https://repository.kopri.re.kr/handle/201206/5288 2026-04-12T05:25:43Z https://repository.kopri.re.kr/handle/201206/9662 Title: An isotopically distinct Zealandia？Antarctic mantle domain in the Southern Ocean Authors: Park, Sung Hyun; Langmuir, Charles H.; Sims, Kenneth W. W.; Blichert-Toft, Janne; Kim, Seung-Sep; Scott, Sean R.; Lin, Jian; Choi, Hakkyum; Yang, Yun Seok; Michael, Peter J. Abstract: The mantle sources of mid-ocean ridge basalts beneath the Indian and Pacific oceans have distinct isotopic compositions with a long-accepted boundary at the Australian？Antarctic Discordance along the Southeast Indian Ridge. This boundary has been widely used to place constraints on large-scale patterns of mantle flow and composition in the Earth's upper mantle. Sampling between the Indian and Pacific ridges, however, has been lacking, especially along the remote 2,000？km expanse of the Australian？Antarctic Ridge. Here we present Sr, Nd, Hf and Pb isotope data from this region that show the Australian？ Antarctic Ridge has isotopic compositions distinct from both the Pacific and Indian mantle domains. These data define a separate Zealandia？Antarctic domain that appears to have formed in response to the deep mantle upwelling and ensuing volcanism that led to the break-up of Gondwana 90？million years ago, and currently persists at the margins of the Antarctic continent. The relatively shallow depths of the Australian？Antarctic Ridge may be the result of this deep mantle upwelling. Large offset transforms to the east may be the boundary with the Pacific domain. 2019-03-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/9521 Title: Petrogenesis of basalts along the eastern Woodlark spreading center, equatorial western Pacific Authors: Park, Sung Hyun; Lee, Kyeong Yong; Hauff, Folkmar; Lee, Sang-Mook; Kamenov, George D.; Michael, Peter J. Abstract: Seafloor spreading in the Woodlark Basin is taking place on pre-existing arc crust that was produced by the sub- duction of the Indo-Australian Plate into the Pocklington Trough (now inactive) to the south during the Paleo- gene. The Woodlark Basin has a unique tectonic setting characterized by two surrounding subduction zones. To the east, a spreading ridge is also currently being subducted beneath the Solomon Arc. Moreover, long-term subduction ofthe Pacific Plateoccurredinthisarea,which was halted by thecollision of theOntong？Java Plateau withtheVitiazTrench atca.10 Ma.Any oneofthesesubductionzonescouldhaveinfluencedthemantlebeneath the Woodlark Basin. In this study, basalts from the eastern Woodlark Basin spreading center (EWLB; eastern WoodlarkBasinbasalts) wereanalyzedfor majorand trace element compositions and Sr-Nd-Pb isotopiccompo- sitionsto investigate themelting processes andmantleheterogeneity inthis unusualtectonic setting. Our results show that theEWLB canbeclassifiedintothreetypes basedonmajorand trace elements, and Sr？Nd？Pb isotopic characteristics: normal EWLB (N-EWLB), very depleted EWLB (VD-EWLB), and ultra-depleted EWLB (UD-EWLB). N-EWLB are similar to normal mid-ocean ridge basalts (N-MORB) and comprise most of the EWLB. The EWLB formed from local mantle, which is similar to depleted MORB mantle. VD-EWLB are more de- pleted than N-EWLB and have a weak subduction fingerprint. These rocks are characterized by increasing Nb/La with increasing Sm/La, which is a trend that is not produced by peridotite melting. As such, VD-EWLB may have formed by melting of a source containing residual eclogite that had previously undergone low-degree partial melting during subduction, leaving residual rutile in the source. UD-EWLB are extremely depleted relative to globalMORB,haveelevatedH 2 O/CeandBa/Nb ratios similartoback-arcbasinbasalts (BABB),andlower concen- trations of H 2 O and Ba than N-MORB. We propose that UD-EWLB was derived from sub-arc residual mantle that wasenrichedbyfluidandthenexperiencedmeltdepletion.ThesubductionfingerprintsintheVD-andUD-EWLB are not related to the current ridge subduction or earlier, long-term subduction of the Pacific Plate in the northeast of the basin, as they are geochemically distinct from the Solomon Arc, which was strongly influenced by both these subduction systems. Instead, we suggest that the subduction fingerprint of the VD- and UD-EWLB was produced during Paleogene subduction of the Indo-Australian Plate to the south. 2018-09-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/6455 Title: Geographical structure of endosymbiotic bacteria hosted by Bathymodiolus mussels at eastern Pacific hydrothermal vents Authors: Phuong-Thao Ho; Won, Yong-Jin; Robert C. Vrijenhoek; Jang, Sook-Jin; Kim, Kangchon; Kim, Eun Hye; Hong, Soon Gyu; Park, Eunji Abstract: Background: Chemolithoautotrophic primary production sustains dense invertebrate communities at deep-sea hydrothermal vents and hydrocarbon seeps. Bathymodiolin mussels, which thrive in these environments, are nourished by symbiotic bacteria that oxidize dissolved sulfur, methane, and hydrogen gases. The mussel symbionts are newly acquired in each generation via infection by free-living forms. This study examined geographical subdivision of the thiotrophic endosymbionts hosted by Bathymodiolus mussels living along the eastern Pacific hydrothermal vents. High-throughput sequencing data of 16S ribosomal RNA encoding gene and fragments of six protein-coding genes of symbionts were examined in the samples collected from nine vent localities at the East Pacific Rise, Galapagos Rift, and Pacific-Antarctic Ridge. Results: Both of the parapatric sister-species, B. thermophilus and B. antarcticus, hosted the same numerically dominant phylotype of thiotrophic Gammaproteobacteria. However, sequences from six protein-coding genes revealed highly divergent symbiont lineages living north and south of the Easter Microplate and hosted by these two Bathymodiolus mussel species. High heterogeneity of symbiont haplotypes among host individuals sampled from the same location suggested that stochasticity associated with initial infections was amplified as symbionts proliferated within the host individuals. The mussel species presently contact one another and hybridize along the Easter Microplate, but the northern and southern symbionts appear to be completely isolated. Vicariance associated with orogeny of the Easter Microplate region, 2.5？5.3 million years ago, may have initiated isolation of the symbiont and host populations. Estimates of synonymous substitution rates for the protein-coding bacterial genes examined in this study were 0.77？1.62%/nucleotide/million years. Conclusions: Our present study reports the most comprehensive population genetic analyses of the chemosynthetic endosymbiotic bacteria based on high-throughput genetic data and extensive geographical sampling to date, and demonstrates the role of the geographical features, the Easter Microplate and geographical distance, in the intraspecific divergence of this bacterial species along the mid-ocean ridge axes in the eastern Pacific. Altogether, our results provide insights into extrinsic and intrinsic factors affecting the dispersal and evolution of chemosynthetic symbiotic partners in the hydrothermal vents along the eastern Pacific Ocean. 2017-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/8953 Title: Investigation of tectonics, mantle characteristics and hydrothermal vent in Australian-Antarctic Ridges, Antarctica Authors: Hahm, Doshik 2016-05-20T00:00:00Z