Tectonics of triple junction at divergent plate boundaries.

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 16540376
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Solid earth and planetary physics
• Research Institution: Chiba University
• Principal Investigator: NAKANISHI Masao Chiba University, Graduate School of Science and Technology, Associate Professor, 大学院自然科学研究科, 助教授 (80222165)
• Project Period (FY): 2004 – 2006
• Keywords: triple junction / spreading system / abyssal hills / bathymetry / magnetic anomaly lineation / mantle Bouguer anomaly / Pacific Plate / Indian Ocean

Research Abstract

I studied the following triple junctions.
1. Rodriguez Triple Junction (Indian Ocean)
I made precise bathymetric, magnetic anomaly lineations, and residual mantle Bouguer gravity anomaly maps around the Rodriguez Triple Junction. I exposed the detailed tectonic history of the triple junction.
2. Spreading system in the Gulf of Aden (Indian Ocean)
I made precise bathymetric, and mantle Bouguer gravity anomaly maps around spreading system in the Gulf of Aden, which connects to the Afar Triple Junction. The maps show the detail topographic and crustal structures of the spreading system.
3. Pacific-Izanagi-Farallon Triple Junction (Pacific Ocean)
I exposed the triple junction trace of the Pacific-Izanagi-Farallon Triple Junction in Late Jurassic using the detailed bathymetric map as well as the revised magnetic anomaly lineation map. I revealed the tectonic history of the fracture zone born near the triple junction.
4. Pacific-Farallon-Phoenix Triple Junction (Pacific Ocean)
I exposed the tectonic evolution of the Manihiki Plateau that had been situated near the Cretaceous Pacific-Farallon-Phoenix Triple Junction from the detailed bathymetric map of the central part of the plateau.
5. Pacific-Izanagi-Phoenix Triple Junction (Pacific Ocean)
I revised the Mesozoic Pacific magnetic anomaly lineation map. The map gives me the information of the plate boundaries around the Pacific-Izanagi-Phoenix Triple Junction.

Research Products

• [Journal Article] Depleted mantle wedge and sediment fingerprint in unusual basalts from the Manihiki Plateau, Central Pacific Ocean (2007)
  • Author(s): Ingle, S.
  • Journal Title: Geology (印刷中)
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Depleted mantle wedge and sediment fingerprint in unusual basalts from the Manihiki Plateau, Central Pacific Ocean (2007)
  • Author(s): Ingle, S., J.J.Mahoney, H.Sato, M.F.Coffin, J.Kimura, N.Hirano, M.Nakanishi
  • Journal Title: Geology, (in press)
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Tectonic Setting of the Danger Islands Troughs in the Manihiki Plateau (2004)
  • Author(s): Nakanishi, M.
  • Journal Title: EOS Trans. AGU 85 Pages: T41A-1156
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Tectonic Setting of the Danger Islands Troughs in the Manihiki Plateau (2004)
  • Author(s): Nakanishi, M., M.F.Coffin, J.J.Mahoney, K.Koizumi, A.Tikku, H.Sato, S.Ingle, R.Miura, H.Kato, M.Kaida, P.Shamberger
  • Journal Title: EOS Trans. AGU, 85 Pages: T41A-1156
  • Description: 「研究成果報告書概要(欧文)」より