Early Ordovician Tectono-Thermal Event in Zhongba Terrane andIts Geological Significance
Liu Qiang
Deng Yubiao
Xiang Shuyuan
Li Hualiang
Abstract：The Zhongba terrane is an important tectonic unit sandwiched between the northern and the southern ophiolitic sub-belts in the western segment of the Yarlung Zangbo Suture Zone (YZSZ), Southwest Tibet.Currently it is still unclear as to whether there exists the Early Paleozoic tectono-thermal events in this terrane as well as its tectonic affinity.BasedBaesed on field and petrological investigations, a suite of gneissic monzogranite that intruded into a biotite plagioclase gneiss was recognized near the Gongzhu Co area in the middle part of the Zhongba terrane in this study.U-Pb dating of zircon from the monzogranite yieldsed ages of ~478Ma, indicating the deformation age for such rock at the Early Ordovician.These monzogranites are characterized by high Si and Al, relatively high contents of total alkalis, A/CNK=1.13-1.20, enrichment of large lithophile elements of Rb and K and depletion of Ba, Sr, Nb and Ti, which should be calc-alkalic alkaline, strong peraluminous granite.To our knowledge, this represents the first report of the Early Ordovician tectono-thermal events taken place within the Zhongba terrane from the western YZSZ.These gneissic monzogranites were formed by the upper crustal melting after subduction of the Proto-Tethys Ocean to the northern margin of the Gondwana supercontinent, and suggesting that the Zhongba terrane should belong to the northern margin of the eastern Gondwana supercontinent at the Early Paleozoic.
Keywords：gneissic monzograniteZhongba terraneYarlung Zangbo Suture ZoneSouthwest Tibetpetrology
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：10( 881-890 )