Geochronological and geochemical feature of the Cenozoic adakites in Hoh Xil, Tibetan Plateau
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ORIGINAL PAPER
Geochronological and geochemical feature of the Cenozoic adakites in Hoh Xil, Tibetan Plateau Chaofeng Zhang 1,2 Received: 23 August 2018 / Accepted: 9 May 2019 / Published online: 22 May 2019 # Saudi Society for Geosciences 2019
Abstract The volcanic rocks in the Tibetan Plateau have undergone complex evolution, as the collision between the Indian and Eurasian Plates proceeds. The volcanic rock samples collected from a volcanic edifice in the Hoh Xil, Tibetan Plateau, are studied in this paper. The geochemistry and zircon U-Pb chronology of the volcanic rock samples are determined. Our results indicate that the volcanic rocks in this area are mostly alkali-rich intermediate-acidic ones, and consist of quartz trachyandesite, andesite, pyroxene andesite, and andesitic tuff. Geochemically, these rocks feature high light rare earth elements and large-ion lithophile elements concentration, with low Nb, Ta, and Ti concentration, and significant Pb positive anomaly. Based on our analysis, we conclude that the volcanic rocks are adakites. The eruption ages of the volcanic rocks in this area are determined for the first time in the literature: 45.23 ± 0.35 Ma for the hornblende trachyandesite; 41.36 ± 0.45 Ma for the biotite trachyandesite; and 42.97 ± 0.23 Ma for the biotite-quartz trachyandesite. This suggests that the volcanic rocks studied in this paper were formed in the Lutetian (Eocene). It is further concluded that the volcanic rocks originated from a mantle provenance that have assimilated large amount of crustal materials. The formation of the volcanic rocks is attributable to the breakoff of oceanic lithospheric slab. Keywords Tibetan plateau . Adakite . Geochemistry . Zircon U-Pb chronology
Introduction The collision between the Indian and Eurasian Plates is the most important orogenic event on the earth during the Cenozoic Era. It is responsible for the emergence of the Tibetan Plateau, one of the largest orogens in the world. As such, this has drawn wide interest across the earth science community (Patriat and Achache 1984; Rowley 1998; Hodges 2000; Yin and Harrison 2000; Wu et al. 2008). During the past several years, one of the most studied topics has been how the Tibetan Plateau extended and uplifted further northward after the collision between the two plates along the Yarlung Zangbo suture zone (Turner et al. 1993; Williams et al. 2004; Mulch and Chamberlain 2006). Cenozoic volcanic Editorial handling: Yalçın Emrah Ersoy * Chaofeng Zhang [email protected] 1
State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, Shaanxi, China
2
No. 203 Research Institute of Nuclear Industry, Xianyang 712000, Shaanxi, China
rocks are extensively exposed in Hoh Xil, an area situated at the northern margin of the Tibetan Plateau. These rocks have become a key to study the northward extension and uplift of the Tibetan Plateau. In previous literatures, the volcanic rocks in the southern Tibetan Plateau have been extensively studied (Turner et al. 1993;
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