Moderate Chemical Weathering of Subtropical Taiwan: Constraints from Solid‐Phase Geochemistry of Sediments and Sedimentary Rocks

The Earth has the greatest abundance and variety of sedimentary strata in our star system, dating back some 3.8 billion years. ‘Sedimentary rocks’ describes the processes that create different types of sedimentary rocks, which form a key guideline in reconstructing Earth’s history. Particles are created by both physical and chemical weathering. These particles are then moved by different modes of transport and sorted by size, which affect the resulting sedimentary rock. Sedimentary layers can remain as soft muds or loose sands for millions of years, but most buried sedimentary layers harden and turn into rock, under the combined effects of increasing heat and pressure, and of changes in chemical environment.

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Chemical weathering east and west of the emerging Caledonides in the Silurian – Early Devonian, with implications for climate

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2015-0156 ◽

2016 ◽

Vol 53 (8) ◽

pp. 774-780 ◽

Cited By ~ 3

Author(s):

Enli Kiipli ◽

Tarmo Kiipli ◽

Toivo Kallaste ◽

Tiiu Märss

Keyword(s):

Chemical Weathering ◽

Sedimentary Rocks ◽

Clay Fraction ◽

Climatic Conditions ◽

Chemical Compositions ◽

Tropical Zone ◽

Early Devonian ◽

Marine Carbonates ◽

Latitudinal Position ◽

Mountain Chain

The late Llandovery (Silurian) – early Lochkovian (Devonian) climate of the tropical zone is tracked considering orogenesis, global glaciation events, and cratonic drift. Mineral and chemical compositions of clay fractions of Canadian (the Franklinian Basin) and Estonian (the Baltoscandian Basin) sedimentary rocks from different sides of the emerging Caledonides were studied, using clay as an index of climatic conditions of the provenance area. Illite is the main clay mineral, with addition of orthoclase, muscovite, and chlorite in both regions. Authigenic chert is present in some Canadian sections. The similarity of clay minerals and elemental composition in the two regions suggest common chemical weathering conditions. Nevertheless, the Al/Ti ratio of the <1 μm clay fraction, the proxy for climate’s aridity–humidity and weathering intensity, reveals differences. The Franklinian Basin in Laurentia shows a shift of climate from humid to semi-humid in pace with the uplift of the Caledonides. The sub-meridional mountain chain in the east reduced the amount of rainfall and, therefore, caused drier climate than could have been expected from the low latitudinal position of the area. The material from the Baltoscandian Basin reveals semi-arid and arid climate for most of the Silurian. Although the southern part of the Fennoscandian Shield was situated in desert latitudes, the evidence from the provenance of clay suggests that the climate was not fully arid. In Baltoscandia, covariation between low Al/Ti of clay and negative shifts of δ13C of marine carbonates is recorded at some stratigraphical levels, suggesting a link between humid climatic episodes in mainland and waning of glaciers at the South Pole.

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A Robust Chemical Weathering Index Applicable to a Wide Range of Sedimentary Rocks

10.46427/gold2020.425 ◽

2020 ◽

Author(s):

Tenichi Cho ◽

Tohru Ohta

Keyword(s):

Chemical Weathering ◽

Sedimentary Rocks ◽

Weathering Index ◽

Wide Range

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Weathering profiles, mass-balance analysis, and rates of solute loss: Linkages between weathering and erosion in a small, steep catchment

Geological Society of America Bulletin ◽

10.1130/0016-7606(2002)114<1143:wpmbaa>2.0.co;2 ◽

2002 ◽

Vol 114 (9) ◽

pp. 1143-1158 ◽

Cited By ~ 154

Author(s):

Suzanne Prestrud Anderson ◽

William E. Dietrich ◽

George H Brimhall

Keyword(s):

Chemical Weathering ◽

Dynamic Equilibrium ◽

Solid Phase ◽

Water Flux ◽

Solute Flux ◽

Denudation Rate ◽

Rock Fragments ◽

Denudation Rates ◽

Uplift Rates ◽

Balance Analysis

Abstract In a headwater catchment in the Oregon Coast Range, we find that solid-phase mass losses due to chemical weathering are equivalent in the bedrock and the soil. However, the long-term rate of mass loss per unit volume of parent rock is greater in the soil than in the rock. We attribute this finding to the effects of biotic processes in the soil and to hydrologic conditions that maximize contact time and water flux through the mineral matrix in the soil. This result stems both from earlier work in which we demonstrated that rock and soil contribute equally to the solute flux and from arguments presented here that the basin is in dynamic equilibrium with respect to erosion and uplift. The silica flux of 10.7 ± 7.1 t·km−2·yr−1 from the basin is several times larger than the flux from older soils elsewhere, but comparable to the flux from sites with similar physical erosion rates. This result argues that physical denudation or uplift rates play an important role in setting the chemical denudation rate. Physical processes appear to influence chemical-weathering rates in several ways. First, they limit chemical evolution by removing material, thus setting the residence time within the weathered rock and the soil. Second, bioturbation mixes rock fragments into the more reactive soil and maintains high soil porosity, allowing free circulation of water. Because the weathering in the soil is more intense than in the rock, we argue that the chemical denudation rate will diminish where uplift rates—and, hence, physical-denudation rates—are great enough to lead to a bedrock-dominated landscape. Chemical denudation rates will increase with physical-denudation rates, but only as long as the landscape remains mantled by soil.

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Chemical weathering rates of clastic sedimentary rocks from the Paraná Basin in the Paulista Peripheral Depression, Brazil

Journal of South American Earth Sciences ◽

10.1016/j.jsames.2019.102369 ◽

2019 ◽

Vol 96 ◽

pp. 102369 ◽

Cited By ~ 2

Author(s):

Eder Paulo Spatti Júnior ◽

Fabiano Tomazini da Conceição ◽

Alexandre Martins Fernandes ◽

Diego de Souza Sardinha ◽

Amauri Antonio Menegário ◽

...

Keyword(s):

Chemical Weathering ◽

Sedimentary Rocks ◽

Weathering Rates ◽

Paraná Basin ◽

Clastic Sedimentary ◽

Parana Basin

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Rare Earth Elements Enrichment in the Upper Eocene Tošići-Dujići Bauxite Deposit, Croatia, and Relation to REE Mineralogy, Parent Material and Weathering Pattern

Minerals ◽

10.3390/min11111260 ◽

2021 ◽

Vol 11 (11) ◽

pp. 1260

Author(s):

Nenad Tomašić ◽

Andrea Čobić ◽

Matija Bedeković ◽

Slobodan Miko ◽

Nikolina Ilijanić ◽

...

Keyword(s):

Rare Earth ◽

Chemical Weathering ◽

Sedimentary Rocks ◽

Parent Material ◽

Upper Eocene ◽

Bauxite Deposit ◽

Lower Eocene ◽

Residual Material ◽

Oxide Phases ◽

Textural Data

Tošići-Dujići bauxite deposit, situated in Dalmatian inlands, Croatia, contains minor remaining bauxite reserves. The deposit lies on Lower Eocene foraminiferal limestone and is covered by Upper Eocene Promina sediments. Bauxite samples were analyzed for textural, mineralogical, and geochemical features in order to determine absolute REE abundances and their relation to mineralogy, as well as to devise the origin of REE enrichment and to trace weathering and bauxitization paths of the parent material. The samples show total REE abundances up to 3500 mg/kg with significant HREE enrichment in some cases. All samples are gibbsitic with hematite and anatase as major phases. Kaolinite occurs in most of the samples, and goethite, böhmite, and nordstrandite are minor phases. Monazite-(Ce) and xenotime-(Y) were identified as detrital REE minerals as well as authigenic florencite-(Ce). In the REE most abundant sample, REE are most likely bound to Fe- and Ti-oxide phases as suggested by correlation analysis. Chemical weathering proxies show intensive weathering. Geochemical and textural data imply that the REE enrichment is influenced by intensive weathering (CIA 97.87–99.26) of detrital material, and also by possible deposition/redeposition of residual material potentially derived and mobilized from various sedimentary rocks of the area.

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