scholarly journals Age, material source, and formation mechanism of bedding-parallel calcite beef veins: Case from the mature Eocene lacustrine shales in the Biyang Sag, Nanxiang Basin, China

2021 ◽  
Author(s):  
Ao Su ◽  
Paul D. Bons ◽  
Honghan Chen ◽  
Yue-xing Feng ◽  
Jian-xin Zhao ◽  
...  
Keyword(s):  
Organic Matter ◽  
Fluid Inclusion ◽  
Host Rock ◽  
Inductively Coupled Plasma ◽  
Driving Forces ◽  
Burial Depth ◽  
Organic Carbon Content ◽  
Gas Generation ◽  
Material Source ◽  
Vein Formation

The mechanisms leading to the formation of bedding-parallel calcite beef veins have been widely debated, with discussions centered on timing or burial depth of vein generation, source of the vein material, driving forces for vein initiation and widening, and growth direction and mechanism. To address these issues, a comprehensive study of drill core samples containing beef veins in the mature Eocene lacustrine Hetaoyuan Formation in the Biyang Sag, Nanxiang Basin, China was undertaken through a combination of microstructural observation, isotopic geochronological, geochemical, and fluid inclusion analyses, as well as basin modeling. X-ray diffraction and total organic carbon content analyses indicate that most of the beef veins accumulated in calcite-rich laminated shales with high organic matter contents. These beef veins yielded an absolute laser ablation−multi-collector−inductively coupled plasma−mass spectrometry U-Pb age of ca. 41.02 ± 0.44 Ma, which corresponds to a burial depth of 500−800 m. Such a shallow burial depth suggests that the full compaction and consolidation of sediments would not yet have been achieved, which is compatible with the following observations: (1) plastic deformation of shale laminae adjacent to the veins, and (2) a beef vein formation temperature of ∼59 °C derived from fluid-inclusion microthermometry. The radio-isotopic age of the beef veins is ∼1−3 m.y. younger than the stratigraphic age of the host rock (ca. 43.1 Ma) but earlier than the model-derived timing of oil generation (ca. 35.8 Ma) and tectonic extrusion (ca. 23.0−13.0 Ma). The beef vein formation predated bacterial sulfate reduction, as evidenced by crosscutting relationships with carbonate concretions, pyrite framboids, and apatite pellets. A two-stage formation model for these beef veins is proposed. When burial depth of laminated shales rich in organic matter and calcite reaches the methanogenic zone, overpressure triggered by biogenetic gas generation results in horizontal hydrofracturing, initiating cracks that act as gas expulsion pathways. Once all the generated gas has migrated, the opened fractures close again due to overburden load. The materials fed by pressure solution of host-rock calcite fractions then mobilized into the unhealed horizontal fractures by diffusion. Subsequently, by a force of crystallization, antitaxial, displacive growth of calcite fibers commenced, contemporaneous with fracture dilation, eventually leading to the formation of bedding-parallel beef veins.

scholarly journals Shale favorable area optimization in coal-bearing series: A case study from the Shanxi Formation in Northern Ordos Basin, China

2017 ◽  
Vol 36 (5) ◽  
pp. 1295-1309 ◽  
Author(s):  
Wei Guo ◽  
Weijun Shen ◽  
Shangwen Zhou ◽  
Huaqing Xue ◽  
Dexun Liu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Shale Gas ◽  
Ordos Basin ◽  
Sedimentary Facies ◽  
Gas Content ◽  
Burial Depth ◽  
Organic Carbon Content ◽  
River Channels

Shales in the Well district of Yu 106 of the Shanxi Formation in the Eastern Ordos Basin is deposited in the swamp between delta plains, distributary river channels, natural levee, the far end of crevasse splay, and depression environments. According to organic geochemistry, reservoir physical property, gas bearing capacity, lithology experimental analysis, combined with the data of drilling, logging, testing and sedimentary facies, the reservoir conditions of shale gas and the distribution of an advantageous area in Shanxi Formation have been conducted. The results show that the total organic carbon content of the Shanxi Formation is relatively high, with an average content value of 5.28% in the segment 2 and 3.02% in segment 1, and the organic matter is mainly kerogen type II2 and III. The maturity of organic matter is high with 1.89% as the average value of Ro which indicates the superior condition for gas generation of this reservoir. The porosity of shales is 1.7% on average, and the average permeability is 0.0415 × 10−3 µm2. The cumulative thickness is relatively large, with an average of 75 m. Brittle mineral and clay content in shales are 49.9% and 50.1%, respectively, but the burial depth of shale is less than 3000 m. The testing gas content is relatively high (0.64 × 104 m3/d), which shows a great potential in commercial development. The total organic carbon of the segment 2 is higher than that of the segment 1, and it is also better than segment 1 in terms of gas content. Based on the thickness of shale and the distribution of sedimentary facies, it is predicted that the advantageous area of shale gas in the segment 2 is distributed in a striped zone along the northeast and the northsouth direction, which is controlled by the swamp microfacies between distributary river channels.

scholarly journals Fracture characteristics from outcrops and its meaning to gas accumulation in the Jiyuan Basin, Henan Province, China

2020 ◽  
Vol 12 (1) ◽  
pp. 1309-1323
Author(s):  
Changyan Sun ◽  
Xianbo Su ◽  
Heng Yang ◽  
Feng Li
Keyword(s):  
Oil Shale ◽  
Vitrinite Reflectance ◽  
Second Phase ◽  
Burial Depth ◽  
Organic Carbon Content ◽  
Hydrocarbon Generation ◽  
Fracture Density ◽  
Gas Generation ◽  
Fracture Characteristics ◽  
Gas Accumulation

AbstractThe target Oil-Shale Member (TOSM) in the Upper Triassic Tanzhuang Formation in the Jiyuan Basin is about 140 m thick and its burial depth is generally between 3,000 and 7,000 m. This paper presents a study of fractures in outcrop analogs for the TOSM based on outcrop observations and experimental measurements. The role of fractures in gas accumulation in the Jiyuan Basin was also analyzed. Also, a workflow used in building discrete fracture models based on the outcrop observed data is described. Results show that the average total organic carbon content and vitrinite reflectance of the oil shale are 4.13 and 1.33%, respectively, with the organic matter type dominated by sapropel-humics (II1), indicating high potential for shale gas generation. Fracture characteristics showing mostly vertical or intersect the bedding at high angles, and partially unfilled. The fracture lengths and widths range from a few centimeters to several hundred meters, and 0.05 to 0.5 cm, respectively, and the average linear fracture density is 6.3 m. In addition, the average brittle-mineral content of the oil shale is 53.7%, indicating that the oil shale in the TOSM has strong fracability. The hydrocarbon generation occurred twice in the TOSM. The primary reservoir formed by the first hydrocarbon generation was destroyed by fractures and tectonic uplift, and partial hydrocarbon migrated to the Paleogene along the second-phase fractures to form a secondary reservoir. The gas formed by the second hydrocarbon generation was mainly migrated into the fracture network of the TOSM.

The Middle Jurassic Source Rock Condition of Circumjacent Depressions and Exploration Potential of Camck-Aral Sea Zones

2013 ◽  
Vol 703 ◽  
pp. 127-130
Author(s):  
Hui Ting Hu ◽  
Hai Tao Xue ◽  
Yi Han Wang ◽  
Xiao Dong Chen
Keyword(s):  
Organic Matter ◽  
Source Rock ◽  
Middle Jurassic ◽  
Thermal Evolution ◽  
Aral Sea ◽  
Geochemical Data ◽  
Maturation Stage ◽  
Organic Carbon Content ◽  
Gas Generation ◽  
Quantitative Calculation

In order to evaluate the exploration potential of CamckAral sea zones, the geological and geochemical data, qualitative appraisement and quantitative calculation method are used to study the Middle Jurassic source rock conditions of circumjacent depressions of CamckAral sea zones. This research indicates that: the Middle Jurassic source rock in these depressions are relatively development, with type II2 and III organic matter which have a higher gas generation potential; and organic carbon content is relatively higher; the thermal evolution of the organic matter has reached maturation stage. It means that the north Camck zone and water area of Aral sea have more exploration potential.

scholarly journals Magma Mixing Genesis of the Mafic Enclaves in the Qingshanbao Complex of Longshou Mountain, China: Evidence from Petrology, Geochemistry, and Zircon Chronology

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 195 ◽  
Author(s):  
Wenheng Liu ◽  
Xiaodong Liu ◽  
Jiayong Pan ◽  
Kaixing Wang ◽  
Gang Wang ◽  
...  
Keyword(s):  
Host Rock ◽  
Inductively Coupled Plasma ◽  
Magma Mixing ◽  
Coarse Grained ◽  
Calc Alkaline ◽  
Quartz Crystals ◽  
Alkaline Rocks ◽  
Mafic Enclaves ◽  
Normal Zoning ◽  
Host Rocks

The Qingshanbao complex, part of the uranium metallogenic belt of the Longshou-Qilian mountains, is located in the center of the Longshou Mountain next to the Jiling complex that hosts a number of U deposits. However, little research has been conducted in this area. In order to investigate the origin and formation of mafic enclaves observed in the Qingshanbao body and the implications for magmatic-tectonic dynamics, we systematically studied the mineralogy, petrography, and geochemistry of these enclaves. Our results showed that the enclaves contain plagioclase enwrapped by early dark minerals. These enclaves also showed round quartz crystals and acicular apatite in association with the plagioclase. Electron probe analyses showed that the plagioclase in the host rocks (such as K-feldspar granite, adamellite, granodiorite, etc.) show normal zoning, while the plagioclase in the mafic enclaves has a discontinuous rim composition and shows instances of reverse zoning. Major elemental geochemistry revealed that the mafic enclaves belong to the calc-alkaline rocks that are rich in titanium, iron, aluminum, and depleted in silica, while the host rocks are calc-alkaline to alkaline rocks with enrichment in silica. On Harker diagrams, SiO2 contents are negatively correlated with all major oxides but K2O. Both the mafic enclaves and host rock are rich in large ion lithophile elements such as Rb and K, as well as elements such as La, Nd, and Sm, and relatively poor in high field strength elements such as Nb, Ta, P, Ti, and U. Element ratios of Nb/La, Rb/Sr, and Nb/Ta indicate that the mafic enclaves were formed by the mixing of mafic and felsic magma. In terms of rare earth elements, both the mafic enclaves and the host rock show right-inclined trends with similar weak to medium degrees of negative Eu anomaly and with no obvious Ce anomaly. Zircon LA-ICP-MS (Laser ablation inductively coupled plasma mass spectrometry) U-Pb concordant ages of the mafic enclaves and host rock were determined to be 431.8 5.2 Ma (MSWD (mean standard weighted deviation)= 1.5, n = 14) and 432.8 4.2 Ma (MSWD = 1.7, n = 16), respectively, consistent with that for the zircon U-Pb ages of the granite and medium-coarse grained K-feldspar granites of the Qingshanbao complex. The estimated ages coincide with the timing of the late Caledonian collision of the Alashan Block. This comprehensive analysis allowed us to conclude that the mafic enclaves in the Qingshanbao complex were formed by the mixing of crust-mantle magma with mantle-derived magma due to underplating, which caused partial melting of the ancient basement crust during the collisional orogenesis between the Alashan Block and Qilian rock mass in the early Silurian Period.

scholarly journals Impact of soil use on aggregate stability and its relationship with soil organic carbon at two different altitudes in the Colombian Andes

2019 ◽  
Vol 37 (3) ◽  
pp. 263-273
Author(s):  
Efraín Francisco Visconti-Moreno ◽  
Ibonne Geaneth Valenzuela-Balcázar
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Aggregate Stability ◽  
Tropical Climate ◽  
Mineral Particle ◽  
Organic Carbon Content ◽  
Rice Soils ◽  
Organic Matter Pool ◽  
Different Altitudes

The stability of soil aggregates depends on the organic matter, and the soil use and management can affect the soil organicmatter (SOM) content. Therefore, it is necessary to know therelationship between aggregate stability and the content of SOMin different types of soil use at two different altitudes of theColombian Andes. This study examined the conditions of soilaggregate stability expressed as a distribution of the size classes of stable aggregates (SA) and of the mean weighted diameter of the stable aggregates (MWD). To correlate these characteristics with the soil organic carbon (OC), we measured the particulate organic matter pool (POC), the OC associated with the mineral organic matter pool (HOC), the total organic carbon content (TOC), and the humification rate (HR). Soils were sampled at two altitudes: 1) Humic Dystrudepts in a cold tropical climate (CC) with three plots: tropical mountain rainforest, pastures, and crops; 2) Fluvaquentic Dystrudepts in a warm tropical climate (WC) with three plots: tropical rainforest, an association of oil palm and pastures, and irrigated rice. Soils were sampled at three depths: 0-5, 5-10 and 10-20 cm. The physical properties, mineral particle size distribution, and bulk density were measured. The content of SA with size>2.36 mm was higher in the CC soil (51.48%) than in the WC soil (9.23%). The SA with size 1.18-2.36 mm was also higher in the CC soil (7.78%) than in the WC soil (0.62%). The SA with size 0.60-1.18 mm resulted indifferent. The SA with size between 0.30 and 0.60 mm were higher in the WC soil (13.95%) than in the CC soil (4.67%). The SA<0.30 mm was higher in the WC soil (72.56%) than in the CC soil (32.15%). It was observed that MWD and the SA>2.36 mm increased linearly with a higher POC, but decreased linearly with a higher HR. For the SA<0.30 mm, a linear decrease was observed at a higher POC, while it increased at a higher HR.

scholarly journals The characteristics of hydrocarbon generation, reserving performances of fine-grained rock, and preservation conditions of coal measure shale gas of an epicontinental sea basin: A case study of the Late Palaeozoic shale gas in the Huanghebei Area of Western Shandong

2018 ◽  
Vol 37 (1) ◽  
pp. 453-472 ◽  
Author(s):  
Ying Li ◽  
Zengxue Li ◽  
Huaihong Wang ◽  
Dongdong Wang
Keyword(s):  
Coal Seam ◽  
Shale Gas ◽  
Late Paleozoic ◽  
Organic Carbon Content ◽  
Hydrocarbon Generation ◽  
Average Content ◽  
Gas Generation ◽  
Geological Structures ◽  
Fine Grained ◽  
Western Shandong

In China, marine and land transitional fine-grained rocks (shale, mudstone, and so on) are widely distributed and are known to have large accumulated thicknesses. However, shale gas explorations of these types of rock have only recently been initiated, thus the research degree is very low. Therefore, this study was conducted in order to improve the research data regarding the gas accumulation theory of marine and continental transitional fine-grained rock, as well as investigate the shale gas generation potential in the Late Paleozoic fine-grained rock masses located in the Huanghebei Area of western Shandong Province. The hydrocarbon generation characteristics of the epicontinental sea coal measures were examined using sedimentology, petrography, geochemistry, oil and gas geology, tectonics, and combined experimental testing processes. The thick fine-grained rocks were found to have been deposited in the sedimentary environments of the tidal flats, barriers, lagoons, deltas, and rivers during the Late Paleozoic in the study area. The most typical fine-grained rocks were located between the No. 5 coal seam of the Shanxi Formation and the No. 10 coal seam of the Taiyuan Formation, with an average thickness of 84.8 m. These formations were mainly distributed in the western section of the Huanghebei Area. The total organic carbon content level of the fine-grained rock was determined to be 2.09% on average, and the higher content levels were located in the western section of the Huanghebei Area. The main organic matter types of the fine-grained rock were observed to be kerogen II, followed by kerogen III. The vitrinite reflectance ( Ro) of the fine-grained rock was between 0.72 and 1.25%, which indicated that the gas generation of the dark fine-grained rock was within a favorable range, and the maturity of the rock was mainly in a medium stage in the northern section of the Huanghebei Area. It was determined that the average content of brittle minerals in the fine-grained rock was 55.7%. The dissolution pores and micro-cracks were the dominating pores in the fine-grained rock, followed by intergranular pores and intercrystalline pores. It was also found that both the porosity and permeability of the fine-grained rock were very low in the study area. The desorption gas content of the fine-grained rock was determined to be between 0.986 and 4.328 m3/t, with an average content of 2.66 m3/t. The geological structures were observed to be simple in the western section of the Huanghebei Area, and the occurrence impacts on the shale gas were minimal. However, the geological structures were found be complex in the eastern section of the study area, which was unfavorable for shale gas storage. The depths of the fine-grained rock were between 414.05 and 1290.55 m and were observed to become increasingly deeper from the southwestern section to the northern section. Generally speaking, there were found to be good reservoir forming conditions and great resource potential for marine and continental transitional shale gas in the study area.

scholarly journals Short-Term Decomposition and Nutrient-Supplying Ability of Sewage Sludge Digestate, Digestate Compost, and Vermicompost on Acidic Sandy and Calcareous Loamy Soils

Agronomy ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2249
Author(s):  
Nikolett Uzinger ◽  
Orsolya Szécsy ◽  
Nóra Szűcs-Vásárhelyi ◽  
István Padra ◽  
Dániel Benjámin Sándor ◽  
...  
Keyword(s):  
Organic Matter ◽  
Sewage Sludge ◽  
Organic Carbon ◽  
Carbon Content ◽  
Plant Biomass ◽  
Test Plant ◽  
Organic Carbon Content ◽  
Short Term ◽  
Mineral N ◽  
Average Residual

Organic waste and the compost and vermicompost derived from it may have different agronomic values, but little work is available on this aspect of sewage sludge. A 75-day pot experiment with perennial ryegrass (Lolium perenne) as the test plant aimed to investigate the fertiliser value and organic matter replenishment capacity of digested sewage sludge (DS) and the compost (COM) and vermicompost (VC) made from it, applied in 1% and 3% doses on acidic sand and calcareous loam. The NPK content and availability, changes in organic carbon content and plant biomass, and the efficiency of the amendments as nitrogen fertilisers were investigated. The final average residual carbon content for DS, COM, and VC was 35 ± 34, 85 ± 46, and 55 ± 46%, respectively. The organic carbon mineralisation rate depended on the soil type. The additives induced significant N mineralisation in both soils: the average increment in mineral N content was 1.7 times the total added N on acidic sand and 4.2 times it on calcareous loam for the 1% dose. The agronomic efficiency of COM and VC as fertilisers was lower than that of DS. In the short term, DS proved to be the best fertiliser, while COM was the best for organic matter replenishment.

scholarly journals Effect of Tillage System and Organic Matter Management Interactions on Soil Chemical Properties and Biological Activity in a Spring Wheat Short-Time Cultivation

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7451
Author(s):  
Barbara Breza-Boruta ◽  
Karol Kotwica ◽  
Justyna Bauza-Kaszewska
Keyword(s):  
Organic Matter ◽  
Biological Activity ◽  
Organic Carbon ◽  
Spring Wheat ◽  
Chemical Properties ◽  
Soil Samples ◽  
Available Phosphorus ◽  
Organic Carbon Content ◽  
Tillage System ◽  
Short Time

Properly selected tillage methods and management of the available organic matter resources are considered important measures to enable farming in accordance with the principles of sustainable agriculture. Depending on the depth and intensity of cultivation, tillage practices affect soil chemical composition, structure and biological activity. The three-year experiment was performed on the soil under spring wheat (cv. Tybalt) short-time cultivation. The influence of different tillage systems and stubble management on the soil’s chemical and biological parameters was analyzed. Organic carbon content (OC); content of biologically available phosphorus (Pa), potassium (Ka), and magnesium (Mg); content of total nitrogen (TN), mineral nitrogen forms: N-NO3 and N-NH4 were determined in various soil samples. Moreover, the total number of microorganisms (TNM), bacteria (B), actinobacteria (A), fungi (F); soil respiratory activity (SR); and pH in 1 M KCl (pH) were also investigated. The results show that organic matter amendment is of greater influence on soil characteristics than the tillage system applied. Manure application, as well as leaving the straw in the field, resulted in higher amounts of organic carbon and biologically available potassium. A significant increase in the number of soil microorganisms was also observed in soil samples from the experimental plots including this procedure.

scholarly journals LA-ICP-MS U-Pb dating and geochemical characterization of oil inclusion-bearing calcite cements: Constraints on primary oil migration in lacustrine mudstone source rocks

2021 ◽  
Author(s):  
Ao Su ◽  
Honghan Chen ◽  
Yue-xing Feng ◽  
Jian-xin Zhao
Keyword(s):  
Fluid Inclusion ◽  
Inductively Coupled Plasma ◽  
Homogenization Temperature ◽  
Source Rocks ◽  
Oil Migration ◽  
Carbon And Oxygen Isotope ◽  
Fluorescence Characteristics ◽  
Calcite Veins ◽  
Migration Event

To date, few isotope age constraints on primary oil migration have been reported. Here we present U-Pb dating and characterization of two fracture-filling, oil inclusion-bearing calcite veins hosted in the Paleocene siliciclastic mudstone source rocks in Subei Basin, China. Deposition age of the mudstone formation was estimated to be ca. 60.2−58.0 Ma. The first vein consists of two major phases: a microcrystalline-granular (MG) calcite phase, and a blocky calcite phase, each showing distinctive petrographic features, rare earth element patterns, and carbon and oxygen isotope compositions. The early MG phase resulted from local mobilization of host carbonates, likely associated with disequilibrium compaction over-pressuring or tectonic extension, whereas the late-filling blocky calcite phase was derived from overpressured oil-bearing fluids with enhanced fluid-rock interactions. Vein texture and fluorescence characteristics reveal at least two oil expulsion events, the former represented by multiple bitumen veinlets postdating the MG calcite generation, and the latter marked by blue-fluorescing primary oil inclusions synchronous with the blocky calcite cementation. The MG calcite yields a laser ablation−inductively coupled plasma−mass spectrometry U-Pb age of 55.6 ± 1.4 Ma, constraining the earliest timing of the early oil migration event. The blocky calcite gives a younger U-Pb age of 47.8 ± 2.3 Ma, analytically indistinguishable from the U-Pb age of 46.5 ± 1.7 Ma yielded by the second calcite vein. These two ages define the time of the late oil migration event, agreeing well with the age estimate of 49.7−45.2 Ma inferred from fluid-inclusion homogenization temperature and published burial models. Thermodynamic modeling shows that the oil inclusions were trapped at ∼27.0−40.9 MPa, exceeding corresponding hydrostatic pressures (23.1−26.7 MPa), confirming mild-moderate overpressure created by oil generation-expulsion. This integrated study combining carbonate U-Pb dating and fluid-inclusion characterization provides a new approach for reconstructing pressure-temperature-composition-time points in petroleum systems.

scholarly journals Modeling biogeochemical processes in sediments from the Rhône River prodelta area (NW Mediterranean Sea)

2011 ◽  
Vol 8 (1) ◽  
pp. 549-592 ◽  
Author(s):  
L. Pastor ◽  
C. Cathalot ◽  
B. Deflandre ◽  
E. Viollier ◽  
K. Soetaert ◽  
...  
Keyword(s):  
Organic Matter ◽  
Oxygen Consumption ◽  
Continental Shelf ◽  
Carbon Mineralization ◽  
River Mouth ◽  
Total Carbon ◽  
Large Contribution ◽  
Organic Carbon Content ◽  
Rhône River ◽  
Rhone River

Abstract. In-situ oxygen microprofiles, sediment organic carbon content and pore-water concentrations of nitrate, ammonium, iron, manganese and sulfides obtained in sediments from the Rhône River prodelta and its adjacent continental shelf were used to constrain a numerical diagenetic model. Results showed that (1) organic matter from the Rhône River is composed of a fraction of fresh material associated to high first-order degradation rate constants (11–33 yr−1), (2) burial efficiency (burial/input ratio) in the Rhône prodelta (within 3 km of the river outlet) can be up to 80%, and decreases to ~20% on the adjacent continental shelf 10–15 km further offshore (3) there is a large contribution of anoxic processes to total mineralization in sediments near the river mouth, certainly due to large inputs of fresh organic material combined with high sedimentation rates, (4) diagenetic by-products originally produced during anoxic organic matter mineralization are almost entirely precipitated (>97%) and buried in the sediment, which leads to (5) a low contribution of the re-oxidation of reduced products to total oxygen consumption. Consequently, total carbon mineralization rates as based on oxygen consumption rates and using Redfield stoichiometry can be largely underestimated in such River Ocean dominated Margins (RiOMar) environments.

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