Black shales

Black shales occur widely in the Lower Cambrian and Neoproterozoic strata on the Yangtze Platform, South China. In this study, Lower Cambrian black shales from Xiuning section and Late Neoproterozoic black shales from Weng'an section were studied and Pb isotopic compositions were analyzed following a stepwise acid-leaching technique.

Nov 22, 2012 · The geochemistry of major and trace elements (including heavy metals and rare earth elements) of the fresh and weathered black shales, and the soils derived from black shales in the Ganziping mine area in western Hunan province (China) were studied using the following techniques: X-ray fluorescence (XRF), inductively coupled plasma mass spectrometer (ICP-MS) and X-ray diffraction (XRD). The ... Sep 30, 2015 · Identification of black shale-hosted critical element deposits in the U.S. (initial focus on the Heath Formation metalliferous oil shales in Montana); and; Evaluation of processes that form metal-enriched black shale deposits. Return to Mineral Resources Program | Geology, Geophysics, and Geochemistry Science Center The black shale in the Lower Cambrian Niutitang Formation in Southwest China is anomalously enriched in sedimentary exhalative Ni- and Mo-sulfides. The occurrence of large fluctuation of ocean redox conditions and thriving of benthic animals highlight the uniqueness of the stratum and its link to the Cambrian Explosion. Here, we …The black shale of the Niutitang Formation is characterized by elevated TOC contents reaching up to 15 wt% at the lower part and decreased to 3-9 wt% upward over a stratigraphic thickness of about 20 to 80 m. Some units up to 30-m-thick consist of alginate with > 30 wt% C (combustible shale). Since first discovered in the 1970 s, the genesis ...Black shales are source rocks for petroleum and natural gas, and thus are both geologically and economically important. Here, we review our recent progress in understanding of the surface ocean ...

Should the black shales of Kentucky prove to be a viable geologic sink for CO2, the extensive occurrence of shales in Paleozoic basins across North America would make them an attractive regional target for economic CO2 storage and enhanced natural gas production. DISCLAIMER This report was prepared as an account of work sponsored by an agency ...The Lower Cambrian black shales of the Sansui vanadium deposits, located in South China, host a thin accumulation of Ni, Mo, V, and platinum group of elements (PGE). However, among them, the origin of V-bearing deposits remains controversial. To characterize the enrichment process of V-bearing deposits, samples of the mineralized layer and surrounding rocks from the Sansui area, South China ... An indicative classification of black shales can be compiled based on the literature that refers to the degree of commodity metal accumulation (Table 1).Vine and Tourtelot (1970) set the threshold of metalliferous black shales' (MBS) definition above the 90th percentile of a metal concentration in given dataset, whereas the final classification depends on the frequency (percentage) of ...We present δ60Ni values for black shales, determined by double-spike MC-ICP-MS. The samples comprise Paleoproterozoic Talvivaara Ni–Zn–Co–Cu black shales from Finland, Neoproterozoic black shales from the Teplá-Barrandian Unit, Czech Republic, Early Cambrian Ni–Mo-rich black shales from the Yangtze Craton, and Devonian Ni–Zn–PGE black shales from Yukon, Canada. In addition, the ...Oct 14, 2010 · Black shales and massive sulfides represent reduced lithofacies that require isolation from oxic environments to be preserved. This, together with the sedimentary affinity of both lithofacies, can explain their common concurrence in the geologic record. The present study is based on the comparison of Rammelsberg in Germany, Tharsis in Spain, and Draa Sfar in Morocco, three massive sulfide ... New and existing Mo isotope data from early Cambrian black shales in South China span a range of greater than 3‰, which can only be explained by multi-stage fractionation of Mo isotopes. The ...Summary. The Global Geochemical Database for Critical Metals in Black Shales (CMIBS) contains new geochemical data compilations for fine-grained sedimentary rocks in which each geologic material sample has one 'best value' determination for each analyzed species, greatly improving speed and efficiency of use (Granitto and others, 2013).

Black shales show lower δ 56 Fe values due to the excess of authigenic pyrite-Fe with a mean δ 56 Fe value of −0.02‰ over detrital Fe in graywacke with a mean δ 56 Fe value of +0.25‰. However, the Fe isotopic signatures of the black shales are not consistent with iron shuttling, mixing of authigenic and detrital sources, or ...Black shales are organic-rich sediments that commonly formed coevally in space and time through Earth history and have been associated with perturbations in the carbon cycle, climate change and ...The Ordovician-Silurian (O S) transition witnessed dramatic tectonic, climatic, marine, and biological coevolution, during which organic-rich black shale was widely deposited and is considered an important source rock. However, the potential links between the differential enrichment pattern of organic matter and climate fluctuations and paleoenvironmental evolution during this period are still ...Correlation of lateral facies changes reveals that the black shales record deposition beneath a nearshore zone of oxygen-poor waters that contracted in lateral extent during parasequence formation. The Boulonnais black shales are similar to other varieties of transgressive black shale, in that they are developed upon surfaces of marine ...The Okchon black shale in Korea provides an important example of natural geological materials containing toxic elements; the Chung-Joo, Duk-Pyung, Geum-Kwan, I-Won and Chu-Bu areas are underlain ...

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The black shale in Niutitang Formation of the Lower Cambrian widely develops in Guizhou Province, and its distribution is controlled by the type of the lithofacies palaeogeography. The black shale ...China’s most successful horizon for shale-gas exploration and development is the Upper Ordovician Wufeng Formation through the Lower Silurian Longmaxi Formation in its Upper Yangtze Region. In this study, the Wufeng–Longmaxi Formation black shales in the Upper Yangtze Region are analysed to determine their microstructural characteristics, total organic carbon (TOC) content, and well log ...The majority of black shale samples in the Dongyuemiao member show a positive correlation between porosity and T max when the T max ranges from ∼440°C to ∼465°C. This correlation consists of the tendency of Posidonia Shale (Type II) ( Han et al., 2017 ) and seems to suggest the thermally driven pore generation, e.g., the secondary OM pore.This work, for the first time, tries to constrain the paleoredox conditions of the Middle-Upper Jurassic black shales in the Blue Nile (Abay) Basin, Ethiopia (Fig. 1, Fig. 2), using redox-sensitive elements and other proxies. This work will help to understand the paleoredox conditions of these shales that controls the preservation of organic ...black shale: [noun] a dark form of shale characterized by a relatively high degree of carboniferous compounds.

Black shale Clarke values are the average trace element contents in the World black shales. It is well known that black shales (carbonaceous, mainly marine sedimentary rocks) often are metalliferous and/or bituminous: enriched in U, V, Mo, Re, many other trace elements, and "shale oil". That is why the Clarke values for black shale are very ...Ninety-seven Wealden black shale samples from three wells in the Lower Saxony Basin have been studied by organic geochemical and organic petrographical methods to determine their maturity, organic facies and depositional environment. The maturities of the three wells range from early mature (Ex-A), late to postmature (Ex-C) to overmature (Ex-B ...First, black shale formations Second, rocks containing organic carbon are host ore deposits containing base and precious encountered near many types of ore ...Using CO2 flooding of coals as a model, the large component of adsorbed natural gas in organic-rich shales suggest that black shale might be an attractive ...Jan 30, 2018 · The black shales in the Qusseir area (Duwi Formation, Campanian–Maastrichtian) were deposited in an anoxic marine environment, and are remarkably high in their enrichment of redox-sensitive and sulfide-forming trace metals. Measurements of Mn, U, V, and Mo reveal that the studied black shales deposited under shallow anoxic-sulfidic conditions. Black shales are intercalated with phosphorites of the Duwi Formation in the Qusseir-Safaga area, on the Red Sea coast. The Duwi Formation overlies the fluvial shale series of the Qusseir Formation and underlies the deeper marine shales and marls of the Dakhla Formation (Fig. 1).Therefore, the Duwi Formation in Egypt represents the early …The paleoenvironment during the Early Cambrian is closely related to the accumulation mechanism of organic matter (OM) from the Lower Cambrian black shales. However, paleoenvironment remains a controversial issue. Here, we reported a lot of detailed data of sedimentary stratigraphy and geochemistry of the Lower Cambrian Yuertusi Formation in the Aksu area, Tarim Basin. The Yuertusi Formation ...Upon oxidative weathering of black shale in surface environments, the enriched reduced fractions of As within pyrite (FeS 2) or arsenopyrite (FeAsS) minerals can cause the release of ferrous Fe, sulfuric acid, and exceptionally high concentrations of As(III) or As(V) into the watershed, which is a key reason for the high As accumulation in ...

Black shales are found beneath almost 70 percent of Kentucky and are important for the oil and natural gas resources they contain. So tracing the presence of the shales in the Appalachian region, where more is known about them, to their Illinois Basin counterparts could be valuable for future resource exploration in the Illinois Basin. ...

The black shales formed in an anoxic environment caused by organisms, and the deposits were affected by hydrothermal fluids (Li, 2019). In summary, the ore-forming elements in mineral deposits from the lower Cambrian black shales of South China were mainly supplied by seawater and hydrothermal fluids, and biological activity was …In this study, Late Neoproterozoic black shales from South China were analysed using slice experiments and ultra-clean organic geochemical laboratory techniques with two main aims. Hydrocarbons were analysed firstly so as to explore the hidden information of ancient ecosystems during a key transition time of Earth, and secondly so …In Deep Sea Sediment A, the MoMo distances are significantly longer than in molybdenite. Among the black shales, only the Marl Slate displays a MoMo distance suggestive of some MOS2. Table 3 presents Mo K-edge EXAFS results for some synthetic materials.Black shale is an important host for redox-sensitive metals, such as Mo, Ni, V, U, Re, and a number of other metals including Cu, Pb, Zn, Au, Ag, Hg, Sb, etc. in various geological periods and settings (Holland 1979; Coveney et al. 1992; Pasava 1993).Metal-enriched black shale of Early Cambrian age occurs over several thousands of kilometers throughout the Yangtze Platform in South China.greater for the black shales (38.1) than for the green claystones (5.7} and is typical of C/N ratios of cellulosic land-plant organic matter 8• The 13 C content of organic matter in black shales ...Aug 1, 2021 · Two immature black shales from the Mesoproterozoic Xiamaling Formation, Xiajiagou outcrop, Zhangjiakou, Hebei Province, China, two immature black shales from the Cambrian Alum Shale Formation, Degerhamn, Öland island, Sweden, and a carboniferous low rank coal with VR o of 0.56% (sample ID ZJJ-C4) were collected for this study (Table 1). A suite of black shales interbedded with thin-bedded cherts occurs at the basal Cambrian in the Northern Tarim Basin (Fig. 2), which is called black rock series in Chinese literature (Li and Gao, 1996a, Li and Gao, 1996b, Li and Gao, 2000).The two studied sections are located at Xiaoerbulake, approximately 60 km away from the Akesu …Black shales occur widely in the Lower Cambrian and Neoproterozoic strata on the Yangtze Platform, South China. In this study, Lower Cambrian black shales from Xiuning section and Late Neoproterozoic black shales from Weng'an section were studied and Pb isotopic compositions were analyzed following a stepwise acid-leaching technique.

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Within the densest black shale are microscopic layers, commonly less than 0.1 mm thick, composed of quartz grains ranging from 0.02 to 0.06 mm and averaging about 0.03 mm in greatest diameter. Still finer quartz ranging in diameter from about 0.004 to 0.012 mm and averaging 0.008 mm is disseminated fairly uniformly throughout the massive shale. . .Black shale tends to suffer from chemical weathering in nature due to its high content of organic matter (OM) and unstable minerals (e.g. feldspar and pyrite). The weathering of black shale has drawn attention over the past decade for its unique environmental and petrophysical impact (Jaffe et al., 2002, Jin et al., 2013, Petsch et al., 1999 ...Black shale, the subject of this article, is a dark-colored muddy sedimentary rock that is substantially enriched in organic matter. Depending on the grade of thermal maturity, black shales are often referred to as sapropel, bituminous shale, or oil shale.Black shale is widely distributed on the northern Yangtze platform, where advanced weathering is present due to the favourable exposure and a humid climate (Ling et al., 2015, 2016). To understand elemental behaviors within the context of catchment-scale weathering, examining vertical weathering profiles is an important approach. ...Section snippets Composition, textures and modes of mineralization. Black shales are in broad terms composed of mineral and organic—kerogenous—matrix, whereas black primarily refers to any kind of organic matter (OM—humic, sapropelic, bituminous, graphitic) that provides the rock its color, and shale refers to fissile fine-grained sedimentary rock.Sub-aerial weathering of black shales drives the gradual leaching of sulphur- and organic-bound heavy metal elements, which are usually abundant in these rocks due to depositional conditions. The formation of oxygen functional groups in kerogen, however, can lead to an opposing mechanism - metal adsorption and binding, similar to a process common in soils.Black Shale Standard. Equivalent expectations of the gamma-ray log response of black shales can be predicted from core or outcrop samples that have analyses of thorium, uranium, and potassium contents. So, for example, the Marine Sciences Group Black Shale Composite (BSC) described by Quinby-Hunt et al. (1989) is characterized by values ofA recent drilling operation in the Triassic Yanchang Formation (Tongchuan District of the Ordos Basin, north-central China) reached a black shale bed with an average in-situ gas content of 1.11 g/ml. Subsequent total organic carbon (TOC) content measurements and rock-eval analysis showed that the black shale section was generally classified as excellent source rock, with TOC contents commonly ...January 1, 1983 Black shales of Devonian age in the Appalachian basin are a unique rock sequence. The high content of organic matter, which imparts the characteristic lithology, has for years attracted considerable interest in the shales as a possible source of energy.Locations of samples of black shales with critical mineral geochemistry (Granitto and others, 2017) were used as an evidential layer to calculate prospectivity models for sediment-hosted Pb-Zn mineralization as described in Lawley and others (2022). ….

Bakken Formation black shales pinch-out landward via intra-shale onlap and stratal thinning; conversely, lower Virden black mudstone thins seaward via downlap and stratal thinning. Acknowledgments. The writer is grateful for helpful suggestions by two anonymous reviewers and editor Jim Schmitt. Special appreciation is expressed for the ...The black shales of the Wufeng Formation and the lower Longmaxi Formation are rich in biogenic siliceous fossils and framboidal pyrite. Their TOC content, GR value, and uranium (U) content ...Among these are black shales: fine-grained laminated sedimentary rocks rich in organic carbon (∼3% by weight or more) that also usually contain chemically distinct distributions of redox sensitive metals and sulfide minerals. When ancient sedimentary rocks rich in organic carbon are exposed on Earth's continents through uplift and erosion ...Black shale contains abundant pyrite and organic matter that are susceptible to weathering when exposed to the air. In the process of weathering, acid mine drainage can be produced, and a range of toxic trace elements including Cr can be released and transported into rivers, groundwater and soils, potentially leading to severe environmental pollution.Oil from Shale: The KGS-IMMR Mississippian-Devonian Black Shales Cores. This month we highlight an important collection of research cores gathered in response to global political crises resulting in oil price spikes, the 1973-74 Arab oil embargo, and the 1979 oil crisis. The recent increase in gasoline prices in response to the Russian invasion ...Sedimentology studies on the Shipu section for the K11 black shales illuminated that the K12 black shales in coastal southeastern China were mainly deposited during transgressive period. The ...Ettensohn and coworkers have proposed more or less persistent and widespread anoxia during accumulation of much of the black shale succession (Ettensohn et al., 1979, Ettensohn and Barron, 1981, Ettensohn, 1985a, Ettensohn, 1985b, Ettensohn, 1998).According to Ettensohn's (1998) model, the extensive black-shale basins formed in response to foreland basin subsidence associated with the Acadian ...At Dotternhausen (Fig. 5), oil shales near the base of Member II (e.g., the Koblenzer, Hainzen, and Fleins) have greater values of ε 205 Tl than the black shales (i.e., the Tafelfleins and Seegrasschiefer) of Member I, which suggests the global expansion of oxygen-minimum zones and anoxic water masses in the marine realm (Them et al., 2018).Of the two black-shale sequences in the basin, the upper is the Devonian and Mississippian shales, which have attracted interest as a source of uranium, oil and gas, and pyrolytic oil. These studies have provided the necessary framework for resource evaluations and for geochemical characterizations, including analysis of the chemical structure ...Few black shales contain concentrations of precious metals higher than average continental crust (i.e. ∼5 ppb Au). Yet Au and Pt alloys have been reported from the Kupferschiefer in Poland. Moreover, thin sulfide beds in certain Chinese and Canadian shales contain several hundred ppb Au, Pd and Pt and average ∼4% Mo and ∼2.5% Ni in an ... Black shales, The Alum Shale Formation is a metal-rich black shale, deposited on the Baltoscandian platform between Middle Cambrian and Early Ordovician. These black shales may be of particular economic interest for their relatively high uranium content (100-300 ppm) and their wide distribution from Norway to Estonia.Scandinavian Alum Shale may thus constitute a great potential resource of uranium, as a ..., Nov 1, 2022 · Black shales are known to be geogenic sources of contamination in soil and water (Parviainen and Loukola-Ruskeeniemi, 2012). Even endemic diseases have been proposed to be linked with the contamination derived from the weathering and leaching of harmful elements from black shale. , Locations of samples of black shales with critical mineral geochemistry (Granitto and others, 2017) were used as an evidential layer to calculate prospectivity models for sediment-hosted Pb-Zn mineralization as described in Lawley and others (2022)., Nov 22, 2012 · The geochemistry of major and trace elements (including heavy metals and rare earth elements) of the fresh and weathered black shales, and the soils derived from black shales in the Ganziping mine area in western Hunan province (China) were studied using the following techniques: X-ray fluorescence (XRF), inductively coupled plasma mass spectrometer (ICP-MS) and X-ray diffraction (XRD). The ... , A suite of black shales and a few pyrite samples were collected for this study from the Bijaigarh shale of the Kaimur Group (Fig. 3). In order to minimize the influence of surficial weathering, the samples were collected from the underground PPCL pyrite mine at Amjhore, in the Rohtas area, about 30 km south of Dehri-on-Sone (Fig. 1). The ..., The majority of black shale samples in the Dongyuemiao member show a positive correlation between porosity and T max when the T max ranges from ∼440°C to ∼465°C. This correlation consists of the tendency of Posidonia Shale (Type II) ( Han et al., 2017 ) and seems to suggest the thermally driven pore generation, e.g., the secondary OM pore., Furthermore, black shales most commonly occur in cyclic alternation with non-organic-rich facies. In these instances, the environment may be poised at conditions close to those favoring preservation of organic matter (e.g. low-oxygen but not anoxic bottom waters), and then external factors periodically tip the balance in favor of preservation., The organic-rich black shale in the Yangtze area is mainly developed in the Upper Ordovician Wufeng Formation (O 3 w) and the Lower Silurian Longmaxi Formation (S 1 l) (Chen et al., 2004, 2015b; Fan et al., 2011) (Fig. 1 C). The sediments of the O 3 w are dominated by organic-rich black shale with a thickness of generally less than 10 m (Fig. 1, Fig. 2), which is easily distinguished from the ..., Early models for Mid-Continent cyclothems placed the black shales in shallow water, with maximum transgression at the fusulinid-bearing zone in the overlying limestone. The most recent model proposed that the black phosphatic shales, which commonly occur between two subtidal carbonates, are widespread and laterally continuous over great ..., Feb 8, 2022 · Devonian Black Shales Eastern USChattanooga, New Albany, Ohio Shales. The Mid-Late Devonian black shales of the Appalachian, Illinois, and Michigan Basins have long been studied to provide clues to past climates, ocean ventilation, mass extinctions, and general earth history. Common misconceptions about these shales are that they represent ... , Black shales are dark-colored, usually thinly laminated mudstones containing appreciable organic matter (>0.5 wt% C), authigenic iron sulfides and, silt- and clay-sized detrital …, We suggest that deposition of black shales represented a major sink for atmospheric carbon. Sequence stratigraphy reveals that widespread black shale deposition occurred in transgressions, whereas regressions are characterized by deposition of bioturbated facies, allowing changes in lithofacies and deep-water redox conditions to be related to ..., that cut down into the underlying black shales (Schieber, 1998a). Contacts between pyrite ooid beds and underlying black shales are sharp, and multiple scour surfaces within py-rite ooid beds indicate a prolonged history of high-energy reworking and winnowing. The strong grain-size contrast between black shale and pyrite ooid beds (coarse sand ..., This fine-grained shale facies is dark grey to black in colour (Fig. 2 a).With respect to the bedding, the outcrops of these facies are very thin-bedded to thinly laminated and fissile in some parts while medium to massive in other areas (Fig. 2 a).The shales are highly fractured at some outcrop locations, possibly due to the composition, high fine sand/silt content, or tectonic activities., However, some black shales with high TOC contents show low concentrations of U (Lüning and Kolonic, 2003), probably a manifestation of the heterogeneity of sedimentary organic matter in organic-rich shales. How different macerals contribute to U content in the New Albany Shale is one of the key aspects of our study (Fig. 8)., These black shales are not only rich in organic matter, but also undergone an unexpectedly low thermal evolution process, both of which contribute to well-preserved indigenous hydrocarbons and promote the convincing discovery of the Precambrian biology. The combination of the absence or low concentrations of gammacerane, dibenzothiophene series ..., The Olentangy Shale consists of gray shales, with minor lenses or thin layers of limestones in the lower part of the unit, and interbedded thin black shales in the upper part of the unit (Stauffer, 1938).Thin black shales at the upper contact have sharp basal contacts and diffuse upper contacts due to bioturbation originating in the overlying …, Black shale, the subject of this article, is a dark-colored muddy sedimentary rock that is substantially enriched in organic matter. Depending on the grade of thermal maturity, black shales are often referred to as sapropel, bituminous shale, or oil shale., Among these are black shales: fine-grained laminated sedimentary rocks rich in organic carbon (∼3% by weight or more) that also usually contain chemically distinct distributions of redox sensitive metals and sulfide minerals. When ancient sedimentary rocks rich in organic carbon are exposed on Earth's continents through uplift and erosion ..., N2 - Outlines the salient features and inferred depositional regimes for black shales in the stratigraphic record and provide guidelines for further study. Includes a discussion of OC preservation in modern marine environments as a prelude to interpretation of the ancient record, and of proposed biotic and geochemical indicators of degree of ..., Brown-black to green-black shales predominate throughout the Ohio/New Albany interval, interbedded with occasional thin beds of siltstone and silty shale. The Cleveland Member was subdivided into upper and lower segments for each core based on organic carbon content: the lower section consistently has a lower carbon content (less …, black shale, also called Carboniferous Shale, variety of shale that contains abundant organic matter, pyrite, and sometimes carbonate nodules or layers and, in some locations, concentrations of copper, nickel, uranium, and vanadium. Fossils are rare in the shale and either are replaced by pyrite or are preserved as a film of graphite. Black shales occur in thin beds in many areas at various ..., The primary source of manganese to the Baltic Sea has been attributed (Suess, 1979) to input of terrestrially domi- nated organic matter. However, we have not found any mac- rofossils of terrestrial origin. Manganese-rich sediments are roughly 2 m thick and contain on average 2 to 5% manga- nese., The basal Member 1 is a cap carbonate with a thickness of approximately 1.5 m. Members 2 and 3 are mainly composed of carbonates and grey siltstones, with a thin layer of interbedded black shale (~2 m). About 9 m of an organic-rich black shale was developed in the uppermost Member 4 of the Doushantuo Formation (Fig. 1 c). 3. …, Sub-aerial weathering of black shales drives the gradual leaching of sulphur- and organic-bound heavy metal elements, which are usually abundant in these rocks due to depositional conditions. The formation of oxygen functional groups in kerogen, however, can lead to an opposing mechanism - metal adsorption and binding, similar to a process common in soils., In geological history, volcanism is closely related to the deposition of many black shales. However, the specific mechanism between volcanism and the deposition of black shales is still unclear. The black shales developed in the Chang 7 Member of the Yanchang Formation in the Ordos Basin are considered the most important hydrocarbon source rocks in Central China. The shales are deposited by ..., Black shales are fine-grained sedimentary rocks containing a high percentage of organic matter. The organic matter is mixed in with clay and silt particles. Generally, these rocks originate from ..., black shale deposition occurred in transgressions, whereas regressions are characterized by depo- sition of bioturbated facies, allowing changes in lithofacies and deep-water redox conditions to be, Chemical and isotopic signatures for black shales serve as potential proxies for reconstruction of paleoenvironmental conditions. Here we bring Rock‐Eval, major and trace element and Re‐Os isotopic data together to examine the environmental record at the Cambrian‐Ordovician Global Stratotype Section and Point (GSSP) at Green Point in western Newfoundland, Canada. The Green Point shales ..., Black shales are mixtures of terrigenous, biogenous, and hydrogenous sediment in which organic matter constitutes at least 0.5% of the material. Shales are the end product of the processes that ..., The Black-Shale Sea and its organic-rich muds were essentially the result of subsidence and sediment-starved conditions created by the collisional event which formed the Acadian Mountains. The interaction of these mountains with the atmospheric circulation patterns of the time is an important aspect of black-shale deposition., The Chang 7 black shale in the Upper Triassic Yanchang Formation is the principal source rock of Mesozoic oil-bearing system in the southwest Ordos Basin, containing high abundances of organic matter and hydrocarbon potential. Our study discusses the role of lake-bottom hydrothermal activities in the enrichment of organic matter during the deposition of the Chang 7 black shale., The basal Member 1 is a cap carbonate with a thickness of approximately 1.5 m. Members 2 and 3 are mainly composed of carbonates and grey siltstones, with a thin layer of interbedded black shale (~2 m). About 9 m of an organic-rich black shale was developed in the uppermost Member 4 of the Doushantuo Formation (Fig. 1 c). 3. …