Abstract In NE China, voluminous granitoids were emplaced in late Paleozoic and Mesozoic times. We report here Sr–Nd–O isotopic and elemental abundance data for two highly evolved granitic plutons, Woduhe and Baerzhe, from the Great Xing'an Mountains. They show a rather “juvenile” Sr–Nd isotopic signature and a spectacular tetrad effect in their REE distribution patterns as well as non-CHARAC (charge-and-radius-controlled) trace element behavior. The emplacement ages are constrained at 130±4 Ma for the Woduhe and 122±5 Ma for the Baerzhe granites by Rb–Sr and Sm–Nd isotope analyses. Both granites are also characterized by low but imprecise initial 87Sr/86Sr ratios of about 0.703. The Nd–Sr isotope data argue for their generation by melting of dominantly juvenile mantle component with subordinate recycled ancient crust. This is largely compatible with the general scenario for much of the Phanerozoic granitoids emplaced in the Central Asian Orogenic Belt. The parental magmas for both the Woduhe and Baerzhe granites have undergone extensive magmatic differentiation, during which intense interaction of the residual melts with aqueous hydrothermal fluids (probably rich in F and Cl) resulted in the non-CHARAC trace element behavior and the tetrad effect of REE distribution. Both the Woduhe and Baerzhe granites show the characteristic trace element patterns of rare-metal granites, but their absolute abundances differ by as much as two orders of magnitude. The oxygen isotope compositions of the two granites have been severely disturbed. Significant 18O depletion in feldspar, but not so much in quartz, suggests that the hydrothermal alteration took place in a temperature condition of 300–500 °C. This subsolidus hydrothermal alteration is decoupled from the late-stage magma–fluid interaction at higher temperatures. Despite the two distinct and intense events of “water–rock” interaction, the Rb–Sr and Sm–Nd geochronological systems seem to have maintained closed, hence, suggesting that the two events occurred shortly after the plutonic emplacements.

Highly evolved juvenile granites with tetrad ree patterns: the woduhe and baerzhe granites from the great xing'an mountains in ne china

Subduction and accretionary tectonics of the East Kunlun orogen, western segment of the Central China Orogenic System

Tectonic evolution, superimposed orogeny, and composite metallogenic system in China

The appearance of detritus shed from mountain ranges along the northern margin of the Tibetan Plateau heralds the Cenozoic development of high topography. Current estimates of the age of the basal conglomerate in the Qaidam basin place this event in Paleocene-Eocene. Here we present new magnetostratigraphy and mammalian biostratigraphy that refine the onset of basin fill to ∼25.5 Myr and reveal that sediment accumulated continuously until ∼4.8 Myr. Sediment provenance implies a sustained source in the East Kunlun Shan throughout this time period. However, the appearance of detritus from the Qilian Shan at ∼12 Myr suggests emergence of topography north of the Qaidam occurred during the late Miocene. Our results imply that deformation and mountain building significantly post-date Indo-Asian collision and challenge the suggestion that the extent of the plateau has remained constant through time. Rather, our results require expansion of high topography during the past 25 Myr.

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Expansion of the Tibetan Plateau during the Neogene

In order to better constrain the evolution of the Tethyan orogenic system, we conducted an integrated investigation involving U-Pb dating of igneous and detrital zircon, geochemical analysis of igneous rocks, compositional analysis of sedimentary strata, and a synthesis of existing work across the Qilian Shan, Qaidam Basin, and the Eastern Kunlun Range of central and northern Tibet. This effort reveals five stages of arc magmatism at 1005–910 Ma, 790–720 Ma, 580–500 Ma, 490–375 Ma, and 290–195 Ma, respectively. Arc activities were interrupted by repeated continent-continent collision followed by ocean opening along the older suture zones first created in the Neoproterozoic. This suggests that Wilson cycles have played a controlling role in constructing the southern Asian continent. The magmatic history and regional geologic constraints allow us to construct a coherent tectonic model that has the following key features. (1) The linked South Qilian suture in the west and North Qinling suture in the east formed the northern boundary of the coherent Kunlun–Qaidam–North Qinling Terrane in the early Paleozoic. (2) The Songpan-Ganzi Terrane has been the western part of the Yangtze craton since the Neoproterozoic. (3) Development of the wide (>700 km) Permian–Triassic arc across the Kunlun-Qaidam Terrane was induced by flat subduction and rapid slab rollback, which also caused extreme extension of the Songpan-Ganzi Terrane. (4) The formation of the Anymaqen-Kunlun-Muztagh Ocean (= the Neo–Kunlun Ocean in this study) was created within Laurasia rather than being a preexisting ocean between Gondwana and Laurasia as postulated by most early studies.

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Pre-Cenozoic geologic history of the central and northern Tibetan Plateau and the role of Wilson cycles in constructing the Tethyan orogenic system

Zircon U-Pb geochronology, geochemical and Sr-Nd-Hf isotopic compositions of the Triassic granite and diorite dikes from the Wulonggou mining area in the Eastern Kunlun Orogen, NW China: Petrogenesis and tectonic implications

The Wulonggou metaluminous A2-type granites in the Eastern Kunlun Orogenic Belt, NW China: Rejuvenation of subduction-related felsic crust and implications for post-collision extension

Mafic–intermediate igneous rocks in the East Kunlun Orogenic Belt, northwestern China: Petrogenesis and implications for regional geodynamic evolution during the Triassic

Geochronology and geochemistry of Late Jurassic to Early Cretaceous granitoids in the northern Great Xing'an Range, NE China: Petrogenesis and implications for late Mesozoic tectonic evolution

Mineralization events in the Xiaokele porphyry Cu (–Mo) deposit, NE China: Evidence from zircon U–Pb and K‐feldspar Ar–Ar geochronology and petrochemistry

Feng-Yue Sun

Papers

Zircon U-Pb geochronology, geochemical and Sr-Nd-Hf isotopic compositions of the Triassic granite and diorite dikes from the Wulonggou mining area in the Eastern Kunlun Orogen, NW China: Petrogenesis and tectonic implications

The Wulonggou metaluminous A2-type granites in the Eastern Kunlun Orogenic Belt, NW China: Rejuvenation of subduction-related felsic crust and implications for post-collision extension

Mafic–intermediate igneous rocks in the East Kunlun Orogenic Belt, northwestern China: Petrogenesis and implications for regional geodynamic evolution during the Triassic

Geochronology and geochemistry of Late Jurassic to Early Cretaceous granitoids in the northern Great Xing'an Range, NE China: Petrogenesis and implications for late Mesozoic tectonic evolution

Mineralization events in the Xiaokele porphyry Cu (–Mo) deposit, NE China: Evidence from zircon U–Pb and K‐feldspar Ar–Ar geochronology and petrochemistry