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Although advanced spaceborne thermal emission and reflection radiometer multispectral analysis for lithological mapping has been widely applied, traditional methods such as band ratios (BR) and principal component analysis (PCA) are still hampered by cumbersome data processing and poor classification performance. In this study, we utilize improved data inputs for random forest (RF) to extract lithological information of granitoids, which are the predominant rock type for intrusion‐related polymetallic ore deposits in the western Junggar Orogen (NW Xinjiang). Based on spectral absorption features of minerals (e.g., orthoclase, K‐feldspar, hornblende, biotite, plagioclase, and oligoclase), image statistical information and textural features, we tested different combinations of bands, BR, PCA, and texture using RF method, and found that the combination of B13678 + T1 (Mean texture) achieved the highest weighted‐F1 score for granitoids, with an accuracy of 87.32%. Compared to the support vector machine, RF effectively distinguishes lithological differences between different types of granitoid and wallrocks, especially the granite, granodiorite, and alkali granite in the Akebasito intrusion, as well as the alkali granite, plagiogranite and biotite granite in the Karamay intrusions. Moreover, the large number of rare metal deposits (including Cu, Au, Mo, etc.) distributed near the granitoid intrusions in the western Junggar, our result facilitates the analysis of regional tectonic evolution and mineralization controlling. Plain Language Summary: Random forest (RF) is a machine learning method widely used in various fields due to its high classification accuracy and ability to handle high‐dimensional data without overfitting. Advanced spaceborne thermal emission and reflection radiometer data provide important information of related minerals for lithological identification because of its characteristic values for different bands and textures. In this study, ArcGIS was used to extract information from different bands and textures as input data for RF model. Then, the RF model was trained using Python, and the lithological mapping were generated through test data set, and the weighted‐F1 score, and kappa coefficient were compared. The combination of B13678 + T1 yielded the optimal result. Key Points: Based on the spectral data, image statistics and texture, select the most suitable bands combination for lithological mappingLithological identification of granitoids subclasses is very important for the exploration of metal deposits in the western Junggar Orogen [ABSTRACT FROM AUTHOR]

The Riduo intermediate-felsic volcanic rocks are located in the eastern Lhasa terrane in southern Tibet. Zircon U–Pb dating, geochemical and Sr–Nd–Hf isotope analyses were carried out to constrain the age, petrogenesis and magma source of the Riduo magma suite, including andesite, dacitic tuff, and quartz diorite. Zircon U–Pb dating yielded Early Miocene ages of 19.5 ± 0.5 Ma (andesite), 17.6 ± 0.3 Ma (dacitic tuff), and 15.6 ± 0.5 Ma (quartz diorite). Geochemically, this early Miocene suite is adakitic with high SiO2 (55.76–69.46 wt.%), Al2O3 (15.21–16.61 wt.%), Na2O (3.82–4.83 wt.%), Sr (427–1033 ppm), and Sr/Y (24.5–145), but low Y (< 17.8 ppm) and Yb (< 1.82 ppm). The rocks also have low to high K2O (0.44–3.82 wt.%). They are enriched in light rare earth elements (LREEs), large ion lithophile elements (LILEs, e.g. K, Rb, Th and U), but depleted in high-field strength elements (e.g. Nb, Ta) and heavy rare earth elements (HREEs), and have weakly negative to positive Eu anomalies. Isotope analyses reveal that most samples have high whole-rock initial 87Sr/86Sr ratios (0.705611–0.708807), low εNd(t) (−2.25 to −1.15), and positive zircon εHf (t) (+1.29 to +6.49). We suggest that the early Miocene magmas in the eastern Lhasa terrane were likely sourced from post-collisional partial melting of the juvenile lower crust with minor mantle input. The magmas may have been crustal-contaminated during their ascent to the upper crust along the N-S-trending Cona-Riduo rift. [ABSTRACT FROM AUTHOR]

Baiyun deposit is a large gold deposit in the Liaodong Peninsula (North China Craton), containing over 31.7 t of gold. Silicic alteration, K‐feldspar alteration, and pyritization are well developed and closely related with mineralization in Baiyun deposit. Based on field and optical microscopic observations, the alteration styles include quartz + K‐feldspar zone, pyrite + sericite +quartz zone, and chlorite zone from orebody outward. In this study, the quartz, K‐feldspar, and pyrite of pre‐ore, syn‐ore stages 1 and 2 were selected for LA‐ICP‐MS trace element analysis and electron probe microanalysis (EPMA) to reveal the alteration‐mineralization link. Results show that the albite was altered to mainly K‐feldspar and minor secondary quartz at syn‐ore stage 1. Fluid‐rock reaction of the silicic‐potassic alteration may have decreased the fluid oxygen fugacity (fO2), which triggered the gold precipitation. Most of invisible gold occurred in the form of solid solution. At syn‐ore stage 2, albite altered to mainly quartz and minor K‐feldspar. The syn‐ore stage 1 K‐feldspar also altered to minor secondary quartz at syn‐ore stage 2. In addition, the release of sulphur from the syn‐ore stage 1 pyrite was likely another trigger for the gold precipitation. Most of syn‐ore stage 2 invisible gold occurred as nano‐particles. The ore‐forming fluids consist mainly of primary magmatic fluids mixed with minor metamorphic fluids. The ore metals may have sourced mainly from the magmatic fluid and the sillimanite‐mica schist of the Gaixian Formation. [ABSTRACT FROM AUTHOR]

Secondary ion mass spectrometry (SIMS) has a wide range of applications in Earth Science research, thanks to its high precision and sensitivity, and its capacity in direct insitu micromeasurement. The technique is operated in ultra‐high vacuum (UHV) conditions, especially for the measurement of volatiles such as hydrogen, or the water content in nominally anhydrous minerals (NAMs). To minimize the water background and obtain accurate and precise water contents in NAMs (eg, olivine) critical parameters such as presputtering time, field aperture (FA), dynamic transfer on/off, and primary beam current intensity were investigated for a CAMECA IMS 1280‐HR system. When the chamber vacuum reaches approximately 2 × 10−9 mbar, we set the DTOS OFF, raster size to 50 μm and primary beam current to 5 nA, and used 2000 μm FA and 170‐second presputtering time. Consequently, an approximately 1.2 ppmw water background and 3.6 ppmw limit of detection (LOD) were yielded, from analyzing the San Carlos olivine. Meanwhile, the water content and homogeneity of a range of olivine minerals were characterized for potential use as reference materials for SIMS water content measurement. Olivine water content calibration curve was also established by comparing the Fourier transform infrared (FTIR) results with the SIMS‐measured 16O1H−/16O− ratios. Accuracy and precision of water content measurement were estimated to be better than approximately 10% in this study. [ABSTRACT FROM AUTHOR]

The Eastern Tianshan Orogen (Xinjiang, NW China) in the Central Asian Orogenic Belt (CAOB) is featured by its many Carboniferous-Triassic mafic-ultramafic intrusions and associated magmatic Fe-Ti-V oxide mineralization. In this study, we present the first systematic data comparison on the age and whole-rock geochemistry of the ore-forming mafic-ultramafic complexes at Yaxi, Niumaoquan, Xiangshanxi, and Weiya. Our new age dating on the Yaxi complex indicates that the mineralized gabbro (zircon SHRIMP U-Pb dated 297.3 ± 4.9 Ma) formed in the latest Carboniferous-Early Permian, similar to the diorite (LA-ICP-MS zircon U-Pb dated 308.3 ± 8.6 Ma) and granodiorite (LA-ICP-MS zircon U-Pb dated 304.9 ± 1.7 Ma). The Yaxi complex is the oldest late Palaeozoic mafic-ultramafic intrusion reported so far in the Eastern Tianshan. The mineralized gabbro at Yaxi contains higher average Fe2O3T (20.83 wt.%), TiO2 (5.91 wt.%), and V (523 ppm) contents than its ore-barren counterpart (7.45 wt.%, 0.99 wt.%, and 133 ppm, respectively). These Eastern Tianshan mafic rocks are mildly large ion lithophile element (LILE) enriched and high field-strength element (HFSE) depleted, and with LREE/HREE enrichment (Yaxi: (La/Yb)N = 2.7 ~ 5.37) and subtle positive Eu anomalies (Yaxi: Eu/Eu* = 0.94 to 3.31). This suggests that the Eastern Tianshan mafic-ultramafic magmas were likely derived from an arc/subduction-modified magma source. The E-W trending crustal-scale faults (e.g. the Aqikkuduk fault) may have acted as magma conduits and controlled the magma emplacement. The spatial-temporal distribution of the Eastern Tianshan Fe-Ti-V ore-forming mafic-ultramafic complexes and their petrologic and geochemical features suggest that the latest Carboniferous-Early Permian magmatic phase was likely emplaced in a collision-related compression setting following the Junggar Ocean closure, whereas the late Early Permian phase may have been related to a post-collisional orogenic setting. [ABSTRACT FROM AUTHOR]

The article discusses the research on the discovery of pyrite in natural coke which was derived from post-magmatic mafic intrusions found in a coal mine in Yangliu, China. It mentions the chemical compositions of colloidal pyrite, fine pyrite aggregates, and skeletal magmatic pyrite in natural coke. Topics include the exchange between coal and magma, and the use of scanning electron microscope and laser ablation inductively coupled plasma mass spectrometry for rock analysis.