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Chlorite is present extensively in many types of deposits. The mechanism underlying the chemical variations in chlorite remains unclear. The Naruo porphyry deposit is a giant copper porphyry deposit in the Duolong ore district of Tibet. Chlorite, which is abundant in this deposit, has yet to be studied systematically; hence, we used principal component analysis (PCA) to assess the correlation between chlorite elements and various types of mineral deposits. We then conducted a preliminary investigation into its mineralogy and geochemistry to better understand its formation process and identify potential prospecting indicators. The PCA method proved effective in discerning two distinctive element signatures within the chlorite and categorising them into four deposit types: orogenic Au deposits, granite-type U deposits, and skarn-type Sn deposits that exhibit high FeOand low MgO distinguishing them from porphyry copper deposits. The chlorite in the Naruo deposit is classified as either early metasomatic (M-type), consisting mainly of clinochlore, or late hydrothermal (H-type), primarily consisting of clinochlore and chamosite. This classification suggests that H-type chlorite formed in a reductive environment conducive to Cu precipitation at medium temperatures (255°C-342°C). Al-Si and Fe-Mg substitutions were found to be the primary processes involved in its generation. Additionally, from the mineralisation centre outwards, there was an observed decrease in Si content as well as the Fe/(Fe+Mg) ratio in H-type chlorite, along with decreases in temperature, sulphur, and oxygen fugacity of allchlorites; conversely, increases were observed for Al content along with Mg and Mn elements in H-type chlorite. Chlorite is useful for exploring porphyry copper systems as an indicator mineral. [ABSTRACT FROM AUTHOR]

The Xiongcun Cu–Au ore district is in the southern middle Gangdese Metallogenic Belt, Tibet, and formed during Neo-Tethyan oceanic subduction. The Xiongcun ore district mainly comprises two deposits, the No. I and No. II deposits, which were formed by two individual mineralization events according to deposit geology and Re–Os isotopic dating of molybdenite. The No. I deposit is similar to a reduced porphyry copper–gold deposit, given the widespread occurrence of primary and/or hydrothermal pyrrhotite and common CH4-rich and rare N2-rich fluid inclusions. The No. II deposit, similar to classic oxidized porphyry copper–gold deposits, contains highly oxidized minerals, including magnetite, anhydrite, and hematite. The halogen chemistry of the ore-forming fluid from the No. I and No. II deposits is still unclear. Biotite geochemistry with halogen contents was used to investigate the differences in ore-forming fluid between the No. I and No. II deposits. Hydrothermal biotite from the No. I deposit, usually intergrown with sphalerite, is Mg-rich and classified as phlogopite and Mg-biotite, and hydrothermal biotite from the No. II deposit is classified as Mg-biotite. Hydrothermal biotite from the No. I deposit has significantly higher SiO2, MnO, MgO, F, Li, Sc, Zn, Rb, Tl, and Pb contents and lower Al2O3, FeOtot, Cl, Ba, Cr, V, Co, Ni, Y, Sr, Zr, Th, and Cu contents than the biotite from the No. II deposit. Hydrothermal biotites from the No. I and No. II deposits yield temperatures ranging from 230 °C to 593 °C and 212 °C to 306 °C, respectively. The calculated oxygen fugacity and fugacity ratios indicate that the hydrothermal fluid of the No. I deposit has a higher F content, oxygen fugacity, and log(fHF/fHCl) value and a lower log(fH2O/fHF) value than the hydrothermal fluid from the No. II deposit. The biotite geochemistry shows that the No. I and No. II deposits formed from different hydrothermal fluids. The hydrothermal fluid of the No. I deposit was mixed with meteoric waters containing organic matter, resulting in a decrease in oxygen fugacity and more efficient precipitation of gold. The No. I and No. II deposits were formed by a Cl-rich hydrothermal system conducive to transporting Cu and Au. The decreasing Cl, oxygen fugacity, and temperature may be the key factors in Cu and Au precipitation. Biotite geochemistry allows a more detailed evaluation of the halogen chemistry of hydrothermal fluids and their evolution within porphyry Cu systems. [ABSTRACT FROM AUTHOR]

We evaluate the controlling factors of hydrothermal wolframite and scheelite precipitation in the quartz vein-type Jiaoxi tungsten deposit situated in the western part of the Lhasa terrane (Tibet, China) using texture, major and trace element mineral geochemistry, and sulfur stable isotope geochemistry. Pyrite and chalcopyrite that are intergrown with Fe-enriched wolframite and siderite, have distinct in situ S isotope compositions (δ34SV-CDT) of −31.38 to +1.77‰, and +2.07 to +2.30‰, respectively. Major and trace element contents and in situ S isotope compositions of pyrite and chalcopyrite indicate that the hydrothermal evolution involved fluid-fluid mixing and greisenization. We report evidence for an early magmatic fluid, which is characterized by the enrichment of W, Mn, Zr, Ti, Sc, and Sn and depletion of Fe. This magmatic fluid was diluted by meteoric water and interacted with biotite monzogranite porphyry to leach Fe, Mg, and Zn into the system to form wolframites with variable Fe/(Fe+Mn) ratios ranging between 0.06–0.84. The late Fe-enriched magmatic fluid released from the muscovite granite mixed with meteoric water that leached minor Fe and S from shale to form late shale-hosted wolframite with a Fe/(Fe+Mn) mass ratio of >0.75 and coeval siderite and sulfides. This study highlights that multiple Fe sources were present in the system, including muscovite granite-released Fe through fluid exsolution, biotite monzogranite porphyry-released Fe during greisenization, and minor Fe released from the shale as a result of meteoric water leaching. [ABSTRACT FROM AUTHOR]

The Xin'gaguo deposit is representative of the skarn Pb–Zn polymetallic zone in the northern Gangdese porphyry metallogenic belt, Tibet. Pb–Zn mineralization is hosted in the Take'na formation skarn. The Xin'gaguo ore‐forming process can be divided into prograde skarn, retrograde skarn and quartz‐sulfides. Skarn minerals include garnet, diopside, and epidote, with minor wollastonite, actinolite, and chlorite. Metallic minerals are mainly sphalerite, galena, chalcopyrite, magnetite, and pyrrhotite, with minor arsenopyrite, marcasite, native bismuth, cosalite, and gersdorffite. The LA–ICP–MS zircon U–Pb age of the diorite is 59.66±0.52 Ma. Diorite samples are characterized by fractioned REE patterns with marked positive Eu anomalies, enriched LILEs (Rb, Ba, Th, U, and K) and depleted HFSEs (Ta, Nb, Zr, Hf, and Ti), belong to the calc‐alkaline series and have metaluminous compositions. Zircon εHf(t) values of the diorite are positive (5.7–11) and lie between the chondrite and mantle values. These geochemical characteristics suggest that the diorite was formed by the partial melting of a young metasomatized asthenospheric mantle wedge deriving basaltic rocks. The δ34S values of sulfides range from −4.7 to 4.5‰ and show a bimodal distribution, indicating interactions of magma‐derived ore fluid with biogenic sulfide minerals from the Take'na formation. The 206Pb/204Pb (18.5–18.629), 207Pb/204Pb (15.599–15.704), and 208Pb/204Pb (38.616–38.975) of sulfides show that ore‐forming metals were derived from mixed sources, in part from the Lhasa Terrane basement. Skarn mineral compositions imply that the ore‐forming environment was variable, and underwent at least three changes in oxidation‐reduction state. The geochemical characteristics of diorite indicate that the Xin'gaguo deposit formed within the Indo‐Asian continental collision tectonic setting. [ABSTRACT FROM AUTHOR]

The Bangong–Nujiang collision zone (BNCZ) is an ideal area for studying postcollisional magmatism. A series of late Early Cretaceous Cu‐bearing magmas are found in this collision zone, which has implications for studying the sources of postcollisional magmas. We completed detailed fieldwork and reported zircon U–Pb and Hf‐isotopic and whole‐rock geochemical data on the Daguo volcanics, Shesuo monzogranite‐granodiorites, and Xiongmei granodiorite porphyries, which represented different types of the Cu‐bearing rocks in the BNCZ. The Shesuo samples are characterized by high contents of SiO2, K2O, and total alkali, with high contents of heavy rare earth elements (HREEs) and Y, and are enriched in large‐ion lithophile elements (LILEs), depleted in Nb and Ta, with a marked negative Eu anomaly (0.29–0.92). The Xiongmei granodiorite porphyries are characterized by moderate SiO2 and MgO, high Al2O3 contents, depletion in Nb, Ta, Ba, Sr, and Ti, enrichment in LILEs, high HREEs and Y contents, and relatively low Sr/Y ratios. Both Shesuo monzogranites and Xiongmei granodiorites belong to calc‐alkaline I‐type magmas, which are associated with a wide range of zircon εHf(t) values (−15.3 to +5.8; −15.4 to +3.2). These geochemical features suggest that the Xiongmei granodiorite porphyries and Shesuo monzogranite‐granodiorites are derived from the melting of a juvenile mafic crust with ancient crustal contamination, and the juvenile mafic crusts are derived from a lithospheric mantle enriched by slab melt (including recycled subducting sediments). The Daguo basalt is derived from the partial melting of a mantle wedge metasomatized by subduction‐related fluids and/or melts and the involvement of asthenospheric mantle. The Daguo intermediate‐felsic rocks are derived from the partial melting of a juvenile crust from a metasomorphic mantle wedge. Our study implies that the genesis of these Cu‐bearing magmas is associated with slab break‐off at the end of the southward subduction of the Bangong–Nujiang Ocean lithosphere. In addition, the postcollisional magmas are multisourced, with a juvenile component from either the metasomorphic lithosphere mantle or the juvenile crust, an ancient crustal component and a subducted‐related component from the recycled subducting sediments, the subducted slab, and/or the asthenosphere. [ABSTRACT FROM AUTHOR]

Diabase dikes are extensively distributed in the Xiongcun porphyry copper–gold district in the southern margin of the Lhasa terrane. Here, we report zircon U–Pb ages determined by laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) along with Hf isotopic, whole‐rock elemental, and Sr–Nd–Pb isotopic data for these diabase dikes. Zircons from one of the Xiongcun diabase dikes yielded an emplacement age of 165.3 ± 1.0 Ma. The Xiongcun diabase dikes display subalkaline features and tholeiite compositions. They are enriched in large‐ion lithophile elements (e.g., Rb, Ba, and K) and light rare earth elements and are depleted in high‐field‐strength elements (e.g., Nb, Ta, and Ti). The Xiongcun diabase dikes exhibit relatively low ratios of (87Sr/86Sr)i (0.70386–0.70501), (206Pb/204Pb)i (18.15–18.40), (207Pb/204P)i (15.52–15.57), and (208Pb/204Pb)i (38.06–39.46) and relatively high values of εNd(t) (5.85–6.92) and εHf(t) (+12.58 to +14.03). Combined with previous research results, these findings suggest that the Xiongcun diabase dikes and Early Mesozoic magmatic rocks in the southern margin of the Lhasa terrane formed in an active continental margin magmatic arc setting related to the northward subduction of the Neo‐Tethys oceanic slab; however, the possibility that the Xiongcun diabase dikes were formed in an intra‐oceanic arc setting cannot be excluded. Their parental magmas were formed by the partial melting of the depleted mantle source that was modified by fluids released from the Neo‐Tethys oceanic slab. The magmas experienced fractional crystallization of olivine and clinopyroxene and underwent limited crustal contamination during magma emplacement. The ~165 Ma Xiongcun diabase dikes, which probably originated under an extensional stress condition in a magmatic arc setting, correspond to the timing of Middle Jurassic subduction‐related porphyry copper mineralization (161–172 Ma) in the southern margin of the Lhasa terrane, likely suggesting that this episode of mineralization occurred during a period of changing stress from compression to extension. [ABSTRACT FROM AUTHOR]

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Copyright of Geology & Exploration is the property of Geology & Exploration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geology & Exploration is the property of Geology & Exploration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geology & Exploration is the property of Geology & Exploration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geology & Exploration is the property of Geology & Exploration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)