Guangzhou Institute of Geochemistry
Institutional Repository of Guangzhou Institute of Geochemistry,CAS(GIGCAS OpenIR)Not a member yet
22838 research outputs found
Sort by
Fractionation Mechanism and Flux Estimation of Strontium Isotopes During Basalt Weathering
No full textThe fluxes of metal cations and isotopes released by weathering of silicate rocks are crucial and a prerequisite for constraining geochemical fluxes to rivers and oceans. This study presents mineral and elemental compositions along with 87Sr/86Sr and d88Sr data from a basaltic weathering regolith on Hainan Island, South China to elucidate Sr isotope fractionation and weathering fluxes. The 87Sr/86Sr ratios vary from 0.703936 to 0.706338 as a result of differential weathering of the minerals. d88Sr values in the weathering regolith range from 0.29 to 0.37%, with the majority of the weathering regolith having lower d88Sr values than the parent rock. Sr is leached into the soil solution during plagioclase decomposition, while 86Sr is preferentially adsorbed on the surface of secondary minerals. As weathering progresses, smectite decomposes and kaolinite desorbs under weakly acidic conditions, releasing the previously adsorbed 86Sr into the soil solution. The differential weathering of kaolinite and smectite controls the d88Sr values of the weathering regolith, with pH being an important determinant of isotope fractionation. Furthermore, Sr elemental fluxes (SrFlux) and Sr isotopic fluxes (d88SrFlux) of this weathering regolith were calculated using a mass balance model, yielding mean values of 0.20 (mg cm 3 Myr 1) and 0.052 (% (mg cm 3 Myr 1)), respectively. The d88SrFlux exhibits a nonlinear positive correlation with the Chemical Index of Alteration (CIA), indicating that enhanced weathering leads to significant stable Sr isotope fractionation at CIA values below 95%. Our research promotes the understanding of Sr recycling and the fractionation behavior of stable Sr isotopes during consecutive weathering.
Plain Language Summary The stable Sr isotopic composition is sensitive to continental weathering processes and offers insights into weathering mechanisms. However, the fractionation mechanism of stable Sr isotopes remains elusive. Significant stable Sr isotope fractionation was observed in a basaltic weathering regolith on Hainan Island, South China. Plagioclase decomposition releases Sr, with isotopically light Sr adsorbed onto the surfaces of secondary minerals during incipient weathering. Smectite decomposition and kaolinite desorption control the stable Sr isotopic composition of the weathering regolith during advanced weathering. The variable pH of the regolith is an important external control factor. We focus on modeling Sr isotopic fluxes and Sr elemental fluxes from weathering regolith. Our results show that within a certain range, an increase in weathering intensity leads to a nonlinear increase in weathering fluxes. The d88 Sr values of the loss component are consistent with those in silicate-dominated river catchments, suggesting that metal cations from the weathering of silicate rocks have a significant influence on the hydrochemical and isotopic composition of river waters in these catchments. Stable Sr isotope fractionation thus provides quantitative constraints on continental weathering fluxes
Syn-tectonic fluids decoding effects of tectono-metamorphic cycles on regional metallogenic evolution of the Chinese Altai, central Asia
No full textDespite their close temporal and spatial relationships, the effects of tectono-thermal events on ore formation remain obscure. To better understand this process, a comprehensive geochemical investigation on paleofluids from syn-tectonic felsic and quartz veins associated with the Devonian subduction and Permian collision of the Chinese Altai was conducted. We found that the Devonian fluids were organic alkanes-CO2-S-Ca-Mg-rich saline fluids with variable CO2/CH4 (0.09-5.03) and lower F-/SO42- (0.02-0.14) and Al3+/Mg2+ (0-0.11) ratios, whereas the Permian fluids were immiscible fluids including CO2-C4H10-CO-rich oxidized gas bubbles and CH4-C3H8-C2H6-Ca-Na-K-Al-S-Cl-F-rich reduced saline fluids with lower CO2/CH4 (0-1.31, mostly <1) and higher F-/SO42- (0.21-0.76) and Al3+/Mg2+ (0.10-2.56) ratios. The Devonian and Permian fluids also have similar delta C-13-CO2 values of -23.8 parts per thousand to -3.5 parts per thousand and -16.5 parts per thousand to -3.7 parts per thousand, respectively. These data suggest that both fluids derived mainly from devolatilization and dehydration melting of metasediments; the Permian fluids likely involve more biotite melting in the deeper crust and more mantle-derived components, whereas the Devonian fluids contain more meteoric components. Base metal-dominated Devonian mineralization occurred as deep-sourced organic matter- and S-rich fluids promoted base metal migration, whereas the relatively oxidized fluid conditions inhibited the mineralization of many other metals. By contrast, the more reduced and F-rich Permian fluids with more mantle contributions facilitated the extraction of Au and uptakes of rare metals from reworked metasediments and promoted their mineralization. These findings provide a more complete picture of how tectono-thermal events fertilize the crust and demonstrate that syn-tectonic fluids can serve as proxies for metallogenic processes during orogenic cycles in general
U-Pb and Re-Os geochronology and geochemistry of the Ulgen hidden porphyry Mo deposit in the Derbugan metallogenic belt (NE China): Insights into petrogenesis and tectonic setting
No full textThe Ulgen porphyry Mo deposit, recently discovered in the northeastern segment of the Derbugan metallogenic belt, NE China, is a large and hidden ore deposit. Investigation of this deposit provides insights into the geodynamic background and metallogenic mechanism of Mesozoic porphyry Mo deposits that are exposed elsewhere in NE China. The host rocks consist of muscovite monzonitic granite (MMG) and biotite granitic porphyry (BGP), which are intruded into Lower and/or Middle Jurassic intermediate-felsic volcanic-sedimentary rocks and pre-ore monzogranitic porphyry (MP). Zircon laser ablation-inductively coupled U-Pb age dating indicates that the MMG and BGP were emplaced at 144.9 Ma and 144.7 Ma, ca. 14 m.y. younger than the intrusion age of MP (159.3 Ma). Molybdenite Re-Os isotopic dating indicates that Mo mineralization occurred at 144.9 Ma, almost simultaneously with the 145 Ma magmatic activity. Geochemically, all of the Ulgen granitoids are enriched in large ion lithophile elements (e.g., Rb, Th, U, and K) and light rare earth elements, and are depleted in high field strength elements (e.g., Nb, Ta, and Ti). The pre-ore MPs belong to I-type granites with moderately negative Eu the syn-ore MMGs exhibit S-type affinity with pronounced negative Eu anomalies (Eu/Eu* = 0.29-0.39). The ore -forming BGPs display adakite-like geochemical features in terms of high -Sr, low -Y, and low-Yb contents, and slightly negative Eu anoma- lies (Eu/Eu* = 0.72-0.74). All intrusive rocks have relatively low initial (87Sr/86Sr)i ratios (0.7044-0.7055) and positive epsilon Nd(t) values (+1.15 to +2.65), positive epsilon Hf(t) val- ues (+4.0 to +9.4), young two -stage Nd and Hf model ages (tDM2(Nd) = 841-731 Ma, tDM2(Hf) = 943-604 Ma), and moderate (206Pb/204Pb)i (18.300-18.402), (207Pb/204Pb)i (15.557-15.564), and (208Pb/204Pb)i (38.180- 38.307) ratios. Therefore, it is most likely that these intrusive rocks originated from a mix- ture of two sources of magma derived from the mantle and juvenile lower crust, in which there were variable degrees of the fractional crystallization of ilmenite, apatite, and pla- gioclase. Rather than the partial melting of oceanic slabs, the fractional crystallization of hornblende and accessory minerals (e.g., il- menite and apatite) induces the adakitic geo- chemical signature of BGPs. Compared with the BGPs, the MPs had a relatively deeper magma source region, whereas the MMGs had a relatively shallower magma source region. The BGPs and the Mo-bearing fluids of the Ulgen deposit were most probably de- rived simultaneously from magma that was generated at an extensional setting following the closure of the Mongol -Okhotsk Ocean during the latest Jurassic. Enrichment of Mo by late -stage fractional crystallization most likely played an important role in concen- trating Mo during the formation of the Ul- gen hidden Mo deposit
Protracted and Progressive Crustal Melting during Continental Collision in the Pamir and Plateau Growth
No full textDetermining crustal melting in parallel with geodynamic evolution provides critical information on plateau crustal thickening and uplift. Here we investigate the timing and duration of crustal melting through in situ analysis of zircon U-Pb ages, trace elements and Hf-O isotopes, and whole-rock elements and Sr-Nd-Hf isotopes for the granites and high-grade metamorphic rocks from the Pamir Plateau. Zircon dates record protracted crustal melting for both Central Pamir (43-33 and 22-12 Ma) and South Pamir (28-10 Ma). The Pamir Cenozoic granites are characterized by significant elemental and isotopic heterogeneity. The elemental variability within the Pamir Cenozoic granites is dominantly attributed to fractional crystallization of K-feldspar and plagioclase with subordinate biotite from a variably fractionated melt, and the accumulation of early crystallized feldspar during magma ascent. Peritectic mineral entrainment and accessory mineral crystallization had some influence on the geochemical characteristics of the garnet-bearing leucogranite dikes. Zircon Hf isotopes and whole-rock Sr-Nd-Hf isotopes show secular variations for both Central and South Pamir granites. The Central Pamir granites show a mild decrease in whole-rock sigma Nd(t) values from Eocene (-4.3 to -4.9) to Miocene (-6.2 to -7.7), and the zircon sigma Hf(t) values decrease from c. 40 Ma (+2 to -5) to c. 10 Ma (-4 to -8). In contrast, the South Pamir granites have highly variable whole-rock Sr-Nd-Hf (87Sr/86Sr(i) = 0.7053 to 0.7830; sigma Nd(t) = -31.5 to +0.2; sigma Hf(t) = -40.0 to +8.2) and zircon Hf isotopes (sigma Hf(t) = -31.7 to +7.5) and display a strong decrease in sigma Nd(t) and sigma Hf(t) values from c. 25 Ma to c. 13 Ma. Geochemical and isotopic data indicate that both the Central and South Pamir experienced crustal melting from juvenile lower crust to ancient lower-middle crustal materials, and Indian crustal materials were incorporated into the melt region of the South Pamir leucogranites from c. 20 Ma. Our study highlights a causal link between a chain of events that includes magma underplating induced by lithosphere thinning and slab breakoff, lithosphere delamination and underthrusting of Indian lithosphere, and formation of the Cenozoic granites in Pamir. This series of processes are incorporated here into a comprehensive model for the geodynamic evolution of the Pamir during the India-Asia collision
The Circumglobal Transport of Massive African Dust and Its Impacts on the Regional Circulation in Remote Atmosphere
No full textAtmospheric dust from North Africa, the largest and most persistently active dust source over the world, spreads widely in the Northern Hemisphere and plays essential roles in the Earth environment evolution. During 7-24 June 2020, an extremely strong dust event occurred with its westward spreading modulated by the North Atlantic Oscillation (NAO) and its eastward spreading regulated by European blocking, ultimately resulting in the circumglobal transport of African dust. The Mediterranean low pressure linked to the European blocking dipole was the key to facilitating the eastward transport of dust. This record -breaking African dust episode caused a notable diurnal precipitation decrease of 0.98 mm day-1 over northeastern India and a decrease of 1.55 mm day-1 over central North America, which was ascribed to the effect of dust -induced radiative heating on large-scale circulation. It triggered a Rossby wave train and caused anomalous high pressure over northeastern India, which weakened the India summer monsoon and consequently inhibited the occurrence of precipitation. Dust -induced radiative heating also supported the stability in the anomalous warm high over North America, further repressing import of moisture from Atlantic. Ambient moisture and atmospheric instability also presented consistent variation over North America and India characterized as strengthen descending motion and sharply reduced moist convection. This study reports, for the first time, the strong modulation of regional circulation by circumglobally transported African dust, especially in Asia and North America. The new aspects on the unexpected consequences on moisture convection indicate broader roles that the dust may play in the global climate change
Distribution, chemical, and molecular composition of high and low molecular weight humic-like substances in ambient aerosols
No full textHumic-like substances (HULIS) encompass a continuum of molecular weight (MW) ranges, yet our understanding of how HULIS characteristics vary with MW is still limited and not well established. In this study, a combination of ultrafiltration and solid-phase extraction protocols was employed to fractionate the high MW (HMW; > 1 kDa) and low MW (LMW; C = O). HRMS analysis further unveiled that molecular formulas within HMW HULIS generally featured smaller sizes but higher degrees of unsaturation and aromaticity compared to those within LMW HULIS fractions. This observation suggests the possibility of small molecules assembling to form the HMW HULIS through intermolecular weak forces. Moreover, HMW HULIS contained a higher proportion of CHON but fewer CHO compounds than LMW HULIS. In both HMW and LMW HULIS, the unique molecular formulas were primarily characterized by lignin-like species, yet the former displayed a prevalence of N-enriched and highly aromatic species. Additionally, HMW HULIS contained more unique lipid-like compounds, while LMW HULIS exhibited a distinct presence of tannin-like compounds. These findings provide valuable insights into the distribution, optical properties, and molecular-level characteristics of HULIS in atmospheric aerosols, thereby advancing our understanding of their sources, composition, and environmental implications
Formation of In-Cloud Aqueous-Phase Secondary Organic Matter and Related Characteristic Molecules
No full textAtmospheric particles are largely represented by secondary organic aerosols (SOAs) produced by either aqueous- or gas-phase reactions. Recently, the contribution of the former to SOA formation has been shown to substantially increase and even reach that of the latter, which necessitates in-depth mechanistic investigations. For a deeper understanding of aqueous-phase SOA generation, we herein studied the production of these aerosols in the dark from glycolaldehyde (GAld) and ammonium sulfate (AS)/amines (methylamine (MAm) and glycine (Gly)). UV-vis spectroscopy showed that reaction mixtures featured two main absorption bands (at 209-230 and 280-330 nm) that were attributed to the pi-pi* transitions of Schiff bases and the n-pi* transitions of oligomers produced in the above reactions, respectively. Further studies revealed that irrespective of reactant concentration and pH, all the investigated reactions were well fitted by first-order kinetics and were accelerated by increasing AS/MAm concentrations and solution pH under acidic conditions. The reaction rate constants (determined from changes of absorption at 300 nm) followed the order of Gly (k(I) = 2.39 x 10(-6) s(-1)) > MAm (k(I) = 1.19 x 10(-6) s(-1)) > AS (k(I) = 8.33 x 10(-7) s(-1)) at identical low AS/amine concentrations and were in the order of MAm (k(I) = 2.5 x 10(-6) s(-1)) > AS (k(I) = 1.39 x 10(-6) s(-1)) at high AS/MAm concentrations. The main reaction pathways corresponded to the aldol self-condensation of GAld and the nucleophilic attack of AS/amines on GAld followed by dehydration, which afforded imines as the major products. The stronger light absorption of (GAld + Gly) mixtures than that of (glyoxal/methylglyoxal + Gly) mixtures was ascribed to the increased amount of imine- and carbonyl group-containing products produced in the former case
Metabolomics perspectives into the co-exposure effect of polycyclic aromatic hydrocarbons and metals on renal function: A meet-in-the-middle approach
No full textStudies on the dose effects of kidney impairment and metabolomes in co-exposure to polycyclic aromatic hydrocarbons (PAHs) and metals are limited. We aimed to identify overall associations and metabolic perturbations in 130 participants (53 petrochemical workers and 77 controls) exposed to a PAHs-metals mixture in Southern China. The urinary 7 hydroxylated PAHs and 15 metal(loid)s were determined, and serum creatinine, beta -2 microglobulin, and estimated glomerular filtration rate were health outcomes. The liquid chromatographymass spectrometry-based method was applied to serum metabolomics. Generalized weighted quantile sum (gWQS) regressions were used to estimate the overall dose -response relationships, and pathway analysis, "meetin -the -middle" approach, and mediation effect analyses were conducted to identify potential metabolites and biological mechanisms linking exposure with nephrotoxic effects. Our results indicated that renal function reduction was associated with a PAHs-metals mixture in a dose -dependent manner, and 1-hydroxynaphthalene and copper were the most predominant contributors among the two families of pollutants. Furthermore, the metabolic disruptions associated with the early onset of kidney impairment induced by the combination of PAHs and metals encompassed pathways such as phenylalanine-tyrosine-tryptophan biosynthesis, phenylalanine metabolism, and alpha-linolenic acid metabolism. In addition, the specifically identified metabolites demonstrated excellent potential as bridging biomarkers connecting the reduction in renal function with the mixture of PAHs and metals. These findings shed light on understanding the overall associations and metabolic mechanism of nephrotoxic effects of co -exposure to PAHs and metals
Mixing state and influence factors controlling diurnal variation of particulate nitrophenol compounds at a suburban area in northern China*
No full textNitrophenols have received extensive attention due to their strong light-absorbing ability in the near-ultravioletvisible region, which could be influenced by the atmospheric processes of nitrophenols. However, our knowledge and understanding of the formation and evolution of nitrophenols are still in the nascent stages. In the present study, the mixing states of four mononitrophenol particles (i.e., nitrophenol, methynitrophenol, nitrocatechol, and methoxynitrophenol), and one nitropolycyclic aromatic hydrocarbon particles (i.e., nitronaphthol (NN)) were investigated using a single-particle aerosol mass spectrometer (SPAMS) in November 2019 in Qingdao, China. The results showed, for the first time, that mononitrophenols and NN exhibit different mixing states and diurnal variations. Four mononitrophenols were internally mixed well with each other, and with organic acids, nitrates, potassium, and naphthalene. The diurnal variation in the number fraction of mononitrophenols presented two peaks at 07:00 to 09:00 and 18:00 to 20:00, and a valley at noon. Atmospheric environmental conditions, including NO2, O3, relative humidity, and temperature, can significantly influence the diurnal variation of mononitrophenols. Multiple linear regression and random forest regression models revealed that the main factors controlling the diurnal variation of mononitrophenols were photochemical reactions during the day and aqueous-phase reactions during the night. Unlike mononitrophenols, about 62-83% of NN were internally mixed with [NH4]+ and [H(NO3)2]-, but not with organic acids and potassium. The diurnal variation of NN was also different from that of mononitrophenols, generally increased from 17:00 to 10:00 and then rapidly decreaed from 11:00 to 16:00. These results imply that NN may have sources and atmospheric processes that are different from mononitrophenols. We speculate that this is mostly controlled by photochemical reactions and mixing with [NH4]+, which may influence the diurnal variation of NN in the ambient particles; however, this requires further confirmation. These findings extend our current understanding of the atmospheric formation and evolution of nitrophenols
Syn-collisional extension and Ni-Cu sulfide-bearing mafic magma emplacement along the Irtysh Shear Zone in the Central Asian Orogenic Belt
No full textThe Central Asian Orogenic Belt was characterized by a long-lived accretionary history from Neoproterozoic to Paleozoic, followed by a collisional phase of orogeny in the latest Paleozoic with the closure of the Paleo-Asian tion associated with mantle-derived mafic magmas in the Central Asian Orogenic Belt was relatively short-lived. Thus, the coherence between the protracted accretionary and collisional history of the Central Asian Orogenic Belt and the transient Ni-Cu sulfide-bearing mafic magmatism is difficult to understand. We investigated both Ni-Cu sulfidebearing and sulfide-barren mafic intrusions along a major suture zone of the Irtysh Shear Zone within the Central Asian Orogenic Belt to understand the origin of shortlived Ni-Cu sulfide mineralization in the context of the collision of two arc systems of the Chinese Altai and the East Junggar regions. Zircon U-Pb dating results for the Ni-Cu sulfide-bearing mafic intrusions show that they were only emplaced briefly from 290 Ma to 280 Ma after subduction terminated (ca. 312 Ma), substantially earlier than Ni-Cu sulfide-barren mafic intrusions (ca. 274-271 Ma). Zircons from all Ni-Cu sulfide-bearing/barren mafic intrusions from 6.0 to 7.4%0, higher than the typical mantle value ( 5.3%0), which indicates their derivation from a metasomatized mantle with inherited subduction signatures. The 611B values of the rocks from these intrusions range from -17.2%0 to -2.3%0, significantly lower than those of typical volcanic arcs (up to +18%0), which suggests that the metaso- matic components in the mantle source were dominated by sediment melts rather than fluids. The pressure calculated using amphi- bole thermobarometry shows that the pa- rental magmas of the Ni-Cu sulfide -bearing mafic intrusions were emplaced shallower than those of Ni-Cu sulfide -barren mafic intrusions. This is supported by the fact that the country rocks of the Ni-Cu sulfide - bearing mafic intrusions are shallow crustal lithologies of sedimentary rocks, whereas the country rocks of the barren intrusions are relatively deeper crustal lithologies of high-grade metamorphic rocks and gran- ites. Olivine from the Ni-Cu sulfide -barren intrusions has forsterite (Fo) contents rang- ing from 51.1 mol% to 76.2 mol% and Ni from 196 ppm to 1312 ppm. These values are much lower than those of the Ni-Cu sulfide -bearing intrusions (Fo = 72.6- 79.4 mol%; Ni = 1022-1925 ppm), which indicates that the parental magmas of the barren intrusions may have experienced ex- tensive olivine crystallization. Notably, the emplacement of the Ni-Cu sulfide -bearing mafic intrusions (290-280 Ma) coincidently overlapped with a transient period of oro- gen -parallel extension (ca. 295-280 Ma) in response to the collision of the Chinese Altai and East Junggar. Syn-collisional extension may lead to the rapid ascent and emplace- ment of mantle -derived mafic magmas at a shallower crustal level, preventing signifi- cant loss of Ni from olivine crystallization at depths, and thus providing metal -rich mafic magmas for potential Ni-Cu sulfide miner- alization. Our results highlight that syn-col- lisional extension is an essential geodynamic mechanism that controls the emplacement of Ni-Cu sulfide -bearing mafic intrusions in orogenic belts