A modified three-dimensional ionospheric tomography algorithm with side rays

The three-dimensional ionospheric tomography (3DCIT) algorithm based on Global Navigation Satellite System (GNSS) observations have been developed into an effective tool for ionospheric monitoring in recent years. However, because the rays that come into or come out from the side of the inversion region cannot be used, the distribution of the rays in the edge and bottom part of the inversion region is scarce and the electron density cannot be effectively improved in the inversion process. We present a three-dimensional tomography algorithm with side rays (3DCIT-SR) applying the side rays to the inversion. The partial slant total electron content (STEC) of side rays in the inversion region is obtained based on the NeQuick2 model and GNSS-STEC. The simulation experiment results show that the algorithm can effectively improve the distribution of GNSS rays in the inversion region. Meanwhile, the iteration accuracy has also been significantly improved. After the same number of iterations, the iterative results of 3DCIT-SR are closer to the truth than 3DCIT, in particular, the inversion of the edge regions is improved noticeably. The GNSS data of the International GNSS Service (IGS) stations in Europe are used to perform real data experiments, and the inversion results show that the electron density profiles of 3DCIT-SR are closer to the ionosonde measurements. The accuracy improvement of 3DCIT-SR is up to 56.3% while the improvement is more obvious during the magnetic storm compared to the case of a calm ionospheric state .     

Dehydration melting of solid amphibolite at 2.0 GPa: Effects of time and temperature

The dehydration melting of the natural rock at high pressure is important to investigating the magma formation in the earth’s interior. Since the 1970s, a lot of geological scientists have paid more atten- tion to the dehydration melting of the natural rock[1―5]. Previous experiments of dehydration melting and observations of fieldwork argued that the dehy- dration melting of the rock was probably the most important fashion for the melting of the lower crust rock[6―12]. The genesis of most …     

物探方法在临清坳陷某区块山西组沉积相分析中的应用

临清坳陷某区块缺少岩心、薄片、录井及常规测井资料。为了研究其目的层山西组沉积相对储层的控制作用,指导非常规天然气的高效开发。通过利用较少的录井岩性统计资料,结合地震物探方法,分析地震剖面特征、优选地震均方根振幅及相对波阻抗属性,确定该区目的层沉积相。通过上述地震属性研究的物探方法,确定山西组储层为河控浅水三角洲相和碳酸盐台地相,主要发育分流河道、分流间湾及局限台地沉积微相。其中三角洲相是主要的沉积相类型,分流河道是有效储层发育的主要微相类型。     

Fe–Cu deposits in the Kangdian region,SW China: a Proterozoic IOCG (iron-oxide–copper–gold) metallogenic province

Numerous Fe–Cu deposits are hosted in the late Paleoproterozoic Dongchuan and Dahongshan Groups in the Kangdian region, SW China. The Dongchuan Group is composed of siltstone, slate, and dolostone with minor volcanic rocks, whereas the Dahongshan Group has undergone lower amphibolite facies metamorphism and consists of quartz mica-schist, albitite, quartzite, marble and amphibolite with local migmatite. Deposits in the Dongchuan Group are commonly localized in the cores of anticlines, in fault bends and intersections, and at lithological contacts. Orebodies are closely associated with breccias, which are locally derived from the host rocks. Fe-oxides (magnetite and/or hematite) and Cu-sulfides (chalcopyrite, bornite) form disseminated, vein-like and massive ores, and typically fill open spaces in the host rocks. The deposits have extensive albite alteration and local K-feldspar alteration overprinted by quartz, carbonate, sericite and chlorite. Deposits in the Dahongshan Group have orebodies sub-parellel to stratification and show crude stratal partitioning of metals. Fe-oxide ores occur as massive and/or banded replacements within the breccia pipes, whereas Cu-sulfide ores occur predominantly as disseminations and veinlets within mica schists and massive magnetite ores. Ore textures suggest that Cu-sulfides formed somewhat later than Fe-oxides, but are possibly within the same mineralization event. Both ore minerals predated regional Neoproterozoic metamorphism. Both orebodies and host rocks have undergone extensive alteration of albite, scapolite, amphibole, biotite, sericite and chlorite. Silica and carbonate alterations are also widespread. Ore-hosting strata have a LA-ICP-MS zircon U–Pb age of 1681 ± 13 Ma, and a dolerite dyke cutting the Fe-oxide orebodies has an age of 1659 ± 16 Ma. Thus, the mineralization age of the Dahongshan deposit is constrained at between the two. All ores from the two groups have high Fe and low Ti, with variable Cu contents. Locally they are rich in Mo, Co, V, and REE, but all are poor in Pb and Zn. Sulfides from the Fe–Cu deposits have δ³⁴S values mostly in the range of +2 to +6 per mil, suggesting a mix of several sources due to large-scale leaching of the strata with the involvement of evaporites. Isotopic dating and field relationships suggest that these deposits formed in the late Paleoproterozoic. Ore textures, mineralogy and alteration characteristics are typical of IOCG-type deposits and thus define a major IOCG metallogenic province with significant implications for future exploration.     

ENSO发展和衰减阶段的陕西夏季降水异常特征

利用1961—2008年陕西78个气象站夏季 (6—8月) 降水资料、NCEP/NCAR位势高度场和风场月平均再分析资料,采用合成及相关分析方法探讨ENSO发展和衰减阶段对陕西夏季降水异常的影响,以期为陕西夏季降水的气候预测提供线索和依据。结果表明:陕西夏季降水异常对ENSO发展和衰减阶段的响应存在显著差异,El Ni?o发展阶段和La Ni?a衰减阶段,陕西夏季降水偏少; El Ni?o衰减阶段和La Ni?a发展阶段,陕西夏季降水偏多; ENSO不同阶段对陕西7月降水影响最为显著。比较而言,El Ni?o事件对陕西夏季降水的影响更加显著。在El Ni?o衰减、La Ni?a发展阶段,西太平洋副热带高压偏强、偏西,东亚夏季风偏弱,而在El Ni?o发展、La Ni?a衰减阶段,西太平洋副热带高压偏弱、偏东,东亚夏季风偏强,El Ni?o过程对东亚夏季风强弱的影响更加显著。ENSO发展和衰减阶段通过影响大气环流变化和东亚夏季风的强弱,进而影响陕西夏季降水。     

板钉连接CFST柱-RC梁节点梁端塑性铰区受力性能数值模拟

建立竖板-栓钉连接钢管混凝土（CFST）柱-钢筋混凝土（RC）梁节点试件（SSJD）拟静力加载试验有限元模型,并在节点损伤情况、梁端荷载-位移曲线等数值模拟结果与试验结果吻合较好的基础上,进一步开展了RC梁混凝土强度、配筋率ρs和连接竖板长度Lb及界面连接情况等对CFST柱-RC梁节点梁端塑性铰区域力学性能的影响。研究结果表明,RC梁混凝土强度对试件SSJD塑性铰区域受力性能的影响较小;适筋范围内RC梁配筋率增加可适当提高试件SSJD承载力和延性;随着连接竖板长度的增加,梁端塑性铰区域外移,梁破坏荷载增大;本研究给出的RC梁与CFST柱之间的界面抗剪承载力模拟值与计算值吻合较好,可用于界面抗剪设计。     

Black band disease as a possible factor of the coral decline at the northern reef-flat of Yongxing Island,South China Sea

Black band disease(BBD),characterized by the Cyanobacterial dominated pathogenic consortium,is thought to play a key role in the global decline of the coral reef ecosystems.The present paper originally documents a case of BBD from Yongxing Island(Xisha Islands,South China Sea),and further probes the reasons of this abnormal phenomenon.Prior to 2007,corals at northern reef-flat of Yongxing Isand were in healthy growth.Catastrophic coral mortality occurred between 2007 and 2008.The 16S rRNA gene sequencing and PCR amplification,with universally conserved primers,were applied to detect the contagious bacterial community of the microbial mat.The results demonstrated that six bacterial divisions constituted the clone libraries derived from the BBD mat,and that Cyanobacteria are the most diversely represented group that inhabit BBD bacterial mats,despite the fact that species in five others divisions(α-Proteobacteria,γ-Proteobacteria,Bacteroidetes,Verrucomicrobia and Actinobacteria) are also consistently diverse within the BBD mats of diseased coral.Other factors such as coral bleaching,typhoons,ocean acidification and crown-of-thorns starfish outbreaks,are not primarily responsible for the coral mortality within such a short time interval.The disaster expansion of BBD associated with Cyanobacterial blooms is a more likely mechanism impacting these coral reefs.Excessive human activity enhances the eutrophication of the marine water of the reefal region and may result in occurrence of the BBD.     

西藏雅鲁藏布江缝合带西段普兰纯橄岩中橄榄石的出溶特征及指示意义

西藏雅鲁藏布江缝合带西段普兰纯橄岩中橄榄石存在透辉石和磁铁矿共生出溶现象。这类纯橄岩非常新鲜,主要由橄榄石、尖晶石和透辉石等矿物组成。橄榄石的Fo值是90.1~90.7,铬尖晶石的Cr~#为19.8~20.8,远小于蛇绿岩地幔橄榄岩中常见纯橄岩中铬尖晶石的铬值(Cr~#60)。基于前人研究结果,提出这种现象是由于亏损方辉橄榄岩与含钛、铝、钙熔体发生交代作用,从而形成橄榄石的固溶体存在Ti~(4+)、Al~(3+)、Ca~(2+)、Fe~(3+),而Cr~(3+)进入铬尖晶石结晶。后期由于岩体在抬升过程中降温,橄榄石中出溶形成单斜辉石和磁铁矿,而铬尖晶石结晶被保留。依据铬尖晶石-橄榄石的矿物化学成分,识别出低铬纯橄岩具有最低的部分熔融程度为~8%,Cr~#最高的纯橄岩壳其部分熔融程度达到~50%,表明不同岩相间其形成背景存在明显差异。因此,笔者认为普兰蛇绿岩具有多阶段的过程。首先是在洋中脊环境下经历富Ca、Al和Na等熔体交代和部分熔融作用,后受到俯冲带玻安质熔体改造。     

宁夏地区的震源机制与应力场

本文利用宁夏地震台网观测资料,讨论了宁夏区内七个地区的区域应力场,并且给出了16次中强地震的震源机制解。结合大地形变测量资料分析认为,宁夏北部银川平原的区域应力场以北北东方向的主压应力占优势。宁夏南部西(吉)、海(原)、固(原)地区的区域应力场以北东方向的主压应力占优势。南部和北部两区域的分界带在中卫、中宁一线。中卫附近的主压应力方位为165°,与其南部、北部地区都不相同。本文研究结果认为,现今宁夏构造应力场的格局与印度板块和太平洋板块的共同作用有关,其中印度板块的推挤起主导作用。