Structural controls on the occurrence and morphology of karstified assemblages in northeastern Vietnam: a regional perspective

Karstified assemblages occur widely in, and distinctively shape, the geological landscape of the northeastern part of Vietnam. These carbonate rocks were deposited during three major periods of basinal evolution including: (1) Late Cambrian, (2) Early Devonian to Early Carboniferous, and (3) Carboniferous to Earliest Triassic. These sedimentary units contain primary sedimentary structures and have undergone numerous post-depositional geological processes including multiple deformational events, which can be regionally correlated. Several thrusting events and associated folding have led to significant thickening of the carbonate units. The subsequent post-thrusting cross-folding events, followed by several phases of brittle faulting and fracturing further modified the spatial geometry and outcrop of these rocks. The combination and interaction of the primary structures with those formed during the long-lived and complicated deformational history is an important controlling factor in local and regional hydrogeological systems in the region. The geological structures now recorded in the carbonate units ultimately govern the formation of the unique modern surface and sub-surface geomorphology of the karstic terrains in northeastern Vietnam. These structures should be further investigated in the context of water resource assessment and natural hazard prediction and mitigation.     

Distribution of eruptive volcanic basalt in the South China Sea and adjacent areas by interpreting gravity,magnetic and seismic data

Volcanic basalt eruption activity in the South China Sea and adjacent areas occurred strongly in Cenozoic E ra. However, it is difficult to define their ranges and spatial locations.This paper presents the methods of reduction to the magnetic equator in low latitudes to bring out a better correlation between magnetic anomalies and their causing-sources; high-frequency filtering is to separate gravity and magnetic anomalies as well as information about the volcanic basalts in the upper part of the Earth’s crust; 3D total gradient is to define the spatial location of high density and magnetic bodies. The distribution of eruptive volcanic basalt is determined by multi-dimensional correlation analysis between high frequency gravity and magnetic anomalies with weighted total gradient 3D.The results from the above-mentioned methods have shown that the distribution of the eruptive volcanic basalt is mainly concentrated along the South China Sea’s sea floor-spreading axis, transitional crust, Manila trench and some large faults zone. These results are improved by existing boreholes and seismic data in the study area.     

朝鲜2009年和2013年两次核爆的地震学特征对比研究

利用布设在长白山地区临时地震台站接收到的朝鲜核爆的波形资料,对2009年5月25日和2013年2月12日两次朝鲜核试验的地震学特征进行比较.震中距范围从145 km到420 km.采用P/S型谱比值方法识别朝鲜核爆,通过与2009年3月20日长春地震和2013年1月23日沈阳地震事件的比较,表明在频率大于3 Hz时P/S型谱比值能够有效识别发生在中朝边境地区的地下核试验.选定参考台站,利用区域震相Pg波的振幅谱比值计算朝鲜核爆至各台站路径上的相对衰减.结合介质速度模型,在一定程度上反映了长白山地区衰减情况,为进一步研究长白山地区衰减层析成像提供初始模型.     

龙须菜配子体发育和不同品系四分孢子体四分孢子形成过程显微结构观察

龙须菜配子体和四分孢子体在生殖结构的形成和发育的过程中,出现一系列的细胞形态和结构层面的变化。本实验以龙须菜雌雄配子体和不同品系龙须菜四分孢子体为实验材料,采用连续徒手切片的方法,观察龙须菜配子体发育和不同品系四分孢子体四分孢子形成过程。观察到,雌雄配子体发育经过幼苗期、毛细胞期、性成熟期,幼苗期和毛细胞期雌雄配子体间无明显差异,进入性成熟期后,产生生殖结构时才能将其区分开。四分孢子起源于四分孢子体表皮层细胞,初始为鲜红色直径约5~10 μm的细胞,逐渐生长形成成熟的直径约20~25 μm的四分孢子囊,并分裂为4个四分孢子聚集在四分孢子囊中,在藻体外,四分孢子释放变形成球形,龙须菜四分孢子的形成和发育过程伴随着髓部细胞中红藻淀粉颗粒的减少。其中"981"龙须菜形成较多的畸形四分孢子,可能是其表现低育的一个原因。龙须菜自基部到尖端的表皮层细胞层数、髓部细胞数目和体积均发生连续的变化。细胞连接广泛存在于龙须菜表皮层、皮层和髓部细胞之间,但各层细胞连接大小、数目、长度等都存在差异。释放的四分孢子可能会附着在四分孢子体上,固着器覆盖包绕四分孢子体甚至侵入到破损有伤口的四分孢子体内,形成四分孢子体和配子体在同一株上的世代混杂现象,这也可能是导致龙须菜表现遗传复杂性的原因。     

江西大吉山脉钨矿床矿化富集特征及其机理初探

大吉山脉钨矿床矿化特征主要是走向上双峰富集,垂向上中部富,上下变贫。剖面上矿化围绕某些地段特别富集,形成“多中心”的富集型式。上述特征是成矿流体贯入裂隙过程中内外因素综合作用的结果,即水化硅氧聚合离子群“准溶液” 粘性流体体系贯入裂隙时,流体运动遵循流体动力学定律,以聚合离子团搬运的钨,随流体运动在有利的条件下产生富集,然后随温度降低,其物质组分就地调整、结晶、形成矿脉。     

Analysis of Vertical Sedimentary Successions in the Lower Part of Kelimoli Formation,Middle Ordovician,Zhuozishan Area

There is significance to study high-frequency cyclicity thin-bedded limestone which deposited in carbonate ramp and deep-water basin for its well record of astronomic cycles. And there is an ideal section for these studies in the lower part of Kelimoli Formation, in Darriwilian Stage, Middle Ordovician of western Ordos Basin(Zhuozishan area in Inner Mongolia) for its well rhythmic alternations of thin-bedded limestones and mudstones. This work focused on detailed vertical sedimentary successions analysis of these thin-bedded limestones based on detailed field work, as well as the data of rare earth elements and other related trace elements in limestones. The results show as follows: ① there are four types of sedimentary successions(bundles) in thin-bedded limestones, including thinning-upward succession, thickening-upward succession, bidirectional succession(thickening- and thinning-upward) and waving-upward succession; ② the section consists of 145 limestone-mudstone rhythmics, 33 bundles and 7 superbundles; ③ the variation in(La/Nd)_N and Mn/Fe molar ratios of limestones along with depth have a similar trend which decreases from bottom to top in general, but have some anomalies distribution; ④ the variation in REE concentrations and Eu anomalies along with depth have a perfect enantiomorphous relationship as well as coupling with the molar ratios of(La/Nd)_N; ⑤ the variation of crystal size, V/Cr and V/(V+Ni) molar ratios also have a similar trend which is increasing and then decreasing from bottom to top, and have some local enantiomorphous relationship with the molar ratios of(La/Nd)_N in the overall similar distribution patterns. Some conclusion can be drawn according to the types of sedimentary successions and its distribution in profile as well as the ratios of some geochemical parameter along depth based on previous works. These include: ① thickening-upward and bidirectional successions maybe reflect the intensity of tectonism and contour current which is controlled by Milankovitch cycle respectively, and the rising of sea level may be was responsible both for the thinning-upward and waving-upward successions; ② the intensity of contour current which is controlled by Milankovitch cycle was acted throughout the depositions, and the range of deposition time is not less than 2.9 Ma; ③ the vertical sedimentary evolution is perhaps controlled by the alternating of tectonism and rising sea levels, and the section suggests two tectonic stages.     

江西省水资源及其开发利用对策

江西省是我国水资源丰富的省份之一,水资源的形成及分布与自然地理及区域地质背景密切相关。在对全省水资源量进行计算的同时,分析了水资源的时空分布规律,并对水资源环境质量进行了评价。根据江西省水资源面临的态势,结合江西省省情和水资源利用现状,就水资源合理开发利用提出了相应的对策。     

Satellite Gravity Anomalies and Their Correlation with the Major Tectonic Features in the South China Sea

The South China Sea (SCS) is a region of interaction among three major plates: the Pacific, Indo-Australian and Eurasian. The collision of the Indian subcontinent with the Eurasian plate in the northwest, back-arc spreading at the center, and subduction beneath the Philippine plate along Manila trench in the east and the collision along Palawan trough in the south have produced complex tectonic features within and along the SCS. This investigation examines the satellite-derived gravity anomalies of the SCS and compares them with major tectonic features of the area. A map of Bouguer gravity anomaly is derived in conjunction with available seafloor topography to investigate the crustal structure. The residual isostatic gravity anomaly is calculated assuming that the Cenozoic sedimentary load is isostatically compensated. The features in the gravity anomalies in general correlate remarkably well with the major geological features, including offsets in the seafloor spreading segments, major faults, basins, seamounts and other manifestations of magmatism and volcanism on the seafloor. They also correlate with the presumed location of continental-oceanic crust boundary. The region underlain by oceanic crust in the central part of the SCS is characterized by a large positive Bouguer gravity anomaly (220–330 mgal) as well as large free-air and residual isostatic anomalies. There are, however, important differences among spreading segments. For example, in terms of free-air gravity anomaly, the southwest section of mid-ocean has an approximately 50 km wide belt of gravity low superimposed on a broad high of 45 mgal running NW–SE, whereas there are no similar features in other spreading segments. There are indications that gravity anomalies may represent lateral variation in upper crustal density structure. For instance, free air and isostatic anomalies show large positive anomalies in the east of the Namconson basin, which coincide with areas of dense volcanic material known from seismic surveys. The Red River Fault system are clearly identified in the satellite gravity anomalies, including three major faults, Songchay Fault in the southwest, Songlo Fault in the Northeast and Central Fault in the center of the basin. They are elongated in NW–SE direction between 20±30'N and 17°N and reach to Vietnam Scarp Fault around 16°30'N. It is also defined that the crustal density in the south side of the Central Basin is denser than that in the north side of the Central Basin.     

安徽铜陵焦冲金矿床成矿流体特征及成矿机制

安徽铜陵焦冲金矿床位于长江中下游铁铜金银铅锌成矿带铜陵矿集区内,矿体主要赋存在下二叠统栖霞组(P1_q)灰岩中。根据野外地质特征及含矿组合,将矿床划分为3个成矿阶段:黄铁矿-石英阶段、石英-硫化物阶段和石英-方解石阶段。笔者对该矿床不同成矿阶段石英和方解石进行了详细的岩相学观察和显微测温研究。结果表明,该矿床的均一温度区间分别为410~440 ℃、320~350 ℃和260~320 ℃。显示早期的黄铁矿-石英阶段、石英-硫化物阶段,直到晚期的石英-方解石阶段均一温度呈现逐渐减低的趋势。根据公式计算矿床成矿深度约1.5 km,成矿压力400×10⁵ Pa。流体沸腾作用是金属硫化物大量沉淀的主要机制。     

有机螯合沉淀剂富集－感耦等离子体质谱法测定地球化学样品中痕量元素

报道了用吡咯烷二硫代氨基甲酸铵（ＡＰＤＣ）有机螯合沉淀剂沉淀富集后，等离子体质谱法测定地球化学样品中２６个痕量元素的方法。研究了ＡＰＤＣ定量沉淀待测金属离子的条件，分别在ｐＨ２和ｐＨ７时使２６个元素富集，回收率在９４％～１０５％；样品测定下限为０．０１～０．４μｇ／ｇ；方法的ＲＳＤ（ｎ＝１０）为３％～１３％。经几种地球化学标准物质验证，结果与推荐值相符。