Letteratura scientifica selezionata sul tema "Carbonate weathering"
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Articoli di riviste sul tema "Carbonate weathering":
1
Huang, Kang-Jun, Fang-Zhen Teng, Bing Shen, Shuhai Xiao, Xianguo Lang, Hao-Ran Ma, Yong Fu e Yongbo Peng. "Episode of intense chemical weathering during the termination of the 635 Ma Marinoan glaciation". Proceedings of the National Academy of Sciences 113, n. 52 (12 dicembre 2016): 14904–9. http://dx.doi.org/10.1073/pnas.1607712113.
Abstract (sommario):
Cryogenian (∼720–635 Ma) global glaciations (the snowball Earth) represent the most extreme ice ages in Earth’s history. The termination of these snowball Earth glaciations is marked by the global precipitation of cap carbonates, which are interpreted to have been driven by intense chemical weathering on continents. However, direct geochemical evidence for the intense chemical weathering in the aftermath of snowball glaciations is lacking. Here, we report Mg isotopic data from the terminal Cryogenian or Marinoan-age Nantuo Formation and the overlying cap carbonate of the basal Doushantuo Formation in South China. A positive excursion of extremely high δ26Mg values (+0.56 to +0.95)—indicative of an episode of intense chemical weathering—occurs in the top Nantuo Formation, whereas the siliciclastic component of the overlying Doushantuo cap carbonate has significantly lower δ26Mg values (<+0.40), suggesting moderate to low intensity of chemical weathering during cap carbonate deposition. These observations suggest that cap carbonate deposition postdates the climax of chemical weathering, probably because of the suppression of carbonate precipitation in an acidified ocean when atmospheric CO2 concentration was high. Cap carbonate deposition did not occur until chemical weathering had consumed substantial amounts of atmospheric CO2 and accumulated high levels of oceanic alkalinity. Our finding confirms intense chemical weathering at the onset of deglaciation but indicates that the maximum weathering predated cap carbonate deposition.
2
Ott, Richard, Sean F. Gallen e David Helman. "Erosion and weathering in carbonate regions reveal climatic and tectonic drivers of carbonate landscape evolution". Earth Surface Dynamics 11, n. 2 (29 marzo 2023): 247–57. http://dx.doi.org/10.5194/esurf-11-247-2023.
Abstract (sommario):
Abstract. Carbonate rocks are highly reactive and can have higher ratios of chemical weathering to total denudation relative to most other rock types. Their chemical reactivity affects the first-order morphology of carbonate-dominated landscapes and their climate sensitivity to weathering. However, there have been few efforts to quantify the partitioning of denudation into mechanical erosion and chemical weathering in carbonate landscapes such that their sensitivity to changing climatic and tectonic conditions remains elusive. Here, we compile bedrock and catchment-averaged cosmogenic calcite–36Cl denudation rates and compare them to weathering rates derived from stream water chemistry from the same regions. Local bedrock denudation and weathering rates are comparable, ∼20–40 mm ka−1, whereas catchment-averaged denudation rates are ∼2.7 times higher. The discrepancy between bedrock and catchment-averaged denudation is 5 times lower compared to silicate-rich rocks, illustrating that elevated weathering rates make denudation more spatially uniform in carbonate-dominated landscapes. Catchment-averaged denudation rates correlate well with topographic relief and hillslope gradients, and moderate correlations with runoff can be explained by concurrent increases in weathering rates. Comparing denudation rates with weathering rates shows that mechanical erosion processes contribute ∼50 % of denudation in southern France and ∼70 % in Greece and Israel. Our results indicate that the partitioning between largely slope-independent chemical weathering and slope-dependent mechanical erosion varies based on climate and tectonics and impacts the landscape morphology. This leads us to propose a conceptual model whereby in humid, slowly uplifting regions, carbonates are associated with low-lying, flat topography because slope-independent chemical weathering dominates denudation. In contrast, in arid climates with rapid rock uplift rates, carbonate rocks form steep mountains that facilitate rapid, slope-dependent mechanical erosion required to compensate for inefficient chemical weathering and runoff loss to groundwater systems. This result suggests that carbonates represent an end member for interactions between climate, tectonics, and lithology.
3
Wu, Huaying, Zhongcheng Jiang, Qibo Huang, Funing Lan, Hongwei Liao, Tengfang Li e Chenhui Huang. "Geochemistry of Weathering Cover and the Main Influencing Factors in Karst Area of Guilin, Southwest China". Water 15, n. 16 (15 agosto 2023): 2944. http://dx.doi.org/10.3390/w15162944.
Abstract (sommario):
The chemical weathering of carbonate rocks is the main form of interaction between earth spheres in the karst critical zone. The karst weathering cover, which is composed by residua from carbonate rocks weathering, contains important information about the climate environment and material cycle. We present the chemical composition of weathering covers in karst area of Guilin, Guangxi province, analyze their weathering process and strength, and compare them with the other weathering covers in other karst area in China, including Yunnan, Guizhou, Hunan, and Qinghai Tibet Plateau. The results showed: (1) the chemical composition of Guilin weathering covers were similar to that of carbonate weathering covers in other areas of China, and had the common characteristics of uniform distribution of chemical composition in the profile and obvious enrichment of Fe, Al and trace elements. During the formation of carbonate weathering cover and the residua, the rapid dissolution of Ca and Mg had an important impact on the migration and enrichment of other elements. (2) The chemical index of alteration (CIA) of carbonate weathering covers in Guilin and other karst areas of China was much larger than that in the upper crust (UCC) (60.13), which showed strong chemical weathering characteristics of the humid and hot climate. (3) The weathering process of carbonate rock was different from that of silicate and loess. In the early stage of carbonate rock weathering, soluble components (calcite and dolomite) had been rapidly dissolved and leached. All the carbonate weathering residua was measured to be in the stage of K2O weathering and Al2O3 increasing. Therefore, the weathering degree of carbonate weathering cover was mainly determined by the leaching of K2O and the increase of Al2O3. As a result, there was no correlation between CIA and Na/K (molar ratio), but was a significant negative correlation between CIA and K/Al (molar ratio) in the carbonate weathering cover. (4) The CIA values of weathering residua and carbonate weathering cover in southern China were negatively correlated with latitude, reflecting the influence of climate factors. From the influence of lithology, the chemical compositions of parent rock can affect the CIA of weathering cover, and the content of insoluble matter in carbonate rock was negatively correlated with CIA. From the influence of topography, the CIA value of weathering residua decreased from the high to the low position and from the shallow to the deep part of the profile.
4
Chen, Wenwen, Huanfang Huang, Haixiang Li, Jianhua Cao, Qiang Li, Yingjie Chen, Bing Bai e Honghu Zeng. "Coupled nitrogen transformation and carbon sink in the karst aquatic system: a review". Blue-Green Systems 3, n. 1 (1 gennaio 2021): 201–12. http://dx.doi.org/10.2166/bgs.2021.120.
Abstract (sommario):
Abstract Carbonate bedrock regions represent that 14% of Earth's continental surface and carbon (C) sink in karst water plays an important role in the global C cycle due to the CO2 consumption during carbonate mineral weathering. Intensive agriculture and urbanization have led to the excessive input of nitrogen (N) into aquatic systems, while the high concentrations of inorganic C in the karst water might affect the N cycle. This paper summarized the characteristics of water in karst regions and discussed the N transformation coupled with the C cycle in the condition of high Ca2+ content, high pH, and high C/N ratios. Carbonates can consume more atmospheric and pedologic CO2 than non-carbonates because of their high solubility and high rate of dissolution, resulting in the higher average CO2 sink in karst basins worldwide than that in non-karst basins. Therefore, carbonate mineral weathering and aquatic photosynthesis are the two dominant ways of CO2 absorption, which are termed as coupled carbonate weathering. As the alkalinity and high C/N content of karst water inhibit the denitrification and mineralization processes, the karst aquatic environment is also served as the N sink.
5
Harbar, Vladyslav, e Andriy Lisovskiy. "Carbonations and carbonate profile forming processes of rendzinas of the Podilski Tovtry". Visnyk of the Lviv University. Series Geography, n. 51 (27 dicembre 2017): 88–97. http://dx.doi.org/10.30970/vgg.2017.51.8741.
Abstract (sommario):
The peculiarities of content and profile distribution of carbonates in rendzinas and soil-forming rocks of the Podilski Tovtry are investigated. It has been determined that the predominant process of weathering of carbonate rocks is a chemical dissolution, in which carbonates are converted into bicarbonates and, in the case of washing water regime, are applied from the soil (the process of decarbonization) and mechanical grinding and destruction of the remaining carbonate inclusions in the process of soil cultivation. The dissolution of carbonate rocks causes accumulation in the soil profile of an insoluble residue, the intensity of which depends on the composition of carbonate rocks, the rate of filtration of aqueous solutions, their aggressiveness and the concentration of destructive substances. The most intensive such accumulation occurs in acidic medium, at a low rate of infiltration of solutions and at high concentrations of CO2. It was established that the highest proportion of CaCO3 is characterized by lithotamium limestone (up to 90–93 %), and the lowest – carbonate polygenetic loams (up to 35–40 %). The feature of the profile distribution of the content of carbonates in rendzinas is its gradual growth in the upper part of the soil profile and rapid in the middle and lower parts. It is determined that the rendzinas of the Podilski Tovtry carbonates are represented predominantly in the form of wreckage of initial soil-forming rocks of different sizes and shapes, as well as amorphous solid-phase crude and finely dispersed products of weathering in the form of powdery and powdery carbonate dusting. It is established that in dense crystallized lithotamium limestones of the main strand, the carbonate mass weakly passes moisture, and the main process of weathering occurs due to surface corrosion. The accumulation of secondary carbonates in the form of mycelium and veins is characteristic on the slopes of the Tovtry (mostly in brown rendzinas and pararendzinas), due to the vertical and lateral migration flows of the dissolved forms of CaCO3. Key words: rendzinas, Podilski Tovtry, carbonates, carbonate profile.
6
Song, Chao, Changli Liu, Guilin Han e Congqiang Liu. "Impact of different fertilizers on carbonate weathering in a typical karst area, Southwest China: a field column experiment". Earth Surface Dynamics 5, n. 3 (26 settembre 2017): 605–16. http://dx.doi.org/10.5194/esurf-5-605-2017.
Abstract (sommario):
Abstract. Carbonate weathering, as a significant vector for the movement of carbon both between and within ecosystems, is strongly influenced by agricultural fertilization, since the addition of fertilizers tends to change the chemical characteristics of soil such as the pH. Different fertilizers may exert a different impact on carbonate weathering, but these discrepancies are as yet not well-known. In this study, a field column experiment was conducted to explore the response of carbonate weathering to the addition of different fertilizers. We compared 11 different treatments, including a control treatment, using three replicates per treatment. Carbonate weathering was assessed by measuring the weight loss of limestone and dolostone tablets buried at the bottom of soil-filled columns. The results show that the addition of urea, NH4NO3, NH4HCO3, NH4Cl and (NH4)2CO3 distinctly increased carbonate weathering, which was attributed to the nitrification of NH4+. The addition of Ca3(PO4)2, Ca–Mg–P and K2CO3 induced carbonate precipitation due to the common ion effect. The addition of (NH4)3PO4 and NaNO3 had a relatively small impact on carbonate weathering in comparison to those five NH4-based fertilizers above. The results of NaNO3 treatment raise a new question: the negligible impact of nitrate on carbonate weathering may result in an overestimation of the impact of N fertilizer on CO2 consumption by carbonate weathering on the regional/global scale if the effects of NO3 and NH4 are not distinguished.
7
Xie, Yincai, Yupei Hao, Jun Li, Yongli Guo, Qiong Xiao e Fen Huang. "Influence of Anthropogenic Sulfuric Acid on Different Lithological Carbonate Weathering and the Related Carbon Sink Budget: Examples from Southwest China". Water 15, n. 16 (14 agosto 2023): 2933. http://dx.doi.org/10.3390/w15162933.
Abstract (sommario):
Accurate estimate of carbonate weathering and the related carbon sink flux induced by anthropogenic H2SO4 is of great significance for improving understanding of the hydrogeochemical evolution and the global carbon cycle. Here, to quantitatively evaluate the influence of anthropogenic H2SO4 on different lithological carbonate weathering and the related carbon sink budget, karst spring water in the typical limestone and mixed limestone–dolomite catchments in Yaji and Beidiping affected by acid precipitation in southwest China were sampled monthly for the analysis of hydrochemical and δ13CDIC characteristics. Results show for the period of sampling (August 2013 to December 2014) that the average contribution rates of atmospheric inputs and carbonate weathering to total dissolved cations are 2.24% and 97.8%, and 3.09% and 96.9% in Yaji and Beidiping, respectively. The δ13CDIC values (−17.0% to −14.7‰) and the [Ca2+ + Mg2+]/[HCO3−] (0.98 to 1.25) and [Ca2+ + Mg2+]/[HCO3− + SO42−] (approximately 1) equivalent ratios of samples prove that H2CO3 and H2SO4 simultaneously participate in carbonate weathering. The contribution rates of H2SO4 to [Ca2+ + Mg2+] and [HCO3−] produced by carbonate weathering in Yaji and Beidiping are 0–30% and 0–18%, and 0–37% and 0–23%, with average values of 14% and 7%, and 19% and 11%, respectively, suggesting that the influence of H2SO4 on different lithological carbonate weathering is different. H2SO4 precipitation participating in carbonate weathering increases the weathering rate by 14–19%, whereas it decreases the flux of karst carbon sink by 7–11% in Southwest China. Therefore, anthropogenic acids have influenced the global carbon cycle and climate change by carbonate weathering due to the large karst areas in the world, and their influences on different lithological carbonate weathering should not be ignored in the regional and global carbon cycles in future studies.
8
DA ROSA, ÁTILA AUGUSTO STOCK, NUNO LAMAS VALENTE PIMENTEL e UBIRATAN FERRUCIO FACCINI. "Paleoalterações e Carbonatos em Depósitos Aluviais na Região de Santa Maria, Triássico Médio a Superior do Sul do Brasil". Pesquisas em Geociências 31, n. 1 (30 giugno 2004): 3. http://dx.doi.org/10.22456/1807-9806.19561.
Abstract (sommario):
Five types of paleo-weathering and carbonate precipitation were recognized in fine-grained deposits of the Alemoa Member, Santa Maria Formation, Middle to Upper Triassic of southern Brazil. The fauna and flora found in these lithologies are important dating tools, but only in a generic way, misleading the time involved in periods of deposition and non deposition. The identified types of deposits are (i) reddish mudstones, with none or little paleo-weathering, (ii) mottled mudstones, with incipient pedogenesis, mainly mottling, destratification, animal and vegetal colonization, (iii) carbonate veins, with more evidences of exposure and root action, (iv) carbonate siltstones/sandstones, where restricted fluvial deposits are cemented by phreatic carbonate, and (v) carbonate nodules and lenses, in which small lenses of a very compact calcrete are at the top and in the center of carbonated siltstone/sandstone beds, distinguished by its crystalinity, hardness and brighter color. The recorded microfacies point to a cyclic variation of the mainly high phreatic level, forming cracks and pedotubules (pedogenesis) filled with carbonate and Fe and Mn oxides (phreatic). The identification of five distinct pedofacies and the stratigraphic correlation in the sedimentary package of the Alemoa Member (base, middle or topmost position) suggest a probable association of paleo-weathering processes and vertebrate preservation. Near channel facies, mainly at the base and top, present smaller exposure periods and higher variations on the phreatic level, and consequently, the best preserved vertebrate fossils. On the other hand, facies which are far from the channel, record more subaerial exposure and more significant phreatic variation, leading to more advanced (although still incipient) paleo-weathering and carbonate precipitation, and to a worst fossil preservation.
9
Cao, Yingjie, Yingxue Xuan, Changyuan Tang, Shuai Guan e Yisheng Peng. "Temporary and net sinks of atmospheric CO<sub>2</sub> due to chemical weathering in subtropical catchment with mixing carbonate and silicate lithology". Biogeosciences 17, n. 14 (31 luglio 2020): 3875–90. http://dx.doi.org/10.5194/bg-17-3875-2020.
Abstract (sommario):
Abstract. The study provided the major ion chemistry, chemical weathering rates and temporary and net CO2 sinks in the Bei Jiang, which was characterized as a hyperactive region with high chemical weathering rates, carbonate and silicate mixing lithology, and abundant sulfuric acid chemical weathering agent of acid deposition and acid mining drainage (AMD) origins. The total chemical weathering rate of 85.46 t km−2 a−1 was comparable to that of other rivers in the hyperactive zones between the latitudes 0 and 30∘. A carbonate weathering rate of 61.15 t km−2 a−1 contributed to about 70 % of the total. The lithology, runoff, and geomorphology had a significant influence on the chemical weathering rate. The proportion of carbonate outcrops had a significant positive correlation with the chemical weathering rate. Due to the interaction between dilution and compensation effect, a significant positive linear relationship was detected between runoff and total carbonate and silicate weathering rates. The geomorphology factors such as catchment area, average slope, and hypsometric integral value (HI) had nonlinear correlation with chemical weathering rate and showed significant scale effect, which revealed the complexity in chemical weathering processes. Dissolved inorganic carbon (DIC) apportionment showed that CCW (carbonate weathering by CO2) was the dominant origin of DIC (35 %–87 %). SCW (carbonate weathering by H2SO4) (3 %–15 %) and CSW (silicate weathering by CO2) (7 %–59 %) were non-negligible processes. The temporary CO2 sink was 823.41×103 mol km−2 a−1. Compared with the temporary sink, the net sink of CO2 for the Bei Jiang was approximately 23.18×103 mol km−2 a−1 of CO2 and was about 2.82 % of the “temporary” CO2 sink. Human activities (sulfur acid deposition and AMD) dramatically decreased the CO2 net sink, even making chemical weathering a CO2 source to the atmosphere.
10
Liu, Zaihua, Wolfgang Dreybrodt e Huan Liu. "Atmospheric CO2 sink: Silicate weathering or carbonate weathering?" Applied Geochemistry 26 (giugno 2011): S292—S294. http://dx.doi.org/10.1016/j.apgeochem.2011.03.085.
Tesi sul tema "Carbonate weathering":
1
Howe, Stephen. "Carbonate weathering in the North of England". Thesis, University of St Andrews, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520237.
2
Reynolds, Amanda Christine. "Geochemical Investigations of Mineral Weathering: Quantifying Weathering Intensity, Silicate versus Carbonate Contributions, and Soil-Plant Interactions". Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/194448.
Abstract (sommario):
This study is the geochemical examination of mineral weathering and its path from hinterland, through sediment deposition and pedogenesis, to its dissolution and eventual uptake into plants or precipitation as carbonate minerals. The three papers examine the rate and character of carbonate and silicate mineral weathering over a wide range of climatic and tectonic regimes, time periods, and lithologies, and focus on very different questions. Examination of the 87Sr/86Sr ratios of architectural ponderosa pine in Chaco Canyon, New Mexico confirms a societally complex style of timber procurement from the 10th to the 12th centuries. In El Malpais National Monument, New Mexico, we measured the 87Sr/86Sr ratios in local bedrock and soils and compared them to the leaf/wood cellulose of four conifers (Pinus ponderosa, Pinus edulis, Juniperus monosperma, Juniperus scopulorum), a deciduous tree (Populus tremuloides), three shrubs (Chrysothamus nauseosus, Fallugia paradoxa, Rhus trilobata), and an annual grass (Bouteloua gracilis) and a lichen (Xanthoparmelia lineola). We found that plant 87Sr/86Sr ratios covaried with variations in plant physiognomy, life history, and rooting depth. In addition, the proportion of atmospheric dust and bedrock mineral contributions to soil water 87Sr/86Sr ratios varied predictably with landscape age and bedrock lithology. On the Himalayan floodplain, soils and paleosol silicate weathering intensities were measured along a climatic transect and through time. Overall, carbonate weathering dominates floodplain weathering. But, periods of more intense silicate weathering between 9 - 2 Ma, identified in soil profile and in the 87Sr/86Sr ratios of pedogenic carbonates, appear to be driven by changes in tectonic, rather than climatic, regime. All three papers are good examples of how 87Sr/86Sr isotopic tracer studies can shed light on pedogenic formation rates and internal processes. The complexity of each system warns against generalizations based on just one locale, one species or lithology, or a few isotopic ratios.
3
Davenport, Jesse. "Isotopic tracing of silicate and carbonate weathering in the Himalayan erosional system". Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0241.
Abstract (sommario):
L'altération des lithologies himalayennes a potentiellement impacté le cycle global du carbone. Pour pouvoir contraindre et comprendre les processus qui se sont produits dans l'Himalaya et qui ont affecté ces cycles, nous devons être distinguer les signatures de l'altération du silicate et du carbonate dans la charge dissoute des fleuves de l'Himalaya. Des études antérieures ont tenté de le faire en utilisant diverses méthodes mais il n’existe toujours pas de consensus clair sur l’ampleur et le flux de l’altération du silicate dans l’Himalaya. Cette thèse propose l'utilisation du 40Ca comme traceur pouvant améliorer la quantification du flux d'altération du silicate et du carbonate dans la charge dissoute des rivières himalayennes. Des travaux antérieurs ont montré que le budget de l'eau de mer 40Ca est dominé par une source de manteau, de sorte que les carbonates marins ont une signature homogène de 40Ca indiscernable par rapport à la valeur du manteau. En revanche, la croûte supérieure de silicate devrait avoir développé une composition radiogénique. La différence entre la signature en Ca radiogénique des lithologies de carbonate et de silicate peut donc être utilisée pour différencier l’altération du carbonate et du silicate dans la charge dissoute des rivières. Nous présentons ici une étude géochimique comprenant des analyses de Ca radiogénique des rivières drainant les principales unités lithologiques de l'Himalaya, ainsi que des résultats provenant de sédiments, de substrat rocheux, de sol et de gravier. Nos résultats montrent que les carbonates de l’Himalaya ne présentent pas d’excès de 40Ca radiogénique malgré des signatures très variables 87Sr/86Sr, alors que les sédiments sont radiogènes (+0.9 à +4). Ceci suggère que pour Ca, contrairement à Sr, l'échange isotopique entre les lithologies silicate et carbonate a été minime. La composition en Ca radiogène de l'eau des rivières va de +0.1 dans les captages à prédominance carbonatée à +11 dans les rivières drainant des bassins versants silicatés. Pour les grandes rivières, les estimations du budget relatives à l’altération du silicate et du carbonate sur la base des éléments principaux et la composition en Ca radiogénique tendent à concorder. Cependant, pour certaines rivières plus petites, en particulier celles drainant des bassins à dominance silicatée dans les formations cristallines de HHC et du LH, certaines divergences sont observées. Celles-ci ne peuvent pas être attribuées à une définition imprécise de la composition chimique ou radiogénique en Ca des pôles de mélange utilisés pour la modélisation budgétaire, car les valeurs requises pour résoudre le modèle ne sont pas raisonnables. Ils ne peuvent pas non plus être expliqués par la précipitation de carbonates secondaires dans les rivières car la composition non radiogénique de carbonates suggère que ce processus n'est que mineur. Au contraire, ces différences peuvent être dues à la dissolution des traces de calcite radiogénique contenues dans les lithologies de silicate HHC et LH. Le vieillissement de ce matériau, qui ne représente qu'une infime partie de la surface du captage du silicate, pourrait produire une proportion substantielle du Ca radiogénique et pourrait ainsi avoir une influence significative sur le calcul des budgets de ces bassins à partir des données isotopiques. Néanmoins, comme cet effet est observé principalement dans les bassins à faible taux d’érosion des silicates, son influence sur les estimations du flux global de vieillissement du silicate sera mineure. Plus généralement, les résultats de cette thèse impliquent que le système 40Ca permet une résolution de problématiques qui ne peuvent pas être approfondies avec succès à l'aide d'isotopes Sr dans l'Himalaya. Des travaux supplémentaires sont nécessaires pour définir la gamme complète des compositions de Ca radiogénique dans l’Himalaya afin de répondre clairement aux questions concernant les flux d’altération des silicatesWeathering of Himalayan lithologies has had a potential impact on the global carbon cycle. To be able to constrain and understand the processes that occurred in the Himalayas that affected these cycles, we must be able to distinguish the signatures of silicate and carbonate weathering in the dissolved load of Himalayan rivers. Previous studies have attempted to do this using a variety of methods but there is still not a clear consensus on the magnitude and flux of silicate weathering in the Himalaya. This thesis proposes the use of 40Ca as a tracer that could improve the quantification of the silicate and carbonate weathering flux in the dissolved load of Himalayan rivers. Previous work has shown that the 40Ca budget of seawater is dominated by a mantle source, such that marine carbonates have a homogeneous 40Ca signature indistinguishable from the mantle value. In contrast, the upper silicate crust is expected to have developed a radiogenic composition. The difference between the radiogenic Ca signature of carbonate and silicate lithologies can be therefore used to differentiate between carbonate and silicate weathering in the dissolved load of rivers. Here, we present a geochemical survey, including radiogenic Ca analyses, of rivers draining the main lithological units of the Himalaya, as well as results from sediments, bedrock, soil and gravel. Our results show that Himalayan carbonates exhibit no radiogenic 40Ca excesses despite highly variable 87Sr/86Sr signatures, whereas sediments are variably radiogenic (+0.9 to +4). This suggests that for Ca, unlike for Sr, isotopic exchange between the silicate and carbonate lithologies has been minimal. The radiogenic Ca composition of river water ranges from +0.1 in carbonate dominated catchments to +11 in rivers draining silicate catchments. For large rivers, silicate and carbonate weathering budget estimates based on major elements and radiogenic Ca compositions tend to agree. However, for some smaller rivers, especially those draining silicate dominated basins in the HHC and LH formations, some discrepancies are observed. These cannot be attributed to poor definition of the chemical or radiogenic Ca composition of the endmembers used for budget modeling, as the values required to bring the estimates into agreement are unreasonable. They also cannot be explained by precipitation of secondary carbonates in the rivers as the non-radiogenic composition of the carbonate fraction of sediments suggests that this process is only minor. Rather, these discrepancies may be due to the dissolution/weathering of trace amounts of radiogenic calcite contained within HHC and LH silicate lithologies. The weathering of such material, which represents only a tiny fraction of the area of the silicate catchment, could yield a substantial proportion of the radiogenic Ca and may thus have a significant influence on the isotopically based weathering budgets of these basins. Nevertheless, as this effect is observed primarily in basins with low silicate erosion rates, its influence on estimates of the overall silicate weathering flux will be minor. More generally, the results of this thesis imply that the 40K–40Ca system can resolve issues that cannot be successfully addressed using Sr isotopes in the Himalaya. Further work is needed to define the full range of radiogenic Ca compositions in the Himalaya in order to clearly answer questions regarding silicate weathering fluxes
4
Salley, Devon Mr. "Advancing Methods to Measure the Atmospheric CO2 Sink from Carbonate Rock Weathering". TopSCHOLAR®, 2016. http://digitalcommons.wku.edu/theses/1603.
Abstract (sommario):
With rising atmospheric CO2 concentrations, a detailed understanding of processes that impact atmospheric CO2 fluxes is required. While a sink of atmospheric carbon from the continents to the ocean from carbonate mineral weathering is, to some degree, offset by carbonate mineral precipitation in the oceans, efforts are underway to make direct measurements of these fluxes. Measurement of the continental sink has two parts: 1) measurement of the dissolved inorganic carbon (DIC) flux leaving a river basin, and 2) partitioning the inorganic carbon flux between the amount removed from the atmosphere and the portion from the bedrock. This study attempted to improve methods to measure the DIC flux using existing data to estimate the DIC flux from carbonate weathering within the limestone karst region of south central Kentucky. The DIC flux from the Barren River drainage basin upstream from Bowling Green in southern Kentucky and northern Tennessee, and the upper Green River drainage basin, upstream from Greensburg, Kentucky, was measured, each for a year, using U.S.G.S. discharge data and water-chemistry data from municipal water plants. A value of the (DIC) flux, normalized by time and area of carbonate rock, of 4.29 g km-3 day-1 was obtained for the Barren River, and 4.95 kg km-3 for the Green. These compared favorably with data obtained by Osterhoudt (2014) from two nested basins in the upper Green River with values of 5.66 kg km-3 day-1 and 5.82 kg km-3 day-1 upstream from Greensburg and Munfordville, respectively. Additional normalization of the values obtained in this study
by average precipitation minus evapotranspiration over the area of carbonate rock, or water available for carbonate dissolution, resulted in values of 5.61x107 g C (km3 H20)- 1 day-1 (grams of carbon per cubic kilometer of water, per day) for the Barren, and 7.43x107g C (km3 H20)-1 day-1 for the Green River. Furthermore, a statistical relationship between the total DIC flux and time-volume of water available for dissolution has been observed, yielding an r2 value of 0.9478. This relationship indicates that the primary variables affecting DIC flux for these drainage basins are time and the volume of water available for dissolution.
5
Devine, Steven M. "Petrographic Controls on Weathering of the Haney Limestone". TopSCHOLAR®, 2016. http://digitalcommons.wku.edu/theses/1594.
Abstract (sommario):
Although karst processes in south central Kentucky have been studied extensively, the Haney Limestone Member of the Golconda Formation has not been studied in detail in contrast to limestones stratigraphically below it that are thicker. In addition, the relationship between petrographic features of the Haney Limestone and the formation of caves and karst features has not been studied extensively compared to lithographic, petrographic, or structural variables
Petrographic data were collected using core and surface exposures across the study area of south central Kentucky from northern Logan and Warren counties up toward the Rough Creek Graben region, and stratigraphic columns were constructed. Twenty-three petrographic thin-sections were made from samples collected at these sites, described, and photo documented. These studies have revealed that grain size and silica content play a role in how the Haney weathers both in surface exposure and in a cave setting. Petrographic thin-section analysis suggests that the Haney possesses a complex diagenetic history that involves several generations of calcite cementation, dolomitization, silicification, and pressure-dissolution features in the form of microstylolites and stylolites. A basal shale in the Big Clifty occurs commonly at the Big Clifty/Haney contact and acts as a confining hydrogeologic unit, which is favorable for the development of springs and caves.
Studying the Haney Limestone petrographically provides an opportunity not only to study a lesser known unit, but also in the context of relating petrographic influences or controls on the morphology of Haney cave-passage development under both vadose and phreatic hydrologic regimens. Heretofore, the vast majority of cave morphological studies have only linked the hydrologic regimen to formation of cave passages, but such studies have not considered petrographic variance. This study not only relates karst features to petrographic variance, but also provides a petrographical description of the Haney across south central Kentucky, whereas many previous studies focused on Illinois and Indiana. Understanding Haney petrographic characteristics also provides context for potential carbonate hydrocarbon reservoirs and groundwater resources in the Illinois Basin region.
6
Osterhoudt, Laura Leigh. "Impacts of Carbonate Mineral Weathering on Hydrochemistry of the Upper Green River Basin, Kentucky". TopSCHOLAR®, 2014. http://digitalcommons.wku.edu/theses/1337.
Abstract (sommario):
Kentucky’s Upper Green River Basin has received significant attention due to the area’s high biodiversity and spectacular karst development. While carbonate bedrock is present throughout the watershed, it is more extensive and homogenous along the river between Greensburg and Munfordville than upstream from Greensburg where the geology is more heterogeneous. This research quantitatively evaluated how lithological differences between the two catchment areas impact hydrochemistry and inorganic carbon cycling. This first required correcting catchment boundaries on previous US Geological Survey Hydrologic Unit Maps to account for areas where the boundaries cross sinkhole plains. Basin boundaries using existing Kentucky Division of Water dye trace data differed from the earlier versions by as much as three kilometers. The river at the downstream site is more strongly influenced by carbonate mineral dissolution, reflected in higher specific conductance (SpC) and pH. The SpC at Munfordville ranges from 0.9 to 4.8 times that at Greensburg, averaging 2.0 times higher. Although rainfall is impacted by sulfuric acid from coal burning, river pH is buffered at both sites. The pH is higher at Munfordville 91% of the time, by an average of 0.28 units. Diurnal, photosynthetic pH variations are damped out downstream suggesting interactions between geologic and biological influences on river chemistry. River temperature differences between the two sites are at least 4oC higher at Greensburg under warm season conditions, but there is a clear trend of temperature differences diminishing as the river cools through the fall and winter. This results from a relatively stable temperature at Munfordville, impacted by large spring inputs of groundwater within the karst region downstream. Although weak statistical relationships between SpC and HCO3 - create uncertainties in high resolution carbon flux calculations, measurement of these fluxes is more highly impacted by discharge variations than concentration variations, which resulted in average daily atmospheric flux estimates within 34% between the two basins using weekly concentration data (3.3x108 vs. 2.2x108 gkm-2 d-1, where km2 is the outcrop area of carbonate rocks), and within only 12% using 15-minute concentration data from regressions (2.6x108 vs. 2.3x108 gkm-2 d-1) for Greensburg and Munfordville, respectively.
7
Zeng, Sibo [Verfasser]. "The evolution of carbonate weathering carbon sinks under climatic and anthropogenic perturbations / Sibo Zeng". Berlin : Freie Universität Berlin, 2021. http://d-nb.info/1238595804/34.
8
Larrahondo-Cruz, Joan Manuel. "Carbonate diagenesis and chemical weathering in the Southeastern United States: some implications on geotechnical behavior". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42912.
Abstract (sommario):
The Savannah River Site (SRS) deposits in the Southeastern US between 30-45 m of depth are calcium carbonate-rich, marine-skeletal, Eocene-aged sediments with varying clastic content and extensive diagenetic alteration, including meter-sized caves that coexist with brittle and hard limestone. An experimental investigation including geotechnical (P- and S-wave velocities, tensile strength, porosity) and geochemical (EDS, XRD, SEM, N2-adsorption, stable isotopes, K-Ar age dating, ICP-assisted solubility, groundwater) studies highlighted the contrast between hard and brittle limestones, their relationship with cave formation, and allowed calculation of parameters for geochemical modeling. Results demonstrate that brittle and hard limestones bear distinct geochemical signatures whereby the latter exhibits higher crystallinity, lower clastic load, and freshwater-influenced composition. Results also reveal carbonate diagenesis pathways likely driven by geologic-time seawater/freshwater cycles, microorganism-driven micritization, and freshwater micrite lithification. The second section of this investigation dealt with SRS surface soils which are largely coarse-grained and rich in iron oxides with various degrees of maturity. These soils were simulated in the laboratory using Ottawa sands that were chemically coated with goethite and hematite. Surface (SEM, AFM, N2-adsorption) and geotechnical properties (fabric, small-strain stiffness, shear strength) were investigated on the resulting "soil analog". Results indicate that iron-oxide coated sands bear distinct inherent fabric and enhanced small-strain stiffness and critical state parameters when compared to uncoated sands. Contact mechanics analyses suggest that iron oxide coatings yield an increased number of grain-to-grain contacts, higher surface roughness, and interlocking, which are believed to be responsible for the observed properties.
9
Thorley, Rachel Marianne Sarah. "The role of forest trees and their mycorrhizal fungi in carbonate weathering and phosphorus biogeochemical cycling". Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/15945/.
Abstract (sommario):
Over millions of years, atmospheric CO2 concentrations, and Earth’s climate, are regulated by continental silicate weathering and associated marine carbonate deposition. On this geological timescale, carbonate weathering has no net effect on CO2 drawdown. However, over the coming decades-to-centuries, accelerated weathering of carbonate rocks may provide a sink for anthropogenic CO2 emissions and increase alkalinity flux to the oceans to counteract ocean acidification. Recent experimental evidence strongly supports trees and their associated mycorrhizal fungi as key drivers of silicate mineral weathering; however, their role in the context of carbonate weathering is largely unknown. Carbonate lithology is abundant globally and underlies many boreal and temperate forest ecosystems in the northern hemisphere. If biological enhancement of carbonate weathering by forests occurs, this might presents a new opportunity for CO2 sequestration. This thesis presents results from a 14-month field experiment at the UK's national pinetum investigating carbonate rock weathering under a common climate. Overall, I find original evidence for biotic enhancement of calcite- and dolomite weathering by an evolutionary diverse range of trees that host either arbuscular (AM) or ectomycorrhizal (EM) root-associating fungal symbionts. Recent soil analyses are integrated with a re-interpretation of historic data to provide an 85-year record of in-situ soil development under different forestry species. This study challenges the classic dogma that divergence of properties is driven by the major tree functional groups, angiosperms and gymnosperms. Instead, we find that over decades, mycorrhizal functional type plays a dominant role in determining soil physico- chemical characteristics, and conditions generated by EM fungi are likely to enhance mineral weathering. Field trials next investigated the impact of tree-mycorrhizal functional group on weathering of the four main carbonate rock types (chalk, limestone, marble and dolomite) and a quartz silicate. Under EM trees carbonate rock grain dissolution was 12 times faster that silicate weathering. In the initial 3 months, calcite weathering intensity increased from gymnosperm to angiosperm species and from AM to later, but independently-evolved EM fungal partnerships. More extensive weathering after 6 months, especially within EM forest soils, confirms the importance of these fungi for carbonate mineral dissolution and nutrient mobilisation. This effect is linked to rhizosphere acidification by EM fungi and is confirmed by a parallel study of tree species’ influence on soil chemistry. Both AM and EM fungi facilitate the mobilisation of nutrient elements, which are provided to their host plants in exchange for carbon from photosynthesis. I applied a suite of nanoscale surface analysis techniques (VSI, SEM) to quantify mineral alteration and provide direct evidence for mycorrhizal involvement in carbonate weathering in the field. Fungal hyphae preferentially colonised chalk and quartz silicate grains, which contained the highest concentrations of phosphorus (P), a growth limiting elemental nutrient. P was selectively depleted from silicate grains, especially in EM forest soils, but accumulated on carbonates. Although the origin of this accumulated P remains uncertain, extensive analyses of different potential P-pools indicated it is likely to be inorganic, but accumulated via active microbial import. These findings lead to new insights linking carbonate weathering with phosphorus biogeochemical cycling in soils. Results show that P from the surrounding environment is concentrated on carbonate grains and this potentially provides a renewable P resource accessible to host trees. Overall, this thesis builds new support for the role of mycorrhizal partnerships in shaping soil properties important for accelerating carbonate rock weathering (Chapter 2); presenting the first field-based evidence for the enhancement of carbonate dissolution by tree roots and their associated mycorrhizal partners (Chapters 3-5) and generating new insights into biogeochemical P cycling in soils (Chapter 4). More broadly, these findings suggest targeted reforestation/afforestation with EM-tree taxa on carbonate-rich terrain as a possible regional-scale land management strategy for promoting short-term anthropogenic CO2 sequestration and perhaps helping ameliorate ocean acidification.
10
Singer, Autumn B. "Measuring Inorganic Carbon Fluxes from Carbonate Mineral Weathering from Large River Basins: The Ohio River Basin". TopSCHOLAR®, 2017. https://digitalcommons.wku.edu/theses/2044.
Abstract (sommario):
Rising atmospheric CO2 concentrations have motivated efforts to better quantify reservoirs and fluxes of Earth’s carbon. Of these fluxes from the atmosphere, one that has received relatively little attention is the atmospheric carbon sink associated with carbonate mineral dissolution. Osterhoudt (2014) and Salley (2016) explored new normalization techniques to improve and standardize a process for measuring this flux over large river basins. The present research extends this work to the 490,600 km2 Ohio River drainage basin and 11 subbasins. The study estimated the DIC flux leaving these basins between October 1, 2013, and September 30, 2014, based on secondary hydrogeochemical, geologic, and climatic data. The total annual DIC flux for the Ohio River basin was estimated to be 7.54 x 1012 g carbon (C). The time-volume normalized value of DIC flux for the Ohio basin was 3.36 x 108 g C/km3 day, where the km3 refers to the amount of water available during the year. This was within 71.4% agreement with the Barren River data (Salley, 2016) and within 63.9% agreement with the Green River data (Osterhoudt, 2014). In general, normalized DIC flux values of sub-basins containing at least modest amounts (more than 8%) of exposed carbonates (Tennessee, Cumberland, Green, Kentucky, Licking, Monongahela, and Allegheny) were in strong agreement with the normalized DIC flux of the Ohio River basin, whereas inclusion of basins with little or no near surface carbonates (Wabash, Great Miami, Scioto and Kanawha) yielded poor agreement. Regression analysis yielded strong agreement between DIC flux and the normalization parameters for the carbonate-bearing sub-basins (R2 = 0.97, p =
Libri sul tema "Carbonate weathering":
1
Ellam, Rob. 7. Reconstructing the past and weathering the future. Oxford University Press, 2016. http://dx.doi.org/10.1093/actrade/9780198723622.003.0007.
Abstract (sommario):
Tiny microfossils called Foraminifera form calcium carbonate shells that record the δ18O composition of the seawater in which they grew. These microfossils are found in sea bed sediment cores, and a lot of information from these oxygen isotope records can be extracted. ‘Reconstructing the past and weathering the future’ looks at the methodology used in palaeoclimate studies and explains gain and phase modelling and Milankovitch orbital cycles. Similar isotope temperature records have been constructed from polar ice cores. Atmospheric CO2 composition can be reconstructed from the amount of CO2 dissolved in the ice. A new sub-discipline of clumped isotope geochemistry—‘isotomics’—will have applications far beyond carbonate palaeothermometry.
2
Hajna, Nadja Zupan. Incomplete Solution: Weathering of Cave Walls & the Production, Transport & Deposition of Carbonate Fines (Carsologica). Zalozhba, 2003.
3
Berner, Robert A. The Phanerozoic Carbon Cycle. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780195173338.001.0001.
Abstract (sommario):
The term "carbon cycle" is normally thought to mean those processes that govern the present-day transfer of carbon between life, the atmosphere, and the oceans. This book describes another carbon cycle, one which operates over millions of years and involves the transfer of carbon between rocks and the combination of life, the atmosphere, and the oceans. The weathering of silicate and carbonate rocks and ancient sedimentary organic matter (including recent, large-scale human-induced burning of fossil fuels), the burial of organic matter and carbonate minerals in sediments, and volcanic degassing of carbon dioxide contribute to this cycle. In The Phanerozoic Carbon Cycle, Robert Berner shows how carbon cycle models can be used to calculate levels of atmospheric CO2 and O2 over Phanerozoic time, the past 550 million years, and how results compare with independent methods. His analysis has implications for such disparate subjects as the evolution of land plants, the presence of giant ancient insects, the role of tectonics in paleoclimate, and the current debate over global warming and greenhouse gases
4
Kirchman, David L. Introduction to geomicrobiology. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198789406.003.0013.
Abstract (sommario):
Geomicrobiology, the marriage of geology and microbiology, is about the impact of microbes on Earth materials in terrestrial systems and sediments. Many geomicrobiological processes occur over long timescales. Even the slow growth and low activity of microbes, however, have big effects when added up over millennia. After reviewing the basics of bacteria–surface interactions, the chapter moves on to discussing biomineralization, which is the microbially mediated formation of solid minerals from soluble ions. The role of microbes can vary from merely providing passive surfaces for mineral formation, to active control of the entire precipitation process. The formation of carbonate-containing minerals by coccolithophorids and other marine organisms is especially important because of the role of these minerals in the carbon cycle. Iron minerals can be formed by chemolithoautotrophic bacteria, which gain a small amount of energy from iron oxidation. Similarly, manganese-rich minerals are formed during manganese oxidation, although how this reaction benefits microbes is unclear. These minerals and others give geologists and geomicrobiologists clues about early life on Earth. In addition to forming minerals, microbes help to dissolve them, a process called weathering. Microbes contribute to weathering and mineral dissolution through several mechanisms: production of protons (acidity) or hydroxides that dissolve minerals; production of ligands that chelate metals in minerals thereby breaking up the solid phase; and direct reduction of mineral-bound metals to more soluble forms. The chapter ends with some comments about the role of microbes in degrading oil and other fossil fuels.
Capitoli di libri sul tema "Carbonate weathering":
1
Flügel, Erik. "Carbonate Rock Resources, Facies, Weathering, Preservation". In Microfacies of Carbonate Rocks, 895–902. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-08726-8_18.
2
Flügel, Erik. "Carbonate Rock Resources, Facies, Weathering, Preservation". In Microfacies of Carbonate Rocks, 895–902. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03796-2_18.
3
Joshi, Moulishree. "Accelerated Weathering of Limestone for CO2 Mitigation". In Petro-physics and Rock Physics of Carbonate Reservoirs, 45–51. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-1211-3_4.
4
Pollak, Davor. "Engineering-Geological Properties of Carbonate Rocks in Relation to Weathering Intensity". In Engineering Geology for Infrastructure Planning in Europe, 162–71. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-540-39918-6_20.
5
Jroundi, Fadwa, Maria Teresa Gonzalez-Muñoz e Carlos Rodriguez-Navarro. "Protection and Consolidation of Stone Heritage by Bacterial Carbonatogenesis". In Microorganisms in the Deterioration and Preservation of Cultural Heritage, 281–99. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-69411-1_13.
Abstract (sommario):
AbstractFor millennia, artists and architects around the world used natural stone for the carving of sculptures and the construction of monuments, such as Roman, Greek, and Maya temples, the European cathedrals, and the Taj Mahal, just to name a few. Currently, the survival of these irreplaceable cultural and historical assets is under threat due to their continued degradation caused by various biotic and abiotic weathering processes that affect not only the aesthetic appearance of these structures, but also their durability and survival. The natural precipitation of calcium carbonate minerals by bacteria has been proposed for conservative interventions in monument restoration. This chapter reviews the application of biomineralization by (indigenous) bacterial carbonatogenesis as a novel technology for the protection and consolidation of altered ornamental materials. Carbonatogenesis is based on the ability of some bacteria to induce calcium carbonate precipitation. Laboratory and in situ results support the efficacy of bacterial carbonatogenesis, since remarkable protection and consolidation are achieved on the surface and in depth, without alterations in color or porosity, and without fostering the development of microbiota that could be harmful to the stone material. A discussion on the advantages of this novel biotechnology is provided. Challenges and future work on bioconsolidation of stone artifacts are also outlined.
6
Schlanger, S. O. "Strontium Storage and Release During Deposition and Diagenesis of Marine Carbonates Related to Sea-Level Variations". In Physical and Chemical Weathering in Geochemical Cycles, 323–39. Dordrecht: Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-3071-1_15.
7
Hagemann, Steffen, Ana-Sophie Hensler, Rosaline Cristina Figueiredo e Silva e Harilaos Tsikos. "Light Stable Isotope (O, H, C) Signatures of BIF-Hosted Iron Ore Systems: Implications for Genetic Models and Exploration Targeting". In Isotopes in Economic Geology, Metallogenesis and Exploration, 373–97. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27897-6_12.
Abstract (sommario):
AbstractStable isotope data from hypogene (i.e., below the line of weathering) iron oxides and gangue minerals from BIF-hosted iron ore deposits in Australia, South Africa, and Brazil have significantly assisted in constraining different hydrothermal fluid sources and fluid flow models during the upgrade of BIF to iron ore. The δ18O values on iron oxides from BIF and different paragenetic stages of enrichment display a consistent decrease from unenriched BIF (4–9‰) to as low as −10‰ for high-grade iron ore. This large shift in oxygen isotope values is interpreted as evidence for enormous incursion of ‘ancient’ meteoric water into fault and fracture zones at the time of iron enrichment during the Archean and Paleoproterozoic time. The δ18Ofluid values of paragenetically early iron oxides of > 4‰ suggest the involvement of magmatic fluids in greenstone belt-hosted Carajás-type iron ore deposits, and basinal brines in basin-hosted Hamersley-type deposits. In contrast, the paragenetically late stage iron oxides in the metamorphosed, basin hosted iron ore deposits of the Quadrilátero Ferrífero display δ18Ofluid values > 6‰. This reflects the renewed deep crustal, hypogene (metamorphic or magmatic) fluid influx. Carbon and oxygen isotope data on carbonates in BIF and hydrothermally altered iron ore indicate that carbon in the latter is not derived from BIF units, but represents either magmatic carbon in the case of the Carajás-type deposits or carbon within the underlying basin stratigraphy as in the case of the Hamersley-type iron deposits. The systematic decrease of δ18O values in iron oxides from the early to late paragenetic stages and from the distal to proximal alteration zone, including the ore zone, may be used as a geochemical vector. In this case, oxygen isotope analyses on iron oxides provide a potential exploration tool, particularly for targeting the extension of iron ore bodies or entirely concealed high-grade iron ore deposits, in which hematite/magnetite are frequently the only mineral that can be readily analysed.
8
Latypov, A., N. Zharkova e F. Mouraviev. "Dispersed weathering products of carbonate rock". In Global View of Engineering Geology and the Environment, 891–96. CRC Press, 2013. http://dx.doi.org/10.1201/b15794-143.
9
Berner, Robert A. "Processes of the Long-Term Carbon Cycle: Organic Matter and Carbonate Burial and Weathering". In The Phanerozoic Carbon Cycle. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780195173338.003.0005.
Abstract (sommario):
The organic subcycle of the long-term carbon cycle, where organic matter burial and weathering are involved, constitutes the major control on the evolution of atmospheric oxygen. It is also important as a secondary factor affecting atmospheric CO2. Thus, it is important to better understand the processes whereby organic matter is buried in sediments and oxidized upon subsequent exposure to weathering during uplift onto the continents. This is especially true of the Paleozoic rise of land plants, which had a large effect on atmospheric CO2 because of increased global organic burial due to the addition of plant debris to sediments. The burial of organic matter in marine sediments is impacted strongly by the availability of the nutrient elements, phosphorus and nitrogen, so a complete discussion of the cycling of organic carbon should involve some discussion of the cycles of these elements. Carbonate burial is the ultimate sink for CO2 derived from the atmosphere via the weathering of Ca and Mg silicates. The location of this burial, shallow water shelves versus the deep sea floor, is important because it affects the probability that the carbonate will be eventually thermally recycled and the carbon returned to the atmosphere. Carbonate weathering is the dominant process affecting river water composition and is a key component of the cycling of carbon. Its importance to the long-term carbon cycle is that, in order to calculate the removal of CO2 from the atmosphere via Ca and Mg silicate weathering, it is necessary to correct total carbonate burial for that derived from carbonate weathering. At present, sedimentary organic matter burial occurs in swamps, lakes, reservoirs, estuaries, and in the open marine environment. The ultimate sources of the organics are land vegetation and marine phytoplankton. Also, soil organic matter, which is intimately associated with clay minerals, is eroded and transported to the sea by rivers (Hedges et al., 1994). A major question is how much of the total global burial is of marine or nonmarine origin. Recent work has shown that organic burial on land is much higher than previously recognized, especially as a result of human activities (Dean and Gorham, 1998; Stallard, 1998).
10
Berner, Robert A. "Processes of the Long-Term Carbon Cycle: Chemical Weathering of Silicates". In The Phanerozoic Carbon Cycle. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780195173338.003.0004.
Abstract (sommario):
Carbon dioxide is removed from the atmosphere during the weathering of both silicates and carbonates, but, over multimillion year time scales, as pointed out in chapter 1, only Ca and Mg silicate weathering has a direct effect on CO2. Carbon is transferred from CO2 to dissolved HCO3– and then to Ca and Mg carbonate minerals that are buried in sediments (reaction 1.4). In this chapter the factors that affect the rate of silicate weathering and how they could have changed over Phanerozoic time are discussed. Following classical studies (e.g., Jenny, 1941), the factors discussed include relief, climate (rainfall and temperature), vegetation, and lithology. However, over geological time scales, additional factors come into consideration that are necessarily ignored in studying modern weathering. These include the evolution of the sun and continental drift. The aim of this book is to consider all factors, whether occurring at present or manifested only over very long times, that affect weathering as it relates to the Phanerozoic carbon cycle. Within the past decade much attention has been paid to the effect of mountain uplift on chemical weathering and its effect on the uptake of atmospheric CO2, an idea originally espoused by T.C. Chamberlin (1899). The uplift of the Himalaya Mountains and resulting increased weathering has been cited as a principal cause of late Cenozoic cooling due to a drop in CO2 (Raymo, 1991). Orogenic uplift generally results in the development of high relief. High relief results in steep slopes and enhanced erosion, and enhanced erosion results in the constant uncovering of primary minerals and their exposure to the atmosphere. In the absence of steep slopes, a thick mantle of clay weathering product can accumulate and serve to protect the underlying primary minerals against further weathering. An excellent example of this situation is the thick clay-rich soils of the Amazon lowlands where little silicate weathering occurs (Stallard and Edmond, 1983). In addition, the development of mountain chains often leads to increased orographic rainfall and, at higher elevations, increased erosion by glaciers. All these factors should lead to more rapid silicate weathering and faster uptake of atmospheric CO2.
Atti di convegni sul tema "Carbonate weathering":
1
Knapp, Will, e Edward Tipper. "Global efficacy of enhancing carbonate weathering". In Goldschmidt2022. France: European Association of Geochemistry, 2022. http://dx.doi.org/10.46427/gold2022.9621.
2
Anovitz, Lawrence, Timothy Prisk, Simon Emmanuel, Michael Cheshire, Juliane Weber, Markus Bleuel, Jan Ilavsky, David Mildner e Cedric Gagnon. "Scale, Carbonate Weathering, and the Laboratory/Field Dichotomy". In Goldschmidt2022. France: European Association of Geochemistry, 2022. http://dx.doi.org/10.46427/gold2022.12354.
3
Zinchuk, N. N. "SPECIFIC FEATURES OF CLAY MINERALS IN ANCIENT CRUSTS OF WEATHERING OF VARIOUS ROCKS". In Проблемы минералогии, петрографии и металлогении. Научные чтения памяти П. Н. Чирвинского. Пермский государственный национальный исследовательский университет, 2021. http://dx.doi.org/10.17072/chirvinsky.2021.54.
Abstract (sommario):
The most important typomorphic indications of clay formations in the studied crusts of weathering are as follows: a) omnipresent dioctahedral hydromica (2М1) in the crust of weathering of terrigenous-carbonate rocks and its association in the most mature profiles with kaolinite of relatively ordered structure, than of kaolinite, having been formed at the expense of other rocks; b) constant availability of trappean formation (tuffs, tufogene rocks, dolerites) in sections of crusts of weathering together with di- and trioctahedral montmorillonite, as well as disordered vermiculite-montmorillonite mixed-layered formation, to this or that degree disordered kaolinite, associated in the crust of weathering of tufogene rocks with halloysite (at complete absence of micaceous minerals in the products of weathering); c) the content in the crust of weathering of kimberlites together with polycationic montmorillonite of a significant quantity of trioctahedral chlorite (packets δ and δ’), serpentine (structural types A and B) and altered to various degree phlogopite, including related with it hydromica 1M.
4
Scheingross, Joel, Aaron Bufe, Jordon Hemingway, Niels Hovius, Anja Schleicher e Tanya Goldberg. "Enhancement of Carbonate, Silicate, and Sulfide Weathering via Fluvial Sediment Abrasion". In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.2301.
5
Briolet, Théo, Elisabeth Bemer, Olivier Sissmann, Valerie Poitrineau, Maxime Pelerin, Mario Bellamy e Jérôme Fortin. "Experimental study of microstructural controls on the weathering of carbonate rocks". In Goldschmidt2022. France: European Association of Geochemistry, 2022. http://dx.doi.org/10.46427/gold2022.10188.
6
Planavsky, Noah, Chris Reinhard e Shuang Zhang. "ENHANCED CARBONATE WEATHERING AS A MEANS OF CO2 CAPTURE". In GSA Connects 2021 in Portland, Oregon. Geological Society of America, 2021. http://dx.doi.org/10.1130/abs/2021am-369068.
7
Zinchuk, N. N., e M. N. Zinchuk. "LITHOLOGIC-MINERALOGICAL FEATURES OF ANCIENT DIAMONDIFEROUS THICKNESSES IN THE REGIONS OF KIMBERLITE MAGMATISM DEVELOPMENT". In Проблемы минералогии, петрографии и металлогении. Научные чтения памяти П. Н. Чирвинского. Пермский государственный национальный исследовательский университет, 2021. http://dx.doi.org/10.17072/chirvinsky.2021.36.
Abstract (sommario):
Complex research of ancient crusts of weathering on terrigenous-carbonate rocks, dolerites, tufogene formations and kimberlites, as well as products of their rewashing in Mesozoic sedimentary thick layers of main diamondiferous regions of the Siberian platform allowed restoring specific features of their structural-formation generation Results of investigations allowed carrying out zoning of the territory on the area of the following distinction of Middle-Upper Triassic crusts of weathering and products of their redeposition: a) unfavorable (lower parts of paleo-depressions); b) favorable (upper parts of paleo-depressions); c) highly favorable (slopes of these structures). The identified typomorphic features of various minerals in various types of crusts of weathering may be successfully used when trying to determine their (including diamondiferous material) impact on various levels of Mesozoic sedimentary thick layers of the region.
8
Xu, Yang, Zhangdong Jin, Long-Fei Gou, Albert Galy, Chenyang Jin, Chen Chen, Chenzi Li e Li Deng. "Carbonate weathering drives magnesium isotopes in large rivers: Insights from the Yangtze River". In Goldschmidt2022. France: European Association of Geochemistry, 2022. http://dx.doi.org/10.46427/gold2022.10852.
9
Erlanger, Erica, Aaron Bufe, Jeremy Caves Rugenstein, Vincenzo Picotti e Sean Willet. "Controls on Chemical Weathering and Physical Erosion in a Mixed Carbonate-Siliciclastic Orogen". In Goldschmidt2021. France: European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.3866.
10
Michalik, Marek, e Wanda Wilczyńska-Michalik. "WEATHERING OF CARBONATE ROCKS IN A POLLUTED URBAN ATMOSPHERE: THE MECHANISM OF PROCESSES". In International Scientific Conference GEOBALCANICA 2017. Geobalcanica Society, 2017. http://dx.doi.org/10.18509/gbp.2017.03.
Rapporti di organizzazioni sul tema "Carbonate weathering":
1
MacNaughton, R. B., e K. M. Fallas. Neoproterozoic-Cambrian stratigraphy of the Mackenzie Mountains, northwestern Canada, part IV: a stratigraphic reference section for the Ediacaran-Cambrian transition in NTS 95-M (Wrigley Lake map area). Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/329217.
Abstract (sommario):
A composite reference section for the upper Ediacaran and lower Cambrian is documented for a location near Moose Horn River in Wrigley Lake map area (NTS 95-M), Mackenzie Mountains, Northwest Territories. Four measured stratigraphic sections cover, in ascending order: the uppermost Sheepbed Formation; the informal Sheepbed carbonate; the lower, middle, and upper members of the Backbone Ranges Formation; the Sekwi Formation; and the lowermost beds of the Rockslide Formation. The uppermost Sheepbed Formation is dominated by dark-weathering shale and siltstone. The Sheepbed carbonate (440 m) lies conformably on the Sheepbed Formation and consists of limestone, dolostone, and dolomitic siltstone, including several horizons of rudstone with clasts up to boulder size. The upper surface of the Sheepbed carbonate has been eroded and the unit thins to a zero edge to the east. The lower member of the Backbone Ranges Formation (253 m) is heterolithic, including interbedded quartzose siltstone and quartzose sandstone, quartz arenite (locally with horizons of quartz pebbles), and dolostone to dolomitic sandstone. The middle member of the Backbone Ranges Formation (93 m) consists mainly of pink to grey-weathering limestone with red mudstone partings. The upper member (501.5 m) is dominated by quartz arenite, but also contains intervals of siltstone. Partway through the upper member there is a marker unit of dolostone to dolomitic sandstone that previous work suggests is a tongue of the Ediacaran Risky Formation. Based on regional correlations, the top of this marker may approximate the Ediacaran-Cambrian boundary in this section. The Sekwi Formation lies abruptly upon the Backbone Ranges Formation. The contact is unconformable at this locality and mapping in the area indicates eastward erosional removal of the upper member of the Backbone Ranges Formation beneath the Sekwi Formation. The Sekwi Formation here consists of variegated siltstone with lesser dolostone, limestone, and quartz sandstone. An abrupt contact with nodular limestone and grey shale of the overlying Rockslide Formation approximates the base of Cambrian Series 3.