.其在世界各地分布广泛,质地坚硬细腻、色彩鲜艳多样、纹理交错、造型千姿百态,是一种平凡而美丽的宝石.本文结合国内外最新研究进展,对玛瑙矿物的结构、水含量和成因机制进行了综合评述.玛瑙以纹带构造为特征,其内部纹带花纹和化学组成呈韵律性变化,并在不同观察尺度表征出来.因此,玛瑙也被定义为条带状玉髓.然而,多数玛瑙实际上是由纤维状玉髓、同心环带状玉髓、水平条带状玉髓、微晶石英和自形石英晶体等组成,它们的相对含量与玛瑙的产地和形成过程密切相关.X射线衍射和电子背散射衍射(EBSD)测量数据揭示,玛瑙中的硅质矿物多发生定向生长,其中微晶石英a轴倾向于垂直韵律环带,c轴则近似平行韵律环带.傅立叶变换红外光谱(FTIR)测量表明,玛瑙含有少量分子水和羟基水,并且总水含量随着硅质矿物结晶度提高而降低.至今实验室仍然无法合成玛瑙,还不清楚玛瑙纹带构造的形成机制和过程.一种代表性假设认为,玛瑙中的纹带源于硅质热液沉淀作用或者硅胶原位结晶作用.但是,最近研究发现玛瑙纹带中共生矿物的结晶度、晶体取向和含水量具有系统差异,揭示其形成过程可能与成岩序列密切相关.将实验岩石学与定量显微结构观察以及多种矿物微区分析测试手段有机结合,深入研究玛瑙环带内部微量元素、水含量和晶体取向数据,获得其系统性变化特征及其内部联系,可以为玛瑙成因机制和形成过程研究提供重要数据支撑和关键性的约束条件.     

Strain and Crystallographic Fabric in Mesoscopic Ductile Shear Zones of Garhwal Himalaya

The MCT Zone of Bhagirathi valley of Garhwal Himalaya is characterized by numerous mesoscopic ductile shear zones. These shear zones are developed in response to nearly NNE-SSW maximum horizontal compression and provide an opportunity to study the variation in strain and crystallographic fabrics within the ductile shear zones.The grain shape and orientation of quartz under microscope reflect that strain is higher in the center and it progressively decreases towards the shear zone boundary. The preferred orientation of quartz c-axes across the shear zone suggests that the single girdle of the quartz c-axes are probably first developed at the shear zone boundary and become prominent in the center of shear zone with increase in the intensity of deformation. The strong crystallographic preferred orientation normal to foliation suggests that the internal deformation of the quartz might have taken place by dislocation creep mechanism exhibiting a non-coaxial deformation history.