Petrology and geochemistry of mid-ocean ridge basalts from the southern central Indian ridge

Hiroshi Sato, Kentaro Nakamura, Hidenori Kumagai, Ryoko Senda, Tomoaki Morishita, Akihiro Tamura, Shoji Arai

研究成果: Chapter in Book/Report/Conference proceedingChapter

2 被引用数 (Scopus)

抄録

Two hydrothermal fields, the Kairei and Edmond hydrothermal fields, are known in the southern Central Indian Ridge (CIR). The Kairei hydrothermal field at 25°19′S is associated with hydrogen-rich hydrothermal activity, whereas the Edmond hydrothermal field at 23°52′S is recognized in the typical mid-ocean ridge type hydrothermal activity. Differences of lithology and geological background between two hydrothermal fields are reflected in the different type of hydrothermal activity. We recovered more than 870 kg of rock samples by dredging from the southern part of the CIR adjacent to the Kairei and Edmond hydrothermal fields during the KH-10-6 cruise. Here, we present new petrological and geochemical data for MORB samples taken between the CIR-S1 and CIR-S4 segments with the aim of constraining distributions of lithology at the southern CIR, and discuss the petrogenesis and the mantle source for these basalts. The MORB melts that formed rocks within the CIR-S1, CIR-S2, and CIR-S4 segments equilibrated with mantle olivine at approximately 10 kbar, and were erupted after undergoing only minor fractionation. MORB samples from the CIR-S4 segment have slightly depleted trace element compositions, whereas MORB samples from the off-ridge part of the CIR-S1 segment are highly depleted. MORB samples from the Knorr seamount have enriched compositions involved a minor amount of hotspot-derived material, as indicated by previous isotope analyses. The presence of a depleted MORB source beneath the off-ridge section of the CIR-S1 segment indicates that the older mantle material at the boundary between the CIR-S1 and CIR-S2 segments was highly depleted. In turn, this suggests that the source mantle beneath the southern CIR is heterogeneous both along and across the present spreading axis, and that the composition of the mantle in this area is a function of the degree of mixing between depleted and enriched sources.

本文言語英語
ホスト出版物のタイトルSubseafloor Biosphere Linked to Hydrothermal Systems
ホスト出版物のサブタイトルTAIGA Concept
出版社Springer Japan
ページ163-175
ページ数13
ISBN(電子版)9784431548652
ISBN(印刷版)9784431548645
DOI
出版ステータス出版済み - 1 1 2015
外部発表はい

All Science Journal Classification (ASJC) codes

  • 地球惑星科学(全般)

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