J 2019

Evolution of Mg/Ca and Sr/Ca ratios during the experimental dissolution of limestone

PRACNÝ, Pavel, Jiří FAIMON, Dalibor VŠIANSKÝ and Antonín PŘICHYSTAL

Basic information

Original name

Evolution of Mg/Ca and Sr/Ca ratios during the experimental dissolution of limestone

Authors

PRACNÝ, Pavel (203 Czech Republic, guarantor, belonging to the institution), Jiří FAIMON (203 Czech Republic, belonging to the institution), Dalibor VŠIANSKÝ (203 Czech Republic, belonging to the institution) and Antonín PŘICHYSTAL (203 Czech Republic, belonging to the institution)

Edition

Chemical Geology, Amsterdam, Elsevier, 2019, 0009-2541

Other information

Language

English

Type of outcome

Článek v odborném periodiku

Field of Study

10505 Geology

Country of publisher

Netherlands

Confidentiality degree

není předmětem státního či obchodního tajemství

References:

Impact factor

Impact factor: 3.363

RIV identification code

RIV/00216224:14310/19:00109975

Organization unit

Faculty of Science

DOI

UT WoS

000480333200010

Keywords in English

Moravian Karst limestone; Experimental dissolution; Trace element proxies; Kinetic model; Cave dripwater

Tags

Tags

International impact, Reviewed
Změněno: 24/5/2022 22:36, Mgr. Pavel Pracný, Ph.D.

Abstract

V originále

Magnesium (Mg) and strontium (Sr) preserved in speleothems are among the terrestrial climatic proxies. The mechanism of their release from impurities in limestone bedrock is usually neglected in paleoclimatic studies mainly because it is not very well understood; most cation release studies focus on pure minerals instead of limestone. Therefore, the Mg and Sr released from six types of limestone from the Moravian Karst (Czech Republic) were studied experimentally and compared with the dripwater data coming from the Punkva Caves (Moravian Karst) formed in two of the studied limestone types. The dissolution data were used to calibrate a kinetic dissolution model. The results show an incongruent dissolution of Mg-calcite and dolomite, pronounced especially in advanced stages of the dissolution. According to the results, the trace element ratios in solution were dependent mainly on (1) the limestone composition (i.e., the Mg-calcite and dolomite availability and the stoichiometry of individual minerals) and (2) on the extent of limestone-solution interaction (controlled by dissolution dynamics). Modeling indicated that the dynamics depend on the ratios of the area of rock–water and air–water interfaces to the water volume. Moreover, modeling suggests that the dynamics and subsequently also the trace element ratios are influenced by (a) the fresh surface dissolution during the initial stages of interaction and by (b) the preferential release of trace elements from mineral surfaces (nonstoichiometric dissolution). The effects of disturbed surfaces and preferential leaching are limited by available fresh surfaces. Fresh surfaces are formed through rock crushing, e.g., during physical weathering (in the field) or sample preparation (in a laboratory). The dripwaters from Punkva Caves had trace element ratios with values between the ratios resulting from the experimental dissolution of the limestones present on the site, indicating a naturally mixed composition of waters. This study has shown that Mg/Ca and Sr/Ca ratios in dripwaters might be controlled by various climate-independent variables, which raises further questions about utilizing the ratios as paleoclimatic proxies.