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(Colour online) (a) Sketch map of part of the Dabie orogen modified from Bryant et al. (2004), with insert showing the location of this area within the Triassic Qinling–Dabie–Sulu orogenic belt in east-central China (red solid line indicates study area); (b) geological map of the Tiantangzhai intrusive complex showing sample locations and weighted average zircon 206 Pb– 238 U ages; (c) cross-section through the North Dabie country rocks and Tiantangzhai intrusive complex.
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Cretaceous granites are widespread in the North Dabie orogen, Central China, but their emplacement sequence and mechanism are poorly known. The Tiantangzhai Complex in the North Dabie Complex is the largest Cretaceous granitic suite consisting of six individual intrusions. In this study, zircon U-Pb ages are used to constrain the crystallization an...
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... Dabie-Sulu orogen is the eastern part of the Qinling-Dabie orogen ( Fig. 1) that formed after Tri- assic collision between the North China and Yangtze cratons (Cong, 1996;Zheng et al. 2003;Zhao et al. 2011). The Dabie Mountains are composed of the fol- lowing tectonic units (from south to north): (1) the Triassic Yangtze foreland fold and thrust belt; (2) the Southern Dabie HP/UHP metamorphic complex; (3) the ...
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... North Dabie Complex (NDC) is bounded by the Xiaotian-Mozitan fault to the north, the Wuhe- Shuihou fault to the south, the Shangcheng-Macheng fault to the west and the Tancheng-Lujiang fault to the east (Fig. 1a), and is transected by several strike- slip faults. The Tancheng-Lujiang fault is a left-lateral syn-orogenic transform fault formed at 236 Ma and its major strike-slip offset took place in the Cretaceous (132 to 128 Ma). Distributions of the Cretaceous gran- ites generally follow the Tancheng-Lujiang fault, and these two faults are ...
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... Tiantangzhai intrusive complex of the NDC cov- ers an area of > 400 km 2 (Fig. 1b). This intrusive com- plex is divided into six sub-intrusions: the Shigujian, Egongbao, Tiantangzhai, Jiuzihe, Bodaofeng and Er- wan granites (Fig. 1c). Previous studies (Hacker et al. 1998;Bryant et al. 2004;Zhao et al. 2005;Wang et al. 2007) reported zircon ages of 141 Ma, 139 to 131 Ma and 125 Ma for the Tiantangzhai intrus- ive ...
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... Tiantangzhai intrusive complex of the NDC cov- ers an area of > 400 km 2 (Fig. 1b). This intrusive com- plex is divided into six sub-intrusions: the Shigujian, Egongbao, Tiantangzhai, Jiuzihe, Bodaofeng and Er- wan granites (Fig. 1c). Previous studies (Hacker et al. 1998;Bryant et al. 2004;Zhao et al. 2005;Wang et al. 2007) reported zircon ages of 141 Ma, 139 to 131 Ma and 125 Ma for the Tiantangzhai intrus- ive complex (Fig. 1b). The NNE-trending Shigujian intrusion was emplaced at 141 Ma, and shows the strongest deformation and local migmatization. The Egongbao, ...
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... 1b). This intrusive com- plex is divided into six sub-intrusions: the Shigujian, Egongbao, Tiantangzhai, Jiuzihe, Bodaofeng and Er- wan granites (Fig. 1c). Previous studies (Hacker et al. 1998;Bryant et al. 2004;Zhao et al. 2005;Wang et al. 2007) reported zircon ages of 141 Ma, 139 to 131 Ma and 125 Ma for the Tiantangzhai intrus- ive complex (Fig. 1b). The NNE-trending Shigujian intrusion was emplaced at 141 Ma, and shows the strongest deformation and local migmatization. The Egongbao, Tiantangzhai, Jiuzihe and Erwan weakly deformed intrusions were emplaced between 139 and 131 Ma. Undeformed post-tectonic granites were em- placed after 132 Ma. Gneissic structures of older gran- ites ...
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... The later Bodaofeng granite shows a homogeneous and fine granular tex- ture consisting of K-feldspar (32-44 %), quartz (20 %), plagioclase (20 to 35 %), biotite (18 %) and accessory minerals (magnetite, titanite and zircon). For this study, eight granite samples (DT07-2, DT16, DT18, DT20-1, DT20-2, DT22, DT31 and DT36) were collected in the NDC (Fig. 1b). These samples were used for the integrated study including cathodo- luminescence (CL) imaging for interpreting zircon in- ternal structures and LA-ICP-MS and SHRIMP for U- Pb dating. Three granite samples (DT07-2, DT20-1 and DT31) were used for zircon Hf isotope analyses. Twenty granite and four orthogneiss samples were ana- lysed for ...
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... geochemical and isotopic characteristics of the Tiantangzhai Complex in the NDC suggest that differ- ent types of granites were derived from different crustal sources. The emplacement ages of the Cretaceous gran- ites in the NDC display a negative correlation with the SiO 2 contents (Fig. 10). The SiO 2 content increases from about 64 to 74 wt % from the Shigujian granite to the Bodaofeng granite. The increase in SiO 2 content indicates the source rocks changed from basic to acidic through time. The emplacement process of the granites shows the foundering of the thickened crust and the reduction of the magma chamber depth, ...
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... emplacement process of the granites shows the foundering of the thickened crust and the reduction of the magma chamber depth, which implies that the order of the intrusion is consistent with the delamination and collapse processes. The interpreted tectonic model is illustrated in Figure 11. ...
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... early Cretaceous granitoids are closely associated with the evolution of the continental crust in the NDC. Figure 11a depicts the thickening of the NDC and eclogitization of its root. Wu et al. (2007) sug- gested that the transition of the tectonic regime from compression to extension occurred at c. 145 Ma. ...
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... intrusion of widespread voluminous granites may have been related to the transition to an extensional tectonic regime and the thinning of the thickened crust in the Dabie orogen. Figure 11b shows the foundering mechanism of the lower continental crust and the ex- tensional collapse of the orogen. The tectonic regime changed to extension along with foundering of the over- thickened lithospheric root of the Dabie orogen as well as the subsequent upwelling of the hot asthenosphere. ...
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... Dabie orogen became normal thickness crust (35 km) again following the large-scale delamination of the lithospheric mantle and the removal of the oro- genic root. Further mantle upwelling as well as the foundering of eclogite restites could have caused the extensive magma emplacement (Fig. 11c). Wang et al. (2007) reported a range of zircon U-Pb ages between 118 and 105 Ma for the late-tectonic granitic dykes. The analyses of two zircon grain rims from sample EW-1 have given ages between 117 and 111 Ma, which are comparable to the age of the granitic dykes in the NDC. This age range implies the continued upwelling of the hot ...
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... In contrast to the sporadically outcropped lenses or blocks of UHP eclogites, composite plutons and batholiths of the early Cretaceous postcollisional granitoid are predominant igneous rocks although a number of coeval small mafic to ultramafic plutons have been documented across the Dabie orogen Ma et al. 1998;Jahn et al. 1999;Zhang et al. 2002;Bryant et al. 2004;Zhao et al. 2004Zhao et al. , 2005Zhao et al. , 2007Zhao et al. , 2011Xu et al. 2005;Wang et al. 2007;Xu et al. 2012;He et al. 2013;Deng et al. 2014;Dai et al. 2015;Chen et al. 2023). Most plutons and batholiths were geochronologically dated with the early Cretaceous ages ranging from 125 to 135 Ma via zircon U-Pb techniques. ...
For a long time, it has been implicitly believed that oxygen isotopes of hydrothermally altered rocks and/or minerals were only elevated by the heavy water enriched in ¹⁸O from the modern geothermal and/or fossil hydrothermal systems around the world. While it is logically likely, there is no any previous attempt to argue for the elevation of oxygen isotopes of hydrothermally altered rocks and/or minerals by a light water depleted in ¹⁸O under appropriate natural conditions. Based on a novel procedure recently proposed for dealing with thermodynamic reequilibration of oxygen isotopes between constituent minerals and water, the initial oxygen isotopes of water (i.e., δ18OWi\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\delta {^{18}{\text{O}}}_{\text{W}}^{\text{i}}$$\end{document} value hereafter) prior to the hydrothermal alteration are theoretically inverted from the early Cretaceous postcollisional granitoid and Triassic gneissic country rock across the Dabie orogen in central-eastern China. The oxygen isotopes of hydrothermally altered rock-forming minerals were concurrently elevated by the magmatic water with moderate to high δ18OWi\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\delta ^{18}{\text{O}}}_{\text{W}}^{\text{i}}$$\end{document} values ranging from 4.21 ± 0.04 (one standard deviation, 1SD) to 6.57 ± 0.05‰ in the course of postmagmatic processes. By contrast, oxygen isotopes of the susceptible alkali feldspar from a gneissic country rock could be preferentially elevated by the ancient meteoric water with low δ18OWi\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\delta {^{18}{\text{O}}}_{\text{W}}^{\text{i}}$$\end{document} values down to -8.52 ± 0.56‰ during exhumation processes of the retrograde metamorphism. These fossil hydrothermal systems could kinetically sustain from a short duration of less than 12 thousand years (Kyr) via the surface-reaction oxygen exchange up to 1 million years (Myr) through the diffusive oxygen exchange, respectively, in this study. Cooling rates are further quantified for rock-forming minerals sequentially blocked and/or isolated from the magmatic water. Hereby, oxygen isotopes of constituent minerals can be hydrothermally elevated by diverse sources of water with paradoxical δ18OWi\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\delta {^{18}{\text{O}}}_{\text{W}}^{\text{i}}$$\end{document} values, especially for the metamorphic rocks with anomalous oxygen isotopes. There is no doubt that more unexpected findings will be scientifically and methodologically decoded and/or unlocked worldwide in the coming decade(s).
... www.nature.com/scientificreports/ Compared with the sporadically outcropped lenses or blocks of UHP eclogites, composite plutons and batholiths of the early Cretaceous post-collisional granitoid are the predominant igneous rocks although a number of coeval small mafic to ultramafic plutons have been documented in the Dabie orogen [18][19][20][55][56][57][58][59][60][61][62][63][64][65][66][67] . Most plutons and batholiths were dated with zircon U-Pb techniques and the early Cretaceous ages ranging from 125 to 135 Ma were therefore yielded. ...
It has been well known that the influxing meteoric water can hydrothermally lower oxygen and hydrogen isotopes of rocks and/or minerals during continental magmatic or metamorphic processes in certain appropriate cases. Its opposite, however, is not implicitly true and needs independent testing. In terms of a novel procedure recently proposed for dealing with thermodynamic re-equilibration of oxygen isotopes between constituent minerals and water from fossil hydrothermal systems, the initial oxygen isotopes of water (δ18OWi) are theoretically inverted from the early Cretaceous post-collisional granitoids and Triassic gneissic country rock across the Dabie orogen in central-eastern China. Despite ancient meteoric waters with low δ18OWi value down to − 11.01 ± 0.43‰ (one standard deviation, 1SD), oxygen isotopes of hydrothermally altered rock-forming minerals from a granitoid were unexpectedly but concurrently lowered by an evolved magmatic water with mildly high δ18OWi value of 2.81 ± 0.05‰ at 375 °C with a water/rock (W/R)c ratio of 1.78 ± 0.20 for the closed system. The lifetime of fossil hydrothermal systems studied herein is kinetically constrained to no more than 1.2 million years (Myr) via surface-reaction oxygen exchange in the late-stage of continental magmatism or metamorphism. Thereby, caution should be paid when lowered oxygen isotopes of hydrothermally altered rocks and/or minerals were intuitively and/or empirically inferred from the external infiltration of the purely meteoric water with a low δ18OWi value alone.
... The granitic veins cutting into the mylonitic A-type folds, with the crystallization age of 130.2 ± 2.5 Ma (weighted mean 206 Pb/ 238 U age), are associated with the post-collisional magmatic activity in the Dabie Mountains. A vast array of massive plutons, Tiantangzhai pluton, Baimajian pluton, Zhubuyuan pluton etc., were formed during this period (140 (Li, 1990;Hacker et al., 1998;Ratschbacher et al., 2000;Wang et al., 2007;Xu et al., 2007;Deng et al., 2014;). These plutons, together with the dykes and veins related to them, occupy nearly a half of the DOB. ...
... Orogenic evolution in most cases undergoes tectonic regime transitions from compressional thickening to extensional thinning, during which the thickened crust begins to collapse, accompanied by increased thermal fluid activities associated with the extension (Ormerod et al., 1988;Johnson and Oliver, 1990;Biellmann et al., 1997;Zhai et al., 2004;Liu et al., 2007;Gordon et al., 2008;Ramos, 2010). Previous research on petrogeochemistry and isotopic geochronology has revealed that the transition of the tectonic regime from compression to extension of the DOB commenced no later than 135 Ma (Ma et al., 2003;Wang et al., 2007;He et al., 2011;Deng et al., 2014). A considerable number of studies have contributed to establishing the voluminous magmatic intrusions and massive migmatites, both of which were formed during 145-130 Ma, as the petrological evidence of this transition (Ma et al., 1998(Ma et al., , 2003Wang et al., 2007Wang et al., , 2013Wu, 2007;Xu et al., 2007;Zhang et al., 2014;Chen et al., 2015;Hu et al., 2016). ...
The Xiaotian–Mozitan shear zone is the boundary of the Dabie high‐grade Metamorphic Complex (DHMC) and the North Huaiyang tectonic belt. It was deformed in ductile conditions with a top‐to‐NW/WNW movement. Geothermometers applied to mineral parageneses in mylonites of the shear zone give a temperature range of 623–691°C for the pre‐deformation and 515–568°C for the syn‐deformation respectively, which indicates a retrograde process of its evolution. A few groups of zircon U‐Pb ages were obtained from undeformed granitic veins and different types of deformed rocks in the zone. Zircons from the felsic ultramylonites are all of magma‐type, producing a weighted mean ²⁰⁶Pb/²³⁸U age of 754 ± 8.1 Ma, which indicates the time of magmatic activities caused by a rifting in the Neoproterozoic. Zircons from the granitic veins, cutting into the mylonites, are also of magmatic origins, producing a weighted mean ²⁰⁶Pb/²³⁸U age of 130 ± 2.5 Ma, which represents the time of regional magmatic activities in the Cretaceous. Zircons from the mylonitic gneisses are of anatectic‐metamorphic origins and are characterized by core‐mantle interior texture, which yielded several populations of ages including the Neoproterozoic ages with a weighted mean ²⁰⁶Pb/²³⁸U age of 762 ± 18 Ma similar to the felsic ultramylonites’ and the early cretaceous ages with a weighted mean ²⁰⁶Pb/²³⁸U age of 143 ± 1.8 Ma indicating the anatectic metamorphism in the Dabie Orogen Belt (DOB). Based on integrated analysis of the structure, thermal conditions of ductile deformation and the contact relations of the dated rocks, the activating time of the Xiaotian‐Mozitan shear zone is constrained between ∼143 Ma and 130 Ma, during which the DOB was undergoing a transition in tectonic regime from compression to extension. Therefore, the deformation and evolution of this shear zone play instrumental roles to deeply understand this process. This research also leads us to incline to the opinion of an extensional detachment with regard to the tectonic property of the shear zone. It might be also part of a continent scale extension in the background of the NCB (North China Block)'s cratonic destruction dominated by the subduction and roll‐back of the paleo‐pacific plate, but more detailed work is needed in order to unravel its complicated development.
... Mesozoic magmatic rocks are spread extensively throughout the DBO, but most of them crop out in the Beihuaiyang (BHY) and the North Dabie (NDB) units. Mesozoic magmatites from the NDB unit have been the focus of most studies (Chen et al., 2002;Deng, Wu, & Yang, 2013;Deng, Yang, Polat, Kusky, & Wu, 2014;Xu et al., 2013;Zhao et al., 2007), resulting in a relatively limited understanding of Mesozoic magmatism in other DBO units. Sikongshan (SKS) pluton is the largest intrusion occurring within the South Dabie (SDB) unit. ...
... An impressive feature of the Dabie orogen is the largescale Cretaceous (143-117 Ma) magmatism, including voluminous granitoids and minor mafic-ultramafic rocks (Ma et al. 1998;Jahn et al. 1999;Chen et al. 2002;Zhao et al. 2004Zhao et al. , 2005Zhao et al. , 2007Zhao et al. , 2011Huang et al. 2007Huang et al. , 2008Wang et al. 2007;Xu et al. 2007Xu et al. , 2012aZhang et al. 2010;He et al. 2011He et al. , 2013Dai et al. 2012;Deng et al. 2014). Cretaceous granitoids occupy nearly half of the surface exposure of the Dabieshan massif (Fig. 1). ...
... By contrast, the granitic plutons emplaced during 143-130 Ma commonly exhibit solid-state or subsolidus deformation more or less. For example, early intrusions of the largest Tiantangzhi batholith in the Luotian dome developed gneissic or banded structure that can be traced into the migmatitic gneiss Xu et al. 2007Xu et al. , 2012aDeng et al. 2014). During our field survey, top-to-the-NW sense of shear indicated by augens of K-feldspar phenocrysts was observed in a small granitic stock to the northwest of Luotian (Fig. 4f). ...
... In addition, a gabbro near Mozitan weakly deformed by the XMF yielded zircon U-Pb ages of 125 ± 2 Ma (TIMS) and 129 ± 2 Ma (SHRIMP), as well as hornblende and biotite 40 Ar/ 39 Ar ages of 120.7 and 120.5 Ma, respectively (Hacker et al. 1998 Ar/ 39 Ar) related to the Early Cretaceous tectono-thermal event in the Dabieshan area. Data sources from (Chen et al. 1991(Chen et al. , 1995(Chen et al. , 2009Mattauer et al. 1991;Eide et al. 1994;Hacker and Wang 1995;Xue et al. 1997;Hacker et al. 1998;Ratschbacher et al. 2000;Wang et al. 2002Wang et al. , 2011bWang et al. , 2013Xu et al. 2002a;Ma et al. 2004;Zhao et al. 2004Zhao et al. , 2005Zhao et al. , 2007Zhao et al. , 2008Zhao et al. , 2011Zhu et al. 2005;Hou et al. 2007;Lin et al. 2007Lin et al. , 2015Wu et al. 2007Wu et al. , 2008Xie et al. 2010;He et al. 2011;Yang et al. 2012;Dai et al. 2012;Deng et al. 2014); this study (gray box) Ratschbacher et al. 2000). Wang et al. (2000b) dated a biotite-plagioclase mylonite from the SMF, and the biotite age of 226.5 ± 0.6 Ma was considered as the onset time of the SMF. ...
The Dabieshan massif is famous as a portion of the world’s largest HP–UHP metamorphic belt in east-central China that was built by the Triassic North–South China collision. The central domain of the Dabieshan massif is occupied by a huge migmatite-cored dome [i.e., the central Dabieshan dome (CDD)]. Origin of this domal structure remains controversial. Synthesizing previous and our new structural and geochronological data, we define the Cretaceous Dabieshan as an orogen-scale metamorphic core complex (MCC) with a multistage history. Onset of lithospheric extension in the Dabieshan area occurred as early as the commencement of crustal anatexis at the earliest Cretaceous (ca. 145 Ma), which was followed by primary (early-stage) detachment during 142–130 Ma. The central Dabieshan complex in the footwall and surrounding detachment faults recorded a consistently top-to-the-NW shearing. It is thus inferred that the primary detachment was initiated from a flat-lying detachment zone at the middle crust level. Removal of the orogenic root by delamination at ca. 130 Ma came into the extensional climax, and subsequently isostatic rebound resulted in rapid doming. Along with exhumation of the footwall, the mid-crustal detachment zone had been warped as shear zones around the CDD. After 120 Ma, the detachment system probably experienced a migration accommodated to the crustal adjustment, which led to secondary (late-stage) detachment with localized ductile shearing at ca. 110 Ma. The migmatite–gneiss with HP/UHP relicts in the CDD (i.e., the central Dabieshan complex) was product of the Cretaceous crustal anatexis that consumed the deep-seated part of the HP–UHP slices and the underlying para-autochthonous basement. Compared with the contemporaneous MCCs widely developed along the eastern margin of the Eurasian continent, we proposed that occurrence of the Dabieshan MCC shares the same tectonic setting as the “destruction of the North China craton”. However, geodynamic trigger of the Cretaceous continental-scale NW–SE extension in eastern Asia is still a mystery.
A dominantly NW-SE directed extensional tectonics in the Early Cretaceous significantly reworked the Late Permian-Triassic orogenic framework of the Dabie orogenic belt. The North Dabie complex (NDC) is the principal domain recording this tectonic event. However, the precise structure-kinematic architectures, particularly those observed in the ductile regime, along with the respective time scales for different extensional stages, have not been adequately established. This significantly impedes our comprehensive understanding of the extensional style and deformation history in the North Dabie complex. To better address these issues, we conducted a systematic structural study and LA-ICP-MS zircon U-Pb dating of the pre-, syn-, and post-kinematic intrusions and syn-kinematically metamorphosed high-grade gneisses/migmatites of the NDC. Our results demonstrate that the extensional deformation in the NDC may initiate at ca. 144 Ma, which is characterized by a pervasive NW-SE oriented coaxial plastic flow in the ductile regime of the middle-lower crust. A large-scale detachment processing zone subsequently started activating at ca. 140 Ma at the upper-middle level of the middle crust, and concentratedly accommodated the extensional strain by top-to-NW ductile shearing. Locally, there was uprising of sub-magmatic flow in the atatexite-diatexite from the deeper lower crust taking place in the manner of top-to-outward shearing as early as ca. 137 Ma. This composite process of extension manifests vertical strain partitioning across the ductile middle-lower crusts and progressive strain localization during the lithospheric thinning. The NW-SE orientation dominated extensional tectonics was strongly driven by the westward subduction of the Paleo-Pacific oceanic plate during the Late Mesozoic.
Ancient environments have been mostly reconstructed with exogenous records, yet the potential constraints from endogenous archives were less emphasised. It has been well known that the outer- and inner-spheres of the planetary Earth are naturally linked and/or interplayed each other among geospheres. As stable isotopes of the meteoric water are globally dependent upon precipitating environments, rocks and/or minerals hydrothermally altered by the meteoric water can thus imprint environmental information of continental settings. These valuable clues, however, have been intuitively and/or qualitatively inferred up to now. On the basis of an innovative procedure recently proposed for dealing with thermodynamic re-equilibration of oxygen isotopes between constituent minerals and water from fossil hydrothermal systems, ancient meteoric waters are theoretically inverted from the early Cretaceous post-collisional granitoid and Triassic gneissic country rocks across the Dabie orogen in central-eastern China. The initial oxygen isotopes of ancient meteoric water (i.e., $\delta ^{18}O_W^i$ value hereafter) range from −11.01 ± 0.43 (one standard deviation, 1SD) to −7.61 ± 0.07‰ in this study, yet systematically and/or statistically deviating from modern local precipitation. These imply that either palaeoclimate could be colder than the present at least during the early Cretaceous or palaeoaltimetry has geographically varied across the Dabie orogen since the Triassic. Moreover, the lifetime of fossil hydrothermal systems is kinetically quantified to less than 1.2 million years (Myr) for the concurrent lowering of oxygen isotopes of hydrothermally altered rock-forming minerals through the surface-reaction oxygen exchange with ancient meteoric waters herein. Our results thus suggest that palaeoenvironments of the continental orogen can be scientifically and methodologically unearthed from endogenous archives and theoretical inversion of $\delta ^{18}O_W^i$ values can be quantitatively applied beyond the Dabie orogen.
The Dabie Orogenic Belt, located in east-central China, is known for the greatest outcrop area of the ultrahigh-pressure metamorphic rocks in the world and is typical for studying deep continental subduction and continent–continent collision. However, since lower-grade metamorphic rock occurrence in the core of the ultrahigh-pressure terrane was reported, it has become a new point of concern. This study reported new results. The so-called lower-grade metamorphic rocks are divided into sedimentary rocks and meta-volcanics. The sedimentary rocks consist mainly of fine-grained turbidites formed under an anoxic deep-water lacustrine basin. Laser Ablation–Inductively Coupled Plasma–Mass Spectrometry U–Pb detrital zircon dating indicates that their maximum deposit age is 119.0±1.1 Ma belonging to the mid-Cretaceous Aptian. U–Pb detrital zircon ages from the sedimentary rocks cluster in three age groups: 1) 2773.8–1550.0 Ma (45.0%); 2) 868.8–622.3 Ma (23.0%); 3) 147.0–100.0 Ma (31.5%). And the provenance and tectonic settings of these sedimentary rocks are discussed by synthesizing U–Pb detrital zircon ages, initial Hf isotope ratios, and trace elements of the zircons. Source rocks of the first group were mainly composed of the Paleoproterozoic basement derived from the reworking of the Paleoarchean–Neoarchean Yangtze continental crust. For the second group, its source rocks consisted of Neoproterozoic volcanics mainly from an island arc system, which derived from the reworking of older continental crust in the northern Yangtze Block. The third group's source rocks were chiefly composed of Cretaceous rift igneous rocks derived from the derivation through melting of middle-aged continental crust in the Dabie Orogenic Belt. The meta-volcanics have weighted mean U–Pb ages from 751.0±16 Ma to 786.3±5.9 Ma, and their protoliths formed under a Middle Neoproterozoic island arc system in the northern Yangtze Block. The meta-volcanics underwent a Triassic subduction of different depths and then an exhumation, but the sedimentary rocks did not. The findings suggest that the ultrahigh-pressure terrane had suffered violent subsidence during the mid-Cretaceous, and a four-stage evolution model of the Dabie Orogenic Belt was established accordingly.
