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Title: Age and duration of the British Tertiary Igneous Province : implications for the development of the ancestral Iceland Plume
Author: Chambers, Lynne Marie
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2000
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Detailed sampling of the lava successions in the BTIP has allowed stratigraphic changes in geochemistry to be determined. These changes were then correlated using a new set of internally consistent 40Ar/39Ar ages precise enough to determine the age and duration of the individual areas in the BTIP. The work presented here shows that the duration of volcanic activity in the BTIP can be confined to within the 3 m.y. of Chron 26r, (60.92-57.99 Ma, Berggren et al, 1995). Only the granites in the later centres in Antrim and Skye are younger than Chron 26r. The new ages highlight a problem in correlating the magnetic stratigraphy of the BTIP to the existing time scale. Precise dates of rocks with normal magnetic polarity place them within Chron 26r, and this paradox can be best resolved by moving the Palaeocene-Eocene boundary to an older position by at least 500,000 years and by postulating the existence of cryptochrons within Chron 26r. Basalts with an 'Icelandic' mantle source are readily distinguished from those with an N-MORB-like source by DNb (= 1.74 + log(Nb/y) -1.92 * log(Zr/Y)). Most of the BTIP basaltic magmas had negative DNb, implying an N-MORB-like mantle plume source. However, stratigraphic changes within the thicker lava succession of Mull, Antrim and Skye suggest that a change from negative to positive DNb occurred simultaneously across the province less than 1 m.y. after the onset of volcanism. This change marked the first arrival of 'Icelandic' plume material or plume core material into the BTIP. After this time, the mantle source of the basalts alternated, with both components of the plume regularly being sampled simultaneously. The large proportion of basalts with an N-MORB-like mantle source in the BTIP suggests that a large volume of the ancestral plume head comprised hot upper mantle material, originating from the thermal boundary layer above the 670 km discontinuity.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available