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• Gradients in white mica wavelength are associated with specific rock units. • White mica wavelength is corresponding with geochemical results. • The clusters of white mica wavelength show the stages of mineralization. • The middle and longer wavelength of white mica are implication for exploration. Field measurement of the short-wave infrared (SWIR) reflectance from drill hole samples proved to be an effective method to map variations in white mica composition (Tschermak substitution) associated with hydrothermal alteration zonation of the Jiama porphyry-skarn Cu deposit, Tibetan Plateau, China. This SWIR mineral spectral information provides geological insights into: (a) the possible nature of the related magmatic intrusions. (b) the physicochemistry of the associated hydrothermal fluids; (c) the interactions between these fluids and country rocks; and (d) potential vectors to economic mineralization. The results suggest that the Al-OH band wavelength of white mica can used as an indicator in the subsequent steps of prospecting. [ABSTRACT FROM AUTHOR]

South China is famous for its large-scale mineralization genetically related to widespread Mesozoic granites. The Jiulongnao complex is one of the largest intrusions in southern Jiangxi Province, and is closely associated with W-dominated polymetallic mineralization. The complex comprises four intrusive phases (I-IV). Phase I consists of medium- to coarse-grained, biotite granite, whereas medium- to coarse-grained, porphyritic, biotite granite and muscovite-bearing granite comprise Phase II. Phase III is composed of medium- to fine-grained, porphyritic, biotite granite and Phase IV consists of medium- to fine-grained, garnet- and biotite-bearing granite. These intrusive phases have LA-ICP-MS zircon U-Pb ages of 160.9 ± 0.6 Ma, 158.6 ± 0.7 Ma, 157.0 ± 1.5 Ma and 154.1 ± 1.2 Ma, respectively. All of the granites are enriched in Rb, Th, U, Ta and Pb, and significantly depleted in Eu, Ba, Nb, Sr, P and Ti. They have ε Hf ( t ) and ε Nd ( t ) values ranging from −17.9 to −8.2, and −10.7 to −9.8, respectively, with two-stage Hf model ages of 1.7–2.3 Ga. They are S-type granites derived by partial melting of Paleo-Proterozoic metasedimentary rocks. The four phases have T Zr of 746–760 °C, 712–802 °C, 798–810 °C, and 648–731 °C, respectively. Oxygen fugacities of Phases I to III display a decreasing trend but Phase IV has much higher oxygen fugacity in its early stage, which decreased in the late stage. The four phases have different accessory mineral assemblages: Phase I is characterized by an assemblage of zircon, apatite, fergusonite, thorite and uraninite, whereas Phase II is rich in thorite, uraninite, REE-bearing minerals (e.g., monazite, fergusonite and xenotime) and fluorite. Monazite is the main accessory mineral in Phase III, whereas Phase IV contains a wide range of minerals, including thorite, uraninite, Nb-Ta-bearing minerals (e.g., fergusonite and pyrochlore), cassiterite and rutile. These mineral assemblages, together with other geological and geochemical features, suggest that W mineralization was genetically related to Phases I, II and IV, whereas U mineralization was most extensive in Phase II. Sn, Nb and Ta mineralization was associated with the highly fractionated of magmas of Phase IV. [ABSTRACT FROM AUTHOR]

• The wavelength 1455 nm is important for the mineralization. • Silicification variation can indicate the fluid flow direction. • Illite crystallinity is associated with mineralization and metallogenic environment. • Illite mapping with SWIR can judge whether low sulfidation epithermal deposit is. Field measurements using shortwave infrared (SWIR) reflectance from drill hole samples provided an effective method to map variations in illite crystallinity and the illite assemblage minerals associated with hydrothermal alteration zonation of the Sinongduo low sulfidation epithermal Ag-Pb-Zn deposit, Tibetan Plateau, China. The SWIR mineral spectral information was combined with electron probe micro-analysis (EPMA) measurements, and microscope observations to provide geological insights into: (a) the likely metallogenic fluid nature of the mixture of magmatic fluids and a cooler water source; (b) the illite physico-chemical properties of the associated hydrothermal fluids; (c) the illite, montmorillonite and sericite evolutionary interactions among these fluids, country rocks, and alteration minerals; and (d) the alteration minerals relationships and illite crystallinity to the economic mineralization. The results suggest that illite characterizations can be used as an indicator for epithermal deposit prospecting. [ABSTRACT FROM AUTHOR]

In South China, extensive multi-phase magmatism was accompanied by W-dominated, polymetallic mineralization. The Xingguo orefield of southern Jiangxi Province in the eastern part of the Nanling region is one of the most important W-dominated mineralized regions in South China. There are more than ten W deposits within or surrounding the Jiangbei complex, including the Huamei’ao quartz vein-type W deposit (WO 3 67,400 tons at a grade of 1.344%), the Yanqian skarn-type W deposit (WO 3 16,000 tons at a grade of 0.365%), and the Zhangjiadi quartz-vein- and greisen-type Mo-W deposit (Mo 31,806 tons at a grade of 0.1% and WO 3 1746 tons at a grade of 0.353%). The orebodies all occur at the contact between the Jiangbei complex and the Sinian metasandstone or Carboniferous-Permian limestone. The Jiangbei complex consists of three lithologies: medium- to coarse-grained, biotite granite (Jγ 1 ), medium- to fine-grained, biotite monzonitic granite (Jγ 2 ), and fine-grained, biotite monzonitic granite (Jγ 3 ), which have zircon U-Pb ages of 160.7 ± 1.1 Ma, 156.3 ± 0.9 Ma, and 153.3 ± 0.8 Ma, respectively. The associated Yanqian, Huamei’ao, Wangnipai, and Liujiazhuang deposits have molybdenite Re-Os ages of 159.2 ± 2.3 Ma, 157.1 ± 1.3 Ma, 157.7 ± 1.4 Ma, and 157.9 ± 1.6 Ma, respectively. A summary of available age dates of intrusions in the Xingguo orefield indicates that the granitic magmatism lasted for ∼8 m.y (ca. 160–153 Ma), whereas the W mineralization occurred in a relatively short period (159–155 Ma), corresponding in age to the episode of large-scale, Mesozoic (165–150 Ma) mineralization in South China. Low εNd(t) values (−10.2–−13.0) of the Jiangbei granitic rocks and low Re contents of the molybdenite suggest that the W-dominated ores and associated granites in the Xingguo orefield were derived mainly from crustal magmas. All three lithologies of the Jiangbei complex have similar geochemical characteristics, and are classified as high-K, calc-alkaline and peraluminous, S-type granites. The Zr/Hf, Nb/Ta, δEu, Rb/Sr, and LREE/HREE ratios all correlate positively with the W contents of the rocks and reach their highest level in the phase II granites. We propose a magmatic-metallogenic model in which W was concentrated by fractionation of crustally derived magmas of phase I and then deposited in skarn-, greisen-, and quartz vein-type ores by both magmatic and hydrothermal processes. [ABSTRACT FROM AUTHOR]

The Yinkeng orefield is located in the eastern Nanling region, South China. The Nanling region hosts numerous W(-Sn)-dominant, polymetallic deposits related to the widely distributed Mesozoic granites, making it one of the most important W-Sn polymetallic metallogenic belts in the world. In this study, we utilized multiple geophysical methods, including gravity, magnetic, audio-frequency magnetotelluric sounding (AMT), and high-resolution reflection seismic techniques, to detect the underground distribution of granites, strata, and structures. Our aims are to understand better the ore-controlling mechanisms for the large-scale W-Ag-Au-Pb-Zn aggregation, to establish a metallogenic model for this type of mineralization, and to supplement a 3000-m scientific drilling program in the Nanling region for the Chinese SinoProbe Program Project (SP-NLSD-1). In the Yinkeng orefield, an ore-controlling, NE-trending nappe structure is composed of several thrust faults at shallow depths (F1 and F2), which merge into a single major fault at depth. The Pre-Sinian sedimentary rocks of the hanging wall of these faults have much higher velocities, densities and wave impedance than the Carboniferous-Permian sedimentary rocks of the footwall. The slip surface of the nappe, which appears to have low resistivity, extends downward to a two-way travel time of more than 2.5 s, equivalent to a depth of more than 4000 m. Thrusting was from SE to NW, and the fault flattens at depth. The nappe structure may have provided channels for magmas and mineralized hydrothermal fluids. Granites in the Yinkeng area, which are spatially associated with the W-Ag-Pb-Zn orebodies, generally show high resistivity, low polarizability, low seismic velocity and medium magnetism, and their geophysical characteristics have revealed their distribution at depth. Specifically, the Gaoshanjiao granodioritic pluton, closely related to precious metal mineralization, is characterized by low density and high magnetism, allowing us to identify a large buried part of the pluton SE of the exposed body. The Jiangbei granitic pluton, which typically hosts W mineralization, has lower magnetism that reveals a NE-trending extension about 2.2–2.8 km wide at a depth of 16.6 km. One completely concealed granite, the Yinkeng pluton, lies below the nappe structure. It is geophysically similar to the Jiangbei granitic pluton but has an obviously higher magnetic signature. The high magnetism may be due to stratiform polymetallic bodies, which could represent a good exploration target for porphyry-skarn-type, W-Cu-polymetallic deposits (drilling site for SP-NLSD-1). Combined with surface mapping, the geophysical data collected in this study allow us to propose a deep exploration model that can serve as a guide for W-polymetallic ore prospecting in the Nanling and adjacent regions. [ABSTRACT FROM AUTHOR]

[Display omitted] • SIMS U-Pb dating of Jiama intrusives brackets magmatic event related to Jiama porphyry-skarn mineralization in 1.3 Myr. • Zircon O-Hf isotopic compositions suggest Jiama ore-forming magmas were derived from melting of the newly formed Tibetan lower crust. • No significant magma mixing has been observed during the magmatic evolution from diorite to granite. The post-collisional Gangdese metallogenic belt with over 45 Mt Cu has attracted worldwide attention. We report the whole-rock geochemistry, zircon SIMS U–Pb geochronology, and in situ zircon Hf–O isotopic compositions of the Jiama deposit in the Gangdese belt. The intermediate to the felsic intrusive rocks are characterized by high SiO 2 (64.8 to 78.8 wt. %) and Al 2 O 3 (12.1 to 16.3 wt. %) contents, high Sr/Y ratios (43–74), showing the geochemical characteristics of adakites. Zircons from four intrusives yield U–Pb ages of 16.19 ± 0.20 Ma, 15.67 ± 0.32 Ma, 15.44 ± 0.16 Ma, and 14.90 ± 0.16 Ma, respectively, which brackets magmatic event related to mineralization in 1.3 Myr (16.19 to 14.90 Ma). Magmatic zircons have intermediate δ18O (+5.21 to + 7.18‰), and depleted Hf isotopic values (εHf(t) = 1.8 to 9.4). In combination of whole rock, plagioclase, and zircon geochemistry, we suggest the main ore-forming magma was derived from the remelting of the newly formed lower crust. During the whole journey of magma ascending from lower crust to the surface, no significant injection or mixing of mafic melt from different source has been observed. This is supported by three lines of evidence: 1) There is no clear reverse zonation in plagioclase, 2) the major and trace element compositions of continuous lithologies from diorite to granite shows no significant mixing, 3) there is no significant change of the zircon O and Hf isotope among different intrusions. Our study suggests that the formation of the giant porphyry deposits such as Jiama in post-collisional setting likely form in a short-term (<1.5 Myr) without significant magma mixing during magmatic evolution from diorite to granite. [ABSTRACT FROM AUTHOR]