Abstract
Abstract By optical microscopy and SEM-energy spectrometry, some phenomena that relate to lake-bottom hydrothermal activities, such as the presence of siliceous rocks, ankerite laminar deposits, evidence for marcasite brassil anhydrite symbiosis systems and authigenetic albite filling in early diagenetic fractures, have been discovered in the Chang 7 high-quality source beds of the Yanchang Formation, Ordos Basin. Various geochemical data of the Chang 7 high-quality source rocks testify further to the existence of lake-bottom hydrothermal activities, and they include abnormally abundant S 2- content (on average 7.37%), Mo, Cu, U and Mn positive anomalies, high ratios of U to Th, the positive carbon isotope composition of crystalline ankerite (δ 13 C from 2.88 to 3.03‰), depleted oxygen isotope composition (δ 18 O PDB from −16.41 to −16.17‰), the enrichment of microelements like Cu and Mn, and isotopically enriched in 34 S sulfur isotope compositions of strawberry-shaped pyrite (δ 34 S CDT from 2.37 to 5.90‰). In the early sedimentary period of the Chang 7, the activation of floor ruptures by violent regional structural activities was a dynamic factor that produced lake-bottom hydrothermal activities. The hydrothermal activities played an important role in accelerating the extensive development of the Chang 7 high-quality source rocks.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
