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Tectono‐thermal records older than ca. 1.8 Ga in the North China craton have been poorly resolved given that they have been strongly overprinted by younger events, despite being key to understanding the tectonic evolution of the craton. We report results of monazite Th–U–Pb isochron geochronology via electron probe microanalysis on the Zanhuang massif in the North China craton, to determine its detailed Precambrian tectono‐thermal history. Results suggest that the ca. 2.1 Ga tectono‐thermal event can be divided into distinct ca. 2.17 Ga and ca. 2.10 Ga stages, reflecting metamorphism related to retroarc regional extension of the North China craton. Similarly, the previously established ca. 1.8 Ga metamorphic event can be divided into distinct ca. 1.88 Ga and ca. 1.79 Ma stages. Through a detailed summary and comparison, we interpret that the ca. 1.88 Ga monazite age reflects the timing of peak metamorphism, which was followed by ca. 1.79 Ga retrogression. [ABSTRACT FROM AUTHOR]

[Display omitted] • We report the discovery of a Molybdenum (Mo) porphyry deposit at Shuvuutai, central-east Mongolian. • Molybdenum mineralization spatially and genetically related to Early Permian multi-phase porphyry intrusions. • Ore-forming fluids were initially magmatic and later hydrothermal mineralization evolved with four main stages. • We suggest a new strategy for exploration for Mo and related porphyry deposits in Mongolia and China. We document the newly discovered Shuvuutai Molybdenum (Mo) porphyry deposit located in the central-east Mongolian volcanic/-plutonic belt of the southern Altaids. The deposit is characterized by quartz vein- and veinlet-disseminated-type Mo ore bodies mainly hosted in a Late Permian-Early Triassic granitic intrusion. In this study, we provide a detailed study that integrates detailed geology with petrographic, mineralogic, geochemical, and geochronologic date to determine the tectonic setting of the deposit. Fluid inclusion analysis is used to reconstruct the fluid evolution history of the Shuvuutai Mo mineralization system and to understand the origin of the deposit. The ore bodies occur mainly as veins, lenses, and pods in positions from inner intrusions through contact zones to the host rocks distal to causative intrusions. The host rocks are variable in lithology, including granites, porphyries, volcanic breccias and tuffs, and sedimentary rocks. Outward from ore bodies to host rocks, the wall rock alteration is zoned from potassic (K-feldspar-quartz-mica), through phyllic (quartz-sericite-chlorite-epidote), to propylitic or argillic alterations. Two samples from porphyry stock intrusions at Shuvuutai were selected for U–Pb zircon geochronology and trace element composition studies, including the ore-hosting monzodiorite porphyry and quartz syenite porphyry. Our new ages are consistent with, or slightly postdate published zircon U-Pb ages of early phase of monzodiorite porphyry (268–232 Ma) and the main phase of quartz syenite porphyry (251.6 ± 1.7 Ma). Hydrothermal mineralization generally includes four stages, from early to late, represented by (1) potassic feldspar-quartz veins or veinlets, (2) quartz-molybdenite stockworks, (3) quartz-sulfide stockworks, and (4) quartz ± carbonate veins or veinlets. The ore-forming fluids were initially magmatic in origin and show high-temperature and high-salinity, containing daughter mineral and CO 2 -bearing fluid inclusions; and eventually evolved to low-temperature, low-pressure, low-salinity and CO 2 -poor meteoric water. S isotopic compositions of sulfides from the Shuvuutai Mo porphyry deposit indicate that the source of the ore-forming material was derived from the felsic magma. The Central-Eastern Mongolian volcanic-plutonic belt continues from Mongolia into northeast China, where similar Mo deposits are not yet recognized, suggesting that a new exploration strategy, based on the characteristics and history of the Shuvuutai discovery, is needed for the Chinese segment of the Altaids. [ABSTRACT FROM AUTHOR]

The formation mechanism of the North China Craton (NCC) is controversial, with one model (Model 1) suggesting that it was formed by progressive accretion of arcs by generally westward subduction in the Archean, then progressive outboard accretion via eastward subduction culminating in a N-S collision when the composite craton was amalgamated with the Columbia Supercontinent. In contrast, another popular model (Model 2) suggests that various coherent blocks collided in the Paleoproterozoic, forming a network of Paleoproterozoic (1.9–1.85 Ga) orogens with high-grade metamorphism defining the belts. Here, we test these contrasting models, using big data analysis of detrital zircons from well-exposed Precambrian massifs in the Mesozoic Taihang Mountains of the central NCC (CNCC), that cut across the boundaries of the sutures and tectonic zones proposed by the different models. The zircons record the magmatic and metamorphic history of the basement, and we use big data and spatio-temporal analysis techniques to test the along-strike variations in ages of magmatism and metamorphism, providing quantitative constraints as tests of the models. Simple age peaks can not represent the real magmatic intensity owing to preferential preservation. However, singularity indices, the time-varied indicators of power-law modeling, can characterize the spatiotemporal heterogeneity of mass distribution under unsteady trends. They can provide more stable and reliable time-series distributions. Our results show a multi-stage ladder-shaped evolutionary trend of ε Hf (t) values for igneous-originated detrital zircon during 3.7 to 1.5 Ga, representing progressive amalgamation of the craton, consistent with Model 1. The detrital zircon age singularity index series revealed three high-flux magmatic and two metamorphic events. The first magmatism and metamorphism occurred over almost the entire CNCC but was concentrated at its eastern margin, with an age peak at ca. 2.5 Ga. This event may have been caused by the arc–continent accretion along the eastern margin of the CNCC and the western margin of the Eastern Block as proposed by Model 1. The second magmatism developed primarily in the central CNCC, in the absence of contemporaneous metamorphism at ca. 2.15 Ga. This event reveals a local lithospheric extension that is probably a retroarc event from the convergent margin on the northern margin of the craton, as this event is recorded elsewhere in the NCC outside of the CNCC. The final magmatic event, with a violent fluctuation in the range of ε Hf (t) values and contemporaneous metamorphism, is almost absent in the central CNCC (only 6% data points) but spread throughout the northern and southern CNCC at ca. 1.85 Ga, and represents collisional assembly of the NCC with other outboard continental blocks representing the Columbia Supercontinent, also consistent with Model 1, but inconsistent with Model 2 that invokes the 1.85 collision to be along the full length of the CNCC, not only at its northern or southern margins. The westward migration of magmatic activity and high εHf(t) value centers after 2.5 Ga indicate the occurrence of a new east-dipping subduction system after collision of the Central (Wutai/Fuping) arc, and progressive migration of the orogenic front in the Paleoproterozoic. [Display omitted] • Local singularity analysis is used in the detrital zircon time-series. • Three magmatic and two metamorphic events are identified in central NCC. • εHf(t) time-series reveals the progressive amalgamation. • Period at ∼2.5 Ga should also be an important metamorphic event in the central NCC. • Temporal and spatial analyses indicated progressive outboard accretion of NCC. [ABSTRACT FROM AUTHOR]

Mafic granulitic and amphibolitic boudins dispersed in Archean felsic gneisses are widely distributed in the Central Orogenic Belt (COB) and the Eastern Block of the North China Craton (NCC) and are considered to constitute deformed mafic dike swarms. Previous studies have demonstrated that the mafic dikes in the Zanhuang Complex of the NCC intruded the fabrics of an Archean mélange belt and were boudinaged during younger deformation. Igneous zircons from an undeformed mafic dike yield a 207Pb/206Pb age of 2535 ± 30 Ma, which is interpreted as the crystallization age. In addition, pegmatites cutting across the mafic dikes in the field also yield an igneous zircon 207Pb/206Pb age of 2504 ± 16 Ma, providing strong evidence that the mafic dikes in the NCC intruded during the Neoarchean. Metamorphic zircons from one deformed mafic dike sample yield a metamorphic 207Pb/206Pb age of 2090 ± 83 Ma, and another four samples from deformed mafic dikes have a consistent metamorphic zircon age of ca. 1850 Ma, indicating that the mafic dikes underwent at least two generations of Paleoproterozoic metamorphism of ca. 2.1 Ga and ca. 1.85 Ga. Previously reported trace element systematics of the mafic dikes are consistent with an arc-related lithospheric mantle source region, rather than an ocean island basalt (OIB)-like source region. The new whole rock Nd isotopic composition (ɛNd(t) = + 0.71 to + 3.70) is relatively more evolved compared to that of the depleted mantle at 2.5 Ga, indicating an enriched lithospheric mantle source. Accordingly, the mafic dikes are proposed to have been formed in a subduction-related environment and their enriched mantle source was metasomatized by the melts and fluids derived from the subducted slab. Based on previous studies of the NCC and new geochronological and isotopic data in this contribution, a new comprehensive tectonic model is proposed for the evolution of the NCC between 2.7 Ga and 1.85 Ga: (1) from 2.7 to 2.5 Ga, an oceanic arc terrane belt developed in what is now the COB of the NCC while a passive margin sequence was deposited on the western edge of the Eastern Block on the margin of the intervening ocean; (2) the oceanic arc terrane collided with the passive margin sequence at 2.5 Ga above a west-dipping subduction zone; (3) the subduction polarity was reversed at ca. 2.5 Ga and a new east-dipping subduction zone gave rise to the intrusion of the 2.5 Ga mafic dikes of the NCC; (4) the final collision between the Western Block and the Eastern Block occurred at ca. 2.1 Ga; (5) the whole NCC then collided with the Columbia Supercontinent along the north margin of the craton at 1.9-1.8 Ga. [ABSTRACT FROM AUTHOR]

Abstract: Whether any Grenvillian magmatic records are preserved in the North China Craton (NCC) is a key issue to understand the Proterozoic tectonic evolution of the NCC and its correlation to the supercontinent Rodinia. Meso- to Neo-proterozoic sedimentary series is well exposed in the NCC, but magmatic events in this period, especially of 1.3–1.0Ga, have seldom been reported. New U–Pb isotopic dating and Hf isotopic composition analyses have been carried out in this study using SIMS and LA–ICP-MS methods on detrital zircons from sandstones of the Tumen Group in the Shandong Peninsula and quartz sandstones of the Sangwon System in the Phyongnam Basin, North Korea. The age populations of the detrital zircons of the Tumen Group are at ~2.5Ga, ~1.85Ga, ~1.7Ga, ~1.58Ga, ~1.5Ga, ~1.36Ga and ~1.2Ga and those of the Sangwon System are at 1.88–1.86Ga, ~1.78Ga, 1.62–1.58Ga, 1.46–1.41Ga, ~1.32Ga, ~1.17Ga and ~980Ma. Most of the age peaks of Neoarchean and Proterozoic correspond to the significant tectonic-magmatic-thermal events previously recognized in the NCC, revealing that the main provenances of the Tumen Group and the Sangwon System are Early Precambrian basement and Late Paleo- to Meso-proterozoic magmatic rocks of the NCC. Furthermore, the youngest detrital zircon ages of ~1.1Ga from the Tumen Group and 984Ma from the Sangwon System, as well as 910Ma Rb–Sr whole rock isochron age of a limestone from the Tumen Group and 899Ma mafic sills intruding the Sangwon System suggest that both groups were deposited in the Neoproterozoic, coevally with the Qingbaikou System in the Yanliao Aulacogen. The common zircon ages of 1.3–1.0Ga from the Tumen Group and the Sangwon System, as well as the contemporaneous Penglai and Yushulazi Group in the eastern margin of the NCC, indicate that during the deposition of these sediments there have been significant contributions from Grenvillian magmatic rocks in the eastern NCC. This may provide clues to understand the possible relationship of the NCC and the supercontinent Rodinia. Moreover, the positive εHf (t) and ~2.8Ga crust model ages of detrital magmatic zircons of 2.8–2.4Ga suggest that there have been significant crustal growth at ~2.8Ga in the eastern margin of the NCC, same as in other areas of the NCC. [Copyright &y& Elsevier]

Abstract: The geometry and timing of amalgamation of the North China Craton have been controversial, with three main models offering significantly different interpretations of regional structure, geochronology, and geological relationships. One model suggests that the Eastern and Western Blocks of the NCC formed separately in the Archean, and an active margin was developed on the Eastern Block between 2.5 and 1.85Ga, when the two blocks collided above an east-dipping subduction zone. A second presumes the Eastern Block rifted from an unknown larger continent at circa 2.7Ga, and experienced a collision with an arc (perhaps attached to the western block) above a west-dipping subduction zone at 2.5Ga, and the 1.85Ga metamorphism is related to a collision along the northern margin of the craton when the NCC joined the Columbia supercontinent. A third model suggests two collisions in the Central Orogenic Belt, at 2.1 and 1.88Ga, but recognizes an early undated deformation event. Recent seismic results reveal details of the deep crustal and lithospheric structure that support both the second and third models, showing that subduction beneath the Central Orogenic Belt was west-directed, and that there is a second, west-dipping paleosubduction zone located to the east of the COB dipping beneath the Western Block (Ordos Craton). The boundaries identified through geophysics do not correlate with the boundaries of the Trans-North China Orogen suggested in the first model, and the subduction polarity is opposite that predicted by that model. High-pressure granulite facies metamorphism at 1.85Ga is not restricted to the “TNCO” as suggested by the first model, but is documented across the NCC, as predicted by the second model, suggesting a major continent–continent collision along the north margin of the craton at 1.85Ga. Further, it has recently been shown that in the southern “TNCO”, there is no record of metamorphism at circa 1.85Ga, but only at 2.7–2.5Ga, showing that the “TNCO”, as defined as a circa 1.85Ga orogen, does not exist. This is further confirmed by recent Re–Os isotopic studies which show that the subcontinental lithospheric mantle beneath the southern COB is late Archean in age, and that a province in the northern NCC is circa 1.8Ga, correlating with the proposed collision belt of the NCC with the Columbia supercontinent across the entire NCC. The COB is an Archean convergent belt, re-worked in the Paleoproterozoic, and the Paleoproterozoic tectonism is widespread across the NCC, as predicted by the model whereby the previously amalgamated Eastern and Western Blocks experienced a continental collision with Columbia at circa 1.85Ga, but uplift/exhumation rates are slow, necessitating a re-evaluation of the tectonic models of the NCC. [Copyright &y& Elsevier]

Abstract: Along the Qinling–Dabie–Sulu orogenic belt in China crops out the world''s largest terrane composed of ultrahigh-pressure (UHP) metamorphic rocks. Differences in the timing and mechanisms of oceanic and continental subductions are assumed to be responsible for different ages of high-pressure (HP) and UHP slices in different parts of the belt. The western part of the Dabie orogen (western Dabie terrane) holds a key to understanding of the transition from oceanic to continental subduction. This paper reports geochronological results to test a two-stage tectonic model for the exhumation of HP/UHP rocks in western Dabie. This model involves two different stages and types of extrusion for exhumation of the HP/UHP rocks in east-central China. Mica Ar/Ar ages, ranging from 241 to 231Ma, indicate a general middle Triassic cooling probably driven by early upward extrusion during the collision between the North and South China Blocks. Late Triassic–Early Jurassic cooling was associated with later eastward extrusion, ranging from 200 to 184Ma. The second event is recorded also in mica in the region that was not affected by later deformation and magmatism. The lateral movement along lithosphere-scale faults resulted in the eastward extrusion of the HP–UHP metamorphic terrane, which was followed, in the Late Triassic–Early Jurassic time, by a major compressive event. These two extrusion events are correlative with the two stages of Triassic exhumation of the western Dabie HP–UHP rocks, respectively. Wintin the framework of the Qinling–Dabie–Sulu orogenic belt, it is suggested for western Dabie that the subduction/exhumation of blueschist-facies unit is related to the Mianlue suture, whereas the subduction/exhumation of HP/UHP eclogite-facies units is related to the Shangdan suture. [Copyright &y& Elsevier]

The Kuwei mafic intrusion, consisting of hornblende gabbro, gabbro, gabbro norite, and olivine norite, lies in the southern Altai Mountains, northern Xinjiang. A combined field, geochronological, and geochemical study of the Kuwei intrusion is reported here. This study provides the first reliable SHRIMP U-Pb zircon dating results for the intrusion, and these yielded an age of 47 ± 1 Ma, which is the first documented report of Eocene magmatism in the region. The chondrite-normalized rare earth element patterns for the Eocene intrusions are flat, and most of the incompatible elements are comparably depleted. Thus, geochemical data suggest that the Kuwei mafic intrusion was produced by partial melting of asthenospheric mantle that was slightly contaminated by lithospheric material. We interpret the 47-Ma magmatism to result from asthenospheric mantle upwelling following the progressive India- Eurasian collision. Although the Kuwei intrusion is laterally beyond the limit of Eocene deformation normally attributed to the India-Asia collision, the timing of magmatism in the intrusion suggests that lateral extension may have initially affected a wider region than the area later thickened by convergence in the Tibetan Plateau. The Kuwei intrusion and other plutons likely related to it may have been emplaced into dilational jogs in fault systems activated by the India-Asia collision. The emplacement depth is estimated to be ∼6 km, based on geobarometric determinations. Erosion was imperceptible before 25 Ma but has worn away an average of 0.024 cm of uplift every year since 25 Ma. The 6 km of exhumation since the late Oligocene is also attributed to far-field effects of the India-Asia collision. [ABSTRACT FROM AUTHOR]

The Archean North China Craton consists of two major blocks, separated by the Central Orogenic Belt. The age of collision of the two blocks along the Central Orogenic Belt is controversial. Some models suggest that the Archean blocks collided at 1.8 Ga, during the Luliang Orogeny (1.7–1.9 Ga). In this model, high-pressure granulite facies metamorphism accompanied collision at 1.8 Ga. Other models have suggested that the Eastern and Western Blocks collided at 2.5 Ga, soon after 2.6–2.5 Ga ophiolitic and arc rocks throughout the orogen were formed. We synthesize the geology, geochronology, and tectonics of the Neoarchean through Mesoproterozoic evolution of the North China Craton. We suggest that the Eastern and Western Blocks collided at 2.5 Ga during an arc/continent collision, forming a foreland basin on the Eastern Block, a granulite facies belt on the western block, and a wide orogen between the two blocks. This collision was followed rapidly by post-orogenic extension and rifting that formed mafic dike swarms and extensional basins along the Central Orogenic Belt, and led to the development of a major ocean along the north margin of the craton. An arc terrane developed in this ocean, and collided with the north margin of the craton by 2.3 Ga, forming a 1400 km long orogen known as the Inner Mongolia–Northern Hebei Orogen. A 1600 km long granulite-facies terrain formed on the southern margin of this orogen, representing a 200 km wide uplifted plateau formed by crustal thickening. The orogen was converted to an Andean-style convergent margin between 2.20 and 1.85 Ga, recorded by belts of plutonic rocks, accreted metasedimentary rocks, and a possible back-arc basin. A pulse of convergent deformation is recorded at 1.9–1.85 Ga across the northern margin of the craton, perhaps related to a collision outboard of the Inner Mongolia–Northern Hebei Orogen, and closure of the back arc basin. This event caused widespread deposition of conglomerate and sandstone of the basel Changcheng Series in a foreland basin along the north margin of the craton. At 1.85 Ga the tectonics of the North China Craton became extensional, and a series of aulacogens and rifts propagated across the craton, along with the intrusion of mafic dike swarms. The northern granulite facies belt underwent retrograde metamorphism, and was uplifted during extensional faulting. High pressure granulites are now found in the areas where rocks were metamorphosed to granulite facies and exhumed two times, at 2.5 and 1.8 Ga, exposing rocks that were once at lower crustal levels. Rifting led to the development of a major ocean along the southwest margin of the craton, where oceanic records continue until 1.5 Ga. [Copyright &y& Elsevier]

[Display omitted] • Three episodes of Neoproterozoic magmatism in the Jiangnan orogen are identified. • More depleted materials were involved in post-820 Ma magmatism. • Extensive slab failure magmatism occurred after ~790 Ma. • Large-stage crustal growth induced by slab failure probably exceeded growth by arc magmatism. The Neoproterozoic NE-striking Jiangnan orogen in the South China Block (SCB) separates the Cathaysia microcontinent on the southeast from the Yangtze craton in the northwest. The origin and evolution of the Jiangnan orogen is unresolved, with individual models explaining part of the history, such as various magmatic, deformational, metamorphic, and sedimentary events including extensional, contractional, and transpressional modes. Here, we present detailed geochronological and Nd-Hf isotopic data for Neoproterozoic mafic and felsic intrusions in the Jiangnan orogen and identify three episodes of Neoproterozoic magmatism. The first stage ranging from ~1013–942 Ma is preserved predominantly in the eastern segment of the orogen, including a series of mafic rocks with ages of ~1010–952 Ma, contrasting with weak magmatic activity in the western segment with a peak at ~997 Ma. The second stage ranges from ~906 Ma to ~820 Ma, with intensive and extensive bimodal magmatism occurring in the eastern and western parts. The last stage mainly occurred in the western Jiangnan orogen in the period from ~800 to 780 Ma, associated with drastic mafic magmatism and weakly bimodal volcanic activities. The bimodal volcanism in the eastern segment exhibits a striking weak trend after ~823 Ma, distinctly different from the western segment where the magmatism lasted until ~785 Ma, indicating its syn- to post-collisional in nature. The pre-800 Ma magmatic rocks in western Jiangnan orogen have a dominant negative Nd isotopic signature but exhibit a significant positive trend after 800 Ma, different from those in east, which have a decreasing trend. Both parts display a roughly decoupled Nd-Hf isotopic character presented by a dominant positive pattern in Hf isotopes of the Neoproterozoic intrusive rocks, indicating a significant addition of previous slab-derived components or accretionary wedges in the pre-800 Ma magma evolution, and more depleted materials involved in the source in the later stages. Oceanic subduction under the northwestern Cathaysia Block occurred around ~1.0 Ga, slightly earlier than the subduction to the southeastern Yangtze. A gradual tectonic transition from post-orogenic extension to intracontinental rifting dominated the tectonics in Jiangnan orogen in the middle-late Neoproterozoic, followed by slab failure after ~790 Ma. Arc magmatism was the dominant source of crustal growth before 820 Ma in the SCB, but was exceeded in volume by later slab failure magmatism after ~790 Ma. [ABSTRACT FROM AUTHOR]

• We document a Neoarchean paired metamorphic belt in the southern North China Craton. • Intermediate T / P metamorphism is consistent with thermal models of 'warm' subduction zones. • Our results support the operation of plate tectonics at the end of the Archean. Paired metamorphism is the hallmark of asymmetric subduction at Phanerozoic convergent plate margins, yet spatially and temporally linked paired metamorphic belts have rarely been documented in the Archean rock record. Here, we investigate the Neoarchean Dengfeng Complex, a typical granite–greenstone belt in the southern part of the North China Craton (NCC). Using petrography, geochronology, and phase equilibrium constraints on rocks from different lithostructural units, we suggest the ca. 2.54–2.50-Ga Dengfeng Complex represents a remnant of a spatially and temporally linked Neoarchean paired metamorphic belt. In the western part of the complex, a garnet amphibolite from a dominantly metabasic unit (MBU) records near peak P – T conditions of 6.3–10 kbar and ∼675–750 °C, corresponding to a high thermobaric ratio (T / P) of ∼720–1200 °C/GPa. Tonalite–trondhjemite–granodiorite (TTG) gneisses preserve evidence for partial melting, also consistent with relatively high T / P (∼875–1400 °C/GPa). In the eastern part of the Dengfeng Complex, two garnet amphibolites and three garnet quartz–mica schists from a dominantly metasedimentary unit (MSU) record peak P – T conditions of >9.8 kbar and ∼525–655 °C, corresponding to intermediate thermobaric ratios of ∼425–600 °C/GPa. Zircon and titanite U–Pb dating, coupled with existing ages of post-kinematic intrusions, constrain the metamorphic age to ca. 2.52–2.50 Ga. The metamorphic P – T data indicate that the MSU was buried to >30 km then exhumed to the near-surface by the early Paleoproterozoic. Our metamorphic results, when combined with recent structural and geochemical data, suggest the Dengfeng Complex records Neoarchean paired metamorphism, in which the higher thermal gradients reflect the arc–forearc region and the lower thermal gradients correspond to the accretionary complex. Our data indicate that the southern NCC experienced accretionary-to-collisional orogenesis with intra-oceanic subduction, forearc accretion (ca. 2.54–2.50 Ga), and subsequent arc–continent collision (ca. 2.50–2.47 Ga). The recognition of paired metamorphism in the NCC is consistent with widespread subduction and the operation of a plate tectonic regime in the late Archean. [ABSTRACT FROM AUTHOR]

The source characteristics and depositional environments of banded iron formations (BIFs) can provide key information on the chemical composition, redox environment, and tectonic evolution of early Precambrian paleo-oceans. Large quantities of Neoarchean to Paleoproterozoic BIFs are exposed in the North China Craton (NCC). This study focuses on petrography, major and trace element geochemistry, zircon U-Pb geochronology, and Sm-Nd isotopic compositions of a set of Neoarchean BIF-bearing sedimentary rocks preserved in the Zanhuang Massif of the NCC, including comparison with Archean to Paleoproterozoic BIFs throughout the NCC. This study provides constraints for deciphering the paleo-ocean chemical composition, redox environment and relationship between the geological-environments co-evolution and the formation of the BIFs in the NCC. The Zanhuang BIFs are mainly composed of quartz and magnetite, with small amounts of grunerite, actinolite (ferroactinolite) and garnet in the Fe-rich bands, and are classified as Algoma-type. Zircon U-Pb ages of the metasedimentary rocks interbedded with the BIFs indicate that the Zanhuang BIFs formed at ∼2.51 Ga and were subjected to metamorphism at ∼2.47–2.48 Ga. Most BIFs have low contents of Al 2 O 3 , TiO 2 and high field strength elements Zr, Hf, Th and U, indicating that they are pure chemical sedimentary rocks. The BIFs are characterized by depleted light rare earth elements (LREEs) and positive La and Y anomalies, which are similar to the geochemical characteristics of modern seawater. The absence of Ce anomalies and the low (Pr/Yb) SN ratios indicate an anoxic state of the ocean. The Zanhuang BIFs precipitated from a mixture of minor high-temperature hydrothermal fluids and seawater mixed with continent-derived freshwater (∼10–20%) or other additional fluids such as ocean crust-derived fluxes indicated by Eu anomalies and Y/Ho and Sm/Yb ratios. The variable initial ε Nd (t) values of Zanhuang BIFs suggest complex and dynamic input of continental crustal fluxes. The statistical comparison with other BIFs shows that the peak formation ages of the Archean to Paleoproterozoic BIFs in the NCC is ∼2.54 Ga. Most of the BIFs in the NCC are Algoma-type, while a few Paleoproterozoic BIFs are Superior-type. A mixture of <0.1%–1% of modern seafloor high-temperature hydrothermal and seawater can account for the REE + Y characteristics of the BIFs, while ε Nd (t) values suggest possible contributions from continental sources. The Eu anomalies indicate that ∼2.7 Ga and ∼ 2.55 Ga are the two peaks of submarine hydrothermal and magmatic activities of the NCC, which correspond to crustal growth and subduction-collision events in the NCC, respectively. The Ce anomalies and Fe isotopes indicate the transition from an anoxic ocean with possible regional oxygen oases before 2.5 Ga to a redox-stratified ocean during the GOE. Most Neoarchean BIFs of the NCC were formed in island arc-related tectonic settings, while the Paleoproterozoic BIFs likely reflect environments of rifting to subduction in the NCC. [ABSTRACT FROM AUTHOR]

We document for the first time the presence of a Paleoproterozoic ophiolitic mélange in the Archean–Paleoproterozoic Kongling Complex in the northern Huangling Dome, Yangtze craton, South China. Detailed field mapping, petrographic, geochronological and geochemical studies reveal that the mélange consists of a suite of amphibolite facies mafic and ultramafic tectonic blocks including serpentinized harzburgite, olivine pyroxenite, pyroxenite, diabase, gabbro and basalt dispersed in a strongly sheared metasedimentary matrix. The mélange displays polyphase deformation and northwest-verging nappe structures, and underwent amphibolite to granulite facies metamorphism in the Paleoproterozoic (2.0–1.95 Ga). The metasedimentary rocks are composed mainly of garnet-biotite-plagioclase gneiss, mica schist, mica-graphite schist, marble, quartzite, and banded iron formation (BIF). The mafic–ultramafic rock association shares the lithological and geochemical characteristics of Phanerozoic suprasubduction zone ophiolites. LA-ICP-MS U–Pb dating of zircons from the diabase yield ages between 2142 and 2148 Ma for the magmatic cores and between 2042–2048 Ma for the metamorphic rims. Zircon cores have ε Hf (t) values ranging from +5.4 to +10.3 (average = +7.2) with corresponding T DM1 ages of 2.24 Ga, indicating that these rocks are remnants of juvenile crust derived from the depleted mantle at ca. 2.2 Ga. All rock types in the mélange underwent Paleoproterozoic (2.0–1.95 Ga) amphibolite–granulite facies metamorphism and were intruded by syn-metamorphic granite (∼2.0 Ga), post-collisional (ca.1.85 Ga) granite and mafic dykes. Intrusion age of one quartz monzonitic dyke crosscutting the serpentinized harzburgite is 1999 Ma, constraining the minimum emplacement age of the mafic–ultramafic complex. The mafic–ultramafic rocks within the metasedimentary matrix in the northern Huangling Dome are fragments of a ca. 2.15 Ga suprasubduction zone ophiolite that was incorporated into the suture zone during the accretionary-collisional process. The mélange recognized in the northern Yangtze craton provides important evidence for the Paleoproterozoic subduction and accretion processes possibly associated with the amalgamation of the proposed Columbia supercontinent. [ABSTRACT FROM AUTHOR]

Abstract: Two layers of basaltic flows intercalated with Late Neoproterozoic (Sinian) sandstones have been identified in the Sugetbrak region in the northwest Tarim block, Northwest China. The basaltic rocks are composed of augite and plagioclase phenocrysts set in a groundmass of plagioclase laths with interstitial subophitic clinopyroxene grains and minor anhedral opaque minerals (magnetite and ilmenite). LA-MC-ICP-MS U–Pb dating of zircons from the lower basaltic flows yields a crystallization age of 783.7±2.3Ma. Both layers of the basaltic rocks are characterized by low SiO2 and high total FeO (>12wt.%), TiO2 (>3wt.%) and P2O5 (>0.5wt.%) contents and extremely high Na2O/K2O ratios, and display a Fenner trend of differentiation that could be ascribed to significant fractional crystallization of clinopyroxene and plagioclase. The mineralogical and geochemical characteristics suggest the affinities of a transitional series between alkaline basalt and tholeiite. However, the lower basaltic flows have higher Nb/Y ratios than the upper ones, indicating that they are more alkaline. Positive age-corrected Nd isotope ratios [ɛ Nd(t)=+0.24–1.07] and positive ɛ Hf(t) values (+1.1–4.5) of the basaltic rocks suggest absence of any significant crustal contamination. High ɛ Nd(t) lavas are isotopically similar to those of several modern oceanic hotspots, and have ocean island-like patterns of incompatible elements. The estimated potential mantle temperature is ∼100–150°C higher than normal asthenospheric mantle, consistent with a plume-head origin. Moderate ratios of light rare earth elements (REE) to heavy REE indicate that the source magma was probably generated by partial melting of garnet–spinel transition facies of peridotite, but the upper basaltic rocks were derived from a relatively shallower mantle source, reflecting progressive lithosphere thinning possibly through plume–lithosphere interaction. We correlate the Sugetbrak basalts to the second Neoproterozoic mantle plume event (780–745Ma) related to the breakup of the Rodinia supercontinent. [Copyright &y& Elsevier]

Abstract: The Tongbai–Dabie Orogenic Belt (DOB) is composed of several fault-bounded terranes with different metamorphic and deformation intensities. These tectonically stacked terranes were extruded along their boundary faults from depths of >120km during the Mesozoic. Systematic structural studies on these boundary faults can provide important information for the exhumation processes of the orogen. In this paper, we focus on the Xincheng–Huangpi fault (XHF) which is located along the southern boundary of the central DOB ultrahigh-pressure complex unit (UC) Comprehensive macro- and micro-structural, U/Pb zircon and 40Ar/39Ar geochronological data are presented here to constraint the structural chronology of the XHF. The XHF represents the lower detachment surface formed during extrusion of the UHP slab and experienced two episodes of ductile shearing. The XHF experienced early southwestward thrusting around 234Ma and was exhumed to middle crustal levels during 234–195Ma with an average exhumation rates of ca. 1.5mm/yr. The UHP rocks then exhumed to the surface by erosion. Later NW–SE trending dextral strike-slip shearing of the XHF occurred between 145 and 140Ma and was generally contemporaraneous with sinistral-oblique slip of the Xiaotian–Mozitan fault along the northern margin of the UC. Coeval dextral and sinistral-oblique shearing along the southern and northern margins of the UC would have caused southeastern lateral extrusion. This lateral extrusion has no relationship with the UHP exhumation. [Copyright &y& Elsevier]

Abstract: The South Tianshan Collisional Belt (STCB), formed by the collision between the Tarim and Central Tianshan blocks, is pivotal for understanding the complex and prolonged tectonic evolution of the Central Asian Orogenic Belt (CAOB). The Chuanwulu complex is located in the eastern part of the STCB, Xinjiang province, NW China. It consists of a gabbro–diorite unit (unit I) and a monzonite–syenite unit (unit II), which are both cut by some granite dykes (unit III). Based on LA-ICP-MS U–Pb zircon dating, the units I and II were emplaced at 287.8±4.3Ma and 286.4±2.5Ma, respectively. The SiO2 contents of the samples from the complex display a wide range from 50.52wt.% to 70.64wt.%, and most samples are of alkaline affinities. The magma mixing process during the formation of the complex is suggested by considerable petrographic and geochemical evidence such as mafic microgranular enclaves (MEEs) that occur within unit II, disequilibrium textures, linear negative correlations between SiO2 and some major elements, and a wide range of (87Sr/86Sr)t ratios and δ18OSMOW values. Unit I is characterized by relatively low SiO2 contents (50.52–55.05wt.%), high MgO contents (3.29–5.43wt.% with Mg# =0.50–0.56), high Sr contents (1646–3101ppm), pronounced negative Nb–Ta anomalies and light rare earth element (LREE) enrichment. In combination with their isotopic compositions [(87Sr/86Sr)t =0.70543–0.70751, εNd (t)=−2.3 to −1.8, δ18OSMOW =5.7–9.4‰, εHf (t)=0.2–4.9], these features indicate that they are derived from an incompatible element-enriched lithospheric mantle. The SiO2 contents of units II and III range from 58.88wt.% to 65.91wt.% and 67.10wt.% to 70.64wt.%, respectively. They exhibit pronounced positive Zr–Hf anomalies and negative P and Ti anomalies, and relatively elevated Sr and O isotopic compositions [(87Sr/86Sr)t =0.70543–0.70751, δ18OSMOW =8.9–9.1‰]. In addition, samples of unit III have high Sr (600ppm to 1201ppm) contents and Sr/Yb (373 to 1905) and low Y/Yb (8 to 12) ratios. The felsic rocks (units II and III) have a “C-type” adakite-like geochemical signature and are comparable with those of rocks derived from an ancient garnet-bearing amphibolite facies lower crust. Our study, complied with other geological evidence, indicate that the collision between the Central Tianshan and Tarim blocks and the final amalgamation of the CAOB should have occurred during Late Carboniferous. On the regional scale, we propose that the recycling of ancient lithosphere is the predominant mechanism which is able to account for Phanerozoic continental evolution in STCB, differing from other tectonic units in CAOB. [Copyright &y& Elsevier]

The Beyşehir-Hoyran Nappes, including Mesozoic carbonate platform rocks, deepsea sediments, and ophiolite-related units, crop out extensively on the western limb of the Isparta Angle in the Central Taurides, Turkey. The ophiolite-related rocks are represented by variably serpentinized harzburgitic mantle tectonites, tectonically underlain by a subophiolitic metamorphic sole and mélange. The harzburgitic mantle tectonites and metamorphic sole are intruded by undeformed isolated dikes. Protoliths of the metamorphic sole are similar to within-plate alkali basalts and associated sediments. The isolated dikes were geochemically derived mainly from tholeiitic magma and, to a lesser extent, from alkaline magma. Five isolated dike samples yielded U-Pb ages ranging from 90.8 ± 1.6 Ma to 87.6 ± 2.1 Ma (zircon) and from 102.3 ± 7.4 Ma to 87.5 ± 7.9 Ma (titanite). Seven amphibolite samples yielded U-Pb age ranges of 91.1 ± 2.1-88.85 ± 1.0 Ma (zircon) and 94.0 ± 4.8-90.0 ± 9.4 Ma (titanite) and a 40Ar-39Ar age range of 93.7 ± 0.3-91.4 ± 0.4 Ma (hornblende). U-Pb and 40Ar-39Ar ages of mineral phases with different closure temperatures (~900-500 °C) from the isolated dikes and metamorphic sole rocks are almost identical and overlapping within 1σ, suggesting that both the magmatic growth of oceanic crust and formation of metamorphic sole were contemporaneous and cooled very rapidly. Hence, all the data should be interpreted as the crystallization ages of the ophiolite and metamorphic sole pair. Genesis of suprasubduction zone-type oceanic crust, genesis and exhumation of the metamorphic sole, and postmetamorphic dike emplacement within the Inner Tauride Ocean can be best explained by subduction initiation and rollback processes during the Late Cretaceous based on petrological and geochronological data obtained from the ophiolitic rocks of the Beyşehir-Hoyran Nappes. [ABSTRACT FROM AUTHOR]

The early Precambrian crustal evolution of the Yangtze craton, especially the Paleoproterozoic orogenic event, has drawn great attention. The early Precambrian magmatism in the Archean-Palaeoproterozoic basement Kongling complex is critical for understanding the early Precambrian tectonic evolution of the Yangtze craton. We report the presence of two distinct groups of Paleoproterozoic felsic rocks in the Kongling complex, providing new insights into the Paleoproterozoic orogenic event in the northern Yangtze craton. Group 1 is composed mainly of deformed or weakly-deformed monzogranite, syenite, and quartz monzonite, and formed at 2.0–1.95 Ga. They have high Sr/Y (60–71) and La/Yb cn (32–464) ratios and are inferred to have equilibrated with garnet-rich residues, suggesting that they have been generated by partial melting of thickened continental crust. Group 2 is represented mainly by undeformed to weakly-deformed K-feldspar granitic rocks, with minor rhyolites, and was emplaced at 1.87–1.84 Ga. In contrast to Group 1, Group 2 rocks display flat HREE patterns and large negative Eu, Sr and Ti anomalies, with low Sr/Y (<10) and La/Yb cn (16–21) ratios. Group 2 rocks have a typical A-type affinity with high Ga/Al ratios (2.83–3.82), and high crystallization temperatures (850–950 °C). Group 2 rocks are interpreted to have been derived from relatively shallow partial melting of thin continental crust during post-orogenic collapse, which marked lithospheric extension of the Yangtze craton in the late Paleoproterozoic (ca. 1.85 Ga). Zircons from Group 1 rocks have ε Hf (t) values ranging from −9.4 to −14.9, whereas zircons from Group 2 rocks have lower ε Hf (t) values ranging from −14.2 to −20.6. Both groups have similar two-stage Hf model ages ranging between 3.2 and 3.6 Ga. The production of the two groups of granitoids in the Huangling dome is ascribed to the reworking (dehydration melting) of Archean rocks in the Paleoproterozoic. Widespread Paleoproterozoic magmatism and metamorphism indicate that the Yangtze craton experienced an orogenic event at ca. 2.0 Ga and subsequent orogenic collapse caused by lithospheric extension at ca. 1.85 Ga. • The 2.0–1.95 Ga granitoids represent syn-collisional magmatic rocks. • ~1.85 Ga A-type granitoids were formed during post-orogenic lithospheric extension. • They were both originated from the reworking of Archean continental crust. • We proposed Paleoproterozoic (~2.0 Ga) collision orogeny within the Yangtze craton. [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]

We present new field observations, whole-rock major and trace elements, Sr-Nd-Pb-Hf isotopes and zircon U Pb ages for the Mesozoic granites in the Mufushan complex, eastern South China. The age determinations by LA-ICP-MS U Pb dating of zircons indicate that the porphyritic biotite granites and two-mica monzogranites have ages of ∼136 Ma and ∼ 130 Ma, respectively. These granites display highly evolved S-type granite geochemical characteristics, with high SiO 2 (70–74 wt%) contents, high 10000*Ga/Al ratios (2.3–3.2, average of 2.8) and weakly peraluminous (A/CNK > 1.1). Both types of granites are enriched in large ion lithophile elements (LILEs, e.g., Rb, K, Ba, Sr) and depleted in high field strength elements (HFSEs, e.g., Nb, Ta, Ti), with negative anomalies of Eu and positive anomalies of Pb, which are akin to continental arc rocks. The two-mica monzogranites have high 87Sr/86Sr (i) (0.71355–0.71535), 206Pb/204Pb (i) (18.105–18.157), low ε Nd(t) (−9.1 to −9.6) and ε Hf(t) (−4.1 to −10.4), similar to those of the porphyritic biotite granites which are characterized by high 87Sr/86Sr (i) (0.717337–0.71692), 206Pb/204Pb (i) (18.134–18.580), low ε Nd (t) (−9.1 to −9.7) and zircon ε Hf(t) (−6.8 to −3.3). The similar emplacement ages and mineral assemblages as well as Sr-Nd-Hf isotopic signatures indicate their derivations were likely derived from a common magma source. These early Cretaceous granites yield two-stage Nd model ages of 1.6–1.7 Ga, similar to the two-stage Hf model ages of 1.3–1.8 Ga. The presence of Neoproterozoic and subordinate Mesoproterozoic zircons within the granitic rocks suggest a significant contribution of ancient crustal materials involved in the genesis of the magmas. In combination with comprehensive studies on the magmatic rocks, the early Cretaceous Mufushan granitic rocks may have experienced an extensive enrichment process, contemporaneously with partial melting of the Neoproterozoic volcanic-sedimentary sequences that produced the arc-like rocks. Almost simultaneously, an extensional event caused by the subduction and slab roll-back of the Paleo-Pacific plate (Izanagi plate) dominates the middle-late Mesozoic tectonics in eastern South China. This extensional regime was accompanied by the underplating of mantle-derived magma and crustal melting, producing the widespread early Cretaceous granites in adjacent regions. The development of coeval basin-and-range structures with the production of contemporaneous magmatic rocks and related polymetallic deposits in eastern South China are all related to slab roll-back tectonics. [Display omitted] • The S-type granites in Mufushan have U Pb ages ranging from 136 Ma to 130 Ma. • Neoproterozoic crustal materials greatly contributed to the formation of the granites. • An extensional regime dominated the early Cretaceous tectonics in eastern South China. [ABSTRACT FROM AUTHOR]

Constraining the timing of tectonothermal events in the Proterozoic Miaowan Ophiolite Complex (MOC) and associated rocks in the southern Huangling dome, Yangtze craton, is critical for understanding late Mesoproterozoic and Neoproterozoic tectonic evolution (ca. 1.2–0.9 Ga) of South China and its relationship with the formation of the Rodinian supercontinent. The MOC consists of metamorphosed dunite and harzburgite, isotropic and layered gabbros, diabasic sheeted dike, basalt, plagiogranite, and calc-silicate-bearing siliceous and carbonaceous mylonitic rocks. In this study, we present new field, petrographic, geochemical, geochronological and isotopic data for these metasedimentary rocks and mylonitic metasandstone between the ophiolite and underlying flysch sequence, to unravel their origin and tectonic significance for the Yangtze craton. The MOC and associated sedimentary rocks underwent amphibolite facies metamorphism. Geochemical data and field relationships indicate that the mylonitic metasandstone was derived from both the autochthonous rocks of the underlying Yangtze craton and the allochthonous MOC during the accretion of the ophiolite to the craton. The calc-silicate-bearing siliceous and carbonaceous rocks are interpreted as tectonic slices of metasomatized and mylonitized chert and limestone, respectively, deposited on the basaltic crust in a Neoproterozoic ocean. Cores of igneous detrital zircons in the calc-silicate-bearing siliceous and carbonaceous mylonitic rocks have yielded two distinct age groups including a 967–1105 Ma (Mean = 1009 Ma) group and a 1011–1095 Ma (Mean = 1054 Ma) group. The majority of initial ε Hf ( t ) values (+9.2 to +14.1) in the zircon cores are similar to those of zircons from the gabbro, diabase and plagiogranite in the MOC, indicating that zircons in the mylonitic rocks were mainly derived from the MOC. Metamorphic overgrowth ages in zircon rims suggest that the latest tectonothermal event in the Precambrian basement rocks of the Yangtze craton took place between 942 and 935 Ma. These metamorphic ages are comparable to those of the Grenvillian-aged collisional events recorded in orogenic belts worldwide. Accordingly, we suggest that this youngest tectonothermal event represents the latest amalgamation time of the heterogeneous tectonic blocks of the Yangtze craton, which were associated with the assembly of the Rodinian supercontinent. [ABSTRACT FROM AUTHOR]

40Ar/39Ar laser incremental heating analyses of supergene K-Mn oxides from weathering profiles at the Baye Mn deposit, southern Yunnan Plateau, SW China, were carried out to place constraints on the timing of weathering and derive insights into local paleoclimatic and landscape evolution. Weathering profiles in the Baye Mn mine are dominated by 20-30 m thick saprolites, which are locally covered by unconsolidated alluvial deposits. We analyzed 70 grains from 35 hand samples collected from four sites located at distinct elevations. In most cases, different grains from the same hand sample and different samples from the same site have reproducible 40Ar/39Ar plateau ages. The plateau ages of individual grains are also consistent with the respective isochron, integrated, and ideogram ages. This age consistency attests to the reliability of the geochronological results as numerical constraints on the formation and evolution of these weathering profiles. Sixty-four grains from 32 hand samples collected from weathering profiles at four sites (A to D) yield well-defined plateau or pseudoplateau ages ranging from 2.98 ± 0.07 to <0.16 Ma (2σ). The age results show that Mn oxides become progressively younger towards lower elevations: samples collected from the highest elevation site (∼1855 m a.s.l.) have the oldest ages at 2.98 ± 0.07 to 2.83 ± 0.13 Ma; samples from intermediate elevations (1821 to 1815 m a.s.l.) yield ages ranging from 2.91 ± 0.10 to 2.08 ± 0.11 Ma; and those from the lowest sites (1768 to 1753 m a.s.l.) are younger than 1.25 ± 0.08 Ma. The age versus elevation relationship indicates fast downward propagation of weathering front since the late Pliocene, and permits estimating the weathering rates at 3.3 ± 3.8, 6.6 ± 1.2, and 11.1 ± 1.9 m Myr−1 during the time periods of 2.98-2.83, 2.91-2.08, and 1.25 to <0.16 Ma, respectively. The average river incision rates estimated from the surface exposed ages range from 235 ± 10 to 416 ± 19 m Myr−1 during the past 3 million years. The incision rate calculated from minimum exposed ages at sites B-D is 33 ± 2 m Myr−1 for the time period of 2.91-1.25 Ma, which is consistent with the slow incision of streams on the ridges over the Yunnan Plateau since the early Pleistocene. Three Mn oxide pebbles contained in the alluvial deposits overlying the saprolite-dominated weathering profiles at the two highest sites provided additional information on the timing of weathering. Four grains from two pebbles yield plateau ages of 6.32 ± 0.19 to 5.27 ± 0.10 Ma, whereas the other two grains from the third pebble indicate the minimum formation ages of 8.2 ± 0.4 and 9.3 ± 0.3 Ma. These ages confirm the existence of older weathering profiles, now dismantled, in the region. Manganese oxide 40Ar/39Ar ages of the Baye deposit, when combined with results from other localities, indicate that lateritic weathering and supergene Mn enrichment and, by inference, warm and humid climates conducive to intense weathering have prevailed over the Plateau since the middle to late Miocene. The climatic conditions inferred from the weathering geochronology are consistent with multiple independent marine and terrestrial sedimentary and paleontological records, confirming that supergene Mn oxides can be used as a useful proxy for past climate. Age clusters of Mn oxides at 2.9-2.4, 1.2-0.8, and 0.6-0.4 Ma are broadly coincident with and thus likely reflect intensification events of the Indian Summer Monsoon that brings moisture and abundant precipitation to the Yunnan Plateau. These clusters also coincide with the periods of significant surface uplift in the Yunnan Plateau, demonstrating a causal link between topographic evolution, plateau uplift, and intensification of the monsoonal climate. [ABSTRACT FROM AUTHOR]

The North China Craton (NCC) consists of Neoarchean to Paleoproterozoic basement, with rare Eo-Paleoarchean crustal relicts. However, the Precambrian tectonothermal evolution of the Central Orogenic Belt (COB) of the NCC is still hotly debated. In this contribution, we present new results of field-based litho-structural analysis, Th-U-Pb geochronology of accessory minerals including zircon, titanite and monazite from paragneiss and marble in a passive margin sequence in the Zanhuang Massif of the COB. Field studies show that two generations of deformation events occurred in the Zanhuang Massif. The earlier deformation is widely distributed in the entire Zanhuang Massif and developed with a top-to-SE shear sense resulting in foliation of the micaschist, metavolcanic rock, marble and paragneiss. The latter deformation is locally occurred in the central Zanhuang Massif and developed with a top-to-SW shear sense represented by the faulting and folding events which are similar to the fold-and-thrust structures of accretionary wedge during the formation of Zanhuang mélange. Zircons from paragneiss yield single-peak age populations with mean ages of 2.52 and 2.51 Ga, and a metamorphic age of 1.84 Ga. Zircon ages from marble are divided into four groups including a main peak of 2.54 Ga, two older groups of 2.77–2.82 and 2.60–2.70 Ga, and a younger metamorphic age of 1.81 Ga. Titanites from paragneiss and marble yield mean metamorphic ages between 1.94 and 1.88 Ga, representing an earlier thermal event. Monazites from paragneiss yield an isochron age of 1.80 Ga, representing a later thermal event. Based on our new litho-structural observations and geochronological data, coupled with previous studies, we suggest that the paragneiss and marble from the marble-siliciclastic unit represent the passive margin sequence, and were mainly deposited at 2.51–2.50 Ga. In addition, the Zanhuang Massif has experienced two tectonothermal events at ca. 1.94–1.88 Ga and ca. 1.83–1.80 Ga, which are widely distributed in the entire NCC, but gradually become weaker from north to south. [ABSTRACT FROM AUTHOR]