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New geochronological, geochemical and Sr-Nd-Hf isotopic data for the early Cretaceous Daying volcanic sequence, eastern Qinling Orogen, provides a probe into the nature of, and tectonic process operating in, the underlying Mesozoic mantle. The volcanic rocks in the sequence are composed of basaltic trachyandesite, pyroxene-andesite, trachyandesite and trachyte. They yield zircon U-Pb and whole-rock 40Ar/39Ar plateau ages of 134–124 Ma, roughly synchronous with the Cretaceous igneous rocks throughout the eastern Qinling and Dabie orogens. Clinopyroxene and plagioclase phenocrysts of the volcanic rocks exhibit simple normal zonation with higher mg-number and An content in the core relative to the rim. The amphibole is characterized by tschermakite and tschermakitic hornblende with mg-number of 50–67. The Daying volcanic rocks have variable SiO2 (54.27–63.44 wt%), Al2O3 (15.39–20.34 wt%), FeOt (5.23–9.94 wt%), and MgO (1.05–4.03 wt%) contents with low mg-number (26–49). They exhibit arc-like REE- and PM-normalized patterns with significant negative Nb-Ta anomalies, and highly- enriched Sr-Nd isotopic composition with (87Sr/86Sr)i ratios of 0.7066–0.7078 and eNd(t) values of −15.5 ∼ −11.0. Their zircons exhibit strongly negative eHf(t) values ranging from −27.3 to −17.2 and two-staged model ages from 2.90 Ga to 2.28 Ga. Such geochemical signatures suggest that the Daying volcanic rocks were derived from a hybridized source of the North China Craton enriched mantle with the input of some Yangtze crustal materials created by Triassic deep-subduction digestion. They also share similar eruption time, as well as elemental and Sr-Nd-Hf isotopic compositions, with those in the southern margin of the North China Craton, suggesting a northward subduction of the Yangtze block. It is proposed that the volcanic rocks are petrogenetically related to an early Cretaceous extensional event along the Qinling- Dabie Orogenic belt in response to unrooting of the thickened lithosphere.

Granites that have high eNd(t) and zircon eHf(t) (here phrased as ‘HNHGs’) can offer significant insights into the processes of crustal growth and reworking. This study investigates Early Jurassic HNHGs in the Southeastern (SE) South China Block (SCB) to determine whether they reflect crustal growth or reworking processes, which has implication for understanding the tectonic setting of the SE SCB. We presented new zircon geochronological and Hf-O isotopic, and geochemical analyses on these HNHGs to assess the fundamental crustal processes. Zircon U-Pb geochronological analyses yield the crystallization ages of 192.9 ± 0.8 Ma, 186.7 ± 2.5 Ma and 188.6 ± 1.3 Ma for the Wengong, Gaokeng and Chabei granites, respectively. These HNHGs display high SiO2 (69.75–77.50 wt%), low MgO (0.07–0.83 wt%) and Rb/Sr (0.74–14.3), belonging to unfractionated granites. They have low (87Sr/86Sr)i and zircon δ18O, high eNd(t) and zircon eHf(t), originating from partial melting of a juvenile crust. The HNHGs show a spatial distribution that overlaps with Early Paleozoic lithospheric mantle-derived mafic igneous rocks in the SE SCB. Isotope modeling results imply that the juvenile crust was likely a consequence of mixing among depleted mantle, subordinate enriched lithospheric mantle and SCB basement rocks during Early Paleozoic. These HNHGs record crustal reworking, rather than crustal growth during Early Jurassic, and formed in a continental extension setting.

Mafic-intermediate igneous rocks in the Bangxi-Chenxing tectonic zone of Hainan Island, South China, can be used to constrain the Paleotethyan tectonic evolution in Southeast Asia. This paper presents petrologic, geochronological, elemental and Sr–Nd–Hf–O isotopic data for Carboniferous basalts, Permian andesites and Triassic gabbro-dolerites in this zone. Zircon grains from these rocks have U-Pb ages of ∼330 Ma, ∼257 Ma and ∼240 Ma, respectively. The ∼330 Ma basalts contain 1400 Ma captured zircon grains, and display MORB-like geochemical characteristics with positive eNd (t) values of +5.86–+9.85, reflective of a MORB source with the input of a slab-derived component in a continental back-arc basin setting. The ∼257 Ma andesites contain older captured zircon grains, and have arc-like geochemical signature with weakly positive eNd (t) values of +0.26–+0.38, zircon eHf (t) values of −0.5–+1.4 and δ18O values of 6.35–7.16‰, which were derived from a metasomatized mantle wedge modified by the sediment-derived component in a continental arc setting. The ∼240 Ma gabbro-dolerites exhibit enrichment in LILEs, depletion in HFSEs, negative eNd (t)-eHf (t) values (−8.45 to −1.05 and −5.9 to −2.7, respectively) and crustal-like δ18O values (7.26–8.70‰), indicative of a post-collisional environment in response to the asthenosphere upwelling shortly after the closure of the Bangxi-Chenxing back-arc basin. The Carboniferous-Triassic mafic-intermediate igneous rocks thus record the Carboniferous-Permian arc-basin system and its Triassic closure. The Bangxi–Chenxing tectonic zone separated South Hainan from North Hainan and westerly extended to the Song Ma–Ailaoshan suture zone.

Early Mesozoic volcanic rocks in northwestern Laos are rarely reported and important for investigating the Paleotethyan tectonic evolution and regional correlation in SE Asia. In this study, New zircon ages and whole-rock geochemical data are presented for the newly identified volcanic rocks in northwestern Laos. Twelve volcanic rocks yield zircon U–Pb ages of 228–234 Ma. The volcanic rocks in northwestern Laos contain basalt, basaltic andesite, andesite, and rhyolite and can be geochemically subdivided into three groups. Both Group 1 and 2 samples belong to the calc-alkaline mafic-intermediate volcanic rocks. Group 1 has eNd (t) values of −0.52 to +1.20, eHf (t) values of +0.9 to +3.6 and δ18O values of 6.3–7.0‰. In contrast, Group 2 has lower eNd (t) values of −2.82 to −5.89 and eHf (t) values of −4.0 to +1.4 and higher δ18O values of 6.6–8.1‰ than Group 1. Group 3 samples are high-K calc-alkaline rhyolites with high eNd (t) (−0.08 to +0.74) and positive eHf (t) (+4.6 to +13.2) values. Geochemical characteristics suggest that the Group 1 and 2 samples were derived from a metasomatized lithospheric mantle modified by sediment-derived components, and Group 3 rhyolites were derived from partial melting of juvenile mafic rocks with a crustal component. Our results, along with the geological observations and reported ages suggest that the Late Triassic volcanic rocks in northwestern Laos were formed in a post-collisional setting, and provide the key studies for the connection between the Lancangjiang and Chiang Khong-Lampang-Tak zones.

One highly disputed topic about the Jurassic igneous rocks in the eastern South China Block (SCB) is whether they were products of the Pacific plate subduction or the intra-continental extension of the SCB. The early Jurassic mafic rocks, which are regarded as important tracers for the mantle nature, geodynamic processes and tectonic setting, are of great importance to solve this controversy. This paper presents the detailed zircon U-Pb geochronological, elemental geochemical and Sr-Nd-Hf isotopic data for the Xialan gabbroic intrusion from the Eastern Nanling Range. SIMS zircon U-Pb dating results for olivine gabbro and hornblende gabbro yield weighted mean 206 Pb/ 238 U ages of 190.6 ± 1.3 Ma and 196.0 ± 2.7 Ma, respectively. Olivine gabbros are high in MgO, Mg-numbers and CaO and low in SiO 2 and depleted in LILEs and LREEs. They have significant Ba, Sr and Eu positive anomalies with e Nd (t) of +0.8 - +2.9, suggestive of their origination from an ancient lithospheric source. Hornblende gabbros have a wide compositional range of SiO 2 , MgO, Cr and Ni and are characterized by enrichment in LILEs and LREEs and insignificantly negative Nb-Ta anomalies, along with positive e Nd (t) values ranging from +1.7 to +6.2 and zircon e Hf (t) values from +9.7 to +12.7, indicative of their origination from the asthenosphere-lithosphere interaction. The estimated mantle potential temperature (1341–1407 °C) of hornblende gabbros is similar to that of the western Basin and Range Province (1350–1450 °C). In combination with the E-W-trending early Jurassic rock-association in the Nanling Range, it is herein proposed that the early Jurassic igneous rocks most likely formed in an intra-continental extension setting in response to the asthenospheric upwelling.

Layered ultramafic-mafic intrusions are usually formed in an arc/back-arc or intra-plate tectonic environment, or genetically related to a mantle plume. In this paper, we report on an ultramafic-mafic intrusion, the Dalongkai intrusion in the Ailaoshan tectonic zone (SW China), whose occurrence is closely associated with arc/back-arc magmatic rocks. The Dalongkai intrusion is composed of plagioclase-lherzolite, hornblende-peridotite, lherzolite and wehrlite at the bottom, cumulate plagioclase-pyroxenite at the middle part, changing to fine-grained gabbro towards the upper part of the intrusion, forming layering structure. Zircons from the plagioclase-pyroxenites and gabbros yielded U-Pb ages of 272.1 ± 1.7 Ma and 266.4 ± 5.8 Ma, respectively. The plagioclase-pyroxenites show cumulate textures, and are characterized by high MgO (25.0–28.0 wt.%; mg# = 80.6–82.3), Cr (1606–2089 ppm) and Ni (893–1203 ppm) contents, interpreted as early cumulate phases. By contrast, the gabbros have relatively lower mg# values (56.3–62.7), and Cr (157–218 ppm) and Ni (73–114 ppm) concentrations, and may represent frozen liquids. The plagioclase-pyroxenites and gabbros share similar chondrite-normalized REE patterns and primitive mantle-normalized trace element profiles which are analogous to those of typical back-arc basin basalts. The eNd(t) values for both rock types range from +2.20 to +4.22. These geochemical and isotopic signatures suggest that the Dalongkai ultramafic-mafic rocks originated from a MORB-like mantle source metasomatized by subduction-related, sediment-derived fluids. Our data, together with other geological evidence, indicate that the emplacement of the Dalongkai ultramafic-mafic intrusion most likely occurred in a back-arc extensional setting associated with subduction of the Ailaoshan Paleotethyan branch ocean during the Middle Permian, thus ruling out the previously speculated linkage to the Emeishan mantle plume, or to an intra-continental rift.

The South China Craton was formed by amalgamation of the Yangtze and Cathaysia Blocks during the Neoproterozoic. During the Mesozoic, voluminous granitic plutons and associated W-Sn polymetallic deposits were formed in the Cathaysia Block. The giant South China low-temperature metallogenic domain (LTMD) includes an area of ∼500,000 km 2 in the Yangtze Block and is composed of the Chuan-Dian-Qian Pb-Zn, Youjiang Au-As-Sb-Hg and Xiangzhong Sb-Au metallogenic provinces. The Chuan-Dian-Qian Pb-Zn province contains numerous MVT Pb-Zn deposits, whereas the other two provinces are characterized by Carlin-type Au deposits and vein-type Sb, Hg and As deposits. These epigenetic deposits, which formed under low temperature conditions (∼100–250 °C), are typically hosted in sedimentary rocks and are locally controlled by faults and fractures. The deposits formed dominantly at 200–230 Ma and 130–160 Ma, corresponding to Indosinian (Triassic) and Yanshanian (Jurassic to Cretaceous) orogenies, respectively. Indosinian mineralization is recognized in all three provinces, but Yanshanian mineralization occurred only in the Youjiang and Xiangzhong provinces. The Indosinian orogeny, which involved collision of the Indochina Block with the South China Craton, resulted in circulation of basinal brines that leached ore-forming elements from adjacent sedimentary strata to form the Chuan-Dian-Qian Pb-Zn province. Deep-seated granitic magmas generated during this orogeny caused extensive circulation of meteoric water that mobilized ore-forming elements from the sedimentary strata to form the Carlin-type Au deposits in the Youjiang province, and the Sb-Au deposits in the Xiangzhong province. The Indosinian orogeny was the key factor in establishing the metallogenic framework of the LTMD. It produced widespread mineralization in the three metallogenic provinces, each of which has unique features reflecting differences in the nature and composition of the basement rocks. The Yanshanian metallogeny was less important and overprinted the older ore deposits in the Youjiang and Xiangzhong provinces.

In order to provide constraints on the interpretation of seismic data of the crust beneath the South China Sea (SCS) and its continental margins, we have measured P-wave velocities and anisotropy as a function of hydrostatic confining pressure, up to 650 MPa, for 31 representative samples (i.e., granite, diorite, felsic gneiss, mylonite and ultramylonite, amphibolite, schist, and marble) from the Yunkai Mts (Guangdong and Guangxi Provinces, China) that represent the crystalline basement beneath the continental margins of the SCS. The intrinsic velocity of each crack-free rock increases with increasing density (ρ) which is linearly dependent on the chemical composition: ρ increases with increasing MgO, CaO, FeO + Fe 2 O 3 , and Al 2 O 3 contents, but decreases with increasing contents of SiO 2 and Na 2 O + K 2 O. Most of the rocks have small ( m/f ) of 41–43% and the ratio shows a general increase from the continental margin to the central basin. The high velocity (7.0–7.6 km/s) materials in the lower crust could be either the former lower crustal mafic rocks that were present before rifting, which have experienced less extensional thinning than the felsic upper crust, or the materials crystallized from mafic magma which underplated the lower crust from the partially molten upper mantle during rifting.

The South China Block (SCB) is tectonically bounded by the Tethyan and Pacific subduction zones and the Qinling-Dabie HP-UHP metamorphic zone. Triassic tectonic activity was a key phase in the tectonic history of the SCB and in creating the fundamental framework of East Asia. The geometry and kinematics of the Triassic deformation sheds light on the mechanism driving intra-continental orogenesis in the SCB. Our new field- and mapped- based structural analysis, along with thermo-chronological dating results, reveal two-stage distinct Triassic deformations in the southern SCB involving top-to-north dextral thrusting at ~250–225 Ma and NE-trending sinistral transpression at ~230–190 Ma. Early Triassic dextral transpression is marked by WNW-trending high-strain zones and thrust nappes/sheets, which might have been rooted beneath the Hainan-Yunkai basement along a low angle, middle-upper crustal basal detachment. It transformed from a thick-skinned fold-and-thrust belt to thin-skinned Jura-like patterns with northerly-propagating deformation. Late Triassic NE-trending sinistral transpression was accompanied by a series of the parallel folds and thrusts in the SCB interior, resulting in the development of the regional positive-flower geometry and reactivation of the pre-existing structures. Such signatures, in combination with the available geological, geochronological, and paleogeographic observations, suggest two-stage (early-middle and late Triassic) intra-continental orogenesis in the SCB, were controlled by the clockwise scissor-like closure of the Paleotethyan Ocean and its interactions with the adjoining blocks including deep-subduction beneath the North China Block and limited lateral extrusion due to the obstructing paleo-Pacific plate.

Southeast Asia was mainly created by the late Paleozoic assemblage of the Eastern Cimmeria with other continental fragments. However, the tectonic nature and geodynamic setting of the key tectonic zones in the Indochina block are still in dispute, hindering the understanding of the Eastern Paleotethyan evolution of Southeast Asia. This study presents a set of new geochronological, elemental and Sr-Nd isotopic data for the late Paleozoic mafic rocks in the Nan and Luang Prabang tectonic zones. The mafic rocks from the Nan and Luang Prabang zones give zircon U-Pb ages of 279–294 Ma and 265–294 Ma, respectively, with xenocryst ages of 302–2524 Ma. They have SiO2 = 45.99–57.47 wt%, Al2O3 = 12.74–21.06 wt%, FeOt = 8.34–15.03 wt% and MgO = 2.79–14.74 wt% with mg-number of 34–74, and fall into the fields of basalt/basaltic andesite and its equivalents. These rocks are characterized by enrichment in LILEs and LREEs, depletion in HFSEs, low initial 87Sr/86Sr ratios (0.7032–0.7057) and high eNd(t) values (+4.8 to +7.4). They might be derived from a mantle wedge source modified by slab-derived components, and formed in a continental back-arc basin setting. Our analysis indicates the development of the Carboniferous-Permian mafic igneous event in the Nan and Luang Prabang tectonic zones, and that the Nan tectonic zone linked northerly with the Luang Prabang zone during the late Paleozoic, tectonically comparable to the Banpo-Nanlinshan back-arc basin in SW Yunnan, SW China. The back-arc basin finally closed in the early-middle Triassic and the subsequent assemblage continued till the latest Triassic in response to the eastward subduction of the Paleotethyan slab.

Widespread extensional half-/grabens with red bed sedimentation, dome structures, and magma intrusions/eruptions with polymetallic mineralization within South China during the Cretaceous-Cenozoic provide a natural laboratory to understand intracontinental deformation and plate tectonics. In order to decipher the tectonic and landscape evolution of eastern South China, this study presents new low-temperature thermochronology from a broad region covering major tectonic units including the Xuefeng, Jiuling, Nanling, and Wuyi mountains. Zircon and apatite fission track dates, length distribution, and thermal history modeling reveal a prominent and rapid cooling phase during ~125–80 Ma across the paleo-highland in eastern South China. A synthesis of existing thermochronologic data and geological observations suggests that NE/NNE-striking syn-sedimentary faults system with half-/graben basins, rapid exhumation of Cretaceous magma and pre-Cretaceous basement, and final extension of dome structures were all initiated in a back-arc setting during this period (~80-125 Ma). Eastern South China during the Paleogene was characterized by a tectonic quiescence during which insignificant exhumation, peneplanation, and local sedimentation occurred, forming regional low-amplitude, long-wavelength topography. Accelerated regional cooling commenced in the late Oligocene or early Miocene in response to the far-field effect of the India-Asia continental convergence. Additionally, the termination of red-colored gypsum-salt-bearing sediment in the Neogene suggests a paleo-environmental change within South China, from an arid to a monsoonal climate; such change was likely the result of the topographic uplift of the Tibetan Plateau and its margins.

The Loei Fold Belt, located at the western margin of the Indochina Block, is considered to be tectonically linked to the subduction of the Paleotethyan Ocean and subsequent collision. In northwestern Laos, the volcanic rocks are traditionally mapped as Permian–Early Triassic sequences. Our LA-ICP-MS zircon U–Pb dating results show that andesitic, rhyolitic and tuffaceous samples from the Muang Feuang region of the Loei Fold Belt have zircon U–Pb ages of 330.4 ± 2.2 Ma, 334.9 ± 1.7 Ma and 349.6 ± 1.7 Ma, which are interpreted as their eruption ages, respectively. These ages are indicative of an Early Carboniferous origin. The basaltic and basaltic–andesitic samples from the Pak Lay region yield zircon U–Pb ages of 314.6 ± 2.7 Ma and 315.4 ± 3.8 Ma, respectively, and have a Late Carboniferous origin. These samples exhibit depletion in HFSEs (e.g., Nb, Ta, Ti) with high LILE/HFSE ratios and exhibit a geochemical affinity to continental arc volcanic rocks. These signatures suggest the presence of an Early to Late Carboniferous active continental margin along the western margin of the Indochina Block. The Loei Fold Belt may extend north into NW Laos.

The Xuefeng Tectonic Belt is an important intraplate structural system in the South China Block. Its west margin is up to 1300 km away the present-day continental margin, and the Mesozoic structural trends in this belt are perpendicular to and have no correlation with the Triassic Qinling-Dabie Orogenic Belt. This belt provides important clues for understanding the mechanism of intraplate deformation and the tectonic history of South China. We identified two generations of folding with different strike directions in the Xuefeng Tectonic Belt based on the youngest folding-involved strata and their overprinting relationship. The early one is NE-striking, overprinted by the N–S-striking folds both during Late Jurassic and Late Cretaceous. Thrust faults in the Xuefeng Tectonic Belt mainly show top-to-west thrust movement, which is approximately coeval with the N–S-striking folding. The thrust fault system can be divided into three zones: the root zone with steep thrusts, the middle zone characterized by imbricate thrusts, and the frontal zone with a few shallow thrusts. In addition, two generations of strike-slip faults with different structural trends have been identified: E–W-striking strike-slip faults showing dextral transpression, and NE-striking strike-slip faults with sinistral offset and controlling the upper Cretaceous basins. According to regional geological relationship and structural overprinting, we interpret that the E–W trending strike-slip faults formed in the first stage, whereas the NE-striking strike-slip faults formed later during an E–W-oriented compressional event. Therefore, the principal stress direction varies from NW–SE to E–W.

U–Pb zircon dating of gneissic granite samples in northwestern Fujian Province, Southeast China, gave Neoarchean to Palaeoproterozoic ages (2.6–1.9 Ga) for the rounded zircon cores and Palaeoproterozoic upper intercept ages (1851 ± 21 Ma, 1857 ± 29 Ma, respectively) for zoned rims that have oscillatory growth zoning and yield e Hf ( t ) values between −8.8 and +3.7 and T DM model ages between 2.1 and 2.6 Ga. These gneissic granites are peraluminous (A/CNK = 0.94–1.28), characterized by high SiO 2 (68–72 wt.%), Al 2 O 3 (14–15 wt.%) and low CaO, MgO, FeO t , TiO 2 and P 2 O 5 contents. They also possess relatively low REE contents and moderate LREE/HREE fractionation and display pronounced negative anomalies in Nb, Ta, Sr, P and Ti. All these features indicate that the precursor magmas were likely formed by partial melting of sedimentary rocks. Clinopyroxenite xenoliths with gneissosity structures are found in these gneissic granites and they have high MgO, Ni and Cr, but low contents of TiO 2 , and are characterized by high CaO/Al 2 O 3 (4.1–5.3), low Al 2 O 3 /TiO 2 ratios (8.7–9.5) and HREE depletion. These features are similar to the typical Al-depleted type komatiites. Their geochemical characteristics, such as high (Gd/Yb) N and low HREE, Y, Zr and Hf suggest partial melting of the upper mantle source with residual garnet. The negative Nb, Ta and Ti anomalies indicate a strong arc-related affinity. Our results and recently published data for granitic and mafic basement rocks in this region, reveal that 1.85 Ga was an important period for the evolution of the Cathaysia Block, possibly related to the Columbia supercontinent assembly. Large amount of granitic magma was emplaced, probably as a result of partial melting of old Neoarchean to Palaeoproterozoic materials.

The Zhoutan Group, made of meta-sedimentary rocks and mafic volcanic, outcrops at the western margin of the Cathaysia Block. These rocks have been previously considered to represent a Mesoproterozoic sequence. However, this study shows that the ages of detrital zircons from the garnet–mica schists of this group are predominantly Neoproterozoic (1.0–0.82 Ga), and the youngest detrital zircon grains clearly constrain that the maximum depositional age of the meta-sedimentary sequence (i.e. the Zhoutan Group) is ca. 826 Ma. Subordinate detrital zircons give Paleo- to Mesoproterozoic (1.9–1.4 Ga) ages and minor zircons yield Neoarchaean (∼2.5 Ga) ages. Because 1.0–0.82 Ga old rocks are common at the southeastern margin of the Yangtze Block, while the 1.9–1.4 Ga rocks occur in the northwestern Fujian and southeastern Zhejiang Provinces, Cathaysia Block, our data suggest that these Neoproterozoic sediments may be derived both from the Yangtze Block and the Cathaysia Block. We proposed that these sediments deposited in a small remnant ocean between the passive margin of the Cathaysia Block and the active margin of the Yangtze Block, thus the timing of the final assembly between the Yangtze and the Cathaysia Block was after 826 Ma. Paleoproterozoic detrital zircons mostly have negative e Hf values, suggesting that much of the Paleoproterozoic crust in South China came from reworked Archean crust. Detrital zircons with oscillatory growth zoning in the 1.0–0.82 Ga age population have approximately the same proportion of positive and negative e Hf values ranging from +17.8 to −27.3. This favors the growth of a significant volume of juvenile crust in the Neoproterozoic time in South China, possibly caused by the subduction before the assembly between the Yangtze and the Cathaysia Block.

Paleoproterozoic (∼1770 Ma) mafic dikes occur throughout the Trans-North China Orogen. These dikes can be divided into three geochemically distinct groups. Group 1 with FeOt of 12.73–18.06%, (Nb/La)N 0.18–0.39, (Th/La)N of, 0.60–1.24, eNd(t) of −5.1 to −2.4, and an enrichment in LILE’s and a depletion in HFSE’s. Group 2 has flat REEs and incompatible elements patterns, and possesses (Nb/La)N = 0.64–0.87, (Th/La)N = 0.61–1.20 and eNd(t) = −1.7 to 1.1. Group 3 has low FeOt contents (8.19–11.57%) and (Th/La)N ratios (0.29–0.72), but similar (Nb/La)N ratios and eNd(t) values to those of Group 1. Petrological and geochemical data suggest that these dikes may have originated from different sources. Group 1 could be derived from a “re-fertilized” lithospheric source incorporating a continental basaltic component trapped from a earlier phase of subduction. Group 2 was likely a product of a subduction-modified lithospheric mantle hybridized by recycled gabbroic lower crust. By contrast, Group 3 originated from a mixture of subduction-modified lithospheric mantle with a MORB component. In combination with the available data, we propose that the sources of the mafic dikes were initially modified by the ∼1.85 Ga subduction/collision event that assembled the North China Craton, and partially melted under subsequent rifting in response to the upwelling convective mantle.