利用Abel-Poisson径向基函数模型化局部重力场

多种类型高分辨率重力场数据的不断增加,使得在局部范围内精化重力场模型成为了可能。本文采用Abel-Poisson核将重力场量表示成有限个径向基函数线性求和的形式,对局部区域的多种重力场数据进行联合建模。为了提高运算速度,运用了基于自适应精化格网算法的最小均方根误差准则(RMS)来求解径向基函数平均带宽。以南海核心地区为例,联合两种不同类型、不同分辨率的重力场资料(大地水准面起伏6'×6'、重力异常2'×2'),构建了局部区域高分辨率的重力场模型。所建模型表示的重力场参量达到了2'×2'的分辨率,对原始的重力异常数据(2'×2')拟合的符合程度达到±0.8×10-5m/s2。结果表明,利用径向基函数方法进行局部重力场建模,避免了球谐函数建模收敛慢的问题,有效提高了模型表示重力场的分辨率。     

Bimodal magmatism of the Tucumã area,Carajás province: U-Pb geochronology,classification and processes

Geological mapping of the Tucumã area has enabled the identification of dike swarms intruded into an Archean basement. The disposition of these dikes is consistent with the well-defined NW-SE trending regional faults, and they can reach up to 20 km in length. They were divided into three main groups: (i) felsic dikes (70% of the dikes), composed exclusively of porphyritic rhyolite with euhedral phenocrysts of quartz and feldspars immersed in an aphyric felsite matrix; (ii) mafic dikes, with restricted occurrence, composed of basaltic andesite and subordinate basalt, with a mineralogical assembly consisting dominantly of plagioclase, clinopyroxene, orthopyroxene and olivine; and (iii) intermediate rocks, represented by andesite and dacite. Dacites are found in outcrops associated with felsic dikes, representing different degrees of hybridization or mixture of mafic and felsic magmas. This is evidenced by a large number of mafic enclaves in the felsic dikes and the frequent presence of embayment textures. SHRIMP U-Pb zircon dating of felsic dikes yielded an age of 1880.9 ± 3.3 Ma. The felsic dikes are peraluminous to slightly metaluminous and akin to A2, ferroan and reduced granites. The intermediate and mafic dikes are metaluminous and belong to the tholeiitic series. Geochemical modeling showed that mafic rocks evolved by pyroxene and plagioclase crystallization, while K-feldspar and biotite are the fractionate phases in felsic magma. A simple binary mixture model was used to determine the origin of intermediate rocks. It indicated that mixing 60% of rhyolite and 40% basaltic andesite melts could have generated the dacitic composition, while the andesite liquid could be produced by mixing of 60% and 40% basaltic andesite and rhyolite melts, respectively. The mixing of basaltic and andesitic magmas probably occurred during ascent and storage in the crust, where andesite dikes are likely produced by a more homogeneous mixture at high depths in the continental crust (mixing), while dacite dikes can be generated in the upper crust at a lower temperature, providing a less efficient mixing process (mingling). The affinities observed between the felsic to intermediate rocks of the Rio Maria and São Felix do Xingu areas and the bimodal magmatism of the Tucumã area reinforce the hypothesis that in the Paleoproterozoic the Carajás province was affected by processes involving thermal perturbations in the upper mantle, mafic underplating, and associated crustal extension or transtension. The 1.88 Ga fissure-controlled A-type magmatism of the Tucumã area was emplaced ∼1.0 to ∼0.65 Ga after stabilization of the Archean crust. Its origin is not related to subduction processes but to the disruption of the supercontinent at the end of the Paleoproterozoic.     

西藏冈底斯尼木后碰撞花岗岩的岩浆混合作用:显微结构证据

岩浆混合过程中不同熔体之间的相互作用会影响晶体的成核与生长,形成矿物内部复杂的成分变化,以及矿物之间的不平衡结构。尼木二长花岗岩位于冈底斯岩浆岩带中部,是代表性的形成于后碰撞构造演化时期的花岗岩体。本文对其中的斜长石与角闪石颗粒进行了详细的结构和成分分析,揭示了斜长石中的港湾状、浑圆状、筛孔状熔蚀结构以及斜长石成分的突然变化和角闪石包裹黑云母的不平衡结构,并探讨了它们的成因以及相关的岩浆混合作用。分析结果显示,斜长石中突变环带的An含量为37.6~40.6,熔蚀环带的An含量为48.2~59.5,均高于两侧斜长石的An含量(18.4~26.4),表明在形成这些结构时有外来基性岩浆的混合使得岩浆成分发生了突变。样品中的部分黑云母被自形的角闪石包裹,黑云母呈浑圆状并且具有港湾状的熔蚀边,这可能是基性岩浆的混合作用使得岩浆的温度升高导致黑云母发生部分熔融,混合后的岩浆在黑云母周围继续结晶形成角闪石。这些显微结构为揭示冈底斯岩浆岩带的岩浆混合作用提供了新证据。     

延边开山屯花岗闪长岩-石英闪长岩体年代学、地球化学特征及对古太平洋板块俯冲作用时限的制约

近年来古太平洋构造域的构造演化备受学者关注。本文报道的延边开山屯地区花岗闪长岩-石英闪长岩体LAICP-MS U-Pb年龄表明其形成时间为早侏罗世早期(198±1Ma),所采样品可根据Zr/Hf值分为高Zr/Hf值组花岗闪长岩和低Zr/Hf值组石英闪长岩。高Zr/Hf值组花岗闪长岩起源深度浅,富集Rb、Th、U、K等大离子亲石元素(LILEs),贫Nb、Ta、Ti等高场强元素(HFSEs),具壳源岩浆的特点。低Zr/Hf值组为壳源岩浆与来自深部的亏损地幔岩浆混合而成,岩石亏损Nb、Ta、Zr、Hf、Ti等高场强元素,具有典型的弧型岩浆地球化学特征。岩体中存在细粒闪长质包体,镜下可见针柱状磷灰石。开山屯岩体属钙碱性系列岩石,结合前人资料,认为其与该地区同时代火成岩组成北-东向分布的早侏罗世活动大陆边缘型火成岩带,而位于该带西侧的小兴安岭-张广才岭地区存在同时代弧后拉张带,两者构成典型的大陆弧与弧后拉张带模型,共同揭示了早侏罗世早期古太平洋板块对东北地区的俯冲作用。     

均生函数与BP神经网络耦合模拟预测模型(MGF-BP-I)的建立与应用

水文气候因子模拟预测对气候变化研究、农业墒情预报、生态环境改善、水资源合理开发利用等具有一定参考意义。均生函数、BP神经网络及其结合改进方式在模拟预测中各有优点,被广泛应用,但仍有进一步改进空间。针对MGF、MGF-OSR、MGF-OSR-BP等方法粗选因子集、粗选集组合筛选、收敛适应性、精度控制等可改进空间,进一步发挥均生函数和BP神经网络优势,建立了MGF-BP-I模拟预测模型。利用MGF-OSR、MGF-OSR-BP、MGF-BP-I对科尔沁沙地区域平均年降水进行了模拟预测。结果表明,建模期MGF-OSR-BP、MGF-BP-I拟合效果均较好,MGF-BP-I建模阶段最优模式精度优于MGF-OSR-BP,MGF-BP-I整体同时最优模式结果也非常好。检验期,MGF-BP-I检验阶段最优及整体同时最优两种模式拟合效果最好,相比其他模式精度有所提高。MGF-BP-I考虑更加全面,充分发挥了均生函数和BP神经网络优势,精度远高于MGF-OSR和MGF-OSR-BP,MGF-BP-I整体同时最优模式更符合实际应用,效果理想,可用于水文气候因子模拟预测。     

Development of A Depth-Integrated Longshore Current Model with Unstructured Grids

A depth-integrated model for simulating wave-induced longshore current was developed with unstructured grids. Effects of surface roller and horizontal mixing under combined waves and currents were incorporated in the numerical model. Recommended values of model coefficients were also proposed based on sensitivity analysis. Field observations and three series of laboratory measurements including two cases conducted on the plane beach and one implemented on the ideal inlet were employed to examine the predictive capability of this model. For the field case and laboratory cases conducted on the plane beach, numerical results were compared favorably with the measured data. For the case with an ideal inlet, simulated circulation pattern is supposed to be reasonable although some deviations between numerical results and measured data still can be detected.     

Petrogenesis of the microcrystalline-dioritic enclaves from Jiuling granitoids in the eastern segment of Jiangnan Orogen and constraints on magma source materials

Numerous dark enclaves with different shapes are found in Jiuling Neoproterozoic granitoids. Precise LA-ICP-MS U-Pb dating was conducted on zircons extracted from two microcrystalline enclave samples, yielding crystallization ages of 822.6±5.8 Ma and 822.2±6.2 Ma, respectively. The consistent ages within analytical errors with the host granitoids suggested that they were the products of the same magmatism. The microcrystalline-dioritic enclaves commonly show plastic forms and contain similar plagioclase megacrysts to the host rocks, and both of the enclaves and host granitoids showed a complex composition and structural imbalance in plagioclases. Furthermore, the apatites with a euhedral acicular shape occurred widely in the microcrystalline-dioritic enclaves. All of these petrographic features above imply magma mixing is involved in their diagenesis. The enclaves and host granitoids show a marked zircon trace element difference and Hf isotopic signatures without correlation in zircon trace element pairs but form their own system between enclaves and host granitoids. Additionally, most of the zircons show extremely high ε_Hf (t) with ε_Hf (t) =3.54–11.94 from the southern samples, and ε_Hf (t) =1.0–9.09 from the central region. Some zircons with the higher ε_Hf (t) are similar to the zircons from the juvenile island arc in the eastern segment of Jiangnan Orogen. Integrated geological and Hf isotopic characteristics suggest microcrystalline-dioritic enclaves were derived from the partial melting process of the Mesoproterozoic crust which enriched juvenile island arc materials and mixed with the granitic magma that remelted from the Mesoproterozoic continental crust which relatively enriched ancient sediments and mixed with the host granitoid in diagenesis.     

两方程湍流模型对内背风波数值模拟的影响

为了深入理解非静力近似下的波-湍相互作用问题,本研究在σ坐标的海洋环境研究和预报模型(MERF)中引入常用的Mellor-Yamada两方程湍混合参数化方案(MY2.5),评估垂向湍混合对小尺度背风波传播过程的影响.瞬时状态场的模拟结果表明,无论是否为非静力近似条件,上述湍参数化方案的引入都会减弱背风波传播的模拟效果.从时间平均场的试验结果来看,垂向湍混合过程会显著减小非静力近似和静力近似之间的差异.此外,能量收支分析的诊断结果表明,MY2.5方案会显著抑制陆坡地形下的背风波传播过程,进而将更多的潮能转化到不可逆的湍混合过程中.     

藏南冈底斯岩基东段朗县杂岩早白垩世岩浆作用:新特提斯洋二次俯冲

新特提斯洋长期俯冲消减作用在早白垩世可能经历二次俯冲启动或板片俯冲几何形态的重大转换。确定西藏南部冈底斯岩基早白垩世岩浆作用的岩石地球化学特征和作用方式是甄别上述过程的关键,对理解新特提斯洋的俯冲演化过程至关重要。本文就冈底斯岩基东段朗县杂岩中保存的各类早白垩世岩浆岩,开展了锆石U-Pb地质年代学和Hf同位素、全岩元素和同位素（Sr-Nd）组成分析。数据结果表明：1）基性岩侵位时代为早白垩世晚期（103.6~100.8Ma）,为高钾钙碱性偏铝质岩石,锆石ε_Hf（t）=+0.3~+5.7,全岩ε_Nd（t）=-0.8和-0.3,暗示其岩浆源区具有大量俯冲沉积物或流体的混入,为沉积物熔体和流体交代的地幔楔物质部分熔融的产物,经历了一定程度的角闪石分离结晶作用;2）中性岩形成于99.8~97.6Ma,略晚于基性岩,其主量元素与基性岩具有较好的线性关系,全岩ε_Nd（t）=+1.1,具有较多的地幔物质参与,为基性岩浆进一步演化形成;3）酸性岩（脉体）记录了多阶段岩浆作用（124.1~95.3Ma）,根据同位素组成不同进一步划分为两类,第一类具有较低的全岩ε_Nd（t）值（-8.3~-6.0）,其岩浆源区显示富集特征,t_DM2=1385~1586Ma,由古老地壳物质的再熔融形成;第二类的锆石ε_Hf（t）值（-2.8~+3.2）变化较大,岩脉的锆石ε_Hf（t）=+0.4~+8.1,t_DM=428~906Ma,全岩ε_Nd（t）=+0.1和+0.8,表明岩浆源区具有不均一性,为古老地壳物质被富流体地幔岩浆改造形成;和4）镁铁质包体的主量元素与寄主花岗岩具有较好的线性关系,锆石的Hf同位素组成变化较大（ε_Hf（t）=-9.3~+4.1）,变化范围可达13个ε单位,为岩浆混合成因。寄主花岗岩和角闪辉长岩分别作为酸性和基性端元,是基性岩浆与其诱发古老地壳熔融形成的花岗质岩浆经混合形成。结合冈底斯岩基早白垩世岩浆岩的研究结果,朗县杂岩在早白垩世（124~97Ma）的岩浆作用具有明显的岩浆混合现象,锆石Hf和全岩Sr-Nd同位素组成变化较大,可达13个ε单位,其岩浆源区复杂且富含流体,代表了新特提斯洋在早期（240~144Ma）经历漫长的俯冲之后,在早白垩世时期（~120Ma）俯冲带发生跃迁或俯冲角度达到临界点,导致大量俯冲沉积物和流体沿俯冲带俯冲下去,与发生部分熔融的地幔楔物质混合,底侵导致上覆古老地壳物质的再熔融,形成早白垩世复杂的岩浆岩组合,很可能是新特提斯洋二次俯冲开始的标志。     

CMIP5多模式集合对江苏省气候变化模拟评估及情景预估

利用中国气象局所属的2 400余个台站观测资料制作的分辨率为0.25°×0.25°数据集中的气温、降水量资料评估了CMIP5中17个模式对于1961—2004年江苏省气温和降水量空间分布特征的模拟能力,筛选出了5个对江苏省气候特征模拟较好的模式。之后基于5个优选模式集合平均的结果预估了3种典型浓度路径(Representative Concentration Pathways,RCPs)下江苏省2006—2100年的气温和降水量变化趋势。结果表明:(1)全球耦合气候模式对江苏省的气温和降水量空间分布特征具有一定的模拟能力,并且模式集合平均的气温和降水量与观测资料的空间相关系数分别为0.85和0.93;(2)在低浓度路径(RCP2.6)、中浓度路径(RCP4.5)和高浓度路径(RCP8.5)3种温室气体排放情景下,江苏省2006—2100年的地表温度均呈现明显的增温趋势,并且苏北的增温幅度要高于苏南;(3)3种温室气体排放情景下,江苏省未来百年降水量均呈现出北方增多南方减少的趋势;(4)未来百年江苏省降水量随气温变化的趋势并不稳定,RCP2.6和RCP4.5情景下降水量随气温的升高而增加,而RCP8.5情景下降水量随气温的增加而减少。