Origin of dolomites in the Cambrian (upper 3rd‐Furongian) formation, south‐eastern Sichuan Basin, China

Hou, M. C.; Jiang, Wenjian; Xing, Fengcun; C., Liu, X.; Xiao, Chengwen

doi:10.1111/gfl.12193

Cited by 17 publications

(5 citation statements)

References 69 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The δ 13 C composition of the Є 3 s dolomite samples ranges from −0.63‰ to −1.91‰, with an average value of −1.24‰ and is in the range of that of the Upper Cambrian seawater (Figure 8) (Mattes & Mountjoy, 1980). Moreover, all of the δ 18 O values of the Є 3 s formation in the study area are higher than −10‰, and so a hydrothermal source for the dolomites can thus be excluded (Hou et al, 2016).…”

Section: Carbon and Oxygen Isotopesmentioning

confidence: 88%

“…Thus, this evidence indicates that Type 3 dolomites have experienced burial processes, with elevated temperatures resulting in the lower δ 18 O values during burial periods (Mattes & Mountjoy, ). Moreover, all of the δ 18 O values of the Є 3 s formation in the study area are higher than −10‰, and so a hydrothermal source for the dolomites can thus be excluded (Hou et al, ).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Geochemistry characteristics and dolomitization mechanism of the Upper Cambrian dolomite, eastern Ordos Basin, China

Zhang

Chen

et al. 2019

Geological Journal

View full text Add to dashboard Cite

There are widely developed carbonate formations in the lower Palaeozoic, Ordos Basin, China. However, previous studies have paid more attention to the Ordovician formations and largely ignored the Cambrian formations, which also have a larger sediment thickness. Recently, with the continuous discovery of dolomite gas fields in the Ordovician Majiagou formation, more investigations have begun to focus on the deeper dolomite in the Cambrian Sanshanzi Formation (Є3s). This study looks into the origin of the dolomite through a combination of petrology, major–trace elements, and stable isotope and rare earth element (REE) analysis of samples from five outcrops. The results show that the main dolomite types in the study area are dolarenite (Type 1), micrite‐fine crystalline dolomite (Type 2), and medium crystalline dolomite (Type 3). The δ13C values and δ18O values of each dolomite formation are close to those of seawater‐derived dolomite and have slightly higher Na2+ concentrations, suggesting that dolomite formation is closely related to the denser seawater. The REE compositions are characterized by enrichment for light REEs and depletion for heavy REEs, exhibiting an apparent negative Eu anomaly and a slight negative Ce anomaly, indicating that the dolomites of the Є3s may form in a weak‐reduction to the weak‐oxidation environment. The total REE (ΣREE) concentrations of Type 3 dolomites are lower than other types, suggesting that those dolomites may mean that the REEs are lost during the diagenesis. Type 1 dolomite has lower MgO and CaO values and a higher Mn2+ concentration than the other two types of dolomites, indicating that Type 1 dolomite suffered the action of atmospheric fresh water. Type 2 dolomite has lower Mg and Ca values than Type 3 dolomite, suggesting that Type 3 dolomite has a higher dolomitization degree. Further study into the combined palaeogeographical background confirms the dolomitization model of the study area: Type 1 and Type 2 dolomites may have been formed by penecontemporaneous or seepage–reflux dolomitization during early‐stage diagenesis. Subsequently, stratigraphic uplift lead to the Type 1 dolomite suffering the action of atmospheric fresh water, but there was no dorag dolomitization. Type 2 dolomite became the main dolomite type by seepage–reflux dolomitization in this period. Later, Type 2 dolomite was converted into Type 3 dolomite during progressive burial.

show abstract

Section: Carbon and Oxygen Isotopesmentioning

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Geochemistry characteristics and dolomitization mechanism of the Upper Cambrian dolomite, eastern Ordos Basin, China

Zhang

Chen

et al. 2019

Geological Journal

View full text Add to dashboard Cite

show abstract

“…The cloudy center often represents post-depositional replacive dolomite or a precursor carbonate [25,26]. D3 could form from direct replacement of carbonate or recrystallization of D1 and D2 [26].…”

Section: Discussionmentioning

confidence: 99%

Multiphase dolomitization in Devonian Shogram Formation, Chitral, Karakorum ranges, Pakistan: Evidence from outcrop analogue, petrography, and geochemistry

Saleem¹,

Rehman²,

Khan³

et al. 2022

ScienceAsia

View full text Add to dashboard Cite

This paper reports the first detailed microscopic and geochemical investigations of multiphase dolomitization in Devonian Shogram Formation, North-Western Karakorum constraining nature and origin of dolomitizing fluids. Field and petrographic studies revealed 4 different types of replacive dolomites, which are (i) fine grained anhedral dolomite (D1), (ii) medium grained subhedral to anhedral dolomite (D2), (iii) medium grained euhedral dolomite (D3), and (iv) coarse grained anhedral dolomite (D4) along with cement phase saddle dolomite (SD). These dolomites had high Fe and Mn concentraions and low Sr content. Stable isotope studies indicated high light isotope δ 18 O values for D1 and D2, higher lighter isotope δ 18 O value for D3, and highest lightest isotope δ 18 O values for D4 and SD, respectively. Petrographical and geochemical data suggested that D1 and D2 are likely formed in compactional flow regime in early stages prior to chemical compaction at shallow burial depths, whereas D3 is formed in late diagenetic deep burial settings. Lastly, D4 and SD are formed from high temperature hydrothermal fluids. These fluids could be related to widespread tectonic activity in the Karakorum region during collision or post-collisional time. Reshun fault acted as an important pathway that channeled Mg-rich hydrothermal fluids from underlying strata into carbonates, which caused intense dolomitization.

show abstract

“…From the bottom to top, the Cambrian strata have been subdivided into six intervals (Figure 1b), including the Qiongzhusi Formation, the Canglangpu Formation, the Longwangmiao Formation, the Gaotai Formation, and the Xixiangchi Formation, which is also referred to as the Loushanguan Group [22,31]. In the Early Cambrian, the sedimentary environment generally evolved from shallow shelf facies in the Qiongzhusi period to the delta and shore facies in the Canglangpu period in response to the decrease in the sea level [32].…”

Section: Geological Settingmentioning

confidence: 99%

“…The carbonate rock of the Middle-Upper Cambrian Xixiangchi Formation, which is an important potential exploration stratum in the Sichuan Basin, experienced extensive dolomitization. Base on comprehensive analysis of petrology, C, O, and Sr isotopes as well as major and minor elements, the previous studies proposed that the Xixiangchi Formation dolomites were mainly formed in penecontemporaneous dolomitization or seepage-reflux dolomitization during early-stage diagenesis, and partially experienced further recrystallization during burial [22][23][24]. In addition, some studies suggest that the saddle dolomite of Xixiangchi Formation is associated with hydrothermal fluid [25,26].…”

Section: Introductionmentioning

confidence: 99%

Petrographic, Rare Earth Elemental and Isotopic Constraints on the Dolomite Origin: A Case Study from the Middle-Upper Cambrian Xixiangchi Formation in Eastern Sichuan Basin, Southwest China

Wen

Zhou

et al. 2022

Minerals

View full text Add to dashboard Cite

The Middle-Upper Cambrian Xixiangchi Formation in the Sichuan Basin is regarded as an important reservoir with great potential for hydrocarbon exploration. It is previously indicated that the Xixiangchi carbonates have experienced extensive dolomitization, however, the origin of dolomitizing fluids and the dolomitization mechanism still remain uncertain. In this study, a set of petrographic and geochemical examinations, including rare earth elements (REE) and isotopic (C, O, and Sr) compositions were used to trace the origins of dolomitizing fluids and associated diagenetic processes. The petrographic examination revealed three types of matrix dolomites (D1, D2, D3) and one cement saddle dolomite (SD). These phases have crystal size ranges of less than 30 μm (very fine to fine crystals, D1), 30–100 μm (fine to medium crystals, D2), 100–300 μm (medium to coarsely crystalline dolomite, D3), and 0.3–4 mm (fracture filling cements, SD), respectively. D1 is characterized by non to very weak luminescence, weakly negative Ce anomalies (Ce/Ce* = 0.84 ± 0.02), strongly negative Eu anomalies (Eu/Eu* = 0.65 ± 0.03), and high 87Sr/86Sr ratios (0.71062 ± 0.00122). In combination with δ13C (−1.5‰ ± 0.2‰) and δ18O (−9.7‰ ± 0.5‰) compositions, D1 is interpreted to be formed by penecontemporaneous dolomitization in the near-surface environment with seawater as the dolomitizing fluid. In contrast, D2 is characterized by intercrystalline pores, dirty crystal surfaces, similar δ13C (−1.4‰ ± 0.4‰) compositions but higher δ18O (−8.9‰ ± 0.7‰) compositions, and lower 87Sr/86Sr ratios (0.70992 ± 0.00035), similar Ce anomalies (Ce/Ce* = 0.87 ± 0.04) and higher Eu anomalies (Eu/Eu* = 0.85 ± 0.04). The coarser D2 is regarded to be formed by the post-penecontemporaneous seepage-reflux dolomitization or by recrystallization of D1 dolomite in a near-surface or shallow burial environment. D3 is distinguished by a cloudy core with clear rims, showing slightly higher Eu anomalies (Eu/Eu* = 0.88 ± 0.02) and similar Ce anomalies (Ce/Ce* = 0.88 ± 0.02) than those of D1 and D2. Combined with the δ18O compositions (−10.4‰ ± 0.4‰) and 87Sr/86Sr ratios (0.70989 ± 0.00048), D3 is thought to be formed by the overgrowth or recrystallization of D1 and D2 dolomites in a shallow to moderate burial environment. The fractures filling SD dolomite consists of nonplanar and much coarser crystals with undulatory extinctions and brighter red luminescence. The lower δ18O (−11.1‰ ± 0.3‰) compositions, lower negative Eu anomalies (Eu/Eu* = 0.70 ± 0.01) of SD than the matrix dolomites, and similar Ce anomalies (Ce/Ce* = 0.83 ± 0.01) are indicative of hydrothermal dolomitization, with possible fluids associated with the magma during the period of Emei taphrogenic movement. In addition, the 87Sr/86Sr ratios (0.70941 ± 0.00003) of SD suggest probable origin from the coeval seawater partially. Therefore, SD dolomite is interpreted to be formed by hydrothermal dolomitization with mixed dolomitizing fluid of seawater and hydrothermal fluids. In summary, all the matrix dolomites have almost the same ΣREE concentrations and exhibit similar near-flat REE partition patterns with weak LREE enrichments, weakly negative Ce anomalies, and negative Eu anomalies. Such characteristics of REE compositions are indicative of similar evolved dolomitizing fluid, such as seawater or seawater- derived fluids. By contrast, SD dolomites have a different REE partition pattern with left-leaning characteristics, LREE depletions, and negative Eu anomalies, thus suggesting a different dolomitizing fluid source from the matrix dolomites. In addition, the development of intercrystalline pores associated with D2 dolomite makes it more likely to be a potential reservoir, indicating that the dolomitizing history of carbonate has a strong influence on the quality of potential dolomite reservoirs.

show abstract

Origin of dolomites in the Cambrian (upper 3rd‐Furongian) formation, south‐eastern Sichuan Basin, China

Cited by 17 publications

References 69 publications

Geochemistry characteristics and dolomitization mechanism of the Upper Cambrian dolomite, eastern Ordos Basin, China

Geochemistry characteristics and dolomitization mechanism of the Upper Cambrian dolomite, eastern Ordos Basin, China

Multiphase dolomitization in Devonian Shogram Formation, Chitral, Karakorum ranges, Pakistan: Evidence from outcrop analogue, petrography, and geochemistry

Petrographic, Rare Earth Elemental and Isotopic Constraints on the Dolomite Origin: A Case Study from the Middle-Upper Cambrian Xixiangchi Formation in Eastern Sichuan Basin, Southwest China

Contact Info

Product

Resources

About