Cockade structures as a paleo-earthquake proxy in upper crustal hydrothermal systems

Berger, Alfons; Herwegh, Marco (2019). Cockade structures as a paleo-earthquake proxy in upper crustal hydrothermal systems. Scientific Reports, 9(1) Nature Publishing Group 10.1038/s41598-019-45488-2

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Cockades are clasts completely surrounded by spheroidal hydrothermal overgrowth rims. they are observed inside hydrothermal fault breccias and can provide insights into fault dynamics. the formation of cockades with spheroidal hydrothermal overgrowth rims is related to fast fracturing and dilation, and requires primary clasts to be suspended in a fluid. The rim growth is driven by drops in fluid pressure and related oversaturation. We use descriptions of cockades, their rims and cements in a fault breccia. Geometrical data are combined with mechano-chemical calculations to gain insights into seismic processes and estimate seismic magnitudes. Fast rates for formation of cockade cores and first rim growth are interpreted to be the result of an earthquake’s main shock. Younger growth rims represent subsequent aftershocks, while cemented cockades record interseismic periods. We propose that by considering growth rates of hydrothermal precipitates and cements, paleo-earthquake cycles can be unraveled and a link between geophysics and fault structures can be established.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Institute of Geological Sciences > Tectonics

UniBE Contributor:

Berger, Alfons and Herwegh, Marco

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

2045-2322

Publisher:

Nature Publishing Group

Language:

English

Submitter:

Alfons Berger

Date Deposited:

26 Aug 2019 16:54

Last Modified:

23 Oct 2019 13:29

Publisher DOI:

10.1038/s41598-019-45488-2

BORIS DOI:

10.7892/boris.132611

URI:

https://boris.unibe.ch/id/eprint/132611

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