The analysis of available Nd isotope data from the Tanzania Craton places important constraints on the crest-mantle separation ages,and events marking juvenile crustal addition and crustal recycling.Nd model ages date...The analysis of available Nd isotope data from the Tanzania Craton places important constraints on the crest-mantle separation ages,and events marking juvenile crustal addition and crustal recycling.Nd model ages date the oldest crust extraction to 3.16 Ga in the Tanzania Craton,although a rock record of such antiquity is yet to be found there.The most significant period of juvenile crustal addition as well as crustal recycling is 2.7-2.6 Ga.The Nd isotopes of marie samples show that chemical heterogeneity existed in the mantle beneath the Tanzania Craton,with some samples originating from significantly depleted mantle, and most samples originating from the mixture of primitive mantle and depleted mantle.The Nd isotope section reveals significant differences in Nd isotopes between the north eraton and central craton;compared to the north craton,the central craton yields a Nd model age that is approximately 100 Ma older, and its εNd(t)values are more negative,indicating that the two parts of the craton have different mantle source regions.Different types of granitoids are distributed in the Tanzania Craton,such as high-K and low-Al granite,ealc-alkaline granite,peraluminous granite and transitional types of tonalite-trondhjemite- granodiorites (TTGs).Most of the granitoids formed later than the marie rocks in syn-collision and postcollision events.展开更多
The Paleoproterozoic tectonic evolution of the Bangweulu Block has long been controversial.Paleoproterozoic granites consisting of the basement complex of the Bangweulu Block are widely exposed in northeastern Zambia,...The Paleoproterozoic tectonic evolution of the Bangweulu Block has long been controversial.Paleoproterozoic granites consisting of the basement complex of the Bangweulu Block are widely exposed in northeastern Zambia,and they are the critical media for studying the tectonic evolution of the Bangweulu Block.This study systematically investigated the petrography,zircon U-Pb chronology,and petrogeochemistry of the granitoid extensively exposed in the Lunte area,northeastern Zambia.The results show that the granitoid in the area formed during 2051±13-2009±20 Ma as a result of Paleoproterozoic magmatic events.Geochemical data show that the granites in the area mainly include syenogranites and monzogranites of high-K calc-alkaline series and are characterized by high SiO2 content(72.68%‒73.78%)and K_(2)O/Na_(2)O ratio(1.82‒2.29).The presence of garnets,the high aluminum saturation index(A/CNK is 1.13‒1.21),and the 1.27%‒1.95%of corundum molecules jointly indicate that granites in the Lunte area are S-type granites.Rare earth elements in all samples show a rightward inclination and noticeably negative Eu-anomalies(δEu=0.16‒0.40)and are relatively rich in light rare earth elements.Furthermore,the granites are rich in large ion lithophile elements such as Rb,Th,U,and K and are depleted in Ba,Sr,and high field strength elements such as Ta and Nb.In addition,they bear low contents of Cr(6.31×10^(−6)‒10.8×10^(−6)),Ni(2.87×10^(−6)‒4.76×10^(−6)),and Co(2.62×10^(−6)‒3.96×10^(−6)).These data lead to the conclusion that the source rocks are meta-sedimentary rocks.Combining the above results and the study of regional tectonic evolution,the authors suggest that granitoid in the Lunte area were formed in a tectonic environment corresponding to the collision between the Tanzania Craton and the Bangweulu Block.The magmatic activities in this period may be related to the assembly of the Columbia supercontinent.展开更多
The 1∶1000000 geochemical mapping of Zambia provides catchment sediment geochemical data for 58elements including Au from 746 sediment samples at 736 sampling sites,corresponding to a sampling density of about one si...The 1∶1000000 geochemical mapping of Zambia provides catchment sediment geochemical data for 58elements including Au from 746 sediment samples at 736 sampling sites,corresponding to a sampling density of about one site per 1000 km2.Under strict quality control using field duplicates,certified reference materials,and analytical replicate samples,the Au was determined by Inductively Coupled Plasma Mass Spectrometry(ICP-MS).The detection limit of Au was 0.20×10^(-9).The 95%range(2.5%–97.5%)of Au concentrations was from 0.24×10^(-9) to 1.36×10^(-9),and the median value was 0.40×10^(-9).The most noticeable Au distribution patterns shown on the map are mainly located between Lusaka and Ndola(Lufilian Arc Belt).In addition,several high Au value areas occurred in Mansa,Muyombe,Chipata,and Livingstone.The spatial distribution patterns of Au in tectonic units,drainage basins,and geomorphological landscapes could be related to the Lufilian Arc Belt and Bangweulu Block.The Au concentrations show metallogenic belts between Muyombe and Mbala areas,between Mansa and Ndola areas,and between Lusaka and Kasempa areas.展开更多
Tanzania is located in eastern Africa with a predominantly agricultural ecomomy,the potential for developing and utilizing cultivated land are promising,but scientific guidance is required.B,Zn and Se are essential mi...Tanzania is located in eastern Africa with a predominantly agricultural ecomomy,the potential for developing and utilizing cultivated land are promising,but scientific guidance is required.B,Zn and Se are essential micronutrients for plants and human body with crucial biological functions,in particular,Se is significant for human health and considered as“the king of anti-cancer”.As these elements required by human or plants are mainly absorbed from soil directly or indirectly,therefore,it is important to understand the contents and distributions of them in the soil of cultivated land for guiding agricultural production.In this work,low-density geochemical survey at the scale of 1∶1000000 was carried out in Tanzania,and the results show that the concentrations of B,Zn and Se in stream sediments are low and their distributions are heterogeneous.According to the distributions of geological units,the existing cultivated land resources can be divided into five regions in Tanzania.Compared with the national background values,the concentrations of B,Zn and Se are insufficient overall but enriched locally in these regions.In general,element concentrations in stream sediments and soil have a positive correlation because of their similar sources,which is essential in agriculture application.Based on the information provided by low-density geochemical data and maps,the Se-sufficient and Se-rich regions were delineated in Tanzania,where can be used to develop Se-rich industries.Finally,this paper believes that geochemical survey is a powerful tool for cultivated land evaluation,agriculture management and land development.展开更多
文摘The analysis of available Nd isotope data from the Tanzania Craton places important constraints on the crest-mantle separation ages,and events marking juvenile crustal addition and crustal recycling.Nd model ages date the oldest crust extraction to 3.16 Ga in the Tanzania Craton,although a rock record of such antiquity is yet to be found there.The most significant period of juvenile crustal addition as well as crustal recycling is 2.7-2.6 Ga.The Nd isotopes of marie samples show that chemical heterogeneity existed in the mantle beneath the Tanzania Craton,with some samples originating from significantly depleted mantle, and most samples originating from the mixture of primitive mantle and depleted mantle.The Nd isotope section reveals significant differences in Nd isotopes between the north eraton and central craton;compared to the north craton,the central craton yields a Nd model age that is approximately 100 Ma older, and its εNd(t)values are more negative,indicating that the two parts of the craton have different mantle source regions.Different types of granitoids are distributed in the Tanzania Craton,such as high-K and low-Al granite,ealc-alkaline granite,peraluminous granite and transitional types of tonalite-trondhjemite- granodiorites (TTGs).Most of the granitoids formed later than the marie rocks in syn-collision and postcollision events.
基金This study was jointly funded by projects of the Ministry of Commerce([2015]352 and[2012]558)the projects of the China Geological Survey(DD20201150 and 1212011220910)。
文摘The Paleoproterozoic tectonic evolution of the Bangweulu Block has long been controversial.Paleoproterozoic granites consisting of the basement complex of the Bangweulu Block are widely exposed in northeastern Zambia,and they are the critical media for studying the tectonic evolution of the Bangweulu Block.This study systematically investigated the petrography,zircon U-Pb chronology,and petrogeochemistry of the granitoid extensively exposed in the Lunte area,northeastern Zambia.The results show that the granitoid in the area formed during 2051±13-2009±20 Ma as a result of Paleoproterozoic magmatic events.Geochemical data show that the granites in the area mainly include syenogranites and monzogranites of high-K calc-alkaline series and are characterized by high SiO2 content(72.68%‒73.78%)and K_(2)O/Na_(2)O ratio(1.82‒2.29).The presence of garnets,the high aluminum saturation index(A/CNK is 1.13‒1.21),and the 1.27%‒1.95%of corundum molecules jointly indicate that granites in the Lunte area are S-type granites.Rare earth elements in all samples show a rightward inclination and noticeably negative Eu-anomalies(δEu=0.16‒0.40)and are relatively rich in light rare earth elements.Furthermore,the granites are rich in large ion lithophile elements such as Rb,Th,U,and K and are depleted in Ba,Sr,and high field strength elements such as Ta and Nb.In addition,they bear low contents of Cr(6.31×10^(−6)‒10.8×10^(−6)),Ni(2.87×10^(−6)‒4.76×10^(−6)),and Co(2.62×10^(−6)‒3.96×10^(−6)).These data lead to the conclusion that the source rocks are meta-sedimentary rocks.Combining the above results and the study of regional tectonic evolution,the authors suggest that granitoid in the Lunte area were formed in a tectonic environment corresponding to the collision between the Tanzania Craton and the Bangweulu Block.The magmatic activities in this period may be related to the assembly of the Columbia supercontinent.
基金financially supported by the Sino-Zambian Cooperation in Geological and Geochemical Mapping(2012–2015)the China-Aid Airborne Geophysical Survey and Geochemical and Geological Mapping Technical Cooperation Project(2015–2019)the geological investigation project of the China Geological Survey(DD20201150,DD20201148,DD20190439)。
文摘The 1∶1000000 geochemical mapping of Zambia provides catchment sediment geochemical data for 58elements including Au from 746 sediment samples at 736 sampling sites,corresponding to a sampling density of about one site per 1000 km2.Under strict quality control using field duplicates,certified reference materials,and analytical replicate samples,the Au was determined by Inductively Coupled Plasma Mass Spectrometry(ICP-MS).The detection limit of Au was 0.20×10^(-9).The 95%range(2.5%–97.5%)of Au concentrations was from 0.24×10^(-9) to 1.36×10^(-9),and the median value was 0.40×10^(-9).The most noticeable Au distribution patterns shown on the map are mainly located between Lusaka and Ndola(Lufilian Arc Belt).In addition,several high Au value areas occurred in Mansa,Muyombe,Chipata,and Livingstone.The spatial distribution patterns of Au in tectonic units,drainage basins,and geomorphological landscapes could be related to the Lufilian Arc Belt and Bangweulu Block.The Au concentrations show metallogenic belts between Muyombe and Mbala areas,between Mansa and Ndola areas,and between Lusaka and Kasempa areas.
基金the cooperation projects between China Geological Survey and geological survey institutions of Africa(DD20190439,DD20160108,DD20221801)。
文摘Tanzania is located in eastern Africa with a predominantly agricultural ecomomy,the potential for developing and utilizing cultivated land are promising,but scientific guidance is required.B,Zn and Se are essential micronutrients for plants and human body with crucial biological functions,in particular,Se is significant for human health and considered as“the king of anti-cancer”.As these elements required by human or plants are mainly absorbed from soil directly or indirectly,therefore,it is important to understand the contents and distributions of them in the soil of cultivated land for guiding agricultural production.In this work,low-density geochemical survey at the scale of 1∶1000000 was carried out in Tanzania,and the results show that the concentrations of B,Zn and Se in stream sediments are low and their distributions are heterogeneous.According to the distributions of geological units,the existing cultivated land resources can be divided into five regions in Tanzania.Compared with the national background values,the concentrations of B,Zn and Se are insufficient overall but enriched locally in these regions.In general,element concentrations in stream sediments and soil have a positive correlation because of their similar sources,which is essential in agriculture application.Based on the information provided by low-density geochemical data and maps,the Se-sufficient and Se-rich regions were delineated in Tanzania,where can be used to develop Se-rich industries.Finally,this paper believes that geochemical survey is a powerful tool for cultivated land evaluation,agriculture management and land development.
