Inferred oxygen isotope profile of Archaean oceanic crust, Onverwacht Group, South Africa

Nature ◽  
1986 ◽  
Vol 321 (6065) ◽  
pp. 55-58 ◽  
Author(s):  
S. E. Hoffman ◽  
M. Wilson ◽  
D. S. Stakes
Keyword(s):  
South Africa ◽  
Oxygen Isotope ◽  
Oceanic Crust ◽  
Isotope Profile

A complete oxygen isotope profile through the lower oceanic crust, ODP Hole 735B

2006 ◽  
Vol 233 (3-4) ◽  
pp. 217-234 ◽  
Author(s):  
Yongjun Gao ◽  
Jochen Hoefs ◽  
Reinhold Przybilla ◽  
Jonathan E. Snow
Keyword(s):  
Oxygen Isotope ◽  
Oceanic Crust ◽  
Isotope Profile ◽  
Lower Oceanic Crust

Typical oxygen isotope profile of altered oceanic crust recorded in continental intraplate basalts

2017 ◽  
Vol 28 (4) ◽  
pp. 578-587 ◽  
Author(s):  
Huan Chen ◽  
Qun-Ke Xia ◽  
Etienne Deloule ◽  
Jannick Ingrin
Keyword(s):  
Oxygen Isotope ◽  
Oceanic Crust ◽  
Isotope Profile

Oxygen isotope and trace element compositions of platiniferous dunite pipes of the Bushveld Complex, South Africa – Signals from a recycled mantle component?

Lithos ◽  
2018 ◽  
Vol 310-311 ◽  
pp. 332-341 ◽  
Author(s):  
T. Günther ◽  
K.M. Haase ◽  
M. Junge ◽  
T. Oberthür ◽  
D. Woelki ◽  
...  
Keyword(s):  
South Africa ◽  
Trace Element ◽  
Oxygen Isotope ◽  
Bushveld Complex ◽  
Mantle Component

scholarly journals A 40 Year Record in an Ice Core from the Dunde Ice Cap, China (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 221 ◽  
Author(s):  
Wu Xiaoling ◽  
Lonnie G. Thompson
Keyword(s):  
Oxygen Isotope ◽  
Ice Core ◽  
Field Work ◽  
Tibet Plateau ◽  
Ice Thickness ◽  
Ice Cap ◽  
Pulse Radar ◽  
The North ◽  
Isotope Profile ◽  
Isotope Content

A cooperative glacio-climatological ice-core drilling and analysis program, administered by LIGC and BPRC, has been carried out since 1984. The major objective of this study is to extract from the Dunde ice cap records of the general environmental conditions, which include drought, volcanic activity, moisture sources, glacier net balance and possibly temperature over the last 3000 years. In 1984 a group of 18 Chinese scientists and an American scientist spent 6 weeks on the Dunde ice cap. The central objective of their research was to evaluate the potential of the ice cap to yield a lengthy ice-core climate record. Results of the 1984 field work and 1985 laboratory analysis are submitted here. The Dunde ice cap (38°96′N, 96°24.5′E) is located in the north-eastern section of the Tibet plateau, China. Its length is 10.9 km; the width varies from 2.5 to 7.5 km. The total area of the ice cap is 57 km2. A 16 m core was drilled at the first site, located on a flat part of the ice cap, 5150 m a.s.l. A 10.2 m ice core was drilled at the ice cap summit (5300 m). A series of shallow cores and 2 m pits were excavated at each of the two sites and in the lower section of the ice cap. A mono-pulse radar unit was used to determine ice thickness. The ice thickness ranged between 94 and 167 m, with an average thickness of 140 m. Using a thermistor cable, minimum temperatures of −9.1° and −9.5 °C were measured in the 16 m hole and 10.2 m hole respectively. Microparticle analysis of the ice core from the Dunde ice cap revealed a very high dust content, on average 16 × 105 particles (≥0.63 to ≤16 μ in diameter) per ml of sample, i.e. 3−4 times higher than the microparticle content in the Quelccaya ice cap, Peru, and 100 times higher than in the core from Byrd Station, Antarctica. Oxygen-isotope content ranged between −12 and −14 per mil. Initially it was anticipated that the oxygen-isotope content would produce a more negative value in the Dunde ice cap. More work is required to explain the mechanism controlling δ18o variation in the ice core from the Dunde ice cap. The microparticles, oxygen-isotope content, conductivity, and tritium measurements, together with stratigraphy, temperature and density, are presented in the figures. The 40 year net-balance record reconstructed from the ice-core and oxygen-isotope profile is in good agreement with data from precipitation and major temperature trends obtained for the last 30 years from Delingha meteorological station, which is located 160 km south-east of the ice cap.

scholarly journals Tracing fluid transfers in subduction zones: an integrated thermodynamic and <i>δ</i><sup>18</sup>O fractionation modelling approach

Solid Earth ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 307-328 ◽  
Author(s):  
Alice Vho ◽  
Pierre Lanari ◽  
Daniela Rubatto ◽  
Jörg Hermann
Keyword(s):  
Oxygen Isotope ◽  
Oceanic Crust ◽  
Subduction Zones ◽  
Integrated Modelling ◽  
Fluid Loss ◽  
Rock Composition ◽  
Oxygen Isotope Fractionation ◽  
Rock Interaction ◽  
Dehydration Reactions ◽  
Modelling Approach

Abstract. Oxygen isotope geochemistry is a powerful tool for investigating rocks that interacted with fluids, to assess fluid sources and quantify the conditions of fluid–rock interaction. We present an integrated modelling approach and the computer program PTLoop that combine thermodynamic and oxygen isotope fractionation modelling for multi-rock open systems. The strategy involves a robust petrological model performing on-the-fly Gibbs energy minimizations coupled to an oxygen fractionation model for a given chemical and isotopic bulk rock composition; both models are based on internally consistent databases. This approach is applied to subduction zone metamorphism to predict the possible range of δ18O values for stable phases and aqueous fluids at various pressure (P) and temperature (T) conditions in the subducting slab. The modelled system is composed of a mafic oceanic crust with a sedimentary cover of known initial chemical composition and bulk δ18O. The evolution of mineral assemblages and δ18O values of each phase is calculated along a defined P–T path for two typical compositions of basalts and sediments. In a closed system, the dehydration reactions, fluid loss and mineral fractionation produce minor to negligible variations (i.e. within 1 ‰) in the bulk δ18O values of the rocks, which are likely to remain representative of the protolith composition. In an open system, fluid–rock interaction may occur (1) in the metasediment, as a consequence of infiltration of the fluid liberated by dehydration reactions occurring in the metamorphosed mafic oceanic crust, and (2) in the metabasalt, as a consequence of infiltration of an external fluid originated by dehydration of underlying serpentinites. In each rock type, the interaction with external fluids may lead to shifts in δ18O up to 1 order of magnitude larger than those calculated for closed systems. Such variations can be detected by analysing in situ oxygen isotopes in key metamorphic minerals such as garnet, white mica and quartz. The simulations show that when the water released by the slab infiltrates the forearc mantle wedge, it can cause extensive serpentinization within fractions of 1 Myr and significant oxygen isotope variation at the interface. The approach presented here opens new perspectives for tracking fluid pathways in subduction zones, to distinguish porous from channelled fluid flows, and to determine the P–T conditions and the extent of fluid–rock interaction.

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