Evolution of melt composition during intrusion of basalts into a silicic magma chamber

The article describes heat exchange between basaltic and rhyolite melts accompanied by fractional crystallization of phases in a basaltic melt. A numerical model has been developed for the homogenization mechanism of magma composition during intrusion of basaltic magma batches into felsic magma chambers. The results of numerical modeling demonstrate that the time needed for cooling the basalts and their fractionation to rhyolite melts is much shorter than the time required for chemical interaction based on diffusive mechanisms.     

Recharge source and hydrogeochemical evolution of shallow groundwater in a complex alluvial fan system,southwest of North China Plain

Many cities around the world are developed at alluvial fans. With economic and industrial development and increase in population, quality and quantity of groundwater are often damaged by over-exploitation in these areas. In order to realistically assess these groundwater resources and their sustainability, it is vital to understand the recharge sources and hydrogeochemical evolution of groundwater in alluvial fans. In March 2006, groundwater and surface water were sampled for major element analysis and stable isotope (oxygen-18 and deuterium) compositions in Xinxiang, which is located at a complex alluvial fan system composed of a mountainous area, Taihang Mt. alluvial fan and Yellow River alluvial fan. In the Taihang mountainous area, the groundwater was recharged by precipitation and was characterized by Ca–HCO₃ type water with depleted δ¹⁸O and δD (mean value of −8.8‰ δ¹⁸O). Along the flow path from the mountainous area to Taihang Mt. alluvial fan, the groundwater became geochemically complex (Ca–Na–Mg–HCO₃–Cl–SO₄ type), and heavier δ¹⁸O and δD were observed (around −8‰ δ¹⁸O). Before the surface water with mean δ¹⁸O of −8.7‰ recharged to groundwater, it underwent isotopic enrichment in Taihang Mt. alluvial fan. Chemical mixture and ion exchange are expected to be responsible for the chemical evolution of groundwater in Yellow River alluvial fan. Transferred water from the Yellow River is the main source of the groundwater in the Yellow River alluvial fan in the south of the study area, and stable isotopic compositions of the groundwater (mean value of −8.8‰ δ¹⁸O) were similar to those of transferred water (−8.9‰), increasing from the southern boundary of the study area to the distal end of the fan. The groundwater underwent chemical evolution from Ca–HCO₃, Na–HCO₃, to Na–SO₄. A conceptual model, integrating stiff diagrams, is used to describe the spatial variation of recharge sources, chemical evolution, and groundwater flow paths in the complex alluvial fan aquifer system.     

湘南中山地区中棚岩体地球化学特征与铀成矿

通过对中棚岩体地球化学特征的研究,探讨其与铀矿化的关系。中棚岩体属于过铝质花岗岩,高钾钙碱性岩石系列。分析认为,岩体具有S型花岗岩特征,为陆壳物质部分熔融的产物,原岩可能为寒武系浅变质砂岩。构造环境判别认为,岩体属于后碰撞花岗岩范畴,在岩石圈伸展作用构造环境下由寒武系部分熔融所形成。岩体的原岩铀含量较高,为富铀的中棚岩体形成奠定了基础,也为后期成矿提供了充足的铀源。     

Quaternary travertine of the Kurai fault zone (Gorny Altai)

In the Kurai fault zone, travertine forms a matrix cementing clastic material of colluvial and glacial deposits or rarely forming a stockwork in a system of fractures in Palaeozoic rocks. The regular change of composition of solutions in the process of travertine formation has resulted in change of stable Mg–calcite by Sr–aragonite. According to the carbon isotopic composition, the travertine has intermediate genesis between thermal and meteogene. The light oxygen isotopic composition of CaCO₃ indicates formational water input. The carbonates inherited Y, Sr, U, and Ni and in some areas, V, As, and Zn from the endogeneous water sources. Given that the Kurai zone travertine cements the Late Pleistocene–Holocene sediments and ¹⁴C dating of the carbonates gives a range of >40 000–3475 ± 35 years, the faults serving as routes of migration of the solutions forming the travertine should be considered as active structures.     

Characteristic of quaternary sedimentation on a shelf of the Laptev Sea according to the molecular composition of n-alkanes

The molecular composition and distribution of the concentration of n-alkanes are considered for sediments of boreholes drilled in the shallow part of the Laptev Sea, in the area of Buor Khaya Gulf. The diverse molecular composition of n-alkanes is dominated by long-chain odd homologs, which indicate terrigenous organic matter (OM). Heterogeneous distribution and burial of OM are shown under conditions of pulsating contribution of river and thermoabrasive material and multiple changes in them up to hiatuses in sedimentation.     

Adsorption of Heavy Metal Cations by Base Metal Sulfides in the Broken Spur and TAG Hydrothermal Fields,Atlantic Ocean

Data on the mineral and chemical composition of samples of sulfide deposits from the Broken Spur and TAG (Mid-Atlantic Ridge) are presented. The main minerals in the Broken Spur field are marcasite, pyrrhotite, pyrite, chalcopyrite, and sphalerite; in sample from TAG: chalcopyrite, pyrite, and marcasite. It has been established that these sulfide minerals of Fe, Cu, and Zn are natural ion exchangers and belong to the class of adsorbents. Exchange capacity of sulfide minerals in terms of heavy metal cations (Ni2+, Co2+, Cd2+, and Pb2+) is 0.022–0.32 mg-equiv/g. In the exchange reaction products, the mineral composition of sulfide deposits is retained, and new phases do not appear. It is suggested that the adsorbed heavy metal cations populate either vacant cationic or interstitial defect sites in the structures of sulfide minerals. Bond strength of the adsorbed heavy metal cations with the main structural elements of minerals is low, which is confirmed by their high extraction in an acid medium. The results of adsorption-desorption experiments indicate two forms of heavy metal cations in sulfide minerals: adsorbed (basic) and chemically bound.     

塔里木南缘布雅花岗岩和暗色包体的锆石U-Pb年代学及地球化学特征

塔里木西南缘铁克里克地区广泛发育早古生代中酸性侵入岩,本文对其中布雅岩体及其暗色包体进行系统的岩石学、年代学及岩石地球化学研究,确定了岩石成因及其构造属性。LA-MC-ICP-MS锆石U-Pb年代学研究表明,寄主石英二长闪长岩结晶年龄为432.6±2.5 Ma(MSWD=1.5),暗色包体结晶年龄为432.4±6.4 Ma(MSWD=0.031),二者形成时代相同,均为志留纪早期岩浆活动的产物。地球化学特征表明,布雅暗色包体应来源于地幔的部分熔融,而寄主岩石岩浆具有壳源岩浆的性质并经历了幔源岩浆不均匀的混合。野外及岩相学特征均显示暗色包体为铁镁质岩浆注入长英质岩浆快速冷凝形成的,是幔源岩浆底侵下地壳形成的岩浆混合作用的产物。它们是塔里木南缘早古生代碰撞造山作用晚期的岩浆记录。     

从地震释能角度试析贵州断裂构造的活动性

地震释放能量的多寡,是构造活动性的最直接的表现。本文从地震释放能量的角度对贵州地质构造的活动性进行了研究。研究结果表明:贵州断裂构造活动性呈现由西向东递减的趋势;地下活动断裂构造走向有北西、北东、南北、东西四组,与地面观察到的情况类似;地下活动断裂构造与地面断裂构造在平面位置上不完全对应;断裂构造的活动呈现时间和空间上的变化。     

Comparative Planetary Space Physics

It has been 60 years since the space physics as new branch of geophysics started to grow in 1957 when the space age was opened by a small satellite called sputnik. The knowledge of Earth and planetary space has been significantly extended and deepened, but the questions we are facing today are more challenging. A consensus reached is that we have to regard the Earth (planet) as an integrated system including all spheres from the inner core to the magnetosphere, and we should try to investigate some questions standing on the ground of interdisciplinary study, especially those questions related to Earth’s (planetary) evolution. Space environment as the outer part of a planetary system, commonly exists in all planets but also exhibits strong diversity. Here, we introduce the short history of basic ideas and methods of comparative study, the advantages on understanding of some issues of global scale, and the prospect from comparative perspective.     

A FINITE ELEMENT SHALLOW WATER CIRCULATION MODEL FOR TOLO HARBOUR, HONG KONG

Numerical solution of two-dimensional shallow water equations has been achieved by the finite element method. In this work, the governing equations were first converted into different equations suitable for explicit, forward marching, integration in the time domain. A second order Taylor's series expansion was used for the continuity equation and an "upwind" differencing was incorporated in the nonlinear convective terms in the momentum equations.The model was applied to Tolo Harbour in Hong Kong. Velocity vector plots and surface elevations obtained from the calculations are reasonably consistent with the expected tidal response of the systems.