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Mercury (Hg) isotopes have shown their power of tracing Hg pollution sources in ecosystems, but their potentials for petrogenetic tracing are yet to be explored. Here we conducted Hg isotope analysis for samples collected from major orebodies of the world‐class Jinchuan Ni‐Cu sulfide deposit, China. These samples show large variations of δ202Hg (−2.65 to +0.19‰) and Δ199Hg (−0.16 to +0.19‰). Some of the Δ199Hg values significantly deviate from current estimates on the primitive mantle (Δ199Hg: 0.0 ± 0.1‰, 2SD). The pronounced Hg mass‐independent fractionation (Hg‐MIF) signals, with significant positive (>0.1‰) and negative (<0.1‰) Δ199Hg values similar to marine sediments and terrestrial soils, respectively, suggests the addition of crustal materials into the Jinchuan deposit, via crustal assimilation during mantle‐derived magma ascending to the crust. These samples show δ34S values (−1.09 to +1.38‰) identical to that of the primitive mantle (0.0 ± 2.0‰), which may indicate a major sulfur source from the mantle. However, δ34S provides poor constraints on the sulfur source, and the early reported anomalous Δ33S values (+0.12 to +2.67‰) in the Jinchuan deposit support the involvement of external sulfur from Archean and Proterozoic sedimentary rocks during the formation of this deposit, similar to the case of Hg. This study shows the powerful use of Hg isotopes as a petrogenic tracer and highlights the importance of interaction between mantle‐derived magmas and crustal materials on the formation of the Jinchuan Cu‐Ni sulfide deposit. Plain Language Summary: Photochemical reactions result in pronounced Hg mass‐independent fractionation (Hg‐MIF) signals (Δ199Hg ≠ 0‰) in marine and terrestrial systems. Recent estimates on 3He‐rich basalts suggest the lack of Hg‐MIF signals in the primitive mantle (Δ199Hg ∼ 0‰). This study observes non‐zero Δ199Hg values (−0.16 to +0.19‰) in the giant Jinchuan Ni‐Cu sulfide deposit, suggesting crustal assimilation during the formation of this deposit. Interaction between mantle‐derived magmas and crustal materials could have played an important role in the formation of the Jinchuan Cu‐Ni sulfide deposit. Hg isotopes have a great potential in understanding crustal‐mantle interactions. Key Points: Significant Hg mass‐independent fractionation signals were observed in the giant Jinchuan Ni‐Cu sulfide depositThe non‐zero Δ199Hg values in the Jinchuan deposit suggest crustal contamination mantle‐derived magma ascendingCrustal materials addition plays an important role in the formation of magmatic sulfide deposits [ABSTRACT FROM AUTHOR]

The genesis of the giant Ag-Cu-Pb-Zn polymetallic mineralization in the northern Lanping basin, Southwest China, remains controversial. To address the sources of metals, a systematic study on Hg isotope compositions was conducted for the Cu-dominated deposit at Baiyangping and the Pb-Zn-dominated deposits at Fulongchang and Liziping. The Cu deposit shows positive Δ199Hg signatures (0.14 ± 0.13‰), in contrast to the Δ199Hg of the Pb-Zn deposits (− 0.09 ± 0.06‰). As positive Δ199Hg values are commonly observed in marine sediments and the Lanping Triassic marine sedimentary rocks show exclusively positive Δ199Hg signals (0.03 ± 0.07‰), the Hg in Cu ores was mainly sourced from the Triassic strata. The negative Δ199Hg signals observed in the Pb-Zn deposits, typical of terrestrial Hg, agree roughly with those of the Jurassic to Paleocene terrestrial sedimentary rocks (− 0.05 ± 0.08 ‰), indicating that the terrestrial strata provided the Hg in Pb-Zn ores. Compared to the source rocks, the Cu deposit shows isotopically lighter Hg enrichments (δ202Hg = − 2.30 ± 0.35‰), possibly resulting from fractionations induced by Hg2+ sorption, organic complexation, and precipitation of Hg-bearing sulfides. The Pb-Zn deposits show comparable or slightly heavier δ202Hg (− 0.56 ± 0.48‰); moreover, δ202Hg values of late-stage sulfides are higher than early-stage δ202Hg values, suggesting that the δ202Hg variation was primarily caused by sulfide precipitation. Thus, Hg isotope data indicate that separate hydrothermal events resulted in Cu and Pb-Zn mineralization. More importantly, this study reveals the great potential of Hg isotopes to discriminate sedimentary sources of metals for low-temperature hydrothermal deposits. [ABSTRACT FROM AUTHOR]

The late Mesozoic antimony (Sb) mineralization belt in South China hosts a large portion of the world's Sb reserves. However, the source and mineralization processes of these Sb deposits remain controversial. Here, we measured mercury (Hg) concentrations and isotopic compositions of stibnite in the Banpo Sb-only and Woxi Sb-polymetallic ore deposits, as well as associated rocks in the Yangtze Block in order to constrain the metal sources and ore formation processes in the South China Sb mineralization belt. Stibnite samples from both deposits exhibit significant enrichment in Hg (4.23–50.6 ppm) and have higher δ202Hg values (−0.47‰ to 2.03‰) than the studied Precambrian basement rocks (−1.42‰ to 0.59‰), Paleozoic sedimentary rocks (−2.40‰ to −0.32‰), and other natural Hg reserves (e.g., marine and continental systems). This indicates that significant mass-dependent fractionation of Hg isotopes occurred during hydrothermal processes. Negative to slightly positive Δ199Hg values of −0.17‰ to 0.02‰ were obtained for stibnite from the studied deposits, similar to values for the Precambrian basement rocks, but different from those of the Paleozoic sedimentary rocks and data previously reported for mantle materials. This suggests that Precambrian basement rocks were the source of Hg and associated metals. Our data and the tectonic evolution of South China indicate that late Mesozoic asthenospheric upwelling, in response to the Paleo-Pacific oceanic slab foundering, generated heat that drove the circulation of fluids in the basement and crustal basinal rocks. These fluids leached Sb, Hg, and other metals from the Precambrian basement rocks and formed the world-class Sb mineralization belt in South China. [ABSTRACT FROM AUTHOR]

It has been well established that metal and sulfur sources in mineral deposits can be very difficult to identify, especially for ore deposits hosted in sedimentary rocks. Using the world's largest Sb deposit at Xikuangshan in southern China as a case study, this study combined Hg isotopes and in situ sulfur isotope measurements to constrain the sources of Sb and sulfur. A variation of 1.1‰ in δ202Hg (0.04 to 1.15‰) was observed in stibnite ore samples, suggesting that mass-dependent fractionation of Hg isotopes occurred during the formation of the deposit. Significant mass-independent fractionation of Hg isotopes, with △199Hg ranging from − 0.03 to − 0.17‰, was also observed in the ore samples, suggesting that Hg transported by the ore fluids was inherited from Proterozoic basement metamorphic rocks as these rocks show similar △199Hg signatures (− 0.03 to 0.07‰). In situ sulfur isotope measurements yielded δ34S values that cluster in the range of + 6.8 to + 10.2‰, providing evidence that sulfur contained in ore fluids may also have been dominantly derived from underlying Proterozoic basement metamorphic rocks (δ34S = +5.6 to + 11.5‰). Using the new results from Hg and S isotopes, we proposed that deep-circulated meteoric water mobilized Sb, Hg, and S from the Proterozoic metamorphic basement, ascended along deep faults, and subsequently deposited Sb at favorable structural zones as a result of boiling of the hydrothermal fluids, generating the world-class Xikuangshan Sb deposit. This study also highlights the combined use of Hg-S isotopes as a novel method to provide new and additional insights into the source regions of ore materials for sedimentary-hosted Sb deposits. [ABSTRACT FROM AUTHOR]

Earth's surface underwent a dramatic transition ~2.3 billion years ago when atmospheric oxygen first accumulated during the Great Oxidation Event, but the detailed composition of the reducing early atmosphere is not well known. Here we develop mercury (Hg) stable isotopes as a proxy for paleoatmospheric chemistry and use Hg isotope data from 2.5 billion-year-old sedimentary rocks to examine changes in the Late Archean atmosphere immediately prior to the Great Oxidation Event. These sediments preserve evidence of strong photochemical transformations of mercury in the absence of molecular oxygen. In addition, these geochemical records combined with previously published multi-proxy data support a vital role for methane in Earth's early atmosphere. Earth's surface underwent a dramatic transition ~2.3 billion years ago when atmospheric oxygen first accumulated during the Great Oxidation Event. Here, the authors find that biogenic methane and volcanic emissions played a vital role in the reduced Late Archean atmosphere. [ABSTRACT FROM AUTHOR]

• Hg isotopes support thermogenic and atmospheric Hg release from CAMP magmatism. • Mass balance is used to constrain Hg sources and release amounts during ETME. • Extrusive volcanism may have played a key role in driving local extinctions. The End-Triassic Mass Extinction (ETME) was broadly coincident with the emplacement of the Central Atlantic Magmatic Province (CAMP). However, the relationship between evolutionary phases of CAMP (i.e. prolonged shallow intrusive pulses and later extrusives) and the ETME is not clear. Here, a high-resolution record of changing magmatic activity is established using mercury (Hg) isotopes through a Triassic-Jurassic sedimentary succession deposited on the northern flank of CAMP. Successive negative and positive mass independent fractionation (MIF) of odd Hg isotopes through the end-Triassic interval in this succession suggest dominantly thermogenic Hg release from intrusive heating of organic-rich sedimentary rocks, followed by mainly volcanogenic input of mantle-sourced Hg. This inferred pattern is also supported by correlations to available CAMP ages. Minimum calculated volumes of thermogenic and volcanogenic Hg needed to drive the observed shifts at the basin-scale are plausible based on likely CAMP Hg release volumes, and biotic turnover in the studied region was unlikely to have occurred before the onset of volcanogenic Hg release. [ABSTRACT FROM AUTHOR]

• Mass independent fractionation of Hg isotopes is observed in the Ediacaran-Cambrian sediments. • Variable Δ199Hg values reflect changing marine and terrestrial metal sources as a function of paleo-depositional setting. • Positive Δ199Hg values in the Early Cambrian V rich black shales suggest Hg of seawater origin. A broad spectrum of marine sediments, including metalliferous black shales, stratiform barite, phosphorite and sapropelite (combustible shale) was widely deposited during the Ediacaran-Cambrian transition on the Yangtze Platform. The source of metals in the metalliferous black shales and the trigger for ocean dynamics during this critical period remain controversial. We analyzed Hg isotopes in late Ediacaran to Early Cambrian carbonaceous sedimentary rocks from the basinal Sansui section, South China, and observed Hg concentrations of 102–103 ppb, which is high but within the global range of black shales. The late Ediacaran carbonaceous chert shows near-zero Δ199Hg values (−0.05–0.09‰), which can be interpreted as input of terrestrial Hg or volcanic Hg. However, the transgressive near-coastal setting supports the terrestrial origin. The Early Cambrian V rich black shales display positive Δ199Hg values (0.03–0.18‰), which are similar to those observed in polymetallic Ni-Mo-rich sulfidic black shales (0.10–0.22‰) and phosphorites (0.13–0.24‰) in the stratigraphically equivalent Maoshi and Zhijin sections, respectively. These positive Δ199Hg values suggest that Hg was of dominantly seawater origin in a restricted basin setting. The variable Δ199Hg values of the rock spectrum reflect the dynamic interplay of marine and terrestrial metal sources as a function of paleo-depositional setting within the transgressive–regressive system on the continental margin of the Ediacaran-Cambrian Yangtze platform. [ABSTRACT FROM AUTHOR]

Mercury (Hg) anomalies in sedimentary rocks have been increasingly used in paleoclimatology studies for tracing volcanic signals, as Hg emissions from volcanic activity can cause contemporaneous sedimentary Hg enrichment. However, non-volcanic sedimentary controls on Hg have clear potential to mask these signals. These factors include host phase variability linked to environmentally controlled sourcing and settling changes, and/or variable preservation conditions associated with weathering, oxidation and diagenesis. Such factors can limit the efficacy of Hg as a paleo-volcanism proxy. In this study, sedimentary effects on Hg concentration within a complex depositional system in southwest England (St. Audrie's Bay) across the end-Triassic have been analyzed, together with published data from coeval end-Triassic sections globally – an interval of time coeval with the Central Atlantic Magmatic Province (CAMP). Our statistical analysis of Hg and associated geochemical data highlights significant fluctuations in sedimentary Hg due to relative supply differences in Hg and host phases, as well as the changing types and preservation conditions of host phases. End-Triassic sections globally show a consistent undersupply of Hg relative to organic matter across the end-Triassic mass extinction (ETME). To better assess the magnitude and significance of possible Hg enrichments in sedimentary rocks, we present a statistical method for quantifying Hg anomalies to robustly distinguish Hg variations linked to host phase/depositional changes from paleo-volcanism. Our method supports the existence of transient but asynchronous Hg anomalies linked to volcanism from the CAMP across the end-Triassic in most global sections, albeit not in the St. Audrie's Bay section. • New statistical method for quantifying Hg enrichment is applied to global end-Triassic sections. • Subaerial exposure and oversupply of host phases alter Hg enrichment signals. • Limited Hg loading compared to organic matter host existed across the global ETME. • Globally distributed Hg enrichments occur in other end-Triassic sections. [ABSTRACT FROM AUTHOR]

Mercury (Hg) concentration and isotopic composition of organic-rich sedimentary rocks have been widely used as proxies to track ancient volcanism and associated environmental perturbations. However, interpretation of the Hg data is based on the assumption that the thermal maturity of the sedimentary rocks has limited effects on Hg abundance and isotopic composition, which is yet to be evaluated. Here we conduct closed-system anhydrous pyrolysis experiments to investigate the changes of Hg concentration and isotope composition during the thermal mature process, using both marine and lacustrine mudrocks. A siliceous shale section (Luocun, China) with heterogeneous thermal maturity caused by dike intrusion was also analyzed for Hg. Significant Hg loss (over 80%), with variations of δ202Hg (by 0.3 to 0.7‰) but small variations of Δ199Hg (by <0.1 to 0.36‰), were observed during the experiment. The Hg isotopic variation may be caused by the release of isotopically distinct Hg in different mineral phases at different temperatures. Samples from the Luocun section have anomalously low Hg and Hg/TOC values, due to thermal maturity. These findings suggest that (1) thermal maturation of organic-rich shales may be an important factor in distribution of Hg in sediments, and (2) the use of Hg, Hg/TOC and Hg isotopes proxies for paleoclimate and paleoceanography reconstruction should be applied in caution in substrates that may have experienced significant thermal alteration, especially if sill/dike intrusions were present that may cause large varieties of thermal maturity within sedimentary sections. [ABSTRACT FROM AUTHOR]

Metamorphic rocks show much lower mercury (Hg) levels than sedimentary rocks, which may be due to the loss of Hg during high-pressure and high-temperature conditions during metamorphism. To test this hypothesis, we conduct high-pressure and high-temperature experiments on ancient and modern sediments (WH black shale and GSS-4 soil). Under 0.3 GPa, the Hg concentrations decrease while the δ202Hg values increase with rising temperatures (WH black shale: 333–89 ppb, −1.34 to −0.79‰, 250–700 °C; GSS-4: 545–265 ppb, −1.39 to −1.01‰, 400–700 °C), suggesting the loss of isotopically light Hg isotopes under high-temperature conditions. Under constant temperatures of both 200 °C and 500 °C, with increasing pressure (0.5–1.4 GPa), GSS-4 shows only a slight decrease in Hg concentration with no variation in δ202Hg, suggesting that high-pressure conditions restrain the loss of isotopically lighter isotopes. Consistent Δ199Hg and Δ200Hg values were observed in both samples during our experiment, implying no Hg isotope mass-independent fractionation (Hg-MIF) under high-temperature and high-pressure conditions. While results of this imply that metamorphism may lead to the emission of isotopically lighter Hg from sedimentary rocks to the surface environment, the lack of Hg-MIF during metamorphism provides important support for the use of Hg isotopes for paleoenvironment reconstruction. [ABSTRACT FROM AUTHOR]

Weathering of silicate rocks, particularly granitic rocks, generates the pedosphere that is of crucial importance in functioning terrestrial ecosystems. The pedosphere hosts large amounts of mercury (Hg). The source of Hg in granite weathering products is currently poorly constrained, however. Here we conducted Hg isotopic analyses on two weathering profiles developed on granitic plutons in Central and South China. Soils from both profiles show a downward decrease in Hg concentration but consistently negative ∆199Hg values. Mercury in precipitation, granites, and vegetation display positive, near-zero, and negative ∆199Hg values, respectively. The negative ∆199Hg values in the two weathering profiles are consistent with estimates of vegetation-derived Hg, supporting that Hg in weathering profiles are dominantly sourced from vegetation. Hg in vegetation is transported into surface soil firmly bonded to organic matter and migrates downwards weathering profiles. This study provides insights into the biogeochemical cycle of Hg in the granite-weathering crust and helps to explain the negative ∆199Hg values observed in terrestrial-derived sedimentary rocks. [ABSTRACT FROM AUTHOR]

Mercury isotopes display both mass-dependent and mass-independent fractionation and allow the tracing of pathways and storage of surface-derived Hg in the lithosphere. While the subduction-related orogenic recycling of Hg from marine reservoirs into hydrothermal systems in continental arc settings has been documented recently, the source of Hg in intracontinental hydrothermal systems remains unclear. We measured Hg isotopes in two intracontinental anorogenic/postorogenic Late Mesozoic hydrothermal gold deposits in the South China craton and the Central Asian orogenic belt of northern China, respectively. The ore and sulfide samples from the studied systems have positive δ 202 Hg (0.70 ± 0.39‰, 1SD, n = 49) and negative Δ 199 Hg values (−0.12 ± 0.05‰, 1SD, n = 49). These values are different from their country rocks and regional geological environment (volcanic arc granites, marine sedimentary rocks) which have positive Δ 199 Hg values, but similar to that of their Precambrian supracrustal basement rocks of largely non-marine continental materials. We conclude that Hg in the intracontinental hydrothermal systems was leached from basement rocks by upper crustal basinal fluid circulation driven by regional heat flow, likely due to lithospheric thinning and upwelling of the asthenosphere in the Late Mesozoic. The intracontinental hydrothermal systems and their continental sources with positive δ 202 Hg and negative Δ 199 Hg values are complementary to volcanic-arc and marine sedimentary rocks with opposite δ 202 Hg - Δ 199 Hg compositions. The distinct Hg isotopic features of hydrothermal systems in different tectonic settings, in particular the indelible Δ 199 Hg signature, allow the tracing of large-scale material cycling in the Earth. • Hydrothermal systems in arc and intracontinental settings show opposite Δ 199 Hg. • Intracontinental systems have negative Δ 199 Hg reflecting a terrestrial Hg source. • Mercury isotope can be a tracer of Hg cycling in hydrothermal systems. [ABSTRACT FROM AUTHOR]

• Low Hg contents in metamorphic rocks support loss of Hg during metamorphism. • Similar Δ199Hg values between the equivalent un- and metamorphosed sedimentary rocks. • No significant Hg-MIF during the metamorphism. • Robust Hg-MIF signals for tracing the material cycling. Mercury isotopes undergo unique mass-independent fractionation (MIF) during photochemical processes on Earth's surface. Studies have observed pronounced Hg-MIF signals in sedimentary and magmatic rocks, suggesting recycling of Hg from Earth's surface systems into the lithosphere via sedimentation and magmatism. However, the isotopic signature of Hg in metamorphic rocks and the geochemical fate of Hg during metamorphism remain unclear. Precambrian basements are important components of cratons or orogenic belts on Earth. Here, we study the Hg concentration and isotopic composition of Precambrian metamorphic and sedimentary rocks from the eastern Central Asian Orogenic Belt, and North and South China cratons. Metamorphic rocks show much lower Hg contents (0.21–7.8 ppb) than sedimentary rocks (2.6–694 ppb), indicating a substantial loss of Hg during metamorphism. The lack of correlation between δ202Hg values (–2.41 to 0.18‰) and metamorphic grades indicates no systematic mass-dependent fractionation (MDF) of Hg isotopes during metamorphism. The Δ199Hg/Δ201Hg ratios of ∼ 1.0 for both metamorphic and sedimentary rocks indicate Hg was sourced from Earth's surface systems. The coupling of Hg-MIF signals between the metasedimentary rocks and the sedimentary settings of their protolith suggests no Hg-MIF during metamorphism. The negative Δ199Hg values (–0.30 to –0.02‰) in the Precambrian coastal sedimentary rocks imply the input of Hg into coastal regions via soil erosion. The positive Δ199Hg values (0.06 to 0.31‰) in the Precambrian marine sedimentary rocks suggest deposition of atmospheric Hg(II) to open oceans via wet deposition. The lack of significant Hg-MIF during metamorphism and other underground geological processes shows that Hg-MIF signals can work as a reliable tracer for indicating material cycling in Earth's interior. [ABSTRACT FROM AUTHOR]

Large igneous province (LIP) eruptions are increasingly considered to have driven mass extinction events throughout the Phanerozoic; however, uncertainties in radiometric age dating of LIP materials, along with difficulty in accurate age dating of sedimentary rocks that record the environmental and biological history of our planet, create inherent uncertainties in any linkage. As such, there is interest in using geochemical proxies to fingerprint periods of major volcanism in the sedimentary record (termed here LIP marks). The use of sedimentary mercury (Hg) contents has been suggested to be the best tool to accomplish this goal, and recent work is reviewed here. Studies to-date show that most extinction events, ocean anoxic events, and other environmental crises through the Phanerozoic have an associated sedimentary Hg anomaly. It remains unclear though if each Hg anomaly is truly a signature of massive volcanism, or if it is controlled by local or regional processes. As Hg has a strong affinity to organic matter (OM), normalisation with total organic carbon (TOC) has been used to assess anomalies. The measurement of TOC has been fraught with error throughout many studies, leaving some claimed Hg/TOC anomalies questionable. Normalisation by other elements that can affect Hg sequestration, such as Al and S, are less common but warrant further investigation. Stable isotope systematics of Hg have helped to further clarify the origin of Hg spikes, and clearly show that not all Hg anomalies are directly related to volcanism. Although a promising tool, the Hg proxy requires more refinement to accurately understand the nuances of an Hg anomaly in the rock record. [ABSTRACT FROM AUTHOR]