scholarly journals Elemental Geochemical Evidence for Depositional Conditions and Organic Matter Enrichment of Black Rock Series Strata in an Inter-Platform Basin: The Lower Carboniferous Datang Formation, Southern Guizhou, Southwest China

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 509 ◽  
Author(s):  
Jianghui Ding ◽  
Jinchuan Zhang ◽  
Xuan Tang ◽  
Zhipeng Huo ◽  
Shuangbiao Han ◽  
...  
Keyword(s):  
Organic Matter ◽  
Southwest China ◽  
Tectonic Setting ◽  
Sedimentary Environment ◽  
Active Continental Margin ◽  
Source Rocks ◽  
Guizhou Province ◽  
Dominant Factor ◽  
Rock Series ◽  
Black Rock Series

The Datang Formation black rock series deposited in an inter-platform basin are considered to be one of the main source rocks in Southwest China. However, their depositional conditions and organic matter enrichment in such a setting are not well understood. In this study, geochemical characteristics of total organic carbon (TOC), major, trace and rare earth elements (REEs) of thirty black rock series samples from a newly-cut roadside outcrop (Zhenning section) in Southern Guizhou, Southwest China are systematically investigated to examine provenance, paleoredox conditions, paleoclimate, paleoproductivity and sedimentary rate, and further to explore their influence on organic matter enrichment. Results show that TOC contents of the investigated samples range from 0.90% to 2.83%, with an average of 1.45%, with TOC variations being in accord with the stratigraphic cyclicity. These data also indicate that the target black rock series were deposited in a combination of continental island arc and active continental margin tectonic setting that exhibited moderate weathering, oxic/dysoxic oxygen levels, hot and arid to semiarid climate, and a higher sedimentary rate. Multiple paleoredox indicators (e.g., Ni/Co, V/Cr, U/Th and V/(V + Ni) ratios), together with slightly negative Ce anomalies and EFU-EFMo covariation, totally suggest an oxic/dysoxic water environment, which is usually considered unfavorable for organic matter preservation. Average (La/Yb)N ratios (1.41) reflect a higher sedimentary rate, resulting in shortening the exposure time of organic matter in the degradation region of aerobic bacteria under oxic/dysoxic conditions. Of the three factors that could affect organic matter enrichment, including paleoproductivity, paleoredox conditions and sedimentary rate, the relatively high paleoproductivity indicated by the relatively high TOC contents appears to be the dominant factor. In contrast, the other two factors, i.e., paleoredox conditions and the rate of sedimentation play relatively less significant roles. Based on these factors, an enrichment model of organic matter for the black rock series in Southern Guizhou Depression is established. These findings also contribute to constraining the sedimentary environment in such a setting and further deepen our understanding of the potential shale gas resources of the Southern Guizhou Province.

scholarly journals Geochemistry of the black rock series of lower Cambrian Qiongzhusi Formation, SW Yangtze Block, China: Reconstruction of sedimentary and tectonic environments

2021 ◽  
Vol 13 (1) ◽  
pp. 166-187
Author(s):  
Hao Liu ◽  
Chan Wang ◽  
Yong Li ◽  
Jianghong Deng ◽  
Bin Deng ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Sedimentary Environment ◽  
Hydrothermal Fluids ◽  
Early Cambrian ◽  
Rock Series ◽  
Yangtze Block ◽  
Tectonic Environment ◽  
Weathering Intensity ◽  
Black Rock Series ◽  
Tectonic System

Abstract The black rock series in the Qiongzhusi Formation contains important geochemical information about the early Cambrian tectonic and ecological environment of the southwestern Yangtze Block. In this paper, major, trace, and rare earth element data are presented in an attempt to reveal the sediment source during the deposition of the early Cambrian Qiongzhusi Formation and to reconstruct the sedimentary tectonic environment and weathering intensity during that time. The basin primarily received continental clastic material with neutral-acidic igneous rocks from a stable source and with a moderate level of maturity during the depositional period of the Qiongzhusi Formation. Furthermore, the strata were weakly influenced by submarine hydrothermal fluids during diagenesis. The reconstruction of the sedimentary environment and weathering intensity shows that P2O5 enrichment and water body stratification occurred due to the effects of upwelling ocean currents during the depositional period of the Qiongzhusi Formation. The combination of upwelling and bottom-water hydrothermal fluids led to environmental changes in the study area, from dry and hot to moist and warm. Last, the reconstruction of the tectonic environment of the Qiongzhusi Formation indicates that deposition occurred in continental slope and marginal marine environments associated with a continental arc tectonic system. These findings provide an essential basis for the comprehensive reconstruction of the early Cambrian sedimentary environment of the Yangtze Block.

scholarly journals Geochemistry of the Paleocene Clastic Rocks From the Southwestern Jianghan Basin, Central China Reveal Their Provenance, Tectonic Setting, and Palaeoenvironment

2021 ◽  
Author(s):  
Kai Yan ◽  
Chun-lian Wang ◽  
Jiu-yi Wang ◽  
Xiao-can Yu ◽  
Xiao-hua Teng ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Active Continental Margin ◽  
Source Area ◽  
Source Rocks ◽  
Central China ◽  
Clastic Rocks ◽  
Ree Distribution ◽  
C Value ◽  
Tectonic Settings ◽  
Jianghan Basin

Abstract This paper intends to learn about the provenance, tectonic setting and paleoenvironment of the Paleocene Shashi Formation in the southern Jianghan Basin by the bulk-rock geochemistry. The K2O/Al2O3 and SiO2/Al2O3 ratios indicate that the major proportion of samples are litharenite. The chondrite-normalized REE distribution pattern of the Shashi Formation’s mudstones are characterized by enriched LREE and flat HREE similar to those of UC with negative Eu anomalies. Combined with the geochemical element ratio discriminant diagram, such as Al2O3-TiO2, Zr-TiO2, La/Sc-Co/Th, and Hf-La/Th, so on, these samples were sourced from mixed felsic/basic rock. Moreover, the discriminant diagrams of K2O/Na2O-SiO2/Al2O3, La-Th-Sc, and Th-Co-Zr/10 suggest that the samples were formed under the tectonic settings of active continental margin and continental island arc. The values of CIA, CIW, PIA, ICV, Zr/Sc-Th/Sc, and ternary diagrams of A-(CN)-K and Al2O3-Zr-TiO2 indicate that weathering in the source area was weak and source rocks have not been reformed by depositional recirculation and hydraulic sorting. And the palaeoenvironmental indicators of C-value, Ni/Co, V/Cr, V/(V+Ni) and Sr/Cu, Ga/Rb indicate that the climate was cool and arid during the evaporite deposition period in the southern Jianghan Basin, and the water was in the condition of oxidation.

scholarly journals Relationships between Alluvial Facies/Depositional Environments, Detrital Zircon U-Pb Geochronology, and Bulk-Rock Geochemistry in the Cretaceous Neungju Basin (Southwest Korea)

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1023
Author(s):  
Hyojong Lee ◽  
Min Gyu Kwon ◽  
Seungwon Shin ◽  
Hyeongseong Cho ◽  
Jong-Sun Kim ◽  
...  
Keyword(s):  
Continental Margin ◽  
Detrital Zircon ◽  
Tectonic Setting ◽  
Active Continental Margin ◽  
Depositional Environments ◽  
Source Rocks ◽  
Bulk Rock ◽  
Zircon Age ◽  
Margin Setting ◽  
Weathering Intensity

Zircon U-Pb geochronology and bulk-rock geochemistry analyses were carried out to investigate their relationship with depositional environments of the non-marine Neungju Basin sediments in South Korea. The Neungju Basin was formed in an active continental margin setting during the Late Cretaceous with associated volcanism. Detrital zircon age distributions of the Neungju Basin reveal that the source rocks surrounding the basin supplied sediments into the basin from all directions, making different zircon age populations according to the depositional environments. Mudstone geochemistry with support of detrital zircon U-Pb age data reveals how the heterogeneity affects the geochemical characteristics of tectonic setting and weathering intensity. The sediments in the proximal (alluvial fan to sandflat) and distal (playa lake) environments differ compositionally because sediment mixing occurred exclusively in the distal environment. The proximal deposits show a passive margin signature, reflecting their derivation from the adjacent metamorphic and granitic basement rocks. The distal deposits properly indicate an active continental margin setting due to the additional supply of reworked volcaniclastic sediments. The proximal deposits indicate a minor degree of chemical weathering corresponding to fossil and sedimentological records of the basin, whereas the distal deposits show lower weathering intensity by reworking of unaltered volcaniclastic detritus from unstable volcanic and volcaniclastic terranes. Overall, this study highlights that compositional data obtained from a specific location and depositional environments may not describe the overall characteristic of the basin.

The Source of Organic Matter and Its Role in Producing Reduced Sulfur for the Giant Sediment-Hosted Jinding Zinc-Lead Deposit, Lanping Basin, Yunnan, Southwest China

2021 ◽  
Author(s):  
Qing Lan ◽  
Ruizhong Hu ◽  
Xianwu Bi ◽  
Hu Liu ◽  
Jiafei Xiao ◽  
...  
Keyword(s):  
Organic Matter ◽  
Sulfate Reduction ◽  
Southwest China ◽  
Sulfide Minerals ◽  
Source Rocks ◽  
Late Triassic ◽  
Sulfide Mineralization ◽  
Solid Bitumen ◽  
Fine Grained ◽  
Reduced Sulfur

Abstract The Jinding deposit, located in the northern part of Lanping basin in southwest China, is the second largest Zn-Pb deposit in China and the third largest Mississippi Valley-type deposit identified globally. The deposit consists of several large tabular orebodies within the Jinding dome. Two stages of sulfide mineralization (sphalerite, galena, and pyrite) are identified, which are mainly hosted in the siliciclastic strata of Early Cretaceous and Paleocene age. The early sulfide minerals are mostly fine grained (<100 μm) and disseminated in the host rocks, whereas the late minerals are ty pically coarse grained (up to 1 mm in diameter) and colloform. It is estimated that about 3.17 × 106 m3 of reduced sulfur (H2S) was involved in the sulfide mineralization of the Jinding deposit, although its origin remains equivocal. Here, we investigate the biomarker signatures of organic matter and the mechanism of generation of the H2S. The organic matter in the Jinding deposit occurs mainly as petroleum filling fractures and cavities in the wall rocks and solid bitumen intergrown with sulfides or calcite. Abundant solid bitumen is also found on the surfaces of the carbonate rocks in the Sanhedong Formation as well as in the rock fractures associated with framboidal pyrite. The petrographic characteristics and maturity-related biomarker parameters show that the solid bitumen in the ores has higher thermal maturity than that in the Sanhedong Formation, suggesting that it was generated at different temperatures in the two settings. The source-related parameters suggest that the solid bitumen in the ores and Sanhedong Formation probably both originated in a mixed marine shale and carbonate environment and that the source rocks for the bitumen precursor were late Triassic marine strata. The δ34S values, ranging from –30 to –10‰ for the fine-grained and disseminated sulfide minerals and from –24.50 to –16.27‰ for the solid bitumen in the early (main) mineralization stage, suggest that H2S was generated by microbial sulfate reduction. We propose that this occurred in the Triassic strata prior to or during migration of hydrocarbons to the Jinding dome to form a H2S-enriched paleo-oil reservoir. This hypothesis is supported by the similarity of the δ34S values (–27.62 to –17.38‰) of solid bitumen in the Sanhedong Formation (the source rocks) to that of bitumen in the ores. The late-ore sulfide, however, displays significantly higher δ34S values, ranging from –8 to 0‰. We propose that the H2S of this stage was mainly generated by thermochemical sulfate reduction as a result of the interaction between hydrocarbons, sulfate, and hydrothermal fluid. The hydrocarbons were oxidized into bitumen that has δ34S values from –7.38 to –4.61‰.

Distribution Characteristics of Nanopores and Discriminant Characteristics of Sedimentary Environment of the Longmaxi Formation in the Southern Sichuan Basin

2021 ◽  
Vol 21 (1) ◽  
pp. 431-437
Author(s):  
Xin Tang ◽  
Yuanchen Guo ◽  
Tingqiang Zhou ◽  
Sen Guo
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Continental Margin ◽  
Sichuan Basin ◽  
Tectonic Setting ◽  
Sedimentary Environment ◽  
Active Continental Margin ◽  
Vertical Direction ◽  
Simulation Method ◽  
Longmaxi Formation

Shale contains a large number of nanopores. The nanopores control the reservoir structure. The formation of nanopores in shale is closely related to the sedimentary environment. The palaeosedimentary structural background determines the provenance and sedimentary diagenesis of mud shale during shale deposition, refines the palaeo-shale and palaeo-sedimentary-tectonic environments of the Longmaxi Formation in the southern Sichuan Basin by elemental geochemical means, and determines the palaeo-deposition of the Longmaxi Formation. The tectonic setting and a numerical simulation method are used to explore the sedimentary tectonic evolution characteristics of the Longmaxi Formation. The results show that the parent rock of the Longmaxi Formation is relatively enriched with light rare earth elements, and the distribution of heavy rare earth elements is relatively stable. The vertical direction shows a trend of increasing from the bottom of the formation to the top of the formation, showing a mixed genesis; the tectonic setting is a passive continental margin, and the active continental margin is the main margin.

Prospect Analysis of Shale Gas Resource Exploration in the Lower Silurian Longmaxi Formation, Southeastern Margin of the Sichuan Basin, China

2014 ◽  
Vol 1014 ◽  
pp. 228-232 ◽  
Author(s):  
Chen Lin Hu ◽  
Yuan Fu Zhang ◽  
Zhi Feng Wang ◽  
Hai Bo Zhang
Keyword(s):  
Shale Gas ◽  
Sedimentary Environment ◽  
Source Rocks ◽  
Guizhou Province ◽  
Mature Stage ◽  
Carbonaceous Shale ◽  
Thin Sections ◽  
Longmaxi Formation ◽  
Lower Silurian ◽  
Longmaxi Shale

In order to understand the sedimentary characteristics of shale and prospects of shale gas exploration in the lower Silurian Longmaxi Formation northern of Guizhou Province, outcrop and core observations, thin sections, X-ray diffraction analysis and other means are used. Studies show that the thickness of Longmaxi formation shale is generally large, range from 20m to 200m, mainly develop in the water shelf. The mineral mainly compose of detrital quartz and clay minerals, and five lithofacies can be identified: black shale, silty shale, carbonaceous shale, calcareous shale and argillaceous siltstone. Longmaxi shale kerogen type is mainlyIand II, and Ro value is average of 1.87%, mainly in the mature - over mature stage. In addition, the TOC content and gas content of Longmaxi shale is high, what’s more, these two parameters have good positive correlation. Compared with the Barnett shale, both of them have some similarities in the development environment shale, shale thickness and type of organic matter and TOC content, while, Longmaxi shale is deeply buried and post-destruction more intense. Longmaxi shale sedimentary environment is stable, high shale thickness and stable distribution, good quality source rocks and high brittle mineral content, which has meet the basic parameters of shale gas exploration and development, and has a large shale gas exploration potential in study area.

Reassessment of the Mesozoic metasedimentary rocks and tectonic setting of Taiwan and the adjacent continental margin of eastern Asia

2016 ◽  
Vol 154 (5) ◽  
pp. 1127-1154 ◽  
Author(s):  
YU WANG ◽  
CHIN-HO TSAI ◽  
LIYUN ZHOU ◽  
YAN QIU ◽  
GUIHUA SUN
Keyword(s):  
Continental Margin ◽  
Tectonic Setting ◽  
Active Continental Margin ◽  
Crystalline Basement ◽  
Detrital Zircons ◽  
Source Rocks ◽  
Metamorphic Belt ◽  
Late Mesozoic ◽  
Sedimentary Sequences ◽  
Se China

AbstractIt remains unclear whether a crystalline basement exists in SE China (including Taiwan), whether the formation of the Tananao metamorphic belt in Taiwan was linked to subduction of the Palaeo-Pacific Plate, and whether the source rocks of the sedimentary sequences in the metamorphic belts are late Mesozoic or Palaeozoic in age. Field investigations and zircon age data in the present study indicate that there is no pre-Palaeozoic gneiss (crystalline basement) in Taiwan (although orthogneisses were produced during deformation and metamorphism of Mesozoic granites), and investigations of the metasediments show that the sedimentary sequences in the Tailuko and Yuli belts are similar. Moreover, LA-ICP-MS dating of detrital zircons from the Pingtan–Dongshan belt in Fujian Province yields a cluster of 206Pb–238U ages at ~ 210–190 Ma, and the Tailuko and Yuli belts in Taiwan have similar clusters of detrital zircon ages at 200 Ma, 160 Ma, 120 Ma and 110 Ma, as well as a later overprinting caused by arc–continent collision. The cathodoluminescence images and trace-element characteristics of the zircons show that they were originally magmatic in origin. This finding, combined with the Hf isotope data, indicates that the sources of sediments in the Tananao belt (Tailuko and Yuli belts) were relatively close to an active continental margin, and that both the Tailuko and Yuli belts have similar sedimentary sources. From the margin of the Chinese mainland to Taiwan, the metasediments seem to represent a continuous sequence of deposits ranging in age from Jurassic to Cretaceous, but with the sediments becoming progressively younger towards the east. It can be inferred that the sediments in the Tailuko and Yuli belts were continental-shelf sequences with sources in SE China.

scholarly journals Geochemical Characteristics and Sedimentary Environment of the Upper Permian Longtan Coal Series Shale in Western Guizhou Province, South China

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Lingyun Zhao ◽  
Peiming Zhou ◽  
Yi Lou ◽  
Youzhou Zhao ◽  
Wei Liu ◽  
...  
Keyword(s):  
Organic Matter ◽  
South China ◽  
Shale Gas ◽  
Vitrinite Reflectance ◽  
Sedimentary Environment ◽  
Guizhou Province ◽  
Upper Permian ◽  
Yangtze Platform ◽  
Western Guizhou ◽  
Exploration And Development

China’s marine-continental transitional facies shale gas resources are abundant with shale gas resources of about 19.8 trillion cubic meters, while the exploration and development of these shale gas resources are still in the initial stage. The Upper Permian Longtan coal series shale is one of the most important transitional shales in the Yangtze platform, China. In this study, the comprehensive methods of mineralogy and organic geochemistry are used to discuss the characteristic of organic matter and sedimentary environment of the Longtan coal series shale in western Guizhou Province, South China. The results show that (1) the total organic carbon (TOC) content of this shale ranges in 0.6%-28.21%, mainly in 3%-12%, indicating a “good-excellent” hydrocarbon source rock, and its vitrinite reflectance ( R o ) ranges from 1.48% to 2.93%, indicating a high-overmature organic matter; (2) the organic matter in this shale is multiorigin, and most of them come from the terrestrial higher plant while the rest come from the plankton; (3) type index (TI) of organic matter is from -65 to 41, indicating most of the kerogens which are II1-III types; and (4) the sedimentary environment of this shale is dominated by suboxic-anoxic fresh water environment, which provides a favorable condition for the preservation of organic matter. In addition, the warm and humid climate during the Late Permian in the Yangtze platform promotes plant growth, and as a result, the Longtan coal series shale is rich in organic matter and has great potential of shale gas exploration and development.

Abstract title; Geology and geochemical characteristics of coal-bearing source rocks in Nariin sukhait deposit, southern Mongolia

2020 ◽  
Author(s):  
Norov Baigalmaa ◽  
Takeyuki Ogata ◽  
Luvsanchultem Jargal ◽  
Bat-Orshih Erdenetsogt ◽  
Jamsran Erdenebayar
Keyword(s):  
Chemical Weathering ◽  
Pore Space ◽  
Sedimentary Environment ◽  
Active Continental Margin ◽  
Source Area ◽  
Source Rocks ◽  
Intergranular Porosity ◽  
Epma Data ◽  
Geological Features ◽  
East West

<p>The Nariin Sukhait mine is located in the southwest of Umnugobi province 50 kilometers from Mongolia's border with China at Shivee Khuren within the Nariin Sukhait deposit, which has relatively complex geological features. The most prominent feature relating to the Nariin Sukhait coal deposit is the arcuate, east-west trending Nariin Sukhait fault. The coal-bearing section, interpreted to be middle Jurassic in age, is exposed primarily in a window adjacent to this fault.</p><p>The chemical composition of whole indicates (variable composition, values of the ratio Th/U > 3.8-4.2, values Th/Sc 0.3-0.8, values LaN/YbN > 5 and values Eu/Eu* 0.6-0.9) indicates components derived from the active continental margin type. The low CIA values (50–60) indicate the absence or poor chemical weathering in the source area.</p><p>SEM-CL-imaging of sandstone quartz from Nariin sukhait show three types of quartz:  early Q1 cementation has gray to slightly grey luminescences, postdated compaction, and reduced intergranular porosity associated with illite formed during eogenesis. Q2 is characterized by dark luminescence overgrowths and is more voluminous in the thinly bedded sandstones than in the thickly bedded sandstones filling most of the remaining pore space during mesogenesis. Q3 was formed during the early telogenesis stage fully cementing the sandstones and the fractures were filled by hydrothermal chlorite and sulfides. Significant amounts of trace elements Al, Ti, Ca, K and Fe has been detected in quartz overgrowths. Al varies consistently between each cement with averages of 1324, 1523, and 1352 ppm for the Q1, Q2, and Q3 generations, respectively.</p><p>The geochemical, SEM-CL imaging and EPMA data results suggest a relatively igneous source, whit felsic composition. The sedimentary environment of the sandstone and argillite of these sedimentary rocks was the poor chemical weathering in the source area.</p>

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