| 大别山榴辉岩氢氧同位素组成及其地球动力学意义 |
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| 引用本文：郑永飞,傅斌,肖益林,龚冰,葛洁宁,李曙光.1997.大别山榴辉岩氢氧同位素组成及其地球动力学意义[J].地球学报,18(3):336. |
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| 基金项目:国家自然科学基金,中国科学院专项基金 |
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| 中文摘要:对大别山东部超高压榴辉岩氧同位素研究表明，这些榴辉岩的δ１８Ｏ值分布表现出显著不均一性，从低达－２．６‰变化至＋０．７‰。榴辉岩中各矿物之间的氧同位素分馏达到并保持了平衡，表明岩石在遭受超高压变质作用之前与亏损１８Ｏ的流体进行过相互作用。含羟基矿物的δＤ值为－５１‰～－８３‰，指示参与的流体是古大气降水，它与榴辉岩原岩（某种玄武质岩石）发生过显著的氧同位素交换。超高压变质榴辉岩中大气降水同位素信息的保存表明，这种榴辉岩的原岩曾经出露于大陆地壳表面，并且当包含榴辉岩原岩的板块俯冲至地幔深度时，地壳与地幔之间的物质交换非常有限，因此滞留时间非常短暂（＜２０Ｍａ）。不同矿物对的氧同位素平衡温度基本一致，反映出这种超高压变质榴辉岩在地幔深度下形成之后，经历了一个快速的冷却和上升过程。长英 |
| 中文关键词:氢氧同位素 大气降水 地球化学再循环 地球动力学 超高压变质 榴辉岩 大别山 |
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| Hydrogen and Oxygen Isotope Compositions of Eclogites from the Dabie Mountains and Its Geodynamic Implications |
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| Abstract:Heterogeneous δ 18 O values as low as -2.6‰ to +7.0‰ are observed for ultrahigh pressure eclogites from the Dabie mountains in East China.Oxygen isotope equilibriun has been approached between the eclogite minerals,suggesting that the rocks would have acquired the unusual δ 18 O values prior to ultrahigh pressure metamorphism by interaction with a 18 O depleted fluid . δ D values of hydroxyl bearing are between-51‰ and -83‰, precluding the possibility of paleoseawater involvement.The only likely fluid is ancient meteoric water that exchanged oxygen isotopes with the eclogite precursor(a kind of basaltic rocks)formerly resident in the continental crust.This suggests a crustal recycling process in the suture zone of plate subduction.Because silicate minerals undergo rapid oxygen isotope exchange at mantle pressures,preservation of the isotopic signature of meteoric water in the eclogites indicates limited crust_mantle interaction and thus a short residence time(<20 Ma)when the plate containing the eclogite precursor was subducted to mantle depths .The agreement in oxygen isotope temperatures for different mineral pairs suggests a rapid cooling and ascent process for the eclogites subsequent to their formation at mantle depths. |
| keywords:oxygen hydrogen isotopes meteoric water geochemical recycling geodynamics ultrahigh pres_ sure eclogite the Dabie mountains |
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