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Carbon and Oxygen Isotopic Composition of Saline Lacustrine Dolomite Cements and Its Palaeoenvironmental Significance: A Case Study of Paleogene Shahejie Formation, Bohai Sea
- Source :
- Minerals, Vol 9, Iss 1, p 13 (2018), Minerals, Volume 9, Issue 1
- Publication Year :
- 2018
- Publisher :
- MDPI AG, 2018.
-
Abstract
- The dolomite reservoirs in the Paleogene Shahejie Formation in the Bozhong area of the Bohai Bay Basin contain a large amount of dolomite cement. Petrologic and mineralogic studies have shown that the dolomite cements can be divided into three types according to their occurrence: coating dolomite (CD), pore-lining dolomite (LD), and pore-filling dolomite (FD). The laser microsampling technique was used to analyze the C and O isotopes in the carbonate minerals. This method is an effective way to produce CO2 gas from a particular carbonate structure in a thin section, and it has a spatial resolution of 20&ndash<br />50 &micro<br />m and an optimal precision of approximately &plusmn<br />0.22&sigma<br />for &delta<br />13C and &delta<br />18O in carbonate standard materials. The carbon and oxygen isotopic compositions and the oxygen isotopic geothermometer results showed that the dolomitization fluid is mainly low temperature fluid, the lake basin environment is relatively closed, and the salinity index Z value is greater than 120, which indicates the invasion of seawater. CD and early-stage LD crystals were mainly very fine crystals with faint cathodoluminescence, which indicates the early formation of diagenesis. The high temperatures of late-stage LD and FD measured by oxygen isotope thermometers indicates that they formed at a deeper depth. The dolomite cements in the study area may have formed in two stages: seepage-reflux dolomitization during the penecontemporaneous period and burial dolomitization.
- Subjects :
- lcsh:QE351-399.2
δ18O
020209 energy
Dolomite
Geochemistry
Carbonate minerals
Bohai Bay Basin
02 engineering and technology
dolomitization
010502 geochemistry & geophysics
01 natural sciences
Isotopes of oxygen
lacustrine carbonates
chemistry.chemical_compound
0202 electrical engineering, electronic engineering, information engineering
0105 earth and related environmental sciences
lcsh:Mineralogy
Geology
Geotechnical Engineering and Engineering Geology
Diagenesis
chemistry
dolomite cements
Shahejie Formation
Dolomitization
Carbonate
Paleogene
carbon-oxygen isotope
Subjects
Details
- Language :
- English
- Volume :
- 9
- Issue :
- 1
- Database :
- OpenAIRE
- Journal :
- Minerals
- Accession number :
- edsair.doi.dedup.....52a4a06112191389a1a80c2711510e36