SHRIMP Zircon U‐Pb Dating of Alkaline Dykes in the Pobei Area,Beishan Rift,Xinjiang Autonomous Region,China: Implications for Tectonic Setting and Mantle Plume Events   总被引：2，自引：0，他引：2  

MAO Jingwen  Franco PIRAJNO  ZHANG Zuoheng  WAN Yusheng 《《地质学报》英文版》2012,86(4):879-884

In the Beishan rift in the eastern Tianshan orogen, Xinjiang Province, a N-S-trending dyke swarm is present in the Pobei area. The swarm cuts through the 270–290 Ma mafic-ultramafic intrusions associated with Ni-Cu sulphide mineralization. These mafic-ultramafic intrusions are typically found along E-W major faults in the Tianshan orogenic belts. We report SHRIMP U-Pb dating of zircons from a dyke of alkaline composition, which yielded a mean age of 252±9 Ma. Alkaline dykes of the same age are found in the Altay region of Siberia. This age is younger than the 270–290 Ma intraplate magmatic events that produced the mafic-ultramafic intrusions in the region, but in general agreement with the 250–260 Ma Permian plume event that gave rise to the Siberian traps and the Emeishan flood basalts in SW China. We suggest that there is a link between the Emeishan event and the dyke swarm in the Beishan rift and that the intraplate magmatism at 270–290 Ma reflects an early stage of mantle plume activity. The N-S trending dyke swarm in the Beishan rift may represent a later stage in the evolution of mantle plume activity in the NW and SW of China. We also speculate that in Beishan rift and possibly elsewhere in the Tianshan region, the dykes fed basaltic volcanism, whose products have since been eroded due to the strong uplift of the Tianshan orogen as a result of the India-Eurasia collision in the Cenozoic.  相似文献   

The influence of the Jahn–Teller effect at Fe<Superscript>2+</Superscript> on the structure of chromite at high pressure     

Atsushi?KyonoEmail author  Stephen?A.?Gramsch  Takamitsu?Yamanaka  Daijo?Ikuta  Muhtar?Ahart  Bj?rn?O.?Mysen  Ho-kwang?Mao  Russell?J.?Hemley 《Physics and Chemistry of Minerals》2012,39(2):131-141

The crystal structure of chromite FeCr₂O₄ was investigated to 13.7 GPa and ambient temperature with single-crystal X-ray diffraction techniques. The unit-cell parameter decreases continuously from 8.3832 (5) to 8.2398 (11) Å up to 11.8 GPa. A fit to the Birch–Murnaghan equation of state (EoS) based on the P–V data gives: K ₀ = 209 (13) GPa, K′ = 4.0 (fixed), and V ₀ = 588 (1) ų. The FeO₄ tetrahedra and CrO₆ octahedra are compressed isotropically with pressure with their Fe–O and Cr–O bond distances decreasing from 1.996 (6) to 1.949 (7) Å and from 1.997 (3) to 1.969 (7) Å, respectively. The tetrahedral site occupied by the Fe²⁺ cation is more compressible than the octahedral site occupied by the Cr³⁺ cation. The resulting EoS parameters for the tetrahedral and the octahedral sites are K ₀ = 147 (9) GPa, K′ = 4.0 (fixed), V ₀ = 4.07 (1) ų and K ₀ = 275 (24) GPa, K′ = 4.0 (fixed), V ₀ = 10.42 (2) ų, respectively. A discontinuous volume change is observed between 11.8 and 12.6 GPa. This change indicates a phase transition from a cubic (space group Fd-[`3]{\overline{3}} m) to a tetragonal structure (space group I4₁ /amd). At the phase transition boundary, the two Cr–O bonds parallel to the c-axis shorten from 1.969 (7) to 1.922 (17) Å and the other four Cr–O bonds parallel to the ab plane elongate from 1.969 (7) to 1.987 (9) Å. This anisotropic deformation of the octahedra leads to tetragonal compression of the unit cell along the c-axis. The angular distortion in the octahedron decreases continuously up to 13.7 GPa, whereas the distortion in the tetrahedron rises dramatically after the phase transition. At the pressure of the phase transition, the tetrahedral bond angles along the c-axis direction of the unit cell begin decreasing from 109.5° to 106.6 (7)°, which generates a “stretched” tetrahedral geometry. It is proposed that the Jahn–Teller effect at the tetrahedrally coordinated Fe²⁺ cation becomes active with compression and gives rise to the tetrahedral angular distortion, which in turn induces the cubic-to-tetragonal transition. A qualitative molecular orbital model is proposed to explain the origin and nature of the Jahn–Teller effect observed in this structure and its role in the pressure-induced phase transition.  相似文献   

内蒙古毕力赫含金花岗岩类侵入岩锆石U-Pb年龄及地质意义   总被引：4，自引：2，他引：2  

路彦明  潘懋  卿敏  张玉杰  韩先菊  朝银银 《岩石学报》2012,28(3):993-1004

毕力赫大型斑岩型金矿位于华北克拉通北缘白乃庙-哈达庙铜-钼-金矿化集中区。矿区侵入岩包括以花岗闪长斑岩为主的含金次火山侵入杂岩体和地表广泛出露的钾长花岗斑岩。次火山杂岩体SiO2含量61.5%～71.4%,属亚碱性钙碱性系列,岩石REE配分具LREE富集型,弱Eu负异常,相对富集大离子亲石元素(LILEs)、亏损高场强元素(HFSEs)和Ba,具壳幔混源特征,除亏损Ba之外总体类似陆缘弧花岗岩。LA-ICP-MS锆石U-Pb测年获得含金次火山侵入杂岩体和钾长花岗斑岩成岩年龄分别为283.8±4.2Ma～279.9±6.8Ma和264.2Ma,为早、中二叠世,与野外地质体穿插关系吻合。哈达庙-白乃庙地区晚古生代中-早二叠世的大规模构造-岩浆-成矿作用,与白云鄂博-西拉木伦缝合带两侧大陆对接碰撞的时间一致,受同碰撞构造环境制约。  相似文献   

ATLAS, and Wide-Angle Tail Galaxies in ATLAS     

Minnie Y. Mao  Rob Sharp  D. J. Saikia  Ray P. Norris  Melanie Johnston-Hollitt  Enno Middelberg  Jim E. J. Lovell 《Journal of Astrophysics and Astronomy》2011,32(4):585-588

Using the Australia Telescope Compact Array (ATCA), ATLAS (Australia Telescope Large Area Survey) is imaging two fields totalling 7 square degrees down to 10 μJy beam^− 1 at 1.4 GHz. We have found 6 wide-angle tail galaxies (WATs), 4 of which have sufficient data to identify associated galaxy overdensities. The largest WAT, at a red-shift of 0.22, appears to be associated with an overdensity of galaxies that is spread over an unusually large extent of 12 Mpc, with a velocity range of 4500 km s^− 1. Here we present the WATs in ATLAS and discuss the implications of these observations for future large-scale radio surveys such as ASKAP-EMU.  相似文献   

Tailed Radio Sources in the CDFS Field     

S. Dehghan  M. Johnston-Hollitt  M. Mao  R. P. Norris  N. A. Miller  M. Huynh 《Journal of Astrophysics and Astronomy》2011,32(4):491-492

Using 1.4 GHz ATCA & VLA images with 5.5 GHz ATCA data, we present a sample of 12 bent-tailed galaxies over the 4 deg² area of the Chandra Deep Field South (CDFS). We find 10 new sources, one of which is possibly the highest red-shift bent-tailed galaxy detected at z ∼ 2.  相似文献   

月球形状及其重力场EI北大核心CSCD     

李斐  郑翀  叶茂  郝卫峰  邓青云  张文松  郑英君  鄢建国  Jean-Pierre Barriot 《测绘学报》2022,51(6):897-908

本文首先从测绘科学与技术在月球探测中的应用角度,对月球形状及重力场的研究进展、获取方法及代表性成果进行了综述;进而针对现有的月球DEM及重力场模型中存在的主要问题进行分析,并提出了解决方案;最后结合各国的探月计划和我国正在实施的“嫦娥”四期工程,对月球形状和重力场研究面临的机遇和挑战进行了展望。  相似文献   

基于SWAT-MODFLOW耦合模型的巴音河中游泽令沟盆地地表水−地下水转换关系研究     

傅笛  金鑫  金彦香  毛旭锋  翟婧雅 《地理科学》2022,42(6):1124-1132

为准确刻画资料缺乏、地表水–地下水转换频繁的泽令沟盆地地表水?地下水不同时空尺度上的转换关系,利用河道径流数据、遥感蒸散发数据、地下水位观测数据等对SWAT-MODFLOW耦合模型进行率定和验证,在此基础上对泽令沟盆地水循环过程进行模拟分析。结果显示：① SWAT-MODFLOW耦合模型模拟效果较好,率定期和验证期月径流量的R²≥0.73,NSE≥0.67,PBIAS在?20%~20%。其各子流域实际蒸散发的R²均大于0.91,NSE均大于0.85,PBIAS在?10%~10%。此外,模拟地下水位与实测值误差在0.6 m以内,R²为0.94。② 地表水补给地下水的河道占整个河道长度90.31%,年平均补给量占年总交换水量的50.20%;季节尺度上,补给的最大值出现在7月,为331043.31 m³/d,最小值出现在12月份,为41208.33 m³/d。地下水对地表水的补给量较为稳定,季节性变幅在?2.5%~2.5%,年际变幅处于?6.5%~0.6%之间。  相似文献   

基于项目式学习的红色文化研学旅行课程设计--以“天山脚下的纪念”为例     

马蕾  叶茂 《地理教学》2022,(4):59-61

青少年红色文化研学旅行把爱国主义、红色传统和红色精神传播到青少年之中,具有特殊的意义。引导青少年坚定理想信念,为实现中华民族伟大复兴的中国梦努力奋斗,是红色研学旅行的重要任务。本文采用PBL模型,依托伊犁有关林则徐的历史文化资源,设计了以“天山脚下的纪念”为主题的高中学段研学旅行实践活动;引导学生通过了解林则徐传奇的一生,懂得继承和弘扬林则徐艰苦奋斗、爱国爱乡的情怀;最后对基于PBL模型的“天山脚下的纪念”研学旅行课程进行了反思。  相似文献   

沙漠、戈壁和黄土表土岩石磁学特征及其对黄土磁化率机制的意义     

毛学刚  赵丽娟 《中国沙漠》2022,42(2):183-193

黄土高原黄土来自于其北部或西北部的沙漠和戈壁被广泛认可。本文选取西北地区典型的沙漠、戈壁和黄土表土样品,进行系统的岩石磁学研究。结果显示：沙漠和戈壁磁学特征相似,以磁铁矿占绝对优势,磁颗粒为多畴和假单畴,几乎不含超顺磁颗粒,磁性矿物总体含量高于黄土表土。黄土表土以磁铁矿为主,同时含有磁赤铁矿,磁颗粒以成壤过程中形成的超顺磁和单畴颗粒为主。虽然沙漠和戈壁细粒中亚铁磁性矿物相对比例明显高于粗粒,但粗粒组分含量大,对磁性稀释作用显著,全样总体表现为粗粒磁性特征。影响沙漠、戈壁和黄土磁化率的主导因素不同,沙漠和戈壁为磁性矿物含量主导型,磁性矿物总含量高,黄土表土为磁性矿物粒度主导型,超顺磁对磁化率贡献占主导。合理区分风速论和成土论两种磁化率机制,需准确判断成壤程度和氧化还原状态。因此,不同环境条件下磁化率的环境意义及古气候重建,需首先准确区分影响磁化率的主导因素。  相似文献   

长江中游城市群潜在增长城市时空演变特征     

吴青青  钟业喜  吴思雨  毛炜圣 《热带地理》2022,42(4):605-615

通过改进引力模型和地缘系数,测算长江中游城市群先行政治、经济增长极的引力,探究潜在增长极的时空演化格局。结果表明：1）长江中游城市群潜在发展城市中心性分布不均,湖南、湖北、江西省分别呈“高值均衡化”“双核心化”“单核心化”特征。2）绝对地缘系数区域差异显著,湖南、江西两省具有“中心低、四周高”的特点,3个城市子群内部联系更多,存在省域行政切割现象;最佳地缘系数呈“双峰”型,受城市地缘政治引力影响较大的城市发展情况稍好于受经济引力影响较大的城市。3）潜在增长城市“边缘性”特征明显,集中于城市群周边,重心在西南方。结合城市发展潜力与城市群协调发展的现实需要,明确株洲、襄阳和九江3个一级增长极以及衡阳、宜昌和新余3个二级潜在增长极。  相似文献