Dispersed elements such as Ge, Ga and Cd attract increasing attention due to their wide use in modern high-tech or emerging industries. These elements are typically enriched in Mississippi valley-type (MVT) Pb-Zn deposits, which have not been well understood for the enrichment mechanisms due to their low-concentration and dispersed features. The Niujiaotang Zn-Cd deposit located at the southwestern China is one of the MVT Pb-Zn deposits extremely enriched in Cd, hosting more than 5000 tonnes of Cd with an average Cd grade of 1.4 wt % in sphalerite. To understand the critical factors controlling the abnormal enrichment of Cd, the elemental compositions and S-Zn-Cd isotopes of Cd-bearing sphalerite were investigated. The results show that the sphalerite in the Niujiaotang deposit can be divided into two generations (Sp1 and Sp2) from the early to the late hydrothermal stage, of which the Sp1 (3208-20521 ppm, mean of 10,812 ppm) has higher Cd concentrations than those of the Sp2 (Cd = 364-13500 ppm, mean of 4222 ppm). The Cd-rich Sp1 is coexistent with bitumen and abundant in organic gas-bearing fluid inclusions (e.g., CH4 and C2H6), suggesting that Cd enrichment might be associated with organic matter involvement. The high delta 34S values (14.0%o to 34.6%o) of sulfides are similar to those of sulfates in the strata, corroborating that TSR (thermochemical sulfate reduction) occurred between sulfates and organic matter. The low delta 66Znsphalerite (-0.27%o to 0.09%o) and delta 114/110Cdsphalerite (-0.72%o to-0.10%o) values, in combination with the widespread paleo-oil reservoirs in the study region, suggest that organic ligands derived from oil-field brines contributed to the transportation of Zn and Cd. The above results support that organic matter played critical roles in both the metal transportation and precipitation, which thus promoted the abnormal enrichment of Cd.

Dispersed elements such as Ge, Ga and Cd attract increasing attention due to their wide use in modern high-tech or emerging industries. These elements are typically enriched in Mississippi valley-type (MVT) Pb-Zn deposits, which have not been well understood for the enrichment mechanisms due to their low-concentration and dispersed features. The Niujiaotang Zn-Cd deposit located at the southwestern China is one of the MVT Pb-Zn deposits extremely enriched in Cd, hosting more than 5000 tonnes of Cd with an average Cd grade of 1.4 wt% in sphalerite. To understand the critical factors controlling the abnormal enrichment of Cd, the elemental compositions and S-Zn-Cd isotopes of Cd-bearing sphalerite were investigated. The results show that the sphalerite in the Niujiaotang deposit can be divided into two generations (Sp1 and Sp2) from the early to the late hydrothermal stage, of which the Sp1 (3208–20521 ppm, mean of 10,812 ppm) has higher Cd concentrations than those of the Sp2 (Cd = 364–13500 ppm, mean of 4222 ppm). The Cd-rich Sp1 is coexistent with bitumen and abundant in organic gas-bearing fluid inclusions (e.g., CH4 and C2H6), suggesting that Cd enrichment might be associated with organic matter involvement. The high δ34S values (14.0‰ to 34.6‰) of sulfides are similar to those of sulfates in the strata, corroborating that TSR (thermochemical sulfate reduction) occurred between sulfates and organic matter. The low δ66Znsphalerite (–0.27‰ to 0.09‰) and δ114/110Cdsphalerite (–0.72‰ to –0.10‰) values, in combination with the widespread paleo-oil reservoirs in the study region, suggesting that organic ligands derived from oil-field brines contributed to the transportation of Zn and Cd. The above results support that organic matter played critical roles in both the metal transportation and precipitation, which thus promoted the abnormal enrichment of Cd.

Mantle metasomatism has been increasingly recognized as a key process in the formation of giant gold deposits at craton margins, but its specific role remains controversial. The lithospheric mantle beneath the Cretaceous Jiaodong gold province at the eastern margin of the North China Craton was metasomatized by both Triassic continental subduction and Jurassic–Cretaceous oceanic subduction. To clarify the influence of mantle metasomatism on this giant gold endowment, this study systematically examined Hg isotopic compositions of pyrite from representative gold deposits across the western (Jiaobei Terrane) to eastern (Sulu Terrane) parts of the Jiaodong Peninsula. Gold deposits in the Jiaobei Terrane exhibit mixed terrestrial and marine Hg isotopic signatures (δ202Hg: −2.51‰ to 0.62‰; Δ199Hg: −0.24‰ to 0.17‰), whereas those in the Sulu Terrane display predominantly marine-derived Hg isotopic characteristics (δ202Hg: −0.73‰ to −0.19‰; Δ199Hg: −0.05‰ to 0.10‰) with no significant terrestrial influence. These findings suggest that the mantle beneath Jiaobei was metasomatized by both continental and oceanic components, while that under Sulu was primarily overprinted by oceanic subduction. Given that most gold resources of Jiaodong occur within the Jiaobei Terrane, we propose that the synergistic effects of continental and oceanic subduction were critical in forming giant gold deposits. Continental subduction might have contributed to Au pre-enrichment in the lithospheric mantle, while oceanic subduction might have introduced oxidizing agents and volatiles that promoted gold mobilization. This implies that the junction between continental and oceanic subduction zones provides a particularly favorable setting for giant gold deposit formation.

The tracing techniques and methods for studying metallogeny are fundamental to the ore deposit research,playing a crucial role in deeply revealing the sources,mobilization,migration and enrichment of the ore-forming materials,and the formation of ore deposits.As the research of critical or strategic mineral resources,which commonly have unique geological characteristics including the"low-grade","fine-grained"and"accessory"features,becomes hotspot of the ore deposit research,the available methods and theories can not meet the research needs of critical or strategic mineral resources.To address these challenges,relevant researchers of the State Key Laboratory of Ore Deposit Geochemistry have developed a series of high-precision and high-spatial-resolution analytical methods for elemental and isotopic(including geochronology)analyses,as well as experimental simulations and theoretical calculations on elemental partitioning and isotopic fractionation,and have progressively established a technical and methodological framework that can be used to strongly support researches of critical mineral resources over the past decade.The techniques and methods have been widely applied to study critical mineral resources such as tungsten,tin,antimony,gold,copper,molybdenum,lithium,rare earth elements and dispersed elements,greatly promoting the innovations of metallogenic theories and breakthroughs of mineral exploration.This paper reviews the developments and applications of these techniques and methods over the past decade,aiming to provide methodological references for critical mineral research and exploration.

This study comprehensively characterizes the natural chromite reference material UG1-W and establishes a methodological framework for its quantitative LA-ICP-MS analysis. Integrated mineralogical and geochemical analysis confirms exceptional homogeneity and validates optimized calibration approaches for UG1-W. High-resolution BSE imaging combined with automated mineralogy (TIMA) reveals a chromite-plagioclase dominated microstructure (80.8% chromite and 17.3% plagioclase) with minor accessory phases. Multi-analytical methods (LA-ICP-MS, EPMA, ICP-OES, ICP-MS, and TXRF) are employed to verify the homogeneity of both major and trace elements. Systematic calibration assessments yield three key findings: (1) persistent matrix-induced analytical biases occur when using synthetic glass standards; (2) calibration strategies yield divergent results despite employing internal standards; (3) matrix-matched calibration achieves superior accuracy for chromite analysis, exhibiting relative deviations below 5% against certified values. Collectively, this work establishes UG1-W as a homogeneous chromite reference material and unequivocally demonstrates the necessity of matrix-matched standardization for accurate LA-ICP-MS analysis of chromite. These findings significantly improve the measurement accuracy for refractory mineral systems and provide a robust analytical framework for geochemical studies of chromite-bearing lithologies.

The world-class Jiaodong gold province in the North China Craton hosts over 5000 t of Au resource and is characterized by abundant visible gold mineralization. However, the critical processes controlling the formation of visible gold in this province remain poorly understood. To solve this problem, integrated microtextural, trace elemental, and sulfur isotopic analyses of pyrite from the high-grade Linglong gold deposit in the Jiaodong gold province were conducted in this study. Two distinct pyrite types were identified within auriferous quartz-sulfide veins: (1) Py1 aggregates in quartz-pyrite veins (hydrothermal stage II), and (2) euhedral to subhedral, coarse-grained Py2 crystals in quartz-polymetallic sulfide veins (hydrothermal stage III). Microtextural and elemental analyses revealed that visible gold predominantly occurs as intergranular particles between primary pyrite crystals within Py1 aggregates. The Py1 exhibits complex microtextures with abundant mineral inclusions of polymetallic sulfides and has low concentrations of Au (median: 0.032 ppm) with a narrow δ34S range (4.86‰–6.75‰), indicative of rapid crystallization under unstable, disequilibrium conditions. By contrast, the Py2 is texturally homogeneous and contains higher Au concentrations (median: 0.304 ppm) with progressively increasing δ34S values (5.25‰–10.14‰) over time, suggesting slow crystal growth under more stable, near-equilibrium conditions. Based on the microtextural and geochemical information, it is proposed that fluid boiling occurred only during the hydrothermal stage II, which resulted in the unstable physicochemical environment and rapid deposition of gold. During the boiling processes, gold colloids likely occurred and promoted the formation of visible gold.

The migration ways of fluids in the crust are important for metal transport and precipitation, which can affect the mineralization depth, type, scale and ore grade. Unlocking the migration processes of fluids is thus significant for understanding the mineralization mechanism, which, however, is difficult due to the lack of suitable geologic sections. In this study, benefitting from the "deep drilling" projects in the giant Sanshaodao goldfield, Jiaodong gold province, gold-bearing quartz + pyrite samples were systematically collected from the drillholes and mining tunnels with a wide depth range of -3554 m to -390 m (in altitude). Using SIMS analytical method, the oxygen isotopic compositions of the above quartz (S18Oquartz) were in-situ analyzed. The results show that the S18Oquartz values from different depths vary from 9.4 %o to 14.9 %o, which increase with shallowing. This trend is considered to be mainly induced by decreasing temperature. After temperature correction, the S18O values of the oreforming fluids (S18Ofluid) in equilibrated with quartz are 3.9-7.6 %o, showing a consistent range of 5.5-6.5 %o at different depths. The consistent S18Ofluid values might represent the original S18O features of the ore-forming fluids and thus indicate a uniform fluid origin probably from mantle-related magmas/rocks. The narrowly varied S18Ofluid values also imply a channelized migration way, which facilitated fluids fast transportation from the deep to the shallow depth in a crustal scale. The variations of S18Ofluid indicate some fluid-rock interaction, showing oxygen isotopic exchange with mafic rocks in the deep but with late Archean metamorphic rocks in the shallow depths. It is recognized that elevated fluid-rock interaction occurred at the shallow depths, which was probably induced by the transformation of channelized to pervasive migration and led to enhanced gold mineralization. Considering the above effects, strong fluid-rock interaction at the depth range of -1000 m to -2000 m along the channelized pathways is favorable for gold mineralization and exploration beneath the study region.

High-purity quartz is a fundamental material that is essential for developing new productive forces, and it is a strategic resource that is in urgent need of development. In recent years, highly fractionated granites (granitic pegmatites) have attracted particular attention due to their high-purity quartz mineralization. Cenozoic Himalayan leucogranites, a type of highly fractionated granite, are promising sources of high-purity quartz. This paper presents the results of systematic analyses of quartz from the Himalayan leucogranites and associated rocks. It investigates impurity concentrations (such as Li, Al, and Ti) and evaluates mineralization potential and the main factors affecting quartz purity. The results indicate that Eocene-Oligocene leucogranites within the Tethyan Himalaya generally contain quartz with low impurity levels, demonstrating promising mineralization potential. Notably, quartz from the Dongbuzhen pluton in the Yala Xiangbo Dome exhibits exceptionally high purity, with impurity concentrations approaching or even surpassing internationally recognized standards for high-purity quartz. Additionally, quartz from biotite-bearing pegmatite (e.g., the Kudy pluton), quartz veins (in the Ramba and Xiaru areas), and Paleozoic granitic gneisses (e.g., in the Yala Xiangbo Dome and Kangma Dome) also shows low impurity contents and high mineralization potential. Comprehensive analyses reveal that the degree of magmatic differentiation and subsequent deformation and metamorphism are key factors controlling quartz purity in the Himalayan leucogranites. Quartz formed from highly fractionated yet fluid-undersaturated magmas tends to have low Ti, Al and Li contents. Furthermore, dynamic recrystallization (predominantly through grain boundary migration) driven by high-temperature metamorphism and deformation can enhance quartz purity by reducing impurity concentrations by more than 50%. Consequently, future prospecting for high-purity quartz in the Himalayan region should prioritize rocks that have undergone high degrees of magmatic differentiation (without reaching fluid saturation) and/or high-temperature metamorphism and deformation. Particular emphasis should be placed on Eocene-Oligocene leucogranites and associated biotite pegmatites within the Tethyan Himalaya, as well as Paleozoic granitic gneisses.

The Southeast Yunnan district is marked by multiple stages of magmatism, metamorphism, and early Paleozoic to Late Cretaceous Sn-W polymetallic mineralization. Numerous large to giant Sn-W deposits have developed and are closely related to skarns. Nevertheless, whether these skarns were contemporaneous with the Sn mineralization (economic skarn) or were superimposed on later tectonic events (noneconomic skarn) and whether the Sn polymetallic deposit formed from co-enrichment of Sn-In-Zn-Cu or enrichment of Sn-In superimposed by a separate Zn-Cu mineralization event remains poorly constrained. The Xinzhai deposit simultaneously developed Sn polymetallic mineralization and skarns (with Zn-Cu mineralization), making it a natural laboratory for exploring the mechanisms. Geological studies reveal that the Xinzhai deposit contains two separate hydrothermal systems: Sn-bearing hydrothermal veins (similar to 2.09 wt% Sn grade) and Sn-barren but sulfide-rich skarns (<0.04 wt% Sn grade). Three generations of cassiterite (Cst1-Cst3) were identified within the Sn-bearing hydrothermal vein. Cst1 and Cst2 are overprinted by newly formed Cst3, resulting in extensive microporosity filled by zoisite, biotite, and Zn-Cu sulfides. Cst3 differs from Cst1-2 in composition (e.g., Zr/Hf, W/Fe, Ti/Sc, Nb/Ta, W, and U) and fO(2), indicating a different origin. LA-ICP-MS U-Pb dating of Cst1 and Cst2 yielded ages of 428.1-425.8 and 416.8-411.3 Ma, respectively. In situ Rb-Sr dating of biotite, contemporaneous with Cst3, yielded an age of 203.9 +/- 5.3 Ma. These ages suggest that primary Sn mineralization (Cst1-2) and metasomatic fluids (formed Cst3, retrograde skarn, and Zn-Cu sulfides) originated from the Caledonian and Indosinian orogenic episodes, respectively. Fluid inclusion studies suggest that the Caledonian Sn-bearing fluid has higher homogenization temperatures, salinities, and metal compositions than Indosinian metasomatic fluids. Caledonian Sn-bearing fluids display higher delta S-34 values of sulfides (-2.34 to - 0.45 parts per thousand) than Indosinian metasomatic fluids (-7.87 to 1.09 parts per thousand). Based on geologic, textural, mineralogical, and geochemical evidences, we suggest that the Caledonian Sn polymetallic event was overprinted by Indosinian skarn and Zn-Cu mineralization episodes in the Xinzhai deposit. Caledonian Sn mineralization fluids were most likely inherited from the exsolution of granitic magma that intruded at ca. 430 Ma, whereas the Indosinian fluids probably derived from the metamorphic devolatilization of the Caledonian gneissic granites. This study further highlights that distinguishing the economic potential and noneconomic skarns in a hydrothermal system is crucial for Sn-Zn-In exploration.

Fluorite is a crucial non-metal mineral, widely used in various industries. It occurs in various rocks and economic deposits, making it a valuable geological indicator. Due to its characteristically low U and Pb contents, high percentages of common Pb, and prevalent multistage growth, fluorite has proven extremely challenging to determine the U-Pb age. The absence of matrix-matched fluorite reference materials (RMs), combined with its poor ablation characteristics under nanosecond lasers sampling, further complicates accurate age determination. Consequently, previous attempts using calcite WC-1 as the primary RM for ns-LA-ICP-MS U-Pb dating of fluorite have yielded results that are difficult to validate. We propose two fluorite samples, XWC and HN, as potential RMs for U-Pb dating. The fluorite XWC, from the Xiuwacu porphyry deposit (83.0 +/- 1.0 Ma), served as the primary RM to calibrate fluorite HN, which yield a U-Pb age 158.7 +/- 1.4 Ma. Owing to its ample availability, relatively high U (3.3-8.79 ppm) and low common lead (f(206) <= 23.8%), and uniform age signature, fluorite HN can be recommended as a potential RM for in-situ U-Pb dating of fluorite. Positive correlations (R-2 > 0.81) between U and Ca, REE, Y, Th, Li, Na, Al, P, and Sc in the fluorite QL-1, HN, and YH confirm that U can incorporate into the fluorite lattice during growth. Using fluorite HN as the RM, the U-Pb dates for calcite DC22 from four different ablation settings deviated significantly (8.6-22.0%) from its reference age of 153.5 +/- 0.8 Ma within uncertainties, indicating a pronounced matrix effect between fluorite and calcite. We utilized fluorite HN to calibrate the U-Pb dates of three stibnite-associated fluorite samples from the large-sized Qinglong Sb deposit in South China. They yielded four indistinguishable dates of 63.3 +/- 5.5, 69.0 +/- 10.5, 57.8 +/- 2.5, and 57.2 +/- 2.2 Ma and a younger U-Pb age of 13.8 +/- 1.6 Ma. The older cluster agrees well with the in-situ U-Pb age of stibnite-related calcite from the giant Xikuangshan (58.1 +/- 0.9 Ma) and medium-sized Bawang (62.8 +/- 1.1 Ma) Sb deposits, supporting a regional Sb mineralization event at similar to 60 Ma and a later hydrothermal overprint at similar to 14 Ma. These results demonstrate that U-Pb dating using a fluorite-matched RM can robustly constrain the timing of fluorite-related mineralization and fluid events.

Apatite has been widely applied as a reliable chronometer and geochemical tool for studies on genesis and provenance. Due to small quantity, most apatite standards for laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb dating were exhausted. Therefore, apatite reference materials with homogeneous age and abundant reserves are still necessary. The famous Qinghu (QH) monzonite in the western Nanling region, South of China was dated well at 159.5 +/- 0.2 Ma (Isotope Dilution Thermal Ionization Mass Spectrometry (ID-TIMS) zircon U-Pb method) and 159.5 +/- 0.7 Ma (Secondary Ion Mass Spectrometry (SIMS) zircon U-Pb method). The QH apatite grains selected from this monzonite are characterized by abundant reserves, euhedral crystals with sizes up to 1mm, high U and Pb contents of 137.30 and 7.82 mu g/g, respectively, and a small Th/U value of 2.6. The QH apatite were analyzed as a quality control over five years in the SKLCMRE lab and yielded an accurate U-Pb age at 161.3 +/- 0.8 Ma (N=110, MSWD= 1.1, calibrated by OD306), which agrees well with the published U-Pb ages within uncertainties. In combination of these age results and microscopic observations on cogenetic minerals in this rock, the zircon ID-TIMS U-Pb age of 159.5 Ma was accepted as a reference age for QH apatite. Up to now, it is the most suitable reference material for apatite samples from the Jurassic to Cretaceous periods owing to its high U and Pb content and formation age. An initial Pb-207/Pb-206 ratio of 0.837 +/- 0.008, which was derived from LA-SF-ICP-MS analyses on intergrown feldspars, is consistent with the calculated value (0.836) in Stacey and Kramers (1975). One hundred and sixty analyses on QH apatite grains have a common lead percentage (f(206)) value ranging from 4.2% to 38.4% and form a good linear trend on the Tera-Wasserburg diagram. Using QH apatite as a primary standard in a two-stage calibration method, four known apatite standards, including OD306, 401, MAD1, and MM, have been accurately determined with age offsets of -0.7% to 1.2% by LA-ICP-MS. These age results are the same as those calibrated by apatite OD306 (-1.1% - 0.1%), MAD1 (-1.2% - -0.1%), and MM (-1.1% - 0.1%), and much improved than those calibrated by apatite 401 (0.3% - 1.4%) and Otter Lake (-3.4% - -2.2%). Moreover, in a method application, MRC-1 apatite yielded a lower intercept Pb-206/U-238 ages of 154.1 +/- 5.3 Ma, which agrees well with the published ID-TIMS U-Pb age of 153.3 +/- 0.2 Ma within uncertainty.

The Vindhyan Basin in north-central India offers a remarkable sedimentary rock record suitable for reconstructing the Proterozoic tectonic evolution of the Northern Indian Block, and its paleogeography through the Columbia-Rodinia supercontinent cycles. We present new sedimentological and geochronological data from Vindhyan successions to refine basin development and evolution process, and to assess regional and global tectonic implications. The detrital zircon geochronologic data constrain a 1,721-1,599 Ma depositional age for Lower Vindhyan rocks and 1,210-752 Ma for the Upper Vindhyan ones. A transition from a foreland basin (Lower Vindhyan) to a tectonically quiescent setting (Upper Vindhyan) was inferred, further supported by increasing detrital input from metamorphic basement as confirmed by detrital quartz geochemistry as well as Monte Carlo unmixing models. The Lower Vindhyan sedimentation, occurred in two independent sub-basins, was terminated by the collision between the Northern and Southern Indian blocks. Continued subsidence and/or uplift of basin margins resulted in the development of a unified large basin during the Upper Vindhyan deposition. Tectonic reactivation driven by the collision of Australia-Antarctic plates with India resulted in uplift and ultimate closure of the basin. Integrating previous findings with our data, we infer the Cathaysia Block was adjacent to NW India at the periphery of Columbia supercontinent, while the Yangtze Block was located within the continental interior. Outward drift of the Yangtze Block from the interior of the Columbia supercontinent and its subsequent amalgamation with the Cathaysia block constituted the South China Block, which later neighbored Northern India at the Rodinia supercontinental margin.

Zircon has a similar U–Pb fractionation and average normalized Pb/U ratio with ilmenite; our direct calibration method using zircon 91500 as an external standard is effective for in situ U–Pb dating of ilmenite under wide ablation settings.

A natural stibnite (BJ-Snt) is recommended as a potential reference material for S isotope analysis employing laser ablation multicollector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS).

The devolatilization model of the metasomatized lithospheric mantle without pre-enriched gold has been proposed to account for the giant gold mineralization. An excellent example is the world-class Jiaodong gold province with >5000 tonnes Au resources in the eastern North China Craton. The auriferous fluid transport and gold enrichment during wallrock alterations are two vital processes to determine the giant gold mineralization formation in this province. However, the effects of the fluid-rock interaction with alterations on the auriferous fluid transport and gold enrichment still keep poor understanding, which leads the above model to be imperfect. The giant Jiaojia goldfield in this province recorded a wallrock alteration evolution from K-feldspar alteration to pyrite-sericite-quartz alteration, and some parts of the latter can become gold orebodies when the gold grade is >1 ppm. This study conducts thermody-namic fluid-rock interaction modeling to reveal auriferous fluid transport and coupled relationship between gold enrichment and alteration mineral assemblage based on the alteration-mineralization and ore fluid characteristics of the goldfield. The modeling of fluid-rock interaction with cooling indicates the transformation of Au-Cl complexes to Au-S complexes combined with the total sulfur concentration decrease by pyrite precipitation when cooling from-460 degrees C can trigger the dispersive gold precipitation, which should hinder the gold long-range transport to lower ambient temperature. The high oxygen fugacity at >400 degrees C can enhance Au-Cl complexes stability, and the low pH can maintain high total sulfur concentration in the auriferous fluid, both of which facilitate the long-range gold transport to a lower-temperature environment. The auriferous fluid would acquire higher pH by the buffering of feldspars or sericite, which was beneficial for the high-efficiency precipitations of pyrite and gold. The ankerite-siderite assemblage without pyrophyllite in the pyrite-sericite-quartz alteration zone indicates that a cumulative fluid to rock mass ratio (f/r) of 3.8-4.8 should be needed for the transformation from K-feldspar alteration to pyrite-sericite-quartz alteration according to the fluid-rock interaction modeling at 300 degrees C and 2000 bar. In the case of auriferous fluids with <= 200 ppb Au concentration, the single fluid-rock interaction can only elevate the gold grade to <= 0.69-0.87 ppm in the pyrite-sericite-quartz alteration zone at f/r 3.8-4.8. Therefore, the fracture-induced fluid flow coupled with fluid-rock interac-tion is proposed to the prerequisite to elevate the gold grade to >1 ppm in the pyrite-sericite-quartz alter-ation zone. The metasomatized lithospheric mantle volume for the required ore fluid and Au in the Jiaodong province is estimated according to the modeling results and alteration-mineralization charac-teristics, which provides a link between the mantle without abnormal Au enrichment and the alteration-mineralization processes.

The Jiaodong Peninsula, the largest gold province in China, hosts proven gold resources of similar to 5,500 t. Knowledge of the accurate occurrence of gold and its formation mechanism is key to a better understanding of the mineralization process of these deposits. In this study, we combined field-emission scanning electron microscopy, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), electron backscattering diffraction (EBSD), and high-resolution X-ray computed tomography (micro-CT) to investigate the predominant gold occurrence type and its formation processes in the Sanshandao and Xincheng giant gold deposits. Microscopic observations confirmed that visible gold in the two-dimensional mode occurred as fracture gold and inclusions in the pyrite. However, high-resolution micro-CT revealed that almost all visible gold in the three-dimensional mode was connected to the fracture, suggesting that the previously so-called gold inclusions were actually fracture gold. The LA-ICP-MS results showed that the pyrite contained low concentrations of invisible gold (<1 ppm). Thus, fracture gold is the predominant type in the Jiaodong gold province. The EBSD analyses showed that the neighboring pyrite fragments shared a similar crystallographic orientation, and these fragments could be assembled into individual grains. The in-situ fracturing texture resulted from structural activities and/or hydraulic fracturing. By combining petrographic, crystallographic, and geochemical analyses with geological information, the mineralization process of the Jiaodong gold deposits can be summarized as follows. When the gold-bearing fluid reacted with the wall rocks, intensive fluid-rock interactions led to the precipitation of massive amounts of pyrite. Subsequent structural activities and/or hydraulic fracturing broke the pyrite and triggered fluid boiling. Boiling induced gold saturation and precipitation in the cracks of the fractured pyrite. Thus, massive ore fluids with low gold concentrations can also form world-class gold deposits via the synergistic mechanisms of intensive fluid-rock interaction and fluid boiling.

Quartz as one of the most stable minerals in sedimentary processes, is widely distributed in clastic sedimentary rocks, making it a potential provenance tracer in the source-to-sink system. In this study, internal morphology and trace element geochemistry of detrital quartz from the Marwar sandstones in NW India were utilized to decipher the source lithologies. Quartz from various source rocks displays distinctive trace element characteristics that correspond to specific cathodoluminescence properties. Phenocrystic quartz in hypabyssal and volcanic rocks is characterized by higher Li (>10 ppm), Al (>90 ppm), and Ti (>60 ppm) contents, medium to bright blue cathodoluminescences, and visible zoning. Quartz in plutonic rocks, especially diorite, contains a lower abundance of trace elements. It exhibits dark brownish red, violet to blue cathodoluminescence, and is marked by dark streaks, patches, and partial healing fractures. Pegmatitic quartz with the lowest Li (0.03 ppm) and the highest Ge (1.38 ppm) contents, displays brown to dark blue cathodoluminescences. Gneissic quartz with the highest Fe (3.98 ppm) and a moderate abundance of other trace elements, exhibits non-luminescence or dark brown to dark blue cathodoluminescence, occasional dark streaks, and healing fractures. Quartz in migmatites generally shows a lower trace elements abundance, non-luminescence, or dark brown to dark blue cathodoluminescence. A robust statistical correlation between the cathodoluminescence properties and trace element characteristics is discernible in the detrital quartz grains through the entire stratigraphy of the Marwar Supergroup, shedding light on the lithological and compositional make-up of the provenances. This study identifies that the early sedimentation in the Marwar basin was predominantly fed by detritus from the Neoproterozoic Malani Igneous Suite and Paleoproterozoic granitoids, whereas the younger strata document a marked increase in contributions from the older Aravalli Craton basement. Our findings demonstrate the utility of quartz trace element geochemistry and internal morphology as effective tools for provenance analysis in source-to-sink systems. Moreover, detrital quartz and zircon in combination can be effectively used in tracing the specific source and quantifying relative contributions from different source rocks that could be applied to provenance studies elsewhere.

Traditionally, gold deposits in the Jiaodong gold province of China have been regarded as gold-only deposits lacking economic base metals. However, recent studies found some cobalt (Co) enrichment in those deposits. The mechanisms of this Co enrichment remain poorly understood. In this study, we identified a type of pyrite highly enriched in Co (concentrations up to 32800 ppm) at the Linglong gold deposit, Jiaodong gold province. The pyrite was collected from a hydrothermally altered mafic dike contacting with gold ore veins. To decipher the enrichment mechanisms of Co, in-situ textural, elemental and sulfur isotopic analyses were conducted on the pyrite. The pyrite typically exhibits core-mantle-rim textures. The cores (Py-m1) have high Co concentrations (up to 5950 ppm) with homogeneous texture and elemental distribution, which could be the primary pyrite formed by pyritization of the mafic dike. The mantles (Py-m2) have the highest Co concentrations (up to 32800 ppm) and contain abundant mineral inclusions (chalcopyrite, galena, and sphalerite) and pores, showing the formation through coupled dissolution-reprecipitation (CDR) reactions. The rims (Py-m3) have low concentrations of Co (0.14-559 ppm) and show cubic shapes, forming directly from hydrothermal fluids. The delta 34S values increase from the cores (4.2 %o to 9.1 %o, mean of 8.0 %o) to the mantles (8.9 %o to 11.9 %o), but vary between the above two in the rims (4.2 %o to 12.2 %o, mean of 9.0 %o). The sulfur isotopic compositions of the Py-m are similar to those of pyrite (4.8 %o to 9.5 %o) from the neighboring auriferous quartz-sulfide veins at Linglong in previous study. Combined with the geological and textural features, it is inferred that hydrothermal fluids during gold mineralization extracted abundant Co from the mafic dikes, leading to the primary enrichment of Co in the Pym1. The Py-m1 was dissolved and re-precipitated during subsequent hydrothermal activities, forming Py-m2 with enhanced re-enrichment of Co. Basically, the Co-rich mafic dike provided the initial enrichment of Co while the gold-bearing hydrothermal fluids contributed to concentrate Co further. Considering the widespread mafic rocks and extensive hydrothermal activities during gold mineralization throughout the Jiaodong gold province, there might be a considerable Co resource formed through the above processes.

Titanomagnetite occurs commonly in igneous and metamorphic rocks, and various types of deposits, and serves as a valuable indicator. Recently, it has been identified as a new geochronometer for U-Pb dating. However, no reference material is available currently. Thus, we used a titanomagnetite sample HG79c with a known age of 259.2 +/- 2.8 Ma to evaluate potential primary standards and establish an accurate calibration method for widespread application. In our in situ U-Pb dating experiments, different ablation settings were optimized, i.e., spot sizes of 44 and 60 mu m, laser frequencies of 6, 8, and 10 Hz, and energy densities of 3, 4, and 8 J cm(-2). 3 ml min(-1) nitrogen was introduced to enhance sensitivity and reduce matrix effects. Five Concordia-intercept Pb-206/U-238 ages were obtained for HG79c using cassiterite AY-4 as an external standard, and four are consistent with or slightly younger than the reference age within errors. Two accurate ages were obtained when HG79c was calibrated by zircon 91500 and garnet PL-57. All these age results and Pb/U fractionation confirm that cassiterite and zircon have a normalized Pb/U ratio consistent with titanomagnetite in some optimized ablation settings. We utilized cassiterite AY-4 as the primary standard, HG79c as quality control in an optimized ablation setting, i.e., a spot size of 60 mu m, energy density of 4 J cm(-2), and laser frequency of 6 Hz, to date titanomagnetite LL22-137 from the Lala Fe-Cu deposit in the Kangdian IOCG metallogenic province, China. This titanomagnetite yielded a Concordia-intercept 206Pb/238U age of 853.2 +/- 9.9 Ma, which agrees well with the intergrown rutile U-Pb age of 850.8 +/- 8.7 Ma and the published U-Pb ages for apatite and secondary allanite, and Re-Os age for molybdenite from the same deposit. This method offers a new tool for directly dating diagenesis and ore-forming processes related to Fe and Ti metals.