New Zircon U‐Pb Age of Granodiorite in Chifeng at the Northern Margin of North China Craton and Constraints on Plate Tectonic Evolution

正Objective The North China Craton(NCC)is one of the oldest cratons in the world.The accretionary belt at its northern margin has been the focus of scholars both at home and abroad(Zhu Junbing and Ren Jishun,2017).In recent years,a series of Late Paleozoic–Mesozoic intrusions trending E–W have been discovered within the northern margin of the NCC,forming a magmatic belt.The study     

Geochemistry and Tectonic History of Seamount Remnants in the Xingshuwa Subduction Accretionary Complex of the Xar Moron Area,Eastern Margin of the Central Asian Orogenic Belt

This study focuses on the geology, geochemistry, zircon U-Pb geochronology and tectonic settings of the three types of seamount basalts from the Xingshuwa subduction accretionary complex in the Xar Moron area, eastern margin of the Central Asian Orogenic Belt(CAOB). The seamount remnants are composed of carbonate 'cap' sediments, large volumes of pillow and massive basalts, carbonate breccia slope facies and radiolarian cherts. Group 1 basalts are characterized by high contents of P2 O5 and TiO2 with alkaline affinity and LREE enrichment, indicating that they are derived from intraplate magma. Group 2 basalts display N-MORB LREE depletion patterns, indicating that they were formed at a mid-ocean ridge. Group 3 basalts have shown distinct Nb depletion and high Th/Yb ratios, indicating that they were generated in an island arc tectonic setting. The zircon U-Pb age of Group 1 basalt sample XWT18-131 is 576.4 ± 9.4 Ma, suggesting that the oceanic island seamount was the product of intraplate magmatism related to a mantle plume or 'hot spot' in the late Neoproterozoic. The zircon U-Pb age of Group 2 basalt sample XWT18-132 is 483 ± 22 Ma, indicating that the Paleo-Asian Ocean(PAO) was continuously expanding in the Early Ordovician. The zircon U-Pb age of Group 3 basalt sample XWT18-101 is 240.5 ± 8.2 Ma, suggesting that this area underwent the evolutionary path of ocean-continent transition, developing towards continentalization during the Middle Triassic. Thus, we believe that there was both mantle plume-related intraplate magmatism and intraoceanic subduction during the evolution of the PAO, the CAOB possibly being an evolutionary model of an intraoceanic subduction and mantle plume magmatism complex.     

Computation of the atmosphere-less light intensity curve during a total solar eclipse by using Lunar Reconnaissance Orbiter topography data and the DE430 astronomical ephemeris

Observations of the sky irradiation intensity in the visible wavelengths during a solar eclipse permit to model the Sun diameter,a key number to constrain the internal structure of our star.In this paper,we present an algorithm that takes advantage of the precise Moon topography from Lunar Reconnaissance Orbiter to compute,with a high resolution in time,the geometrical part(i.e.top-of-atmosphere,and for a given wavelength)of the sky irradiation at any given location on the Earth during these events.The algorithm is also able to model the Baily’s beads.We give as an application the theoretical computation of the light curve corresponding to the solar eclipse observed at Lakeland(Queensland,North Australia)on 2012 November 13.The application to real data,with the introduction of atmospheric and instrumental passbands,will be considered in a forthcoming paper.     

Does palynological diversity reflect floristic diversity? A case study from Northeast China

Fossil pollen data can provide important information of past vegetation diversity, on the basis of established relationship between modern palynological and floristic diversity. However, current studies on modern pollen assemblages in China have not examined this relationship yet. Herein, we report a case study from Northeast China, aiming to investigate the representation of modern palynological diversity to regional floristic diversity. A total of 87 sets of modern pollen and vegetation data f...     

Adaptive Statistical Spatial Downscaling of Precipitation Supported by High-Resolution Atmospheric Simulation Data for Mountainous Areas of Nepal

In complex terrain regions, it is very challenging to obtain high accuracy and resolution precipitation data that are required in land hydrological studies. In this study, an adaptive precipitation downscaling method is proposed based on the statistical downscaling model MicroMet. A key input parameter in the MicroMet is the precipitation adjustment factor(PAF) that shows the elevation dependence of precipitation. Its value is estimated conventionally based on station observations and suffers sp...     

Vertical variations of dissolved carbohydrates in the North Yap Trench

The concentrations of dissolved monosaccharides(MCHO),polysaccharides(PCHO),and total carbohydrates(TCHO)in the seawater samples collected from the north of the Yap Trench in the western Pacific Ocean were measured by 2,4,6-tripyridine-s-triazine(TPTZ)spectrophotometry method.The results show that the concentrations of MCHO,PCHO,and TCHO ranged from 4.6 to 22.1μmol C/L,3.5 to 27.3μmol C/L,and 13.8 to 36.3μmol C/L,respectively.In different sampling stations,the concentrations of MCHO,PCHO,and TCHO with water depth showed complex variation patterns.In the study area,the maximum concentrations of MCHO,PCHO,and TCHO occurred in the euphotic layer and the minimum concentrations occurred in mesopelagic seawater layer.Generally,the concentrations of MCHO,PCHO,and TCHO decreased with water depth from the euphotic layer to the hadal zone.The average value of PCHO/TCHO was higher than the average value of MCHO/TCHO,indicating that PCHO was the main component of TCHO in north of the Yap Trench.