Early Paleozoic Structural Deformation Of The Chencai Domain In The Eastern Segment Of The Shaoxing-Jiangshan Fault Zone

South China was formed through the Neoproterozoic amalgamation of the Yangtze and Cathaysia Blocks.After the amalgamation,the united South China continent was overprinted by a significant tectono-thermal event in the early Paleozoic.The Shaoxing-Jiangshan fault zone(SJFZ),as a fundamental Neoproterozoic block boundary that separates the Yangtze Block from the Cathaysia Block,is the key to understanding the evolution of South China from Neoproterozoic block amalgamation to early Paleozoic crustal reworking.However,the paucity of structural data hampers delineating its geometric and kinematic features,and inhibits understanding its role in shaping early Paleozoic tectonic framework of South China.New structural observations coupled with geochronological ages from the Chencai domain indicate that intense ductile deformation and metamorphism along the SJFZ occurred at?460-420 Ma,in response to the early Paleozoic orogeny in South China.To the east of the SJFZ,the deformation involves widespread generations of NE-striking foliation,intrafolial folds,and local development of sinistral-oblique shear zones.The shearing deformation occurred under amphibolite facies conditions at temperatures of>550 ?(locally even>650 ?).To the west of the SJFZ,the deformation corresponds to sinistral-oblique shearing along NE-striking,steep-dipping zones under greenschist facies conditions at temperatures of 400-500 ?.These deformation styles,as typical mid-crustal expressions of continental reworking,reflect tectonic reactivation of the pre-existing,deeply rooted Neoproterozoic block boundary in the early Paleozoic.We infer that the tectonic reactivation,possibly induced by oblique underthrusting of north Cathaysia,facilitated ductile shearing and burial metamorphic reactions,giving rise to the high-strain zones and high-grade metamorphic rocks.With respect to pre-existing mechanical weakness,our work highlights the role of tectonic reactivation of early structures in localizing later deformation before it propagates into yet undeformed domains.