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Anders Lindh

Anders Lindh

Professor emeritus

Anders Lindh

Has the tectonic regime of the Baltic Shield always remained the same?

Författare

  • Anders Lindh

Summary, in English

Recent theories on the growth of continental crust stress its formation in pre-Archean and Archean times with minor additions at later times. The Earth has gone through a unidirectional evolution including surface changes, the genesis of life and an important loss of energy. The energy loss drives tectonic processes, but at a rate declining with available energy and thus with time. Semiquantitative modelling of energy-changes and transport indicates important differences between today’s Earth and the Paleoproterozoic Earth. Actualistic but non-uniformitarian arguments suggest that principal tectonic processes have changed over time. The Baltic Shield displays a fundamental difference in conditions between the c. 0.9 Ga high-pressure metamorphism including the occurrence of eclogite in the western Sveconorwegian Orogen and c. 2 Ga low-pressure metamorphism in the eastern Svecokarelian Orogen. This suggests that modern platetectonic processes were operative at c. 0.9 Ga but leaves the question whether it was active during the Svecokarelian orogeny open. The lack of eclogite in the Svecokarelian Orogen is explained with a change with time of the geotherm slope. The occurrence of two generations of granitic rocks of different compositions in the Svecokarelian is easily explained by an increased mantle heat flow in a stratified continental crust. In contrast to calc-alkaline platetectonic compositions, alkali-calcic rocks occur in a quarter-circle around the Svecokarelian core. The question arises whether modern plate-processes successively replaced proto-plate processes during Paleo- and Mesoproterozoic times.

Avdelning/ar

  • Berggrundsgeologi

Publiceringsår

2022-02-08

Språk

Engelska

Sidor

59-70

Publikation/Tidskrift/Serie

GFF

Volym

144

Issue

1

Dokumenttyp

Artikel i tidskrift

Förlag

Taylor & Francis

Ämne

  • Geology

Nyckelord

  • Baltic Shield
  • crustal growth
  • energy loss
  • Mylonite Zone
  • proto-plate processes
  • Svecokarelian
  • Sveconorwegian
  • Temperature modelling

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1103-5897