TY - JOUR

T1 - Contrasting rifted margin styles south of Greenland

T2 - Implications for mantle plume dynamics

AU - Nielsen, Thomas K.

AU - Larsen, Hans Christian

AU - Hopper, John R.

N1 - Funding Information: We wish to thank Dan Lizarralde, Trine Dahl-Jensen, Michael Storey, and Christoph Hieronymus for stimulating discussions and comments on earlier versions of this paper. Trine Dahl-Jensen is also thanked for supervision during the processing of line BGR/77-2. Karl Hinz provided access to the BGR-data. Geco-Prakla International Ltd. and their crew on M/V Geco-Echo collected the ICE-data. Norman Sleep and Millard Coffin are thanked for providing thoughtful and constructive reviews. This work was funded by the Danish National Research Foundation. [RV]

PY - 2002

Y1 - 2002

N2 - We present new and reprocessed seismic reflection data from the area where the southeast and southwest Greenland margins intersected to form a triple junction south of Greenland in the early Tertiary. During breakup at 56 Ma, thick igneous crust was accreted along the entire 1300-km-long southeast Greenland margin from the Greenland Iceland Ridge to, and possibly ~ 100 km beyond, the triple junction into the Labrador Sea. However, highly extended and thin crust 250 km to the west of the triple junction suggests that magmatically starved crustal formation occurred on the southwest Greenland margin at the same time. Thus, a transition from a volcanic to a non-volcanic margin over only 100-200 km is observed. Magmatism related to the impact of the Iceland plume below the North Atlantic around 61 Ma is known from central-west and southeast Greenland. The new seismic data also suggest the presence of a small volcanic plateau of similar age close to the triple junction. The extent of initial plume-related volcanism inferred from these observations is explained by a model of lateral flow of plume material that is guided by relief at the base of the lithosphere. Plume mantle is channelled to great distances provided that significant melting does not take place. Melting causes cooling and dehydration of the plume mantle. The associated viscosity increase acts against lateral flow and restricts plume material to its point of entry into an actively spreading rift. We further suggest that thick Archaean lithosphere blocked direct flow of plume material into the magma-starved southwest Greenland margin while the plume was free to flow into the central west and east Greenland margins. The model is consistent with a plume layer that is only moderately hotter, ~ 100-200°C, than ambient mantle temperature, and has a thickness comparable to lithospheric thickness variations, ~ 50-100 km. Lithospheric architecture, the timing of continental rifting and viscosity changes due to melting of the plume material are therefore critical parameters for understanding the distribution of magmatism.

AB - We present new and reprocessed seismic reflection data from the area where the southeast and southwest Greenland margins intersected to form a triple junction south of Greenland in the early Tertiary. During breakup at 56 Ma, thick igneous crust was accreted along the entire 1300-km-long southeast Greenland margin from the Greenland Iceland Ridge to, and possibly ~ 100 km beyond, the triple junction into the Labrador Sea. However, highly extended and thin crust 250 km to the west of the triple junction suggests that magmatically starved crustal formation occurred on the southwest Greenland margin at the same time. Thus, a transition from a volcanic to a non-volcanic margin over only 100-200 km is observed. Magmatism related to the impact of the Iceland plume below the North Atlantic around 61 Ma is known from central-west and southeast Greenland. The new seismic data also suggest the presence of a small volcanic plateau of similar age close to the triple junction. The extent of initial plume-related volcanism inferred from these observations is explained by a model of lateral flow of plume material that is guided by relief at the base of the lithosphere. Plume mantle is channelled to great distances provided that significant melting does not take place. Melting causes cooling and dehydration of the plume mantle. The associated viscosity increase acts against lateral flow and restricts plume material to its point of entry into an actively spreading rift. We further suggest that thick Archaean lithosphere blocked direct flow of plume material into the magma-starved southwest Greenland margin while the plume was free to flow into the central west and east Greenland margins. The model is consistent with a plume layer that is only moderately hotter, ~ 100-200°C, than ambient mantle temperature, and has a thickness comparable to lithospheric thickness variations, ~ 50-100 km. Lithospheric architecture, the timing of continental rifting and viscosity changes due to melting of the plume material are therefore critical parameters for understanding the distribution of magmatism.

KW - Accreting plate boundary

KW - Dehydration

KW - Lava channels

KW - Mantle plumes

KW - North Atlantic

KW - Rift zones

UR - http://www.scopus.com/inward/record.url?scp=0036302964&partnerID=8YFLogxK

U2 - 10.1016/S0012-821X(02)00616-7

DO - 10.1016/S0012-821X(02)00616-7

M3 - Journal article

AN - SCOPUS:0036302964

VL - 200

SP - 271

EP - 286

JO - Earth and Planetary Science Letters

JF - Earth and Planetary Science Letters

SN - 0012-821X

IS - 3-4

ER -