Geochemical response to varying tectonic settings: an example from southern Sulawesi (Indonesia) |
| |
| Institution: | 1. Department of Geology and Environmental Earth Science, Miami University, Oxford, OH 45056, USA;2. State Key Laboratory of Continental Tectonics and Dynamics of China, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China;3. Department of Earth Science & Centre for Geobiology, University of Bergen, Bergen 5007, Norway;4. Department of Earth Sciences, The University of Hong Kong, Hong Kong, China |
| |
| Abstract: | The South arm of Sulawesi was an active continental margin from approximately 60 to 10 Ma, when it collided with the microcontinental fragment of Buton. Pre-collisional samples analyzed for this study are characterized by a geochemical signature typical of arc volcanics: high LILE/HFSE ratios; 87Sr/86Sr slightly higher than MORB; 143Nd/144Nd ratios similar to MORB. Syn-collisional samples have more enriched isotopic signatures, and are relatively potassium rich. This is interpreted to reflect a larger contribution from subducted sediments, added to the mantle wedge as a silicic melt. Melting of subducted sediments is interpreted to result from a decrease in subduction rate and an increase of temperature in the slab. Magmatism that postdates the collisional event by 10 Ma is characterized by higher Nb/Y ratios than 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 similar, but isotopic characteristics are variable. The latter are likely to reflect both the age of the sub-continental lithospheric mantle and the time lag between cessation of subduction and formation of the post-collisional magmas. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
