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Jinliang Feng - One of the best experts on this subject based on the ideXlab platform.

  • Chromium speciation and its stable isotopic signature in the dolomite–Terra Rossa weathering system
    Geoderma, 2019
    Co-Authors: Jinliang Feng
    Abstract:

    Abstract We present the results of a study of chromium (Cr) content, Cr speciation and its stable isotope composition in a Terra Rossa weathering profile, which includes ferromanganese concretions (FMCs) and gibbsite spots, developed on dolomite in the Yunnan–Guizhou Plateau in south central China. Sequential extraction results show that the Cr in all samples is present mainly within the residual fraction and oxidizable fraction, and that the Cr content of the exchangeable fraction and reducible fraction is very low. The significantly high Cr content (mean of 21.0 ppm) of the oxidizable fraction is a potential environmental hazard. The Cr in the Terra Rossa and gibbsite spots exhibits absolute accumulation throughout the profile; correspondingly, the FMCs are significantly enriched in most trace elements, except for Cr. Re-oxidation of Cr(III) to soluble Cr(VI) by MnO2 is likely responsible for the relative depletion of Cr in the FMCs. In the bulk dolomite, the δ53Cr values of the carbonate component and detrital component are 0.447‰ and −0.437‰, respectively. The δ53Cr signal in both fractions is heterogeneous, while both δ53Cr signals are significantly different from that of bulk silicate Earth (BSE; −0.124 ± 0.101‰). Our results provide a proof of concept that the allogenic Cr-isotopic composition of terrigenous minerals in carbonate rocks, can provide new insights into paleo-terrestrial oxidative weathering. Overall, the Terra Rossa is characterized by the enrichment of heavy Cr isotopes compared to the detrital component of dolomite. Hence, the isotopic signature of Cr does not support the idea that the detrital component in dolomite is the sole parent material of the Terra Rossa. The absolute accumulation of Cr and heavy Cr isotope enrichment in Terra Rossa indicate that the extraneous input of dissolved Cr(VI) with a heavy isotopic signature occurred during dolomite weathering and Terra Rossa formation.

  • chromium speciation and its stable isotopic signature in the dolomite Terra Rossa weathering system
    Geoderma, 2019
    Co-Authors: Jinliang Feng
    Abstract:

    Abstract We present the results of a study of chromium (Cr) content, Cr speciation and its stable isotope composition in a Terra Rossa weathering profile, which includes ferromanganese concretions (FMCs) and gibbsite spots, developed on dolomite in the Yunnan–Guizhou Plateau in south central China. Sequential extraction results show that the Cr in all samples is present mainly within the residual fraction and oxidizable fraction, and that the Cr content of the exchangeable fraction and reducible fraction is very low. The significantly high Cr content (mean of 21.0 ppm) of the oxidizable fraction is a potential environmental hazard. The Cr in the Terra Rossa and gibbsite spots exhibits absolute accumulation throughout the profile; correspondingly, the FMCs are significantly enriched in most trace elements, except for Cr. Re-oxidation of Cr(III) to soluble Cr(VI) by MnO2 is likely responsible for the relative depletion of Cr in the FMCs. In the bulk dolomite, the δ53Cr values of the carbonate component and detrital component are 0.447‰ and −0.437‰, respectively. The δ53Cr signal in both fractions is heterogeneous, while both δ53Cr signals are significantly different from that of bulk silicate Earth (BSE; −0.124 ± 0.101‰). Our results provide a proof of concept that the allogenic Cr-isotopic composition of terrigenous minerals in carbonate rocks, can provide new insights into paleo-terrestrial oxidative weathering. Overall, the Terra Rossa is characterized by the enrichment of heavy Cr isotopes compared to the detrital component of dolomite. Hence, the isotopic signature of Cr does not support the idea that the detrital component in dolomite is the sole parent material of the Terra Rossa. The absolute accumulation of Cr and heavy Cr isotope enrichment in Terra Rossa indicate that the extraneous input of dissolved Cr(VI) with a heavy isotopic signature occurred during dolomite weathering and Terra Rossa formation.

  • Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and Terra Rossa formation
    Chemical Geology, 2018
    Co-Authors: Jinliang Feng, Le-le Pei, Xiangkun Zhu, Shao-peng Gao
    Abstract:

    Abstract The behavior of silicon (Si) and iron (Fe) and their isotope fractionation during carbonate weathering and Terra Rossa formation are unclear. Here, we focus on a 4.05-m-thick Terra Rossa profile developed on dolomite in the Yunnan-Guizhou Plateau, China. We measured the mineral and geochemical composition, magnetic susceptibility and Si and Fe isotopic composition of the Terra Rossa, ferromanganese concretions (FMCs), and the dolomite and its insoluble residues. The results indicate that there is absolute accumulation of Si and Fe during dolomite weathering and Terra Rossa formation, due to the extraneous input of dissolved Si and Fe. This means that the insoluble residues of dolomite are not the only source for Terra Rossa formation. In addition, we suggest that the high frequency-dependent magnetic susceptibility (χ fd , %) and rubification of the Terra Rossa are the result of the oxidation of extraneous dissolved Fe and the neoformation of finely dispersed Fe oxides. Overall, the Terra Rossa is characterized by the enrichment of light Si and Fe isotopes, compared with insoluble dolomite residues and bulk dolomite. The extraneous input of dissolved Fe is characterized by a light isotopic signature, whereas the Si isotopic signature of the extraneous source is unclear due to modification by late desilicification. Si isotope fractionation in the Terra Rossa is mainly controlled by chemical weathering and associated mobilization and redistribution of Si. The δ 30 Si values of Terra Rossa decrease with increasing weathering intensity, while the re-precipitation of mobilized Si leads to the significant enrichment of isotopically heavy Si in the basal Terra Rossa. The δ 30 Si values of Terra Rossa are not significantly affected by the adsorption of the Fe and Al (oxyhydr)oxides. By contrast, the major process that fractionates Fe isotopes in the dolomite-Terra Rossa weathering system is unclear. In the Terra Rossa profile, the δ 56 Fe values of the FMCs are significantly lower than those of the surrounding Terra Rossa matrix. These low δ 56 Fe signatures of the FMCs reflect the preferential translocation of the light Fe isotope, while the FMCs may be able to record the low-δ 56 Fe characteristics of pore water.

  • enrichment of trace elements in ferromanganese concretions from Terra Rossa and their potential desorption
    Geochemical Journal, 2012
    Co-Authors: Jinliang Feng, Shao-peng Gao, Yongchong Lin, Ji-feng Zhang
    Abstract:

    The distributions of trace elements in ferromanganese concretions (FMCs) and the surrounding Terra Rossa (TR) matrix overlying dolomite have been examined to extend our understanding of their mobilization, redistribution and fractionation during karst weathering and pedogenesis. This study demonstrates that the characteristics of trace elements in TR have been severely overprinted by weathering and pedogenetic processes. The composition of trace elements in FMCs within TR soil profiles varies greatly with depth. The concentrations of Be, Ni, Cu, Zn, As and Bi in FMCs fluctuate and tend to increase with depth; other trace element concentrations fluctuate in the profile but show no clear trend. The toxic elements Cr, As, Cd, Tl and Pb, as well as Co, are significantly enriched in FMCs relative to the surrounding TR matrix: arsenic exhibits strong affinity with Fe, but Cr and Cd contents are not significantly correlated with either Mn or Fe. Correspondingly, Co, Tl and Pb are related to the Mn in FMCs rather than the Fe. In FMCs, trace element distribution and partitioning in the Mn‐Fe phases are governed by the location-specific formational pedoenvironment, with the weathering front etching downwards. Experiments with simulated acid rain indicate that desorption of elements from FMCs is generally pH-dependent regardless of the variation of the released amounts and their desorbability. Moreover, it seems that toxic elements bonded to Mn-phase were easily desorbed from FMCs. As a result, the bioavailability, mobility and activity of some toxic elements in FMCs and TR are potentially increased in field areas experiencing severe soil erosion and acid rain.

  • Lanthanide tetrad effect in ferromanganese concretions and Terra Rossa overlying dolomite during weathering
    Chemie Der Erde-geochemistry, 2011
    Co-Authors: Jinliang Feng, Shao-peng Gao, Ji-feng Zhang
    Abstract:

    Abstract The lanthanide tetrad effect was investigated in a 5.4 m thick Terra Rossa profile overlying dolomite on the Yunnan-Guizhou Plateau, China. The results demonstrate that the chondrite-normalized rare earth element pattern of dolomite bedrock displays a W-type tetrad effect. The insoluble residue from the dolomite bedrock does not exhibit any significant tetrad effect. In contrast, some ferromanganese concretions and the Terra Rossa show tetrad effect. It is worth noting that the conjugate M- and W-types of the tetrad effect are observed in some Terra Rossa samples. The tetrad effect in the ferromanganese concretions and the Terra Rossa possibly originates from redistribution of dissolved rare earth elements during their downwards movement in the profile and not only from water/rock interaction. Within the dolomite weathering system, the ferromanganese concretions and surrounding Terra Rossa present similar correlations of Eu/Eu*, Y/Ho, Sm/Nd, Ce/Ce*, with the size of the tetrad effect. The ferromanganese concretions and the Terra Rossa with tetrad effect are characterized by a reduced, non-chondritic Y/Ho ratio. Also the Y/Ho ratio exhibits a clear negative correlation with the size of the tetrad effect in the ferromanganese concretions and the Terra Rossa. In addition, the Eu/Eu* tends to increase with increasing size of the tetrad effect in the ferromanganese concretions and the Terra Rossa, as does the Sm/Nd ratio. The regular variation for Eu/Eu*, Y/Ho and Sm/Nd is likely a result of the fractionation of rare earth elements and yttrium with the tetrad effect. On the other hand, the correlation of the Ce/Ce* with the size of the tetrad effect in the ferromanganese concretions and the Terra Rossa is random. This likely indicates that the Ce behavior within weathering system is mainly controlled by redox condition, rather than tetrad effect. Comparative study indicates that the correlations of Eu/Eu*, Y/Ho, Ce/Ce*, with the size of the tetrad effect in the ferromanganese concretions and the Terra Rossa, are not similar to those found in a highly evolved igneous system. Nevertheless, the correlation of Sm/Nd with the size of tetrad effect in weathering system is similar to that in igneous system. In general, it appears to indicate that the tetrad effect occurrence in granitic rocks is not associated with weathering.

Goran Durn - One of the best experts on this subject based on the ideXlab platform.

  • Impact of iron oxides and soil organic matter on the surface physicochemical properties and aggregation of Terra Rossa and Calcocambisol subsoil horizons from Istria (Croatia)
    Catena, 2019
    Co-Authors: Goran Durn, Franz Ottner, Srečo D. Škapin, Neda Vdović, Thilo Rennert, Stanko Ružičić, Nuša Cukrov, Ivan Sondi
    Abstract:

    Abstract We investigated the influence of Fe oxides and soil organic matter (SOM) on the surface physicochemical properties of mineral particles involved in the formation of nanostructured and micron-sized mineral aggregates of two Terra Rossa and one Calcocambisol soils developed on limestone. We determined the mineral composition and particle-size distribution (PSD) by X-ray diffraction (XRD) and laser diffraction (LD), respectively. The morphologies of the mineral particles were investigated using field-emission scanning electron microscopy (FE-SEM), while soil organic matter (SOM) was characterized by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). The electrophoretic mobility (EPM), specific surface area (SSA) and cation exchange capacity (CEC) of the samples were also examined. We analysed surface physicochemical properties on soil prior and after selective removal of SOM and Fe oxides. The soils were characterized by their relatively simple bulk and clay mineral compositions, distinctly different contents of SOM and diverse Fe oxides. The EPM data showed that the removal of the SOM did not significantly affect the negative charge of particles, but the removal of Fe oxides shifted the EPM to more negative values, indicating an increase in permanently negatively charged clay surfaces. The removal of SOM did not affect the SSA of the Terra Rossa soils, but doubled the SSA in the Calcocambisol. The SSA of the Terra Rossas were exceptionally high, up to 130–145 m2 g−1, probably because of nano-sized authigenic (pedogenic) kaolinite. The presence of larger clay mineral particles in the Calcocambisol samples resulted in lower SSA (32–76 m2 g−1). The LD analyses showed that the removal of the SOM did not influence the PSD of the Terra Rossa soils, while the removal of the Fe oxides, mainly nanosized hematite, governed the disintegration of the micron-sized soil aggregates and induced a significant increase of the submicron-sized mineral fraction. In contrast, the removal of the SOM significantly influenced the PSD of the Calcocambisol, causing the disintegration of the native, micron-sized aggregates and an increase in the clay fraction. This study demonstrated the important role of the SOM in the aggregation processes for the Calcocambisol and the Fe oxides, especially hematite, in the Terra Rossa subsoil horizons. It was also shown that the surface properties of the Terra Rossa, particularly EPM and SSA, were determined by the presence of a nano-sized mineral fraction that mostly contains authigenic kaolinite.

  • Provenance and formation of the red palaeosol and lithified Terra Rossa-like infillings on the Island of Susak: a high-resolution and chronological approach
    Quaternary International, 2017
    Co-Authors: Goran Durn, Neven Tadej, Stjepan Husnjak, Lara Wacha, Mateja Bartolin, Christian Rolf, Manfred Frechen, Sumiko Tsukamoto, Vedran Rubinić
    Abstract:

    Abstract Red palaeosol (RP) covering the carbonate basement exposed at the bottom of the loess section and lithified Terra Rossa-like materials situated in cavities (LTR1) and karstified fissures (LTR2) in Cretaceous limestones were investigated by means of high-resolution approach, to give a systematic and deeper palaeopedological insight into reddish materials and the exposed red palaeosols on the island of Susak. Both, selected geochemical indicators of weathering (Al/Si, (Na + K)/Al and Fed/Fet) and provenance (La/Ce), as well as detailed mineralogical analysis clearly showed differences among LTR1, LTR2 and RP, respectively. LTR1 and LTR2 represent erosional remains of different soils that existed on the surface of the limestone bedrock prior to the formation of the RP. LTR2 has the highest ZTR (zircon-tourmaline-rutile index) index and contains bauxite minerals (gibbsite and boehmite), clays (kaolinite and mixed-layer clay minerals), and haematite. LTR2 bears characteristics of reworked bauxitic materials mixed with other soils that existed on the surface of the carbonate basement. Those materials might have been mixed and transported until they were captured in the karstified fissure, and, subsequently interlocked with calcite veins and lithified. This might have happened from the Eocene age on. Our attempt to resolve the age of LTR2 formation more precisely, using palaeomagnetic investigations, did not give unambiguous results because the extremely viscous behaviour of the LTR2 samples hinders the acquisition of a stable remanent magnetisation. If we exclude the secondary calcite, LTR1 bears typical mineralogical and geochemical characteristics (e.g. Fed/Fet ratio) similar to those of Istrian Terra Rossa. Insoluble residues of Cretaceous limestone might have been the main parent materials for the LTR1 formation while the most likely additional fluxes influencing Terra Rossa formation on the island of Susak were aeolian dust and flysch. The erosion remains ended in limestone cavities and were mixed with cm to dm sized angular and subangular limestone clasts and, subsequently, interlocked with calcite veins and lithified. The investigated RP profile comprised the following mineral horizons: Bwb1-Bwb2-Bwb3-R. The RP formed in a lithologically uniform material that dominantly presents a mixture of loess and, partly, remains of older soils (e.g. rounded clay coatings not related to macrovoids) that existed on the surface of the Cretaceous limestone. Fed/Fet ratio in RP reflects a low degree of weathering of Fe-containing primary silicates. Therefore, we can conclude that the RP does not fit a rather limited variation of selected Fe-oxide characteristics typical for Terra Rossa. The investigated RP was classified independently of the overlying material. The full name of the palaeosol that we classified is as follows: Hypereutric Chromic Cambisol (Episiltic, Endoloamic). Since no reversal of the EMF was recorded in the RP, we concluded that the RP formed during the Brunhes epoch. Luminescence dating was applied to establish the age of the RP. Based on the acquired data, we assume that the RP very likely formed during the Penultimate Interglacial (OIS7).

  • Red paleosols on limestone at the base of loess sequence on Susak vs. Terra Rossa infillings in limestone cracks and cavities: high-resolution depth and chronological approach
    2015
    Co-Authors: Goran Durn, Lara Wacha, Christian Rolf, Manfred Frechen, Mateja Sedak
    Abstract:

    The cracks in Senonian limestones on the island of Susak are filled by red clayey materials (Terra Rossa) which we consider remain of the oldest paleosol(s) on the island. The same limestone is covered by loess-paleoosol sequence up to 90 m thick. The lowermost red paleosol in this sequence covers the carbonate bedrock. From the mineralogical and geochemical view point two different types of Terra Rossas are situated within limestone cracks. The first dating study of the loess – palaeosol sequence on Susak was performed by Wacha et al. (2011 a, b) and showed that that most of the exposed sedimentary record can be correlated with oxygen isotope stages (OIS) 5 to 2. With the means of IRSL dating methods and high-resolution palaeomagnetic measurements we will try to provide age(s) of the lowermost red paleosol that covers the carbonate bedrock and acquire knew information about Terra Rossa in limestone cracks. Wacha, L., Mikulcic Pavlakovic, S., Novothny, A., Crnjakovic, M. & Frechen, M. 2011a: Luminescence Dating of Upper Pleistocene Loess from the Island of Susak in Croatia. Quaternary International 234/ 1–2, 50–61. Wacha, L., Mikulcic Pavlakovic, S., Frechen, M. & Crnjakovic, M. 2011b: The Loess Chronology of the Island of Susak, Croatia. Quaternary Science Journal (E&G) 60/1, 153–169.

  • Mineralogy and geochemistry of soils/paleosols formed in contrasting pedoenvironments (oxidizing vs. reducing) on pure cretaceous limestones in Istria, Croatia
    2015
    Co-Authors: Goran Durn, Franz Ottner, Jens Stummeyer, Nediljka Gaurina Međimurec
    Abstract:

    The main difference between Terra Rossa soils and GGP observed in the field is their color which indicates that, generally, Terra Rossa soils formed in oxidizing while GGP formed in reducing pedoenvironment. Our investigation showed that mineral data corresponds well with chemical data of those soils/paleosols. Higher SiO2 and Na2O in Terra Rossa soils compared to GGP is the result of quartz and plagioclase, mineral phases that were not detected in GGP. Higher Fe2O3 in Terra Rossa soils is the result of hematite and goethite formation, mineral phases that are specific for the oxidizing, well drained and slightly alkaline to neutral pH pedoenvironment in which Terra Rossa is formed. The values obtained for P2O5 and MnO in Terra Rossa match that finding well. Compared to GPP, Terra Rossa soils are slightly enriched in Co and Pb and significantly enriched in REE. The important difference in the total REE in analyzed Terra Rossa soils can be attributed to the REE content of both parent carbonate rocks (their insoluble residues) and different external materials which have contributed in the genesis of Terra Rossa (loess, flysch, bauxite), modified by weathering processes which characterize specific pedoenvironment in which Terra Rossa is formed and which favors LREE enrichment. Sequential extraction analysis showed that Mn, Co and Pb, mainly bound to reducible fraction (III), are the most mobile trace elements in Terra Rossa, while the most available are Cd, Ba, Sb and As, bound to adsorbed fraction (I). Mobility of Co, Pb and especially Mn, elements enriched in Terra Rossa soils is higher in Terra Rossa soils than in GGP showing that formation of Mn oxides might have played important role in their accumulation in Terra Rossa soils. Partitioning of REE in sequential fractions of Terra Rossa soils showed that authigenic Fe-oxides and/or Mn oxides are probably important sink for REE. K2O contents in GGP clearly indicate that illitic material is the dominant mineral phase in the GGP. Ottner et al. (1999) found that the smectites in illite/smectite mixed-layer minerals from clays in the Tri Jezerca quarry are aluminum rich montmorillonites without iron substitution in the octahedral position. The values obtained for MgO in GGP match that finding well. Higher SO3 in GGP is the result of pyrite and gypsum formation, mineral phases that were not detected in Terra Rossa soils. Pyrite indicates acidic and reductive pedogenic paleoenvironment of GGP formation. (Sub)recent pyrite oxidation at the surface results in the formation of the secondary mineral gypsum. The enrichment of GGP in Cd, Sb, Ni, V and especially in U and Mo is considered typical for reducing environments. Variation of the total REE content in GGP is much narrow compared to Terra Rossa soils. Total REE in GGP is dominated by residual fraction and probably also reflects parent materials (insoluble residue of limestone, aeolian and volcanic dust) modified in acidic and reductive marshy pedoenvironment which favors HREE enrichment. Enrichment of HREE in GGP is probably the result of higher mobility of LREE in this type of pedoenvironment. Cd, Ni and Co, mainly bound to adsorbed fraction (I) are most mobile and available trace elements in GGP. It is interesting to note that the mobility of Mo, Ni and Cd, trace elements enriched in GGP is higher in GGP than in Terra Rossa soils indicating that the adsorption processes might have played important role in their accumulation in GGP.

  • Bulk and clay mineral composition indicate origin of Terra Rossa soils in Western Herzegovina
    Geologia Croatica, 2014
    Co-Authors: Goran Durn, Radica Ćorić, Neven Tadej, Uroš Barudžija, Vedran Rubinić, Stjepan Husnjak
    Abstract:

    The B horizons of Terra Rossa soils developed on three different carbonate lithologies having variable insoluble residue contents were studied in Western Herzegovina. Comparison of  their composition and properties illustrates to what extent mineral (especially clay mineral assemblage) and particle size composition of those horizons and the insoluble residue of the underlying carbonate rocks can be used as indicators of the polygenetic nature of Terra Rossa in this region. Terra Rossa B horizons have characteristic red colours, neutral to slightly acid pH, high base saturation with calcium as the predominant cation and high CIA (Chemical Index of Alteration). The CIA values obtained are generally in accordance with mineral composition and particle size distribution of the analysed B horizons.  The predominant clay mineral phases in B horizons and related insoluble residues match. Kaolinite is the predominant clay mineral phase in the B horizons overlying carbonate rocks containing low amounts of insoluble residue, while smectite predominates in calcarenites areas with a high insoluble residue content.  However, the presence of plagioclase, gibbsite, chlorite-vermiculite mixed layer mineral and vermiculite in B horizons overlying carbonate rocks containing low amounts of insoluble residue support a polygenetic origin for the Terra Rossa. In contrast, Terra Rossa formed on calcarenites containing high amounts of insoluble residue might have formed almost exclusively from the parent carbonate rock although some influence of external materials (e.g. gibbsite) cannot be excluded. This investigation shows that in Western Herzegovina, an area with no important aeolian input, the content and mineral composition of carbonate rock insoluble residue plays a major role in Terra Rossa composition.  We can tentatively conclude that the lower the insoluble residue content of the parent materials, the greater is the expectation of a more polygenetic origin for the Terra Rossa.

Liping Zhu - One of the best experts on this subject based on the ideXlab platform.

  • Quartz features constrain the origin of Terra Rossa over dolomite on the Yunnan-Guizhou Plateau, China
    Journal of Asian Earth Sciences, 2009
    Co-Authors: Jinliang Feng, Liping Zhu, Zhijiu Cui
    Abstract:

    Abstract The origin of Terra Rossa and the relationship between Terra Rossa and its underlying carbonate rocks pose long-standing and controversial questions. Little insoluble residue content in carbonate rocks makes it difficult to believe that the Terra Rossa derives only from their underlying carbonates. This study focuses on one 4.05 m thick Pingba Farm Terra Rossa profile over dolomite on the Yunnan-Guizhou Plateau, China. It is characterized by its ferromanganese concretion, gibbsite and Terra Rossa coexistence in profile. The Al2O3 contents in the Terra Rossa rise to 34%. The authors examined the quartz content, particle size distribution of quartz, surface micro-textures and quartz morphology, quartz oxygen isotope ratios, mineral composition, chemical composition, and other tracers in the Terra Rossa and dolomite to determine the derivation of the Terra Rossa. The results indicate that Terra Rossa in the Pingba Farm profile is an in situ weathering solum. The Terra Rossa comes partly, but not completely, from insoluble residues from the underlying dolomite. The debris minerals (quartz, feldspar, etc.) derive completely from the underlying dolomite. The clay minerals, and the Al, Fe and Mn oxides and hydroxides likely have three origins. One portion derives from insoluble residues of the underlying dolomite. A second portion transforms from primary minerals in the underlying dolomite. The final portion possibly comes from antigenic minerals which formed from aqueous solutes imported by the leaching water. The Terra Rossa is mainly composed of antigenic minerals.

  • Origin of Terra Rossa over dolomite on the Yunnan-Guizhou Plateau, China
    Geochemical Journal, 2009
    Co-Authors: Jinliang Feng, Zhijiu Cui, Liping Zhu
    Abstract:

    The origin of Terra Rossa and its relationship with its underlying carbonate rocks pose long-standing and controversial questions. This study focuses on one 5.4 m thick Terra Rossa profile on dolomite. The authors examined the quartz content, size distribution of quartz grains, mineral composition, surface micro-texture and crystal morphology of quartz, oxygen isotope ratios of quartz, and other tracers in the Terra Rossa and underlying dolomite to determine the derivation of Terra Rossa. The results indicate that Terra Rossa in the Dashandong profile on the Yunnan-Guizhou Plateau, China, is an in situ weathering solum. The Terra Rossa originates mostly from insoluble residues of the parent dolomite. The debris minerals (quartz and feldspar) derive completely from the parent dolomite. The clay minerals, and Al, Fe and Mn oxides and hydroxides likely have three origins. One portion derives from insoluble residues of the parent dolomite. A second portion converts from primary minerals in the parent dolomite. The last contribution comes from authigenic minerals from aqueous solutes transported by the water cycle. Authigenic minerals constitute the main components of the Terra Rossa. During weathering processes, the dolomite weathering functions as a “trap” against the escape of in situ insoluble residues and external aqueous solutes by means of poly-genetic chemical and physical barriers.

  • Origin of Terra Rossa on Amdo North Mountain on the Tibetan plateau, China: Evidence from quartz
    Soil Science and Plant Nutrition, 2009
    Co-Authors: Jinliang Feng, Liping Zhu
    Abstract:

    Abstract Terra Rossa was found overlying limestone on a planar erosion surface at approximately 5100 m on the summit of Amdo North Mountain on the Tibetan Plateau. The present study examined the quartz content, size distribution of the quartz grains, mineral composition, oxygen isotope ratios in the quartz, surface microtexture and crystal morphology of the quartz in the Terra Rossa and its potential source rocks to determine the derivation of the Terra Rossa. The results indicated that the component of the Terra Rossa on Amdo North Mountain is a mixture of weathering products from the underlying limestone, the overlying red sandy limestone and the adjacent limestone breccia. These different parent materials can result from being introduced under gravity and other mass transport during geological epoch. Therefore, the Terra Rossa on Amdo North Mountain is primarily a transported sedimentary deposit, not an in situ weathering solum. The source of much of the Terra Rossa is likely to be weathering products ...

Shao-peng Gao - One of the best experts on this subject based on the ideXlab platform.

  • Absolute accumulation and isotope fractionation of Si and Fe during dolomite weathering and Terra Rossa formation
    Chemical Geology, 2018
    Co-Authors: Jinliang Feng, Le-le Pei, Xiangkun Zhu, Shao-peng Gao
    Abstract:

    Abstract The behavior of silicon (Si) and iron (Fe) and their isotope fractionation during carbonate weathering and Terra Rossa formation are unclear. Here, we focus on a 4.05-m-thick Terra Rossa profile developed on dolomite in the Yunnan-Guizhou Plateau, China. We measured the mineral and geochemical composition, magnetic susceptibility and Si and Fe isotopic composition of the Terra Rossa, ferromanganese concretions (FMCs), and the dolomite and its insoluble residues. The results indicate that there is absolute accumulation of Si and Fe during dolomite weathering and Terra Rossa formation, due to the extraneous input of dissolved Si and Fe. This means that the insoluble residues of dolomite are not the only source for Terra Rossa formation. In addition, we suggest that the high frequency-dependent magnetic susceptibility (χ fd , %) and rubification of the Terra Rossa are the result of the oxidation of extraneous dissolved Fe and the neoformation of finely dispersed Fe oxides. Overall, the Terra Rossa is characterized by the enrichment of light Si and Fe isotopes, compared with insoluble dolomite residues and bulk dolomite. The extraneous input of dissolved Fe is characterized by a light isotopic signature, whereas the Si isotopic signature of the extraneous source is unclear due to modification by late desilicification. Si isotope fractionation in the Terra Rossa is mainly controlled by chemical weathering and associated mobilization and redistribution of Si. The δ 30 Si values of Terra Rossa decrease with increasing weathering intensity, while the re-precipitation of mobilized Si leads to the significant enrichment of isotopically heavy Si in the basal Terra Rossa. The δ 30 Si values of Terra Rossa are not significantly affected by the adsorption of the Fe and Al (oxyhydr)oxides. By contrast, the major process that fractionates Fe isotopes in the dolomite-Terra Rossa weathering system is unclear. In the Terra Rossa profile, the δ 56 Fe values of the FMCs are significantly lower than those of the surrounding Terra Rossa matrix. These low δ 56 Fe signatures of the FMCs reflect the preferential translocation of the light Fe isotope, while the FMCs may be able to record the low-δ 56 Fe characteristics of pore water.

  • enrichment of trace elements in ferromanganese concretions from Terra Rossa and their potential desorption
    Geochemical Journal, 2012
    Co-Authors: Jinliang Feng, Shao-peng Gao, Yongchong Lin, Ji-feng Zhang
    Abstract:

    The distributions of trace elements in ferromanganese concretions (FMCs) and the surrounding Terra Rossa (TR) matrix overlying dolomite have been examined to extend our understanding of their mobilization, redistribution and fractionation during karst weathering and pedogenesis. This study demonstrates that the characteristics of trace elements in TR have been severely overprinted by weathering and pedogenetic processes. The composition of trace elements in FMCs within TR soil profiles varies greatly with depth. The concentrations of Be, Ni, Cu, Zn, As and Bi in FMCs fluctuate and tend to increase with depth; other trace element concentrations fluctuate in the profile but show no clear trend. The toxic elements Cr, As, Cd, Tl and Pb, as well as Co, are significantly enriched in FMCs relative to the surrounding TR matrix: arsenic exhibits strong affinity with Fe, but Cr and Cd contents are not significantly correlated with either Mn or Fe. Correspondingly, Co, Tl and Pb are related to the Mn in FMCs rather than the Fe. In FMCs, trace element distribution and partitioning in the Mn‐Fe phases are governed by the location-specific formational pedoenvironment, with the weathering front etching downwards. Experiments with simulated acid rain indicate that desorption of elements from FMCs is generally pH-dependent regardless of the variation of the released amounts and their desorbability. Moreover, it seems that toxic elements bonded to Mn-phase were easily desorbed from FMCs. As a result, the bioavailability, mobility and activity of some toxic elements in FMCs and TR are potentially increased in field areas experiencing severe soil erosion and acid rain.

  • Lanthanide tetrad effect in ferromanganese concretions and Terra Rossa overlying dolomite during weathering
    Chemie Der Erde-geochemistry, 2011
    Co-Authors: Jinliang Feng, Shao-peng Gao, Ji-feng Zhang
    Abstract:

    Abstract The lanthanide tetrad effect was investigated in a 5.4 m thick Terra Rossa profile overlying dolomite on the Yunnan-Guizhou Plateau, China. The results demonstrate that the chondrite-normalized rare earth element pattern of dolomite bedrock displays a W-type tetrad effect. The insoluble residue from the dolomite bedrock does not exhibit any significant tetrad effect. In contrast, some ferromanganese concretions and the Terra Rossa show tetrad effect. It is worth noting that the conjugate M- and W-types of the tetrad effect are observed in some Terra Rossa samples. The tetrad effect in the ferromanganese concretions and the Terra Rossa possibly originates from redistribution of dissolved rare earth elements during their downwards movement in the profile and not only from water/rock interaction. Within the dolomite weathering system, the ferromanganese concretions and surrounding Terra Rossa present similar correlations of Eu/Eu*, Y/Ho, Sm/Nd, Ce/Ce*, with the size of the tetrad effect. The ferromanganese concretions and the Terra Rossa with tetrad effect are characterized by a reduced, non-chondritic Y/Ho ratio. Also the Y/Ho ratio exhibits a clear negative correlation with the size of the tetrad effect in the ferromanganese concretions and the Terra Rossa. In addition, the Eu/Eu* tends to increase with increasing size of the tetrad effect in the ferromanganese concretions and the Terra Rossa, as does the Sm/Nd ratio. The regular variation for Eu/Eu*, Y/Ho and Sm/Nd is likely a result of the fractionation of rare earth elements and yttrium with the tetrad effect. On the other hand, the correlation of the Ce/Ce* with the size of the tetrad effect in the ferromanganese concretions and the Terra Rossa is random. This likely indicates that the Ce behavior within weathering system is mainly controlled by redox condition, rather than tetrad effect. Comparative study indicates that the correlations of Eu/Eu*, Y/Ho, Ce/Ce*, with the size of the tetrad effect in the ferromanganese concretions and the Terra Rossa, are not similar to those found in a highly evolved igneous system. Nevertheless, the correlation of Sm/Nd with the size of tetrad effect in weathering system is similar to that in igneous system. In general, it appears to indicate that the tetrad effect occurrence in granitic rocks is not associated with weathering.

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  • Quartz features constrain the origin of Terra Rossa over dolomite on the Yunnan-Guizhou Plateau, China
    Journal of Asian Earth Sciences, 2009
    Co-Authors: Jinliang Feng, Liping Zhu, Zhijiu Cui
    Abstract:

    Abstract The origin of Terra Rossa and the relationship between Terra Rossa and its underlying carbonate rocks pose long-standing and controversial questions. Little insoluble residue content in carbonate rocks makes it difficult to believe that the Terra Rossa derives only from their underlying carbonates. This study focuses on one 4.05 m thick Pingba Farm Terra Rossa profile over dolomite on the Yunnan-Guizhou Plateau, China. It is characterized by its ferromanganese concretion, gibbsite and Terra Rossa coexistence in profile. The Al2O3 contents in the Terra Rossa rise to 34%. The authors examined the quartz content, particle size distribution of quartz, surface micro-textures and quartz morphology, quartz oxygen isotope ratios, mineral composition, chemical composition, and other tracers in the Terra Rossa and dolomite to determine the derivation of the Terra Rossa. The results indicate that Terra Rossa in the Pingba Farm profile is an in situ weathering solum. The Terra Rossa comes partly, but not completely, from insoluble residues from the underlying dolomite. The debris minerals (quartz, feldspar, etc.) derive completely from the underlying dolomite. The clay minerals, and the Al, Fe and Mn oxides and hydroxides likely have three origins. One portion derives from insoluble residues of the underlying dolomite. A second portion transforms from primary minerals in the underlying dolomite. The final portion possibly comes from antigenic minerals which formed from aqueous solutes imported by the leaching water. The Terra Rossa is mainly composed of antigenic minerals.

  • Origin of Terra Rossa over dolomite on the Yunnan-Guizhou Plateau, China
    Geochemical Journal, 2009
    Co-Authors: Jinliang Feng, Zhijiu Cui, Liping Zhu
    Abstract:

    The origin of Terra Rossa and its relationship with its underlying carbonate rocks pose long-standing and controversial questions. This study focuses on one 5.4 m thick Terra Rossa profile on dolomite. The authors examined the quartz content, size distribution of quartz grains, mineral composition, surface micro-texture and crystal morphology of quartz, oxygen isotope ratios of quartz, and other tracers in the Terra Rossa and underlying dolomite to determine the derivation of Terra Rossa. The results indicate that Terra Rossa in the Dashandong profile on the Yunnan-Guizhou Plateau, China, is an in situ weathering solum. The Terra Rossa originates mostly from insoluble residues of the parent dolomite. The debris minerals (quartz and feldspar) derive completely from the parent dolomite. The clay minerals, and Al, Fe and Mn oxides and hydroxides likely have three origins. One portion derives from insoluble residues of the parent dolomite. A second portion converts from primary minerals in the parent dolomite. The last contribution comes from authigenic minerals from aqueous solutes transported by the water cycle. Authigenic minerals constitute the main components of the Terra Rossa. During weathering processes, the dolomite weathering functions as a “trap” against the escape of in situ insoluble residues and external aqueous solutes by means of poly-genetic chemical and physical barriers.