桐柏杂岩南北边界剪切带的对比以及对桐柏造山带构造格局的制约     

李海龙  宋传中  韩建军  任升莲  李加好  张妍  王微  杨帆 《岩石学报》2018,34(3):813-836

桐柏杂岩的南北边界的剪切带分别是殷店-马垅韧性剪切带和晓天-磨子潭韧性剪切带,这两条韧性剪切带内都发育杆状构造,且杆状构造具有层状结构,层与层之间通过一种特殊的滑脱面结合。由于晓天-磨子潭韧性剪切带相对于殷店-马垅剪切带位置明显更靠近商丹断裂带,早期商丹断裂带的活动在岩石中留下的变形痕迹导致了后期晓天-磨子潭韧性剪切带的变形程度要略强于殷店-马垅剪切带。这两条剪切带都是以简单剪切为主的剪切带,变质条件也相似,都属于角闪岩相变质,处于中-下地壳流变层位置。U-Pb同位素测年结果显示,晓天-磨子潭韧性剪切带的活动年龄为171~142Ma,殷店-马垅韧性剪切带的活动年龄为164~137Ma,两条剪切带的主活动期都在中-晚侏罗世,在早白垩世随着岩浆活动的峰期到来慢慢减弱停止。桐柏造山带在印支晚期碰撞挤压背景下的向东挤出不是一个整体的挤出,而是有层次的差异挤出,挤出的同时层与层之间会发生滑动,滑脱面类似滑动的润滑剂,酷似"管状流动"的构造。在晓天-磨子潭韧性剪切带和殷店-马垅韧性剪切带的牵引作用下,整个桐柏造山带由西向东发生管状流动。  相似文献   

中朝边境天池破火山口湖底地形多波束测深探测   总被引：4，自引：3，他引：1  

杨清福  原晓军  武成智  盘晓东  张羽 《岩石学报》2018,34(1):185-193

为调查天池破火山口湖的基本参数和湖底地形特征,研究破火山口的内部构造、破火山口的组合样式和垮塌堆积分布,本文采用多波束测深方法,对天池湖底地形进行了探测。探测结果显示:天池最大水深值为373.2m,天池水域边界实测周长为13.44km,天池湖水面面积9.4km~2,天池总蓄水量约为19.88×10~8m~3。天池周边分布4个温泉,温度为7~47℃。根据湖底地形推断,现今的天池破火山口形成于千年大喷发。其后,在天池西侧形成一个喷火口,东侧形成一个熔岩丘。天池湖底存在5个较大的破火山口内壁垮塌堆积区,但在湖底未见熔岩流。天池边缘出露的温泉点对应环状断裂,同时反映深部存在岩浆体。  相似文献   

基于神经网络的页岩微纳米孔隙微结构分析的正则化和最优化方法   总被引：1，自引：1，他引：0  

王彦飞  邹安祺 《岩石学报》2018,34(2):281-288

页岩气成藏机理与页岩内部孔隙结构紧密相关,对页岩孔隙结构的研究成为页岩气勘探开发技术中至关重要的一环。页岩内部不同结构体组分对X-射线的吸收能谱不一样,这样就导致观测数据是由不同页岩组分衰减不同波段的X-射线构成的。经过对CT图像分割,能够获得页岩微孔结构的图像,尤其是获得有机质中孔隙类别、形状、尺寸、空间分布、连通特性。本文利用同步辐射X射线扫描重构的页岩CT数据,研究并设计基于多能CT图像的神经网络图像分割技术和算法,以期得到页岩体三维结构特征及空间分布,可以为建立有机质种类和无机矿物组成与微纳孔隙特征的联系以及最终实现页岩气的资源储量评估和勘探开发提供技术支持。  相似文献   

内蒙古南部晚二叠世同生变形构造与陆缘裂陷     

田树刚  张永生  翟大兴  宫月萱 《地球学报》2018,39(2):144-154

内蒙南部林西县至正镶白旗林西—正镶白旗地区晚二叠世地层中,发现类型繁多的同生变形构造。除前人报道的滑卷层理、滑塌褶皱、滑塌砾岩和浊积砂砾岩以外,还有本文首次发现的大量球状体,包括滚动纺锤体、叠加滑卷球核、砾核滚动球、砂质滚动球和泥质滚动球。形态结构、成分组成和地层分布研究表明,这些构造形体均属重力成因和形成在陆棚—斜坡上。不同类型的构造形体可以组成来源演变序列,显示重力作用的加强,如滑卷层理通过"叠加滑卷"变成滑卷叠加球核,再通过"滚动粘结"变成滚动球体。它们形成和保存都受特定环境因素控制,因此各自具有特殊指相意义。大量同生变形构造出现,反映沿华北板块北缘出现陆棚、斜坡和深水海槽环境,证明晚二叠世兴—蒙海槽再次裂开,并形成"林西—九台裂陷带"。  相似文献   

2017年九寨沟7.0级地震序列震源机制解和构造应力场特征     

祁玉萍  龙锋  肖本夫  路茜  江鹏 《地球学报》2018,39(5):622-634

九寨沟余震序列的震源机制和构造应力场有助于认识本次地震的发震构造和孕震机理。本文基于四川区域地震台网的波形资料, 采用波形拟合(CAP)方法和P波初动+振幅比(HASH)方法反演得到2017年8月8日九寨沟7.0级地震序列中59次ML≥3.0地震的震源机制解, 并基于该结果采用阻尼线性逆推法(DRSSI), 计算研究区域的平均构造应力场, 给出该区域的应力场特征。结果显示, 利用CAP方法反演得到的本次主震的最佳双力偶机制解节面I: 走向248°/倾角86°/滑动角–169°, 节面II: 走向157°/倾角79°/滑动角–4°, 矩震级为Mw6.31, 矩心深度5 km, 属走滑型地震事件; 大部分余震的震源机制解错动类型与主震一致, 矩心深度集中在3~10 km; 应力场反演结果显示, 该区域周边的应力性质为走滑型, 最大主应力方向呈NWW–SEE向, 与该区域的应力场方向一致, 表明本次地震主要受区域应力的控制。结合该区域的地震地质构造等已有研究成果, 分析认为此次地震的发震断层为走向NW–SE、倾向SW的左旋走滑断裂——树正断裂, 巴颜喀拉块体向E-SE向的水平运动受到华南块体的强烈阻挡导致此次地震的发生, 汶川地震的发生对本次地震具有一定的促进作用。  相似文献   

开敞式潮滩-潮沟系统发育演变动力机制——Ⅲ.海平面上升影响          下载免费PDF全文

龚政  严佳伟  耿亮  朱思谕  李欢  张长宽 《水科学进展》2018,29(1):109-117

为研究海平面上升对潮滩-潮沟系统的影响,以江苏中部粉砂淤泥质海岸为原型,建立变态物理模型,模拟研究在不同海平面潮汐过程作用下的潮沟发育和演变过程,分析了潮滩淹没历时、排水密度、潮沟断面形态等特征参数变化规律。研究表明:潮沟在发育初期伸长速率高于拓宽速率,最终趋于动态平衡;海平面上升后,潮滩淹没历时增加,露滩时间缩短,归槽水对潮沟底床的塑造作用减弱;平均归槽水流长度和Horton排水长度均随海平面上升呈现出减小趋势,潮沟的排水能力增强;潮沟断面宽深比服从对数正态分布,随着海平面上升,潮沟断面面积和宽深比均呈现出增大趋势,宽深比分布范围变广。  相似文献   

开挖条件下含陡倾结构面顺层岩质边坡破坏模式与稳定性预测     

王章琼  江志红 《中国地质灾害与防治学报》2018,29(1):40-45

顺层岩质边坡易发生失稳破坏,当边坡中发育有顺坡向陡倾结构面时,更不利于边坡稳定。以贵州某水电站大坝左岸含陡倾结构面顺层边坡为例,在综合分析地质条件及开挖扰动的基础上,结合离散元软件UDEC,分析了边坡的变形破坏模式和稳定性。研究结果表明,边坡可能发生的变形破坏模式主要有滑移、拉裂—滑移两种;自然状况下及开挖后,边坡都有沿断层f_9、卸荷裂隙L_1及岩层面发生滑移的趋势,且工程开挖导致边坡沿该结构面发生内部滑动;对边坡采用预应力锚索加固后,变形得到有效控制,位移数值计算值与实际监测值基本吻合。  相似文献   

Generation and Development of Structures and Their Controls on Ore Mineralization in the Lehong Zinc-lead Deposit,Northeastern YunnanEI北大核心CSCD     

Cui J.  Han R.  Wang J.  Ren T.  Wu Y.  Zhao D. 《大地构造与成矿学》2018,(4):664-680

The Lehong zinc-lead deposit is one of the new-found large Zn-Pb deposits in the Sichuan- Yunnan-Guizhou Zn-Pb poly-metallic mineralization area. The ore-bodies of the Lehong deposit are strictly controlled by structures, and the fault tectonites can be divided into four groups which include morbruk rock, cataclastic rock and tectonic breccia. The mechanical properties of the faults suggest that there are five tectonic systems formed in the Caledonian-early Hercynian, Indosinian-early Yanshanian, mid-Yanshanian, late Yanshanian and Himalayan periods, respectively. The Lehong fault and the Qiaojia-Lianfeng fault are two important ore-controlling structures which might have acted as channel ways of the ore fluids. The ores are hosted in the subordinary fracture zone, joint fracture zone and interlayer fault zones in trailing folds of the Lehong fault and the Baobaoshang syncline and Jinjiagou anticline. Hence, the Lehong deposit is a tectonic -controlled ore deposit. These research do not only lay a foundation for studying deposit genesis and ore-finding direction in the Lehong deposit, but also provides important enlightenments for the ore-finding prognosis of lead-zinc deposits in northwestern Guizhou ore concentration district. © 2018, Science Press. All right reserved.  相似文献   

Paleogene Deformation and its Control Mechanism in the Central Part of Raoyang SagEI北大核心CSCD     

Wang Y.  Qi J.  Zheng R.  Miao Q.  Niu X.  Chen S.  Gao Y. 《大地构造与成矿学》2018,(4):628-638

Various Palaeogenic deformations have been recognized in the central part of the Raoyang Sag. Based on seismic interpretation, the sedimentary sequences, structure features and activity of main faults have been studied. The results show that the Xianxian detachment fault, which is located in the eastern boundary of the Raoyang Sag, was still active during the Cenozoic and controlled the basinal deformation. The detachment depth and deformation of the Xianxian detachment fault are discussed based on the area-balance theory. The results reveal that patterns of the Paleogene structures vary considerably from the north to the south. Activity of the main faults in the hanging wall of the Xianxian detachment led to a westward migration of the deposition center. On the other hand, the uplifting of the dome related to the detachment resulted in fast denudation of the overlying sediments in locals. The deformation of detachment fault and activities of the major faults controlled the Paleogene deformation in the central part of the Raoyang Sag. © 2018, Science Press. All right reserved.  相似文献   

Late Quaternary chironomid community structure shaped by rate and magnitude of climate change     

Roseanna J. Mayfield  Peter G. Langdon  C. Patrick Doncaster  John A. Dearing  Rong Wang  Gaute Velle  Kimberley L. Davies  Stephen J. Brooks 《第四纪科学杂志》2021,36(3):360-376

Much is known about how climate change impacts ecosystem richness and turnover, but we have less understanding of its influence on ecosystem structures. Here, we use ecological metrics (beta diversity, compositional disorder and network skewness) to quantify the community structural responses of temperature-sensitive chironomids (Diptera: Chironomidae) during the Late Glacial (14 700–11 700 cal a bp ) and Holocene (11 700 cal a bp to present). Analyses demonstrate high turnover (beta diversity) of chironomid composition across both epochs; however, structural metrics stayed relatively intact. Compositional disorder and skewness show greatest structural change in the Younger Dryas, following the rapid, high-magnitude climate change at the Bølling–Allerød to Younger Dryas transition. There were fewer climate-related structural changes across the early to mid–late Holocene, where climate change was more gradual and lower in magnitude. The reduced impact on structural metrics could be due to greater functional resilience provided by the wider chironomid community, or to the replacement of same functional-type taxa in the network structure. These results provide insight into how future rapid climate change may alter chironomid communities and could suggest that while turnover may remain high under a rapidly warming climate, community structural dynamics retain some resilience.  相似文献