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Magmatic rocks in the North China Craton (NCC) are crucial to unraveling the tectonic background during the tectono-magmatic lull (TML, 2.45–2.20 Ga) and to constraining the initiation of plate tectonics. In this study, previously published zircon U–Pb–Hf–O data and whole-rock geochemistry are collected from the early Paleoproterozoic felsic intrusive rocks in the southern Trans-North China Orogen (TNCO) and new data presented. The formation ages and petrogenesis of the early Paleoproterozoic felsic intrusive rocks in the southern TNCO are summarized to constrain the tectonic setting during the TML. Zircon U-Pb geochronology of the tonalite–trondhjemite–granodiorite (TTG) gneisses yielded intrusive ages of ∼2.3 Ga and ∼2.2 Ga. Geochemically, the gneisses can be classified as ∼2.3 Ga high-Al and ∼2.2 Ga low-Al types, and were likely derived from the partial melting of pre-existing lower crust at medium and low pressure, respectively. The heavy rare earth depletion and have high Sr/Y and La/Yb values of the ∼2.3 Ga TTG gneisses indicates that they were derived from the partial melting of thickening lower crust in the garnet-hornblende phase, which is consistent with a gradual thickening of the crust. The potassic granitoids are geochemically divided into I-type and A-type granites and have early Paleoproterozoic ages at ∼2.3 Ga and ∼2.27 Ga. Zircon U-Pb geochronology of the dioritic gneisses yielded intrusive ages of ∼2.3 Ga. These potassic granitoids and dioritic gneisses were generated by the partial melting of ancient basement rocks, with variable degrees of juvenile contributions. Considering the large variety of zircon ε Hf (t) values, and Sr/Y and (La/Yb) N ratios obtained for the early Paleoproterozoic felsic intrusive rocks, the crustal thickening that occurred via tectonic compression prior to ∼2.3 Ga is most likely due to convergence. The high δ18O and low δ18O values in the southern TNCO may have been the result of slab subduction, which can effectively transfer surface material directly or indirectly to the lower crust, and the TTGs that formed as a result of the subsequent partial melting inherited the high δ18O characteristics to varying degrees. Glacial meltwater is an important source of low δ18O fluids and a large number of rift events developed during the 2.5–2.4 Ga interval. The resulting fractured environment provided sufficient space for the infiltration of surface water, and rocks with low δ18O characteristics are likely produced by the remelting of crustal rocks that have been thermally altered by surface water or atmospheric hydrothermal processes. Combined with evidence such as the Paleoproterozoic Alaska-type intrusive rocks, diabases, sanukitoids and sedimentary rocks, the TNCO is proposed to have been in a subduction compression setting at ∼2.3 Ga. Meanwhile, the alkaline and related elements (such as Rb, Th, Ba and Nb), K 2 O/Na 2 O ratios, and zircon δ18O values of the magmatic rocks increased significantly during the TML, which indicate that plate subduction started prior to ∼2.3 Ga. The difference in the intensity of the magmatism during the TML may be related to continental freeboards in different regions– [ABSTRACT FROM AUTHOR]

Highlights • Early Paleoproterozoic magmatism were reported in Phan Si Pan Complex in North Vietnam of the Yangtze Block. • The ca. 2.3 Ga quartz monzonite formed at a collision-related crustal thickening event. • The ca. 2.1 Ga A-type gneissic granite formed within an extensional tectonic setting. • The Phan Si Pan Complex was an independent terrane separated from other parts of the Yangtze Block during the early Paleoproterozoic. • The Yangtze Block was linked to northwestern Laurentia in the Pre-Nuna supercontinent. Abstract Our understanding of the early evolution of the Yangtze Block is limited by the sparsely dispersed nature of pre-Neoproterozoic exposures. New, integrated petrographic, zircon U-Pb age and Hf-Nd isotope analyses, and whole-rock geochemical data for early Paleoproterozoic granites in the Phan Si Pan Complex provides new insights into the evolution of the Yangtze Block as well as its role in the Pre-Nuna supercontinent. LA-ICP-MS zircon U-Pb dating of magmatic zircons from quartz monzonite and gneissic granite yielded 207Pb/206Pb ages of 2306 ± 12 Ma and 2096 ± 15 Ma, respectively. Zircons from the quartz monzonite have ε Hf(t) values ranging from −4.1 to −2.1, corresponding to T DM2 model ages of 3002–2890 Ma, whereas zircons in the gneissic granite have ε Hf(t) values between −0.95 and +1.72 and corresponding T DM2 model ages of 2660–2516 Ma, which are consistent with their whole-rock Nd isotope values. Geochemically, the quartz monzonites are I-type granites. Combined with their relatively high Sr/Y ratios and low Y concentrations, as well as fractionated REE patterns with relatively high LREE but low HREE concentrations, they were probably generated by partial melting of the thickened middle-lower crust under elevated temperature. Geochemical and isotopic signatures suggest that the ca. 2.1 Ga gneissic granites are high-K calc-alkaline, ferroan A-type granites formed by partial melting of juvenile crustal source at high temperature and low pressure with little involvement of ancient crustal material. The Phan Si Pan complex has a distinct early Paleoproterozoic crustal evolution history compared with the other crustal provinces of the Yangtze Block, suggesting independent histories that were not unified until the late Paleoproterozoic during the assembly of Nuna. Moreover, the magmatism and tectonic evolution of the north Vietnam region is broadly similar to that of the Arrowsmith Orogen of the Rae craton in Laurentia suggesting a potential spatial linkage. The geologic record of the Yangtze Block does not support an early Paleoproterozoic shutdown of plate tectonics. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • 2.4 Ga granitoids of the Quanji Massif show high-K I-type and A 2 -type affinities. • The magmas were derived from early Paleoproterozoic juvenile crust and ancient crust. • The plate tectonics did not shut down during the early Paleoproterozoic. Abstract The global plate tectonic regime in the early Paleoproterozoic period is highly debated. Granitoids bear key information to address such a debate. Petrological, geochemical and geochronological studies are conducted on two post-collisional granitoid plutons in the Quanji Massif, northwestern China, to investigate the tectonic regime during this period. The granitoids are composed of syenogranite, monzogranite, and granodiorite, with minor tonalite, which intruded into the Delingha and Hudesheng regions at ca. 2.39–2.37 Ga. These plutons are high-K I-type granitoids with variable Ga/Al ratios, showing some characteristics of A 2 -type granitoids. They are characterized by enrichment of LILEs and LREEs and depletion of Sr, P, Ti, and Eu. They show depleted Nd and Hf isotope signatures with whole rock ε Nd (t) = +0.7 to +4.8 and zircon ε Hf (t) = −1.0 to +7.8, indicating a juvenile crustal growth event at ca. 2.44–2.37 Ga. Our new results together with other coeval post-collisional granitoids in the Quanji Massif suggest that the protracted post-collisional magmatism at ca. 2.39–2.34 Ga occurred just after a short interval of subduction and generation of juvenile magmas before or around ca. 2.4 Ga. Collectively, the formation of these ca. 2.4–2.3 Ga granitoids in the Quanji Massif may correlate with coeval granitoids in the Tarim and North China cratons, and is broadly coeval with magmatism in several other cratons in the West African and Canadian Shields. Thus, the globally well-documented magmatism at early Paleoproterozoic, or Siderian, provides further information for filling up the age gap of the so-called plate tectonic "shutdown" in the early Paleoproterozoic period worldwide. The geologic record therefore suggests no Siderian shutdown of plate tectonics, but instead, continuous global subduction and generation of juvenile magmas from the Archean through the Paleoproterozoic. [ABSTRACT FROM AUTHOR]

A global database of zircon ages from both granitoids and detrital sediments shows an exceptional and robust age gap between 2.45 and 2.20 Ga. The early Paleoproterozoic magmatism dramatically decreased on the Earth, which was proposed to relate to the global plate tectonic shutdown. However, the available data indicate that 2.45–2.20 Ga magmatic rocks are widespread in the Taihua Complex during the quiet interval. The Taihua Complex is located in both the Lushan and Xiaoqinling areas along the southern segment of North China Craton (NCC). The Complex is composed mainly of a gneiss series and the Khondalite-dominated supracrustal rocks. There was an original unconformable relationship between the two rock associations. The latter occurs as a linear structural belt and was named the Khondalite Belt. The gneiss series in the Lushan area has an age of 2.85–2.72 Ga, whereas the Xiaoqinling region contains widespread tonalitic–trondhjemitic–granodioritic gneisses with ages of 2.45–2.20 Ga. Significant variations of Hf isotopes in zircons and whole-rock ɛ Nd( t ) values suggest that these rocks were produced by variable mixing of a juvenile materials with older crust in an Andean-type continental margin arc or island arc setting. The depositional age of the sedimentary protoliths of the khondalite series can be roughly constrained in the period between 2300 and 1970 Ma. It has been considered that they were deposited in a stable continental margin environment. The U–Pb dating of metamorphic zircons from the Taihua Complex suggest that the southern NCC underwent a polyphase tectonic evolution during the period 1.97–1.82 Ga, and the peak metamorphism coeval with crustal thickening has occurred at ∼1.94 Ga. [ABSTRACT FROM AUTHOR]

Tectonic regimes took different forms worldwide during the early Paleoproterozoic, ranging from a slowing or halting of plate tectonics to vigorous subduction-related magmatism. A detailed study is conducted on the Delingha granitoid pluton in the Quanji Massif of northwestern China to reveal the crustal evolution of this Precambrian microcontinent and to provide potential insight on complex and heterogeneous evolutionary processes occurring in this period. The Delingha pluton was mainly composed of gneissic biotite granite and gneissic granodiorite, which formed at ca. 2.48 – 2.44 Ga and 2.38 – 2.35 Ga, respectively, as evidenced by LA-ICP-MS zircon U-Pb ages. The gneissic biotite granite exhibited high-K I-type granite affinities and variable zircon ε Hf (t) values (−12.9 −4.7) with a major peak of approximately 2.8 and a secondary peak of approximately 3.9, indicating that the source rock was dominated by heterogeneous mafic crustal materials. The gneissic granodiorite shows A-type granite affinities and a nearly unimodal distribution of zircon ε Hf (t) values (−3.1 −4.0, with a peak of approximately 1.5). These data indicate that the gneissic granodiorite was mainly sourced from Archean mafic igneous rocks. Our study suggests that the gneissic biotite granite formed in a subduction-related environment while the gneissic granodiorite formed in a post-collisional tectonic regime. Alongside previous studies on other Siderian granitoids in the Quanji Massif, we propose a tectonic evolution model, including (1) plate subduction occurring before 2.44 Ga; (2) a collision occurring from ca. 2.43 to ca. 2.40 Ga; (3) a post-collisional extension occurring from ca. 2.39 to ca. 2.32 Ga. This tectonic evolution reveals that the operation of plate tectonics continued during the Siderian and that a slowdown or pause might have occurred in the Quanji Massif after ca. 2.3 Ga. Unlabelled Image • A 2.48 – 2.44 Ga subduction-related granitoid was recognized in the Quanji Massif. • The A-type granitoid suggests a post-collision setting during 2.38-2.35 Ga. • An orogenic cycle from subduction to collision and then post-orogeny is revealed. [ABSTRACT FROM AUTHOR]