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Marine sepiolite in Middle Permian carbonates of South China; implications for secular variation of Phanerozoic seawater chemistry

Yan Jiaxin, Axel Munnecke, Thomas Steuber, Ernest H. Carlson and Yilin Xiao
Marine sepiolite in Middle Permian carbonates of South China; implications for secular variation of Phanerozoic seawater chemistry
Journal of Sedimentary Research (May 2005) 75 (3): 328-338

Abstract

It is now widely accepted that the composition of seawater varied significantly during the Phanerozoic, and that the Mg/Ca ratio of seawater is a major factor in synchronized secular oscillations in the mineralogical composition of marine evaporites and nonskeletal as well as biogenic carbonates. However, the nature of the Mg sink is still subject to debate. We describe early diagenetic sepiolite from the Chihsia Formation (Middle Permian) of South China. The Mg incorporated in sepiolite likely was furnished by stabilization of high-Mg calcite, and silica was derived from siliceous fossils. Two factors facilitated the accumulation of sepiolite in the Chihsia Formation. The first is a Chihsian depositional environment of an intra-oceanic carbonate platform that lacked detrital terrestrial input, which enhanced the availability of biogenic silica for sepiolite formation. The second is the chemical composition of Permian seawater, as the precipitation of high-Mg calcite was aided by a high Mg/Ca ratio associated with an aragonite sea. The formation of sepiolite is significant in constraining the recycling flux of Mg during recrystallization of carbonate sediments with a high proportion of high-Mg calcite (periods of aragonite seas). Worldwide, major occurrences of marine sepiolite and palygorskite in the Phanerozoic correlate with periods of aragonite seas. This temporal distribution implies that minerals of the sepiolite-palygorskite group play an important role in the geochemical recycling of Mg, and that major sepiolite and palygorskite deposits indicate episodes of high Mg concentrations in seawater. The formation of sepiolite also was probably related to an abundance of silica-secreting organisms, which interacted with the chemical evolution of Phanerozoic seawater. In addition, authigenic sepiolite and palygorskite are not indicators of arid and semi-arid climates.


ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 75
Serial Issue: 3
Title: Marine sepiolite in Middle Permian carbonates of South China; implications for secular variation of Phanerozoic seawater chemistry
Affiliation: China University of Geosciences, Faculty of Earth Sciences, Wuhan, China
Pages: 328-338
Published: 200505
Text Language: English
Publisher: Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States
References: 67
Accession Number: 2005-044680
Categories: Geochemistry of rocks, soils, and sedimentsSedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Appendices not printed are available at SEPM data archive; http://www.sepm.org/archive/index.html
Illustration Description: illus. incl. sect., 2 tables, geol. sketch maps
N24°40'00" - N30°10'00", E109°00'00" - E114°15'00"
N29°00'00" - N33°19'60", E108°30'00" - E116°00'00"
N24°30'00" - N30°00'00", E113°40'00" - E118°30'00"
Secondary Affiliation: Universitaet Erlangen, DEU, Federal Republic of GermanyRuhr-Universitaet, DEU, Federal Republic of GermanyKent State University, USA, United StatesUniversitaet Goettingen, DEU, Federal Republic of Germany
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 200526
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