辽北开原地区房木花岗斑岩LA-ICP-MS锆石U-Pb年龄及地球化学特征     

豆世勇 《吉林大学学报(地球科学版)》2020,50(6):1752-1765

研究区位于华北克拉通北缘东段、华北克拉通与兴蒙造山带的交接部位。本文通过对辽北开原地区房木花岗斑岩的岩石学、年代学和地球化学研究，探讨了其形成时代、岩石成因和构造环境，并进一步探讨了华北克拉通东部岩石圈减薄的起始时间。用LA-ICP-MS技术测定了花岗斑岩的锆石U-Pb同位素，获得其锆石²⁰⁶Pb/²³⁸U加权平均年龄为（117±1）Ma，表明花岗斑岩形成于早白垩世。花岗斑岩具有高硅、富碱、贫镁和钙的特征，富集大离子亲石元素（K、Rb）和高场强元素（Th、Ta、Nb），亏损Sr、Ba、P、Ti元素，稀土配分曲线均呈现右倾海鸥型，具有明显的负Eu异常；显示研究区花岗斑岩为A型（A₁亚型）花岗岩，形成于古太平洋俯冲的后造山伸展环境，其岩浆源于地幔物质上涌而导致的地壳物质重熔。研究区在（156±1）Ma之前，属于挤压造山环境，表明研究区岩石圈减薄时间应处于156~117 Ma之间。  相似文献   

再探温跃层有孔虫B/Ca与温度和[CO₃^2-]的依赖性及其在24 ka以来热带西太平洋次表层碳酸盐系统重建中的应用     

郭景腾  李铁刚  熊志方  仇晓华  常凤鸣 《海洋学报(英文版)》2019,38(9):71-86

The B/Ca ratio of planktonic foraminifer shells has been used as a proxy for reconstructing past ocean carbonate chemistry. However, recent studies have revealed significant uncertainties associated with this proxy, such as whether seawater temperature or [ CO_3~(2-)] is the dominant control on the partition coefficient(K_D) of planktonic foraminiferal B/Ca. To address these uncertainties and thus improve our understanding of the planktonic foraminiferal B/Ca proxy, we analysed B/Ca ratios in the tests of Neogloboquadrina dutertrei(300–355 μm) and Pulleniatina obliquiloculata(355–400 μm) in surface sediment samples from the tropical western Pacific and South China Sea. The relationship between these B/Ca ratios and bottom water calcite saturation states(Δ[ CO_3~(2-)]) is weak, thus suggesting only a small dissolution effect on the B/Ca of the two species. The correlation coefficients(R~2) between the B/Ca ratios of N. dutertrei and P. obliquiloculata and environmental parameters(e.g., temperature, salinity, phosphate, DIC and ALK) in the tropical western Pacific and South China Sea are not high enough to justify using B/Ca ratios as a palaeoenvironmental proxy in the study areas. The significant correlation between K_D values of N. dutertrei and P. obliquiloculata and carbonate system parameters(e.g.,[ CO_3~(2-)], DIC, ALK, pH and [ HCO_3~-]) in the study area reflect chemical links between the K_D denominator and these variables. Based on our surface sediment calibration, an empirical relationship between the K_D of N.dutertrei and temperature is proposed in the tropical western Pacific. We also generated a record of B/Ca ratios in N. dutertrei(300–355 μm) from Core MD06-3052 in the tropical western Pacific over the past 24 ka to evaluate the application of the revised B/Ca proxy method. Based on the reconstructed empirical relationship for B/Ca and subsurface seawater ALK, we estimated subsurface seawater carbonate system parameters in the tropical western Pacific since 24 ka. In general, the estimated subsurface seawater pH and [ CO_3~(2-)] show an increase with time, and the record of subsurface seawater pCO_2 shows a decrease with time, in the tropical western Pacific over the past 24 ka. The consistent trends in subsurface seawater pCO_2 and opal flux during deglaciation may imply that the reported increase in subsurface water pCO_2 in the study area was promoted by enhanced upwelling in the Southern Ocean.  相似文献   

基于GPT2w模型化加权平均温度反演可降水量     

翟树峰  吕志平  李林阳  吕浩  邝英才  王方超 《大地测量与地球动力学》2019,39(7):733-737

提出一种基于GPT2w模型化加权平均温度反演大气可降水量的方法，并分析附加系统偏差改正的模型化加权平均温度对可降水量的影响。结果表明，基于GPT2w模型化加权平均温度反演的大气可降水量的精度与基于Bevis公式计算的加权平均温度反演的大气可降水量的精度相当；对GPT2w模型化加权平均温度进行系统偏差改正后，大气可降水量的精度有一定改善，但改善率不到1%。  相似文献   

Landsat长时间序列的阳澄湖湖面围网时空变化     

计璐艳  尹丹艳  宫鹏 《遥感学报》2019,23(4):717-729

准确提取湖泊围网区域的时空分布信息对湖泊的保护和可持续发展具有重要意义。本文以阳澄湖为研究区域,收集该地区1984年—2017年所有的Landsat 5和Landsat 8影像(共计396景),提出了结合光谱和纹理特征的围网提取新算法,同时利用时间序列滤波消除年际间因数据不一致造成的偏差。以高清影像人工解译作为参考,阳澄湖围网提取结果的生产者精度在72.57%—88.53%,用户者精度在79.79%—98.10%,围网面积变化与文献记录吻合。结果表明,阳澄湖围网经历了"无围网期"(1984年—1994年)、"快速增长期"(1994年—1998年)、"巅峰期"(1999年—2002年)、"快速下降期"(2003年—2006年)和"稳定期"(2007年—2017年)5个阶段,最高达到100 km2,目前稳定在30 km2;通过研究围网区植被指数发现,2002年之后围网区浮水植物的种植面积增大;通过对比水质数据发现,2002年至今持续15年的围网拆除并未使阳澄湖恢复到80年代无围网养殖时期的II类水,其水质依然处于Ⅲ—Ⅳ类。因此在湖泊养殖开发过程中,政府应该坚持可持续发展道路,在不破坏湖泊水质的基础上发展湖泊经济。  相似文献   

辽宁省海洋生态修复现状、存在的问题及对策建议          下载免费PDF全文

王鹏  张连杰  闫吉顺  于永海  张盼 《海洋开发与管理》2019,36(7):49-52

随着沿海经济带的开发建设,海洋生态环境承受着巨大压力,湿地、河口、海湾、海岛等重要生态系统面临前所未有的威胁。对海洋生态的保护修复已经迫在眉睫、刻不容缓。文章基于辽宁省海洋资源环境的特征,结合海域开发利用及海洋生态修复现状,探索辽宁省海洋生态修复工作面临的主要问题,并提出生态修复重点及对策建议,截至2017年,累计整治修复岸线长度约140km,整治修复海域面积超过50km~2。辽宁省海洋生态修复工作面临的主要问题有:近岸局部海域水体污染、生态受损;湿地、滩涂面积有缩减趋势;河口生态系统脆弱,生物多样性指数降低;海湾生态功能退化;海岛生态环境失衡。辽宁省应重点开展海湾环境综合治理以及滨海湿地、岸滩、岛礁等整治修复工作。  相似文献   

贵州省松桃县木耳溪锰矿地质特征及找矿方向     

陈旭  许乔 《云南地质》2020,(1):31-36

贵州松桃县木耳溪锰矿为典型的层控型锰矿床,矿体呈层状赋存于南华系下统大塘坡组第一段(Pt2b3d 1)底部的炭质页岩中,产出层位稳定,矿体产状与围岩产状一致。通过统计对比,锰矿层的矿化程度与含锰岩系的厚度呈正比,即当南华系大塘坡组地层厚度大于15m时,有可能成为锰矿的主要找矿方向。  相似文献   

Geochemical study of the Neoproterozoic clastic sedimentary rocks of the Khambal Formation (Sindreth Basin), Aravalli Craton,NW Indian Shield: Implications for paleoweathering,provenance, and geodynamic evolution     

《Chemie der Erde / Geochemistry》2020,80(1):125596

Petrographic and geochemical studies characterize lithologies of the Khambal Formation deposited in the Sindreth Basin as arkosic, subarkosic, and quartzarenite. Weathering indices, such as CIA and CIW in conjunction with the ACNK diagram, prescribe mostly moderate chemical weathering with intermittent pulses of extreme weathering in the source area. The discrimination diagrams suggest that these Neoproterozoic clastics were deposited in an active rift basin. Provenance indicators of the detritus components point to a terrane possessing subordinate mafic material in conjunction with large felsic components. A comparison of immobile element ratios with probable source rocks suggest that the Mesoproterozoic Delhi arc situated to the east of the Sindreth Basin could be the possible source. Our mixing calculation defines the proportion of end member components in the Delhi arc. Geodynamic considerations relate the origin of the Sindreth Basin to the processes of disintegration and reassembly of supercontinents.  相似文献   

黑龙江黑宝山-罕达气盆地早白垩世九峰山组年代地层划分     

杨雅军  江斌  王筱筝  庞雪娇  石国明 《地质与资源》2020,29(5):403-410

为了确定黑龙江黑宝山-罕达气盆地九峰山组形成的气候环境及时代，对九峰山组生物地层特征进行了系统的总结与对比.植物及其孢粉化石反映了典型的亚热带潮湿气候环境，时代为早白垩世.对九峰山组下部所夹流纹质凝灰岩进行了LA-ICP-MS锆石U-Pb同位素测年，获得了119±0.89 Ma成岩年龄.综合古生物和同位素年龄确定九峰山组形成于早白垩世阿普特阶中晚期，这一研究成果可为东北地区晚中生代区域性地层、成煤时代、含煤盆地对比提供精确的年代依据.  相似文献   

鄂尔多斯盆地南部奥陶系马六段白云岩特征及形成机制研究     

刘丽红  王春连  李丽霞  杜治利  唐跃  韩淼 《中国地质》2020,47(3):810-820

鄂尔多斯盆地马六段在盆地大部分地区被剥蚀,仅在盆地周缘地区分布,因此,有关该盆地马六段白云岩成因研究较少。本文通过对马六段白云岩岩石学特征、阴极发光特征、微量元素特征以及碳氧同位素地球化学特征进行分析,对鄂尔多斯盆地南部马六段白云岩特征及形成机制进行了研究。研究结果表明,盆地南部马六段白云岩主要由细—中晶白云岩组成,白云石具"雾心亮边"结构,阴极发光呈暗红色光。微量元素总体上具有较低的Fe、Mn值,平均值分别为447×10~(-6)和62×10~(-6),较高的K、Na值,平均值分别为517×10-6和252×10~(-6),以及中等含量的Sr元素值,平均值为155×10~(-6)。δ~(13)C值平均为-0.617‰,δ~(18)O值平均为-7.6‰,以上特征均反映出海源流体特征。白云石的"雾心"和"亮边"结构中微量元素含量相差不大,认为是在相同成岩环境的不同成岩阶段形成,其中"雾心"形成于浅埋藏环境的渗透回流白云石化作用,而"亮边"是在深埋藏环境下对早期白云石的调整和加强。  相似文献   

Understanding the hydrological system dynamics of a glaciated alpine catchment in the Himalayan region using the J2000 hydrological model          下载免费PDF全文

S. Nepal  P. Krause  W.‐A. Flügel  M. Fink  C. Fischer 《水文研究》2014,28(3):1329-1344

This paper provides the results of hydrological modelling in a mesoscale glaciated alpine catchment of the Himalayan region. In the context of global climate change, the hydrological regime of an alpine mountain is likely to be affected, which might produce serious implications for downstream water availability. The main objective of this study was to understand the hydrological system dynamics of a glaciated catchment, the Dudh Kosi River basin, in Nepal, using the J2000 hydrological model and thereby understand how the rise in air temperature will affect the hydrological processes. The model is able to reproduce the overall hydrological dynamics quite well with an efficiency result of Nash–Sutcliffe (0.85), logarithm Nash–Sutcliffe (0.93) and coefficient of determination (0.85) for the study period. The average contribution from glacier areas to total streamflow is estimated to be 17%, and snowmelt (other than from glacier areas) accounts for another 17%. This indicates the significance of the snow and glacier runoff in the Himalayan region. The hypothetical rise in temperature scenarios at a rate of +2 and +4 °C indicated that the snowmelt process might be largely affected. An increase in snowmelt volume is noted during the premonsoon period, whereas the contribution during the monsoon season is significantly decreased. This occurs mainly because the rise in temperature will shift the snowline up to areas of higher altitude and thereby reduce the snow storage capacity of the basin. This indicates that the region is particularly vulnerable to global climate change and the associated risk of decreasing water availability to downstream areas. Under the assumed warming scenarios, it is likely that in the future, the river might shift from a ‘melt‐dominated river’ to a ‘rain‐dominated river’. The J2000 model should be considered a promising tool to better understand the hydrological dynamics in alpine mountain catchments of the Himalayan region. This understanding will be quite useful for further analysis of ‘what‐if scenarios’ in the context of global climate and land‐use changes and ultimately for sustainable Integrated Water Resources Management in the Himalayan region. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献