查看更多>>摘要：The Curnamona Province is a Paleoproterozoic to Mesoproterozoic domain that hosts the Broken Hill Pb-Zn ore body and a number of IOCG type Cu-Au deposits, but is mostly covered in Neoproterozoic to Quaternary cover. Three-dimensional resistivity modelling of 55-km gridded long-period (0.1-0.0001 Hz) magnetotelluric (MT) data collected as part of the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) previously revealed the presence of the Curnamona Conductor that exhibits extremely low resistivities <1 Omega.m at upper-crustal depths (<15 km) which has a lateral extent of >200 km in a north-south orientation. The conductor appears to dip to the west, centred under the large igneous province Benagerie Suite Volcanics with resistivity similar to 10-100 Omega.m in a broader lower crustal region. To yield higher resolution of the Curnamona Conductor, a 56-site broadband (200-0.001 Hz) MT transect was undertaken with 2 km spacing. The east- west line intersected the observed conductive structures orthogonally. We show consistency between long-period MT AusLAMP 3D models, and new 2D and 3D broadband MT inversions, but with higher spatial and vertical resolution compared to the AusLAMP model. The linearity, depth extent and western dipping morphology of the Curnamona Conductor is remarkably similar to other Paleoproterozoic conductors in Australia along the eastern margin of the Mount Isa Province in northern Australia, and the eastern margin of the Gawler Craton in southern Australia. Plate reconstructions of Paleoproterozoic Nuna supercontinent suggests that these now disparate continental cratons were originally contiguous, with extensive subduction along their eastern margin between 2200 and 1850 Ma. Marine sedimentation in accretionary wedges prior to continental collision occurred during the Lomagundi-Jatuli Event, which recorded a global increase in delta C-13 (2300-2000 Ma) with a significant increase in burial of organic carbon. We argue that these Paleoproterozoic conductors thus represent graphitic suture zones that are uniquely representative of a time of enhanced carbon burial in Earth's history. (C) 2021 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
Pimentel Mizusaki, Ana MariaFerreira, Alanielson C. D.Conceicao, Rommulo Vieira
19页
查看更多>>摘要：For over 50 years, Mesozoic tholeiites, kimberlites and carbonatites from the South American platform have been enabled the understanding of melting processes in the Earth's upper mantle. However, the genetic relationship between alkaline and tholeiitic magmatism remains unknown. In this context, an extensive review, based on a compilation of published geochemical and isotopic data, shows an integrated evolution for mantle-derived magmatism in South America. The K-rich alkaline-carbonatite intrusions occur widespread through time at 255-209 Ma, 146-106 Ma and 91-71 Ma. Moreover, the Na-rich magmatic episodes are also documented at 130-120 Ma and 66-32 Ma. Tholeiitic basaltic lavas and dikes are recorded at -200 Ma in Northern Brazil and mainly between 134 and 131 Ma in the Parana Magmatic Province. Simultaneous tholeiitic lavas and carbonatitic complexes are related to near isothermal decompression of enriched asthenospheric and lithospheric mantle sources at different depths (80-200 km). Likewise, the 267-226 Ma kimberlites in the Amazonian Craton, -128 Ma Rosario kimberlite in the Rio de la Plata Craton and 88-80 Ma Alto Paranaiba kimberlites in the western edge of the Sao Francisco Craton provide evidence for deeper (>200 km) metasomatized mantle sources. Compiled numerical, geophysical and geological data support the proposal that the thickness of the lithosphere, extension rates and the presence of previous weak crustal structures contributed to the generation and emplacement of multiple tholeiitic and alkaline intrusions from 250 to 30 Ma. We propose that several crustal extension events induced repeated thermal convection cells in the metasomatized asthenosphere, which triggered partial melting in the previously enriched and heterogeneous lithospheric mantle. The local mantle composition, depth and crustal extension ratios controlled the magma composition. Thus, West Gondwana break-up and dispersal played a crucial role in the Mesozoic to Paleogene melting processes of the metasomatized mantle in South America. (c) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
查看更多>>摘要：The Changbaishan volcanic field is one of the most dangerous active volcanic fields in Northeast Asia. Its Millennium eruption at 946-947 CE is considered to be one of the world's largest explosive eruptions over the past 2000 years. However, little attention has been paid to the other Late Holocene tephrostratigraphic sequence of this volcanic field. Here we present petrographic, geochemical, and AMS(14)C chronological data of a newly discovered Late Holocene tephrostratigraphic sequence of the Changbaishan volcanic field recorded in the Dongfanghong peatland, Northeast China. Results suggest that four tephra layers were preserved in this peatland. Tephra layer 1 was the weathering product of Early Pleistocene shield construction trachyandesite of the Changbaishan volcanic field. Tephra layer 2 was the product of a comendite magma chamber that erupted at 3356 cal. yr BP, which erupted from the secondary caldera. Tephra layers 3 and 4 were the products of the better known Millennium eruption of Changbaishan Tianchi volcano. Tephra layer 3 was also sourced from the comendite magma chamber, which was the first sub-stage of the Millennium eruption. Tephra layer 4 was sourced from the trachyte magma chamber, which was the second sub-stage of the Millennium eruption. This newly discovered tephrostrati-graphic sequence could act as a key isochronous marker horizon for the chronological framework in a range of sedimentary contexts across Northeast Asia, and provide important historic eruptive information of the Changbaishan volcanic field. Significantly, this study also suggests that the peatlands developed on the volcanic fields have great potential in tephrostratigraphic sequence reconstructions. (C) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
查看更多>>摘要：In the past few years, the investigation into the case of ecological footprint and its determining factors has remained the core subject of debate among policy analysts. But some of the crucial determinants of ecological footprint have not been sufficiently covered in the literature. This study employed government expenditures, inflation dynamics, and economic growth from 1971 to 2016 as moderator variables to examine the impact of alternative energy sources on Germany's environmental quality. We applied advanced econometric methodologies for empirical analysis. The results of fully modified least squares, dynamic least squares, and robust canonical cointegrating regressions indicate that alternative energy sources, government expenditures, and inflation are negatively associated while economic growth is positively associated with the environmental quality in Germany. Policymakers are encouraged to eliminate subsidies for domestic coal productions, promote cost-efficient ecological policy designs, price environmental resources, intensify green budget, decouple economic growth from the harmful emissions, and generate a trade-off between stabilizing inflation and stabilizing fluctuations through a sustainable monetary policy. (c) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
Khan, Javeria RehmanKalugina, Olga A.Zafar, Muhammad WasifMirza, Faisal Mehmood...
14页
查看更多>>摘要：This study decomposes energy intensity into structural and activity effects, and empirically examines their impact on CO2 emissions in environmental Kuznets curve framework for the 30 developing countries over 1990-2016. Second generation methodological approach is adopted. The decomposed indices reflect that energy efficiency has played a key role in decreasing energy intensity, while structural shifts have caused only a minor reduction in energy intensity. The findings suggest that energy efficiency improvements have largest influence on CO2 emissions mitigation. In developing countries as a whole, energy efficiency has positive while structural shifts have negative relation with CO2 emissions in long run. The findings presented that energy efficiency is major contributor of CO2 emissions reduction. While structural shifts in developing countries tend to increase CO2 emissions because these countries are moving towards the sectors that are producing more pollution. However, the income is one of the major contributors of CO2 emissions. While renewable energy consumption has negative and industrialization has positive impact on CO2 emissions in developing countries. The study outcomes are utilized to develop a policy framework for attaining the SDG 7 and SDG 13 in the chosen countries. (C) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
Cai, Fu-LongGuo, Xu-DongDing, LinLaskowski, Andrew K....
14页
查看更多>>摘要：Accretionary complexes offer important source of information for studying the subduction history and source-to-sink system and neighboring terranes. In this study, we conducted field mapping, detrital zircon U-Pb age and trace element analyses, and electronic microprobe composition analysis of detrital Crspinel in sandstones from the Cretaceous Bainang accretionary complex in the central part of the Yarlung-Zangpo suture zone (YZSZ). The Bainang accretionary complex is located in a structural window that is mainly composed of Xigaze ophiolite, Late Triassic-Early Cretaceous radiolarite chert with a Late Cretaceous hemipelagic siliceous shale matrix, and Late Cretaceous sandstone. The obtained detrital zircon geochronological dataset confirms two spectra. Detrital zircons from the Canggasaba and Lianxiang sections are dominated by Precambrian grains with subordinate numbers of Mesozoic grains clustering at 243-178, 164-117, and 109-91 Ma, consistent with the melange and trench-fill Rongmawa Formation, and all the trace elements of the Mesozoic grains match continental arc affinity. Provenance analysis suggests that detritus in these sections was mainly derived from the eastern part of the Gangdese arc and the central-northern Lhasa terrane. These results confirm the existence of the ancestral Lhasa River that transports sediments from the eastern Lhasa terrane to the subduction zone and further westward along the east-west axial system parallel to the trench. Conversely, the Qiajiu section is mainly dominated by Mesozoic detrital zircon grains, representing submarine fan deposits that were sourced from the adjacent Gangdese arc and transported through a local north-south-flowing river system. Detrital Cr-spinel compositions and detrital zircon trace elements from the Qiajiu section also revealed the contribution of ophiolites. Considering the abundance of Eurasia-affinity detrital zircons, this study supports the single subduction model that was developed along the southern margin of the Lhasa terrane. (c) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
查看更多>>摘要：Currently, one of the most significant challenges of agricultural sector of an economy is to keep pace with the world's rapidly growing population in order to feed them. But continuous environmental degradation is posing serious threat to the agricultural production. The objective of this study is to look at how envi-ronmental degradation in the form of biodiversity loss, deforestation and agricultural emissions can affect agricultural production as well as cereal and vegetable production in 35 countries of Europe. The study utilizes Driscoll and Kraay estimator to understand the potential impacts of environmental degra-dation as well as other variables such as organic farming, renewable energy, political stability, e-governance, social progress and women empowerment on agriculture. The result reveals that biodiversity loss harms agricultural, cereal and vegetable production while forest area increase positively affect the cereal production and vegetable production. Agricultural emissions, on the other hand, does not signifi-cantly affect the three independent variables but it has a negative effect on cereal and positive impact on vegetable production. Renewable energy use, political stability and women empowerment all have pos-itive and significant impacts on all the three dependent variables. E-governance significantly and posi-tively affects agricultural and vegetable production and social progress has positive but insignificant effect on the dependent variables. Finally, the study provides crucial policy implications for the agricul-tural sector of Europe. (c) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
Olierook, Hugo K. H.Gale, JasminePirajno, FrancoJourdan, Fred...
21页
查看更多>>摘要：The recognition of lithospheric delamination as a mechanism for magmatism and uplift is underrecognized in the geological record. A pertinent example is the terminal phase of the New England Orogen in eastern Australia, where current explanations of slab roll-back-driven extension are incompatible with plate motions in the Late Triassic. Although abundant mafic rocks are present, almost all Late Triassic temporal information is from felsic rocks. To investigate potential Late Triassic mafic magmatism in the New England Orogen, we date a series of tholeiitic and alkaline mafic products in its back-arc (Sydney Basin) using plagioclase Ar-40/Ar-39 and apatite U-Pb geochronology. We obtained a plagioclase Ar-40/Ar-39 plateau age of 202.77 +/- 0.68 Ma (2 sigma) from tholeiitic magmatic products and an apatite U-Pb age of 202 +/- 7 Ma (2 sigma) from a proximal alkaline sill some 70 m deeper, both of which overlap within uncertainty. Complementary trace element geochemistry shows that the tholeiitic and alkaline magmatic products were derived from a similar deep, garnet-bearing source, which we attribute to upwelling asthenosphere underneath a thickened lithosphere. Our data suggest that extension occurred similar to 10 m.y. later in the back-arc basin than along its arc, further supporting the notion that slab roll-back could not have caused this terminal phase of Late Triassic extension in the New England Orogen. The Late Triassic magmatism in the New England Orogen is best explained by lithospheric delamination as it accounts for the orogenic architecture, chemical signature of the ca. 200 Ma products and spatiotemporal distribution of Late Triassic magmatic products. (C) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
查看更多>>摘要：The Mesozoic gold deposits in the North China Craton (NCC) were hosted by the Precambrian basement and Mesozoic intrusions. Thus, most researchers consider that these gold deposits were genetically linked to the Mesozoic intrusions. However, we suggest that a metamorphic devolatilization model provides an alternative based on a combined Fe and in-situ S isotopes study on auriferous pyrites from the Baiyun gold deposit in the NCC. The Triassic Baiyun gold deposit contains the quartz vein and altered rock ores that were developed in the Paleoproterozoic metavolcanic-sedimentary rocks (the Liaohe Group). Our insitu S isotopic analyses show that pyrites from the quartz vein ores are characterized by negative delta S-34 values (-10.7 similar to -5.5 parts per thousand), while those from the altered rock ores have two distinct groups of delta S-34 values, one being positive (+13.5 similar to +16.2 parts per thousand) and the other negative (-10.6 similar to -3.0 parts per thousand). We suggest that pyrite grains with positive delta S-34 values should be relicts from the host rocks, because they show comparable delta S-34 values with those from the host rocks schists (+3.3 similar to +16.1 parts per thousand). Thus, only the negative delta S-34 values of pyrites in ores (-10.7 similar to -3.0 parts per thousand) and the Fe isotopes of the quartz vein ores (delta Fe-56 = +0.30 similar to +0.48 parts per thousand) can represent the isotopic characteristics of ore-forming fluids at Baiyun. Our study shows that the sulfur were probably from the pyritic volcanic-sedimentary sequences of the Liaohe Group, rather than from magmas. The calculated delta Fe-56 values of the ore-forming fluids (-0.78 similar to -0.37 parts per thousand; pyrite-fluid isotope fractionation) could be modelled in a metamorphic devolatilization model with Fe-species (pyrite&magnetite) of the Liaohe Group as sources. Therefore, our combined S- and Fe- isotope data indicate that the metamorphic devolatilization of the Liaohe Group could account for the genesis of the Baiyun gold deposit. (C) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
查看更多>>摘要：The Greater Maldive Ridge (GMR), consisting of the Maldive Ridge (MR) and Deep Sea Channel (DSC) region, is the N-S trending, middle segment of Chagos-Laccadive Ridge system. This ridge system is widely considered to be the repository representing the interaction between Central Indian Ridge spreading centre and Reunion plume. The present study investigates in detail, spatial variations in effective elastic thickness (Te), isostasy and crustal structure of GMR using high resolution satellite derived gravity, residual geoid and bathymetry data. Estimated Te values along the GMR from 2D and 3D flexural modelling ranges from 6.5-16.5 km with comparatively lower Te values over MR (7-9 km) and slightly higher values over the DSC region (>10 km). Geoid to Topography Ratio computed for two wavelength bands shows almost similar kind of variation along the ridge with a maximum value of 1.4 m/km in the DSC region, decreasing northwards to 0.6 m/km over MR. Integrating results from the present study with crustal thickness, Moho undulations and Curie depth along the entire length of the GMR suggest that MR was formed in the vicinity of spreading centre while DSC region was under a long transform fault which has given rise to the gap zone between Chagos Bank and Maldive Ridge during plume-ridge interaction. (c) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
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