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Late Mesozoic granitoids are widely emplaced in the Qinling Orogen on the southern margin of North China Craton (NCC), and can provide important clues on the Late Mesozoic regional geodynamic setting. The Late Jurassic Laoniushan granitic pluton is located in the western end of the southern NCC margin. Zircon U–Pb dating for the granodiorite, quartz diorite, and biotite monzogranite of the pluton yielded 152.5 ± 1.6 Ma, 148.7 ± 1.2 Ma, and 149–146 Ma, respectively. Compilation of the single zircon ages revealed magmatic peaks at ca. 146, 152, and 163 Ma, suggesting multiphase Late Jurassic magmatism. These granitoids are high‐K calc‐alkaline, I‐type, and metaluminous to weakly peraluminous. The rocks show chondrite‐normalised LREE enrichments, HREE depletions and flat HREE patterns, together with (slightly) negative Eu, Nb, Ta, P, and Ti anomalies. The Laoniushan granodiorite and biotite monzogranite have similar REE patterns to the quartz diorite, but the former two have much smaller Eu anomalies than the latter. The negative zircon εHf(t) (−32.6 to −13.7), εNd(t) (−20.7 to −14.3) and crustal‐like whole‐rock trace‐elemental ratios (e.g., Nb/Ta, Th/U, Nb/U, and Ce/Pb), together with the low Mg (MgO = 0.18–2.02 wt%, Mg# = 20–34), Cr (7.00–39.0 ppm), and Ni (0.80–4.00 ppm) contents, suggests that the Late Jurassic granitoids were probably derived from the partial melting of ancient crustal rocks with minor mantle‐derived input. The granodiorite and quartz diorite have similar average εHf(t) (−26.5 and −26.7, respectively), εNd(t) (−20.5 and −20.2, respectively), TDM2(Hf) (2880 and 2885 Ma, respectively) and TDM2(Nd; 2607 and 2578 Ma, respectively), whereas the biotite monzogranite has higher average εHf(t) (−17.1) and εNd(t) (−15.3), and younger TDM2(Hf) (2281 Ma) and TDM2(Nd) (2176 Ma). This suggests that the biotite monzogranite has different magma sources and shallower magma formation depths compared to the granodiorite and quartz diorite. The latter two were likely formed by the partial melting of continental crustal rocks (notably the Taihua Group basement rocks), which was triggered by mantle underplating led by asthenospheric upwelling. The Late Jurassic Laoniushan granitoids may have formed in an extensional setting caused by the Palaeo‐Pacific Plate subduction beneath Eastern China. Commencement of Late Jurassic Laoniushan granitic magmatism likely marked the incipient of lithospheric thinning along the southern NCC margin. Considering also the regional geological evolution, we conclude that although the Laoniushan pluton exhibits spatial–temporal relationships with the nearby Mo (–U) and REE deposits, there is still no unambiguous metallogenic link with these deposits. [ABSTRACT FROM AUTHOR]

The Miocene Cuonadong leucogranites in the easternmost section of the Tethyan Himalaya, Southern Tibet, are characterized by two types of tourmaline. Tourmaline occurs as needle-like crystals in the two-mica ± tourmaline granites (Tur G) and large patches in the pegmatites (Tur P). Both the granite and the pegmatites yield Miocene ages (ca. 20 Ma) based on monazite U(-Th)-Pb dating, whereas 40Ar/39Ar geochronology of the coarse-grained tourmalines (Tur P) crosscut by pegmatite veins yielded an Eocene mini-plateau age of 43 ± 6 Ma. Major element concentrations of tourmaline indicate that both Tur P and Tur G belong to the schorl group with a magmatic origin, but trace elements such as V indicate that they are not cogenetic. Boron isotopes suggest that Tur P (average –9.76‰) was derived from typical crustal sources, whereas Tur G (average –7.65‰) contains relatively more mafic input. The capture of Eocene tourmaline by the Miocene leucogranites at Cuonadong suggests that the crustally derived Eocene magmatism may have occurred in the southern Tethyan Himalaya. Identification of the inherited magmatic tourmaline (Tur P), although not common, challenges the current application of tourmaline chemistry to the investigation of magmatic-hydrothermal systems. [ABSTRACT FROM AUTHOR]

The morphology, trace-element composition and geochronology of 43 zircon grains from two monzogranite samples from the Northeast Xing'an Block, northeastern China, were determined using cathodoluminescence imaging and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Three morphological subtypes (S3, S8 and S9) are recognized in the zircon grain samples, and subtype S8 is dominant, reflecting a calc-alkaline, moderately aluminous, high-pressure crystallization medium and a crystallization temperature of 700 ± 50 °C. The zircon grains are characterized by oscillatory zoning, relatively high Th/U ratios (0.3–1.0), steep chondrite-normalized rare-earth element patterns, high Hf contents (>9000 ppm), positive Ce (Ce/Ce* = 4.84 to 2914) and negative Eu (Eu/Eu* = 0.24 to 0.90) anomalies, indicating a magmatic source. The 206Pb/238U ages of the two monzogranite samples are 180 ± 1 and 181 ± 1 Ma, respectively, implying an Early Jurassic emplacement age for the intrusion. The disparate geochemical behaviors of Hf, Th, and Nb within the zircons, as well as the U/Yb, Nb/Yb, Th/U, Nb/Hf, Th/Nb, and Hf/Th ratios, suggest a continental-crust source in a compressional-magmatic-arc or orogenic-tectonic setting, and a calc-alkaline parent magma. All of the grains show relatively high Ce4+/Ce3+ ratios, suggesting that they were derived from an oxidized magma, which favors enrichment of Cu-Mo elements in the granite porphyry. [ABSTRACT FROM AUTHOR]

• Four types of chlorite identified in the Tongshankou Cu–Mo–W skarn deposit. • Chemical variations of the Tongshankou chlorite likely inherited from both protolith and ore fluid. • Spatial chlorite geochemical variations could vector toward concealed mineralized porphyry at Tongshankou. Recent years, the depletion of shallow mineral resources has drawn increasing attention to the exploration of hidden ore bodies in deep of skarn type deposits. Chemical composition of chlorite is an effective tool for tracing the hydrothermal fluid evolution, and has been increasingly used for deep-level exploration of porphyry Cu (–Au) deposits (PCDs). However, the technique was rarely applied onto (porphyry-related)-skarn deposits. The Tongshankou Cu–Mo–W deposit (0.55 Mt Cu @ 0.86%, 0.01 Mt Mo @ 0.10% and 0.12 Mt WO 3 @ 0.19%) is one of the largest skarn–porphyry deposits in the Middle–Lower Yangtze River Metallogenic Belt (MLYRB) in Eastern China. In this study, new petrographic and trace element data of the hydrothermal chlorites from Tongshankou were presented to constrain the ore-fluid evolution, and to explore the vectoring potential of the concealed orebodies at Tongshankou. Four types of chlorite have been identified, i.e., G-type chlorite that replaced the original magmatic biotite or hornblende, V-type chlorite in chlorite–quartz–sulfides veins in the granodiorite porphyry (alteration zones I and II), S-type chlorite that replaced garnet in the intensive skarn alteration zone (III) and M-type chlorite–quartz–calcite–sulfides veins that cut the (dolomitic)-marble in the distal alteration zones IV and V. All the four types of chlorites are typically trioctahedral chlorite. The Fe-Mg, Tschermark and di-trioctahedral substitution mechanisms likely control the geochemical variations of the Tongshankou chlorites. Empirical thermometer indicates that the Tongshankou chlorites were crystallized at 169–322 ℃. Compared with typical metamorphic chlorites, the higher Zn and Sr contents but lower Al content in the Tongshankou chlorites can potentially distinguish the skarn-type hydrothermal chlorites from typical metamorphic ones. Compared with the chlorites in the typical PCDs, the Tongshankou G-type chlorite has higher Fe, Zn, As and Sn contents, but lower Al, Mg, Co and Cu contents, which likely reflect its protolithic and/or fluid geochemical inheritance. The Tongshankou V-, M- and S-type chlorites have high contents of mobile elements (such as Sr, Ca, Sn and B) and metals (such as Fe, Cu, As, Zn and Pb), indicating that they were directly precipitated from the hydrothermal fluids. From the granodiorite porphyry to the marble wallrocks, the spatial chlorite geochemical variations at Tongshankou indicate that the increasing Zn, Mn, Ga, Ge and Pb contents, and decreasing V, Sc and Ti contents are potential vectors toward concealed mineralized porphyries at Tongshankou. Our study highlights that the chlorite geochemistry is a potential tool for ore-fluid tracer and vectoring tool toward concealed skarn–porphyry orebodies in the MLYRB. [ABSTRACT FROM AUTHOR]