Статті в журналах з теми "Regolith carbonate"
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1
Ben-Asher, Matan, Itai Haviv, Onn Crouvi, Joshua J. Roering, and Ari Matmon. "The convexity of carbonate hilltops: 36Cl constraints on denudation and chemical weathering rates and implications for hillslope curvature." GSA Bulletin 133, no. 9-10 (January 15, 2021): 1930–46. http://dx.doi.org/10.1130/b35658.1.
Повний текст джерелаАнотація:
Abstract Carbonate hillslopes are often soil mantled and display a classic convex morphology. In this study we examine controls on carbonate hillslope denudation and morphology using a modified regolith mass balance equation to account for chemical weathering and dust input—two fluxes that are commonly neglected in settings with silicate-dominated bedrock. We utilize seven study sites in the Eastern Mediterranean across a significant gradient in the mean annual rainfall and dust deposition flux. Combining cosmogenic 36Cl-derived hilltop denudation rates with an estimate of the regolith chemical depletion and the quantified fraction of dust in the regolith we predict hilltop curvature and compare our predictions with observations based on high-resolution airborne LiDAR (light detection and ranging). Denudation rates vary from 5 to 210 mm/k.y. and increase with mean annual rainfall. Less resistant carbonates (chalk) experience faster denudation rates relative to more resistant dolo-limestone and are less prone to chemical weathering. Soil production exhibits a humped dependency on soil thickness. The observed hilltop curvature varies as a function of rainfall and dust flux with a minimum at sub-humid sites. While trends in hilltop convexity are often solely attributed to variations in erosion rate, our results illustrate the additional effects of dust production and chemical depletion. Our mass balance model implies that drier sites in the south probably experienced a more intricate history of regolith production due to dust flux fluctuations. Thus, by incorporating dust flux and chemical weathering to the classic hillslope evolution model we are able to identify a complex relation between hilltop curvature, soil production, and climate.
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Shaheen, Robina, Paul B. Niles, Kenneth Chong, Catherine M. Corrigan, and Mark H. Thiemens. "Carbonate formation events in ALH 84001 trace the evolution of the Martian atmosphere." Proceedings of the National Academy of Sciences 112, no. 2 (December 22, 2014): 336–41. http://dx.doi.org/10.1073/pnas.1315615112.
Повний текст джерелаАнотація:
Carbonate minerals provide critical information for defining atmosphere–hydrosphere interactions. Carbonate minerals in the Martian meteorite ALH 84001 have been dated to ∼3.9 Ga, and both C and O-triple isotopes can be used to decipher the planet’s climate history. Here we report Δ17O, δ18O, and δ13C data of ALH 84001 of at least two varieties of carbonates, using a stepped acid dissolution technique paired with ion microprobe analyses to specifically target carbonates from distinct formation events and constrain the Martian atmosphere–hydrosphere–geosphere interactions and surficial aqueous alterations. These results indicate the presence of a Ca-rich carbonate phase enriched in 18O that formed sometime after the primary aqueous event at 3.9 Ga. The phases showed excess 17O (0.7‰) that captured the atmosphere–regolith chemical reservoir transfer, as well as CO2, O3, and H2O isotopic interactions at the time of formation of each specific carbonate. The carbon isotopes preserved in the Ca-rich carbonate phase indicate that the Noachian atmosphere of Mars was substantially depleted in 13C compared with the modern atmosphere.
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Ott, Richard F., Sean F. Gallen, and Darryl E. Granger. "Cosmogenic nuclide weathering biases: corrections and potential for denudation and weathering rate measurements." Geochronology 4, no. 2 (July 6, 2022): 455–70. http://dx.doi.org/10.5194/gchron-4-455-2022.
Повний текст джерелаАнотація:
Abstract. Cosmogenic radionuclides (CRNs) are the standard tool to derive centennial-to-millennial timescale denudation rates; however, it has been demonstrated that chemical weathering in some settings can bias CRNs as a proxy for landscape denudation. Currently, studies investigating CRN weathering biases have mostly focused on the largely insoluble target mineral quartz in felsic lithologies. Here, we examine the response of CRN build-up for both soluble and insoluble target minerals under different weathering scenarios. We assume a simple box model in which bedrock is converted to a well-mixed regolith at a constant rate, and denudation occurs by regolith erosion and weathering either in the regolith or along the regolith–bedrock interface, as is common in carbonate bedrock. We show that weathering along the regolith–bedrock interface increases CRN concentrations compared to a no-weathering case and how independently derived weathering rates or degrees can be used to correct for this bias. If weathering is concentrated within the regolith, insoluble target minerals will have a longer regolith residence time and higher nuclide concentration than soluble target minerals. This bias can be identified and corrected using paired-nuclide measurements of minerals with different solubility coupled with knowledge of either the bedrock or regolith mineralogy to derive denudation and long-term weathering rates. Similarly, single-nuclide measurements on soluble or insoluble minerals can be corrected to determine denudation rates if a weathering rate and compositional data are available. Our model highlights that for soluble target minerals, the relationship between nuclide accumulation and denudation is not monotonic. We use this understanding to map the conditions of regolith mass, weathering, and denudation rates at which weathering corrections for cosmogenic nuclides become large and ambiguous, as well as identify environments in which the bias is mostly negligible and CRN concentrations reliably reflect landscape denudation. We highlight how measurements of CRNs from soluble target minerals, coupled with bedrock and regolith mineralogy, can help to expand the range of landscapes for which centennial-to-millennial timescale denudation and weathering rates can be obtained.
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Sevin, B., P. Maurizot, D. Cluzel, E. Tournadour, S. Etienne, N. Folcher, J. Jeanpert, et al. "Chapter 7 Post-obduction evolution of New Caledonia." Geological Society, London, Memoirs 51, no. 1 (2020): 147–88. http://dx.doi.org/10.1144/m51-2018-74.
Повний текст джерелаАнотація:
AbstractThe post-obduction formations of Grande Terre, New Caledonia, comprise igneous intrusions, regolith cover, and marine and terrestrial sedimentary rocks. Two restricted Late Oligocene granitoid bodies are intruded into the Peridotite Nappe and its substrate in the south of the island. Thick regolith cover developed over the Peridotite Nappe from the Late Oligocene or earlier. The Népoui Group comprises Late Oligocene–Early Miocene mixed marine carbonate and siliciclastic deposits. It mainly reworks the Peridotite Nappe and its regolith cover. Its development pattern is mainly controlled by tectonic uplift and subsidence. The Gwa N'Doro Formation on the eastern coast and the Fluvio-lacustrine Formation in the south are remnants of the Miocene–Present river network. Offshore, thick Oligocene to Neogene sedimentary successions are imaged by seismic surveys on the margins of Grande Terre, although these successions have not been drilled and remain undated. Several dredges have recovered shallow Miocene sedimentary rocks, indicating substantial Neogene subsidence. Quaternary formations are represented inland by aeolianite, vertisols and calcrete and offshore by the large barrier reef–lagoon complex, the onset of which is dated at c. 400 ka. This chapter discusses the different models proposed for the post-obduction evolution of Grand Terre.
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Helvacı, Cahit, Tolga Oyman, İbrahim Gündoğan, Hasan Sözbilir, Osman Parlak, Selahattin Kadir, and Necip Güven. "Mineralogy and genesis of the Ni–Co lateritic regolith deposit of the Çaldağ area (Manisa, western Anatolia), Turkey." Canadian Journal of Earth Sciences 55, no. 3 (March 2018): 252–71. http://dx.doi.org/10.1139/cjes-2017-0184.
Повний текст джерелаАнотація:
The Çaldağ Ni–Co deposit is characterized by a reddish brown oxide lateritic regolith, containing residual Ni deposit formed by the intense tropical weathering of peridotites. Nickel–Co ore is associated with transported ferricrete during the late Paleocene – middle Eocene, represented by colloform Fe oxides and residual lateritization during the Oligocene. The lateritic regoliths are developed over dunitic ultramafic rocks and consist mainly of smectite, berthierine, kaolinite, gypsum, pyrite, takovite, and pecoraite. These units were examined using polarized-light microscopy, X-ray diffraction, scanning and transmission electron microscopy, and geochemical methods. Mineralogical zonation from the base of the profile upwards has the following zones: ultramafic bedrocks, serpentinized ultramafic rocks (saprock), saprolite, carbonate- and sulfide-bearing zone, ferruginous saprolite zone, and silcrete. In addition, Fe oxides, smectite and opal-CT, and quartz increase towards the surface, whereas olivine, pyroxene, and serpentine decrease upwards in response to chemical weathering. Nickel–Co mineralization associated with Fe oxides and smectitic clays formed under wet and dry conditions, respectively, as a result of an increased Fe2O3 + Al2O3 + Ni + Co/MgO ratio. Field observations and mineralogical and geochemical analyses reveal that the smectite formed under basic conditions was controlled by multistage chemical weathering of ultramafic and volcanic rocks and by the concentrations of Si, Al, Fe, and Mg. Locally, concentrations of S in conjunction with Fe and Ca resulted in precipitation of goethite–hematite, gypsum, and pyrite in dissolution voids in association with smectite under acidic conditions that developed in a well-drained system.
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Kang, He, and George R. Dix. "Upper Ordovician (Sandbian–Katian) carbonate outliers in the northern Ottawa–Bonnechere graben (central Canada): records of transgressions and sedimentation patterns in the Laurentian platform interior." Canadian Journal of Earth Sciences 58, no. 1 (January 2021): 1–20. http://dx.doi.org/10.1139/cjes-2020-0065.
Повний текст джерелаАнотація:
Small Ordovician sedimentary outliers, including Brent Crater, within the northern Ottawa–Bonnechere graben are remnants of a once expansive Upper Ordovician sedimentary cover extending across the southern Canadian Shield. Facies successions along with updated macrofossil and conodont biostratigraphy, and isotope (C, O, Sr) chemostratigraphy provide additional insights into the terrestrial-to-marine transformation, carbonate-platform development, and oceanographic communication across the southern Laurentian platform. Four of the outliers document Sandbian shoreline-to-nearshore deposition: near Deux Rivières, Manitou Islands, the upper part of the Brent Crater sedimentary fill, and at nearby Cedar Lake. Marine transgression initially reworked local fine-grained to boulder-rich regolith within high-energy shoreface siliciclastic environments that gave way to low- to high-energy inner carbonate-ramp setting. Continued transgression resulted in more offshore rhythmic and diverse lithofacies successions defining mixed heterozoan, photozoan, and microbial productivity and marine isotope (C, Sr) signatures, but δ13C excursions suggest periods of greater mixing of terrestrial and marine carbon reservoirs. Lower Katian strata are preserved near Lake Nipissing and characterize deepening from high-energy ooid-heterozoan skeletal shoals to deeper water mid-ramp siliciclastics and skeletal carbonates, host to a Cruziana ichnofacies. An upsection decline in δ13C values through this succession may identify deposition during the post-peak decline of the global Guttenberg δ13C excursion. This lithic succession fits well with contemporary expansion of heterozoan skeletal lithofacies across the Laurentian platform, yet the presence of ooids identifies prevailing warm waters within the platform interior during early stages of transgression.
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Sadooni, Fadhil N., Fares Howari, Howell G. M. Edwards, and Ayman El-Saiy. "Lithology, mineral assemblages and microbial fingerprints of the evaporite-carbonate sediments of the coastal sabkha of Abu Dhabi and their extraterrestrial implications." International Journal of Astrobiology 9, no. 3 (March 29, 2010): 147–56. http://dx.doi.org/10.1017/s1473550410000078.
Повний текст джерелаАнотація:
AbstractDeep-core and surface samples collected from the coastal sabkha of Abu Dhabi were subjected to a multi-proxy study, including petrographic, geochemical and spectroscopic analyses. The sediments studied are composed of biochemical carbonate-evaporite mineral suites, such as calcite, dolomite, aragonite and gypsum, as well as clastic minerals, such as quartz, feldspar and serpentine. These sediments were also strongly influenced by microbial activities as reflected by the presence of cyanobacterial mats, boring, gas bubble structures, pustular and other macro and micro textures. A combination of marine, fluvial, aeolian, and groundwater processes shaped the geomorphology of the area and led to the formation of such mineral suites, as well as their microbial contents. Data collected from Mars indicate that its surface regolith contains sandstone composed of siliciclastic basaltic debris, as well as carbonate (e.g. magnesite) and evaporite (e.g. jarosite and relics of gypsum) mineral assemblages. Additional data suggest the presence of geomorphic features, characteristic of an arid climate, such as sand dunes and desert varnish. The hydrological model for the Late Noachian-Hesperian period of the plant proposed the existence of a surficial layer containing endolithic and stromatolitic cyanobacterial lamina. The combination of the coastal sabkha of Abu Dhabi with its carbonate-evaporite mineral suites, the neighbouring sand dune fields of the Empty Quarter Desert and the basaltic sediments resulted from weathering the ophiolitic Northern Oman Mountains to form a candidate terrestrial geologic province that may explain the mineral association of Mars and its potential biosignatures. The lithological features and the mineral association of the sabkha can be recognized by the present day detection equipment used on Mars, and even if their biosignatures are degraded, their existence may be inferred from these features.
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McQueen, K. G., S. M. Hill, and K. A. Foster. "The nature and distribution of regolith carbonate accumulations in southeastern Australia and their potential as a sampling medium in geochemical exploration." Journal of Geochemical Exploration 67, no. 1-3 (December 1999): 67–82. http://dx.doi.org/10.1016/s0375-6742(99)00071-0.
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Dredge, Lynda A. "Late Pleistocene and Holocene glaciation and deglaciation of Melville Peninsula, Northern Laurentide Ice Sheet." Géographie physique et Quaternaire 55, no. 2 (June 21, 2004): 159–70. http://dx.doi.org/10.7202/008300ar.
Повний текст джерелаАнотація:
Abstract Melville Peninsula lies within the Foxe/Baffin Sector of the Laurentide Ice Sheet. Pre-Foxe/Pre-Wisconsin ice may have covered the entire peninsula. Preserved regolith in uplands indicates a subsequent weathering interval. Striations and till types indicate that, during the last (Foxe) glaciation, a local ice sheet (Melville Ice) initially developed on plateaus, but was later subsumed by the regional Foxe ice sheet. Ice from the central Foxe dome flowed across northern areas and Rae Isthmus, while ice from a subsidiary divide controlled flow on southern uplands. Ice remained cold-based and non-erosive on some plateaus, but changed from cold- to warm-based under other parts of the subsidiary ice divide, and was warm-based elsewhere. Ice streaming, generating carbonate till plumes, was prevalent during deglaciation. A late, quartzite-bearing southwestward ice flow from Baffin Island crossed onto the north coast. A marine incursion began in Committee Bay about 14 ka and advanced southwards to Wales Island by 8.6 ka. The marine-based ice centre in Foxe Basin broke up about 6.9 ka. Northern Melville Peninsula and Rae Isthmus were deglaciated rapidly, but remnant ice caps remained active and advanced into some areas. The ice caps began to retreat from coastal areas ~6.4 to 6.1 ka, by which time sea level had fallen from 150-180 m to 100 m.
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Sepahvand, Alireza, Mitja Prelovsek, Ali Akbar Nazari Samani, and Robert Wasson. "Solute transport and solutional denu-dation rate of carbonate karst in the semi-arid Zagros region (southwes-tern Iran)." Journal of Cave and Karst Studies 83, no. 3 (September 30, 2021): 93–108. http://dx.doi.org/10.4311/2020es0102.
Повний текст джерелаАнотація:
We conducted a one-year-long study of solute load measured three times per month in three neighboring subwatersheds (Alashtar, Khorram Abad, and Biranshahr) located in the Karkheh River basin in the Zagros region of southwestern Iran. Research was focused on the chemical composition of water (solute load), karst denudation rate, spatial and temporal variability, as well as comparison of solute load with suspended load. Results show that Ca-Mg-HCO3 is the dominant water type that reflects the lithological characteristics of the catchment areas. Lack of seasonal fluctuation of solute load and absence of dilution during high water levels but evident seasonal course of discharge defines the highest solute flux during the annual maximum of discharge in spring months. The highest solute flux is related to flood events. High annual variation of Na1 concentration compared to conservative Cl2 as well as Chloro-Alkali indexes (CAI and CAI2) suggests that Na1 adsorption and desorption during ion-exchange reactions occur in the regolith. This Na+ variability, to some extent, explains weak Ca21 and Mg21 dilution effect during high water levels. During the measurement period (2014-2015), solute flux calculated per catchment area amounted to 49-69 t km-2 a-1 (tons per km per year). The chemical composition of water and discharge shows by far the highest chemical denudation of limestones and dolomites (87−89 %), while dissolution of gypsum is of minor importance (11−13 %). As a result, the carbonate karst solutional denudation rate is between 0.010 and 0.040 mm a21 , where the higher values are more probable for longer periods due to the relatively low discharge during the spring of 2015. Comparison of dissolved and suspended loads indicates that the transport of suspended load is an order of magnitude less than transport of the dissolved load; the only exception is one flash flood event when suspended load exceeded the dissolved load. Besides a small decrease in solute flux as well as carbonate karst dissolution rates from NW to SE, no large hydrochemical differences between the three subwatersheds were detected.
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Alfimova, Nadezhda A., Anton B. Kuznetsov, Ekaterina V.Klimova, and Andrey Bekker. "Archean-Proterozoic unconformity on the Fennoscandian Shield: Geochemistry and Sr, C and O isotope composition of Paleoproterozoic carbonate-rich regolith from Segozero Lake (Russian Karelia)." Precambrian Research 368 (January 2022): 106459. http://dx.doi.org/10.1016/j.precamres.2021.106459.
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Emil, GACHEV. "High mountain relief in marble in Pirin Mountains, Bulgaria: structure, specifics and evolution." Revista de Geomorfologie 19, no. 1 (December 30, 2017): 118–35. http://dx.doi.org/10.21094/rg.2017.012.
Повний текст джерелаАнотація:
The present article is focused on high mountain relief in marble, which combines glacial, periglacial and karstic morphology. High mountain karst is found in Northern Pirin (Vihren and Sinanitsa area) and central Pirin (Orelek area), the latter lacking traces of glaciation due to its low altitude. In the most representative area, Vihren part, several vast and deep cirques-uvalas were formed, which comprise a large diversity of landforms. Main factor for the specifics of relief in marble is the structure of the rock, which combines carbonate mineral content and crystalline properties; they favour both the occurrence of karstification and frost weathering. The high elevation of Northern Pirin (up to 2914 m a.s.l.), and the resulting extensive former glaciation enhanced the karst processes by weathering of the morphological surface. At present, surface karst is most developed on elevated sections of cirque bottoms, which were ice free before the beginning of the Holocene and are away from rockfall creep accumulation. A special element of glaciokarstic relief in Pirin are the summer lasting snow/ice features (glacierets and snow patches), two of which are considered centuries old, and still survive despite the temperature warming. In general, karst processes in the high mountain areas of Pirin are less developed than in the western part of the Balkan Peninsula (the Dinarides), due to the greater susceptibility of marble to physical weathering compared to limestone, which leads to a more intensive formation of regolith on the surface, and in result of the generally colder and dryer climate.
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Searl, Alison, and Sharon Rankin. "A preliminary petrographic study of the Chilean nitrates." Geological Magazine 130, no. 3 (May 1993): 319–33. http://dx.doi.org/10.1017/s0016756800020008.
Повний текст джерелаАнотація:
AbstractThe nitrate deposits of the northern Atacama Desert occurin a narrow zone between the low-lying Pampa del Tamarugal to the east and the hills of the Coastal Range to the west. High purity nitrate ore occurs as stratiform seams about 20 cm thick, present at depths of 3–7 m below thedesert surface. The ore is hosted by a variety of lithologies and overlain by salt-cemented regolith. The ore is largely composed of nitratite (= sodanitre or Chilean salt peter) and halite with locally abundant humberstonite, polyhalite and mirabilite. Other salts present include Ca iodates and a variety of sulphate, borate and chromate minerals. Textural relationships can be used to deduce paragenetic sequences for individual salt samples and these combined to produce a generalized paragenetic web for the nitrate ore.These textural data can be combined with published solubility data to investigate the course of fluid evolution during ore genesis. The multiplicity of paragenetic relationships within the ore reflects the derivation of precipitating fluids from a variety of sources: westwards flowing Andean groundwater, coastal fogs, occasional rainfall and Andean-derived surface floodwaters. The unusual mineralogy of the nitrate ore reflects the extreme chemical evolution of the precipitating brines through multiple episodes of salt precipitation and remobilization during transport to the nitrate horizons. The formation of high purity nitrate ore appears to be the result of multiple phases of dissolution, reprecipitation and recrystallization, that have separated the highly soluble nitrate salts from less soluble salts in the overlying profile. Salts have largely accumulated through displacive growth, but some of the host silicate and carbonate lithologies have also undergonea small degree of salt replacement.
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Warren, Paul H. "Mars regolith versus SNC meteorites: Possible evidence for abundant crustal carbonates." Icarus 70, no. 1 (April 1987): 153–61. http://dx.doi.org/10.1016/0019-1035(87)90082-0.
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Babechuk, Michael G., and Balz S. Kamber. "The Flin Flon paleosol revisited." Canadian Journal of Earth Sciences 50, no. 12 (December 2013): 1223–43. http://dx.doi.org/10.1139/cjes-2013-0076.
Повний текст джерелаАнотація:
A ca. 1.85 Ga paleosol developed on seafloor-altered mafic rocks is preserved beneath continental sandstones and conglomerates of the Missi Group near Flin Flon, Manitoba. Previous work has focused on a locality where the paleosol is developed on pillowed greenstone (chlorite + albite + epidote + calcite + quartz + Fe–Ti oxides ± mica). This area has been revisited and a new (∼5 m) profile was excavated and sampled at a very high density for geochemical (major element; ∼60 samples) and mineralogical (petrography, X-ray diffraction) investigation. The high sampling density has revealed a relatively sharp immobile-element offset (e.g., Al/Ti) in the profile. This could reflect weathering across two separate parent rocks or preferential addition of allochthonous material into the top of the profile. Regardless, comparison with a wide suite of volcanic rocks in the stratigraphy suggests that the original concentration of Fe and probably also Ca and Mg in the greenstone on either side of the boundary was similar, permitting quantitative treatment of major-element trends. The profile shows pronounced upward loss of Ca, Mg, Mn2+, and Fe2+ and a corresponding increase in Al, Ti, and total Fe. Physical weathering features, such as corestones, are well preserved and show progressive alteration upwards in the profile in parallel with the chemical trends. Deep in the profile, Na and Ca are lower than the greenstone due to the weathering of albite and epidote, whereas Mg, Fe, and Mn were largely retained in chlorite and secondary dolomite. Upwards in the profile, the loss of chlorite and dolomite and the increase of illite – mixed-layer clays and white mica (probably 2:1 layer or mixed-layer clays originally) and hematite are accompanied by a transition from green to maroon colour. Above a well-defined depth in the profile, carbonate is virtually absent, and the paleosol is highly depleted in Ca. This transition in the paleosol coincides with the immobile-element offset. The significance of this coincidence remains to be explored. Reworking of regolith (e.g., rip-up clasts) occurred during deposition of the Missi sediments, and burial and subsequent metamorphism resulted in the upward enrichment of K and Na and the associated conversion of pedogenic clays to illite and micas (muscovite and paragonite). Crosscutting quartz and epidote veins and tourmaline formation near the unconformity contact implies minor post-burial fluid movement. Despite these complexities, there is consistent retention of Fe through formation of pedogenic Fe oxides, attested by the near-constant ∑Fe/Al ratio in the profile. There is very little evidence for subsequent Fe reduction by hydrothermal or organic fluids. Instead, trends in the Fe speciation are controlled predominantly by the modal variation of Fe–Ti oxides in the greenstone and spheroidal weathering textures in the paleosol.
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Tandon, S. K., and J. E. Andrews. "Lithofacies associations and stable isotopes of palustrine and calcrete carbonates: examples from an Indian Maastrichtian regolith." Sedimentology 48, no. 2 (April 6, 2001): 339–55. http://dx.doi.org/10.1046/j.1365-3091.2001.00367.x.
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Dart, Robert C., Karin M. Barovich, David J. Chittleborough, and Steven M. Hill. "Calcium in regolith carbonates of central and southern Australia:Its source and implications for the global carbon cycle." Palaeogeography, Palaeoclimatology, Palaeoecology 249, no. 3-4 (June 2007): 322–34. http://dx.doi.org/10.1016/j.palaeo.2007.02.005.
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Twidale, Charles Rowland. "Horace R. Blank and the origin of rock doughnuts." Cadernos do Laboratorio Xeolóxico de Laxe. Revista de Xeoloxía Galega e do Hercínico Peninsular 40 (December 21, 2018): 187–213. http://dx.doi.org/10.17979/cadlaxe.2018.40.0.4919.
Повний текст джерелаАнотація:
Rock doughnuts are annular rims developed around rock basins that intermittently carry pools of water. They are developed in granitic rocks, and in arenaceous and calcareous sediments and in coastal as well as interior settings. Rock levees are found adjacent to gutters but are of a similar nature and origin. Both doughnuts and levees can be attributed to the development of protective coatings or veneers by biota, and of silica, iron oxides, and carbonates by overflowing pool waters. Contrasts in drainage from regolithic covers, weathering at sheltered interfaces and variations in runoff can also be cited at causative factors and situations.
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Dart, R. C., K. M. Barovich, S. M. Hill, and D. J. Chittleborough. "Sr-isotopes as a tracer of Ca sources and mobility in profiles hosting regolith carbonates from southern Australia." Australian Journal of Earth Sciences 59, no. 3 (April 2012): 373–82. http://dx.doi.org/10.1080/08120099.2012.662912.
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Reshma, K., T. Paradkar Trigun, and Nibin G. Tom. "Rare Earth Mineralization in Regolith Zones of the Neoarchean Phoscorite from the Carbonatite-syenite Complex, Dombarahalli Area, Eastern Dharwar Craton, Koppal District, Karnataka." Journal of the Geological Society of India 98, no. 8 (August 9, 2022): 1114–20. http://dx.doi.org/10.1007/s12594-022-2131-x.
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Lien, Nguyen Thi, and Nguyen Van Pho. "Formation of secondary nonsulfide zinc ore in Cho Dien Pb-Zn deposits." VIETNAM JOURNAL OF EARTH SCIENCES 40, no. 3 (June 4, 2018): 228–39. http://dx.doi.org/10.15625/0866-7187/40/3/12615.
Повний текст джерелаАнотація:
In Viet Nam, non-sulfide zinc ore in the Cho Dien deposit has been exploited for a long time. Up to the present, zinc ore remains the major exploited ore in Cho Dien. There are numerous studies of Pb-Zn ore in Cho Dien. However, most of the studies have dedicated only to description of mineralogical and chemical composition of Pb-Zn ore. There has been no publication on this non-sulfide zinc ore. Based on the mineralogical studies, the content of Pb and Zn in groundwater determined by reflective microscope, SEM, EPMA and ICP-MS methods, the study explained the formation of secondary non-sulfide zinc ore in the Cho Dien deposit. Strong weathering process makes the upper part of ore bodies completely oxidized. Difference in geochemical behavior of lead (Pb) and zinc (Zn) in the oxidation process of Pb-Zn ore is the reason to form non-sulfide zinc ore in the Cho Dien deposit. Oxidation of primary Pb-Zn ore is mainly sphalerite, pyrite, galena minerals which creates a low pH environment and transforms of zinc from immobile (sphalerite - ZnS) to mobile (Zn2+) and retained in solution under acid pH conditions whereas lead has the tendency to form soluble minerals (anglesite, cerussite). The acid neutralization actions of the surrounding rocks make zinc precipitate, to form secondary non-sulfide zinc minerals.ReferencesAndreas Nuspl, 2009. Genesis of nonsulfide zinc deposits and their future utilization (www.geo.tu-frei berg.de/oberseminar/OS_09/Andreas_Nuspl.pdf.Boland M.B., et al., 2003. The Shaimerden supergene zinc deposit, Kazakhstan: Economic Geology, 98(4), 787-795.Chau N.D., Jadwiga P., Adam P., D.V. Hao, L.K. Phon, J. Paweł, 2017. General characteristics of rare earth and radioactive elements in Dong Pao deposit, Lai Chau, Vietnam, Vietnam J. Earth Sci., 39(1), 14-26.Dao Thai Bac, 2012. Characteristics and distribution law of lead-zinc metallogenic fomations in Viet Bac region. Doctoral thesis.Heyl A.V., Bozion C.N., 1962. Oxidized zinc deposits of the United States, Part 1. General Geology: U.S. Geological Survey Bulletin 1135-A.Hoa T.T., et al., 2010. By-products in lead-zinc and copper ores of Northeast Vietnam. J. Sci. of the Earth, 289-298 (in Vietnamese).Hoang Minh Thao, Tran Thi Hien, Dao Duy Anh, Pham Thi Nga, 2017. Mineralogical characteristics of graphite ore from Bao Ha deposit, Lao Cai Province and proposing a wise use. Vietnam J. Earth Sci., 39(4), 324-336.Jurjovec J., et al., 2002. Acid neutralization mechanisms and metal release in mine tailings: A laboratory column experiment: Geochimica et Cosmochimica Acta, 66, 1511-1523.Large D., 2001. The geology of non-sulphide zinc Deposits - an Overview: Erzmetall, 54(5), 264-276.Maria Boni, 2003. Nonsulfide Zinc Deposits: a new - (old) type of economic mineralization. Society for geology applied to mineral deposits (SGA) News, Number 15. https://www.e-sga.org/fileadmin/sga/newsletter/news15/art01.html.McPhail D.C., et al., 2003, The geochemistry and mobility of zinc in the regolith: in Roach, I.C., ed., Advances in Regolith, 287-291.Murray W. Hitzman, et al., 2003. Classification, genesis, and exploration guides for non-sulfide zinc deposits: Economic Geology, 98(4), 685-714.Nguyen V.P., 2013. Wet tropical wethering in Viet Nam. Natural Science and Technology Publisher.Nicola Mondillo, 2013. Supergene Nonsulfide Zinc-Lead Deposits: The Examples of Jabali (Yemen) and Yanque (Peru). Doctoral thesis.Nordstrom D.K., Alpers C.N., 1999. Geochemistry of acid mine waste. Review in Economic Geology, the environmental geochemistry of ore deposits/Eds. G.S.Plumlee, M.J. Logsdon. Part A: Processes, techniques, and health issues, 6A, 133-160.Reynolds N.A., et al., 2003. The Padaeng Supergene Nonsulfide Zinc Deposit, Mae Sod, Thailand. Economic Geology, 98(4), 773-785.Sangameshwar S.R., Barnes H.L., 1983. Supergene Processes in Zinc-Lead-Silver Sulfide Ores in Carbonates: Economic Geology, 78, 1379-1397.Stumm W., Morgan J.J., 1996. Aquatic Chemistry, Third Edition. John Wiley & Sons, New York, NY.Takahashi T., 1960. Supergene alteration of zinc and lead deposits in limestone: Economic Geology, 55, 1083-1115.Thornber M.R. and Taylor G.F., 1992. The mechanisms of sulphide oxidation and gossan formation, in: Butt, C.R.M., and Zeegers H., (Eds.)., Regolith exploration geochemistry in tropical and subtropical terrains, in Govett G.J.S., ed., Handbook of exploration geochemistry: Amsterdam, Elsevier, 4, 119-138.Tran Trong Hoa, 2005. Potential assessment of By- products in lead-zinc and copper deposits of Northeast Vietnam. Final report.Tran Tuan Anh, 2010. Studying accompanying component in the types of potential deposits of basic metals and precious - rare metals of north Viet Nam to improve the efficiency of mining and environmental protection. Final report. KC.08.24/06-10.Tran Tuan Anh, et al., 2011. Mineralogical and geochemical characteristics and forming conditions of lead - zinc deposits in Lo Gam structure, northern Vietnam. J. Sci. of the Earth, 33(3DB), 393-408 ( in Vietnamese).Vito Coppola et al., 2009. Nonsulfide zinc deposits in the Silesia - Cracow district, Southern Poland. Springer Link, 44, 559-580.Vito Coppola, et al., 2007. Non-sulfide zinc deposits in Upper Silesia, Southern Poland. Proceeding of the Ninth Biennial SGA Meeting, Dublin, 1401-1404.Williams P.A., 1990. Oxide zone geochemistry: Ellis Horwood Ltd., Chichester, UK, 286p.
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Palmieri, Matheus, José Affonso Brod, Pedro Cordeiro, José Carlos Gaspar, Paulo Afonso Ribeiro Barbosa, Luis Carlos de Assis, Tereza Cristina Junqueira-Brod, et al. "The Carbonatite-Related Morro do Padre Niobium Deposit, Catalão II Complex, Central Brazil." Economic Geology, August 17, 2022. http://dx.doi.org/10.5382/econgeo.4951.
Повний текст джерелаАнотація:
Abstract The Morro do Padre deposit contains a valuable niobium resource estimated at 14.5 Mt at 1.52 wt % Nb2O5 (at a cut-off grade of 0.5% Nb2O5) hosted in carbonatite-related rocks and their regolith in the southern part of the Catalão II Complex, in central Brazil. Morro do Padre shares numerous geologic features with some of the biggest niobium producers in the world (the Boa Vista mine, also in Catalão II, the Mina II in Catalão I, and the CBMM mine in the Araxá Complex) and can help advance our understanding of the ore formation processes involved. The Morro do Padre hypogene zone is characterized by E-W–trending dike swarms of tetraferriphlogopite phoscorites (magnetite-apatite-carbonate-tetraferriphlogopite-pyrochlore rocks) and carbonatites intrusive within Precambrian rocks. The magmatic origin of these Nb-rich rocks is supported by country rock xenoliths within dikes and ponding into a stratified sill with repetitive cumulus layers. At least two tetraferriphlogopite phoscorite phases (apatite-rich or pegmatoidal P1 and the magnetite-rich P2) and two carbonatite phases (C1 calcite carbonatite and C2 dolomite carbonatite) are present. The bulk of hypogene mineralization is primarily controlled by the emplacement of P2 dikes and secondarily by C1 and C2 dikes where pyrochlore is accessory. Whole-rock and pyrochlore chemistry and textural and spatial relationships suggest that the genesis of P2 (and that of the niobium deposit) is due to the emplacement of a parental dolomite carbonatite magma that crystallized medium- to coarse-grained magnetite, apatite, tetraferriphlogopite, and pyrochlore on dike walls upon cooling, in an elaborate magmatic type of “cumulate dike build-up.” Weathering generated the regolith zone, where the dissolution of barren phases compounded the Nb concentration even further. Morro do Padre showcases the role of carbonatite-phoscorite magmatism in producing Fe-P-Nb–rich rocks and economic niobium mineralization.
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Francisco-Catarina, Magdalena, Demetrio Salvador Fernández-Reynoso, Rogelio Carrillo-González, Daniel Hernández-Díaz, José Donaldo Ríos-Berber, and Patricio Sánchez-Guzmán. "Control de infiltración en regolito volcánico con diferentes técnicas de sellado." REVISTA TERRA LATINOAMERICANA 39 (July 30, 2021). http://dx.doi.org/10.28940/terra.v39i0.939.
Повний текст джерелаАнотація:
En la parte alta del municipio de Huasca de Ocampo, Hidalgo, el suelo (regolito) es producto de la intemperización de materiales volcánicos con altas tasas de infiltración de agua (13.25 mm día-1) con serias dificultades para almacenar agua. El objetivo de la investigación fue evaluar, en términos de su permeabilidad y costo económico, técnicas de sellado para reducir la infiltración en el área de embalse de un proyecto de bordo de almacenamiento localizado en un suelo residual volcánico. Se evaluaron variables físicas, químicas y mecánicas del suelo. Se aplicaron 46 tratamientos con sus respectivas repeticiones, para sellar el suelo. Se midió en permeámetro de carga constante el coeficiente de permeabilidad del suelo en dos etapas para comparar el efecto a través del tiempo. Los datos de permeabilidad se sometieron a un análisis de varianza (ANDEVA) y la comparación de medias se hizo con el método de la diferencia mínima significativa (LSD), para un nivel de significancia α = 0.05. Con resultados de permeabilidad se elaboró un análisis económico, comparando los precios unitarios de los tratamientos contra el precio de la geomembrana. En términos económicos y en control de la infiltración los tratamientos con dispersantes de partículas (carbonato de sodio, tripolifosfato de sodio y fosfato de sodio) son recomendables, aunque hay que considerar aplicaciones de mantenimiento cada dos o tres años. El tratamiento más económico fue la compactación próctor estándar, sin embargo, esta alternativa no es recomendable por presentar el suelo incrementos de permeabilidad con el tiempo. El uso del cemento-arena y la bentonita sódica resultaron muy eficaces, aunque sus costos son elevados, tienen la ventaja de ser una alternativa duradera.
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Nuñez Ravelo, Franklin Antonio. "Geomorfología y sedimentología del sistema de cárcavas en el borde costero al suroeste del Castillo de Araya, Estado Sucre, Venezuela." Investigaciones Geográficas, no. 92 (March 31, 2017). http://dx.doi.org/10.14350/rig.53428.
Повний текст джерелаАнотація:
El área de estudio se ubica en la costa al sur-oeste de Araya en el Estado Sucre, entre los 10° 33´30´´ N – 10°33´59´´ N y 64°15´32´´ O – 64°15´36´´ O, la cual se encuentra afectada por procesos erosivos que impactan a los centro poblado que allí se asienta. De allí que la investigación se centró en analizar los procesos geomorfológicos que se desarrollan, basado en un modelo de campo con diseño cuasiexperimental, en niveles descriptivo y explicativo, operacionalizada en tres fases: (a) campo, (b) análisis de imágenes, y (c) laboratorio. En general, se tiene que el acantilado afectado por la erosión retrograda tipo cárcavas, está constituido por un material franco-limoso cuyo análisis de rocas totales muestra una abundancia de Arcillas (52 %), Oxido de silicio (28%), Carbonato de Calcio (18 %), Plagioclasas (5 %), Sulfuro de hierro (5%) y Carbonato de hierro (2 %), por su parte, el análisis de arcillas en fracción menor a dos micras, muestra como predominantes: la Caolinita (47%), Ilita (39%), Clorita (14 %), y Esméctica (1%). Se trata de un regolito dispersivo, con muy bajo contenido de MO, que favorece la ocurrencia de flujo de lodo, suelo y desplome de la roca, detonado posiblemente a partir del leve incremento en las precipitaciones registrado entre julio y noviembre, así como las fuertes pendientes del terreno, lo que ha generado un retroceso del contorno apical, estimado en 1.31 m/año
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Cogliati, Simone, Elliot Wolsey, Nisha K. Ramkissoon, Susanne P. Schwenzer, Victoria K. Pearson, and Karen Olsson-Francis. "Geochemical bio-signatures in Martian analogue basaltic environments using laboratory experiments and thermochemical modelling." Frontiers in Astronomy and Space Sciences 9 (November 17, 2022). http://dx.doi.org/10.3389/fspas.2022.1062007.
Повний текст джерелаАнотація:
The identification of geochemical bio-signatures is important for assessing whether life existed on early Mars. In this paper, experimental microbiology and thermochemical modelling were combined to identify potential inorganic bio-signatures for life detection on early Mars. An analogue mixed microbial community from an analogue terrestrial fluvio-lacustrine environment similar to an ancient lacustrine system at Gale Crater was used to study microbial dissolution of a basalt regolith simulant and the formation of bio-signatures over a short time frame (1°month) at 14°C, 2 bar. Microbial growth influenced element dissolution (Mg, Fe, Mn, Ca and K) and the formation of morphologies and Fe-Si amorphous layers on mineral surfaces. Thermochemical models were performed at 14°C, 2 bar; the results were compared with experimental data to predict bio-signatures that would occur over geological timescales. The pH was varied to simulate abiotic and biotic experimental conditions. Model results suggest that, at water to rock ratios of 100 to 38, a less complex secondary mineral assemblage forms during biotic dissolution compared to abiotic weathering. Carbonates, quartz, pyrite and hydroxyapatite form under biotic conditions, whereas in the abiotic system magnetite and phyllosilicates would also precipitate. These results could be used to distinguish between abiotic and biotic basalt weathering processes, aiding the interpretation of data from Mars exploration missions.