Effect of sedimentary environment on the formation of organic-rich marine shale: Insights from major/trace elements and shale composition

AbstractThe Ordos Basin is the largest and most important intracontinental sedimentary depression in China, and a significant amount of crude oil resources has developed within this Mesozoic formation. High-grade organic-rich shale is prevalent in the large-scale areas of the Chang 7 sedimentary stage and provides essential hydrocarbon resources for abundant oil enrichment in the Mesozoic. This research investigated the geochemical characteristics of Chang 7 shale using core samples and well logs and via laboratory tests. In addition, the microscopic components of the shale organic matter (OM), biological marker compounds, carbon isotopes, enrichment grade of trace elements, and elemental ratio were analysed systematically. Moreover, the aspects related to the shale OM source, sedimentary environment and resource potential were evaluated. Our results revealed that spherical alginate and calcium spherical alginate were predominant in the micropetrological components of the shale. Many biomarkers, including n-alkanes, steranes and terpanes, were detected in the gas chromatography – mass spectrometry spectra. An analysis of n-alkanes, regular sterane shapes (C21−/C22− and C26+C27/C28+C29), odd–even predominance index (OEP) and carbon preference index (CPI) values and carbon isotope distributions showed that OM was produced from aquatic organisms. The indicators of trace elements, such as Sr/Ba and V/V+Ni, combined with the biomarker compound in Pr/Ph and the gammacerane index showed the presence of a semi-deep – deep lake environment containing fresh–brackish water. In addition, the hydrocarbon conversion rate index and shale rock pyrolysis parameters revealed that Chang 7 has a high hydrocarbon generation ability and hydrocarbon expulsion efficiency.

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Paleogeographic Characteristics of the Mengyejing Formation in the Simao Basin during Its Depositional Period and Its Indication of Potash Mineralization: A Case Study of MZK-3 Well

Minerals ◽

10.3390/min11040338 ◽

2021 ◽

Vol 11 (4) ◽

pp. 338

Author(s):

Pengcheng Lou ◽

Zhongying Miao ◽

Mianping Zheng ◽

Xuefei Zhang ◽

Zhuang Ruan ◽

...

Keyword(s):

Trace Elements ◽

Sedimentary Environment ◽

Protective Layer ◽

Major Elements ◽

Oxidation Condition ◽

Average Value ◽

Marine Strata ◽

Clastic Sediments ◽

Post Archean Australian Shale ◽

Deep Source

In China, pre-Quaternary solid potash deposit has only been discovered in the Simao Basin, and the Lower Cretaceous Mengyejing (MYJ) Formation (Fm.) is the productive layer of potash deposit. In this study, we investigated the clay conglomerates which are distributed in upper and lower members of the potash-bearing salt rock layer. We analyzed the relative contents of major elements (Al2O3, Fe2O3T, MgO, CaO, Na2O, K2O) and trace elements (B, Ba, Co, Cr, Cu, Ga, Mn, Ni, Rb, Sr, V, Zn, Zr) in the samples. The results show that MgO and CaO in the major elements are rich relative to Post Archean Australian Shale (PAAS), whose average enrichment factor values of the MgO (EFMgO) is 2.61 and CaO (EFCaO) is 4.57, and the others major elements are relatively minor; trace elements (B, Ga, Mn, Zr) are rich relative to PAAS, and the others trace elements are minor relative to PAAS. The study of paleogeographic conditions using various parameters shows that the paleoclimate is generally dry and hot during the period of clay conglomerate deposition, but it was warm and humid in certain periods; the main sedimentary environment is weak oxidation condition with strong oxidation conditions in individual periods; the average value of paleosalinity is ~21‰, and the highest is no more than ~92‰. The significance of the paleogeographic characteristics of MYJ Fm. to potash mineralization are as follows: (1) they indicates that the clay conglomerates of MYJ Fm. are not clastic sediments in brine formed by seawater, because the paleosalinity of clay conglomerates deposition period is obviously lower than that of seawater; (2) MYJ potassic salt ore is not formed by evaporation and concentration of seawater in clay conglomerates in the sedimentary basin, because there is no carbonate rock and sulfate rock of corresponding scale after the deposition of clay conglomerates in the basin; (3) clay conglomerates of MYJ Fm. were deposited in continental shallow water basin; (4) the matter source of potash minerals is deep marine strata; (5) in the MYJ Fm. sedimentation period, deep source salt moved to the surface under the background of extensional structure, and the subsequent sedimentary clastic rock formed a protective layer of potash-bearing rock, thus completing the “deep source and shallow mineralization” metallogenic process.

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Factors Controlling Organic Matter Accumulation in the Wufeng–Longmaxi Formations in Northwestern Hunan Province: Insights from Major/Trace Elements and Shale Composition

Energy & Fuels ◽

10.1021/acs.energyfuels.9b04415 ◽

2020 ◽

Vol 34 (4) ◽

pp. 4139-4152 ◽

Cited By ~ 1

Author(s):

Zhaodong Xi ◽

Shuheng Tang ◽

Songhang Zhang ◽

Yapei Ye

Keyword(s):

Trace Elements ◽

Organic Matter ◽

Hunan Province ◽

Organic Matter Accumulation ◽

Shale Composition

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Geochemical characteristics and depositional environment of the Shahejie Formation in the Binnan Oilfield, China

Journal of Geophysics and Engineering ◽

10.1093/jge/gxaa013 ◽

2020 ◽

Vol 17 (3) ◽

pp. 539-551 ◽

Cited By ~ 2

Author(s):

Xiaochun Zuo ◽

Cunlei Li ◽

Jinliang Zhang ◽

Guiyang Ma ◽

Panpan Chen

Keyword(s):

Trace Elements ◽

Inductively Coupled Plasma ◽

Environmental Changes ◽

Salt Water ◽

Sedimentary Environment ◽

Effective Means ◽

Research Area ◽

Major Elements ◽

Sedimentary Environments ◽

Shahejie Formation

Abstract Trace elements in sedimentary rocks are highly sensitive to palaeoaquatic environmental changes in a sedimentary environment, making them an effective means for studying the paleoclimate and paleoenvironment during the deposition of sediments. The trace elements and major elements of mudstone cores sampled in the Binnan Oilfield in China were tested by inductively coupled plasma mass spectrometry (ICP–MS). Strontium (Sr), barium (Ba), vanadium (V), nickel (Ni) and boron (B), which are all sensitive to the sedimentary environment, were selected as discriminant indicators, and the sedimentary environment of the Shahejie Formation in the Binnan Oilfield was studied by combining with sedimentary indicators. The results show that the equivalent B content and the Sr/Ba ratio discriminate the research area for salt water and freshwater sedimentary environments. The V/(V + Ni) ratio is between 0.65 and 0.81, meaning that this area has a highly reductive sedimentary stratum. The trend of the Rb/Sr curve indicates that the paleoclimate of the Shahejie Formation changed from dry to humid and then back to dry.

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Distribution of Trace Elements, Sr-C Isotopes, and Sedimentary Characteristics as Paleoenvironmental Indicator of the Late Permian Linxi Formation in the Linxi Area, Eastern Inner Mongolia

Journal of Chemistry ◽

10.1155/2020/7027631 ◽

2020 ◽

Vol 2020 ◽

pp. 1-17 ◽

Cited By ~ 1

Author(s):

Linlin Wang ◽

Yongsheng Zhang ◽

Enyuan Xing ◽

Yuan Peng ◽

Dongdong Yu

Keyword(s):

Trace Elements ◽

Rare Earth ◽

Inner Mongolia ◽

Sedimentary Environment ◽

Late Permian ◽

Hydrocarbon Source Rock ◽

Sedimentary Characteristics ◽

C Isotopes ◽

Eastern Inner Mongolia ◽

Linxi Formation

The Late Permian on the periphery of the Songliao Basin, eastern Inner Mongolia, is an important hydrocarbon source rock system. Its sedimentary environment plays an important role in the evaluation of hydrocarbon prospects in the area. Unfortunately, until now, the interpretation of the sedimentary environment of this area has been controversial. We investigated the Late Permian sedimentary environment by studying the sedimentary characteristics and geochemistry. Based on these investigations, we conclude that the Linxi Formation is mainly composed of clastic sediments, interbedded with limestone lenses, with bioherm limestone at the top of the formation. Inner-layer marine fossils (calcium algae, bryozoans, and sponges) and freshwater and blackish water microfossils (bivalves) are all present, indicative of a typical shallow water sedimentary environment with an open and concussion background. In terms of geochemistry, the formation is relatively light rare Earth enriched, with significant positive Eu anomaly, slight positive La and Y anomaly, weak positive Gd anomaly, and lack of Ce anomaly. The average B/Ga ratio of the mudstone is greater than 3.3, and the average Sr/Ba ratio of the limestone is greater than 1.0. The range of the 87Sr/86Sr ratio is from 0.707285 to 0.707953. The range of δ13C values is from −4.0‰ to 2.4‰. The sediment assemblages, rare Earth elements, trace elements, and 87Sr/86Sr and C isotopes of the formation indicate that the Linxi Formation formed in a marine sedimentary environment and occasional marine-terrestrial transitional facies. The formation can be further divided into littoral facies, neritic facies, bathyal facies, and delta front.

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The Research of the Mineralogical and Element Geochemical Characteristics of Bauxite in Yunfeng, Qingzhen, in Central Guizhou Province, China

The Open Chemical Engineering Journal ◽

10.2174/1874123101509010134 ◽

2015 ◽

Vol 9 (1) ◽

pp. 134-142 ◽

Cited By ~ 1

Author(s):

Yang Wu ◽

Dai Tagen ◽

Long Yongzhen

Keyword(s):

Trace Elements ◽

Sedimentary Environment ◽

Geochemical Characteristics ◽

Guizhou Province ◽

Element Geochemistry ◽

Ore Deposit ◽

Thin Section Analysis ◽

Main Components ◽

Mineral Analyses ◽

Section Analysis

The mineralogical and geochemical characteristics of the Yunfeng bauxite in Qingzhen were investigated through the handle specimen observation, thin section analysis, XRD、SEM and Element geochemistry. The mineral analyses reveal that diaspore, kaolinite and chlorite are the major minerals in the bauxite with small amounts of boehmite and pyrite. Geochemical investigations reveal that the main components in the bauxite are Al2O3, SiO2 and TFe2O3, the minorcomponents are TiO2, MgO and P2O5. In the process of weathering, some trace elements, such as Zr, Cr, Nb and Hf, are enriched. Zr vs Hf and Nb vs Ta display higher positive correlation. Trace elements show that Loushanguan Formation is the main source of material for the bauxite formation and there may be exist other precursor rock provide few material for the bauxite formation. Ore deposit formed in a O-poor,reducing Marine sedimentary environment.

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