Geological evolution of the world class Gejiu Ore District, SW China: information from magmatism, mineralization and microanalysis studies

This study targets the magmatic rocks and Sn polymetallic ores in the Gejiu district, Yunnan Province, with the aim of resolving problems related to geodynamic setting, ore-forming processes and genesis of the mineralization in the study area. Systematic new SHRIMP/LA-ICP-MS U-Pb zircon dating results indicate that all the intrusive rocks in the Gejiu district are broadly coeval, ranging from 78 Ma to 85 Ma. Elemental and isotopic geochemistry of these rocks reveal that the granites in the Gejiu district experienced different degrees of fractionation, and they were mainly sourced from crustal materials with minor input from mantle-derived magma. The Jiasha gabbro derived from the partial melting of the ithospheric mantle with some contamination of crustal materials, and the mafic microgranular enclaves represent the results of magma mingling and mixing between the crustal- and mantle-derived magmas. Both alkaline rocks and mafic dykes were sourced from lithospheric mantle but experienced different evolutionary processes. Based on all of these concepts, I conclude that extensive interaction between mantle and crustal materials occurred in Gejiu district during Late Cretaceous. Metal zonation away from granitic intrusions, both in horizontal and vertical directions, are clearly developed in the Gejiu Sn polymetallic ore district, commonly from W-Be-Bi±Mo±Sn zone closest to the granites, out to Cu-Sn zone and then to a Pb-Zn zone. New data indicate that the homogenization temperature and salinity of the ore-forming fluid display continuous variations in different mineralization stages, which is a typical characteristic of the granite-related hydrothermal deposits. Sulfur isotopes of various sulfides, and hydrogen and oxygen isotopic compositions of different quartz generations exhibit obvious differences, which further supports varying conditions for mineralisation. Moreover, application of different geochronological methods on different minerals, which include mica Ar-Ar, molybdenum Re-Os and LA-ICP-MS cassiterite U-Pb dating, reveal that all the ore styles in the Gejiu district formed in a short time period, and mineralization and magmatism ages are contemporaneous. Above all, the large scale metallic accumulation and mineralization in Gejiu district are of hydrothermal origin. Iron isotope variations in ores from Gaosong deposit show primary sulfide ores enriched in lightest isotopes, while δ⁵⁷Fe values of oxidized ores and gossan ores becoming heavier progressively. Moreover, the range of δ⁵⁷Fe values of primary ores and oxidized ores are larger than that of gossan samples. Combined with the mineral association, this Fe isotope features suggest that Fe isotope compositions are affected by mineralogy, and it is the primary mechanism of the large Fe isotopic variations in the primary ores. On the whole, the systematic variations of Fe isotope composition show that Fe isotope studies have potential to constrain metal sources, ore genesis and evolutionary of hydrothermal deposit. Furthermore, CL textural results indicate distance between samples and granites may be one of the key factors controlling the cassiterite size and internal micro-texture variations. Fe, Ti and W are the most abundant elements in cassiterite, and variation of Zr/Hf ratios maybe caused by various tourmaline and fluorite contents. Cassiterite geochemical and textural variations may reflect the temperature, oxygen fugacity and redox station of ore forming fluids experienced significant changes during the tin mineralization process

Unique continuation property with partial information for two-dimensional anisotropic elasticity systems

In this paper, we establish a novel unique continuation property for two-dimensional anisotropic elasticity systems with partial information. More precisely, given a homogeneous elasticity system in a domain, we investigate the unique continuation by assuming only the vanishing of one component of the solution in a subdomain. Using the corresponding Riemann function, we prove that the solution vanishes in the whole domain provided that the other component vanishes at one point up to its second derivatives. Further, we construct several examples showing the possibility of further reducing the additional information of the other component. This result possesses remarkable significance in both theoretical and practical aspects because the required data is almost halved for the unique determination of the whole solution.Comment: 14 pages, 1 figur

Geodynamic setting of Late Cretaceous Sn–W mineralization in southeastern Yunnan and northeastern Vietnam

The Sn–W mineralization in SE Yunnan Province, China and NE Vietnam shares many similarities. Through comparing the geological and geochronological data, we suggest the Sn–W deposits and the associate igneous rocks in the region represent one regional magmatic-mineralization event. To explore the geodynamic setting of these mineralization and magmatic activities, a geochronological dataset in the regions has been presented, containing data of this study and previously published. The dataset shows that the Late Cretaceous magmatic–mineralization–metamorphic activities widely distribute along the eastern Asian continental margin. Existing studies support that this is the product of the subduction of the Palaeo-Pacific Plate beneath the Eurasian continent, which probably formed under an Andean-type active continental margin setting. According to the exhibited data, we preliminarily conclude that the late Cretaceous magmatic and Sn–W mineralization activities in the southeast Yunnan and northeast Vietnam region is one part of this subduction activities and should have formed under the same geodynamic setting

Centimeter-deep tissue fluorescence microscopic imaging with high signal-to-noise ratio and picomole sensitivity

Fluorescence microscopic imaging in centimeter-deep tissue has been highly sought-after for many years because much interesting in vivo micro-information, such as microcirculation, tumor angiogenesis, and metastasis, may deeply locate in tissue. In this study, for the first time this goal has been achieved in 3-centimeter deep tissue with high signal-to-noise ratio (SNR) and picomole sensitivity under radiation safety thresholds. These results are demonstrated not only in tissue-mimic phantoms but also in actual tissues, such as porcine muscle, ex vivo mouse liver, ex vivo spleen, and in vivo mouse tissue. These results are achieved based on three unique technologies: excellent near infrared ultrasound-switchable fluorescence (USF) contrast agents, a sensitive USF imaging system, and an effective correlation method. Multiplex USF fluorescence imaging is also achieved. It is useful to simultaneously image multiple targets and observe their interactions. This work opens the door for future studies of centimeter-deep tissue fluorescence microscopic imaging

GmWRKY16 Enhances Drought and Salt Tolerance Through an ABA-Mediated Pathway in Arabidopsis thaliana

The WRKY transcription factors (TFs) are one of the largest families of TFs in plants and play multiple roles in plant development and stress response. In the present study, GmWRKY16 encoding a WRKY transcription factor in soybean was functionally characterized in Arabidopsis. GmWRKY16 is a nuclear protein that contains a highly conserved WRKY domain and a C2H2 zinc-finger structure, and has the characteristics of transcriptional activation ability, presenting a constitutive expression pattern with relative expression levels of over fourfold in the old leaves, flowers, seeds and roots of soybean. The results of quantitative real time polymerase chain reaction (qRT-PCR) showed that GmWRKY16 could be induced by salt, alkali, ABA, drought and PEG-6000. As compared with the control, overexpression of GmWRKY16 in Arabidopsis increased the seed germination rate and root growth of seedlings in transgenic lines under higher concentrations of mannitol, NaCl and ABA. In the meantime, GmWRKY16 transgenic lines showed over 75% survival rate after rehydration and enhanced Arabidopsis tolerance to salt and drought with higher proline and lower MDA accumulation, less water loss of the detached leaves, and accumulated more endogenous ABA than the control under stress conditions. Further studies showed that AtWRKY8, KIN1, and RD29A were induced in GmWRKY16 transgenic plants under NaCl treatment. The expressions of the ABA biosynthesis gene (NCED3), signaling genes (ABI1, ABI2, ABI4, and ABI5), responsive genes (RD29A, COR15A, COR15B, and RD22) and stress-related marker genes (KIN1, LEA14, LEA76, and CER3) were regulated in transgenic lines under drought stress. In summary, these results suggest that GmWRKY16 as a WRKY TF may promote tolerance to drought and salt stresses through an ABA-mediated pathway

Impact of intercropping on the coupling between soil microbial community structure, activity, and nutrient-use efficiencies

Sugarcane-soybean intercropping has been widely used to control disease and improve nutrition in the field. However, the response of the soil microbial community diversity and structure to intercropping is not well understood. Since microbial diversity corresponds to soil quality and plant health, a pot experiment was conducted with sugarcane intercropped with soybean. Rhizosphere soil was collected 40 days after sowing, and MiSeq sequencing was utilized to analyze the soil microbial community diversity and composition. Soil columns were used to assess the influence of intercropping on soil microbial activity (soil respiration and carbon-use efficiency: nitrogen-use efficiency ratio). PICRUSt and FUNGuild analysis were conducted to predict microbial functional profiling. Our results showed that intercropping decreased pH by approximately 8.9% and enhanced the soil organic carbon, dissolved organic carbon, and available nitrogen (N) by 5.5%, 13.4%, and 10.0%, respectively. These changes in physicochemical properties corresponded to increased microbial diversity and shifts in soil microbial communities. Microbial community correlated significantly (p < 0.05) with soil respiration rates and nutrient use efficiency. Furthermore, intercropping influenced microbial functions, such as carbon fixation pathways in prokaryotes, citrate cycle (TCA cycle) of bacteria and wood saprotrophs of fungi. These overrepresented functions might accelerate nutrient conversion and control phytopathogens in soil