Guangzhou Institute of Geochemistry
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Marine sulfate sulfur isotopic evidence for enhanced terrestrial weathering and expansion of oceanic anoxia during the Devonian-Carboniferous transition
No full textThe Hangenberg mass extinction during the Devonian-Carboniferous (D-C) transition represents one of the largest biodiversity losses of the Phanerozoic, while the underlying cause remains controversial. An improved understanding of the contemporaneous sulfur cycle can provide insights into the latest Devonian environmental changes that potentially affected marine biotas. Here, we report on a high-resolution chemostratigraphic study of the sulfur isotopic composition of carbonate-associated sulfate (CAS) through the D-C transition in the Long'an and Qilinzhai sections of South China. The delta S-34(CAS) profiles exhibit a long-term (i.e., >10(5) yr) negative excursion from +19.0 parts per thousand in the upper Lower Si. praesulcata Zone to +13.0 parts per thousand in the middle Upper Si. praesulcata Zone, and terminated with a recovery to 20.3 parts per thousand in the lower Si. sulcata - Si. duplicata zones, representing a depositional interval of similar to 0.9 Myr. In addition, this long-term negative excursion is punctuated by episodic sharp negative shifts. The negative delta S-34(CAS) excursion coincided with the end-Devonian biotic crisis, a positive shift in carbonate delta C-13, and negative shifts in bulk-sediment delta N-15 values and I/Ca ratios. Increasing organic carbon burial indicated by the positive shift in delta C-13 precludes decreased pyrite burial as an explanation for the negative shift of delta S-34(CAS), supported by intensified marine anoxia revealed by the negative shifts in delta N-15 and I/Ca. We attribute the long-term negative shift in delta S-34(CAS) to enhanced inputs of S-34-depleted riverine sulfate in conjunction with low seawater sulfate concentrations within the semi-restricted Yangtze Sea, whereas the transient negative spikes in delta S-34(CAS) were possibly caused by episodic upwelling and oxidation of H2S in expanded oceanic oxygen-minimum zones. In conjunction with the positive shift in delta C-13, the negative shift in delta S-34(CAS) supports a significant role for enhanced subaerial weathering in intensifying marine anoxia and triggering the biotic crises that occurred during the latest Devonian, the most likely driver of which was the spread of vascular (especially seed-bearing) land plants
Discovery of 1.79Ga dacite porphyry in the Taiyueshan Mts: Constraints on the genesis of the southern rift system in the North China Craton
No full textThe volcanic rocks of the Xiong'er Group mainly distribute in the southern North China Craton (NCC), and the main eruption peak time is ca. 1.75 similar to 1.80Ga. As a distinctive large-scale magmatic activity of the Earth's middle age in the NCC, its formation time, temporal and spatial distribution and geodynamic background is still controversial, that hinders further research of tectonic evolution of the NCC during the Early Mesoproterozoic. In this study, Mesoproterozoic dacite porphyry is distinguished in the Taiyueshan Mts in central NCC. It intrudes into the surrounding Paleoproterozoic gneissic granitoids with weak metamorphism and deformation. The SHRIMP and LA-ICP-MS zircon U-Pb age of the dacite porphyry is ca. 1.79Ga, which is consistent with the formation time of the Xiong'er volcanic rocks. 90% zircon grains show two age peaks of similar to 1.92Ga and similar to 2.16Ga, which are speculated to be captured from surrounding rocks. The dacites belong to shoshonite series with SiO2 content from 65.12% to 66.11%, alkali content (K2O+Na2O) from 6.85% to 7.28%, A/CNK ratios of 0.91 similar to 1.05, and Na2O/K2O ratios of 0.48 similar to 0.54. They have a high content of REE with depletion in HFSE such as Nb, Ta, Zr and Hf, and enrichment in LILE such as Rb, Ba, and La, which is completely consistent with the geochemical characteristics of Xiong'er dacite-rhyolite porphyry in the southern part of NCC. Currently, more scholars believe that the Xiong'er Group was formed in a trigeminal rift system, indicating the background of within-plate extension. This dacite porphyry connects the Xiong'er Group volcanic rock series in the Zhongtiaoshan area with the Hangaoshan Group and Xiaoliangling volcanic rock series in the Luliang area. They complete the northern branch of the Xiong'er trigeminal rift system, recording the initial Mesoproterozoic rifting in the central part of the NCC
Informal E-waste recycling in nine cities of Pakistan reveals significant impacts on local air and soil quality and associated health risks
No full textThe global increase in electronic waste (e-waste) has led to a rise in informal recycling, emitting hazardous heavy metals (HMs) that threaten human health and ecosystems. This study presents the first comprehensive assessment of HM levels in dry deposition and soils at proximity of forty (40) informal e-waste recycling sites across Pakistan, between September 2020 to December 2021. Findings reveal that Zn (1410), Pb (410) and Mn (231) exhibited the higher mean deposition fluxes (mu g/m2.day), derived from air samples, particularly in Karachi. Similarly, soils showed higher mean concentrations (mu g/g dw) of Mn (477), Cu (514) and Pb (172) in Faisalabad, Lahore, and Karachi, respectively. HMs concentrations were found higher in winter or autumn and lower in summer. In addition, HM levels were significantly (p = 0.05) higher at recycling sites compared to background sites year-round, highlighting the e-waste recycling operations as the major source of their emissions. The Igeo index indicated moderate to extremely contaminated levels of Cu, Pb, Cd, and Ni in Karachi, Lahore and Gujranwala. Ingestion was found as a leading human exposure route, followed by dermal and inhalation exposure, with Pb posing the greatest health risk. The Cumulative Incremental Lifetime Cancer Risk (ILCR) model suggested moderate to low cancer risks for workers. Strategic interventions recommend mitigating health and environmental risks, prioritizing human health and ecosystem integrity in Pakistan's e-waste management
Microbial Sulfur and Arsenic Oxidation Facilitate the Establishment of Biocrusts during Reclamation of Degraded Mine Tailings
No full textDegraded tailings generated by the mining of metal ores are major environmental threats to the surrounding ecosystems. Tailing reclamation, however, is often impeded due to adverse environmental conditions, with depleted key nutrients (i.e., nitrogen (N) and phosphorus (P)) and elevated sulfur and metal(loid) concentrations. Formation of biocrusts may significantly accelerate nutrient accumulation and is therefore an essential stage for tailing reclamation. Although suggested to play an important role, the microbial community composition and key metabolisms in biocrusts remain largely unknown and are therefore investigated in the current study. The results suggested that sulfur and arsenic oxidation are potential energy sources utilized by members of predominant biocrust bacterial families, including Beijerinckiaceae, Burkholderiaceae, Hyphomicrobiaceae, and Rhizobiaceae. Accordingly, the S and As oxidation potentials are elevated in biocrusts compared to those in their adjacent tailings. Biocrust growth, as proxied by chlorophyll concentrations, is enhanced in treatments supplemented with S and As. The elevated biocrust growth might benefit from nutrient acquisition services (i.e., nitrogen fixation and phosphorus solubilization) fueled by microbial sulfur and arsenic oxidation. The current study suggests that sulfur- and arsenic-oxidizing microorganisms may play important ecological roles in promoting biocrust formation and facilitating tailing reclamation
Multiple isotopes (C-S-N-H) and bound biomarkers in asphaltenes: New constraints on the classification and genesis of reservoir bitumens from the northwestern Sichuan Basin, South China
No full textReservoir bitumens in the northwestern Sichuan basin are significant for elucidating the sources and charging history of oil and gas, given their widespread occurrence in multiple strata in the area and abundant biomarkers. The debate regarding the origin and genesis of these bitumens has persisted for a long time, due to severe biodegradation and the development of multiple sets of high maturity source rocks with few biomarkers for oilsource correlation. To resolve these questions, asphaltenes, which are more resistant to biodegradation than free hydrocarbons, were systematically analyzed with the bulk multi-isotopes (C-S-N-H), bound molecules and the carbon isotopic compositions of bound individual n-alkanes. These characteristics were then compared to those of bulk bitumen and free hydrocarbons, leading to three main conclusions. In most samples, relatively abundant 25-norhopanes and 17-nortricylic terpanes were identified along with n-alkanes in free hydrocarbons, suggesting at least two oil charging events. In the samples having free n-alkanes, the carbon isotopic compositions of asphaltene-bound n-alkanes closely resemble those of corresponding free n-alkanes. Moreover, the bulk C-S-N isotopic compositions of asphaltene also approach those of corresponding bulk bitumen. These results suggest that the source of the oil charges occuring at different times are mostly the same for an individual sample, though different bitumen samples may have distinct sources. Free hydrocarbons, including n-alkanes and biomarkers, may have been produced by the secondary cracking of asphaltenes. Second, the integration of bulk C-S-N isotopic compositions of the asphaltenes and bitumens has enabled the studied samples to be classified into four groups. Source facies is the primary control of the distinct isotopic compositions with other factors like biodegradation, thermal maturity and migration having only minor influence. In combination with biomarkers, the organic matter and sedimentary environment of source rocks could be characterized for each group. A careful comparison of the bulk C-S-N isotopic compositions of asphaltenes and bitumens with those previously reported for source rocks (organic C and S and bulk N isotopes) suggests the main source rocks in the Upper Ediacarian-Lower Cambrian Formations, supporting the conclusions of previous studies. Furthermore, those source rocks in much younger formations, such as the Middle Permian as well as the Middle Devonian Formations, may also have contributed significantly to the widespread reservoir bitumens in the region. These findings highlight the usefulness of bulk C-S-N isotopic composition of asphaltenes for distinguishing oils with complex genesis and large gas exploration potential of the Upper Paleozoic source rocks in the region
Tectonic evolution of the South Pamir Orogen: Insights from the Permian to cretaceous magmatism
No full textThe Pamir orogen originated through the amalgamation of various arc terranes. Despite undergoing numerous studies, the subduction polarity and time regarding the accretion processes remain inadequately constrained. To address these issues, we carried out a detailed study of zircon and apatite U -Pb ages, zircon Hf isotopes, and whole-rock geochemistry for the Permian to Cretaceous gabbro, volcanic rocks and granitoids from the Southern Pamir and the Rushan-Pshart suture. Three stages of magmatism are identified, including 279-266 Ma gabbro and andesite to dacite, 209-208 Ma granitoids, and 108-103 Ma gabbro and granitoids, respectively. The Permian gabbro and basaltic andesite to dacite in Pshart Range are enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), but are depleted in Ta, Nb, and Ti, suggesting formation from an enriched mantle source in a subduction zone. The Late Triassic I-type granitoids are typical arc calc-alkaline magmatic rocks with epsilon Hf(t) values varying from -8.7 to -3.5, which mainly sourced from the partial melting of mixed crustal sources predominately consisting mafic rocks with minor metasedimentary rocks. The Early Cretaceous Pshart granites are I-type granites with relatively low epsilon Hf(t) values ranging from -14.6 to -2.9, suggesting that they were crust-derived rocks. The Early Cretaceous Bazardara granites are identified as A2-type granites with the epsilon Hf(t) values ranging from -18.3 to +5.3, and were derived from mixing of mantle-derived and crust-derived magmas, or interaction between mantle melts and old crustal rocks. The early Cretaceous gabbro exhibits -MORB-like geochemical characteristics with flat REE pattern (La/YbN = 4.96), moderate enrichment of LILEs and weak depletion of Nb, Ta and Ti (Nb/LaPM = 0.94). Thus, the early Cretaceous A2-type granite, EMORB-like gabbro and volcanic rocks were formed in an extensional setting. Our new data indicate that the southward subduction of the Rushan-Pshart oceanic slab started in the Early Permian and continued to the Late Triassic. Moreover, combining the previous data, we conclude that the Early Cretaceous granites and gabbro in the Southern Pamir formed in an extensional environment due to the southward rollback after northward nearflat subduction of the Neo-Tethyan oceanic lithosphere
Ferric Iron in Eclogitic Garnet and Clinopyroxene from the V. Grib Kimberlite Pipe (NW Russia): Evidence of a Highly Oxidized Subducted Slab
No full textEstimates of oxygen fugacity of eclogitic rocks are linked to the redox evolution of the oceanic protolith during subduction and its residence in the lithospheric mantle, and, based on knowledge of pressures and temperatures, allow modelling of the speciation of volatile elements and diamond (or graphite) versus carbonate stability. To date, the oxygen fugacity of mantle eclogites has been shown to vary between -6 (Kasai, Congo and Udachnaya, Siberia) and -0.1 (Udachnaya, Siberia) log units (relative to the fayalite-magnetite-quartz buffer, FMQ), linked to the low Fe3+ contents of garnets. In this study, we investigated the Fe oxidation state of coexisting garnet and clinopyroxene hand-picked out of 17 diamond-free high-MgO and low-MgO mantle eclogites (dated at 2.84 Ga) from the Grib kimberlite pipe (East-European platform). Measured Fe3+/& sum;Fe values range between 0.03 and 0.19 for garnet and 0.18-0.38 for clinopyroxene, the former being higher than what was measured previously in garnets equilibrated at mantle conditions. The Fe3+/& sum;Fe of the reconstructed bulk rock ranges between 0.10 and 0.15 for high-MgO eclogites and 0.10 and 0.24 for low-MgO eclogites (with uncertainties of +/- 0.02 and +/- 0.03 in both cases). Thermobarometric calculations result in equilibration pressures and temperatures of 3.0-5.2 (+/- 0.4) GPa and 720-1050 (+/- 60) degrees C for both high-MgO and low-MgO eclogites, slightly lower than previous P-T estimates of mantle eclogites from the Udachnaya kimberlite pipe (Siberian craton). At these conditions, triangle logfo(2) (FMQ) calculated using the available oxythermobarometric model varies from -1.7 to -0.6 log units for high-MgO eclogites and from -2.9 to 0.9 log units for low-MgO eclogites. Samples recording triangle logfo(2) (FMQ) 0.10) and for reconstructed bulk rocks in the case of both low-MgO and high-MgO samples cannot be due to metasomatic interaction with an oxidized fluid, but rather are the consequence of Fe3+ redistribution in an unusually oxidized mafic protolith upon metamorphism. Our results highlight the redox variability of eclogites of Archaean age at conditions more oxidized than present-day mid-ocean ridge basalts (MORBs) and imply an oxidizing nature of the convective mantle source where magma was formed with consequent speciation of C in the form of carbonate fluid explaining, therefore, the lack of eclogitic diamonds in V. Grib kimberlite pipe
Ferric Iron in Eclogitic Garnet and Clinopyroxene from the V. Grib Kimberlite Pipe (NW Russia): Evidence of a Highly Oxidized Subducted Slab
No full textEstimates of oxygen fugacity of eclogitic rocks are linked to the redox evolution of the oceanic protolith during subduction and its residence in the lithospheric mantle, and, based on knowledge of pressures and temperatures, allow modelling of the speciation of volatile elements and diamond (or graphite) versus carbonate stability. To date, the oxygen fugacity of mantle eclogites has been shown to vary between -6 (Kasai, Congo and Udachnaya, Siberia) and -0.1 (Udachnaya, Siberia) log units (relative to the fayalite-magnetite-quartz buffer, FMQ), linked to the low Fe3+ contents of garnets. In this study, we investigated the Fe oxidation state of coexisting garnet and clinopyroxene hand-picked out of 17 diamond-free high-MgO and low-MgO mantle eclogites (dated at 2.84 Ga) from the Grib kimberlite pipe (East-European platform). Measured Fe3+/& sum;Fe values range between 0.03 and 0.19 for garnet and 0.18-0.38 for clinopyroxene, the former being higher than what was measured previously in garnets equilibrated at mantle conditions. The Fe3+/& sum;Fe of the reconstructed bulk rock ranges between 0.10 and 0.15 for high-MgO eclogites and 0.10 and 0.24 for low-MgO eclogites (with uncertainties of +/- 0.02 and +/- 0.03 in both cases). Thermobarometric calculations result in equilibration pressures and temperatures of 3.0-5.2 (+/- 0.4) GPa and 720-1050 (+/- 60) degrees C for both high-MgO and low-MgO eclogites, slightly lower than previous P-T estimates of mantle eclogites from the Udachnaya kimberlite pipe (Siberian craton). At these conditions, triangle logfo(2) (FMQ) calculated using the available oxythermobarometric model varies from -1.7 to -0.6 log units for high-MgO eclogites and from -2.9 to 0.9 log units for low-MgO eclogites. Samples recording triangle logfo(2) (FMQ) 0.10) and for reconstructed bulk rocks in the case of both low-MgO and high-MgO samples cannot be due to metasomatic interaction with an oxidized fluid, but rather are the consequence of Fe3+ redistribution in an unusually oxidized mafic protolith upon metamorphism. Our results highlight the redox variability of eclogites of Archaean age at conditions more oxidized than present-day mid-ocean ridge basalts (MORBs) and imply an oxidizing nature of the convective mantle source where magma was formed with consequent speciation of C in the form of carbonate fluid explaining, therefore, the lack of eclogitic diamonds in V. Grib kimberlite pipe
Metabolic Characterization and Geochemical Drivers of Active Hydrocarbon-Degrading Microorganisms
No full textUnderstanding the metabolic characteristics and controlled geochemical factors of functional microorganisms in petroleum-contaminated areas at different locations is pivotal for enhancing pollutant removal strategies. To address the existing research gap in this domain, we employed stable-isotope-probing (SIP) with multi-isotope labeling substrates, combined with 16S amplicon sequencing, metagenomic sequencing, and geochemical factor analysis. Utilizing n-hexadecane and phenanthrene as model compounds, our study revealed location-specific differences in the composition of functional microorganisms. Despite these variances, key players such as Pseudomonas, Marinobacter, Alcanivorax, Ochrobactrum, and Sphingomonas consistently emerged as active degraders of n-hexadecane and/or phenanthrene. Several genera, including Pseudomonas, Ochrobactrum, Alcanivorax, Nitriliruptoraceae, and Sphingobacterium, demonstrated versatility by effectively degrading both contaminants. SIP-metagenomic binning facilitated the acquisition of genomes from key active degraders, such as Pseudomonas sp., Ochrobactrum sp., Sphingomonas sp., and Shinella sp. This enabled a comprehensive analysis of petroleum hydrocarbon degradation pathways and genes, encompassing PAH dioxygenase genes, alkB genes, phthalate, and salicylate-related pathways. Environmental factor and variation partitioning analysis revealed that oil pollution significantly influences the functional microbial community (12%), followed by available potassium and available nitrogen. Geochemical parameters and geographic location independently explained 14% and 21% of total variations, respectively. Intriguingly, more than half (51%) of the variation in functional microbial community structure remains unexplained, possibly due to unmeasured environmental variables. Our study contributes valuable insights into the in situ bioremediation mechanism for petroleum-contaminated soil, elucidating factors influencing functional microbial structures across locations. These findings provide a vital theoretical reference for in situ regulation and bioremediation of petroleum hydrocarbon pollution in diverse environmental contexts.
Understanding how microorganisms function in petroleum-contaminated areas at different locations is crucial for improving pollutant removal strategies. In our study, we used stable-isotope probing (SIP) and various techniques to analyze the metabolic characteristics and controlled geochemical factors influencing these microorganisms. By focusing on n-hexadecane and phenanthrene, we identified location-specific variations in microbial composition, with consistent roles played by key degraders like Pseudomonas, Marinobacter, Alcanivorax, Ochrobactrum, and Sphingomonas. Some genera, including Pseudomonas, Ochrobactrum, Alcanivorax, Nitriliruptoraceae, and Sphingobacterium, demonstrated versatility in degrading both contaminants. SIP-metagenomic binning allowed genome acquisition for a comprehensive analysis of hydrocarbon degradation pathways. Our findings emphasize the crucial role of these microorganisms in in situ petroleum biodegradation and their bioremediation potential. Environmental factor analysis revealed oil pollution as a significant influencer (12%), followed by AK and AN. Geochemical parameters and geographic location independently explained 14% and 21% of total variations. Over half (51%) of the variation remains unexplained, suggesting unknown environmental factors. Our study provides vital insights into in situ bioremediation mechanisms, elucidating factors influencing microbial structures across locations and offering a theoretical foundation for regulating and remediating petroleum pollution in diverse environmental contexts.
Our study unveils distinct microbial compositions involved in hydrocarbon degradation, varying across specific locations for the first time Using stable-isotope probing-metagenomics, we obtained key hydrocarbon degraders' genomes, enhancing pathway analysis and genomic insights Oil pollution (12%) impacts microbial communities; geochemical factors and location contribute 14% and 21% to variation
