First Determination of the Isotope Age of the Andesite–Dacite Complex of the Eastern Zone of the Middle Urals

Doklady Earth Sciences - This paper reports on the first U–Pb dating of zircons from dacites of the volcanic paleo-edifice of the andesite–dacite complex of the Eastern Zone of the...     

Present-day tectonics of the western part of the Dzhugdzhur–Stanovoi Terrane of the southeastern frame of the North Asian Craton

The first results on current movements are presented for the western part of the Dzhugdzhur–Stanovoi Terrane based on GPS geodesy of a geodynamic survey area of the Upper Amur region. Processing of the GPS data resulted in a vector field of the displacement rates of points of the geodynamic survey area with zones of intense deformations. It was concluded from a comprehensive analysis of geological–geophysical data and estimates of the displacement rates that the terrane is characterized by kinematic integrity and was subjected to a complex of tectonic factors related to the evolution of the eastern segment of Baikal Rift Zone in the area of transpression interaction of the Eurasian and Amur plates.     

Analysis of the degree of contamination and evolution in the last 100 years of the composition of the bed sediments of the Anllóns Basin

In this study, five cores of the Anllóns River bed sediments were analyzed in order to evaluate the downcore and downstream variations in their chemical composition. The first step was the evaluation of the metal distribution in the bulk (<2 mm) and fine fractions (<63 μm). The analysis revealed that most of the metals followed the same trend in both fractions, although the fine fraction presented usually higher concentrations. However, the concentration of both fractions tended to equalize with increasing contamination. No general increase was observed in the metal concentrations toward the surface which could be attributed to recent anthropogenic contributions. Instead, the distributions were homogeneous or peaked at various depths downcore. The most important historical feature was observed at the mouth of the river, at 96-cm depth, corresponding to the end of the eighteenth century. Upcore increased metal concentrations in parallel with increased fine fraction occurred from this depth, which were attributed to a bridge construction and consequent changes in sediment dynamics. As the metal concentrations can be influenced by variations in texture or other sediment characteristics, the second step was to evaluate the efficiency of several normalized indexes in the assessment of the degree of contamination, by calculating the enrichment factor (EF), the geoaccumulation index (I _GEO) and the pollution load index (PLI). The EFs obtained were <10, thus revealing little anthropogenic inputs to the basin. The I _GEO produced higher values when compared with the EFs. Instead of absolute EF or I _GEO absolute values, the use of cumulative probability plots allowed identifying more accurately potential outliers indicating contamination. Only one population was identified for Zn and Pb, with a reduced number of outliers at the highest concentrations for Pb. As shown, a more complex plot with the outliers identified at C4 and C5. Finally, the PLI allowed determining the absence of a significant contamination in the bed sediments. The bioavailable and non-geogenic fractions contribute up to a 90% of the total concentrations in the case of As and Cu, and showed similar (dissimilar) profiles in comparison with total metals. Also, the quality guidelines were surpassed, so the high solubility of As, Zn, Pb and Ni in the sediments revealed the need to monitor the bed sediment quality of the Anllóns River.     

Features of the Influence of Weather Conditions on the Deformation Processes of the Upper Layer of the Earth’s Crust

Doklady Earth Sciences - The influence of the temperature and moisture content of the near-surface soil layer on variations of the barodeformation interaction of the boundary layer of the...     

Bursting the limits of time： the reconstruction of geohistory in the age of revolution

Bursting the Limits of Time by the distin- guished historian of geology Martin Rudwick is a massive, two-part book. The first part contains what he calls a synchronous history of what eventually became historical geology in western Europe between the time of de Sans- sure＇s epoch-making ascent of Mont Blanc in 1787 and the discovery of the Kirkdale hyaena cave by Buckland in the winter of 1821-1822,     

Numerical Modeling of the Effects of Major Elements on the Solubility of Chrome–Spinel and a Likely Solution of the Problem of the Origin of Chromitite

Doklady Earth Sciences - The influence of variations in fo-, fa-, en-, fs-, di-, an-, and ab-components in a high-Mg basaltic melt on the topology of the spinellide liquidus was analyzed using the...     

On the Origin of the Carat as the Unit of Weight for Gemstones

The carat is the unit of weight for diamonds and other gemstones.It corresponds to the average weight of the seeds of a leguminous tree.What kind of tree is this?We have studied the samples from Ethiopia,Egypt,Cyprus and the United States.The tree is neither“Kuara“nor“Locust“（Robina pseudoacacia Linn.）,but rather Carob(Ceratonia Siliqua).In Ethiopia,as called by local inhabitants,“Kuara“is a species of Erythrina-E.brucei rather than E.abyssinica.As might be expected,using the seeds as a means of weighing an extremely valuable commodity is not very scientific.Before 1907,at various times and in various countries,there were at least twenty-three stan-dards for the carat ranging from 187.00mg to 215.990mg.The metric carat equal to 200mg was proposed in Paris in 1907.It was adopted in the United States on July1,1913 and now is the world-accepted standard.But in reality,the standard of the carat is still confused with respect to its usage throughout the world .This is why the author reiterates that the standard of the car-at should be integrated with the metric system.     

Estimation of the stress state of the Earth’s crust and the upper mantle in the area of the Southern Kuril Islands

The catastrophic Shikotan earthquake of October 4 (5), 1994, occurred in the Pacific Ocean. Its focus was located 80 km eastward of Shikotan Island. The stress state of the Earth’s crust in this area was estimated by the method of the cataclastic analysis of the whole range of the earthquake mechanisms. The performed reconstruction of the parameters of the current stress state of the Earth’s crust and the upper mantle in the area of the Southern Kuril Islands made it possible to establish that this area is characterized, on the one hand, by the presence of extensive areas of steady behavior of the stress tensor parameters and, on the other hand, by the presence of local sections of anomalously fast changes in these parameters.     

The Nature of the “Voice of the Sea”

Strong vibrations of the Earth’s crust in the frequency range of 7–9 Hz, referred to as the “voice of the sea,” have been recorded in the course of processing synchronous experimental data obtained during recording of variations in the deformation of the Earth’s crust using a shore laser strainmeter, atmosphere pressure variations using a laser nanobarograph, and hydrosphere pressure variations using a laser meter for hydrospheric pressure and wind velocity variations. The nature of these vibrations and their transformation to adjacent geospheres have been discussed.     

U–Pb zircon age of the base of the Ediacaran System at the southern margin of the Qinling Orogen

Global abrupt climate change from Marinoan snowball Earth to greenhouse Earth, recorded as cap carbonate overlain on diamictite, had shed the first light on Cambrian bio-radiation. The most documented cap carbonate sections are typical with comprehensive δ¹³C negative values and ubiquitous sedimentary structures, such as tepee-like, sheet-crack etc., which are associated with successive glacial eustatic variation caused by isostatic rebound in shallow-water facies. Here we report a deep-water basinal cap carbonate section with strong negative δ¹³C values in the southern margin of the Qinling Orogen, Heyu, Chengkou County, Chongqing in China, which consists of massive dolostone with abundant carbonaceous laminae. However, it lacks the sedimentary structure as mentioned above and is overlain by thin-bedded silicious shales and cherts. A K-bentonite bed was discovered within the base of cap carbonates, about 0.7 m above the top of the Marinoan diamictite. Magmatic zircons that were separated from the K-bentonite bed yield a SIMS concordia U–Pb age of 634.1 ± 1.9 Ma (1σ, MSWD_CE = 0.31, Probability_CE = 1.000, n = 20). The age is in good agreement with previously reported TIMS U–Pb ages for the termination of Marinoan glaciation and provides a geochronological constraint for the Ediacaran successions in the Qinling Orogen.     

The Silurian Reservoir Bed—Differentiated Asphalts in Tarim Basin and Modeling Experiments on Their Origin

There is a type of asphalt that originated from differentiation from reservoir bed (named reservoir bed-differentiated asphalt)in the Silurian asphaltic sandstones of the Tarim Basin.These asphalts are the result of second-time charging of hydrocarbons into the Silurian reservoir,which were derived from Lower Paleozoic source rocks.Asphalt was differentiated from the reservoir bed in the hydrocarbon gathering area of secondary migration.The different-tiation is caused by changes in reservoir physical properties when pearl or chain hydrocarbons migrating through and gathering in the reservoir bed,and light components are lost and heavy ones are involved in the formation of asphalt or heavy oil.There are two kinds of occurrence of these asphalts in the Silurian system of the Tarim Basin.One is the poor heavy oil layer with lower oil saturation in trap and the other is scattered hydrocarbon distributed along the trans-port layer and unconformity surface.Reservoir bed-differentiated asphalts have two characteris-tics:total hydrocarbon content is high in extractable organic matter and the ratio of saturated to aromatic hydrocarbon is usually greater than unity.The physically modeling experiment has confirmed these characteristics and the genesis of the reservoir bed-differentiated asphalts.     

塔里木盆地志留系沥青砂岩的形成期次及演化

从志留纪起,塔里木盆地下古生界烃源岩经历了三期生、排烃。下古生界源岩的生烃期和志留系的圈闭形成期控制了志留系沥青砂岩的形成期次及演化。志留系早期沥青砂岩形成后,经历了后期多次的构造沉积事件和三次烃类注入、混染,改变了志留系古油藏沥青形成时的原始产状。志留系沥青砂岩的三次注入分别是 :第一次是晚加里东注入期;第二次是晚海西-印支注入期;第三次是燕山-喜山注入期。志留系砂岩中沥青、稠油或其它油气显示是这三期作用的综合结果。     

塔里木盆地典型砂岩油气储层自生伊利石K-Ar同位素测年研究与成藏年代探讨

塔里木盆地共发现 8套砂岩油气储层 ,对其中的 5套典型砂岩油气储层进行了自生伊利石K Ar同位素测年分析与研究。利用该项技术对其成藏史进行初步探讨是本次研究的主要目的。中央隆起下志留统沥青砂岩的自生伊利石年龄为 383.4 5～ 2 35 .17Ma ,表明志留系古油藏形成于加里东晚期—海西晚期 ;上泥盆统东河砂岩的自生伊利石年龄为 2 6 3.82～ 2 31.34Ma ,表明东河砂岩油气藏主要形成于海西晚期 ;库车坳陷依南 2气田 (依南 2井 )下侏罗统阳霞组砂岩的自生伊利石年龄为 2 8.0 8～ 2 3.85Ma ,表明油气充注发生在中新世以来 ;喀什凹陷阿克莫木气田 (阿克 1井 )下白垩统砂岩的自生伊利石年龄为 2 2 .6 0～ 18.79Ma ,表明中新世可能有古油气运移或古油藏形成 ;库车坳陷迪那 2气藏 (迪那 2 0 1井 )古近系砂岩中的伊利石主要为碎屑成因 ,不能用于进行油气成藏史研究 ,但该气藏白垩系砂岩的自生伊利石年龄为 2 5 .4 9～ 15 .4 7Ma ,表明可能为中新世成藏。本次研究表明 ,该项技术在塔里木盆地初步显示出较好的应用效果 ,具有较为广阔的应用前景。     

一个典型的寒武系油藏:塔里木盆地塔中62井油藏成因分析

塔里木盆地志留系沥青砂岩广泛发育,主要原因是来源于寒武系的原油在进入志留系储层后区域性的抬升剥蚀使油藏遭到严重破坏,但到目前为止,究竟是寒武系烃源岩还是中上奥陶统烃源岩或是两者都对现今的志留系沥青砂岩中的有机质有贡献还不清楚.对塔中62井原油的化学组成和油源的分析表明,其甾萜类组成具有寒武系烃源岩的组成特征,反映该油藏原油主要来源于寒武系.另一方面,塔中62井砂岩透镜体被泥岩圈闭,油藏具有较好的保存条件,且后期中上奥陶统生成的烃类难以充注进入油藏.塔中62井志留系油藏破坏作用较弱、保存较好,是塔里木盆地在志留系发现的第一例来源于寒武系的油藏.     

塔里木盆地塔中隆起志留系油气成藏及分布特点

塔里木盆地塔中隆起志留系油气成藏具有两源三期的成藏特点,"两源"是指油气来源于寒武系、中、上奥陶统两套烃源岩;"三期"是指从沥青到可动油的形成经历了加里东晚期、海西晚期、燕山—喜山期三个成藏期,沥青的形成是早期油气运移聚集过程中遭破坏的结果,目前所发现的可动油是以中、上奥陶统油气源为主的晚期成藏的结果。发育三种油气藏类型,即背斜构造、地层岩性以及火山岩遮挡型。塔中隆起志留系油气聚集受三大因素控制,一是隆起构造背景,围绕古隆起构成多种圈闭类型组合的复合油气聚集区;二是有效盖层,志留系中的油气显示十分活跃,包括沥青、稠油和正常油,沥青和稠油分布在红色泥岩段以下,而可动油集中分布在灰色泥岩段之下;三是优质储层,砂岩储层分布广泛,储层储集空间有次生-原生孔隙型、原生-次生孔隙型、微孔隙型三种类型,孔隙度3.3 %～17.4 %,渗透率(0.1 ～667.97)×10-3μm2。     

Accumulation and Reformation of Silurian Reservoir in the Northern Tarim Basin

Silurian sandstone in Tarim Basin has good reservoir properties and active oil and gas shows, especially thick widely-distributed bituminous sandstone. Currently, the Silurian was found containing both bitumen and conventional reservoirs, with petroleum originating from terrestrial and marine source rocks. The diversity of their distribution was the result of "three sources, three stages" accumulation and adjustment processes. "Three sources" refers to two sets of marine rocks in Cambrian and Middle-Upper Ordovician, and a set of terrestrial rock formed in Triassic in the Kuqa depression. "Three stages" represents three stages of accumulation, adjustment and reformation occurring in Late Caledonian, Late Hercynian and Late Himalayan, respectively. The study suggests that the Silurian bitumen is remnants of oil generated from Cambrian and Ordovician source rocks and accumulated in the sandstone reservoir during Late Caledonian-Early Hercynian and Late Hercynian stages, and then damaged by the subsequent two stages of tectonic uplift movements in Early Hercynian and Pre-Triassic. The authors presumed that the primary paleo-reservoirs formed during these two stages might be preserved in the Silurian in the southern deep part of the Tabei area. Except for the Yingmaili area where the Triassic terrestrial oil was from the Kuqa Depression during Late Himalayan Stage, all movable oil reservoirs originated from marine sources. They were secondary accumulations from underlying Ordovician after structure reverse during the Yanshan-Himalayan stage. Oil/gas shows mixed-source characteristics, and was mainly from Middle-Upper Ordovician. The complexity and diversity of the Silurian marine primary properties were just defined by these three stages of oil-gas charging and tectonic movements in the Tabei area.     

塔里木盆地塔中隆起志留系油气聚集控制因素

塔中隆起志留系中沥青及可动油气显示十分丰富。油气聚集的基本特征是多油气源、多成藏期、多油气藏类型、多油气产状。纵向上志留系油气分布受盖层控制,沥青和稠油分布在塔塔埃尔塔格组下段红色泥岩段以下,而现今可动油则集中分布在柯坪塔格组上二亚段灰色泥岩之下。平面上,志留系油气聚集受构造背景控制,继承性发育的古隆起决定各个时期油气运移指向,塔中地区油气基本上是自北西向南东方向运移。潮坪相沉积决定了薄砂层单个砂体规模不大,一系列砂体靠断层沟通。塔中地区志留系形成了油气丰度不高、在空间上叠置连片、大面积分布、受多种圈闭类型控制的油气聚集特征。     

塔里木盆地北部地区下志留统柯坪塔格组物源分析与物源区母岩年龄确定

根据柯坪（KP）大湾沟剖面及塔北地区TP3,TP7和KQ1等井下志留统柯坪塔格组砂岩样品岩石薄片、重矿物、锆石SHRIMP U-Pb测年分析结果,应用Dickinson三角图法,结合区域地质背景分析,认为塔北西部地区和中东部地区的志留系柯坪塔格组砂岩物源明显不同。西部地区物源构造背景为大陆岛弧环境,物源物质为大陆上地壳,年代为元古代,推测物源区为塔北隆起;中东部地区物源构造背景为再旋回造山带环境,年代为奥陶纪,推测物源区为库鲁克塔格隆起带。物源母岩普遍含深成中酸性侵入岩。塔北西部物源距离远于塔北中东部地区,这对于恢复当时的沉积古地理环境以及塔里木盆地的类型和盆地演化有重要意义。     

华南下寒武统Ni-Mo-Se多金属层S-Se同位素体系

为了进一步理解华南下寒武统Ni-Mo-Se多金属层的物质来源及形成环境,文中分析了遵义中南村和张家界后坪两个Ni-Mo-Se矿层及其围岩的黄铁矿硫同位素和全岩的硒同位素组成。硫同位素组成显示两个Ni-Mo-Se矿层形成时的环境存在区域性差别,中南村矿层形成于间歇开放的海洋环境,而后坪矿层形成于封闭的缺氧（静海）环境。较大的硫同位素范围暗示硫酸盐还原菌控制硫同位素的分馏,而热液流体可能提供了大量金属元素,从而导致矿层富集大量的硫化物和稀有金属。硒同位素组成指示牛蹄塘组底部热液流体的Se可能重新经历了氧化还原循环,而Se的富集过程可能受有机质和粘土矿物吸附或类质同象过程控制。因此,控制多金属富集的因素主要为富集金属的热液流体的参与和缺氧环境下的自生沉积。     

塔里木盆地塔中隆起构造演化与油气关系

笔者结合塔里木盆地形成的构造背景对塔中隆起的主要构造演化过程进行了研究，并具体分析了各构造演化阶段与志留系油气的关系。研究表明，塔中隆起源于早古生代拉张背景下的正断层，寒武-奥陶纪为其烃源岩形成的重要时期；早奥陶世末-晚奥陶世末的构造反转是塔中隆起的主要形成期，同时也为志留系的形成及复合圈闭提供了古地理背景；泥盆纪末塔中鼻状隆起基本定型，古油藏遭受破坏，形成了沥青砂岩；早二叠世晚期的构造变形使古油藏遭受进一步的破坏；二叠纪后构造变动主要以调节为主。伴随整个构造的演化，志留系的油气聚集也是分期次、不同规模的进行。