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The Yungbwa ophiolite is a thrust sheet of about 800 km 2 tectonically overlying an Upper Cretaceous melange south of the Indus-Tsangpo Suture Zone in SW Tibet. Both units have been thrust over the sedimentary series of the Tibetan Tethys zone in the course of the India-Eurasia collision. Harzburgite and clinopyroxene-poor lherzolite are the dominant lithologies. Occasional gabbronoritic and...
The Tibetan crust is twice as thick as average continental crust. Crustal compression and shortening as a result of Indian–Asian collision is often considered to be the primary cause for the crustal thickening. In this paper, we show that magmatic contribution is also important. We come to this conclusion by documenting the Paleogene Linzizong volcanic succession (LVS), its coeval granitoid batholiths...
The shear wave velocity V s as a function of depth z can be obtained from surface wave tomography, using the phase velocities of fundamental and higher mode Rayleigh waves. Since V s is principally controlled by temperature, rather than by composition, it can be used to map the lithospheric thickness. Extensive regions of thick lithosphere underlie some, but not all, cratons. Conversely,...
The Gangdese batholith emplaced from the Cretaceous to Eocene in southern Tibet has been widely regarded as the major constituent of an Andean-type convergent margin resulting from northward subduction of the Neo-Tethyan oceanic lithosphere under Asia. While the Gangdese batholith consists predominantly of calc-alkaline rocks, we identify from the eastern part of the batholith a suite of epidote-bearing...
Strongly foliated amphibolite clasts are found embedded within the ophiolitic mélange underlying the Xigaze Ophiolite near Bainang and Angren, Yarlung Zangbo Suture Zone, Southern Tibet. These high-grade amphibolites are interpreted as remnants of a dismembered subophiolitic metamorphic sole that would have formed during the inception of a subduction. They include garnet-clinopyroxene amphibolites,...
The Yarlung Zangbo Suture Zone (YZSZ), southern Tibet, is a discontinuous belt that is more than 2000km long, composed of the remnants of Neo-Tethyan Mesozoic ocean. One of these relicts is the Xiugugabu ophiolitic massif which is a mantle thrust sheet of more than 260km 2 overlying the Cretaceous tectonic mélange south of the YZSZ in SW Tibet. The massif is composed of harzburgites and clinopyroxene–harzburgites...
High-pressure (HP)/low-temperature (LT) metamorphic rocks, such as eclogite and blueschist, are generally regarded as an indicator of subduction-zone metamorphism. Eclogites have recently been discovered in the central Qiangtang Block. Their occurrence is highly significant to the understanding of the closure of the Paleo-Tethys and tectonic evolution of northern Tibet. We report the results of petrological,...
This study reports age, petrologic and geochemical data for andesites and dacites from the Late Triassic sedimentary strata of northern Hohxil, in the Hohxil–Songpan–Ganzi Block (northern Tibet), which constitutes the most voluminous Triassic strata on Earth. LA-ICP-MS zircon U-Pb analysis of dacite (210.4±1.9Ma) and whole rock 40 Ar– 39 Ar analyses for both the andesites and dacites...
The Tibetan Plateau is the result of several collision events between a series of Gondwana-derived blocks (e.g., Qiangtang, Lhasa and India) and the Asian continent since the early Paleozoic. The occurrence of high-pressure eclogites has a significant bearing on the Paleo-Tethys subduction and plate suturing processes in this area. A quartzite, together with its host eclogite from the Jilang County...
The Duolong porphyry Cu–Au deposit (5.4Mt at 0.72% Cu, 41t at 0.23g/t Au), which is related to the granodiorite porphyry and the quartz–diorite porphyry from the Bangongco copper belt in central Tibet, formed in a continental arc setting. Here, we present the zircon U–Pb ages, geochemical whole-rock, Sr–Nd whole-rock and zircon in-situ Hf–O isotopic data for the Duolong porphyries. Secondary ion mass...
Ophiolite plays a key role in identifying paleo-ocean and paleo-plate and rebuilding the evolutionary history of ancient orogen. Mafic–ultramafic rocks are distributed in a broadly E–W direction in the middle of the Qiangtang terrane, northern Tibetan plateau. However, interpretation of these rocks as ophiolite and subsequent tectonic implications have been much disputed, and they were regarded by...
The Yanhu area in the northern Lhasa subterrane exposes diverse rock types including basalts, rhyolites, quartz dioritic porphyries, and associated dioritic enclaves. The basalts and rhyolites occur as a bimodal volcanic suite, and the quartz dioritic porphyries intrude into the older basalts as a small apophysis. In this paper, we report for the first time the zircon LA-ICP-MS U–Pb age and Hf isotopic...
The rare occurrences of active volcanoes on the Tibetan Plateau provide a unique opportunity to investigate time scales of magma chamber processes for post-collisional potassic volcanism. This research utilizes high-spatial resolution U–Th disequilibrium dating methods to date zircons from the active Dayingshan volcano, Tengchong, SE Tibetan Plateau, which erupted last during the Holocene. Zircon...
At more than 500km in length, the mainly Jurassic–Early Eocene Gangdese batholith is one of the most important constituents of the southern Lhasa sub-block and provides an ideal site for study of Tibetan orogenesis. Recent studies on Gangdese intermediate-felsic intrusive rocks, mainly granites, demonstrate that remarkable crustal growth as well as an early Late Cretaceous (ca. 100–80Ma) magmatic...
Regional mafic dyke swarms are commonly emplaced in extensional tectonic settings and are typically considered to be linked with continental break-up. A large number of mafic dykes (areal extent of ~40,000km 2 ) have recently been documented in the middle of the Qiangtang terrane, northern Tibet. Zircon U–Pb isotope analyses using a sensitive high-resolution ion microprobe (SHRIMP) indicate...
Rapid Mesozoic–Early Cenozoic crustal growth in the Gangdese area, southern Tibet, has commonly been attributed to pre-collisional and syn-collisional underplating of mantle-derived magmas. Here, we report on adakitic magnesian charnockites (i.e., hypersthene-bearing diorites and granodiorites) near Milin, in eastern Gangdese, that provide new insights into the crustal growth process of the region...
A geologic investigation was undertaken in the Hoh-Xil–Songpan-Ganzi (HXSG) complex, northern Tibet in order to better understand magma genesis and evolution during the late stages of Paleo-Tethys ocean closure. The HXSG complex is composed of vast accumulations of Middle–Upper Triassic marine gravity flow deposits that were extensively intruded by igneous rocks. These early Mesozoic rocks exposed...
Cenozoic adakitic rocks in the Lhasa block (southern Tibet) have been widely used to trace the lateral extent of crustal thickening. However, their petrogenesis remains controversial. Here, we report geochronological and geochemical data for the Napuri intrusive rocks in the core area of the Quxu batholith, southern Lhasa. Zircon U-Pb dating suggests that they were generated at approximately 48Ma...
Mesozoic intermediate–felsic intrusions are widely distributed in the southern Qiangtang terrane, central Tibet. Zircon U–Pb dating shows that these intrusions formed in two periods in the Jurassic (169–150Ma) and Cretaceous (127–113Ma). They mostly belong to the high-K calc-alkaline series, and show strong enrichments in large ion lithophile elements (e.g., Cs, Rb, and K), depletions in Nb, Ta, and...
The Sangri Group volcanic rocks are distributed along the southern margin of the Lhasa Terrane on the northern side of the Indus-Yarlung Zangbo suture zone. This Group consists of the Mamuxia and Bima formations and has long been considered to be Late Jurassic to Early Cretaceous in age. In this paper, we report for the first time zircon LA-ICPMS U-Pb ages, whole-rock major and trace element geochemistry,...
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