Granite Weathering Research Articles

The geochemistry and isotopic compositions of the Nakdong River, Korea: weathering and anthropogenic effects.

The Nakdong River is the longest river in South Korea, and flows through various geological terrains with different land use characteristics; therefore, the geochemistry of its water is expected to be influenced by many factors. In this work, the geochemical characteristics of the Nakdong River were examined, and its chemical compositions, δD, δ18O, and δ13CDIC values, and 87Sr/86Sr ratios were determined to investigate the geological and anthropogenic effects on the geochemistry of the Nakdong River water. The obtained concentrations of major ions were strongly affected by both the anthropogenic activity and weathering of the rocks. With increasing the flow distance, the ion concentrations slightly increased; and after the inflow of the Kumho River, which was the largest tributary running through Daegu (the fourth largest city in South Korea), the concentrations of Na and SO4 ions abruptly increased and decreased again, suggesting the existence of strong anthropogenic effects caused by sewage treatment plants and dyeing industrial complex. Other activities such as agricultural ones also increased the NO3 concentration. In July, the high precipitation level from tropical cyclones and downpours decreased the ion concentrations as well as the δD and δ18O values. The δ13CDIC magnitudes showed that the dissolved inorganic carbon mainly originated from mineral weathering upstream, while the oxidation of soil organic materials influenced by agricultural activity became more important downstream. The 87Sr/86Sr ratios revealed that in the upstream regions, the weathering of granite and gneiss complex was dominant, while in the downstream regions, the weathering of sedimentary rocks became more important. The weathering and anthropogenic effects on the river water chemistry were also demonstrated using statistical analysis, which revealed that the water geochemistry was mostly influenced by the anthropogenic sources, including industrial complex, represented by Na, Cl, and SO4. The obtained results show that, as compared to the geochemistry of the Han River (which is also a major river in Korea), the geochemistry of the Nakdong River is more influenced by anthropogenic activities (including agriculture and the industrial complex) due to the different land use.

Nucleation of Th-rich cerianite on halloysite surface in a regolith-hosted rare earth elements deposit in South China

AbstractThe ion-adsorption rare earth element (REE) deposit, a valuable type of REE deposit, has been thought to be derived from the release and enrichment of REE during granite weathering. Understanding the REE occurrence in regolith-hosted deposits is crucial for more efficient extraction. We investigated a weathering granite profile of a regolith-hosted REE deposit located in South China. X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) analysis of the clay fractions reveal that the highest Ce(IV) content located in intensely weathered layers and cerianite nanoparticles (CeNPs) can be observed, besides invisible adsorbed REEs. Interestingly, most of the CeNPs scatter on halloysite basal surface and exhibit preferred orientation. Detailed analysis demonstrates that the diagonal plane of cerianite matches with the exposed basal surfaces (Si-O tetrahedron) of halloysite. Such a lattice match may contribute to the nucleation and growth of CeNPs after oxidation of the adsorbed Ce(III), which results in great REE enrichment by clays. The findings provide new insight into the mechanism of Ce precipitation and REE mineralization during granite weathering.

Review on Granitic Rocks in Sumatra: Intrusion Process, Classification, Mineralization and Potential Uses

Granitic rocks are widely distributed in Sumatra and surrounding areas. These granitoids are classified into several granite provinces of Southeast Asia with different intrusion processes and specific characteristics. This paper aims to review the intrusion of granitic rocks in Sumatra and describe the opportunities associated with it. Granite rocks are used to manufacture cultural heritage, works of art, and ornaments because of their weathering resistance, color diversity, and hardness characters. S-type granite intrusion in Sumatra might be associated with tin mineralization while silver-gold with the I-type. Theoretically, granite contains more REE than other igneous rocks. Mining and extraction difficulties complicate the direct REE exploitation from fresh granite. A-type granite relatively contains more REE than the other types, but this type of granite is not correlated with certain provinces. Indonesia has a tropical climate which is prone to weathering. Therefore, it is possible for REE and/or bauxite enrichments in the granite weathering horizon. Granite is assumed to be a potential source of uranium and thorium, especially for the S-type, because it is formed through the compression of sediments that can absorb these radioactive elements from the continental crust.

Petrographical and Geochemical Study of Syn-Rift Sediments, Pranhita-Godavari Intracratonic Gondwana Basin, India: Genesis and Paleo-Environmental Implications

The approximately 2 km thick fluvio-lacustrine deposits of Pranhita-Godavari Gondwana syn-rift basin, ranging in age from 235 to 196 Ma, track the compositional changes from the Middle Triassic to Early Jurassic. Mineralogical and geochemical investigations, as well as paleocurrent data of the siliciclastic deposits of the four conformable formations—Yerrapalli, Bhimaram, Maleri and Dharmaram—trace the source of sediments to the south and southwest of the Gondwana basin. The dominance of arkosic to sub-arkosic sandstones in all the formations suggests mostly felsic sources. The high value of Zr/Sc, as well a high content of Hf, reflects the addition of zircon by sediment recycling. The index of compositional variability (ICV) and chemical index of alteration (CIA) values of these Gondwana samples suggest intermediate weathering of Proterozoic shales, granites and gneisses. The concentration of Cr and Ni, ratios of Eu/Eu* and (GdN/YbN) suggest a dominant post-Archean source. The insignificant variation in ICV and CIA values across the studied Mesozoic formations corroborates the continuation of syn-rift tectonics of the Pranhita-Godavari Gondwana basin since the Late Paleozoic. Sandstone samples show a gradual shift from arkose to subarkose in Yerrapalli, Barakar and Maleri formations, and to sublithic arenite sandstones in the younger Dharmaram formation, indicating recycling. However, the insignificant variation of feldspar and/or quartz content throughout these Mesozoic formations suggests lesser tectonic activity. The paleocurrent direction, shifting from NNW to NE direction, suggests a change in basin tectonism and/or sediment supply, which is corroborated by mineralogical and geochemical data.

Chemical weathering indices and how they relate to the mechanical parameters of granite regolith from southern China

In most cases, chemical weathering reduces the strength and stability of granite regolith and increases its water sensitivity. When combined with external agents such as climate, these alterations facilitate geomorphological evolution, such as gully erosion in hilly regions. The lack of fundamental understanding about how gully erosion forms have led to an increasing trend of gully erosion in recent years. Because the weathering-controlled properties of granite regolith have a significant effect on gully development, it is vital to assess the chemical weathering degree. However, despite extensive studies on quantifying weathering degree using chemical weathering indices, less is known about how these parameters are correlated with the mechanical properties of granite regolith. To this end, a typical weathering profile is established for granite in Jiangmen, China. This paper investigates the chemical weathering of granite, evaluates the appropriateness of previous chemical weathering indices, and correlates them with the mechanical parameters of granite regolith. Several suitable indices, including CIA, Bases/Al2O3, Bases/R2O3, ba1, ba3, CIW, Imob, and PIA, are selected and correlated with the mechanical parameters. These indices apply well, with some scattering when they are correlated with the internal frictional angle of granite residual soil. This paper provides a comprehensive datset regarding the physical, mineralogical, petrographical, geochemical, and mechanical properties of granite regolith, and enhances the understanding of chemical weathering, especially its correlations with the mechanical properties of regolith.

Variations in weathering characteristics of soil profiles and response of the Atterberg limits in the granite hilly area of South China

Red loam hills with granitic parent material are susceptible to gully erosion under continuous runoff. Laterite soils from granitic parent material in South China are continuously weathered. Soil profile weathering and Atterberg limits, as indirect indicators of soil erosion resistance, are often neglected. Here, three typical granite weathering profiles in Hubei (HB), Fujian (FJ) and Guangxi (GX) were selected to investigate the granite weathering zonation characteristics and their relationships with the Atterberg limits. The main soil profile oxides were SiO2, Fe2O3 and Al2O3, and their total content exceeded 80.00%. Moreover, the chemical weathering indicators consistently showed highly weathered states and increase in weathering degree from bottom to top in the soil profiles; the weathering degree had zonal characteristics from north to south, and the weathering mantle thickness gradually increased. The liquid limit (LL), plastic limit (PL), shrinkage limit (SL), plasticity index (PI) and shrinkage index (SI) decreased as the soil profile depth increased, while the liquidity index (LI) decreased, indicating more stability and less susceptibility to erosion in the surface soil layers. During heavy rainfall, the soil moisture content in the sandy layer was more likely to approach the PL or even LL, which easily cause soil loss. Further, the red soil layers tended to shrink under higher moisture contents, thereby forming fissures and leading to preferential flow, which increased the interstitial pressure of the soil and led to a reduction in shear strength, and resulted in gully erosion. Regression analyses showed that Si mobility was significantly positively correlated with LL (R2 = 0.712), PL (R2 = 0.732), SL (R2 = 0.669), SI (R2 = 0.709), and PI (R2 = 0.592) and significantly negatively correlated with LI (R2 = 0.554). The correlations between Fe mobility and Atterberg limits were the opposite of those for Si. According to path analysis, the Fe2O3 content and Atterberg limits had the largest decision coefficients, indicating that the weathering intensity was significantly correlated with the Atterberg limits.

The influence of parent rock, mining and processing technologies on the industrial quality of kaolin concentrate –case study from Bombowha kaolin, Ethiopia

Bombowha kaolin deposit is a primary deposit formed mainly through weathering of granite and pegmatite. This research was designed to evaluate the influence of parent material, mining practices and processing technology on the quality of processed kaolin. Geochemical, mineralogical, and technological properties of kaolin were analyzed and field observations conducted to evaluate the influence. Samples of the parent rocks, kaolin deposit, Run-Of-Mine, and processed kaolin were analyzed for their geochemistry, mineralogy and physical properties. Results show that the kaolin derived from pegmatite has better quality (high alumina, low silica, better plasticity, low coloring elements and others) than the granite-derived one. The poor quality of the granite-derived kaolin is ascribed to its incomplete kaolinization as evidenced by the presence of minor halloysite. The geochemical analysis of the Run-Of-Mine shows close similarity to that of the parent granite demonstrating severe dilution during mining, hauling and storage of kaolin ore. The high pit-wall angle (80-85°), the rheologically weak overburden, old excavation machinery and unsystematic delineation of mineable portion of the deposit contributed to high level of dilution. The properties of processed kaolin show the wet processing method brought substantial improvement in the quality of the kaolin (Al2O3 increased by nearly 98% and SiO2 decreased by 36% with respect to the Run-Of-Mine). Had the feed kaolin ore not been diluted, the kaolin concentrate would have been better than what is achieved through the adopted processing method. Systematic mine design, selective mining, and graded stockpiling of kaolin ore are advised for better quality kaolin concentrate.

KAJIAN PELAPUKAN GRANIT DAERAH LEATO BERDASARKAN ANALISIS XRD DAN SEM

Weathering is a natural process due to the work of exogenous forces both physically and chemically which results in the breakdown of rocks and constituent minerals into loose materials. Weathering can cause compact and resistant granite to move easily, causing rock fall in the Leato area, Gorontalo City. This study aims to assess the level of weathering of granite based on X-Ray Diffraction (XRD) and Scanning Electron Microscope Analysis (SEM) analysis. The research objectives will be achieved using two methods consisting of field surveys and laboratory analysis in the form of XRD and SEM analysis. Based on the results and discussion that granite rocks have undergone weathering. Evidence of weathering is clearly shown in SEM photos, namely weathering occurs at the edges of granite rocks.

Complexity and Geoheritage Importance of Granite Pseudokarst from the Belaya River Gorge (Western Caucasus)

New investigations in the Western Caucasus contribute to the understanding of granite pseudokarst (sensu lato) and megaclasts linked to river erosion. A plot on the bank of the Belaya River (Mountainous Adygeya, Western Caucasus) was selected to examine diverse and abundant pseudokarst features (small rock basins, hollows, potholes, and channels) and large clasts. Morphological analysis of these features clarifies their general characteristics and genetic interpretations. Pseudokarst features can be classified into two major categories, namely the relatively small (<1 m) and large (>1 m) features. Potholes, which are usually 1–3 m in size, are the most characteristic features occurring on two levels, i.e., on steep walls of the gorge (half-filled with river water) and on slightly inclined surfaces of a terrace-like landform (subaerial exposure). In both cases, their walls from the side of the river are broken. Apparently, these potholes were formed on the river bottom. Subsequent incision of the gorge elevated potholes and the river has eroded them from one side. Apparently, some pseudokarst features are related to macroturbulent flood flows and granite weathering. Due to its scientific uniqueness and aesthetic attractiveness, this granite pseudokarst constitutes geoheritage, which can be exploited for the purposes of geoscience research and geotourism development.

A system of the granite weathering degree assessment using hyperspectral image and CNN

ABSTRACT Due to weathering processes that occur all around the world, rocks that are exposed eventually undergo physical and chemical changes. These weathering processes have the potential to turn fresh rocks into soft and weakened derivatives, leading to the collapse and subsidence of structures, such as tunnels, dams, and others, as well as natural structures, such as cliffs and slopes. This study attempts to employ hyperspectral imaging and a deep learning network called Convolutional Neural Network (CNN) in the effort to achieve a reliable process for rock weathering degree assessment. This study employs a hyperspectral image camera capable of detecting electromagnetic radiation from 400 nm-1000 nm with a spectral resolution of 204 bands. The CNN algorithm used in this study is based on a modified VGG-16 architecture. The total amount of data from granite samples employed amounts to 19,456 files. 80% of the total data were used as learning data and the remaining 20% as testing and validation data. The results show that the system has an average precision of over 94%. The study, therefore, concludes that the conjunction of hyperspectral imaging with CNN is a practicable process for the evaluation of the degree of weathering granite without the need for specialised human expertise or prejudice.

Distribution of Pb isotopes in different chemical fractions in bed sediments from lower reaches of the Xiangjiang River, Hunan province of China

This paper reports Pb isotopes in different fractions following the three step BCR and 1 M HCl extractions on river sediments from lower reaches of the Xiangjiang river in China, and highlights the importance of Pb isotopes in heavy metal contamination assessment. Lead concentrations and Pb isotopes in bulk sediments and sediment fractions (leachates and residues) from the river were analysed using ICP-MS techniques. Results showed that sediments were highly enriched with Pb with enrichment factors >5.5, while Pb in sediments was dominated by reducible and residual Pb fractions, residing mainly in Fe-oxide and silicate minerals. Pb isotopes in sediments was characterized by radiogenic Pb produced from the decay of uranium and thorium with 206Pb/207Pb ratios of 1.1744 for less radiogenic Pb and 1.1816 for more radiogenic Pb. The leachates and residues from BCR extraction generally had similar Pb isotope compositions, of which the 206Pb/207Pb ratios were 1.1798 ± 0.002 and 1.1844 ± 0.008 respectively. Differentiation of Pb isotopes between BCR leachates and residues was insignificant. However, differentiation between leachates and residues using 1 M HCl extraction was significant, as shown by average 206Pb/207Pb ratios of 1.1746 ± 0.005 and 1.1858 ± 0.008 for leachates and residues respectively. Pb isotopic tracing suggests that Pb in sediments from Zhuzhou section arose from the mixing of anthropogenic Pb from coal combustion (39%) and mining-smelting for Pb-Zn ores (58%); while Pb in sediments from Xiangtan, Changsha and Xiangyin sections arose from the mixing of anthropogenic Pb from mining-smelting for Pb-Zn ores (54%), and lithologically inherited Pb from granite weathering (35%) with a small amount of contribution from coal combustion (10%). The present study suggests that the BCR extraction scheme was not appropriate for ecological risk assessment of heavy metal contamination in mining-impacted (ore-Pb dominated) river sediments.

Soil physical properties and slope stability in Serra do Mar, southeastern Brazil

Soil physical properties play an important role in landslide rupture mechanisms, since changes in soil texture, structure, and porosity can affect slope permeability. This study characterized a granitic weathering profile and assessed the changes in the properties of the materials related to the main mechanisms that trigger landslides. The study identified three layers with distinctive particularities in macromorphological and micromorphological terms: mature residual soil (well-developed), young residual soil (saprolitic soil), and saprolite. Morphological characterization was carried out in addition to textural analysis, and soil porosity and saturated hydraulic conductivity (Ksat) tests. The weathering profile presented clear differences in morphology, pore size and soil texture, which could indicate distinct weathering grades. The results suggested that continuous heavy rainfall could contribute to the increase in pore-water pressure between mature residual soil and young residual soil, favoring the occurrence of slope failure.

STRUCTURAL AND LITHOLOGICAL MODEL OF THE SHABERIVSKE DEPOSIT OF ELUVIAL KAOLIN

Data on the zonation and material composition of the weathering crust within the Shaberivkske deposit of the eluvial kaolin, which is located in Baranivka district of Zhytomyr region and is the part of the Dubrivsko-Khmelivsky kaolin district of Volyn kaolin subprovince. The minerals of the Shaberivske deposit are normal and alkaline kaolins, which were formed due to the weathering of granitoids. Some areas of conditioned kaolin are present in the upper part of the weathering crust of gneisses. On the basis of coordinates and the description of wells the relief of a sole and a surface of a deposit of eluvial kaolins, and also lateral change of their thickness is investigated. Layer-like kaolin deposits have been found to have complex morphology and internal structure. It was established that the greatest thicknesses of kaolins are confined to depressions in the topography of their soles. The maximum thicknesses of kaolin are inherent in the areas of the weathering crust formed by the weathering of granites and migmatites. Based on the results of well testing and chemical analysis of kaolins, the distribution of the contents of Al2O3, Fe2O3, TiO2 oxides and the index of whiteness along the lateral and vertical sections of kaolins was investigated. It was established that in the greater part of the deposit, beyond the lateral, there is a direct correlation between the average content of Al2O3 and TiO2 and the reverse – between the content of Fe2O3 and TiO2 and between Al2O3 and Fe2O3. In the vertical section of the kaolin layer, the distribution of oxides of iron, titanium, aluminum and whiteness index is uneven. As a rule, these indicators do not always correlate with each other. In general, the deposit is characterized by an uneven sole and surface with elevations and depressions, an uneven lateral distribution of the thickness of the kaolin deposit. The lateral distribution of the average contents of iron oxides, titanium and the whiteness index, as well as the vertical distribution of the contents of iron oxides, aluminum, titanium and the whiteness index, is uneven. It was found that the geological heterogeneity of the rocks of the crystalline foundation was reflected in the structure and material composition of the weathering crust and, accordingly, in the structure (character of the relief of the sole and surface, thickness) and quality parameters (whiteness, harmful impurities) of eluvial kaolins.

Geochemistry of a spheroidal weathering profile in a tropical mountainous landscape, Rio de Janeiro, Brazil

Boulders are an important material in debris flow and their source is coupled with spheroidal weathering profiles that produce corestones. The goal of this work was to establish the geochemical transformations that produced corestones and distinguished them from the surrounding grus in two tropical granite weathering profiles (P1 and P2). Sampling was not performed in a vertical profile; instead, we gathered 13 (P1) to 16 (P2) samples displaying different weathering degrees (corestone and saprolite) and spatial positions in the profiles. We conducted the geochemistry (EDXRF/EDX and INAA) and mineralogy (petrography and XRD) of the samples. The CIA values ranged from 46 (corestones) to 93 (saprolite). Granite spheroidal weathering under a tropical mountainous slope develops mostly due to feldspar weathering (foremost plagioclase) in the following sequence: porosity growth, kaolinite, and gibbsite crystallization. Zircon weathering stability and its probable mobility as grain along the weathering profile play an important role in REE concentration. Spheroidal weathering is mainly a lixiviation process, yet specific locations (below the individualized corestones) presented REE enrichment due to translocation. They are hosted mainly by clay minerals and, to some extent, by amorphous Fe oxyhydroxide. The evolution of spheroidal weathering results in a vertical patchy weathering profile.

PALEOPEDOLOGICAL INVESTIGATION OF LATE CENOZOIC DEPOSITS ON THE ARCHEOLOGICAL LOCATIONS GOLOVCHYNCY-1 IN KHMELNITSKAYA DISTRICT

It is represented paleopedological investigation of the new archeological section on the watershed inside of the territory of granite quarry near v. Golovchyncy with detail morphological description of deposits and scale field drawing with sticks of natural material; 10 samples with undisturbed structure are selected on micromorphological analysis. It is analysised 10 thin sections with undisturbed structure from site Golovchyncy-1 deposits under polarizate microscope are looked through, peculiarities of micromorphological building are interpretated. According to the results of the obtained new paleopedological data, three stratigraphic horizons have been singled out in the archeological section, located above the granite weathering crust – Illichiv, Shyrokyno and Holocene. Illichiv horizon is represented by yellowish-light-gray sands with a large number of fragments of stony material. The Shyrokyno horizon is represented by dark brown sandy-clay leached soil-pedosidiment (sh3), a layer of crumbly sand (sh2) and orange-rusty-brown in color, brown forest (southern facies) soil-pedosidiment (sh3). The modern Holocene horizon is represented by brown forest leached soil. The obtained paleopedological (morpho- and micromorphological) data allowed to reproduce the natural conditions during certain paleogeographic stages of the Pleistocene and to reconstruct the living conditions of ancient man in the Lower Paleolithic. In particular, Shyrokyno soils with artifacts, formed in temperate climate. Their ancient age is confirmed by the high position on the modern watershed, the presence of a strong weathering crust grants and a primitive culture of processing the artifacts found. The upper Shyrokyno soil (sh3) reflects the conditions of the warm-temperate, warmer temperate-humid climate of the zone shifted to the north compared to the modern temperate. The lower (sh1) was formed in a warm-temperate, warmer than modern climate with a sufficiently precipitation regime, when the zones were shifted further north, compared to sh3 soil. Key words: paleopedology; Pleistocene; soils; morphology; micromorphology.

Effects of Na2SO4 concentration and surface shape on the weathering of granite during wet–dry cycling

The presence of salts during cyclic wet and dry conditions can cause weathering of rock and is the main cause of damage to ancient and modern buildings. Accordingly, salt weathering, especially of granite, has aroused great interest. Determining the relationship between wet–dry cycling and the physical properties of rock is of great significance to geotechnical engineering. In this paper, granite samples were processed into two shapes (round and semicircular) and subject to 0, 10, 20, 30, 40 and 50 wet–dry cycles, with the wetting achieved with 0%, 5%, 10% or 20% concentrations of Na2SO4 solution. The mass loss, roughness and indentation hardness of granite samples all changed to some extent with cycle number, with greater changes occurring at higher salt concentrations. Rock shape also affects the extent of weathering damage, as surface area and features such as corners facilitate the ingress of salt solution.

Glaciers Control the Hydrogeochemistry of Proglacial Streams During Late Summer in the Wind River Range, Wyoming, United States

Glaciers alter the geochemistry of sensitive alpine streams by exposing freshly weathered bedrock and releasing atmospherically deposited trace metals from melting ice. Changes in the timing and quantity of glacial melt also affect discharge and temperature of alpine streams. To investigate the effects of glacier meltwater on the geochemistry and hydrology of proglacial streams in the western US, we sampled supraglacial meltwaters and proglacial streams in the Dinwoody Creek watershed in the Wind River Range, Wyoming during a one-week period in 2015. The upper watershed contains Gannett Glacier ( ∼ 5 km2) and Dinwoody Glacier ( ∼ 4 km2) at elevations between 3,300–4,000 m asl. Samples were collected during late summer (27 August–4 September) when the contributions of glacier meltwater were highest. Supraglacial meltwater was enriched in a suite of trace metals (Cd, Co, Cu, Hg, Mn, Pb, Zn) relative to proglacial streams, suggesting an atmospheric source of metals to the glaciers. Concentrations of major ions and the remaining 30+ analyzed trace elements were enriched in proglacial streams relative to supraglacial meltwater, reflecting weathering of granite and gneiss bedrock. To evaluate the diurnal effects of glacier meltwater inputs, we deployed loggers to monitor water levels, temperature, and specific conductance at 15 min intervals over a one-week period and collected hourly water samples from Dinwoody Creek for a 24 h period. The influx of glacial meltwater during the daytime diluted major ion and rare earth element concentrations and caused increased concentrations for a subset of trace metals. Stable water isotopes (δD and δ18O) in Dinwoody Creek were more depleted during peak flow relative to baseflow due to contributions from isotopically depleted meltwater. The combination of multiple hydrologic tracers (solute concentrations, high frequency logger data, water isotopes) shows strong potential to improve estimates of glacier meltwater contributions to proglacial streams. Changes in water chemistry and discharge need to be monitored as glaciers recede across the Wind River Range and other midlatitude mountain ranges for mitigating negative impacts on alpine ecosystems and downstream water resources.

Structural characteristics of pools in headstream areas

Pools play an important role among stream bed morphologies in mountain streams. They provide habitat and contribute to energy dissipation. However, they have received only marginal attention compared with step structures, and their forms and driving factors, such as stream-channel characteristics and structural characteristics of upstream morphologies, remain unclear. Therefore, the purpose of this study was to determine the structural characteristics of pools, including morphology, size, and deposit conditions, and the factors controlling them. Based on the results of a field survey for a channel length of 9524 m, with 428 reaches and 1302 pools, the correlations between the pool spacing, morphology, size, and deposit conditions of the pool, and controlling factors were investigated for three rock types (granite, rhyolite, and sandstone). The average pool spacing calculated by dividing the interval length of the pool by the channel width was 8.80, 12.87, 4.56, and 16.14 for fall-pool, cascade, step-pool and pool-riffle respectively. This is due to the fact that the target streams are first-order streams with small widths as well as their regional characteristics, that is, few log jams and forced pools. In addition, the depositional depth of the pools varies depending on the geology. The maximum percentage of sediment deposition in the pool was 78%, 33%, and 34% for granite, rhyolite, and sandstone, respectively. Thus, the sedimentation in granite is significantly greater than in the rhyolite and sandstone headstream areas. This is probably due to the discontinuous weathering of granite during which it is broken down into large-sized core stones and fine grains. The difference in the depositional environment of the pools depending on the geology indicates that the biota that use those pools as a habitat may also differ. However, research on the microhabitats of pools is lacked, and research regarding the future perspectives of ecosystems is required.

화강암 분지를 흐르는 미호천의 지형학적 특색

The drainage area of the Miho stream is composed of granitic basins, gneissic and sedimentary mountains. 80 percent of the Miho stream flows through the Jincheon basin and the Cheongju inner-plain within the Daebo granite belt. Because the deep weathering of granitic hills provides a large amount of sands to the streams, there are wide floodplains with thick alluvium developed in the basin and plain. The thickness of the alluvium is 5~10m and the width of the floodplains is 2~2.5km. In the basin outlet area where a stream passes through the mountain canyon, wide floodplains and deep alluvium are developed in other riverside. The Miho stream is a sand-gravel channel flowing through the Cheongju inner-plain with wide floodplains and deep alluvium formed by deep weathering of granite.

Study of Chemical Weathering and CO2 Consumption Rate of Granite in a Small Subtropical Watershed

Study of Chemical Weathering and CO2 Consumption Rate of Granite in a Small Subtropical Watershed