Abstract
Boron contents and boron isotopic compositions were determined for the uppermost 1.3 km section of typical 6.2 Ma oceanic crust from DSDP/ODP Hole 504B, Costa Rica Rift, Galapagos Spreading Center. Both the boron content and the δ11B value in the oceanic crust are controlled by two types of alteration: 1. (1) low-temperature alteration (0 to 60°C; Zones I and II) and 2. (2) high-temperature hydrothermal alteration (200 to 400°C; Zones III and IV). Basalts subjected to the low-temperature alteration are characterized by their relatively high boron contents (0.69 to 19.3 ppm) and high δ11B values (+2.2 to +10.6%.), indicating uptake of boron into secondary phases in equilibrium with seawater or evolved seawater. Hydrothermally altered basalts contain less abundant boron (0.17 to 0.52 ppm) and relatively constant δ11B values (-0.1 to +1.0%.). Although basalts from the upper part of these hydrothermal zones (<1300 mbsf) show equilibrated boron content and δ11B value with aqueous fluid, effective leaching of boron from basalt is predominant in the lower part (>1300 mbsf). Original boron content and δ11B value of the Hole 504B MORB were 0.35 ppm and +0.2%., respectively. The present data provide fundamental information in understanding of the distribution of boron and boron isotopes in the oceanic crust.
| Original language | English |
|---|---|
| Pages (from-to) | 1633-1639 |
| Number of pages | 7 |
| Journal | Geochimica et Cosmochimica Acta |
| Volume | 56 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - 1992 |
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ASJC Scopus subject areas
- Geochemistry and Petrology
Cite this
Boron isotope geochemistry of the oceanic crust from DSDP/ODP Hole 504B. / Ishikawa, Tsuyoshi; Nakamura, Eizou.
In: Geochimica et Cosmochimica Acta, Vol. 56, No. 4, 1992, p. 1633-1639.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Boron isotope geochemistry of the oceanic crust from DSDP/ODP Hole 504B
AU - Ishikawa, Tsuyoshi
AU - Nakamura, Eizou
PY - 1992
Y1 - 1992
N2 - Boron contents and boron isotopic compositions were determined for the uppermost 1.3 km section of typical 6.2 Ma oceanic crust from DSDP/ODP Hole 504B, Costa Rica Rift, Galapagos Spreading Center. Both the boron content and the δ11B value in the oceanic crust are controlled by two types of alteration: 1. (1) low-temperature alteration (0 to 60°C; Zones I and II) and 2. (2) high-temperature hydrothermal alteration (200 to 400°C; Zones III and IV). Basalts subjected to the low-temperature alteration are characterized by their relatively high boron contents (0.69 to 19.3 ppm) and high δ11B values (+2.2 to +10.6%.), indicating uptake of boron into secondary phases in equilibrium with seawater or evolved seawater. Hydrothermally altered basalts contain less abundant boron (0.17 to 0.52 ppm) and relatively constant δ11B values (-0.1 to +1.0%.). Although basalts from the upper part of these hydrothermal zones (<1300 mbsf) show equilibrated boron content and δ11B value with aqueous fluid, effective leaching of boron from basalt is predominant in the lower part (>1300 mbsf). Original boron content and δ11B value of the Hole 504B MORB were 0.35 ppm and +0.2%., respectively. The present data provide fundamental information in understanding of the distribution of boron and boron isotopes in the oceanic crust.
AB - Boron contents and boron isotopic compositions were determined for the uppermost 1.3 km section of typical 6.2 Ma oceanic crust from DSDP/ODP Hole 504B, Costa Rica Rift, Galapagos Spreading Center. Both the boron content and the δ11B value in the oceanic crust are controlled by two types of alteration: 1. (1) low-temperature alteration (0 to 60°C; Zones I and II) and 2. (2) high-temperature hydrothermal alteration (200 to 400°C; Zones III and IV). Basalts subjected to the low-temperature alteration are characterized by their relatively high boron contents (0.69 to 19.3 ppm) and high δ11B values (+2.2 to +10.6%.), indicating uptake of boron into secondary phases in equilibrium with seawater or evolved seawater. Hydrothermally altered basalts contain less abundant boron (0.17 to 0.52 ppm) and relatively constant δ11B values (-0.1 to +1.0%.). Although basalts from the upper part of these hydrothermal zones (<1300 mbsf) show equilibrated boron content and δ11B value with aqueous fluid, effective leaching of boron from basalt is predominant in the lower part (>1300 mbsf). Original boron content and δ11B value of the Hole 504B MORB were 0.35 ppm and +0.2%., respectively. The present data provide fundamental information in understanding of the distribution of boron and boron isotopes in the oceanic crust.
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U2 - 10.1016/0016-7037(92)90230-G
DO - 10.1016/0016-7037(92)90230-G
M3 - Article
AN - SCOPUS:0026442931
VL - 56
SP - 1633
EP - 1639
JO - Geochmica et Cosmochimica Acta
JF - Geochmica et Cosmochimica Acta
SN - 0016-7037
IS - 4
ER -