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 research examines the dynamic relationships between green improvisation, green absorptive capacity, environmental management initiatives (EMIs), corporate social responsibility (CSR) authenticity, and their combined impact on firms' green competitive advantage and environmental performance. The study empirically tested seven hypotheses, utilising structural equation modelling (SEM) via SmartPLS. Data was collected from the employees of firms situated in Pakistan through a survey in a time span of 6 months. Results indicate that green improvisation significantly enhances EMIs, highlighting the importance of innovative and adaptive approaches in environmental stewardship. Green absorptive capacity was found to effectively acquire and assimilate environmental knowledge, positively influencing EMIs. Additionally, EMIs were shown to strengthen CSR authenticity, thereby improving firms' green competitive advantage and environmental performance. The mediating role of CSR authenticity was confirmed, revealing its significance in translating effective environmental management into tangible outcomes. Moreover, green creativity was found to moderate the relationship between EMIs and CSR authenticity, with novel environmental solutions enhancing the effectiveness of CSR activities. These findings contribute to the literature on environmental management by elucidating the mechanisms through which environmental initiatives lead to competitive and ecological benefits. The study provides actionable insights for firms aiming to integrate environmental strategies into their core business practices, achieving a sustainable competitive edge in today's green economy.

Industrial shale oil/gas flow have been discovered in the Luanping Basin, and the hydrocarbon potential of the Lower Cretaceous Xiguayuan Formation (Luanping Basin, North China) has attracted the attention of geologists in recent years. The paleoenvironmental conditions, provenance and chert origin of the Xiguayuan Formation were studied using the geochemistry of lacustrine sediments in the Caoying section. A pronounced positive correlation between the oxygen and carbon isotopes of autogenous carbonates indicates the Early Cretaceous Luanping paleolake was an alternating depositional environment of open and closed, with obvious evaporation. The V/(V + Ni) ratios, negative Ce and Eu anomalies suggest that the Xiguayuan Formation was deposited in anoxic conditions with fewer instances of euxinic conditions. Sr/Ba, Z and S values together demonstrate a brackish to saline waterbody under semi-arid and fluctuating semi-humid paleoclimatic conditions. Various indicators show that they are predominantly derived from felsic igneous rocks and minor probable basic source supply with minor sedimentary recycling. The cherts are developed in Unit 1 and Unit 2, compared with Unit 3, Unit 1 and Unit 2 show relatively open, less reductive, high salinity. A theoretical formation model of alternating rise and drop in lake levels in the basin was established to show syndepositional bedded chert-bearing sedimentary succession. The acid river dominate water and the evaporation in front fan delta environment maybe the main factor that lead silica precipitation.

The Wajrakarur Kimberlite Field (WKF) in Anantapur, Andhra Pradesh, India, stands as a pivotal region for kimberlite exploration in the South Indian Kimberlite Province. It features distinct gravity highs and lows, sandwiched between Closepet Granite (CG) and Cuddapah Basin (CB), with notable gold-mineralized Ramagiri-Penakacherla Greenstone Belt (RPGB) and Jonnagiri Greenstone Belt (JGB). The structural features of gravity modelling include upwarping beneath the western CG and downwarping beneath Peninsular Gneissic Complex-II (PGC-II). Gravity signatures allow for the identification of shallow geological features such as granite structures and fault/shear zones around 3–4 km deep in the WKF region, with kimberlite pipes showing a preferential concentration along these zones. Deep-seated fault structures reveal the area's geological characteristics, offer insights into lithospheric fluid migration, and are key for evaluating fluid flow pathways associated with deep-seated minerals and kimberlite exploration. The study reveals regional variations and geological characteristics, providing valuable avenues for future research.

Until recently, no physical rock samples from the Palaeozoic to Mesozoic eras had been recovered from the South Yellow Sea (SYS), leaving the palaeoclimatic significance of this period largely unexplored. This study analyzes data from the Lower Silurian to Lower Triassic strata of the CSDP-2 Well, including magnetic susceptibility (MS) data from 251 samples and geochemical element data for 345 samples, to determine environmental changes and their implications. We successfully establishes vertically continuous and complete MS and geochemical curves within the SYS, and two depth segments with anomalous values and four climatic shifts are identified. Through the coupled analysis of MS and geochemical data, along with the synthesis of previously published data, one anomalous segment from 1690-2006. 9 meters below sea floor (mbsf) could represent the Late Devonian-Early Permian Ice Age, which lasted approximately 80 Ma. Another segment from 820-930 mbsf represents Emeishan and Siberian volcanism, with an interval between the two events spanning approximately 2.7 Ma. And 15 variation cycles are identified by analyzing changes of MS values, we found that geological event cycles spanned 3-9 Ma during the Early Silurian to Permian, but the interval shorten to approximately 28.6 Kyr in the Early Triassic. In summary, the CSDP-2 Well records several significant geological events and the SYS underwent an exceptionally complex evolution of geological environments during the Early Mesozoic. Additionally, MS data from CSDP-2 Well reveal unique variation patterns not seen in adjacent areas or other blocks, indicating that while the SYS was influenced by global climate and tectonic activities at block-level, it also experienced distinct regional geological environmental changes.