The study area is located around Guider and belongs to the Northern Cameroon Pan-African fold belt.It is essentially made of three generations of granitoids.The first generation G1 comprises diorites,tonalites and gra...The study area is located around Guider and belongs to the Northern Cameroon Pan-African fold belt.It is essentially made of three generations of granitoids.The first generation G1 comprises diorites,tonalites and granodiorites.The second one G2 is constituted by biotite granites and biotite-muscovite granites deformed in the solid-state.The third generation G3 is constituted by biotite-syenites,monzosyenites,and leucogranites. All the granitoids are cross cut by aplite veins展开更多
We present the first large dataset of dissolved silicon isotopes signatures(δ<sup>30</sup>Si)in different tropical rivers,including the Amazon and the Congo,the two largest silicon suppliers to the world ...We present the first large dataset of dissolved silicon isotopes signatures(δ<sup>30</sup>Si)in different tropical rivers,including the Amazon and the Congo,the two largest silicon suppliers to the world ocean.A two-year long monthly series was obtained in the Congo River upstream of the Kinshasa/Brazzaville urban zone.Spatial and temporal variations in the Amazon River and its main tributaries were studied for one year.Both the Congo and Amazon rivers convey similar meanδ<sup>30</sup>Si signatures to the ocean （close to +0.8‰）,in the range of the few previously published data for those rivers.The Congo River exhibits limited seasonal variations,with the exception of some largeδ<sup>30</sup>Si variations that展开更多
The second(O2)observational campaign of gravitational waves(GWs)organized by the LIGO/Virgo Collaborations has led to several breakthroughs such as the detection of GW signals from merger systems involving black holes...The second(O2)observational campaign of gravitational waves(GWs)organized by the LIGO/Virgo Collaborations has led to several breakthroughs such as the detection of GW signals from merger systems involving black holes or neutrons stars.During O2,14 GW alerts were sent to the astronomical community with sky regions mostly covering over hundreds of square degrees.Among them,six were finally confirmed as real astrophysical events.Since 2013,a new set of ground-based robotic telescopes called Ground-based Wide Angle Camera system(GWAC)project and its pathfinder mini-GWAC has been developed to contribute to the various challenges of multi-messenger and time domain astronomy.The GWAC system is built up in the framework of the ground-segment system of the SVOM mission that will be devoted to the study of the multi-wavelength transient sky in the next decade.During O2,only the mini-GWAC telescope network was fully operational.Due to the wide field of view and fast automatic follow-up capabilities of the mini-GWAC telescopes,they were adept to efficiently cover the sky localization areas of GW event candidates.In this paper,we present the mini-GWAC pipeline we have set up to respond to GW alerts and we report our optical follow-up observations of eight GW alerts detected during the O2 run.Our observations provided the largest coverage of the GW localization areas with a short latency made by any optical facility.We found tens of optical transient candidates in our images,but none of those could be securely associated with any confirmed black hole-black hole merger event.Based on this first experience and the near future technical improvements of our network system,we will be more competitive in detecting the optical counterparts from some GW events that will be identified during the upcoming O3 run,especially those emerging from binary neutron star mergers.展开更多
Over 20 sets of dolerite dykes crosscutting Paleoproterozoic basement in West Africa were distinguished via the interpretation of regional and high resolution magnetic airborne data of West African Craton
Time series of sea level heights have been collected at different stations along the Cameroon coast. The dataset covers a period ranging from 2007 to 2012. Tide data measured by float type recorders have been digitali...Time series of sea level heights have been collected at different stations along the Cameroon coast. The dataset covers a period ranging from 2007 to 2012. Tide data measured by float type recorders have been digitalized and quality-controlled with tools developed at Laboratoire d’Etudes Géophysique et Océanographie Spatiale (LEGOS). Short gaps in the data have been interpolated while large gaps were not. Tide constituents were retrieved through harmonic analysis using 123 waves having a period ranging from long ones to eighth-diurnal ones. The reconstructed signal is used to assess the quality of both the data and the analysis and the erroneous records were examined and corrected. The effect of the hourly averaging of the raw data on the quality of the analysis is also investigated. The tide constituents having the largest amplitudes are, as expected, the semi-diurnal, diurnal, fourth-diurnal and long term constituents. The major components of semi-diurnal waves are the M2 and S2 tides. The M2 tide height ranges between 0.5 and 0.85 m. The maximum height is found at Cameroon estuary and the minimum at the Kribi station located in the South coast. The S2 constituent varies similarly as the M2 constituent. Its amplitude ranges between 0.18 and 0.52 m. The lowest S2 amplitude occurs also at Kribi station. In the Dibamba estuary the spectrum shows a larger number of significant semi-diurnal and fourth-diurnal waves than other zones. Concerning diurnal waves, the dominant one is the K1 tide and its amplitude is homogeneous along the coast. The influence of the long-term components is the strongest in the Cameroon estuary due to important fluctuations of the rivers run-off.展开更多
文摘The study area is located around Guider and belongs to the Northern Cameroon Pan-African fold belt.It is essentially made of three generations of granitoids.The first generation G1 comprises diorites,tonalites and granodiorites.The second one G2 is constituted by biotite granites and biotite-muscovite granites deformed in the solid-state.The third generation G3 is constituted by biotite-syenites,monzosyenites,and leucogranites. All the granitoids are cross cut by aplite veins
文摘We present the first large dataset of dissolved silicon isotopes signatures(δ<sup>30</sup>Si)in different tropical rivers,including the Amazon and the Congo,the two largest silicon suppliers to the world ocean.A two-year long monthly series was obtained in the Congo River upstream of the Kinshasa/Brazzaville urban zone.Spatial and temporal variations in the Amazon River and its main tributaries were studied for one year.Both the Congo and Amazon rivers convey similar meanδ<sup>30</sup>Si signatures to the ocean （close to +0.8‰）,in the range of the few previously published data for those rivers.The Congo River exhibits limited seasonal variations,with the exception of some largeδ<sup>30</sup>Si variations that
基金supported by the National Natural Science Foundation of China(Grant Nos.11533003,11673006,U1331202,U1931133 and U1938201)the Guangxi Science Foundation(2016GXNSFFA380006,AD17129006and 2018GXNSFGA281007)+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB23040000)the Strategic Pioneer Program on Space Science,Chinese Academy of Sciences(XDA15052600)financial support from the Chinese Academy of Sciences PIFI post-doctoral fellowship program(program C)financial support of the Univ Earth S Labex program at Sorbonne Paris Cité(ANR-10-LABX-0023 and ANR-11-IDEX-0005-02)
文摘The second(O2)observational campaign of gravitational waves(GWs)organized by the LIGO/Virgo Collaborations has led to several breakthroughs such as the detection of GW signals from merger systems involving black holes or neutrons stars.During O2,14 GW alerts were sent to the astronomical community with sky regions mostly covering over hundreds of square degrees.Among them,six were finally confirmed as real astrophysical events.Since 2013,a new set of ground-based robotic telescopes called Ground-based Wide Angle Camera system(GWAC)project and its pathfinder mini-GWAC has been developed to contribute to the various challenges of multi-messenger and time domain astronomy.The GWAC system is built up in the framework of the ground-segment system of the SVOM mission that will be devoted to the study of the multi-wavelength transient sky in the next decade.During O2,only the mini-GWAC telescope network was fully operational.Due to the wide field of view and fast automatic follow-up capabilities of the mini-GWAC telescopes,they were adept to efficiently cover the sky localization areas of GW event candidates.In this paper,we present the mini-GWAC pipeline we have set up to respond to GW alerts and we report our optical follow-up observations of eight GW alerts detected during the O2 run.Our observations provided the largest coverage of the GW localization areas with a short latency made by any optical facility.We found tens of optical transient candidates in our images,but none of those could be securely associated with any confirmed black hole-black hole merger event.Based on this first experience and the near future technical improvements of our network system,we will be more competitive in detecting the optical counterparts from some GW events that will be identified during the upcoming O3 run,especially those emerging from binary neutron star mergers.
文摘Over 20 sets of dolerite dykes crosscutting Paleoproterozoic basement in West Africa were distinguished via the interpretation of regional and high resolution magnetic airborne data of West African Craton
文摘Time series of sea level heights have been collected at different stations along the Cameroon coast. The dataset covers a period ranging from 2007 to 2012. Tide data measured by float type recorders have been digitalized and quality-controlled with tools developed at Laboratoire d’Etudes Géophysique et Océanographie Spatiale (LEGOS). Short gaps in the data have been interpolated while large gaps were not. Tide constituents were retrieved through harmonic analysis using 123 waves having a period ranging from long ones to eighth-diurnal ones. The reconstructed signal is used to assess the quality of both the data and the analysis and the erroneous records were examined and corrected. The effect of the hourly averaging of the raw data on the quality of the analysis is also investigated. The tide constituents having the largest amplitudes are, as expected, the semi-diurnal, diurnal, fourth-diurnal and long term constituents. The major components of semi-diurnal waves are the M2 and S2 tides. The M2 tide height ranges between 0.5 and 0.85 m. The maximum height is found at Cameroon estuary and the minimum at the Kribi station located in the South coast. The S2 constituent varies similarly as the M2 constituent. Its amplitude ranges between 0.18 and 0.52 m. The lowest S2 amplitude occurs also at Kribi station. In the Dibamba estuary the spectrum shows a larger number of significant semi-diurnal and fourth-diurnal waves than other zones. Concerning diurnal waves, the dominant one is the K1 tide and its amplitude is homogeneous along the coast. The influence of the long-term components is the strongest in the Cameroon estuary due to important fluctuations of the rivers run-off.
