Geochronology of Serpentinized Harzburgite in Miaowan Ophiolite, Yangtze Block and Its Tectonic Implications
Qiu Xiaofei
Yang Hongmei
Zhang Liguo
Zhao Xiaoming
Duan Guiling
Lu Shansong
Tan Juanjuan
Shi Nian
Abstract：A series of strongly-deformed mafic-ultramafic rocks occur at the Kongling high-grade metamorphic terrain in Yan-gtze continental nucleus,scattering in the Miaowan Formation in layers and podiforms.This metamafic-ultramafic rock associa-tion is of great significance to the early tectonic evolution of Yantgze block.In this study,ID-TIMS whole-rock Sm-Nd isochron dating is carried out for the serpentinized harzburgite and amphibolite from this rock suite.The results indicate that the serpen-tinized harzburgite was formed at 1 063 ± 12 Ma,showing that it is feasible to date tiny amount of heavily-altered ultramafic rocks by means of the Sm-Nd isotopic system.The comparatively uniform Nd isotopic composition (withεNd (t )value ranging from 6.90 to 7.32)indicates that they were formed in a closed system.Two-stage Nd modal age of 1.13 -1.09 Ga is close to their emplacement time,implying an origin of partial melting from depleted asthenospheric mantle.Combined with documented work on late Mesoproterozoic to early Neoproterozoic tectonic-magmatic events in the area,it is suggested that the Yangtze block may have been composed of several microcontinents at that time.There could have been an ocean separating the Yangtze continental nucleus from western Yangtze continental segment.
Keywords：Yangtze continental nucleusMiaowan ophioliteSm-Nd isochronisotopegeochronologypetrologygeochemistry
Publication Date：2015-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：8( 1121-1128 )