“全新特提斯洋”概念与广义特提斯构造域     

余星  许绪成  韩喜球  丁巍伟  胡航  何虎  余娅娜 《地质学报》2022,96(12):4131-4139

特提斯最初是指欧亚大陆南缘的古海洋，后逐渐引申出从元古宙、古生代到中生代的一系列位于劳亚大陆与冈瓦纳大陆之间的古大洋，如原特提斯洋、古特提斯洋和新特提斯洋，不同大洋在时间上前后交叠。如今横亘在冈瓦纳大陆(南极洲)和欧亚大陆之间的是印度洋，是新特提斯洋的继承者，可以另称为“全新特提斯洋”。这一概念的引申直接体现了印度洋与特提斯构造域一脉相承的关系，有助于将今论古、由此及彼，更直观地了解特提斯构造域的演化过程。本文按时间序列梳理了印度洋的大地构造演化和岩浆作用过程，识别了印度洋在155 Ma、120 Ma、90~84 Ma、76 Ma、65 Ma、52 Ma、45 Ma、38 Ma等关键时期的异常海底扩张记录，这些扩张事件将为标定新特提斯构造域的演化提供参照。其中155 Ma可能指示了新特提斯洋的鼎盛期，90 Ma指示了新特提斯洋的洋中脊俯冲，76~52 Ma是非洲- 阿拉伯大陆与欧亚大陆初始碰撞- 主碰撞(即新特提斯洋西部关闭)的时期，65~45 Ma是印度次大陆与欧亚大陆初始碰撞- 主碰撞(即新特提斯洋中部关闭)的时期，38 Ma是澳大利亚北部大洋开始净俯冲(即新提斯洋东部开始消减)的时间。印度洋扩张历史的研究为理解新特提斯洋消亡提供参考标尺。站在“后方”印度洋的角度，可以更清晰地透视“前线”特提斯构造域的演化过程，为理解板块构造活动规律提供支撑。  相似文献   

西准噶尔紫苏花岗岩成因岩石学研究   总被引：8，自引：1，他引：8  

张立飞  冼伟胜  孙敏 《新疆地质》2004,22(1):36-42

紫苏花岗岩呈岩体形式侵入于石炭纪地层中．又为碱长花岗岩侵入．紫苏花岗岩由斜方辉石、单斜辉石、铁橄榄石、条纹长石、石英组成．以正εNd为特征(εNd= 4．8- 5．8)矿物组成、结构和野外产状表明：这些紫苏花岗岩是火成成因的．温压计算估测其结晶条件是T=700～800℃，P=420～575kPa．紫苏花岗岩中有小的富云母包体和巨大的条带状捕虏体．前被认为是残留体，后与其围岩．火山碎屑岩相当．残留体中较低的εNd正值(εNd= 2．6- 3．5)要求新生的下部地壳是紫苏花岗岩的主要源岩：来自这些源岩的紫苏花岗岩的母岩浆在结晶前与一些来自于亏损地幔中的融体混合．该地区体积巨大的碱性花岗岩可能也来自相同的岩浆源，只不过它是在较浅的地壳深度上结晶的．  相似文献   

Crust and upper mantle structure of the Ailao Shan-Red River fault zone and adjacent regions   总被引：4，自引：1，他引：4  

XU Yi  LIU Jianhua  LIU Futian  SONG Haibin  HAO Tianyao & JIANG Weiwei Institute of Geology  Geophysics  Chinese Academy of Sciences  Beijing  China 《中国科学D辑(英文版)》2005,48(2):156-164

Using arrival data of the body waves recorded by seismic stations, we reconstructed the velocity structure of the crust and upper mantle beneath the southeastern edge of the Tibetan Plateau and the northwestern continental margin of the South China Sea through a travel time tomography technique. The result revealed the apparent tectonic variation along the Ailao Shan-Red River fault zone and its adjacent regions. High velocities are observed in the upper and middle crust beneath the Ailao Shan-Red River fault zone and they reflect the character of the fast uplifting and cooling of the metamorphic belt after the ductile shearing of the fault zone, while low velocities in the lower crust and near the Moho imply a relatively active crust-mantle boundary beneath the fault zone. On the west of the fault zone, the large-scale low velocities in the uppermost mantle beneath western Yunnan prove the influence of the mantle heat flow on volcano, hot spring and magma activities, however, the upper mantle on the eas  相似文献   

The Scientific Conceptual Framework for Ecological Quality of the Dryland Ecosystem: Concepts,Indicators, Monitoring and Assessment     

WU Rina  CONG Weiwei  LI Yonghua  LI Siyao  WANG Dongfang  JIA Zhiqing  WANG Feng 《资源与生态学报(英文版)》2019,10(2):196-201

The dryland ecosystem is the dominant component of the global terrestrial ecosystem since arid regions occupy 45% of the earth’s land area and feed 38% of the world's population. The stability and sustainable development of the dryland ecosystem are critical for achieving the millennium development goal (MDG) in the arid and semiarid areas. However, there is still no scientific guideline for measuring and conserving the health and productivity of dryland ecosystems. Therefore, the purpose of this study is to develop the scientific conceptual framework of defining, monitoring and evaluating the ecological quality of dryland ecosystems. The ecological quality of dryland ecosystems is represented by a system of comprehensive indicators that are each extracted from the ecological elements, and structural and functional indices of the ecosystem. These indicators can be monitored by integrating satellites and unmanned aerial vehicles with ground-based sensor networks at the scale of either observational sites or regional scales. Finally, the ecological quality can be evaluated by evaluation models based on the normalized index values and their thresholds. This paper presents a conceptual framework for monitoring and evaluating the ecological quality of drylands, which provides a way of advancing the monitoring, diagnosis, and evaluation of the ecological quality of the dryland ecosystems.  相似文献   

Variability in the vertical hyporheic water exchange affected by hydraulic conductivity and river morphology at a natural confluent meander bend          下载免费PDF全文

Jinxi Song  Guotao Zhang  Weize Wang  Qi Liu  Weiwei Jiang  Weiqiang Guo  Bin Tang  Haifeng Bai  Xinyi Dou 《水文研究》2017,31(19):3407-3420

River confluences and their associated tributaries are key morphodynamic nodes that play important roles in controlling hydraulic geometry and hyporheic water exchange in fluvial networks. However, the existing knowledge regarding hyporheic water exchange associated with river confluence morphology is relatively scarce. On January 14 and 15, 2016, the general hydraulic and morphological characteristics of the confluent meander bend (CMB) between the Juehe River and the Haohe River in the southern region of Xi'an City, Shaanxi Province, China, were investigated. The patterns and magnitudes of vertical hyporheic water exchange (VHWE) were estimated based on a one‐dimensional heat steady‐state model, whereas the sediment vertical hydraulic conductivity (K_v) was calculated via in situ permeameter tests. The results demonstrated that 6 hydrodynamic zones and their extensions were observed at the CMB during the test period. These zones were likely controlled by the obtuse junction angle and low momentum flux ratio, influencing the sediment grain size distribution of the CMB. The VHWE patterns at the test site during the test period mostly showed upwelling flow dominated by regional groundwater discharging into the river. The occurrence of longitudinal downwelling and upwelling patterns along the meander bend at the CMB was likely subjected to the comprehensive influences of the local sinuosity of the meander bend and regional groundwater discharge and finally formed regional and local flow paths. Additionally, in dominated upwelling areas, the change in VHWE magnitudes was nearly consistent with that in K_v values, and higher values of both variables generally occurred in erosional zones near the thalweg paths of the CMB, which were mostly made up of sand and gravel. This was potentially caused by the erosional and depositional processes subjected to confluence morphology. Furthermore, lower K_v values observed in downwelling areas at the CMB were attributed to sediment clogging caused by local downwelling flow. The confluence morphology and sediment K_v are thus likely the driving factors that cause local variations in the VHWE of fluvial systems.  相似文献   

渝东南下古生界页岩构造裂缝形成及分布控制因素          下载免费PDF全文

岳锋  程礼军  焦伟伟  王飞 《地质科学》2016,(4):1090-1100

天然裂缝对页岩气储集和渗流有重要影响,但目前对页岩构造裂缝研究不够深入。本文通过露头、岩心裂缝观察和分析,探讨了渝东南下古生界页岩构造裂缝类型、形成机理及分布控制因素。基于裂缝特征及力学成因,将剪切裂缝分为高角度剪切裂缝、倾斜滑脱裂缝和水平滑脱裂缝。倾斜滑脱裂缝是在上覆岩层重力和水平构造应力共同作用下沿应力集中的软弱面发生剪切滑动形成,水平滑脱裂缝是在构造挤压应力作用条件下主要沿页理面方向的剪切或层间滑动形成;页理发育程度及岩层曲率是控制水平滑脱裂缝形成的关键因素,岩石矿物组成、构造作用及岩层厚度是控制其它类型构造裂缝形成和分布的主要因素,页岩岩石力学层的划分需要根据裂缝特征、岩性变化特征、岩石力学参数及沉积界面等综合确定,岩层厚度与层间构造裂缝密度呈负相关关系。  相似文献   

地表覆盖遥感产品更新完善的研究动向     

陈军  张俊  张委伟  彭舒 《遥感学报》2016,20(5):991-1001

近年来,多尺度地表覆盖遥感产品的不断涌现,为环境变化研究、地球系统模拟、地理国(世)情监测和可持续发展规划等提供了重要科学数据。为更好地满足广大用户日益增长的应用需求,应对地表覆盖遥感产品进行持续更新完善,保持其时效性、增强时序性、丰富多样性。针对大面积地表覆盖遥感产品更新完善所面临的主要问题,介绍和评述了国内外有关研究动向,包括影像与众源信息相结合的更新、数据类型细化与完善、地表覆盖真实性验证,并作了简要展望。  相似文献   

总梯度模方法在低纬度地区航磁资料解释中的应用          下载免费PDF全文

梁建  线纪安  郭玉峰 《地质找矿论丛》2016,31(4):570-575

对于低纬度地区的航空磁测的ΔT资料,如果化极处理时对磁化方向判断存在误差,用目前的化极方法进行资料处理,要比在高纬度地区化极发生更大的畸变,不适于对资料进行解释。通过一些模型计算及一些实际资料对比,在低纬度地区用航磁总场梯度模划分磁性体地面投影边界是简单实用的一种方法。  相似文献   

紫色土水分特征曲线室内测定方法的对比   总被引：1，自引：0，他引：1       下载免费PDF全文

王红兰  唐翔宇  鲜青松  刘琛  关卓 《水科学进展》2016,27(2):240-248

为探寻全吸力范围内土壤水分特征曲线的可靠测定方法,采用沙箱排水法、Hyprop仪蒸发法、压力膜仪排水法和露点水势仪蒸发法分吸力段测定盐亭紫色土耕地表层2~7 cm和亚表层7~12 cm土壤的水分特征曲线,对比测定结果的方法间差异,并分析其原因。结果表明:对于表层和亚表层土壤,低吸力段(h >-100 cm)水分特征曲线的沙箱法和Hyprop仪法的均方根误差E_RMS (θ)均较小,在0.026~0.082 cm3/cm3范围内,确定系数R2均大于0.962,说明这两种方法测定结果之间差异不大。高吸力段(h <-330 cm)的压力膜仪法与露点仪法测定结果之间的差异较大,E_RMS (θ)为0.062~0.097 cm3/cm3,R2较低,为0.775~0.952。因此,全吸力范围内水分特征曲线测定方法的选择与组合应考虑土壤孔径分布特征和研究目的。  相似文献   

白缘(鱼央)5S rDNA的扩增分析及其在染色体上的FISH定位     

张伟伟  付元帅  邵燕  王宝琴  石东里  张兰 《海洋学报》2016,38(6):82-88

本文分别对雌雄白缘(鱼央)的5S rDNA进行了PCR扩增和序列分析,并采用双色荧光原位杂交(FISH)技术,以白缘(鱼央)的5S rDNA序列和小麦的45S rDNA为探针,对其在白缘(鱼央)雌雄中期染色体上进行了FISH定位研究。结果表明,白缘(鱼央)5S rDNA序列无雌雄差异;5S rDNA的保守区序列为117 bp;5S rDNA和45S rDNA分别被定位于白缘(鱼央)的性染色体和第5号染色体上。同时从GenBank中获得了22种鱼的5S rDNA,运用DNAman软件构建了23种鱼的系统发育树,对白缘(鱼央)的进化地位进行了初步研究。本研究为阐明白缘(鱼央)在鱼类系统进化中的位置、重复序列在脊椎动物性染色体上的分布状况以及与性别决定与分化的关系,提供了资料积累和分析依据。  相似文献