Guangzhou Institute of Geochemistry
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Five series of benzohopanes in early Cretaceous sediments from the Chaoyang Basin, NE China
No full textFive series of benzohopanes were identified in a set of immature to early-oil-window early Cretaceous sediments from the ZK1006 well, Chaoyang Basin, NE China. Series a (C31 31-C35), 35 ), b (C33 33-C35), 35 ), and c (C31 31-C35) 35 ) benzohopanes form by different pathways, while the newly-found series d (C31 31-C34, 34 , maybe to C35?) 35 ?) and e (C31 31-C32, 32 , maybe to C35?) 35 ?) benzohopanes have similar formation mechanisms. Series a is usually the predominant benzohopane series, but occasionally samples are dominated by series c benzohopanes. Series b benzohopanes may be associated with terrigenous organic matter. Series a and b benzohopanes are possibly influenced by redox properties, while paleosalinity more likely controls the formation and enrichment of series c benzohopanes. Two novel parameters (a benzohopane index, and the C 35 /C 34 benzohopane ratio) are proposed to be useful paleoenvironmental proxies in the study area. A high benzohopane index and C 35 /C 34 benzohopane ratio may indicate an anoxic environment
Impacts of seasonality, drought, nitrogen fertilization, and litter on soil fluxes of biogenic volatile organic compounds in a Mediterranean forest
No full textBiogenic volatile organic compounds (BVOCs) play critical roles in ecosystems at various scales, influencing above-and below-ground interactions and contributing to the atmospheric environment. Nonetheless, there is a lack of research on soil BVOC fluxes and their response to environmental changes. This study aimed to inves-tigate the impact of drought, nitrogen (N) fertilization, and litter manipulation on soil BVOC fluxes in a Medi-terranean forest. We assessed the effects of drought and N fertilization on soil BVOC exchanges and soil CO2 fluxes over two consecutive years using a dynamic chamber method, and solid-phase microextraction was uti-lized to quantify soil BVOCs in one year. Our findings revealed that the soil acted as an annual net sink for isoprenoids (1.30-10.33 mu g m- 2 h-1), with the highest uptake rates observed during summers (25.90 +/- 9.36 mu g m- 2 h-1). The increased summer uptake can be attributed to the significant concentration gradient of BVOCs between atmosphere and soil. However, strong seasonal dynamics were observed, as the soil acted as a source of BVOCs in spring and autumn. The uptake rate of isoprenoids exhibited a significant positive correlation with soil temperature and atmospheric isoprenoid concentrations, while displaying a negative correlation with soil moisture and soil CO2 flux. The effects of drought and N fertilization on soil BVOCs were influenced by the type of VOCs, litter layer, and season. Specifically, drought significantly affected the exchange rate and quantities of sesquiterpenes. N fertilization led to increased emissions of specific BVOCs (alpha-pinene and camphene) due to the stimulation of litter emissions. These findings underscore the importance of the soil as a sink for atmospheric BVOCs in this dry Mediterranean ecosystem. Future drought conditions may significantly impact soil water content, resulting in drier soils throughout the year, which will profoundly affect the exchange of soil BVOCs between the soil and atmosphere
Clay minerals inhibit the release of Cd(II) during the phase transformation of Cd(II)-ferrihydrite coprecipitates
No full textClay minerals and iron (hydr)oxides are important geosorbents in controlling the migration of heavy metal cations in the environment. Despite the widespread occurrence of clay minerals/iron (hydr)oxides composites, their complex mutual effects on the fate of heavy metal cations are not well recognized. In this work, we investigated the effect of clay minerals on the redistribution of Cd(II) during the phase transformation of ferrihydrite containing coprecipitated Cd(II) (Cd-Fh). Three systems were considered: i.e., Cd-Fh, Cd-Fh/kaolinite composite, and Cd-Fh/montmorillonite composite. Our results showed that the transformation of Fh into goethite and hematite caused the release of Cd(II), while the presence of kaolinite and montmorillonite inhibited the phase transformation of Fh and the release of Cd(II), with montmorillonite being more effective in these process. Multiple factors contributed to the reduced release of Cd(II), including the retarded transformation of Fh, the buffering of solution pH, and the re-adsorption of the released Cd(II). Our findings show that clay minerals have multiple effects in reducing the release of heavy metal cations from Fh during its transformatio
Application of geological and short wavelength infrared (SWIR) spectroscopy mapping in the Mailong gold deposit, East Kunlun: Implications for exploration targeting
No full textWidespread regolith cover makes it difficult to identify the anomalous size of their mineralogical or geochemical footprint at the surface in gold exploration. Short wavelength infrared (SWIR) spectroscopy with effective identification of clays and other hydrous minerals shows potential application in gold exploration. The detailed geological and short wavelength infrared (SWIR) spectroscopy mapping was conducted in the newly-discovered orogenic-type Mailong gold deposit (13.06 t @ 6.29 g/t Au), East Kunlun, to determine alteration stage and mineral assemblages and discuss the potential values of SWIR spectral in gold exploration. In the Mailong area, magmatic rocks consist of granodiorite, biotite granodiorite, plagiogranite and mafic dikes, and the gold mineralization shows a close spatial and temporal relationship with mafic dikes. The earliest chloritization (chlorite-quartz) is widely distributed in granodiorite, biotite granodiorite and plagiogranite. The following potassic alteration (hydrothermal K-feldspar and quartz) is developed along high-angle fault/fracture, which cut through granodiorite, biotite granodiorite and plagiogranite. The subsequent sulfide alteration (chlorite-muscovite-sulfide-carbonate) overprints the former potassic and chloritization alteration, and shows spatial association with mafic dikes. Native gold occurs in fracture arsenopyrite or associated with minerals such as pyrite, and chalcopyrite during the early sulfide stage. Supergene alteration is characterized by limonite and malachite. At Mailong, the SWIR data indicate that the most abundant alteration minerals (chlorite, white micas and ankerite) mainly occurred in the northern area. White mica Al-OH absorption occurs at longer wavelengths (Pos2200 = 2202.5 similar to 2203 nm) and higher Illite crystallinity (IC = 1.2 similar to 3.1) probably reflecting a higher temperature and pH conduit at the bottom of ZK0001 and ZK0801. The sharp shift of IC values near the bottom reflects the control of fault. This area is also situated at the V-shaped intersections of the three granitic intrusions and structural transection, indicating more of a possible hydrothermal fluid channel than a mineralization center. Low-grade Au mineralization (Au = 0.1 similar to 0.5 g/t) is mainly distributed within hydrothermal channels with higher Pos2200 (mainly 2022.5 similar to 2203 nm) and IC values (mainly 1.2 similar to 3.1), while high-grade Au endowment associated with mafic dikes has low Pos2200 (mainly 2201 similar to 2202.5 nm) and IC values (mainly 0.43 similar to 1.2). Meanwhile, an equation of distance = -15*IC + 31 (R-2 = 0.47) can be summarized for low-grade orebodies vectoring. Integrating geological mapping and spectral data, target areas for high-grade ore bodies can be outlined using the criteria of white mica, shorter wavelength of Al-OH absorption position (Pos2200 = 2201 similar to 2202.5 nm), lower IC values (IC = 0.43 similar to 1.2), and chlorite Fe-OH absorption position Pos2250 (>2247 nm) along with occurrences of mafic dikes. This study demonstrates that utilizing the detailed SWIR identification in conjunction with accurate geological mapping has great potential for greenfield exploration of orogenic gold deposits
First Report on the Trophic Transfer and Priority List of Liquid Crystal Monomers in the Pearl River Estuary
No full textLiquid crystal monomers (LCMs) are emerging organic pollutants due to their potential persistence, toxicity, and bioaccumulation. This study first characterized the levels and compositions of 19 LCMs in organisms in the Pearl River Estuary (PRE), estimated their bioaccumulation and trophic transfer potential, and identified priority contaminants. LCMs were generally accumulated in organisms from sediment, and the LCM concentrations in all organisms ranged from 32.35 to 1367 ng/g lipid weight. The main LCMs in organisms were biphenyls and analogues (BAs) (76.6%), followed by cyanobiphenyls and analogues (CBAs) (15.1%), and the least were fluorinated biphenyls and analogues (FBAs) (11.2%). The most abundant LCM monomers of BAs, FBAs, and CBAs in LCMs in organisms were 1-(4-propylcyclohexyl)-4-vinylcyclohexane (15.1%), 1-ethoxy-2,3-difluoro-4-(4-(4-propylcyclohexyl) cyclohexyl) benzene (EDPBB, 10.1%), and 4 '-propoxy-4-biphenylcarbonitrile (5.1%), respectively. The niche studies indicated that the PRE food web was composed of terrestrial-based diet and marine food chains. Most LCMs exhibited biodilution in the terrestrial-based diet and marine food chains, except for EDPBB and 4,4 '-bis(4-propylcyclohexyl) biphenyl (BPCHB). The hydrophobicity, position of fluorine substitution of LCMs, and biological habits may be important factors affecting the bioaccumulation and trophic transfer of LCMs. BPCHB, 1-(prop-1-enyl)-4-(4-propylcyclohexyl) cyclohexane, and EDPBB were characterized as priority contaminants. This study first reports the trophic transfer processes and mechanisms of LCMs and the biomonitoring in PRE
A negligible role for forearc serpentinites and melange diapirism in contributing halogens to Mariana arc magmas
No full textTrace element enrichment in arc lavas has traditionally been linked to the presence of slab-derived materials introduced by a combination of aqueous slab-fluids derived from altered oceanic crust (AOC) and subducted lithosphere and sediment-melts. However, an alternative is that slab material could be mobilised in m & eacute;lange diapirs formed from forearc serpentinites admixed with sediments and AOC in a subduction channel. In order to further constrain the relative importance of slab-fluids, sediment-melts and m & eacute;lange diapirs in the Marianas and track how the contributions of these components evolves across the arc, we selected submarine volcanic glasses from pillow rinds recovered from the Southeast Mariana Forearc Rift, and the Mariana arc and backarc basin. The glasses are all enriched in halogens and other fluid mobile elements relative to immobile elements of similar compatibility, demonstrating a strong subduction signature. Irrespective of their position in the arc, the lavas all have Br/Cl weight ratios of 0.0016-0.0037 and I/Cl of 8.3 x 10(-6)-127 x 10(-6), which encompasses a similar range as reported for arc and backarc glasses from the SW Pacific. The Br/Cl and I/Cl of the subduction component overlaps with altered ocean crust suggesting dehydration of altered ocean crust (+/- lithospheric serpentinites) as the dominant source of halogens and related slab-fluids. The Br/Cl and I/Cl of the Marianas glasses are much lower than forearc serpentinites from the Marianas, which does not favour a role for either dehydration of forearc serpentinites entrained with the subducting slab or direct melting of m & eacute;lange diapirs formed from serpentinised forearc material. The halogen data are most easily reconciled with the conventional model for arc magma generation, in which halogen-bearing aqueous fluids are progressively released from a dehydrating subducting slab. The importance of sediment-melts and/or forearc serpentinites in significantly contributing to the subduction zone budgets of other elements is not precluded, but the high halogen content of forearc serpentinites means that direct melting of m & eacute;lange diapirs is unlikely
Translithospheric magma plumbing system fossilized in the Emeishan large igneous province
No full textLighting up the magma plumbing system beneath a large igneous province (LIP) is challenging because the complex magma migration paths are often covered by flood basalts and sediments. Here, we present a three-dimensional seismic image of the Permian Emeishan LIP in Southwest China, constructed by joint inversion of Rayleigh wave dispersions and receiver functions. The results outline a cylindrical, high-velocity anomaly extending to similar to 135 km depth below the inner zone of this continental LIP. The geometry and magnitude of the high-velocity anomaly suggest that it represents culminated crystallized materials of primary magmas, thereby mirroring a magma plumbing system fossilized in the lithosphere. Furthermore, our geodynamic models illustrate that the nearly vertical plumbing system was controlled by slow plate motion during the magma emplacement. The plume head beneath a nearly static plate has higher thermal buoyancy and thus promotes more intensive magma emplacement. This phenomenon may apply to other LIPs throughout Earth's histor
Opposite Effects of Planting on Antibiotic Resistomes in Rhizosphere Soil with Different Sulfamethoxazole Levels
No full textAchieving consensus about the rhizosphere effect on soil antibiotic resistomes is challenging due to the variability in antibiotic concentrations, sources, and the elusory underlying mechanisms. Here, we characterized the antibiotic resistomes in both the rhizosphere and bulk soils of soybean plants grown in environments with varying levels of antibiotic contamination, using sulfamethoxazole (SMX) as a model compound. We also investigated the factors influencing resistome profiles. Soybean cultivation altered the structure of antibiotic-resistant genes (ARGs) and increased their absolute abundance. However, the rhizosphere effect on the relative abundance of ARGs was dependent on SMX concentrations. At low SMX levels, the rhizosphere effect was characterized by the inhibition of antibiotic-resistant bacteria (ARBs) and the promotion of sensitive bacteria. In contrast, at high SMX levels, the rhizosphere promoted the growth of ARBs and facilitated horizontal gene transfer of ARGs. This novel mechanism provides new insights into accurately assessing the rhizosphere effect on soil antibiotic resistomes
A Chromatographic Approach for High-Precision Eu Isotope Analysis
No full textEu isotopes are promising tracers across various scientific domains such as planetary, earth, and marine science, yet their high-precision analysis has been challenging due to the similar geochemical properties of rare earth elements (REEs). In this study, a novel two-column chromatographic approach was developed utilizing AG50W-X12 and TODGA resins to separate Eu effectively from matrix and interfering elements like Ba, Nd, Sm, and Gd, while ensuring high Eu yields (99.4 +/- 0.4%, n = 19) and low blanks (<20 pg). The robustness of this method is evidenced by various rock types and different Eu loading masses. The efficient purification of Eu facilitated the establishment of a high-precision calibration technique with standard-sample bracketing (SSB) and internal normalization (Nd). When a Nu Plasma 1700 multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS) instrument was employed, repeated purification and analysis of various Geological Reference Materials (GRMs) confirmed that the long-term external precision of delta Eu-153/151 is better than 0.04 parts per thousand (2 standard deviation (2SD)), which represents a 2-5-fold increase in precision compared to previously reported methods. Additionally, the high-precision Eu isotopic compositions of five GRMs, including basalts, andesite, syenite, and marine sediment, were measured. The high-precision Eu isotope techniques presented herein open up new avenues for Eu isotope geochemistry
Ages and geochemistry of garnet reveal multi-types of iron-copper mineralization in the Eastern Tianshan, NW China
No full textThe Aqishan-Yamansu Fe-Cu-Au metallogenic belt in the Eastern Tianshan, NW China, hosts numerous Fe and FeCu deposits that may have different genetic models, such as volcanic-hosted and skarn/IOCG types. These variations in genetic models are attributed to whether the mineralization is associated with hydrothermal activity related to volcanic or intrusive rocks. This study primarily focuses on garnets formed during the early skarn alteration in the Shuanglong Fe-Cu and Shaquanzi Fe deposits within this belt. Garnets from the Shuanglong deposit can be divided into two types and exhibit general homogeneity, with SL-Grt1 being Fe-rich and subsequently replaced by the Fe-poor SL-Grt2. Garnets from the Shaquanzi deposit display complex zonation patterns, SQZ-Grt1 show core-oscillatory zoned rim and SQZ-Grt2 show core-mantle-oscillatory zoned rim. Laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) dating of SL-Grt1 and SL-Grt2 produced lower intercept 206Pb/238U ages ranging from 318.0 f 6.4 Ma to 303.7 f 16.4 Ma, coinciding with the multi-stage granite occurrence. In contrast, SQZ-Grt1 and SQZ-Grt2 yielded ages between 328.0 f 2.6 Ma and 320.4 f 1.7 Ma, corresponding to the timing of the hosted rhyolite. SL-Grt1 show light rare earth element (LREE) enrichment, and low concentrations of high field strength elements (HFSE), such as V and Zr, and appears to have formed rapidly within an open system. Conversely, SL-Grt2 is characterized by heavy rare earth element (HREE) enrichment and elevated HFSE contents, which could be formed slowly in a closed system. The variable composition in the SQZ-Grt1 and SQZ-Grt2 record cyclical changes in fluid kinetics (vigorous fluid flow vs. fluid stagnation). The cyclical zones in SQZ-Grt2 with HREE and HFSE concentrations below the detection limit indicate multiple inputs of external seawater. The distinct characteristics between Shuanglong and Shaquanzi garnets may reflect the difference between the single magma intrusion and complex volcanic activity. Combining previously published chronological data, this study elucidates a transition from the Middle Carboniferous volcanic-hosted Fe deposits (335-320 Ma) to the Late Carboniferous intrusion-related skarn or IOCG type Fe-Cu deposits (310-300 Ma) in the Aqishan-Yamansu belt