Ma. Elburg et J. Foden, Geochemical response to varying tectonic settings: An example from southern Sulawesi (Indonesia), GEOCH COS A, 63(7-8), 1999, pp. 1155-1172
The South arm of Sulawesi was an active continental margin from approximate
ly 60 to 10 Ma, when it collided with the microcontinental fragment of Buto
n. pre-collisional samples analyzed for this study are characterized by a g
eochemical signature typical of are volcanics: high LILE/HFSE ratios; Sr-87
/Sr-86 slightly higher than MORB;Nd-143/Nd-144 ratios similar to MORE. Syn-
collisional samples have more enriched isotopic signatures, and are relativ
ely potassium rich. This is interpreted to reflect a larger contribution fr
om subducted sediments, added to the mantle wedge as a silicic melt. Meltin
g of subducted sediments is interpreted to result from a decrease in subduc
tion rate and an increase of temperature in the slab. Magmatism that postda
tes the collisional event by 10 Ma is characterized by higher Nb/Y ratios t
han the pre- or syn-collisional samples, and Sr and Nd isotopic signatures
intermediate between these two groups. This is likely to reflect melting of
a subduction-modified mantle, with a significant contribution from the sub
continental lithospheric mantle. Comparison with post-collisional magmatism
from other areas of the world suggests that trace element signatures are s
imilar, but isotopic characteristics are variable. The latter are likely to
reflect both the age of the sub-continental lithospheric mantle and the ri
me lag between cessation of subduction and formation of the post-collisiona
l magmas. Copyright (C) 1994 Elsevier Science Ltd.