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Recrystallization-induced oxygen isotope changes in inclusion-hosted water of speleothems - Paleoclimatological implications

机译:重结晶诱导杂原子寄主宿主水中的氧同位素变化-古气候学意义

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摘要

The issue of diagenetic alteration of carbonate deposits in caves (speleothems) has gained increasing importance in recent years, as this process has serious consequences for speleothem-based paleoclimate studies. In this study stable hydrogen and oxygen isotope data of water trapped in fluid inclusions were collected for recently forming stalagmites and flowstones in order to determine how dripwater compositions are reflected and preserved in the inclusion water compositions. Hydrogen isotope compositions were found to reflect dripwater values, whereas the oxygen isotope data were increasingly shifted from the local dripwater compositions with the time elapsed after deposition. The delta O-18 data are correlated with X-Ray diffraction full width at half maximum values (related to crystal domain size and lattice strain), suggesting that the oxygen isotope shift is related to recrystallization of calcite. Transmission electron microscope analyses detected the presence of nanocrystalline (<50 nm) calcite, whose crystallization to coarser-grained calcite crystals (>200 nm) may have induced re-equilibration between the carbonate and the trapped inclusion water. The Ostwald ripening process provides an explanation for unexpectedly low oxygen isotope compositions in the inclusion water. The detected diagenetic alteration and its isotopic effects should be taken into consideration during sampling strategies and data evaluation as speleothems containing nanocrystalline calcite during their deposition are prone to late-stage oxygen isotope water-carbonate re-equilibration, which may shift the oxygen isotope composition of the inclusion water to more depleted values while the hydrogen isotope composition remains intact. (C) 2016 Published by Elsevier Ltd.
机译:近年来,洞穴中碳酸盐沉积的成岩作用改变(石窟科)变得越来越重要,因为该过程对基于蛇麻草的古气候研究具有严重的后果。在这项研究中,收集了流体包裹体中捕获的水的稳定氢和氧同位素数据,用于近期形成的石笋和浮石,以确定在包裹体水成分中如何反映和保留滴水成分。发现氢同位素组成可反映滴水值,而氧同位素数据随着沉积后时间的增加而从局部滴水组成中逐渐转移出来。 δO-18数据与X射线衍射半峰全宽相关(与晶畴尺寸和晶格应变有关),表明氧同位素位移与方解石重结晶有关。透射电子显微镜分析检测到方解石存在纳米晶体(<50 nm),其结晶为粗粒方解石晶体(> 200 nm)可能导致碳酸盐与捕集的包裹体水之间重新平衡。奥斯特瓦尔德(Ostwald)熟化过程为包裹水中的低氧同位素组成提供了解释。在采样策略和数据评估中应考虑到检测到的成岩作用变化及其同位素效应,因为在沉积过程中,含有纳米晶方解石的蛇麻草易于后期氧同位素水碳酸盐的重新平衡,这可能会改变氧同位素的组成。当氢同位素组成保持完好无损时,夹杂物水的含量将进一步降低。 (C)2016由Elsevier Ltd.出版

著录项

  • 来源
    《Quaternary International》 |2016年第10期|25-32|共8页
  • 作者单位

    Hungarian Acad Sci, RCAES, Inst Geol & Geochem Res, Budaorsi Ut 45, H-1112 Budapest, Hungary;

    Hungarian Acad Sci, RCAES, Inst Geol & Geochem Res, Budaorsi Ut 45, H-1112 Budapest, Hungary;

    Hungarian Acad Sci, RCAES, Inst Geol & Geochem Res, Budaorsi Ut 45, H-1112 Budapest, Hungary;

    Eotvos Lorand Univ, Dept Phys & Appl Geol, Pazmany Peter Setany 1-C, H-1117 Budapest, Hungary;

    Hungarian Acad Sci, RCAES, Inst Geol & Geochem Res, Budaorsi Ut 45, H-1112 Budapest, Hungary;

    Hungarian Acad Sci, RCAES, Inst Geol & Geochem Res, Budaorsi Ut 45, H-1112 Budapest, Hungary;

    Hungarian Acad Sci, RCAES, Inst Geol & Geochem Res, Budaorsi Ut 45, H-1112 Budapest, Hungary;

    Natl Taiwan Univ, Dept Geosci, High Precis Mass Spectrometry & Environm Change L, Taipei 10617, Taiwan;

    Natl Taiwan Univ, Dept Geosci, High Precis Mass Spectrometry & Environm Change L, Taipei 10617, Taiwan;

    Hungarian Acad Sci, Inst Nucl Res, Bem Ter 18-C, H-4026 Debrecen, Hungary;

    Hungarian Acad Sci, RCAES, Inst Geol & Geochem Res, Budaorsi Ut 45, H-1112 Budapest, Hungary;

    Hungarian Acad Sci, Res Ctr Nat Sci, Inst Mat & Environm Chem, Magyar Tudosok Korutja 2, H-1117 Budapest, Hungary;

    Eotvos Lorand Univ, Inst Chem, Pazmany Peter Setany 1-C, H-1117 Budapest, Hungary;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Speleothem; Fluid inclusion; Hydrogen and oxygen isotope compositions; Diagenesis; Ostwald ripening;

    机译:蝶粉;流体包裹体;氢和氧同位素组成;成岩作用;奥斯特瓦尔德熟化;

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