Petrogenesis of the Payangazu Complex in Southern Mandalay, Central Myanmar and Its Tectonic Implications

The Payangazu complex in the central Myanmar is composed mainly of quartz diorite,granodiorite,and some synplutonic mafic dikes.The quartz diorite and granodiorite have zircon U-Pb ages of 130.5±4.0(MSWD=3.5)and 118.4±2.5 Ma(MSWD=2.4),respectively.Rock samples of the quartz diorite and granodiorite are metaluminous,enriched in large-ion lithophile elements like LREE,Rb,Th,and U,and depleted in high field-strength elements such as HREE,Nb,Ta,P,and Ti,indicative of arc-type magmatic affinities.Whole rock samples of the quartz diorite haveε_(Hf)(t)value of+0.6,initial ^(87)Sr/^(86)Sr ratios of 0.708 6 to 0.710 0,andε_(Nd)(t)values of-4.8 to-4.9;whereas rocks of the granodiorite are relatively isotopically enriched,withε_(Hf)(t)values of-5.1 to-7.2,initial ^(87)Sr/^(86)Sr ratios of 0.711 7 to 0.711 8,andε_(Nd)(t)values of-8.7 to-8.8.The isotopic data together with the high Mg~#(both the quartz diorite and granodiorite have Mg~#values of>40)suggest a strong involvement of mantle materials in the genesis of the parent magmas.The possible petrogenetic process may be that the ascending of melts from partial melting of metasomatized mantle wedge triggered by dehydration of subducted slab resulted in partial melting of the lower crust and mixed with the latter.These Early Cretaceous intrusions from the complex are older than those found in the eastern Wuntho-Popa arc in western Myanmar,eastern Himalaya,and western Yunnan which are interpreted to be related to the Neo-Tethyan subduction,and haveε_(Nd)(t),ε_(Hf)(t)values lower than the latter.On the contrary,the ages and geochemical characteristics of the Payangazu complex are consistent with some of the intrusions in the northern magmatic belt in Tibet,eastern Himalaya,and western Yunnan which are believed to be associated with the subduction of the Bangong-Nujiang Ocean crust.Thus,we propose that the Early Cretaceous intrusions in the central Myanmar are most likely related to the southward subduction of an ocean slab that was possibly an extension of the Bangong-Nujiang Ocean.

Improved energy storage performance of nanocomposites with Bi_(4.2)K_(0.8)Fe_(2)O_(9+δ) nanobelts

Modern electronics and electric power grids require high performance polymer-based dielectric nanocomposites.To realize large-scale applications,the energy density of nanocomposites needs to be further increased.Here,we demonstrate a remarkable improvement in energy density of poly(vinylidene fluoride)(PVDF)matrix upon the incorporation of high-k Bi_(4.2)K_(0.8)Fe_(2)O_(9+δ)(BKFO)nanobelts.High aspect ratio BKFO nanobelts can enhance the Young's moduli of the nanocomposites and increase the path tortuosity of electrical trees,which are favorable for increasing the breakdown strength of the system.Thus,the dielectric constant and breakdown strength increase simultaneously at a low volume fraction(0.35 vol%)of BKFO nanobelts,and an ultrahigh recoverable energy density of 25.4 J/cm^(3) is achieved.These results provide a strategy to develop high performance flexible high-energy-density devices.