月球同位素地质年代学与月球演化

同位素地质年代学是月球形成与演化研究的重要工具。目前对月岩和月球陨石的研究积累了大量的同位素年代学资料,其测试的主要方法包括K—Ar、Ar_Ar、Rh-sr、Sm—Nd、Lu—Hf、Re-0s、Pb—Pb和U—Pb等。根据目前获得的资料,本文对月球上不同类型岩石的形成年龄进行了总结,发现月球高地岩石主要形成于45～38亿年,而月海玄武岩相对年轻,大致形成于38～31亿年。根据这-年代资料,结合对月岩样品进行的短半衰期Hf-W与Sin-Nd同位素体系的研究结果,认为月球大致形成于45亿年,其后开始由岩浆海导致的内部核-幔-壳的分异,岩浆结晶的低密度斜长岩构成最初的月壳,而密度大的岩石构成月幔,而此月幔则成为后来月海玄武岩的主要岩浆源区。同时指出了当前月岩同位素地质年代学存在的问题,并根据技术进展的情况,对未来月岩同位素年代学的发展趋势作了全面的分析．     

矿山地质环境问题与治理对策研究——以云南迪庆普朗铜矿一期采选工程为例

矿产资源开发在创造大量财富的同时,也对矿区生态环境产生了严重的负面影响。本文以云南迪庆有色金属有限责任公司普朗铜矿一期采选工程为例,简要分析了临近世界自然遗产"云南三江并流保护区"的普朗铜矿存在的矿山地质环境问题及影响程度,进行了矿山地质环境影响程度分区,同时提出了相应的矿山地质环境保护与恢复治理措施。     

试论湖南省莫霍面形态及地壳厚度特征

在分析重力异常与地壳厚度存在相关性的基础上,对全省1:500000重力资料采用多种窗口求平均重力场,进行相关分析,以选定最佳窗口,再与已知地震测深资料进行回归分析,推出本省新系数公式,反演编出准确度较高的湖南省莫霍面深度图。将其形态特征概括为:“一陡,一缓,二斜、二凹、三隆起”。指出它与现代地势有镜像对应关系,并提出武陵山区地壳失衡的见解。最后,探讨了莫霍面形态与岩浆岩侵入体、矿产间的联系。     

复杂周边条件下异形基坑承压水抽水试验研究

以上海自然博物馆深大异形基坑为背景,为了保护周边环境,针对日益突出的承压水问题,降压前进行了承压水抽水试验。试验结果表明,当地下连续墙插入承压含水层的深度小于承压含水层厚度的1/3时,可以忽略地下连续墙的阻隔效果;用水头恢复比 表征抽水试验结束后的水位恢复情况,发现停抽10 min 可达到10%,水位稳定时 只能达到94.5%;单井抽水能够达到的降压效果是有限的,与降压前的承压水头埋深无关;群井的降压效果随着抽水井数量的增大而增大,但是随着承压水头埋深的加大,增加相同数量的降压井产生的效率降低。     

Microfabric of folded quartz veins in metagreywackes: dislocation creep and subgrain rotation at high stress

The microfabrics of folded quartz veins in fine‐grained high pressure–low temperature metamorphic greywackes of the Franciscan Subduction Complex at Pacheco Pass, California, were investigated by optical microscopy, scanning electron microscopy including electron backscatter diffraction, and transmission electron microscopy. The foliated host metagreywacke is deformed by dissolution–precipitation creep, as indicated by the shape preferred orientation of mica and clastic quartz without any signs of crystal‐plastic deformation. The absence of crystal‐plastic deformation of clastic quartz suggests that the flow stress in the host metagreywacke remained below a few tens of MPa at temperatures of 250–300 °C. In contrast, the microfabric of the folded quartz veins indicates deformation by dislocation creep accompanied by subgrain rotation recrystallization. For the small recrystallized grain size of ～8 ± 6 μm, paleopiezometers indicate differential stresses of a few hundred MPa. The stress concentration in the single phase quartz vein is interpreted to be due to its higher effective viscosity compared to the fine‐grained host metagreywacke deforming by dissolution–precipitation creep. The fold shape suggests a viscosity contrast of one to two orders of magnitude. Deformation by dissolution–precipitation creep is expected to be a continuous process. The same must hold for folding of the vein and deformation of the vein quartz by dislocation creep. The microfabric suggests dynamic recrystallization predominantly by subgrain rotation and only minor strain‐induced grain boundary migration, which requires low contrasts in dislocation density across high‐angle grain boundaries to be maintained during climb‐controlled creep at high differential stress. The record of quartz in these continuously deformed veins is characteristic and different from the record in metamorphic rocks exhumed in seismically active regions, where high‐stress deformation at similar temperatures is episodic and related to the seismic cycle.     

沉积盆地碎屑岩地层孔隙度演化模型分析——以鄂尔多斯盆地延长组为例

碎屑岩地层孔隙度演化特征的研究已经从定性分析向定量化方向发展,掌握了地层孔隙度在地史过程中的演化规律有助于深化油气成藏机理的认识。本文分别以鄂尔多斯盆地镇泾地区延长组8段砂岩和姬塬地区延长组7段泥岩为研究对象,以现今孔隙度特征为切入点,以地史时间为主线,分别建立了适用于砂岩孔隙度和泥岩孔隙度演化的数学模型。砂岩孔隙度演化模型是总体减孔效应和局部增孔效应数学模型的叠加,前者主要受机械压实和化学压实作用的影响,而后者以溶蚀作用为主。泥岩孔隙度是正常压实趋势下孔隙度演化模型与欠压实段孔隙度增量模型的叠加。     

金川镍矿尾矿砂中Ni和Cu赋存状态研究

金川镍矿浮选尾矿数量巨大,含有相当可观的有价金属,其中有价金属的回收受到越来越多的关注。金川老尾矿库尾矿砂中Ni和Cu赋存状态复杂,水溶性矿物态、可交换离子态、碳酸盐态、结晶度较差的Fe氧化物态、结晶度较好的Fe氧化物态、硫化物态和残渣态中都含有数量不等的有价金属Ni和Cu;尾矿砂风化作用释放的金属阳离子大多数在发生氧化的硫化物位置原位发生水解沉淀形成次生矿物,有价金属Ni和Cu在尾矿库中没有发生明显的富集。金川镍矿尾矿砂中Ni和Cu适于用化学酸溶浸出的方法进行二次回收。     

深海硬岩连续取心钻头的研制

气举反循环技术是一种可用于深井硬岩地层的高效钻进技术,不受地层裂隙、溶洞影响,排渣彻底。通过研究专用的连续取心钻头,可实现深海硬岩的连续取心作业,提高深海硬岩钻井效率及取心率,为深海钻探提供一种全新的取心方案。本文从牙掌选型、卡断器结构、岩渣及岩心通道优化设计等方面进行研究,提出了连续取心钻头的设计方案,并试制加工钻头。在地热井中进行了验证性应用,灰岩地层、砂岩地层取心率可达80%以上,高于大洋钻探统计取心率。陆地验证性应用为该技术方法在海洋取心钻探中的应用奠定了技术基础。     

利用层序地层学恢复岩溶古地貌技术--以塔河油田6区为例

塔河油田奥陶系油藏属于多期构造和岩溶作用形成缝洞型碳酸盐岩油藏，缝洞系统受控于岩溶作用，岩溶作用强烈程度明显受控于古地貌形态．本利用层序地层学理论，重点突出地层的等时格架，利用层序界面的等时性研究古地貌．以塔河油田6区为例，提出下石炭统中下部“双峰灰岩”属于海进体系域的最大海泛期沉积，是一明显且横向可对比的沉积层；同时奥陶系顶面属于风化剥蚀面，亦属于等时界面．利用两个等时界面进行岩溶古地貌恢复，划分出岩溶高低、岩溶斜坡等，进而预测次生孔隙发育区块，最终指导与岩溶有关的油气勘探和开发工作．     

Microbial deposits in the aftermath of the end‐Permian mass extinction: A diverging case from the Mineral Mountains (Utah,USA)

The Lower Triassic Mineral Mountains area (Utah, USA) preserves diversified Smithian and Spathian reefs and bioaccumulations that contain fenestral‐microbialites and various benthic and pelagic organisms. Ecological and environmental changes during the Early Triassic are commonly assumed to be associated with numerous perturbations (productivity changes, acidifica‐tion, redox changes, hypercapnia, eustatism and temperature changes) post‐dating the Permian–Triassic mass extinction. New data acquired in the Mineral Mountains sediments provide evidence to decipher the relationships between depositional environments and the growth and distribution of microbial structures. These data also help to understand better the controlling factors acting upon sedimentation and community turnovers through the Smithian–early Spathian. The studied section records a large‐scale depositional sequence during the Dienerian(?)–Spathian interval. During the transgression, depositional environments evolved from a coastal bay with continental deposits to intertidal fenestral–microbial limestones, shallow subtidal marine sponge–microbial reefs to deep subtidal mud‐dominated limestones. Storm‐induced deposits, microbialite–sponge reefs and shallow subtidal deposits indicate the regression. Three microbialite associations occur in ascending order: (i) a red beds microbialite association deposited in low‐energy hypersaline supratidal conditions where microbialites consist of microbial mats and poorly preserved microbially induced sedimentary structure; (ii) a Smithian microbialite association formed in moderate to high‐energy, tidal conditions where microbialites include stromatolites and associated carbonate grains (oncoids, ooids and peloids); and (iii) a Spathian microbialite association developed in low‐energy offshore conditions that is preserved as multiple decimetre thick isolated domes and coalescent domes. Data indicate that the morphologies of the three microbialite associations are controlled primarily by accommodation, hydrodynamics, bathymetry and grain supply. This study suggests that microbial constructions are controlled by changes between trapping and binding versus precipitation processes in variable hydrodynamic conditions. Due to the presence of numerous metazoans associated with microbialites throughout the Smithian increase in accommodation and Spathian decrease in accommodation, the commonly assumed anachronistic character of the Early Triassic microbialites and the traditional view of prolonged deleterious conditions during the Early Triassic time interval is questioned.