TY - JOUR
T1 - Temporal geochemical trends in Kerguelen Archipelago basalts
T2 - Evidence for decreasing magma supply from the Kerguelen Plume
AU - Frey, F. A.
AU - Weis, D.
AU - Yang, H. J.
AU - Nicolaysen, K.
AU - Leyrit, H.
AU - Giret, A.
PY - 2000/3/6
Y1 - 2000/3/6
N2 - The Kerguelen Archipelago, a ~39 Ma to recent volcanic-plutonic complex, is interpreted to be a manifestation of the Kerguelen Plume. Most, ~85%, of the surface area is covered by flood basalts ranging in age from ~29 to 25 Ma. The youngest (~25 Ma) studied flood basalts are in the Southeast (SE) Province of the archipelago. A composite 460 m section of this southeast flood basalt dominantly consists of evolved (3 to 6% MgO) alkalic basalt and trachybasalt with a few interbedded highly evolved lavas (trachyandesites), a 40-70 m conglomerate which contains lignite beds, and a trachytic breccia/tuff unit. All of the lavas in this composite section have Sr and Nd isotopic ratios that are typical of the Kerguelen Plume; e.g., >80% of the 115 analyzed archipelago lavas with >2.3% MgO have (87Sr/86Sr)(i) = 0.70515 ± 12 and (143Nd/144Nd)(i) = 0.51259 ± 5. These ranges include the southeast flood basalts. Pb isotopes, however, are more variable; these 25 Ma lavas have high 206Pb/204Pb at ~18.4 to 18.6, relative to other archipelago lavas. The temporal trend of the archipelago flood basalt from older, ~29 Ma, transitional basalts to younger, ~25 Ma, alkalic basalt with an increasing proportion of highly evolved lavas and intra-bedded sediments in the relatively young southeast section indicates: (a) a temporal decrease in extent of melting and (b) a decreasing supply of magma from the plume to the crust. These temporal trends are attributed to increasing lithosphere thickness as the plume evolved from a spreading ridge-centered plume at ~43 Ma to its intraplate setting. Supporting evidence for this interpretation is: (a) the absence of a MORB geochemical signature in these 25 Ma lavas; and (b) the relatively low abundances of heavy rare-earth elements in these southeast lavas which reflect partial melting within the garnet stability field. (C) 2000 Elsevier Science B.V. All rights reserved.
AB - The Kerguelen Archipelago, a ~39 Ma to recent volcanic-plutonic complex, is interpreted to be a manifestation of the Kerguelen Plume. Most, ~85%, of the surface area is covered by flood basalts ranging in age from ~29 to 25 Ma. The youngest (~25 Ma) studied flood basalts are in the Southeast (SE) Province of the archipelago. A composite 460 m section of this southeast flood basalt dominantly consists of evolved (3 to 6% MgO) alkalic basalt and trachybasalt with a few interbedded highly evolved lavas (trachyandesites), a 40-70 m conglomerate which contains lignite beds, and a trachytic breccia/tuff unit. All of the lavas in this composite section have Sr and Nd isotopic ratios that are typical of the Kerguelen Plume; e.g., >80% of the 115 analyzed archipelago lavas with >2.3% MgO have (87Sr/86Sr)(i) = 0.70515 ± 12 and (143Nd/144Nd)(i) = 0.51259 ± 5. These ranges include the southeast flood basalts. Pb isotopes, however, are more variable; these 25 Ma lavas have high 206Pb/204Pb at ~18.4 to 18.6, relative to other archipelago lavas. The temporal trend of the archipelago flood basalt from older, ~29 Ma, transitional basalts to younger, ~25 Ma, alkalic basalt with an increasing proportion of highly evolved lavas and intra-bedded sediments in the relatively young southeast section indicates: (a) a temporal decrease in extent of melting and (b) a decreasing supply of magma from the plume to the crust. These temporal trends are attributed to increasing lithosphere thickness as the plume evolved from a spreading ridge-centered plume at ~43 Ma to its intraplate setting. Supporting evidence for this interpretation is: (a) the absence of a MORB geochemical signature in these 25 Ma lavas; and (b) the relatively low abundances of heavy rare-earth elements in these southeast lavas which reflect partial melting within the garnet stability field. (C) 2000 Elsevier Science B.V. All rights reserved.
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U2 - 10.1016/S0009-2541(99)00144-8
DO - 10.1016/S0009-2541(99)00144-8
M3 - Article
AN - SCOPUS:0034611174
VL - 164
SP - 61
EP - 80
JO - Chemical Geology
JF - Chemical Geology
SN - 0009-2541
IS - 1-2
ER -