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Your search keyword '"Li, Minghui"' showing total 2 results
Start Over Author "Li, Minghui" Topic dolomite Publication Year Range Last 50 years
2 results on '"Li, Minghui"'

1. Lacustrine-evaporitic microbial dolomite from a Plio-Pleistocene succession recovered by the SG-1 borehole in the Qaidam Basin, NE Tibetan Plateau

Author

Zhao, Yanyang, Wei, Xiangyu, Han, Zuozhen, Han, Chao, Gao, Xiao, Meng, Ruirui, Wang, Qiyu, Tucker, Maurice E., Li, Minghui, Sánchez-Román, Mónica, and Geology and Geochemistry

Subjects
Saline lake, Geochemistry and Petrology, Geology, Microbial mediation, SDG 14 - Life Below Water, Burial effect, Dolomite, Ordering degree
Abstract

The Plio-Pleistocene evaporitic lacustrine succession in the Qaidam Basin, which was recovered by drill core SG-1, provides the material for understanding the maturation of dolomite since dolomite is present in the core from 7.6 to 870 m depth, spanning a time interval of 0.1–2.8 Ma. Twenty-two samples were collected at different burial depths. The samples were examined by thin-section petrography and SEM for textures, and analyzed for mineralogy (XRD), trace elements and carbon and oxygen isotopes. The main mineral compositions of each sample are dolomite, quartz, halite and gypsum. Dolomite is mostly scattered with spheroidal to ellipsoidal shapes, several microns in diameter, partially encapsulated in gypsum. Microbial micropores and calcified microorganisms are observed on and within the dolomite crystals and in the thin sections. The degree of ordering of the dolomite gradually increases with burial depth, which basically conforms to the first-order reaction function. The crystal constants of dolomite decrease with burial depth, indicating recrystallisation with increasing overburden. The trace elements of the dolomites are significantly different from those of hydrothermal dolomites, but close to lacustrine microbial carbonate. It is concluded that the dolomites in core SG-1 are mainly authigenic, with microbial processes a likely facilitator of dolomite precipitation. The dolomite formed and then evolved in crystal structure during burial, gradually approaching ordered stochiometric dolomite. This study gives clues to link microbial dolomite to the massive ideal dolomite rock encountered in the geological record.

Published
2023

2. Origin of modern dolomite in surface lake sediments on the central and western Tibetan Plateau.

Author

Li, Jiao, Zhu, Liping, Li, Minghui, Wang, Junbo, and Ma, Qingfeng

Subjects
*DOLOMITE, *LAKE sediments, *PLATEAUS, *CRYSTAL morphology, *MINERALOGY, *X-ray diffraction
Abstract

Modern dolomite was found in the sediments of 20 lakes on the central and western Tibetan Plateau during lake surveys, in August to November of 2012–2015. We analyzed the mineralogy of authigenic carbonates and the chemical composition of lake water to investigate the environmental factors affecting dolomite formation and to determine the mechanisms of dolomite formation. X-ray diffraction analysis suggested that the dolomite content ranged from 3% to 10%, with a mean of 5%, and that the majority of the dolomite in the surface lake sediments was Ca-dolomite. Dolomite formed in a wide range of salinity environments. There was a positive linear relationship between salinity and Mg/Ca ratio, whereas the pH and sulfate (SO 4 2−) concentration are not significantly correlated with Mg/Ca ratio. High Mg/Ca ratio, high salinity, high sulfate concentration, and high pH are important environmental factors in favor of dolomite precipitation. Evaporation and microbial activity are potential mechanisms for dolomite formation in the central and western Tibetan Plateau. The positive relationship between δ18O and δ13C indicates that the dolomite formed in lakes has a long residence time and undergoes continuous evaporation. The crystal morphologies of dolomite were scattered euhedral grains with diameters of 2–10 μm, as well as sub-spherical and spherical grains (<2 μm) which were present either as dispersed crystals or were aggregated into dolomite clusters. Dolomite crystals were identical both in shape and size to those of microbial dolomite previously discovered in modern lake environments and culture experiments. The dolomite precipitation temperature range calculated using the low-temperature microbial equation was close to the measured temperature, further indicating that microbial activity may be involved in dolomite formation. This study provides natural locations with different water salinities and other environmental factors for dolomite precipitation, which has important significance for studying the mechanism of dolomite formation. [ABSTRACT FROM AUTHOR]

Published
2020
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