Large-scale Infiltration Research Articles

Evaluating the hydraulic behavior of sandy fouled ballast: A case study from Inner Mongolia, China

This study examines the hydraulic behavior of sandy fouled ballast from Wuhai-Jilantai railway in Inner Mongolia, China, with a focus on its response to variable wetting and drying conditions influenced by climate change. The material characteristics were investigated, and it was classified as poorly-graded gravel (GP) according to the Unified Soil Classification System (USCS). This classification indicated that the material consisted primarily of gravel and sand with few fine particles. Large-scale infiltration column tests were conducted to assess the hydraulic properties, simulating precipitation rates of Wuhai (8 mm/hr) and Marsa Matruh (43 mm/hr). The results showed that under Wuhai conditions, saturation levels reached 49.3 % at the column top and 75.8 % at the bottom. In contrast, the ballast was fully saturated under Marsa Matruh’s precipitation rate. The saturated hydraulic conductivity, determined using constant head permeability tests, was measured at 1.06*10−5 m/s. Saturation levels after drainage were 39 % and 97 % at the column top and bottom, respectively. Then, a notable increase in evaporation rates facilitated by enhanced ventilation compared to applying high temperatures only. Unimodal and bimodal models were applied for understanding the Soil-Water Characteristic Curve (SWCC) and hydraulic conductivity. This research uncovers previously unreported heterogeneity in sandy fouled ballast and demonstrates the efficacy of bimodal models, providing a superior fit and more accurate prediction of hydraulic behavior, underscoring the critical role of sophisticated modeling techniques in predicting the impacts of climate variability on railway infrastructure.

A Concept of Fuzzy Dual Permeability of Fractured Porous Media

The interpretation of the results of hydrogeological field observations and the modeling of fractured porous subsurface media is often conducted using dual-porosity and/or dual-permeability concepts. These concepts, however, do not consider the effects of spatial and temporal variations and uncertainties, or fuzziness, in the evaluation of the subsurface flow characteristics of fractured porous media. The goal of the paper is to introduce a concept of fuzzy dual permeability of fractured porous media based on the fuzzy system analysis of the results of ponded infiltration tests in fractured basalt. The author revisited the results of the tests conducted in areas close to the Idaho National Laboratory (INL), Idaho, USA: small-scale (approximately 0.5 m2) ponded tests at the Hell’s Half Acre site, mesoscale (56 m2) ponded tests at the Box Canyon site, and a large-scale infiltration test (31,416 m2) at the Radioactive Waste Management Complex at INL. Methods of fuzzy clustering and fuzzy regression were applied to describe the time-depth waterfront penetration and to characterize the phenomena of rapid flow through a predominantly fractured component and slow flow through a predominantly porous matrix component. The concept of fuzzy dual permeability is presented using a series of fuzzy membership functions of the waterfront propagation with depth and time. To describe the time variation of the flux, a fuzzy Horton’s model is presented. The developed concept can be used for the uncertainty quantification in flow and transport in geologic media.

Immune-related gene set prediction model contributes to the evaluation of prognosis in lung adenocarcinoma patients.

e20550 Background: In recent years, rapid progress of immunotherapy (I/O therapy) development brings new hope to LUAD patients. The subtypes and/or quantality of TIL-IC cells were closely related to the prognosis and to the I/O therapy’s response in patients with a variety of solid tumors. In order to stratify high-risk and low-risk LUAD patients, we herein established a prognostic prediction model based on the expression of large-scale immune infiltration genes in LUAD patients. Methods: RNA sequencing data and relevant clinical information of LUAD patients ( n = 501) were obtained from the TCGA cohort. Stromal and immune scores were calculated using ESTIMATE algorithm. The differentially expressed immune-related genes (IRGs) were identified using the “DESeq2” package in R platform. Patients were randomly divided into training set and validation set with a ratio of 8:2. Univariate and Lasso Cox regression analyses were performed to identify overall survival (OS)-related IRGs. Next, stepwise multivariate Cox regression analysis was carried out to establish an optimal risk model of immune-related prognostic gene sets in the training cohort. Kaplan-Meier curves and receiver operating characteristic (ROC) curves were used to examine the predictive performance of the model in the validation cohort. Results: A total of 643 IRGs were identified in these LUAD patients, of which 140 IRGs were significantly associated with OS by univariate Cox regression analysis (P < 0.05). Lasso Cox and stepwise multivariate Cox regression analysis identified IRGs as independent prognostic factors, including C20orf197, SPRR1B, CHRNA5, SLC14A2, RP11-284F21.9, IGLV9-49, IGF2BP1, and C5orf64. The final immune-related gene set model was as follow: risk score = −0.13 * expression level of C20orf197 + 0.074 * expression level of SPRR1B + 0.23 * expression level of CHRNA5 − 0.11 * expression level of SLC14A2 + 0.11 * expression level of RP11-284F21.9 - 0.076 * expression level of IGLV9-49 + 0.048 * expression level of IGF2BP1 - 0.42 * expression level of C5orf64. Patients were divided into high-risk group and low-risk group with the median risk score. Kaplan–Meier survival analysis showed that the high-risk group had a significantly poor prognosis, when compared to the low-risk group in the training set ( HR 2.77, 95%CI; [1.96 - 3.93], P < 0.0001). The ROC curve analysis equally revealed that the area under curves for OS in the first and fifth year were 0.82 and 0.81, respectively, in the validation cohort. Taken together, the eight IRGs risk prediction model could effectively stratify LUAD patients according to prognosis. Conclusions: We constructed a prognostic prediction model for LUAD patients, which consisted of a robust signature of eight IRGs. This model could effectively stratify high-risk and low-risk LUAD patients and help to customize personalized treatment plans.

Evaluation of Infiltration Discharge as a Strategy to Meet Effluent Temperature Limits

AbstractRecognizing that elevated stream temperatures can harm aquatic organisms, regulatory agencies have begun to enforce thermal total daily maximum load (TMDL) limits on wastewater discharges. Infiltration discharge, where treated wastewater is allowed to infiltrate into the soil and then percolate toward the stream or river, represents a potential method for meeting temperature requirements and for supplementing flow. This study combines observed and simulated temperature data to assess the efficacy of using infiltration discharge to meet effluent temperature limits. Observational data collected during operation of a 0.15-ha pilot-scale infiltration discharge system revealed the pattern of groundwater heating beneath the site by the wastewater, with the largest temperature increases occurring near the infiltration point. Numerical simulations used to examine the long-term groundwater response to operation of a 5.5-ha large-scale infiltration wetland system confirmed this trend and demonstrated how mu...

Formation of multiple high-pressure veins in ultrahigh-pressure eclogite (Hualiangting, Dabie terrane, China): Fluid source, element transfer, and closed-system metamorphic veining

Multiple high-pressure (HP) metamorphic veins and their host ultrahigh-pressure (UHP) eclogites in the Hualiangting area (Dabie terrane, China) were investigated to constrain the provenance of vein-forming fluids, element transfer during UHP fluid–rock interaction, and “closed-system” vein crystallization in a deep subduction zone. The HP veins consist of significantly different mineral assemblages and can be classified as omphacite–epidote (Omp–Ep), epidote-quartz (Ep–Qz), and kyanite–epidote–quartz (Ky–Ep–Qz) veins from the vein-eclogite boundary to the vein interior. Towards the veins, the abundances of coesite-enclosing epidote, kyanite, and quartz in the eclogite systematically decrease, indicating an intensive fluid-rock interaction between the eclogite and vein-forming fluid. Mass-balance calculations indicate that the interaction resulted in strong depletion of Sr and Pb (up to −80% to −90%); moderate depletion of U (up to −80%), Th (up to −50%), light rare earth elements (LREEs) (up to 40–60%), and transition metal elements (TMEs) (Cr, V, Sc, Co, and Ni) (up to −40%); and low depletion of heavy rare earth elements (HREEs) (<−25%) in the eclogites near the vein. The mass losses of these trace elements gradually increase towards the vein and are largest in the eclogite nearest the vein.Whole-rock and epidote in situ Sr isotopic analyses indicate that the fluids responsible for all types of HP veins originated from the eclogites themselves rather than from external gneisses (i.e., “internal” fluids). Petrologic studies and phase equilibrium modeling indicate that the vein-forming fluids were primarily produced by the breakdown of UHP lawsonite in the host eclogite during exhumation at P–T conditions of ~2.7–3.0GPa and 660–720°C. Therefore, the formation of multiple HP veins and the relevant dissolution-transport-precipitation processes were isolated from the large-scale infiltration of external fluid (i.e., in a geochemically closed system). The contents of the fluid-mobile elements (Cs, Rb, U, Th, and LREEs) in the veins gradually increase from the vein-eclogite boundary towards the vein interior, whereas the contents of the sparingly soluble elements (Mg, Ti, TMEs, and HREEs) and the δEu values gradually decrease, suggesting multi-stage crystallization of a solute-rich UHP fluid. The geochemical characteristics (La, Cr, and δEu values) of the veins and vein epidote, coupled with the modeled fluid compositions, indicate that the Omp–Ep veins first crystallized from the solute-rich vein-forming fluid and that the Ep–Qz and Ky–Ep–Qz veins formed by the crystallization of residual fluids after the formation of Omp–Ep and Ep–Qz veins, respectively. This study indicates that internally derived UHP fluids in eclogite are key agents for efficiently extracting important trace elements from a deeply subducted continental slab through fluid–rock interactions and that the multi-stage crystallization of a highly restricted fluid could produce multiple HP veins and significant trace element fractionations during slab exhumation.

Development of a Large-Scale Infiltration Column for Studying the Hydraulic Conductivity of Unsaturated Fouled Ballast

Abstract To study the hydraulic behavior of fouled ballast, an infiltration column 600 mm high and 300 mm in diameter was developed. Five time domain reflectometer (TDR) sensors and five tensiometers were installed at various levels, allowing the measurement of volumetric water content and matric suction, respectively. The material studied was fouled ballast that was formed in the railway track-bed by penetration of fine-grained soil into the ballast. This material is characterized by a high contrast of size between the largest and the smallest particles. During the test, three stages were followed: saturation, drainage, and evaporation. Based on the test results, the water-retention curve and the unsaturated hydraulic conductivity were determined. The quality of the results shows the capacity of this large-scale infiltration column in studying the unsaturated hydraulic properties of such fouled ballast.

AttenuatedPik3r1Expression Prevents Insulin Resistance and Adipose Tissue Macrophage Accumulation in Diet-Induced Obese Mice

Obese white adipose tissue (AT) is characterized by large-scale infiltration of proinflammatory macrophages, in parallel with systemic insulin resistance; however, the cellular stimulus that initiates this signaling cascade and chemokine release is still unknown. The objective of this study was to determine the role of the phosphoinositide 3-kinase (PI3K) regulatory subunits on AT macrophage (ATM) infiltration in obesity. Here, we find that the Pik3r1 regulatory subunits (i.e., p85α/p55α/p50α) are highly induced in AT from high-fat diet–fed obese mice, concurrent with insulin resistance. Global heterozygous deletion of the Pik3r1 regulatory subunits (αHZ), but not knockout of Pik3r2 (p85β), preserves whole-body, AT, and skeletal muscle insulin sensitivity, despite severe obesity. Moreover, ATM accumulation, proinflammatory gene expression, and ex vivo chemokine secretion in obese αHZ mice are markedly reduced despite endoplasmic reticulum (ER) stress, hypoxia, adipocyte hypertrophy, and Jun NH2-terminal kinase activation. Furthermore, bone marrow transplant studies reveal that these improvements in obese αHZ mice are independent of reduced Pik3r1 expression in the hematopoietic compartment. Taken together, these studies demonstrate that Pik3r1 expression plays a critical role in mediating AT insulin sensitivity and, more so, suggest that reduced PI3K activity is a key step in the initiation and propagation of the inflammatory response in obese AT.

Design and analysis of a social botnet

Online Social Networks (OSNs) have attracted millions of active users and have become an integral part of today’s web ecosystem. Unfortunately, in the wrong hands, OSNs can be used to harvest private user data, distribute malware, control botnets, perform surveillance, spread misinformation, and even influence algorithmic trading. Usually, an adversary starts off by running an infiltration campaign using hijacked or adversary-owned OSN accounts, with an objective to connect with a large number of users in the targeted OSN. In this article, we evaluate how vulnerable OSNs are to a large-scale infiltration campaign run by socialbots: bots that control OSN accounts and mimic the actions of real users. We adopted the design of a traditional web-based botnet and built a prototype of a Socialbot Network (SbN): a group of coordinated programmable socialbots. We operated our prototype on Facebook for 8weeks, and collected data about user behavior in response to a large-scale infiltration campaign. Our results show that (1) by exploiting known social behaviors of users, OSNs such as Facebook can be infiltrated with a success rate of up to 80%, (2) subject to user profile privacy settings, a successful infiltration can result in privacy breaches where even more private user data are exposed, (3) given the economics of today’s underground markets, running a large-scale infiltration campaign might be profitable but is still not particularly attractive as a sustainable and independent business, (4) the security of socially-aware systems that use or integrate OSN platforms can be at risk, given the infiltration capability of an adversary in OSNs, and (5) defending against malicious socialbots raises a set of challenges that relate to web automation, online-offline identity binding, and usable security.

Soil hydraulic properties for moisture redistribution in a large-scale heterogeneous landscape

Guidelines of effective soil hydraulic parameters were developed to be applicable in simulating average infiltration and subsequent moisture redistribution over a large-scale heterogeneous field. Average large-scale infiltration and redistribution in heterogeneous soils were quantified through multiple simulations of local-scale processes. The effective hydraulic parameters were derived to simulate the average amount of infiltrating water, and to capture the subsequent surface soil moisture redistribution averaged over the large heterogeneous landscape. The results demonstrated that the effective hydraulic parameters typically exhibited a step change from infiltration to redistribution, with the size of the step change being related to the degree of hydraulic parameter heterogeneity and the correlations among the hydraulic parameters. However, the effective hydraulic parameters did not change significantly over time for the moisture redistribution. It was further demonstrated that the size of the step change was smallest for effective saturated hydraulic conductivity. Editor Z.W. Kundzewicz; Associate editor Y. Guttman Citation Zhu, J.T. and Sun, D.M., 2012. Soil hydraulic properties for moisture redistribution in a large-scale heterogeneous landscape. Hydrological Sciences Journal, 57 (6), 1196–1206.

Development of a Large-Scale Infiltration Tank for Determination of the Hydraulic Properties of Expansive Clays

Abstract A large-scale infiltration tank was developed to study the water transfer in compacted expansive clay. Volumetric water content sensors were buried in a soil column for water content monitoring during infiltration. In addition to water content, soil suction and temperature at various locations and the heave at the soil surface were also monitored. Emphasis was put in minimizing the effect of sensors installation on water transfer and soil deformation. The results obtained for 338 days of infiltration were presented in terms of changes in suction, volumetric water content, temperature, and the soil heave. Based on the recorded data, the performance and limitation of different suction and volumetric water content sensors and the adopted test procedure were analyzed. The recorded data on soil suction and volumetric water content were finally analyzed for determining the unsaturated hydraulic properties of soil, such as the water retention curve and the unsaturated hydraulic conductivity. Note also that the results constitute useful data for further physical analysis or numerical models’ calibration.

Effective Soil Hydraulic Parameters for Transient Flows in Heterogeneous Soils

This study investigated the use of effective soil hydraulic properties (expressed in terms of hydraulic parameters) applicable to large‐scale transient infiltration problems in a landscape with horizontally heterogeneous soil hydraulic properties. The heterogeneous landscape was conceptualized as an equivalent homogeneous medium with effective hydraulic properties. The main objectives were to investigate: (i) which effective soil hydraulic property schemes are suitable to represent average behavior of large‐scale infiltration processes, (ii) how the effective hydraulic parameters are sensitive to the process time frame, and (iii) how hydraulic parameter variability and correlation impact the effective hydraulic parameters. The heterogeneous landscape was represented by a series of vertically homogeneous stream tubes or parallel columns. Large‐scale average infiltration behavior in the heterogeneous soils was quantified through Monte Carlo simulations of multiple realizations (stream tubes) of local‐scale infiltration. The optimal effective hydraulic parameters were then calculated with an inverse procedure that minimized the difference between average cumulative infiltration and cumulative infiltration based on a single set of effective parameters. Three scenarios were used to optimize either two hydraulic parameters simultaneously or only one hydraulic parameter while using the arithmetic mean for the other parameter. Results indicate that while the effective hydraulic parameters could simulate average infiltration more closely when multiple parameters were optimized together, the effective parameter values were more variable as time evolved. Optimizing only one hydraulic parameter while keeping the arithmetic mean for the other parameter produced more uniform effective hydraulic parameters with time, but this approach did not represent average infiltration behavior of the heterogeneous soils as well as when multiple hydraulic parameters were optimized simultaneously.

Geophysical experiments to image the shallow internal structure and the moisture distribution of a mine waste rock pile

Several field surveys of a waste rock pile were carried out during the summers of 2002 and 2003 using ground-penetrating radar, electromagnetic conductivity and DC resistivity imaging. The waste rock deposit is prone to generate acid mine drainage (AMD) due to the oxidation of sulphidic minerals. One of the most critical factors that lead to the production of AMD is unsaturated water flow and the ensuing moisture distribution in the waste rock. This geophysical characterization study, performed over a 30 m × 30 m test zone, was designed to image the internal structure controlling the water flux at shallow depth. The subsurface was found to consist of three zones for the first 6 m of the pile, mainly based on electrical resistivities: a thin superficial conductive material, an intermediate 2 to 3 m thick highly resistive zone, and a lower, more conductive medium. With the help of hydrogeological tests, chemical analyses and two 2.5 m-deep trenches, it is shown that the two conductive zones are correlated with fine-grained waste rock and the resistive zone correlates with a coarser material. In the two deeper zones, the contact between the two types of waste rock is typically highlighted by a sharp resistive/conductive boundary. An increase of conductance in the relatively thin upper layer towards the edge of the pile appears to be caused by an increase in thickness of the fine-grained material. Additional geophysical surveys carried out on a profile along the flank of the upper bench of the pile show that the main features of the internal structure are sub-parallel to the slope, at least for the first 3 m in depth. The data also show an increase in resistivity from the top to bottom of the slope, in accordance with expected particle segregation, from fine-grained material at the top to coarser material at the bottom. Wide-angle reflection GPR monitoring during large scale infiltration tests seems to indicate preferential flow paths towards the direction of coarser, more pervious material (which also appears to be less oxidized). Water preferentially flows through the coarse-grained material, but it is stored by capillary forces in the fine-grained material. Apart from the deposition methods, the results strongly suggest that factors such as machinery-induced mechanical alteration, construction history of the pile, and increased oxidization near the edges could explain the resistivity model. The model interpreted from geophysical imaging agrees well with the conceptual model of the rock pile. The resistivity and GPR methods appear to be efficient geophysical methods to characterize the internal structure and preferential flow patterns within unsaturated waste rock piles.

Long-term accumulation and material balance of organic matter in the soil of an effluent infiltration basin

The fate of organic matter (OM) in large-scale infiltration basins used for wastewater treatment by the soil aquifer treatment (SAT) system was investigated. Measured changes in the organic matter concentrations in the soil profiles of the infiltration basins and detailed long-term records of OM concentrations in the recharged effluent and in the observation wells and recovery wells water, were used to calculate OM material balances in the SHAFDAN wastewater treatment plant, serving the City of Tel-Aviv, Israel, since 1977. The average annual total organic matter (TOM) load delivered by the effluents to the soil was ~ 5 kg m − 2 y − 1 . Soil OM concentrations increased from 0.11% in the pristine soil to ~ 0.8% and ~ 0.6%, in the 0–0.15 m and 0.15–0.30 m soil layers, respectively, after ~ 20 y of effluent recharge, but did not change significantly in the 1.80–2.10 m deep layer. The OM accumulation rates in the top two soil layers were fast initially, then declined slowly and the OM concentrations approached a steady state following 10–15 y of effluent recharge. This suggests that stabilization of the ‘active biofilm’ layer in the infiltration basins' soils is a relatively slow process. Material-balance calculations showed, that accumulated OM in the top 0–2.1 m soil layer amounted to only ~ 4% of the TOM added by the effluents during ~ 20 y of recharge. Along the flow pathway of the effluent through the vertical 50–100 m thick soil-sediment column, DOC concentrations decreased by 70–90% (from ~ 18.9 mg L − 1 to ~ 3.7 mg L − 1 ). Continued flow in the aquifer from the observation wells to the recovery wells further decreased DOC concentrations by about 50% (from ~ 3.7 to ~ 1.5 mg L − 1 ).

High Resolution Seismic Reflection and Radar for Hydrogeology: The Gnangara Mound, Perth Basin, Western Australia

Curtin University Department of Exploration Geophysics in collaboration with Water Corporation of Western Australia have undertaken a comprehensive geophysical program with the overall objective of resolving hydraulic properties and boundaries below the Gnangara mound. Initial results have been highly encouraging. Radar transects, more than 15 km in length, reveal up to three shallow potentially ``water retentive' layers above the regional water table for the superficial aquifer. Both shallow sedimentation such as buried dunes and post deposition layering can be readily interpreted over large areas from the radar data. Interpretation of the radar data is assisting in developing a large scale infiltration distribution models for the Gnangara Mound. The high resolution seismic reflection surveys aim to resolve hydrostratigraphy from surface to 1500m depth. Of particular interest is large scale hydraulic separation between Perth?s major aquifers, which include the Superficial, Leederville and Yarragadee. Previous seismic surveys in this area produced low-resolution discontinuous events that could not be used for such purposes. Recently we acquired high-resolution seismic profiles using our telemetric system and a high-power impact source. High CMP fold combined with careful target oriented data processing produced quality images. These enable interpretation of up to 20 layers including several unconformities in the top 1500m. Further advance in acquisition, particularly application of high-power, high-frequency seismic sources and data processing are hoped to enable routine application of reflection seismic methods in hydrogeology. Current results demonstrate significant advances have been achieved with respect to the past trials even at these early stages of the Gnangara Mound research program. Results from the seismic reflection and radar surveys will feed into the PRAMS hydraulic flow model for the Perth Basin.

Large-scale infiltration experiments into unsaturated stratified loess sediments: Monitoring and modeling

Two large-scale field experiments were conducted to track water flow through unsaturated stratified loess deposits. In the experiments, a trench was flooded with water, and water infiltration was allowed until full saturation of the sediment column, to a depth of 20 m, was achieved. The water penetrated through a sequence of alternating silty-sand and sandy-clay loess deposits. The changes in water content over time were monitored at 28 points beneath the trench, using time domain reflectometry (TDR) probes placed in four boreholes. Detailed records were obtained from a 21-day-period of wetting, followed by a 3-month-period of drying, and finally followed by a second 14-day-period of re-wetting. These processes were simulated using a two-dimensional numerical code that solves the flow equation. The model was calibrated using PEST. The simulations demonstrate that the propagation of the wetting front is hampered due to alternating silty-sand and sandy-clay loess layers. Moreover, wetting front propagation is further hampered by the extremely low values of the initial, unsaturated, hydraulic conductivity; thereby increasing the water content within the onion-shaped wetted zone up to full saturation. Numerical simulations indicate that above-hydrostatic pressure is developed within intermediate saturated layers, enhancing wetting front propagation.

Fluid characteristics of high- to ultrahigh-temperature metamorphism in southern India: A quantitative Raman spectroscopic study

We report the first quantitative compositional data on fluid inclusions in Late Neoproterozoic to Cambrian ultrahigh-temperature (UHT) granulites from major crustal blocks and shear zones in southern India. Fluid inclusions in various high-grade minerals such as garnet, orthopyroxene, plagioclase, cordierite, and quartz from these rocks were studied in terms of petrography, microthermometry and laser Raman spectroscopy. Measured melting temperatures of the inclusions indicate that the trapped fluid phase is dominantly carbonic. Raman analyses confirmed a CO 2-rich composition with only minor dilutants such as N 2 (≤5.0 mol%), H 2O (≤0.50 mol%), and CH 4 (≤0.47 mol%). The range of most CO 2 isochores computed from density measurements in fluid inclusions from the UHT granulites pass below the peak pressure–temperature conditions of metamorphism indicating considerable resetting of fluid densities during decompression. In contrast, garnetiferous granulites from the Salem area along the Palghat-Cauvery Shear Zone System, which underwent high-pressure prograde metamorphism, contain very high-density syn-metamorphic pure CO 2 inclusions. Such dense carbonic fluid inclusions in garnet and plagioclase coexist with carbonate minerals (calcite or dolomite), indicating probable derivation from deep-seated primary magmatic sources. Although models on the origin of CO 2 are debatable, the ubiquitous association of carbonic fluids in the UHT mineral assemblages is in favour of large-scale infiltration of CO 2-rich fluids during extreme crustal metamorphism associated with collisional orogeny and subsequent extensional collapse at the final stage of amalgamation of the Gondwana supercontinent.

Stable Isotope Evidence for Large-Scale Infiltration of Metamorphic Fluids Generated during Shallow Subduction into the Eastern Peninsular Ranges Mylonite Zone (EPRMZ), Southern California

New δ18O and δD data confirm and amplify the conclusion by Holk et al. (1991) that, during the late Cretaceous or earliest Tertiary, there was large-scale infiltration of metamorphic water at depths of at least 15 km into the lower plate of the EPRMZ, a major crustal shear zone that transects a 15 x 15 km tonalite pluton west of Borrego Springs, California. Whole-rock δ18O values in undeformed tonalite are +11.2 ± 0.4 (n = 9) and in mylonitized tonalite are +12.3 ± 0.3 (n = 21), indicating a 1 per mil increase in 18O during open-system water-rock exchange. Quartz, feldspar, and biotite δ18O values in undeformed tonalite are +12.9 ± 0.4 (n = 8), +11.0 ± 0.6 (n = 8), and +7.7 ± 0.7 (n = 8), compared with +13.5 ± 0.2 (n = 8), +11.8 ± 0.3 (n = 9), and +9.2 ± 0.3 (n = 10) in mylonitized tonalite. The extremely uniform quartz-feldspar and quartz-biotite 18O fractionations in the mylonitized tonalite indicate equilibration at 500-600°C. Biotite and hornblende δD values from undeformed tonalite are -73 ± 3 (n = 12), compared with -52 to -68 (n = 21) in mylonitic tonalite, even though the biotite and hornblende have the same Fe/Mg (≈1.25; Anderson, 1983) in both kinds of tonalite. This implies that the EPRMZ was infiltrated by large amounts of high-D water (δD ≈ -10 to -30) at 500-600°C, probably derived at depth by dehydration of subducted oceanic crust or underplated volcanogenic sediments. Syndeformational tonalitic pegmatites have quartz and feldspar δ18O values of +13.5 ± 0.3 (n = 4) and +12.2 ± 0.3 (n = 6), and biotite and muscovite δD values of -64 ± 1 (n = 2) and -42 (n = 1), suggesting a genetic relationship between the pegmatites and these deep-seated fluids. Higher whole-rock δ18O values (+13.2 to +16.1, n = 3) and much lower δD values (-72 to -114, n = 3) occur where the EPRMZ cuts upper-plate amphibolite-facies metasediments. The shift to lower δD values in these finer grained rocks probably occurred during interactions with heated meteoric groundwaters during Pliocene detachment faulting associated with the opening of the Gulf of California.

Simulating infiltration in unsaturated basalt for the Large-Scale Aquifer Pumping and Infiltration Test at INEEL

The Large-Scale Aquifer Pumping and Infiltration Test (LPIT) conducted at the Idaho National Engineering and Environmental Laboratory was modeled using TOUGH2 to simulate the highly transient water infiltration and perched-water conditions in the fractured basalt and sedimentary interbeds existing at the site. The fracture and matrix continua of the basalt were represented using a dual-permeability approach. Six perched-water hydrographs, measured during the infiltration test, were used for calibration with iTOUGH2 to estimate six parameters that controlled unsaturated flow in the fractured basalt and the dense clay sedimentary interbed underlying the basalt flow. These parameters included the interfacial area between the basalt fracture and matrix continua, the basalt fracture continuum permeability, the basalt matrix continuum permeability, the interbed matrix continuum permeability, and the interbed van Genuchten capillary pressure parameters. The intent of the calibration was to obtain large-scale properties of the lithological units affecting the field-scale LPIT test. Finally, we tested the applicability of the dual-permeability conceptual model for representing transient variably saturated flow in fractured basalt. Parameters obtained from the calibration were within the range of hydrogeological parameters measured from cores obtained in the field, substantiating the physical relevance of the calibration effort.

Simulation of Large-Scale Field Infiltration Experiments Using a Hierarchy of Models Based on Public, Generic, and Site Data

Comparative simulations of a large-scale field infiltration experiment at the Maricopa Agricultural Center (MAC) near Phoenix, AZ, were conducted using a hierarchy of models based on public, generic, and site data joined with pedotransfer functions and an inverse procedure. Our purpose was to investigate the ability of simple models and relatively inexpensive data to reproduce and predict reliably the time evolution of water content profiles in nine 10-m-deep neutron monitoring boreholes at the site. By relying solely on public sources of information one might conclude that soil at the MAC site is uniform to a depth of 16 m, with a water table at about 22 m. Upon collecting soil samples at the site, we learned the soils are layered and laterally discontinuous, with a perched water table at about 13 m. To identify the least level of complexity required to simulate infiltration at the MAC, we compared models that consider one- and two-dimensional flow in a uniform soil, a soil consisting of uniform layers, and a stratified soil with laterally distinct zones. There is a paucity of hydraulic characterization data for the site. To investigate the feasibility of obtaining hydraulic parameter estimates for the models on the basis of soil type, we ascribed uniform properties to each layer or zone using mean values of three generic databases. To improve these estimates, we ascribed variable soil hydraulic properties to individual soil samples using regression and neural network pedotransfer functions based on soil type and bulk density; we then used them to obtain Bayesian updates of mean hydraulic properties in each layer or zone. We used the various models and mean parameter estimates to simulate water contents during one of several infiltration experiments at the MAC. None of the results compared well with measured water contents, although one set of generic mean parameter values yielded much better results than the other two. Estimating parameters using pedotransfer functions and Bayesian updating does not lead to improved simulations. Only when the parameters are estimated by means of an inverse procedure does one notice a significant improvement in model fit. We compared and ranked the various models and parameter estimates using likelihood-based model discrimination criteria and confirmed our choice of best model by successfully simulating flow during an earlier infiltration experiment.

Subsea-floor replacement in volcanic-hosted massive sulfide deposits

Recent research on volcanic-hosted massive sulfide (VMS) deposits indicates that syngenetic subsea-floor replacement ores form an important component of many deposits. In the context of VMS deposits, subsea-floor replacement can be defined as the syn-volcanic formation of sulfide minerals within pre-existing volcanic or sedimentary deposits by infiltration and precipitation in open spaces (fractures, inter- and intra-granular porosity) as well as replacement of solid materials. There are five criteria for distinguishing subsea-floor replacement in massive sulfide deposits: (1) mineralized intervals are enclosed within rapidly emplaced volcanic or sedimentary facies (lavas, intrusions, subaqueous mass-flow deposits, pyroclastic fallout); (2) relics of the host facies occur within the mineral deposit; (3) replacement fronts occur between the mineral deposit and the host lithofacies; (4) the mineral deposit is discordant to bedding; and (5) strong hydrothermal alteration continues into the hanging wall without an abrupt break in intensity. Criteria 1–3 are diagnostic of replacement, whereas criteria 4 and 5 may suggest replacement but are not alone diagnostic. Because clastic sulfide ores contain accessory rock fragments collected by the parent sediment gravity flow(s) during transport, criteria 2 can only be applied to massive, semi-massive, disseminated or vein style deposits, and not clastic ores. The spectrum of VMS deposit types includes deposits that have accumulated largely subsea-floor, and others in which sedimentation and volcanism were synchronous with hydrothermal activity, and precipitation of sulfides occurred at and below the sea floor over the life of the hydrothermal system. Deposits that formed largely subsea-floor are mainly hosted by syn-eruptive or post-eruptive volcaniclastic facies (gravity flow deposits, water-settled fall, autoclastic breccia). However, some subsea-floor replacement VMS deposits are hosted by lavas and syn-volcanic intrusions (sills, domes, cryptodomes). Burial of sea-floor massive sulfide by lavas or sediment gravity flow deposits can interrupt sea-floor mineralization and promote subsea-floor replacement and zone-refining. The distance below the sea floor at which infiltration and replacement took place is rarely well constrained, with published estimates ranging from less than 1 to more than 500 m, but mainly in the range 10–200 m. The upper few tens to hundreds of metres in the volcano-sedimentary pile are the favoured position for replacement, as clastic facies are wet, porous and poorly consolidated in this zone, and at greater depths become progressively more compacted, dewatered, altered, and less amenable to large scale infiltration and replacement by hydrothermal fluids. Furthermore, sustained mixing between the upwelling hydrothermal fluid and cold seawater is regarded as a major cause of sulfide precipitation in VMS systems, and this mixing process generally becomes less effective with increasing depth in the volcanic pile. The relative importance of subsea-floor replacement in VMS systems is related principally to four factors: the permeability and porosity patterns of host lithofacies, sedimentation rate, the relative ease of replacement of host lithofacies (especially glassy materials) and early formed alteration minerals during hydrothermal attack, and physiochemical characteristics of the hydrothermal fluid.