Newly discovered youngest UHT metamorphism on Earth,Western Sulawesi,Indonesia  

作　　者：Juiyen Hsia Jian Zhang Guochun Zhao Jiahui Qian Jin Liu Min Sun Changqing Yin Peng Gao Welson Weisheng Xian Minjie Guo 

机构地区：[1]School of Earth Sciences and Engineering,Sun Yat-sen University,Guangzhou,China [2]Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai,China [3]Department of Earth Sciences,University of Hong Kong,Pokfulam Road,Hong Kong,China [4]College of Earth Sciences,Jilin University,Changchun,China [5]Pt.Enersteel,Jl.Pejaten Barat II No.20 Kav.C,South Jakarta 12510,Indonesia

出　　处：《Geoscience Frontiers》2023年第2期14-26,共13页地学前缘（英文版）

基　　金：supported by the National Natural Science Foundation of China[42025204,41890831,41803029,41973025 and 92155306];Guangdong Province Introduced Innovative R&D Team of Geological Processes and Natural Disasters around the South China Sea[2016ZT06N331];HKU Seed Fund for Basic Research[201811159089].

摘　　要：Ultrahigh-temperature(UHT)metamorphism represents an extreme crustal thermal event with peak conditions exceeding 900C at 7–13 kbar.In the modern-style plate tectonic system,records of the UHT metamorphism are relatively rare due to the secular cooling of Earth.In the Palu region of Western Sulawesi,we newly discovered a series of HT-UHT metamorphic rocks including amphibolite,granulite,eclogites and gneiss.Of them,two granulite samples(18CS14-2,18CS14-4)with high garnet content(>50 mol%)are chosen for petrographic observation,phase equilibrium modelling,and zircon U-Pb dating.These rocks are characterized by a relic M1 assemblage of Grt+Ky+Bt+Rt and a M2 assemblage of Grt+Sil+Pl+Spl+Crd±Qtz+Ilm+melt.Phase equilibrium modelling based on effective bulk compositions yields UHT conditions of 7.2–8.5 kbar/940–1080C(18CS14-2)and 7.0–7.3 kbar/1000–1040C(18CS14-4).U-Pb analysis reveals two generations of metamorphic zircon with evolving REE content that is intimately related to garnet growth and decomposition.Zircon age of 36–5.3 Ma is ascribed to syn-to post-M1 metamorphism,whereas the young zircon age of 5.1–3.8 Ma is linked to syn-and post-M2 stage.The UHT metamorphism was probably the consequence of the upwelling of asthenospheric mantle triggered by post-collisional delamination of lithosphere in the MiocenePliocene(ca.5 Ma).It could represent the youngest known UHT metamorphism on Earth.

关 键 词：UHT metamorphism GRANULITE SULAWESI Indonesia Lithosphere delaimination 

分 类 号：P588.3[天文地球—岩石学]