Natural qtz-fs

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Naturally deformed quartzo-feldspathic rocks

TOP

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Experimentally deformed quartz aggregates

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Naturally deformed quartz-rich rocks

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Experimentally deformed feldspar aggregates

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Naturally deformed feldspar rocks

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Experimentally deformed quartzo-feldspathic rocks

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Naturally deformed quartzo-feldspathic rocks

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Experimentally deformed pyroxenite and diabase

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Deformation and metamorphic reactions in polyphase rocks

Naturally deformed quartzo-feldspathic rocks

weak deformation (Mulwaree) / strong deformation (Mulwaree) / mylonites (Redbank) / ultramylonites (Redbank)

Introduction

The samples illustrated in photos 68 to 76 were taken from a granodiorite cut by the Mulwaree fault zone, about 40 km east of Canberra, Australia. The samples represent stages of progressively higher shear strain found around less deformed boudins embedded in a more strongly deformed mylonitic matrix. Deformation occurred at mid-greenschist temperature conditions in the absence of significant amounts of aqueous fluids, because intermediate feldspars have remained chemically stable. Some alteration of feldspar to white mica is visible in these images but is due to later fracturing and fluid infiltration. Deformation has been accommodated by crystal plastic deformation in the quartz and biotite. Most of the feldspar in this rock is plagioclase, and plagioclase and K-feldspar are similar in their mechanical behavior; both deform only by fracturing at the relatively low temperatures of this deformation.
The samples illustrated in photos 77 to 87 were taken from the Redbank shear zone. The Redbank shear zone has a long history of activation through Proterozoic time, culminating with the development of mylonites during the late Paleozoic Alice Springs orogeny. This mylonite zone is several kilometers thick and is defined by a strong foliation and a prominent down-dip lineation. The Redbank shear zone contains the whole spectrum of mylonitic rocks, and pseudotachylite zones occur locally. Deformation at exposure level developed under greenschist-facies conditions.

6		Naturally deformed quartzo-feldspathic rocks
6

TOP	1-	Experimentally deformed quartz aggregates	2-	Naturally deformed quartz-rich rocks
	3-	Experimentally deformed feldspar aggregates	4-	Naturally deformed feldspar rocks
	5-	Experimentally deformed quartzo-feldspathic rocks	6-	Naturally deformed quartzo-feldspathic rocks
	7-	Experimentally deformed pyroxenite and diabase	8-	Deformation and metamorphic reactions in polyphase rocks

Naturally deformed quartzo-feldspathic rocks		weak deformation (Mulwaree) / strong deformation (Mulwaree) / mylonites (Redbank) / ultramylonites (Redbank)

		Introduction The samples illustrated in photos 68 to 76 were taken from a granodiorite cut by the Mulwaree fault zone, about 40 km east of Canberra, Australia. The samples represent stages of progressively higher shear strain found around less deformed boudins embedded in a more strongly deformed mylonitic matrix. Deformation occurred at mid-greenschist temperature conditions in the absence of significant amounts of aqueous fluids, because intermediate feldspars have remained chemically stable. Some alteration of feldspar to white mica is visible in these images but is due to later fracturing and fluid infiltration. Deformation has been accommodated by crystal plastic deformation in the quartz and biotite. Most of the feldspar in this rock is plagioclase, and plagioclase and K-feldspar are similar in their mechanical behavior; both deform only by fracturing at the relatively low temperatures of this deformation. The samples illustrated in photos 77 to 87 were taken from the Redbank shear zone. The Redbank shear zone has a long history of activation through Proterozoic time, culminating with the development of mylonites during the late Paleozoic Alice Springs orogeny. This mylonite zone is several kilometers thick and is defined by a strong foliation and a prominent down-dip lineation. The Redbank shear zone contains the whole spectrum of mylonitic rocks, and pseudotachylite zones occur locally. Deformation at exposure level developed under greenschist-facies conditions.