Exsolution textures of orthopyroxene and clinopyroxene in high‐grade BIF of the Voronezh Crystalline Massif: evidence of ultrahigh‐temperature metamorphism
Abstract Archaean banded iron formation (BIF) of the Voronezh Crystalline Massif (VCM) contains coexisting clino‐ and orthopyroxenes with exsolution textures. The pyroxene in the VCM BIF is found in two generations, with only the first generation containing such textures. Clinopyroxene contains larg...
Published in: | Journal of Metamorphic Geology |
---|---|
Main Authors: | , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Wiley
2006
|
Subjects: | |
Online Access: | http://dx.doi.org/10.1111/j.1525-1314.2006.00630.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.2006.00630.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.2006.00630.x |
id |
crwiley:10.1111/j.1525-1314.2006.00630.x |
---|---|
record_format |
openpolar |
spelling |
crwiley:10.1111/j.1525-1314.2006.00630.x 2024-06-09T07:40:52+00:00 Exsolution textures of orthopyroxene and clinopyroxene in high‐grade BIF of the Voronezh Crystalline Massif: evidence of ultrahigh‐temperature metamorphism FONAREV, V. I. PILUGIN, S. M. SAVKO, K. A. NOVIKOVA, M. A. 2006 http://dx.doi.org/10.1111/j.1525-1314.2006.00630.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.2006.00630.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.2006.00630.x en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Journal of Metamorphic Geology volume 24, issue 2, page 135-151 ISSN 0263-4929 1525-1314 journal-article 2006 crwiley https://doi.org/10.1111/j.1525-1314.2006.00630.x 2024-05-16T14:27:36Z Abstract Archaean banded iron formation (BIF) of the Voronezh Crystalline Massif (VCM) contains coexisting clino‐ and orthopyroxenes with exsolution textures. The pyroxene in the VCM BIF is found in two generations, with only the first generation containing such textures. Clinopyroxene contains large (up to 5–10 μ m) (0 0 1) orthopyroxene (Opx1L) lamellae in a host clinopyroxene (Cpx1H). This host Cpx, in turn, exsolves into thin (∼1 μ m) (1 0 0) lamellae of orthopyroxene (Opx2L) and clinopyroxene (Cpx2H). Orthopyroxene exhibits similar exsolution textures with large (up to 50 μ m) (0 0 1) clinopyroxene (Cpx1L) lamellae developed in a host orthopyroxene (Opx1H). This clinopyroxene Cpx1L shows further exsolution of thin (1 0 0) Opx2LL lamellae and clinopyroxene (Cpx2LH). Point microprobe analysis, raster‐mode microprobe analysis, and microprobe element mapping of mineral grains with a large number of point analysis were used to determine the composition of the exsolution products and the primary chemistry of the coexisting clinopyroxene (CaO = 14.86–17.26 wt%) and pigeonite (CaO = 4.45–6.23 wt%). These pyroxenes crystallized during the peak of metamorphism, and application of the Lindsley geothermometer suggested that they formed at extremely high temperatures of about 1000 °C. Primary very dense CO 2 ‐rich fluid inclusions ( ρ = 1.152 g cm −3 , T h = −49.2 °C) were discovered for the first time in these BIF. With these data, the metamorphic pressure was estimated as 10–11 kbar (depth 36–40 km). Such ultrahigh temperature–high pressure (UHT–HP) conditions for the regional metamorphism of the Precambrian BIF have previously been reported only for Archaean meta‐ironstone from the Napier Complex (Enderby Land, Antarctica). They give an insight into the peak metamorphic conditions of the BIF of the VCM, their burial under thickened continental crust during this period of Earth evolution and suggest a more complicated multistage metamorphic and tectono‐thermal history for the region than has previously been postulated. Article in Journal/Newspaper Antarc* Antarctica Enderby Land Wiley Online Library Napier ENVELOPE(-58.440,-58.440,-62.167,-62.167) Journal of Metamorphic Geology 24 2 135 151 |
institution |
Open Polar |
collection |
Wiley Online Library |
op_collection_id |
crwiley |
language |
English |
description |
Abstract Archaean banded iron formation (BIF) of the Voronezh Crystalline Massif (VCM) contains coexisting clino‐ and orthopyroxenes with exsolution textures. The pyroxene in the VCM BIF is found in two generations, with only the first generation containing such textures. Clinopyroxene contains large (up to 5–10 μ m) (0 0 1) orthopyroxene (Opx1L) lamellae in a host clinopyroxene (Cpx1H). This host Cpx, in turn, exsolves into thin (∼1 μ m) (1 0 0) lamellae of orthopyroxene (Opx2L) and clinopyroxene (Cpx2H). Orthopyroxene exhibits similar exsolution textures with large (up to 50 μ m) (0 0 1) clinopyroxene (Cpx1L) lamellae developed in a host orthopyroxene (Opx1H). This clinopyroxene Cpx1L shows further exsolution of thin (1 0 0) Opx2LL lamellae and clinopyroxene (Cpx2LH). Point microprobe analysis, raster‐mode microprobe analysis, and microprobe element mapping of mineral grains with a large number of point analysis were used to determine the composition of the exsolution products and the primary chemistry of the coexisting clinopyroxene (CaO = 14.86–17.26 wt%) and pigeonite (CaO = 4.45–6.23 wt%). These pyroxenes crystallized during the peak of metamorphism, and application of the Lindsley geothermometer suggested that they formed at extremely high temperatures of about 1000 °C. Primary very dense CO 2 ‐rich fluid inclusions ( ρ = 1.152 g cm −3 , T h = −49.2 °C) were discovered for the first time in these BIF. With these data, the metamorphic pressure was estimated as 10–11 kbar (depth 36–40 km). Such ultrahigh temperature–high pressure (UHT–HP) conditions for the regional metamorphism of the Precambrian BIF have previously been reported only for Archaean meta‐ironstone from the Napier Complex (Enderby Land, Antarctica). They give an insight into the peak metamorphic conditions of the BIF of the VCM, their burial under thickened continental crust during this period of Earth evolution and suggest a more complicated multistage metamorphic and tectono‐thermal history for the region than has previously been postulated. |
format |
Article in Journal/Newspaper |
author |
FONAREV, V. I. PILUGIN, S. M. SAVKO, K. A. NOVIKOVA, M. A. |
spellingShingle |
FONAREV, V. I. PILUGIN, S. M. SAVKO, K. A. NOVIKOVA, M. A. Exsolution textures of orthopyroxene and clinopyroxene in high‐grade BIF of the Voronezh Crystalline Massif: evidence of ultrahigh‐temperature metamorphism |
author_facet |
FONAREV, V. I. PILUGIN, S. M. SAVKO, K. A. NOVIKOVA, M. A. |
author_sort |
FONAREV, V. I. |
title |
Exsolution textures of orthopyroxene and clinopyroxene in high‐grade BIF of the Voronezh Crystalline Massif: evidence of ultrahigh‐temperature metamorphism |
title_short |
Exsolution textures of orthopyroxene and clinopyroxene in high‐grade BIF of the Voronezh Crystalline Massif: evidence of ultrahigh‐temperature metamorphism |
title_full |
Exsolution textures of orthopyroxene and clinopyroxene in high‐grade BIF of the Voronezh Crystalline Massif: evidence of ultrahigh‐temperature metamorphism |
title_fullStr |
Exsolution textures of orthopyroxene and clinopyroxene in high‐grade BIF of the Voronezh Crystalline Massif: evidence of ultrahigh‐temperature metamorphism |
title_full_unstemmed |
Exsolution textures of orthopyroxene and clinopyroxene in high‐grade BIF of the Voronezh Crystalline Massif: evidence of ultrahigh‐temperature metamorphism |
title_sort |
exsolution textures of orthopyroxene and clinopyroxene in high‐grade bif of the voronezh crystalline massif: evidence of ultrahigh‐temperature metamorphism |
publisher |
Wiley |
publishDate |
2006 |
url |
http://dx.doi.org/10.1111/j.1525-1314.2006.00630.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.2006.00630.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.2006.00630.x |
long_lat |
ENVELOPE(-58.440,-58.440,-62.167,-62.167) |
geographic |
Napier |
geographic_facet |
Napier |
genre |
Antarc* Antarctica Enderby Land |
genre_facet |
Antarc* Antarctica Enderby Land |
op_source |
Journal of Metamorphic Geology volume 24, issue 2, page 135-151 ISSN 0263-4929 1525-1314 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1111/j.1525-1314.2006.00630.x |
container_title |
Journal of Metamorphic Geology |
container_volume |
24 |
container_issue |
2 |
container_start_page |
135 |
op_container_end_page |
151 |
_version_ |
1801369273534251008 |