藏北龙木错—双湖—澜沧江板块缝合带发现晚石炭世—早二叠世洋岛型岩石组合

天泉群岛出露于龙木错—双湖—澜沧江板块缝合带的中西段,也是目前该缝合带上所发现的第一套洋岛型岩石组合。通过野外踏勘、剖面测制等对天泉群岛进行了较为详细的研究,结果显示,天泉群岛由9个孤立、岩石组合不同的洋岛组成,其中独泉沟洋岛、屏风岭洋岛的洋岛组分齐全,见玄武岩、灰岩、砾岩、硅质岩等,其他洋岛的洋岛组分不全。天泉群岛与展金组复理石沉积为整合接触,表明其形成时代为晚石炭世—早二叠世。天泉群岛的厘定,说明龙木错—双湖—澜沧江大洋在晚石炭世—早二叠世仍具有成熟的洋壳。该项研究进一步丰富了龙木错—双湖—澜沧江板块缝合带的演化内容,为反演区域地质演化历史提供了依据。     

根据烈度分布确定华北历史地震破裂区的经验准则及其应用

地震破裂区是地震时沿发震断裂带的同震错动面或破裂面在地表的垂直投影区域,指示了震源断层/破裂的位置与尺度。确定过去长期的强震/大地震破裂区是鉴别地震空区、研究与预测强震危险性的重要基础。对于现代强震,破裂区可运用多种现代技术方法确定,但对于历史强震,破裂区确定的方法需要探索与发展。以华北地区为例,研究利用烈度/等震线资料、结合地震构造与震区地表地质环境等信息确定历史强震破裂区的方法,并开展应用试验。结果表明:研究区现代地震破裂区延伸的烈度区间与极震区烈度、震区环境之间存在密切关系,基于这种关系建立了2条经验准则,可分别用于根据烈度分布确定华北2类震区环境(基岩区和厚层第四纪松散堆积覆盖区)历史强震破裂区的位置与延伸。文中还提出通过综合地震构造、现代小震/余震分布等信息,辅助确定历史强震破裂区横向宽度的思路与途径。作为应用试验,文中确定了5次历史地震的破裂区,结果表明本文发展的经验准则及相应方法适用于华北地区历史强震破裂区的确定。     

Investigation of inner-basin variation: Impact of large reservoirs on water regimes of downstream water bodies

Large dams and reservoirs alter not only the natural flow regimes of streams and rivers but also their flooding cycles and flood magnitudes. Although the effect of dams and reservoirs has been reported for some vulnerable locations, the understanding of the inner-basin variation with respect to the effects remains limited. In this study, we analyse the Three Gorges Dam (TGD) built on the Changjiang mainstream (Yangtze River) to investigate the dam effect variations in the system of interconnected water bodies located downstream. We investigated the effect of flow alterations along the downstream river network using discharge time series at different gauging stations. The river–lake interactions (referring to the interactions between the Changjiang mainstream and its tributary lakes i.e. the Dongting and Poyang lakes) and their roles in modifying the TGD effect intensity were also investigated in the large-scale river–lake system. The results show that the water storage of the tributary lakes decreased after the activation of the TGD. Severe droughts occurred in the lakes, weakening their ability to recharge the Changjiang mainstream. As a consequence, the effect of the TGD on the Changjiang flow increase during the dry season diminished quickly downstream of the dam, whereas its impact on the flow decrease during the wet season gradually exacerbated along the mainstream, especially at sites located downstream of the lake outlets. Therefore, when assessing dam-induced hydrological changes, special attention should be paid to the changes in the storage of tributary lakes and the associated effects in the mainstream. This is of high importance for managing the water resource trade-offs between different water bodies in dam-affected riverine systems.     

东昆仑断裂带东部塔藏断裂地震地表破裂特征及其构造意义

The East Kunlun fault zone is located in the northern margin of the Bayan Har block. The study of earthquake rupture behavior in the fault zone is of importance for understanding the future seismic risk in northwest Sichuan. A number of geological field investigations, typical micro topography DGPS measurements and sample dating show that the earthquake activity of the East Kunlun fault zone extends to the north boundary of Zoige basin, a segment known as the Luocha segment of Tazang fault. In the satellite image, the segment is seen clearly as gray and yellow strips. The earthquake deformation zone mainly features fault scarp, valleys on the slope, offset gullies and terraces, linear distribution of plants, waterfall, fault spring, fault sag pond, and landslide, collapse and talus associated with surface rupturing. These phenomena are distributed intermittently along the re-existing fault and form a ～50km-long inverse L-shaped deformation zone. Fault activities caused left-lateral offset of gullies and terraces, with horizontal displacement concentrated at 5.5m~6m, 18m～23m, 68m～75m, and 200m～220m, respectively. The recent earthquake occurred between 340±30～500±30BP. The macro epicenter is located 5km～7km northwest of Benduo village, with magnitude of MW7.3～7.4, maximum coseismic displacement of 6m, horizontal displacement 5.5m～6m and vertical displacement 0.2m～0.5m, being in a proportion of 5∶1～10∶1. These phenomena show that the Tazang fault is the causative fault of this earthquake. The fault is a Holocene active fault and was dominated recently by left-lateral movement with a small amount of thrust component under compressive shear stress. This characteristic is similar to the movement in other segments of the East Kunlun fault zone. The results of this study support the "continental escape" model.     

地下洞室超欠挖问题非线性有限元分析

运用数值分析的方法,采用ANSYS10.0版有限元分析程序对洞室超欠挖进行三维模拟计算,分析了不同超挖位置、超挖深度、超挖数量等对洞室围岩稳定性的影响,得出了超欠挖部位应力集中数值解及塑性区产生的影响范围,为地下工程掘进施工和初期支护设计提供重要的参考依据。     

海岸带及其调查技术进展

海岸带是重要海陆过渡带地貌单元与区域,兼受海陆动力双重作用与影响,包括不同类型的沉积相,经历复杂的动力沉积、地貌演变及灾变过程。海岸带调查涉及学科交叉融合,调查要素相对独立与内容多学科交叉并存。我国曾分别于1960年、1981年和2003年组织开展过全国海岸带综合调查工作,调查获取了大量丰硕成果。当前海岸带调查与研究过程中亦暴露出一些亟需突破问题,包括:1)海岸带存在大范围"盲区",浅水易陷、礁石养殖等区域难以到达,成为海岸带数据"空白区"、调查"禁区";2)我国海岸带观测平台数量少、分布零散,未形成综合有效观测网,导致长时间序列、多源准同步调查数据缺乏,难以准确把握海岸带变化规律,破解资源环境有关问题;3)海岸带数据获取智能化程度低,严重阻碍制约有关对策及时有效性;4)海岸带不同学科协同调查、交叉融合研究模式尚未建立,不能及时发现海岸带科学问题。今后海岸带调查将在海岸带高分辨率过程数据、全覆盖无死角实时动态数据获取技术,长时间序列综合数据采集平台建设,陆海空全天候立体化数据采集传输及快速智能决策,以及海岸带多学科交叉攻关研究等方面取得突破。     

青海野马泉矽卡岩铁锌多金属矿区侵入岩、交代岩及矿化蚀变特征

野马泉铁锌多金属矿床位于柴达木盆地西南缘和青海祁漫塔格山之间的盆山结合部位.矿区出露有印支期及海西期侵入岩.矿区内矽卡岩呈层状、似层状产于上石炭统四角羊沟组中,矽卡岩矿物主要是石榴子石、单斜辉石、角闪石、绿帘石、符山石等;金属矿物主要有磁铁矿、黄铜矿、黄铁矿、闪锌矿等.文章基于详细野外地质调查、剖面和钻孔岩芯观察结果,开展了侵入岩和交代岩的岩石地球化学及矽卡岩矿物学的系统研究.结果表明,野马泉矿区闪长岩具有低w(SiO2) (51.90％～59.03％)、高w(MgO) (2.04％～3.44％)、w(TFeO)(5.33％～11.67％),高REE[(318.57×10-6～327.67×10-6)],低LREE/HREE比值(7.36～7.48)的特点;二长花岗岩具有高w(SiO2) (77.36％ ～77.41％)、低w(MgO)(0.04％～0.10％)、w(TFeO) (0.76％～1.08％)的特点,LREE/HREE比值较高(9.14～9.37).透辉石-钾长石交代岩比原岩低w(MgO)(1.17％ ～ 2.86％)、低w(TFeO)(3.89％～7.76％),且具有更强的Eu负异常(δEu=0.07～0.52),LREE/HREE比值更低(3.19～7.87).透辉石-钠长石交代岩相对原岩具有低w(MgO) (0.36％～0.92％)、高w(TFeO)(3.05％ ～8.13％)的特点.野马泉矿区的矽卡岩包括钙矽卡岩和锰质矽卡岩,钙矽卡岩主要产于接触带附近,组成矿物主要为单斜辉石和石榴子石,接近岩体的单斜辉石中透辉石端员组分较高,石榴石主要分布在接触带附近,内环带钙铁榴石组分高于外环带.综合矿物学、岩石地球化学结果,推断野马泉矿区闪长岩具有较大成矿潜力,野马泉矿区钙矽卡岩主要形成于氧化条件,锰质矽卡岩形成于还原条件.     

不同地质背景地热系统水-岩作用下温泉水的地球化学特征——以重庆市温塘峡背斜温泉、滇东小江断裂带温泉为例

本文以重庆市温塘峡背斜和滇东小江断裂带出露温泉为例,探讨了其水文地球化学特征的差异。研究发现,由于地质背景条件基本相同,温塘峡背斜出露的温泉水文地球化学特征比较接近,水化学类型为SO4-Ca（Mg）型,而小江断裂带温泉水文地球化学特征差异较大,泉水水化学类型主要有HCO3-Na型（YN1）、HCO3-Ca型（YN2）、SO4-Ca（Mg）型（YN3和YN5）和SO4-HCO3-Ca-Na型（YN4）,这与各泉点所处地质背景条件不同有很大关系。此外,通过对Na-K-Mg和Na-K-Mg-Ca图解模型的解读得出,所有样品均未达到水-岩平衡,仅有YN1泉点样品接近完全平衡线,表明YN1接近水-岩作用平衡状态,并由上述图解模型估算得到YN1点热储温度大概为100~120℃,与运用SiO2温标计算的热储温度（133~139℃）相差不大。此外,水化学特征和Na-K-Mg-Ca图解分析也表明,YN2与温塘峡背斜温泉水-岩作用过程比较相似。     

Capture-zone design in an aquifer influenced by cyclic fluctuations in hydraulic gradients

Design of a groundwater pumping and treatment system for a wood-treatment facility adjacent to the tidally influenced Fraser River estuary required the development of methodologies to account for cyclic variations in hydraulic gradients. Design of such systems must consider the effects of these cyclic fluctuations on the capture of dissolved-phase contaminants. When the period of the cyclic fluctuation is much less than the travel time of the dissolved contaminant from the source to the discharge point, the hydraulic-gradient variations resulting from these cycles can be ignored. Capture zones are then designed based on the average hydraulic gradient determined using filter techniques on continuous groundwater-level measurements. When the period of cyclic fluctuation in hydraulic gradient is near to or greater than the contaminant travel time, the resulting hydraulic-gradient variations cannot be ignored. In these instances, procedures are developed to account for these fluctuations in the capture-zone design. These include proper characterization of the groundwater regime, assessment of the average travel time and period of the cyclic fluctuations, and numerical techniques which allow accounting for the cyclic fluctuations in the design of the capture zone. Electronic Publication