Basal lherzolites in the Bay of Islands Ophiolite: origin by detachment-related telescoping of a ridge-parallel melting gradient
✍ Scribed by Suhr; Batanova
- Book ID
- 104463190
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 234 KB
- Volume
- 10
- Category
- Article
- ISSN
- 0954-4879
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✦ Synopsis
Decompression melting under a spreading centre should generate a residual upper mantle section with a weak vertical gradient in the degree of chemical depletion. Chemical data from the 6 km‐thick ophiolitic mantle section of the Table Mountain massif (Bay of Islands Ophiolite, Newfoundland) reveal, however, a depletion gradient of 1% melting/100 m in the basal mantle section of the massif. Within the framework of a segmented ridge we suggest that during ophiolite detachment intermittent accretion of progressively less depleted peridotites occurred to the (former) base of the ophiolite, amounting to a several hundred metre‐thick lherzolitic sole. In this view, the basal mantle section in Table Mountain extends a structural concept previously established for the metamorphic sole: both metamorphic gradient in the sole and melting gradient in the basal mantle rocks are apparent and of tectonic nature. Like the sole, the basal mantle sequence may thus expose mantle material derived from a scale larger than the preserved ophiolite complex.