Fault plane processes and mesoscopic structure of a strong-type seismogenic fault in tonalites (Adamello batholith, Southern Alps)   总被引：3，自引：3，他引：3  

Giulio Di Toro  Giorgio Pennacchioni   《Tectonophysics》2005,402(1-4):55

The Gole Larghe Fault is an exhumed paleoseismic fault crosscutting the Adamello tonalites (Italian Southern Alps). Ambient conditions of faulting were 9–11 km in depth and 250–300 °C. In the study area the fault accommodates 1100 m of dextral strike-slip over a fault thickness of 550 m. Displacement is partitioned into three hierarchically different sets of discrete subparallel cataclastic horizons (faults_1–2–3). Fault displacement is in the range of few centimeters (faults₃) to a maximum of a few tens of meters in major faults₁. Faults_1–2 nucleated on pre-existing joints, whereas faults₃ are newly generated fractures produced during slip along faults_1–2. Each fault within the Gole Larghe Fault records the same evolution with development of indurated cataclasites precursory to pseudotachylyte production. Pseudotachylytes are usually generated at the host rock/cataclasite boundary and within cataclasites the mean clast size decreases getting closer to pseudotachylyte fault veins. Pseudotachylytes and cataclasites have a similar chemical composition which is enriched in Loss On Ignition, K, Rb, Ba, U and Fe³⁺ compared to host rock.We envision two models for the evolution of the Gole Larghe Fault. In both models synkinematic fluid–rock interaction along a fault causes fault hardening by precipitation of abundant K-feldspar+epidote (and minor chlorite) in the cataclasite matrix conducive to final production of pseudotachylyte. In the first model, induration occurs progressively by differential precipitation related to fabric evolution in cataclasites. In the second model, induration occurs abruptly dependent on the development of full connectivity within the fault network and to fluid reservoir. Whatever the model, the Gole Larghe Fault represents a strong fault, where hardening processes resulted in a low displacement/fault thickness ratio and contrast with many mature weak faults where localized repeated seismic slip along the same weak horizons yields high displacement/fault thickness ratios.  相似文献   

Electron paramagnetic resonance and electron spin echo spectroscopy study of natural bornite     

M. Borgheresi  G. P. Bernardini  C. Cipriani  F. Di Benedetto  M. Romanelli 《Mineralogy and Petrology》2005,85(1-2):3-18

Summary A minero-chemical and spectroscopic characterisation has been performed on a natural bornite sample from the Natural History Museum of the University of Florence, through the use of EPMA, XRD, continuous-wave (cw) and pulsed EPR spectroscopy. The use of different EPR techniques allowed to fully investigate the distribution and valence states of Cu and Fe and to study the early oxidation products of bornite. The microanalytical and XRD characterisation proved bornite to be homogeneous and stoichiometric. Cw-EPR measurements confirmed the presence of Fe(III) as fundamental valence state in bornite; moreover, no evidence of Cu(II) as a bulk transient species, due to a charge transfer process, has been revealed. The broadening of the Fe(III) EPR spectrum is ascribed to a partial transfer of spin density from Fe(III) to the surrounding cationic sublattice. In contrast, the pulsed EPR experiments, registered at 4.2 K, revealed the presence of both Fe(III) and Cu(II). These species were supposed to be present at the early stage of the surface alteration. The data provided by the electron spin-echo decay and modulation suggest both the oxidised Cu(II) and Fe(III) species to belong to premature surface water adducts (evidenced by proton nuclear modulation), which may evolve to sulphate species.  相似文献   

Natural Fe-oxide and -oxyhydroxide nanoparticles: an EPR and SQUID investigation     

C. Carbone  F. Di Benedetto  P. Marescotti  C. Sangregorio  L. Sorace  N. Lima  M. Romanelli  G. Lucchetti  C. Cipriani 《Mineralogy and Petrology》2005,85(1-2):19-32

Summary Magnetic hematite (α-Fe₂O₃) and goethite (α-FeOOH) nanoparticles, formed in the abandoned Libiola Mine (Liguria, Italy) as a result of Acid Mine Drainage (AMD) processes that involved sulfide-bearing rocks and sulfide-rich waste material, were investigated through the study of their magnetic properties in combination with electron paramagnetic resonance (EPR) spectroscopy. Both techniques revealed that the behaviour of the nanominerals involved was predominantly superparamagnetic. In contrast, the bulk antiferromagnetic behaviour of both hematite and goethite was substantially reduced. The observed magnetic properties reflected a great variability in the particle dimensions and confirmed that both nanominerals were the transformation products of a metastable amorphous species. Moreover, two peculiar phenomena were hypothesised: the transformation to hematite may occur before the coarsening of the amorphous transient and hematite and goethite can interconvert without intermediate crystallisation of metastable precursors. Goethite, in fact, appears to be formed as an alteration product of hematite, after a drastic change of the physico-chemical boundary conditions.  相似文献   

TBM掘进技术的发展应用及相关工程地质问题探讨          下载免费PDF全文

隆威  尹俊涛  刘永正  吴煜宇 《探矿工程》2005,32(2):55-59

阐述了TBM(隧道掘进机)半个世纪以来的发展及其在国内外隧道建设中的应用，指出优先采用TBM掘进技术进行隧道开挖已成为未来隧道建设总的发展趋势；并在分析大量国内外工程实例的基础上，结合TBM施工中的经验及教训，对TBM掘进过程中存在的诸如断层破碎带、挤压地层、地下水、岩溶等相关工程地质问题进行了探讨，并提出了相应的处理措施。  相似文献   

柴达木盆地第四系放射性异常及成因机制     

魏祥荣  龙期华 《物探与化探》2006,30(3):189-193,198

运用地质、物探、水文等多种手段,在分析异常区沉积环境、水文地质环境、砂体物质成分等基础上,对第四系航放异常的成因作了深入研究,确认:①异常元素主要来自于Q_3-4自身碎屑物的淋离;②异常在空间上受Q_3-4冲积扇前缘泥坪相与潜水氧化还原界面控制,因此认为该异常对成矿过程研究有重要价值,但对指导深部找矿意义不大。  相似文献   

基于COM+对Web地图服务性能影响的建模与分析     

陈引川  王青山  龙明  张立朝 《北京测绘》2006,(2):5-7,37

Web地图服务的后台是否使用COM+服务对其性能影响非常大。本文通过分析两种方式的原理模型并通过测试实验来比较这两种方式对Web服务系统性能的影响,得出使用COM+服务后,Web地图服务的稳定性与响应速度有明显提高。  相似文献   

Management of karst water resources in mining area: dewatering in mines and demand for water supply in the Dongshan Mine of Taiyuan, Shanxi Province, North China   总被引：6，自引：0，他引：6  

Qiang Wu  Wanfang Zhou  Duo Li  Zhiqiang Di  Ying Miao 《Environmental Geology》2006,50(8):1107-1117

Coalfields in North China contain six to seven coal seams in the Permo-Carboniferous strata. The coal seams are underlain by the Ordovician limestone. Large-scale dewatering or depressurizing of the karst aquifer was considered essential to avoid water inrushes and keep the mines safely operational. This practice, however, has caused water supply shortage in the mining areas. The most effective solution to this conflict is to use the uncontaminated karst water from the mines for water supply. This paper explores a management model to maximize the utilization of the karst water while maintaining the safe operation of the mines. The model can provide essential information on water resource distribution for decision makers. The model was applied to the Dongshan Coal Mine in Taiyuan City, China.  相似文献   

Groundwater quality monitoring in Italy for the implementation of the EU water framework directive   总被引：1，自引：0，他引：1  

G. Onorati  T. Di Meo  C. Fabiani  A. Fava  F. Mion  A. Martinelli 《Physics and Chemistry of the Earth》2006,31(17):1004-1014

In 1999 the Italian Parliament approved a law encompassing all the themes of the water cycle, including monitoring of groundwater. The new regulation takes into account the EU Directives, and charges the Regions to create monitoring networks, according to Art. 8 of the Water Framework Directive (WFD). The approach of the Italian regulation is, on the whole, coherent with the technical guidelines listed in annexes II and V of the WFD. On basis of the new law, the national environment agency (APAT) gathers data and produces assessment reports on the contamination of groundwater in Italy.  相似文献   

Using Rock‐Eval 6 pyrolysis for tracking fossil organic carbon in modern environments: implications for the roles of erosion and weathering     

Yoann Copard  Christian Di‐Giovanni  Thomas Martaud  Patrick Albric  Jean‐Emmanuel Olivier 《地球表面变化过程与地形》2006,31(2):135-153

This work relates to the debate on the fossil organic carbon (FOC) input in modern environments and its possible implication for the carbon cycle, and suggests the use of Rock‐Eval 6 pyrolysis as a relevant tool for tracking FOC in such environments. Considering that such a delivery is mainly due to supergene processes affecting the continental surface, we studied organic matter in different reservoirs such as bedrocks, alterites, soils and rivers in two experimental catchments at Draix (Alpes de Haute Provence, France). Samples were subjected to geochemical (Rock‐Eval 6 pyrolysis) investigations and artificial bacterial degradations. After comparing the geochemical fingerprint of samples, geochemical markers of FOC were defined and tracked in the different reservoirs. Our results confirm the contribution of FOC in modern soils and rivers and display the various influences of weathering and erosional processes on the fate of FOC during its exchange between these pools. In addition, the contrasting behaviour of these markers upon the supergene processes has also highlighted the refractory or labile characters of the fossil organic matter (FOM). Bedrock to river fluxes, controlled by gully erosion, are characterized by a qualitative and quantitative preservation of FOM. Bedrock to alterite fluxes, governed by chemical weathering, are characterized by FOC mineralization without qualitative changes in deeper alterites. Alterite to soils fluxes, controlled by (bio)chemical weathering, are characterized by strong FOC mineralization and qualitative changes of FOM. Thus weathering and erosional processes induce different FOM evolution and affect the fate of FOC towards the global carbon cycle. In this study, gully erosion would involve maintenance of an ancient sink for the global carbon cycle, while (bio)chemical processes provide a source of CO₂. Finally, this study suggests that Rock‐Eval 6 pyrolysis can be considered as a relevant tool for tracking FOC in modern environments. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Major-ion bulk deposition around an active volcano (Mt. Etna, Italy)     

A. Aiuppa  S. Bellomo  L. Brusca  W. D'Alessandro  R. Di Paola  M. Longo 《Bulletin of Volcanology》2006,68(3):255-265

Bulk atmospheric deposition of major cations (Na, K, Ca, Mg) and anions (Cl, F, SO₄) were measured at 15 sites around an active volcano, Mount Etna, from 2001 to 2003. Their composition indicates several natural sources, among which deposition of plume-derived volcanogenic gas compounds is prevalent for F, Cl and S. Plume-derived acidic compounds are also responsible for the prevailing acidic composition of the samples collected on the summit of the volcano (pH in the 2.45–5.57 range). Cation species have complex origin, including deposition of plume volcanogenic ash and aerosols and soil-dust wind re-suspension of either volcanic or carbonate sedimentary rocks. Variation of the deposition rates during the March 2001–March 2003 period, coupled with previous measurements from 1997 to 2000 (Appl Geochem 16:985–1000, 2001), were compared with the variation of SO₂ flux, volcanic activity and rainfall. The deposition rate was mainly controlled by rainfall. Commonly, about 0.1–0.9% of HF, HCl and SO₂ emitted by the summit crater's plume were deposited around the volcano. We estimate that ∼2 Gg of volcanogenic sulphur were deposited over the Etnean area during the 2002–2003 flank eruption, at an average rate of ∼24 Mg day⁻¹ which is two orders of magnitude higher than that typical of quiescent degassing phases.  相似文献