Chemical Composition Of Rocks Research Articles

Pore-scale Imaging and Characterization of Hydrocarbon Reservoir Rock Wettability at Subsurface Conditions Using X-ray Microtomography.

In situ wettability measurements in hydrocarbon reservoir rocks have only been possible recently. The purpose of this work is to present a protocol to characterize the complex wetting conditions of hydrocarbon reservoir rock using pore-scale three-dimensional X-ray imaging at subsurface conditions. In this work, heterogeneous carbonate reservoir rocks, extracted from a very large producing oil field, have been used to demonstrate the protocol. The rocks are saturated with brine and oil and aged over three weeks at subsurface conditions to replicate the wettability conditions that typically exist in hydrocarbon reservoirs (known as mixed-wettability). After the brine injection, high-resolution three-dimensional images (2 µm/voxel) are acquired and then processed and segmented. To calculate the distribution of the contact angle, which defines the wettability, the following steps are performed. First, fluid-fluid and fluid-rock surfaces are meshed. The surfaces are smoothed to remove voxel artefacts, and in situ contact angles are measured at the three-phase contact line throughout the whole image. The main advantage of this method is its ability to characterize in situ wettability accounting for pore-scale rock properties, such as rock surface roughness, rock chemical composition, and pore size. The in situ wettability is determined rapidly at hundreds of thousands of points. The method is limited by the segmentation accuracy and X-ray image resolution. This protocol could be used to characterize the wettability of other complex rocks saturated with different fluids and at different conditions for a variety of applications. For example, it could help in determining the optimal wettability that could yield an extra oil recovery (i.e., designing brine salinity accordingly to obtain higher oil recovery) and to find the most efficient wetting conditions to trap more CO2 in subsurface formations.

Computational approach to integrate 3D X-ray microtomography and NMR data

Nowadays, most of the efforts in NMR applied to porous media are dedicated to studying the molecular fluid dynamics within and among the pores. These analyses have a higher complexity due to morphology and chemical composition of rocks, besides dynamic effects as restricted diffusion, diffusional coupling, and exchange processes. Since the translational nuclear spin diffusion in a confined geometry (e.g. pores and fractures) requires specific boundary conditions, the theoretical solutions are restricted to some special problems and, in many cases, computational methods are required. The Random Walk Method is a classic way to simulate self-diffusion along a Digital Porous Medium. Bergman model considers the magnetic relaxation process of the fluid molecules by including a probability rate of magnetization survival under surface interactions. Here we propose a statistical approach to correlate surface magnetic relaxivity with the computational method applied to the NMR relaxation in order to elucidate the relationship between simulated relaxation time and pore size of the Digital Porous Medium. The proposed computational method simulates one- and two-dimensional NMR techniques reproducing, for example, longitudinal and transverse relaxation times (T1 and T2, respectively), diffusion coefficients (D), as well as their correlations. For a good approximation between the numerical and experimental results, it is necessary to preserve the complexity of translational diffusion through the microstructures in the digital rocks. Therefore, we use Digital Porous Media obtained by 3D X-ray microtomography. To validate the method, relaxation times of ideal spherical pores were obtained and compared with the previous determinations by the Brownstein-Tarr model, as well as the computational approach proposed by Bergman. Furthermore, simulated and experimental results of synthetic porous media are compared. These results make evident the potential of computational physics in the analysis of the NMR data for complex porous materials.

Improving Gross Count Gamma-Ray Logging in Uranium Mining With the NGRS Probe

AREVA Mines and the Nuclear Measurement Laboratory of CEA Cadarache are collaborating to improve the sensitivity and precision of uranium concentration measurement by means of gamma-ray logging. The determination of uranium concentration in boreholes is performed with the Natural Gamma Ray Sonde (NGRS) based on a NaI(Tl) scintillation detector. The total gamma count rate is converted into uranium concentration using a calibration coefficient measured in concrete blocks with known uranium concentration in the AREVA Mines calibration facility located in Bessines, France. Until now, to take into account gamma attenuation in a variety of boreholes diameters, tubing materials, diameters and thicknesses, filling fluid densities, and compositions, a semiempirical formula was used to correct the calibration coefficient measured in Bessines facility. In this paper, we propose to use Monte Carlo simulations to improve gamma attenuation corrections. To this purpose, the NGRS probe and the calibration measurements in the standard concrete blocks have been modeled with Monte Carlo N-Particles (MCNP) computer code. The calibration coefficient determined by simulation 5.3 $\text{s}^{-1}\cdot \text {ppm}_{U}^{-1}$ with 10% accuracy is in good agreement with the one measured in Bessines (and for which no uncertainty was provided), 5.2 $\text{s}^{-1}\cdot \text {ppm}_{U}^{-1}$ . The calculations indicate that the concrete blocks used for measuring the calibration coefficients measured in Bessines are underestimated by about 10%. Based on the validated MCNP model, several parametric studies have been performed. For instance, the rock density and chemical composition proved to have a limited impact on the calibration coefficient. However, gamma self-absorption in uranium leads to a nonlinear relationship between count rate and uranium concentration beyond approximately 1% of uranium weight fraction, the underestimation of the uranium content reaching more than a factor 2.5 for a 50% uranium weight fraction. Parametric studies have also been performed with different tubing materials, diameters, and thicknesses, as well as different borehole filling fluids representative of real measurement conditions, in view to validate gamma attenuation corrections based on the semiempirical formula. In addition, a multilinear analysis approach has been tested to further improve accuracy on uranium concentration determination, leading to only a few percent uncertainties on a large range of configurations.

Improving gross count gamma-ray logging in uranium mining with the NGRS probe

AREVA Mines and the Nuclear Measurement Laboratory of CEA Cadarache are collaborating to improve the sensitivity and precision of uranium concentration measurement by means of gamma ray logging. The determination of uranium concentration in boreholes is performed with the Natural Gamma Ray Sonde (NGRS) based on a NaI(Tl) scintillation detector. The total gamma count rate is converted into uranium concentration using a calibration coefficient measured in concrete blocks with known uranium concentration in the AREVA Mines calibration facility located in Bessines, France. Until now, to take into account gamma attenuation in a variety of boreholes diameters, tubing materials, diameters and thicknesses, filling fluid densities and compositions, a semi-empirical formula was used to correct the calibration coefficient measured in Bessines facility. In this work, we propose to use Monte Carlo simulations to improve gamma attenuation corrections. To this purpose, the NGRS probe and the calibration measurements in the standard concrete blocks have been modeled with MCNP computer code. The calibration coefficient determined by simulation, 5.3 s-1.ppmU-1 ± 10%, is in good agreement with the one measured in Bessines, 5.2 s-1.ppmU-1. Based on the validated MCNP model, several parametric studies have been performed. For instance, the rock density and chemical composition proved to have a limited impact on the calibration coefficient. However, gamma self-absorption in uranium leads to a nonlinear relationship between count rate and uranium concentration beyond approximately 1% of uranium weight fraction, the underestimation of the uranium content reaching more than a factor 2.5 for a 50 % uranium weight fraction. Next steps will concern parametric studies with different tubing materials, diameters and thicknesses, as well as different borehole filling fluids representative of real measurement conditions.

Mycobiota of the disused ore mine of Marcinków in Śnieżnik Masiff (western Poland)

Marcinkow (Lower Silesia, Śnieznik Masiff, south-western Poland) has been a well-known mining centre since the mid-15th century. Mineral extraction ended in 1949 with the ores of Pb, Ag, Cu and occasionally Au, U or graphite mined there. The mine is surrounded by metamorphic graphite and mica schist. It is not open to the public and no bats have been recorded living in. The aim of this study was the mycological analysis of the air, the rock surface and the water of the disused ore mine of Marcinkow. Additionally, the chemical composition of rocks and water, and microclimate conditions of the adit were determined. Fungi were identified using a combination of phenotypic and molecular methods. Six taxa of fungi were cultured from the indoor air samples of the adit, whereas the outdoor air samples contained only five taxa. On the other hand, nine taxa were isolated from both the rocky walls and the water. The Aspergillus group was present only on the rocks and in the water, whereas Cladosporium herbarum, Dumontinia tuberosa, Epicoccum nigrum, Hirsutella sp., were found exclusively in the air. The mycobiota found in the ore mine were mostly similar to those recorded in other mines and natural caves. However, it should be noted that the internal microclimate and chemical compounds of the rocks.

Influence of Rock Chemical Composition in Microwave Heating and Decontamination of Drill Cuttings

Drill cuttings generated by oil and gas drilling process are incorporated into the drilling fluid to ensure an efficient drilling and solids removal. The drilling rigs have a separation system accountable for separating drill cuttings and drilling fluids. Microwave drying is a new technology of separation that has been studied as an alternative to the currently drill cuttings dryer used. The results obtained in preliminary studies showed that this microwave drying is sensitive to different oxides presents into the rock. Thus, this study aimed to describe the microwave heating kinetics of some rocks in order to verify the interaction of oxides with electromagnetic waves. For this, the oxide contents of the rocks were determined by X-ray Fluorescence and different rocks were heated in a microwave heating unit. The results showed that the relationship between the temperature and heating time is exponential and depends on the rock oxide contents. It was found that the iron oxides may be unstable at microwave and rocks with high levels of magnesium oxides and sulfates tend to be good absorbers of microwave. Rocks containing high levels of calcium, silicon, titanium, barium and chloride (NaCl) are not good absorbers of microwave. It was also noted that faster solid heating, lesser the efficiency of microwave drying.

GEOLOGIA E GÉNESE DOS DEPÓSITOS DE CAULIM FLORESTA E CAMBUÍ (FORMAÇÃO CAMPO ALEGRE - SC) - 2. PETROQUÍMICA E MODELO GENÉTICO

The wide compositional band overlap of the Cambui and Floresta mines argillaceous facies preveni the use of chemical composition as indicator of their origins. Despite this fact, the main ore types have chemical peculiarities, and the disseminated green ore is andesitic in composition, the disseminated white ore from the Cambui mine is rhyolitic and the disseminated white ore from Floresta Mine is dacitic. Rock chemical composition also show that besides the low depth ore evolution line represented by the argillaceous facies related to fractures, stockworks veins and supergenic zones, displayed by mineralogy, with strong K 2 O content variations, another evolution line exists, developed at higher depths, with constant or very small K 2 O variations. This high depth hydrothermal alteration changes the rhyolite composition, strongly leaching SiO 2 and moderately leaching K 2 O, Na 2 O, Fe 2 O 3 , CaO and MgO. These chemical changes transform rhyolites in argilised rocks with kaolin and mica. The hydrothermalism developed according to these two lines have changed rocks making easy the later action of supergenic alteration and weathering, responsible for chemical changes that develop up today. It is proposed a genetic model in which hydrothermal alteration has developed in a proximal volcanogenic environment. If hydrothermalism attained the surface, supergenic alterations occurred simultaneously with the hydrothermal alterations. On the contrary, weathering started and continues until today, only after the exhumation of the hydrothermalized rocks. At least three other models could explain the genesis of Cambui and Floresta kaolin deposits: the volcanic porphyry copper model, the volcanogenic high sulfidation model and the autometassomatic model.

Ferromanganese carbonate metasediments of the Sob area, Polar Urals: Bedding conditions, composition, and genesis

The paper presents the results of study of ferromanganese carbonate rocks in the Sob area (Polar Urals), which is located between the Rai-Iz massif and the Seida–Labytnangi Railway branch. These rocks represent low-metamorphosed sedimentary rocks confined to the Devonian carbonaceous siliceous and clayey–siliceous shales. In terms of ratio of the major minerals, ferromanganese rocks can be divided into three varieties composed of the following minerals: (1) siderite, rhodochrosite, chamosite, quartz, ± kutnahorite, ± calcite, ± magnetite, ± pyrite, ± clinochlore, ± stilpnomelane; (2) spessartite, rhodochrosite, and quartz, ± hematite, ± chamosite; (3) rhodochrosite, spessartite, pyroxmanite, quartz ± tephroite, ± fridelite, ± clinochlore, ± pyrophanite, ± pyrite. In all varieties, the major concentrators of Mn and Fe are carbonates (rhodochrosite, siderite, kutnahorite, Mn-calcite) and chlorite group minerals (clinochlore, chamosite). The chemical composition of rocks is dominated by Si, Fe, Mn, carbon dioxide, and water (L.O.I.): total SiO2 + Fe2O 3 tot + MnO + L.O.I. = 85.6−98.4 wt %. The content of Fe and Mn varies from 9.3 to 55.6 wt % (Fe2O 3 tot + MnO). The Mn/Fe ratio varies from 0.2 to 55.3. In terms of the aluminum module AlM = Al/(Al + Mn + Fe), the major portion of studied samples corresponds to metalliferous sediments. The δ13Ccarb range (–30.4 to–11.9‰ PDB) corresponds to authigenic carbonates formed with carbon dioxide released during the microbial oxidation of organic matter in sediments at the dia- and/or catagenetic stage. Ferromanganese sediments were likely deposited in relatively closed seafloor zones (basin-traps) characterized by periodic stagnation. Fe and Mn could be delivered from various sources: input by diverse hydrothermal solutions, silt waters in the course of diagenesis, river discharges, and others. The diagenetic delivery of metals seems to be most plausible. Mn was concentrated during the stagnation of bottom water in basin-traps. Interruption of stagnation promoted the precipitation of Mn. The presence of organic matter fostered a reductive pattern of postsedimentary transformations of metalliferous sediments. Fe and Mn were accumulated initially in the oxide form. During the diagenesis, manganese and iron oxides reacted with organic matter to make up carbonates. Relative to manganese carbonates, iron carbonates were formed under more reductive settings and higher concentrations of carbon dioxide in the interstitial solution. Crystallization of manganese and iron silicates began already at early stages of lithogenesis and ended during the regional metamorphism of metalliferous sediments.

Raman and XRD characterization of Moroccan Marbles

Various marbles collected from Moroccan careers, and two white reference marbles originating from Carrare-Italy and Drama-Greece, have been studied by different analytical techniques. Chemical composition of rocks has been determined by X-Ray fluorescence. X-Ray diffraction and Raman spectroscopy allowed the identification of both major (calcite and dolomite) and minor (quartz) mineralogical components. Moreover, Raman spectroscopy has been used to identify the calcium carbonate phases and to examine the graphitic ones in the marbles.

Discussion of Suitable Chemical Weathering Proxies in Sediments by Comparing the Dissolution Rates of Minerals in Different Rocks

In studies of paleoclimate change, variations in major and minor elements are often used as proxies for chemical weathering in soil or lake sediments. To prove the suitability of chemical weathering proxies and further discuss the impact of mineral dissolution on element migrations, various parent rocks in Taiwan were chosen to react with sulfuric acid for discussing mineral dissolution rankings and element leaching during chemical weathering processes. The parent rocks include granite, andesite, actinolite schist, slate, quartz sandstone, calcium sandstone, and mudstone. Experimental results show that dissolution rates are mainly controlled by mineral structures and the chemical compositions of rocks. The ranking of rock dissolution rates is as follows: mudstone > slate > actinolite schist > quartz sandstone > granite. Dissolution rates of andesite and calcium sandstone cannot be compared due to secondary minerals being produced in experiments. Moreover, the dissolution sequences of minerals are of the following order: calcite > chlorite > muscovite and illite > augite > hornblende ≈ feldspar > quartz. This result is consistent with the stability of silicate polymerization. Most notable among the results was that the dissolution rates of clay minerals were faster than those of feldspar. Element migration ranking in dissolution processes is as follows: Mg > Ca ≈ Rb > K > Na > Sr > Al > Zr > Fe ≈ Ti. The dissolution rates of univalent elements follow the sequence of bonding forces; however, those of divalent elements are less ordered. This is due to divalent elements being rich in different mineral phases. Therefore, the study suggests that univalent elements are more suitable as chemical weathering proxy candidates. Moreover, whether ratios of Rb/Sr and K/Rb or chemical index of alteration values in sediments are suitable proxies of paleorainfall intensity is discussed in detail.

Initial gold enrichment within a Neoarchean granite-greenstone belt: Evidence from ore-bearing and ore-barren samples in the Jiapigou deposits, NE China

The Jiapigou gold mineralization hosted in a Neoarchean granite-greenstone belt in the southern Jilin Province, at the easternmost part of the northern margin of the North China Craton (NCC), is one of the important gold deposits in China. However, its evolution, in particular the initial Au source and enrichment, have not been well constrained. The initial gold enrichment defined by Au concentrations of Neoarchean unaltered gneisses of this region, range from <0.005ppm to 0.001ppm, increasing to 0.006–0.031ppm Au for the ore-hosting Neoarchean altered mylonite gneisses. A combined study of zircon trace element, UPb dating, Hf isotope compositions, as well as whole rock chemical compositions was performed for dioritic gneisses from both ore-bearing (close to the ore body) and ore-barren zones (within the nearby rock body) with a view to constrain the gold initial enrichment. The dioritic gneisses have varied SiO2 contents (54.19–61.34wt.%), Al2O3 (13.06–16.75wt.%) with moderate to high K2O/Na2O ratios (0.7–1.3) and MgO (2.20–3.77%). Based on their chemical compositions, positive zircon εHf(t) values, and their formation ages of 2512±9Ma, we infer that these dioritic rocks were generated by partial melting of a juvenile source, most likely thickened mafic lower continental crust (LCC) with residual plagioclase associated with minor amphibole. The ore-bearing sample (H5) from a ductile shear zone has been extensively altered by fluids and is the sample containing zircons with blurred zoning and reverse discordance. Zircons from H5 have much higher radiogenic Pb but lower U and Pb contents than those in the ore-barren sample (H3), which contains zircons with oscillatory zoning and represents the basement rock. Based on the available petrological, geochronological and geochemical constraints, we propose the following model for Au initial enrichment within the Neoarchean granite-greenstone belt. At ca. 2.54Ga, associated with the accretionary processes in the proto-NCC, subduction-related fluids infiltrated the metasomatised subcontinental lithospheric mantle (SCLM), scavenging Au and Pb (mainly radiogenic Pb, henceforth Pb*) and triggering partial melting. The resulting basaltic magmas underplated the LCC and were re-melted at 2512±9Ma, when the onset of an extensional regime permitted the advection of heat and melts/fluids into the LCC. This generated voluminous dioritic magmas with juvenile Hf isotope signatures with little evidence of interaction with the mantle. Subsequent ca. 2505Ma re-melting of some granodioritic rocks led to the formation of potassic granite and residual fluids further enriched in Au and Pb*, both focused into ductile shear zones and other lithospheric weak zones. The fluids with anomalous UPb fractionation resulted in the rarely reported zircon reverse discordance, alteration and also enrichment in Au, as observed in sample H5 and H4, representing the initial stage of Au enrichment within the Neoarchean granite-greenstone belt.

Petrogenesis of the ∼500 Ma Fushui mafic intrusion and Early Paleozoic tectonic evolution of the Northern Qinling Belt, Central China

The Fushui mafic intrusion in the Qinling orogenic belt (QOB) is composed of meta-gabbro, meta-gabbro-diorite, diorite, and syenite. Most of these rocks are metamorphosed under the upper greenschist facies to lower amphibolite facies metamorphism. Zircon separates from eight samples have LA-ICP-MS U-Pb ages of 497–501Ma which are taken to be the emplacement age of magmas that formed the Fushui intrusion. Most of the zircon grains exhibit negative εHf values, correspond to TDM2 model ages of late Paleoproterozoic-early Mesoproterozoic or Neoproterozoic and suggest that the mafic rocks were most probably derived from mafic melts produced by partial melting of a previously metasomatized lithospheric mantle.The intrusion is not extensively contaminated by crustal materials and most chemical compositions of rocks are not modified during the greenschist to amphibolite-facies metamorhism. Rocks from the intrusion have primitive mantle-normalized trace element patterns with significant enrichment in light-REE and large ion lithophile elements (LILE) and depletion in high field-strength elements (HFSE). On the basis of the trace element contents, the Fushui intrusion was derived from parental magmas generated by <10% partial melting of both phlogopite-lherzolite and garnet-lherzolite mantle sources. These sources are best interpreted to be in a subduction-related arc environment and have been modified by fluids released from a subducting slab. The formation of the Fushui intrusion was related to the subduction of the Paleotethyan Shangdan oceanic lithosphere at ∼500Ma.

Detecting homogenous clusters using whole-rock chemical compositions and REE patterns: A graph-based geochemical approach

The rock chemical composition may be affected by a wide variety of primary and secondary geological processes. Analyzing geochemical datasets of highly altered rocks is usually faced with the challenges in detecting the relationships among objects. Using traditional clustering methods in such datasets with high-dimensional data and various types of attributes commonly leads to poor quality results. Hence, a graph-based geochemical approach was proposed in this study to solve this problem. In order to determine the relationship between objects, various similarity measures related to whole-rock composition, REE pattern, and the geographical location were employed in combination to weight the edges of a similarity graph. A spectral method was effectively used to identify clusters (communities) representing rock groups, geological units, or geochemical zones in the weighted similarity graph. It could also recognize the corresponding groups being compositionally and genetically similar to each other and distinguish sub-groups or anomalous samples in the dataset with regard to the different levels of clustering. Firstly, the performance and effectiveness of the proposed approach was evaluated by testing on a GEOROC11Geochemistry of Rocks of the Oceans and Continents. dataset based on some graph clustering quality functions. Then the approach was applied to the geochemical dataset of Choghart orebody comprising various altered rocks. The obtained clusters were visualized by a k-nearest neighbor classification technique to represent geochemical zones as a continuous map.

Tenoumer impact crater, Mauritania: Impact melt genesis from a lithologically diverse target

AbstractImpact melt rocks from the 1.9 km diameter, simple bowl‐shaped Tenoumer impact crater in Mauritania have been analyzed chemically and petrologically. They are heterogeneous and can be subdivided into three types based on melt matrix color, occurrence of lithic clast components, amount of vesiculation (melt degassing), different proportions of carbonate melt mingled into silicate melt, and bulk rock chemical composition. These heterogeneities have two main causes (1) due to the small size of the impact crater, there was probably no coherent melt pool where a homogeneous mixture of melts, derived from different target lithologies, could be created; and (2) melt rock heterogeneity occurring at the thin section scale is due to fast cooling during and after the dynamic ejection and emplacement process. The overall period of crystal growth from these diverse melts was extremely short, which provides a further indication that complete chemical equilibration of the phases could not be achieved in such short time. Melt mixing processes involved in the generation of impact melts are, thus, recorded in nonequilibrium growth features. Variable mixing processes between chemically different melt phases and the formation of hybrid melts can be observed even at millimeter scales. Due to extreme cooling rates, different mixing and mingling stages are preserved in the varied parageneses of matrix minerals and in the mineral chemistry of microlites. 40Ar39Ar step‐heating chronology on specimens from three melt rock samples yielded five concordant inverse isochron ages. The inverse isochron plots show that minute amounts of inherited 40Ar* are present in the system. We calculated a weighted mean age of 1.57 ± 0.14 Ma for these new results. This preferred age represents a refinement from the previous range of 21 ka to 2.5 Ma ages based on K/Ar and fission track dating.

レーザー分光分析による海底岩石のリアルタイム化学分析

Long-pulse Laser-Induced Breakdown Spectroscopy (LIBS) is a promising method for an in-situ analysis of chemical compositions of rocks and sediments on the seafloor. We have developed a real-time LIBS device, “Chemicam” and have successfully performed in-situ analysis at the bottom of the deep sea using the device. In order to develop a real-time quantitative analytical method, principal component regression analysis is applied to underwater LIBS measurements. The non-linear effects of plasma temperature fluctuation on the signals are treated as systematic errors in the analysis. The effect of these errors on the analytical performance is evaluated by comparing the conventional PCR, PCR with a temperature segmented database, and calibration-free LIBS. Improvement of accuracy in the proposed PCR model indicates that non-linear systematic effects contribute to fluctuation of underwater plasmas, where temperature-based segmentation can improve the performance of PCR. The results suggest that the proposed method can be applicable to real-time automated quantitative analysis of rocks in the deep sea.

The relationship between constituent minerals and whole rock chemical composition of the Kumano Acidic Rocks in southeastern Kii peninsula, Japan.

The relationship between constituent minerals and whole rock chemical composition of the Kumano Acidic Rocks in southeastern Kii peninsula, Japan.

암괴류 구성 암괴의 반발 강도 특성과 풍화각의 화학적 조성에 대한 연구 -비슬산을 사례로-

우리나라 암괴 관련 지형에 대한 연구는 암괴류의 형성 과정과 시기, 형태적 특성에 대한 분석이 주로 이루어졌고 암괴의 강도나 암괴의 화학적 특성 변화, 암괴 표면의 미지형 대한 논의는 거의 이루어지지 못했다. 본 연구에서는 비슬산 사면의 암괴들의 물리적, 화학적 특성을 조사하였다. 특히 암괴 표면에 형성된다 각형 균열의 특성을 관찰하였다. 균열이 형성된 암괴들을 중심으로 풍화 진행에 따른 강도를 알아보기 위해 슈미트 해머를 이용한 반발 강도를 측정하였고, WD-XRF(X-ray fluorescene)를 이용하여 각 시료의 화학적 조성을 분석하였다. 암괴의 표면에 풍화각이 반발 강도를 측정한 결과 풍화각이 남아 있는 부분과 제거된 부분 간의 경향성이 모든 시료에서 일치하는 것은 아니었으며, 풍화각이 제거된 부분의 강도가 더 큰 경우와 반대의 경우가 공존하고 있다. 물론 풍화각의 두께가 측정 값에 영향을 줄 수 있으나, 전반적으로 풍화 진행에 다른 강도의 약화로 판단할 수 있다. 이러한 강도의 약화는 이후의 균열의 성장에 영향을 준 것으로 보인다. 다각형 균열은 암석의 크기와 상관없이 다양한 크기의 암석에서 모두 발견되었으며 상당히 불규칙한 형상을 하고 있었다. 또한 균열의 형상은 암괴 표면의 경사나 구조적 취약선에 의해 거의 영향을 받고 있지 않았으며, 균열이 암석의 모서리 부분에서 끊어지지 않고 이어지고 있었다. 풍화각의 화학 조성은 전반적으로 유사하게 나타났으며, 풍화각 상부와 하부 간의 물질 조성 비율에서는 다소 차이를 보였다. 이러한 차이는 풍화로 인한 물질 용출에서 기인한 것으로 추정되지만 그 경향성을 일반화시키기엔 어려운 점이 있어 향후 세부적인 연구가 필요해 보인다.

Study on Volcanic Rock Chemical Composition and Physical Properties in Hainan Province

In order to study the chemical composition of volcanic rock and physical properties in Hainan province, used the method of X-ray fluorescence, analysises on its chemical composition, and researched the physical properties of volcanic rocks including density test, porosity test, acoustic test, resistance test. The results showed that: the volcanic rock is tholeiitic at the cavity of lava area in Hainan province, P-wave velocity and S-wave velocity would change with the changing of porosity.

Petrographic study of the Miocene Mizunami Group, Central Japan: Detection of unrecognized volcanic activity in the Setouchi Province

A petrographic study of sandstones from the Miocene Mizunami Group in Central Japan has been performed on core samples from a single borehole, in order to evaluate the provenance of the sedimentary rock. Evaluation of the provenance is based on bulk mineral, heavy mineral and plagioclase contents and on whole rock chemical compositions. The sandstones studied are divisible into three types; the first type is characterized by the occurrence of biotite and plagioclase ranging from albite to oligoclase, the second type is characterized by the dominance of amphibole and labradorite with pyroxene (clinopyroxene > orthopyroxene), and the third type is characterized by the dominance of pyroxene (orthopyroxene > clinopyroxene) and andesine with lesser labradorite, bytownite and anorthite. The first type is interpreted to be derived from the basement granite, whereas the others were derived mostly from volcanic ash, judging from their mineral compositions. The volcanic activity that supplied the volcanic ash to the Mizunami Basin occurred in two phases, distinguishable by variations in their mineralogical and geochemical compositions, an indication of change in character of the volcanic activity. This petrographic study of the sandstones in the Mizunami Group suggests that unrecognized volcanic activity occurred around the Mizunami Basin, even though potential provenance of the volcanic ash has not yet been identified.

The Mesoproterozoic Rayner Province in the Lambert Glacier area: its age, origin, isotopic structure and implications for Australia–Antarctica correlations

Abstract Within the Rayner Province in the Lambert Glacier area, two Proterozoic lithotectonic zones are distinguished, which differ in age and lithology. In the Fisher Zone, a significant juvenile component (ε Nd ( t )=+2 to +4) is represented by mafic, intermediate and felsic plutonic and volcanic rocks; the tectonomagmatic processes were concentrated at c. 1400–1200 Ma. In the Beaver Zone, orthogneisses record multiple emplacement, metamorphism and ductile deformation at c. 1150–930 Ma. New U–Pb SHRIMP-II zircon ages ( c. 1140 Ma and 1095 Ma – protolith emplacement; c. 950–850 and c. 540 Ma – metamorphism), chemical and Sm–Nd isotopic data indicate that both zones have their continuations in the eastern Amery Ice shelf coast. The Rayner Province has some geological features in common with the Albany-Fraser Orogen in Western Australia, suggesting that these regions evolved in similar tectonic environments at c. 1400–1300 Ma, followed by steady closure, from east to west, of the ocean that separated the Mawson Continent from Western Australia. Supplementary material: Chemical compositions of rocks, a summary of trace element ratios, a summary of published U–Pb dates, field photo views, new U–Pb analyses by SIMS SHRIMP-II and new Sm–Nd data are available at www.geolsoc.org.uk/SUP18621