Carbon and oxygen isotopic compositions, and palaeoenvironmental significance of saline lacustrine dolomite from the Qaidam Basin, Western China

Yuan, Jianying; Huang, Chenggang; Zhao, Fan; Pan, Xing

doi:10.1016/j.petrol.2015.10.024

Cited by 32 publications

(15 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Despite the limitations of the above calculations, the limestones (calcite) and dolostones of the Bira Formation were apparently deposited under distinctly different conditions, and the high δ 18 O values of the dolostones reflect dolomite precipitation in equilibrium with alkaline–saline waters under shallow conditions (Bellanca et al ., ; Major et al ., ; Calvo et al ., ; Arenas et al ., ; Abdul Aziz et al ., ; Bréhéret et al ., ; Mauger & Compton, ; Yuan et al ., ). This stands in line with the bedded and muddy character of the dolostones, which show no intraclasts or freshwater fossils (unlike the limestones; Figs 3 to 5).…”

Section: Discussionmentioning

confidence: 97%

Formation of lacustrine dolomite in the late Miocene marginal lakes of the East Mediterranean (Northern Israel)

et al. 2019

View full text Add to dashboard Cite

The study focuses on the formation of lacustrine dolomite in late Miocene lakes, located at the East Mediterranean margins (Northern Israel). These lakes deposited the sediments of the Bira (Tortonian) and Gesher (Messinian) formations that comprise sequences of dolostone and limestone. Dolostones are bedded, consist of small-sized (<7 lm), Ca-rich (52 to 56 mol %) crystals with relatively low ordering degrees, and present evidence for replacement of CaCO 3 components. Limestones are comprised of a wackestone to mudstone matrix, freshwater macrofossils and intraclasts (mainly in the Bira Formation). Sodium concentrations and isotope compositions differ between limestones and dolostones: Na =~100 to 150 ppm;~1000 to 2000 ppm; d 18 O = À3Á8 to À1Á6&; À2Á0 to +4Á3&; d 13 C = À9Á0 to À3Á4&; À7Á8 to 0& (VPDB), respectively. These results indicate a climate-related sedimentation during the Tortonian and early Messinian. Wet conditions and positive freshwater inflow into the carbonate lake led to calcite precipitation due to intense phytoplankton blooms (limestone formation). Dry conditions and enhanced evaporation led to precipitation of evaporitic CaCO 3 in a terminal lake, which caused an increased Mg/Ca ratio in the residual waters and penecontemporaneous dolomitization (dolostone formation). The alternating lithofacies pattern reveals eleven short-term wet-dry climate-cycles during the Tortonian and early Messinian. A shift in the environmental conditions under which dolomite formed is indicated by a temporal decrease in d 18 O of dolostones and Na content of dolomite crystals. These variations point to decreasing evaporation degrees and/or an increased mixing with meteoric waters towards the late Messinian. A temporal decrease in d 13 C of dolostones and limestones and appearance of microbial structures in close association with dolomite suggest that microbial activity had an important role in allowing dolomite formation during the Messinian. Microbial mediation was apparently the main process that enabled local growth of dolomite under wet conditions during the latest Messinian.

show abstract

Section: Discussionmentioning

confidence: 97%

Formation of lacustrine dolomite in the late Miocene marginal lakes of the East Mediterranean (Northern Israel)

et al. 2019

View full text Add to dashboard Cite

show abstract

“…(6) The ISCO pump was opened to set the displacement pressure. (7) The ISCO pump and data collection system were started. (8) Under a constant displacement pressure, the confining pressure was continuously increased within the interval of 3-5 MPa.…”

Section: Core Flow Experimentsmentioning

confidence: 99%

“…After decades of exploration, many lacustrine carbonate reservoirs have been discovered in China and abroad [3][4][5]. Under the comprehensive influence of the Cenozoic paleostructure and paleoclimatic conditions, a typical plateau saline lake basin was developed in the Qaidam Basin [6,7].…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of the Flow Mechanism of Deep Lacustrine Carbonate Reservoirs in the Yingxi Area of the Qaidam Basin

Luo

Zheng

Huang³

et al. 2022

Geofluids

View full text Add to dashboard Cite

Many of the exploration and development theories derived for conventional clastic rock reservoirs are not applicable to pore-fracture lacustrine carbonate reservoirs. The fluid flow mechanisms under reservoir conditions are still unclear. Therefore, in this study, the rock samples were characterized using X-ray diffraction (XRD), porosity-permeability analysis, scanning electron microscopy (SEM), plain thin sections, and casting thin sections. The core samples were classified into two types (fractures and matrix pores) based on their reservoir spaces. The core flow experiments were performed under reservoir conditions using reservoir core plugs. The experimental results demonstrate that the cores, especially the fractured cores, have a strong stress sensitivity. The oil phase flow in the core has the characteristics of non-Darcy flow, and the threshold pressure gradient is 0.01–0.003 MPa/m. Additionally, for the oil-water two-phase flow in the fractured core, the water phase relative permeability of the residual oil is high. In contrast, the water phase relative permeability of the matrix core is less than 0.2. The nuclear magnetic resonance (NMR) transverse relaxation time ( T 2 ) spectra were used to analyze the differences between the water flooding characteristics of the two pore structures. The experimental results show that the peaks of the T 2 spectra after water flooding are lower than those before water flooding, and the matrix cores have a better oil displacement effect. The relaxation time of 0.1–10 ms makes the greatest contribution to the water flooding efficiency. The micropores smaller than 10 μm in diameter play an important role in the water flooding of the matrix core. These results will provide theoretical basis for solving the difficult problems of developing deep lacustrine carbonate reservoirs.

show abstract

“…5), where it has a sensitive response to the matrix effect. Notably, oxygen isotopes of dolomite are widely used to trace the conditions of sediment diagenesis 9 and metamorphism, 10,11 characterize the mantle magma evolution and alteration of carbonatite, 12,13 and reconstruct the paleoenvironmental evolution 14,15 on Earth and Mars. 16−18 In this study, a novel rapid and accurate "online" method is developed for the SIMS determination of dolomite δ 18 O and Fe# by the concurrent analysis of 18 Mg 16 O, considering that the molar Fe/(Mg + Fe) ratio is the major contributor to the matrix effect during SIMS dolomite O-isotopic analysis.…”

mentioning

confidence: 99%

“…Moreover, dolomite exhibits solid-solution behavior and covers the expected low Fe# range (<0.5), where it has a sensitive response to the matrix effect. Notably, oxygen isotopes of dolomite are widely used to trace the conditions of sediment diagenesis and metamorphism, , characterize the mantle magma evolution and alteration of carbonatite, , and reconstruct the paleoenvironmental evolution , on Earth and Mars. − …”

mentioning

confidence: 99%

Accurate and Efficient SIMS Oxygen Isotope Analysis of Composition-Variable Minerals: Online Matrix Effect Calibration for Dolomite

Tang

et al. 2022

Anal. Chem.

View full text Add to dashboard Cite

High-quality oxygen isotope analysis of composition-variable minerals (e.g., ubiquitous carbonates) using secondary ion mass spectrometry (SIMS) is extremely challenging. The classical off-line procedure, which requires additional electron probe microanalyzer (EPMA) chemical compositions for calibrating instrumental mass fractionation (IMF), is inherently inaccurate and analytically inefficient. In this study, the first accurate and paired SIMS analysis of δ18O and Fe# [molar Fe/(Mg + Fe)] in dolomite is reported. Based on five newly developed dolomite O-isotopic standards with an Fe# range of 0.01–0.35 obtained by SIMS, a novel accurate and rapid online matrix effect calibration method for dolomite O-isotope analysis was developed using concurrent SIMS 18O–16O–56Fe16O–24Mg16O measurements without additional chemical electron probe microanalysis. A logistic equation was proposed as the best-fit curve to represent the δ18O matrix effect based on the 56Fe16O/24Mg16O ratios. For CTD-4 carbonatitic dolomite with variable Fe# but homogeneous oxygen isotopes, the off-line method exhibited highly variable apparent δ18O values in the range of 5.74–10.11‰. The online method yielded a homogeneous δ18O value of 7.94 ± 0.34‰ (2SD, n = 40), which is comparable with that of bulk analysis (7.94 ± 0.20‰; 2SD). Comprehensive analyses validated the online method as the best strategy for performing accurate δ18O analysis of samples with highly heterogeneous compositions. Based on its accuracy, simplicity, and economic feasibility, this method has potential applications in the analysis of composition-complex dolomites, detrital dolomites, and other precious terrestrial and extraterrestrial materials.

show abstract

Carbon and oxygen isotopic compositions, and palaeoenvironmental significance of saline lacustrine dolomite from the Qaidam Basin, Western China

Cited by 32 publications

References 24 publications

Formation of lacustrine dolomite in the late Miocene marginal lakes of the East Mediterranean (Northern Israel)

Formation of lacustrine dolomite in the late Miocene marginal lakes of the East Mediterranean (Northern Israel)

Experimental Study of the Flow Mechanism of Deep Lacustrine Carbonate Reservoirs in the Yingxi Area of the Qaidam Basin

Accurate and Efficient SIMS Oxygen Isotope Analysis of Composition-Variable Minerals: Online Matrix Effect Calibration for Dolomite

Contact Info

Product

Resources

About