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High ɛ( t)- ɛ( t) granites are robust evidence for crustal growth. In this paper we report results of petrologic, geochronological and geochemical investigations on the Huashiban granites from the Ailaoshan tectonic zone in western Yunnan (SW China). Zircon grains separated from the two samples (10HH-119A and 10HH-120A) yield the weighted mean Pb/U ages of 229.9 ± 2.0 Ma and 229.3 ± 2.3 Ma, respectively, interpreted as the crystallization ages of the granites. Based on our results, in combination with the existing U-Pb geochronological data for the Ailaoshan metamorphic rocks, we propose that the Ailaoshan Group might be a rock complex composed of the Mesoproterozoic, Neoproterozoic, Hercynian, Indosinian and Himalayan components, rather than a part of the crystalline basement of the Yangtze block. The zircon grains show highly depleted Lu-Hf isotope compositions, with positive ɛ( t) values ranging from 8.4 to 13.1. The Huashiban granites have high SiO (72.66 wt%-73.70 wt%), low Mg (0.28-0.34) with A/CNK=1.01-1.05, and can be classified as peralumious high-K calc-alkaline I-type granites. A synthesis of these data indicates that the Ailaoshan tectonic zone had evolved into a post-collisional setting by the Late-Triassic (229 Ma). Genesis of the Huashiban high ɛ( t)- ɛ( t) granites involved into two processes: (1) underplating of the sub-arc mantle into the lower crust, and (2) remelting of the juvenile crustal materials in response to the upwelling of the asthenospheric mantle in the post-collisional setting. [ABSTRACT FROM AUTHOR]

Abstract: Three groups of coeval plutonic rocks with different petrogenetic histories and geochemical features have been recognized in the Late Archean Taishan granite–greenstone terrain (TSGT) in the Eastern Block of the North China Craton. Zircon U–Pb dating indicate that they were emplaced contemporaneously at around 2.54Ga. Geochemically, all of the three groups have high Al2O3 and Sr concentrations, low Y and Yb concentrations, and high Sr/Y and La/Yb ratios. They have high-SiO2 concentrations ranging from 57.56 to 67.98wt%, indicating that they are typical high-SiO2 adakites. Granodiorites from the Taishan area and monzodiorites from the Zoucheng area have similar geochemistries. However, the Zoucheng monzodiorites have wider ranges in element concentrations than the Taishan granodiorites, with the latter having higher Mg numbers. The Yishui monzodiorites have higher MgO, Cr, and Ni concentrations, higher Mg numbers, and lower SiO2 concentrations, but similar REE and spidergram patterns to the Zouchang and Taishan intruisions. These geochemical features indicate that their parental magmas were all derived from the partial melting of a downgoing oceanic slab. The Zoucheng high-SiO2 adakitic rocks were probably produced by this process alone; however, the Taishan and Yishui high-Si adakite groups were formed by interaction between primary adakitic melts and overlying peridotitic mantle. In combination with coeval sanukitoid or low-SiO2 adakitic magmatism in the study area, the rock association indicates partial melting of a peridotitic mantle wedge that was metasomatized by adakitic melts and aqueous fluids derived from the subducting slab, the presence of these three high-SiO2 adakite groups supports a genetic model involving slab subduction in the Late Archean (∼2.54Ga). The adakitic intrusions and associated rocks in the region postdate the earlier (∼2.7–2.6Ga) voluminous TTG rocks suggesting that the angle of subduction changed from flat or shallow subduction, to steeper subduction likely related to the arrival of an oceanic plateau or thickened lithospheric keel at the subduction zone. [Copyright &y& Elsevier]

Abstract: A kinematic and geochronological study has been carried out on the Triassic high-strain shear zones in Hainan Island, the southern South China Block. There are WNW- and NE-trending high-strain shear zones with greenschist- to amphibolite-facies metamorphism in this island. Kinematic indicators suggest a dextral top-to-the-NNE thrust shearing for the WNW-trending high-strain shear zones and a sinistral top-to-the-SE thrust shearing for the NE-trending shear zones. The quartz c-axis orientations of mylonitic rocks exhibit the domination of basal slip and some activation of a rhombohedra gliding system. The timing of shearing for these shear zones has been constrained by the 40Ar/39Ar dating analyses of synkinematic minerals. Middle Triassic (242–250Ma) and late Triassic–early Jurassic (190–230Ma) have been identified for the WNW- and NE-trending shear zones, respectively. A synthesis of these kinematic and thermogeochronological data points to a two-stage tectonic model for Hainan Island, that is, top-to-the-NNE oblique thrusting at 240–250Ma followed by top-to-the-SE oblique thrusting at 190–230Ma. In combination with the available data from the southern South China and Indochina Blocks, it is inferred that South Hainan and North Hainan have affinity to the Indochina and South China Blocks, respectively. The tectonic boundary between South Hainan and North Hainan lies roughly along the WNW-trending Changjiang–Qionghai tectonic zone probably linking to the Song Ma and Ailaoshan zones. The middle Triassic structural pattern of Hainan Island is spatially and temporally compatible with those of the South China and Indochina Blocks, and thus might be a derivation from the amalgamation of the Indochina with South China Blocks in response to the closure of the Paleotethys Ocean and subsequent subduction/collision. [Copyright &y& Elsevier]

Abstract: This paper presents a set of new SHRIMP zircon U–Pb geochronological, elemental and Sr–Nd–Pb isotopic data for the Wusu and Yaxuanqiao basaltic rocks (the Mojiang area) along the Ailaoshan tectonic zone. The Wusu basaltic sequence is dominated by SiO2-poor, MgO- and TiO2-rich basalts with a major mineral assemblage of plagioclase+clinopyroxene. These rocks gave a SHRIMP zircon U–Pb age of 287±5Ma (MSWD=0.58). In contrast, the Yaxuanqiao basaltic sequence is predominantly composed of high-Al basaltic andesite, which gave a SHRIMP zircon U–Pb age of 265±7Ma (MSWD=0.34). The analyzed samples for both sequences exhibit significant enrichment in LILEs and depletion in HFSEs with (Nb/La)n of 0.38–0.81, similar to arc-like volcanics. They have positive εNd(t) values (+3.52 to +5.54). In comparison with MORB-derived magmatic rocks, the Wusu basalts are more enriched in LILEs and REEs, and the Yaxuanqiao samples are more enriched in LILEs but variably depleted in Ti, Y and HREE. The Wusu samples show high Pb isotopic ratios, similar to the Tethyan basalts, whereas the Yaxuanqiao samples plot in the field of the global pelagic sediments. The geochemical and Sr–Nd–Pb isotopic characteristics suggest that the Wusu basalts originated from a MORB-like source metasomatised by slab-derived fluids, while the Yaxuanqiao rocks have a fluid-modified MORB source with the input of subducted sediments. The geochemical affinity to both MORB- and arc-like sources, together with other geological observations, appears to support the development of a Permian arc–back-arc basin along the Ailaoshan–Song Ma tectonic zone in response to the northward subduction of the Paleotethys main Ocean. The final closure of the arc–back-arc basin took place in the uppermost Triassic due to the diachronous amalgamation between the Yangtze and Simao–Indochina Blocks. [ABSTRACT FROM AUTHOR]

Abstract: The Sr–Nd and Pb isotopic compositions of middle Jurassic to late Cretaceous mafic rocks across the Chenzhou–Linwu Fault within the South China Block are presented to constrain the characteristics and evolution of Mesozoic mantle source. These data, in combination with geochronological results, can be divided into four groups. Group 1 (~175–170 Ma) occurs on either side of the Chenzhou–Linwu Fault and has moderately depleted Sr–Nd and radiogenic Pb isotopes, akin to a FOZO-like source and is inferred to have originated from deep asthenospheric mantle with delaminated lower crustal signatures. Group 2 (~175–145 Ma) is restricted to the west of the fault and shows a significant Dupal anomaly and a binary mixing array between a component from an enriched mantle source (EM1) with low ε Nd(t) values and 206Pb/204Pb, and intermediate 87Sr/86Sr ratios and a FOZO-like component characterized by Group 1. Group 3 (~175–125 Ma) occurs to the east of the fault and exhibits low ε Nd(t) values and high Sr–Pb isotopic ratios, similar to EM2 component with minor DMM component. The Sr–Nd–Pb isotopic systematics for Group 4 (~93–80 Ma) resembles those of SE China Cenozoic basalts, suggestive of DMM-EM2 reservoir in response to the uppermost asthenospheric mantle source. These temporal and spatial variations, together with other geologic and paleomagnetic data, suggest that (1) the multiple mantle reservoirs include FOZO-, DMM-, EM1- and EM2-like components beneath the South China Block; (2) DMM-EM2 sources have dominated the mantle domains beneath SE Asia since late Cretaceous; (3) the Chenzhou–Linwu Fault corresponds with the early Mesozoic lithospheric boundary between the Yangtze and Cathaysia blocks within the South China Block. The Mesozoic mafic rocks within the South China Block developed in an active rift setting in response to the delamination of partially over-thickened lithospheric keel and upwelling of asthenosphere rather than a supra-subduction environment. [Copyright &y& Elsevier]

Abstract: Geochronological, elemental and Sr–Nd isotopic data are presented for the syenites, trachyandesites and trachybasalts from the Southern Awulale Mountain, Xinjiang. The syenites were emplaced and crystallized in the late Carboniferous (312 Ma), and are characterized by high positive ε Nd(t) values and high initial 87Sr/86Sr ratios, Th and Th/Ce ratios. They were thought to have generated dominantly by the partial melting of the underplated juvenile basaltic crust that originated from the mantle previously modified by subducted sediments. The trachybasalts have high positive ε Nd(t) values, medium initial 87Sr/86Sr ratios and high Rb, Ba, Sr contents, and are interpreted as the derivatives of a mantle source modified by subduction zone fluids. The trachyandesites also exhibit high positive ε Nd(t) values, medium initial 87Sr/86Sr ratios, but relatively low Th, Rb, Ba, Sr contents, and as such are considered as the products of crystal fractionation of a basaltic magma that was originated from the mantle slightly modified by subducted sediments. The systematic geochemical variations of the Carboniferous magmatism indicate that the western Tianshan Orogen experienced a transformation from convergence to extension in the late Carboniferous, probably in response to the upwelling of an asthenospheric mantle triggered by the detachment of an orogenic root zone. [Copyright &y& Elsevier]

Abstract: The Emeishan flood basalts are part of an important large igneous province (LIP) along the western margin of the Yangtze Block, Southwest China. Mafic rocks interlayered with Permian sedimentary rocks in western Guangxi Province, on the southeastern margin of the Yangtze Block, have SHRIMP zircon U–Pb weighted mean ages of 259.6±5.9 Ma and 259.1±4.0 Ma, identical to mafic plutons associated with the Emeishan basalts. The basaltic rocks, which are SiO2-poor, and FeO-, TiO2- and P2O5-rich, geochemically resemble the Emeishan high-Ti basalts. These rocks are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE), and have (Nb/La)n =0.75–0.94 and (Hf/Sm)n =0.78–0.90. They are characterized by moderate 86Sr/87Sr(i) ratios (0.704922–0.705804), intermediate ɛ Nd(t) values (−0.23 to 1.50), high 206Pb/204PbI ratios (18.77–19.67) and prominent positive Δ8/4 (67.7–82.7) and Δ7/4 (0.96–8.19) values. These geochemical signatures are also comparable to the Emeishan high-Ti basalts and the associated high-Ti intrusions in SW China, and might be attributed to low degrees of melting of a garnet-bearing mantle source. The elemental and isotopic compositions suggest that the magma source reservoir may have involved HIMU- and EM1-components, indicative of plume-lithosphere interaction at the periphery of the plume. We propose that these basalts in western Guangxi Province are spatially and temporally associated with the Emeishan LIP and that the Emeishan flood basalts extend over a broader region than previously thought. [Copyright &y& Elsevier]

Abstract: This paper presents new zircon U–Pb data and interpretations for the gneissic rocks in the Yunkai massif in order to constrain the timing and evolution of the Caledonian tectonothermal event in the South China Block (SCB). Magmatic and inherited zircons from the orthogneiss in the region, previously thought to be of Precambrian origin, yielded 206Pb/238U apparent ages of 421–441 Ma and 513–1343 Ma, respectively. Also a weighted mean 206Pb/238U age of 236.0±3.1 Ma was obtained, interpreted as the metamorphic resetting age during the Indosinian tectonic event. Our analyses show that the paragneiss in the region, previously regarded as Proterozoic sedimentary rocks, contains detrital zircons of the Archaean to Paleozoic origin, of which the youngest zircons yielded the U–Pb age of ∼423 Ma. These data indicate that (1) the Proterozoic and Archaean components may exist beneath the Yunkai massif; (2) most of the metaigneous rocks are actually the Caledonian anatectic granites possibly overprinted by Indosinian (∼236 Ma) reactivation; (3) some paragneiss might have originally deposited during the Devonian time; and (4) a subsequently rapid uplifting took place after the emplacement of the Caledonian granites, revealed by the observation that the Devonian clastic strata uncomfortably overlie the Caledonian granites. In combination with other geochronological data and geological observations throughout the SCB, we propose that the Caledonian tectonothermal event around Silurian (∼450–400 Ma) might be a result from an intracontinental collision between the Yangtze and Cathaysian blocks in response to the subduction/collision between the North China block and SCB. [Copyright &y& Elsevier]

Abstract: The Gaoligong and Chongshan shear systems (GLSS and CSSS) in western Yunnan, China, have similar tectonic significance to the Ailaoshan–Red River shear system (ASRRSS) during the Cenozoic tectonic development of the southeastern Tibetan syntaxis. To better understand their kinematics and the Cenozoic tectonic evolution of SE Asia, this paper presents new kinematic and 40Ar/39Ar geochronological data for these shear systems. All the structural and microstructural evidence indicate that the GLSS is a dextral strike-slip shear system while the CSSS is a sinistral strike-slip shear system, and both were developed under amphibolite- to greenschist-grade conditions. The 40Ar/39Ar dating of synkinematic minerals revealed that the strike-slip shearing on the GLSS and CSSS at least began at ∼32Ma, possibly coeval with the onset of other major shear systems in SE Asia. The late-stage shearing on the GLSS and CSSS is dated at ∼27–29Ma by the biotite 40Ar/39Ar ages, consistent with that of the Wang Chao shear zone (WCSZ), but ∼10Ma earlier than that of the ASRRSS. The dextral Gaoligong shear zone within the GLSS may have separated the India plate from the Indochina Block during early Oligocene. Combined with other data in western Yunnan, we propose that the Baoshan/Southern Indochina Block escaped faster southeastward along the CSSS to the east and the GLSS to the west than the Northern Indochina Block along the ASRRSS, accompanying with the obliquely northward motion of the India plate during early Oligocene (28–36Ma). During 28–17Ma, the Northern Indochina Block was rotationally extruded along the ASRRSS relative to the South China Block as a result of continuously impinging of the India plate. [Copyright &y& Elsevier]

The wide occurrence of Paleoproterozoic mafic dikes in the basement of the Trans-North China Orogen provides important constraints on the major ∼1800Ma tectonothermal event of the North China Craton. These mafic dikes form a tholeiitic series dominated by basalts and basaltic andesites, and can be geochemically classified into three groups: The Groups 1 and 2 rocks are characterized by high total FeO contents (12.69–15.61%), of which the Group 1 rocks are more enriched in LILE and LREE contents and depleted in HFSE ((Th/Nb)n = 2.5–3.8, (La/Yb)cn = 3.0–5.8; (Nb/La)n = 0.27–0.38) and have more radiogenic Nd isotopic ratios (εNd(t) = -3.40 to -5.14), than the Group 2 rocks ((Th/Nb)n = 0.8–1.2, (La/Yb)cn = 1.5–2.1, (Nb/La)n = 0.65–0.87, εNd(t) = -0.60 to -1.67). In contrast, the Group 3 rocks are typified by low FeOt (7.86–11.04%) and high MgO (5.62–9.56%) contents. Higher (La/Yb)cn (4.22–7.13) ratios, less radiogenic Nd isotopic ratios (εNd(t) = -2.75 to -5.52), and more significant Th–U and Nb–Ta depletion are also apparent features. 40Ar/39Ar geochronology of three representative samples from each group yielded plateau ages of 1780.7 ± 0.5Ma, 1765.3 ± 1.1Ma and 1774.7 ± 0.7Ma, respectively. These elemental and isotopic data suggest that the geochemical variations of these rocks cannot be simply explained by crystallization from a common parental magma involving crustal contamination during emplacement. Instead, they most likely originated from variable sources under different degrees of partial melting. The Group 1 rocks were derived from relatively low degrees of partial melting of a refractory lithospheric mantle previously metasomatised by subduction-related fluids, whereas the Group 2 rocks originated from a hybridized source involving ca. 40% subduction-modified lithospheric mantle, similar to the Group 1, and ca.60% N-MORB component. In contrast, the Group 3 rocks show significant Th–U depletion that may mark the involvement of portions of gabbroic lower crust trapped in the source region during subduction. Based on all the available data, we propose a tectonic model of a full subduction-syncollision-postcollision-rifting cycle for the evolution of the NCC between 1870 and 1765Ma. A variety of source regions beneath the southern Taihang Mountains initially developed during the period of subduction/collision, and subsequent extension/rifting resulted in the melting of the subduction-modified lithospheric mantle, which produced widespread Paleoproterozoic mafic dikes on the Trans-North China Orogen in response to upwelling of convective mantle. [Copyright &y& Elsevier]

Located in the eastern portion of the Xing'an-Mongolian Orogenic Belt (XMOB), the Xinkailing-Kele complex has previously been considered to be Precambrian metamorphic rocks, mainly according to its relatively high metamorphic grade. Our filed observation, however, revealed that the complex is composed mainly of metamorphic rocks (Kele complex), tectono-schists ("Xinkailing Group"), and granitoids (Xinkailing granitic complex). Dating on these rocks using advanced SHRIMP zircon U-Pb technique indicates that: (1) Biotite-plagioclase gneiss from the Kele complex has a protolith age of 337±7 Ma (2σ) and a metamorphic age of 216±3 Ma (2σ); (2) the tectono-schist of the "Xinkailing Group" gave a magmatic age of 292±6 Ma (2σ), indicative of felsic volcanic protolith of the schist formed in Late Paleozoic time; and (3) the Menluhedingzi and Lengchuan granites of the Xinkailing granitic complex were emplaced at 167±4 (2σ) and 164±4 Ma (2σ), respectively. These results suggest that the Xinkailing-Kele complex is not Precambrian metamorphic rocks and the so-called Precambrian "Nenjiang Block" does essentially not exist. In combination with regional geological data, we propose that the Kele metamorphic complex is likely related to a collisional tectonism that took place in Triassic time, as indicted by its metamorphic age of 216±3 Ma. The Xinkailing granitic complex was emplaced along the collisional zone during Mid-Jurassic time, likely in a post-orogenic or anorogenic setting. [ABSTRACT FROM AUTHOR]

Highlights: [•] The granitic gneisses from Wuyi-Yunkai yield zircon U–Pb age of 913–982Ma. [•] The early Neoproterozoic S-type granitic magmatism is identified in Cathaysia. [•] They originated from the metapelitic and metaigneous source with little input of juvenile materials. [•] They are petrogenetically related to the closure of the Wuyi-Yunkai arc-back-arc system. [•] The arc-basin system is finally closed at ∼920Ma and the SCB is placed to the Rodinia margin. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two main episodes of magmatism at ∼225Ma and ∼216Ma occurred in the Yidun terrane. [•] Two major episodes of Mesoproterozoic juvenile crust formed in the Yidun terrane. [•] The adakitic magma and ore fluids were not resulted from a common magmatic chamber. [•] The Mesozoic magmatism and Cu mineralization was related to orogenic collapse. [Copyright &y& Elsevier]

Abstract: In the eastern South China Block (SCB), the presence of middle Paleozoic volcanics and mafic rocks is poor in spite of the extensive occurrence of granites in response to the synchronous (Kwangsian) intracontinental orogen event. The nature of the lithosphere and its associated orogenic process are poorly known for such a major orogen. In this paper, a set of new U–Pb zircon geochronological, elemental and Sr–Nd isotopic data are presented for several gabbroic plutons, which were recently identified in the Cathaysia Block. The representative samples of the Longhugang, Xinchuan and Xinsi plutons yielded the weighted mean 206Pb/238U ages of 423±8Ma, 434±6Ma and 420±3Ma, respectively, and their gneissoid country-rocks are dated at 442–466Ma. This evidences the presence of Silurian mafic rocks in the Cathaysia Block. These gabbroic rocks can be geochemically classified into three groups. Group 1 from the western Longhugang pluton exhibits flat REE patterns represented by (La/Yb)cn=1.1–1.7, (Gd/Yb)cn=0.99–1.15, and δEu=1.29–1.51 with negative Nb–Ta and P and markedly positive Sr anomalies. It shows enrichment in LILEs and 87Sr/86Sr(t) ratios of 0.70412–0.70727 and εNd(t) values of −2.6 to −0.6. Group 2 from the Xinchuan, Zhouya and Yunlu plutons is characterized by high MgO (11.4–15.8wt.%), mg-number (66–74) and Cr and Ni contents. It is marked by significantly negative Nb–Ta, Zr–Hf and P–Ti anomalies with high 87Sr/86Sr(t) (0.70920–0.71072) and low εNd(t) values (−3.9 to −7.9). Group 3 from the Xinsi and eastern Longhugang plutons has εNd(t) values from −2.8 to −5.7 and shows high Nb content of 7.05–9.89ppm with pronounced enrichment in LILE and weak depletion in HFSE, resembling Nb-enriched arc basalt in HFSE composition. A synthesis of these geochemical data points to the following petrogenesis: Groups 1 and 2 derived from a spinel-bearing, plagioclase-rich source and a garnet-bearing, orthopyroxene-rich source, respectively, proportionally modified by slab- and sediment-derived melts plus fluid fluxing from the earliest Neoproterozoic subduction. The HFSE composition for Group 3 inherited from a metasomatized mantle wedge column with the input of large-proportional slab melts and the absence of residual rutile during partial melting. In conjunction with other available observations, it is proposed that there preserved a paleosubduction-modified wedge column beneath the Cathaysia Block, which might be undisturbed until the Kwangsian intracontinental orogen. During the Silurian post-orogenic collapse of the event, the elevated lithosphere thermal boundary facilitated the partial melting of the column to generate these Silurian gabbroic rocks. [Copyright &y& Elsevier]

Abstract: The tectonic nature of the Cathaysia Block during earliest Neoproterozoic period has been long disputed and attracted considerable attentions. One reason for this problem is rare exposure and few data for the igneous rocks of Grenvillian age in this Block. In this paper, a set of new U–Pb zircon geochronological, elemental and Nd isotopic data are presented for the metabasites in the Yunkai Group which shows WNW-trending extension with a length of more than 100km along the northern Yunkai Domain of the Cathaysia Block. The plagioclase amphibolite and metabasite from Shiwo (Beiliu) and Tantu (Xinyi) from the northern Yunkai Domain, representative of Groups 1 and 2, yielded the 206Pb/238U weighted mean ages of 997±21Ma and 978±19Ma, respectively, evidencing the presence of the Grenvillian mafic rocks within the Cathaysia Block. Based on the Nb, Nb/La and Nb/U, these samples can be geochemically subdivided into two groups (Groups 1 and 2). Group 1 has Nb/La=0.33–0.54 and Nb=1.71–2.85ppm, and exhibits similar geochemical signatures to those of Saunders island-arc. Group 2 gives Nb/La of 0.57–0.86 and Nb of 7.58–12.70ppm, resembling to those of Phanerozoic Nb-enriched basalts, and shows the geochemical affinity to the Okinawa back-arc basin basalt. Both groups have positive ɛ Nd (t) values, ranging from +3.84 to +5.36 and +3.93 to +6.55, respectively. These geochemical and isotopic characteristics suggest that Group 1 might have been originated from a MORB-like source modified by subduction-derived fluids. The source of Group 2 Nb-enriched basalt might be metasomatized by melt released from a newly subducted slab. In conjunction with other geological observations, it is identified for the Grenville-aged (ca. 1.0Ga) arc and back-arc basin along the northern Yunkai Domain of the Cathaysia Block, analog to the modern West Pacific. The South China Block probably located at the margin of Rodinia supercontinent between west Australia and east India. [Copyright &y& Elsevier]

Abstract: The amalgamation process of the Yangtze with Cathaysia Blocks has been one of the disputed issues that have attracted considerable attention due to its significance in understanding the assembly and breakup of the supercontinent Rodinia. However, it has been a matter of debate as to the tectonic nature (plume vs. subduction/collision vs. plate-rift) and timing of the amalgamation (1000Ma vs. 880Ma vs. 800Ma) along the Jiangnan domain. To evaluate the previously proposed models and to constrain the final amalgamation timing of the Yangtze with Cathaysia Blocks, this paper presents a set of integrated geochemical and geochronological data for the high-mg volcanic sequence that is bounded between the Lengjiaxi and Banxi Groups. Two andesitic samples from the volcanic sequence (Cangshuipu) were dated at 824±7Ma (CSP-35) and 822±28Ma (CSP-8) using the SIMS and SHRIMP techniques, respectively. These samples have mg-numbers ranging from 71 to 25 with SiO2 of 57.51–73.80wt%, classified as high-mg andesite and dacite. They show significant enrichment in LILEs and depletion in HFSEs with marked negative Nb–Ta, P and Ti anomalies. Their ɛ Nd(t) values range from −1.7 to −4.7 and initial 87Sr/86Sr values from 0.7051 to 0.7123. The generation of the Cangshuipu high-mg rocks might have been attributed to an interaction of the subducted sediment-derived fluid with the overlying refractory mantle. The contemporaneous dacitic rocks should be the product of the highly fractional crystallization from the high-mg andesitic magma. Integrated with the regional geology and available geochronological data, we propose that the Cangshuipu volcanic sequence might have formed in a collisional setting related to the Neoproterozoic orogenic process along the Jiangnan domain. The final amalgamation of the Yangtze with Cathaysia Blocks along the Jiangnan domain probably occurred between 815Ma and 822Ma (probably 820Ma) rather than 1000Ma, ca. 880Ma or 800Ma as previously proposed. Taking into account the subsequent development of the Nanhua rifting (probably after 815Ma), it is inferred that a plate-rift model might be a more reasonable mechanism for the Neoproterozoic tectonic evolution along the Jiangnan domain. [Copyright &y& Elsevier]

Abstract: Gneissoid granites were traditionally thought to be the components of the Precambrian basement in the eastern South China Block, but twenty-four gneissoid granite samples from the Wugong, northern Wuyi, southern Wuyi and Yunkai Domains gave zircon U–Pb ages of 424–456Ma, 410–457Ma, 426–438Ma and 415–450Ma, respectively. The existence of the abundant Kwangsian gneissoid granites, which have incorrectly been assigned to the Precambrian basement, indicates that the “so-called” Precambrian stratigraphic sequence of the Cathaysia Block should be termed “Complex” rather than “Group”. These gneissoid granites are peraluminous granites with relatively high Al2O3, MgO, TiO2, FeOt and CaO/Na2O but low CaO, Al2O3/(MgO+FeOt) and Rb/Sr ratios. They exhibit strongly negative Ba, Sr, Nb, P and Ti and positive Pb anomalies in primitive mantle-normalized diagrams, and have initial 87Sr/86Sr ratios ranging from 0.70924 to 0.72935 and negative εNd(t) values from −6.4 to −11.4, similar to those of paragneissic enclaves and Precambrian sedimentary rocks in the eastern South China Block. The zircons crystallized in the Kwangsian gneissoid granites gave εHf(t) values ranging from +2.4 to −19.4 with the peak at −4 (almost all grains clustering at −1 to −12) and Hf model ages of 1.1–2.1Ga. The synthesis of these geochemical and in-situ zircon Hf isotopic data indicates that the Kwangsian gneissoid granites dominantly originated from Proterozoic metapelitic and meta-igneous components with insignificant input of juvenile mantle-derived magmas. A model of two-stage crustal anatexis is proposed for the Kwangsian granitic magma in the eastern South China Block, with (1) the formation of 460–430Ma granite through the breakdown of hydrous minerals under the condition of the doubly thickened crust, and (2) the generation of the 430–400Ma granite accompanying promoted melting along a path of isothermal decompression due to the increasing thermal weakening for the collapse of the thickened crust. The crustal anatexis has probably occurred in an intracontinental tectonic regime that was geodynamically linked to the far-field response to the assembly of the Australian–Indian plate with the Cathaysia Block during middle Paleozoic (Kwangsian) time. [Copyright &y& Elsevier]

Abstract: The Xiaodingxi and Manghuihe volcanic sequences represent key components of the Lancangjiang igneous zone in southwest China. Their petrogenesis provides important constraints on the tectonic evolution of the eastern Paleotethys ocean. The basaltic rocks from the Xiaodingxi and Manghuihe sequences yield SHRIMP zircon U–Pb weighted mean ages of 214±7Ma and 210±22Ma, respectively, which is 15–20Ma younger than the ages of the syn-collisional granite magmatism (230–241Ma). Samples from the volcanic sequences are dominated by alkaline basalts and basaltic andesites, and can be geochemically classified into two groups. Group 1 samples, mainly from the Xiaodingxi sequence and the lower part of the Manghuihe sequence, are characterized by low MgO (1.49–7.50wt.%) and Zr/Nb (9.4–15.3), and high Al2O3 (15.95–18.39wt.%). They are enriched in LILE and LREE contents and depleted in HFSE, and have 87Sr/86Sr(t) ratios of 0.705473–0.706972, εNd(t) of −1.47–0.75, and similar Pb isotopic compositions to the global average composition of pelagic sediments. In contrast, Group 2 samples from the middle–upper parts of the Manghuihe sequence have similar Al2O3 (16.62–18.23wt.%) but higher MgO (8.08–11.74wt.%) and Zr/Nb (15.9–23.9) than those of Group 1 samples. They exhibit relatively flat REE patterns, significantly negative Nb–Ta and Th–U anomalies and positive Sr anomalies. In comparison with Group 1, Group 2 samples show higher Cr, Ni contents and εNd(t) values (1.17–5.02), and lower 87Sr/86Sr(t) and Pb isotopic ratios (Δ8/4=43.2–59.8 and Δ7/4=11.8–19.8). The geochemical data suggest that Group 1 samples might be the differentiated product of primitive high MgO and low Al2O3 melts originating from a refractory modified mantle with the involvement of 5–10% recycled pelagic sediments. The parental magma for Group 2 samples may have been derived from a plagioclase-rich, garnet-free source comprising 80–85% fluid-metasomatized and 15–20% asthenospheric components. Based on all available data, a tectonic model involving eastward subduction in the Permian and collision in the Triassic can be proposed for the evolution of the eastern Paleotethys ocean. During the late Triassic, the progressive upwelling of the asthenospheric mantle, shortly after slab detachment, may have led to the melting of the metasomatized mantle wedge, resulting in the post-collisional Group 1 and Group 2 magmas. [Copyright &y& Elsevier]

Abstract: LA-ICP-MS U–Pb zircon geochronological, elemental and Sr–Nd isotopic data are presented for Paleoproterozoic mafic dykes in western Shandong Province to characterize the Paleoproterozoic tectonic process in the Eastern Block, North China Craton. These dykes are predominantly dolerite with a major mineral assemblage plagioclase+clinopyroxene and yield a LA-ICP-MS U–Pb zircon age of 1841±17Ma. They are geochemically low- to medium-potassium subalkaline basalts and basaltic andesites. (87Sr/86Sr)(i) ratios range from 0.702859 to 0.703706, and ɛ Nd(t) values are from +3.82 to +7.42, which are slightly enriched comparable to a MORB source. The arc-like signatures are revealed in these dykes by the enrichment in LILEs and LREEs and depletion in HFSEs and HREEs. Such signatures suggest an origination from a MORB-like source metasomatized by newly subduction-related fluids potentially via source contamination. The geochemical affinity to both MORB- and arc-like sources, together with incompatible elemental ratios (e.g., Zr/Y, Th/Yb, Ta/Yb, Th/Nb and Ba/La), appears to support a development of a Paleoproterozoic intra-continental extension or failed back-arc basin setting within the Eastern Block in response to an upwelling asthenosphere, accompanied by the amalgamation of the Western and Eastern Blocks along the Trans-North China Orogen at ∼1.85Ga. Such a proposed tectonic setting might be analogue to modern back-arc basins along the western Pacific. [Copyright &y& Elsevier]

Abstract: To advance our understanding of the kinematics of the Xuefengshan tectonic belt (XFSTB) and the Mesozoic tectonics of the South China Block (SCB), this paper presents new data and interpretations from our structural studies and thermochronological dating. The XFSTB is characterized by greenschist-facies metamorphism and development of S and S–L tectonic fabrics. An asymmetric positive flower structural pattern is composed of NW–WNW- and SE–ESE-dipping cleavages, faults and shear zones. Kinematic indicators indicate a dominant top-to-WNW-thrusting with a sinistral strike-slip component on the ESE-dipping shear zones and top-to-ESE-back-thrusting on the WNW-dipping shear zones. The quartz c-axis orientations of mylonitic rocks exhibit monoclinic point-maximum asymmetry, indicative of a sinistral shear sense under the 〈a〉 basal gliding condition. The timing of the major deformation event has been constrained to the middle Triassic to early Jurassic (244–195Ma) on the basis of 40Ar/39Ar geochronology and other geological observations. The structural characteristics of the XFSTB are probably related to an Indosinian oblique convergent zone, in combination with tectonic wedging and associated back thrusting, all above a low-angle, SE-dipping basal detachment. Oblique northwestward and upward movement along the basal detachment was partitioned into the NW–WNW-directed thrusting, SE–ESE-directed back-thrusting and subsidiary strike-slip movement along the NE- and NNE-trending faults and shear zones. The XFSTB may represent part of a huge structural fan between the Yangtze and Cathaysian blocks, and can be interpreted as a product of the Indosinian intracontinental collision involving a weak zone. [Copyright &y& Elsevier]

Abstract: The Jiapigou area, at the northeastern corner of the North China Craton (NCC), is one of the most important gold-producing areas in China. It was responsible for nearly half of China''s gold production in the 1960s and at present has >100 t Au reserves. Although numerous studies, mostly not published in international literature, have been undertaken on these deposits, their genesis, age, and tectonic setting are still controversial, mainly because of the lack of reliable geochronological data. Gold deposits at Jiapigou are hosted by several ductile shear zones within late Archean gneissic tonalite, trondhjemite, and granodiorite (TTG) and amphibolite (2523±6 Ma), which have been retrogressed to greenschist facies. The deposits occur as massive auriferous quartz veins that contain sulfides (<10 vol.%) and less common disseminated- and stockwork-style mineralization. The lodes are characterized by high Au/Ag ratios and relatively higher Cu (up to 1.3%) and Pb (as much as 10.3%) contents than most other gold deposits in the NCC. Although phyllic alteration is most common, potassic and chloritic alterations characterize felsic and mafic host rocks, respectively. Compiled stable isotope and fluid inclusion data show δ34S, δ13C, δ18O and δD values ranging from −0.2‰ to 12.6‰, −4.2‰ to −5.0‰, 5‰ to 12‰, and −70‰ to −94‰, respectively. These data likely indicate consistent sources of sulfur, carbon, and hydrothermal fluids, but do not actually indicate any specific reservoir. Fluid inclusions from the deposits show variable homogenization temperatures between 150 and 350 °C, and are characterized by low salinity (0.7 to 6.5 wt.% NaCl equiv.) and H2O–CO2±CH4, N2 solutions. The initial lead isotope compositions of the deposits have considerable variations, even within individual deposits, possibly indicating multiple lead sources for the deposits. In the Jiapigou gold orefield, there are no major intrusions, but felsic, alkaline, and mafic dikes are common. These dikes usually occupy the same fault system as the gold lodes, with dikes locally hosting gold mineralization. Zircon SHRIMP U–Pb dates on pre-ore dikes yield ages of ca. 220 Ma, which constrains the maximum age of gold mineralization, whereas 40Ar/39Ar dates on hydrothermal sericite give an age of ca. 204 Ma. The timing of major gold mineralization in the Jiapigou area is therefore constrained between 220 and 204 Ma; this suggests a late Triassic gold-forming event. This episode of gold mineralization is coeval with, or slightly later than, the post-orogenic magmatism that followed the final orogenesis of the Inner Mongolian-Daxinganling orogenic belt (IMDOB), suggesting that a post-orogenic tectonic setting is appropriate for the late Triassic gold mineralization. Zircon SHRIMP dating of a granitic batholith adjacent to the Jiapigou region and also hosting gold lodes that have been previously constrained by Ar–Ar geochronology between 144 and 120 Ma yielded an age of 166±2 Ma, indicating that a mid-Jurassic (Yanshanian) gold-forming episode occurred at Jiapigou and in neighboring regions. This Yanshanian gold mineralization was contemporaneous with subduction of the Pacific plate. On the basis of the nature, timing, and tectonic setting, we favor a classification of ‘orogenic gold’ for the Jiapigou deposits. [Copyright &y& Elsevier]

New U-Pb geochronological, petrologic, elemental and Sr-Nd-Hf-O isotopic data for the granites from the Inthanon and Sukhothai zones in NW Thailand in conjunction with correlations with SW China are presented to constrain the age and position of the Paleotethys Ocean in this region and the associated assembly of Southeast Asia. The geochronological data show that the granitic rocks in the Inthanon and Sukhothai zones, herein named Group 1 and Group 2 granites, respectively, yield similar crystallization ages of 230–200 Ma. Group 1 samples are characterized by monzogranite and granite with I- and S-type geochemical affinity and Group 2 samples by I-type monzogranite and granodiorite. They have generally similar chondrite-normalized REE and PM-normalized multi-element patterns but distinct Sr-Nd-Hf-O isotopic compositions. Group 1 samples have slightly higher initial 87 Sr/ 86 Sr ratios (0.7111–0.7293) but lower ε Nd (t) values (− 11.1 to − 14.1) than those of Group 2 samples ( 87 Sr/ 86 Sr (i) = 0.7073–0.7278 and ε Nd (t) = − 8.3 to − 11.0). Group 1 samples show the lower ε Hf (t) values (− 5.4 to − 18.2), older T DM (1.62–2.40 Ga) and higher δ 18 O values (+ 7.95 to + 9.94) than those of Group 2 samples (ε Hf (t) of − 11.1 to + 4.80, T DM of 0.96–1.95 Ga and δ 18 O of + 4.95 to + 7.98) for the Triassic crystallization zircons. These geochemical signatures are similar to the Kwangsian and Indosinian granites in the South China and Indochina blocks but distinct from those of the Gangdese I-type granite and Sibumasu Paleozoic granite. Our data suggest that Group 1 samples mainly originated from the early Paleozoic supracrustal rocks containing metapelite and metavolcanic components, which had previously experienced the surface weathering. Group 2 samples were derived from a hybridized source of an old metamorphic and a newly underplated mafic component. Synthesis of our data with available regional observations indicates that the Inthanon zone represents the main suture zone of the eastern Paleotethyan Ocean in NW Thailand and links with the Changning-Menglian suture zone in SW Yunnan (SW China). In NW Thailand, a switch from the eastward subduction of the Paleotethyan oceanic plate to the collision of the Sibumasu with Indochina blocks occurred at ~ 237 Ma, and syn- and post-collisional time being at ~ 237–230 Ma and ~ 200–230 Ma, respectively. The late Triassic granites in the Inthanon and Sukhothai zones are representative of the post-collisional magmatic products. [ABSTRACT FROM AUTHOR]

The Neoproterozoic tectonic pattern of the South China Block (SCB) is considered to be a key element in the Rodinia reconstruction and subsequent Gondwana assembly. Numerous studies have been done on the Neoproterozoic igneous rocks along the SE and NW Yangtze Block of the SCB, but the contemporaneous igneous rocks in the SW Yangtze Block has poorly been known so far. This paper documents a comprehensive set of U–Pb geochronological, elemental and Sr–Nd–Hf isotopic data for the granitic gneiss and migmatite from the Ailaoshan tectonic zone of the SW Yangtze Block on the basis of field investigations. These granitic rocks are mainly granodiorite, monzogranite and quartz diorite and spatially associated with the synchronous mafic and dioritic rocks. On the basis of the A/CNK values and CIPW-normative corundum contents, these samples are subdivided into Group 1 with A/CNK > 1.1 and corundum of 1.5–6.5 vol.% and Group 2 with A/CNK = 0.87–1.09 and corundum = 0–1.5 vol.%, generally similar to the S- and I-type granitic rocks, respectively. The representative samples from Group 1 and 2 give the weighted mean ages of 810–785 Ma and 790–764 Ma, respectively, interpreted as the crystallization ages. They show strong Nb–Ta and P–Ti negative anomalies and variable Eu/Eu ∗ (0.10–0.92). The ε Nd (t) and ε Hf (t) values are in the ranges of −6.5 ∼ −4.2 and −3.8 ∼ +3.1 for Group 1 and of −6.2 ∼ +1.8 and −6.3 ∼ +5.7 for Group 2, respectively. These Neoproterozoic granitic rocks might originate from a hybridization source of metagreywacke with proportionally “ancient” mafic component for Group 1 but with abundant juvenile mafic-derived rocks for Group 2. Our data, along with the available geological observations, demonstrate the extensive occurrence of the Neoproterozoic (761–833 Ma) igneous rocks in the Ailaoshan tectonic zone. The previously-mapped Ailaoshan and Yaoshan groups might be the Complexes including the Neoproterozoic, Triassic and Cenozoic igneous rocks. A persistent and long-lived Neoproterozoic (∼830–760 Ma) subduction zone along the southwestern and northwestern margins of the Yangtze Block from Ailaoshan to Panxi and then to Hannan is proposed. The Yangtze Block might locate at the periphery of Rodinia during the early Neoproterozoic. [ABSTRACT FROM AUTHOR]

Highlights: [•] Amphibolites in the Ailaoshan tectonic zone give U–Pb age of 815–800Ma. [•] They originated from a metasomatised source or slab-melt modified wedge. [•] The formation is related with an arc-back-arc setting. [•] The South China Craton located at the margin of Rodinia. [ABSTRACT FROM AUTHOR]

Highlights: [•] The metabasic rocks in Cathaysia yield U–Pb ages of 969–984Ma and TDM(Hf) of 0.92–1.44Ga. [•] They originated from a subduction-modified MORB-like source linked to an arc–back-arc setting. [•] The South China Block was created by episodic amalgamation of a series of arc fragments between ∼970 and 820Ma. [•] The South China Block is an exterior accretionary orogen along the periphery of Rodinia rather than in the interior. [Copyright &y& Elsevier]

Highlights: [•] The mafic rocks in NE Hunan and NW Jiangxi were dated at ∼850Ma. [•] They were formed in a back-arc basin along the central Jiangnan Orogen. [•] The eastern SCB was part of an exterior accretionary orogen along the periphery of Rodinia. [Copyright &y& Elsevier]

Abstract: To achieve a better understanding of the Kwangsian orogenic event of the eastern South China Block, this paper documents a set of new zircon U–Pb geochronological and Hf isotopic data and whole-rock elemental and Sr–Nd isotopic analytical results for the representative massive granite intrusions across the Jiangshan-Shaoxing fault. The studied samples are classified into two groups, representing the rocks from the Cathaysia Block to the east of the Jiangshan-Shaoxing Fault (Group 1) and those from the eastern Yangtze Block between the Anhua-Luocheng and Jiangshan-Shaoxing faults (Group 2). The Group 1 samples gave the zircon U–Pb ages of 405–454Ma and εHf(t) values of −3.6 to −15.2 with Hf model ages of 1.6–2.4Ga. Group 2 yielded the zircon U–Pb ages of 400–432Ma and εHf(t) values of −0.2 to −12.7 with Hf model ages of 1.3–2.2Ga. Geochemically, the Group 1 samples (A/CNK=1.02–1.43) have relatively lower Al2O3, MgO, CaO, P2O5 and εNd(t) but higher K2O+Na2O than those of Group 2 (A/CNK=0.93–1.44). Both groups show similar chondrite-normalized patterns of rare-earth elements with Eu/Eu* values of 0.15–0.92 and strongly negative Ba, Sr, Nb, P and Ti anomalies in primitive mantle-normalized spider diagrams. Their εNd(t) values range from −11.1 to −8.0 for Group 1, and −8.9 to −5.0 for Group 2, generally similar to those of Precambrian paragneiss and contemporaneous gneissoid granites in the eastern South China Block. Our geochronological results indicate that the Kwangsian massive granites in the eastern South China Block were crystallized between 400Ma and 454Ma, synchronous to the Kwangsian gneissoid granites along the Wugong and Wuyi-Baiyun-Yunkai domains in the eastern South China Block. The synthesis of these whole-rock geochemical and in-situ zircon Hf isotopic data suggests that both the Group 1 and 2 granites across the Jiangshan-Shaoxing Fault were predominantly derived from a crustal source with some proportional metapelitic and metaigneous components from the Precambrian basement. The input of juvenile mantle-derived magma is insignificant. Taking into account other available evidences, it is proposed that the Jiangshan-Shaoxing Fault might be a pre-existing boundary between the Yangtze and Cathaysia Blocks, which was reactivated during the middle Paleozoic (Kwangsian) orogenic event. The massive granitic magmatism was probably resulted from the doubly crustal thickening and subsequent isostatic readjustment in an intracontinental tectonic regime. [Copyright &y& Elsevier]

Abstract: To constrain temporal–spatial patterns of the Kwangsian and Indosinian orogenic events and the Phanerozoic tectonic evolution of the eastern South China Block, this paper documents the zircon U–Pb geochronology of the high-grade metamorphic rocks for key outcrops in the eastern SCB and the P–T path for the Indosinian metamorphic amphibolites. Our data show that the representative amphibolites from the originally-defined Badou, Mayuan, Chencai, Zhoutan and Yunkai Groups and associated granulites yielded zircon U–Pb metamorphic ages of 428–468Ma. The weighted mean ages of 221–246Ma are also given by the metamorphic zircons from amphibolites and granulites in the Yunkai, Shiwandashan, northern Wuyi and southern Hunan regions. The two age groups are followed by the 40 Ar/ 39 Ar plateau ages of 406–438Ma and 195–217Ma for synkinematic minerals from major shear zones in the eastern South China Block, respectively. The age-spans of 406–468Ma and 195–246Ma roughly coincide with the formation time of the Kwangsian (396–462Ma) and Indosinian (202–248Ma) granites of the eastern South China Block, respectively. The strongly compressive deformation, metamorphism and granitic magmatism are roughly contemporaneous for the Kwangsian and Indosinian tectonothermal events in the eastern South China Block. They occurred over a similar spatial extent, only reaching westward to the Jiangnan–Xuefeng Domains across the Jiangshan–Shaoxing Fault. The amphibolites from Zhouyuan (SW Zhejiang Province) of the Cathaysia Block, which have the Indosinian zircon U–Pb metamorphic ages of 243–246Ma, underwent three episodes of metamorphism (M1–M3) and yielded a near-isothermal decompression clockwise P–T path. In combination with other geological data, it is proposed that the ages of ca. 430Ma and ca.230Ma might be interpreted as the transformational time from the prograde- to retro-metamorphism for the Kwangsian and Indosinian events, respectively. The Kwangsian and Indosinian orogenic events occurred in a similar tectonic setting where the Cathaysia and Yangtze Blocks remained contiguous, and both involved initial crustal thickening followed by rapid exhumation and final cooling, respectively. Their occurrence can be attributed to intra-plate deformation and orogenesis without the Phanerozoic subduction of the Cathaysia Block underneath the Yangtze Block, in response to the far-field stress fields for the subduction/collision beyond the southern margin of the South China Block. Our geochronological data for the amphibolites and granulites also indicate the development of abundant Neoproterozoic (ca. 800Ma) mafic magmatism in the Cathaysia interior. [Copyright &y& Elsevier]

Abstract: Elemental, Sr–Nd–Pb isotopic and geochronological data are presented for the Taishan high-mg dioritic rocks (western Shandong) from the Eastern Block of the North China Craton in order to better understand the Archean tectonic evolution and crustal growth of the Craton. The rocks gave the zircon U–Pb age of 2536–2540Ma. They show low SiO2 and Al2O3 contents, high MgO, mg-number, Cr, Ni, Y, Yb, Sr and Ba, enriched LILEs and LREEs, depleted HFSEs and HREEs with (Nb/La)N of 0.07–0.12. They exhibit ɛ Nd(t) values of 1.53–3.30, (206Pb/204Pb)i of 11.20–15.30, (207Pb/204Pb)i of 14.14–14.83 and (208Pb/204Pb)I of 31.10–33.93. Such geochemical features with an affinity to both a mantle- and crust-like source for the Taishan dioritic rocks are similar to those of the typical Archean sanukitoids, suggesting an origination from a sub-arc mantle wedge variably metasomatized by the slab-derived dehydration fluids and melts before ∼50–100Ma of the emplacement of the Taishan sanukitoid plutons. It is proposed that the Taishan sanukitoids resulted from the sudden change of the downgoing slab from a flat subduction to subsequently steeper subduction in an active continental margin regime during Neoarchean time. [Copyright &y& Elsevier]

Abstract: This paper presents the results of an integrated U-Pb detrital zircon geochronology and Si-in-white mica analysis for synorogenic sediments in the Jianghan Basin to the south of the Dabie Orogen. The results provide an improved understanding of the provenance of these sediments and the unroofing pattern of the early Mesozoic Dabie Mountain. Si contents of detrital white micas range from 3.09 to 3.34atoms pfu for the upper Triassic sandstones whereas 3.06 to 3.59atoms pfu for the lower and middle Jurassic sandstones. The majority of detrital white micas in the lower Jurassic sandstones is phengitic and originated exclusively from the Dabie high- to ultrahigh- pressure rocks. The U-Pb dating results of the detrital zircons for seven samples suggest that these synorogenic sediments have a significant change of provenance from late Triassic to early and middle Jurassic. For the upper Triassic sandstone, the U-Pb age clusters of these zircons are characterized by ~420-450Ma, ~750-820Ma, ~1050-1200Ma and ~2500Ma with minor Luliangian (~1700–2000Ma) components. In contrast, the zircon ages of the Jurassic sandstones are dominated by the Luliangian (~1700–2000Ma) ages with only minor Caledonian (~420-450Ma) and Greenville (~1050-1200Ma) ages. In combination with other available geological data, it can be concluded that the Dabie HP-UHP rocks might initially be exposed to the surface at the beginning of early Jurassic (~190Ma). The Jiangnan terrain (also named “Jiangnan old continental in Chinese) to the south of the Jianghan basin provided the predominant supply of upper Triassic sediments, whereas the Paleoproterozoic Yangtze crustal materials (overlying the present Dabie Complex at the time) were the important provenance of the Jurassic sediments in the Jianghan basin. [Copyright &y& Elsevier]

The Dongping area in the central part of the northern marginal zone of the North China Craton (NCC) is one of the most important gold-producing areas in China, and has been intruded by a number of alkaline and granitic batholiths or plutons spatially associated with gold deposits. Previous dates on these intrusions yield contradictory data, depending on the isotopic methodology used, and have led to ambiguity in understanding magmatic evolution and gold mineralization of the region. Detailed SHRIMP U–Pb zircon geochronology of the alkaline and granitic rocks in the study area now reveals details of its tectono-magmatic history. Zircons from a granitic gneiss hosting the Xiaoyingpan gold deposit yielded concordant ages of ca. 2.5 Ga. This constrains regional metamorphism of the Archaean basement to late Archaean time. A second magmatic event at ca. 1.8 Ga is revealed by xenocrystic/inherited zircons with this age. These two Precambrian events are coeval with those in other parts of the NCC. The largest igneous intrusion in the region, the Shuiquangou syenite–monzonite complex, was emplaced at ca. 390 Ma, as indicated by the magmatic zircon populations of the two samples from the central and eastern parts of the complex. The accretion of a volcanic arc onto the northern margin of the NCC is considered as a plausible cause of this alkaline magmatism. The emplacement of the Guzuizi porphyritic granite pluton at 236±2 Ma represents another major magmatic event in the region, probably a response to postcollisional orogeny following amalgamation of the North China and Angara cratons. Latest magmatism is marked by the emplacement of the Shangshuiquan monzogranite at 142.2±1.3 Ma, which is most likely related to an underplating event that took place in the Dongping and its adjacent areas at ca. 140 Ma. More importantly, these results suggest that gold mineralization in the area, essentially a single event as indicated by similar deposit characteristics, is broadly coeval with this latest granite magmatism. Hence, this mineralization is about 250 Ma later than the emplacement of the Shuiquangou alkaline complex and, thus, is interpreted to preclude the widely accepted model that suggests gold deposits have genetic relationships with alkaline magmatism. The late timing of gold mineralization with respect to felsic magmatism in the area is similar to those observed in other major gold-producing provinces in the NCC. In all these major gold provinces, we suggest that gold mineralization is coeval with the latest granite magmatic event at about 140–120 Ma. This farther suggests that these mesothermal gold deposits were formed from similar tectono-magmatic environments. [Copyright &y& Elsevier]