Factors controlling the growth rate,carbon and oxygen isotope variation in modern calcite precipitation in a subtropical cave,Southwest China

摘要：

　　A prerequisite for using cave speleothems to reconstruct palaeoenvironmental conditions is an accurate understanding of specific factors controlling calcite growth,in particular the isotopic partitioning of oxygen(δ18O)and carbon(δ13C)which are the most commonly used proxies.An in situ monitoring study from April 2008 to September 2009 at Xueyu Cave,Chongqing,SW China,provides insight into the controls on calcite growth rates,drip water composition,cave air parameters and δ18O andδ13C isotopic values of modern calcite precipitation.Both cave air PCO2 and drip water hydrochemical characteristics show obvious seasonality driven by seasonal changes in the external environment.Calcite growth rates also display clear intra-annual variation,with the lowest values occurring during wet season and peak values during the dry season.Seasonal variations of calcite growth rate are primarily controlled by variations of cave air PCO2 and drip water rate.Seasonal δ18O-VPDB and δ13C-VPDB in modern calcite precipitates vary,with more negative values in the wet season than in the dry season.Strong positive correlation of δ18O-VPDB vs.δ13C-VPDB is due to simultaneous enrichment of both isotopes in the calcite.This correlation indicates that kinetic fractionation occurs between parent drip water and depositing calcite,likely caused by the variations of cave air PCO2 and drip rate influenced by seasonal cave ventilation.Kinetic fractionation amplifies the equilibrium fractionation value of calcite δ18O(by~1.5‰)and δ13C(by~1.7‰),which quantitatively reflects surface conditions during the cave ventilation season.These results indicate that the cave monitoring of growth rate and δ18O and δ13C of modern calcite precipitation are necessary in order to use a speleothem to reconstruct palaeoenvironment.

关键词： Modern calcite precipitation Oxygen and carbon isotope Cave air PCO2 Isotopic fractionation

作者: Junbing Pu Aoyu Wang Licheng Shen Jianjun Yin Daoxian Yuan Heping Zhao

作者单位: Key Laboratory of Karst Dynamics,MLR & Guangxi,Institute of Karst Geology,Chinese Academy of Geologi School of Geography Sciences,Southwest University,Chongqing 400715,China;Sichuan Earthquake Administ School of Geography Sciences,Southwest University,Chongqing 400715,China Key Laboratory of Karst Dynamics,MLR & Guangxi,Institute of Karst Geology,Chinese Academy of Geologi

会议类型: 国内会议

会议名称: 国土资源部广西岩溶动力学重点实验室和国土资源部岩溶生态系统与石漠化治理重点实验室2016年度学术委员会会议

会议地点: 广西桂林

会议语种:英文

页码: 167-178

在线出版日期: 2016-12-02（万方平台首次上网日期，不代表论文的发表时间）