新疆库车盆地钾盐科探1井含盐系地球化学特征及找钾指示

在盐湖沉积演化过程中,钾盐矿物在盐类沉积的中晚期阶段才开始析出。因此,研究含盐系盐类的沉积地球化学特征,不仅可以从侧面获取岩盐的沉积物源和成盐古卤水蒸发浓缩程度等地球化学信息,而且更能揭示古盐湖钾盐富集趋势。文章通过对库车盆地钾盐科探1井钻取的岩芯样品进行高精度采样测试,得出岩盐中Mg×103/Cl、K×103/Cl、Li×103/Cl与K+、Mg2+、Li+、Ca2+、Cl-含量的垂向变化规律。并与库车盆地其他钻孔中的岩盐含钾性进行对比,同时,依据钻井剖面岩性特征,与潜江凹陷和大汶口凹陷含盐系剖面进行对比,论述研究区成盐的地球化学特征,对其钾盐成矿前景进行分析和评价。     

蒙古国满都拉探矿区地质特征及流体包裹体研究

满都拉探矿区位于蒙古国南戈壁省满都拉苏木。矿区地表中元古界白云岩中出露大面积含孔雀石、蓝铜矿和辉铜矿的硅化蚀变带,含铜矿物与石英脉在空间上紧密共生,石英中的流体包裹体可能保留了原生成矿流体特征。为确定其成矿地质体和成因类型,指导后续找矿工作,本文对硅化蚀变带中的石英进行了流体包裹体研究。根据石英中包裹体的产状可将包裹体分为早晚两个阶段,早阶段富含CO2(C型)和水溶液(W型)包裹体,偶见含子矿物(S型)包裹体,流体均一温度为195~384℃,盐度为2.77%~21.37%Na Cl.eqv,反映了原生成矿流体的特征。晚阶段仅出现水溶液(W型)包裹体,流体均一温度集中在95~213℃,盐度为1.27%~12.63%Na Cl.eqv。流体由早阶段的中高温、中盐度、富CO2流体向晚阶段低温、低盐度、贫CO2流体演化。据此推测成矿流体可能为岩浆流体,流体形成深度大约在5.7 km以上。     

中国地热研究的进展与展望(1995～2014)

地热是主要地球物理场之一,地热能是地球的本土能源。李四光在20世纪60年代开创了我国地热科学。到90年代,学科体系基本建立。在过去20年里,我国地热研究得到了进一步深化和拓展。本文从大地热流、岩石圈热结构、地热系统、油气盆地地热、矿山地热、天然气水合物以及气候变化等方面回顾地热研究代表性的创新进展,并对深层地热、海洋地热、环境地热等研究方向作了展望。本文认为,过去20年我国地热研究成果丰硕,国际影响力得到提高,未来发展势头强劲。在经历了由浅入深,从今到古的成长之后,地热研究还将不断拓展领域,为我国地球科学,特别是能源与环境安全做出更大贡献。     

Comparison of Blast-Induced Damage Between Presplit and Smooth Blasting of High Rock Slope

This paper focuses on the comparison of damage induced by smooth blasting and presplit blasting based on the excavation of high rock slope. The whole damage process of the smooth blasting and presplit blasting excavation method is studied by using a cumulative blasting damage numerical simulation technology based on the secondary development of the dynamic finite element code LS-DYNA. The results demonstrate that, in the case of contour blasting with the method of smooth blasting, the total damage of rock slope is a result of cumulated damage induced by the production hole, buffering hole, and smooth hole. Among the total damage, the blasting of the production hole is the main resource, followed by the smooth and buffering holes. For the presplit blasting, the final damage of rock slope is mainly induced by presplit blasting itself. The spatial distribution characteristics of the final damage zone of two methods are compared. Two classes of damage zone could be found in smooth blasting excavation; one of them is the columnar high-degree damage zone around the slope surface and the other is the low-degree damage zone located in the middle of the slope. But in the case of presplit blasting, there is only the columnar high-degree damage zone around the slope surface. Finally, a damage control suggestion for two blasting excavation methods is proposed and verified based on the excavation of the temporary shiplock slopes of the Three Gorges Project in China.     

Micromechanical Modeling of Anisotropic Damage-Induced Permeability Variation in Crystalline Rocks

This paper presents a study on the initiation and progress of anisotropic damage and its impact on the permeability variation of crystalline rocks of low porosity. This work was based on an existing micromechanical model considering the frictional sliding and dilatancy behaviors of microcracks and the recovery of degraded stiffness when the microcracks are closed. By virtue of an analytical ellipsoidal inclusion solution, lower bound estimates were formulated through a rigorous homogenization procedure for the damage-induced effective permeability of the microcracks-matrix system, and their predictive limitations were discussed with superconducting penny-shaped microcracks, in which the greatest lower bounds were obtained for each homogenization scheme. On this basis, an empirical upper bound estimation model was suggested to account for the influences of anisotropic damage growth, connectivity, frictional sliding, dilatancy, and normal stiffness recovery of closed microcracks, as well as tensile stress-induced microcrack opening on the permeability variation, with a small number of material parameters. The developed model was calibrated and validated by a series of existing laboratory triaxial compression tests with permeability measurements on crystalline rocks, and applied for characterizing the excavation-induced damage zone and permeability variation in the surrounding granitic rock of the TSX tunnel at the Atomic Energy of Canada Limited’s (AECL) Underground Research Laboratory (URL) in Canada, with an acceptable agreement between the predicted and measured data.     

Time-Varying Multifractal Characteristics and Formation Mechanism of Loaded Coal Electromagnetic Radiation

Dynamic collapses of deeply mined coal rocks are severe threats to miners. To predict the collapses more accurately using electromagnetic radiation (EMR), we investigate the time-varying multifractal characteristics and formation mechanism of EMR induced by underground coal mining. A series of uniaxial compression and multi-stage loading experiments with coal samples of different mechanical properties were carried out. The EMR signals during their damage evolution were monitored in real-time; the inherent law of EMR time series was analyzed by fractal theory. The results show that the time-varying multifractal characteristics of EMR are determined by damage evolutions process, the dissipated energy caused by damage evolutions such as crack propagation, fractal sliding and shearing can be regard as the fingerprint of various EMR micro-mechanics. Based on the Irreversible thermodynamics and damage mechanics, we introduced the damage internal variable, constructed the dissipative potential function and established the coupled model of the EMR and the dissipative energy, which revealed the nature of dynamic nonlinear characteristics of EMR. Dynamic multifractal spectrum is the objective response of EMR signals, thus it can be used to evaluate the coal deformation and fracture process.     

Assessment of spatio-temporal variations in vegetation recovery after the Wenchuan earthquake using Landsat data

The 8.0-magnitude Wenchuan earthquake in 2008 damaged the ecology of northwestern Sichuan, China. This study assessed ecological changes within a few years of the earthquake through satellite observations of vegetation dynamics in the earthquake area. As an ecological indicator, the fractional vegetation cover was extracted using the Normalized Difference Vegetation Index based on multi-year Landsat images and was validated using airborne images. We found that the entire mountainous disaster area had recovered by 68.45 % 3 years after the 2008 earthquake. After rapid recovery of vegetation in 2009, the recovery process slowed. The vegetation recovery rate (VRR) in the area heavily damaged by landslides was slightly lower but nearly that of the entire disaster area. In addition, because of differences in the proportions of soil and rock in the damaged areas, recovery of vegetation in the southwest portion of the study area was slower than in the northeast areas. Topographic analysis of vegetation recovery patterns indicated that damage to vegetation was closely related to slope, while recovery of vegetation was more sensitive to elevation. The landscape analysis showed that the recovery rate (65.21 %) of the excellent vegetation cover type was slower than the overall VRR. This study suggests that vegetation recovery is a slow ecological process and that ecological restoration should be implemented in mountainous regions affected by the earthquake.     

Geochemistry of mafic rocks and melt inclusions and their implications for the heat source of the 14.0°S hydrothermal field,South Mid-Atlantic Ridge

Fresh rocks sampled from the 14.0°S hydrothermal field of the South Atlantic Ridge can be divided into two categories： olivine-gabbro and basalt. The olivine-gabbro is composed mainly of three types of minerals： olivine, clinopyroxene and plagioclase, while a multitude of melt inclusions occur in the plagioclase phenocrysts of the basalts. We analyzed the whole-rock, major and trace elements contents of the basaks, the mineral chemistry of phenocrysts and melt inclusions in the basalts, and the mineral chemistry of olivine-clinopyroxene-plagioclase in the olivine-gabbro, then simulated magma evolution within the crust using the COMAGMAT program. The whole-rock geochemistry shows that all the basalts exhibit typical N-MORB characteristics. In addition, the mineral chemistry characteristics of the olivine-gabbro （low-Fo olivine, low-Mg# clinopyroxene, high-TiO2 clinopyroxene, low-An plagioclase）, show that strong magma differentiation occurred within the crust. Nevertheless, significant discrepancies between those minerals and phenocrysts in the basalts （high-Fo olivine, high-An plagioclase） reflect the heterogeneity of magma differentiation. High Mg# （-~0.72） melt inclusions isobaric partial crystallization simulations suggest that the magma differentiation occurred at the depth shallower than 13.03 km below the seafloor, and both the vertical differentiation column shows distinct discrepancies from that of a steady-state magma chamber. Instead, a series of independent magma intrusions probably occurred within the crust, and their corresponding crystallized bodies, as the primary high-temperature thermal anomalies within the off-axis crust, probably act as the heat source for the development of the 14.0°S hydrothermal system.     

A Preliminary Study of Holocene Climate Change and Human Adaptation in the Horqin Region

Abstract: Human activity during the Holocene in the Horqin region, northeastern China, has been widely documented. As an important proxy record of human activity, black carbon (BC) in sediments has been linked to climate change and human adaptation. A loess-paleosol section located in south Horqin was chosen for this study. Holocene climate change and human adaptation to the environment were discussed by analyzing BC, organic carbon (OC) and other proxies. The conclusions included: (1) before 3900 cal BP, human activity was closely related to the natural environment and cultural development was dominated by climate change. For example, the rapid decline of the agrarian Hongshan culture was caused by a slight decrease in temperature at ~5000 cal BP; (2) during 3900-3200 cal BP, the heavy dependence of human societies on nature gradually lessened and the ability of those human societies to adapt to the environment was enhanced. However, the farming-dominated Lower Xiajiadian culture was nonetheless replaced by the pastoralist Upper Xiajiadian culture due to an extremely cooling event at ~3200 cal BP; (3) during the late Holocene period, the marked influence of climate change on human activity might have lessened as a result of a clear improvement in human labor skills. After this, human living styles were influenced by cultural developments rather than climate change because humans had mastered more powerful means of productivity.