Geochemistry and Zircon U-Pb-Hf Isotopes of Metamorphic Rocks from the Kaiyuan and Hulan Tectonic Mélanges, NE China: Implications for the Tectonic Evolution of the Paleo-Asian and Mudanjiang Oceans

Abstract

The Late Paleozoic–Early Mesozoic tectonic evolution of the Changchun-Yanji suture (CYS) was mainly associated with the Paleo-Asian and Mudanjiang tectonic regimes. However, the spatial and temporal overprinting and variations of these two regimes remains are still dispute. In order to evaluate this issue, in this contribution, we present new zircon U-Pb ages and a whole-rock geochemical and zircon Hf isotopic dataset on a suite of metamorphic rocks, including gneisses, actinolite schist, leptynites, and biotite schists, from tectonic mélanges in northern Liaoning and central Jilin provinces, NE China. Based on zircon LA-ICP-MS U-Pb dating results, protoliths show wide ranges of aging spectrum, including Paleoproterozoic (2441 Ma), Early Permian (281 Ma), Late Permian (254 Ma), and Late Triassic (230 Ma). The Permian protoliths of leptynites from the Hulan Tectonic Mélange (HLTM) and gneisses from the Kaiyuan Tectonic Mélange (KYTM) exhibit arc-related geochemical signatures, implying that the Paleo-Asian Ocean (PAO) did not close prior to the Late Permian. The Late Triassic protoliths of gneisses from the KYTM, in combination with previously reported coeval igneous rocks along the CYS, comprises a typical bimodal igneous suite in an E–W-trending belt, suggesting a post-orogenic extensional environment. Consequently, we infer that the final closure of the PAO took place during the Early–Middle Triassic. The Early Permian protoliths of biotite schists from the HLTM are alkali basaltic rocks and contain multiple older inherited zircons, which, in conjunction with the geochemical features of the rocks, indicate that they were generated in a continental rift related to the initial opening of the Mudanjiang Ocean (MO). Data from this contribution and previous studies lead us to conclude that the MO probably opened during the Middle Triassic, due to the north–south trending compression caused by the final closure of the PAO.

The Late Triassic Molasse Deposits in Central Jilin Province, NE China: Constraints on the Paleo-Asian Ocean Closure

“…Moreover, all the samples plot within or close to the typical arc-rock field in the Sr/Y vs. Y and (La/Yb) N vs. Yb diagrams (Figure 12c,d), which are further indicative of arc-type magmatism in association with subduction process. Therefore, a subduction-related tectonic setting linking with the sub-duction of the Paleo-Asian oceanic plate likely created the above-mentioned end-Permian granitic rocks, as well as some previously reported contemporaneous magmtic rocks, which exhibit arc-related geochemical signatures along the CYS, such as the Doushantouzi syenogranites (256 Ma), the Daheishan volcanic rocks (255-253 Ma), the Kaiyuan metamorphosed basaltic volcanic rocks (258 Ma and 254 Ma), and the Kaishantun basalt (252 Ma) [17,25,26,31]. In addition, coeval high-Mg andesites (252 Ma and 250 Ma) that formed in a subduction-related setting also distributed along the CYS [23,34].…”

“…These granitoids, which display high SiO2, low Mg#, low Cr and Ni, and notably high La/Yb and Sr/Y, were proposed to have originated from thickened lower crust that resulted from collision [20][21][22]24,27,28]. Some recently reported Early Triassic ages from igneous rocks or metamorphic complexes (e.g., the Daheishan volcanic rocks and the Kaiyuan and Hulan complexes) in the adjacent areas probably correspond to the above collisional events [10,25,26,31]. Importantly, molasse sequences provide reliable evidence for the end of an orogeny [5,46].…”

“…This region is adjacent to the Dunhua-Mishan Fault and the Songliao Basin to the east and west, respectively (Figure 1b). The CYS is composed mainly of Phanerozoic granitoids with a series of subduction-related tectonic mélanges, including the Kaiyuan, Xia ertai, Hulan, Seluohe, Qinglongcun, and Kaishantun tectonic mélanges [12,15,[21][22][23][25][26][27][28]31,35,47]. In addition, minor Paleozoic and Mesozoic sediments are also distributed in the "granite ocean" [39,[43][44][45][46][48][49][50].…”

“…This region is Dunhua-Mishan Fault and the Songliao Basin to the east and west, respe 1b). The CYS is composed mainly of Phanerozoic granitoids with a series related tectonic mélanges, including the Kaiyuan, Xia′ertai, Hulan, Seluohe and Kaishantun tectonic mélanges [12,15,[21][22][23][25][26][27][28]31,35,47]. In additio zoic and Mesozoic sediments are also distributed in the "granite ocean" [3 The study area is to the southeast of Jilin City, in central Jilin Prov According to the 1:200,000 geological map, this area mainly contains the Daheshen, the Upper Permian Fanjiatun and Yangjiagou, and the Triass dingzi formations [80] (Figure 2).…”

Editorial for Special Issue “U-Pb Dating and Chemistry of Zircon in Metamorphic, Magmatic and Sedimentary Rocks”

“…The ability of zircon to record the geological history of the Carboniferous-Permian orogeny and its evolution over the Mesozoic was documented by collecting U-Pb age data from magmatic protoliths of a tectonic mélange. The geochemical features of magmatism constrain the extensional and compressional phases of tectonic evolution in northeastern China [4]. Analogously, Fornelli et al [5] show how zircon ages from metasediments affected by polymetamorphism in the Variscan orogen can reveal the timing of tectonic phases during the construction of the belt, thus establishing the origin and the maximum sedimentation age of protoliths.…”