Geological Journal最新文献

The tectonic evolution of terranes and microblocks is crucial for understanding the supercontinental cycle. Sri Lanka, centrally located between East and West Gondwana, offers insights into late Neoproterozoic continental tectonics. Ambiguities in defining boundaries between the Highland Complex (HC) and Wanni Complex (WC) of Sri Lanka prompted this study. Utilising whole-rock major and trace element geochemistry, and U–Pb zircon geochronology, we explore charnockites at the inferred HC-WC boundary, revealing their tectonic nature. Charnockites on the WC side (CWCs) display tholeiitic trends, characterised as Fe-rich, metaluminous A2-type granites. Tectonic discrimination diagrams position CWCs in the within-plate granite field. The ²³⁸U/²⁰⁶Pb zircon geochronology of three WC-side charnockites gave Late Neoproterozoic metamorphic ages from 576 ± 37 to 561 ± 50 Ma and middle to early Neoproterozoic protolith crystallisation ages from 1011 ± 46 to 690 ± 15 Ma. Hence, protoliths of CWCs suggest some form of extensional tectonics in a continental environment during the early to middle Neoproterozoic that played a major role in the crustal evolution of the northeastern part of the WC. Out of the collected seven charnockites in the HC side (CHCs), three samples shared geochemical signatures resembling the CWCs. The ²⁰⁶Pb/²³⁸U zircon ages of one of the samples yielded crystallisation age of ~780 ± 6 Ma and, metamorphic ages from 608 ± 9 to 541 ± 16 Ma, respectively. The rest of the CHCs exhibit calc-alkaline trend, identified as Mg-rich, metaluminous, I-type granites. Tectonic discrimination diagrams reveal volcanic arc signatures, indicating a subduction-related collisional tectonic setting. Geochemical and geochronological findings, coupled with field relations and prior research, lead to the interpretation that charnockites in the northeastern HC-WC boundary possess a distinctive geodynamic history, implying involvement in two distinct tectonic settings. Presently, at the erosion surface, the north-eastern portion of the HC-WC boundary, exhibits a highly diffused nature and manifests as a mixed rock zone.

The Northern Sichuan Foreland Basin, which is located in the northwest of South China Craton (SCC), was formed by the intracontinental thrusting between the Qinling Orogenic Belt (QOB) and SCC. The Upper Triassic to Jurassic sedimentary successions within this foreland basin, contain crucial information for revealing the intracontinental deformation sequence between the QOB and the SCC. In this study, based on a systematic dataset, including the palaeocurrent orientation, sandstone modal composition, and detrital zircons U–Pb age data, we attempt to reveal the tectonic processes during the Late Triassic to Jurassic interval. The palaeocurrent orientations, which is primarily directed in the southward and northwestward directions, indicate that the sediments were sourced from the north and southeast. The sandstone clastic components reveal multiple sources, including the magmatic arc and continental crust. Detrital zircons from six samples yield six major U–Pb age groups, including 2650–2350, 2050–1720, 1000–620, 520–380, 350–210, and 205–160 Ma. The Upper Triassic sediments contain a relatively high density of 2490, 1860, 810, 440, and 230 Ma, which are mostly consistent with the QOB, northern SCC and Jiangnan Suture Zone provenances. The majority age population of 2050–1750 Ma observed within the Xujiahe Formation, is considered to be primarily sourced from northern SCC, suggesting the uplift and erosion of the northern SCC, probably imply extreme shortening between the QOB and SCC. The Baitianba and Xintiangou formations, which contain lesser 2050–1720 Ma aged zircons, indicate a period of lacustrine expansion and tectonic quiescence after the shortening. The Middle Jurassic Shaximiao Formation, and the Upper Jurassic Suining and Penglaizhen formations, involve a major age population of 2050–1720 Ma that were sourced from northern SCC, indicate another phase of uplifting of the northern SCC related to a second stage of extreme intracontinental shortening and deformation between the SCC and the QOB. In summary, the above results indicate that, an initial phase of extensive shortening between the QOB and the SCC during the Late Triassic, was followed by a period of tectonic quiescence during the Early Jurassic, and another phase of extreme intracontinental shortening between the QOB and SCC during the Middle to Late Jurassic.

Rare earth element fractionation in volcanic rocks can be used to recognise both petrogenetic processes and tectonic settings. We present a simple geochemical modelling approach using CeYb proxy employing the Magma Chamber Simulator tool and the binary mixing model to understand the range and the limits of variation in the enrichment of incompatible trace elements, brought about in evolved magmas by differentiation processes in known Phanerozoic tectonic settings in conjunction with the ThNbYb proxy. By extending this approach to the volcanic rocks of the Meso-Neoarchean greenstone belts it is observed that rocks, which fall beyond the limits set by binary mixing and fractional crystallisation in a bivariant trace element plot were most likely generated by the modification of the mantle source by subducting slab-derived fluids prior to the melting of the source and the diversification of the magmas into differentiated rocks. Subduction–accretion process was established at least by the Meso-Neoarchean. The greenstone belts of the Dharwar and Yilgarn cratons represent Archean analogues of oceanic crust that were predominantly emplaced in a convergent-margin tectonic setting and probably acted as suture zones that juxtaposed continental crustal masses by horizontal tectonic forces.

This study aims to identify the primary issues leading to the pause in geothermal energy development at Aluto-Langano and Tulu-Moye sites, while also exploring opportunities in new drilling wells and assessing compliance with occupational safety, health and environmental standards. The geothermal energy development status was evaluated through focus group discussions, site visits and field data collection. The Tulu-Moye Geothermal Operation (TMGO) project is underway to establish a power plant, with a phased development spanning 6 years targeting a total capacity of 150 MW, comprising 50 MW for Phase 1 and 100 MW for Phase 2, though with some constraints. The Aluto-I Geothermal Pilot Plant marked the initial efforts to produce electricity from geothermal sources but faced shutdown due to declining thermal energy in some wells, turbine corrosion, pentane leakage, frequent in efficiency of fans and instability of foundations. Consequently, Phase 2 of the project aims to integrate with Phase 1 wells to mitigate potential thermal energy losses. Geothermal energy development demands substantial initial investment but entails minimal ongoing costs and workforce requirements. Its eco-friendliness benefits communities, offering higher efficiency and lower maintenance compared to hydroelectricity. Leveraging Ethiopia's geothermal potential is crucial for electricity generation, mineral extraction, and water supply, with plans involving nationwide field expansion to enhance renewable energy capacity.

The North Qilian Accretionary Belt, situated at the northernmost extent of the Proto-Tethys tectonic domain, preserves key tectonic events such as Proto-Tethys Ocean subduction and accretion. Despite ongoing debates about the closure mechanisms and timing of the North Qilian Ocean, our study presents novel findings on granitoids from the Changma region in the western segment of the North Qilian Accretionary Belt. Zircon U–Pb dating indicates an emplacement age of 436 Ma for the Qingshixia pluton and 425 Ma for the Heixialao pluton. The ε _Hf (t) values of the Qingshixia granodiorite range from +8.25 to +10.89, with T_DM2 model ages estimated between 614 and 716 Ma. In contrast, the ε _Hf (t) values of the Heixialao monzogranite range from +1.79 to +4.48, with T_DM2 model ages spanning from 1127 to 1291 Ma. The Qingshixia granodiorite displays adakitic traits, characterised by high Sr, low Y, low Yb, and a low K₂O/Na₂O ratio, whilst the Heixialao monzogranite exhibits peraluminous, high-potassium calc-alkaline features. The low concentrations of Ni and Cr, along with moderate Mg# values, suggest that the Qingshixia granodiorite likely originated from the partial melting of a subducting slab. By comparison with experimental melts, the relatively low Rb/Ba and Rb/Sr ratios and higher zircon saturation temperatures of Heixialao monzogranite suggest that it may have formed from partial melting of the mafic middle and lower crust. Integrating these findings with regional geological features and differences between east and west segments, we propose that the western segment of the North Qilian Ocean basin may have closed during the Late Silurian, contributing to a diachronic closure process from east to west and offering insights into the tectonic evolution of the Proto-Tethys Ocean.

This article provides a detailed taxonomic study of mammalian fossil fauna from five localities situated within the Middle Siwalik subgroup including the Nagri and Dhok Pathan formations in Punjab, Pakistan. Twenty-three euungulate specimens comprised of isolated teeth, and maxillary and mandibular fragments, are described. This collection includes the bovid, Elachistoceras; a very rare faunal element in the Siwaliks of Pakistan, as well as Elachistoceras khauristanensis, Pachyportax latidens, Giraffa punjabiensis, Bramatherium grande, Merycopotamus dissimilis, Dorcatherium minus, Dorcatherium majus, Hippopotamodon sivalense, Sivalhippus theobaldi, Sivalhippus nagriensis and Brachypotherium perimense These fossil remains add important new insights into the taxonomy and diversity of Late Miocene mammal faunas of the Middle Siwaliks. The data is important for understanding the biogeographical and palaeoenvironmental history of the region. The characteristics of the fossils described in this study further support the currently hypothesised presence of a massive open land environment with variable wet and dry seasons alike to that of the current climate in Eurasia and Africa. The variable habitat niches of these co-existing fauna also give further support to the supposition that there was a much more mixed array of palaeoenvironments ranging from a prevalence of woodland to expansive savannah territory during the deposition of Nagri and Dhok Pathan formations.