含煤地层中石英组构的成因与意义

根据我国东部煤田一些实例和高温高压变形实验模拟结果表明,含煤地层中石英C-轴组构普遍具有稀疏小圆环带型式,其环带轴具有显著的应力指向意义。稀疏小圆环带型式组构的形成与石英底面滑移系的运动有关,是点极密型式的过渡状态,与石英颗粒的塑性应变量较小有关。造成含煤地层中石英颗粒塑性应变量较小的原因,除构造变形强度较小外,还与岩石中普遍存在软弱矿物有关。软弱矿物的存在吸收了大部分塑性应变。     

新疆哈密黄山韧性挤压带超塑性拉伸砾石的特征及形成机制

新疆哈密黄山韧性挤压带变形砾石具超塑性拉伸的特征，变形砾石平均棉球体长短轴比（Ｘ／Ｚ）大于１０．变形砾石的微观构造、超微观构造、石英组构、及变形砾石拉伸量与砾内石英颗粒轴比（Ｘ／Ｚ）和砾内面理间隔（Ｄ）关系等的综合研究表明，挤压及其所导致的砾内矿物的细粒化和拉伸及砾内面理间隔的减小是砾石超塑性拉伸的重要变形机制。变形砾石粒度大小和岩性对砾石拉伸变形具一定的敏感性。另外，随着拉伸应变量的增大，硅质岩砾石石英组构有从Ｖ型极密、小圆环带、交叉环带向Ⅷ型极富和Ⅰ型极密演化的特征。     

煤田构造中石英C轴组构的成因和意义研究

煤田构造研究中石英组构分析逐渐受到重视,但其成因和意义问题却远未能得以解决。笔者根据赣中武功山两侧煤田滑脱构造的石英C轴组构分析结果,提出石英C轴“似不完整小圆环带”型式的组构主要是在岩层早期总体压缩及稍后的褶皱时的压缩变形过程中形成,是由低压缩应变量条件下晶格的底面滑移所致,环带中心的方位指示构造主压应力方向。此外还根据石英组构进行了运动学分析的初步尝试。     

大别造山带现今构造格局的形成——来自石英C轴组构的证据

石英C轴组构常常记录递进变形过程中晚期增量变形的构造特征,因而可以通过对大别造山带内岩石中石英C轴组构的分析来确定造山带构造变形历史中的晚期变形事件的运动学特征。本次工作在大别造山带各单元中采集了一系列样品,对其进行石英C轴组构分析。石英C轴组构结果表明,北淮阳带就位于同造山折返第一阶段,其运动型式为上盘向NW的剪切变形;南大别高压—超高压榴辉岩带与宿松杂岩带就位于同造山折返第二阶段,运动型式表现为上盘向SE的剪切变形;北大别带就位于早白垩世穹状隆升过程中。北大别带在穹状隆升过程中表现为上盘向NW的运动型式,在深部可能存在向NW方向的下地壳物质的塑性流动。     

电子背散射衍射技术(EBSD)在组构分析中的应用和相关问题

在过去的二十年里,EBSD (Electron Backscattered Diffraction),即电子背散射衍射测试技术,已广泛应用于韧性组构分析,成为变形运动学、流变学分析的常规手段。该方法主要应用于流变条件下矿物晶轴组构定向性分析,以判定流变剪切指向、对比应变强度、估算变形温度。理论上讲,EBSD法适用于所有矿物的全部晶轴定向的分析测试。然而鉴于天然变形的复杂性,笔者建议EBSD分析应以石英,特别是经历了动态重结晶的石英条带为组构分析的主要对象。长期以来,石英晶轴组构的不对称性被视作独立的剪切指向标志。然而,近年来基于天然变形和一般剪切实验的研究结果表明,塑性流变的剪切指向含义应为多重流变剪切指向标志综合判别比对的结果。尽管在提出之初,石英的轴组构开角被视作独立可靠的变形温度计(Kruhl,1998)。然而限于天然变形的复杂性,特别是对变质与变形阶段的对应、耦合的认识;尽管石英变形滑移系及石英晶轴组构开角可为动力变质温度提供重要的参考,但是石英晶轴组构开角并非独立的变形温度计。     

石英c轴组构影响因素探讨:以郯庐断裂带糜棱岩为例

石英是自然界中最主要的造岩矿物之一,也是地壳流变过程的主要变形矿物,其c轴组构特征与变形温度、剪切指向具有密切的关系,因而常被用来获取剪切指向、估计变形温度、计算运动学涡度等。但由于受到变形分解、先存构造、流体等因素的影响,同一岩石中常会得到多个不同的石英c轴组构结果。如果天然变形岩石同时受到多种因素的影响,其石英c轴组构会表现为何种特征?与岩石变形温度、剪切旋向是否仍具有很好的对应性?基于以上问题,本次工作以大别山东缘郯庐断裂带内经历了多期变形、富含流体活动的超糜棱岩为研究对象,在同一岩石薄片中选择不同区域,利用EBSD开展石英c轴组构分析。分析结果表明,选择的超糜棱岩的石英c轴组构点极密分布形态指示岩石变形发生于非共轴变形条件下;剪切指向方面,6个分析区域中区域1表现为左旋剪切指向特征,与薄片中优势剪切指向一致,而除区域4外的其他4个区域显示出与优势剪切指向相反的右旋剪切指向特征;变形温度方面,区域4以柱面滑移为主,显示了高温变形特征,而其余5个区域均以底面滑移为主,指示了低温变形环境。根据本次石英c轴组构特征分析结果,可以得出一些认识:岩石中石英表现为完全的GBM动态重结晶,所指示的温度明显高于大量沿糜棱面理分布的绿泥石所指示的绿片岩相环境,显示流体活动促进了岩石变形;而石英c轴组构指示的变形温度为绿片岩相环境,与绿泥石存在的现象一致,表明糜棱岩化过程中流体活动对石英c轴组构的影响并不明显。在发生过多期变形事件的岩石中,岩石中早期高温变形信息有可能保留下来并记录在石英c轴组构特征中,因而通过石英c轴组构分析有可能获得早期事件的信息;虽然石英c轴组构影响因素众多,但首先开展详细的显微镜下观察,然后有选择地对剪切指向清晰区域开展石英c轴组构分析,仍然能够得到与岩石中优势剪切指向一致的石英c轴组构结果。     

花岗质超糜棱岩的微观构造与变形机制

花岗质岩石的变形方式和过程决定大陆地壳的流变学特性。本文聚焦藏南拆离系超糜棱岩化的花岗质岩石，借助传统显微构造分析方法和扫描电镜、阴极发光、矿相自动分析系统和电子背散射衍射等新技术手段，开展微观组分、结构、组构定量化观测和分析。超糜棱岩主要造岩矿物为钾长石、斜长石、石英、黑云母等，显微构造呈现为单矿物相域与多相矿物混合域交织结构。相平衡模拟与斜长石钙含量等值线变形温度估算结果为390～410℃。单相域的矿物集合体条带主要分为钾长石条带与石英条带，其中钾长石条带内变形颗粒呈现典型的核 幔构造。组构分析表明钾长石颗粒具有强烈的晶格优选定向，残斑与动态重结晶的钾长石颗粒具有相似的晶格优选方位(CPOs)特征。施密特因子法分析揭示钾长石残斑变形过程中主要活动的滑移系为(100)\[010\]、(010)\[001\]和(001)\[100\]，基质钾长石颗粒形成机制主要为位错蠕变驱动的亚颗粒旋转重结晶。在混合相域，矿物颗粒发生强烈细粒化而只含有少量残斑，基质颗粒主要为斜长石，斜长石颗粒间广泛分布微米级黑云母颗粒。斜长石无组构或弱组构，主导变形机制为颗粒边界滑动。在单相域条带与混合相域基质内，石英颗粒均发生强烈细粒化，颗粒表面发育溶蚀结构以及细小的新晶晶核，石英＜c＞轴晶格优选定向及形态学长轴优选定向皆平行于线理X方向，变形机制为溶解 沉淀蠕变。这显示在由单相域向混合相域的演化过程中，流体作用至关重要，流体与单相域钾长石进行交代使其分解为细粒的斜长石与石英，并导致花岗质岩石变形机制由位错蠕变向非位错蠕变转换，并诱发岩石的流变弱化。     

舒兰韧性剪切带应变分析及石英动态重结晶颗粒分形特征与流变参数估算

舒兰北东向韧性剪切带位于佳木斯-伊通断裂带(佳-伊断裂带)中南段, 剪切带内糜棱岩具有明显左行走滑特征, 片麻理产状近NNE向.糜棱岩中长石有限应变Flinn图解判别岩石类型为L-S型构造岩, 属拉长型应变.石英C轴EBSD组构分析表明, 石英组构以中低温菱面为主, 滑移系为{0001} < 110>.剪切带内糜棱岩的剪应变为0.44, 不同方法计算所得运动学涡度值均大于0.95, 指示剪切变形以简单剪切为主.综合矿物变形温度计、石英C轴EBSD组构、石英的粒度-频数图及Kruhl温度计综合估计该韧性剪切带变形机制以位错蠕变机制为主, 变质相为低绿片岩相, 发生韧性变形和糜棱岩化温度范围在400~500 ℃之间.糜棱岩内石英动态重结晶新晶粒边界普遍具有锯齿状或港湾状结构, 利用分形方法对其重结晶新晶边界研究表明, 这些晶粒边界具有自相似性, 表现出分形特征, 分形维数值为1.195~1.220.根据石英重结晶粒径估算差应力值为24.35~27.59 MPa, 代表了舒兰韧性剪切带糜棱岩化作用过程的差异应力下限.使用不同实验方法估算、比较和分析了该剪切带古应变速率, 认为该速率应为10-12.00~10-13.18 s-1, 与区域性应变速率10-13.00~10-15.00 s-1对比, 说明舒兰韧性剪切带的应变速率与世界上大多数韧性剪切带中的糜棱岩应变速率一致, 是缓慢变形的结果, 其形成可能与早白垩世伊泽纳崎板块向欧亚大陆俯冲发生转向有关.      

大别山晓天—磨子潭韧性剪切带主要造岩矿物的变形与应变分析

大别山北缘的晓天—磨子潭韧性剪切带主体发育在北大别片麻岩之上,具有近水平左行剪切的运动学特征;剪切带自中心向外围依次发育超糜棱岩、糜棱岩、初糜棱岩、变形片麻岩(片岩)、围岩,发生变形的主要造岩矿物包括石英、长石、角闪石、云母等。岩石有限应变测量和矿物颗粒形态学优选方位统计显示,随着糜棱岩化程度的加强,主要造岩矿物平均粒径均呈递减变化;矿物长短轴所反映的应变均呈加强的趋势,矿物长轴与X的锐夹角皆逐渐变小;以90°为一个区间统计的矿物长轴定向显示,变形矿物的长轴在钝角区间(顺剪切方向)有优选,以15°为一个区间统计的矿物长轴定向显示,矿物定向存在一定对称性,即在锐夹角区的优选区间和钝夹角区的优选区间互为补角区间。此外,云母矿物的应变在不同样品中均显示最大,其次为石英、角闪石、长石;随着构造岩类型的不同,应变的变化趋势最明显的也是云母,其次为石英,角闪石和长石变化不明显;矿物长轴与X轴夹角的统计表明,云母、角闪石长轴与X轴锐夹角比石英、长石均偏小。矿物的变形还表明,指示剪切带剪切方式最明显的是云母类矿物,尤其是云母鱼构造,是判定运动方向的可靠标志,其次是角闪石,较之斜长石更易形成不对称残斑构造;综合矿物在剪切带中的含量和分布,结构特点,以及对剪切带应变反映的"灵敏性"等方面的因素,石英矿物最能表现剪切带的整体应变状态,是较为理想的应变标志矿物。上述结果表明不同矿物随变形环境的渐变,在粒径、应变、形态学优选等方面具有较统一的变化,即不同变形矿物在反映剪切带的剪切作用方式、应力—应变等特征时是较为一致的;同时不同矿物在上述变化中又表现出区别于其他矿物的各自特点,这反映了矿物自身的晶体结构、结晶形态、力学性质、变形习性等特性。所以,对于研究韧性剪切带而言,针对不同研究内容,要综合不同矿物的变形情况来选取合适的变形矿物及其变形组构来研究,才能得到更准确的结果和更合理的解释。     

辽西兴城—台里韧性剪切带北段变形特征

辽西兴城—台里地区发育系列花岗质岩石,强烈构造变形特征均显示其具有韧性剪切带的特点。对剪切带北段进行详细宏微观构造解析,结合岩石变形强度差异性分析、有限应变测量、石英C轴EBSD测试以及古差异应力值估算等研究,结果表明剪切带内花岗质片麻岩和眼球状花岗质片麻岩具有NEE向左行剪切变形特征,变形岩石为S-L构造岩,应变类型属于平面应变,古差异应力值介于30~40 MPa之间。长石-石英矿物温度计以及石英C轴EBSD组构指示剪切带以中低温变形为主,温度在400℃~500℃,属绿片岩相变质,具中-低温韧性剪切带特征。韧性剪切带内普遍存在变形分解现象,弱变形带内岩石残斑含量较高,眼球状构造和S-C组构较为发育;强变形带岩石残斑含量较低,剪切面理较为发育,糜棱面理发育较弱或者不发育。     

High Temperature Mylonitization of Quartzofeldspathic Gneisses: Example from the Schirmacher Hills, East Antarctica

In the Schirmacher Hills, most of the ductile shearing took place under high to medium grade amphibolite facies metamorphism. The microstructure of the mylonites shows characteristic features of high temperature deformation and thus gives us an idea of deformation mechanisms of the constituent minerals at great crustal depth. The variation in microstructure of the sheared rock is partly due to heterogeneity of the intensity of strain from domain to domain, producing protomylonites, orthomylonites and ultramylonites. However, a large part of the microstructural variation has resulted from syn- to post-tectonic recrystallization and grain growth of constituent minerals. Both quartz and feldspar have deformed by crystal plastic processes with dominant grain boundary migration. The present aspect ratio of the feldspar grains is a result of various degrees of dynamic recrystallization along the grain boundary. The ratio varies between 1.5 and 2. Presence of exsolution lamellae in perthites and formation of myrmekite at the strained grains of K-feldspar suggest diffusion assisted dislocation creep. These mylonites are characterized by the presence of weakly strained or unstrained long quartz ribbons. The development of quartz ribbons with the absence of significant strain suggests grain recovery and grain growth during high temperature mylonitization. The growth of quartz ribbons took place by coalescing neighbouring grains both along and across the ribbon length. At the ultramylonite stage the fine-grained matrix of quartz and feldspar mostly accommodates the bulk strain.     

Review of Microstructural Evidence of Magmatic and Solid-State Flow

Evidence of magmatic flow includes: (a) parallel to sub-parallel alignment of elongate euhedral crystals (e.g., of feldspar or hornblende) that are not internally deformed, (b) imbrication (‘tiling’) of elongate euhedral crystals that are not internally deformed, (c) insufficient solid-state strain in regions between aligned or imbricated crystals to accommodate phenocryst rotation, (d) elongation of microgranitoid enclaves without plastic deformation of the minerals, (e) magmatic flow foliations and elongate microgranitoid enclaves deflected around xenoliths, and (f) schlieren layering (if due to flow sorting) in the absence of plastic deformation of the minerals involved. These features are consistent with rotation of crystals in a much weaker medium, namely a melt phase, at a stage when the magma has become viscous enough to preserve the alignment.Evidence of solid-state flow includes: (a) internal deformation and recrystallization of grains, (b) recrystallized “tails,” (c) elongation of recrystallized aggregates (e.g. of quartz and mica), (d) grainsize reduction, (e) fine-grained folia anastomosing around less deformed relics, (f) microcline twinning, (g) myrmekite, (h) flame perthite, (i) boudinage of strong minerals, typically with recrystallized aggregates of weaker minerals (e.g. quartz and mica) between the boudins, (j) foliation passing through, rather than around enclaves, and (k) heterogeneous strain with local mylonitic zones.Several criteria suggest “submagmatic flow,” including recrystallized feldspar, inferred transitions from magmatic imbrication to solid-state S/C arrangements, evidence of c-slip in quartz, and especially evidence of migration of residual melt into lower-pressure sites.Recent experimental studies indicate that a change from grain-supported flow to suspension flow typically occurs in deforming magmas at melt contents of between 20% to 40%, and that large amounts of strain may accumulate in magmas without being recorded by the final fabric. At lower melt percentages, perhaps as low as a few percent, depending on the minerals and their shapes, strain may be accommodated by: (a) melt-assisted grain-boundary sliding, (b) contact-melting assisted grain-boundary migration, (c) strain partitioning into melt-rich zones, (d) intracrystalline plastic deformation (c-slip in quartz indicating plastic deformation at temperatures near the granite solidus), and (f) transfer of melt to sites of low mean stress. The only indication of strain in the absence of crystal plasticity may be an alignment of crystals. Moreover, magmatic flow microstructures may be destroyed by fracturing, crystal plasticity and recrystallization before the magma reaches its solidus.Many rocks show evidence of solid-state flow superimposed on magmatic flow. Evidence of magmatic flow is commonly preserved in deformed felsic metamorphic rocks: for example the alignment of rectangular K-feldspar megacrysts and of microgranitoid enclaves. However, absence of alignment does not preclude a magmatic origin for K-feldspar megacrysts in felsic gneisses, as magmatic flow may cease before the magma becomes viscous enough to preserve an alignment.     

米仓山构造带的应变与涡度分析

米仓山构造带东西向的断裂逆冲兼左旋走滑,西段的韧性变形较强,东段脆性为主。北东向三个主断裂带由北而南逆冲兼左行剪切,早期可能发生脆韧性变形,后期叠加了脆性变形。前震旦系基底岩系变形特征主要表现为透入性流变,碎斑结构和糜棱结构发育,镶嵌构造、S-C组构、带状构造、眼球构造为主,局部偶见"δ"和"σ"旋转碎斑以及矿物鱼。石英颗粒以亚颗粒旋转动态重结晶为主。显微特征反映岩石变形温度相当于绿片岩相。利用Fry法测定石英颗粒三维应变应变强度集中在1.35～1.60之间,显示出从北到南逐渐增强的趋势。Flinn指数K和Nadei-Hossack图解均表明应变类型为近似平面应变的拉长型。运动学涡度分析表明米仓山应变以简单剪切变形作用为主,具有由南向北递增趋势。     

Volume strain, strain type and flow path in a narrow shear zone

This study explores the state of finite strain and changes in the mean kinematic vorticity number, grain size, whole-rock chemistry and mineralogy across an upper amphibolite-facies shear zone in a metadiorite, northern Malawi, east-central Africa. P–T conditions during shear-zone formation and deformation were approximately 700–750^?°C and 5–7?kbar and are slightly less than P–T conditions for the regional peak of metamorphism. The major rock-forming minerals, plagioclase, hornblende, biotite, and quartz, were deformed by crystal-plastic processes accompanied by, except for hornblende, dynamic recrystallization. The modal abundance of all four major rock-forming minerals shows no systematic change from the country rock into and across the shear zone, indicating that shear-zone development was not associated with retrograde mineral reactions. The grain size of the major rock-forming minerals decreases within the shear zone. Plagioclase and hornblende, which occur as porphyroblasts outside the shear zone, exhibit a bimodal grain-size distribution within the shear zone. Quartz has a unimodal grain-size distribution in the shear zone. Major and trace element chemistry does not change systematically across the shear zone, implying no volume change in the mylonite. Matrix strain data for plagioclase and hornblende by the Fry method and fabric strain as deduced from R_f/φ analysis of plagioclase and quartz grains demonstrate a slightly constrictional strain type (K≈1.5) across the shear zone. The quantitative finite-strain data for the different residual minerals as obtained by unlike methods show no systematic variation, but recrystallized plagioclase grains record higher strain than the residual grains. The mean kinematic vorticity number changes from approximately 0.3 outside to approximately 0.8 within the shear zone, indicating that the bulk deformation path deviated from progressive simple shear. The estimates for finite strain and the degree of noncoaxiality account for approximately 50% of thinning normal to the shear zone.     

软硬相间岩层底板变形研究

引入损伤变量ω理论,分析水平状软硬相间岩层在竖向应力下的应力-应变关系：再引用弹性模量E和岩层厚度L两个变形参数建立软硬相间岩层底板变形参数方程,得出竖向应力随着底板深度的增加而减小的规律：运用数值模拟软件,建立煤层开采模型,模拟软硬相间岩层底板在采动作用下的变形过程。通过数值分析底板在采动作用下的应力-应变关系和位移特征,发现竖向应力作用下软岩受到的水平应力比硬岩大,竖向应变也比硬岩大,而竖向应力和水平应变变化不大,认为在采动影响下软硬相间岩层底板中的软岩具有吸收更多的应变能来保护软岩下硬岩的变形特点。     

阿尔泰造山带内韧性剪切带的显微、超显微构造和变形机制

阿尔泰造山带的剪切带中发育大量S-C糜棱岩,其内云母产生云母鱼和扭折构造并发生边界重结晶。长石发生不同性质的系列变形,并以出熔成核为主的动态重结晶为主要变形机制,同时伴有强烈的扩散作用,属Naborrow-Herring蠕变。石英的变形呈条带状并发生完全的旋转和边界迁移动态重结晶。石英晶内变形以位错运动和动态恢复为主,形成亚颗粒构造及动态重结晶,以致产生应变弱化和超塑性变形,定量分析确定的石英变形机制主要为低温幂指数蠕变。     

Microfabric analyses applied to the Witwatersrand gold- and uranium-bearing conglomerates: constraints on the provenance and post-depositional modification of rock and ore components

Microfabrics of detrital quartz grains and quartz cement of four gold- and uranium-bearing conglomerates of various goldfields of the Witwatersrand Basin, South Africa, were investigated by optical and cathodoluminescence microscopy. The study revealed that the vast majority of quartz grains (<5 mm) originate from felsic magmatic source rocks. Cherts and polymineralic mineral grains, pointing to greenschist to amphibolite facies metasedimentary rocks, follow in abundance, whereas diagenetic to weakly metamorphosed quartzites are subordinate. Material from hydrothermal vein quartz is almost completely lacking, both in the sand and in the pebble fraction. No obvious relationships are discernible between the varying proportions of detrital siliciclastic components of the different reefs and their ore grades. Assuming a sedimentological control of gold distribution, this finding supports multiple sources for the detrital components, which were thoroughly mixed during transport. The post-depositional history of the sediments is characterized by a complex polyphase succession of deformation, cementation and hydrothermal alteration events. Both fragmentation and pressure solution features within detrital quartz, quartz cement and round grains of pyrite, zircon, chromite and uraninite demonstrate that these materials were present in the conglomerates during diagenesis, and, thus, are true detrital grains with abraded, rounded grain morphologies. By analogy, it is assumed that gold is also a detrital component, although most of the gold grains display characteristics of hydrothermal overprinting. During subsequent metamorphism, micro-shear zones are developed, and brittle-ductile crystal-plastic deformation and limited quartz recrystallization occur. Maximum temperatures of about 350 °C were reached on the prograde metamorphic path. Recrystallization and redistribution of detrital siliciclastic and ore minerals took place, and various hydrothermal/metamorphic minerals including chlorite, sericite, pyrophyllite and chloritoid were formed. These redistribution processes involved existing detrital minerals only and were generally isochemical because little evidence exists for the development of a secondary porosity and permeability that would allow major external inputs into the Witwatersrand conglomerates. Most of the gold grains have hydrothermal characteristics, as evidenced by their authigenic, crystalline shapes and their chemical compositions. However, these features are regarded to result from overprinting. Most likely, the gold grains experienced more drastic modifications relative to other ore components because of the ductile and mobile nature of gold. The retrograde metamorphic path is characterized by percolating radioactive fluids at T<300 °C, recorded by radiation damage indicated by cathodoluminescence alteration rims along quartz grain boundaries and microcracks. The degrees of radiation damage observed are proportional to the uranium contents of the conglomerate ores. The collective evidence of our study supports the modified placer model for the genesis of the Witwatersrand ores. This model explains most of the observations on the detrital mineral assemblage and its post-depositional modification elegantly and in a satisfactory manner.     

北喜马拉雅穹隆带然巴韧性剪切带石英动态重结晶颗粒的分维几何分析与主要流变参数的估算

位于北喜马拉雅穹隆带东段的然巴构造穹隆外围发育环形韧性剪切带,带内岩石经韧性剪切形成各类糜棱状岩石。石英为带内变形岩中最为常见的造岩矿物,在不同的温度、应变速率下产生不同的显微构造,其中动态重结晶最为常见。重结晶新晶颗粒边界普遍具有锯齿状或港湾状结构,是应变和变形环境的天然记录。新晶粒分维几何统计分析表明:带内动态重结晶石英颗粒边界形态具有自相似性(1≤D≤2),表现出分形特征,分维数值为1.14～1.19,变形温度大约500℃。同构造变质环境属中——高绿片岩相;初步估算古应变速率可能低于10^-9.5S^-1;根据重结晶粒径估算变形古应力6.2～58.8MPa。     

山东省牛庄洼陷古近系沙河街组沙三中亚段储集层成岩作用研究

山东省牛庄洼陷古近系沙河街组沙三中亚段储集层岩石类型以长石岩屑砂岩和岩屑长石砂岩为主,岩石结构成熟度和成分成熟度均较低。砂岩成岩作用包括压实作用、胶结作用、交代作用、溶解作用等。压实作用主要有刚性颗粒发生脆性破裂、颗粒之间呈线接触和凹凸接触、岩石碎屑颗粒呈明显的定向排列、塑性颗粒挤压变形或刚性颗粒嵌入变形颗粒中、粘土质碎屑被挤压变形发生假杂基化等五种表现形式。胶结物主要有泥质胶结物、碳酸盐胶结物、自生粘土矿物和自生石英、长石。交代作用主要有石英交代长石颗粒、碳酸盐胶结物交代石英、长石及岩屑颗粒、碳酸盐胶结物之间的相互交代。发生溶解作用的主要是石英、长石和岩屑颗粒,胶结物中主要是碳酸盐矿物。目前研究区沙三中亚段储集层成岩演化处于晚成岩A期。影响成岩作用的主要因素为岩石成分、沉积环境、孔隙流体性质等。成岩作用对储集物性的影响主要表现在孔隙度和渗透率的变化,其中压实作用和胶结作用使储层原生孔隙迅速减少、渗透率降低,使得储集物性变差;而溶解作用是次生孔隙发育的主要因素,从而改善砂岩的储集性能。     

华北克拉通基底花岗质片麻岩变形和流变学研究——以辽西寺儿堡地区为例

辽西寺儿堡镇新太古代花岗质片麻岩内发育的宏观、微观构造变形特征表明该地区曾遭受了强烈的韧性变形改造。花岗质岩石变形程度在初糜棱岩–糜棱岩之间,岩石经历了SWW向左行剪切作用改造。岩石中石英有限应变测量判别结果表明,构造岩类型为L-S型,为平面应变。岩石的剪应变平均值为1.43,运动学涡度值为0.788~0.829,指示岩石形成于以简单剪切为主的一般剪切变形中。此外,石英颗粒以亚颗粒旋转重结晶和颗粒边界迁移重结晶作用为主,长石颗粒塑性拉长,部分发生膨凸式重结晶作用;石英组构特征(EBSD)揭示石英以中–高温柱面滑移为主;石英颗粒边界具有明显的分形特征,分形维数值为1.151~1.201,指示了中高温变形条件。综合石英、长石的变形行为、石英组构特征以及分形法Kruhl温度计的判别结果,推断辽西寺儿堡镇新太古代花岗质片麻岩经历过480~600℃的中高温变形,其同构造变质相为高绿片岩相-低角闪岩相。花岗质岩石的古差异应力为10.62~12.21 MPa,估算的应变速率为10~(–11.67)~10~(–13.34) s~(–1),即缓慢的变形,可能记录早期中高温、低应变速率的韧性变形过程,反映华北克拉通基底中下部地壳变形特征。