Syngenetic rapid growth of ellipsoidal silica concretions with bitumen cores

Abstract Isolated silica concretions in calcareous sediments have unique shapes and distinct sharp boundaries and are considered to form by diagenesis of biogenic siliceous grains. However, the details and rates of syngenetic formation of these spherical concretions are still not fully clear. Here w...

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Autores principales:	Hidekazu Yoshida, Ryusei Kuma, Hitoshi Hasegawa, Nagayoshi Katsuta, Sin-iti Sirono, Masayo Minami, Shoji Nishimoto, Natsuko Takagi, Seiji Kadowaki, Richard Metcalfe
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/127fcb93f04b49e38d737ceffc70cbf0
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spelling	oai:doaj.org-article:127fcb93f04b49e38d737ceffc70cbf02021-12-02T12:11:28ZSyngenetic rapid growth of ellipsoidal silica concretions with bitumen cores10.1038/s41598-021-83651-w2045-2322https://doaj.org/article/127fcb93f04b49e38d737ceffc70cbf02021-02-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-83651-whttps://doaj.org/toc/2045-2322Abstract Isolated silica concretions in calcareous sediments have unique shapes and distinct sharp boundaries and are considered to form by diagenesis of biogenic siliceous grains. However, the details and rates of syngenetic formation of these spherical concretions are still not fully clear. Here we present a model for concretion growth by diffusion, with chemical buffering involving decomposition of organic matter leading to a pH change in the pore-water and preservation of residual bitumen cores in the concretions. The model is compatible with some pervasive silica precipitation. Based on the observed elemental distributions, C, N, S, bulk carbon isotope and carbon preference index (CPI) measurements of the silica-enriched concretions, bitumen cores and surrounding calcareous rocks, the rate of diffusive concretion growth during early diagenesis is shown using a diffusion-growth diagram. This approach reveals that ellipsoidal SiO2 concretions with a diameter of a few cm formed rapidly and the precipitated silica preserved the bitumen cores. Our work provides a generalized chemical buffering model involving organic matter that can explain the rapid syngenetic growth of other types of silica accumulation in calcareous sediments.Hidekazu YoshidaRyusei KumaHitoshi HasegawaNagayoshi KatsutaSin-iti SironoMasayo MinamiShoji NishimotoNatsuko TakagiSeiji KadowakiRichard MetcalfeNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-11 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Hidekazu Yoshida Ryusei Kuma Hitoshi Hasegawa Nagayoshi Katsuta Sin-iti Sirono Masayo Minami Shoji Nishimoto Natsuko Takagi Seiji Kadowaki Richard Metcalfe Syngenetic rapid growth of ellipsoidal silica concretions with bitumen cores
description	Abstract Isolated silica concretions in calcareous sediments have unique shapes and distinct sharp boundaries and are considered to form by diagenesis of biogenic siliceous grains. However, the details and rates of syngenetic formation of these spherical concretions are still not fully clear. Here we present a model for concretion growth by diffusion, with chemical buffering involving decomposition of organic matter leading to a pH change in the pore-water and preservation of residual bitumen cores in the concretions. The model is compatible with some pervasive silica precipitation. Based on the observed elemental distributions, C, N, S, bulk carbon isotope and carbon preference index (CPI) measurements of the silica-enriched concretions, bitumen cores and surrounding calcareous rocks, the rate of diffusive concretion growth during early diagenesis is shown using a diffusion-growth diagram. This approach reveals that ellipsoidal SiO2 concretions with a diameter of a few cm formed rapidly and the precipitated silica preserved the bitumen cores. Our work provides a generalized chemical buffering model involving organic matter that can explain the rapid syngenetic growth of other types of silica accumulation in calcareous sediments.
format	article
author	Hidekazu Yoshida Ryusei Kuma Hitoshi Hasegawa Nagayoshi Katsuta Sin-iti Sirono Masayo Minami Shoji Nishimoto Natsuko Takagi Seiji Kadowaki Richard Metcalfe
author_facet	Hidekazu Yoshida Ryusei Kuma Hitoshi Hasegawa Nagayoshi Katsuta Sin-iti Sirono Masayo Minami Shoji Nishimoto Natsuko Takagi Seiji Kadowaki Richard Metcalfe
author_sort	Hidekazu Yoshida
title	Syngenetic rapid growth of ellipsoidal silica concretions with bitumen cores
title_short	Syngenetic rapid growth of ellipsoidal silica concretions with bitumen cores
title_full	Syngenetic rapid growth of ellipsoidal silica concretions with bitumen cores
title_fullStr	Syngenetic rapid growth of ellipsoidal silica concretions with bitumen cores
title_full_unstemmed	Syngenetic rapid growth of ellipsoidal silica concretions with bitumen cores
title_sort	syngenetic rapid growth of ellipsoidal silica concretions with bitumen cores
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/127fcb93f04b49e38d737ceffc70cbf0
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Syngenetic rapid growth of ellipsoidal silica concretions with bitumen cores

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