Model for the development of kyanite during partial convective overturn of Archean granite-greenstone terranes

The Pilbara Craton, Australia

W. J. Collins, Martin Van Kranendonk

Research output: Contribution to journalArticle

44 Citations (Scopus)

Abstract

Restricted occurrences of early, syn- and late-kinematic kyanite adjacent to large domal batholiths in the Archean granite-greenstone terrane of the east Pilbara craton, Australia, are considered to result from partial convective overturn of the crust. The analogue models of Dixon and Summers (1983) and thermomechanical models of Mareschal and West (1980), involving gravitational overturn of dense greenstone crust that initially overlay sialic basement, successfully explain the geometry, dimension, kinematics and strain patterns of the batholiths and greenstone rims. Application of these models suggests that andalusite and sillimanite are the stable aluminosilicate polymorphs in domal crests and rims, where prograde clockwise P-T-t paths, with small pressure changes, should be recorded. Both aluminosilicates are predicted to overprint kyanite, which is observed locally around the east Pilbara domes. Kyanite is the predicted aluminosilicate polymorph in the deeper parts of domal rims and within sinking greenstone keels, reflecting rapid, near-isothermal burial. The narrow zones of kyanite-bearing schists adjacent to some batholiths in the Pilbara craton are metamorphosed, highly strained equivalents of altered felsic volcanic rocks in the low-grade greenstone succession, dragged to mid-crustal depths (6 kbar) during greenstone sinking. The schists rebounded as an arcuate tectonic wedge along the southern Mount Edgar batholith rim, during the later stages of doming, and were juxtaposed against regional, greenschist facies, low-strain greenstones. Thus, kyanite was preserved: if the walls had remained at depth, it would have been overprinted by the higher-temperature aluminosilicate polymorphs during thermal recovery. Kyanite growth in the Pilbara craton is unlikely to have resulted from ballooning of plutons, mantled gneiss doming, metamorphic core complex formation, or early crustal overthickening. The typical subvertical foliations and lineations of the tectonic wedge suggest that subvertical fabrics extended to mid-crustal depths (c. 20 km) before rebound, providing a three-dimensional glimpse of Archean dome-and-keel structures. The general occurrence of large granitoid domes in Archean granite-greenstone terranes, restriction of rare kyanite to the adjacent, high-strain batholith margins, and its absence from the batholiths, suggest that partial convective overturn of the crust may have been a common process at this early stage of Earth history.

Original languageEnglish
Pages (from-to)145-156
Number of pages12
JournalJournal of Metamorphic Geology
Volume17
Issue number2
DOIs
Publication statusPublished - Mar 1 1999
Externally publishedYes

Fingerprint

overturn
greenstone
kyanite
craton
Archean
terrane
granite
aluminosilicate
Domes
Polymorphism
tectonic wedge
dome
Tectonics
crust
batholith
Kinematics
schist
Bearings (structural)
kinematics
Volcanic rocks

Keywords

  • Archean
  • Diapirs
  • Granite-greenstone terranes
  • Kyanite
  • P-T-t paths

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

Cite this

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title = "Model for the development of kyanite during partial convective overturn of Archean granite-greenstone terranes: The Pilbara Craton, Australia",
abstract = "Restricted occurrences of early, syn- and late-kinematic kyanite adjacent to large domal batholiths in the Archean granite-greenstone terrane of the east Pilbara craton, Australia, are considered to result from partial convective overturn of the crust. The analogue models of Dixon and Summers (1983) and thermomechanical models of Mareschal and West (1980), involving gravitational overturn of dense greenstone crust that initially overlay sialic basement, successfully explain the geometry, dimension, kinematics and strain patterns of the batholiths and greenstone rims. Application of these models suggests that andalusite and sillimanite are the stable aluminosilicate polymorphs in domal crests and rims, where prograde clockwise P-T-t paths, with small pressure changes, should be recorded. Both aluminosilicates are predicted to overprint kyanite, which is observed locally around the east Pilbara domes. Kyanite is the predicted aluminosilicate polymorph in the deeper parts of domal rims and within sinking greenstone keels, reflecting rapid, near-isothermal burial. The narrow zones of kyanite-bearing schists adjacent to some batholiths in the Pilbara craton are metamorphosed, highly strained equivalents of altered felsic volcanic rocks in the low-grade greenstone succession, dragged to mid-crustal depths (6 kbar) during greenstone sinking. The schists rebounded as an arcuate tectonic wedge along the southern Mount Edgar batholith rim, during the later stages of doming, and were juxtaposed against regional, greenschist facies, low-strain greenstones. Thus, kyanite was preserved: if the walls had remained at depth, it would have been overprinted by the higher-temperature aluminosilicate polymorphs during thermal recovery. Kyanite growth in the Pilbara craton is unlikely to have resulted from ballooning of plutons, mantled gneiss doming, metamorphic core complex formation, or early crustal overthickening. The typical subvertical foliations and lineations of the tectonic wedge suggest that subvertical fabrics extended to mid-crustal depths (c. 20 km) before rebound, providing a three-dimensional glimpse of Archean dome-and-keel structures. The general occurrence of large granitoid domes in Archean granite-greenstone terranes, restriction of rare kyanite to the adjacent, high-strain batholith margins, and its absence from the batholiths, suggest that partial convective overturn of the crust may have been a common process at this early stage of Earth history.",
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author = "Collins, {W. J.} and {Van Kranendonk}, Martin",
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T1 - Model for the development of kyanite during partial convective overturn of Archean granite-greenstone terranes

T2 - The Pilbara Craton, Australia

AU - Collins, W. J.

AU - Van Kranendonk, Martin

PY - 1999/3/1

Y1 - 1999/3/1

N2 - Restricted occurrences of early, syn- and late-kinematic kyanite adjacent to large domal batholiths in the Archean granite-greenstone terrane of the east Pilbara craton, Australia, are considered to result from partial convective overturn of the crust. The analogue models of Dixon and Summers (1983) and thermomechanical models of Mareschal and West (1980), involving gravitational overturn of dense greenstone crust that initially overlay sialic basement, successfully explain the geometry, dimension, kinematics and strain patterns of the batholiths and greenstone rims. Application of these models suggests that andalusite and sillimanite are the stable aluminosilicate polymorphs in domal crests and rims, where prograde clockwise P-T-t paths, with small pressure changes, should be recorded. Both aluminosilicates are predicted to overprint kyanite, which is observed locally around the east Pilbara domes. Kyanite is the predicted aluminosilicate polymorph in the deeper parts of domal rims and within sinking greenstone keels, reflecting rapid, near-isothermal burial. The narrow zones of kyanite-bearing schists adjacent to some batholiths in the Pilbara craton are metamorphosed, highly strained equivalents of altered felsic volcanic rocks in the low-grade greenstone succession, dragged to mid-crustal depths (6 kbar) during greenstone sinking. The schists rebounded as an arcuate tectonic wedge along the southern Mount Edgar batholith rim, during the later stages of doming, and were juxtaposed against regional, greenschist facies, low-strain greenstones. Thus, kyanite was preserved: if the walls had remained at depth, it would have been overprinted by the higher-temperature aluminosilicate polymorphs during thermal recovery. Kyanite growth in the Pilbara craton is unlikely to have resulted from ballooning of plutons, mantled gneiss doming, metamorphic core complex formation, or early crustal overthickening. The typical subvertical foliations and lineations of the tectonic wedge suggest that subvertical fabrics extended to mid-crustal depths (c. 20 km) before rebound, providing a three-dimensional glimpse of Archean dome-and-keel structures. The general occurrence of large granitoid domes in Archean granite-greenstone terranes, restriction of rare kyanite to the adjacent, high-strain batholith margins, and its absence from the batholiths, suggest that partial convective overturn of the crust may have been a common process at this early stage of Earth history.

AB - Restricted occurrences of early, syn- and late-kinematic kyanite adjacent to large domal batholiths in the Archean granite-greenstone terrane of the east Pilbara craton, Australia, are considered to result from partial convective overturn of the crust. The analogue models of Dixon and Summers (1983) and thermomechanical models of Mareschal and West (1980), involving gravitational overturn of dense greenstone crust that initially overlay sialic basement, successfully explain the geometry, dimension, kinematics and strain patterns of the batholiths and greenstone rims. Application of these models suggests that andalusite and sillimanite are the stable aluminosilicate polymorphs in domal crests and rims, where prograde clockwise P-T-t paths, with small pressure changes, should be recorded. Both aluminosilicates are predicted to overprint kyanite, which is observed locally around the east Pilbara domes. Kyanite is the predicted aluminosilicate polymorph in the deeper parts of domal rims and within sinking greenstone keels, reflecting rapid, near-isothermal burial. The narrow zones of kyanite-bearing schists adjacent to some batholiths in the Pilbara craton are metamorphosed, highly strained equivalents of altered felsic volcanic rocks in the low-grade greenstone succession, dragged to mid-crustal depths (6 kbar) during greenstone sinking. The schists rebounded as an arcuate tectonic wedge along the southern Mount Edgar batholith rim, during the later stages of doming, and were juxtaposed against regional, greenschist facies, low-strain greenstones. Thus, kyanite was preserved: if the walls had remained at depth, it would have been overprinted by the higher-temperature aluminosilicate polymorphs during thermal recovery. Kyanite growth in the Pilbara craton is unlikely to have resulted from ballooning of plutons, mantled gneiss doming, metamorphic core complex formation, or early crustal overthickening. The typical subvertical foliations and lineations of the tectonic wedge suggest that subvertical fabrics extended to mid-crustal depths (c. 20 km) before rebound, providing a three-dimensional glimpse of Archean dome-and-keel structures. The general occurrence of large granitoid domes in Archean granite-greenstone terranes, restriction of rare kyanite to the adjacent, high-strain batholith margins, and its absence from the batholiths, suggest that partial convective overturn of the crust may have been a common process at this early stage of Earth history.

KW - Archean

KW - Diapirs

KW - Granite-greenstone terranes

KW - Kyanite

KW - P-T-t paths

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DO - 10.1046/j.1525-1314.1999.00187.x

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JO - Journal of Metamorphic Geology

JF - Journal of Metamorphic Geology

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