Using stable isotopes (δ 17 O, δ 18 O and δD) of gypsum hydration water to ascertain the role of water condensation in the formation of subaerial gypsum speleothems
Using stable isotopes (δ 17 O, δ 18 O and δD) of gypsum hydration water to ascertain the role of water condensation in the formation of subaerial gypsum speleothems
复制标题
利用石膏水合水的稳定同位素（δ 17 O、δ 18 O 和 δD）确定水凝结在地下石膏洞穴形成中的作用
DOI：
10.1016/j.chemgeo.2017.01.021
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发表时间：
2017
期刊：
影响因子：
3.9
通讯作者：
D. Hodell
中科院分区：
文献类型：
--
作者：
F. Gázquez;J. Calaforra;Nicholas P. Evans;D. Hodell
本文分析了西班牙东南部阿尔梅里亚Sorbas盆地半干旱石膏岩溶区不同洞穴沉积物中石膏水化水（GHW）的稳定同位素（δ 17 O、δ 18 O和δD），以及5个洞穴中凝结水和渗透沃茨的稳定同位素。小气候参数（空气温度，相对湿度和有效冷凝率）也监测了一年的周期。我们发现，大多数石膏洞穴沉积物生长的母液是由冷凝水（约60%）和渗透水（约40%）的混合物组成的。虽然渗透水的蒸发被认为是负责二次石膏沉淀在渗流洞穴，我们的研究结果表明，冷凝可以是一个主要的水的来源，形成石膏洞穴。蒸发过程中水的d-过量和Δ 17 O的模拟轨迹证实，大多数洞穴沉积物是在相对湿度为75- 85%的条件下从冷凝水和渗透水的混合物中沉淀出来的，与冬季洞穴大气中测量的结果相似。这些发现对今后石膏洞穴沉积物作为古环境档案的研究具有重要意义。
We analyzed the stable isotopes (δ17O, δ18O and δD) of gypsum hydration water (GHW) in a variety of speleothems, as well as condensation and infiltration waters in five caves of the semiarid gypsum karst of Sorbas basin (Almeria, SE Spain). Microclimate parameters (air temperature, relative humidity and effective condensation rate) were also monitored over an annual cycle. We found that the mother solution from which the majority of gypsum speleothems grow is composed of a mixture of condensation (~ 60%) and infiltration water (~ 40%) that undergoes evaporation. Although evaporation of infiltration water alone was thought to be responsible for secondary gypsum precipitation in vadose caves, our results suggest that condensation can be a major source of water for the formation of gypsum speleothems. The modelled d-excess and Δ17O trajectories of water during the evaporative process confirm that the majority of speleothems precipitate from a mixture of condensation and infiltration water under relative humidity of 75–85%, similar to that measured in the cave atmosphere during winter. These findings have important implications for future studies of gypsum speleothems as paleoenvironmental archives.