Guangzhou Institute of Geochemistry
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Paleozoic tectonothermal history of the amalgamation of the Tarim-North China and Mongolian collages
No full textIn the Mongolian Collage, metamorphic pressure-temperature (P-T) and timing reveal a one-stage evolution defined by a duality of late Neoproterozoic-Ordovician subduction-related low T/P metamorphism and suprasubduction high T/P metamorphism recorded in the Mongolia-Manchuria and Baikal-Sayan belts. This was followed by gradual prevalence of suprasubduction high T/P metamorphism towards the late Paleozoic corresponding to the Altai and South Altai cycles. In the Tarim-North China Collage, metamorphic P-T and timing reveal a two-stage evolution, from dominant intermediate T/P metamorphism possibly resulting from Ordovician-Devonian amalgamation and Andean-type evolution of the collage, to dual low and high T/P metamorphism in the Carboniferous-Permian reflecting subduction-collision processes along the South Tianshan suture in the west and a suprasubduction evolution along the Solonker suture in the east. Altogether, the Paleozoic tectonometamorphic evolution of the two collages in the Central Asian Orogenic Belt shows remarkable differences, with the Mongolian Collage displaying features typical of peripheral accretionary style reflecting recurrent tectonic switches that can be regarded as a single orogenic system, and a two-stage evolution of the Tarim-North China Collage with features of both peripheral-accretionary and interior-collisional orogenic cycles, but mostly related to recurrent subductions of interior oceans
Crystallinity and dissolution-recrystallization mechanism controlled As(V) retention by calcium phosphate
No full textRetention of toxic metals/metalloids like arsenic via mineral-water interaction plays a crucial role in the environmental behavior of pollutants. However, the influence of mineral crystallinity on the retention of toxic elements, the evolution of liquid composition, and the interaction mechanism are poorly understood. This study investigated the interaction between As(V) and calcium phosphate (CaP) under oxic conditions with varying crystallinities, particularly amorphous CaP (ACP), across varying As(V) concentrations and pH conditions. Results revealed that the amorphous phase substantially influenced As(V) fate, with the As(V) retention potential of ACP and poorly crystalline hydroxylapatite (HAP) being 13.65 and 12.61 times higher than highly crystalline HAP, respectively. As(V) retention involves the dissolution of ACP and the recrystallization of As(V)-substituted HAP, correlated with three distinct ACP transformation stages during recrystallization. The lower pH (7.5) facilitated ACP dissolution, and the elevated Ca2+ concentration enhanced the volume of CaP recrystallization. Conversely, higher pH levels (8.0, 8.5, and 9.0) promoted a higher degree of recrystallization, evidenced by reduced residual Ca2+ levels after 48 hrs (post-crystallization stage). Meanwhile, As-bearing CaP forms with greater competition between PO43-and AsO43- at higher initial As(V) concentrations than lower ones. Addi- tionally, lattice distortion, increases in species of surface bond groups, and reduced crystallinity were observed in the As(V)-bearing CaP product. Overall, this study underscores the pivotal role of ACP and its poorly crystalline counterparts in arsenic retention through the dissolution-recrystallization mechanism
Effects of solvent extraction on pore structure properties and oil distribution in shales of alkaline lacustrine basins
No full textShale contains numerous nano-scale pores, whose pore structure property changes affect petroleum flow, complicating shale oil accumulation and exploration. Twelve shale samples from the Permian Fengcheng Formation in the Mahu Sag and the Permian Lucaogou Formation in the Jimusar Sag in northwestern China were analyzed to investigate the coupled oil distribution and pore structure in shales from alkaline lacustrine basins. Shale samples were comprehensively analyzed before and after solvent extraction using X-ray diffraction, total organic carbon measurement, Rock-Eval analyses, field emission-scanning electron microscopy, nitrogen physisorption (NP), and (ultra) small-angle X-ray scattering [(U)SAXS] to assess nanoscale pore structure (2-300 nm in diameter) and oil distribution. Solvent extraction increased total pore volume and specific surface area (SSA). However, the accessibility of nanoscale pores remains limited. Additionally, even after retained oil removal, (U) SAXS-derived total pore volumes are 1-10.4 times larger than NP-derived connected pore volumes. Complex variations in pore volume and SSA mainly result from the removal of extractable organic matter (EOM) and the refilling of small pores by organic matter. Despite the relatively small pore volume of mesopores (2-50 nm), the amount of EOM distribution in mesopores is comparable to that in macropores (50-300 nm); therefore, it is crucial not to overlook the retention capacity of mesopores for EOM. Macropores, particularly interparticle pores associated with quartz and feldspar, play a crucial role in oil mobility. The quantity and composition of EOM, along with other factors, can alter pore structure before and after solvent extraction and should be considered in evaluating the distribution and content of free oil
Molecular and carbon isotopic geochemistry of oils with different fluorescence color from the Upper Jurassic Qigu formation and oil accumulation process in Yongjin area, Junggar Basin in China
No full textThe Yongjin area, located in the middle of the Junggar Basin, is an important oil-producing region. Its major oilproducing formation is the Upper Jurassic Qigu Formation, which has experienced multiple oil-charging events that have resulted in oils with various fluorescent colors. However, the source of oils from the Qigu Formation is currently debated. As exploration and development progressed, the productivity of the Qigu Formation was observed to vary owing to oil viscosity differences. Conventional extraction methods can only be used to obtain a mixture of fluorescing oils of different colors, making it difficult to analyze the properties of oils that charge during different periods. Using microscopy to observe fluorescence the characteristics of oil in various samples were analyzed. Then, accelerated sequential extraction was used to separate the oils with different fluorescent colors (Groups I-IV). Through GC-MS (gas chromatography), GC-IRMS (gas chromatography-mass spectrometry), FT-IR (fourier transform infrared spectroscopy), and fluid inclusion observations and measurements, in conjunction with the geological context, the sources of oils from different charge periods and genesis of heavy oil were determined and the process of oil accumulation was reconstructed. Three stages of oil charging were identified: (1) During the Middle to Late Jurassic, low-mature and mature oil from the Lower Permian Fengcheng Formation and a low quantity of low-mature oil from the Middle Permian Lower Wuerhe Formation charged the Qigu Formation. These oils underwent notable biodegradation and oxidation, with some captured by inclusions (Group III) for preservation. (2) During the Late Cretaceous to Early Paleogene, mature oil from the Wuerhe Formation charged the Qigu Formation. This oil mixed with early oil that was not captured by the inclusions, resulting in the formation of black-brown fluorescing oil (Group IV) and yellow fluorescing inclusion oil (Group II). (3) From the Late Paleogene to the present, highly mature condensates from the Lower Wuerhe Formation charged the Qigu Formation. The oil mixed with early oil to generate yellow-brown (Group II) and blue-white (Group I) fluorescing oils. Low-mature and mature oil from the Fengcheng Formation charged the Jurassic reservoirs and underwent secondary alteration, whereas high-mature oil and gas did not. These oils likely predominantly accumulated in reservoirs between the Fengcheng and Lower Wuerhe formations. Although the Jurassic source rocks began to generate oil, this oil did not migrate upward to the Qigu Formation, indicating that the conventional and unconventional reservoirs under the Jurassic Qigu Formation have exploration potential
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
Compositions and Distributions of Secondary Organic Aerosols and Their Tracers over the Pearl River Estuary Region Influenced by Continental and Marine Air Masses
No full textThe compositions and distributions of monoterpenes, isoprene, aromatics and sesquiterpene SOA tracers (SOAM, SOAI, SOAA and SOAS, respectively) at an island site (Da Wan Shan Island, DWS) were investigated in the context of the influence of continental and marine air masses over the Pearl River Estuary (PRE) region in winter 2021. The sum concentration of SOA tracers was 6.2-132.8 ng m-3, with SOAM and SOAI as the main components in both continental (scenarios A1 and A2) and marine air masses (scenario A3), as well as their combination (scenario A4). The highest and lowest levels of SOAM were observed in A1 and A3, respectively, which were mainly related to the variations in meteorological conditions, precursor concentrations, and the degree of photochemical processes. Higher MBTCA/HGA (3-methyl-1,2,3-butanetricarboxylic acid/3-hydroxyglutaric acid) ratios suggested a less significant contribution from alpha-pinene to SOAM. The variations of SOAI in the different scenarios were associated with differences in relative humidity, particle acidity, and isoprene/NOx ratios. The respective highest and lowest concentrations of aromatics SOA tracers in A1 and A3 revealed the influence of anthropogenic precursors from upwind continental areas, which was confirmed by the correlation among biogenic and anthropogenic precursors. The results of the tracer-based-method suggested dominant contributions of SOAs from aromatics and monoterpenes, with the highest concentrations in A1. A WRF-Chem simulation revealed that the SOAs from the above precursors only contributed 12%-25% to the total SOA at DWS, while the spatial distributions of SOAs further highlighted that the abundance of SOAs over the PRE region in winter is highly associated with air masses transported from upwind continental areas
Distinct trophic transfer of rare earth elements in adjacent terrestrial and aquatic food webs
No full textGrowing demand and usage of rare earth elements (REEs) lead to significant pollution in wildlife, but trophic transfer of REEs in different food webs has not been well understood. In the present study, bioaccumulation and food web transfer of 16 REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Sc) were investigated in different terrestrial and aquatic species. Median concentrations of REEs in plant, invertebrate, fish, amphibian, reptile, bird, and vole samples were 488-6030, 296-2320, 123-598, 17.5-88.1, 88.0, 14.2-92.0, and 170 mu g/kg, respectively. The REE concentrations decreased as plants > invertebrates > fishes > amphibians and snakes > birds. The biomagnification factors (BMFs) and trophic biomagnification factors of most REEs were lower than 1, indicating trophic dilution of REEs. Most poikilotherms including fishes, amphibians, and snakes presented higher BMFs of REEs than homotherms including birds and voles (p 0.05) in terrestrial organisms, while REE concentrations were negatively correlated with delta N-15 (p 0.05) in aquatic organisms. The result implies diet source and trophic level as key factors affecting the cycling of REEs in terrestrial and aquatic food webs, respectively
Accumulation of lipophilic and proteinophilic halogenated organic pollutants (HOPs) in the different types of feathers of laying hens
No full textThis study investigated the bioaccumulation of halogenated organic pollutants (HOPs) in three types of feathers from laying hens through exposure experiments. The HOPs included lipophilic polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), as well as proteinophilic perfluoroalkyl carboxylic acids (PFCAs). Concentrations of PCBs, PBDEs, and short-chain PFCAs (8) showed no significant differences among primary, tail, and body feathers. The concentration order in the feathers was & sum;12PFCAs > & sum;7PBDEs > & sum;(13)PCBs, which was completely reversed by the exposure dose. The transfer rates (TRs) (concentration ratio of feather to serum) of PFCAs (0.11-6.8) were one order of magnitude higher than those (0.01-0.30) of PCBs and PBDEs. These results indicate that PFCAs preferentially accumulate in feathers compared to PBDEs and PCBs. TRs, regardless of whether they were lipophilic or proteinophilic HOPs, were significantly and positively correlated with the protein-water partition coefficient (log K-pw). Strong and significant correlations between feathers and inner tissues were primarily observed in body feathers. Egg-laying significantly affects PFCA accumulation in feathers and even distorts the actual exposure dose in hens; however, its impact on PCBs and PBDEs is limited. These findings provide crucial insights into HOP deposition in bird feathers
Light iron isotopes in high-silica granites record fluid evolution in magmatic-hydrothermal systems
No full textHigh-silica (SiO2 > 70 wt%) granites in continental collisional zones are crucial for understanding formation and evolution of the upper continental crust. Fluids released from felsic magmas can help drive the transition from magmatic to magmatic-hydrothermal systems in shallow magma chambers. However, the influence of these fluids on compositional variations and Fe isotope fractionation during the later stages of evolution of felsic magmas are unclear. In this contribution, we report stable Fe-Mg isotope compositions for the Paleocene Zhengga leucogranite pluton, part of the Gangdese batholith in southern Tibet. The pluton consists of both biotite granite and garnet-bearing two-mica granite, the latter of which contains zoned plagioclase and patchy K-feldspar that show fluid-mediated partial replacement textures, recording complicated magmatic and hydrothermal processes. Compared to high-silica granites worldwide (delta Fe-57 = +0.10 parts per thousand to +0.74 parts per thousand), all rocks from the Zhengga leucogranite pluton have light and variable delta Fe-57 values (+0.03 parts per thousand to +0.28 parts per thousand relative to IRMM-014), which display wave-shaped variations with progressive magmatic differentiation. However, their delta Mg-26 values (relative to DSM-3) decrease from -0.12 parts per thousand to -0.72 parts per thousand with increasing SiO2. The variable Fe and Mg isotope signatures of the Zhengga pluton can be best explained by a three-stage process, comprising initial fractional crystallization of biotite and magnetite, followed by deuteric fluid exsolution with decreasing temperatures and pressures, and final interaction between trapped fluids and residual melts in the highly crystalline magma mush. In combination with previously published Sr-Nd-Mo isotopes on the same samples, our new results suggest that fluid exsolution is required to elevate the delta Fe-57 of the felsic melts by up to 0.15 permil, but subsequent fluid-melt reaction reduces the Fe isotopes and leads to similar light-Fe isotope compositions of final residual melts to their primary magma. Therefore, the high-silica granites can be enriched in light Fe isotopes due to the effects of magmatic fluids, which make a significant contribution to the formation and evolution of upper continental crust
The key constraints on large-scale mineralization of Cenozoic potassic alkaline rocks in the Eastern Tibet-Sanjiang Belt
No full textDuring the Cenozoic Indo-Asian continental collision, a 1500km long, north-south oriented potassium-rich magmatic belt emerged in the Eastern Tibet-Sanjiang region. In this belt's northern sector, magmatic activity produced the extensive Yulong porphyry ore belt, while only sporadic deposits appeared in the central and southern sectors. This study employs SIMS water and oxygen isotope analyses, LA-ICP-MS trace element analyses, and Lu-Hf isotope analyses on primary zircon grains from three potassium-rich, barren rocks located in the middle and southern parts of the Sanjiang Belt. By comparing these with contemporaneous ore-forming porphyries in the Yulong ore belt, we delve into critical factors influencing large-scale porphyry mineralization of potassium-rich rocks in the Eastern Tibet-Sanjiang Belt. Our results reveal that zircon epsilon(Hf)(t) values (-6.00 to 2.70, average -2.94) from the barren rocks are significantly lower than those from fertile porphyries (-3.37 to 6.63, average 2.68), indicating that magmatic sources in the central and southern sectors have more ancient crustal material, while the northern sector's source is enriched with juvenile crustal material. Zircon grains of the three barren rocks display high H2O and OH-contents (average (734 +/- 184)x10(-6) and (14 +/- 4)apfux1000), akin to those from the giant porphyry deposit (average (640 +/- 213)x10(-6) and (12 +/- 5)apfux1000), and much higher than those from the medium-sized porphyry deposit (average (335 +/- 181)x10(-6) and (5.3 +/- 3)apfux1000) in the Yulong belt. Elevated zircon H2O contents in the barren rocks are primarily influenced by high pressures during zircon crystallization, which resulted from the regional high-pressure stress background and deep magmatic storage depths. These factors inhabited early fluid exsolution from the magmas, as indicated by the absence of fluid inclusions in zircons from the barren rocks, subsequently impeding metal extraction and porphyry mineralization. In summary, we propose that juvenile crust-rich sources, extensive regional stress, and early fluid exsolution of water-rich magmas collectively facilitated the large-scale porphyry mineralization of Cenozoic potassium-rich magmas in the Sanjiang Belt's northern segment. Additionally, the inputs of mantle-derived ore-rich potassic magmas controlled the porphyry mineralization and its spatial distribution in the belt's central and southern segments. Moreover, our approach suggests that zircon H2O is regulated by regional stress fields, storage depths, and magmatic water content. Zircons from different tectonic setting formed under different regional stresses, thus caution should be exercised when interpreting the zircon water contents