新疆塔县地区片麻岩冻融劣化机理与规律试验研究

新疆塔县地区广泛分布小规模岩质崩塌,是该地区频繁爆发泥石流的主要物源。调查发现,这些崩塌主要受区域性节理和风化作用控制。为揭示塔县地区岩体冻融劣化及崩塌机理,本文选取崩塌岩体中岩性比例最高的片麻岩,在干燥和饱和条件下进行不同次数的冻融循环试验,通过SEM电镜扫描和吸水率、大开空隙率以及质量损失测试,研究片麻岩样微观结构和宏观物理特性的变化。结果表明,在内部应力以及冻胀力的作用下,片麻岩微观结构发生劣化,联结较弱颗粒的破碎、剥落以及微观裂隙的扩展导致斜坡表层岩体强度降低,抗风化能力下降。而在冻融循环作用的长期影响下,这种风化作用会逐渐进入坡体内部,最终导致连续小规模崩塌,并在坡脚处堆积,为泥石流提供物源。     

黔北习水县桑木场铅锌矿岩相学、矿相学特征 及与MVT型铅锌矿床的对比

习水县桑木场铅锌矿,容矿层为震旦系灯影组白云岩,属于局限台地相的碳酸盐盆地;铅锌矿受断层与裂隙控制,属于开放式空隙充填,矿石与容矿层呈脉状、网脉状接触。矿石矿物为闪锌矿及方铅矿,脉石矿物为重晶石、方解石、白云石、萤石、黄铁矿及石英。样品表现出两期成矿特征,根据矿物穿插关系可判定与流体活动相关的矿物生成顺序。本文结合习水县桑木场区域地质特征及样品岩相学、矿相学特征,初步判定研究区铅锌矿属于密西西比河谷型(MVT)铅锌矿,并以此典型矿床的成矿模式为指导,尝试在研究区内寻找较大型铅锌矿床。     

鄂尔多斯盆地延长组长7段沉积岩元素地球化学特征及沉积环境分析

沉积岩的地球化学特征可以反映盆地沉积环境。为了探讨鄂尔多斯盆地延长组沉积时期古气候、氧化还原条件、古盐度等特征,对鄂尔多斯盆地东南部铜川延长组长7段的5个砂岩、8个页岩样品进行主量、微量以及稀土元素地球化学分析。结果显示,长7段细粒沉积物Al₂O₃/SiO₂值与K₂O/Na₂O值指示样品成分成熟度差别不大,黏土矿物含量较高。∑REE平均值为132.65×10^-6,明显低于北美页岩平均稀土元素含量,也低于全球平均大陆上地壳值;LREE分异程度较高,呈微弱的Eu正异常,无Ce异常。“C值”、Sr/Cu、Rb/Sr、Mg/Ca等指标显示延长组沉积期整体处于温暖潮湿的气候区。研究区样品富集微量元素U、Sc、Cs(平均20.11×10^-6、9.66×10^-6、6.08×10^-6),结合V、δU、Th/U、V/Cr、V/Sc、V/(V+Ni)等指标分析,结果指示延长组沉积期以底层水体呈强分层的还原环境为主。Li、Sr、Ni、Sr/Ba、(MgO/Al₂O₃)×100等值显示沉积期水体总体为淡水-微咸水。     

Discovery of Kilometer-Scale Uplift and Exhumation Related to the Late Indosinian Movement in the Northern Ordos Basin,North China

The tectonic response of the Ordos Basin to Indosinian movement mainly occurred in the southwestern part of the basin due to the Late Triassic collisional Qinling orogeny to the south.The orogeny resulted in intense uplift and exhumation of the southwestern section of the Ordos Basin,where the upper and middle parts of the Upper Triassic Yanchang Formation were exhumated and the magnitude of exhumation progressively decreased to the northeast(Liu Chiyang et al.,2008).However,little attention has been paid to the influence of Indosinian movement to the northern Ordos Basin.In this study,stratigraphic observations and new apatite fission track(AFT)data are integrated to characterize the effect of Indosinian movement in the northern Ordos Basin.     

四川省青川玉石矿的地质特征及其找矿意义

青川石英质玉是近年在四川省发现的新玉石矿。玉石矿体赋存于新元古界通木梁群太阳坪组云母石英片岩中。玉石的矿物成分主要为石英、铬云母、铬绢云母,具显微细粒粒状、片状变晶结构,片状、条带状构造。玉石种类分为绿色和白绿色,具油脂光泽;矿体规模大、块度好,玉石品质佳、可加工性强,可制作手镯、摆件、挂件、雕件等。根据野外地质工作判断,青川石英质玉属于区域变质成因,青川玉石矿的发现填补了四川石英质玉的空白,对丰富区域成矿系列和拓展区域玉石矿找矿方向具有重要意义。     

鄂尔多斯盆地纳岭沟铀矿床成矿流体来源及与铀成矿关系：来自含矿层碳酸盐胶结物C-O同位素的约束

正近年来,随着铀矿勘查与研究程度的深入,在鄂尔多斯盆地北缘发现了皂火壕、纳岭沟、大营、东胜等一系列大型—特大型砂岩型铀矿床。大量学者对这些铀矿床的成矿环境、成矿年龄、铀源和成矿流体来源及有机质在铀成矿中的作用、成矿模式等方面做了非常系统的研究,但是关于成矿流体来源方面不同的学者具有不同的观点。一部分学者认为该区铀矿富集所需的还原剂主要来自下伏古生     

Effect of an incremental change in external water pressure on tunnel lining: a case study from the Tongxi karst tunnel

Tunnel water inrush disaster is a serious problem in karst tunnel construction and occurs extensively in southwestern China. To prevent water inrush, hydraulic lining has been utilized extensively in karst tunnel construction. The failure of the hydraulic lining in the Tongxi tunnel is an example of a typical failure case that has yet to be fully analyzed. In this paper, the failure of the waterproof liner was studied by theoretical and numerical methods. By field investigation, the failure of the tunnel lining was attributed to a high hydraulic pressure head converging in the large karst caves behind the lining. The corresponding mechanical model can be simplified as a “karst cave water pressure” model. The key to the mechanical model was to determine the water pressure of the karst caves produced by the lining. The variation in water pressure was directly related to the cave’ reservoir volume, catchment flow and catchment time. Thus, volume calculation formulas for two types of karst caves (strike and oblique caves) in the studied tunnel were constructed based on the engineering geological conditions. Considering the precipitation, the flow rate in the karst caves was regarded as nearly constant during the catchment period. Hence, reservoir volumes during different periods can be calculated and converted to the stress boundary conditions of the lining. Then, the mechanical response of the tunnel under different water levels was calculated by numerical simulation. Combining the field investigation and monitoring data, the tunnel lining failure was mainly believed to be triggered by hydraulic fracturing failure due to a high-pressure head. Finally, prevention measures were proposed based on the results of this study.

     

高庙子膨润土强度时效性试验研究

本文用试验方法研究了静置时间对不同含水率高庙子钠基（GMZ07）膨润土强度的影响。在保持试样干密度和含水率不变的情况下,将初始含水率为10%、18%和24%（饱和）3组压实试样分别静置0、5、15、30、90 d,之后采用精度较高的直剪仪在400、800和1 600 kPa垂直压力下进行剪切试验;同时完成了部分试样的压汞试验。结果表明：GMZ07膨润土的剪切强度随静置时间增长而减小;静置前期,强度下降较快;静置时间超过一定天数后,其剪切强度逐渐趋于稳定。根据3种含水率试样的强度包线可得到：随着静置时间增加,饱和试样的内摩擦角略微下降而黏聚力变化不大;含水率10%和18%试样的黏聚力明显变小而内摩擦角几乎不变。根据Alonso等提出的非饱和土有效应力,结合压实膨润土试样的孔径分布,认为集聚体内孔隙增多是非饱和膨润土强度随静置时间而变小的原因。     

藏东南嘎龙曲冰川泥石流的物源特征及其对扎墨公路的影响

在全球气候变暖的大背景下,冰川消融加剧,冰舌后退,冰川泥石流加剧。扎墨公路是目前通往西藏墨脱的唯一公路,公路必经的嘎龙曲发育藏东南地区典型的海洋性冰川泥石流,针对嘎龙曲冰川泥石流的物源特征,经现场调查得出,嘎龙曲冰川泥石流物源类型有冰碛物物源、崩塌型物源以及沟道堆积型物源三类,总结分析了三种物源类型的分布特征和启动模式。通过建立物源计算模型,定量计算嘎龙曲沟域内可参与泥石流活动的松散固体物源动储量为366.28×104 m3,其中冰碛物物源为主要的动储量物源,物源补给特征在藏东南海洋性冰川发育区域具有一定代表性。嘎龙曲沟域内水动力分布的不均一特性决定了物源启动参与泥石流活动的不均一性,随着全球气候变暖影响下水动力条件的增强,嘎龙曲冰川泥石流对扎墨公路的危害会愈加严重。      

鄂尔多斯盆地北部中生代中晚期地层碎屑锆石U-Pb定年与物源示踪

本文采用LA-ICP-MS碎屑锆石原位微区测年方法,对鄂尔多斯盆地北部杭锦旗地区中侏罗统直罗组和下白垩统志丹群进行了砂岩碎屑锆石U-Pb年龄分布及其变化特征研究,统计和对比了前人对该区周缘岩体的同位素年代学结果,结合区域构造背景,系统地研究了盆地北部直罗组及志丹群地层物源及其演变。结果表明:(1)4个直罗组样品和2个志丹群样品锆石年龄总体呈现出270~280Ma、320~340Ma、1800~2000Ma、2300~2500Ma 4个峰值年龄段,在志丹群样品中出现有少量230~240Ma锆石年龄;(2)杭锦旗地区上述砂岩的物源主要来自阴山、大青山—乌拉山的片麻岩、麻粒岩、孔兹岩以及形成于海西期的中酸性侵入岩,同时也有狼山地区岩体、集宁地区孔兹岩的一部分贡献;(3)1800~2000Ma、2300~2500Ma峰值年龄均为华北克拉通基底构造热事件的反映,270~280Ma、320~340Ma两个峰值年龄可能记录了早石炭世—中二叠世古亚洲洋向华北板块北缘的两次快速俯冲事件;(4)下白垩统志丹群样品中出现的230~240Ma的锆石,指示晚侏罗世的燕山运动在盆地北缘引起的强烈逆冲推覆造山作用使得印支期侵入岩被抬升至地表并遭受剥蚀,从而为研究区地层进一步增加了来自蚀源区印支期侵入岩的物源;(5)与中侏罗统直罗组样品相比,下白垩统志丹群样品在2300~2500Ma峰值测点所占比例明显增加,这可能是由于早白垩世时期盆地北部沉积边界较中侏罗世相对扩展,使来自阴山的物源比例增加。