Early Neoproterozoic granulite facies metamorphism of mafic dykes from the Vestfold Block,east Antarctica

Proterozoic mafic dykes from the southwestern Vestfold Block experienced heterogeneous granulite facies metamorphism, characterized by spotted or fractured garnet‐bearing aggregates in garnet‐absent groundmass. The garnet‐absent groundmass typically preserves an ophitic texture composed of lathy plagioclase, intergranular clinopyroxene and Fe–Ti oxides. Garnet‐bearing domains consist mainly of a metamorphic assemblage of garnet, clinopyroxene, orthopyroxene, hornblende, biotite, plagioclase, K‐feldspar, quartz and Fe–Ti oxides. Chemical compositions and textural relationships suggest that these metamorphic minerals reached local equilibrium in the centre of the garnet‐bearing domains. Pseudosection calculations in the model system NCFMASHTO (Na₂O–CaO–FeO–MgO–Al₂O₃–SiO₂–H₂O–TiO₂–Fe₂O₃) yield P–T estimates of 820–870 °C and 8.4–9.7 kbar. Ion microprobe U–Pb zircon dating reveals that the NW‐ and N‐trending mafic dykes were emplaced at 1764 ± 25 and 1232 ± 12 Ma, respectively, whereas their metamorphic ages cluster between 957 ± 7 and 938 ± 9 Ma. The identification of granulite facies mineral inclusions in metamorphic zircon domains is also consistent with early Neoproterozoic metamorphism. Therefore, the southwestern margin of the Vestfold Block is inferred to have been buried to depths of ~30–35 km beneath the Rayner orogen during the late stage of the late Mesoproterozoic/early Neoproterozoic collision between the Indian craton and east Antarctica (i.e. the Lambert Terrane or the Ruker craton including the Lambert Terrane). The lack of penetrative deformation and intensive fluid–rock interaction in the rigid Vestfold Block prevented the nucleation and growth of garnet and resulted in the heterogeneous granulite facies metamorphism of the mafic dykes.     

桂林岩溶洼地和洞穴发生、发展的构造控制剖析

通过对桂林地质构造和岩溶建造的研究,并对岩溶洼地、洞穴发育特征进行分析,认为它们在发生、发展上具有成生的内在联系,从而反映在时空方面具有特定的关系。 这些关系集中表现在岩溶洼地、洞穴是岩溶水沿断裂、裂隙溶蚀、侵蚀扩大、改造、堆积、再改造的结果。其规律性主要反映在方向性、等距性、继承性、成层性及形态关系等几个方面。 实践表明,研究岩溶发育规律,要对构造控制因素进行分析,必须从构造形迹鉴别入手,分析其成生联系、体系归属,了解地质构造的发生。发展阶段和序次,并以此和岩溶岩系(建造)为依据,联系成岩环境(特征)和水文地质条件进行综合分析,才能客观反映构造的控制规律。      

大别山北麓梅山群中韧性剪切带变形特征及形成机制

梅山群为分布于北淮阳地区位于佛子岭群之下、逆掩于晚泥盆世—石炭纪杨山煤系和中侏罗统红层之上的一套中—浅变质岩系，在其中、上部发育ＮＷ走向的韧性剪切带，产状与区域片理一致。对韧性剪切带及其变形岩石———糜棱岩的宏微观构造研究表明，韧性剪切变形发生于区域变质岩形成之后，具有右旋剪切的运动特点，反映大别山地块向北仰冲过程中所派生的侧向滑移作用     

Nitrogen and oxygen isotopic compositions of water-soluble nitrate in Taihu Lake water system, China: implication for nitrate sources and biogeochemical process

The stable isotope nitrogen-15 (¹⁵N) is a robust indicator of nitrogen (N) source, and the joint use of δ¹⁵N and δ¹⁸O–NO₃ ^? values can provide more useful information about nitrate source discrimination and N cycle process. The δ¹⁵N and δ¹⁸O–NO₃ ^? values, as well as major ion tracers, from Taihu Lake in east China were investigated to identify the primary nitrate sources and assess nitrate biogeochemical process in the present study. The results show that the nitrate concentration in West Taihu Lake (WTL) was generally higher than those in East Taihu Lake (ETL) and its upstream inflow rivers. The NO₃ ^?/Cl^? value combined with mapping of δ¹⁵N–NO₃ ^? and NO₃ ^? concentration suggest that the mixing process should play a major effect in WTL, and denitrification was the dominant N transformation process in WTL. A linear relationship of close to ~1: 2 was observed between δ¹⁵N–NO₃ ^? and δ¹⁸O–NO₃ ^? values in WTL, confirming the occurrence of denitrification in WTL. The δ¹⁵N–NO₃ ^? data imply that sewage and manure were the principal nitrate sources in WTL and its feeder rivers, while the nitrate in ETL might derive from soil organic nitrogen and atmospheric deposition. The δ¹⁸O–NO₃ ^? data indicate most of nitrate from microbial nitrification of organic nitrogen matter possibly make a significant contribution to the lake.     

黄河源区陆面过程观测和模拟研究进展

陆面过程对黄河源区水资源变化有重要的影响,探索黄河源区陆面过程和水分循环特征的关联机理有十分重要的意义.首先简述了黄河源区气候变化背景和陆面过程的基本特征,并详细介绍了近年来在黄河源区开展的一系列陆面过程野外观测试验及相关研究主题和研究进展;进一步给出了在野外试验观测资料分析、卫星遥感、数据同化应用和数值模拟等方面取得...     

交通设计院所网络系统建设与思考

本文主要介绍了交通设计院所计算机网络系统建设的设计方案,并就计算机网络建设中应注意的问题提出几点思考.     

新疆阿尔泰克因布拉克铜锌矿床地质特征及成矿作用

克因布拉克中型铜锌矿床赋存于早二叠世花岗岩外接触带的上志留统-下泥盆统康布铁堡组黑云石英片岩、变质石英砂岩中。矿床的形成经历了夕卡岩期、热液期和表生期,铜锌矿主要形成于热液期。矿石中石英和方解石流体包裹体划分为H_2O-NaCl型和H_2O-CO_2(±CH_4/N_2)-NaCl型。成矿温度变化于146～448℃,在170℃、270℃和350℃出现峰值;流体盐度变化于0.2%～46.9%NaCl_(eq),峰值为1.5%NaCl_(eq)和5.5%NaCl_(eq);流体的密度0.55～1.19g/cm~3。硫化物的δ~(34)S集中变化于-8.4‰～1.9‰,峰值为0‰,表明硫来自岩浆。石英和方解石δD_(SMOW)介于-130‰～-79‰,δ~(18)O_(SMOW)值介于8.0‰～11.6‰,δ~(18)O_(H2O)值为-1.7‰～4.43‰,表明成矿流体主要是岩浆水,混合大气降水。方解石中δ~(13)C_(PDB)变化于-5.3‰～-1.1‰,暗示碳来自花岗质岩浆。成矿时代为早中二叠世,成矿作用与花岗质岩浆期后的热液活动有关。     

Response of groundwater chemistry to water deliveries in the lower reaches of Tarim River,Northwest China

In this paper, we analysed the monitored data from nine groundwater-monitoring transects in the lower reaches of Tarim River during the five times of stream water deliveries to the river transect where the stream flow ceased. The results showed that the groundwater depth in the lower reaches of Tarim River rose from −9.30 m before the conveyances to −8.17 and −6.50 m after the first and second conveyances, −5.81 and −6.00 m after the third and fourth the conveyance, and −4.73 m after the fifth. The horizontal extent of groundwater recharge was gradually enlarged along both sides of the channel of conveyance, i.e., from 250 m in width after the first conveyance to 1,050 m away from the channel after the fourth delivery. With the rising groundwater level, the concentrations of major anions Cl⁻, SO₄²⁻ and cations Ca²⁺, Mg²⁺, Na⁺, as well as total dissolved solids (TDS) in groundwater underwent a significant change. The spatial variations in groundwater chemistry indicated that the groundwater chemistry at the transect near Daxihaizi Reservoir changed earlier than that farther from it. In the same transect, the chemical variations were earlier in the monitoring well close to watercourse than that farther away from the stream. In general, the concentration of the major ions and TDS at each monitoring well increased remarkably when the water delivery started, and decreased with the continued water delivery, and then increased once again at the end of the study period. Hence, the whole study period may be divided into three stages: the initial stage, the intermediate stage and the later stage. According to the three stages of groundwater chemistry reaction to water delivery and the relationships between groundwater chemical properties and groundwater depths, we educe that under the situation of water delivery, the optimum groundwater depth in the lower reaches of the Tarim River should be −5 m.     

硅酸盐细菌解钾作用机理的综合效应

硅酸盐细菌能释放土壤含钾硅酸盐矿物中的磷、钾、硅等元素，直接供给植物生长利用，同时亦具有固氮能力。这为挖掘土壤潜在肥力、发展可持续农业提供了一条新的思路。本文分析了硅酸盐细菌对钾长石、伊利石的解钾作用过程，细菌-矿物复合体的形成，细菌对矿物的溶蚀作用，矿物晶体结构与细菌的解钾作用关系，复合体微环境的变化对细菌解钾作用的影响以及细菌对K^ 的主动吸收等，从微生物矿物学的角度讨论了硅酸盐细菌对含钾硅酸盐矿物解钾作用的机理问题，提出了硅酸盐细菌解钾作用综合效应的看法，并就农业生产上的利用问题指出，应根据当地的土壤环境，选择适宜的生产菌种和吸附剂，并配合使用其它化学肥料和有机肥料。     

鄂尔多斯盆地南部三叠系延长组深水重力流沉积特征及其石油地质意义*

通过大量岩心观察、钻测井资料分析及野外露头观察,对鄂尔多斯盆地南部延长组长6—长7深水重力流沉积特征、触发机制、沉积过程、沉积模式及石油地质意义进行了系统分析。研究结果表明:研究区共存在滑动岩体、滑塌沉积、砂质碎屑流沉积、浊流沉积及泥质碎屑流沉积5种类型的重力流沉积物,各类型的沉积物特征明显。不同类型重力流沉积物垂向组合可分为5类,研究区重力流的形成过程可分为5个阶段:三角洲前缘沉积阶段、滑动阶段、滑塌变形阶段、砂质碎屑流及泥质碎屑流形成阶段以及浊流形成阶段。滑动、滑塌砂体多呈孤立透镜体状,砂质碎屑流砂体多以扇沟道的形式展现出来,浊流砂体多分布在扇沟道的前端或侧翼,呈席状砂展布。深水重力流砂体垂向叠置厚度大,可形成规模大的油藏,大大扩展了深湖的勘探范围。研究区长6、长7油层组砂质碎屑流砂体储集层物性较好,含油性好,是重点勘探层位。