Submarine basalts of the Northern Kerguelen Plateau: Interaction between the Kerguelen Plume and the Southeast Indian Ridge revealed at ODP site 1140
Weis, D.; Frey, F.A. (2002). Submarine basalts of the Northern Kerguelen Plateau: Interaction between the Kerguelen Plume and the Southeast Indian Ridge revealed at ODP site 1140. J. Petrol. 43(7): 1287-1309. dx.doi.org/10.1093/petrology/43.7.1287
In: Journal of Petrology. Clarendon: Oxford. ISSN 0022-3530; e-ISSN 1460-2415, more
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| Author keywords |
isotopic geochemistry; Kerguelen plume; Northern Kerguelen Plateau; |
| Abstract |
During Ocean Drilling Program Leg 183, basaltic cores were retrieved from the Northern Kerguelen Plateau (NKP) at Site 1140 on the extreme north of the plateau, similar to270 km north of the Kerguelen Archipelago. Amongst the six basement units recovered, five were pillow basalts with fresh glassy rims together with flow lobes. This is the first evidence for submarine eruption anywhere on the Kerguelen Plateau. Each flow unit has distinct geochemical and isotopic characteristics that span the range from Southeast Indian Ridge (SEIR) mid-ocean ridge basalt to tholeiitic-transitional basalts derived from the Kerguelen mantle plume. Relationships between element abundance ratios involving incompatible elements and isotopic ratios reflect mixing of near-primary melts from an SEIR source and the Kerguelen plume with an increasing role for an incompatible element-rich end-member in the order: Unit 1 < 6 &LE; 5 < 2 < 3; that is, there is no systematic downcore geochemical variation. Modeling results show that the depleted SEIR component is dominant, ranging from 99-90% in Unit 1 to 76-63% in Unit 3. Comparison with Kerguelen Archipelago flood basalts with similar geochemical characteristics indicates that in the northern part of the archipelago, where 29-28 Ma tholeiitic-transitional basalts are present, incorporation of asthenospheric mantle by the plume on its way to the surface may have been significant. At 34 Ma, when Site 1140 basalts were formed, the SEIR was only &SIM;50 km away. Apparently, the proximity of the spreading center and plume allowed mixing of geochemically diverse magmas. In contrast to older Cretaceous parts of the Kerguelen Plateau, the Cenozoic Northern Kerguelen Plateau appears oceanic in origin and there is no evidence for a component derived from continental crust in Site 1140 basalts. |
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