Greigite Formation Modulated by Turbidites and Bioturbation in Deep-Sea Sediments Offshore Sumatra

Yang，Tao1,2; Dekkers，Mark J.2; Zhao，Xixi3; Petronotis，Katerina E.4; Chou，Yu Min3

2022-11-01

10.1029/2022JB024734

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH   Impact Factor & Quartile

2169-9313

2169-9356

Authigenic greigite may form at any time within a sediment during diagenesis. Its formation pathway, timing of formation, and geological preservation potential are key to resolving the fidelity of (paleo-)magnetic signals in greigite-bearing sediments. In the cored sequence of the International Ocean Discovery Program Expedition 362 (Sumatra Subduction Margin), multiple organic-rich mudstone horizons have high magnetic susceptibilities. The high-susceptibility horizons occur immediately below the most bioturbated intervals at the top of muddy turbidite beds. Combined mineral magnetic, microscopic, and chemical analyses on both thin sections and magnetic mineral extracts of sediments from a typical interval (∼1,103.80–1,108.80 m below seafloor) reveal the presence of coarse-grained greigite aggregates (particles up to 50–75 μm in size). The greigite formed under nonsteady state conditions caused by the successive turbidites. Organic matter, iron (oxy)(hydr)oxides, Fe, and sulfides and/or sulfate were enriched in these intensively bioturbated horizons. This facilitated greigite formation and preservation within a closed diagenetic system created by the ensuing turbidite pulse, where pyritization was arrested due to insufficient sulfate supply relative to Fe (oxy)(hydr)oxide. This may represent a novel greigite formation pathway under conditions modulated by turbidites and bioturbation. Paleomagnetic analyses indicate that the early diagenetic greigite preserves primary (quasi-)syn-sedimentary magnetic records. The extremely high greigite content (0.06–1.30 wt% with an average of 0.50 wt% estimated from their saturation magnetization) implies that the bioturbated turbiditic deposits are an important sink for iron and sulfur. Mineral magnetic methods, thus, may offer a window to better understand the marine Fe–S–C cycle.

bioturbation greigite IODP Expedition 362 mineral magnetism Nicobar Fan turbidite

SCI

English

NI Journal Papers

Corresponding

National Natural Science Foundation of China[41874076];National Natural Science Foundation of China[41874105];National Science Foundation[EAR-1250444];National Science Foundation[OCE-1326927];

Geochemistry & Geophysics

Geochemistry & Geophysics

WOS:000888604000001

AMER GEOPHYSICAL UNION

GEOSCIENCES

2-s2.0-85142878971

Scopus

1.State Key Laboratory of Geological Processes and Mineral Resources,School of Geophysics and Information Technology,China University of Geosciences,Beijing,China
2.Paleomagnetic Laboratory Fort Hoofddijk,Department of Earth Sciences,Utrecht University,Utrecht,Netherlands
3.Department of Ocean Science and Engineering,Southern University of Science and Technology,Shenzhen,China
4.International Ocean Discovery Program,Texas A&M University,College Station,United States

Yang，Tao,Dekkers，Mark J.,Zhao，Xixi,et al. Greigite Formation Modulated by Turbidites and Bioturbation in Deep-Sea Sediments Offshore Sumatra[J]. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,2022,127(11).

Yang，Tao,Dekkers，Mark J.,Zhao，Xixi,Petronotis，Katerina E.,&Chou，Yu Min.(2022).Greigite Formation Modulated by Turbidites and Bioturbation in Deep-Sea Sediments Offshore Sumatra.JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,127(11).

Yang，Tao,et al."Greigite Formation Modulated by Turbidites and Bioturbation in Deep-Sea Sediments Offshore Sumatra".JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 127.11(2022).