Journal
JOURNAL OF GEODYNAMICS
Volume 47, Issue 1, Pages 30-38Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jog.2008.06.004
Keywords
Subduction; Slab rollback; Tear fault; Magmatism; Tyrrhenian Sea
Categories
Funding
- Italian CNR-NATO
- ARC [A39600213]
- Italian and Indonesian ultra-potassic rocks
- University of Queensland
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The magmatic island of Capraia in the northern Tyrrhenian Sea records late stages in the evolution of a retreating subduction zone following continental accretion. Subduction rollback in the northern Tyrrhenian Sea was accompanied by an eastward migrating magmatic arc that coincided with Capraia at similar to 7.7 Ma. This was followed by segmentation of the subducting slab through eastward propagating tear faults. We present high-precision. step-heating 40Ar/39Ar data that provide robust constraints for the timing of magmatism in Capraia, indicating that the island was subjected to two distinct magmatic episodes. The bulk of the island, characterised by typical calcalkaline, subduction-related volcanic rocks, formed during a relatively short period between 7.7 and 7.2 Ma. This major magmatic event was followed by a period of quiescence between 7.1 and 4.8 Ma. Magmatic activity resumed at 4.8 Ma, with the eruption of shoshonites from a monogenic centre in the southern part of the island. We interpret the latter as a magmatic event triggered by the formation of a tear fault within the subduction slab. The example provides a unique insight into the destruction of a subduction system during the interlinked process of subduction rollback, slab segmentation, and the development of slab tear faults. (c) 2008 Elsevier Ltd. All rights reserved.
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