Final-stage Southward Subduction of the Eastern Paleo-Asian Ocean: Evidence from the Middle Permian Mafic Intrusions in the Northern Margin of the North China Craton

The northern margin of the North China Craton(NCC)contains widespread Permian magmatic rocks,but the origin of these rocks remains controversial.This uncertainty hampers us from better understanding of tectonic framework and evolution of the eastern Paleo-Asian Ocean,particularly with respect to its final-stage subduction and closure time.To address these questions,this study presents petrological,zircon U-Pb geochronological,whole-rock geochemical and in situ zircon Hf isotopic data for these Permian mafic intrusions in the northern margin of the NCC.Precise zircon U-Pb dating results indicate that these mafic intrusions were emplaced in the Middle Permian(ca.260 Ma).Geochemically,the studied mafic intrusions have high MgO and transition metals element contents,with high Mg^# values,indicating a mantle origin.These mafic intrusions are characterized by enrichments in large ion lithophile elements(LILEs;e.g.,Rb,Ba,and K)and light rare earth elements(LREEs),and depletions in high field strength elements(HFSEs;e.g.,Nb,Ta,and Ti)and heavy rare earth elements(HREEs),indicating that they were formed in a subduction-related setting.These geochemical features,together with zircon ε_Hf(t)values(-1.1 to+11.2),indicate that their parental magmas were derived from partial melting of heterogeneous mantle wedge metasomatized by subduction-related fluids,with the contributions of slab sediments.The studied mafic intrusions also show wide range of major and trace elements contents,and variable Mg^# values,Eu and Sr anomalies,suggesting that their parental magmas had undergone variable degrees of fractional crystallization.Together with the E-W trending Permian continental arc along the northern margin of the NCC,we confirm that the generation of the Middle Permian mafic intrusions was related to southward subduction of the Paleo-Asian oceanic lithosphere beneath the NCC and the Paleo-Asian Ocean had not closed prior to the Middle Permian.     

保定市一亩泉漏斗区地下水水化学特征演变及驱动机制解析

笔者等在对比分析一亩泉漏斗区地下水开采前—开采中—压采全过程地下水水化学特征基础上,综合利用数理统计分析、离子比例分析、水文地球化学模拟技术,揭示了漏斗区地下水水化学特征演化规律,解析了水化学特征演变驱动机制。结果表明,研究区地下水水化学特征演化表现出阶段性,在开采初期至压采初期,水化学类型、TDS、总硬度保持稳定,水化学类型以HCO^-₃—Ca²⁺·Mg²⁺型为主;在漏斗恢复期地下水水化学类型种类增多,TDS和总硬度显著增大,表现出向盐化和硬化方向演化趋势;1960～2010年研究区地下水水化学成分主要受脱白云石化作用、阳离子交换作用控制,呈自然演化规律;2010年以后,在漏斗恢复背景下,包气带中水岩相互作用过程加剧,地下水水化学演变受溶滤作用和离子交换作用控制,人类活动对地下水水化学特征的影响逐渐显现。研究结果可为漏斗区地下水保护与修复提供科学依据。     

BDS/GPS实时钟差估计中ISB分析与函数模型设计

实时钟差产品是高精度广域差分位置服务（亚米级、分米级、厘米级）的基础产品,通过研究BDS/GPS融合的ISB,研究了各类型接收机BDS GEO/IGSO/MEO ISB差异,提出了在BDS/GPS联合的实时钟差估计中引入3个ISB参数的函数模型,在此基础上基于非差法实现了BDS/GPS联合的实时钟差估计。采用MGEX和湖南CORS实时观测数据进行了实时钟差解算,利用iGMAS产品综合中心提供的事后精密钟差产品作为基准,对比分析了新方法与原有方法的实时钟差产品的精度差异。结果表明,该方法与原方法估计的GPS钟差精度相当,对BDS实时钟差精度改进显著,尤其对BDS IGSO/MEO卫星,改进幅度在20%以上,验证了算法的有效性。     

一种基于图像灰度直方图相似度计算的室内定位方法

近年来,视觉定位由于定位精度高广泛应用于室内定位与导航。然而,室内环境复杂多变,视觉定位在很多场景下无法实现高精度定位,而且多数视觉定位算法耗时和计算复杂度高,不适用于智能手机。为实现基于智能手机的准确高效定位,本文提出了一种基于图像灰度直方图相似度计算的定位方法。该方法分为两个阶段：离线阶段和在线阶段。离线阶段在已知坐标的格网点分别利用智能手机采集图像,提取图像灰度直方图,建立图像灰度直方图图像特征库;在线阶段智能手机在待测点采集图像提取灰度直方图,然后与图像特征库进行相似度计算,选取相似度和最大值的格网作为概略位置,以相似度为权重采用加权均值法得到准确位置。将所提方法和KNN算法进行对比,试验结果表明,该方法的平均定位误差优于0.3 m,与KNN算法相比定位精度提高了40.7%,计算时间优于1.7 s。     

REE Characteristics of a New Uranium Mineral from the Xianshi Uranium Deposit,South China

正Objective Galuskin et al.(2011)firstly discovered that vorlanite(CaU~(6+/4+))O_4 is a rare Ca-rich mineral with a fluorite-type structure,which is isostructural with uraninite(U~(4+)O_2).Previous studies of the Xianshi granite-related uranium deposit reported that uraninite and pyrite are the major ore minerals whereas galena,clausthalite(PbSe),and pyrite are minor phases in the ores.A more detailed petrographic     

改进D-LinkNet模型在国产卫星影像云检测中的应用

大部分国产卫星波段少,利用传统方法难以进行云检测。本文提出了基于改进D-LinkNet模型的云检测算法,并应用于国产卫星遥感影像的云检测。首先,利用自然资源部国土卫星遥感应用中心提供的人工勾云样本生成二值图标签;其次,对D-LinkNet50的编码器进行改进,使用带有通道注意力机制的ResNeSt50-Block替换原始的ResNet50-Block;然后,对损失函数进行加权,测试分析发现只用交叉熵损失作为损失函数时,检测精度更高;最后,使用条件随机场（CRF）对预测结果进行后处理。试验结果表明,改进D-LinkNet模型在测试集上的IoU提升了1.93%,精度提升了2.45%,保持了较好的云边缘信息,云检测效果高于原D-LinkNet模型。     

松辽盆地现今地温场分布特征及主控因素

松辽盆地不仅是世界上已发现油气资源最为丰富的陆相沉积盆地之一,同时也存在十分丰富的中低温地热资源,是当前油气勘探和地热勘探的主力区块。本文结合近10年来新增的一大批测温数据,借助571口钻井地层测温资料和150余个岩石热物性参数,重新剖析了松辽盆地现今地温场分布特征及其主控因素。研究表明,松辽盆地地温梯度在19～55 ℃/km之间,平均为41. 4 ℃/km,现今大地热流分布在38. 9～111. 2 mW/m 2之间,平均为78. 9 mW/m2。相比其他盆地而言,松辽盆地具有高温“热盆”的特点。平面上,盆地中央坳陷区地温梯度和大地热流均较高。嫩江组底界面温度约为15～88℃,平均为48. 6℃;姚家组底界面的温度为18～95℃,平均值为53℃;青山口组底界面的温度为25～128℃,平均值为64℃;泉四段底界面的温度为26～131℃,平均值为67℃。松辽盆地现今温度分布主要受到成盆演化动力学背景、岩石热物性特征、岩浆作用等多种因素的影响。松辽盆地经历了强烈的区域伸展作用和岩石圈减薄,并发育丰富的基底断裂和地壳断裂,造成深部地幔热物质沿着基底断裂运移至浅部,因此地表热流偏高。     

Compiling distribution of karst in Southern China and Southeast Asia

As China and Southeast Asian countries have accelerated and globalized their economic development, karst environmental problems have become increasingly prominent and studying on and compiling maps of karst geology is quite important. Therefore, based on a wide collection of data in Southeast Asian countries, a cooperative map compilation has been carried out internationally. Through comprehensive research and analysis, a unified understanding has been achieved in terms of compiling principles, contents and representing methods, Distribution of Karst in Southern China and Southeast Asia (1/5 000 000) has been compiled, which provides foundations for environmental protection and scientific studies of karst geology.     

基于 BDS 利用海洋上冰山为人类服务的设想

海洋上冰山虽然被人们称为“海洋杀手”,但是如果人类能够在远航之前做好充分的准备,亦可以利用冰山为人类服务。本文阐述了海洋上冰山的特点,而且研讨了基于北斗卫星导航系统（BDS ）利用海洋上冰山为人类服务的设想。本文研讨的结论也可以为以后数字海洋的建设提供参考。