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Magmatic and metasomatic zircon occurs in many alkaline igneous rocks and both are potential economic reservoirs of Zr, and in some places, rare-earth elements. The Baerzhe deposit in China is an example of a system where both types of zircon occur. Previous studies recognized deuteric and variably altered magmatic zircon in a transsolvus miaskitic granite, as well as four types of metasomatic zircon in a transsolvus agpaitic granite. In this study, the relationships among, and origins of, zircon and how these relate to models for rare-metal mineralization are assessed. In situ backscattered electron (BSE) and cathodoluminescence (CL) imaging, Raman spectroscopy (including mapping), and chemistry of zircon from the agpaitic granite were conducted, combined with evaluation of published data on zircon from Baerzhe. Their textural, spectroscopic, and chemical characteristics suggest that the four types of metasomatic zircon in the agpaitic granite were not subjected to metamictization or intense alteration, with trace-element accommodation largely following a xenotime substitution mechanism. The most abundant type of metasomatic zircon in the agpaitic granite occurs in zircon-quartz pseudomorphs and exhibits comparable CL, Raman spectral, and chemical features to rare zircon that has partially replaced elpidite. This confirms that the pseudomorphs formed by complete replacement of elpidite. The pseudomorph zircon occurs in association with snowball quartz that contains inclusions of zircon, aegirine, and albite, and with secondary quartz containing aegirine. This is consistent with their coeval formation during Na metasomatism. The restriction of Na metasomatism to the agpaitic granite indicates that this event and the associated zircon formation resulted from early autometasomatism of the agpaitic phase. REE- and Be-rich zircon that replaced magmatic amphibole crystallized as a result of reaction with a REE- and Be-rich fluid that most likely was responsible for the later REE-Nb-Be mineralization that affected both the miaskitic and agpaitic granites. The miaskitic granite contains deuteric and altered magmatic zircon with diferent chemical characteristics to the four types of metasomatic zircon in the agpaitic granite. This suggests that secondary Zr mineralization in the miaskitic granite formed from diferent fluids to those that metasomatized the agpaitic granite and may also have resulted from autometasomatism. This study reveals a complex picture for the formation of zircon at Baerzhe, the character of which can vary significantly, both temporally and spatially. Such variable chemistry of the various types of zircon resulted not only from their diferent origins (magmatic vs. metasomatic), but also from localized water-rock interaction that involved multiple stages of fluids. Zircon in both the miaskitic and agpaitic phases was mainly the product of autometasomatism that was constrained to their parental granites. [ABSTRACT FROM AUTHOR]

The world-class Shizhuyuan W–Sn–Mo–Bi deposit is spatially related to the Qianlishan granite complex (QGC) in Hunan Province, China. However, the age and classification of the QGC are still debated, and a better understanding of the temporal genetic relationship between the QGC and the Shizhuyuan deposit is essential. Here, we present chemical compositions the intrusive phases of the QGC and the results of detailed zircon U–Pb dating and muscovite Ar–Ar dating of a mineralized greisen vein. Our new zircon laser ablation inductively coupled plasma mass spectrometry U–Pb age data constrain the emplacement of the QGC to 155–151.7 Ma. According to petrological, geochemical and geochronological data and the inferred redox conditions, the QGC can be classified into four phases: P1, porphyritic biotite granites; P2, porphyritic biotite granites; P3, equigranular biotite granite; and P4, granite porphyry dikes. All phases, and especially P1-P3, have elevated concentrations of ore-forming metals and heat-producing elements (U, Th, K; volume heat-producing rate of 5.89–14.03 μWm−3), supplying the metal and heat for the metalogic process of the Shizhuyuan deposit. The Ar–Ar muscovite age (154.0 ± 1.6 Ma) of the mineralized greisen vein in the Shizhuyuan deposit is consistent with the emplacement time of the QGC, suggesting their temporal genetic relationship. [ABSTRACT FROM AUTHOR]

The Tongcun ore-bearing porphyry is located in the Tongcun porphyry Mo Cu deposit of NW Zhejiang Province, which is a key domain for providing deep insight into crust–mantle interaction and tectonic evolution of the South China block. SHRIMP zircon U Pb geochronology indicates an emplacement age of 168.7 ± 2.8 Ma. Its inherited zircon age spectrum recorded the assembly and breakup of the Rodinia supercontinent, and the Triassic collision of the Yangtze and North China blocks. This porphyry does not contain peraluminous minerals (e.g. muscovite, cordierite and garnet), and has high SiO 2 (73.52–64.68 wt.%) and low FeO T /MgO and Zr + Nb + Ce + Y contents. It thus fits the I-type granite definition. Some major and trace elements show strong correlations with SiO 2 , indicating extensive fractional crystallization during magma evolution. Tectonic discrimination diagrams suggest a volcanic arc setting probably related to the subduction of the paleo-Pacific plate. Hf isotope of zircons with Jurassic age and bulk-rock Sr Nd isotopic data yield mostly negative ε Hf (t) values (2.5 to − 4.5) and ε Nd (t) values (− 3.55 to − 5.83), together with high Mg # ratios (average 46.1), suggesting a mixed source of ancient crust and 30–50% juvenile components. Compared with the Dexing Cu-bearing porphyies, which have relatively higher Mg # ratios, more positive ε Hf (t) and ε Nd (t) values, the Jurassic porphyries in NW Zhejiang Province probably lack metallogenic potential to form a giant porphyry Cu deposit. [ABSTRACT FROM AUTHOR]

SHRIMP U-Pb zircon analyses for a gabbro sample from the Garzê ophiolite block yielded a mean age of 292±4 Ma, which indicated that the spreading time of the Garzê-Litang Tethys was most likely at the earliest Permian. Combined with previous studies, we suggest that the opening of the Tethys! in southwest China was derived from breakup of the East Gondwanaland in the late Paleozoic. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Qianlishan granite complex last for 38.8–57.4 Ma. • The duration of the QGC has positive correlation with the volumetric heat production. • Mineralization events well accord with the protracted hydrothermal lifespan. The Dongpo ore field, containing a series of W-Sn-Mo-Bi-Pb-Zn granite-related deposits, is a typical reduced intrusion-related system centered with the causative zoned Qianlishan granite complex (QGC). The QGC comprises porphyritic granite, equigranular granite and granite porphyry. According to zircon U-Pb age data, the emplacement timing of the QGC was constrained to 155–151.7 Ma. Here, we conducted a set of geochronological analyses with different closure temperatures (including monazite, apatite U-Pb, biotite and muscovite Ar-Ar and zircon fission track dating) on the QGC, revealing that the QGC experienced a protracted magmatic-hydrothermal timespan of 38.8–53.8 my. The protracted lifespan is probably due to radiogenic heat supplied by highly enriched high-heat-producing elements. The mineralizing blossom time (149–154.2 Ma) in the Dongpo ore field is in accordance with the prolonged lifespan (5.7 my: from 149.3 Ma to 155 Ma) of the magmatic-hydrothermal process caused by the QGC over the temperature range of 300–800 °C. This result implies that successive inputs of magma with high heat-producing elements (U, Th, K) play a fundamental role in the metal enrichment process of intrusion-related deposits and the formation of large economic ore fields. [ABSTRACT FROM AUTHOR]

[Display omitted] • The parental granite formed by significant crustal contamination of partial mantle melts. • The hydrothermal fluids were derived from magmatic sources and gradually mixed with meteoric waters. • The precipitation of Mo was triggered by boiling and fluid-wallrock interactions. The Shiyaogou deposit in Luanchuan County, China, is a large concealed porphyry Mo deposit within the East Qinling metallogenic belt (EQMB). Major and trace element analyses reveal that the host granite is defined by high silica (SiO 2 = 71.56 to 75.25%) and alkali (Na 2 O + K 2 O = 6.91 to 7.88%) contents and has typical I-type characteristics. Zircons derived from the pluton yield U–Pb ages of 133.2 ± 1.1 Ma, indicating an early Cretaceous magmatic event in the EQMB. The ε Hf (t) values and T DM2 ages range from − 15.1 to − 11.2 and from 2.1 to 1.9 Ga, respectively, suggesting that the granite mainly originated from the lower crust melting with the involvement of mantle components. The mineralization process can be divided into three stages: (1) quartz + K-feldspar + pyrite + molybdenite; (2) quartz + pyrite + molybdenite; and (3) quartz + calcite veins. Three different types of fluid inclusions (FIs) are present in quartz veins: NaCl–H 2 O (W-type), CO 2 –H 2 O (C-type), and daughter mineral-bearing (S-type). Hematite is recognized as a daughter mineral in S-type inclusions of stage 1, whereas the daughter sulfide and reducing CH 4 gases can be observed in the stage 2 quartz, suggesting that the ore-forming fluids were initially oxidizing and then evolved to more reducing conditions. The FIs in stages 1 mainly display Th above 428 °C with salinities up to 57.62 wt% NaCl eqv; in stage 2, the FIs display Th of 132–423 °C and salinities of 3.23–50.03 wt% NaCl eqv; in stage 3, the FIs homogenized in the range of 117–247 °C with low salinities of 2.74–8.95 wt% NaCl eqv. The coexisting W-, S- and/or C-type inclusions homogenized at similar temperatures, but contain different salinities during stages 1 and 2, suggesting that the fluids boiled during both stages. Our study reveals that the ore-forming fluids are magmatic in origin. These high-temperature magmatic fluids gradually evolved from high salinities and high CO 2 contents to a mixture of magmatic and meteoric water with lower temperature, lower salinity, and lower CO 2 content. The precipitation of Mo mainly resulted from the decreasing temperature and salinity. Additionally, the changes in pH and CO 2 content due to boiling and the water–rock reaction could have contributed toward the precipitation of Mo. [ABSTRACT FROM AUTHOR]