Dissolution Of Debris Research Articles

Mineralogy, geochemistry and genesis of the polymetallic crusts from the Chagos-Laccadive Ridge, Arabian Sea, India

Recent offshore exploration by the Geological Survey of India (GSI) located ferromanganese crusts (FeMn) along the Chagos-Laccadive Ridge (CLR) offshore western continental margin of India. CLR FeMn crusts grew on phosphorite substrate rock (phosphorite cemented sand/silt with moderate carbonate fluorapatite (CFA) cement and goethite). Phosphorite precipitation is the product of intense upwelling and phosphorus regeneration due to organic matter degradation and fish debris dissolution. CLR FeMn crusts are of hydrogenetic origin precipitated in an oxic environment. As a result of hydrogenetic processes under oxic conditions, Fe-vernadite dominated the mineral phase of FeMn crusts. CLR FeMn crusts formed when the North Indian deep-water layer mixed with oxygen-depleted waters from the Arabian Sea, Persian Gulf, and Red Sea. Three genetic layers are identified in the FeMn crusts; Type-I, Type-II, and Type-III developed in response to fluctuation in dissolved oxygen during periods of intensified suboxic bottom waters and monsoon maxima associated with past climatic events in the Arabian Sea. Type-I layers are columnar showing low Mn/Fe ratio (∼1), reflectivity, Mg (average 1.24%), and Ni (average 0.29%). Dendritic Type-II layers show high Mn/Fe ratios (average 12.29), reflectivity, Mg (average 3.51%) and Ni (average 1.69%). Type-III layers show very low Mn/Fe ratios (average 0.21), reflectivity, Mg (average 1.4%) and Ni (average 0.01%) and contain a substantial amount of terrigenous debris of aeolian origin. Elements of economic interest such as Mn, Co, Ni, Cu, Mo, Li, Te, and REY in CLR FeMn crusts are depleted owing to terrigenous contribution.

Pore Structure Characteristics and Main Control Factors of Sandstone in the Jurassic Zhiluo Formation in the Northern Ordos Basin

The Jurassic Yan’an Formation in the Ordos Basin is one of the main coal seams mined in the basin, and the enrichment of water bodies in the upper part of this coal seam is closely related to the sand bodies in the Zhiluo Formation. This study is based on the use of core observations in the northern part of the Ordos Basin for studying the pore characteristics of the permeable sand layer of the Zhiluo Formation in the study area through testing methods such as ordinary thin sections, cast thin sections, scanning electron microscopy (SEM), mercury intrusions, and physical property analysis. The results indicate that the primary pores of the Zhiluo Formation sandstone in the study area include primary intergranular pores, residual intergranular pores, and interstitial micropores. The secondary pores are mainly intergranular pores, feldspar dissolution pores, and rock debris dissolution pores. The throat-type pores are mainly variable fault contractions, sheets, curved sheets, and bundle-shaped throats. The pore structures of the Zhiluo Formation sandstone in the research area are complex, and the permeability is influenced by the throat characteristics. The main controlling factors of the pore structure characteristics of the Zhiluo Formation sandstone in the study area are sedimentation and diagenesis. Compaction and cementation are the main factors that destroy the sandstone pore structure, while later dissolution plays a certain role in the improvement of the pores. Section 1 of the Zhiluo Formation is greatly affected by diagenesis, and section 2 is greatly affected by sedimentation.

Effect of Endodontic Irrigating Solutions on Radicular Dentine Structure and Matrix Metalloproteinases-A Comprehensive Review.

Irrigating solutions play an important role in the eradication of intracanal microbes and debris dissolution during endodontic treatment. Different combinations of solutions and protocols have been advocated, with sodium hypochlorite (NaOCl), ethylenediamine tetra acetic acid (EDTA), and chlorhexidine (CHX) remaining the most widely used ones by many clinicians. Although these solutions provide efficient inorganic dissolution and antimicrobial capacity, their use has also been reported to cause undesired effects on root dentin composition and mechanical and biomechanical properties, such as microhardness, surface roughness, bond strength, and matrix metalloproteinase (MMP) activity. Several corroborating studies attribute these changes in mechanical properties of dentine to the use of irrigating solutions, and there are limited reports on how the solutions affect the expression of MMPs, which may be a correlating link to understanding the role of these enzymes in dentin collagen and changes in the mechanical properties of dentin. Hence, using the basis of several studies from the literature, the objective is to comprehensively review the influence of individual and combined irrigating solutions on root dentine structure and the activity of the MMPs.

Diverse effects of intragranular fractures on reservoir properties, diagenesis, and gas migration: Insight from Permian tight sandstone in the Hangjinqi area, north Ordos Basin

As petroleum industry tilts towards unconventional petroleum resources, the significance of fractures in exploration and development becomes increasingly prominent. In this study, thin sections and scanning electron microscopic (SEM) observation, porosity and permeability measurement, mercury injection porosimeter (MIP) and computerized tomography (CT) analysis were carried out to investigate the morphology and development characteristics of intragranular fractures, and their effects on physical properties, reservoir diagenesis, and gas migration of the He-1 Member tight sandstones in the Hangjinqi area. Results show that the tight sandstones have intergranular and intragranular dissolved pores, intercrystalline pores and heterogeneous distributed intragranular fractures. The average porosity and permeability of the tight sandstones with intragranular fractures are 12.76% and 4.70 × 10−3 μm2, while those lack of fractures are 6.06% and 0.574 × 10−3 μm2, respectively. The fracture density increases with the enlargement of clastic-grain size and the content of rigid grains. Results indicate that the intragranular fractures greatly enhance permeability, but they have limited direct contribution to total porosity. And the sandstones rich in intragranular fractures have a more homogeneous and connective pore structure with larger radius of pore throat. Intragranular fractures are beneficial to the latter feldspar and debris dissolution caused by organic acids derived from hydrocarbon generation in coal-bearing strata. The dissolved pores directly enhance the porosity of tight sandstones compared to intragranular fractures, and together they form a percolation network to increase permeability. Faults mainly control the lateral petroleum migration from the south to the north, and intragranular fractures affect the local accumulation of gas. This study helps to illustrate the influences of intragranular fractures on reservoir properties, diagenetic difference, and gas migration of the He-1 Member tight sandstones in the Hangjinqi area, and can guide the evaluation and exploration of tight sandstone reservoirs in the Ordos Basin and other basins with similar settings around the world.

Study on diagenesis and diagenetic evolution of reservoir in Wuerxun depression

Wuerxun depression is one of the main oil-bearing depressions in the middle of the Hailar District Basin with high exploration degree. With the deepening of exploration degree, the pore structure and distribution law of tight reservoir in trough are not clear. In this paper, through the combination of quantitative and qualitative, micro and macro, following the idea of “phenomenon characterization, essence exploration, law summary”, the diagenesis analysis and diagenetic evolution of tight reservoirs are studied to find areas with relatively good reservoir properties in the depression, which provides theoretical basis for tight reservoir exploration. Diagenesis controls the formation, evolution and distribution of the reservoir. The diagenesis of the reservoir in this area mainly includes compaction, cementation and dissolution, thus forming five kinds of secondary dissolution pores (intergranular dissolution pore, feldspar and debris dissolution pore, mold pore, interstitial dissolution pore and dissolution fracture). Vertically, the physical properties of the reservoir are generally poor, but the reservoir is well developed locally. The reservoir is well developed at 1300-1900m and 2300-2700m in Wuerxun depression.

Chlorite authigenesis and its impact on reservoir quality in tight sandstone reservoirs of the Triassic Yanchang formation, southwestern Ordos basin, China

Authigenic chlorite plays an important controlling role in reservoir quality, and is widely distributed in the tight sandstone reservoirs of the Triassic Yanchang Formation in the Southwestern Ordos Basin, China. The occurrence and origins of authigenic chlorite were investigated using an integrated approach of optical microscopy, scanning electron microscopy, X-ray diffraction, electron probe microanalysis, and fluid inclusion analysis. The sandstones are fine-grained lithic arkoses and feldspathic litharenite with 11.5% volcanic rock fragments. Authigenic chlorite occurs in two morphotypes, including pore-lining and pore-filling chlorite. Pore-lining chlorite occurs as coatings on the framework grains and covers the entire fining-upward sandstones. Pore-filling chlorite is restricted to the middle to upper part of the fining-upward sandstones and appears as discrete flaky plates or rosettes in the pores or attaches to the surfaces of pore-lining chlorite. Pore-lining chlorite originated from smectite precursors that were derived from volcanic material alteration in the early stage of diagenesis, with temperatures primarily about 90 °C. In contrast, pore-filling chlorite was precipitated in pore spaces with higher concentrations of Mg2+ and Fe2+ released from volcanic rock fragments and mica debris dissolution. Moreover, the chemical composition of pore-filling chlorite was affected by early calcite cementation which consumed some ions at temperatures lower than about 110 °C. The thin and continuous pore-lining chlorite is the only chlorite type with a positive effect on reservoir quality, whereas the very thick pore-lining chlorite (>6.7 μm) or pore-filling chlorite significantly reduce the porosity and permeability. Systematic studies of authigenic chlorite can provide important insights into the reservoir heterogeneity and are applicable to the exploration and development of tight oil.

Reservoir characteristics and control factors of Tongbomiao formation in Hongqi sag

Hongqi sag is located in the north of Beiehur depression in Hailar Basin, which is a secondary structural unit in the peripheral depression of Hailar Basin, with great exploration potential. Based on SEM, conventional thin sheet, cast thin sheet, mercury pressure and physical property data, this paper discusses the reservoir characteristics, types and control factors of high quality reservoir in Tongbomiao formation, Hongqi sag, so as to provide a strong geological basis for the exploration of oil and gas in this area. The reservoir space of Hongqi sag is mainly composed of four types: primary intergranular pore, micro fracture, feldspar dissolution pore and debris dissolution pore. It is of the type of ultra low porosity and low permeability. Although Tongbomiao formation in Hongqi sag is of very low porosity and low permeability type, high quality reservoir is still developed, and its reason is mainly controlled by sedimentary environment, diagenesis and structural fracture.

Effects of pore structures on the movable fluid saturation in tight sandstones: A He8 formation example in Sulige Gasfield, Ordos Basin, China

A complex pore structure is a crucial factor influencing the movable fluid saturation in tight sandstones, which poses a significant challenge to the exploration and development of the He8 formation in the Sulige Gasfield. To confront this challenge, various experimental methods, including, thin section, scanning electron microscopy (SEM), cathode luminescence (CL), high pressure mercury injection (HPMI), constant rate mercury injection and nuclear magnetic resonance (NMR), were introduced to investigate the factors that affect the movable fluid saturation. The results showed that coarse to medium-grained quartz sandstone and lithic quartz sandstone were the dominant sandstone types. The main pore types were intercrystalline pores and dissolution pores. The mercury injection and NMR test results showed that the pore structure can be divided into three main types with different curve morphologies and different peak amplitudes. The pore structures were highly correlated with movable fluid saturation. Multiple factors were shown to influence the movable fluid saturation, including pore radius, throat radius, pore-throat radius ratio, sorting coefficient, pore mercury saturation and throat mercury saturation. Among these factors, throat radius and pore mercury saturation were dominant in influencing the movable fluid saturation in all three types. The throat mercury saturation had the greatest effect on type 3, demonstrating that the throat volume strongly contributed to the total volume in tight sandstones. The pore-throat radius ratio, and the sorting coefficient, had a degree of influence on the movable fluid saturation. Meanwhile, strong diagenesis was the internal reason for the complex pore structure that further influenced the movable fluid saturation. Mechanical compaction and cementation led to the rearrangement and compactness of detrital grains, which resulted in the reduction of effective space and the decline in the movable fluid saturation. Feldspar dissolution and debris dissolution provided significant storage space and enhanced the seepage capacity.

Diagenetic characteristics and quantitative evolution of porosity in tight gas sandstone reservoirs: A case study from the middle and lower Permian in the northwestern Ordos Basin, China

Tight sandstone gas is widespread in the middle and lower Permian Shan 1 and He 8 Members in the northwestern Ordos Basin. We have studied the diagenesis by means of many petrographic techniques and determined its important influence on reservoir quality. The quantitative characterization of porosity evolution is important when analyzing reservoir consolidation. We found that reservoir rock types are mainly sublitharenite, quartz arenite, and litharenite in the deltaic facies through petrological and mineralogical analyses. Metamorphic rock (quartzite), followed by volcanic rock, dominates the lithic fragment types. In the early diagenetic stage, the reservoirs mainly underwent intensive compaction, hydrolysis, and alteration of volcanic debris. Sandstones in the middle diagenesis stage were characterized by quartz overgrowth, volcanic debris dissolution, cementation, and calcite and kaolinite replacement. Based on the formula from Beard and Weyl, we calculated that the original porosity of tight gas sandstones was 38.61%. The porosity loss during compaction was 26.64%; by cementation, it was 11.46%; and carbonate, siliceous, and authigenic clay cements accounted for 1.31%, 3.61%, and 6.44% loss in porosity, respectively. Dissolution was relatively weak, with an average increase in porosity of 4.86%, whereas the present porosity is 7.47%. We observed that the pore types in the study area are composed of intragranular dissolution pores and kaolinite intercrystalline pores, followed by residual primary pores and intergranular dissolution pores. However, microcracks were not common. Based on the results of the rate-controlled mercury intrusion, the pore diameters in different samples are similar but there were clear differences in the throat diameters. Nuclear magnetic resonance results indicate that the cutoff value is 13 ms with the movable fluid mainly distributed in larger pores. As the pressure increased, fluid in the larger pores was discharged in large quantities but there was no discharge of nonmovable fluid in the small pores. We conclude that intensive diagenetic transformation was the main cause of reservoir consolidation and multistage cementation resulted in a complicated pore-throat network and reduced reservoir permeability.

Benthic cycling of phosphorus in the Eastern Arabian Sea: Evidence of present day phosphogenesis

Abstract Results of a study on phosphorus (P) cycling in the Eastern Arabian Sea provides convincing evidence of present-day phosphogenesis in the study area. This finding contrasts with previous reports of the occurrence of only old phosphorites along the Indian margin. Extensive benthic P regeneration is observed in the sediments that are deposited on topographic highs in the western Indian continental margin , which is impinged by a perennial oxygen minimum zone (OMZ). The phosphate flux from the sediments ranged between 1.1 and 22 mmol m− 2 yr− 1. Among the P reservoirs, biogenic P (Pbio) is the major pool of P within the upper 30 cm of sediment. P released from organic matter decomposition and fish debris dissolution mainly controls benthic P regeneration while the role of redox cycling of iron is weak. The change in authigenic P (Pauth ) with depth in the sediment and concomitant decrease in porewater dissolved inorganic phosphate (DIP), solid phase P bio and organic P (Porg) content collectively indicate the transformation of P from labile phases to an authigenic phase. Molar Corg/Porg and Corg/Preactive ratios also support the notion of ongoing phosphogenesis in the area. The content of carbonate fluroapatite (CFA) is elevated especially in one of the three study sites as a result of in-situ precipitation and a contribution from eolian and water column authigenesis . The estimated burial efficiency of P at the sediment-water interface at two locations is only about 2%, which is much less than in the western Arabian Sea also indicating extensive P regeneration.

The role of surface pre-treatment on the microstructure, corrosion and fretting corrosion of cemented femoral stems

The use of cemented femoral stems is common practice worldwide with strong clinical data supporting their use. Over the years, different surface processing techniques have been employed to enhance the performance of the stem–cement interface. As a result different clinical outcomes and visual presentation at revision has been observed. Whilst research has focussed on increasing adhesion and better load bearing capacity, the effects of surface processing on the degradation of cemented femoral stems has not been investigated. The aims of this study was to investigate the effects of surface processing on the subsurface microstructure, surface chemistry and tribocorrosion degradation mechanisms of cemented tapered femoral stems subjected to polishing and blasting (Vaquasheen) processes. Cemented femoral stems were orientated and loaded according to ISO 7206-4 for 500,000cycles in 0.9% NaCl at 37°C. A three-electrode electrochemical cell was integrated into the mechanical test to facilitate in-situ corrosion measurements. The severity and mechanism of damaged were assessed scanning and transmission electron microscopy, X-ray photoelectron spectrometry, solution mass spectrometry and white light interferometry. Surface processing influenced the level of tribocorrosion at the interface with polished surfaces demonstrating higher levels of tribocorrosion and ion release when compared to the blasted surfaces. Surface analysis consistently demonstrated the presence of a SiO2 layer on the vaquasheened stems thought to originate from the glass bead blast matrix. This resulted in lower levels of corrosion both under static and tribocorrosion assessment. In conclusion, blasted surfaces resulted in lower wear induced corrosion when compared to the polished surfaces. However the total metallic ion levels did not follow the same trend. This is thought to be due to the formation of metallic debris and dissolution of debris due to abrasion of the femoral stems.

Cloning and characterization of a novel Drosophila stress induced DNase.

Drosophila melanogaster flies mount an impressive immune response to a variety of pathogens with an efficient system comprised of both humoral and cellular responses. The fat body is the main producer of the anti-microbial peptides (AMPs) with anti-pathogen activity. During bacterial infection, an array of secreted peptidases, proteases and other enzymes are involved in the dissolution of debris generated by pathogen clearance. Although pathogen destruction should result in the release a large amount of nucleic acids, the mechanisms for its removal are still not known. In this report, we present the characterization of a nuclease gene that is induced not only by bacterial infection but also by oxidative stress. Expression of the identified protein has revealed that it encodes a potent nuclease that has been named Stress Induced DNase (SID). SID belongs to a family of evolutionarily conserved cation-dependent nucleases that degrade both single and double-stranded nucleic acids. Down-regulation of sid expression via RNA interference leads to significant reduction of fly viability after bacterial infection and oxidative stress. Our results indicate that SID protects flies from the toxic effects of excess DNA/RNA released by pathogen destruction and from oxidative damage.

Distribution of lead and thallium in the matrix of the Allende meteorite and the extent of terrestrial lead contamination in chondrites

Selective chemical dissolution has been used to study the distribution of Pb and Tl in an ultrafine −20-μm matrix separate of Allende. The matrix was exposed to high-purity reagents ranging from H 2O, then HCl of increasing concentration and finally HF-HCl mixtures. A total of 17 extractions were obtained, each for a minimum period of 10 days. The isotopic compositions of the Pb released during the slow dissolution of the matrix fall into four distinct groups. The first, consisting of four extractions, released a component of terrestrial Pb isotopic composition with a total abundance of about 1 ppb. The next six extractions, which contained the bulk of the indigenous Pb and Tl corresponding to 96% and 94%, respectively, of the total matrix abundance, was of a reasonably homogeneous Pb isotopic composition with mean ratios of 206Pb 204Pb= 10.00and 207Pb 204Pb= 10.74 . In the final seven extractions, the released Pb falls into two higher isotopic groupings and probably results from the dissolution of debris from chondrules and inclusions. The apparent age of the internal matrix isochron is 4562 ± 14 My. The release of Pb and Tl shows a reasonable correlation with the matrix dissolution. This indicates that the Pb and Tl reside predominantly within the matrix phases rather than as a localised phase. The Tl isotopic composition of two matrix fractions and whole meteorite were measured and found to be indistinguishable from the terrestrial 205Tl/ 203Tl ratio. Measurement of a terrestrial reagent standard in the range 1–10 ng Tl gave, for 20 analyses, a mean 205Tl/ 203Tl ratio of 2.38907 ± 0.00102 (2σ). The estimate of terrestrial Pb contamination is considerably lower than the 6–300 ppb assumed in some recent studies in order to explain the phenomenon of apparent excess radiogenic Pb in chondrites. The problem of terrestrial Pb pollution and the evidence which argues against a relatively severe and homogeneous Pb contamination of meteorites, is briefly considered. The apparent initial isotopic composition of the bulk of the indigenous Pb in the Allende matrix was found to be 206Pb 204Pb= 9.57and 207Pb 204Pb= 10.47 . This is of a higher composition than the Pb in the Can˜on Diablo troilite phase and further indicates that the phenomenon of apparent excess radiogenic Pb in chondrites is real.

The isolation of lytic enzymes from Cytophaga and their application to the rupture of yeast cells

AbstractYeast–lytic enzymes have been isolated on a pilot scale from Cytophaga species by precipitation and the light, enzyme‐rich solid phase recovered by liquid‐liquid separation. The enzyme complex was immobilized to soluble polymeric carbohydrates and the effectiveness of the free and immobilized enzyme for protein release and cell debris dissolution has been assessed.