Diamond in metasedimentary crustal rocks from Pohorje,Eastern Alps: a window to deep continental subduction          下载免费PDF全文

M. Janák  N. Froitzheim  K. Yoshida  V. Sasinková  M. Nosko  T. Kobayashi  T. Hirajima  M. Vrabec 《Journal of Metamorphic Geology》2015,33(5):495-512

We report the first finding of diamond and moissanite in metasedimentary crustal rocks of Pohorje Mountains (Slovenia) in the Austroalpine ultrahigh‐pressure (UHP) metamorphic terrane of the Eastern Alps. Microscopic observations and Raman spectroscopy show that diamond occurs in situ as inclusions in garnet, being heterogeneously distributed. Under the optical microscope, diamond‐bearing inclusions are of cuboidal to rounded shape and of pinkish, yellow to brownish colour. The Raman spectra of the investigated diamond show a sharp, first order peak of sp³‐bonded carbon, in most cases centred between 1332 and 1330 cm^?1, with a full width at half maximum between 3 and 5 cm^?1. Several spectra show Raman bands typical for disordered graphitic (sp²‐bonded) carbon. Detailed observations show that diamond occurs either as a monomineralic, single‐crystal inclusion or it is associated with SiC (moissanite), CO₂ and CH₄ in polyphase inclusions_. This rare record of diamond occurring with moissanite as fluid‐inclusion daughter minerals implies the crystallization of diamond and moissanite from a supercritical fluid at reducing conditions. Thermodynamic modelling suggests that diamond‐bearing gneisses attained P–T conditions of ≥3.5 GPa and 800–850 °C, similar to eclogites and garnet peridotites. We argue that diamond formed when carbonaceous sediment underwent UHP metamorphism at mantle depth exceeding 100 km during continental subduction in the Late Cretaceous (c. 95–92 Ma). The finding of diamond confirms UHP metamorphism in the Pohorje Mountains, the most deeply subducted part of Austroalpine units.  相似文献   

Torsional dynamic response of a large‐diameter pipe pile in viscoelastic saturated soil     

Changjie Zheng  Hanlong Liu  Xuanming Ding  Yaru Lv 《国际地质力学数值与分析法杂志》2014,38(16):1724-1743

An analytical solution is developed in this paper to investigate the dynamic response of a large‐diameter end‐bearing pipe pile subjected to torsional loading in viscoelastic saturated soil. The wave propagation in saturated soil and pile are simulated by Biot's two‐phased linear theory and one‐dimensional elastic theory, respectively. The dynamic equilibrium equations of the outer soil, inner soil, and pile are established. The solutions for the outer and inner soils in frequency domain are obtained by Laplace transform technique and the separation of variables method. Then, the dynamic response of the pile is obtained on the basis of the perfect contacts between the pile and the outer soil as well as the inner soil. The results in this paper are compared with that of a solid pile in elastic saturated soil to verify the validity of the solution. Furthermore, the solution in this paper is compared with the classic plane strain solution to verify the solution further and check the accuracy of the plane strain solution. Numerical results are presented to analyze the vibration characteristics and illustrate the effect of the soil parameters and the geometry size of the pile on the complex impedance and velocity admittance of the pile head. Finally, the displacement of the soil at different depth and frequency is analyzed. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Modeling nonlinear wave–wave interactions with the elliptic mild slope equation     

《Applied Ocean Research》2014

An approach is developed to simulate wave–wave interactions using nonlinear elliptic mild-slope equation in domains where wave reflection, refraction, diffraction and breaking effects must also be considered. This involves the construction of an efficient solution procedure including effective boundary treatment, modification of the nonlinear equation to resolve convergence issues, and validation of the overall approach. For solving the second-order boundary-value problem, the Alternating Direction Implicit (ADI) scheme is employed, and the use of approximate boundary conditions is supplemented, for improved accuracy, with internal wave generation method and dissipative sponge layers. The performance of the nonlinear model is investigated for a range of practical wave conditions involving reflection, diffraction and shoaling in the presence of nonlinear wave–wave interactions. In addition, the transformation of a wave spectrum due to nonlinear shoaling and breaking, and nonlinear resonance inside a rectangular harbor are simulated. Numerical calculations are compared with the results from other relevant nonlinear models and experimental data available in literature. Results show that the approach developed here performs reasonably well, and has thus improved the applicability of this class of wave transformation models.  相似文献   

莺歌海盆地乐东地区石英裂隙内流体包裹体特征及其对天然气成藏制约     

税蕾蕾  梁茹  孟祥豪  郭来源  许克伟 《沉积与特提斯地质》2020,40(1):45-52

莺歌海盆地乐东地区是我国典型高温超压天然气勘探领域,其关键储层黄流组砂岩以天然气富含CO_2为特征,对其中石英颗粒内裂隙包裹体的研究能为CO_2来源和天然气成藏信息提供重要线索。本文通过对黄流组砂岩石英颗粒内包裹体进行岩相学、显微测温与激光拉曼分析,结果表明黄流组砂岩石英颗粒内正常捕获流体包裹体均一温度主要分布在155～165℃与170～180℃两个温度区间,流体包裹体成分为CO_2(气)和H_2O(液)两种或CO_2(气)和CO_2(液)、H_2O(液)三种。这些特征表明乐东地区黄流组至少经历两期富含CO_2的热液活动,记录了埋藏晚期无机CO_2在火山活动或深大断裂发育期充注成藏的信息。  相似文献   

封闭系统中的白云石化作用过程及其油气地质意义——以南羌塘拗陷中侏罗统布曲组白云岩为例     

孙伟  陈明  万友利  何江林  兰叶芳  卫红伟  陈浩 《地质论评》2020,66(5):1217-1229

南羌塘拗陷中侏罗统布曲组结晶白云岩作为盆地最优质的储层是通过埋藏成岩过程中封闭条件下的白云石化作用形成的，岩石所具有的高孔隙度与封闭系统中白云石化反应有关。根据对羌资11井和羌资12井布曲组的岩石结构分类、碳氧同位素组成及温度计算、流体包裹体均一温度等分析结果，可以认为：结晶白云岩碳同位素值分布区间较窄（2. 86‰~4. 27‰），氧同位素值随着白云石晶体变粗（自形程度变差）逐渐偏负（-3. 27‰~-8. 17‰），显著低于保留原始组构的白云岩，表明结晶白云岩碳源来自于先驱灰岩中的碳，其白云石化作用应是在远离大气水的封闭成岩环境中进行；结晶白云岩流体包裹体均一温度主峰值区间为90~140 ℃，且随着白云石晶粒变粗（自形程度变差），均一温度呈升高的趋势，与氧同位素计算温度变化趋势一致，表明白云石化作用过程是在封闭的条件下进行，白云石随地热增温而生长，并非受外来流体的影响。开放系统中的白云石化作用对油气储集空间的形成没有实际意义，而埋藏成岩过程中封闭系统的白云石化是形成南羌塘拗陷优质储层最为重要的成岩机制。  相似文献   

宁夏灵武幅、磁窑堡幅综合地质调查LS01孔冲洗液护壁技术          下载免费PDF全文

何玉云  王发民 《探矿工程》2020,47(1):31-35

宁夏灵武幅、磁窑堡幅综合地质调查LS01孔设计深度800 m，钻探过程中钻遇200余米第四系未胶结松散地层，主要有砾石（漂砾）—粗砂—中砂—细砂互层，钻孔护壁难度大，容易发生掉块、塌孔事故，取心困难；进入第三系钻遇清水营组紫红色泥岩，地层造浆且易打滑；进入白垩系宜君组，钻遇365.91 m的破碎砾岩，地层松散破碎，钻进过程易卡钻，回转阻力大，回次进尺少，进尺慢。根据类似钻孔施工资料及地层情况最终采用成膜护壁冲洗液，钻进过程中穿过多层复杂地层，成膜护壁冲洗液在破碎砾岩孔段起到了很好的护壁效果，没有出现掉块、塌孔事故；岩心采取率满足地质设计要求，全孔平均采取率达到95.89%；节约了套管下入深度，终孔深度800 m，终孔口径124.00 mm。  相似文献   

中国还原性斑岩矿床研究进展及判别标志   总被引：1，自引：1，他引：0  

申萍  潘鸿迪 《岩石学报》2020,36(4):967-994

世界上大多数斑岩矿床的成矿流体为氧化流体(CO_2 CH_4)。然而,Rowins(2000)提出一些斑岩Cu-Au矿床的成矿流体为富含CH_4的还原流体,矿床缺乏磁铁矿、赤铁矿和硬石膏等表征高氧逸度的矿物,而发育大量的磁黄铁矿,矿床规模小,矿床形成与含钛铁矿的还原性的Ⅰ型花岗岩类有关,并将其称之为还原性斑岩Cu-Au矿床。我国学者研究发现,中国不但发育还原性斑岩铜矿床,还发育还原性斑岩-矽卡岩铜矿床和还原性斑岩钼矿床,我们建议将这三种矿床统称为还原性斑岩矿床。本文基于课题组近十年来的研究工作,并结合前人的研究成果,综合分析了中国发育的大中型还原性斑岩矿床的典型实例,在此基础上,重点阐明中国大型还原性斑岩矿床的特点、流体中CH_4来源及其有关的成矿作用、容矿围岩特点、成矿岩浆氧化还原状态及其成因、矿床形成的构造背景等。与Rowins(2000)提出的还原性斑岩铜矿床规模小的特点不同,中国发育的一些还原性斑岩矿床规模大;我们研究还识别出该类矿床发育独特的热液矿物和矿石矿物,比如,还原性斑岩铜矿发育热液钛铁矿,矿石矿物以黄铜矿为主,罕见斑铜矿、辉铜矿等矿物;还原性斑岩钼矿床出现热液钛铁矿,矿石矿物以辉钼矿为主,罕见黑钨矿和锡石等矿物;还原性斑岩-矽卡岩铜矿床的矽卡岩期发育钙铝榴石、钙铁辉石等还原性矽卡岩矿物和大量的磁黄铁矿,热液期以发育黄铜矿而非斑铜矿和辉铜矿等矿石矿物为特征。因此,还原性斑岩矿床除了Rowins(2000)提出的发育富CH_4还原流体和磁黄铁矿等识别标志之外,还可辅以独特的脉石矿物(如钛铁矿、钙铝榴石、钙铁辉石等)和简单的矿石矿物(如黄铜矿、辉钼矿等)这两个标志进行识别。中国还原性斑岩矿床含矿岩体的围岩中普遍发育还原性岩石(如含碳质沉积岩或火山沉积岩、含亚铁的火山岩或火山沉积岩等);对于成矿流体中CH_4、C_2H_6等还原性气体的来源,多数学者认为CH_4、C_2H_6等还原性气体主要源于还原性围岩,部分源于岩浆。关于还原性斑岩矿床的成矿岩体是否为含钛铁矿的、还原性的花岗岩类,目前研究较少且存在争议,多数学者认为成矿原始岩浆为氧化性岩浆,但其氧逸度偏低,少数学者认为成矿岩浆始终为还原岩浆。还原性斑岩矿床与经典的斑岩矿床的成矿构造背景类似,二者没有明显区别。还原性斑岩矿床显示的还原性热液蚀变和成矿特点均与成矿流体富含CH_4还原气体密切相关,因此,富含CH_4还原流体是还原性斑岩矿床形成的关键。  相似文献   

滇东南南秧田钨矿床白钨矿原位Sr同位素对成矿的指示     

王忠强  李超  张定才  江小均  周利敏  严清高 《岩矿测试》2020,39(2):285-299

南秧田钨矿床位于滇东南老君山W-Sn矿集区,地处扬子地块和印支地块的结合部位,地质背景复杂并遭受了多期岩浆活动和区域变质事件,其成矿时代和成因一直存在争议。本文对矽卡岩型和长石-石英脉型白钨矿开展了年代学、原位微量元素、Sr同位素研究,分析了两类白钨矿年龄、成因以及物质来源的差异。结果表明,长石-石英脉内与白钨矿共生辉钼矿的Re-Os同位素等时线年龄为151.0±1.3Ma,明显晚于矽卡岩矿体年龄,属于后期成矿事件。矽卡岩型白钨矿的轻稀土富集、重稀土强烈亏损,Eu呈明显负异常(δEu=0.46),∑REE平均含量为65.60μg/g,Mo平均含量为240.16μg/g,Sr平均含量为883.43μg/g;长石-石英脉型白钨矿稀土呈Eu正异常(δEu=2.8)的平坦型,∑REE平均含量为194.40μg/g,Mo平均含量为16.01μg/g,Sr平均含量为129.26μg/g。以上两者微量、稀土元素含量的差别显示它们具有性质明显不同的流体来源,Eu异常指示矽卡岩型白钨矿形成于氧逸度较高的环境,长石-石英脉型白钨矿形成于还原性环境。矽卡岩白钨矿~(87)Sr/~(86)Sr值相对较低,并且比较均一,介于0.71319～0.71491之间,表明成矿流体主要来自岩浆热液;长石-石英脉型白钨矿~(87)Sr/~(86)Sr值较高且变化范围大,介于0.71537～0.72803之间,平均0.72079,呈现出变质流体特征。两种不同类型白钨矿Sr同位素都具有二元混合的特征,显示长石-石英脉型白钨矿对矽卡岩型白钨矿有叠加改造作用,成矿流体与围岩的强烈交代作用是白钨矿形成的关键。  相似文献   

An Eocene/Oligocene blueschist‐/greenschist facies P–T loop from the Cycladic Blueschist Unit on Naxos Island,Greece: Deformation‐related re‐equilibration vs. thermal relaxation          下载免费PDF全文

Alexandre Peillod  Uwe Ring  Johannes Glodny  Alasdair Skelton 《Journal of Metamorphic Geology》2017,35(7):805-830

Geothermobarometric and geochronological work indicates a complete Eocene/early Oligocene blueschist/greenschist facies metamorphic cycle of the Cycladic Blueschist Unit on Naxos Island in the Aegean Sea region. Using the average pressure–temperature (P–T) method of thermocalc coupled with detailed textural work, we separate an early blueschist facies event at 576 ± 16 to 619 ± 32°C and 15.5 ± 0.5 to 16.3 ± 0.9 kbar from a subsequent greenschist facies overprint at 384 ± 30°C and 3.8 ± 1.1 kbar. Multi‐mineral Rb–Sr isochron dating yields crystallization ages for near peak‐pressure blueschist facies assemblages between 40.5 ± 1.0 and 38.3 ± 0.5 Ma. The greenschist facies overprint commonly did not result in complete resetting of age signatures. Maximum ages for the end of greenschist facies reworking, obtained from disequilibrium patterns, cluster near c. 32 Ma, with one sample showing rejuvenation at c. 27 Ma. We conclude that the high‐P rocks from south Naxos were exhumed to upper mid‐crustal levels in the late Eocene and early Oligocene at rates of 7.4 ± 4.6 km/Ma, completing a full blueschist‐/greenschist facies metamorphic cycle soon after subduction within c. 8 Ma. The greenschist facies overprint of the blueschist facies rocks from south Naxos resulted from rapid exhumation and associated deformation/fluid‐controlled metamorphic re‐equilibration, and is unrelated to the strong high‐T metamorphism associated with the Miocene formation of the Naxos migmatite dome. It follows that the Miocene thermal overprint had no impact on rock textures or Sr isotopic signatures, and that the rocks of south Naxos underwent three metamorphic events, one more than hitherto envisaged.  相似文献   

A coupled discrete element model for the simulation of soil and water flow through an orifice          下载免费PDF全文

Yao Tang  Dave H. Chan  David Z. Zhu 《国际地质力学数值与分析法杂志》2017,41(14):1477-1493

Soil erosion around defective underground pipes can cause ground collapses and sinkholes in urban areas. Most of these soil erosion events are caused by fluidization of the surrounding soil with subsequent washing into defective sewer pipes. In this study, this soil erosion process is simplified as the gradual washout of sand particles mixed with water through an orifice. The discrete element method is used to simulate the large deformation behavior of the sand particles, and the Darcy fluid model is coupled with this approach to simulate fluid flow through porous sand media. A coupled 3D discrete element model is developed and implemented based on this scheme. To simulate previous experiments using this coupled model considering the current computing capacity, we incorporated a ‘supply layer’ to study the continuous erosion process. The coupled model can predict the erosion flow rates of sand and water and the shape of erosion void. Thus, the model can be used as an effective and efficient tool to investigate the soil erosion process around defective pipes. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献