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首頁(yè)> 外文學(xué)位 >Oxygen isotopic fractionation in carbon dioxide-laser microprobes: Testing the metal oxide-metal fluoride chemical and isotopic exchange hypothesis.
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Oxygen isotopic fractionation in carbon dioxide-laser microprobes: Testing the metal oxide-metal fluoride chemical and isotopic exchange hypothesis.

機(jī)譯：二氧化碳激光微探針中的氧同位素分餾：測(cè)試金屬氧化物-金屬氟化物化學(xué)和同位素交換假說(shuō)。

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摘要

Slow heating of standard silicate mineral powders by a focused CO2-laser beam in a CIF3 environment gave different oxygen isotopic results depending on the types of materials used to contain the powders. Stainless steel, nickel, gold-plated nickel, and pure gold sample holders were evaluated. Nickel was most reactive to the oxygen gas released from the silicates in the presence of CIF3, followed by stainless steel and gold. Preferential release of the heavier isotope, 18O, on the surface and release of the lighter isotope, 16O, caused the residual gas collected from quartz to be isotopically lighter than expected by ∼1‰. However, ferromagnesian garnet and olivine gave higher than expected δ18O values, possibly due to fluoride melt phases that formed during laser fluorination.; Rapid heating of NBS28 and NCSU-Q quartz in the pure gold sample holder by a defocused beam also produced lower than expected values. However, Achala and Rose quartz, UWG-2 garnet, and San Carlos olivine gave results that agreed with conventionally accepted values. The offsets from the laser-based to the accepted values were not always consistent from one standard to another, irrespective of heating rate. Gold silicide was identified on the surface of the pure gold sample holder by X-ray diffraction analysis. The presence of oxygen with silicon indicated simultaneous release from the silicate and incorporation in the silicide during laser fluorination.; An empty nickel reaction vessel previously acid etched and exposed to atmospheric oxygen, released large aliquots of gas extremely depleted in 18O (−8, −30, and −27‰), when fluorinated and heated externally to ∼100°C. Continued fluorination and heating at >600°C for 5hrs released a much smaller amount of oxygen enriched in 18O (+12‰).; The experiments performed as part of this study indicate that metal surfaces may serve as hosts for oxygen, and that strong oxygen isotopic fractionation may accompany oxygen release and exchange. The importance of metal substrates in oxygen isotopic fractionation was highlighted by the replacement of the stainless steel chamber by a nonmetallic one made of chlorotrifluoroethylene. NBS28 quartz gave results that nearly coincided with the standard value of +9.6‰ on three separate occasions, averaging +9.5‰ (n = 7).
機(jī)譯：在CIF 3 環(huán)境中，通過(guò)聚焦的CO 2 -激光束緩慢加熱標(biāo)準(zhǔn)硅酸鹽礦物粉末，根據(jù)所含粉末的材料類(lèi)型，氧同位素結(jié)果不同。對(duì)不銹鋼，鎳，鍍金鎳和純金樣品架進(jìn)行了評(píng)估。在CIF 3 的存在下，鎳對(duì)從硅酸鹽釋放出的氧氣的反應(yīng)性最高，其次是不銹鋼和金。較重的同位素 18 O在表面的優(yōu)先釋放和較輕的同位素 16 O的釋放導(dǎo)致從石英收集的殘留氣體的同位素比預(yù)期的輕減少約1‰。然而，鐵鎂石榴石和橄欖石給出的δ 18 O值高于預(yù)期，可能是由于激光氟化過(guò)程中形成的氟化物熔體相。通過(guò)散焦束將純金樣品架中的NBS28和NCSU-Q石英快速加熱也產(chǎn)生了低于預(yù)期的值。但是，Achala和Rose石英，UWG-??2石榴石和San Carlos橄欖石給出的結(jié)果與常規(guī)接受的值一致。不管加熱速率如何，從激光基準(zhǔn)到可接受值的偏差在一個(gè)標(biāo)準(zhǔn)與另一個(gè)標(biāo)準(zhǔn)之間并不總是一致的。通過(guò)X射線衍射分析在純金樣品架的表面上鑒定出硅化金。氧與硅的存在表明在激光氟化過(guò)程中同時(shí)從硅酸鹽中釋放和摻入硅化物中。一個(gè)空的鎳反應(yīng)容器，先前被酸蝕并暴露在大氣中的氧氣中，在外部氟化并加熱至約100°C繼續(xù)氟化并在> 600°C加熱5小時(shí)，釋放出的 18 O中的氧氣量要少得多（+ 12‰）。作為這項(xiàng)研究的一部分進(jìn)行的實(shí)驗(yàn)表明，金屬表面可能是氧氣的主體，強(qiáng)氧同位素分餾可能伴隨著氧氣的釋放和交換。通過(guò)用由三氟氯乙烯制成的非金屬容器代替不銹鋼室，凸顯了金屬基質(zhì)在氧同位素分餾中的重要性。 NBS28石英在三個(gè)不同的場(chǎng)合給出的結(jié)果幾乎與標(biāo)準(zhǔn)值+ 9.6‰相符，平均為+ 9.5‰（n = 7）。

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  • 作者

    Johnson, Timothy Whipple.;

  • 作者單位

    Indiana University.;

  • 授予單位 Indiana University.;
  • 學(xué)科 Geochemistry.
  • 學(xué)位 Ph.D.
  • 年度 2001
  • 頁(yè)碼 108 p.
  • 總頁(yè)數(shù) 108
  • 原文格式 PDF
  • 正文語(yǔ)種 eng
  • 中圖分類(lèi) 地質(zhì)學(xué);
  • 關(guān)鍵詞

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