Flood Basalt to Rhyolite Suites in the Southern Paranà Plateau (Brazil): Palaeomagnetism, Petrogenesis and Geodynamic Implications
The petrology and palaeomagnetism of basic and acidic volcanic rocks of the Paran� plateau (South Brazil) have been investigated. The lower sections of the sequence are largely composed of tholeiitic basalts and tholeiitic basaltic andesites while the upper portions are essentially represented by rh...
Published in: | Journal of Petrology |
---|---|
Main Authors: | , , , , , , |
Format: | Text |
Language: | English |
Published: |
Oxford University Press
1984
|
Subjects: | |
Online Access: | http://petrology.oxfordjournals.org/cgi/content/short/25/3/579 https://doi.org/10.1093/petrology/25.3.579 |
id |
fthighwire:oai:open-archive.highwire.org:petrology:25/3/579 |
---|---|
record_format |
openpolar |
spelling |
fthighwire:oai:open-archive.highwire.org:petrology:25/3/579 2023-05-15T18:21:10+02:00 Flood Basalt to Rhyolite Suites in the Southern Paranà Plateau (Brazil): Palaeomagnetism, Petrogenesis and Geodynamic Implications BELLIENI, G. BROTZU, P. COMIN-CHIARAMONTI, P. ERNESTO, M. MELFI, A. PACCA, I. G. PICCIRILLO, E. M. 1984-08-01 00:00:00.0 text/html http://petrology.oxfordjournals.org/cgi/content/short/25/3/579 https://doi.org/10.1093/petrology/25.3.579 en eng Oxford University Press http://petrology.oxfordjournals.org/cgi/content/short/25/3/579 http://dx.doi.org/10.1093/petrology/25.3.579 Copyright (C) 1984, Oxford University Press Articles TEXT 1984 fthighwire https://doi.org/10.1093/petrology/25.3.579 2007-06-24T18:36:11Z The petrology and palaeomagnetism of basic and acidic volcanic rocks of the Paran� plateau (South Brazil) have been investigated. The lower sections of the sequence are largely composed of tholeiitic basalts and tholeiitic basaltic andesites while the upper portions are essentially represented by rhyodacites showing intercalations of basaltic and/or andesitic rock-types. Tholeiitic andesites prevail at the basic-acidic boundary. Petrography, mineral chemistry and bulk-rock composition (major and trace elements) data clearly define tholeiitic suites displaying possible liquid lines of descent related to different degrees of partial melting and crystal fractionation controls. Mass balance calculations, based on phenocrysts and/or microphenocrysts present in the different rock-types are consistent with the hypothesis that rhyodacitic melts may be derived from basalts through low-pressure crystal fractionation processes accompanied by crustal contamination. Palaeomagnetic data indicate high rates of magma emission (e.g. 700 m in <1 m.y.) and sometimes the contemporaneous eruption in different areas of basic and acidic lavas. Moreover, the positions of the palaeomagnetic poles indicate that the volcanic fields of Paran� and Namibia (southern Africa) were joined at 120 m.y. B.P. All the data consistently indicate that Paran� volcanism occurred during the Lower Cretaceous after the formation of up-doming structures, and that the initial opening of the South Atlantic Ocean, at the latitudes of the Paran� basin, occurred not before 120 m.y. B.P. Text South Atlantic Ocean HighWire Press (Stanford University) Journal of Petrology 25 3 579 618 |
institution |
Open Polar |
collection |
HighWire Press (Stanford University) |
op_collection_id |
fthighwire |
language |
English |
topic |
Articles |
spellingShingle |
Articles BELLIENI, G. BROTZU, P. COMIN-CHIARAMONTI, P. ERNESTO, M. MELFI, A. PACCA, I. G. PICCIRILLO, E. M. Flood Basalt to Rhyolite Suites in the Southern Paranà Plateau (Brazil): Palaeomagnetism, Petrogenesis and Geodynamic Implications |
topic_facet |
Articles |
description |
The petrology and palaeomagnetism of basic and acidic volcanic rocks of the Paran� plateau (South Brazil) have been investigated. The lower sections of the sequence are largely composed of tholeiitic basalts and tholeiitic basaltic andesites while the upper portions are essentially represented by rhyodacites showing intercalations of basaltic and/or andesitic rock-types. Tholeiitic andesites prevail at the basic-acidic boundary. Petrography, mineral chemistry and bulk-rock composition (major and trace elements) data clearly define tholeiitic suites displaying possible liquid lines of descent related to different degrees of partial melting and crystal fractionation controls. Mass balance calculations, based on phenocrysts and/or microphenocrysts present in the different rock-types are consistent with the hypothesis that rhyodacitic melts may be derived from basalts through low-pressure crystal fractionation processes accompanied by crustal contamination. Palaeomagnetic data indicate high rates of magma emission (e.g. 700 m in <1 m.y.) and sometimes the contemporaneous eruption in different areas of basic and acidic lavas. Moreover, the positions of the palaeomagnetic poles indicate that the volcanic fields of Paran� and Namibia (southern Africa) were joined at 120 m.y. B.P. All the data consistently indicate that Paran� volcanism occurred during the Lower Cretaceous after the formation of up-doming structures, and that the initial opening of the South Atlantic Ocean, at the latitudes of the Paran� basin, occurred not before 120 m.y. B.P. |
format |
Text |
author |
BELLIENI, G. BROTZU, P. COMIN-CHIARAMONTI, P. ERNESTO, M. MELFI, A. PACCA, I. G. PICCIRILLO, E. M. |
author_facet |
BELLIENI, G. BROTZU, P. COMIN-CHIARAMONTI, P. ERNESTO, M. MELFI, A. PACCA, I. G. PICCIRILLO, E. M. |
author_sort |
BELLIENI, G. |
title |
Flood Basalt to Rhyolite Suites in the Southern Paranà Plateau (Brazil): Palaeomagnetism, Petrogenesis and Geodynamic Implications |
title_short |
Flood Basalt to Rhyolite Suites in the Southern Paranà Plateau (Brazil): Palaeomagnetism, Petrogenesis and Geodynamic Implications |
title_full |
Flood Basalt to Rhyolite Suites in the Southern Paranà Plateau (Brazil): Palaeomagnetism, Petrogenesis and Geodynamic Implications |
title_fullStr |
Flood Basalt to Rhyolite Suites in the Southern Paranà Plateau (Brazil): Palaeomagnetism, Petrogenesis and Geodynamic Implications |
title_full_unstemmed |
Flood Basalt to Rhyolite Suites in the Southern Paranà Plateau (Brazil): Palaeomagnetism, Petrogenesis and Geodynamic Implications |
title_sort |
flood basalt to rhyolite suites in the southern paranà plateau (brazil): palaeomagnetism, petrogenesis and geodynamic implications |
publisher |
Oxford University Press |
publishDate |
1984 |
url |
http://petrology.oxfordjournals.org/cgi/content/short/25/3/579 https://doi.org/10.1093/petrology/25.3.579 |
genre |
South Atlantic Ocean |
genre_facet |
South Atlantic Ocean |
op_relation |
http://petrology.oxfordjournals.org/cgi/content/short/25/3/579 http://dx.doi.org/10.1093/petrology/25.3.579 |
op_rights |
Copyright (C) 1984, Oxford University Press |
op_doi |
https://doi.org/10.1093/petrology/25.3.579 |
container_title |
Journal of Petrology |
container_volume |
25 |
container_issue |
3 |
container_start_page |
579 |
op_container_end_page |
618 |
_version_ |
1766200295396737024 |