Large debris flows in Chosica,Lima, Peru: the application of hydraulic infrastructure for erosion control and disaster prevention     

S. P. Villacorta  K. G. Evans  K. Nakatani  I. Villanueva 《Australian Journal of Earth Sciences》2020,67(3):425-436

Abstract

Large debris flows in steep-sloped ravines debouching to the Rimac River, in metropolitan Lima (Peruvian capital), have resulted in considerable loss of life and property adversely impacting communities in the region. Temporal, spatial and volumetric features of debris flows are difficult to predict, and it is of utmost importance that achievable management solutions are found to reduce the impact of these catastrophic events. The emotional and economic toll of these debris flows on this increasingly densely populated capital city in South America is devastating where communities must live in such inadequate and dangerous conditions. To address this problem, the application of advanced Japanese technology, Sustainable Actions Basin Orientation (SABO), has been investigated using a geomorphological modelling to develop an implementation plan. Rayos de Sol stream basin in Chosica, was selected as a pilot to develop the proposal, as it is considered high risk due to the presence of ancient debris flows and recent flows in 2012, 2015 and 2017. The recurrence of debris flows in this location has resulted in numerous deaths and catastrophic property losses. This study combines geologic and geomorphic mapping and hydraulic and landform evolution numerical modelling. The implementation of a SABO Master Plan based on the multidisciplinary assessment hazard scenarios, will allow the implementation of feasible mitigation actions. The SABO technology has been applied successfully in Japan and other countries in areas with steep short slopes, similar to the conditions surrounding the Peruvian capital. Results from this study will be presented to the Peruvian Government as part of an action plan to manage debris-flow impact.

1. KEY POINTS

2. High-risk mass slope failure is linked to poor urban planning in urban developing regions of Lima the capital of Peru.

3. A multidisciplinary study including geotechnical and hydrological analysis, engineering design, and socio-economic research is required to implement a SABO Master Plan, and this basin is pilot study basin.

4. At the present time, a maintenance programme for existing hydraulic structures should be implemented, and a flood risk management plan developed may propose the relocation of some communities and infrastructure.

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Automated Extraction of a Five‐Year LA‐ICP‐MS Trace Element Data Set of Ten Common Glass and Carbonate Reference Materials: Long‐Term Data Quality,Optimisation and Laser Cell Homogeneity          下载免费PDF全文

David Evans  Wolfgang Müller 《Geostandards and Geoanalytical Research》2018,42(2):159-188

LA‐ICP‐MS is increasingly applied to obtain quantitative multi‐element data with minimal sample preparation, usually achieved by calibration using reference materials (RMs). However, some ubiquitous RMs, for example the NIST SRM 61× series glasses, suffer from reported value uncertainties for certain elements. Moreover, no long‐term data set of analyses conducted over a range of ablation and tuning conditions exists. Thus, there has been little rigorous examination of the extent to which offsets between measured and reported values are the result of error in these values rather than analytically induced fractionation. We present new software (‘LA‐MINE’), capable of extracting LA‐ICP‐MS data with no user input, and apply this to our system, yielding over 5 years of data (~ 5700 analyses of ten glass and carbonate RMs). We examine the relative importance of systematic analytical bias and possible error in reported values through a mass‐specific breakdown of fourteen of the most commonly determined elements. Furthermore, these data, obtained under a wide range of different ablation conditions, enable specific recommendations of how data quality may be improved, for example the role of diatomic gas, the effect of differential inter‐glass fractionation factors and choice of transport tubing material. Finally, these data demonstrate that the two‐volume Laurin ablation cell is characterised by no discernible spatial heterogeneity in measured trace element ratios.  相似文献   

Homogeneity and mechanical behaviors of sands improved by a temperature-controlled one-phase MICP method     

Xiao  Yang  Wang  Yang  Wang  Shun  Evans  T. Matthew  Stuedlein  Armin W.  Chu  Jian  Zhao  Chang  Wu  Huanran  Liu  Hanlong 《Acta Geotechnica》2021,16(5):1417-1427

Acta Geotechnica - Microbially induced carbonate precipitation (MICP) has been actively investigated as a promising method to improve soil properties. A burning issue impeding its wide application...  相似文献   

Titanite dates crystallization: Slow Pb diffusion during super‐solidus re‐equilibration     

Michael I. H. Hartnady  Christopher L. Kirkland  Chris Clark  Catherine V. Spaggiari  R. Hugh Smithies  Noreen J. Evans  Brad J. McDonald 《Journal of Metamorphic Geology》2019,37(6):823-838

Titanite can be found in rocks of wide compositional range, is reactive, growing or regrowing during metamorphic and hydrothermal events, and is generally amenable to U–Pb geochronology. Experimental evidence suggest that titanite has a closure temperature for Pb ranging from 550 to 650°C, and thus titanite dates are commonly interpreted as cooling ages. However, this view has been challenged in recent years by evidence from natural titanite which suggests the closure temperature may be significantly higher (up to 800°C). Here, we investigate titanite in an enclave of migmatitic gneiss included within a granite intrusion. The titanite crystals exhibit textural features characteristic of fluid‐mediated mass transfer processes on length scales of <100 µm. These textural features are associated with variation in both Pb concentrations and distinct U–Pb isotopic compositions. Zr‐in‐titanite thermometry indicates that modification of the titanite occurred at temperatures in excess of 840°C, in the presence of a high‐T silicate melt. The Pb concentration gradients preserved in these titanite crystals are used to determine the diffusivity of Pb in titanite under high‐T conditions. We estimate diffusivities ranging from 2 × 10^?22 to 5 × 10^?25 m²/s. These results are significantly lower than experimental data predict yet are consistent with other empirical data on natural titanites, suggesting that Pb diffusivity is similar to that of Sr. Thus our data challenge the wide‐held assumption that U–Pb titanite dates only reflect cooling ages.  相似文献   

Multi-stage metasomatism of lithospheric mantle by asthenosphere-derived melts: evidence from mantle xenoliths in daxizhuang at the eastern North China craton     

Zhao  XinMiao  Wang  Hui  Li  ZhiHan  Liu  FengLin  Evans  Noreen J.  Zhang  HongFu 《Mineralogy and Petrology》2020,114(2):141-159

Mineralogy and Petrology - A detailed study on petrology and mineral chemistry of 12 mantle xenoliths from Late Cretaceous basaltic lava flows at Daxizhuang has been conducted to constrain the...  相似文献   

Using large-scale diagnostic quantities to investigate change in East Coast Lows     

Fei Ji  Jason P. Evans  Daniel Argueso  Lluis Fita  Alejandro Di Luca 《Climate Dynamics》2015,45(9-10):2443-2453

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Water resources sustainability in a globalizing world: who uses the water?          下载免费PDF全文

Megan Konar  Tom P. Evans  Morgan Levy  Christopher A. Scott  Tara J. Troy  Charles J. Vörösmarty  Murugesu Sivapalan 《水文研究》2016,30(18):3330-3336

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Relationship among titanium,rare earth elements,U–Pb ages and deformation microstructures in zircon: Implications for Ti-in-zircon thermometry     

Nick E. Timms  Peter D. Kinny  Steven M. Reddy  Katy Evans  Chris Clark  Dave Healy 《Chemical Geology》2011,280(1-2):33-46

A zircon grain in an orthopyroxene–garnet–phlogopite–zircon–rutile-bearing xenolith from Udachnaya, Siberia, preserves a pattern of crystallographic misorientation and subgrain microstructure associated with crystal–plastic deformation. The zircon grain records significant variations in titanium (Ti) from 2.6 to 30 ppm that corresponds to a difference in calculated Ti-in-zircon temperatures of over several hundred degrees Celsius. The highest Ti concentration is measured at subgrain centres (30 ppm), and Ti is variably depleted at low-angle boundaries (down to 2.6 ppm). Variations in cathodoluminescence coincide with the deformation microstructure and indicate localised, differential enrichment of rare earth elements (REE) at low-angle boundaries. Variable enrichment of U and Th and systematic increase of Th/U from 1.61 to 3.52 occurs at low-angle boundaries. Individual SHRIMP-derived U–Pb ages from more deformed zones (mean age of 1799 ± 40, n = 22) are systematically younger than subgrain cores (mean age of 1851 ± 65 Ma, n = 7), and indicate that open system behaviour of Ti–Th–U occurred shortly after zircon growth, prior to the accumulation of significant radiogenic Pb. Modelling of trace-element diffusion distances for geologically reasonable thermal histories indicates that the observed variations are ~ 5 orders of magnitude greater than can be accounted for by volume diffusion. The data are best explained by enhanced diffusion of U, Th and Ti along deformation-related fast-diffusion pathways, such as dislocations and low-angle (< 5°) boundaries. These results indicate chemical exchange between zircon and the surrounding matrix and show that Ti-in-zircon thermometry and U–Pb geochronology from deformed zircon may not yield information relating to the conditions and timing of primary crystallisation.  相似文献   

Submarine hydrothermal activity and gold-rich mineralization at Brothers Volcano, Kermadec Arc, New Zealand     

Cornel E. J. de Ronde  Gary J. Massoth  David A. Butterfield  Bruce W. Christenson  Junichiro Ishibashi  Robert G. Ditchburn  Mark D. Hannington  Robert L. Brathwaite  John E. Lupton  Vadim S. Kamenetsky  Ian J. Graham  Georg F. Zellmer  Robert P. Dziak  Robert W. Embley  Vesselin M. Dekov  Frank Munnik  Janine Lahr  Leigh J. Evans  Ken Takai 《Mineralium Deposita》2011,46(5-6):541-584

Brothers volcano, of the Kermadec intraoceanic arc, is host to a hydrothermal system unique among seafloor hydrothermal systems known anywhere in the world. It has two distinct vent fields, known as the NW Caldera and Cone sites, whose geology, permeability, vent fluid compositions, mineralogy, and ore-forming conditions are in stark contrast to each other. The NW Caldera site strikes for ??600?m in a SW?CNE direction with chimneys occurring over a ??145-m depth interval, between ??1,690 and 1,545?m. At least 100 dead and active sulfide chimney spires occur in this field and are typically 2?C3?m in height, with some reaching 6?C7?m. Their ages (at time of sampling) fall broadly into three groups: <4, 23, and 35?years old. The chimneys typically occur near the base of individual fault-controlled benches on the caldera wall, striking in lines orthogonal to the slopes. Rarer are massive sulfide crusts 2?C3?m thick. Two main types of chimney predominate: Cu-rich (up to 28.5?wt.% Cu) and, more commonly, Zn-rich (up to 43.8?wt.% Zn). Geochemical results show that Mo, Bi, Co, Se, Sn, and Au (up to 91?ppm) are correlated with the Cu mineralization, whereas Cd, Hg, Sb, Ag, and As are associated with the dominant Zn-rich mineralization. The Cone site comprises the Upper Cone site atop the summit of the recent (main) dacite cone and the Lower Cone site that straddles the summit of an older, smaller, more degraded dacite cone on the NE flank of the main cone. Huge volumes of diffuse venting are seen at the Lower Cone site, in contrast to venting at both the Upper Cone and NW Caldera sites. Individual vents are marked by low-relief (??0.5?m) mounds comprising predominately native sulfur with bacterial mats. Vent fluids of the NW Caldera field are focused, hot (??300°C), acidic (pH????2.8), metal-rich, and gas-poor. Calculated end-member fluids from NW Caldera vents indicate that phase separation has occurred, with Cl values ranging from 93% to 137% of seawater values. By contrast, vent fluids at the Cone site are diffuse, noticeably cooler (??122°C), more acidic (pH?1.9), metal-poor, and gas-rich. Higher-than-seawater values of SO₄ and Mg in the Cone vent fluids show that these ions are being added to the hydrothermal fluid and are not being depleted via normal water/rock interactions. Iron oxide crusts 3?years in age cover the main cone summit and appear to have formed from Fe-rich brines. Evidence for magmatic contributions to the hydrothermal system at Brothers includes: high concentrations of dissolved CO₂ (e.g., 206?mM/kg at the Cone site); high CO₂/³He; negative ??D and ??¹⁸O_H2O for vent fluids; negative ??³⁴S for sulfides (to ?4.6??), sulfur (to ?10.2??), and ??¹⁵N₂ (to ?3.5??); vent fluid pH values to 1.9; and mineral assemblages common to high-sulfidation systems. Changing physicochemical conditions at the Brothers hydrothermal system, and especially the Cone site, occur over periods of months to hundreds of years, as shown by interlayered Cu?+?Au- and Zn-rich zones in chimneys, variable fluid and isotopic compositions, similar shifts in ³He/⁴He values for both Cone and NW Caldera sites, and overprinting of ??magmatic?? mineral assemblages by water/rock-dominated assemblages. Metals, especially Cu and possibly Au, may be entering the hydrothermal system via the dissolution of metal-rich glasses. They are then transported rapidly up into the system via magmatic volatiles utilizing vertical (??2.5?km long), narrow (??300-m diameter) ??pipes,?? consistent with evidence of vent fluids forming at relatively shallow depths. The NW Caldera and Cone sites are considered to represent stages along a continuum between water/rock- and magmatic/hydrothermal-dominated end-members.  相似文献   

The long term operation of a biologically based treatment system that removes As, S and Zn from industrial (smelter operation) landfill seepage     

Mattes AlLes J. Evans  W. Douglas GouldW.F.A. Duncan  Susan Glasauer 《Applied Geochemistry》2011,26(11):1886-1896

Passive treatment systems have a long history in the remediation of mining impacted water. The functioning of these systems is poorly understood, in particular the microbial processes that underpin metal removal. A biologically based engineered wetland treatment system that has operated in Trail, B.C. to treat seepage from a historic Pb and Zn smelter landfill, was investigated. The system has functioned for more than a decade, an unusually long life span for a passive bioreactor design. The study focuses on the 5a of operation from 2003 until 2007. Arsenic is a major contaminant in the ore that is processed in Trail, which has caused high As concentrations in the seepage. In addition to As, Zn and Cd removal were investigated. During the 5-a period, the system sequestered 2990 kg of As, 7700 kg of Zn and 85 kg of Cd. Nearly 90% of these elements were removed in two biochemical reactors (BCRs) that comprise the first two components of the six cell system, with the remainder removed in plant-based polishing cells. Average input concentrations over the 5-a period were 2.3 and 4.1 mM for As and Zn, respectively and 0.45 μM for Cd. Final output concentrations were reduced to 0.01 mM for As, 0.05 mM for Zn and 0.18 μM for Cd. Sulfur removal averaged 34% of input concentration. Analysis of mineral formation in the system using X-ray diffraction and scanning electron microscopy indicated kottigite (Zn₃(AsO₄)₂⋅8H₂O) and sphalerite (ZnS) as the major mineral phases controlling As and Zn sequestration; Cd appears to be immobilized as CdS. Evidence for orpiment was obtained from X-ray absorption spectroscopy (XANES) studies, and arsenopyrite was not detected. Although microbial activity dominates the removal of Zn, As and Cd from the soluble phase, abiotic removal mechanisms contribute including sorption of As and Zn to biosolids and filtration of metal precipitates by the solid matrix. The removal of toxic elements over the period appeared to be relatively consistent. Seasonal fluctuations, a large spike in input element concentrations over a 2-month period, and removal of the two biochemical reactors during a period of reconstruction appeared to have relatively little impact on the system as a whole.  相似文献