柴达木盆地北缘上石炭统碎屑岩—碳酸盐岩高频转换过程及驱动机制*

碎屑岩和碳酸盐岩分别产自“外源、浑水”与“内源、清水”环境,二者的交替互层沉积可反映古水体性质、物源供给及气候等环境要素的频繁改变。晚石炭世,柴达木盆地北缘构造相对稳定,盆内发育巨厚的、多级次嵌套的“碎屑岩—碳酸盐岩混积层系”,记录了“冰室地球”冰川活动下的古海平面大幅度升降和古气候、古环境频繁交替信息。文中以柴达木盆地北缘连续完整露头剖面和钻井取心剖面为研究对象,结合区域地质资料、前人研究成果,通过详细的岩心、露头及镜下薄片观察,在研究区重点层段识别出下切谷充填型碎屑岩沉积和碳酸盐岩台地沉积组成的频繁互层序列。碎屑岩—碳酸盐岩互层组合序列在垂向上的有序叠加,构成了复合海平面变化旋回层序,其从碳酸盐岩—改造型台地沉积开始,向上依次发育碎屑岩下切谷充填序列的底部冲积河道沉积、中部河口湾序列和顶部代表海泛面的泥岩沉积,最后转变为碳酸盐岩向海到向陆台地亚相,反映了一个显著的早期海退—中期逐渐海侵—后期再次海退的旋回过程。冰川期急剧变冷的气候和冰川型高频的大幅度海平面升降,驱动滨线及相带迁移,影响到碎屑岩供给速率和碳酸盐生产率,造成了碎屑岩—碳酸盐岩的高频转换。     

新疆西天山伊犁地块晚古生代火山岩地质特征及构造意义

对新疆西天山伊犁盆地晚古生代火山岩时空分布和地质特征、岩石化学等进行系统总结,认为该盆地晚古生代火山岩主要由晚泥盆世至早二叠世的火山岩组成,其形成与南北天山洋盆演化有关.晚泥盆—早石炭世大哈拉军山组火山岩为天山南北洋盆大洋板块俯冲而成的钙碱性火山岩,晚石炭世伊什基里克组火山岩为挤压环境向拉张环境过渡的钙碱性火山岩和碱性火山岩,早二叠世乌郎组火山岩为后造山具裂谷特征的双峰式火山岩组合.     

Characteristics of groundwater in Northeast Qinghai-Tibet Plateau and its response to climate change and human activities: A case study of Delingha,Qaidam Basin

Delingha is located in the northeast margin of Qaidam Basin. Bayin River alluvial proluvial fan is the main aquifer of Delingha, in which groundwater generally flows from north to south. The hydrochemistry results showed that two different hydrochemical evolution paths formed along southeast and southwest directions, respectively. Cl-Na type groundwater was formed in front of Gahai Lake, and SO₄·HCO₃-Na·Ca type groundwater was formed in front of Keluke Lake. The results of deuterium (D) and ¹⁸O revealed that the groundwater mainly originated from the continuous accumulation of precipitation during geological history under cold and humid climate conditions. In addition, results of ¹⁴C indicated that the groundwater age was more than 1140 years, implying relatively poor renewal capability of regional groundwater. Moreover, our numerical modeling results showed that the regional groundwater level will continue to rise under the warm and humid climate conditions.© 2021 China Geology Editorial Office.     

柴达木盆地东北部晚古生代盆地构造环境:来自碎屑岩地球化学的证据

在对采集到的27件碎屑岩主微量元素系统测试与分析的基础上,结合前人已有研究成果,对柴达木东北部晚古生代盆地构造环境及原型盆地类型进行讨论。研究表明:较大陆上地壳,柴达木东北部地区上古生界碎屑岩整体呈现SiO2含量富集、其余主量氧化物亏损的特点,稀土元素含量整体偏低,但与大陆上地壳具有极为类似的分配型式,微量元素中相容元素整体强烈亏损,大离子亲石元素中等亏损,高场强元素无亏损-弱亏损。主量元素、微量元素含量及特征比值显示,测试样品与被动大陆边缘砂岩具有极为接近的地球化学特点,并且显示出与其他构造环境沉积物地球化学特征差别极为明显的特点。相关构造环境及物源岩石组合判别图解同样表明：柴达木东北部地区晚古生代持续发育被动大陆边缘盆地,物源区岩石几乎不存在中基性物质的加入且以大陆上地壳中酸性岩类为主。在地球化学分析的基础上,结合前人对岩石学特征、沉积相类型与沉积对比、古流向以及锆石年代学的工作,综合认为,柴达木东北部地区晚古生代为一个向北倾斜的被动大陆边缘海盆,其物源区为加里东造山运动形成的柴北缘加里东期造山带,海侵来自宗务隆裂陷海槽且自北向南进行。     

海拉尔盆地基底晚古生代adakite的发现及其地质意义

海拉尔盆地的前中生代基底隶属中亚造山带东段的兴蒙造山带。 在盆地基底地层中发现了具有adakite成分特征的粗面安山岩、英安岩和闪长玢岩。 这些火成岩与晚古生代沉积地层交互或伴生, 共同构成晚中生代裂陷盆地的基底。 地球化学研究表明, 这些火成岩基本上属于高钾钙碱性和准铝质岩石系列, 具有高SiO₂和Al₂O₃含量, 高Sr、Sr/Y和La/Yb值, 富集轻稀土(LREE), 亏损重稀土(HREE)、Y和高场强元素(HFSE),Eu表现弱的负异常或轻微的正异常, 相容元素Mg、Cr和Ni含量低, 这些特征与增厚下地壳部分熔融成因的adakite非常相似, 而明显不同于典型的由俯冲洋壳熔融形成的adakite。 样品的(⁸⁷Sr/⁸⁶Sr)_i值基本一致,为0.7041, (¹⁴³Nd/¹⁴⁴Nd)_i值为0.51243~0.51247, ε_Nd (t)为正值(+3.7~+4.5), 显示其岩浆源区可能源于弱亏损地幔, 或亏损地幔受到地壳物质混染。 本文认为海拉尔地区晚古生代adakite型岩浆很可能是由当时新底侵的玄武质下地壳在角闪岩相向榴辉岩相过度或榴辉岩相条件下部分熔融形成。 这些adakite岩石的出现反映了兴蒙造山带晚古生代受到了古亚洲洋的俯冲消减引起的强烈的地幔玄武质岩浆底侵作用, 并由此导致地壳垂向上显著的增生加厚过程。     

嫩江黑河构造带收缩与伸展——源自晚古生代花岗岩类的地球化学证据

黑龙江省嫩江至黑河一带发育大量的晚古生代花岗岩类岩石,同位素测年结果显示主要集中在3个时代:早石炭世、晚石炭世和早二叠世。岩石类型从花岗闪长岩-二长花岗岩-正长花岗岩-碱长花岗岩等均有不同出露,石炭纪部分岩石遭受韧性剪切变质变形作用改造形成花岗质糜棱岩。岩石整体具有高硅、富钾钠特征;稀土元素总量偏高,铕负异常明显;微量元素具明显的大离子亲石元素(LILE)K、Rb、Th富集和高场强元素(HFSE)Nb、P、Ti亏损特征。其中石炭纪花岗岩类地球化学特征显示陆缘弧及同碰撞花岗岩特点,二叠纪花岗岩则表现后造山花岗岩特点。二者反映了由碰撞造山向板内后造山阶段转变的构造环境特点,也反映了嫩江-黑河构造带汇聚拼合与伸展的活动史。     

大别山北麓与华北上古生界稀土元素特征的对比研究

采用等离子体光谱方法测试了大别山北麓和华北东南部晚古生代砂泥岩样品的稀土元素含量，结果表明，大别山北麓石炭系样品具微弱的Eu负异常，δEu为0．915，分布曲线基本上呈近似直线或呈左高右低的宽缓的弧型；华北石炭－二叠系样品具明显的Eu负异常，δEu为0．637，分布曲线基本上呈左高右低的宽缓的“V”型，两者的稀土元素地球化学特征存在明显差异，根据稀土元素特征和其他地质资料，认为两者沉积物质的来源具有差异，在晚古生代，两者的物源没有联系，大别山北石炭系沉积的物源主要来自不成熟的上地壳的岛弧体系，反映华北板块南缘的活动大陆边缘性质，淮南矿区晚古生代沉积的物源主要来自北部成熟的上地壳，反映华北板块板内稳定的地台沉积。δ     

Late Paleozoic retrograded eclogites from within the northern margin of the North China Craton: Evidence for subduction of the Paleo-Asian ocean

Retrograded eclogites from the central part of the northern margin of the North China Craton, Hebei Province, China occur as separate tectonic lenses or boundins within garnet–biotite–plagioclase gneisses of the Paleoproterozoic Hongqiyingzi Complex characterized by amphibolite facies paragneisses. The petrographic features and mineralogical compositions represent three main metamorphic stages: (1) the peak eclogite facies stage (P > 1.40–1.50 GPa, T = 680–730 °C), (2) the granulite facies stage and (3) the amphibolite facies stage (P = 0.67–0.81 GPa, T = 530–610 °C) formed during decompression. The major and trace element and Sm–Nd isotopic data suggest that most of the retrograded eclogite samples had protoliths of tholeiitic oceanic crust with geochemical characteristics of mid-ocean ridge basalt (MORB) or island arc tholeiite (IAT) environment, and were contaminated by crustal components during subsequent subduction. Zircon SHRIMP isotopic dating of two different textural varieties of retrograded eclogite defines a weighted mean age of 325 Ma, which is interpreted as the peak metamorphic age of the eclogites and reflects the occurrence of eclogite facies metamorphism related to subduction of Paleo-Asian Oceanic crust beneath the North China Craton during the Late Paleozoic. Finally, we show that the retrograded eclogite from Hebei Province is not related to the Baimashi retrograded eclogite at the northern foot of the Heng Mountains, approximately, 300 km to the southwest.     

A Reconstruction for the Late Paleozoic Tectonic Evolution of the Tekes Daban Area, Western Tianshan Mountains: Evidence from Unconformities

The identification of unconformities is the key to reconstructing tectonic evolution, revealing crust movement and establishing tectonic cycle. For a long time, there were some controversial issues on the episodes of Variscan cycle (especially on the period of Carboniferous-Permian stages) of the Tianshan area. The essential questions fall on the numbers and property of unconformities in this area, for example, in the western Tianshan area. Previous research only recognized three or four fold movements. Detailed regional geological mapping of 1:50000 in the Tekes Daban area, western Tianshan have allowed us to characterize the seven unconformities within the Carboniferous-Permian strata and understand its implications for tectonic reconstruction of the Tianshan orogen. Seven angular unconformities, which indicate that seven tectonic episodes occurred in the Late Paleozoic Period, were identified in this area. Therein, the newly discovered unconformities based on the angle-unconformity between the Dongtujinhe and Keguqinshan Formations, and angle-unconformity between the Wulansayi and Wulang Formations, respectively indicates the Tekes episode and Gongliu episode. The unconformity between the Dongtujinhe and Yishijilike Formations is angle-unconformity instead of parallel unconformity indentified by previous research, so the former Bogda ascending can be revised as Bogda movement. Therefore, these newly identified seven episodes, including the Tekes episode, suggest that there are seven tectonic movements in the Tianshan area at least. This has significant implications for reconstruction of the Late Paleozoic tectonics in the Tianshan Area, NW China     

鄂尔多斯盆地东北缘准格尔煤田煤中超常富集勃姆石的发现

运用X射线衍射分析(XRD)、带能谱仪的扫描电镜(SEM-EDX)和光学显微镜等技术,首次在鄂尔多斯盆地东北缘准格尔矿区6号巨厚煤层中发现了超常富集的勃姆石及其特殊的矿物组合,勃姆石含量可高达13.1%,与勃姆石伴生的矿物有磷锶铝石、锆石、金红石、菱铁矿、方铅矿、硒铅矿和硒方铅矿。重矿物的组合特征与华北地区本溪组铝土矿中的重矿物组合特征相似,高含量的勃姆石主要来源于聚煤盆地北偏东方向本溪组风化壳铝土矿,三水铝石以胶体溶液的形式从铝土矿中被短距离带入泥炭沼泽中,在泥炭聚积阶段和成岩作用早期经压实作用脱水凝聚而形成勃姆石。     

青藏高原北缘的隆升时期——来自阿尔金山和柴达木盆地的证据

根据柴达木盆地西部中新世上、下油砂山组的沉积特征及其地震反射界面的特征,推断阿尔金山的主隆升时期为中晚中新世,山体的隆升导致盆地沉积中心向东迁移.盆地周缘山系的隆升年代学资料也表明,青藏高原北缘在中晚中新世发生了快速抬升,与青藏高原南部的同期区域构造事件一致,表明中晚中新世是青藏高原向北生长的重要时期.阿尔金山此次隆升事件与塔里木板块向柴达木地块楔入有关,整个高原的隆升动力源自印度板块与欧亚大陆拼合后持续向北的俯冲.     

Determination of the early Paleozoic accretionary complex in Southwestern Yunnan,China: Implications for the tectonic evolution of the Proto-Tethys Ocean

Accretionary complex study provides important knowledge on the subduction and the geodynamic processes of the oceanic plate, which represents the ancient ocean basin extinction location. Nevertheless, there exist many disputes on the age, material source, and tectonic attribute of the Lancang Group, located in Southwest Yunnan, China. In this paper, the LA-ICP-MS detrital zircon U–Pb chronology of nine metamorphic rocks in the Lancang Group was carried out. The U–Pb ages of the three detrital zircons mainly range from 590–550 Ma, 980–910 Ma, and 1150–1490 Ma, with the youngest detrital zircons having a peak age of about 560 Ma. The U–Pb ages of the six detrital zircons mainly range from 440–460 Ma and 980–910 Ma, and the youngest detrital zircon has a peak age of about 445 Ma. In the Lancang Group, metamorphic acidic volcanic rocks, basic volcanic rocks, intermediate-acid intrusive rocks, and high-pressure metamorphic rocks are exposed in the form of tectonic lens in schist, rendering typical melange structural characteristics of “block + matrix”. Considering regional deformation and chronology, material composition characteristics, and the previous data, this study thinks the Lancang Group may be an early Paleozoic tectonic accretionary complex formed by the eastward subduction of the Changning-Menglian Proto-Tethys Ocean, which provides an important constraint for the Tethys evolution.©2023 China Geology Editorial Office.     

显微荧光光谱技术在油气成藏研究中的应用——以塔里木盆地巴什托上古生界油气藏为例

根据原油在紫外光的激发下产生荧光的特点,通过显微荧光光谱方法,对有机包裹体的荧光光谱进行定量化分析,利用其主峰波长与荧光强度、主峰波长与红/绿商的相关性,对塔里木盆地巴什托上古生界油气藏的成藏特征进行了初步研究。在研究区所采集的32块岩石样品中共获得64个荧光光谱数据。分析结果表明,巴什托上古生界油气藏存在3个油源,其主峰波长主要集中在439~443nm、469~472 nm和498~503 nm三个值段上,且为不同演化阶段的混源充注。前两者来自于寒武—奥陶系烃源岩,由下至上充注成藏;后一油源来自于石炭系巴楚组,随演化程度的变化同时向上、下两个方向充注。综合同期捕获不同主峰波长的有机包裹体,推测研究区至少存在4期油充注、1期天然气充注。     

银川盆地PL02钻孔孢粉记录的晚上新世-早更新世时期的古气候变化周期

晚上新世-早更新世时期是全球环境发生转折的重要过渡时期。银川盆地位于中国西北内陆地区,同时又处于干旱与半干旱区域的交界地带,在盆地内部蕴藏着丰富的新生代沉积,是研究古环境演化的理想区域,深度为720.77 m的PL02钻孔位于盆地内部的沉降中心附近,属于典型沉降盆地的洪泛沉积环境。本文选取银川盆地PL02钻孔下部(深度705.7~247.9 m)晚上新世-早更新世时期(古地磁年龄3.3~1.5 Ma)的孢粉、磁化率及粒度等指标,通过孢粉分析、频谱分析和小波变换等方法,恢复了银川盆地晚上新世-早更新世时期的古环境演化特征,并对该时期的古气候变化周期进行分析。研究结果显示：银川盆地在晚上新世时期(约2.8 Ma)气候已经开始逐渐变冷变干;进入早更新世时期(约2.6 Ma),研究区气候变得更加干旱并且冷暖波动较大;同时,孢粉、磁化率和粒度等指标均反映出银川盆地晚上新世-早更新世时期古气候变化具有较显著的约20 ka的岁差周期与约40 ka的地轴倾角周期,但约100 ka的地球轨道偏心率周期仅在个别指标中有所表现。另外,本研究结果与中国黄土高原和深海氧同位素记录所揭示的晚上新世-早更新世时期气候变化周期较为一致。因此,认为银川盆地在该时期的气候波动可能受到了地球轨道因素的影响,且与全球环境变化具有相似性。

     

地球化学记录揭示的柴达木盆地北缘地区中—晚侏罗世古环境与古气候*

沉积岩的地球化学特征是古环境变化良好的示踪剂,柴达木盆地北缘地区侏罗系记录了中国西北地区古环境、古气候演化的重要信息。本研究通过对柴达木盆地北缘地区大煤沟侏罗系标准剖面沉积岩的元素地球化学分析,尝试恢复了研究区中—晚侏罗世的古环境特征。结果显示:(1)研究区中—晚侏罗世以富氧的浅水环境为主,仅在短期内出现较深湖相沉积;整体上侏罗纪湖盆水体盐度较低,而部分层段沉积物盐度增大系降雨量相对减小导致。(2)基于多元地球化学参数建立的古气候演化曲线表明,中—晚侏罗世柴达木盆地北缘地区古气温、古湿度均在一定幅度内频繁变化;自中侏罗世晚期开始,研究区古气候开始由温暖潮湿向炎热干旱转变,至晚侏罗世进入了干热环境主导的阶段。多元地球化学参数剖面的建立为中国西北地区中—晚侏罗世“干热化事件”和区域古气候的研究对比提供了新的证据和材料。     

Landslides as a geomorphological proxy for climate change: A record from the Dolomites (northern Italy)

The periphery of the Qinghai-Tibet Plateau is renowned for its susceptibility to landslides. However, the northwestern margin of this region, characterised by limited human activities and challenging transportation, remains insufficiently explored concerning landslide occurrence and dispersion. With the planning and construction of the Xinjiang-Tibet Railway, a comprehensive investigation into disastrous landslides in this area is essential for effective disaster preparedness and mitigation strategies. By using the human-computer interaction interpretation approach, the authors established a landslide database encompassing 13003 landslides, collectively spanning an area of 3351.24 km² (36°N-40°N, 73°E-78°E). The database incorporates diverse topographical and environmental parameters, including regional elevation, slope angle, slope aspect, distance to faults, distance to roads, distance to rivers, annual precipitation, and stratum. The statistical characteristics of number and area of landslides, landslide number density (LND), and landslide area percentage (LAP) are analyzed. The authors found that a predominant concentration of landslide origins within high slope angle regions, with the highest incidence observed in intervals characterised by average slopes of 20° to 30°, maximum slope angle above 80°, along with orientations towards the north (N), northeast (NE), and southwest (SW). Additionally, elevations above 4.5 km, distance to rivers below 1 km, rainfall between 20‒30 mm and 30‒40 mm emerge as particularly susceptible to landslide development. The study area’s geological composition primarily comprises Mesozoic and Upper Paleozoic outcrops. Both fault and human engineering activities have different degrees of influence on landslide development. Furthermore, the significance of the landslide database, the relationship between landslide distribution and environmental factors, and the geometric and morphological characteristics of landslides are discussed. The landslide H/L ratios in the study area are mainly concentrated between 0.4 and 0.64. It means the landslides mobility in the region is relatively low, and the authors speculate that landslides in this region more possibly triggered by earthquakes or located in meizoseismal area.     

宁夏清水河盆地晚更新世两期湖相沉积物的形成时代、沉积环境及构造背景

为了解宁夏清水河盆地晚更新世以来的沉积、构造演化规律,采用钻探、粒度分析、光释光测年等技术,对盆地中部发现的2期晚更新世湖相地层进行了沉积学、年代学研究。结果表明,下部湖相地层萨拉乌苏组的形成时代为76~63 ka,上部湖相地层水洞沟组形成时代为25~11 ka,二者之间存在明显的侵蚀面。根据沉积证据和粒度分析结果,将萨拉乌苏组自下而上划分为4个沉积阶段,构成了一个完整的湖进-湖退序列,代表了一期温暖湿润的气候环境;而水洞沟组为干冷环境下形成的浅湖。构造、环境对比分析表明,清水河盆地2期古大湖的形成、消亡指示该地区晚更新世经历了拉张-挤压-拉张的构造转换。两次拉张作用是萨拉乌苏湖和水洞沟湖形成的主要因素,古大湖发育的间断期存在的强烈构造隆升事件是导致萨拉乌苏湖消亡的根本原因,末次冰期MIS4和MIS2晚期的异常寒冷气候也是古湖衰退的原因之一。清水河盆地2期古湖的演化规律,为研究青藏高原周缘晚更新世古大湖形成与演化、古气候变迁及青藏高原的隆升提供了重要的证据。     

吉黑东部晚古生代构造体制转换: 来自佳木斯-兴凯地块的双增生杂岩及岛弧岩浆岩带的制约

佳木斯-兴凯地块是吉黑东部地区至关重要的地质组成单元, 其东缘和西缘分别平行对称分布着两条晚古生代岛弧岩浆岩带和中生代增生杂岩带, 它们是古亚洲洋闭合向古太平洋俯冲-增生构造体制转换的关键地质记录。本文对佳木斯-兴凯地块西缘吉黑高压带中的青龙村群斜长角闪岩进行了系统的岩石学、锆石年代学和全岩地球化学研究, 结果表明青龙村斜长角闪岩原岩为拉斑系列玄武岩, 其原岩时代为~260Ma, 具有富集型洋中脊玄武岩(E-MORB)的地球化学特征。同时结合前人对佳木斯地块东缘和西缘分布的大量晚古生代岛弧岩浆岩以及增生杂岩的研究, 本文识别出佳木斯-兴凯地块东、西缘的"双带双弧"结构。"双带"即东缘和西缘平行对称分布的那丹哈达增生杂岩带和吉黑高压变质带, "双弧"则是东缘和西缘同样平行对称分布的早-中二叠世和中-晚二叠世岛弧岩浆岩带。通过对双带双弧的组成、形成时代以及构造背景的研究, 进一步为吉黑东部地区晚古生代时期的古大洋构造体制转换提供新的证据, 并重建了中亚造山带东缘晚古生代到早中生代的构造演化历史。     

四川盆地及周缘下古生界海相页岩气富集高产主控因素——以焦石坝地区五峰组—龙马溪组为例

利用钻井、地震及样品实验数据资料,首先对焦石坝地区五峰组—龙马溪组页岩气的形成条件进行了评价,然后探讨了四川盆地及周缘下古生界海相页岩气富集高产主控因素。研究认为:焦石坝地区五峰组—龙马溪组泥页岩具有厚度大、有机质丰度高、类型好、热演化程度较高、储集物性以及含气性好、以及良好保存条件和可压性等特点;四川盆地及周缘下古生界海相页岩气富集高产主控因素是富有机质泥页岩的发育程度、保存条件、天然裂缝的发育和泥页岩的可压裂性等,因为富有机质泥页岩的发育为页岩气的生成和储集提供了丰富的物质基础,良好的保存条件是页岩气富集的关键,天然裂缝和可压裂性是高产的重要保证。     

内蒙古温都尔庙地区晚古生代石炭系沉积背景:沉积岩石学、古生物学及锆石U-Pb测年证据

苏尼特右旗温都尔庙地区作为内蒙古兴蒙造山带南侧晚古生代构造研究的重点区域,对其研究有助于了解区内盆地的沉积年代、物质来源和构造演化等问题。选择区内石炭系酒局子组、阿木山组进行剖面、古生物以及LA-ICP-MS U-Pb定年等系统研究。分析结果显示:两组地层锆石年龄均在440Ma±,具有岩浆锆石特征,锆石磨圆分选特征均显示盆地有快速沉积、近源沉积的特征。酒局子组为一套滨浅海--沼泽-湖相沉积,磨圆分选差,局部含煤层;阿木山组为一套滨-浅海沉积环境下以灰岩为主的碳酸盐岩沉积地层。两组地层中发现了Neuropteris pseudovata、Callipteridium sp.及Schubertella sp.、Psedoschwagerina borealis等典型的晚石炭世-早二叠世植物、筳类化石。