K-Ar Dating of Fault Gouges from the Red River Fault Zone of Vietnam

Constraining the timing of fault zone formation is fundamentally important in terms of geotectonics to understand structural evolution and brittle fault processes.This paper presents the first authigenic illite K-Ar age data from fault gouge samples collected from the Red River Shear Zone at Lao Cai province,Vietnam.The fault gouge samples were separated into three grain-size fractions（〈0.1 μm,0.1-0.4 μm and 0.4-1.0 μm）.The results show that the K-Ar age values decrease from coarser to finer grain fractions（24.1 to 19.2 Ma）,suggesting enrichment in finer fraction of morerecently grown authigenic illites.The timing of the fault movement are the lower intercept ages at 0%detrital illite（19.2 ± 0.92 Ma and 19.4 ± 0.49 Ma）.In combination with previous geochronological data,this result indicates that the metamorphism of the Day Nui Con Voi（DNCV） metamorphic complex took place before ca.26.8 Ma.At about 26.8 Ma-25 Ma,the fault strongly acted to cause the rapid exhumation of the rocks along the Red River-Ailoa Shan Fault Zone（RR-ASFZ）.During brittle deformation,the DNCV slowly uplifted,implying weak movement of the fault.This brittle deformation might have lasted for ca.5 Ma.

Structural and Geochronological Evidence for Multiple Episodes of Tertiary Deformation along the Ailaoshan-Red River Shear Zone, Southeastern Asia, Since the Paleocene

Structural analyses show that the Ailaoshan-Red River shear zone （ASRRSZ） in Ailao Mountain is composed of three different deformational domains. These domains may represent three episodes of left-lateral slip experienced by the ASRRSZ. The first episode of such deformation occurred throughout the eastern high-grade belt of the ASRRSZ under a transtensional regime and produced L- type tectonites of amphibolite grade. The second episode of left-lateral slip formed high strain zones overprinting the high-grade belt. Its deformational mechanism is similar to simple shear and the deformed rocks are L-S mylonites of greenschist grade. The third episode of left-lateral slip took place chiefly in a western low-grade belt of the ASRRSZ. This deformation occurred in a transpressional regime, formed an overall structure pattern of a sinistral thrust system and produced phyllonites of low-greenschist grade. Geochronological data indicated that the three episodes of left-lateral slip happened before ～58-56 Ma, at least from ～27 Ma to 22 Ma and at ～13-12 Ma respectively. The first episode of slip in the ASRRSZ appeared to correspond to the initial collision of India and Asia at ～60 Ma. The second episode took place almost at the same time as the most intensive compression and uplift in Tibet. The latest event might represent a further eastward material flow in Tibet after ～16-13 Ma. Thus, the ASRRSZ of southeastern Asia probably experienced three main episodes of Tertiary left- lateral slip in the course of intracontinental convergence since the India-Asia collision.

High Temperature Strain Structures and Quartz C-Axis Fabrics from Mylonitic Rocks in the Ailaoshan-Red River Shear Zone,Yunnan,and Their Tectonic Implication

The Ailaoshan-Red River（ASRR） shear zone is one of the major Southeast Asian tectonic discontinuities that have figured the present tectonic framework of the eastern Tibet.Several metamorphic massifs are distributed linearly along the shear zone,e.g.Xuelongshan,Diancangshan, Ailaoshan and Day Nui Con Voi from north to south.They bear a lot of lines of evidence for the tectonic evolution of the eastern Tibetan at different crustal levels in different tectonic stages.Controversy still exists on the deformation structures,microstructures and their relationship with metamorphisms along the ASRR.In this paper detailed microstructural and EBSD（Electron Backscattered Diffraction） fabric analysis of some highly sheared granitic rocks from different massifs along the ASRR are conducted.High temperature structures and microstructures are preserved in unsheared gneisses,in weakly sheared xenoliths or in some parts of the highly sheared rocks（mylonites）.Several types of high temperature quartz c-axis fabrics show symmetrical patterns or transitions from symmetrical to asymmetrical patterns.The former are attributed to coaxial deformation during regional shortening in an early stage of the Indian-Eurasian tectonic interaction and the latter are related to the transitions from coaxial compression to noncoaxial shearing during the post-collisional ASRR left lateral shearing.

New Zircon U-Pb Geochronology of the Post-kinematic Granitic Plutons in the Diancang Shan Metamorphic Massif along the Ailao Shan-Red River Shear Zone and Its Geological Implications

The Ailao Shan-Red River fault zone is the boundary between the Yangtze block to the northeast and the Indochina block to the southwest.It is an important tectonic zone due to its role in the southeastward extrusion of the Indochina block during and subsequent to the Indian-Eurasian collision.Diancang Shan（DCS） high-grade metamorphic complex,located at the northwest extension along the Ailao Shan-Red River（ASRR） shear zone,is a representative metamorphic complex of the ASRR tectonic belt.Structural and microstructural analysis of sheared rocks in the high-grade metamorphic rocks reveals that they are coherent with solid-state high-temperature ductile deformation,which is attributed to left-lateral shearing along the ASRR shear zone.New LA-ICP-MS zircon U-Pb geochronological and microstructural studies of the post-kinematic granitic plutons provide a straightforward time constraint on the termination ductile left-lateral shearing and exhumation of the metamorphic massif in the ASRR shear zone.It is suggested that the left-lateral shearing along the ASRR shear zone ended at ca.21 Ma at relative lower-temperature or decreasing temperature conditions.During or after the emplacement of the young dikes at ca.21 Ma,rapid brittle deformation event occurred,which makes the DCS massif start fast uplift/exhumation and cooling to a shallow crustal level.

Effect of Root-Zone Temperature on Growth and Quality of Hydroponically Grown Red Leaf Lettuce (Lactuca sativa L. cv. Red Wave)

Soil temperature influences crop growth and quality under field and greenhouse conditions;however, precise investigation using controlled cultivation systems is largely lacking. We investigated effects of root-zone temperatures on growth and components of hydroponically grown red leaf lettuce (Lactuca sativa L. cv. Red Wave) under a controlled cultivation system at 20&degC. Compared with ambient root-zone temperature exposure, a 7-day low temperature exposure reduced leaf area, stem size, fresh weight, and water content of lettuce. However, root-zone heating treatments produced no significant changes in growth parameters compared with ambient conditions. Leaves under low root-zone temperature contained higher anthocyanin, phenols, sugar, and nitrate concentrations than leaves under other temperatures. Root oxygen consumption declined with low temperature root exposure, but not with root heating. Leaves of plants under low rootzone temperature showed hydrogen peroxide production, accompanied by lipid peroxidation. Therefore, low temperature root treatment is suggested to induce oxidative stress responses in leaves, activating antioxidative secondary metabolic pathways.

EARTHQUAKE FOCAL MECHANISM AND ITS TECTONIC SIGNIFICANCE ALONG THE TWO SIDES OF THE RED RIVER FAULT ZONE

The Red River Fault Zone is a gigantic slide-slip fault zone extending up to 1000km from Tibet to SouthChina Sea. It has been divided into the north, central and south segments according to the difference of thegeometry, kinetics, and seismicity on the land, but according to the contacted relationship between the old pre-Cenozoic block in Indochina Peninsula and the South China block, the Red River Fault Zone was divided into two parts extending from land to ocean, the north and south segments. Since the Tertiary, the Red River Fault Zone suffered first the sinistral movement and then the dextral movement. The activities of the north and the south segments were different. Based on the analysis of earthquakes and focal mechanism solutions,earthquakes with the focus depths of 0-33km are distributed over the whole region and more deep earthquakes are distributed on the northeastern sides of the Red River fault. Types of faulting activities are the thrust in the northwest, the normal in the north and the strike-slip in the south, with the odd type, viz. the transition type, in the other region. These show the Red River Fault Zone and its adjacent region suffered the extruding force in NNW direction and the normal stress in NEE direction and it makes the fault in the region extrude-thrust,horizontal strike-slip and extensional normal movement.

Large-Scale Dextral Strike-Slip Movement and Associated Tectonic Deformation Along the Red-River Fault Zone

Field investigation has revealed that the large-scale dextral strike-slip movement and the associated tectonic deformation along the Red River fault zone have the following features: geometrically, the Red River fault zone can be divided into three deformation regions, namely, the north, central and south regions. The north region lies on the eastern side of the Northwest Yunnan extensional taphrogenic belt, which is characterized by the 3 sets of rift-depression basins striking NNW, NNE and near N-S since the Pliocene time, and on its western side is the Lanping-Yunlong compressive deformation belt of the Paleogene to Neogene; the deformation in the central region is characterized by dextral strike-slip or shearing. The east Yunnan Miocene compressive deformation belt lies on the eastern side of the fault in the south, and the Tengtiaohe tensile fault depression belt is located on its west. In terms of tectonic geomorphology, the aforementioned deformation is represented by basin-range tectonics in the north, linear faulted valley-basins in the central part and compressive (or tensional) basins in the south. Among them, the great variance in elevation of the planation surfaces on both sides of the Cangshan-Erhai fault suggests prominent normal faulting along the Red River fault since the Pliocene. From the viewpoint of spatial-temporal evolution, the main active portion of the fault was the southern segment in the Paleogene-Miocene-Pliocene, which is represented by “tearing” from south to north. The main active portion of the fault has migrated to the northern segment since the Pliocene, especially in the late Quaternary, which is characterized by extensional slip from north to southeast. The size of the deformation region and the magnitude of deformation show that the eastern plate of the Red River fault has been an active plate of the relative movement of blocks.

DIRECT DATING OF LEFT-LATERAL SLIP ALONG THE RED RIVER SHEAR ZONE

The Red River Shear Zone (RRSZ), which extends from eastern Tibet to the South China Sea, plays a central role in the hypothesis that strike\|slip extrusion of Indochina accommodated a significant portion of Indo\|Asian convergence. The massifs of the RRSZ, the only known mid\|crustal section exposed through a transform plate boundary, contain high\|grade metamorphic rocks that are believed to have been plastically deformed in a left\|lateral sense during the mid\|Tertiary. While the history of diachronous transtension along the RRSZ was previously obtained for temperatures below the brittle\|ductile transition from argon thermochronometry, the precise timing of high temperature deformation and the magnitude of strain have not been directly determined. This is a significant limitation to testing the extrusion model as magnetic anomalies from the South China Sea, interpreted to be a pull apart basin at the SE termination of the RRSZ, specifically predict that slip occurred between 35～17Ma at a rate of 3～5cm/a.

Structural Architecture for Development of Marginal Extensional Sub-Basins in the Red Sea Active Rift Zone

This paper presents a robust kinematic model that describes northern Red Sea and Gulf of Suez rifting and the development of marginal extensional half-graben sub-basins (ESB). A combination of Landsat Enhanced Thematic Mapper Plus (ETM+) and structural data was used to provide model constraints on the development of rift segments and ESB in the active rift zones. Structural analysis shows rotation and change in strike of rift-bounding faults. The model describes the northern Red Sea region as a poly-phase rift system initiated by late Oligocene (30 - 24 Ma) orthogonal rifting and the development of marginal ESB (now inland ESB), followed by oblique rifting and flank uplift during the early Miocene (24 - 18 Ma). The oblique rifting fragmented the rift depression into segments separated by oblique-slip accommodation within reactivated Pan-African (ca. 600 Ma) fracture zones, resulting in the development of antithetic faults and an en-echelon distribution of inland ESB. The current phase of rifting was instigated by the development of the Dead Sea Transform in response to increased northeasterly extension during the middle Miocene (ca. 18 Ma). The model explains the widening of the Red Sea rift during the last phase more than the Gulf of Suez rift by developing more antithetic faults and formation of offshore ESB, and deepening the rift depression.

Geographic Object-Based Image Analysis of Changes in Land Cover in the Coastal Zones of the Red River Delta (Vietnam)

The majority of the population and economic activity of the northern half of Vietnam is clustered in the Red River Delta and about half of the country’s rice production takes place here. There are significant problems associated with its geographical position and the intensive exploitation of resources by an overabundant population (population density of 962 inhabitants/km2). Some thirty years after the economic liberalization and the opening of the country to international markets, agricultural land use patterns in the Red River Delta, particularly in the coastal area, have undergone many changes. Remote sensing is a particularly powerful tool in processing and providing spatial information for monitoring land use changes. The main methodological objective is to find a solution to process the many heterogeneous coastal land use parameters, so as to describe it in all its complexity, specifically by making use of the latest European satellite data (Sentinel-2). This complexity is due to local variations in ecological conditions, but also to anthropogenic factors that directly and indirectly influence land use dynamics. The methodological objective was to develop a new Geographic Object-based Image Analysis (GEOBIA) approach for mapping coastal areas using Sentinel-2 data and Landsat 8. By developing a new segmentation, accuracy measure, in this study was determined that segmentation accuracies decrease with increasing segmentation scales and that the negative impact of under-segmentation errors significantly increases at a large scale. An Estimation of Scale Parameter (ESP) tool was then used to determine the optimal segmentation parameter values. A popular machine learning algorithms (Random Forests-RFs) is used. For all classifications algorithm, an increase in overall accuracy was observed with the full synergistic combination of available data sets.

藏东昌都红层滑坡的地质成因模式

藏东昌都红层紧邻北澜沧江结合带(LCS),是近年来新厘定的红层岩系。为进一步丰富和完善红层及滑坡灾害研究,文章基于翔实的现场调查,从构造地质学角度约束滑坡发育的边界条件,总结归纳了藏东昌都红层滑坡的地质成因模式,并对不同类型滑坡典型案例进行了剖析。结果表明:受区域造山作用影响,藏东昌都红层掀斜,发育大量透入性构造面,导致岩体物理力学性能弱化。藏东昌都红层滑坡的地质成因模式主要包括原生层理型、层理断层型、层理节理型、褶皱节理型和断层节理型等5类。构造面是红层滑坡发育的主控因素,建议在明确研究区构造演化过程及构造框架的基础上,精细刻画滑坡区构造面发育特征。研究成果可为揭示滑坡发育的内在机制及监测预警、工程防治等提供理论支撑。

基于语义的湘鄂川黔苏区红色记忆知识发现研究

革命苏区红色记忆资源价值挖掘和知识发现是实现红色文化活化利用的必经之举,迫切需要采用语义技术等现代信息技术。文章在调研湘鄂川黔苏区红色记忆知识发现需求基础之上,基于语义本体、RDF技术构建了涵盖数据层、语义层、关联层、应用层的湘鄂川黔苏区红色记忆知识发现体系,建立了湘鄂川黔苏区红色记忆本体模型并搭建了知识发现平台,以期为其他苏区传承、开发红色记忆资源提供技术借鉴。

滇西剑川始新世粗面岩及其包体成因:印度-欧亚大陆碰撞过程的约束和大地构造意义

新生代以来,印度-欧亚大陆碰撞导致青藏高原发生大规模隆升和岩石圈挤出,这一过程引发了金沙江-哀牢山-红河构造带等深大断裂带的大规模剪切走滑,并沿该构造带发生强烈的碱性岩浆作用。这些始新世碱性岩记录了印度-欧亚大陆的早期碰撞过程,因而可以作为研究青藏高原早期隆升和岩石圈挤出过程及其深部动力学机制的重要“探针”。本文针对剑川盆地甸南地区始新世粗面岩及其二长岩包体和辉长岩包体开展了系统的锆石U-Pb年代学、Lu-Hf同位素和全岩主-微量元素和Sr-Nd同位素组成研究。锆石U-Pb定年结果显示,剑川盆地甸南粗面岩形成时代为36Ma;其内部包含的两件二长岩包体的形成年龄分别为41.6±3.4 Ma和35.7±0.3 Ma,一件辉长岩包体的形成时代为35.8±0.2 Ma。地球化学研究结果显示,粗面岩与二长岩包体K_(2)O含量均较高,属于钾玄质系列岩石,且富集轻稀土元素(LREE)和大离子亲石元素(LILE),亏损高场强元素(HFSE)。结合锆石Hf同位素和全岩Sr-Nd同位素组成,表明甸南地区寄主粗面岩和二长岩包体来自相同的交代富集岩石圈地幔的部分熔融,并经历了不同程度的橄榄石和辉石分离结晶作用。包体研究显示,~41Ma二长岩包体为寄主粗面岩岩浆上升过程中捕获自早期围岩,而~36Ma二长岩包体为同源岩浆房内与围岩接触淬冷的早期结晶产物,它们被寄主粗面岩岩浆裹挟而存在其内部。堆晶辉长岩包体较寄主粗面岩和二长岩包体具明显低的K2O、稀土和微量元素含量,其全岩Nd同位素组成与剑川盆地二龙山橄榄玄武岩相似,但高于寄主粗面岩,表明其源自弱富集地幔的部分熔融,并在壳-幔过渡带堆晶形成。此外,~41 Ma碱性岩包体和碱性岩内46~38 Ma捕获锆石年龄,以及剑川盆地内近源沉积岩内碎屑锆石的同期年龄记录,均表明金沙江-哀牢山-红河碱性岩带的岩浆作用并非存在从高原内部向东南方向的滇西地区逐渐变年轻的趋势,而是印度-欧亚大陆碰撞过程中,岩石圈向东南向挤出导致兰坪-思茅地块和印支地块旋转挤出的响应。

重庆市不同BMI类型初中生零食摄入类型的差异研究

目的分析重庆市不同身体质量指数(BMI)类型初中生零食摄入类型的差异,为提高学生对零食的科学认知,针对不同体型的学生开展营养教育提供参考。方法本研究为现况调查,采用方便抽样方法,抽取重庆市所有区县300余所中学共计175513名初中生作为调查对象,匿名填写课题组设计的包括身高、体质量、零食摄入情况(红区零食、绿区零食)等信息的调查问卷。单因素分析采用t检验或方差分析进行组间比较;多因素分析采用线性回归。结果本研究调查对象的超重/肥胖发生率为17%,超重/肥胖学生摄入红区/绿区2类零食均较多。单因素分析结果表明,除住校情况不同的初中生红区零食得分差异无统计学意义外,不同社会人口学特征的初中生红区/绿区零食得分差异均有统计学意义(P<0.05)。多因素线性回归分析结果显示,摄入绿区零食与超重/肥胖呈负相关,摄入红区零食与超重/肥胖呈正相关(P<0.05)。学生摄入绿区零食越多,超重/肥胖发生率越低(β=-0.17,95%CI:-0.25~-0.08);学生摄入红区零食越多,超重/肥胖的发生率越高(β=0.13,95%CI:0.07~0.21)。在校正混杂因素后,以上结论也成立。结论超重/肥胖的学生摄入红区零食、绿区零食都较多,绿区零食是超重/肥胖的保护因素。提高初中生对零食的认知迫在眉睫,学校要加强开展营养健康教育,培养学生健康的零食习惯。

GNSS约束的红河断裂带现今三维闭锁耦合程度及时空演变特征研究

为研究红河断裂带近年来活动状态的演变特征,并分析该区域地震危险性,基于1999~2007年、1999~2017年2期GNSS速度场数据,采用负位错块体模型反演红河断裂带的闭锁程度与滑动亏损空间动态分布。结果表明,红河断裂带的闭锁程度具有两端强、中间弱的特点。红河断裂带北段和南段局部断层闭锁深度为20 km,闭锁程度较高;中段为浅层闭锁,闭锁深度为5 km。在滑动亏损方面,北段为2.5~5 mm/a,积蓄能量速度较快;中段为0.4~1.8 mm/a,南段为1.5~2 mm/a,中、南两段较为平稳。在2008年以后,红河断裂带整体闭锁特点不变,南、北两段深度闭锁状态开始向中间扩散,红河断裂带整体闭锁程度加深,同时滑动亏损速率有所增加,断层北段地震风险继续增大,而断层南段活动状态变得不稳定。

黑白红气候旋回与聚煤环境

关于成煤环境,多数学者认为发育于暖湿气候。但现代沉积却得出了不同的认识,认为寒冷气候更有利于固碳,这个矛盾的解决具有重要的科学意义。基于现代沉积理论,研究了泥炭、湿地、土壤有机质的分布特征,结合各地质年代煤的分布,分析了煤的发育与气候、纬度的关系。结果显示,煤、蒸发盐岩、红层和铝土矿作为气候敏感沉积物,可分别代表高纬度的冷湿气候、中纬度的干热气候和低纬度热带雨林气候,可指示不同古环境或古纬度。提出煤的发育和是否缺氧没有联系,红层及铝土矿的发育不是因为富氧;寒温带的纬向滑移控制了煤的分布;用气候敏感沉积物建立了黑白红气候旋回,并限定了聚煤环境。

红河断裂对莺歌海盆地地热系统的控制作用

基于莺歌海盆地地热背景,从地热系统的水源、流体通道、热储和盖层4个方面系统地去评价红河断裂对其的控热作用。研究结果表明,通过水样、气样分析,断裂构造在地热水循环中起到重要的控制作用;红河断裂的差异变形显著影响裂隙型热液热储的平面分布范围和纵向发育深度的异质性;莺歌海盆地地热系统是以地幔热物质作为主要热源,红河断裂带和盆地内中央凹陷底辟带为主要通道,裂隙型热液热储和上部大面积水道、海底扇、三角洲等储集体为主要热储,莺歌海组巨厚泥岩为主要盖层。

基于生态保护红线的生态安全格局构建与国土空间修复分区

国土空间生态修复分区有助于针对生态服务、农业生产、居民生活等功能分类施策,具有提高生境质量、保障区域生态安全、促进区域可持续发展的重要作用。该研究以福建省三明市为研究区,采用生态保护红线划定方法全域识别生态源地,构建生态源地扩展阻力评价体系,采用最小累积阻力模型判别生态廊道和生态节点,提取生态断裂点,从而构建三明市生态安全格局。根据生态安全等级划分和“三生空间”范围界定,进行生态修复分区,并提出针对性生态修复和保护建议。研究结果:1)三明市生态源地共有34处,面积2185.44 km^(2),约占三明市国土面积9.5%,围绕中部盆地分布于周边丘陵山地,北部为密集区。2)判别重要生态廊道和一般生态廊道分别为12和70条,提取重要生态节点和一般生态节点分别为30和47个,提取生态断裂点66个。三明市生态安全格局完整,生态安全水平总体较高,但南部地区廊道稀疏却断裂点密集,网络连通性较低。3)划分生态安全等级、叠加“三生空间”范围,将三明市划分成核心重点区(16.13%)、监测预警区(25.04%)、缓冲过渡区(35.53%)、保育防护区(23.30%)四大类12类生态修复小区。在此基础上,针对不同修复分区提出生态防护建议,以期达到南方丘陵地区维护区域生态安全、实现城市高质量发展的目标。

赣州市建设全国红色基因传承示范区路径研究

习近平总书记在党的二十大报告中强调“传承红色基因,赓续红色血脉”。赣州作为土地革命战争时期中央苏区的主体和核心区域,在中国共产党的革命历史上具有重要地位,蕴含着丰富的红色资源。2022年,国家发改委印发《赣州革命老区高质量发展示范区建设方案》,明确提出“弘扬革命精神,在传承红色基因上作示范”,赣州迎来建设红色基因传承示范区的重大历史机遇。赣州应充分发挥自身丰富的红色资源优势,从增强社会意识、健全体制机制、创新内容与方法、发展红色旅游等方面着手,建设全国红色基因传承示范区。

福建游击区红军构建抗日民族统一战线的认知历程——以闽西南红军游击区为中心的讨论

抗日民族统一战线是中国共产党带领全国人民取得战争胜利的三大法宝之一,它是抗战时期中国共产党在敌后战场得以立足的关键。也是马克思主义统战理论与中国革命实际相结合的产物。梳理福建红军游击队对于统一战线问题的认知变化,旨在管窥三年游击战争期间,南方八省红军游击队在寻求抗日统一战线建立过程中的路径、特点及其效果。