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Geochemistry of basalt from the super-segment of the Australian-Antarctic Ridge

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Title
Geochemistry of basalt from the super-segment of the Australian-Antarctic Ridge
Other Titles
호주-남극 중앙해령 거대 맨틀 부분에서 나온 현무암 지구화학 연구
Authors
Park, Sung Hyun
Langmuir, Charles H.
Michael, Peter J.
Sims, Kenneth W. W.
Scott, Sean R.
Blichert-Toft, Janne
Kim, Seung-Sep
Lin, Jian
Choi, Hakkyum
Yang, Yun Seok
Issue Date
2019
Citation
Park, Sung Hyun, et al. 2019. Geochemistry of basalt from the super-segment of the Australian-Antarctic Ridge. Polar Symposium. KOPRI. 2019.05.14~2019.05.15.
Abstract
The 300-km-long super-segment in the middle of the Australian-Antarctic Ridge system is a first-order segment bounded by two large-offset transform faults, with an intermediate spreading rate (70 mm/yr) and relatively shallow axial depth (~2,000 m). This super-segment has only small offsets along its entire length, but there are large varitions in axial morphology. From west to east, there is an axial high plateau, a small rift valley, a narrow axial high with small graben, a flat region with no high or valley, and a pronounced axial valley in the east. Magmatism is highly variable in its morphological expression along strike. Most recovered samples by wax coring are very fresh slightly phyric basaltic glasses. MgO contents of the lavas, indicative of eruption temperature, do not correlate well with axial depth. Sub-segments with an axial high in the middle of the segment tend to have MgO contents of less than 8 wt.%, while sub-segments with a rift valley are associated with MgO of around 8 wt.%. A few andesites were recovered from the western ridge- transform intersection (MgO < 4.3 wt.%), as well as a single recovery in the middle of the super-segment. This indicate the magmatic fractionation was intensively going on beneath the middle of the super-segment. The large variations of La/Sm and Sr-Nd-Pb-Hf isotopes indicate that the mantle beneath the super-segment is highly heterogeneous. Variations in axial morphology from axial high to rift valley correspond with large changes in La/Sm and Sr- Nd-Pb-Hf isotopic composition, suggesting that mantle composition is influencing ridge morphology. However, several samples from the western sub- segments are isotopically enriched, but low in La/Sm similar to N-MORB, suggesting recent depletion processes were occurred in this section. Mantle heterogeneity and recent dynamic process beneath the super-segment might strongly influenced to the geochemistry and morphology of the super- segment.
URI
https://repository.kopri.re.kr/handle/201206/12495
Conference Name
Polar Symposium
Conference Place
KOPRI
Conference Date
2019.05.14~2019.05.15
Type
Proceeding
Indexed
세미나-학술발표
Appears in Collections  
2019-2019, Characterizing mantle domain beneath West Antarctic Rift System and Antarctic mid-ocean ridges (19-19) / Park, Yongcheol (PE19050)
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