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Morphology and features of Cambrian oncoids and responses to palaeogeography of the North China Platform

Journal of Palaeogeography 2020年第2期9卷 150-167页

作者： En-Zhao Xiao Ming-Xiang Mei Shu Jiang tehseen zafar School of Earth Sciences and Resources China University of Geosciences(Beijing)Beijing 100083China Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education and Faculty of Earth Resources China University of Geosciences(Wuhan)Wuhan 430074China Institute of Geochemistry Chinese Academy of SciencesGuiyang 550081China Institute of Geology University of the PunjabLahore 54590Pakistan

The Cambrian strata in the North China Platform are fully exposed. A wide variety of carbonate oncoids with different shapes occur in the Xuzhuang and Zhangxia formations(Miaolingian Series) from six Cambrian sections in the study area. A comprehensive study involving outcrop description, microscopic observation, scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDX), X-ray diffraction(XRD), and carbon and oxygen isotope analysis is conducted to determine the facies, morphology, internal structure, and geochemical properties of the oncoids. The oncoids are divided into six types based on their morphology and internal *** and ultrastructural observations reveal typical microbial fossils(Girvanella) and microbially-related sediments(framboidal pyrite), indicating the biogenicity of the oncoids. Additionally, the XRD and carbon and oxygen isotope analysis results suggest that the formational environments of these oncoids are different due to terrestrial influences. Statistical data on the oncoids from the six sections show that there are obvious differences in the types of oncoids and the proportions of different varieties in each section. The spatial differences in the oncoid morphologies are associated with different palaeogeographic settings. The rough oncoid growth patterns developed in nearshore environments were influenced by terrigenous debris and steep terrain, whereas the delicate oncoid growth patterns developed in offshore environments were less affected by terrestrial factors and were featured by more stable depositional processes related to microbial mats.

关键词： Morphological classification Microbial m at Girvonello Carbon and oxygen isotopes Miaolingian series North China

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Trace element geochemistry and stable isotopic(δ^(13)C andδ^(15)N)records of the Paleocene coals,Salt Range,Punjab,Pakistan

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International Journal of Mining Science and Technology 2022年第3期32卷 551-561页

作者： Noshin Masood tehseen zafar Karen A.Hudson-Edwards Hafiz U.Rehman Abida Farooqi Environmental Geochemistry Laboratory Department of Environmental SciencesFaculty of Biological SciencesQuaid-i-Azam UniversityPO 45320Pakistan Institute of Geochemistry Chinese Academy of SciencesGuiyang 550081China Institute of Geology University of the PunjabLahore 54590Pakistan Environment&Sustainability Institute and Camborne School of Mines University of ExeterTR109EZUK Graduate School of Sciences and Engineering Kagoshima UniversityKagoshima 890-0065Japan

The Paleocene coals of the Salt Range in the Punjab Province of Pakistan have great economic potential;however,their trace element and stable isotopic characteristics have not been studied in detail except for a few sporadic *** this study,a total of 59 coal samples of which 14 are obtained from open cast mines have been investigated for elemental composition andδ^(13)C-δ^(15)N isotopic *** contents of trace elements such as Co,Cr,Cu,Pb,Sr,Th,U,V,and Zn are 7.4,41.7,11.2,12.5,90.2,4.0,1.9,128,and 31.1 mg/kg,*** values,when compared with the World Coal Clarke values,were relatively higher in low-rank coals in comparison with Clarke values for brown ***,As(20.4 mg/kg),Co(6.6 mg/kg),Cr(22.4 mg/kg),Cu(^(13).3 mg/kg),Pb(19.2 mg/kg),Sr(^(15)4.7 mg/kg),Th(2.5 mg/kg),V(47.8 mg/kg),and Zn(75.1 mg/kg)were significantly higher in the sub-bituminous to bituminous coals of the Salt *** analysis,based on X-ray diffraction and energy dispersive X-ray spectroscopy,revealed that the studied samples contain illite,kaolinite calcite,gypsum,pyrite,and *** affinity with organic and inorganic phases of coals calculated by an indirect statistical approach indicated a positive association of ash content with Ag,Al,Co,Cr,Cs,Cu,Mn,P,Rb,Pb,Th,U,and V,suggesting the presence of inorganic components in studied ***,As,Fe,Sr,and Zn exhibit negative correlations that imply their association with the organic ***δ^(13)C andδ^(15)N isotopic range and average−24.94‰to−25.86‰(−25.41‰)and−2.77‰to 3.22‰(0.96‰),respectively,reflecting 3C type modern terrestrial vegetation were common in the palaeomires of studied coal *** addition,the trivial variations of 0.92‰and 0.45‰among^(13)C and^(15)N values can be attributed to water level fluctuations and plant assemblies.

关键词： Coal Salt Range Pakistan Geochemistry Trace elements δ^(13)C andδ^(15)N isotopes

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