On the problem of variability in the chemical composition of mud–volcanic waters: Evidence from the Yuzhno-Sakhalinsk mud volcano

The results of hydrogeochemical observations on the Yuzhno-Sakhalinsk mud volcano in 2010–2014 are considered. The chemical analysis of samples of mud–volcanic waters was carried out at various analytical centers, which is similar to the common situation where hydrochemical data for a volcano are obtained by different researchers. It is shown that the chemical composition of the mud–volcanic waters is relatively stable in time and space (for different gryphons of the volcano). This allows us to determine the characteristic range of hydrogeochemical indicators. For each year of observations, the coefficients of variation for the concentrations of Na, Mg, Ca, K, and HCO₃ mostly range from 10 to 30%. However, the concentrations analyzed in individual samples may differ significantly from each other. These natural variations are a likely source of errors in the interpretation of hydrochemical data. In addition, it is necessary to account for the specifics of mud–volcanic waters as an object of analytical chemical investigations.     

Stabilities of heavy metals in soils treated with red mud

This paper discussed the stabilities of heavy metals in soils treated with red mud. Soil has been polluted by heavy metals more and more seriously during recent several decades, and they are harmful to mankind and animals. The current tendency is to develop in-situ technique by using industrial processing waste as additives to stabilized heavy metals to minimize the disturbance of contaminated soils. Soil samples were collected from the Niujiaotang mining area, Guizhou Province, southwestern China. They were farmed soils polluted weakly by fly ash （QBT） and polluted badly by waste water （BXT） from smelter, respectively. One of the red mud samples （BRM） was collected from Bayer process and the other （CRM） from confederate process in the Alumina Plant of Guizhou. Free metal ion concentrations were analyzed with Donnan Membrane Technique and predicted with ECOSAT. The concentrations of free heavy metal ions in QBT increased after appending CRM, but decreased when adding BRM. The more the red mud was added, the higher the concentration would be, and the free concentrations of nickel and cadmium ions would vary more greatly than those of copper and zinc ions. When appending red muds into BXT, the free concentrations of copper and zinc ions varied little. While those of free nickel and cadmium decreased obviously at the ratio of 2.00%. The variation of the concentration was still biggish after appending BRM at the ratio of 0.50%, but smaller than that of 2.00%. The concentrations of free cadmium ions increased after adding CRM at the ratio of 0.50%. All experimental processes were modeled through ECOSAT. The predicted and measured results were consistent, except for zinc. Contributions of soil sorbents to the heavy metal adsorptions were also modeled through ECOSAT. The sorbents in soil included soil organic matter, iron hydroxides, clay and the Donnan gel of soil organic matter. Compared to the soils without red muds, no matter what kind of red mud and how much was added in soil, the contributions changed slightly.     

Sand–mud couplets deposited by spontaneous remobilization of subaqueous transitional flows

Clean basal and capping argillaceous sandstone couplets in deep water settings have been previously interpreted as the result of spatially segregated turbidity currents and debris flows or spatio-temporal transitioning of a turbulent flow to a transitional/laminar state. However, this paper presents three-dimensional laboratory experiments demonstrating that a single sediment-gravity flow can develop sand–mud couplets by autogenic remobilization of sediments that are still in the process of being deposited. This remobilization appears common to flows composed of mixtures of sand and mud with viscosities and strengths measurably greater than water, but not so high as to fully suppress the settling of sand through the depositional current. Dewatering in the early sand deposit acts to lubricate the basal portion of the increasingly muddy upper division of the flow, causing it to accelerate downslope, triggering a secondary flow with a sediment composition distinct from the original mixture. Sediment deposition and remobilization processes in a single sediment-gravity flow and their resultant deposit were imaged acoustically and cored at representative locations within the deposit. The acoustic data and cores show sand–mud couplets that are qualitatively similar to interpreted turbidite–debrite-like couplets in natural systems.     

Trinidad mud volcanoes: where do the expelled fluids come from?

In order to establish the origin of fluids expelled from mud volcanoes in Trinidad, we analyzed their major-element, trace-element, and isotopic (H, O, Sr) compositions. The mineralogical, chemical, and Sr isotope compositions of associated expelled muds were also determined.On the basis of their chemical and Sr isotope compositions, the fluids were divided into two groups—those southwest and northeast of a major right lateral wrench fault (the Los Bajos fault) that both controls the chemical quality of the fluids and acts as a drain. Strontium isotopes were derived via mixing between a radiogenic source (0.71135) and a nonradiogenic source (≤0.70671) for both southwest and northeast groups. However, the nonradiogenic source possibly feeding the northeast group showed a lower Sr concentration than that of the southwest group. H and O isotope data show that the fluids became enriched in δ¹⁸O through interaction with wall rocks. The fluids were originally oceanic, but their properties were subsequently modified by diagenesis as evidenced by chemical data, and mixing between fluids issued from two deep-seated reservoirs and surface aquifer end-members.The gas phase expelled with the mud and the fluid through the mud volcanoes is composed mainly of methane with minor carbon dioxide. The amount of expelled gas seems the same in samples from both sides of the Los Bajos fault. The almost unique methane content of the gas phase and the large positive δ¹⁸O shifts of the reservoir end-member, as well as B, Li, and Ba contents, reveal that the fluids from the deep-seated reservoirs inherited their chemical compositions at high-temperature fluid–rock interactions. Estimates of equilibrium temperatures of the two deep-seated reservoirs suggest that, to acquire the estimated higher temperature (150°C), the mud volcanoes must have been fed partly by a reservoir located at a depth of more than 3 km. This depth corresponds to previous geologic information, which located the deep-seated reservoir in Miocene sediments at such a comparable depth. The mixing of the original fluids with a less deep-seated reservoir and meteoric waters on the ascending path suggests the presence of a recharge mechanism and contributes to the dynamics of the expulsion itself.     

Feasibility of red mud neutralization with seawater using Taguchi’s methodology

In this study, feasibility of using seawater to neutralize alkaline red mud for its safe disposal has been studied using Taguchi’s design of experimental methodology. Parameters such as weight of red mud, volume of seawater, stirring time and temperature were tested at three levels to study their effect on response characteristic, i.e., pH of the neutralized slurry. The analysis of variance showed that volume of seawater added and quantity of red mud are the two significant parameters with 53.59 and 44.92 % contribution each, respectively. Under the optimized parameters, pH value of red mud slurry reaches to about 8.0 which is within disposable limits. When seawater or other Ca- and Mg-rich brines are added to caustic red mud, the pH of the mixture is reduced causing hydroxide, carbonate or hydroxy carbonate minerals to be precipitated. This mechanism of neutralization process has been explained with emphasis on chemical analysis, mineralogy and morphology of the neutralized red mud. The process improved the physical characteristics of red mud with entrained liquor becoming non-hazardous water with reduced alkalinity. The results would be extremely useful in the process of safe disposal of red mud.     

Newly discovered mud volcanoes in the Coastal Belt of Makran,Pakistan—tectonic implications

The Makran accretionary wedge has a much larger number of mud volcanoes then those reported earlier. Using high-resolution satellite images, over 70 active mud volcanoes were identified. These mud volcanoes occur within a well-defined zone; we call it the Makran zone of active mud volcanoes (MZAMV), which is parallel to the regional trend of the accretionary wedge. Mud volcanoes within the zone occur as clusters, which form linear belts parallel to the regional thrusts associated with anticlines. The MZAMV zone also includes the offshore mud volcanoes occurring in the shallow shelf area, including the recurrently emerging mud islands. Several occurrences of thick deposits of old mud volcanoes (Pleistocene or even older) are also present within this zone, which also display recognizable features that are characteristic of the fossil mud volcanoes. We propose that the MZAMV developed and evolved in response to the continued compression within the Makran accretionary wedge, which in turn, is a response of the subduction process. Mud diapirism has been an ongoing phenomena since Pleistocene or even earlier. The events of enhanced mud extrusion in mud volcanoes and/or emergence of island(s) have relevance with seismic phenomena and, therefore, may be closely monitored.     

Characterization of red mud derived from a combined Bayer Process and Calcining method for alumina refining

Red mud is the residue of bauxite processing for alumina. Red mud varies in physical, chemical and mineralogical properties due to differing mineral sources and refining processes adopted. In this project, red mud produced using a combined Bayer Process and Calcining （BPC） method was investigated. Red mud samples of varying ages were collected from the red mud storage facilities of the Zhenzhou Changcheng Aluminium Limited. The objective of this study is to （1） characterize the BPC red mud, and （2） examine the effects of this red mud on treating heavy metal-containing water and soil. Red mud samples were analyzed for pH, EC, water extractable salts and exchangeable basic cations, total element composition （by XRF）, mineral composition （by XRD）, micromorphological characteristics （by SEM） and thermogravimetric analysis （TGA）. The results show that the pH of the red mud decreased with increasing duration of storage time. The pH of the fresh, 5-year-old and 10-year-old red mud was 11.58, 10.56 and 9.61, respectively. Sodium dominated among the soluble cations, but the concentration of soluble Na decreased with increasing duration of storage time as a result of leaching. Cation exchange capacity as estimated from the sum of exchangeable cations also decreased with increasing duration of storage time, probably due to the decreasing pH which causes a reduction in negatively charged sites of the red mud. Calcium was the predominant exchangeable cation in the fresh red mud but the concentrations of exchangeable Ca markedly decreased in the old red mud which was dominated by exchangeable Na.XRF results showed that the red mud consists mainly of oxygen, calcium, iron, silicon, aluminium and titanium. Other important elements include sodium, carbon, magnesium and potassium. It is important to note that the red mud also contains elevated concentrations of radioactive elements, predominantly thorium （Th）, cerium （Ce） and rubidium （Rb）. XRD results showed that the major mineral types in the red mud were calcite, perovskite, illite, hematite and magnetite. There is a trend that the contents of magnetite decreased while the contents of hematite increased with increasing storage time, suggesting the conversion of magnetite to hematite. Observation using a SEM revealed that fresh red mud sample was amorphous while the 10-year-old red mud sample was fairly well crystallized. TGA results showed that the temperature at which the valley of weight loss occurred increased from 681.9℃ for fresh red mud to 722.9℃ for the 5-year-old red mud to 734.7℃ for the 10-year-old red mud. These results suggest that the contents of calcium carbonate increased with increasing storage time. Slow titration of the red mud samples with standardized acid solutions for two years indicated that the fresh red mud had an acid neutralizing capacity （ANC） of about 10 mol/kg while the ANC of old red mud samples was around 9 mol/kg. The ANC values obtained from the determination of BPC red mud here are much higher than those previously reported for red mud derived from the pure Bayer Process at the Queensland Alumina Limitd, Australia, and at the Pinggno Alumina Refinery, China.     

Flocculation–solidification combined method for treatment of hydraulically dredged mud at extra high water content

A new method, i.e., flocculation–solidification combined method (FSCM), is proposed for building a working platform efficiently and economically at the surface of newly reclaimed ground filled with hydraulically dredged mud slurry at extra high water content (EHW-MS). A number of laboratory experiments are performed in this paper to identify the feasibility and mechanism of the proposed FSCM. First, the reasonable flocculant dosage range suitable for FSCM is determined by the simple sedimentation tests. Second, the engineering properties of FSCM, pure cement solidification method (PCSM) and pure flocculation conditioning method (PFCM) treated EHW-MS are compared in detail via a series of model tests, to demonstrate the superiority of FSCM over PCSM and the influence of flocculant dosage on FSCM efficiency. Third, the superiority of FSCM over PCSM is rationalized from the perspective of intrinsic working mechanism of flocculant and PCSM. Results demonstrate well that FSCM shows substantial superiority over PCSM, and at the reasonable flocculant dosage, the strength of FSCM-treated EHW-MS is at least 5.7 times larger than that of the corresponding PCSM-treated EHW-MS. The superiority of FSCM over PCSM can be attributed to two aspects, i.e., the dewatering effect and the other detrimental effect. The former is predominant and primarily governs the strength gain of FSCM-treated EHW-MS, while the latter is less significant but not negligible.

     

Changes in Seagrass-associated fish and crustacean communities on Florida Bay mud banks: The effects of recent ecosystem changes?

The fauna of seagrass-covered mud banks in Florida Bay, documented in the mid 1980s prior to recent seagrass die-off, phytoplankton blooms, and other ecosystem changes, was reexamined in the mid 1990s for faunal changes that might be associated with environmental perturbations. During both decades, decapod crustaceans and fishes were collected with 1-m² throw traps from seagrass beds at six sites that differ in the amount of freshwater and/or marine influence and in seagrass community metrics. The most common faunal changes were declines in seagrass-canopydwelling forms and increases in benthic forms. At three sites with relatively lush seagrass meadows, above-ground seagrass standing crop declined and abundance of the benthic predatory fishOpsanus beta increased. The degree of faunal change among these sites appeared to be related either to salinity variability or to the degree of exposure to the ecosystem changes that have taken place in Florida Bay. At two sites with poorly developed seagrass meadows, seagrass standing crop and canopy height did not change significantly between decades, but there was an increase in shoot density and total leaf area. The animal communities at these sites were characterized by significant increases in the abundance of benthic crustaceans. At the site on the edge of Rankin Lake, the basin where seagrass die-off was first observed in Florida Bay during 1987, seagrass standing crop, canopy height, shoot density, and leaf area declined significantly between decades, but species richness of both crustaceans and fishes increased. The abundance of canopy-dwelling crustaceans and fishes declined markedly at this site, whereas the abundance of benthic forms less dependent on seagrass cover generally increased. In retrospect, we believe the fauma at this site during the 1980s, characterized by high productivity but few species, was already showing signs of the stresses that led to the seagrass die-off that began in 1987.     

Evaluation of earthquake-induced strain in promoting mud eruptions: the case of Shamakhi–Gobustan–Absheron areas,Azerbaijan

Although a relationship between the occurrence of large earthquakes and the eruptions of close mud volcanoes is well known, several uncertainties remain on understanding the triggering mechanisms. In the present study, we evaluate both the static and dynamic strains induced by earthquakes in the substratum of mud volcanoes. We studied the effects of two earthquakes of M _w 6.18 and 6.08 occurred in the Caspian Sea on 25 November 2000 close to Baku city, Azerbaijan. A total of 33 eruptions occurred at 24 mud volcanoes within a maximum distance of 108 km from the epicentres in the 5 years following the earthquakes. The overall eruption rate in the studied area of the 50 years before the 2000 earthquakes was 1.24 that is much smaller than the eruption rate of 6.6 of the 5 years following these earthquakes. The largest number of eruptions occurred within 2 years from the earthquakes with the highest frequency within 6 months. Our calculated earthquake-induced static effects show that crustal dilatation might have triggered only seven eruptions at a maximum distance of about 60 km from the epicentres and within 3 years. Based on our data, dynamic rather than static strain is likely to have been the dominating “promoting” factor because it affected all the studied unrest volcanoes and its magnitude was much larger.     

Characteristics and formation mechanism of a catastrophic rainfall–induced rock avalanche–mud flow in Sichuan, China, 2010

A catastrophic rock avalanche–mud flow was triggered by the heavy rainfall in Sichuan, China, on July 27, 2010. A mass of strongly weathered basalts with a volume of ∼480,000 m³ was initiated from a valley side slope and then moved downstream along the valley, entraining a large amount of unconsolidated substrate and bilateral materials and colluviums. The entrainment increased the volume of slide to ∼1.0 million m³ and may also enhance the mobility of the landslide. Approximately 30 min after the first failure, the deposits of the rock avalanche in the steepest part of the valley started to creep slowly down as a mud flow. It reached a small town at the foot of the slope after several hours, causing the damage of 92 houses and the urgent evacuation of 1,500 people. The field investigation, mapping, grain size test, and aerial photo interpretation were applied to analyze the dynamic process and the formation mechanism of the landslide. The strongly weathered and fragmented basalts as well as the most vulnerable combination of joint sets were revealed to be the most contributive factors. The antecedent torrential rainfall is the direct trigger, which affected the slope stability in three aspects: induced debris flow that scoured the toe of the sliding surface of rock avalanche; caused the increase of the slope unit weight, and penetrated into the steep joints reducing the strength of the materials.     

High-resolution sedimentary record of lead in the coastal mud of the East China Sea in the past one hundred and fifty years

In the East China Sea （ECS）, there are some mud areas, including the south coastal mud area, the north coastal mud area, and the mud area to the southwest of Cheju Island. X-ray fluorescence （XRF） techniques and Thermal Ionization Mass Spectrometry （TIMS） were used to study the high-resolution sedimentary record of Pb concentrations and Pb stable isotopic compositions in the past one hundred and fifty years in the coastal mud of the ECS. Pb concentrations of a ^210Pb dating S5 core in the study area have increased rapidly since 1980, and reached the maximal value with 65.08 μg/g in 2000, corresponding to the fast economic development of China since the implementation of the ＂Reform and Open Policy＂ in 1978; ^206Pb/^207Pb ratios generally had stabilized at 1.195 from 1860 to 1966, and decreased gradually from 1966 to 2000, indicating that the anthropogenic source Pb contribution to the ECS has increased gradually since 1966, especially since 1980. Pb concentrations decreased distinctly from 2000 to 2003 and ^206Pb/^207Pb ratios increased from 2001 to 2003, corresponding closely to the ban of lead gasoline from 2000 in China. From 1950 to 2003, there occurred four distinct decrease events of ^206Pb/^207Pb, possibly responding to the Changjiang River （Yangtze River） catastrophic floods in 1998, 1991, 1981 and 1954; from 1860 to 1966, there were two decrease periods of ^206Pb/^207Pb, which may respond to the catastrophic floods of Changjiang River in 1931 and 1935, and 1870. As a result of the erosion and drowning by the catastrophic floods, the anthropogenic lead accumulated in soil and water environments over a long period of time was brought into the Changjiang River, then part of them was finally transported into the ECS, which leads to changes in Pb stable isotopic composition.     

Subsidence and uplift of Sidoarjo (East Java) due to the eruption of the Lusi mud volcano (2006–present)

Global positioning system (GPS) and satellite-based InSAR (Interferometric Synthetic Aperture Radar) measurements of the subsidence and uplift of a populated area of Sidoarjo, East Java are due to the eruption of the Lusi mud volcano (2006–present). These data are the first direct quantitative measurements of deformation due to the growth of a mud volcano edifice. The GPS data were recorded over periods of a few hours to several months and show that between June 2006 and September 2007, the earth’s surface has been subsiding at rates of 0.1–4 cm/day. Maximum rates of subsidence occurred in an area 300–400 m to the northwest of the main mud volcano vent. Horizontal displacements were 0.03–0.9 cm/day and were also towards this area. In general uplifts of up to 0.09 cm/day were recorded in areas outside of the edifice. Changes in elevation measured using satellite imagery (InSAR technique) provide regional datasets of subsidence and uplift. They confirm that during the first year a roughly circular area was undergoing sag-like subsidence centered to the northwest of the main vent and that uplift was occurring 3–4 months after the initiation of the eruption due to the movement Watukosek fault system. Subsidence occurred due to the weight of mud and man-made dams and the collapse of the overburden due to removal of mud from the subsurface. Assuming constant rates of subsidence of 4 cm/day, then in the centre of the edifice there would be up to 44 m of subsidence in 3 years, and up to 16 m in 10 years. The mud volcano is now in a self-organizing state with new fluid conduits forming as a result of the collapse. An erratum to this article can be found at     

Recurring emergence of the mud islands on shelf of the Arabian Sea along the Makran coast of Pakistan – Historical perspective using remote sensing techniques

Recurring emergences of mud islands on shelf of the Arabian Sea, along the Makran coast of Pakistan are now known to be submarine mud volcanoes. They are expressions of enhanced extrusions of fluidized mud and gases coupled with compressional tectonics in convergent margin settings. Since 1945 the Malan island has emerged four times, and some other mud islands have also been emerging repeatedly, at their own positions.The first known emergence, during November 1945, was concurrent with an earthquake of magnitude 8.0 (M8.0), the 2^nd and 3^rd emergences, in March 1999 and November 2010 respectively, were not related apparently with earthquakes. The 4^th emergence concurred with the Awaran earthquake (M7.7) of 24th September 2013. Landsat images of March 1999 and November 2010 emergences indicate appearance of round-shaped island of 4.4 and 5.2 hectare area, followed by erosion and disappearance. The island was composed of mud breccias and circular vents spewing mud slurry and methane gas.The emergence of Malan island, in March 1999 and November 2010 was compared with earthquake data before and after the emergences. The earthquakes data, two years before March 1999 and November 2010 emergences and two years afterwards, shows correlation with both small and large earthquakes, prior to the emergence, in the radius of over 400 km. It is proposed that mud islands develop in response to the episodes of enhanced mud extrusion, which inturn are related with the enhanced compressional and/or seismic events. These events are followed by periods of relative quiescence characterized by normal activity of mud extrusion and marine erosion.     

Relationships between seep-carbonates,mud volcanism and basin geometry in the Late Miocene of the northern Apennines of Italy: the Montardone mélange

The Montardone mélange (Mm) is a chaotic, block-in-matrix unit outcropping in the Montebaranzone syncline in the northern Apennines. The Mm occurs in the uppermost part of the Termina Fm, the Middle–Late Miocene interval of a succession deposited in a wedge-top slope basin (Epiligurian succession). The Mm is closely associated with bodies of authigenic carbonates, characterized by negative values of δ¹³C (from ?18.22 to ?39.05 ‰ PDB) and chemosynthetic benthic fauna (lucinid and vesicomyid bivalves). In this paper, we propose that the Mm is a mud volcano originated by the post-depositional reactivation and rising of a stratigraphically lower mud-rich mass transport body (Canossa–Val Tiepido sedimentary mélange or olistostrome) triggered by fluid overpressure. We base our conclusion on (1) the Mm pierces the entire Termina Fm and older Epiligurian units and represents the direct continuation of the underlying Canossa–Val Tiepido mélange; (2) the geometry and facies distribution of the Montebaranzone sandstone body, which are compatible with a confined basin controlled by the rising of the Mm; (3) the systematic presence of large-scale (lateral extension 300–400 m) seep-carbonates associated with the mélange, suggesting a persistent gas-enriched fluid vent from the ascending overpressured mud; (4) blocks and clasts sourced from the Mm, hosted by the authigenic carbonates, conveyed by ascending mud and gas-enriched fluids. The Mm represents one of the few fossil examples of reactivation of a basin-scale sedimentary mélange (olistostrome); a three-stage model showing mechanisms of Mm raising is proposed.     

Isotopic evidence (Sr/Sr, δLi) for alteration of the oceanic crust at deep-rooted mud volcanoes in the Gulf of Cadiz, NE Atlantic Ocean

The chemical and isotopic composition of pore fluids is presented for five deep-rooted mud volcanoes aligned on a transect across the Gulf of Cadiz continental margin at water depths between 350 and 3860 m. Generally decreasing interstitial Li concentrations and ⁸⁷Sr/⁸⁶Sr ratios with increasing distance from shore are attributed to systematically changing fluid sources across the continental margin. Although highest Li concentrations at the near-shore mud volcanoes coincide with high salinities derived from dissolution of halite and late-stage evaporites, clayey, terrigenous sediments are identified as the ultimate Li source to all pore fluids investigated. Light δ⁷Li values, partly close to those of hydrothermal vent fluids (δ⁷Li: +11.9‰), indicate that Li has been mobilized during high-temperature fluid/sediment or fluid/rock interactions in the deep sub-surface. Intense leaching of terrigenous clay has led to radiogenic ⁸⁷Sr/⁸⁶Sr ratios (∼0.7106) in pore fluids of the near-shore mud volcanoes. In contrast, non-radiogenic ⁸⁷Sr/⁸⁶Sr ratios (∼0.7075) at the distal locations are attributed to admixing of a basement-derived fluid component, carrying an isotopic signature from interaction with the basaltic crust. This inference is substantiated by temperature constraints from Li isotope equilibrium calculations suggesting exchange processes at particularly high temperatures (>200 °C) for the least radiogenic pore fluids of the most distal location.Advective pore fluids in the off-shore reaches of the Gulf of Cadiz are influenced by successive exchange processes with both oceanic crust and terrigenous, fine-grained sediments, resulting in a chemical and isotopic signature similar to that of fluids in near-shore ridge flank hydrothermal systems. This suggests that deep-rooted mud volcanoes in the Gulf of Cadiz represent a fluid pathway intermediate between mid-ocean ridge hydrothermal vent and shallow, marginal cold seep. Due to the thicker sediment coverage and slower fluid advection rates, the overall geochemical signature is shifted towards the sediment-diagenetic signal compared to ridge flank hydrothermal environments.