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[ Objective ] Carbonatites, as magmatic-origin rocks, are crucial source rocks for uranium, rare earth, and other minerals. They are widely distributed in the Xiaoqinling region of Shaanxi, giving rise to numerous large to super-large carbonatite deposits of uranium, molybdenum, and rare earth, represented by Huayangchuan and Dashigou, attracting attention from scholars in recent years. Previous studies on carbonatite deposits in the area focused on petrology, mineralogy, genesis, and mineralization chronology. However, they were often limited to individual deposits, needing more regional cross-sectional comparative studies. [ Methods ] This study employs field geological surveys, petrographic analysis, and geochemical characterization of typical rocks and ores to reclassify different types and stages of Xiaoqinling carbonatites. It analyzes the geochemical characteristics of various carbonatite types and explores the mineralization processes of uranium and rare earth elements associated with carbonatites. [ Results ] Xiaoqinling carbonatites exhibit a large vein, vein group, and vein network morphology, intruding into the Archean metamorphic basement, Xiong'er Group volcanic sedimentary rocks of the Changchengian System, and Gaoshanhe Group clastic rocks of the Jixianian System along fault structures. Based on field crosscutting relationships and primary mineral assemblage characteristics, Xiaoqinling carbonate rocks can be re-divided into five stages from old to new: aegirine syenite stage (I), aegirine carbonatite stage (II), potassium feldspar carbonatite stage (III), quartz carbonatite stage (IV) and zeolite-bearing carbonatite stage (V). Spatially, the division is roughly along the nearly EW-striking Xiaohe Fault, with northern carbonatite veins dominated by aegirine syenite and aegirine carbonatite, rich in aegirine, biotite and other dark minerals, distributed in the Archean gneiss basement. The southern part is mainly composed of light-colored potassic feldspar carbonatites and quartz carbonatites, almost devoid of dark minerals, with surrounding rocks consisting of Xiong'er Group volcanic sedimentary rocks and Gaoshanhe group clastic rocks. Zeolite-bearing carbonatites are distributed throughout the region. Temporally, the carbonatites formed in the Late Triassic, but distinct temporal differences exist among different sections. Previous data indicate a possible 30 Ma gap in the formation times of various carbonatite types in the Xiaoqinling area. The geochemical characteristics of Xiaoqinling carbonatites reveal an average SiO2 content of 30.43%, significantly higher than the global average for carbonatites. CaO is relatively low, with an average content of 28.71%, exhibiting a clear negative correlation with SiO2 content. Total alkali (Na2O+K2O) content is relatively high, averaging 2.25%, with a maximum value of 10.23%. The total alkali content decreases gradually from early to late stages, strongly correlating with CaO and Al2O3 content. The potassium-sodium ratio (w(K2O)/w(Na2O)) is exceptionally high, with an average of 4.625 and a maximum value of 36.55. Ferromagnesian content (TFe2O3+MgO) varies significantly, with early-stage carbonatites (Stages I, II, III) having higher ferromagnesian content (average 8.29%), while late-stage carbonatites (Stages IV, V) generally have lower ferromagnesian content (average 1.92%). Ferromagnesian content correlates positively with TiO2 content. MnO has an average content of 1.22%, reaching up to 4.49%, notably enriched in late-stage quartz carbonatites. REE content averages 0.26%, with a maximum value of 0.96%, exhibiting a positive correlation with MgO content. The ∑LREE/∑HREE ratio ranges from 0.47 to 27.72, with early-stage carbonatites (Stages I, II, III) showing strong heavy REE depletion. Late-stage quartz carbonatites have an average ∑LREE/∑HREE ratio of 2.15, indicating relatively heavy REE enrichment, especially in Tm, Yb, Lu, and Y. Heavy REE content correlates linearly with MnO content. The overall REE distribution pattern of carbonatites is a steep-left and gentle-right, relatively flat-right-trending model, showing continuous variations in REE distribution patterns throughout different stages. Ore-related element content characteristics of various carbonatite types reveal significant U and Nb enrichment in aegirine syenite, aegirine carbonatite, and potassium feldspar carbonatite. Mo-mineralization is closely associated with potassium feldspar carbonatite and quartz carbonatite, while Pb and Ba-Sr mineralization is evident in all carbonatite stages. [ Conclusions ] (1) Xiaoqinling carbonatites are categorized into aegirine syenites, aegirine carbonatites, potassium feldspar carbonatites, quartz carbonatites, and zeolite-bearing carbonatites in chronological order. (2) Xiaoqinling carbonatites exhibit notably high SiO2 and total alkali content, low MgO content, and exceptionally high potassium-sodium ratio. There is a gradual decrease in CaO, TiO2, Al2O3, ferromagnesian, and total alkali content from early to late stages, while MnO content shows an opposite trend. Carbonatites evolve from early ferrocarbonatite to late calciocarbonatite. (3) Different types of carbonatites show distinct ore-related characteristics, with early stages (aegirine syenite, aegirine carbonatite, and potassium feldspar carbonatite) mainly enriched in U (Nb), and Potassic Feldspar Carbonate additionally enriched in Mo. Late-stage quartz carbonatites are characterized by Mo and HREE enrichment. [ Significance ] The findings of this study provide valuable information for the exploration and research of carbonatite-type uranium, rare earth, and polymetallic deposits in the Xiaoqinling area, holding significant practical importance.

Xiazhuang uranium ore field, located in the southern part of the Nanling Metallogenic Belt, is considered one of the largest granite‐related U regions in South China. In this paper, we contribute new apatite fission track data and thermal history modeling to constrain the exhumation history and evaluate preservation potential of the Xiazhuang Uranium ore field. Nine Triassic outcrop granite samples collected from different locations of Xiazhuang Uranium ore field yield AFT ages ranging from 43 to 24 Ma with similar mean confined fission track lengths ranging from 11.8 ± 2.0 to 12.9 ± 1.9 μm and Dpar values between 1.01 and 1.51 μm. The robustness time‐temperature reconstructions of samples from the hanging wall of Huangpi fault show that the Xiazhuang Uranium ore field experienced a time of monotonous and slow cooling starting from middle Paleocene to middle Miocene (∼60–10 Ma), followed by relatively rapid exhumation in the late Miocene (∼10–5 Ma) and nearly thermal stability in the Pliocene–Quaternary (∼5–0 Ma). The amount of exhumation after U mineralization since the Middle Paleogene was estimated as ∼4.3 ± 1.8 km according to the integrated thermal history model. Previous studies indicate that the ore‐forming ages of U deposits in the Xiazhuang ore field are mainly before Middle Paleocene and the mineralization depths are more than 4.4 ± 1.2 km. Therefore, the exhumation history since middle Paleocene plays important roles in the preservation of the Xiazhuang Uranium ore field. [ABSTRACT FROM AUTHOR]

The present study has assessed the preliminary placer LREEs resource potential of mid-Siwalik Group Dhok Pathan Formation from Surghar-Shingar Range of NW Himalayan foreland Fold-and-Thrust-Belt and regarded them as indicative resources only. The analytical results of bulk samples of sandstone did not show any anomalous concentration of REEs. However, the ICP-MS results of heavy minerals laminations (black sands) revealed high concentrations (ppm) of LREEs (La: 975, Ce: 2831, Pr: 193, Nd: 746, Sm: 127, Gd: 98.70). We identified monazite-(Ce) [Ce, La, Nd]PO4 as the primary LREEs-bearing mineral through Electron Probe Micro Analysis (EPMA). The representative quantitative micro-mineral analysis of monazite confirmed promising concentration of Rare Earth Oxides (REOs) maximum (in weight %) - La2O3: 16.20, Ce2O3: 37.82, Pr2O3: 4.77, Nd2O3: 21.72, Sm2O3: 5.23, Gd2O3: 4.88. Considering the thickness, lateral extension and depositional setting of host sediments along-with anomalously high concentrations of LREEs, it has been concluded that these Siwalik sediments host good indicative placer resource potential for low-cost recovery of LREEs.

The Jiadi gold deposit, situated in the Southwestern region of Guizhou, is a large-scale, recently discovered, basalt-hosted, and fine-grained disseminated gold deposit. This study has unveiled that the tectonic deformation of the Jiadi gold deposit can be categorized into four stages: the Late Paleozoic crustal uplift and brittle deformation (D1-deformation) stage; the Early Yanshanian NW-trending compressive ductile deformation (D2-deformation) stage; the Late Yanshanian NS-trending strike-slip fault (D3-deformation) stage; and the Himalayan EW-trending nappe structure (D4-deformation) stage. The outcomes of the C-O isotope analysis revealed that the fluid responsible for ore formation exhibits the attributes of magmatic water blended with meteoric water, and the metallogenic constituents primarily originate from a deep source. The formation of the Jiadi gold deposit occurred during the D2-deformation stage and extended to the D3-deformation stage. The D2-deformation stage induced hydrothermal activity and rock devolatilization, leading to the generation of CO2-rich and low-salinity fluids. The D3-deformation stage, which is intimately associated with mineralization, can be classified into three stages: the pyrite stage; the smoky quartz stage; and the sulfide stage. The findings obtained from laser Raman spectroscopy indicate that the inclusions typically comprise CO2, CH4, N2, and SO2. These deep fluids ascended along the fault to the interlayer fracture zone during the D3-deformation stage. The alteration of the geochemical environment was accompanied by fluid immiscibility or boiling, resulting in the rapid precipitation of metallogenic materials. [ABSTRACT FROM AUTHOR]

We report evidence for the seawater origin of an extremely metal-enriched sulfide- and organic carbon-rich marker bed in a transgressive Early Cambrian black shale sequence along the passive margin of the Yangtze platform. The element concentration pattern in this marker bed suggests that it formed in a sediment-starved, stratified basin with a euxinic water column below an oxic surface layer. Biological activity was high in the surface layer, which was resupplied by communication with oxic oceans. The extremely low terrigenous input and the sulfate-reducing environment in the deeper part of the basin led to exceptionally high metal enrichments by factors of ~[10.sup.7] with respect to modern seawater. The composition of the sulfidic rocks reflects the composition of the Early Cambrian oceans. The molybdenum isotope ratio suggests that during this time Keywords: Cambrian, black shale, anoxic environments, molybdenum isotopes, China.

This study examined the stable carbon isotope ( δ 13C) and characterization of sources of organic matter from core samples of sandstones of mid-Siwalik group Dhok Pathan Formation from Surghar-Shingar Range of NW Himalayan foreland Fold-and-Thrust-Belt. These sediments have recorded valuable information regarding the palaeo-vegetation type and paleo-environment/depositional environments. The analytical results of stable carbon isotope range from -24.50 to -28.43% with an average value of-26.56%. These values correspond to C3 vegetation of cool growing season and support the hypothesis of the dominance of C3 biomass in the ecosystem during the late-Miocene in this area. The phytoclasts are characterized as huminite/vitrinite, derived from terrestrial plants and referred to as type-Ill kerogen. The fungal attack, scaring and pitting of bacterial activity, biochemical degradation, replacement/diagenetic development of pyrite suggest that these sandstones of Dhok Pathan Formation were deposited under dyoxic conditions and thus these sandstones are primary reduced sandstones. [ABSTRACT FROM AUTHOR]