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Hydrothermal rutile (TiO2) is a widely distributed accessory mineral in hydrothermal veins or alteration assemblages of porphyry deposits and provides important information for further understanding hydrothermal fluid signatures. This study determines the geochemical composition and U-Pb dates of hydrothermal rutile from the Yulong porphyry Cu-Mo deposit in east Tibet, China. Three types of TiO2 polymorphs have been identified based on their Raman spectroscopic, textural, and chemical characteristics. (1) Brookite and anatase pseudomorphs after titanite in a fine-grained matrix, indicating low-temperature hydrothermal fluids destabilizing primary Ti-bearing minerals during argillic alteration (type-I). (2) Elongated and prismatic rutile present in hydrothermal veins or in clusters in accompanying alteration envelope characterized by weak zoning (type-II). And (3) rutile intergrown with sulfides in hydrothermal veins, characterized by well-developed patchy and sector zoning (type-III). In contrast to the type-I and type-II TiO2 polymorphs, tungsten is enriched in backscattered bright patches and sector zones in type-III rutile, which is due to the substitution of W6+ in the Ti4+ octahedral site. The mechanism of the enrichment of tungsten is effectively driven by the halogen-rich (F, Cl) aqueous fluids during hydrothermal mineralization. In situ U-Pb dating of the type-III rutile yields a lower intercept age of 41.8 ± 1.2 Ma, which brackets the timing of the Cu-Mo mineralization. The relationship between rutile textures and composition indicates that W-bearing rutile can serve as a recorder of hydrothermal processes in porphyry Cu deposits.

The East Kunlun Orogen (EKO) in the northern Tibetan Plateau records two continental collisional orogenic events and magmatism in early Paleozoic and early Mesozoic. However, possible magmatic additions to the continental crust growth of the EKO in different tectonic stages of early Paleozoic collisional orogeny have been overlooked. Three phases of early Paleozoic plutons from the Xiangride-Kuhai area in the east of the EKO have been chosen for detailed investigation and the results are reported here. The oldest magmatic suite (Stage 1) includes the ca. 471 Ma Qurelong Monzodiorite and ca. 454 Ma granodiorite in the Zhiyu Intrusive Complex. The monzodiorite has a sanukitoid-like composition with high TiO2 and Y contents and is interpreted as being derived from partial melting of metasomatized mantle wedge lherzolite. The granodiorite is typified by its high SiO2 content, high Sr/Y ratio, and depleted Hf isotope, and is interpreted as an adakite-like melt derived from the melting of a subducted Proto-Tethys oceanic crust. The magmatism can be linked to northward subduction of the Proto-Tethys Ocean between 520 and 450 Ma. Stage 2 magmatism is represented by a plutonic suite emplaced during ca. 450−431 Ma with an I-type granitic composition. Of these, the ca. 447 Ma Kengdenongshe Intrusion composed of peraluminous granite with enriched Nd-Hf isotopes is indicative of a Mesoproterozoic igneous source in the orogen. The ca. 450−434 Ma monzogranite and granodiorite in the Walega and Zhiyu intrusive complexes exhibit variable element and isotope compositions. They would have been generated by magma mixing of felsic melts from the old crust and mafic magmas derived from the metasomatized lithospheric mantle, with a mafic melt proportion of >30%. The ca. 431 Ma quartz diorite in the Walega Intrusive Complex is formed through crustal assimilation and fractional crystallization of mafic magmas derived from the metasomatized lithospheric mantle, with a mafic melt proportion >60%. Stage 2 suite was emplaced during the closure of Proto-Tethys oceanic branches and subsequent continental collision during 450−426 Ma. Magmatism diminished between ca. 426 and 410 Ma during exhumation of the continental lithosphere as indicated by the presence of retrograde eclogites in the EKO. Stage 3 magmatic suite includes the ca. 408 Ma Langmuri Intrusion and ca. 403 Ma Niantang Syenogranite. These plutons are adakite-like or have an A-type granitic composition and are enriched in Nd-Hf isotopes. They might have been derived from the remelting of old and juvenile continental crust in a post-collisional extensional setting during 410−390 Ma. Identification of partial melts, derived from the subducted Proto-Tethys oceanic crust and metasomatized lithospheric mantle in stage 1 and 2 plutons, show that the subcrustal materials have been significantly transferred to the overlying continental crust. Hence the magmatism in oceanic subduction (Stage 1) and continental collision (Stage 2) settings contributes to the early Paleozoic juvenile continental crust growth of the EKO. The post-collisional extensional setting (Stage 3) is dominated by the reworking of a pre-existing continental crust. The early Paleozoic continental crust growth processes in the EKO are different from the previous view in which the continental collision orogens have no crust growth, and inconsistent with the proposal that crust growth is significant only in a continental collision setting.

Although China is well-endowed with tungsten deposits, while the tungsten resources in the Central Asian Orogen Belt (CAOB) are rarely reported. Recently, many W-skarn deposits have been discovered in the East Tianshan, but the source and evolution of the mineralising fluids are poorly understood. The Xiaobaishitou W(–Mo) deposits are hosted by carbonaceous limestone or banded crystalline limestone in the Mesoproterozoic Jianshanzi Formation, which is intruded by Triassic biotite monzogranite. The deposit comprises garnet-dominated prograde skarn and retrograde skarns followed by oxides (scheelite–cassiterite–magnetite), sulphides (quartz–molybdenite–bismuthinite–pyrite–chalcopyrite–sphalerite–galena), and carbonate stages. The types of fluid inclusions are composed of liquid-rich aqueous, vapour-rich aqueous, aqueous carbon-dioxide, and daughter mineral-bearing inclusions. The homogenization temperatures of fluid inclusions change from > 400 °C in garnet, through > 380 °C in epidote and 310–280 °C in scheelite, to 280 °C in quartz and 220 °C in calcite indicating a complex magmatic-hydrothermal process. The δ18Owater values varied from + 6.1 to + 8.4‰ in garnet, + 5.2 to + 7.4‰ in epidote, + 2.0 to + 3.0‰ in quartz, to − 0.7 to − 0.1‰ in calcite. The corresponding δD values are − 95 to − 71‰ in garnet, − 84 to − 80‰ in epidote, − 115 to − 90‰ in quartz and − 101 to − 89‰ in calcite. Both O and H isotopic compositions show the mineralisation fluids are originated from deep-sourced magmatic fluids. The δ13CCO2 values in the calcite range from − 7.8 to − 7.7‰, which is characteristic of magmatic fluids interacting with reduced carbon from metamorphic rocks. The δ34S values of hydrothermal fluids range from + 4.5 to + 5.1‰, and 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of sulphide are 18.072–18.664, 15.566–15.708, and 38.245–38.658, respectively, representing a mixed characteristic of magmatic and sedimentary sulphur. Considering the coexisting of L-type and V-type inclusions in the scheelite, we proposed that pH increase caused by fluid boiling may be the major cause for the precipitation of scheelite at the Xiaobaishitou deposit.

The Dahongliutan rare-metal pegmatite deposit, associated with the pegmatite dikes hosted by Dahongliutan pluton and metasedimentary rocks, is a new discovered Li–Be deposit in the the West Kunlun ...

Late Mesozoic igneous intrusions and extensional structures in Carboniferous to Permian sequences in the SW Fujian region acted as important controls on the localisation of Fe-polymetallic deposits. Here we document the identification of extensional deformation at shallow crustal levels and syn-tectonic granites related to normal faults. Based on spatial distribution and structural features, the extensional deformation can be divided into cover-only and basement-intersecting styles. A series of syn-tectonic plutons were emplaced into the footwall of normal faults. Representative samples of the Tangquan Granite have high SiO2 (66.4 wt.%–73.9 wt.%) assays and Mg# values (37–59). The samples also have relatively homogenous initial 87Sr/86Sr (0.708 3–0.708 9) and eNd (−9.2–−10.2) values. Geochemical and isotopic evidences indicate that the Tangquan granite originates from a hybrid source including lower crustal-derived felsic and lithospheric mantle-derived mafic magmas. Zircon U-Pb dating indicates that the granodiorite phase from the pluton crystallised at 161±4 Ma and the monzogranite phase crystallised at 159±1 Ma. Combined with the granitic rocks in a wider region of SE China, the widespread granitic magmatism and polymetallic mineralisation have been synchronous during the Late Mesozoic, probably resulting from extensional tectonics related to the lithospheric thinning.

North China (NC) is a region recording a long and complex geological history spanning from the Archaean to Cenozoic. This included magmatism, sedimentation, metamorphism, and deformation, demonstra...

The Huaishuping gold deposit is located in the Xiong’ershan Mountains of the Qinling-Dabie Orogen of central China. The mineralisation is structurally controlled and hosted by faulted rhyolite, quartz andesite, volcaniclastic rocks and volcanic breccia assigned to the Jidanping Formation towards the top the Palaeoproterozoic Xiong’er Group. The deposit has a resource of around 32 t with an average grade of 5.5 g/t Au. Alteration at the deposit progressed from an early K-feldspar–quartz–pyrite assemblage through quartz–pyrite–gold, quartz–base-metal sulfides, to a late-stage assemblage of quartz–carbonate. The δ34S (V-CDT) values for pyrite in the ore range from − 13.3 to + 1.6‰. The calcite has C-isotopes ranging from − 6.1 to + 2.5‰ (V-PDB) and O-isotopes from + 10.6 to + 15.8‰ (V-SMOW). The δ18O quartz ranges from 10.5 to 15.1‰, and the δD values for fluid inclusions in quartz range from − 93 to − 76‰. The δ56Fe value for the mineralisation varies between 0.1 and 0.5‰ with corresponding δ57Fe values between 0.2 and 0.7‰. The isotope systematics indicates that the hydrothermal fluids were derived from metamorphic fluid, but the source of gold remains uncertain. Re–Os dating of molybdenite yields a date of 202 ± 8 Ma interpreted as the age of the gold mineralisation. This age is consistent with the Triassic onset of extensional tectonics following the collision between North and South China.

Paleoproterozoic orogens of the North Australian Craton are related to the assembly of the Columbia Supercontinent. The roles of the distinct orogens in the Paleoproterozoic craton amalgamation are poorly understood due to the lack of surface exposure. The age and isotopic systematics of detrital zircon grains hosted in Paleoproterozoic sedimentary sequences are used to unravel the geological history of the craton, in terms of paleogeography and tectonic setting. The oldest (Early Paleoproterozoic) metasedimentary units are characterised by detrital zircon ages peaking at ca. 2500 Ma. The zircon eHf values show large variations in the different orogens and range from −18 to +6. The overlaying youngest turbiditic units show minor accumulation of Archean detritus. Units from apparently different metasedimentary sequences have a major detrital zircon age population at ca. 1865 Ma, and a relatively restricted range of zircon eHf values between −7.3 and +2.6. The isotopic distinctiveness of the oldest units is attributed to local variations in the depositional environment, probably due to horst-graben architecture of the early Paleoproterozoic basin. The youngest turbiditic units blanketed this early horst-graben architecture and in part have a local provenance. Potential detritus sources include South Australian Craton, Dharwar Craton and Aravalli-Lesser Himalayan terrains in India, South China, and Madagascar (Africa). This finding indicates that these regions might have been connected before the Columbia Supercontinent was formed. The ubiquitous ca. 2500 Ma magmatic event records the assembly of these cratonic fragments in a previous supercontinent called Kernorland. In addition, the data do not support a proximity of the North Australian Craton with the North China Block, Western Laurentia (North America), and Kaapvaal Craton (Africa) during Columbia amalgamation.

The Wulanba granite, consisting of biotite monzogranite and syenogranite, is located in the southern part of the Great Xing’an Range, NE China. Whole-rock major- and trace-element geochemistry suggests the Wulanba granite is a high-K–shoshonitic, slightly peraluminous and highly differentiated I-type granite. The Sr–Nd–Hf isotopes indicate that it originated from partial melting of juvenile crust derived from the depleted mantle with a minor input of old crust. The relatively young T2DM and tDM2 ages indicate it was most likely derived from a Late Neoproterozoic to Early Palaeozoic source. We have demonstrated that the biotite monzogranite is the ore-related intrusion of the Haobugao Zn–Fe mineralization based on the following geological, geochronological and geochemical evidence: (1) the chalcopyrite/pyrite in the biotite monzogranite and the continuous mineralization of drill core ZK2508; (2) the consistence of the emplacement age of the biotite monzogranite (~141–140/138 Ma) with the skarn mineralization age (~142 Ma); and (3) the presence of rich ore-forming elements (Fe–Zn–Cu) in the biotite monzogranite, and the similar Pb compositions of the sulfides from the Haobugao deposit and the biotite monzogranite. Compared to the barren syenogranite, the fertile biotite monzogranite is more oxidized, while the edges of the apatite grains in the biotite monzogranite are more oxidized than the centres. The average F/Cl ratio of the fertile biotite monzogranite (~123.45) is much higher than that of the barren syenogranite (~73.98). We conclude that these differences reflect unique geochemical signatures, and the geochemical composition of the apatite can be used to infer the economic potential of granites.

The Chamuhan Granite is located in the eastern part of the Central Asian Orogen where it crops out as an elongated, NE-trending composite monzogranite. The pluton consists of two phases with a fine – grained monzogranite (G2) at depth in sharp contact with a medium – grained monzogranite (G1) above. The medium-grained monzogranite can be subdivided into G1a and G1b based on the degree of metasomatism affecting it, with the G1b being more altered. Tungsten–molybdenum mineralisation is hosted by quartz (−fluorite) veins or forms disseminated sulfides in G1a, indicating a genetic association between the monzogranite and ore. Magmatic zircons from G1a yield a weighted mean age of 144 ± 2 Ma, and hydrothermal zircons from G1a yield a weighted mean age of 143 ± 1 Ma, indicating that the hydrothermal zircons are very close in age to the medium-grained monzogranite. Monazite grains yield U – Pb isotope ages of 138 ± 3 Ma for G1a, 137 ± 1 Ma for G1b, and 139 ± 2 Ma for the fine-grained monzogranite (G2) phase. These dates are the same within analytical error, and are coeval with the molybdenite Re – Os weighted mean age of 140 ± 2 Ma, indicating that the monazite and molybdenite were deposited during hydrothermal alteration. The Chamuhan Granite is geochemically a metaluminous to slightly peraluminous high – K calc-alkaline granite, and is especially characterised by its REE tetrad pattern and a huge Eu depletion that are accompanied by a non – “Charge-and Radius-Controlled” (CHARAC) trace element behaviour. This and the O-isotopic data from the granite phases are indicative of a highly differentiated magma that interacted strongly with a co–existing fluid emanating from the magma during the late stage of its crystallisation. The interaction between the magma and related hydrothermal fluid resulted in the enrichment of W–Mo(–Nb–Ta–Th–U–Hf–Rb–Y). All the studied granitic rocks have homogeneous initial isotope values with positive eNd(t) values of 0.1–3, and TDM2 dates between 924 and 691 Ma. This is consistent with granites derived from a pre-existing juvenile crust derived from a depleted mantle during the Neoproterozoic. The molybdenite in the Chamuhan W – Mo deposit has a narrow δ34SVCDT range of 0.1–1.6‰ characteristic of a magmatic origin, and the Pb isotopic compositions with 206Pb/204Pb ratios between 18.298 and 18.882, 207Pb/204Pb ratios between 15.494 and 15.538 and 208Pb/204Pb ratios between 38.046 and 38.206, are similar to the calculated initial Pb isotopic ratios of the Chamuhan Granite. We thus suggest that there is an intimate relationship between the Chamuhan Granite and mineralisation, and that the mineralising process is related to a post-collisional extensional event following the formation of an over-thickened continental crust and during closure of the Mongol-Okhotsk and Paleo-Pacific oceanic plates.

The East Kunlun Orogen is located in the northern part of the Tibetan Plateau and has received significant attention in tracing the evolution of Paleo-Tethys Ocean. In this study, we present U-Pb zircon geochronology, geochemistry and Sr-Nd isotopic data on the Kengdenongshe tholeiitic gabbro in the eastern part of the orogen. The gabbro is characterised by high and variable MgO and Fe2O3, as well as low K2O and TiO2 contents, typical of low-K tholeiitic series. The rock shows enrichment in large-ion lithophile elements, depletion in high field strength elements, with rare earth element signature similar to that of a back-arc basin basalt. The rock displays relatively low and uniform (87Sr/86Sr)i ratios and high eNd(t) values. These geochemical and isotopic features are interpreted to represent magma derivation from partial melting of an enriched asthenospheric source. Our model envisages that the initial melting started in the garnet-facies (~4%) and continued in the spinel-facies (~6%). The geochemical and isotopic systematics of the gabbro are consistent with magma generation in a back-arc basin setting triggered by the subduction of the Paleo-Tethys Ocean. In conjunction with the data on mafic magmatic suites in the region, we trace a progressive change in source from asthenosphere to increasingly enriched mantle wedge. Our study proposes a transition in the geodynamic setting of the east Paleo-Tethys Ocean from back-arc extension during the Late Permian to continued subduction during the Late Permian and Middle Triassic.

The Himalayan mineral field includes over 50 quartz-vein type Sb-Au deposits, and placer Au deposits. The poorly documented Laqiong deposit is a typical example of quartz-vein type Sb-Au mineralisation in Tethys Himalayan sequence. The orebody are controlled by shallow north-dipping normal faults and north–south trending faults. Magmatic zircons extracted from muscovitic leucocratic granite from the southern part of the Laqiong mine area yield a Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry U-Pb age of 14 ± 1 Ma (n = 12, MSWD = 0.9) that is similar to the 40Ar/39Ar age of ca. 14 Ma from hydrothermal sericite in auriferous sulphide-quartz veins. The eHf(t) values for the magmatic zircon rims range from −5.4 to −1.9, corresponding to two-stage Hf model ages of 1403–1214 Ma. Quartz from the mineralised veins has δ18OH2O-SMOW values varying from +4.97 to +9.59‰ and δDH2O-SMOW values ranging from −119.7 to −108.1‰. The δ13CV-PDB values for calcite from the ore Stage III range from −6.9 to −5.3‰, and calcite from Stage IV are −3.5 to −1.7‰. The δ18OV-SMOW values for calcite from Stage III are +20.3 to +20.6‰ and for Stage IV are −6.3 to −4.9‰. The stibnite and pyrite samples have 208Pb/204Pb ratios of 38.158 to 39.02, 207Pb/204Pb ratios of 15.554 to 15.698, and 206Pb/204Pb ratios of 17.819 to 18.681, and bulk and in-situ δ34SV-CDT values for stibnite, arsenopyrite and pyrite range from −1.1 to +2.3‰. The calcite from the orebodies are enriched in MREE and depleted in LREE and HREE. Fieldwork, petrological, and geochemical data collected during our study leads to the following salient findings: the mineralising fluid is a mix of magmatic and meteoric fluids; and the deposit is closely related to the emplacement of Miocene granites originating from a thickened continental crust.

Many Mesozoic Mo-bearing granites, present along the northern margin of the Precambrian North China Block (NCB) and Phanerozoic Xing'an-Mongolian Belt (XMB) within the Central Asian Orogen (CAO) have hydrated sources. These granites are temporally and spatially related to biotite-rich mafic, alkali syenitic plutons, are highly evolved, have an arc-like trace element geochemical pattern, and were emplaced between ca. 245–129 Ma bracketed by A2- and A1-type granites. This conflicts temporally with the current model involving the westward subduction of the Pacific oceanic plate. We use Sm/Nd and Th/Yb ratios of Mesozoic nepheline-bearing pyroxene-biotite syenites (biotite-syenites), mantle-peridotite xenoliths from Palaeozoic diamondiferous kimberlites, and Mesozoic to Cenozoic alkali basalts to define a hydrous melt-extraction trend. The results indicate a Palaeozoic mantle-peridotite source that is more metasomatised than the lower continental crust and the source of the Mesozoic (

GeoPyTool is an open source application developed for geological calculations and plots, such as geochemical classification, parameter calculation, basic statistical analysis and diagrams for structural geology. More than acting as a link from raw data stored in Microsoft Excel® (MS Excel) files to vector graphic files, GeoPyTool includes recently developed routines that have not been included in previous software, such as the calculation of the Ce(IV)/Ce(III) ratio for zircons as a method to examine the temporal evolution of oxygen fugacity in the magmatic source for igneous rocks, and the temperature calculator with titanium in zircon and zirconium in rutile. Besides these routines, GeoPyTool also allows users to load any figure from articles or books as a base map. As a Python-based cross-platform program, GeoPyTool works on Windows®, MacOS X® and GNU/Linux. GeoPyTool can do the whole process from data to results without the dependence of Microsoft Excel®, CorelDraw® and other similar software. It takes Excel® XLSX and CSV (Comma Separated Value) as the formats of both the input data source files and the output calculation results files. The figures generated by GeoPyTool can be saved as portable network graphics (PNG), scalable vector graphics (SVG) or portable document format (PDF). Another highlight of GeoPyTool is the multilingual support, the official version of GeoPyTool supports both Chinese and English, and additional languages can be loaded through interface files. GeoPyTool is still in the development stage and will be expanded with further geochemical and structural geology routines. As an open source project, all source code of GeoPyTool are accessible on Github (https://github.com/GeoPyTool/GeoPyTool). Users with Python experience can join in the development team and build more complex functions expanding the capabilities of GeoPyTool. Keywords: Python, Geochemistry, Structural geology, Calculation, Cross platform

The large Bilugangan porphyry Mo deposit is one of the oldest Mo deposit in eastern part of the Central Asian Orogen in Inner Mongolia. The orogen is currently regarded as the most important Phanerozoic region with widespread crustal growth between the Siberian Craton to the north, and North China Block to the south. The Bilugangan Mo mineralisation is hosted by a porphyritic monzogranite and along the contact with the Late Permian Linxi Formation. The mineralisation is disseminated in places and includes various types of hydrothermal veins. The mineralising stages of the deposit includes the pre-ore quartz–K-feldspar(–biotite) pegmatite succeeded by quartz–K-feldspar–molybdenite–muscovite–sericite(–pyrite) veins, quartz–molybdenite–chalcopyrite–perthite–muscovite–sericite(–pyrite–sphalerite), and post-ore quartz–fluorite–calcite (–sericite–muscovite–) veins. Seven molybdenite samples from the mineralisation yield a Re-Os Mo weighted mean date of 238 ± 1 Ma, which is the same, within error, as the Re-Os isochron age of 238 ± 2 Ma, and the ca. 240 Ma age of the porphyritic monzogranite. This is the oldest porphyry Mo – type deposit in the eastern part of the orogen, and the only large –sized Mo deposit in the region, which shows that the east CAO is prospective for Triassic mineralisation. Thirty-three samples of sulfide from the deposit have a narrow δ34SVCDT(‰) range of 1.5 to 4.3‰, indicating that the sulfur the sulfur has primarily a magmatic source. The sulfides from the Mo-bearing veins have relatively concentrated Pb isotopic compositions with 206Pb/204Pb ratios between 18.295 and 19.576, 207Pb/204Pb ratios between 15.535 and 15.662, and 208Pb/204Pb ratios between 38.066 and 38.653. These values are consistent with those of the initial Pb isotope ratios for whole rock samples from the porphyritic monzogranite and hornfels. Fifteen gangue quartz samples from various veins define a range of δ18Ofluid values from 0.5 to 5.2‰ with δDfluid values ranging from −115 to −60‰, indicating that the onset of the mineralising fluid was generated from in-situ degassing of a magmatic source, followed by an input of meteoric water during the late ore-forming stage. It is proposed that the deposit is a collision-related Dabie-type deposit, which is related to the closure of the Paleo-Asian Ocean between the North China Block and Siberian Craton.

The Xiaoshuijing Syenogranite is the host of Mo mineralisation recently discovered in the Tengchong Terrane of southwestern China. Here, we present new zircon U-Pb ages and molybdenite Re-Os ages, whole-rock geochemical data, and zircon Hf isotopic data for the Xiaoshuijing Syenogranite hosting disseminated Mo mineralisation. The syenogranite’s mineralogical and geochemical characteristics indicate it is a high-K, alkaline, and peraluminous granite. LA-ICP-MS analysis of zircon yields an age of 65 ± 1 Ma (n = 14, MSWD = 2.1), and yields negative zircon eHf(t) values ranging from −18.23 to −12.92, interpreted to have a crustal source. The Re-Os Mo age of 64 ± 2 Ma (n = 4, MSWD = 2.2) for the mineralisation is the same as the syenogranite’s age, within error. The geochemistry also indicates that the syenogranite is related to a thickened crust resulting from the eastward subduction of the Neo-Tethyan oceanic lithosphere shortly before the collision of the Indian and Eurasian continental crusts.

Research on history of the Earth’s continents and the genesis of mineral deposits has been one of the hotspots in geology. But only limited studies have been completed on iron deposits hosted by banded iron-formations (BIFs), such as the large Hanwang iron deposit located in the eastern North China Craton (NCC). In this contribution, we present the petrology, zircon U–Pb geochronology, Lu–Hf isotopes and whole-rock geochemistry on Hanwang iron deposit hosted by the metamorphosed Neoarchean to early Paleoproterozoic Taishan Group and orthogneiss derived from tonalite–trondhjemite–granodiorite (TTGs). Magnetite-bearing amphibolite, magnetite-bearing quartz amphibolite, and gneiss host the Hanwang iron deposit, which is characterised by subhedral to euhedral magnetite, pyrite with minor galena and BIF laminations. Gangue minerals include hornblende, plagioclase and quartz with minor amounts of biotite, chlorite, epidote and microcline. This mineral assemblage is indicative of amphibolite-facies metamorphism with regression to greenschist-facies. The deposit is located in a transition zone between metamorphosed mafic to felsic volcanic rocks. The age of the Hanwang BIF-hosted iron deposit is late Neoarchean. Lu–Hf isotope systematics indicate that the protolith for the biotite amphibolite is derived from a Neoarchean mantle contaminated by the crust, and orthogneiss is derived from the Neoarchean crust. The biotite amphibolite is characterised by high Na, Fe and low K assays, enrichment in light rare earth elements (LREE), and relatively depletion in heavy REEs (HREE) without an obvious Ce anomaly. The geochemistry of the orthogneiss is characteristic of a volcanic–arc granite, although this must be accepted with caution given that the orthogneiss is metamorphosed and deformed at amphibolite-facies. It is proposed that Hanwang iron deposit was deposited in a marine volcanic–arc environment and derived from hydrothermally leached volcanic units, and similar to the Algoma-type iron deposit. Most BIFs occurring in Neoarchean granite-greenstone succession of the eastern NCC belong to the Algoma-type iron deposits. Globally, this sequence appears to be coeval with the Yilgarn Craton in Western Australia.

The Yinachang Fe-Cu-Au-U-REE deposit is located in the Kangdian region at the southwestern margin of the Yangtze Block. This contribution presents petrological, geochronological, whole rock geochemical, and Rare Earth Elements (REE) geochemistry of zircons of gabbro and diorite dykes associated with the Yinachang Fe-Cu-Au-U-REE deposit, aiming to constrain the age of the mineralisation and help refine our understanding of the tectonic setting of the region. Zircons from diorite have a Palaeoproterozoic U-Pb age of 2014 ± 30 Ma, and zircons from the gabbro could not be dated because they are metamict, having a high concentration of uranium. The ca. 2014 Ma age of the zircons in the diorite indicates that the southwestern part of the Yangtze Block is partly synchronous with the Columbia Supercontinent. Geochemically, the diorite and gabbro are enriched in large-ion lithophile elements (LILEs) such as Rb and U, and depleted in high-field-strength elements (HFSEs) such as Nb, P, Ti, Ba, and Sr. The diorite is enriched in light REEs (LREEs) and has a slight to negligible Eu anomaly, which are characteristic of ocean-island basalts containing mantle-derived high potassic calc-alkaline rocks. In contrast, the gabbro is weakly enriched in LREEs and has a slightly negative Eu anomaly similar to those of potassic calc-alkaline enriched mid-ocean-ridge basalt. The average combined REE content of zircons from the gabbro is 19401 ppm and is significantly higher than that of the zircons from the diorite averaging 1020 ppm. This indicates that the gabbro is closely related with the REE mineralisation at the deposit. The geochemistry of the diorite indicates that it formed at the continental margin of a volcanic-arc. It also indicates that the magmatic rocks in the region have a possible mantle plume origin contaminated by crustal material and located at a transitional zone between a rift and an ocean-continent tectonic setting.

Precise geochronology is a crucial tool for understanding the genesis of low-temperature hydrothermal mineral deposits, but datable minerals are not always available; e.g., mineralization within sedimentary rocks, such as Carlin-type or Carlin-like Au deposits. Here, we demonstrate that hydrothermal apatite associated with Au from the large Nibao deposit in the Yunnan–Guizhou–Guangxi region of South China can be dated to yield the age of Au mineralization. Nibao is a Carlin-like deposit hosted in a Permian carbonate-bearing pyroclastic breccia. The auriferous minerals are predominantly zoned pyrite containing As-, Cu-, and Au-rich rims. Euhedral and subhedral apatite forms a mosaic texture and is intergrown with hydrothermal quartz, sericite, and zoned auriferous pyrite, indicating that the apatite is of hydrothermal origin and was coeval with Au mineralization. Unlike sedimentary and igneous apatite, hydrothermal apatite is relatively depleted in LREEs, enriched in MREEs, and slightly depleted in Eu. Hydrothermal apatite also has high Th/U ratios, negligible U concentrations, and very low concentrations of common Pb. This makes the apatite a potential candidate for Th Pb dating. Our SIMS Th Pb analyses yield a weighted mean 232Th/208Pb age of 141 ± 3 Ma (N = 23, MSWD = 2.2) for apatite coeval with auriferous pyrite, and this is the best estimate of the timing of Au mineralization. Hydrothermal apatite is also present in similar deposits in the Golden Triangle of South China. Therefore, Th Pb dating of hydrothermal apatite potentially allows for the accurate dating of low-temperature hydrothermal deposits in China and worldwide.

Jurassic and Late Cretaceous granites are spatially and temporally associated with mineralisation in the Paleozoic Dayaoshan Terrane in South China (also known as South China Block). The porphyritic Baoshan Monzogranite of Late Cretaceous is an example that is petrographically studied in this contribution. Sensitive High-Resolution Ion-Microprobe (SHRIMP) zircon U-Pb ages, in-situ zircon O-Hf isotopic analyses, and whole-rock geochemistry are here used to better constrain the genesis of the monzogranite, which is porphyritic, and located in the Baoshan Cu mining area. SHRIMP zircon dating yields a weighted mean 206Pb/238U age of 89 ± 1 Ma, interpreted to be the crystallisation age of the porphyritic monzogranite. Its geochemical data indicates it is derived from partial melting of the lower to crust, followed by fractionation, and emplacement in secondary faults related to the major Bobai-Cenxi Fault. The monzogranite has a Paleo- to Mesoproterozoic source in the crust, which was metasomatised during Neoproterozoic subduction. The rotation of Izanagi Plate’s subduction from NW to NE resulted into the reactivation of NW and NE-trending thrust faults as transpressional or extensional ones. It was during this period that Late Cretaceous intrusions such as the Baoshan porphyritic monzogranite were emplaced in the terrane near the NW-trending faults and other intrusions at the edges of basins such as Yangchun, Luoding and Bobai basins near NE-trending faults.

The Baiganhu W-Sn ore field in the northwestern area of the East Kunlun Orogen, NW China, contains three economically important W-Sn deposits, namely Kekekaerde, Baiganhu and Bashierxi. Timing of the W-Sn mineralization remains under debates due to lack of precise isotope dating directly conducted on ore minerals. We herewith report LA-MC-ICP-MS (laser ablation (multi-collector) inductively coupled plasma mass spectrometry) and ID-TIMS (isotope dilution thermal ionization mass spectrometry) cassiterite U−Pb ages for the Kekekaerde W-Sn deposit in the Baiganhu W-Sn ore field. The ID-TIMS cassiterite 206 Pb/ 238 U results yield a weighted mean age of 416 ± 1 Ma (95% confidence, MSWD = 0.8), and the LA-MC-ICP-MS analytical data give a 206 Pb/ 207 Pb– 238 U/ 207 Pb isochron age of 426 ± 13 Ma (95% confidence, MSWD = 0.1). These two ages are same within errors, suggesting that the mineralization in the Baiganhu W-Sn ore field occurred at ca. 416 Ma. These new ages and understandings are consistent with the previously reported zircon U−Pb ages of 430–420 Ma for the ore-bearing granites in the ore-field, and with the 40 Ar/ 39 Ar plateau ages of ca. 412 Ma for the hydrothermal muscovite from ore-bearing quartz veins and greinsenized granite. It shows that the granite magmatism and its associated hydrothermal mineralization resulted from the Caledonian Orogeny that accommodated the closure of the Proto-Tethys, followed by the continental collision between the Central Kunlun, Northern Kunlun terranes and the Qaidam Block.

The Caojiaba tungsten deposit (19.03 Mt@ 0.37 wt% WO3) is hosted by skarn along the contact between clastic and carbonate rocks in the Xiangzhong Metallogenic Province of southern China. The deposit is characterized by an early prograde skarn containing low andraditic garnet (Ad0.7–21.9) and hedenbergitic pyroxene (Hd52.9–77.3) overprinted by a retrograde biotite–chlorite assemblage and then by quartz–scheelite veins, similar to well-studied reduced tungsten skarns worldwide. Scheelite has low MoO3 (0.01–0.16 wt%), and ore commonly contains up to 1.5 ppm Au and up to 0.33 wt% Sb. Sensitive high-resolution ion microprobe (SHRIMP) U–Pb analyses of hydrothermal titanite coexisting with scheelite in three skarn ore samples provide ages between 206 ± 5 Ma and 196 ± 3 Ma (2σ). Our new ages demonstrate that the tungsten mineralization took place at Caojiaba between 206 and 196 Ma, overlapping the 228–201 Ma emplacement age of granitic rocks in the Xiangzhong Metallogenic Province. Mineralogical and geochronological evidence collectively indicates that Caojiaba is a distal reduced W skarn deposit. The 226–196 Ma granite-related W mineralization recognized throughout the province has a possible link with the widespread Sb–Au mineralization in the region.

Widespread Mesozoic magmatism and intracontinental deformation is recorded in the North China Block (NCB), but few studies have considered the link between the emplacement of the granite and deformation. The Malanyu Anticline is a large-scale east-trending fold exposed in the eastern part of NCB and is intruded by many plutons. Whole rock geochemistry, LA-ICP-MS zircon U–Pb ages, Sr–Nd isotopic composition, as well as zircon Hf isotopic data for eight granitic bodies in the anticline have been studied in detail and are reported in this contribution. Fourteen zircon LA-ICP-MS U-Pb ages have been obtained ranging from ca. 218 to 126 Ma spanning the Triassic to Cretaceous, with a major population at ca. 220–160 Ma. This age range is different from rest of the Mesozoic igneous rocks in NCB, indicating the emplacement of the granites in the anticline was structurally controlled, although the regional tectonic setting during the Mesozoic played an important role in magmatism in the region. All of the granites in the Malanyu Anticline are enriched in light Rare Earth Elements relative to heavy Rare Earth Elements, and have similar trace elements patterns, with depletions in Ba, Nb, Sr, P and Ti, and enrichments in Rb, Th, U, K, La, Ce, Sm and Tb. The Triassic to Jurassic granites' two-stage depleted mantle Nd model (T2DM) ages are both Paleoproterozoic, with similar eNd(t) values and two-stage depleted mantle Nd model ages. Their in-situ zircon two-stage depleted mantle Hf model ages (tDM2) range from ca. 2861 to 1406 Ma. Integrated with the Sr-Nd-Hf data from previous studies, the Triassic Dushan Granite in the study area has high Sr and low Y assays derived from the partial melting of Archean TTGs in the lower crust with a minor contribution from a depleted mantle source. The emplacement was during a post-collisional setting following the closure of the Paleo-Asian Ocean along the Suolun Suture in the north. The emplacement of most of the Jurassic granites involved the superimposition of the initial subduction of the Paleo-Pacific Ocean plate beneath NCB, while the emplacement of the minor Jurassic and Cretaceous granites are probably related to the partial melting of the Precambrian crust due to widespread extensional tectonics at the northern margin of the NCB.

The south-eastern part of the North China Craton (NCC), the major historical source of gold supply to the former Emperors of China, continues to be a potential target for gold exploration. With a view to gain insights on the crustal architecture and gold metallogeny of this region, this contribution combines geological and Nd–Hf–isotopic data from magmatic rocks associated with the ore mineralisation. We integrate Nd–Hf isotopic data from published works as a tool to present isotopic maps. These maps highlight the location of major tectonic structures, and their relationship with the distribution of mineral deposits in the south-eastern NCC. The porphyry and porphyry–skarn Cu(–Au–Mo) deposits in the Luxi area in eastern NCC are associated with magmatic rocks and are located in zones with variable eNd–eHf values and TDMc–TDM2 ages representing dominant Paleoproterozoic to Mesoproterozoic and reworked crustal components with minor mantle material. In contrast, the Jiaodong type Au and porphyry–skarn Mo(–W–Cu) deposits are associated with magmatic rocks emplaced in domains with low–eNd–eHf values and older TDMc–TDM2 ages characterised by dominantly Archean–Paleoproterozoic reworked crustal components in the Jiaobei Terrane and the Sulu Orogen. Our study thus demarcates distinct crustal provinces and source components in generating some of the world-class gold deposits.

Knowledge of the history of the Earth’s continents and the genesis of mineral deposits is poorly understood on a crustal-scale. This contribution combines geological and zircon Hf-isotopic data collected from igneous rocks associated with mineralisation to gain a better understanding of the nature of the growth of, and mineral genesis in the North China Craton. The new zircon U–Pb dates reported here are 2587 ± 62 Ma for syenogranite at Zanhuang in the northeast part of craton, 2552 ± 24 Ma for trondhjemitic gneiss and 2554 ± 29 Ma for metadiorite at Dengfeng in the eastern and central part of, and 2820 ± 6 and 2821 ± 32 Ma for tonalite at Lushan in the southeast part of the craton. Lu-Hf isotopic data collected from granitic rocks for this study yield eHf(t) values and Hf crustal model ages (TDMc) of 3–5.8 and 2580–2600 Ma for the syenogranite at Zanhuang, 1.9–7.4 and 2550–2580 Ma for trondhjemitic gneiss and metadiorite at Dengfeng, and 0.5–5.2 and 3120–2840 Ma for tonalite at Lushan. Six major magmatic events have been recognised throughout the region. The crustal growth and reworking of the craton includes Eo- to Mesoarchean, early Neoarchean, and Paleoproterozoic events. The consistency in the evolution of Neoarchean magmatism coupled with zircon Hf isotope systematics indicate that similar crustal growth and reworking were in action in the Eastern, Trans-North China, and Western blocks. The crust architecture indicated by Hf isotopic mapping of the North China Craton constrains the distribution of mineral deposits. The BIF-hosted Fe deposits are spatially related to juvenile or reworked crustal domains, with groups of deposits located internal to and at the margins of Archean terranes, and orogenic Au deposits are spatially associated with juvenile crustal domains.

The duration (or time scales) of multistage combined magmatic and hydrothermal events provides key information constraining the metallogenic history of porphyry deposits, but the duration (time scale) of the mineralising hydrothermal process remains uncertain. Here, we report zircon U–Pb isotopic age, fluorite Sm–Nd isochron ages, and Ti-in-quartz diffusion chronometry for the giant Chalukou porphyry Mo deposit with reserves of 2.46 Mt @ 0.087 wt% Mo in NE China. The deposit is genetically related to hydrothermal fluids associated with a Late Jurassic (148–147 Ma) porphyritic magmatic event coincident with our new fluorite Sm–Nd isochron age of 148 Ma. Porphyry Mo mineralisation is characterised by the superposition of multiple generations of crosscutting quartz-bearing veins including: quartz veins with minor magnetite and hematite associated with K-silicate alteration (A-veins), quartz-molybdenite veins with K-feldspar alteration halos that host the bulk of the Mo mineralisation (B-veins), and late base-metal mineralisation with phyllic alteration (D-veins), as well as post-mineralisation veins with argillic alteration. Hydrothermal veins from the Chalukou porphyry Mo deposit contain multiple generations of quartz that are distinct in their Ti concentrations and scanning electron microscope-cathodoluminescence images. The A-veins preserve subhedral to euhedral characteristics with alternating CL bright and dark growth zoning. The A-veins probably formed at a near-lithostatic pressure of ∼1.35 kbar and contain CL-bright quartz assaying 31–71 ppm Ti with Ti-in-quartz temperatures averaging 603 ± 30°C, and CL-dark quartz assaying 6–25 ppm Ti with Ti-in-quartz temperatures averaging 496 ± 36°C. The mineralised B-veins also CL-dark quartz, although they display less growth zoning with lower Ti assays of 0.4–27.9 ppm. These veins have near 0.7 kbar pressure and Titanium-in-quartz temperature averaging 390 ± 79°C. The D-veins are dominated by CL-dark quartz and systematically lower Ti concentrations of 0.4–8 ppm, being lower than the relatively latter vein generations, formed at a temperature of 348 ± 58°C and pressure of 0.4 kbars. The Ti diffusion in quartz has become a successful method constraining time scales and duration of magmatic and hydrothermal processes. Ti diffusion modelling indicates that the A-veins were deposited and cooled in a period between 2500 and 50,000 years. This shows that the earliest magma-related hydrothermal fluids activities formed within tens of thousands of years.

The Zhaibei Granite in Jiangxi Province, southern China, hosts an ion-adsorption light rare earth element (LREE) deposit. Recently, heavy REE (HREE) ores have also been reported from weathered crusts of the granitic rocks. In this study, petrological, geochemical, and mineralogical characteristics of the Zhaibei pluton were analysed to establish the genesis of this REE deposit. The pluton contains coarse-grained biotite syenogranite and minor hornblende–biotite–quartz monzonite in its central zone, medium-grained biotite syenogranite in its transitional zone, and fine-grained muscovitic alkali-feldspar granite and porphyritic muscovitic biotite–alkali-feldspar granite together with monzogranite porphyry intrusions in its marginal zone. The REE minerals include titanite, allanite, monazite, bastnasite, and thorite-(Y) in the central zone, allanite, monazite, xenotime, bastnasite, and thorite-(Y) in the transitional zone, and synchysite-(Y), thorite-(Y), and xenotime in the marginal zone. The SiO2 content increases from 62 to 77 wt% from the centre to the margin, whereas the Al2O3, TiO2, MgO, FeO, and CaO contents decrease. In addition, the size of the negative Eu anomaly and HREE content increase, accompanied by decreases in Co, Zr, Hf, Sr, and Ba and increases in Rb, Cs, Nb, and Sn. These observations indicate that the Zhaibei Granite might have been formed by crystallisation differentiation of magma. The granitic pluton was also influenced by reactions with late-magmatic F-, CO2–, and REE-rich fluids that altered magmatic minerals and crystallised as REE-fluorocarbonates and thorite. The hydrothermal REE minerals constitute ∼ 40% of the total REEs in the bedrock and are the major supplier of ion-exchangeable REEs in the ores of the Zhaibei deposit. LREE-rich ores may have been derived from the LREE-rich granitic rocks, which contain bastnasite, titanite, and allanite, whereas HREE-rich ores were sourced mainly from the HREE-rich granites, which contain synchysite-(Y) and thorite-(Y). Furthermore, REE ores with enrichment in both HREEs and LREEs were probably sourced from the monzogranite porphyry bedrock, which contains bastnasite-(Y), bastnasite, allanite, and thorite-(Y).

Accurate determination of the time scales of multiple magmatic-hydrothermal pulses is a critical and difficult problem, which can provide information needed to better constrain the genesis of porphyry deposits. Here, we take advantage of zircon U-Pb dating and improvements in the field of diffusion chronology to determine time scales of multistage magma-related hydrothermal events at the giant Yulong porphyry Cu-Mo deposit in eastern Tibet. New LA-ICP-MS zircon U-Pb data showing that the mineralised Yulong porphyry crystallised at ca. 41 Ma, with the emplacement of the subeconomic Ganlongla intrusion at ca. 41 Ma, indicating a contemporaneous magmatism and mineralisation. Quartz from porphyry and hydrothermal veins exhibits cathodoluminescence (CL) images with a variety of brightness and textures, whereas trace element analyses show that the CL intensity is strongly related to the Ti contents of quartz. The Ti-in-quartz analyses of quartz precipitated in equilibrium conditions yield TitaniQ temperatures that agree with the temperatures calculated using independent thermometers. The sharpness of the Ti gradients observed in the CL images coupled with Ti diffusion modelling for different quartz generations indicate that the bulk of the mineralisation at Yulong formed in a short period of between 880,000 and 16,000 years. These data, together with available isotopic dating data, suggest that the mineralisation is coeval with the emplacement of the porphyries. Complex multi-stage hydrothermal stockwork veins and shorter time scales reveal that the individual magma and fluid pulses at Yulong formed rapidly within tens of thousands of years.

The Bilugangan porphyry Mo deposit is located in the southern Great Xing'an Range, and the Bilugangan area near the Hegenshan-Heihe Fault in the eastern part of the Central Asian Orogen (CAO). The deposit is hosted by a NE-trending, partly concealed, composite granite consisting of highly altered porphyritic granite (G1), porphyritic monzogranite (G2), fine- to medium-grained monzogranite (G3), medium -grained monzogranite (G4), and monzogranitic porphyry dykes (G5). The Mo mineralisation forms hydrothermal stockworks or disseminated sulphides in the G2 and G3 phases and the adjoining hornfels. Magmatic zircons from the intrusions yield 206Pb/238U weighted mean ages of 295 ± 2 Ma for G1, 240 ± 1 Ma for G2, 235 ± 2 Ma for G3, 230 ± 1 Ma for G4, and 100 ± 2 Ma for G5,indicating that multiple magmatic events have been active during the Early Permian to Early Cretaceous emplacement of the Bilugangan Granite. The age of the Mo is constrained between the Middle and Late Triassic and the magma-related hydrothermal activity proceeded in at least two pulses over a period of around 5 Ma. The first pulse has a molybdenite Re-Os weighted mean age of 238 ± 2 Ma, and the second dates at 236 ± 1 Ma. These dates are coeval with those of G2 and G3, indicating a genetic association between them and the mineralisation. The Sr-Nd-Hf isotopic systematics shows that the Bilugangan Granite was probably formed by partial melting of at least two sources. The first source is a dominant Late Mesoproterozoic to Early Carboniferous juvenile lower crust indicated by the whole rock eNd(t) values of −1.9 to 5.1 and zircon eHf(t) values of 3.5 to 14.3 with two-stage depleted mantle Nd (TDM2) and Hf (tDM2) model ages of ca. 1086 to 350 Ma, which is possibly related to the evolution of the Palaeo-Asian Ocean. The second source includes Neoarchaean to Palaeoproterozoic crustal components and a subordinate Mesoproterozoic crustal component. The Neoarchaean to Palaeoproterozoic component is indicated by the presence of ca. 2700 to 2600 Ma xenocrystic zircons, negative eHf(t) values of −16.4 to −10.1 with tDM2 ages of ca. 2300 to 1900 Ma. The Mesoproterozoic component yields eHf(t) values of −4.5 to 1.1 and tDM2 ages of ca. 1600 to 1200 Ma. These data show that pre- Mesoproterozoic substrate is present beneath the southern Great Xing'an Range. Although the post-mineralisation G4 and G5 phases have comparable positive eHf(t) values with the earlier granitic phases, the G2 and G3 phases have a more complex source with distinctly negative eHf(t) values of −16.4 to –1.3, indicating that the older crustal components in the magma’s source are also probable sources for the Mo mineralisation.

Magmatism was widespread in the Proterozoic to Early Paleozoic Altyn-Tagh Orogen of NW China. Rare metal deposits hosted by ca. 472 Ma pegmatite dykes with a monzogranitic geochemistry have recently been discovered in the orogen, including the Tugeman Li-Be deposit. The pegmatites contain spodumene – beryl (– columbite – tantalite – cassiterite), and are coeval with the ca. 482 Ma biotite monzogranite as a late-stage phase of the monzogranite, and both the monzogranite and pegmatite intrude orthogneiss and gneissic syenogranite. Two samples of biotite monzogranite yield weighted mean Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) U–Pb zircon dates of 482 ± 5 and 475 ± 5 Ma, and columbite-tantalite dates of 472 ± 8 Ma for the pegmatite, and minimum dates of 438–412 Ma for hosts of the columbite-tantalite. The gneissic syenogranite and orthogneiss in the deposit’s wallrocks have zircon U–Pb ages of ca. 900 Ma. The geochemistry and Hf-Lu isotopic systematics indicated that the protoliths for the gneissic syenogranite and orthogneiss have a mantle source with a contribution from the Proterozoic crust, and the biotite monzogranite has a Proterozoic crustal source. The Tugeman Li-Be deposit, therefore, has a Precambrian crustal source and was deposited during the Ordovician, which we propose was a post-collision extensional event and a previously unknown mineralising event in China.

We report Neoproterozoic (ca. 785-780 Ma) granites from the western margin of the Yangtze Block that are characterised by magmatic zircons with δ 18 O values as low as 2.98‰. The lack of low- δ 18 O magmatic zircons in the ca. 820-805 Ma rhyolite samples from the Neoproterozoic Suxiong Formation indicates that there is no recycling of pre-existing hydrothermally altered crust in the study area prior to the emplacement of the ca. 785-780 Ma granites. Thus the ca. 785-780 Ma granites with low- δ 18 O values from the western margin of the Yangtze Block can be linked to assimilation of syn-magmatically altered rocks (rather than the assimilation of a pre-existing hydrothermally altered crust). The granites have a source constrained by their depleted Hf isotopes and low- δ 18 O values resulting from high temperature hydrothermal alteration. The δ 18 O values of the zircons from core to rim exhibit a decrease indicative of the remelting of material during the interaction between magma and water at high temperatures. In combination with the widespread low- δ 18 O signatures that occur in the northern and southern margins of the Yangtze Block and Cathaysia Block, the locations of low- δ 18 O magmatic zircons exhibit a Neoproterozoic low- δ 18 O magmatic ring around South China. This continent-scale Neoproterozoic extensional and magmatic event cannot be attributed to subduction processes in South China resulting in the emplacement of a magmatic ring of felsic igneous rocks with low- δ 18 O values. We therefore propose a model involving a Neoproterozoic super-mantle plume with a diameter of approximately 1500 km controlling the development of the rift systems around South China.