鄂尔多斯地块西南缘中元古代玄武安山岩地球化学特征及其构造意义     

高山林  刘士林  张仲培 《地质论评》2022,68(4):2022082004-2022082004

铁马河玄武安山岩位于鄂尔多斯地块西南缘,沿六盘山东麓断裂带出露。岩石发育气孔和杏仁状构造,具有斑状结构—间隐结构,斑晶主要为长条状斜长石和少量蚀变暗色矿物。岩石地球化学呈现富Na2O、FeOT、Al2O3,贫MgO、TiO2、K2O的特点,稀土配分曲线为右倾轻稀土富集型,LREE/ HREE=6. 50~7. 01,(La/Yb)N为5. 62~7. 14,富集Ba、Th、U、K等大离子亲石元素,Nb、Sr和Ti相对亏损,δEu= 0. 69~0. 91。样品n（87Sr)/n(86Sr)i为0. 70587~0. 70934,εNd(t)介于-6. 9 ~ -4. 8之间,TDM为2562~2730 Ma,Nb/Ta（6. 60~8. 25）低于大陆地壳的平均值,指示了受俯冲流体改造的古老富集地幔参与了岩浆形成。SHRIMP锆石U- Pb定年结果显示铁马河玄武安山岩形成于中元古代早期（~1740 Ma）,其形成与研究区中元古代早期陆内伸展作用引起的古老岩石圈地幔减压熔融有关,是华北克拉通陆内裂谷发育过程在鄂尔多斯地块西南缘的体现。  相似文献   

Petrogenesis of Early Permian Intrusive Rocks from Southeastern Inner Mongolia, China: Constraints on the Tectonic Framework of the Southeastern Central Asian Orogenic Belt     

QIAN Cheng  LU Lu  SHI Lu  DU Jiyu  WANG Yan  YANG Xiaoping  ZHANG Yujin 《《地质学报》英文版》2022,96(5):1566-1586

The late Paleozoic tectonic framework of the southeastern Central Asian Orogenic Belt is key to restricting the accretion orogeny between the Siberia Craton and the North China Craton. To clarify the framework, petrogenesis of early Permian intrusive rocks from southeastern Inner Mongolia was studied. Zircon U-Pb dating for bojite and syenogranite from Ar-Horqin indicate that they were emplaced at 288–285 Ma. Geochemical data reveal that the bojite is highly magnesian and low-K to middle-K calc-alkaline, with E-MORB-type REE and IAB-like trace element patterns. The syenogranite is a middle-K calc-alkaline fractionated A-type granite and shows oceanic-arc-like trace element patterns, with depleted Sr-Nd-Hf isotopes, (87Sr/86Sr)I = 0.7032–0.7042, εNd(t) = +4.0 to +6.6 and zircon εHf(t) = +11.14 to +14.99. This suggests that the bojite was derived from lithospheric mantle metasomatized by subducted slab melt, while the syenogranite originated from very juvenile arc-related lower crust. Usng data from coeval magmatic rocks from Linxi?Ar-Horqin, the Ar-Horqin intra-oceanic arc was reconstructed, i.e., initial transition in 290–280 Ma and mature after 278 Ma. Combined with regional geological and geophysical materials in southeastern Inner Mongolia, an early Permian tectonic framework as ‘one narrow ocean basin of the PAO’, ‘two continental marginal arcs on its northern and southern’ and ‘one intra-oceanic arc in its southern’ is proposed.  相似文献   

Oldest Basement (ca. 462 Ma) in Indonesian Borneo and its Implication for Early Paleozoic Tectonic Evolution of SE Asia     

ZHU Junbin  LI Shan  Sayed MURTADHA 《《地质学报》英文版》2022,96(6):2093-2104

The lack of preserved basement results in uncertain placements of many terranes in Southeast Asia. Here, we flag the first evidence of the oldest basement in Indonesian Borneo, which can help locate terranes in Borneo on the northern margin of Gondwana in the early Paleozoic and explain the regional tectonic setting of the island. Two schist samples from the Embuoi Complex in the Semitau Block, Northwest Kalimantan yielded zircon U-Pb dates of 453.3 ± 1.9 Ma and 462.4 ± 2.6 Ma, respectively, representing the formation time of the protolith. Petrographic, internal structural and high Th/U ratios of zircons indicate that the protolith of schists is of magmatic origin. The zircons have εHf(t) values of ?4.1 to +1.1 and Hf model ages of 1.37–1.69 Ga, indicating they were derived from a mixed source of juvenile crust with old components. By comparison of zircon age distribution, two-stage Hf model ages and εHf(t) variations of the early Paleozoic igneous rocks from Semitau with those of South China, Tengchong–Baoshan, and Indochina, the Semitau Block was most likely a part of or placed next to the Indochina Block of northern Gondwana during the early Paleozoic. Such a similar tectono-magmatic pattern on northern Gondwana formed a prolonged early Paleozoic arc-related belt associated with subduction of the Proto-Tethyan Ocean.  相似文献   

基于透明地质的唐家会煤矿奥灰水防治技术     

高耀全  高银贵  陆自清  孔皖军 《煤田地质与勘探》2022,50(1):101-108

唐家会煤矿6号煤开采面临导水断层多、隐伏导水构造发育,奥陶纪灰岩(简称奥灰)水害防治难度大的问题。经过不断的探索和实践,唐家会煤矿引进多种先进技术,获取大量地质、水文地质数据,构建智能地质保障系统,形成“物探钻探探查、井上下联合注浆治理、孔中瞬变电磁精细探查、注浆效果孔间电阻率检测、煤层底板微震电法联合监测”的技术思路。通过融合各类静态数据、动态数据、实时数据,完成断层、破碎带、含水层、低阻异常区等充水因素的数字建模,使地质要素、钻探物探数据可视化、透明化,以此为依托,建立一套基于透明地质的奥灰水害全时空防治体系,实现带压开采条件下奥灰水害的精细探查、靶向治理、效果检测和回采监测,取得了良好的应用效果。   相似文献   

粤东地区侏罗纪代表性剖面火山岩成因：对古太平洋板块俯冲早阶段的地质响应     

岳晓涵  刘磊  张治国  赵增霞  孙杰  赵阳 《高校地质学报》2022,28(2):199-210

通常认为中国东南部大规模分布的白垩纪火成岩是古太平洋板块俯冲作用晚阶段的产物,而俯冲过程早阶段的地质响应形式尚不明确。研究针对中国东南部侏罗纪火山岩规模最大的粤东地区代表性剖面开展了年代学及岩石成因研究,锆石U-Pb年代学研究表明该地区侏罗纪火山岩断续形成于192~183 Ma（嵩灵组）、177~163 Ma（吉岭湾组）和162~156 Ma（高基坪群）。结合前人研究数据,中国东南部晚中生代火山岩表现出沿粤东—闽东—浙东南方向的年轻化趋势。锆石Lu-Hf同位素分析表明,粤东地区侏罗纪火山岩主要源于古元古代地壳基底物质的重熔,并有不同程度的亏损幔源物质贡献,从早侏罗世到晚侏罗世亏损幔源物质贡献的比例呈现出由高到低的规律性变化。粤东地区侏罗纪火山岩岩石成因的规律性变化暗示了地壳应力环境的伸展程度逐渐减弱,对应了古太平洋板块的前进式俯冲。综合分析表明,粤东地区侏罗纪火山岩是古太平洋板块俯冲早阶段的地质产物,反映古太平洋板块俯冲作用开始于早侏罗世左右。  相似文献   

地震预警仪观测地脉动差异与评估场地条件的可行性研究     

师黎静  崔迪宇  刘佳轩  高凯 《震灾防御技术》2022,17(3):502-515

根据台站场地条件进行地震动参数校正,有助于提高地震预警的有效性和准确性。针对我国地震预警台网中部分台址场地条件信息不完整及观测仪器的多样性,通过采用不同灵敏度的力平衡式加速度仪、速度仪和MEMS烈度仪,同时进行大量不同类别场地的地脉动观测,多角度对比分析时、频差别,探讨基于地震预警仪观测地脉动评价场地条件的可行性。结果表明,加速度仪灵敏度越高,H/V谱比卓越频率越易识别;速度仪与力平衡式加速度仪观测的地脉动,三分向傅氏谱和H/V谱比的谱形与卓越频率均一致;与TAG-33M强震仪相比,TMA-53烈度仪观测的地脉动整体幅值略高,波形较差,但随着振幅增大趋于一致;在近80%的场地上,TAG-33M强震仪与TMA-53烈度仪观测的地脉动傅氏谱卓越频率相差＜0.5 Hz;当幅值均方根值＞0.05 Gal时,TAG-33M强震仪与TMA-53烈度仪观测的地脉动竖向和水平向傅氏谱均趋于一致;当幅值均方根值为0.02 Gal～0.05 Gal时,TAG-33M强震仪与TMA-53烈度仪观测的地脉动竖向和水平向傅氏谱谱形均有较高的相似性;当幅值均方根值＜0.02 Gal时,TAG-33M强震仪与TMA-53烈度仪观测的地脉动傅氏谱谱形相差较大,相似性低;依据TAG-33M强震仪观测地脉动H/V谱比的卓越频率判定场地类别,准确率达83.3%;TMA-53烈度仪观测地脉动的H/V谱比过于平坦,大多数场地上卓越频率识别困难。  相似文献   

金星:认识早期地球的窗口     

陈乐  张少兵  余金霏 《地球与行星物理论评》2022,53(1):66-84

无论在行星大小、质量还是轨道速度等方面,金星都是太阳系中与地球最相似的行星.自1960年代初期开始,金星一直是人类深空探测的重要目标.本文简要地回顾了人类探索金星的历史,总结了对金星已有的认识,梳理了金星的主要科学问题,最后介绍了未来的国际探测计划,并建议了我国的金星探测目标.早期对金星的探测以苏联的金星计划(Венера)和美国的水手系列(Mariner)为代表,后期的探测器以欧盟、日本等国家的“金星快车(Venus Express)”、“拂晓号(Akatsuki)”为代表.这些探测结果为我们认识金星大气成分、地表地形和内部结构提供了重要的数据.金星的大气组成以CO₂为主,含少量N2,与现在地球的大气组成显著不同,类似早期地球的大气组成.虽然金星地表目前没有液态水,但部分理论模拟工作表明金星地表可能曾经有液态水.一系列探测器对金星地表成分的分析表明,金星地表主要由玄武岩组成.在地形地貌方面,由于金星特殊的地表环境,金星表面风化作用对地表地貌影响很小.金星的地表主要受控于比较年轻的火山作用,发育了许多不同于地球的地貌特征,主要包括区域平原、盾状火山平原、冕状地形以及瓦片状地形等,其动力学机制可能是地幔柱—岩石圈相互作用或地幔对流,至今未发现与板块构造相关的地貌.现阶段金星没有太多大型的、活跃的火山热点,虽然无法估测准确的火山活动速率,但相比地球来说火山活动速率小很多.在内部结构方面,金星具有与地球类似的核幔壳结构.金星的内部组成也与地球类似,例如金星地幔很可能是与地球相似的橄榄岩成分.不存在内部磁场和缺乏板块构造是金星区别于地球的两个重要特征.关于金星为什么没有自身磁场,主流观点是金星地核缺乏对流,无法演化出磁场.而针对金星为什么没有演化出板块构造,目前认为主要有三个可能的原因:地表温度过高,没有软流圈,金星缺乏液态水,其中液态水的缺乏接受度最广.从大气组成、地表岩石组合、构造作用等角度来看,金星都与早期地球非常相似,是我们理解类地行星演化的天然实验室.研究金星和地球为什么会朝不同方向演化,是深入理解包括系外行星在内的行星的宜居性形成与演变的重要途径。因此,金星一直是优先级别最高的深空探测目标之一.近几年,美国、俄罗斯以及欧洲等国家和地区分别针对金星目前主要的科学问题,例如金星是否存在早期海洋、金星的宜居性以及结构和重力场等,先后提出各自的金星探测计划.我国在新的国际竞争中应该、也必然有所作为.  相似文献   

A continental back-arc setting for the Namaqua belt: Evidence from the Kakamas Domain     

《地学前缘(英文版)》2022,13(4):101408

A study of the NW Kakamas Domain in South Africa/Namibia provides a new, unified lithostratigraphy and evolutionary history applicable to the whole Namaqua Sector. The Mesoproterozoic history ranges from ～1350 Ma to 960 Ma, but isotopic evidence suggests it was built upon pre-existing Paleoproterozoic continental crust that extended west from the Archaean Craton. In eastern Namaqualand, early rift-related magmatism and sedimentation at ～1350 Ma occurred in a confined ocean basin. Subsequent tectonic reversal and subduction at ～1290–1240 Ma led to establishment of the Areachap, Konkiep and Kaaien Domains. In the Kakamas Domain, widespread deposition of pelitic sediments occurred at ~1220 Ma (Narries Group). These contain detrital zircons derived from proximal crust with ages between ～2020 Ma and 1800 Ma (western Palaeoproterozoic domains) and 1350–1240 Ma (eastern early Namaqua domains), suggesting pre-sedimentation juxtaposition. The pelites underwent granulite grade metamorphism at ～1210 Ma (peak conditions: 4.5–6 kbar and 770–850 °C), associated with voluminous, predominantly S-type granitoid orthogneisses between ～1210 Ma and 1190 Ma (Eendoorn and Ham River Suites) and low-angle ductile (D₂) deformation which continued until ～1110 Ma, interspersed with periods of sedimentation. This enduring P-T regime is inconsistent with the expected crustal over-thickening associated with the generally-accepted collision-accretion Namaqualand model. Rather, we propose the Namaqua Sector is a ‘hot orogen’ developed in a wide continental back-arc with subduction west of the present-day outcrop. The observed high geotherm resulted from thinned back-arc lithosphere accompanied by an influx of mantle-derived melts. Ductile D₂ deformation resulted from “bottom-driven” tectonics and viscous drag within the crust by convective flow in the underlying asthenospheric mantle. This extended tectonothermal regime ceased at ～1110 Ma when SW-directed thrusting stacked the Namaqua Domains into their current positions, constrained in the Kakamas Domain by late- to post-tectonic I-type granitoids intruded between ～1125 Ma and 1100 Ma (Komsberg Suite). The thermal peak then shifted west to the Bushmanland and Aus Domains, where voluminous granites (1080–1025 Ma) were associated with high-T/low-P granulite facies thermal metamorphism and mega-scale open folding (D₃). Unroofing of the Namaqua Sector is marked by large-scale, NW-trending, sub-vertical transcurrent dextral shear zones and associated pegmatites and leucogranites at ～990 Ma.  相似文献   

基于InSAR技术的澜沧江卡贡乡—如美镇段崩滑隐患探测     

陈俊伊  李为乐  陆会燕  李鹏飞  铁永波 《中国地质调查》2022,9(4):134-143

澜沧江卡贡乡—如美镇段位于青藏高原东南部,具有海拔较高、河谷深切、地势起伏大、水力资源丰富的特点。该区域地质构造复杂,发育较多高位地质灾害隐患,严重影响下游水电站建设安全。为保证澜沧江下游水电站的安全建设,利用Stacking-InSAR技术探测澜沧江卡贡乡—如美镇段及其干流两侧5 km范围内的隐患点,获取研究区隐患点数量及分布特征,并选取典型隐患点,分析其在时间序列上的形变特征。结果表明: ①研究区内升轨、降轨影像共探测出崩滑隐患点149处,多具有坡体临空条件好、植被覆盖较少等特点,坡体表面多发育有冲沟,局部多发育浅层崩塌,受风化侵蚀较为严重,结构较为松散; ②研究区的隐患点类型主要为崩塌和滑坡,共探测出崩塌隐患54处,滑坡隐患95处; ③研究区滑坡隐患点坡体多发育有局部崩塌现象,且多处于匀速变形阶段,但视线向年均形变速率与累积形变量较大,坡体较不稳定,对澜沧江沿岸居民及下游水电站建设威胁较大。  相似文献   

Petrogenesis and tectonic implications of early Palaeozoic igneous rocks of the western South Qilian Belt,central China   总被引：1，自引：0，他引：1  

Dongsheng Wang  Jing Yan  Xin Lin 《International Geology Review》2018,60(7):844-864

Early Palaeozoic granitoids in the South Qilian Belt, central China, record details of the tectonic evolution and crustal growth of the Qilian orogenic belt. Five representative granitoids from the western South Qilian Belt were sampled for zircon LA-ICPMS U–Pb dating, Lu–Hf isotopes, and whole-rock geochemical analyses. Zircon U–Pb dating of two porphyritic granodiorites and a porphyritic monzogranite yielded ages of 442.7 ± 3.5, 441.8 ± 4.3, and 435.4 ± 3.5 Ma, respectively. These granitoids exhibit a geochemical affinity to I-type granite, are metaluminous with a low aluminium saturation index (A/CNK = 0.75–1.15), have moderate Al₂O₃ and low MgO contents, high La/Yb and low Sr/Y ratios, and are depleted in Nb, Ta, P, and Ti, which suggests a subduction zone magmatic arc affinity, with mixing between a primary mantle-derived magma with lesser continental crustal material. The syenogranite and monzogranite from the South Qilian Belt, which yield U–Pb zircon ages of 440.4 ± 9.0 and 442.3 ± 1.2 Ma, respectively, have pronounced S-type geochemical affinities, are peraluminous with A/CNK values of 1.07–1.16, have relatively high SiO₂, Al₂O₃, K₂O, and Rb contents, low Y and Yb, low Sr/Y and La/Yb ratios, positive Th, U, and light Rare Earth Element (REE) anomalies, and depletions in Nb, Ta, Sr, and Ti. Their geochemical signature suggests derivation from partial melting of continental crust in a syn-collisional setting. The Hf isotopic data of zircons from the granitoids show a significant input of Paleoproterozoic crust in the crustal formation of the western South Qilian Belt in Palaeozoic. Compare the ε_Hf(t) value of S-type granite with that of I-type granite, the former may have a comparatively homogeneous source. Together with regional evidence, it is proposed that a collisional event occurred between the South Qilian Belt and the Central Qilian Belt at ca. 442–435 Ma.  相似文献