Taohong Diorite from Pingshui Region in Eastern Jiangnan Orogen:Evidence for Early Neoproterozoic Oceanic Crust Subduction
Tan Qingli
Wang Yuejun
Zhang Yuzhi
Li Shubo
Zhou Yongzhi
Wang Yukun
Abstract：The fine chronological constraints and the determination of tectonic setting of the Early Neoproterozoic magmatic rocks in the Pingshui area are important breakthroughs for the Neoproterozoic evolution mechanism in South China.This paper presents a synthesis of zircon U-Pb geochronological,whole rock elementaland Sr-Nd isotopic geochemistry study on the Taohong diorite from Pingshui region along the Eastern Jiangnan Oroger.Two representative samples yielded weighed mean 206 pb/238U ages of 913±2 Ma and 898 ±2 Ma,respectively,representing the crystallization ages of the dioritic pluton.In the case of loss on ignition free,the dioritic samples are characterized by SiO2 of 58.33 ％-63.36 ％,Al2 O3 of 15.76 ％-17.42 ％,Na2O of 2.62％-3.12％,K2O of 0.53％-1.53％ and A/CNK of 0.84-0.92,classified as low to medium-K metaluminous series.Their chondrite-normalized rare earth elements (REEs) patterns exhibit a right-sloping tendency with more enriched light rare earth elements(LREEs) relative to heavy rare earth elements(HREEs) ((La/Yb)N =4.65-6.09) and slightly Eu abnormality(δEu=0.82-1.01).On the primitive mantle-normalized multi-elements patterns,these samples have strong enrichment in large iron lithophile elements(LILEs) (Rb,Ba,K and Sr) and depletion in high field-strength elements (HFSEs) with marked negative Nb,Ta and Ti,similar to those of typical arc magmatites.The samples show low (87 Sr/86 Sr)i of 0.703 060-0.703 076 ratio and high positive εNd (t) of +6.58 to +6.76 values.It is inferred that the formation of the rocks is attributed to the partial melting of the mantle wedge peridotite,which was modified by the subducted slab-derived fluid and melt during the southeastwards subduction of ancient oceanic crust between the Yangtze and Cathaysia Block.In conjunction with previous studies,it is proposed that the Shuangxiwu Group along Eastern Jiangnan Orogen resulted from suturing of the Yangtze and Cathaysia Block,and is not related to Grenvillian Orogen in petrogenesis.
Keywords：dioritessubduction of oceanic crustzircon U-Pb DatingSr-Nd isotopeJiangnan Orogengeochemistry
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：18( 173-190 )