scholarly journals The hydrochemical signature of incongruent weathering in Iceland

2021 ◽  
Author(s):  
Trevor Cole ◽  
Mark Torres ◽  
Preston Kemeny
Keyword(s):  
Geochemical Data ◽  
Silicate Weathering ◽  
Carbonate Dissolution ◽  
Weathering Processes ◽  
Mineral Phases ◽  
Inverse Models ◽  
Wide Range ◽  
Basalt Weathering ◽  
Clay Formation ◽  
End Members

Basaltic watersheds such as those found in Iceland are thought to be important sites of CO₂ sequestration via silicate weathering. However, determining the magnitude of CO₂ uptake depends on accurately interpreting river chemistry. Here, we compile geochemical data from Iceland and use them to constrain weathering processes. Specifically, we use a newly developed inverse model to quantify solute supply from rain and hydrothermal fluids as well as allow for different mineral phases within basalts to react at different rates, solutes to be removed via clay formation, and some Ca to be sourced from carbonate dissolution. While some of these processes have been considered previously, they have not been considered together allowing us to newly determine their relative contributions.We find that weathering in Iceland is incongruent in two ways. Firstly, solute release from primary silicates is characterized by a higher proportion of Na than would be expected from bulk basalts, which may reflect preferential weathering or some contribution from rhyolites. This Na enrichment is further enhanced by preferential Mg and K uptake by clays. No samples in our dataset (n=537) require carbonate dissolution even if isotopic data (δ26Mg, δ30Si, δ44Ca, and/or 87Sr/86Sr) are included. While some carbonate weathering is allowable, silicate weathering likely dominates. The complexity we observe in Iceland underscores the need for inverse models to account for a wide range of processes and end-members. Given that riverine fluxes from Iceland are more Na-rich than expected for congruent basalt weathering, the characteristic timescale of CO₂ drawdown is likely affected.

scholarly journals ENVIRONMENTAL GEOCHEMICAL AND MINERALOGICAL STUDY OF THE PELLANA LIGNITE (PREFECTURE OF LAKONIA)

2004 ◽  
Vol 36 (1) ◽  
pp. 300
Author(s):  
Α. Χατζηαποστόλου ◽  
Σ. Καλαϊτζίδης ◽  
Σ. Παπαζησίμου ◽  
Κ. Χρηστάνης ◽  
Δ. Βάγιας
Keyword(s):  
Power Generation ◽  
Trace Elements ◽  
Major Elements ◽  
Geochemical Data ◽  
Element Mobility ◽  
Minor Elements ◽  
Mineral Phases ◽  
Wide Range ◽  
Mineralogical Study ◽  
Type Factor

The aim of this study is to estimate the environmental impacts in case of exploitation the Pellanalignites for power generation. The object of the study is to predict the element mobility during lignite combustion using mineralogical and geochemical data from bulk-lignite samples and their ashes of two cores from this area. The mineralogical determinations on the ashes revealed that quartz, K-feldspars and illitemicas are the major mineral phases contained in the lignite. The identification of anhydrite in ashes implies the presence of gypsum, althought neoformation of anhydrite from organic associated with Ca+2 and SO42 can not be excluded. These minerals correspond to primary phases. Oxides and hydroxides occur subordinately and probably represent minerals that do not correspond to primary phases. The results of the elemental analysis show that the major elements (>1000 ppm) are AI, Fe, Ca, Mg and Κ in the bulk samples of both cores. Minor elements (100-1000 ppm) are Na, Mn and Ba, while the concentrations of Be, Bi, Cd, Ce, Co, Cs, Cu, Eu, Ga, Hf, La, Li, Lu, Mo, Nb, Nd, Pb, Rb, Sb, Se, Sm, Sn, Sr, Tb, Te, Th, TI, U, Y, Yb and Zr do not exceed 100 ppm. The concentrations of many elements like As, Ba, Cr, Ni, V and Zn have a wide range among the bulk samples. In order to assess the geochemical affiliation of the studied elements, R-type factor analysis was applied on the element contents of bulk lignite and ash. The elements Ca, S, V, As, Μη, Mo, Na, Sb, Hf, Zr and U provide both organic and inorganic affiliations, while Se and Nb provide organic affiliations. To approach the mobility of each trace element, the relative enrichment factor (RE) was calculated. The most depleted trace elements according to RE mean (<0.5) are Hf and Sb, while the elements Se and Ba are moderately depleted (0.7>RE mean>0.5).

Lithium isotopes tracing weathering processes in a time series through soil porewaters

2020 ◽  
Author(s):  
David Wilson ◽  
Philip Pogge von Strandmann ◽  
Gary Tarbuck ◽  
Jo White ◽  
Tim Atkinson ◽  
...  
Keyword(s):  
Time Series ◽  
Chemical Weathering ◽  
Silicate Weathering ◽  
Lithium Isotope ◽  
Lithium Isotopes ◽  
Drip Water ◽  
Weathering Processes ◽  
Li Isotope ◽  
Clay Formation ◽  
Isotope Measurements

&lt;p&gt;Chemical weathering is a key process that controls Earth&amp;#8217;s geochemical cycles and global climate, yet at present the climate-weathering feedback is poorly understood. Lithium (Li) isotopes are sensitive to silicate weathering processes [1] and can be applied in a range of settings to improve our understanding of weathering mechanisms and timescales, and hence to quantify the role of weathering in the global carbon cycle. While marine carbonates [2] and speleothems [3] are suitable for recording changes over million year and thousand year timescales, respectively, it is equally important to assess how weathering operates over seasonal [4] and shorter [5] timescales.&lt;/p&gt;&lt;p&gt;In order to explore seasonal variability in a natural system, we analysed Li isotopes and major/trace elements in a time series of cave drip-water samples from Ease Gill and White Scar caves (Yorkshire Dales, U.K.). Since the drip-waters are sourced from the overlying soil porewaters, these measurements provide a record of the evolving weathering fluid chemistry at approximately monthly intervals. Our data reveal striking temporal variations in &amp;#8706;&lt;sup&gt;7&lt;/sup&gt;Li of 4 to 8 permil, hinting at rapid changes in weathering processes over monthly to seasonal timescales. We assess the sources of Li using isotope measurements on local rocks and soils, which enables a first order quantification of the temporal changes in Li removal by clay formation. Comparison to records of temperature, precipitation, drip rates, and drip-water chemistry allows the local controls on weathering to be assessed and indicates that a dominant control is exerted by the fluid residence time.&lt;/p&gt;&lt;p&gt;These data are further complemented by batch reactor experiments, which were conducted to replicate rock weathering over timescales of hours to weeks. In combination, the time series and experiments contribute to a better understanding of weathering changes over short timescales and their influence on Li isotopes. In addition, results from the drip-waters provide key ground-truthing for interpreting our ongoing Li isotope measurements on speleothems, which will provide new records of weathering changes over longer timescales in response to regional climate forcing.&lt;/p&gt;&lt;p&gt;[1] Pogge von Strandmann, P.A.E., Frings, P.J., Murphy, M.J. (2017) Lithium isotope behaviour during weathering in the Ganges Alluvial Plain. GCA 198, 17-31.&lt;/p&gt;&lt;p&gt;[2] Misra, S. &amp; Froelich, P.N. (2012) Lithium isotope history of Cenozoic seawater: changes in silicate weathering and reverse weathering. Science 335, 818-823.&lt;/p&gt;&lt;p&gt;[3] Pogge von Strandmann, P.A.E., Vaks, A., Bar-Matthews, M., Ayalon, A., Jacob, E., Henderson, G.M. (2017) Lithium isotopes in speleothems: Temperature-controlled variation in silicate weathering during glacial cycles. EPSL 469, 64-74.&lt;/p&gt;&lt;p&gt;[4] Liu, X.-M., Wanner, C., Rudnick, R.L., McDonough, W.F. (2015) Processes controlling &amp;#948;&lt;sup&gt;7&lt;/sup&gt;Li in rivers illuminated by study of streams and groundwaters draining basalts. EPSL 409, 212-224.&lt;/p&gt;&lt;p&gt;[5] Pogge von Strandmann, P.A.E., Fraser, W.T., Hammond, S.J., Tarbuck, G., Wood, I.G., Oelkers, E.H., Murphy, M.J. (2019) Experimental determination of Li isotope behaviour during basalt weathering. Chemical Geology 517, 34-43.&lt;/p&gt;

Vermiculite, with hydroxy-aluminium interlayer, and kaolinite formation in a subtropical sandy soil from south Brazil

Clay Minerals ◽  
2008 ◽  
Vol 43 (2) ◽  
pp. 185-193 ◽  
Author(s):  
E. C. Bortoluzzi ◽  
B. Velde ◽  
M. Pernes ◽  
J. C. Dur ◽  
D. Tessier
Keyword(s):  
Parent Material ◽  
Subtropical Climate ◽  
Rio Grande Do Sul ◽  
X Ray Diffraction ◽  
X Ray ◽  
Weathering Processes ◽  
Mineral Phases ◽  
Clay Formation ◽  
Santa Maria ◽  
South Brazil

AbstractThe purpose of this study was to investigate the clay mineral phases in a Rhodic Acrisol soil and to discuss their evolution in subtropical conditions. Prairie and forest soil profiles were sampled and clay fractions of the parent material and soil horizons analysed by X-ray diffraction (XRD) at the Federal University of Santa Maria, Rio Grande do Sul-Brazil. The XRD results show the presence of interstratified kaolinite-smectite and illite-smectite as well as illite in the parent material. These minerals were also found in the soil samples but with two new phases: hydroxy-aluminium interlayered vermiculite (HIV), which showed incomplete collapse with treatment at 550ºC, and a newly formed kaolinite (d = 7.17 Å). Under a subtropical climate and a sandy lithology, HIV and kaolinite appear to be a result of a specific pedogenic clay formation, related to the natural vegetation. Originally, under the prairie area, the intensity of the weathering processes was weak (within 2:1 clay minerals), as only small quantities of kaolinite and Fe oxides, and no evidence of gibbsite, were found.

scholarly journals Lithium and Lithium Isotopes in Earth’s Surface Cycles

Elements ◽  
2020 ◽  
Vol 16 (4) ◽  
pp. 253-258 ◽  
Author(s):  
Philip A.E. Pogge von Strandmann ◽  
Simone A. Kasemann ◽  
Josh B. Wimpenny
Keyword(s):  
Climate Change ◽  
Atmospheric Co2 ◽  
Silicate Weathering ◽  
Lithium Isotope ◽  
Climatic Warming ◽  
Pore Waters ◽  
Lithium Isotopes ◽  
Weathering Processes ◽  
Isotope Evidence ◽  
Clay Formation

Lithium and its isotopes can provide information on continental silicate weathering, which is the primary natural drawdown process of atmospheric CO2 and a major control on climate. Lithium isotopes themselves can help our understanding of weathering, via globally important processes such as clay formation and cation retention. Both these processes occur as part of weathering in modern surface environments, such as rivers, soil pore waters, and groundwaters, but Li isotopes can also be used to track weathering changes across major climate-change events. Lithium isotope evidence from several past climatic warming and cooling episodes shows that weathering processes respond rapidly to changes in temperature, meaning that weathering is capable of bringing climate back under control within a few tens of thousands of years.

Early Cretaceous crust–mantle interaction linked to rollback of the Palaeo-Pacific flat-subducting slab: constraints from the intermediate–felsic volcanic rocks of the northern Great Xing’an Range, NE China

2021 ◽  
pp. 1-22
Author(s):  
Jia-Hao Jing ◽  
Hao Yang ◽  
Wen-Chun Ge ◽  
Yu Dong ◽  
Zheng Ji ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
Ne China ◽  
Asthenospheric Mantle ◽  
High K ◽  
Wide Range ◽  
Great Xing’An Range ◽  
Subducting Slab

Abstract Late Mesozoic igneous rocks are important for deciphering the Mesozoic tectonic setting of NE China. In this paper, we present whole-rock geochemical data, zircon U–Pb ages and Lu–Hf isotope data for Early Cretaceous volcanic rocks from the Tulihe area of the northern Great Xing’an Range (GXR), with the aim of evaluating the petrogenesis and genetic relationships of these rocks, inferring crust–mantle interactions and better constraining extension-related geodynamic processes in the GXR. Zircon U–Pb ages indicate that the rhyolites and trachytic volcanic rocks formed during late Early Cretaceous time (c. 130–126 Ma). Geochemically, the highly fractionated I-type rhyolites exhibit high-K calc-alkaline, metaluminous to weakly peraluminous characteristics. They are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) but depleted in high-field-strength elements (HFSEs), with their magmatic zircons ϵHf(t) values ranging from +4.1 to +9.0. These features suggest that the rhyolites were derived from the partial melting of a dominantly juvenile, K-rich basaltic lower crust. The trachytic volcanic rocks are high-K calc-alkaline series and exhibit metaluminous characteristics. They have a wide range of zircon ϵHf(t) values (−17.8 to +12.9), indicating that these trachytic volcanic rocks originated from a dominantly lithospheric-mantle source with the involvement of asthenospheric mantle materials, and subsequently underwent extensive assimilation and fractional crystallization processes. Combining our results and the spatiotemporal migration of the late Early Cretaceous magmatic events, we propose that intense Early Cretaceous crust–mantle interaction took place within the northern GXR, and possibly the whole of NE China, and that it was related to the upwelling of asthenospheric mantle induced by rollback of the Palaeo-Pacific flat-subducting slab.

Neogene continental denudation and the beryllium conundrum

2021 ◽  
Vol 118 (42) ◽  
pp. e2026456118
Author(s):  
Shilei (李石磊) Li ◽  
Steven L. Goldstein ◽  
Maureen E. Raymo
Keyword(s):  
Fold Increase ◽  
Silicate Weathering ◽  
Late Cenozoic ◽  
Glacial Cycles ◽  
Denudation Rates ◽  
Geological Processes ◽  
Basalt Weathering ◽  
Beryllium Isotopes ◽  
Continental Weathering ◽  
Pyrite Weathering

Reconstructing Cenozoic history of continental silicate weathering is crucial for understanding Earth’s carbon cycle and greenhouse history. The question of whether continental silicate weathering increased during the late Cenozoic, setting the stage for glacial cycles, has remained controversial for decades. Whereas numerous independent proxies of weathering in ocean sediments (e.g., Li, Sr, and Os isotopes) have been interpreted to indicate that the continental silicate weathering rate increased in the late Cenozoic, beryllium isotopes in seawater have stood out as an important exception. Beryllium isotopes have been interpreted to indicate stable continental weathering and/or denudation rates over the last 12 Myr. Here we present a Be cycle model whose results show that variations in the 9Be weathering flux are counterbalanced by near-coastal scavenging while the cosmogenic 10Be flux from the upper atmosphere stays constant. As a result, predicted seawater 10Be/9Be ratios remain nearly constant even when global denudation and Be weathering rates increase by three orders of magnitude. Moreover, 10Be/9Be records allow for up to an 11-fold increase in Be weathering and denudation rates over the late Cenozoic, consistent with estimates from other proxies. The large increase in continental weathering indicated by multiple proxies further suggests that the increased CO2 consumption by continental weathering, driven by mountain-building events, was counterbalanced by other geological processes to prevent a runaway icehouse condition during the late Cenozoic. These processes could include enhanced carbonate dissolution via pyrite weathering, accelerated oxidation of fossil organic carbon, and/or reduced basalt weathering as the climate cooled.

scholarly journals Evidence of mingling between contrasting magmas in a deep plutonic environment: the example of Várzea Alegre, in the Ribeira Mobile Belt, Espírito Santo, Brazil

2001 ◽  
Vol 73 (1) ◽  
pp. 99-119 ◽  
Author(s):  
SILVIA R. MEDEIROS ◽  
CRISTINA M. WIEDEMANN-LEONARDOS ◽  
SIMON VRIEND
Keyword(s):  
Partial Melting ◽  
Granitic Magma ◽  
Geochemical Data ◽  
Mobile Belt ◽  
Tholeiitic Magma ◽  
Rock Types ◽  
Upper Proterozoic ◽  
Incompatible Elements ◽  
Wide Range ◽  
Intermediate Rock

At the end of the geotectonic cycle that shaped the northern segment of the Ribeira Mobile Belt (Upper Proterozoic to Paleozoic age), a late to post-collisional set of plutonic complexes, consisting of a wide range of lithotypes, intruded all metamorphic units. The Várzea Alegre Intrusive Complex is a post-collisional complex. The younger intrusion consists of an inversely zoned multistage structure envolved by a large early emplaced ring of megaporphyritic charnoenderbitic rocks. The combination of field, petrographic and geochemical data reveals the presence of at least two different series of igneous rocks. The first originated from the partial melting of the mantle. This was previously enriched in incompatible elements, low and intermediate REE and some HFS-elements. A second enrichment in LREE and incompatible elements in this series was due to the mingling with a crustal granitic magma. This mingling process changed the composition of the original tholeiitic magma towards a medium-K calc-alkalic magma to produce a suite of basic to intermediate rock types. The granitic magma from the second high-K, calc-alkalic suite originated from the partial melting of the continental crust, but with strong influence of mantle-derived melts.

scholarly journals Global whole-rock geochemical database compilation

2019 ◽  
Author(s):  
Matthew Gard ◽  
Derrick Hasterok ◽  
Jacqueline Halpin
Keyword(s):  
Database Management ◽  
Temporal Trends ◽  
Physical Property ◽  
Database Management System ◽  
Geochemical Data ◽  
Data Sets ◽  
Unique Contribution ◽  
Data Set ◽  
Wide Range ◽  
Geochemical Indices

Abstract. Dissemination and collation of geochemical data are critical to promote rapid, creative and accurate research and place new results in an appropriate global context. To this end, we have assembled a global whole-rock geochemical database, with other associated sample information and properties, sourced from various existing databases and supplemented with numerous individual publications and corrections. Currently the database stands at 1,023,490 samples with varying amounts of associated information including major and trace element concentrations, isotopic ratios, and location data. The distribution both spatially and temporally is quite heterogeneous, however temporal distributions are enhanced over some previous database compilations, particularly in terms of ages older than ~ 1000 Ma. Also included are a wide range of computed geochemical indices, physical property estimates and naming schema on a major element normalized version of the geochemical data for quick reference. This compilation will be useful for geochemical studies requiring extensive data sets, in particular those wishing to investigate secular temporal trends. The addition of physical properties, estimated by sample chemistry, represents a unique contribution to otherwise similar geochemical databases. The data is published in .csv format for the purposes of simple distribution but exists in a format acceptable for database management systems (e.g. SQL). One can either manipulate this data using conventional analysis tools such as MATLAB®, Microsoft® Excel, or R, or upload to a relational database management system for easy querying and management of the data as unique keys already exist. This data set will continue to grow, and we encourage readers to contact us or other database compilations contained within about any data that is yet to be included. The data files described in this paper are available at https://doi.org/10.5281/zenodo.2592823 (Gard et al., 2019).

Exemples de mélange de magmas en contexte plutonique: les enclaves des tonalites–granodiorites du massif de Bono (Sardaigne septentrionale)

1989 ◽  
Vol 26 (6) ◽  
pp. 1264-1281 ◽  
Author(s):  
C. Cocirta ◽  
J. B. Orsini ◽  
C. Coulon
Keyword(s):  
Geochemical Data ◽  
Mixing Process ◽  
Calc Alkaline ◽  
Specific Group ◽  
Mineralogical Analysis ◽  
Magmatic Origin ◽  
Interaction Mechanisms ◽  
Compositional Variations ◽  
End Members ◽  
Host Rocks

In calc-alkaline orogenic plutons, the dark xenoliths and their host rocks must be considered the expression of partial mixing of magma.Three associations of this type have been investigated and are illustrated by the Bono pluton (northern Sardinia)— a composite pluton including three intrusives of different nature (tonalitic to granodioritic) and containing a very large number of basaltic xenoliths of magmatic origin. Detailed mineralogical analysis of the two end members in each association, coupled with geochemical data, has determined the major petrogenetic mechanisms intervening in the mixing process in a plutonic setting: temperature equilibration, mechanical exchanges of crystals, chemical exchanges, etc. The most important result of this article, however, is to show that each intrusion is related to a specific group of xenoliths that is characterized by constant FeOt/MgO. The latter reflects the different composition of basaltic components, and it is concluded that each intrusive event is associated with a unique mixing episode. As in volcanic settings, the mixing process may have initiated the intrusion.The extreme compositional variations in the magmatic xenoliths, recognized in several series of orogenic plutons, is explained here by different initial basaltic end members and by variation in the intensity of the interaction mechanisms. [Journal Translation]

Linking data systems into a collaborative pipeline for geochemical data from field to archive

2021 ◽  
Author(s):  
Kerstin Lehnert ◽  
Daven Quinn ◽  
Basil Tikoff ◽  
Douglas Walker ◽  
Sarah Ramdeen ◽  
...  
Keyword(s):  
Analytical Data ◽  
Data System ◽  
Standard Reference Materials ◽  
Data Management System ◽  
Geochemical Data ◽  
Data Repository ◽  
Data Systems ◽  
Raw Data ◽  
Wide Range ◽  
Data Lifecycle

&lt;div&gt; &lt;p&gt;Management of geochemical data needs to consider the sequence of phases in the lifecycle of these data from field to lab to publication to archive. It also needs to address the large variety of chemical properties measured; the wide range of materials that are analyzed; the different ways, in which these materials may be prepared for analysis; the diversity of analytical techniques and instrumentation used to obtain analytical results; and the many ways used to calibrate and correct raw data, normalize them to standard reference materials, and otherwise treat them to obtain meaningful and comparable results. In order to extract knowledge from the data, they are then integrated and compared with other measurements, formatted for visualization, statistical analysis, or model generation, and finally cleaned and organized for publication and deposition in a data repository. Each phase in the geochemical data lifecycle has its specific workflows and metadata that need to be recorded to fully document the provenance of the data so that others can reproduce the results.&lt;/p&gt; &lt;/div&gt;&lt;div&gt; &lt;p&gt;An increasing number of software tools are developed to support the different phases of the geochemical data lifecycle. These include electronic field notebooks, digital lab books, and Jupyter notebooks for data analysis, as well as data submission forms and templates. These tools are mostly disconnected and often require manual transcription or copying and pasting of data and metadata from one tool to the other. In an ideal world, these tools would be connected so that field observations gathered in a digital field notebook, such as sample locations and sampling dates, can be seamlessly send to an IGSN Allocating Agent to obtain a unique sample identifier with a QR code with a single click. The sample metadata would be readily accessible for the lab data management system that allows the researchers to capture information about the sample preparation, and that connects to the instrumentation to capture instrument settings and the raw data. The data would then be seamlessly accessed by data reduction software, visualized, and further compared to data from global databases that can be directly accessed. Ultimately, a few clicks will allow the user to format the data for publication and archiving.&lt;/p&gt; &lt;/div&gt;&lt;div&gt; &lt;p&gt;Several data systems that support different stages in the lifecycle of samples and sample-based geochemical data have now come together to explore the development of standardized interfaces and APIs and consistent data and metadata schemas to link their systems into an efficient pipeline for geochemical data from the field to the archive. These systems include StraboSpot (www.strabospot.org;&amp;#160;data system for digital collection, storage, and sharing of both field and lab data), SESAR (&lt;span&gt;www.geosamples.org&lt;/span&gt;; sample registry and allocating agent for IGSN), EarthChem (www.earthchem.org; publishers and repository for geochemical data), Sparrow (sparrow-data.org; data system to organize analytical data and track project- and sample-level metadata), IsoBank (isobank.org; repository for stable isotope data), and MacroStrat (macrostrat.org; collaborative platform for geological data exploration and integration).&lt;/p&gt; &lt;/div&gt;

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