0 INTRODUCTION Orogenic belts are commonly built by multiple-stage processes involving oceanic subduction and continental collisions that result in the generation of magma with distinct geochemical compositions,as exe...0 INTRODUCTION Orogenic belts are commonly built by multiple-stage processes involving oceanic subduction and continental collisions that result in the generation of magma with distinct geochemical compositions,as exemplified by Central Asian Orogenic Belts(e.g.,Wang et al.,2024;Yin et al.,2024;Xiao et al.,2005)and the Tethyan tectonic domains(e.g.,Chen et al.,2024;Li et al.,2024;Tao et al.,2024a;Gehrels et al.,2011;Yin and Harrison,2000).展开更多
Plutonic rocks from the Mineiro Belt, Brazil record a delayed onset of the transition from TTG to sanukitoid-type magmatism（high Ba-Sr）, starting during the Siderian magmatic lull when little juvenile magma was adde...Plutonic rocks from the Mineiro Belt, Brazil record a delayed onset of the transition from TTG to sanukitoid-type magmatism（high Ba-Sr）, starting during the Siderian magmatic lull when little juvenile magma was added to the continental crust. Rocks mostly belong to the calc-alkaline series, meta-to peraluminous and originally ＂Ⅰ-type＂,meaning that oxidized magmas were formed by partial melting of subducted material. The temporal distribution and apparent secular changes of the magmas are consistent with the onset of subduction-driven plate tectonics due to an increase of the subduction angle and opening of the mantle wedge. New isotopic analyses（Sm-Nd whole rock and Lu-Hf in zircon）corroborate the restricted juvenile nature of the Mineiro Belt and confirm the genetic link between the Lagoa Dourada Suite,a rare ca. 2350 Ma high-Al tonalite-trondhjemite magmatic event, and the sanukitoid-type ca. 2130 Ma Alto Maranhao Suite. U-Pb dating of zircon and titanite constrain the crystallisation history of plutonic bodies; coupled with major and trace element analyses of the host rocks, they distinguish evolutionary trends in the Mineiro Belt. Several plutons in the region have ages close to 2130 Ma but are distinguished by the lower concentration of compatible elements in the juvenile high Ba-Sr suite.展开更多
The southern portion of the Sao Francisco Palaeocontinent in Brazil is denoted by Archean nuclei and Paleoproterozoic magmatic arcs that were amalgamated during Siderian to Orosirian orogenic processes(ca.2.4-2.1 Ga)....The southern portion of the Sao Francisco Palaeocontinent in Brazil is denoted by Archean nuclei and Paleoproterozoic magmatic arcs that were amalgamated during Siderian to Orosirian orogenic processes(ca.2.4-2.1 Ga).New isotopic U-Pb in zircon and Sm-Nd whole rock combined with major and trace element composition analyses constrain the crystallization history of the Neoarchean Piedade block(at ca.2.6 Ga)and the Paleoproterozoic Mantiqueira Complex(ca.2.1-1.9 Ga).These therefore display quite different magmatic histories prior to their amalgamation at ca.2.05 Ga.Sm-Nd and Rb-Sr isotopes imply a mixed mantle-crustal origin for the samples in both units.A complete Palaeoproterozoic orogenic cycle,from subduction to collision and collapse,is recorded in the Piedade Block and the Mantiqueira Complex.Rhyacian to Orosirian subduction processes(ca.2.2-2.1 Ga)led to the generation of coeval(ca.2.16 Ga)TTG suites and sanukitoids,followed by late(2.10-2.02 Ga)high-K granitoids that mark the collisional stage.The collisional accretion of the Mantiqueira Complex against the Piedade Block at 2.08-2.04 Ga is also recorded by granulite facies metamorphism in the latter terrane,along the Ponte Nova suture zone.The collisional stage was closely followed by the emplacement of within-plate tholeiites at ca.2.04 Ga and by alkaline rocks(syenites and enriched basic rocks)at ca.1.98 Ga,marking the transition to an extensional tectonic regime.The discovery of two episodes of TTG and sanukitoid magmatism,one during the Neoarchean in the Piedade Complex and another during the Rhyacian in the Mantiqueira Complex,indicates that the onset of subduction-related melting of metasomatized mantle was not restricted to Neoarchean times,as generally believed,but persisted much later into the Paleoproterozoic.展开更多
This paper describes a study into the development of more robust dust emission factors by means of dust and meteorological monitoring. Emission factors for nuisance dusts in the literature are scarce, with estimates o...This paper describes a study into the development of more robust dust emission factors by means of dust and meteorological monitoring. Emission factors for nuisance dusts in the literature are scarce, with estimates of dust output given for many processes in mass per unit area per year. Temporal variations and the extent and conditions in which maximum concentrations occur can therefore be impossible to predict with any accuracy. This investigation aims to improve predic-tions by “back calculating” emission levels based on dust monitoring around known dust sources. Nuisance dust and meteorological monitoring has been undertaken at a sand and gravel quarry in the UK for a consecutive period of two years. Sticky pad directional dust monitors were used to collect dust at eight locations at and around the site with meteorological data collected at an elec-tronic weather station within the site. Air quality modelling software (ADMS) was used to test emission factors from the European Environment Agency (EEA) and the US Environmental Protec-tion Agency (EPA) for emissions from mineral workings. Predictions were compared with the dust monitoring data to assess accuracy, with results showing limited poor correspondence (r<sup>2</sup> < 0.3). Trends showed that emission predictions were poorest in winter;this is likely because most emis-sion calculations are not weather dependent and seasonal fluctuations will occur. Dust emission rate calculations were altered with respect to the dust monitoring data for one monitoring location on the mineral site boundary and the model was run again. Results were then tested at two different locations up to 200 m from the site boundary, with very positive correlations (r<sup>2</sup > 0.89) and similar maximum concentrations (<5% difference). This study has therefore shown that ac-curate site-specific emission rates can be produced in combination with site boundary sticky pad dust monitoring in order to accurately derive estimations elsewhere.展开更多
基金supported by the National Key Research and Development Project(No.2022YFC2903302)the Second Tibet Plateau Scientific Expedition and Research Program(STEP),(No.2019QZKK0802)+2 种基金the National Natural Science Foundation of China(No.42361144841)the Chinese Academy of Geological Sciences Basal Research Fund(No.JKYZD202402)the Scientific Research Fund Project of BGRIMM Technology Group(No.JTKY202427822)。
文摘0 INTRODUCTION Orogenic belts are commonly built by multiple-stage processes involving oceanic subduction and continental collisions that result in the generation of magma with distinct geochemical compositions,as exemplified by Central Asian Orogenic Belts(e.g.,Wang et al.,2024;Yin et al.,2024;Xiao et al.,2005)and the Tethyan tectonic domains(e.g.,Chen et al.,2024;Li et al.,2024;Tao et al.,2024a;Gehrels et al.,2011;Yin and Harrison,2000).
基金CNPq (National Counsel of Technological and Scientific Development, Brazil) grant (234610/2014-0)CAPES (Brasília, Brazil)+4 种基金FAPEMIG (Belo Horizonte, Brazil)UFOP (Ouro Preto, Brazil)UPS/Laboratoire de Volcanologie-Pétrographie (Orsay, France)UQàM/GEOTOP (Montreal, Canada)APQ3793-16 project funding
文摘Plutonic rocks from the Mineiro Belt, Brazil record a delayed onset of the transition from TTG to sanukitoid-type magmatism（high Ba-Sr）, starting during the Siderian magmatic lull when little juvenile magma was added to the continental crust. Rocks mostly belong to the calc-alkaline series, meta-to peraluminous and originally ＂Ⅰ-type＂,meaning that oxidized magmas were formed by partial melting of subducted material. The temporal distribution and apparent secular changes of the magmas are consistent with the onset of subduction-driven plate tectonics due to an increase of the subduction angle and opening of the mantle wedge. New isotopic analyses（Sm-Nd whole rock and Lu-Hf in zircon）corroborate the restricted juvenile nature of the Mineiro Belt and confirm the genetic link between the Lagoa Dourada Suite,a rare ca. 2350 Ma high-Al tonalite-trondhjemite magmatic event, and the sanukitoid-type ca. 2130 Ma Alto Maranhao Suite. U-Pb dating of zircon and titanite constrain the crystallisation history of plutonic bodies; coupled with major and trace element analyses of the host rocks, they distinguish evolutionary trends in the Mineiro Belt. Several plutons in the region have ages close to 2130 Ma but are distinguished by the lower concentration of compatible elements in the juvenile high Ba-Sr suite.
基金FAPERJ,CNPQ,CAPES and FINEP funding agenciesjoint projects with CPRM and Petrobras。
文摘The southern portion of the Sao Francisco Palaeocontinent in Brazil is denoted by Archean nuclei and Paleoproterozoic magmatic arcs that were amalgamated during Siderian to Orosirian orogenic processes(ca.2.4-2.1 Ga).New isotopic U-Pb in zircon and Sm-Nd whole rock combined with major and trace element composition analyses constrain the crystallization history of the Neoarchean Piedade block(at ca.2.6 Ga)and the Paleoproterozoic Mantiqueira Complex(ca.2.1-1.9 Ga).These therefore display quite different magmatic histories prior to their amalgamation at ca.2.05 Ga.Sm-Nd and Rb-Sr isotopes imply a mixed mantle-crustal origin for the samples in both units.A complete Palaeoproterozoic orogenic cycle,from subduction to collision and collapse,is recorded in the Piedade Block and the Mantiqueira Complex.Rhyacian to Orosirian subduction processes(ca.2.2-2.1 Ga)led to the generation of coeval(ca.2.16 Ga)TTG suites and sanukitoids,followed by late(2.10-2.02 Ga)high-K granitoids that mark the collisional stage.The collisional accretion of the Mantiqueira Complex against the Piedade Block at 2.08-2.04 Ga is also recorded by granulite facies metamorphism in the latter terrane,along the Ponte Nova suture zone.The collisional stage was closely followed by the emplacement of within-plate tholeiites at ca.2.04 Ga and by alkaline rocks(syenites and enriched basic rocks)at ca.1.98 Ga,marking the transition to an extensional tectonic regime.The discovery of two episodes of TTG and sanukitoid magmatism,one during the Neoarchean in the Piedade Complex and another during the Rhyacian in the Mantiqueira Complex,indicates that the onset of subduction-related melting of metasomatized mantle was not restricted to Neoarchean times,as generally believed,but persisted much later into the Paleoproterozoic.
文摘This paper describes a study into the development of more robust dust emission factors by means of dust and meteorological monitoring. Emission factors for nuisance dusts in the literature are scarce, with estimates of dust output given for many processes in mass per unit area per year. Temporal variations and the extent and conditions in which maximum concentrations occur can therefore be impossible to predict with any accuracy. This investigation aims to improve predic-tions by “back calculating” emission levels based on dust monitoring around known dust sources. Nuisance dust and meteorological monitoring has been undertaken at a sand and gravel quarry in the UK for a consecutive period of two years. Sticky pad directional dust monitors were used to collect dust at eight locations at and around the site with meteorological data collected at an elec-tronic weather station within the site. Air quality modelling software (ADMS) was used to test emission factors from the European Environment Agency (EEA) and the US Environmental Protec-tion Agency (EPA) for emissions from mineral workings. Predictions were compared with the dust monitoring data to assess accuracy, with results showing limited poor correspondence (r<sup>2</sup> < 0.3). Trends showed that emission predictions were poorest in winter;this is likely because most emis-sion calculations are not weather dependent and seasonal fluctuations will occur. Dust emission rate calculations were altered with respect to the dust monitoring data for one monitoring location on the mineral site boundary and the model was run again. Results were then tested at two different locations up to 200 m from the site boundary, with very positive correlations (r<sup>2</sup > 0.89) and similar maximum concentrations (<5% difference). This study has therefore shown that ac-curate site-specific emission rates can be produced in combination with site boundary sticky pad dust monitoring in order to accurately derive estimations elsewhere.
