Limestone Samples Research Articles

Thermochemical acid fracturing of tight and unconventional rocks: Experimental and modeling investigations

The exploitation of unconventional formations requires propped hydraulic fracturing treatments. Propped fracturing is an expensive process that usually suffers from operational challenges. In this study, a new technology is proposed which targets implementing thermochemical fluids to stimulate unconventional formations. These fluids release large pressure pulses upon a reaction that creates networks of cracks along the fracture. Triggering thermochemical fluids with acid creates differential etching along the fracture surfaces due to the acid/rock dissolution. The new technology was tested experimentally through coreflooding on Indiana limestone and Kentucky sandstone samples and through breakdown pressure experiments on Eagle Ford shale samples. The breakdown pressure of the Eagle Ford shale samples was reduced from 2400 to 900 pisa using thermochemical fluids triggered with acid. It was also observed that the acid triggered thermochemical fluids could maintain the permeability of the fractures at high closure stresses due to the acid/rock dissolution. A laboratory and field-scale models were also developed in this study to understand thermochemical reactions. The laboratory-scale model could capture the pressure pulses generated experimentally and the system temperature. The field-scale model was then used to understand the thermochemical reactive transport in a hydraulic fracture. The model showed that thermochemical concentration is the most significant parameter in controlling the temperature and pressure magnitudes in the field.

Mg isotopic systematics during early diagenetic aragonite-calcite transition: Insights from the Key Largo Limestone

The seawater magnesium (Mg) isotopic composition (δ26MgSW) can be applied to quantify marine Mg cycle in Earth's history. However, reconstruction of δ26MgSW by using marine carbonate has been challenged by the large range of variation in Mg isotopic composition of carbonate (δ26Mgcarb). Such variation, on the one hand, reflects, e.g. the mineralogy, temperature, and precipitation rate dependent isotopic fractionation during Ca‑carbonate precipitation. On the other hand, the pristine seawater record could be modified in carbonate diagenesis, during which less stable carbonate minerals would spontaneously convert to more stable mineral phases. In the modern ocean with high Mg/Ca (molar) ratio (~5), aragonite precipitation is favored. However, aragonite is thermodynamically less stable than low-Mg calcite at ambient surface environment, resulting in the spontaneous transition from aragonite to low-Mg calcite in the earliest stage of diagenesis (i.e. the aragonite-calcite transition). As a common process in the modern ocean, Mg isotopic fractionation in aragonite-calcite transition may provide valuable constraints on the variation of δ26Mgcarb. In this study, we measured Mg isotopic compositions of Pleistocene Key Largo Limestone (Florida), which has been experiencing the aragonite-calcite transition during early diagenesis. The Key Largo Limestone samples consist of a mixture of calcite and aragonite. δ26Mg of aragonite (δ26Mgarag) shows higher and more stable values, while calcite has lower yet more variable Mg isotopes (δ26Mgcal). We suggest a model conceptualizing a water-film attached to the mineral surface, in which the aragonite-calcite transition initiates with aragonite dissolution and the Mg exchange with external fluid can be variable, followed by Mg isotopes fractionate during low-Mg calcite precipitation. In this model, δ26Mgcal is controlled by (1) the chemical composition of water-film, which is dependent on the mineralogical composition of aragonite (i.e. Mg content and δ26Mgarag), the composition of external fluid (i.e. fresh water, seawater, or mixed fresh water and seawater), and the mixing ratio between dissolved aragonite and external fluid, and (2) the isotopic fractionation during calcite precipitation. Because the isotopic fractionation in calcite is sensitive to the rate of calcite precipitation that is dependent on the calcite saturation state of solution. Therefore, δ26Mgcal could be highly heterogeneous depending on the aragonite dissolution and calcite precipitation processes, further complicating the interpretation of carbonate data. Thus, the process-controlled Mg isotopic fractionation should be taken into consideration when reconstructing δ26MgSW by using carbonate sediments/rocks.

A study of suitability of limestone for fluoride removal by phosphoric acid-crushed limestone treatment

Limestone samples collected from different locations have been characterised using IR spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and Brunauer-Emmett-Teller analysis and correlated with their fluoride removal abilities by phosphoric acid (PA)-crushed limestone treatment (PACLT). The effects of varying initial fluoride [F]0 and initial phosphoric acid [PA]0 concentrations, contact time and coexisting anions on fluoride removal and pH of treated water have been studied. PHREEQC was used to analyse the mechanism of fluoride removal and effects of impurities in limestone on the defluoridation process. Three of the limestone samples were found suitable for PACLT, with the treated water conforming to WHO guideline. With all limestone samples, defluoridation increased with increasing [PA]0 and decreasing [F]0. Fluoride removal and pH of treated water attained stability within 3 h. The influence of coexisting anions on fluoride removal was low for all limestone samples and followed the order sulfate > chloride > nitrate. The surface area and total pore volume above 2.55 m2/g and 0.0094 cm3/g respectively, and density below 2.68 g/cm3 are required for a limestone sample for defluoridation from 10 mg/L [F]0 to 1.5 mg/L with 0.68 mM [PA]0. PHREEQC analysis suggests the mechanism of defluoridation to be a combination of precipitation and adsorption, and that the presence of acidic metal oxides in limestone, viz., Fe2O3 and Al2O3 contributes in fluoride removal and lowers the pH of treated water from the predicted equilibrium pH of 7.93 in presence of PA. The results may be useful for predicting suitability of limestones for PACLT.

Reactivity of secondary phases in weathered limestone using isotopic tracers (D and 18O)

For a long time, limestone has been massively used in stone building and monuments because of its easy extraction and common presence in the landscape. On ancient monuments, mostly built in urban areas, it is exposed to urban-borne pollutants responsible for specific alteration mechanisms and weathering kinetics. Especially, the dissolution of calcite and the precipitation of new phases will affect the limestone pore network, modify the stones capillary properties, and influence the further alteration. In order to better understand these processes, an altered limestone sample from 'Tribunal Administratif' (TA) in Paris was studied. The main secondary phase was found to be syngenite, which can be explained by the location of the sample close to the soil, a potential source of K (fertilizers). This phase is more soluble than gypsum that is commonly found on altered limestone. In order to assess the reactivity of the system (limestone and new phases), oxygen and hydrogen isotopes were used to trace the transfer of water (D218O) and identify the location of the reactive areas (susceptible to alteration). For that, TA samples were exposed in a climatic chamber to relative humidity (RH) cycles (25% RH for 2.5 days and 85% RH for 4.5 days) for 2 months with a D218O vapor to simulate alteration occurring in conditions sheltered from the rain. Results have shown that the water vapor easily circulates deep in the sample and reacts preferentially with syngenite the most reactive phase (compared with calcite and quartz). This phase could evolve in gypsum when exposed to an environment different from the one resulting in its formation.

Assessment of reliability of natural limestone cladding material

The goal of research was identifying possible application of natural limestone samples as a cladding material for facades by means of evaluation of physical and chemical properties and inclusive of external aggressive factors. As the object of research, there were used the samples of naturally occurring limestone, of Afanasyevskiy deposit, Moscow region, designated for face slabs manufacturing of ventilated facades. In compliance with the All-Union Standard (GOST) 30629-2011, the samples have been exposed to the following testing, namely determination of mean density and true specific gravity, kg/m3, pore-saturation coefficient with water; ultimate compressive strength, MPa, water fastness (lowering of compressive strength in the water-saturated state, %); ultimate bending strength, MPa; freeze-thaw resistance, cycles, acid fastness. Chemical (elemental) analysis was carried out by the method of scanning electron microscope investigation. The tests were implemented on the electronic microscope FEI Quanta 200. The microscope is equipped by X-ray spectrometer that is designated for elemental analysis (EDAX). Both masonry units have satisfactory freeze-thaw resistance. As far as acid fastness is concerned, only marmorized limestone has demonstrated satisfactory performance. Thus, only the second group of samples presented by marmorized limestone could be recommended as a reliable material for façade cladding.

Origin of the Stone Varieties used in the Cultural Heritage Buildings of Lumbarda, Island of Korčula, Croatia

The aim of this paper is to determine the possible origin of the stone used for the construction in five cultural heritage buildings dating from the different historical epochs in Lumbarda, on the island of Korcula, Croatia. Micropetrographic determination of limestone samples taken from the Roman Villae Rusticae, the old apse of St Križ Church, the Venetian Tower, the Bishop’s Summer House and St Barbara Church, was done. For comparison, micropetrographic analysis on the rock samples taken from two abandoned quarries near Lumbarda: the Brendana Quarry in Lumbarda and Gornja Spilja Quarry at Sutvara islet, was also made. After comparison of their petrographic characteristics, it was concluded that the stone for construction of the Roman Villae Rusticae and St Križ Church was quarried in Brendana Quarry, while for the other three investigated buildings the material was quarried on Sutvara islet in Gornja Spilja Quarry.Accordingly, petrographic analysis proved to be useful tool for determination of the origin of stone and useful for restoration purposes.

REE Characteristics of Lower Cretaceous Limestone Succession in Gümüşhane, NE Turkey: Implications for Ocean Paleoredox Conditions and Diagenetic Alteration

Trace and rare earth elements (REEs) are considered to be reliable indicators of chemical processes for the evolution of carbonate systems. One of the best examples of ancient carbonate successions (Berdiga Formation) is widely exposed in NE Turkey. The Lower Cretaceous limestone succession of Berdiga Formation may provide a case study that reveals the effect of ocean paleoredox conditions on diagenetic alteration. Measurement of major, trace and REEs was carried out on the Lower Cretaceous limestones of the Berdiga Formation, to reveal proxies for paleoredox conditions and early diagenetic controls on their geochemistry. Studied micritic limestone microfacies (MF-1 to MF-3) indicate deposition in the inner platform to a deep shelf or continental slope paleoenvironment during the Hauterivian-Albian. The studied limestone samples mainly exhibit low Mg-calcite characteristics with the general chemical formula of Ca98.35–99.34Mg0.66–1.65(CO3). They are mostly represented by a diagnostic REE seawater signature including (1) slight LREE depletion relative to the HREEs (ave. 0.72 of Nd/YbN and ave. 0.73 of Pr/YbN), (2) negative Ce anomalies (Ce/Ce* = 0.38–0.81; ave. 0.57), (3) positive La anomaly (La/La* = 0.21–3.02; ave. 1.75) and (4) superchondritic Y/Ho (ave. 46.26). Studied micritic limestones have predominantly low Hf (bdl to 0.5 µg/g), Sc (bdl to 2 µg/g) Th (bdl to 0.9 µg/g) contents suggesting negligible to minor shale contamination. These findings imply that micritic limestones faithfully record chemical signals of their parental and diagenetic fluids. The succession also exhibits high ratios of Eu/Eu* (1.01–1.65; ave. 1.29 corresponding to the positive Eu anomalies), Sm/Yb (1.26–2.74; ave. 1.68) and La/Yb ratios (0.68–1.35; ave. 0.9) compared to modern seawater and wide range of Y/Ho ratios (29.33–70.00; ave. 46.26) which are between seawater and hydrogenetic Fe-Mn crusts. Several lines of geochemical evidence suggest water-rock interaction between parental seawater and basaltic rocks at elevated temperatures triggered by hydrothermal activity associated with Early Cretaceous basaltic magma generation. The range of Ce/Ce* values is suggestive of mostly oxic to dysoxic paleoceanographic conditions, with a sudden change to dysoxic conditions (Ce/Ce* = 0.71–0.81), in the uppermost part of the MF-1. This is followed by an abrupt deepening paleoenvironment with a relative increase in the oxic state of the seawater and deposition of deeper water sediments (MF-2 and MF-3) above a sharp transition. The differences in microfacies characteristics and foraminifera assemblage between MF-1 and overlying facies (MF-2 and MF-3) may also confirm the change in paleoceanographic conditions. Therefore, REEs data obtained from studied limestones have the potential to contribute important information as to regional paleoceanographic conditions of Tethys during an important period in Earth history.

Estimation of microfracture porosity in deep carbonate reservoirs based on 3D rock-physics templates

Carbonate reservoirs in the S area of the Tarim Basin (China) are ultradeep hydrocarbon resources, with low porosity, complex fracture systems, and dissolved pores. Microfracturing is a key factor of reservoir connectivity and storage space. We have performed measurements on limestone samples, under different confining pressures, and we used the self-consistent approximation model and the Biot-Rayleigh theory of double porosity to study the microfractures. We have computed the fluid properties (mainly oil) as a function of temperature and pressure. Using the dependence of seismic [Formula: see text] on the microfractures, a multiscale 3D rock-physics template (RPT) is built, based on the attenuation, P-wave impedance, and phase velocity ratio. We estimate the ultrasonic and seismic attenuation with the spectral-ratio method and the improved frequency-shift method, respectively. Then, calibration of the RPTs is performed at ultrasonic and seismic frequencies. We use the RPTs to estimate the total and microfracture porosities. The results indicate that the total porosity is low and the microfracture porosity is relatively high, which is consistent with the well log data and actual oil production reports. This work presents a method for identification of deep carbonate reservoirs by using the microfracture porosity estimated from the 3D RPT, which could be exploited in oil and gas exploration.

Solid state and phase transformation mechanism of kaolin sintered with limestone for alumina extraction

The present work aims to investigate the effects of the solid-state thermal reactions at different sintering temperatures on the phase transformation mechanisms and the microstructural changes, the self-disintegration mechanism as well as the efficiency of alumina percent recovery during alumina extraction from kaolin by the lime-sinter process. The sinters were produced at different temperatures within the range 800 °C - 1400 °C then subjected to leaching process (at the optimum dissociation of 1:5 solid : liquid ratio) by using sodium carbonate solutions (120 g/L) which finally were given to the alumina-pregnant solution. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used for characterizing the transformational changes resulted during the thermal reactions between the sintered mineral components in the raw kaolin and limestone samples (i.e., kaolinite and calcite). Microstructural and textural changes of the obtained sinters and sludges were characterized by means of X-ray diffractometry (XRD/XRF), scanning electron microscopy (SEM/EDX) and particle size granulometry. The results indicated that the sintering temperature at 1360 °C was the optimum for inducing of the solid-state reaction between the clay and carbonate components with enhancement of alumina productivity by the highest recovery (80.49%). At this superlative sintering condition, the kaolinite was dehydroxylated and transformed into metakaolinite while the calcite was decomposed into calcium oxide, then they reacted together forming to the calcium aluminates that are considered as the highly effective and generative precursor phases in the alumina extraction. Moreover, the obtained sludges were obviously exhibited morphological changes with size enlargements during the leaching process due to the formation of calcium carbonate particles that agglomerated at the surfaces of the insoluble sludge particles.

Aggregate Suitability of the Late Permian Wargal Limestone at Kafar Kot Chashma Area, Khisor Range, Pakistan

This study was carried out for the investigation of the Late Permian Wargal limestone at Kafar Kot Chashma area, Khisor Range to determine its suitability as an aggregate that is used in road construction and civil structures with the help of geological engineering testing. The results of geological engineering testing of Wargal limestone samples show the tolerable values of all standard engineering parameters including the Loss Angles Abrasion value (23.37%), Aggregate impact (16.8%), Crushing value 13.1%, Unit weight 1.67, Soundness (1.007%), Specific gravity (2.70), Water Absorption (0.48%), Flakiness Index (6.5%), Elongation value (7.1%), Coating of bitumen (> 95%), stripping of bitumen (<5%), California Bearing Ratio (CBR) value (93.6%), Maximum Dry Density 2.307g/c and Optimum Moisture Content (5.79%). As per different International and National Standards like AASHTO, ASTM, BS and NHA, the mentioned results of various engineering tests were within the tolerable limits. The petrography of the selected samples of the Late Permian Wargal limestone revealed very minor value of quartz (0.5%), hematite/limonite (0.6%) and clay content 1.0% showing the insignificant threat of ASR. The values of dolomite are limited to (1%) which shows that there is no ACR reaction with ordinary Portland cement. The results of geological and engineering parameters of the study area strongly suggest its suitability as a potential aggregate (i.e. for the base course, subbase course, cement concrete and asphalt) in the road construction.

Development of a New Experimental Technique for Dynamic Fracture Toughness Measurement of Rocks using Drop Weight Test

The dynamic fracture characteristics of rock specimens play an important role in analyzing the fracture issues such as blasting, hydraulic fracturing, and design of supports. Several experimental methods have been developed for determining the dynamic fracture properties of the rock samples. However, many used setups have been manufactured for metal specimens, and are not suitable and efficient for rocks. In this work, a new technique is developed to measure the dynamic fracture toughness of rock samples and fracture energy by modifying the drop weight test machine. The idea of wave transmission bar from the Hopkinson pressure bar test is applied to drop weight test. The intact samples of limestone are tested using the modified machine, and the results obtained are analyzed. The results indicate that the dynamic fracture toughness and dynamic fracture energy have a direct linear relationship with the loading rate. The dynamic fracture toughness and dynamic fracture energy of limestone core specimens under the loading rates of 0.12-0.56kN/µS are measured between 9.6-18.51MPa√m and 1249.73-4646.08J/m2, respectively. In order to verify the experimental results, a series of numerical simulation are conducted in the ABAQUS software. Comparison of the results show a good agreement where the difference between the numerical and experimental outputs is less than 4%. It can be concluded that the new technique on modifying the drop weight test can be applicable for measurement of the dynamic behavior of rock samples. However, more tests on different rock types are recommended for confirmation of the application of the developed technique for a wider range of rocks.

Diagenesis processes impact on the carbonate Mishrif quality in Ratawi oilfield, southern Iraq

This paper aims to identify the impact of the diagenesis processes on the carbonate reservoir’s characteristics (porosity and permeability) of the Mishrif Formation. A detailed investigation of available core samples and microscopic study of more than 200 thin sections of the core limestone samples were examined from two wells (Ratawi-2 and Ratawi-5) in Ratawi oilfield, which are located in the Basrah Governorate, southern Iraq which revealed that different diagenetic parameters influence the reservoir quality in Mishrif Formation. Diagenetic features and four identified diagenetic environments that have affected the carbonate rocks in the Ratawi oilfield were the meteoric vadose, meteoric phreatic, marine phreatic and mixing zone. Petrographic examinations revealed that diagenesis varies in intensity from microfacies to another, micritization, dissolution, cementation, compaction, neomorphism, dolomitization and authigenic minerals (pyrite) are the dominant diagenetic parameters which are identified in the current field of study. Among all the observed diagenetic features, dissolution and neomorphism (recrystallization) were formed as a result of subaerial exposure during the meteoric diagenesis and contribute to porosity enhancement and reservoir quality. The cementation (calcite and dolomite), compaction, dolomitization, and micritization have a negative impact on the reservoir behavior, through reducing porosity and permeability that led to reducing reservoir quality. Other processes such as authigenic minerals (pyrite) did not have strong effects on reservoir quality. Based on the genetic classification of porosity, most of the porosity within Mishrif Formation is a combination of depositional, diagenetic and fracturing. The diagenetic porosity is the far more dominant types of porosity such as vuggy, intraparticles, fractured and moldic, implying that carbonate Mishrif reservoir is the type of diagenetic reservoirs.

First record of organic-walled microfossils from the Tonian Shiwangzhuang Formation of the Tumen Group in western Shandong, North China

Organic-walled microfossils offer important information on the biospheric evolution in pre-Cryogenian and provide biostratigraphic implications for many Proterozoic fossiliferous sequences that are poorly age constrained for the lack of reliable radiometric date. Recently, macroscopic carbonaceous compression fossils have been reported for the first time from the Tonian Shiwangzhuang Formation of the Tumen Group in western Shandong, North China. However, organic-walled microfossils have never been discovered from this formation up till now. To improve our knowledge about Proterozoic biodiversity in North China, we conducted a micropaleontological survey on the argillaceous limestone samples of the Shiwangzhuang Formation, which also contain macroscopic carbonaceous compression fossils, from the Baishicun section in Anqiu, western Shandong, North China. Our investigation shows that the Shiwangzhuang microfossil assemblage is dominated by smooth-walled sphaeromorphic acritarchs and cyanobacterium-like filaments and relatively low abundance of other acritarchs, including 16 taxa, such as Polysphaeroides filliformis, Ostiana microcystis, Simia annulare, ?Jacutianema sp., Arctacellularia tetragonala, Pellicularia tenera, Polythrichoides lineatus, and Navifusa actinomorpha. The Shiwangzhuang organic-walled microfossil assemblage, although consisting of long-ranging and not age diagnostic taxa, is consistent with a Tonian age suggested by macroscopic carbonaceous compression fossils, including the Chuaria-Tawuia and Sinosabellidites-Protoarenicola-Pararenicola assemblages, revealed from the same fossiliferous horizon of the Shiwangzhuang Formation and by organic-walled microfossil assemblage, including the late Mesoproterozoic to Tonian index fossil Trachyhystrichosphaera aimika, from the underlying Tongjiazhuang Formation. However, it is also worth noting that a Cryogenian or Ediacaran age cannot be completely excluded based just on the Shiwangzhuang microfossils because of their limited biostratigraphic utility.

Shear Characteristics and Failure Mode of Hard Brittle Marl with Parallel Discontinuous Structural Plane

Engineering practice shows that the failure of rock bridges between structural planes which makes the discontinuous structural plane evolve into a continuous sliding fracture plane leads the instability of many slopes. In order to further understand the shear failure mechanism of rock mass with discontinuous structural plane, the direct shear tests under different normal pressures were carried out on the hard brittle limestone samples with different structural plane dip angles. The test results show that the fracture surface of rock bridge is mainly tensile failure, while both sides of the fracture surface are mainly shear failure. Both two flanks and the middle fracture surface show that both ends of the fracture surface are mainly shear failure, while the middle of the fracture surface is mainly tensile failure. When σ is large and α is small, the rock is mainly shear failure. When σ is large and α is large, or σ is small and α is small, the rock is mainly tension-shear mixed failure. When σ is small and α is large, the rock is mainly tensile failure. The failure mode of the sample may vary with the change of the structural plane inclination and normal stress. But overall speaking, it can be summarized as five typical failure modes that are STS–STS–STS, STS–T–STS, S–STS–S, S–S–S and T–T–T. The peak shear stress of the sample increases with the increase in normal stress, and decreases first and then increases with the increase in the dip angle of the structural plane. When α = 0°, the peak shear stress is the largest; when α = 45°, the peak shear stress is the smallest. When α is small, the shear strength of the sample is mainly affected by the inclination angle θ of the rock bridge. When α is large, the shear strength of the sample is mainly affected by the length L of the rock bridge.

CARACTERÍSTICAS FÍSICAS, QUÍMICAS E FÍSICO-QUÍMICAS DE CALCÁRIO EXTRAIDO DO SULDOESTE DA REGIÃO AMAZÔNICA

O presente trabalho tem por objetivo, analisar a concentração de cálcio, magnésio, Poder de Neutralização, Reatividade e Poder Relativo de Neutralização Total em calcário da região Norte. Foram determinados os teores totais de óxidos de cálcio (CaO) e magnésio (MgO) por volumetria utilizando o EDTA (ácido etilenodiaminotetracético) como agente complexante, solução tampão em pH = 10, e como indicador complexométrico, o corante orgânico Negro de eriocromo T. As análises foram realizadas em dez amostras de calcários, em que cada amostra corresponde a jazidas distintas. As amostras encontram-se dentro dos parâmetros que as classificam como calcário. Na classificação pelo teor de MgO, constatou-se que, das dez amostras analisadas, todas podem ser classificadas como calcário dolomítico, além de apresentar as quantidades mínimas de PRNT admitidas pela legislação.

Analysis of measured thermally induced rock deformation

Abstract In order to improve the accuracy of laboratory measurement of thermally induced rock deformation in a thermo-triaxial rock testing apparatus, the present study investigated the factors offsetting the readouts of the extensometers as applied for this measurement. Via conducting a calibration experiment heating an aluminum sample from 30 °C to 60 °C, it was observed that the expansion in the metallic parts built in the extensometers offset the measured sample deformation. Moreover, the heterogeneous temperature distributed in the extensometer-amplifier circuit yielded a varying pre-amplification coefficient. Such coefficient further reduced the measured deformation in the sample setup. A method was then developed quantifying the time (heating path)-dependent evolution of the pre-amplification coefficient and the reading offsets due to the expansion in the metallic parts. The applicability of this method was exemplified by correcting the deformation in a limestone sample as measured in a drained heating test. The so obtained coefficient of thermal expansion of the tested limestone was in accordance with the theoretical bounds, which validated the present correction method. Hence, our study could be referenced by laboratory investigations on thermally induced rock deformation using similar experimental setup and following defined heating paths.

Thermoluminescence Studies of β and γ-Irradiated Geological Materials for Environment Monitoring.

In the present report, thermally stimulated luminescence (TSL) of quartz and limestone samples irradiated with β and γ-rays has been investigated. Herein the formation of trap depths and calculation of kinetic parameters of β and γ - irradiated quartz and limestone samples were studied through thermoluminescence (TL) glow curve analyses. The quartz and limestone samples were collected from various sites of Chhattisgarh (Patharia and Dalli-Rajhara mines). The collected raw samples were annealed at 400°C. The phase formation of collected samples is confirmed by X-ray diffraction studies. The grain sizes of the samples are determined by using Debye-Scherrer formula. TL glow curves of the collected samples were recorded for various doses of β and γ-rays. Kinetic parameters such as order of kinetics frequency factor and trap depth were calculated by employing CGCD methods. A comparative study on the TL properties of the geological materials under β and γ-irradiation was done. The trap model analysis was executed to determine the nature of traps responsible for dominant TL peaks of β and γ-irradiated limestone and quartz samples.

<p><strong><em>Lecanicillium gracile </em></strong><strong>(Cordycipitaceae), a new species isolated from mineral building materials</strong></p>

Lecanicillium isolates were obtained from deteriorated limestone and plaster inside historic buildings in Russia. Phylogenetic analysis of ITS and TEF1a sequence data coupled with morphological observations showed that three of the Lecanicillium isolates represent a new species, which we herein describe as Lecanicillium gracile. Lecanicillium gracile is morphologically similar to the closely related species, such as L. coprophilum, L. restrictum and L. testudineum, but differs by producing phialides secondarily on the initial phialides. Two another Lecanicillium isolates grouped with L. testudineum and L. coprophilum and hence we leave those isolates unidentified. In addition, we have isolated Parengyodontium album from deteriorated indoor mineral surfaces, which is phylogenetically close to Lecanicillium and produces zigzag-shaped tips of conidiogenous cells. Given high CFU counts of the isolated species in limestone and/or plaster samples and their physiological traits, we conclude that they are involved in deterioration of stone material inside historic buildings and deserve attention during restoration works.

Sedimentologi Batugamping Formasi Jayapura di Sepanjang Lintasan Dewarebru, Mamei-Waibron, Jayapura

The Pleistocene of the Jayapura Formation limestones well cropped out at Dewarebru Section, Mamey-Waybron, Jayapura Regency. Detailed descriptions of rock outcrops and petrography analysis of selected limestone samples is used to find out the limestone sedimentology characters. This Jayapura limestone was divided onto four limestone facies, including lithoclastic rudstone, bioclastic packstone, bioclastic grainstone and bioclastic wackesone rock facies. The rocks was deposited in a fore slope talus forming submarine alluvial fan, furthermore the rocks was deposited in a local slope on the back reef environment.Keywords: Limestone, petrography, stratigraphy, sedimentology, Jayapura

Inversion of polyphase calcite-twin data for deviatoric stress tensors: 2. Application to the Huangling Dome, northern South China

The north-trending Huangling Dome, located on the northern margin of the reactivated Yangtze Platform, provides an appropriate place to understand the complexity of intraplate deformation of the South China continent since the Early Mesozoic. In this study, palaeostress analysis using calcite twins was carried out to address the deformation mechanism of the dome, poorly understood at present. Ten limestone samples and three marble samples were collected from the platform cover on the eastern and western flanks and the core basement, measured under the universal stage, and inverted for stress analysis using our recently proposed method. All the stress estimates for the samples were classified into two layer-parallel shortening (LPS) subsets and two non-LPS subsets. They represent NW–SE compression, NE–SW compression, N–S compression, and N–S or E–W extension, respectively, in correspondence to principal tectonic events since the Early Mesozoic. They do not verify existing explanations about the genesis of the dome, for example, extrusion-induced E–W compression and differential uplift-related E–W extension. A new formation model was therefore proposed: under the nearly N–S compression, the dome initiates as an E–W trending brachy anticline and, owing to basement inheritance and variation of regional shortening, gains the current configuration.