Geochemical Characteristics and Geological Significance of Early Permian Baya’ertuhushuo Gabbro in South Great Xing’an Range

Field geological investigation and geochemical analysis are carried out on Baya’ertuhushuo Gabbro in South Great Xing’an Range. Field investigation reveals that the gabbro is a magmatic intrusion rather than a component of an ophiolite suite as previously thought. Zircon laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) U-Pb dating indicates the gabbro was formed in 274–275?Ma, just as the widespread volcanic rocks of Dashizhai Formation (P1d), monzogranites and miarolitic alkali-feldspar granites in the study area. The gabbro has SiO2 content between 47.23 wt% and 50.17 wt%, high MgO and FeOT contents of 6.95–11.29 wt% and 7.32–12.24wt%, respectively, and it belongs to low-K tholeiitic series in the SiO2-K2O diagram. The Chondrite-normalized rare earth element (REE) patterns and primitive mantle-normalized spider diagrams of the gabbro are similar to those of Normal Mid-Ocean Ridge Basalt (N-MORB) except for the enrichment of large ion lithophile elements (LILE), such as Rb, Ba and K. In trace element tectonic discriminative diagrams, the samples are mainly plotted in the N-MORB field, and Zircon in?situ Lu-Hf isotopic analysis also indicates the gabbro originated from depleted mantle. Through synthetic studies of the geochemical characteristics and petrogenesis of Baya’ertuhushuo gabbro, volcanic rocks of Dashizhai Formation and granitoids in the area, it is suggested that the early Permian magmatism in the Xilinhot-Xiwuqi area formed in the tectonic setting of asthenosphere upwelling, which was caused by breaking-off of the subducted Paleo-Asian Ocean slab.     

JYZ11A钻孔记录的居延泽演化历史

我国内陆干旱区在末次冰期(含深海氧同位素第3阶段)是否存在古大湖近年来持续存在争论。居延泽是黑河的尾闾湖之一, 位于我国典型干旱区, 是开展这项研究的理想区域。依据居延泽盆地最低处的JYZ11A钻孔(全孔长61.13m, 本文侧重上部27m岩芯), 使用石英光释光测年获得3个可靠释光年龄并据此建立年代框架。全孔10cm间距测量沉积物粒度, 钻孔上部16.7m以2cm间距测量低频磁化率, 本文侧重分析JYZ11A钻孔上部10m的指标记录。综合岩性地层、沉积物粒度分布特征和粒度、磁化率指标记录, 并与前人已有研究进行对比, 本研究发现末次冰期时居延泽盆地主要堆积棕色冲洪积物和风沙沉积物, 早全新世为风沙沉积, 中全新世出现浅灰色湖相沉积与风沙交替沉积, 而稳定湖泊只在约3ka时才逐渐形成, 可能存在多次湖面波动并留下古湖岸堤。因此, 居延泽盆地在末次冰期包括深海氧同位素第3阶段晚期并不存在稳定大湖。居延泽早全新世干涸、中晚全新世湖泊较稳定发育的全新世成湖模式与季风区湖泊演化模式明显不同, 而与许多中亚干旱区的湖泊、风成沉积等古环境记录相似, 它们可能共同指示了一种有别于中国季风区的全新世区域湿度演化模式。     

从强化弱化性质建立大理岩本构模型

强化和弱化性质在岩石变形过程中对立统一,分别或同时主导了应力及时间效应下形变特征,在上地壳温压条件下,弱化和强化的微观观机制主要是裂纹扩展和位错滑移及成核,本文在关于大理岩等应变率循环中载全过程的实验结果基础上,通过含有强化弱化函数的弹粘塑模型与无穷个弹簧连续夫并联的力学物理模型,建立和描述了大理岩的流变本构关系,根据该模型,可由等应变率的实验结果,预测出蠕变曲线。     

Interannual variability of summer monsoon rainfall over Myanmar

Observed summer (May–October) rainfall in Myanmar for the period 1981–2010 was used to investigate the interannual variability of summer monsoon rainfall over Myanmar. Empirical orthogonal function, the sequential Mann-Kendall test, power spectrum analysis, and singular value decomposition (SVD) were deployed in the study. Results from spectral analysis showed that the variability of rainfall over Myanmar exhibits a 2- to 6-year cycle. An abrupt change in rainfall over the country was noted in 1992. There was a notable increasing rainfall trend from 1989. After the sudden change, the mean rainfall increased by 36.1 mm, compared with the mean rainfall before the sudden change, and was associated with a rise in temperature of about 0.2 °C. An increase in heavy rainfall days was observed from the early 1990s to 2010. IOD and ENSO play an important role in the interannual variability of the summer rainfall over Myanmar. The covariability between rainfall over Myanmar and Indian Ocean SST generally suggests that a positive IOD mode is associated with suppressed rainfall in the central and northern parts of Myanmar. During a negative IOD mode, nearly the whole Myanmar experiences enhanced rainfall, which is associated with devastating socioeconomic impacts. The covariability between the rainfall over Myanmar and the sea surface temperature in the Pacific Ocean in the first and second SVD modes was dominated by warming in the east and central Pacific—an El Niño-like pattern—resulting in dry conditions in central Myanmar.     

煤中碳酸盐矿物的测试技术和方法及测试数据的应用

我国西北及华北侏罗纪煤系地层中含有较高的碳酸盐矿物,其形成与成煤地质时代、沉积环境密切相关.根据化学组成、性质以及成因等相关因素,可将分为碱土金属碳酸盐与过渡金属碳酸盐二类.目前测试煤中碳酸盐矿物的指标有4个,即:ICC指数、碳酸盐CO2总量、NP值、矿物相分析.结合煤田地质勘探工作中测试煤中碳酸盐矿物的需要,提出了定性分级、定量测试、和矿物相分析等3个级别的测试方案,并根据每个级别测试的目的、测试的样品种类,设计了相关指标的测试方案与测定方法.煤中碳酸盐矿物的相关指标数据可广泛应用于煤质评价、煤矿废水酸碱性预测、煤加工利用、煤岩层对比与成煤地质环境等地质研究工作.     

Impacts of coastal reclamation on tidal and sediment dynamics in the Rui’an coast of China

Ocean Dynamics - Coastal reclamation projects have been extensively constructed along the coastline of the East China Sea over the past decades. To investigate the impact of reclamations on the...     

青藏高原岩石圈三维电性结构

本文报道通过综合大地电磁调查数据研究青藏高原岩石圈三维电阻率模型的初步成果.大地电磁法调查区域已经覆盖了高原大部分面积,为全区三维电阻率成像研究打下了可靠的基础.对多个测区大地电磁数据进行精细的同化处理和反演成像,取得了青藏高原可靠的岩石圈三维电阻率结构图像.成像的区域为28°N—35°N,80°E—104°E.三维反演计算时采用的网格尺寸为20 km×20 km,垂直方向不等间距剖分为26层.结果表明,青藏高原现今岩石圈电阻率扰动主要反映印度克拉通对亚欧大陆板块俯冲引起的热流体运动和大陆碰撞和拆离产生的构造.在岩石圈地幔,察隅地块、喜马拉雅地块和拉萨地块东部联成统一的高电阻率地块,它们反映了向北东俯冲的印度克拉通.雅鲁藏布江、班公—怒江和金沙江缝合带都有明显的低电阻率异常,表明岩石圈深处有热流体活动.雅鲁藏布江、班公—怒江和金沙江缝合带都有明显的低电阻率异常,也表明它们的岩石圈还有流体活动.青藏高原东部的低阻区沿100°E向地幔下方扩大,反映了金沙江断裂带有切穿岩石圈的趋势.地幔电阻率平面扰动的模式显示,青藏高原东西部的地体碰撞拼合形式和方向是不同的.在青藏高原西部,羌塘、拉萨和喜马拉雅等地体从北到南碰撞拼合.在青藏高原东部,羌塘—拉萨、察隅、印支、雅安和扬子等地体多方向拆离拼合,在地壳造成不正交的拆离带和压扭构造系.从高阻-低阻区的分布看,东部的地体拼合有地幔的根源,今后还会进一步发展.察隅地块岩石圈对青藏高原东部的楔入,使其北部和东部地块的岩石圈发生拆离撕裂,也造成热流体上涌的低电阻率异常.

     

北京2004年“7.10”突发性对流强降水的雷达回波特征分析

利用新一代天气雷达回波资料和一个雷暴单体识别、追踪和分析算法, 对2004年7月10日下午造成北京局地短时强降水的雷暴特征进行了初步分析。在偏南暖湿气流中生成的对流云团, 在北京上空迅速发展, 逐渐形成了一个覆盖城区的β-中尺度对流超级复合体, 导致了这次强降水过程。详细分析表明, 强对流主要是来自城区西南和东南两个方向生成和发展起来的雷暴。在北京西南部的雷暴逐渐向东北的城近郊区移动和发展, 并与新生成的雷暴合并加强, 造成了石景山、门头沟和海淀部分地区的大雨。在北京东南部逐渐形成的两个小雷暴单体迅速增长并向西北方的城区移动, 在到达城区时合并且迅速加强, 但移速缓慢, 在北京城区维持了两个多小时, 造成了城区的大暴雨过程, 降水量大但空间分布不均匀。雷暴顶高度和最大反射率因子的关系呈反位相变化, 雷暴最大反射率因子出现的高度均位于0 ℃等温线之下 (≥0 ℃) 或其附近, 雷暴的中心和反射率因子权重质心也基本位于0 ℃等温线之下, 均证实了这是一个典型的液态强降水对流系统。分析还表明, 20:00 (北京时) 左右的超强雷达回波是由大气异常传播造成的虚假超折射回波。     

多隐层BP神经网络在模式预报中的简化应用

EC细网格预报效果好,基本满足业务需要,在工作中被广泛应用。为进一步提升预报准确性,做好迪士尼园区的气象服务保障,选取2016年7月至2017年6月1年的2 m温度预报场,24 h预报时效的时间分辨率为3 h,72 h预报时效的时间分辨率为24 h,分别用回归分析法、S型和简化Line型BP神经网络法进行模式释用,与迪士尼气象站观测数据对比。结果表明:阈值为1℃时,对模式结果释用后,均方根误差减少了0.5℃到1.0℃,3—9 h和21—72 h预报时效的准确率由原来的50%和30%分别上升到70%和50%。采用S型多隐层BP神经网络误差最小,不同预报时效释用稳定性最高,同时该释用方法对t_(min)的预报特征把握更精准,释用效果明显优于对t_(max)的预报释用,但迭代计算耗费时间大幅增多,与预报效果的提升不成正比。简化Line型的BP神经网络通过8个半月的数据量和简单的网络模式,捕获了EC预报的特征,不但减小了计算量,大幅缩短了计算时间,而且预报结果也有显著提升,预报稳定性较好,具有广泛的业务应用空间。