Showing papers in "Geological Journal in 2019"

Petrogenesis and metallogenic implications of Cretaceous magmatism in Central Lhasa, Tibetan Plateau: A case study from the Lunggar Fe skarn deposit and perspective review

Abstract: Chengdu Center, China Geological Survey, Chengdu, China State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, College of Environment and Civil Engineering, Chengdu University of Technology, Chengdu, China School of Earth Sciences and Resources, China University of Geosciences, Beijing, China Centre for Tectonics, Exploration and Research, University of Adelaide, Adelaide, South Australia, Australia 5 iCRAG (Irish Centre for Research in Applied Geosciences), School of Earth Sciences, University College Dublin, Belfield, Ireland Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan Correspondence Yun‐Hui Zhang, State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, College of Environment and Civil Engineering, Chengdu University of Technology, Chengdu 610059, China. Email: zhangyunhui0710@163.com Funding information National Key R&D Programme of China, Grant/Award Numbers: 2016YFC0600308 and 2018YFC0604103; China Geological Survey, Grant/Award Number: DD20160015

Depositional history and provenance of cratonic "Purana" basins in southern India: A multipronged geochronology approach to the Proterozoic Kaladgi and Bhima basins

Abstract: Peninsular India is a collage of Archaean cratonic domains separated by Proterozoic mobile belts. A number of cratonic basins, known as “Purana basins” in the Indian literature, formed in different parts of the Indian Peninsula during extensional tectonic events, from Paleoproterozoic through Neoproterozoic times. In this contribution, we present a diversity of new geochronological data for different units within the Kaladgi and the Bhima basins, which overlie the western and eastern Dharwar cratons, respectively. The new geochronology data are discussed in terms of depositional history and provenance of these poorly understood Proterozoic intracratonic basins. For the Kaladgi Group, a U–Pb baddeleyite age of 1,861 ± 4 Ma obtained for a dolerite dyke intruding the Yendigere Formation is used to constrain the minimum age of deposition of the lower Kaladgi Group. This result demonstrates that this part of the succession is comparable in age to the Papaghni Group of the Cuddapah Basin, heralding onset of Purana sedimentation at ~1,900 Ma. The detrital zircon populations from the clastic rocks of the Kaladgi and Bhima basins show unique and distinct age patterns indicating different source of sediments for these two basins. Palaeocurrent analysis indicates a change in provenance from south or southeast to west or northwest between the Kaladgi and Bhima clastic sedimentation. New U–Th–Pb and Rb–Sr radiometric dates of limestones and glauconite-bearing sandstones of the Bhima Group (Bhima Basin) and the Badami Group (Kaladgi Basin) indicate deposition at around 800–900 Ma, suggesting contemporaneity for the two successions. Thus, the unconformity between the Kaladgi Group and the overlying Badami Group represents a time gap of up to 1,000 Myr. These new results demonstrate the complex multistage burial and unroofing history of the Archaean Dharwar Craton throughout the Proterozoic, with important implications for exploration of metal deposits and diamonds in Peninsular India. (Less)

Sedimentary flow heterogeneities in the Triassic U.K. Sherwood Sandstone Group: Insights for hydrocarbon exploration

Abstract: Fluvial and aeolian sedimentary successions host important hydrocarbon resources as well as major groundwater aquifers. This review of the lithological characteristics of Triassic fluvio‐aeolian successions of the Sherwood Sandstone Group (United Kingdom) demonstrates how distance from a fluvial sediment source and rate of rift‐related tectonic subsidence play important roles in governing reservoir quality in continental successions. Increasing distance from the fluvial sediment source area results in increased porosity and permeability in deposits of mixed fluvial and aeolian reservoir successions that accumulated in arid and semiarid settings. Indeed, successions of the U.K. Sherwood Sandstone Group reveal an increase in the proportion of highly permeable deposits of aeolian origin with increasing distance from the principal uplands, represented by the Armorican Massif in northern France, which formed the main source for delivery of fluvial sediment to a series of rift basins. A progressive reduction in the discharge of fluvial systems entering and passing through a series of interlinked rift basins encouraged aeolian accumulation in more distal basins. Extensional tectonics enabled preservation of highly permeable aeolian facies in basins subject to high rates (≳100 m/Myr) of tectonic subsidence by rapidly placing such deposits below the water table. However, successions exclusively characterized by fluvial lithofacies record decreases in both porosity and permeability with increasing distance (~250–750 km) from the sediment source due to the coupling of porosity reduction and increasing clay content.