Isotopic and petrological evidence of fluid–rock interaction at a Tethyan ocean–continent transition in the Alps: implications for tectonic processes and carbon transfer during early ocean formation

We report overprinting stable isotope evidence of fluid–rock interaction below two detachment faults along which mantle rocks were exhumed to the seafloor, between the respective landward and seaward limits of oceanic and continental crust, at a Tethyan ocean–continent transition (OCT). This OCT, which is presently exposed in the Tasna nappe (south‐eastern Switzerland) is considered an on‐land analogue of the well‐studied Iberian OCT. We compare our results with the fault architecture (fault core–damage zone–protolith) described by Caine et al. [Geology (1996) Vol. 24, pp. 1025–1028]. We confirm the existence of a sharp boundary between the fault core and damage zone based on isotopic data, but the boundary between the damage zone and protolith is gradational. We identify evidence for: (1) pervasive isotopic modification to 8.4 ± 0.1‰ which accompanied or post‐dated serpentinization of these mantle rocks at an estimated temperature of 67–109°C, (2) either (i) partial isolation of some highly strained regions [fault core(s) and mylonite] from this pervasive isotopic modification, because of permeability reduction (Caine et al.) or (ii) subsequent isotopic modification caused by structurally channelled flow of warm fluids within these highly strained regions, because of permeability enhancement, and (3) isotopic modification, which is associated with extensive calcification at T = 54–100°C, primarily beneath the younger of the two detachment faults and post‐dating initial serpentinization. By comparing the volumetric extent of calcification with an experimentally verified model for calcite precipitation in veins, we conclude that calcification could have occurred in response to seawater infiltration, with a calculated flux rate of 0.1–0.2 m year^?1 and a minimum duration of 0.2–4.0 × 10⁴ years. The associated time‐averaged uptake flux of carbon during this period was 8–120 mol m^?2 year^?1. By comparison with the estimated area of exhumed mantle rocks at the Iberian OCT, we calculate a maximum annual uptake flux for carbon of 2–30 Tg year^?1. This is an order of magnitude greater than that for carbon exchange at the mid‐ocean ridges and 0.1–1.4% of the global oceanic uptake flux for carbon.     

高校人才流动原因及对策探析

近年来,高校人才流动频繁已成为制约高校发展的瓶颈和高校人事管理一大难题。运用马斯洛需要层次理论,探析高校人才流动的原因,并提出相关对策。     

我国旅游热点城市境外游客旅游流空间分布特征分析

通过对北京、上海、西安等旅游热点城市境外游客抽样调查资料和多年统计资料的分析,总结出境外游客入境旅游流空间分布的规律性特征,为旅游热点城市的旅游业发展提供基础信息。     

黄河断流对山东沿黄区域可持续发展的影响

山东省是一个严重缺水地区,水资源缺乏一直是困扰着国民经济发展的重要制约因素。黄河是山东省最大的客水资源,对本省的可持续发展起着重要的支撑作用。黄河断流是在发展中遇到的问题,严重影响着山东省农业的稳产高产、人畜饮水和工业的发展,反映了黄河流域发展的非可持续性,须用可持续发展的手段来解决。     

图们江地区物流长期预测研究的理论与方法

本文运用路线比较模型与重力模型,对通过图们江地区的港口与相关路线的物流状况(2000~2020)进行了预测与研究,深入探讨了影响图们江地区物流的主要障碍因素,对不同障碍因素的变化及其对图们江地区物流的影响进行了分析。     

初论人性时空场

在缜密论述了人地关系中人性时空场基本概念和特征的基础上,从人性时空场意识流与人地关系的相互作用的角度认知了人性时空场的科学哲学内涵。最后分析了人性时空场意识流的随机变化特点之表达。提出:随着行为地理学研究深入,人性时空场意识流将成为它新的研究对象;与此同时,本文首次导出潜意识地理学(Potential Sense Geography)的学科概念,认为潜意识地理学会弥补行为地理学的不足,它将发挥人文关怀的当代学科优势,继而为人性的完善和人的可持续发展及人地关系的根本和谐作出贡献。     

珠江三角洲客、货运量的空间演化研究

本文分析了改革开放以来珠江三角洲地区客运量、货运量的总体变化特点。根据珠江三角洲各县市客运量与货运量在珠江三角洲地区各自所占的比重,选取了1980、1985、1990、1995、1998五个时间段,分析客运量与货运量在珠江三角洲地区的空间分布形态。     

An exhumed palaeo-hydrocarbon migration fairway in a faulted carrier system, Entrada Sandstone of SE Utah, USA

The Moab Anticline, east‐central Utah, is an exhumed hydrocarbon palaeo‐reservoir which was supplied by hydrocarbons that migrated from the Moab Fault up‐dip towards the crest of the structure beneath the regional seal of the Tidwell mudstone. Iron oxide reduction in porous, high permeability aeolian sandstones records the secondary migration of hydrocarbons, filling of traps against small sealing faults and spill pathways through the Middle Jurassic Entrada Sandstone. Hydrocarbons entered the Entrada Sandstone carrier system from bends and other leak points on the Moab Fault producing discrete zones of reduction that extend for up to 400 m from these leak points. They then migrated in focused stringers, 2–5 m in height, to produce accumulations on the crest of the anticline. Normal faults on the anticline were transient permeability barriers to hydrocarbon migration producing a series of small compartmentalized accumulations. Exsolution of CO₂ as local fault seals were breached resulted in calcite cementation on the up‐dip side of faults. Field observations on the distribution of iron oxide reduction and calcite cements within the anticline indicate that the advancing reduction fronts were affected neither by individual slip bands in damage zones around faults nor by small faults with sand: sand juxtapositions. Faults with larger throws produced either sand: mudstone juxtapositions or sand: sand contacts and fault zones with shale smears. Shale‐smeared fault zones provided seals to the reducing fluid which filled the structural traps to spill points.     

Quantitative basin modeling: present state and future developments towards predictability

A critique review of the state of quantitative basin modeling is presented. Over the last 15 years, a number of models are proposed to advance our understanding of basin evolution. However, as of present, most basin models are two dimensional (2‐D) and subject to significant simplifications such as depth‐ or effective stress‐dependent porosity, no stress calculations, isotropic fracture permeability, etc. In this paper, promising areas for future development are identified. The use of extensive data sets to calibrate basin models requires a comprehensive reaction, transport, mechanical (RTM) model in order to generate the synthetic response. An automated approach to integrate comprehensive basin modeling and seismic, well‐log and other type of data is suggested. The approach takes advantage of comprehensive RTM basin modeling to complete an algorithm based on information theory that places basin modeling on a rigorous foundation. Incompleteness in a model can self‐consistently be compensated for by an increase in the amount of observed data used. The method can be used to calibrate the transport, mechanical, or other laws underlying the model. As the procedure is fully automated, the predictions can be continuously updated as new observed data become available. Finally, the procedure makes it possible to augment the model itself as new processes are added in a way that is dictated by the available data. In summary, the automated data/model integration places basin simulation in a novel context of informatics that allows for data to be used to minimize and assess risk in the prediction of reservoir location and characteristics.     

The link between fluids and rank variation in the South Wales Coalfield: evidence from fluid inclusions and stable isotopes

Fluid inclusion and stable isotope data from quartz and carbonate minerals in fracture fillings and ‘ironstone’ nodules from the South Wales Coalfield have been used to characterise the fluids generated during basin evolution and associated coalification. Carbonates grew first, probably at relatively shallow depths and low temperatures (<100°C). The carbonates exhibit a trend of increasing C‐isotopic values across the coalfield, ranging from δ¹³C = ?12‰ VPDB in the SE of the coalfield to 0‰ VPDB in the NW, possibly as a result of increasing methanogenesis in the deeper (NW) parts of the coalfield. Quartz formed at a later stage of basin formation, probably at temperatures between 150 and 200°C. Fluid inclusions in these minerals suggest that burial and coalification of the sediments were associated with mixed aqueous–petroleum fluids. Furthermore, the density of these petroleum fluids decreases towards the NW of the coalfield, where the rank of the associated coal increases to anthracite grade. The study confirms that the composition and temperature of these fluids closely correlate with the variations in coal rank, indicating a possible causal link. The data also give general support to models that propose regional fluid flow in the basin. and are consistent with the erosion of approximately 2 km of section which is not preserved today. A geothermal gradient (at maximum burial) of 45°C km^?1 is proposed, and thus no exceptionally anomalous thermal regime is required to explain coal rank variation.