Episodic rapakivi magmatism due to distal orogenesis? Correlation of 1.69-1.50 Ga orogenic and inboard, "anorogenic" events in the Baltic Shield

The temporal overlap of 1.69-1.55 Ga westward growth of the Baltic Shield and voluminous, episodic, 1.65-1.50 Ga rapakivi magmatism in the Svecofennian domain to the east has long been recognized. New U-Pb data from southwest Sweden indicate that this westward growth occurred in at least three disti...

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Bibliographic Details
Published in:Geology (Boulder) 2000-09, Vol.28 (9), p.823-826
Main Authors: Ahall, Karl-Inge, Connelly, James N, Brewer, Tim S
Format: Article
Language:English
Subjects:
Europe
Fennoscandian Shield
Geological time
Geology
granites
igneous and metamorphic rocks
igneous rocks
Lava
magmatism
Mesoproterozoic
orogenic belts
Petrology
plutonic rocks
Precambrian
Proterozoic
rapakivi
Scandinavia
southwestern Sweden
Structural geology
Sweden
syntectonic processes
tectonics
upper Precambrian
Western Europe
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Summary:The temporal overlap of 1.69-1.55 Ga westward growth of the Baltic Shield and voluminous, episodic, 1.65-1.50 Ga rapakivi magmatism in the Svecofennian domain to the east has long been recognized. New U-Pb data from southwest Sweden indicate that this westward growth occurred in at least three distinct stages involving convergent-margin magmatism (Gothian orogenesis) at 1.69-1.65, 1.62-1.58, and 1.56-1.55 Ga. This improved resolution along the margin reveals an interesting temporal correlation between these events and the intracratonic rapakivi magmatism. Each stage of convergent-margin magmatism was echoed by a phase of bimodal rapakivi magmatism at 1.65-1.62, 1.58-1.56, and 1.55-1.50 Ga. In addition to this temporal correlation, rapakivi suites form distinct north-trending arrays that are subparallel to, but 500-1500 km east of, the active margin. These temporal and spatial links suggest that recurring subduction along oceanward-stepping zones provided first-order control(s) on episodic mantle melting and consequent bimodal rapakivi magmatism in distal, inboard settings. At the very least, emerging constraints from Baltica do not support previous, purely anorogenic models for the 1.65-1.50 Ga rapakivi magmatism or models that singularly implicate lingering effects from the preceding Svecofennian orogeny.
ISSN:0091-7613
1943-2682
DOI:10.1130/0091-7613(2000)28<823:ERMDTD>2.0.CO;2