Clay Mineral Suite Research Articles

Boron adsorption in clay minerals: Implications for martian groundwater chemistry and boron on Mars

Boron has been detected on Mars in calcium-sulfate veins found within clay mineral rich rocks on Mars by the Mars Science Laboratory (MSL) Curiosity rover using Laser Induced Breakdown Spectroscopy (LIBS) analysis. Borates play a vital role in stabilizing ribose on Earth and has been suggested as a key requirement for life. Borate ions readily adsorb to phyllosilicate clay minerals. The discovery of boron on Mars in proximity to phyllosilicate-bearing bedrock may have strong implications for potential past prebiotic conditions on Mars. In this study we generated a suite of clay minerals with adsorbed borate, including both typical terrestrial clay minerals (montmorillonite) and Mars-analog clay minerals (nontronite, saponite, griffithite), to understand controls on borate adsorption and to analyze with LIBS to compare with MSL data. Clay minerals were subjected to mineralogical and chemical analysis before and after adsorption. Adsorption analysis revealed that the Mars analog clay minerals adsorbed less boron than terrestrial counterparts, but within comparable amounts to those detected on Mars and in meteorites. Post-adsorption analysis by X-ray diffraction (XRD) revealed slight changes in the interlayer spacing of many of the clay minerals. Based on the adsorption analysis of the Mars-analog clay minerals, phyllosilicate-bearing bedrock in Gale crater may contain up to 90-110 ppm B. A series of borate-enriched samples were created for analysis of LIBS spectra from ChemCam on the Curiosity rover and SuperCam on the Perseverance Rover. The results of this study may provide insight into martian groundwater geochemistry processes and the mobility of a key molecule connected with life.

Pedogenic processes in a chronosequence of very deeply weathered soils in southeastern Brazil

Brazil has some of the oldest soils of the world. Landscapes in southeastern Brazil are very old and stable. Some of the soils formed therein have suffered many pedogenetic cycles and hence are difficult to study thoroughly due to their depth and age. In the southeastern State of Minas Gerais, Brazil, we studied four soils developed from gneiss formed on these old surfaces (one sampled to a depth of 26 m) that comprised a chronosequence. For most soils of the world, the major change in properties is at the C/B horizon interface, but in these soils the major change is at the R/C interface. In each soil, a certain suite of clay minerals (kaolinite, gibbsite, goethite, and hematite) had weathered from the primary minerals of gneiss. The composition of the suite differed among the four soils, but in an individual soil it was relatively constant with depth, including through the C/B boundary. In the C horizon, many of the minerals were in the form of aggregates in the silt fraction. Across the C/B boundary there was little change in chemistry and mineralogy, but there the aggregates broke down to clay particles that were incorporated into soil structure. Overall, the chronosequence showed that soil properties changed greatly from the youngest, lowest part of the landscape, while between the older soils, higher in the landscape, the change was small. Soil properties appeared influenced by the different zones of the weathered mantle, hypothesized to be gibbsitic on the very top, kaolinitic in the most part, and bissialitic (2:1 clay minerals) closer to the fresh rock.

Tectonic and paleoclimatic controls on the composition of inland wetland deposits, Chaco foreland basin, Central Andes

ABSTRACTIn recent decades, the growing interest in wetlands highlights the fundamental role of these complex ecosystems. Integrated sedimentological and geochemical studies that refer to wetlands appear more frequently in the literature, since such approaches provide a window into understanding the functions they have played through geologic time. The Miocene Yecua Formation (Chaco foreland basin, Central Andes, Bolivia) presents sedimentological features that show how siliciclastic, chemical, and biological processes lead to lithofacies and compositional features that are distinctive of wetlands related to back-bulge settings. The succession is composed of shallowing-upward parasequences with various compositional characteristics controlled by tectonic and climatic factors.Data integration obtained from paleocurrents, petrography, and clay mineralogy show the influence of the Central Andes fold and thrust belt located to the west of the basin as a principal source area. The high compositional maturity of sandstones reflects the tectonic control as the main allocyclic variable associated with reworking of already mature sediment sources and transport factors in relation to the distal position of the basin (back-bulge), combined with climatic and paleoenvironmental conditions. XRD and SEM-EDS analyses show that illitic clays represent the main mineral phase of the clay assemblages, and have a detrital origin related to physical weathering processes in the source area. Al-rich smectitic minerals have an authigenic origin and were likely formed by alteration of volcanic detritus as well as from precursor minerals such as illite and feldspars. Kaolinite is determined to be detrital and likely derived from the erosion of floodplains with soil development. Throughout the parasequences, illite–smectite–kaolinite minerals are arranged in different proportions, showing a general vertical trend (from base to top) in which the illitic clays decrease at the expense of the increase in Al-rich smectite and kaolinite. The increase in smectite is accompanied by mixed siliciclastic–carbonate sedimentation, which points to a reduction in the clastic contribution linked to drier conditions. This vertical compositional arrangement reveals a paleoclimatic control, influenced by middle-term wet and dry periods. This work demonstrates that source-rock composition and transport distance (tectonic processes) are the key factors influencing quartz-rich sandstones and illite-rich clay mineral suites in distal positions of continental foreland basins. The long-term tropical to subtropical climate favored the development of inland wetlands and played a secondary role in the final composition of these depositional systems.

Paleoenvironmental, paleoclimatic and stratigraphic implications of the mineralogical content of the Irati Formation, Paraná Basin, Brazil

The Irati Formation documents a singular moment in the evolution of the Paraná Basin, when an effective restriction of water circulation between the syneclise and the Panthalassa Ocean finally established a favorable environment for the deposition of oil shales. The present study presents data from X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) for the determination of different mineralogical components in the entire interval of the Irati Formation. Seeking to correlate the varying mineralogical content of the formation with the paleoenvironmental, paleoclimatic and stratigraphic conditions, total organic carbon (TOC), total sulfur (S) and insoluble residue (IR) data were also utilized. The results showed that variations in mineralogical content occurred mainly in the interval where the greatest values of TOC, S and IR are found. The authigenesis of minerals such as analcime, pyrite, gypsite and barite are closely tied to the environment where they were formed, and these minerals bear within them characteristics of paleoenvironmental conditions, such as restricted water circulation, abundant organic matter, alkalinity and pelagic sedimentation. Variations in the mineralogical content of clay minerals point to an enrichment of illite in the upper interval of the Assistência Member, thus constituting a syndepositional process. The mineralogical data indicate a predominance of illite, chlorite and kaolinite in the Taquaral Member. However, clay mineral suite change in the different depositional domains of the Assistência Member: the internal platform has clay mineral suite dominated primarily by illite and saponite. Kaolinite increase in the intermediary platform and disappear in distal platform. The kaolinite increase probably is the result of intensified weathering due to increase temperature and precipitation. Kaolinite characterizes the transgressive systems tracts under warm and humid paleoclimatic conditions. In contrast, illite and saponite indicate warm and dry conditions in the highstand systems tracts.

Weathering of Permian sedimentary rocks and soil clay minerals transformations under subtropical climate, southern Brazil (Paraná State)

Mineral evolution in weathering zones is usually a complex process. Mixed-layered minerals (MLMs) can form as a result of progressive weathering advancement, promoting important geochemical changes in soils. In this contribution, four soil profiles located in Paraná State (southern Brazil) and formed from different fine-grained Permian sedimentary rocks (one siltstone, two Al-rich shales and one organic black shale) were characterized on mineralogical and geochemical bases. General physico-chemical/morphological characterization, XRD profile modeling of clay fractions, geochemical mass balance and weathering index calculations were performed to relate clay minerals transformation with the geochemical transformations in soils. MLMs dominate clay mineral suite, in progressive compositional ranges. The three soils developed from Al-rich shales (P1, P2 and P4) are dominated by several R0 K-I (kaolinite-illite) phases, and exhibit a trend of progressive kaolinization towards surface soil horizons. The soil developed from Mg-rich organic black shale (P3), however, has R0 I-S (illite-smectite) as the dominant phase, and a progressive dominance of smectite in I-S phase prevails towards surface. These results suggest the prevalence of topotactic transformations (solid-state reactions) during the transition of one clay into another as weathering advances. In the three soils where kaolinization of K-I phases prevails, geochemical mass balance calculations indicate massive losses of SiO2, Al2O3 and alkalis, in addition to high values for weathering indices. Conversely, SiO2 and MgO accumulate, and values for weathering indices are lower in the P3 soil profile. The agreement between the pathways of clay mineral transformations and the mass balance calculations and weathering indices suggests that transformations involving MLMs drive geochemical transformation in soils. The nature of clay suites, in turn, is highly dependent on the chemical compositions of fresh rocks, which determine how transformations involving clays proceed.

Sedimentologic and palaeoenvironmental evolution of the Mamfe Cretaceous Basin (SW Cameroon): Evidence from lithofacies analysis, tectonics and evaporite minerals suite

Lithofacies analysis, optical microscopic and X-ray diffraction approaches were employed to investigate basin-fill configuration and palaeodepositional environments of the Mamfe Cretaceous Basin in SW Cameroon. The asymmetric basin-fill comprises six lithofacies associations whose vertical architectures are influenced by early syn-rift, mid syn-rift and post-rift tectonics episodes coupled with climatic and sedimentological factors: (1) basal conglomerates-breccias-sandstones (association A1) is interpreted as proximal alluvial fans and fluvial channel deposits; (2) thinly bedded mixed siliceous and carbonate sandstones-siltstones-shales (association A2) with ripple marks and desiccation cracks is interpreted as floodplain deposits; (3) sandstones with pebble lags-, scour-filled heterolithic facies-shales-palaeosols (facies association A3) characterises fluvial channel deposits with wave-dominated bars or dunes deposited in marginal fluvio-deltaic environments; (4) organic-rich micritic, oolitic and pelletoidal shales-siltstones-limestones-sandstones (association A4) reflects open lake pro-deltaic deposits; (5) prograding cross-bedded sandstones-shales-pyroclastics-coals-palaeosols (association A5) reflects subaqueous fluvio-lacustrine deltaic and swamp deposits; (6) pebble sandstones and sandy-mudstones (association A5) is interpreted as fluvial channel deposits at the terminal stage of the life cycle of the basin.Evidence from evaporite minerals suite (halite, dolomite, gypsum and polyhalite) associated with metal sulphides suggests deposition in mixed oxic and sulphur reducing anoxic hypersaline environments subjected to evaporation and reflux under arid climate. Dolomite-rich evaporite-host lithofacies (oolitic, pelletoidal and algal mats) with low faunal diversity in ostracods, algae, fish bones, gastropods and conchostracans indicate stressed hypersaline settings common in fluvio-lacustrine and lagoon environments.Humid and warm palaeoclimate regimes with cyclic sub-aerial exposure prevailed from Early to Middle Cretaceous. A pronounced arid climate with restricted drainage and low detrital to carbonate sediment fluxes into a confined fluvio-lacustrine lake prevailed during Aptian-Albian. The deposition of evaporite and clay (chlorite/chamosite-illite-muscovite) mineral suites, palaeosols, caliches, hardgrounds and desiccation cracks are thumbprint vestiges of arid climate.

Clay Mineral Suites in Submarine Mud Volcanoes in the Kumano Forearc Basin, Nankai Trough: Constraints on the Origin of Mud Volcano Sediments

Clay mineralogy is an important characteristic of mud volcano sediments. This study determined the clay mineral compositions of sediment from two submarine mud volcanoes in the Kumano forearc basin, Nankai Trough, by X-ray diffraction analysis. Similar compositions dominated by smectite in the two mud volcanoes indicate that the mud volcanoes in the basin are rooted in the same source sequence. These clay mineral compositions differed from those in Pleistocene basin sediment, suggesting that the mud volcano sediment originated beneath the Pleistocene sediment. The illite content in the illite–smectite mixed layer averaged 32% in the mud volcano sediment, which implies that the sediment experienced temperatures above 60 °C that promoted the smectite-to-illite transformation. However, porewater extracted from the mud volcano sediment had Cl‒ concentrations roughly half that of seawater and proportional enrichment in 18O and depletion in D, indicating that dehydration reactions of clay minerals had previously occurred in a deeply buried sedimentary layer. The smectite and illite contents (<60%) in the clay-size fraction rule out in situ smectite dewatering as the cause of the dilution of Cl‒ in porewater. Thus, fluids derived from clay dewatering must have originated from deeper than the source of the mud volcano sediment.

Iodide uptake by negatively charged clay interlayers?

Understanding iodide interactions with clay minerals is critical to quantifying risk associated with nuclear waste disposal. Current thought assumes that iodide does not interact directly with clay minerals due to electrical repulsion between the iodide and the negatively charged clay layers. However, a growing body of work indicates a weak interaction between iodide and clays. The goal of this contribution is to report a conceptual model for iodide interaction with clays by considering clay mineral structures and emergent behaviors of chemical species in confined spaces. To approach the problem, a suite of clay minerals was used with varying degrees of isomorphic substitution, chemical composition, and mineral structure. Iodide uptake experiments were completed with each of these minerals in a range of swamping electrolyte identities (NaCl, NaBr, KCl) and concentrations. Iodide uptake behaviors form distinct trends with cation exchange capacity and mineral structure. These trends change substantially with electrolyte composition and concentration, but do not appear to be affected by solution pH. The experimental results suggest that iodide may directly interact with clays by forming ion-pairs (e.g., NaI(aq)) which may concentrate within the interlayer space as well as the thin areas surrounding the clay particle where water behavior is more structured relative to bulk water. Ion pairing and iodide concentration in these zones is probably driven by the reduced dielectric constant of water in confined space and by the relatively high polarizability of the iodide species.

Distribution and dispersal pattern of clay minerals in surface sediments, eastern Beibu Gulf, South China Sea

Clay minerology of sediments are useful in determining distribution, sources and dispersal routes of fine-grained sediments. In the present paper, clay minerals of surface sediments throughout the eastern part of Beibu Gulf has been investigated to reveal sources and transport of detrital finegrained sediments. Four distinct clay mineral suites were observed from cluster analysis of clay mineral compositions of the samples. From the distribution pattern of clay minerals, we conclude that kaolinte in the eastern gulf is mainly derived from South China Landmass; Smectite could not be transported mainly by surface current from north-western Hainan Island, and maybe minor portion of it from Red River; Illite is mainly transported by the currents from South China Sea. Chlorite has two sources, namely South China Sea and South China Landmass. The Zhujiang River derived sediments could not be one of the sources for the clay mineral here, because of very different composition and ratios. The distribution pattern of clay minerals in the eastern Beibu Gulf is mainly controlled by fine-grained sediment source and local currents. The Silt/Clay, Smectite/Kaolinte, and Smetite/(Chlorite+Illite) ratios could be used as indicators of fine-grained sediment dispersal in the gulf.

Mineralogy, geochemistry, and reserve estimation of the Euphrates limestone for Portland cement industry at Al-Najaf area, South Iraq

This study deals with the mineralogical and geochemistry of the Euphrates Formation (Lower Miocene) in Bahr Al-Najaf area in order to assess the lithofacies of the Euphrates Formation for Portland cement manufacturing. Petrographic and mineralogical studies were carried out on 210 core samples, collected from 21 boreholes, and showed that calcite is the dominant mineral with few amounts of quartz, gypsum, feldspar, and a rare amount of dolomite. Clay mineral suites (palygorskite, kaolinite, montmorillonite, and illite) formed about 5% from the total mineral composition. Palygorskite precipitated directly in alkali shallow water rich with Si and Mg ions. Chemical weathering of feldspar under acidic conditions participated in formation of Kaolinite. Geochemistry showed that there is no high variation in chemical constituents with depth, and the average of CaO (51.5), MgO (0.83), SO3 (0.54), SiO2 (4.3), Fe2O3 (0.45), Al2O3 (0.93), L.O.I (40.7), Na2O3 (0.08), K2O (0.14), and Cl- (0.1) qualified the lithofacies of Euphrates Formation to be raw materials suitable for manufacturing the Portland cement. Triangle Block method is applied to estimate the reserve on square area (2 × 2 km2) which is computed to be 63 million tons of medium-tough limestone as potential probable reserve.

Bioreduction of Fe-bearing clay minerals and their reactivity toward pertechnetate (Tc-99)

99Technetium ( 99Tc) is a fission product of uranium-235 and plutonium-239 and poses a high environmental hazard due to its long half-life ( t 1/2 = 2.13 × 10 5 y), abundance in nuclear wastes, and environmental mobility under oxidizing conditions [i.e., Tc(VII)]. Under reducing conditions, Tc(VII) can be reduced to insoluble Tc(IV). Ferrous iron, either in aqueous form (Fe 2+) or in mineral form [Fe(II)], has been used to reduce Tc(VII) to Tc(IV). However, the reactivity of Fe(II) from clay minerals, other than nontronite, toward immobilization of Tc(VII) and its role in retention of reduced Tc(IV) has not been investigated. In this study the reactivity of a suite of clay minerals toward Tc(VII) reduction and immobilization was evaluated. The clay minerals chosen for this study included five members in the smectite–illite (S–I) series, (montmorillonite, nontronite, rectorite, mixed layered I–S, and illite), chlorite, and palygorskite. Surface Fe-oxides were removed from these minerals with a modified dithionite–citrate–bicarbonate (DCB) procedure. The total structural Fe content of these clay minerals, after surface Fe-oxide removal, ranged from 0.7% to 30.4% by weight, and the structural Fe(III)/Fe(total) ratio ranged from 45% to 98%. X-ray diffraction (XRD) and Mössbauer spectroscopy results showed that after Fe oxide removal the clay minerals were free of Fe-oxides. Scanning electron microscopy (SEM) revealed that little dissolution occurred during the DCB treatment. Bioreduction experiments were performed in bicarbonate buffer (pH-7) with structural Fe(III) in the clay minerals as the sole electron acceptor, lactate as the sole electron donor, and Shewanella putrefaciens CN32 cells as a mediator. In select tubes, anthraquinone-2,6-disulfate (AQDS) was added as electron shuttle to facilitate electron transfer. In the S–I series, smectite (montmorillonite) was the most reducible (18% and 41% without and with AQDS, respectively) and illite the least (1% for both without and with AQDS). The extent and initial rate of bioreduction were positively correlated with the percent smectite in the S–I series (i.e., layer expandability). Fe(II) in the bioreduced clay minerals subsequently was used to reduce Tc(VII) to Tc(IV) in PIPES buffer. Similar to the trend of bioreduction, in the S–I series, reduced NAu-2 showed the highest reactivity toward Tc(VII), and reduced illite exhibited the least. The initial rate of Tc(VII) reduction, after normalization to clay and Fe(II) concentrations, was positively correlated with the percent smectite in the S–I series. Fe(II) in chlorite and palygorskite was also reactive toward Tc(VII) reduction. These data demonstrate that crystal chemical parameters (layer expandability, Fe and Fe(II) contents, and surface area, etc.) play important roles in controlling the extent and rate of bioreduction and the reactivity toward Tc(VII) reduction. Reduced Tc(IV) resides within clay mineral matrix, and this association could minimize any potential of reoxidation over long term.

Impact of sodium adsorption ratio of irrigation water on the structural form of two Vertosols used for cotton production

In recent years, the production of cotton in Australia has been limited by the availability of irrigation water. To overcome this problem, poorer quality (Na+-rich) irrigation sources have been used in some situations, despite the effects elevated levels of Na+ may have on soil physical and chemical properties. This paper reports on changes in the surface-connected structural form attributes of two Vertosols from eastern Australia (one Red Vertosol, one Black Vertosol) after treatment with a range of different water-quality solutions. Intact soil columns from each of the Vertosols were irrigated through six wet–dry cycles using one of six treatment solutions with varying Na+ concentrations. Replicate columns for each treatment of each soil were analysed post-irrigation for selected chemical attributes. A second set of replicate columns was impregnated with a fluorescent resin post-irrigation, horizontally sectioned, and photographed under ultraviolet light. Image analysis was carried out on the section photographs to yield quantitative estimates of porosity (P), surface area (Sv), solid and pore star lengths (ls* and lp*), and solid and pore genus (gs and gp). Generally, the soil treated with the low-Na+ solution had the most desirable structural form attributes (larger P, Sv, and gp and smaller ls* and gs), while the soil treated with the high-Na+ solution had the least desirable structural attributes. The structural attributes and chemical properties of the Red Vertosol changed more markedly with water quality than did those of the Black Vertosol. The difference in response to water quality between these two soils is presumed to be related to the clay mineral suites and the exchange capacity of these soils; the Black Vertosol contains appreciably more smectite and has a much larger effective cation exchange capacity than the Red Vertosol.

Holocene debris flows on the Colorado Plateau: The influence of clay mineralogy and chemistry

Holocene debris flows do not occur uniformly on the Colorado Plateau province of North America. Debris flows occur in specific areas of the plateau, resulting in general from the combination of steep topography, intense convective precipitation, abundant poorly sorted material not stabilized by vegetation, and the exposure of certain fine-grained bedrock units in cliffs or in colluvium beneath those cliffs. In Grand and Cataract Canyons, fine-grained bedrock that produces debris flows contains primarily single-layer clays—notably illite and kaolinite—and has low multilayer clay content. This clay-mineral suite also occurs in the colluvium that produces debris flows as well as in debris-flow deposits, although unconsolidated deposits have less illite than the source bedrock. We investigate the relation between the clay mineralogy and major-cation chemistry of fine-grained bedrock units and the occurrence of debris flows on the entire Colorado Plateau. We determined that 85 mapped fine-grained bedrock units potentially could produce debris flows, and we analyzed clay mineralogy and major-cation concentration of 52 of the most widely distributed units, particularly those exposed in steep topography. Fine-grained bedrock units that produce debris flows contained an average of 71% kaolinite and illite and 5% montmorillonite and have a higher concentration of potassium and magnesium than nonproducing units, which have an average of 51% montmorillonite and a higher concentration of sodium. We used multivariate statistics to discriminate fine-grained bedrock units with the potential to produce debris flows, and we used digital-elevation models and mapped distribution of debris-flow producing units to derive a map that predicts potential occurrence of Holocene debris flows on the Colorado Plateau.

Climato-environmental controls on clay mineralogy of the Hettangian–Bajocian successions of the Mecsek Mountains, Hungary: An evidence for extreme continental weathering during the early Toarcian oceanic anoxic event

Clay mineralogy has been successfully used in palaeoclimatic interpretation of Jurassic rocks. In the Mecsek zone (Hungary), the clay mineral assemblages of the Hettangian–Sinemurian fluvial and shallow marine coal-bearing siliciclastic rocks (Gresten facies, Mecsek Coal and Vasas Marl Formations) comprise predominantly illite/smectite (I/S) mixed-layer minerals, illite (ill), and kaolinite (kao) with the presence of berthierine and/or chlorite. These clay mineral suites suggest a humid-subtropical climate with short-term climate changes of high and low rainfall and a high supply of terrigenous clastics to the basin. In the Pliensbachian part of the sequence studied, which is composed of predominantly hemipelagic mudstones (Allgäu facies) with intercalations of redeposited sandstone and limestone bodies, the Hosszúhetény Calcareous Marl, Mecseknádasd Sandstone and Kecskehát Limestone Formations are predominantly made up of illite and very little kaolinite and I/S mixed-layer minerals (kao/ill < 1). Based on these results, the Pliensbachian time interval is interpreted to represent warm and seasonally humid (monsoon-like) climatic conditions and a moderate input of terrigenous clastics relative to the underlying formations. Towards the Toarcian, kaolinite becomes the dominant clay mineral (Óbánya Siltstone Formation; kao/ill > 1) suggesting a humid climate and intense continental weathering possibly related to the oceanic anoxic event. In contrast, rocks of the Bajocian Komló Calcareous Marl Formation contain high proportions of I/S mixed-layer mineral and illite with sparse occurrence of kaolinite (kao/ill = 0 or kao/ill < 1). This clay mineral assemblage reflects a warm climate with a seasonal (monsoon-like) contrast in humidity and a minor input of terrigenous clastics from a relatively distant source area.

Paleosol evidence for Quaternary uplift and for climate and ecosystem changes in the Cordillera de Talamanca, Costa Rica

A noncalcareous volcanic paleosol succession from the upper montane rain forest of the Cordillera de Talamanca, Costa Rica (Lat. 9°41′03.3″ N; Long. 83°53′45.9″ W; 2507 m elev.) provides evidence for changing Quaternary elevation, climate, and ecosystems. Basal deposits (Crb horizons) are saprolitized, porphyritic andesite enriched in Si, Al, and Fe, and depleted in base cations, which record an earliest period of very intense weathering forming a leached residuum of smectite–kaolinite and Fe-oxides (or oxyhydroxides) on a mature paleolandscape, probably in tropical lowlands. Paleo-saprolite deposits are sharply overlain by interbedded lapilli tuffs and two paleosols with dark-colored, organic C-rich (2–3 wt.%) Ab horizons (one containing abundant grass pollen), interpreted as mollic epipedons of grassland soils (andic Mollisol-like paleosols) with δ 13C values (− 24.5‰ PDB) that record a former C3 grassland ecosystem. Possible pedogenic carbonate (Btkb) horizons (with all carbonate removed by overprinting by younger pedogenic processes) provide evidence of former drier and drained conditions. Uppermost buried soils (mainly Btb horizons) are non-calcareous, clay-rich, andic Ultisol-like paleosols that record pedogenesis under climates similar to current conditions, with highly weathered clay mineral suites. AMS dating of charcoal from the upper (Btb) paleosol constrains a latest glacial age (36,640 ± 650 14C yr BP; ages for two additional deeper samples were > 43–48 ka) for the 2Btb paleosol. Uplift rates of the Cordillera de Talamanca are estimated as 1 km/1 Ma. Consequently, the described paleosols provide evidence for: 1) initial lowland pedogenesis, perhaps at 2–3 Ma, 2) regional uplift and major unconformity, volcanism and development of a grassland ecosystem that has δ 13C values similar to those measured in modern, high-elevation páramo sites in the cordillera (− 24.4 to − 26.3‰ PDB) but formed mollic epipedons and pedogenic carbonates, which do not characterize modern páramo soils, followed by 3) continued late Pleistocene volcanism and pedogenesis in environments similar to current oak-dominated montane rain forest conditions. The paleosol succession provides a valuable record of dynamic climate-ecosystem change and uplift history in the Cordillera de Talamanca that can complement and extend existing bog and lake sediment records.

Clay Mineral Analysis of Sediments in the Changjiang Delta Plain and Its Application to the Late Quaternary Variations of Sea Level and Sediment Provenance

Abstract Clay mineral analysis was conducted on the fine-grained sediments of a 20-meter core of Late Quaternary deposit in the south-central portion of the modern Changjiang delta plain to understand and characterize paleoenvironmental depositional conditions. Four clay mineral suites (Zones I to IV) were recognized in the core. The lowest level (Zone I, Late Pleistocene) of kaolinite (48%) and illite (45%) is representative of a pedogenic formation of alluvial environment. The next upper suite (Zone II, Early Holocene) of kaolinite (44%) and chlorite (22%) is related to an erosional coastal environment associated with an encroaching sea level. The suite (Zone III, Early to mid-Holocene) overlying Zone II incorporates the addition of smectite (6%), the abundance of which is closely linked to the topographic change and the relative sea level fluctuation in the study area. The uppermost suite (Zone IV, Late Holocene) of illite (53%) and smectite (7%) accumulated during the period of major deltaic progradat...

Clay mineralogy of the Permo-Triassic strata of the British Isles: onshore and offshore

AbstractThe regional distribution, mineralogy, petrology and chemistry of the detrital and authigenic clay minerals associated with the Permo-Triassic strata (excluding the Rotliegend: see Ziegler, 2006; this volume), of the onshore and offshore regions of the British Isles are reviewed within their stratigraphical framework. The origin of these clay minerals is discussed in relation to current hypotheses on the developments of the Mg-rich clay mineral assemblages associated with the evaporitic red-bed Germanic facies of Europe and North Africa.Composite clay mineral successions are described for seven regions of the British Isles — the Western Approaches Trough; SW England; South Midlands; Central Midlands; the Cheshire Basin; NE Yorkshire; and the Central North Sea. The detrital clay mineral assemblages of the Early Permian strata are variable, consisting of mica, smectite, smectite-mica, kaolin and chlorite, whereas those of the Late Permian and the Trias are dominated by mica, usually in association with minor Fe-rich chlorite. The detrital mica consists of a mixture of penecontemporaneous ferric mica, probably of pedogenic origin, and recycled Pre-Permian mica. In the youngest Triassic strata (Rhaetian), the detrital clay assemblages may contain appreciable amounts of poorly defined collapsible minerals (irregular mixed-layer smectite-mica-vermiculite) and kaolin, giving them a Jurassic aspect. There are two types of authigenic clay mineral assemblages. Kaolin may occur as a late-stage diagenetic mineral where the original Permo-Triassic porewaters of the sediment have been replaced by meteoritic waters. A suite of early-stage diagenetic clay minerals, many of them Mg-rich, are linked to the evaporitic red-bed facies — these include sepiolite, palygorskite, smectite, irregular mixed- layer smectite-mica and smectite-chlorite, corrensite, chlorite and glauconite (sensu lato). The sandstones and mudstones of the onshore regions of the British Isles display little or no difference in their detrital and authigenic clay mineral assemblages. In contrast, the sandstones of the offshore regions (North Sea) show major differences with the presence of extensive chloritic cements containing Mg-rich and Al-rich chlorite, irregular mixed-layer serpentine-chlorite, and mica.

Clay mineral associations in soils of the Lusikisiki area, Eastern Cape Province, and their agricultural significance

The study deals with changes in clay mineral associations with soil development and related implications for land users in the Lusikisiki area of the Eastern Cape Province of South Africa. Fifteen profiles, encompassing all major soil forms in the region, were investigated. The pedons developed from pre-Jurassic sedimentary rocks or Jurassic dolerite under a modeled annual precipitation of −950 to 1250 mm. The least weathered horizons in soils, derived from sedimentary rocks, contained mica, illite/smectite interstratifications (I/S) and minor amounts of kaolinite, a clay mineral suite, characteristic of the geothermal history of the region. Profiles, developed from dolerite, formed from an association of plagioclase and pyroxene. The A horizons in the vast majority of the profiles were dominated by either kaolinite, quartz or gibbsite, but generally contained an association of at least two of the above minerals. In some profiles significant amounts of hydroxy-interlayered vermiculite (HIV) were also present. The weathering pathway, therefore, seems to lead from illite, I/S and smectite to HIV, kaolinite and gibbsite. Quartz is hypothesized to be of aeolian origin, possibly reflecting desert loess. Mineral parageneses were not related to topographic position and little related to parent material. Soils with greatly different degrees of pedogenesis had almost identical clay mineral suites in their uppermost horizons.

Geology and Hydrothermal Alteration of the Low Sulfidation

Abstract. The Pantingan Gold System (PGS) is a vein-type epithermal prospect exposed within the summit caldera of Mount Mariveles, Bagac, Bataan (Luzon), Philippines. It consists of nine major veins, eight of which trend NW-WNW and distributed in an en echelon array. The eastern tips of these veins appear to terminate near the NE-NNE trending Vein 1, which is located in the easternmost portion of the prospect. Metal assay results on vein and wall rock samples indicate concentrations of 0.01 to 1.1 g/ton Au, trace to 34 g/ton Ag and 0.003 to 0.02 % Cu. Andesite lava flow deposits host the PGS. Potassium-Argon isotopic dating of these andesites yields anarrow age range of 0.88± 0.13 to 1.13 ± 0.17 Ma. The surface exposures of the veins (up to 5 m wide) are encountered at different levels between 590–740 masl. These commonly display a massive texture although banding prominently occurs in Vein 1. The veins consist of gray to cream-colored crystalline and chalcedonic quartz and amorphous silica. Pyrite is the most ubiquitous sulfide mineral. It occurs either as fine-grained disseminations and aggregates in quartz or as infillings in vugs. Calcite, marcasite and bornite are also occasionally noted in the deposit. The prospect shows silicic, argillic, propylitic and advanced argillic alteration zones. Silicic and argillic alterations are confined in the immediate wall rocks of the quartz veins. Argillic alteration grades to a propylitic zone farther away from the veins. The advanced argillic alteration zone, indicated by a suite of acidic clay minerals that include kaolin-ite, dickite, pyrophyllite and alunite, might have been imprinted during the late stages of gold deposition. As a whole, the PGS displays geological and mineralogical features typical of gold mineralization in a low sulfidation, epithermal environment. It is also representative of a young, tectonically undisturbed gold deposit.

Low-temperature illitization of smectite in the late eocene and early oligocene of the Isle of Wight (Hampshire basin), U.K.

Variegated palaeosols, which formed from weathering of clays, silts, and brackish to freshwater limestones, are present in the late Eocene-early Oligocene Solent Group of the Hampshire Basin, southern U.K. The detrital clay mineral suite is dominated by illite and illite-smectite with minor kaolinite and chlorite. In pedogenically modified (palaeosol) and evaporitic lacustrine clay-rich sediments, the proportion of illite in the illite-smectite is greater than in the non-pedogenically modified sediments, and where alteration is most intense, kaolinite and chlorite are absent. The smectite to illite transition has been investigated in the <0.5 μm fraction by XRD analysis (powder and oriented mounts), thermogravimetry (TG), analytical SEM, and chemical analysis of Fe2+. Modeling of XRD data reveals that the illite-smectite is a mixture of compositions (overall 60–95% illite), R 0, with high rotational stacking disorder. Dehydroxylation occurs mainly at 500 °C, but also at higher temperatures, indicating heterogeneous octahedral cation composition. Analytical SEM and chemical analysis of Fe2+ indicate that the illite to smectite transition occurs through Fe reduction in octahedral sites leading to increased layer charge, coupled with K fixation. The driving mechanism for what appears to be irreversible Fe3+ reduction is wetting (reducing) and drying (oxidizing) cycles in gley soil, in which reoxidation of reduced Fe is never complete.