Guangzhou Institute of Geochemistry
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Mantle metasomatism by subducted Indian continental crust: Evidence from post-collisional basaltic ultrapotassic rocks in southern Tibetan plateau
No full textAt continental collisional zones, the continental crust is known to subduct, penetrating the deep lithospheric mantle and undergoing partial melting. However, the extent to which these melts can effectively alter, or metasomatize, the overlying mantle remains a contentious issue. This debate is especially pronounced in the Cenozoic Himalayan-southern Tibet collisional orogen. The complexity arises from the fact that previous research has predominantly concentrated on the post-collisional intermediate ultrapotassic rocks. However, these rocks could have originated either from the subducted Indian continental crust through a process of mantle assimilation or from melange rocks, thereby primarily reflecting crustal recycling rather than mantle metasomatism by subducted continental crust. In this study, we shift our focus to the less-well-studied post-collisional basaltic ultrapotassic rocks (BUPRs) from the Sailipu region in the Lhasa block of southern Tibet. Our aim is to evaluate the characteristics of the orogenic mantle and the dynamics of crust-mantle interactions. In this study we report major and trace elements and Sr-Nd-Pb-Mo-B isotopes for these Miocene post-collisional BUPRs. The rocks are typically characterized by alkaline affinity, arc-like trace element distribution patterns, and enriched Sr-Nd-Pb isotopes, which point to their derivation from an enriched mantle source. Moreover, the Mo-B isotope ratios of these BUPRs - delta 98/95Mo ranging from -0.85 %o to -0.27 %o and delta 11B from -20.2 %o to -14.4 %o - are notably lower than those found in Mid-Ocean Ridge Basalts (MORBs) and arc lavas. Instead, they are similar to the isotopic compositions of basalts associated with continental subduction, as well as intermediate ultrapotassic rocks from western Anatolia and the Lhasa block, and the gneisses and schists of the Himalayas. These similarities strongly suggest the input of subducted Indian continental crust to the mantle source for these rocks. In conclusion, our study supports the metasomatism of the mantle beneath southern Tibet by subducted Indian continental crust. These results show that continental subduction zones, much like their oceanic counterparts, are key regions for mantle metasomatism, and thus expands our understanding of the geological processes at work in these dynamic areas
Algorithm for improving the sizing accuracy in real-time bioaerosol single particle mass spectrometer
No full textThe newly developed bioaerosol single particle mass spectrometer (Bio-SPAMS) has been innovatively designed for its optical sizing system. The first laser beam in the previous single particle mass spectrometer was split into near distance double beams, similar to the design of APS (Aerodynamic Particle Sizer) and SBS-LIBS (Single Beam Splitting-Laser Induced Breakdown Spectroscopy). All the particles focused by the aerodynamic lens can be sized and got number concentration statistic. However, due to the imperfect beam quality and the large scattering intensity of the large-sized particles, there may be some noise in the scattered signals, particle diameter measured by this sizing system was often larger than actual value if the same trigger threshold was set. In this study, when measuring PSL microspheres with diameters of 1.9, 3.1, and 4.9 mu m, the identification rates of the fixed threshold algorithm were only 75.25%, 55.26%, and 0.27%, respectively. To address such issue, we developed a dynamic threshold waveform recognition algorithm based on field programmable gate array (FPGA), which could process the photoelectric signals collected by a photomultiplier tube (PMT) in real time. The algorithm can dynamically adjust the trigger threshold of the collected scattered signals and accurately calculate the interval time between the near distance double beam. For PSL microspheres with diameters of 1.9, 3.1, and 4.9 mu m, the accuracy of the dynamic threshold algorithm increased by 19.09%, 25.72%, and 88.20%, respectively. This algorithm effectively solves the problem of particle sizing deviation, and improves the particle size measurement accuracy of the bioaerosol mass spectrometer in a wide particle size range from 0.3-6 mu m
Evaluating Heavy Metal Contamination in Water and Tissues of <i>Tor putitora</i>: Implications for Human Health Risk Assessment
No full textAnthropogenic activities have led to the release of heavy metals, posing significant threats to both aquatic ecosystems and human health. This study focused on evaluating the concentrations of Chromium (Cr), Nickel (Ni), Zinc (Zn), Cadmium (Cd), and Lead (Pb) in water and Tor putitora fish along the River Kabul in Pakistan, considering upstream and downstream sites with varying anthropogenic influences. Our analysis revealed detectable levels of all studied heavy metals at both sites, with concentrations surpassing the permissible limits set by the World Health Organization (WHO), with except for Zinc. At Site-1, average concentrations (mg L- 1) were: Cr 1.46 +/- 1.03, Ni 1.61 +/- 0.53, Zn 0.65 +/- 1.09, Cd 0.23 +/- 0.28, and Pb 0.75 +/- 0.07, while Site-2 values were: Cr 1.57 +/- 0.03, Ni 1.54 +/- 0.94, Zn 1.55 +/- 0.98, Cd 1.12 +/- 0.46, and Pb 1.47 +/- 0.82. Analysis of Tor putitora fish indicated significant metal concentrations, particularly in metabolically active tissues such as the kidney and liver, with Cr showing significant accumulation across all tissues and Cd exhibiting the lowest accumulation. Notably, muscle, a less metabolically active tissue, demonstrated the lowest metal accumulation. Evaluation of the Target Hazard Quotient and Hazard Index revealed no considerable risk for non-carcinogenic effects. However, in Site-1, Pb exhibited a carcinogenic risk surpassing the acceptable threshold (< 1 x 10(- 4)), suggesting an elevated cancer risk associated with consuming Tor putitora. These findings emphasize the urgent need for comprehensive environmental policies in developing countries to address long-term heavy metal pollution and safeguard both ecosystems and human health
Uphill diffusion of lithium along phosphorus gradients in olivine from mafic layered intrusions
No full textLithium (Li) concentration and Li isotopes of olivine have been widely adopted to decipher the mantle-crust interaction and short-lived magmatic processes in the shallow magma chambers. However, the diffusion behavior of Li in olivine has not yet been fully understood, which may bias the interpretation of Li concentration and Li isotopes observed in natural olivine. In this study, high-resolution elemental mapping (Li, P, Fe, Mn, Ca, Al, and Ni) combined with in situ Li concentration and Li isotope analyses were conducted for olivine grains from two ca. 260 Ma mafic layered intrusions in SW China, to decode the origin of coupled Li-P zoning and multimode diffusion of Li in natural olivine. The 2-D elemental maps and compositional profiles reveal complex, coupled Li-P zoning patterns. The Li-P-rich zones contain 3.5 to 6.1 ppm Li and 187 to 776 ppm P, higher than those of Li-P-poor olivine domains that contain 0.7 to 2.8 ppm Li and 29 to 166 ppm P. Particularly, the Li-P-rich zones in each grain commonly have lower delta 7Li* than that of the Li-P-poor domains, with the maximum fractionation of Li isotopes in a single grain being up to 15 parts per thousand. Numerical modeling shows that rapid olivine growth can result in variable degrees of Li and P enrichment in concentration and an increase of delta 7Li* in the Li-P-rich zone of olivine, which is inconsistent with our observations. Instead, the inverse variations of Li concentration and Li isotopic profiles can be well simulated in an uphill diffusion mode of Li along pre-existing sharp P gradients, accompanying by simultaneous coupled and non-coupled diffusion of Li within a single olivine. The large variation of delta 7Li* is thus interpreted as kinetic fractionation, which may be caused by dehydration of olivine due to exsolution of a fluid phase from the interstitial liquid of a crystal mush. Three distinct Li-P variation trends of olivine are summarized in this study and can be used to distinguish the process of crystal growth from postcrystallization diffusion. Our results should have important bearings on the understanding of complex crystallization and solidification processes of crustal magma chambers
Revisiting the high temperature Darongshan-Shiwandashan granitoids in the South China: A response to slab tearing associated with diachronous collision between Indochina and South China blocks
No full textThe Darongshan-Shiwandashan granite belt (DSGB) is composed of S-type granites and granodiorite intrusions, which are characterized by high- or ultrahigh-temperature cordierite, orthopyroxene, and granulite xenoliths. The petrogenesis of these plutons is a subject of debate, and a thorough overview of regional tectonic evolution and geochemistry is still absent despite the numerous research conducted in this granite belt. This study is a comprehensive overview of geochronology, whole-rock major-trace elements, Sr-Nd isotopes, and zircon Hf-O isotopes in the DSGB, focusing on their petrogenesis and tectonic setting of formation. The geochronological data indicates that DSGB granitoids emplaced at ca. 250 Ma, with a southwestward-younging trend. Moreover, mineral assemblages of cordierite + orthopyroxene suggest that the DSGB was formed in a high-temperature (similar to 850 degrees C) and low-pressure (3.7-6 kbar) tectonic setting. Three main plutons (Darongshan, Jiuzhou, and Taima) of the DSGB exhibit distinctly different compositions. The Darongshan and Taima granitoids display high silica (SiO2 = 68.65-78.10 wt%), low-maficity (FeO + MgO = 1.97-7.28 wt%), along with negative whole-rock epsilon Nd(t) values (-13.9 to -9.7) and elevated initial Sr-87/Sr-86 values (0.71638 to 0.73165). The Jiuzhou granitoids, on the other hand, exhibit relatively low silica (SiO2 = 63.90-72.72 wt%) and high maficity (FeO + MgO = 3.03-9.88 wt%), with largely overlapping but relatively high epsilon Nd(t) values ranging from -12.9 to -9.9 and lower initial Sr-87/Sr-86 values from 0.71453 to 0.72401. Two-component mixing model results indicate these different compositions represent varying degrees of mixing between crust- and mantle-derived magmas, with 0-10 %, 0-20 % and 20-40 % basaltic melts involved for Taima, Darongshan and Jiuzhou plutons, respectively. The subducting slab tearing, induced by the diachronous collision between the South China Block (SCB) and Indochina Block (ICB), provide the most feasible interpretation for the petrogenesis and spatio-temporal geochemical pattern of the granitic rocks in the DSGB. The onset of the diachronous collision initiated at the Hainan-Yunkai massif, southwest of SCB, while the Tethys Ocean still existed in the northwest (Nanpanjiang area), causing notable disparities in the convergence velocities of the subducting ocean slab. The heterogeneous stresses resulting from the different subduction rates were accommodated by bending and tearing of the subducting slab. Then, ultrahigh-temperature basaltic melts derived from the decompression melting of the lithospheric mantle facilitated the melting of metasedimentary rocks, which resulted in the formation of high-temperature S-type granitoids. The Jiuzhou pluton, located at the center of slab tearing, received more mantle contributions than the Darongshan and the Taima plutons, which are emplaced away from the slab tearing center. The younging trend in age from the Darongshan to Jiuzhou and Taima plutons indicates a progressive tearing from the northeast (the far end of the subducting slab) to the southwest
Molecular characteristics of organic matters in PM 2.5 associated with upregulation of respiratory virus infection<i> in</i><i> vitro</i>
No full textThe extent to which organic matters (OM) in PM 2.5 affect virus infections and the key organic molecules involved in this process remain unclear. Herein, this study utilized ultra-high resolution mass spectrometry coupled with in vitro experiments to identify the organic molecules associated with respiratory virus infection for the first time. Water-soluble organic matters (WSOM) and water-insoluble organic matters (WIOM) were separated from PM 2.5 samples collected at the urban area of Guangzhou, China. Their molecular compositions were analyzed using Fourier transform ion cyclotron resonance mass spectrometry. Subsequently, in vitro experiments were conducted to explore the impact of WSOM and WIOM exposure on the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pseudo-virus infection in A549 cells. Results revealed that WSOM and WIOM respectively promoted 1.7 to 2.1-fold and 1.9 to 3.5-fold upregulation of SARS-CoV-2 pseudo-virus infection in a concentration- dependent manner (at 25 to 100 mu g mL-1) compared to the virus-only control group. Partial least squares model analysis indicated that the increased virus infection was likely related to phthalate ester and nitro-aromatic molecules in WSOM, as well as LipidC molecules with aliphatic and olefinic structures in WIOM. Interestingly, the molecules responsible for upregulating SARS-CoV-2 receptor angiotensin-converting enzyme 2 ( ACE2 ) expression and virus infection differed. Thus, it was concluded that ACE2 upregulation alone may not fully elucidate the mechanisms underlying increased susceptibility to virus infection. The findings highlight the critical importance of aromatic and lipid molecules found in OM in relation to respiratory virus infection
Unravelling the mechanisms underlying marine redox shifts during sedimentary manganese metallogenesis: insights from the Carboniferous Muhu deposit, China
No full textSedimentary manganese (Mn) mineralization requires a switch between anoxic and oxic water column conditions, which is commonly explained by the "bathtub ring" model and more recently interpreted by the emerging "episodic ventilation" model. To date, however, it remains unclear regarding how to distinguish between these two mechanisms, profoundly influencing Mn ore prospecting. Here, we conducted a comprehensive investigation on the Muhu Mn deposit in northwestern China. The upward lithological variations from breccia-dominated to fine-grained siliciclastic units (e.g., black shales) are typical of sequence characteristics of rifted basins. Black shales were deposited in deep waters due to continued tectonic subsidence that resulted in hydrographic restriction and bottom water euxinia, as indicated by their high ratios of FeHR/FeT and FePy/FeHR, as well as relatively low Mo/TOC ratios. The Mn ore beds are interbedded with black shales and consist of divalent Mn minerals (e.g., rhodochrosite). They display shale-normalized positive cerium anomalies and negative inorganic carbon isotopes and Mo isotopes, suggesting that these Mn carbonate minerals originated from the diagenetic conversion of primary buried Mn oxides deposited under oxic benthic conditions. Taken together, the intimate spatial association between Mn ore beds and black shales records a dynamic temporal redox change. Such a redox shift is consistent with the "episodic ventilation" scenario, where incursions of oxygenated seawater triggered the deposition of initial Mn oxides. In contrast with the "bathtub ring" model, the ventilation scenario represents distinct spatial-temporal configurations of redox-hydrological conditions. Therefore, deciphering the detailed redox variations of Mn-hosting sedimentary successions, in conjunction with paleogeographic reconstruction, is the key to distinguishing between these two mechanisms
Apatite low-temperature thermochronology constraints on the Cenozoic differential uplift/denudation of the Ke'eryin lithium ore field in western China: Implications for lithium exploration
No full textThe Ke'eryin pegmatite-type lithium ore field is a major lithium concentration area in the Songpan-Garze fold belt, western China. However, there is a notable spatial variability in lithium mineralization, with the northeastern and southeastern regions showing higher mineralization intensity than the western and northern parts. Previous studies suggest that this difference is likely related to the development of a Cenozoic thrust fault, the Ke'eryin thrust fault (KEYF), which traverses the eastern and southern parts of the ore field. However, direct chronological evidence is lacking. This study employs apatite fission track thermochronology on three representative deposits located in the northeastern, southeastern, and western regions of the Ke'eryin ore field, offering insights into differential uplift/denudation. The integration of regional tectonic evolution, apatite fission track age data, and thermal modelling results reveals that the Ke'eryin ore field has underwent two primary phases of rapid cooling after its formation: initially from the Late Jurassic to the Cretaceous, and subsequently from the Early Miocene to the present. The initial rapid cooling phase is mainly attributed to the LhasaQiangtang collision, whereas the subsequent phase is connected to significant fault activity and regional river incision due to the India-Asia continental collision. Apatite fission track age data and thermal modelling results indicate that differential uplift/denudation between the eastern and western Ke'eryin ore field primarily took place during the Late Miocene of the Cenozoic. The development of the thrust fault, which has been constrained to have initiated since 12 Ma, has led to the denudation of lithium deposits in the hanging wall (the western and northern parts of the Ke'eryin ore field), whereas those in the footwall (the eastern part) remain relatively well preserved. Based on these characteristics, this study recommends focusing exploration efforts for pegmatite-type lithium resources in the footwall regions, particularly in exploration gaps that are away from river valleys between large and super-large deposits. Additionally, in the entire Songpan-Garze fold belt, there is significant pegmatite-type lithium exploration potential in the high elevation, arid, and less topographically relieved western regions
Apatite low-temperature thermochronology constraints on the Cenozoic differential uplift/denudation of the Ke'eryin lithium ore field in western China: Implications for lithium exploration
No full textThe Ke'eryin pegmatite-type lithium ore field is a major lithium concentration area in the Songpan-Garze fold belt, western China. However, there is a notable spatial variability in lithium mineralization, with the northeastern and southeastern regions showing higher mineralization intensity than the western and northern parts. Previous studies suggest that this difference is likely related to the development of a Cenozoic thrust fault, the Ke'eryin thrust fault (KEYF), which traverses the eastern and southern parts of the ore field. However, direct chronological evidence is lacking. This study employs apatite fission track thermochronology on three representative deposits located in the northeastern, southeastern, and western regions of the Ke'eryin ore field, offering insights into differential uplift/denudation. The integration of regional tectonic evolution, apatite fission track age data, and thermal modelling results reveals that the Ke'eryin ore field has underwent two primary phases of rapid cooling after its formation: initially from the Late Jurassic to the Cretaceous, and subsequently from the Early Miocene to the present. The initial rapid cooling phase is mainly attributed to the LhasaQiangtang collision, whereas the subsequent phase is connected to significant fault activity and regional river incision due to the India-Asia continental collision. Apatite fission track age data and thermal modelling results indicate that differential uplift/denudation between the eastern and western Ke'eryin ore field primarily took place during the Late Miocene of the Cenozoic. The development of the thrust fault, which has been constrained to have initiated since 12 Ma, has led to the denudation of lithium deposits in the hanging wall (the western and northern parts of the Ke'eryin ore field), whereas those in the footwall (the eastern part) remain relatively well preserved. Based on these characteristics, this study recommends focusing exploration efforts for pegmatite-type lithium resources in the footwall regions, particularly in exploration gaps that are away from river valleys between large and super-large deposits. Additionally, in the entire Songpan-Garze fold belt, there is significant pegmatite-type lithium exploration potential in the high elevation, arid, and less topographically relieved western regions
Chemical characteristics, source apportionment of precipitation ion and the response to air quality in Kunming, southwest monsoonal area of China
No full textChemical composition (ion) of precipitation contains the information of atmospheric pollution, provides key scientific evidence for improving air quality and deposition flux to ecological environmental assessment in study region. The ion concentrations of 99 precipitation events (January 2013 to December 2014) in Kunming (southwest monsoonal region of China) were reported here with detailed study on the ion characteristics, sources tracing and influencing factors by correlation analysis (SPSS software), Positive Matrix Factorization (PMF) and Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) models analysis. The results showed that the major ions were NH4+, Ca2+, SO42- and NO3-, accounting for 81% of the total ions. PMF model results estimated six sources: secondary inorganic product, metal-cement industrial source, construction dust source, chlorination industrial source, marine source and biomass combustion source. In addition, HYSPLIT results showed that Kunming was mainly affected by five air masses, with highest ionic flux from the southwest direction (Indian Ocean). The annual average concentration of precipitation ions from 2013 to 2020 show positive relationships to air quality index (AQI), which indicate that precipitation ions can record different types of human activities (i.e. "coal ban", energy structure transformation, fertilizer usage, etc.) contribute to AQI