Balance of small watersheds from data on long-term experimental research at the Valdai Affiliation of the state hydrological institute (SHI)

Results of detecting water balance components of experimental watersheds from long-term observations at the Valdai Affiliation of the SHI are presented. Methods of measurements, calculations, and corrections of precipitation amount, measurement of evaporation from the land, changes in the soil moisture reserves and ground water reserves are considered. All components of the water balance of watersheds are measured independently which allows estimating quantitatively the residuals and measurement and calculation errors. A preliminary analysis is performed of seasonal values of the water balance components and their changes in the period of most intensive observations (1952–1985) which is of a great value for studying the conditions of the river runoff formation in small watersheds.     

新疆气候变化与生态环境的初步评估

近50a来,新疆气候变暖、降水增多的趋势明显,并将持续到21世纪末.新疆生态环境系统的总体特征是:水资源是新疆生态环境的核心;形成了山地、绿洲、荒漠三大生态环境系统;生态环境脆弱;土地有效利用率低;加强生态建设和环境保护具有很大潜力.在全球和新疆气候变暖的背景下,新疆极端天气、气候事件频发,防灾减灾形势更为严峻,而且绝大部分冰川退缩,并呈加速减退的趋势;但因气候变暖的同时降水增多,河流径流量呈增加趋势,生态环境随之有所恢复与改善,加之新疆又地处欧亚大陆中部,因而全球气候变化造成直接的、近期的负面影响,在新疆的表现比世界大多数地区要轻、要小.由于新疆气候变化、人类活动的负面影响以及资源利用效率低下、经济结构不合理等因素,新疆生态环境形势依然相当严峻,完全遏制生态环境恶化和实现生态环境全面改善任重道远.基于以上评估结论,提出了三项对策建议.     

Gold solubility in aqueous-chloride solutions interacting with epidote propylites and epidote-hedenbergite skarns

The interaction of chloride solutions with the mineral assemblages of epidote propylites and hedenbergite skarns with and without sulfides was studied by experimental (at 300 and 400°C) and theoretical (250–400°C) at P_tot = 1 kb simulation. The buffer properties of combined ore-silicate assemblages were estimated. It was shown that the limit of the efficient operation of the buffer within the T-P range studied depends on the pH of starting solutions. It is ≤ 0.01 m HCl in the absence of sulfides and increases up to 0.1 m HCl in the presence of sulfides. It was found that gold solubility in chloride solutions is low owing to their neutralization by interaction with sulfide-free epidote propylites. The appearance of sulfides suppresses this effect and leads to an increase in gold solubility. The bulk solubility of gold is determined by the ore component of buffer mixture, mainly sulfide minerals. Gold precipitation begins at a threshold concentration, which is 0.004 mg/l (at 300°C) for sulfide-free epidote propylites, 0.06 mg/l (at 400°C) for sulfide-free hedenbergite skarns, and up to 0.29 mg/l in the same assemblages in the presence of pyrite.     

Major factors of the evolution of basins and faults in the Baikal Rift Zone: Tectonophysical analysis

In order to identify the major factors of the formation of the Baikal Rift Zone, tectonophysical analysis is carried out based on physical modeling with the application of similarity criteria. A single-layer model of elastoplastic clayey paste is superposed on two metal plates. One of the metal plates is displaced leftward according to the simple shear mechanism and its contact with the second metal plate has a bend morphologically similar to the Baikal segment of a marginal suture of the Siberian Craton. This scheme of loading corresponds, to a great extent, to the passive mechanism of rifting; i.e., the deformed layer is destructed due to strikeslip displacement of blocks and development of pull-apart structure in the model without any uplift and thermal impact related to the influence of mantle asthenolith in nature. The series of runs reproduces the major spatiotemporal trends in the evolution of the Baikal Rift Zone. Some experiments achieve for the first time a high degree of similarity in the morphology and mutual alignment of its main basins. This makes it possible to conclude that the evolution of basins and faults in the Baikal Rift Zone was governed by the following factors: (1) elastoplastic response of the substrate with a regular localization of strain; (2) left-lateral displacement of blocks; and (3) the presence of curved (in plan view) initiating structural heterogeneity.     

Pseudosecondary clastic rocks of the Dzuramtai massif (Southern Mongolia)

Specific rocks (tectonomixtites) developed in the framing of Mongolian granite massifs (Dzuramtai and some others) at the Mesozoic section bottom are studied. It is shown that the tectonomixtites are tectonic rocks rather than eluvial or sedimentary rocks, as was considered previously. They formed in the Cenozoic in the process of granite protrusion beneath a thick sedimentary cover owing to the crushing of granites and abrasion of granite fragments with the subsequent transformation of clastic rocks by groundwaters (suffosion). In this process, clastic rocks yielded fine products of the destruction of feldspars and quartz was concentrated. The rocks formed at relatively low temperatures (no more than 200–300°C) under stress strains.     

冈底斯带中段渐新世花岗质岩石锆石LA-ICP-MS U-Pb年龄、岩石地球化学特征及其意义

以藏南冈底斯带中段渐新世花岗质岩石为研究对象,对其进行了岩相学、年代学、岩石地球化学及Hf同位素研究,结果表明区内渐新世花岗质岩石岩性主要为中粗粒花岗闪长岩、中粗粒黑云母二长花岗岩和似斑状黑云母二长花岗岩。锆石U-Pb定年表明,似斑状黑云母二长花岗岩的成岩年龄为26.4±0.4 Ma,属晚渐新世岩浆活动产物。岩石地球化学特征上里特曼指数σ为1.58～3.20,为高钾钙碱性—钾玄岩系列;铝饱和指数A/CNK值为0.90～1.04,属准铝质—弱过铝质;岩石相对富集Rb、K和亏损Ba等大离子亲石元素,亏损Nb、Ta、Zr、Hf、Ti等高场强元素;轻稀土元素明显富集,轻重稀土元素分馏较强(La_N/Yb_N值为5.37～14.26),具有较弱的Eu负异常。岩相学及岩石地球化学指示花岗岩成因类型为I型。似斑状黑云母二长花岗岩锆石ε_(Hf)(t)值为0.08～6.31,Hf同位素一阶段模式年龄变化范围为445～687 Ma,主要来自新生地壳的部分熔融,并有幔源物质的加入;岩浆在成岩过程中存在分离结晶作用。综合分析认为,冈底斯带在渐新世时期处于印度与亚洲板块的碰撞造山环境,挤压作用及幔源物质侵位导致地壳加厚,使青藏高原在该时期发生了一次强烈的隆升。     

Relationship between Radon and the Tectonic Activity of Faults in Central Mongolia

Doklady Earth Sciences - The relationship between radon and the tectonic activity of faults for two geodynamically active regions of Central Mongolia is shown with account for the influence of...     

Change in the River Water Regime of the Ural River Basin

Doklady Earth Sciences - Based on analysis of the annual and seasonal variability of river runoff, the specificity of the water regime of the Ural River basin is determined. It is established that...     

中国大陆地区大地热流数据汇编(第三版)

大地热流是地球内部热作用过程最直接的地表显示，其中蕴涵着丰富的地质、地球物理和地球动力学信息.我国大陆地区已定期进行了6次热流汇编，其中第一、二次汇编的热流数据已正式公布(第一、二版)，此后4次汇编仅发表了统计结果.而未再公布汇编数据.本文基于第六次热流数据汇编，将自第二版以来新增的450个热流数据汇编成中国大陆地区大地热流数据第三版.新版热流数据的统计结果表明，中国大陆地区实测热流值变化于23-319mW/m2，平均63±24.2mW/m2;剔除与地表热异常相关的数据后，热流值变化范围为30-140mW/m2，平均61±15.5mW/m2.