‘Single shot'laser-ablation split-stream(SS-LASS)technique analyzing unpolished zircon grains makes their thin rims tenable for determination,which thus offers great potential in deciphering the timing of multipl...‘Single shot'laser-ablation split-stream(SS-LASS)technique analyzing unpolished zircon grains makes their thin rims tenable for determination,which thus offers great potential in deciphering the timing of multiple and short-lived episodes of anatexis and metamorphism in deeplysubducted continental crusts.Dominated granitic gneisses in the deeply subducted continental crust undergoing considerable fluid-melt activities persist multistage growth of zircon.Therefore,a comparative study of SS-LASS and laser ablation inductively coupled plasma mass spectrometer(LA-ICP-MS)zircon dating was conducted on the granitic gneisses from the Sulu belt in this study.Zircons mostly show a core-mantle-rim structure with CL-bright rims thinner than 5μm.For LA-ICP-MS dating,relict magmatic zircon cores yield protolith ages of ca.756-747 Ma;whereas the dark mantles record synexhumation anatexis at ca.214 Ma.By contrast,according to the U-Pb dates,trace element features,zircon crystallization temperatures and geological context,SS-LASS zircon petrochronology deciphers three episodes of anatectic events,as follows:(i)the first episode of anatexis at ca.218-217 Ma dominated by phengite-breakdown melting,likely facilitating the exhumation of the UHP slice from mantle depth;(ii)the second episode of anatexis at ca.193–191 Ma indicating part of northern Dabie-Sulu belt was still“hot”because of buried in the thickened orogenic crust at that time;(iii)the third episode of anatexis(ca.162–161 Ma)consistent with the intrusion ages(ca.161–141 Ma)of the Jurassic to Cretaceous granitoids in this orogen,suggesting the initial collapse of the orogenic root of the Sulu belt occurred at Late Jurassic due to the Izanagi plate initially subducting beneath the margin of Eastern Asia.This study sheds new light upon the utilization of SS-LASS petrochronology deciphering multiple anatectic events in the deeply-subducted continental crust and supports us in better understanding the tectonic evolution of Dabie-Sulu Orogen.展开更多
The exhaust flow velocity of the engine is an important parameter affecting the comprehensive performance of the muffler.The exhaust flow velocity increases by the regenerated noise generated in the muffler,which make...The exhaust flow velocity of the engine is an important parameter affecting the comprehensive performance of the muffler.The exhaust flow velocity increases by the regenerated noise generated in the muffler,which makes the sound absorption effect of the muffler worse.In order to solve this problem,a sound absorption method was proposed to reduce the flow rate of exhaust air by diverting and hedging the exhaust air,so as to improve the sound absorption.First of all,the airflow into the muffler was shunted by a conical shunt unit.Subsequently,the airflow entered the cavity of the perforated tube through the hole on the perforated tube.When the airflow was offset in the cavity of the perforated tube,it could reduce the flow rate of the exhaust airflow and improve the sound absorption effect.It could be concluded that the influence factors and the characteristics of the transmission loss were obtained by dividing the anechoic sub units of the whole structure,calculating the transfer matrix,and analyzing the function relationship between the independent variable and the dependent variable of the transmission loss,and the theoretical model was verified by experiments.The results of the experiment showed that the proposed sound absorption method can keep the transmission loss at a stable state under the condition of high⁃speed exhaust flow.For example,when the inlet air velocity increases from 15 m/s to 45 m/s,the maximum reduction of transmission loss is 6.5 dB in the range of 0-3000 Hz,which proves that the structure has a good effect of sound absorption.展开更多
基金supported by National Natural Science Foundation of China(Nos.42072228,42102060,41902036,41572182)China Postdoctoral Science Foundation(No.2021M692983)+4 种基金the Chinese Ministry of Education(No.BP0719022)the Most Special Fund(Nos.MSFGPMR02-3,MSFGPMR30)Open funds from the State Key Laboratory of Geological Processes and Mineral ResourcesChina University of Geosciences(Nos.GPMR201703,GPMR201704 and GPMR201903)the Fundamental Research Funds for National University(No.CUG-G1323511572)。
文摘‘Single shot'laser-ablation split-stream(SS-LASS)technique analyzing unpolished zircon grains makes their thin rims tenable for determination,which thus offers great potential in deciphering the timing of multiple and short-lived episodes of anatexis and metamorphism in deeplysubducted continental crusts.Dominated granitic gneisses in the deeply subducted continental crust undergoing considerable fluid-melt activities persist multistage growth of zircon.Therefore,a comparative study of SS-LASS and laser ablation inductively coupled plasma mass spectrometer(LA-ICP-MS)zircon dating was conducted on the granitic gneisses from the Sulu belt in this study.Zircons mostly show a core-mantle-rim structure with CL-bright rims thinner than 5μm.For LA-ICP-MS dating,relict magmatic zircon cores yield protolith ages of ca.756-747 Ma;whereas the dark mantles record synexhumation anatexis at ca.214 Ma.By contrast,according to the U-Pb dates,trace element features,zircon crystallization temperatures and geological context,SS-LASS zircon petrochronology deciphers three episodes of anatectic events,as follows:(i)the first episode of anatexis at ca.218-217 Ma dominated by phengite-breakdown melting,likely facilitating the exhumation of the UHP slice from mantle depth;(ii)the second episode of anatexis at ca.193–191 Ma indicating part of northern Dabie-Sulu belt was still“hot”because of buried in the thickened orogenic crust at that time;(iii)the third episode of anatexis(ca.162–161 Ma)consistent with the intrusion ages(ca.161–141 Ma)of the Jurassic to Cretaceous granitoids in this orogen,suggesting the initial collapse of the orogenic root of the Sulu belt occurred at Late Jurassic due to the Izanagi plate initially subducting beneath the margin of Eastern Asia.This study sheds new light upon the utilization of SS-LASS petrochronology deciphering multiple anatectic events in the deeply-subducted continental crust and supports us in better understanding the tectonic evolution of Dabie-Sulu Orogen.
基金Sponsored by the National Nature Science Foundation of China(Grant Nos.51705545 and 15A460041).
文摘The exhaust flow velocity of the engine is an important parameter affecting the comprehensive performance of the muffler.The exhaust flow velocity increases by the regenerated noise generated in the muffler,which makes the sound absorption effect of the muffler worse.In order to solve this problem,a sound absorption method was proposed to reduce the flow rate of exhaust air by diverting and hedging the exhaust air,so as to improve the sound absorption.First of all,the airflow into the muffler was shunted by a conical shunt unit.Subsequently,the airflow entered the cavity of the perforated tube through the hole on the perforated tube.When the airflow was offset in the cavity of the perforated tube,it could reduce the flow rate of the exhaust airflow and improve the sound absorption effect.It could be concluded that the influence factors and the characteristics of the transmission loss were obtained by dividing the anechoic sub units of the whole structure,calculating the transfer matrix,and analyzing the function relationship between the independent variable and the dependent variable of the transmission loss,and the theoretical model was verified by experiments.The results of the experiment showed that the proposed sound absorption method can keep the transmission loss at a stable state under the condition of high⁃speed exhaust flow.For example,when the inlet air velocity increases from 15 m/s to 45 m/s,the maximum reduction of transmission loss is 6.5 dB in the range of 0-3000 Hz,which proves that the structure has a good effect of sound absorption.
