Publication Date:
2016-02-16
Description:
The growth of oceanic plates at mid-ocean ridges, crustal accretion, occurs by a combination of magmatic and tectonic
processes. Magmatic processes along ridges spreading at fast, intermediate and slowrates, continually add volcanic material to
a centrally located spreading axis. This creates a narrowband of young volcanic rocks. However, at ridges spreading at ultraslow
rates, diminished volcanism allows entire blocks of mantle to spread on the sea floor by tectonic processes. Remote imaging
has advanced our observational understanding of crustal accretion, but temporal constraints are required to quantitatively
understand ultraslow-spreading ridge construction. Here, we use U-series eruption ages of volcanic rocks collected from the
ultraslow-spreading Southwest Indian Ridge. Unexpectedly, we find young volcanic eruption ages that are broadly dispersed
throughout the rift valley, indicating that crustal accretion of young volcanic rocks is not confined to a narrow central spreading
axis. As areas of young volcanism are observed close to distinct fault surfaces, we propose that the widely dispersed volcanism
may result frommagma rising along faults. Our results indicate that axial-centric spreading models may not accurately describe
crustal accretion at ultraslow-spreading ridges, prompting the re-evaluation of these models.
Type:
Article
,
PeerReviewed
Format:
text
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