Article
Geosciences, Multidisciplinary
Jixin Jia, Xuebin Du, Ke Zhao, Yongchao Lu, Chao Tan
Summary: During the Ordovician-Silurian transition, large-scale explosive volcanism occurred globally, including in South China. The tectonic activities leading to this volcanism in the South China Block, particularly on the northern and southern margins, are still debated. Through the analysis of the sources of K-bentonite layers in South China during this transition, it is revealed that there were two different sources of volcanic activity, suggesting different geodynamic settings, including within-plate extension and subduction-collision processes.
MARINE AND PETROLEUM GEOLOGY
(2022)
Article
Geosciences, Multidisciplinary
Omer Bozkaya, Asuman Gunal-Turkmenoglu, Mehmet Cemal Goncuoglu, Cengiz Okuyucu
Summary: The study identified K-bentonite layers in the south of Aksehir, Turkey, showing characteristics of volcanic origin with illite and various non-clay minerals, reflecting high-temperature diagenetic conditions. A comparison with K-bentonites from other regions reveals geological and geochemical differences in these studied K-bentonites.
JOURNAL OF AFRICAN EARTH SCIENCES
(2021)
Article
Geography, Physical
Yanjun Wang, Bo Wang, Ming Li, Shengnan Cao, Hongbin Wang, Shuxin Pan, Juanjuan Guo, Delong Ma, Fang Song, Tingting Cao, Inna Y. Safonova, Linglin Zhong, Xinghua Ni
Summary: This study provides new evidence through zircon LA-ICP-MS UPb dating and LuHf isotopic analysis to determine the subduction of the Junggar Ocean beneath the Yili Block in the Middle-Late Ordovician. These findings are significant for the reconstruction of early Paleozoic paleogeography and tectonics in the Paleo-Asian Ocean domain, as well as for understanding the possible causes of global climate change and mass extinction during the Ordovician-Silurian transition.
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
(2022)
Review
Cardiac & Cardiovascular Systems
Andrew D. Althouse, Jonathan G. Yabes, Kaleab Z. Abebe
Summary: Small clinical trials in cardiology encompass a variety of types with different objectives, including pilot trials, early-stage or proof-of-concepts trials, rare diseases or difficult-to-recruit populations trials, and underpowered trials. Each type requires specific design and interpretation methods to achieve meaningful results.
CANADIAN JOURNAL OF CARDIOLOGY
(2021)
Article
Geography, Physical
Tianjia Liu, Zhentao Wang, Xunlian Wang, Xifang Liu, Pengcheng Ju, Jiaai Zhong
Summary: This study investigates the source and characteristics of K-bentonites in South China during the Late Permian, suggesting that volcanic activities associated with the Paleo-Tethys Ocean convergence may have led to the formation of K-bentonites. The integration of zircon Hf isotope and trace element compositions indicates that the K-bentonites in South China may have multiple sources, with major volcanic eruptions occurring at the Ailaoshan-Sanjiang continental margins and potentially smaller eruptions at the East Kunlun or West Qinling continental margins.
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
(2021)
Article
Geosciences, Multidisciplinary
Allen J. Schaen, Brian R. Jicha, Kip Hodges, Pieter Vermeesch, Mark E. Stelten, Cameron M. Mercer, David Phillips, Tiffany A. Rivera, Fred Jourdan, Erin L. Matchan, Sidney R. Hemming, Leah E. Morgan, Simon P. Kelley, William S. Cassata, Matt T. Heizler, Paulo M. Vasconcelos, Jeff A. Benowitz, Anthony A. P. Koppers, Darren F. Mark, Elizabeth M. Niespolo, Courtney J. Sprain, Willis E. Hames, Klaudia F. Kuiper, Brent D. Turrin, Paul R. Renne, Jake Ross, Sebastien Nomade, Herve Guillou, Laura E. Webb, Barbara A. Cohen, Andrew T. Calvert, Nancy Joyce, Morgan Ganerod, Jan Wijbrans, Osamu Ishizuka, Huaiyu He, Adan Ramirez, Jorg A. Pfander, Margarita Lopez-Martinez, Huaning Qiu, Brad S. Singer
Summary: The 40Ar/39Ar dating method is versatile and can provide precise age constraints for a wide range of materials, but age dispersion must be considered. The interpretation of dates depends on the geological problem being addressed and the assumptions associated with each data set, highlighting the need for collateral information to better constrain interpretation.
GEOLOGICAL SOCIETY OF AMERICA BULLETIN
(2021)
Article
Geosciences, Multidisciplinary
Shanjin Yang, Mingzhong Zhou, Jack Longman, Li Zhou, Enlin Yang, Guiyun Wang, Di Zhang, Zongling Zhang, Hongwei Zhang
Summary: This study focuses on the K-bentonite beds in the upper part of the Ediacaran system in South China and investigates their primary magmas, tectonic setting, geochemical correlation, and potential implications to the evolution of late Ediacaran life. Through geochemical analysis of whole-rock and zircon samples, it is determined that the K-bentonites have trachyandesitic primary magmas and were formed in a convergent environment. The geochemical correlation of the K-bentonites suggests that the age of a specific K-bentonite may not be accurate as the end time of a carbon isotope excursion event. The widespread volcanism in the late Ediacaran may have contributed to enhanced oceanic productivity and played a role in the evolution of life at that time.
PRECAMBRIAN RESEARCH
(2023)
Article
Chemistry, Analytical
Lylia Hamidatou, Fahd Arbaoui, Mohamed Nadir Boucherit, Hocine Slamene
Summary: K(0)-NAA and WDXRF techniques were used for a complete chemical analysis of two Algerian bentonites: Mag and Mos. The concentration values of 37 elements, including 10 rare earth elements (REE), were determined. The k(0)-NAA results showed trace element concentrations of 290 and 285 mg/kg for Mag and Mos respectively. The REE content was higher in Mos at 176 mg/kg compared to Mag at 87 mg/kg. The SiO2/Al2O3 values for Mos and Mag were found to be 4.5 and 2.8 respectively. Mag exhibited a higher proportion of transition elements (38%) and a more reductive character compared to Mos (29%). Additionally, Mag was more affected by anthropogenic activity due to the presence of As and Sb.
JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY
(2023)
Article
Crystallography
Jorge Luis Costafreda, Domingo Alfonso Martin
Summary: This research aimed to investigate the pozzolanic properties of bentonites found at the San Jose-Los Escullos deposit for the manufacturing of durable and environmentally compatible pozzolanic cements, mortars, and concretes. The study conducted mineralogical, petrological, chemical, and thermogravimetric analyses on the samples, showing potential for the materials to be used as quality pozzolans in construction.
Article
Geosciences, Multidisciplinary
Jack Longman, Benjamin J. W. Mills, Hayley R. Manners, Thomas M. Gernon, Martin R. Palmer
Summary: The Late Ordovician period was characterized by global cooling, glaciation, and severe mass extinction, potentially driven by increased delivery of phosphorus to the oceans from volcanic eruptions. By studying the effects of volcanic ash on marine ecosystems, researchers have reconstructed the impact of Late Ordovician volcanic phosphorus delivery on the marine system, showing that massive volcanism can lead to significant global cooling over million-year timescales. This offset the transient warming from greenhouse gas emissions associated with volcanic eruptions, suggesting potential long-term cooling and marine eutrophication effects from volcanism-driven global events.
Article
Geosciences, Multidisciplinary
J. Garrecht Metzger, Jahandar Ramezani, Samuel A. Bowring, David A. Fike
Summary: By utilizing high-precision U-Pb zircon geochronology, the study successfully constrained the duration of the Late Ordovician Guttenberg isotopic carbon excursion (GICE) to less than 400,000 years at two locations in eastern Missouri, United States. The abruptness of the GICE suggests more rapid environmental drivers, such as changes in eustatic sea level associated with pre-Hirnantian glacial activity.
GEOLOGICAL SOCIETY OF AMERICA BULLETIN
(2021)
Article
Geosciences, Multidisciplinary
Wenhao Zheng, Fei Tian, Qingyun Di, Wei Xin, Fuqi Cheng, Xiaocai Shan
Summary: Machine learning methods were used to classify electrofacies in the paleokarst reservoirs of the Tarim Basin Ordovician strata. An electrofacies-lithology database was established, and a prediction model was built with a 92.2% accuracy rate for automatically identifying electrofacies in carbonate strata. This approach could improve exploration efficiency and reduce economic costs in the Tarim Basin and similar paleokarst reservoirs.
MARINE AND PETROLEUM GEOLOGY
(2021)
Article
Plant Sciences
Hengchi Chen, Yuhan Fang, Arthur Zwaenepoel, Sanwen Huang, Yves Van de Peer, Zhen Li
Summary: In this study, the researchers revisited the previously identified whole-genome duplication (WGD) events in ferns, particularly in the core leptosporangiate ferns. By analyzing K-S-age distributions and conducting statistical gene tree-species tree reconciliation analyses, they identified four ancient WGDs in the sampled core leptosporangiate ferns. The study also highlighted the importance of substitution rate corrections and uncertainties in gene tree-species tree reconciliations when calling WGD events.
Article
Chemistry, Inorganic & Nuclear
Lylia Hamidatou, Fahd Arbaoui, Radji Chahra, Hocine Slamene, Kamel Djebli, Mohamed Nadir Boucherit
Summary: This study focused on determining the rare earth elements (REE) in Algerian bentonites named Mos and Mag using the k(0)-NAA method. Results showed that Mos has a higher concentration of total light REE (LREE) compared to Mag. Ce and Eu were found to have the highest and lowest trace amounts of REE, respectively, in both bentonites. The study discussed the amounts and proportion of LREE in comparison to HREE, and compared the results with those from other literature.
Article
Geochemistry & Geophysics
Achim D. D. Herrmann, John T. T. Haynes, Richard Robinet, Peter D. D. Clift, Keith E. E. Goggin
Summary: By analyzing detrital zircons in sedimentary rocks and volcanic ash, researchers found that volcanic activity and sandstone deposition were separated in the Sarika region, supporting a tectonic setting similar to New Guinea and Sumatra.
