HR: 0800h
AN: T31B-0469    [Abstracts]
TI: Zircon U-Pb geochronology of the eastern Transhimalayan batholiths, SE Tibet
AU: * Chiu, H
EM: r91224204@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan
AU: Chung, S
EM: sunlin@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan
AU: Liang, Y
EM: crystal.liang@msa.hinet.net
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan
AU: Lin, I
EM: r94224201@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan
AU: Liu, D
EM: liudunyu@public.bta.net.cn
AF: Institute of Geology, Chinese Academy of Geological Sciences, Baiwanzhuang Road 26, Beijing, 100037, China
AU: Wang, Y
EM: yanbinw@cags.net.cn
AF: Institute of Geology, Chinese Academy of Geological Sciences, Baiwanzhuang Road 26, Beijing, 100037, China
AB: Before the India-Asia collision, northward subduction of the Neo-Tethyan oceanic lithosphere beneath South Asia produced an Andean-type convergent margin marked with arc magmatism starting from the early Jurassic (≥190 Ma) and lasting until the Eocene (~45 Ma). The magmatic arc is now exposed as widespread intrusive bodies or the so-called Transhimalayan batholiths in the Lhasa terrane of southern Tibet that have been divided into two suites, i.e., the northern plutonic belt and the southern Gangdese belt. However, the temporal distribution of the batholiths, in particular their eastern/southeastern extension, remains poorly constrained. We therefore conducted a field excursion from Chayu to Basu areas (~95.5-97.5°E and ~28.5- 30°N), SE Tibet, from which intrusive rocks were collected for a combined geochronological and geochemical analysis. Our preliminary results of zircon U-Pb dating show that these granotoids were emplaced between the Cretaceous (~133-110 Ma) and Paleocene (~60 Ma). They all are characterized by depletions in the high field strength elements (HFSE), enrichments in the large ion lithophile elements (LILE) and light rare earth elements (LREE), and thus show spidergram patterns similar to those of arc magmas from the subduction zones. These granitoids have heterogeneous Sr and Nd isotope ratios, with eNd(T) values varying from -1.0 to -13.0, which suggest the continental crust to have played a significant role in the petrogenesis. Furthermore analyses on the age, geochemistry and Sr-Nd isotopes of the samples will be performed and combined with the above data set to comprehend our understanding of the temporal and spatial distribution of the Transhimalayan batholiths and their tectonic significance.
DE: 1040 Radiogenic isotope geochemistry
DE: 1100 GEOCHRONOLOGY
DE: 1115 Radioisotope geochronology
DE: 1120 Isotopic disequilibrium dating
SC: Tectonophysics [T]
MN: 2007 Fall Meeting