【摘 要】
:
Monazite is an important accessory mineral in the pelitic granulites (Weihai area,Sulu orogen),and is also a powerful monitor for understanding the metamorphic evolution of the granulites.The pelitic granulites incongruously occur as lenses in granitic gn
【机 构】
:
School of Earth Sciences,China University of Geosciences,Wuhan 430074,China
论文部分内容阅读
Monazite is an important accessory mineral in the pelitic granulites (Weihai area,Sulu orogen),and is also a powerful monitor for understanding the metamorphic evolution of the granulites.The pelitic granulites incongruously occur as lenses in granitic gneisses.The lithologies of the lenses gradually change from core to margin:The undeformed coarse-grained granulite,the foliated fine-grained granulite,the garnet-biotite-gneiss,and the migmatized granulite.The lens cores mostly preserve a peak granulite-facies metamorphic mineral assemblage of garnet + plagioclase (antiperthite) + quartz + sillimanite + biotite with accessory minerals of rutile,zircon,and monazite.The lens margins display a fluid-induced retrogression.In order to decipher the metamorphic processes of the pelitic granulites,a combined study of BSE imaging,U-Pb dating,and trace element composition for the monazites from the metapelitic lens were conducted.Monazites from the undeformed coarse-grained granulite only record a Paleoproterozoic age (1832±7 Ma,n=40).Monazites from the other lithologies yield the inherited Paleoproterozoic age and Triassic overgrowth age.For example,monazites from the migmatite yield intercept ages of 1818±10 and 211±22 Ma (n=56) with Triassic concordant age of 223.8±2.9 Ma.The Paleoproterozoic monazites are characterized by remarkable depletion in HREE and Y with obviously negative Eu anomalies,indicating their formation equilibrated with garnet and feldspar under granulite-facies conditions.During Triassic fluid modification,the monazite bright rims assimilated Th and Si but released U,HREE,Y,and P.This process resulted in that the Triassic overgrowth monazites have higher HREE and Y contents,and lower Th and U contents with relatively low Th/U ratios.Thus,the monazites in the pelitic granulites recorded a Paleoproterozoic metamorphic event and Triassic fluid modification.The Weihai pelitic granulites might have a tectonic affinity with the North China Craton.Therefore,the Paleoproterozoic pelitic granulites were mechanically drawn into the orogen during the Triassic continental collision,and subsequently were remoulded by the fluids during its exhumation.
其他文献
Carbonate reservoirs have complex pore structures,which not only significantly affect the elastic properties and seismic responses of the reservoirs but also affect the accuracy of the prediction of the physical parameters.The existing rock-physics invers
In order to improve the agility and applicability of trajectory planning algorithm for autonomous vehicles,this paper proposes a novel actor-critic based learning method for decision-making and planning in multi-vehicle complex traffic.It is the coupling
This paper solves the robust control problem of robotic manipulator systems with uncertain dynamics by friction compensation approach.A weighting factor is introduced to distinguish the role of friction in control process by comparing the directions of sl
The experimental measurement of supercritical pressure carbon dioxide (sCO2) heat transfer in vertical downward flow was performed in a circular tube with inner diameter of 10 mm.Then,a three-dimensional numerical investigation of sCO2 heat transfer in up
Since the beginning of the 21st century,the geoscience research has been entering a significant transitional period with the establishment of a new knowledge system as the core and with the drive of big data as the means.It is a revolutionary leap in the
The implementation of large-scale vegetation restoration over the Chinese Loess Plateau has achieved clear improvements in vegetation fraction,as evidenced by large areas of slopes and plains being restored to grassland or forest.However,such large-scale
The China Seismo-Electromagnetic Satellite (CSES),China\'s first satellite to measure geophysical fields with scientific goals in both space and solid earth physics,was launched successfully in February 2018.It carries high-precision magnetometers to me
Latest advances have witnessed the laser induction process on polyimide (PI) films for the formation of porous graphene.Herein,a fully converted graphene film was prepared by Nd:YAG laser scribing a gelatin coated PI film.It was found that the gelatin pla
Geophysical and geochemical evidence revealed that certain amounts of water are stored in the Earth\'s interior,and its distribution exhibits temporal and spatial differences.Recent studies indicate that the H2O-in-zircon has a potential to reveal magma
The design of the high-temperature microwave absorbing materials (MAMs) with temperature-insensitive and considerable microwave absorption (MA) capacity is a tremendous challenge.TiB2-Al2O3/MgAl2O4 MAMs are prepared by the spark plasma sintering (SPS).Fur