Petrogenesis of E-type Mid-Ocean Ridge Basalts near Longitude 46.DEG.E, the Gulf of Aden

• ORIHASHI Yuji

  Earthquake Research Institute, The University of Tokyo

• HARAGUCHI Satoru

  Ocean Research Institute, The University of Tokyo

• ISHII Teruaki

  Ocean Research Institute, The University of Tokyo

• TAMAKI Kensaku

  Ocean Research Institute, The University of Tokyo

• AL-KHIRBASH Salah

  Department of Earth and Environment Sciences, Faculty of Science, Sana'a University

Bibliographic Information

Other Title

• アデン湾，東経４６°近傍のＥタイプ中央海嶺玄武岩類の成因
• アデンワン トウケイ 46 キンボウ ノ Eタイプ チュウオウカイレイゲンブガンルイ ノ セイイン

Abstract

We report major and trace element compositions for 45 fresh basalts from 13 dredge sites between 45.5° E and 49° E along the Gulf of Aden obtained during the Aden New Century cruise (KH-005 : RN Hakuho-maru, ORI, University of Tokyo). The basalts from Aden New Century (ANC) Seamount at around 45.5° E, discovered by bathymetric mapping during the cruise, have the highest Nb/Zr (0.22-0.27) and La/Sm_N (3.1-3.7) and show the strongest OIB signature among those in the Gulf of Aden. The longitudinal variation of Nb/Zr and La/Sm_N of the dredged basalts shows two enrichment peaks, i.e., first “keen” enrichment peak with OIB signature near ANC Seamount (45.5°E) and second “broad” enrichment peak with E-MORB signature along the ridge axis from 46° E to 48° E, and at 49° E, N-MORB is dominant. In spite of variable Nb/Zr and La/Sm_N, the estimated pressure of magma segregation and degree of partial melting from the dredged basalts, using reported results of experimental melting on spinel lherzolite, are relatively constant and almost similar to those of N- and T-MORBs in Pacific, Atlantic, and Indian Oceans. This suggests that the longitudinal variation of the dredged basalts reflects mantle compositions equilibrated with their primitive magmas. Nb/Zr, Nb/Y, and La/Sm_N systematics for the dredged basalts suggest binary magma mixing of the NMORB source with the OIB source, composed of FOZO (or C) mantle component with the incorporation of minor, if any, HIMU components.<BR>Recent studies (George et al., 1998; Orihashi et al., 1998) have suggested that two mantle plumes might be impinged beneath the Afar province in Eocene to Oligocene (45-30 Ma) and Miocene (19-15 Ma) times. Considering the above, two enrichment peaks of the mantle in the Gulf of Aden must be produced by two mantle plumes impinged in the Afar province and spread sideways sequentially, with the front of spreading first plume head corresponding to the broad enrichment peak. This broad peak is formed because the plume head emplaced beneath the lithosphere, producing a Large Igneous Province (30-26Ma), was progressively defused into and diluted by the upper mantle component (N-MORB source) over time.

Journal

• Journal of Geography (Chigaku Zasshi)

  Journal of Geography (Chigaku Zasshi) 112 (5), 732-749, 2003

  Tokyo Geographical Society

Keywords

• Gulf of Aden
• Afar
• rift system
• basalt
• MORB
• major and trace element compositions
• mantle plume
• mantle plume/lithosphere interaction process

Details

• CRID: 1390001204229864704
• NII Article ID: 10013950059
• NII Book ID: AN00322536
• DOI: 10.5026/jgeography.112.5_732
• ISSN: 18840884
• ISSN: 0022135X
• ISSN: http://id.crossref.org/issn/00221341
• NDL BIB ID: 6748520
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I6748520
• Text Lang: ja
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
• Abstract License Flag: Disallowed