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Carbonate Deformation Across the Brittle-Ductile Transition and How It Affects the Architecture of Thrust Systems /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Carbonate Deformation Across the Brittle-Ductile Transition and How It Affects the Architecture of Thrust Systems // Inga Boianju.
作者:	Boianju, Inga,
面頁冊數:	1 electronic resource (181 pages)
附註:	Source: Dissertations Abstracts International, Volume: 87-01, Section: B.
Contained By:	Dissertations Abstracts International87-01B.
標題:	Friction. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=32110764
ISBN:	9798290632834

Carbonate Deformation Across the Brittle-Ductile Transition and How It Affects the Architecture of Thrust Systems /
Boianju, Inga,

Carbonate Deformation Across the Brittle-Ductile Transition and How It Affects the Architecture of Thrust Systems /Inga Boianju. - 1 electronic resource (181 pages)

Source: Dissertations Abstracts International, Volume: 87-01, Section: B.

Continental thrust systems are responsible for mountain building and associated earthquake hazard. Carbonate and pelitic rocks dominate fault systems in shallow marine settings in both continental and subduction convergent plate boundaries, and are potential 'weak links' in the downgoing plates of low-latitude oceanic subduction zones.Exposed fold & thrust belts are excellent natural laboratories preserving records of diverse deformation processes. Study of these can test the interplay between brittle and ductile deformation, the different deformation mechanisms involved in ductile shearing, the effects of fluid alteration, and how these feedbacks ultimately control the structural architecture through embrittlement, affecting fault localisation.This thesis investigates the role of carbonate deformation in controlling structural architecture and seismic hazard within continental thrust systems, focusing on the Naukluft Mountains in central Namibia. The Naukluft Nappe Complex is an excellently exposed Cambrian meta-sedimentary fold & thrust belt. It is composed of mostly shallow marine, greenschist-facies metamorphosed carbonates and phyllites that were emplaced at the last stage of Damara Orogeny.First, I present a regional study, focused on the structures at the southern edge of the Naukluft. Through field mapping and 2D fault modelling, I mapped thrust structures which display evidence of early ductile deformation overprinted with discrete brittle features. I report two metamorphic gaps in the tectono-stratigraphy, and attribute the trend of embrittlement to be caused by syn-exhumation cooling, which is not a factor usually considered for forward propagating fold-thrust belts. Exhumation controlled the mechanical stratigraphy, making different lithologies favourable to accommodate strain at changing temperatures. Using the 3D modelling of the younger brittle thrusts, this study is the first to map an out-of-sequence thrust in the Naukluft complex.In my second chapter, I explore the ways that carbonate mylonites, hosted in the ductile shear zones, accommodate regional deformation. I sampled calcitic and dolomitic mylonites from multiple nappe-bounding faults. Using electron microscopy (SEM+EDS) and electron backscatter diffraction (EBSD), I interpret the deformation mechanisms of these carbonate mylonites, at a variety of calcite to dolomite ratios, phyllite to carbonate ratios, in the lower to upper greenschist facies. I found evidence of multi-phase deformation of both solution precipitation creep and dislocation creep, along with clear evidence for recovery through sub-grain rotation recrystallisation. In heterogeneous lithologies, calcite vein enrichment assisted fabric development during shear, affecting the rheology of the shear zones, that with continued shear in the steady state, became increasingly calcite-rich, acting as strain weakening.In the third chapter I present a focused mapping and microstructural study of the most deeply exhumed exposure of the Naukluft Thrust, bearing both brittle and ductile fault rocks. In this chapter, I explore how carbonate mineral transformations through fluid-rock interaction drive brittle-ductile cycling, affecting the rock strength. Mixing of iron silicates from the footwall schists contribute to crystallization of new phases - chlorite and iron carbonates - which significantly affect the rheology of the shear zone. I present this interpreted record of the strength evolution of carbonate rocks during open-system fluid-rock reaction through the brittle-ductile transition. This result is instructive for understanding the strength evolution of shear zones in naturalistic conditions where the structures are conduits for reactive fluids during deformation.

English

ISBN: 9798290632834Subjects--Topical Terms:

650299
Friction.

Carbonate Deformation Across the Brittle-Ductile Transition and How It Affects the Architecture of Thrust Systems /
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520 $a Continental thrust systems are responsible for mountain building and associated earthquake hazard. Carbonate and pelitic rocks dominate fault systems in shallow marine settings in both continental and subduction convergent plate boundaries, and are potential 'weak links' in the downgoing plates of low-latitude oceanic subduction zones.Exposed fold & thrust belts are excellent natural laboratories preserving records of diverse deformation processes. Study of these can test the interplay between brittle and ductile deformation, the different deformation mechanisms involved in ductile shearing, the effects of fluid alteration, and how these feedbacks ultimately control the structural architecture through embrittlement, affecting fault localisation.This thesis investigates the role of carbonate deformation in controlling structural architecture and seismic hazard within continental thrust systems, focusing on the Naukluft Mountains in central Namibia. The Naukluft Nappe Complex is an excellently exposed Cambrian meta-sedimentary fold & thrust belt. It is composed of mostly shallow marine, greenschist-facies metamorphosed carbonates and phyllites that were emplaced at the last stage of Damara Orogeny.First, I present a regional study, focused on the structures at the southern edge of the Naukluft. Through field mapping and 2D fault modelling, I mapped thrust structures which display evidence of early ductile deformation overprinted with discrete brittle features. I report two metamorphic gaps in the tectono-stratigraphy, and attribute the trend of embrittlement to be caused by syn-exhumation cooling, which is not a factor usually considered for forward propagating fold-thrust belts. Exhumation controlled the mechanical stratigraphy, making different lithologies favourable to accommodate strain at changing temperatures. Using the 3D modelling of the younger brittle thrusts, this study is the first to map an out-of-sequence thrust in the Naukluft complex.In my second chapter, I explore the ways that carbonate mylonites, hosted in the ductile shear zones, accommodate regional deformation. I sampled calcitic and dolomitic mylonites from multiple nappe-bounding faults. Using electron microscopy (SEM+EDS) and electron backscatter diffraction (EBSD), I interpret the deformation mechanisms of these carbonate mylonites, at a variety of calcite to dolomite ratios, phyllite to carbonate ratios, in the lower to upper greenschist facies. I found evidence of multi-phase deformation of both solution precipitation creep and dislocation creep, along with clear evidence for recovery through sub-grain rotation recrystallisation. In heterogeneous lithologies, calcite vein enrichment assisted fabric development during shear, affecting the rheology of the shear zones, that with continued shear in the steady state, became increasingly calcite-rich, acting as strain weakening.In the third chapter I present a focused mapping and microstructural study of the most deeply exhumed exposure of the Naukluft Thrust, bearing both brittle and ductile fault rocks. In this chapter, I explore how carbonate mineral transformations through fluid-rock interaction drive brittle-ductile cycling, affecting the rock strength. Mixing of iron silicates from the footwall schists contribute to crystallization of new phases - chlorite and iron carbonates - which significantly affect the rheology of the shear zone. I present this interpreted record of the strength evolution of carbonate rocks during open-system fluid-rock reaction through the brittle-ductile transition. This result is instructive for understanding the strength evolution of shear zones in naturalistic conditions where the structures are conduits for reactive fluids during deformation.
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