木其滩岩组形成时代、地球化学特征——对北秦岭构造演化的制约

出露于北秦岭造山带中的木其滩岩组主要由斜长角闪岩组成,其原岩为玄武岩-亚碱性玄武岩。对木其滩岩组斜长角闪岩中的锆石进行LA-ICP-MS U-Pb年代学分析,获得同位素年龄762.5±4.6Ma,为成岩年龄。地球化学上,这些斜长角闪岩显示低钛 (TiO₂=0.57%~2.16%),低K₂O/Na₂O比值(0.06~0.55)和中等-高 Mg^#(45.3~68.7)特征,为低钛拉斑玄武岩。在球粒陨石标准化图解中,表现出轻重稀土分异,无Eu异常的特征,类似于E-MORB。这些斜长角闪岩以Rb、Ba、Th和La富集,低(⁸⁷Sr/⁸⁶Sr)_i 比 (0.7038~0.7040) 和高的ε_Nd(t)值(+4.1~+6.9)为特征,表明其来源于地幔,成分上相似于FOZO。(Th/Nb)_N, Nb/La 和 Ba/La的比值特征表明它们经历了不同程度的地壳混染。所有这些特征,结合区域地质资料阐明木其滩岩组斜长角闪岩代表的是大约762.5±4.6Ma商丹洋盆初始裂解时的洋壳残片。     

从阿巴拉契亚-阿钦塔造山带看中国北方大陆南缘古生代的油气前景

阿巴拉契亚-阿钦塔造山带是北美乃至世界著名的大陆边缘挤压碰撞推覆造山带,是地质学研究的经典地区之一,也是许多经典地学理论和概念的发源地.其中,对地质学影响最大的当属地槽学说.继20世纪60年代由深海钻探带来地学革命之后,由COCORP实施的地震反射剖面和深钻揭示了该造山带的巨大推覆构造.人们惊奇地发现,在巨大推覆体之下...     

华北油田留58潜山雾迷山组储层非均质性研究

留58潜山蓟县系雾迷山组油藏为块状裂缝性灰岩油藏,储层空间类型包括了原生孔隙,溶蚀孔隙,以及裂缝等类型.潜山储层物性的分布特点表现为纵向上的分层发育和横向上的分带发育.综合本区测井解释及岩心观察认为,影响潜山储层发育的因素包括储层岩性,纵向上不同储层段与内幕隔层的配置关系,以及平面上储层发育带是否处于潜山构造顶部或断层...     

北太平洋涡旋振荡研究进展

从观测事实和动力机制两方面,对近年发现的新的气候模态——北太平洋涡旋振荡（NPGO）的研究成果进行系统总结。NPGO的空间结构表现为北太平洋上海表高度异常（SSHA）的正负中心呈南北偶极子分布,当NPGO位于正位相时,南北涡流都加强,这种加强是由风应力旋度及风生涌流所驱动的。关于NPGO的机制研究发现,NPGO是中纬太...     

Comparison of Results of Recent Seismic Profiles with Tectonic Models of the North China Craton

The geometry and timing of amalgamation of the North China craton(NCC) have been controversial,with three main models with significantly different interpretations of regional structure,geochronology,and geological relationships.The model of Zhao G C et al.suggests that the eastern and western blocks of the NCC formed separately in the Archean,and an active margin was developed on the eastern block between 2.5 and 1.85 Ga,when the two blocks collided above an east dipping subduc-tion zone.The model of Kusky ...     

苏北盆地溱潼凹陷殷庄—台兴区块阜宁组三段沉积特征及砂体展布

苏北盆地溱潼凹陷殷庄—台兴区块阜宁组三段自上而下分为Ⅰ、Ⅱ、Ⅲ、Ⅳ4个砂组,沉积相组合为三角洲前缘相——包括前缘近端坝、远端坝、分流间湾相砂体夹浅湖—半深湖相泥岩互层。各砂组在分布上具有不同的形态。广山、殷庄、台兴、戴南地区发育的三角洲前缘近端坝和远端坝为有利储集相带。     

北武夷蔡家坪铅锌矿床硫化物特征、矿床成因类型及成矿时代

北武夷蔡家坪矿床是近年来新发现的一个中型铅锌矿床.矿床赋矿围岩为侏罗系水北组(J1s)、漳平组(J2z)砂岩,铅锌矿体多产在断裂旁侧破碎带及流纹斑岩与砂岩接触带.在野外调查基础上,通过显微镜下观察及电子探针分析,对矿区主要金属硫化物进行了细致研究.初步将成矿过程划分为沉积成矿期、岩浆热液期与表生期,其中岩浆热液期包括中...     

地幔橄榄岩中橄榄石的指示意义

橄榄石是地幔橄榄岩和辉石岩的主要组成矿物,但也经常以斑晶和捕虏晶的形式出现在玄武质岩石中。结合近年来在地幔橄榄岩的主要元素(如Mg和Fe)组成特征以及Li、Mg和Fe稳定同位素地球化学方面的研究成果,重点对橄榄石的地球化学特征与华北克拉通岩石圈地幔演化过程之间的联系进行了讨论,旨在加深对华北克拉通岩石圈地幔演化过程的理解。现有研究表明:地幔橄榄岩中橄榄石的矿物学特征、元素和同位素地球化学组成能够很好地指示岩石圈地幔的特征及其演化过程,因而具有重要的意义。对于克拉通地区的地幔橄榄岩来说,橄榄石的Mg#通常可以指示岩石圈地幔的属性,古老、难熔的地幔橄榄岩中的橄榄石一般具有较高的Mg#(>92),而新生的岩石圈地幔橄榄岩中的橄榄石则具有较低的Mg#(<91)。因此,地幔橄榄岩中橄榄石的Mg#在一定程度上具有年龄意义。橄榄岩中橄榄石的Li、Mg和Fe同位素组成也可以明确指示岩石圈地幔的属性及其所经历的演化过程,正常地幔的δ7Li、δ26Mg和δ57Fe组成相对均一,如果上述同位素组成偏离正常地幔值,则说明岩石圈地幔经历了熔体/流体的交代作用。华北克拉通地区地幔橄榄岩捕虏体中橄榄石的Li、Mg和Fe同位素组成研究表明:该区的岩石圈地幔经历了多个阶段、不同来源的熔体/流体的改造过程。     

Numerical study on the bifurcation of the North Equatorial Current

A 1.5-layer reduced-gravity model forced by wind stress is used to study the bifurcations of the North Equatorial Current(NEC).The authors found that after removing the Ekman drift,the modelled circulations can serve well as a proxy of the SODA circulations on the σθ=25.0 kg m～-3 potential density surface based on available long-term reanalysis wind stress data.The modelled results show that the location of the western boundary bifurcation of the NEC depends on both zonal averaged and local zero wind stress curl latitude.The effects of the anomalous wind stress curl added in different areas are also investigated and it is found that they can change the strength of the Mindanao Eddy(ME),and then influence the interior pathway.     

Low-frequency variability of the North Equatorial Current bifurcation in the past 40 years from SODA

The low-frequency variability of the North Equatorial Current (NEC) bifurcation during 1958 to 2001 was investigated with the Simple Ocean Data Assimilation (SODA) 2.0.2 dataset.In agreement with recent observations,the NEC bifurcation latitude (NBL) shifted northward as depth increases, from about 12.7°N near the surface to about 17.1°N at depths around 500 m for the annual average. This study reveals that the interannual variations of NBL,with five years period,mainly focused on the upper 500 m with amplitude increasing as depth increased.The NBL shifted southward in the past 40 years,which was more significant in the subsurface at more than -0.02°/a.The NBL manifests itself in the transports of NMK (NEC-Mindanao Current (MC)-Kuroshio) system in strong relationship with MC (0.7) and Kuroshio (-0.7).The EOF analysis of meridional velocity off the Philippine coast shows that the first mode,explaining 62% of variance and 5 years period,was highly correlated with the southward shift of NBL with coefficient at about 0.75.The southward shift of NBL consists with the weakening of MC and strengthening of Kuroshio,which exhibited linear trends at -0.24Sv/a and 0.11Sv/a.Both interannual variation and trend of NBL were closely related to the variation of NMK system.