Guangzhou Institute of Geochemistry
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Unraveling the link between worldwide adakite-like rocks and porphyry Cu deposits
No full textAdakite-like rocks, as an important recorder of magmatic evolution in mantle and crust, are closely associated with major porphyry Cu deposits. However, the underlying mechanism connecting these associations remains insufficiently elucidated. This study compiles ca. 7000 whole-rock geochemical data from Phanerozoic adakitelike rock samples and from ore-forming porphyries in porphyry Cu deposits. Machine learning investigations are performed to characterize the geochemical variations of adakite-like rocks from various orogenic or cratonic systems and investigate any geochemical similarities with rocks associated with porphyry ore systems. Principal component analysis (PCA), along with t-distributed Stochastic Neighbor Embedding (t-SNE), highlights elemental distinctions between adakite-like rocks formed in mature and juvenile crust and the similarities of rocks from porphyry Cu-Mo deposits with the former and rocks from porphyry Cu-Au deposits with the latter. Extreme Gradient Boosting (XGBoost) and Support Vector Machine (SVM) analyses are applied to the original dataset and the PCA data derived from the dataset to discriminate adakite-like rocks from various geodynamic settings from each other and from rocks associated with porphyry ore deposits. Our models show that XGBoost and SVM can identify the tectonic regions of adakite-like rocks and rocks from porphyry copper systems with high efficiency and confidence e.g., accuracy = 0.88-0.94 and area under curve (AUC) = 0.69-0.86. The application of SHapley Additive exPlanations (SHAP) values is employed to elucidate the parameters that discriminate the different environments, providing insight into the underlying petrogenetic processes, including diverse levels of formation depth and extent of mantle interaction. Additionally, when examining ore-forming porphyries and adakite-like rocks, the incorporation of heatmaps into taxonomic classification (HTC) provides significant distinguishing factors with substantial geological implications. These findings suggest potential geological processes (e.g., remelting of Cu-sulfide-bearing cumulates or flotation of Cu-sulfide phases attached to vapor bubbles) that may enrich the source magma of ore-forming porphyries beyond the conventional geological processes responsible for adakite-like rock formation, which could serve as an exploration indicator
A comprehensive characterization biotransformation of chlorinated paraffin by human and carp liver microsomes via liquid chromatography-high-resolution mass spectrometry and screening algorithm
No full textThe chlorinated paraffin (CP) monomer 1,2,5,6,9,10-Hexachlorodecane (CP-4) was subjected to in vitro biotransformation using human and carp liver microsomes. Five types of CP-4 metabolites (OH-, keto-, enol-, aldehyde- and carboxy-CP-4) were identified in human liver microsomer while only mono-OH-CP-4 was found in the carp liver microsomes. Kinetic studies revealed that the formation of mono-, di-, tri-hydroxylated CP-4, keto-, enol-, and aldehyde-CP-4 in human liver microsomes was best described by substrate inhibition models, whereas the formation of carboxylated CP-4 metabolites best fit the Michaelis-Menten model. Notably, keto-CP-4, enolCP-4 and aldehyde-CP-4 were the predominant metabolites. The estimated Vmax values for these metabolites were significantly higher in the human liver microsomes than in the carp liver microsomes. The intrinsic hepatic clearance (CLint) of CP-4 was higher in humans than in carp, indicating species-specific differences in its metabolism. This study also highlighted potential toxicity concerns, with computational predictions showing varying degrees of acute oral toxicity for CP-4 and its metabolites. These findings indicate significant speciesspecific differences in the biotransformation of CP-4, emphasizing the potential health and environmental risks associated with chlorinated paraffins and their metabolites, and underscore the need for further research to address these concerns
The δ<SUP>13</SUP>C composition and genetic origin of a series straight long-chain alkyl naphthalene isomer pairs in the Upper Cretaceous lacustrine sediments of Songliao Basin, China
No full textA series of straight long-chain alkyl naphthalene isomer pairs (LANs) have been detected in the Upper Cretaceous lacustrine sediments of Nenjiang Formation (K2n1+2) in the Songliao Basin, and their distribution and carbon isotopic composition were investigated. The results indicate that the composition and distribution of LANs exhibit significant variations. The relative abundance of methyl- and dimethyl-naphthalenes shows a reciprocal correlation with that of LANs, increasing and declining in tandem. The delta 13C composition of LANs varies from -24.6 %o to -32.6 %o, with an average of -28.5 %o, which is notably higher than that of n-alkanes, ranging from -31.9 %o to -34.5 %o. The delta 13C composition of methylnaphthalenes (MNs) ranges from -26.9 %o to -27.1 %o, which is generally more positive than the average delta 13C composition of LANs. Analysis of the carbon isotopic composition of n-alkanes, methylnaphthalenes, and the series of LANs, along with their distribution patterns, suggests the presence of multiple formation mechanisms. Specifically, the observed declining variation pattern of delta 13C values for LANs along with the increasing carbon number of the alkyl chain may indicate a novel formation pathway. This pathway likely involves a direct reaction between 13C-enriched naphthalene and 13C-depleted straight long-alkyl chains during diagenesis. The relative abundance ratio of total methyl-substituted naphthalenes (Sigma MNs) to the total LANs (Sigma LANs), expressed as the Sigma MNs/Sigma LANs ratio, exhibits a profile variation that correlates with the profile changes of the Pr/Ph ratio, TOC content, and HI index. This correlation indicates that specific environmental conditions or source inputs, such as reduced sedimentary conditions or specific algal contributions, may be conducive to the formation of LANs
Coral-derived seasonal seawater 518O records from the Northern South China Sea: Hydroclimatic insights into the Medieval Climate Anomaly and Little Ice Age
No full textSeawater oxygen isotopes ( 5 18 O sw ) are critical for reconstructing past climate and hydrological conditions, yet high-resolution 5 18 O sw reconstructions during the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) remain scarce. Using paired monthly coral Sr/Ca-518O records from Hainan Island in the northern South China Sea (NSCS), we reconstructed wet and dry season 5 18 O sw for these periods. During the MCA, 5 18 O sw values were relatively positive, indicating drier conditions, while the LIA exhibited relatively negative 5 18 O sw values, reflecting wetter conditions. Compared to 1984-2014 CE, the frequency of seasonal extreme 5 18 O sw events increased by 25 %-74 %, likely driven by global warming caused by human activities. Long term trends reveal that dry season 5 18 O sw closely mirrored wet season values, emphasizing the key role of the wet season 5 18 O sw baseline in shaping seasonal hydrological conditions. When examined in the broader late Holocene context, East Asia exhibited a persistent meridional dry-wet contrast, with cold periods characterized by wet oceanic and dry inland conditions, and warm periods showing the opposite. These contrasting patterns were primarily driven by the combined influence of the East Asian Summer Monsoon and El Nino, with additional influences from the meridional shifts of the Intertropical Convergence Zone and zonal movements of the Pacific Walker Circulation. These findings underscore the dynamic interplay of regional climate drivers in shaping hydrological variability and highlight the NSCS's critical role in East Asia's climate. They provide valuable baselines for understanding natural climate variability and predicting future climate changes in this densely populated and economically significant region
Terrestrial ecosystem response to Early Cretaceous global environmental change: A calibrated, high-resolution Aptian record from Northeast China
No full textExtensive studies of Aptian oceanic anoxic events and carbon cycle perturbations have significantly advanced our understanding of marine responses to global climate change. However, further exploration of possible volcanism-climate-environment linkages is hindered by the scarcity of continuous, well-documented terrestrial records. In an attempt to address this gap, the Yanshan Scientific Drilling Project extracted a 1497.5 m core from the shale-dominated, lacustrine, Jiufotang Formation in the Kazuo Basin of Northeast China. High-precision U-Pb geochronology of two interlayered tuffs yielded depositional ages of 121.05 +/- 0.32 Ma and 117.359 +/- 0.031 Ma, and a Bayesian age-depth model for the lower half of the formation. An astrochronological model based on delta 13Corg and major element chemostratigraphy has suggested a duration of 9.03-9.14 Ma for the entire core, from 121.05 to 121.30 to 111.91-112.20 Ma. A 75.2 m core interval with unequivocal correlation to the oceanic anoxic event (OAE) 1a was identified by carbon isotope stratigraphy, which has a calibrated onset at 120.2 Ma and a total duration of ca. 450 kyr. Our results highlight the potential of lacustrine strata in recording at highresolution the marine-correlated carbon cycle changes and in deciphering the drivers and mechanisms of climate change across the marine and terrestrial realms
Nontarget screen and identify sulfate and sulfonate surfactants in personal care products using UHPLC-Q-Orbitrap-HRMS based on fragmentation characteristics and sulfur isotopologue pattern
No full textSulfate and sulfonate compounds are extensively used as anionic surfactants in personal care products (PCPs), which might pose adverse potential to human health. However, available research mostly identified certain subsets of sulfated and sulfonated surfactants based on target analysis. In this study, we developed a comprehensive nontarget strategy for identification of sulfated and sulfonated surfactants in PCPs using UHPLC-HRMS supplemented by an in-lab R script based on characteristic fragment ions and sulfur isotope patterns. A total of 20 sulfate and 12 sulfonate surfactants of confidence level 3 and above were identified in the range of alkyl chain length from C12 to C26 with 0-7 ethoxy groups and molecular weights of 200-600 Da in the PCP samples. The sulfates included 4 alkyl sulfates and 16 alkyl ether sulfates. In addition to commonly reported 4 alkyl benzene sulfonates, this study identified eight sulfonate surfactants for the first time, which were 3 alkyl sulfonates, 3 methyl ammonium sulfonates, and 2 bis-sulfonate sulfonates in the PCPs. Interestingly, 22 sulfate and sulfonate compounds were identified in the negatively labeled PCP samples which were not supposed to contain sulfate and sulfonate surfactants. The results demonstrated robustness of the developed nontarget analyzing strategy in identifying and characterizing sulfate and sulfonate surfactants and consequently providing guidance for management and regulation of chemical addition in PCPs to ensure safe use
Heavy metal dynamics in riverine mangrove systems: A case study on content, migration, and enrichment in surface sediments, pore water, and plants in Zhanjiang, China
No full textMangroves serve a crucial role as metal accumulators in tropical and subtropical marine ecosystems, particularly in riverine mangroves, which frequently interact with terrestrial sources. In this study, we focused on the Gaoqiao and Jiuzhou Rivers within the Zhanjiang mangrove forest in Guangdong, China, and collected leaves and surface sediments from the dominant mangrove plant, Aegiceras corniculatum, near the riverbanks. We focused on seven heavy metals (Cr, Cu, Zn, As, Cd, Pb, and Hg) in mangrove leaves, surface sediments, and pore water due to their environmental significance and frequent occurrence in mangrove ecosystems. We employed multivariate statistical methods and pollution indicators to assess the potential sources and risk levels of heavy metals in these sediments. Our results reveal that the concentrations of the seven heavy metals in the sediments of the Gaoqiao and Jiuzhou Rivers varied significantly, ranging from 0.03 mg/kg to 100.00 mg/kg. Cd posed the highest ecological risk, followed by Hg and As. The comprehensive potential ecological risk in the Gaoqiao River was lower than that in the Jiuzhou River, likely due to the distribution of industrial enterprises (such as printing and cement plants) in the upper reaches of the Jiuzhou River. Additionally, the heavy metal content in the leaves of A. corniculatum and in pore water within surface sediments ranged from 0.01 to 51.58 mg/kg and 0.001 to 133.70 mu g/L, respectively. A significant correlation was observed between the heavy metal concentrations in the A. corniculatum leaves and those in the pore water. Notably, the leaves of A. corniculatum exhibited a remarkable Hg-enrichment capability, highlighting its potential as a mercury accumulator. Most heavy metals in A. corniculatum leaves, pore water, and sediment were concentrated in the middle and upper reaches of the river, primarily due to anthropogenic terrestrial inputs from residential production activities upstream. Consequently, heavy metal pollution in riverine mangroves is primarily associated with human activities such as aquaculture, agricultural planting, and industrial production
Molecular Composition Evolution of Dissolved Organic Matter With Water Depth in Prydz Bay of East Antarctic: Carbon Export Implications
No full textThis study analyzes the molecular composition of dissolved organic matter (DOM) in Prydz Bay by Fourier Transform Ion Cyclotron Resonance mass spectrometry to probe the carbon sequestration capacity in the continental shelf system. Concentrations of particulate organic carbon (POC), particulate nitrogen and dissolved organic carbon (DOC) with water depth show that POC could be mainly decomposed into DOC and/or microbially degraded. Highly labile DOC is further degraded and remineralized by microorganisms within the upper 200 m, as evidenced by a downward enrichment of 13CPOC and increases in the average molecular weight, oxygen atom number (O) and double bond equivalents of DOM molecules, indicating that biodegradation is the main driver for particulate organic matter and DOM evolution with water depth. Semi-quantitative calculation demonstrates that similar to 83% of POC was transformed to DOC as well as dissolved inorganic carbon (DIC), and similar to 30% of DOC further to DIC via microbial degradation within the upper 200 m in summer, resulting in a relatively low total organic carbon content in sediments of Prydz Bay. The newly transformed DIC and residue DOC can be preserved in the deep layer due to the formation of well stratified and stable water body in summer of Prydz Bay, ultimately entering the regional circulation system instead of being released back into the atmosphere. This could be one of the most important processes determining the atmosphere CO2 uptake in the continental shelf system of Southern Ocean.
The continental shelf system in the Southern Ocean, especially with the development of polynyas, plays a critical role in the global carbon cycle and disproportionally accounts for almost half of the anthropogenic CO2 uptake by the biological pump, with ensuing deep-sea sequestration by the form of particulate and dissolved organic carbon, and even CO2 due to microbial degradation of primary productivity. However, complex interactions between physical, chemical and biological processes significantly affect the fate of organic carbon through the water column, resulting in an uncertainty of vertical carbon export. In this study, we conduct an investigation on the dissolved organic matter sources and evolution with water depth in summer of Prydz Bay, a typical polynya-developed continental shelf system in the East Antarctica. The results clearly show that biodegradation is the main factor controlling organic carbon mineralization and mainly occurs within the upper 200 m of water column, with a transformation into dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC). Integrated with regional circulation system and hydrological characteristics, our study further indicates that newly formed DIC and DOC can be preserved in the deep layer of Prydz Bay, then into the regional circulation system rather back to the atmosphere.
Novel evidence at molecular level shows the vital role of biodegradation during carbon sink in Prydz Bay The conversion of POC into DOC/DIC mainly occurs within the upper 200 m of water column Highlighting regional circulation's contribution to carbon transport and sequestration in the Southern Ocea
The influence of asphaltene matrix on the thermal evolution of polycyclic aromatic hydrocarbons: Experimental evidence and geochemical implications
No full textThe thermal evolution of components trapped in matrix of asphaltenes is supposed to be retarded, as compared to the free ones. Studying the geochemical evolution of trapped polycyclic aromatic hydrocarbons (PAHs) may provide insight for the characterization of high-maturity organic matter. The discrepancies in the thermal evolution between free and trapped (asphaltene-adsorbed/occluded) PAHs (phenanthrene, chrysene, pyrene, and their methylated isomers) were studied by thermal maturation (gold tubes, 300 similar to 400 degrees C) experiments on a low-maturity solid bitumen from the Sichuan Basin, southwestern China. The results show that the thermal evolution of asphaltene-adsorbed PAHs is retarded compared to that of free ones. This is attributed to slight differences in reaction kinetics due to steric hindrance by the asphaltene structure. The asphaltene matrix appears to act as a reaction inhibitor leading to a retardation of the thermal evolution of the methylphenanthrene index (MPI) in asphaltene-adsorbed hydrocarbons. This could provide a possibility for maturity assessment of high-maturity organic matter. The thermal evolution of asphaltene-occluded PAHs in the experiments resulted in thermodynamically controlled isomer distributions of occluded methylphenanthrenes and methylchrysenes. However, the occluded methylpyrene isomers were hardly affected by thermal stress. They probably retained their original distributions and may serve as source indicators
Diverse Late Triassic arc magmatism and porphyry Cu deposits in the southeastern Tibetan Plateau: Related to slab tear along a subducting passive margin?
No full textThe subduction of the ocean-continent transition (OCT) zone on a passive margin has received limited attention, despite its significant impact on tectono-magmatic processes. This study focuses on the Late Triassic basalts and andesites in the southeastern Tibetan Plateau, where the Yushu-Yidun Arc belt intersects the Longmen Shan Fault system. The goal is to understand the interplay between these linear systems. The basalts exhibit trace element and isotopic signatures resembling those of within-plate enriched mid-ocean ridge basalts or ocean island basalts (EOBs), such as positive Nb-Ta anomalies, high Nb/Th (7.72 to 10.3) and epsilon Nd(t) (+2.23 to +6.34) values, and low La/Sm values (2.69 to 4.05), suggesting an asthenospheric mantle source. The contemporaneous andesites display typical arc-like geochemical characteristics (e.g., enrichment in Ba, Th, and U but depletion in Nb, Ta, and Ti), with negative epsilon Nd(t) values (-2.41 to -1.08), indicating a mantle wedge source affected by subducted components. Geological evidence indicates that the Longmen Shan Fault zone, previously defined by its magmatic rocks, was an active OCT belt during the Late Triassic, separating the South China Continent from the Garze-Litang Ocean. Consequently, we propose a model suggesting the tearing of a subducted oceanic slab from the continental lithosphere within the OCT belt under the southernmost segment of the Yushu-Yidun Arc belt, driven by strong slab pull in the Garze-Litang Ocean subduction zone. This model effectively explains the intriguing geology of the Songpan-Garze-Hoh Xil Terrane, in which Late Triassic EOBs and normal arc-related igneous rocks coexist and are accompanied by abundant slab-derived mineralized porphyries. Our findings have global implications for investigating geochemically diverse magmatism and associated mineralization on passive continental margins