内蒙古大型银矿集区地球化学预测

如何利用地球化学填图数据预测潜在大型矿集区是寻找大型矿床亟待解决的问题.本文利用1:20万区域化探扫面数据和1:100万中蒙边界地球化学填图数据进行综合研究,在全区共圈出面积大于1000km2银的地球化学省40个,其中具有良好Ag-Pb-Zn综合异常的有31处.内蒙已发现的4处大型银矿有3处位于地球化学省内,已发现的11处中型银矿有10处位于地球化学省或区域异常内,这说明大型银矿与地球化学省有高度的相关性.大型银矿区银异常强度(异常内银平均含量/背景含量)大于1.5.利用面金属量模型和地球化学块体模型对31处潜在的大型银矿区的潜在资源量进行了预测.     

Origin of fine-scale sheeted granites by incremental injection of magma into active shear zones: examples from the Pilbara Craton, NW Australia

In the Archaean Pilbara Craton of Western Australia, three zones of heterogeneous centimetre- to metre-scale sheeted granites are interpreted to represent high-level, syn-magmatic shear zones. Evidence for the syn-magmatic nature of the shear zones include imbricated and asymmetrically rotated metre-scale orthogneiss xenoliths that are enveloped by leucogranite sheets that show no significant internal strain. At another locality, granite sheets have a strong shape-preferred alignment of K-feldspar, suggesting magmatic flow, while the asymmetric recrystallisation of the grain boundaries indicates that non-coaxial deformation continued acting upon the sheets under sub-solidus conditions. Elsewhere, randomly oriented centimetre-wide leucogranite dykes are realigned at a shear zone boundary to form semi-continuous, layer-parallel sheets within a magma-dominated, dextral shear zone.

It is proposed that the granite sheets formed by the incremental injection of magmas into active shear zones. Magma was sheared during laminar flow to produce the sheets that are aligned sub-parallel to the shear zone boundary. Individual sheets are fed by individual dykes, with up to 1000s of discrete injections in an individual shear zone. The sheets often lack microstructural evidence for magmatic flow, either because the crystal content of the magma was too low to record internal strain, or because of later recrystallisation.     

48ka以来日本海古生产力和古氧化还原环境变化的地球化学记录

通过对日本海Ulleung盆地KCES-1孔元素地球化学分析,探讨了过去48 ka以来日本海古生产力和古氧化还原环境的变化规律和影响因素。多种替代指标质量累积速率(总有机碳、CaCO3,磷、过剩钡、镉含量)显示日本海古生产力自48 ka以来发生了显著的变化。在48~18 ka低海平面和有限的水体交换导致表层水古生产力相对较低。在18~11 ka随着海平面的上升,富营养盐水团(亲潮和东海沿岸流水团)的流入导致古生产力逐渐增大,在12.6~11.5 ka古生产力达到最大值。在全新世对马暖流成为影响古生产力变化的重要因素,并且自5 ka以来古生产力保持相对稳定。古氧化还原替代指标(总有机碳、钼、铀、锰、碳与硫含量之比、自生铀、自生钼含量)显示在12~9 ka日本海底层水可能为无氧环境。古生产力高和底层水体有限的交换是诱发底层水缺氧的主要因素,而这又与全球气候变化和海平面变化有关。     

Spectral analysis of continuous redox data reveals geochemical dynamics near the stream–aquifer interface

Changes in streamflow and water table elevation influence oxidation–reduction (redox) conditions near river–aquifer interfaces, with potentially important consequences for solute fluxes and biogeochemical reaction rates. Although continuous measurements of groundwater chemistry can be arduous, in situ sensors reveal chemistry dynamics across a wide range of timescales. We monitored redox potential in an aquifer adjacent to a tidal river and used spectral and wavelet analyses to link redox responses to hydrologic perturbations within the bed and banks. Storms perturb redox potential within both the bed and banks over timescales of days to weeks. Tides drive semidiurnal oscillations in redox potential within the streambed that are absent in the banks. Wavelet analysis shows that tidal redox oscillations in the bed are greatest during late summer (wavelet magnitude of 5.62 mV) when river stage fluctuations are on the order of 70 cm and microbial activity is relatively high. Tidal redox oscillations diminish during the winter (wavelet magnitude of 2.73 mV) when river stage fluctuations are smaller (on the order of 50 cm) and microbial activity is presumably low. Although traditional geochemical observations are often limited to summer baseflow conditions, in situ redox sensing provides continuous, high‐resolution chemical characterization of the subsurface, revealing transport and reaction processes across spatial and temporal scales in aquifers.     

区域水资源可持续利用的综合评价方法

水资源可持续利用指标体系及评价方法是水资源可持续利用研究的核心问题之一。以复合系统理论为基础,将水资源、社会经济和环境组成的复合系统定义为水资源可持续利用系统(RSWRS系统)。应用Bossel可持续发展基本定向指标框架,建立了水资源可持续利用指标评价体系。应用系统综合评价法,权重采用基于Bossel评分标准,以参考状态的离差平方和最大法计算,建立了以RSWRS系统发展综合指数和发展态势度量模型。以陕西省为例,进行了水资源可持续利用的综合定量评价。     

An indicator-based adaptive management framework and its development for data-limited fisheries in Belize

Decisions regarding the selection and implementation of management strategies that constrain fishing pressure can be among the most difficult choices that fisheries managers and stakeholders must make. These types of decisions often need to be confronted in a data-limited context, where few if any management measures are currently in place or fisheries are managed independent of adequate scientific advice. This situation can sometimes create a high risk of overfishing and potential loss of economic and social benefits. To address this situation, simple model-free indicator-based frameworks have the potential to be effective decision-making platforms for fisheries where quantitative estimates of biomass and fishing mortality based reference points are lacking. In this paper, a multi-indicator framework is developed that enables decision-makers to proceed with management decisions in data-limited situations. Model-free indicators are calculated using trends in observed data, rather than stock assessment derived estimates of biomass and fishing mortality. The framework developed is adaptive so that adjustments to catch or effort are recursive and can respond to changing environments, socioeconomic conditions, and fishing practices. Using stakeholder-defined objectives as a foundation, indicators and reference points of fishery performance are chosen that can be evaluated easily by undertaking analyses of available data. Indicators from multiple data streams are used so that uncertainty in one indicator can be hedged through careful interpretation and corroboration of information from alternative indicators. During the adaptive management cycle, managers and stakeholders evaluate each indicator against the associated reference points to determine performance measures, interpret the results using scientific and local knowledge, and adjust fishery management tactics accordingly using pre-defined harvest control rules. The framework facilitates the interpretation of situations in which performance measures suggest divergent stock abundance or productivity levels. A case study is presented on this framework's development for conch and lobster fisheries of Belize.     

Desertification in the Eastern Province of Saudi Arabia

The problem of land degradation in the Eastern Province of Saudi Arabia is not a new phenomenon, but during the last decade it has grown to be a serious threat to the delicate desert ecosystems, and also to the urban and industrial areas, due to an increase in sand movement. The area under investigation is situated on the Gulf coast north of Jubail and is approximately 20 km in width centered along the coastline. The total area is almost 1000 km². Eight vegetation types were classified according to the dominant and co-dominant species. A comparative study of the vegetation in a fenced, non-grazed area and in an open grazed area showed that the impact of grazing and recreational activities have largely reduced the value of the rangelands. The reduction in species diversity and density leads to an increase in wind and sand dynamics. Exposed roots, giant ripples, changes in the extension of inland sabkhas and new active dunes could be observed in many parts of the study area. It could be proved that most inland sabkhas in the area are pure deflational features with considerable dynamic due to the reduction in vegetation cover during the recent years. The monitoring of vegetation density was carried out during helicopter flights with the help of GPS and a video camera. Image processing on a personal computer allowed accurate calculations of vegetation density. Observations on active dune fields in the area showed that the size of the dune fields almost doubled in 15 months. Tests in small enclosures showed that there is a potential for natural recovery even in severely damaged areas. In just one year without grazing and with average precipitation there is a significant difference in vegetation cover. Strict grazing management and camping regulations are required to prevent further degradation and allow the recovery of damaged ecosystems. Community involvement and education is necessary for the development of an understanding of regulations and the need for preservation.     

A land-use-based modelling chain to assess the impacts of Natural Water Retention Measures on Europe’s Green Infrastructure

This article details the process of integrating models to answer a specific policy-driven question: ‘What could be the impact of proposed Natural Water Retention Measures (NWRMs) on Europe’s Green Infrastructure (GI)?’ It describes the new Land Use Modelling Platform (LUMP), now enabling a high spatial scale (100-m) and large coverage (pan-European), whereby several sector-specific models contribute to assessing the impact of regional-level policy on a given spatial topic of concern. The configuration (land claims and land allocations modules) and calibration (accessibility and biophysical suitability) of the LUMP are explained. Four NWRM scenarios (riparian areas, afforestation, grassland and baseline scenario) are configured to run the simulations. For the reference: year 2006, the spatial representation of GI is based on land-use features of a refined version of the CORINE Land Cover (CLC), and resumed as connected components made of nodes and links.

Mathematical morphological image processing and network graph theory model, available from the free software package GUIDOS (the Joint Research Center of the European Commission), enabled the measurement of the GI connectivity and identified most critical links. Results show that the competition for land claimed by different economic sectors, combined with policy-driven rule-sets for the implementation of different NWRMs, yields very different results for the 2030 land-use projections, and subsequently for the morphology of GI. Three indicators associated with the morphology of GI are computed in order to assess the model outputs for 2030. The indicators are computed to answer the following questions: (1) How is the quantity of GI affected by each of the NWRM, and what proportion of that GI is most valuable? (2) What is the location of the most critical nodes and connectors of GI, and what land-use conversions occur under these? (3) Are the average components getting larger or smaller?

Whereas the grassland measure results in the largest net increase of GI, the afforestation measure results in the overall largest number of hectares of key nodes and links within the network. Land conversions occur under the critical GI nodes and links, with a large increase in agricultural areas, especially for the riparian measure under critical nodes and the grassland measure under critical links. Also predominant is the swapping of land from pasture to forest under critical links with the afforestation measure. The riparian measure most increases the average size of GI components, and all three measures contribute to bridging two large components which were divided in the 2006 land-use map, thus increasing the size of the largest component by more than 50%.     

利用碳酸盐岩的Fe/Mn比值恢复海洋的氧化还原状态

碳酸盐岩的Fe/Mn元素比值,作为一项新的地球化学指标,可以用于恢复海洋的氧化还原状态.在氧化条件下,Fe3+和Mn4+均不可溶,因此氧化海水中的溶解Fe和Mn的含量均很低.Fe3+和Mn4+在还原条件下可以被细菌还原为可溶的Fe2+和Mn2+,而氧化还原电位的计算表明,Mn4+的还原要早于Fe3+的还原,因此细菌的Mn还原过程发生在沉积物的更浅层.可溶的Fe2+和Mn2+向上扩散到海水中,替代碳酸盐岩晶格里的Ca2+,因此碳酸盐岩晶格中的Fe2+和Mn2+的含量受控于来自沉积物孔隙水的扩散,而后者又与水岩界面的氧化还原状态相关.因此可以预测,随着海水变得逐渐缺氧,碳酸盐岩中的Fe/Mn比值会逐渐增高.为了验证这一假说,我们分析了中元古代高于庄组白云岩的Fe/Mn比值.研究发现,几乎所有的样品的Fe/Mn比值介于20~30之间,显著高于泥盆纪末期深水碳酸盐岩和浅水台地碳酸盐岩的Fe/Mn比值.高于庄组碳酸盐岩高的Fe/Mn比值一方面可能指示了中元古代低的大气氧气浓度和海洋的广泛缺氧,也可能反映了白云岩形成于缺氧的沉积物空隙水里.     

豆荚状铬铁矿床成矿地球化学指标对比和成矿作用讨论

豆荚状铬铁矿主要赋存于地幔橄榄岩中,与方辉橄榄岩密切相关。在全球的分布与蛇绿岩带分布基本一致,但并非所有蛇绿岩体都赋存有铬铁矿,且其中赋存的铬铁矿体规模和分布都是很不规律的。我们对比研究了国内外9个含铬矿和4个不含铬矿蛇绿岩中地幔橄榄岩的地球化学组成,认为含铬矿地幔橄榄岩具有全岩低含量的CaO(<1.91%)和Al_2O_3(<1.76%)、方辉橄榄岩轻稀土元素富集,橄榄石高Fo值(>90),斜方辉石低Al_2O_3含量(<3.8%)以及副矿物铬尖晶石高Cr/Fe值(>1.5)等特征,可以作为该蛇绿岩体含矿评价的地球化学指标。通过这些指标可知豆荚状铬铁矿床是较高程度部分熔融和地幔交代作用的共同结果,结合前人提出的铬铁矿成矿模式,对铬铁矿的成矿过程有了进一步的认识。