Radiating Dyke Swarms in the BAT Region on Venus: A Study from the Helen Planitia Quadrangle

正The Beta-Atla-Themis(BAT)region on Venus is characterized by large volcanic rises,major rift zones(chasmata),radiating,linear,and circumferential grabenfissure systems,and coronae.Its most prominent features     

Giant Circumferential Dyke Swarms on Earth: Possible Analogues of Coronae on Venus and Similar Features on Mars

正Venusian coronae are large(60-2600 km diameter)tectono-magmatic features characterized by quasi-circular graben-fissure systems and topographic features such as a central dome,central depression,circular rim or circular     

深井地下灌注数值模型SWIFT

深井地下灌注是一种有效处理工业废液的方法,随着认识的不断深入和技术的不断提高,将成为未来我国对难处理、高毒性废液实行最终处理的重要选择之一。SWIFT数值模型能够同时模拟灌注层中水流运动、热量运移、盐分运移和放射性核素运移过程,并且能够充分考虑深部灌注层高温高压等特殊地质环境。其多方面的模拟功能不但适用于深井灌注的数值模拟,还可用于海水入侵、高放射性核废料填埋的模拟分析。在美国,该数值模型已经被用于多个深井灌注项目的数值模拟。对SWIFT进行了较全面的介绍,并指出该模型使用过程中应特别注意的几个问题。     

Global Mesozoic and Cenozoic Rift Systems: Constrain on the Tectonic Setting of Mafic Dyke Swarms

正The primary tectonic setting of dyke swarms,especially those formed in the pre-Cambrian era,are under controversy(Peng et al.,2005).However,Mesozoic and Cenozoic rift systems,which are supposed to be the     

Age and depositional setting of the Permian Black Dyke Formation: implications for the paleogeography and structural evolution of western Nevada

Abstract

In western Nevada, the Black Dyke Formation includes volcanic rocks overlain conformably by volcaniclastic sediments. At the base, hornblende-phyric basalts with cognate hornblende-bearing gabbroic cumulates are interbedded with tuffs and pyroclastic breccia. Amphiboles give ⁴⁰Ar/³⁹Ar ages of 276 Ma. Clinopyroxene-phyric pillow basalts and plagioclase-phyric andesitic lava flows are present higher in the section. Facies changes between exposures reflect development near volcanic centers.

According to our investigations, the Black Dyke Formation is involved in east–west-trending folds overturned toward the south, and overlain unconformably by the Mesozoic Dunlap Formation, which unconformably overlies the Mississippian–Permian Mina Formation. Interpreted until now as tectonic slices within the Luning allochthon, we suggest that the Black Dyke Formation is part of the Sonoma allochthon associated with the Mina Formation. The Sonoma records closure of the Havallah basin (Golconda allochthon), and collision of an arc- trench system with the North American margin.

The Black Dyke Formation exhibits similarities with the Permian arc sequence of the northern Sierra Nevada. Both sequences are characterized by amphibole-bearing breccias, clinopyroxene-phyric pillow-basalts, plagioclase-phyric andesites and overlying volcaniclastic sediments. These sequences developed in the same geodynamic environment (an island- arc). © Elsevier, Paris     

Age and depositional setting of the Permian Black Dyke Formation: Implications for the paleogeography and structural evolution of western Nevada

In western Nevada, the Black Dyke Formation includes volcanic rocks overlain conformably by volcaniclastic sediments. At the base, hornblende-phyric basalts with cognate hornblende-bearing gabbroic cumulates are interbedded with tuffs and pyroclastic breccia. Amphiboles give ⁴⁰Ar/³⁹Ar ages of 276 Ma. Clinopyroxene-phyric pillow basalts and plagioclase-phyric andesitic lava flows are present higher in the section. Facies changes between exposures reflect development near volcanic centers.According to our investigations, the Black Dyke Formation is involved in east-west-trending folds overturned toward the south, and overlain unconformably by the Mesozoic Dunlap Formation, which unconformably overlies the Mississippian-Permian Mina Formation. Interpreted until now as tectonic slices within the Luning allochthon, we suggest that the Black Dyke Formation is part of the Sonoma allochthon associated with the Mina Formation. The Sonoma records closure of the Havallah basin (Golconda allochthon), and collision of an arctrench system with the North American margin.The Black Dyke Formation exhibits similarities with the Permian arc sequence of the northern Sierra Nevada. Both sequences are characterized by amphibole-bearing breccias, clinopyroxene-phyric pillow-basalts, plagioclase-phyric andesites and overlying volcaniclastic sediments. These sequences developed in the same geodynamic environment (an islandarc).     

深基坑支护结构计算的改进平面框架模型方法

传统的平面框架模型分析方法在基坑支护结构位移计算中,存在着计算模型误差和地基土力学参数取值误差等因素,对计算结果影响较大。改进平面框架模型分析方法是通过修正地基土力学参数,修正上述两种误差对计算结果的影响,以达到提高计算精度的目的。地基土力学参数可采用正反分析方法取值。取值过程将结合径向基神经网络方法和空间作用协同分析模型。结果表明,该方法较传统方法而言计算精度更高。     

Compositional and Lithological Controls on the PGE-Bearing Sulphide Zones in the Selukwe Subchamber, Great Dyke: a Combined Equilibrium-Rayleigh Fractionation Model

The platinum group element (PGE)-bearing Main and Lower SulphideZones of the Selukwe Subchamber of the Great Dyke are made upof a series of subzones within which the ratios Pd:Pt are effectivelyconstant, whereas these ratios vary significantly between thesubzones. Fractionation of Pd with respect to Pt varies by afactor of 10 and cannot be modelled using a sulphide collectorphase and constant partition coefficients. The link with sulphideis indisputable and the control is likely to have been the degreeof oversaturation of PGE micro-nuggets in the magma. The apparentpartition coefficients for Pt and Pd between silicate and sulphideliquid are dependent on the degree of oversaturation and therebyexhibit spurious correlation with the PGE content of the sulphide.Modelling replicates the Pt and Pd distribution and ratios onlyby dramatically changing the effective partition coefficients.Pyroxene compositions (including TiO₂) are shown to be stronglydependent on the incompatible element content of the whole rock,and specific linear arrays relating these variables can be relatedto the PGE subzones. The overall control is Rayleigh fractionation,but constancy of the ratio Pd:Pt and the initial pyroxene composition(before re-equilibration with trapped liquid) within the subzonesis indicative of equilibrium crystallization. This layered structuremay have been derived from liquid layers in the magma chamber. KEY WORDS: platinum group elements; sulphide; Great Dyke; pyroxene compositions     

基于优化的BP神经网络地层可钻性预测模型

提出了一种粒子群算法（PSO）优化的BP网络模型预测地层可钻性的新方法。利用粒子群算法优化BP网络模型的参数,避免了BP网络陷入局部极小值的缺点,提高了模型的预测速度和精度。结合钻探实例,利用测井资料和地层可钻性级别的关系建立了可钻性级别实时预测模型,并将该模型与传统的BP网络进行对比,结果表明,该模型优于BP网络,具有较高的精度和较快的收敛速度,有一定的适用性。     

Palaeomagnetic Study on a 1765 Ma Dyke Swarm from Singhbhum Craton: Implications to the Paleogeographic Position of India

正The paleogeographic position of India within the Columbia supercontinent during Paleoproterozoic era is still uncertain because of very few reliable,high-quality palaeomagnetic data with precise geochronology.Here we     

An Isotope and Trace Element Study of the East Greenland Tertiary Dyke Swarm: Constraints on Temporal and Spatial Evolution during Continental Rifting

Dykes of the East Greenland Tertiary dyke swarm can be dividedinto pre- and syn-break-up tholeiitic dykes, and post-break-uptransitional dykes. Of the pre- and syn-break-up dykes, themost abundant group (Tholeiitic Series; TS) has major elementcompositions similar to the main part of the East Greenlandflood basalts. A group of high-MgO tholeiitic dykes (Picrite–AnkaramiteSeries; PAS) are much less common, and are equivalent to someof the oldest lavas of the East Greenland flood basalts. Isotopiccompositions of the TS and PAS dykes partly overlap with thosefor Iceland, but Pb isotopic compositions extend to less radiogenicvalues than those seen in either Iceland or North Atlantic mid-oceanridge basalt (MORB). The isotopically depleted source requiredto account for this isotopic variation is interpreted as subcontinentallithospheric mantle with low ⁸⁷Sr/⁸⁶Sr and ²⁰⁶Pb/²⁰⁴Pb and high     

横向惯性效应对基桩动测的影响分析

在桩的振动理论中,对大直径桩,不能把桩简单看成一维杆件,必须考虑其横向尺寸产生的横向惯性效应。通过横向惯性效应的运动方程进行拉氏变换,推导出桩顶在正弦激振力作用下的位移和速度的响应传递函数以及速度导纳表达式,并分析了横线惯性效应对基桩动测时域曲线的影响以及其影响因素。在不考虑材料阻尼、桩周土条件下,发现横向惯性效应会降低应力波速度,并产生衰减作用,同时脉冲宽度和桩径大小直接影响着横向惯性效应的强弱。     

基于热流固耦合的增强型地热有机朗肯循环发电系统性能分析

本文建立了耦合井筒、热储、有机朗肯循环发电系统的详细数学模型, 包括三维非稳态热流固耦合模型和有机朗肯循环发电系统热动力学模型, 参考青海省共和县恰卜恰干热岩体地热地质特征, 包括压裂储层、围岩、裂隙、井筒等特征参数, 研究了注入流量、注入温度和井间距对系统净输出功、年均净输出功和热效率的影响规律。结果表明: 在一定的注入流量、注入温度和净间距下, 随着时间的推移, 岩石孔隙压力和热应力作用使得裂隙渗透率增大, 注入泵功耗是降低的, 净输出功和热效率也是降低的。注入流量的增大提高了膨胀机轴功、注入泵功耗和生产温度衰减速率, 进而导致热效率降低, 存在最优的注入流量50 kg/s, 使得年均净输出功达到最大值1 470.1 kW。注入温度的增大可以提高系统热效率, 降低净输出功的年均衰减速率, 当注入温度为60 ℃时, 年均净输出功最大。井间距的增大减缓了生产温度的衰减速率, 有利于热效率的提高, 但是也同时也增大了膨胀机轴功和注入泵功耗。当分支井间距为450 m时, 年均净输出功达到最大值1 497.3 kW。此研究可为增强地热发电系统的开发利用提供指导。     

辫状河-曲流河转换模式探讨--以准噶尔盆地南缘头屯河组露头为例

为探讨辫状河向曲流河转换的模式,以准噶尔盆地南缘头屯河剖面中侏罗统头屯河组为例,在层序地层学与沉积学的理论指导下,在层序划分与河流成因岩相类型确定的基础上,通过野外露头实测、剖面精细解剖及沉积观察描述,对头屯河组辫状河-曲流河（辫-曲）转换进行成因分析与特征总结,明确了辫-曲转换的控制因素,再现了辫-曲转换的沉积背景。研究表明:基准面旋回、物源供给、地形坡度及古气候4个方面控制着头屯河组辫-曲转换的过程。随着基准面的逐渐升高,物源供给的减弱,地形坡度的减缓,古气候环境炎热干旱,头屯河组逐渐由辫状河向曲流河转换。最终由头屯河组野外露头垂向序列,建立了辫-曲转换的局部沉积构型模式和区域沉积演化模式。     

Application of a Simulation Model for the Formation of Methane Hydrate to the Nankai Trough and the Blake Ridge: Natural Examples of Two End-member Cases

Abstract. Simulation experiments with a one-dimensional static model for formation of methane hydrate are used to demonstrate models of hydrate occurrence and its generation mechanism for two end-member cases. The simulation results compare well with experimental data for two natural examples (the Nankai Trough and the Blake Ridge).
At the MITI Nankai Trough wells, the hydrate occurrence is characterized by strongly hydrated sediments developing just above the BGHS. Such occurrence can be reproduced well by simulation in which the end-member case of upward advective fluid flow from below the BGHS is set. The strongly hydrated sediments is formed by oversaturated solution with free gas which directly enters the BGHS by the upward advective fluid flow. The recycling of dissociated methane of preexisting hydrate also contributes to the increase of hydrate saturation.
At the Site 997 in the Blake Ridge area, the hydrate occurrence is characterized by thick zone with poorly hydrated sediments and no hydrate zone developing above the hydrate zone. Such occurrence can be reproduced well by simulation in which the end-member case of in-situ biogenic production of methane in the sediment of methane hydrate zone is set. The distribution pattern of hydrate saturation is basically controlled by that of TOC. However, the hydrate concentration near the bottom of the hydrate zone is increased by the effect of recycling of dissociated methane of pre-existing hydrate. No hydrate zone expresses the geologic time needed until the local concentration of methane exceeds the solubility by gradual accumulation of in-situ biogenic methane with burial.     

裂后沉降期碳酸盐岩缓坡沉积响应及成储特征 ——以塔里木盆地下寒武统肖尔布拉克组为例

裂后充填阶段的碳酸盐岩缓坡沉积已逐渐成为深层油气勘探的重点领域之一。以塔里木盆地下寒武统肖尔布拉克组为例,基于最新拼接处理42条二维地震大测线、柯坪地区9个剖面点及12口完钻井测井及取芯等资料,系统开展了其沉积前古构造格局及岩相古地理响应特征、储层宏观分布与内部结构差异等研究。结果表明: 1）沉积期盆内发育“三隆两洼”古构造格局,对肖尔布拉克期碳酸盐岩缓坡体系（组合）内部分异产生明显控制作用,高能颗粒滩及丘滩带分布在古隆起周缘,古洋流进一步复杂化了沉积物构成,划分出塔西南古隆起北缘颗粒滩为主的坡坪式缓坡、柯坪—温宿低隆起丘滩复合体均斜型缓坡、轮南—牙哈低隆起丘滩复合体孤岛型缓坡;2）古隆起周缘中缓坡高能相带构成了肖尔布拉克组储层发育的重要载体,早期云化作用有效保存了原始孔隙,埋藏期以先期孔隙为基础进一步调整改造,预测规模储层主要分布于三大古（低）隆区周缘高能丘滩带内,面积达9×104 km2。不同类型缓坡体系的储层差异明显,其中坡坪式缓坡的颗粒滩储层以Ⅱ类储层为主、分布稳定为特点,最具规模性,可作为下一步油气勘探的重点关注区带。基于实例解剖认为,裂后沉降期碳酸盐岩缓坡体系分异具明显受构造控制特点,深化沉积前古构造格局认识是预测有利储集相带的关键,直接影响后续规模储层预测及品质评价。     

砂砾岩体不同岩相油气充注期储集性能差异及成藏意义--以玛湖凹陷西斜坡区百口泉组油藏为例

玛湖凹陷西斜坡区三叠系百口泉组岩性油藏生、储、盖、运等成藏条件配置优越,有效的侧向及上倾方向圈闭封挡条件为制约油气成藏的关键。在明确泥质含量为影响本区砂砾岩储层储集性能关键因素基础上,以泥质含量为主分类参数,将砂砾岩储层划分为贫泥砂砾岩(泥质含量<5%)、含泥砂砾岩(泥质含量5%~8%)和富泥砂砾岩(泥质含量>8%)三种岩相。早侏罗世的早期油气充注期,上述三种岩相储层均可作为有效储层;早白垩世的主要油气充注期,富泥砂砾岩相储层的储集性能明显变差,成为研究区主要的致密封挡带,而贫泥砂砾岩和含泥砂砾岩仍可作用作为有效储层,且前者的储集性能优于后者。扇三角洲前缘亚相(牵引流)沉积主要对应于贫泥砂砾岩岩相,在油气充注期为有效储层,构成玛湖凹陷西斜坡区百口泉组大面积岩性油藏的主体储集层;扇三角洲平原亚相(牵引流)、砂质碎屑流(重力流)沉积主要对应于富泥砂砾岩岩相,在油气充注期储集性能均较差,主要构成研究区大面积岩性油藏的底部及侧向的致密封挡带,上述两致密封挡带与扇三角洲前缘亚相(牵引流)有效储层配置,共同形成玛湖凹陷西斜坡区百口泉组大型岩性油藏。     

臼齿状构造成因新解——以天津蓟县高于庄组第三段为例

臼齿状构造（Molar—tooth structure）是一种主要发育在前寒武纪非叠层石碳酸盐岩中的沉积构造。由于形态多样且缺乏现代的类比物,国内外地质学家曾先后建立多种模式来解释其成因,这些模式大致可以归为两类：地震液化模式和生物成因模式。近年来,一种新的模式：气泡膨胀与迁移模式得到了地质学家的广泛引用。产在天津蓟县剖面高于庄组第三段非叠层石碳酸盐岩沉积序列上部的臼齿状构造,虽然可以应用气泡膨胀与迁移模式来解释其形成机制,但是,考虑到臼齿状构造可能是微生物席封闭沉积面所激发的气泡膨胀与迁移作用的产物,并且气泡可能是由于细粒沉积中微生物提供的有机质的裂解作用的结果,表明了臼齿状构造的形成间接地与微生物生命活动存在关联。因此,可以将臼齿状构造归为席底构造（第五类原生沉积构造）的一种类型。     

Zabyat Formation, Semail Nappe, Oman: sedimentation on to an emplacing ophiolite

ABSTRACT The pelagic sediments of the Semail Ophiolite are depositionally overlain by ophiolite-derived sediments of the Zabyat Formation, dominated by matrix-supported rudites, with subordinate arenites and lutites. The detritus was locally derived from the ophiolite, in a deep marine environment indicated by both underlying and overlying pelagic carbonates. The Zabyat rocks are restricted to fault zones in the ophiolite which were active during emplacement. They are interpreted as debris shed from the sub-vertical fault zones during the initial disruption of the Semail ocean floor, prior to the final emplacement on to the Arabian continental margin. This interpretation places constraints on possible mechanisms of ophiolite emplacement.     

Geobarometry for Peridotites: Experiments in Simple and Natural Systems from 6 to 10 GPa

Experiments with peridotite minerals in simple (MgO–Al₂O₃–SiO₂,CaO–MgO–SiO₂ and CaO–MgO–Al₂O₃–SiO₂)and natural systems were conducted at 1300–1500°Cand 6–10 GPa using a multi-anvil apparatus. The experimentsin simple systems demonstrated consistency with previous lowerpressure experiments in belt and piston–cylinder set-ups.The analysis of spatial variations in pyroxene compositionswithin experimental samples was used to demonstrate that pressureand temperature variations within the samples were less than0·4 GPa and 50°C. Olivine capsules were used in natural-systemexperiments with two mineral mixtures: SC1 (olivine + high-Alorthopyroxene + high-Al clinopyroxene + spinel) and J4 (olivine+ low-Al orthopyroxene + low-Al clinopyroxene + garnet). Theexperiments produced olivine + orthopyroxene + garnet ±clinopyroxene assemblages, occasionally with magnesite and carbonate-richmelt. Equilibrium compositions were derived by the analysisof grain rims and evaluation of mineral zoning. They were comparedwith our previous experiments with the same starting mixturesat 2·8–6·0 GPa and the results from simplesystems. The compositions of minerals from experiments withnatural mixtures show smooth pressure and temperature dependencesup to a pressure of 8 GPa. The experiments at 9 and 10 GPa producedandradite-rich garnets and pyroxene compositions deviating fromthe trends defined by the lower pressure experiments (e.g. higherAl in orthopyroxene and Ca in clinopyroxene). This discrepancyis attributed to a higher degree of oxidation in the high-pressureexperiments and an orthopyroxene–high-P clinopyroxenephase transition at 9 GPa. Based on new and previous resultsin simple and natural systems, a new version of the Al-in-orthopyroxenebarometer is presented. The new barometer adequately reproducesexperimental pressures up to 8 GPa. KEY WORDS: garnet; mineral equilibrium; multi-anvil apparatus; orthopyroxene; geobarometry