Definition of early Cambrian chronostratigraphic boundaries is problematic with many subdivisions still awaiting ratification. Integrated multi-proxy data from well-resolved regional-scale schemes ...are ultimately the key to resolving broader issues of global correlation within the Cambrian. In Australia, early Cambrian biostratigraphy has been based predominantly on trilobites. Phosphatic shelly fauna have great potential as biostratigraphic tools, especially in pre-trilobitic strata because they are widespread and readily preserved, but they have remained underutilised. Here we demonstrate their value in a new biostratigraphic scheme for the early Cambrian of South Australia using a diverse shelly fauna including tommotiids, brachiopods, molluscs and bradoriids.
Biostratigraphic data are derived from ten measured stratigraphic sections across the Arrowie Basin, targeting Hawker Group carbonates including the Wilkawillina, Wirrapowie and Ajax limestones and the Mernmerna Formation. The stratigraphic ranges of shelly fossils are predictable and repeatable across the Arrowie Basin, allowing three discrete shelly biozones to be identified, spanning Terreneuvian, Stage 2 to Series 2, Stages 3–4. The Kulparina rostrata Zone (new) and part of the overlying Micrina etheridgei Zone (new) are pre-trilobitic (predominantly Terreneuvian). The Cambrian Series 2, Stage 3 Dailyatia odyssei Zone (new) features a very diverse shelly fauna and will be described in detail in a separate publication. These zones provide robust means to correlate Terreneuvian–Series 2 successions in neighbouring coeval basins in Australia, particularly the Stansbury Basin. Wider correlation is possible throughout East Gondwana, and especially with South China.
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•New early Cambrian shelly fossil biostratigraphy for South Australia•Three assemblage zones span Terreneuvian, Stage 2–Series 2, Stages 3–4•Enables regional and global correlation of pre-trilobitic strata
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Wide carbonate platform environments developed on the western passive margin of the Tethys during the Late Triassic, after a major climate change (Carnian Pluvial Episode) that produced a crisis of ...high‐relief microbial carbonate platforms. The peritidal succession of this epicontinental platform (Dolomia Principale/Hauptdolomit, Dachstein Limestone) is widespread in the Mediterranean region. However, the start‐up stage is not fully understood. The original platform to basin depositional geometries of the system have been studied in the north‐eastern Southern Alps, close to the Italian/Slovenian boundary where they are exceptionally preserved. Sedimentological features have been investigated in detail by measuring several stratigraphic sections cropping out along an ideal depositional profile. The analysis of the facies architecture allowed reconstruction of the palaeoenvironments of the Dolomia Principale platform during its start‐up and early growth stages in the late Carnian. The carbonate platform was characterized by an outer platform area, connected northward to steep slopes facing a relatively deep basin. Southward, the outer platform was connected to inner sheltered environments by a narrow, often emerged shelf crest. Behind this zone, carbonate sedimentation occurred in shallow lagoons and tidal flats, passing inward to a siliciclastic mudflat. The Dolomia Principale platform was initially aggrading and able to keep pace with a concomitant sea‐level rise, and then prograding during the late Carnian. This stratigraphic interval was correlated with the Tuvalian succession of the Dolomites, allowing depiction of the depositional system on a wide scale of hundreds of kilometres. This large‐scale depositional system presents features in common with some Palaeozoic and Mesozoic carbonate build‐ups (for example, the Permian Capitan Reef complex, Anisian Latemar platform), both in terms of architecture and prevailing carbonate producers. A microbial‐dominated carbonate factory is found in the outer platform and upper slope. The recovery of high‐relief microbial carbonate platforms marks the end of the Carnian Pluvial Episode in the Tuvalian of Tethys.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A laboratory study demonstrates that high volume, 45% by mass replacement of portland cement (OPC) with 30% finely-ground basaltic ash from Saudi Arabia (NP) and 15% limestone powder (LS) produces ...concrete with good workability, high 28-day compressive strength (39MPa), excellent one year strength (57MPa), and very high resistance to chloride penetration. Conventional OPC is produced by intergrinding 95% portland clinker and 5% gypsum, and its clinker factor (CF) thus equals 0.95. With 30% NP and 15% LS portland clinker replacement, the CF of the blended ternary PC equals 0.52 so that 48% CO2 emissions could be avoided, while enhancing strength development and durability in the resulting self-compacting concrete (SCC). Petrographic and scanning electron microscopy (SEM) investigations of the crushed NP and finely-ground NP in the concretes provide new insights into the heterogeneous fine-scale cementitious hydration products associated with basaltic ash-portland cement reactions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UM, UPCLJ, UPUK
•Acid mine drainage (AMD) is a worldwide concern in coal and metal mining.•Mine planners must predict AMD potential before disturbance.•If AMD is predicted, planners must install control measures ...such as spoil handling plans, alkaline amendment, and covers.•Treatment of AMD uses chemicals such as Ca(OH)2, CaO, NaOH, Na2CO3, and NH3. It is costly, requires equipment and facilities, and often extends for decades.•Passive treatment of AMD is effective under certain flow and acidity conditions, and includes wetlands, anoxic limestone drains, open limestone channels, and alkaline leach beds.
Acid mine drainage (AMD) occurs after mining exposes metal sulfides to oxidizing conditions. Leaching of reaction products into surface waters pollute over 20,000 km of streams in the USA alone. The coal mine permitting process requires prediction of AMD potential via overburden analysis. Where a potential exists, AMD control measures including spoil handling plans, alkaline amendment, and oxygen barriers or water covers may be required to stop or hinder AMD generation. Other AMD control technologies include injection of alkaline materials (coal ashes and limestone products) into abandoned underground mines and into buried acid material in mine backfills, remining of abandoned areas, and installation of alkaline recharge trenches. Where AMD already exists, effluent treatment is required. Active treatment includes adding alkaline chemicals such as Ca(OH)2, CaO, NaOH, Na2CO3, and NH3, but chemical treatment is costly, requires dispensing equipment and facilities, and often extends for decades. Passive treatment systems may also be employed to treat problem drainages and are effective under certain flow and acidity conditions. Such systems include aerobic and anaerobic wetlands, anoxic limestone drains, vertical flow wetlands, open limestone channels, and alkaline leach beds. This article discusses the process of AMD formation, preventative and control measures, and describes treatment methods for existing AMD discharges.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, the hydration of Portland-limestone cement (PLC) pastes and the relationship between compressive strength and porosity of PLC mortar samples containing various levels of supplementary ...cementitious materials were examined using XRD and MIP techniques. The results revealed that part of the limestone portion of Portland-limestone cements reacts with the alumina phases and produces carboaluminates, which increases compressive strength and reduces porosity. There is an optimum level of limestone corresponding to the available amount of alumina in the binder. Addition of slag or metakaolin provided more alumina, causing more limestone to participate in the hydration reaction and increasing the optimum level of limestone.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UM, UPCLJ, UPUK
46.
Carbonatite research: The African Legacy Zaitsev, Anatoly N.; Spratt, John
Journal of African earth sciences (1994),
September 2024, 2024-09-00, Volume:
217
Journal Article
Peer reviewed
Almost all igneous rocks are composed of silicate minerals; carbonatites are the main exception to this rule. They form only a minor proportion of the continental crust but are of fundamental ...scientific and economic importance. These rocks, originally described as a limestone (Kaiserstuhl, Germany) or magmatic limestone (Alnö, Sweden), were recognized in 1921 by W. C. Brøgger as a distinct magmatic rock type under the name “Karbonatite” in the Fen complex (Norway). Extensive field mapping in Africa, and particularly studies within the Chilwa Alkaline Province (Malawi), have led to the discovery of diverse intrusive and extrusive carbonatites. The latter, including the Fort Portal volcanic field in Uganda, Rufunsa Province in Zambia, and Oldoinyo Lengai volcano in Tanzania (the only volcano ever to have been seen to erupt carbonatites), have been exceptionally important in the recognition of carbonatites as truly magmatic rocks. The possibility of the existence of carbonate melts has been confirmed and shown by experimental studies of diverse carbonate systems with added volatile components (H2O, F) and alkali elements (Na, K). The study of the Oldoinyo Lengai gregoryite-nyerereite carbonatites, which are mineralogically and compositionally different from all known carbonatites worldwide, has led to long-lasting discussions about the origin of carbonatites. This includes composition of primary/parental carbonate melt, derivation of carbonatites by either liquid immiscibility or fractional crystallization, carbonatite evolution, and especially, the possible genetic relationships between alkali-rich and alkali-poor carbonatites. The rapid alteration of Oldoinyo Lengai carbonatites and their transformation to calcite carbonatite-like rocks has been proposed as the explanation for the absence of alkali-rich carbonatites in the geological past. Detailed mineralogical studies have shown that the occurrence of nyerereite is not restricted to Oldoinyo Lengai and that this mineral is now known to occur in other carbonatites (e.g., Guly, Kovdor, Oka, Kerimasi), alkaline rocks, and kimberlites (and even in diamond). This would suggest compositionally different mantle-derived melts enriched in alkali elements. In addition, carbonatite tephra has an important role in the preservation of some key paleontologic and anthropologic localities in East Africa. Despite these important discoveries, several problems related to carbonatite petrogenesis are not yet resolved. Future work is required, and carbonatites within Africa, with its key localities, may help to solve these problems.
•The Kaiserstuhl volcano is the first locality where carbonatites were described in 1783.•Field observations are the key evidences for recognition of carbonatites as magmatic rocks.•Oldoinyo Lengai is the only active volcano that erupts gregoryite-nyerereite carbonatite.•Alkali-rich carbonatites are important for the understanding of carbonatite genesis and evolution.•Existence of compositionally different carbonatite melts is confirmed by experimental studies.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Effects of a blended additive on the formation of particulate matter were studied.•The blended additive reduced mass yields of PM0.3 and PM2.5 by 29.77 % and 40.91 %.•The blended ...additive exhibited a good capture performance for PM0.3–1 (by ∼43 %).•Enhanced melting of the additive/ash particles promoted the scavenging of PM0.3–1.
Effects of a blended additive made of kaolin and limestone on the formation and emission characteristics of particulate matter (PM) was discussed for the first time. Systemic characterizations on the concentration, size distribution, elemental composition, micromorphology, specific resistivity of the PM were performed. Results revealed that the blended additive diminished the mass concentrations of the ultrafine PM and PM2.5 out of the furnace by 29.77 % and 40.91 % respectively. Interestingly, the additive also significantly reduced coarse PM, with the reduction efficiency for PM in 0.3–1 μm of ∼43 %. The additive captured the mineral vapors and thereby suppressed their migration into the ultrafine PM. Well, interactions among additive and ash promoted melting of the additive/ash particles. This improved the scavenging of both ultrafine and coarse PM via the liquidus capture mechanism. After the electrostatic precipitators (ESPs), emission of the ultrafine PM slightly increased after adding the additive because of the increasing of the specific resistivity of the ash particles and the reduction of electronegative gas (e.g., SO2) in the ESPs. The emission of total PM2.5 decreased by 32.31 % as less fly ash entering ESPs. Additionally, the leaching behaviours of heavy metals Cr, Mn, As and Pb in the fly ash were investigated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The establishment of the Late Triassic time scale has given rise to considerable controversy, particularly regarding the Rhaetian duration and the inferred absolute age models. In this respect the ...astronomical polarity time scale (APTS) established from the continental successions of the Newark Basin (eastern North America) is considered as a reference record, although its completeness is questioned. Numerous magnetostratigraphic correlation schemes have been proposed between the APTS and biostratigraphically well-constrained Tethyan marine sections. This has led to two main contrasting options: a “short” Rhaetian duration (about 4–5 myr), and a “long” one (about 8–9 myr). Astronomical calibration of the Tethyan Rhaetian and estimate of its duration is necessary to help advance this debate. We have undertaken a cyclostratigraphic analysis of a Rhaetian composite record built from four overlapping Austrian reference sections. Magnetic susceptibility variations of the 131.5 m thick record are astronomically paced by the precession and 405-kyr orbital eccentricity cycles. 405-kyr orbital tuning allows to establish a floating time scale, and thus to suggest a minimum duration of 6.69 myr of the Rhaetian stage. Given the well-established radioisotopic age of the Rhaetian-Hettangian boundary of 201.36 Ma, an age no younger than 208.05 Ma for the Norian-Rhaetian boundary can be proposed. This result will contribute to the refinement of the Late Triassic time scale, but it does not solve the long-standing debate on bio-magnetostratigraphic correlations between the continental Newark APTS and the Tethyan marine sections, nor the question of the completeness of the Rhaetian Newark Basin.
•First high resolution cyclostratigraphic study of a marine Rhaetian (Late Triassic) record.•Proposed minimal duration for the Rhaetian: 6.69 myr.•Suggested age for the Norian-Rhaetian boundary: 208.05 Ma.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Understanding the distribution of hydraulic parameters is essential for preventing water-related hazards in limestone mines. Tracer testing is a technique to elucidate the spatial heterogeneity of ...hydraulic parameters and transport properties within an aquifer. In order to estimate fluid flow characteristics and the distribution of hydrogeologic properties of the limestone aquifer, this study performed an integrated tracer-based tomographic inversion and heterogeneity characterization for the Hejing limestone mine in southwest China. The temporal moment analysis was conducted on the recorded tracer breakthrough curves (BTCs), and the swept volumes and flow geometries were estimated. Furthermore, potential flow paths for water inflow were identified by inverting the travel-time dataset via tomographic inversion using the simultaneous iterative reconstruction technique (SIRT) algorithm and the staggered grid method. The estimated high-conductivity zones estimated by travel-time tomography were consistent with areas of high mass recovery, short mean residence times, and large tracer-swept volumes. Potential paths of water inflow were confirmed to be distributed in the southeast and northeast of the limestone mine. Based on the reconstructed high-conductivity distributions, three sets of grouting curtains were designed to avoid further hazards. The groundwater levels measured during grouting demonstrated that the grouting was satisfactory. The findings of this study can provide valuable references for solving the preferential flow paths and subsurface heterogeneity in aquifers and for characterizing of subsurface heterogeneity. Future joint inversion studies based on tracer, geophysical and head data are expected to refine the outcomes on stratigraphic heterogeneity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper examines the acid resistance of cement pastes where a portion of the cement clinker is replaced with limestone (LS or calcium carbonate, CaCO3) or ground silica (GS). Specifically, the ...work is intended to better understand the acid resistance of ASTM C595 IL cement as compared with ASTM C150 cement. The performance of OPC, OPC + GS, and OPC + LS systems were tested in sulfuric acid baths where the pH was held constant at 2.0 and 3.0 using an automated setup that uses titration to add acid. The degradation of the cement paste was measured as a function of time. Thermogravimetric analysis (TGA) was used to quantify changes in the calcium hydroxide (Ca(OH)2) and calcium carbonate (CaCO3) contents of the paste. In addition, the flexural strength of the cement paste specimens was measured. Results indicate that the dissolved sulfate and calcium concentrations due to acidification were not noticeably different for the OPC + GS and OPC + LS mixtures exposed to the same pH. However, as expected, differences were observed between the samples immersed in the solution of pH∼2 and pH∼3 sulfuric acid with the lower pH corresponding to more severe deterioration. TGA results showed that Ca(OH)2 is more susceptible to acid attack than limestone as evidenced by the larger Ca(OH)2 and sulfuric acid consumption in samples immersed at pH∼2. The additional acid consumption that is beyond the consumption of Ca(OH)2 can be explained by the acid attack of other hydration products such as CSH and unreacted cement phases. This results in a significant B3B flexural strength loss for the samples immersed in a pH∼2 as compared to those in the pH∼3 solution. The results demonstrated that the performance of ASTM C595 IL cements was promising and comparable with ASTM C150 cements.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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