Search

The Zhangxuan district in North China, also known as Northwestern Hebei "Golden Triangle," develops many intrusion-hosted lode-gold deposits. The Dongping gold deposit in the Zhangxuan district is well known for its unique hosting of rocks and ore mineral assemblages. Magnetite and pyrite are common minerals that widely exist in ores of the Dongping deposit. To get a better understanding of the evolution of the ore-forming fluids responsible for mineralization, we report on an integrated study on the electron microprobe analysis (EMPA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis of magnetite and pyrite from the deposit. The major results are as follows: The magnetite grains from the Dongping deposit show a variable content of major and trace elements such as Ti, Al, Si, Fe, Mn, Cr, Na, V, and Co, and the majority of the magnetite contain low Ti contents, revealing potential properties of hydrothermal magnetite. The flat time-resolved signals of LA-ICP-MS imply that the majority of trace elements in magnetite exist in the form of isomorphism, except for some incompatible trace elements. Magnetites from the Dongping deposit have compositional characteristics of hydrothermal origins, and the genetic discriminant diagrams of Ti–V, Ti–Ni/Cr or (Ca + Al + Mn)–(Ti + V) show that they may be originated from magma differentiated hydrothermal solutions. Co, Ni in pyrite from Dongping mainly enter the lattice via isomorphism, and Cu, Zn, Ag, W, Sn, Au, Pb, and Bi are partitioned into pyrite as micro/nano- mineral inclusions. The Co, Ni content, and the Ni/Co ratios, indicated that the temperature of the ore-forming fluids has decreased from Py-1 to Py-2, and the enrichment of Au in Py-2 may be related to the cooling and boiling of the fluids. [ABSTRACT FROM AUTHOR]

The Sadaigoumen Mo deposit is a typical porphyry‐type deposit which is located in the northern margin of the North China Craton (NCC), China. Mineralization of the deposit mainly occurs as finely disseminated within the host granites. To get a better understanding of the ore‐forming process of the deposit and the genetic link between mineralization and host igneous rocks, we report LA‐ICP‐MS zircon U–Pb and whole‐rock major and trace elements data from the magmatic rocks which are exposed in the mining area. LA‐ICP‐MS U–Pb analyses yield weighed mean ages of 239.5 ± 0.58 Ma for alkali‐feldspar granites and 1872.8 ± 5.1 Ma for porphyritic granodiorite. The porphyritic granodiorite, which was previously considered to be part of the Hongqiyingzi Group, is redefined as Palaeoproterozoic highly fractionated I‐type granites: (1) They have high contents of SiO2 (69.57–72.21 wt.%) and Al2O3 (13.24–13.90 wt.%) and high Na2O + K2O (up to 7.1 wt.%) and FeOT/MgO values (6.7 to 7.7), and (2) significant depletion of Eu, Sr, Ba, P, and Ti elements; (3) compared with typical A‐type granites, they have lower Ga (around 20.5 ppm) and 10000 × Ga/Al values (around 2.8); the Triassic alkali‐feldspar granite samples also show highly fractionated I‐type geochemical signatures with high Na2O + K2O (8.40–8.50 wt.%), FeO*/MgO (12.67–13.49), and Ga/Al (2.58–2.81) ratios. The higher ∑REE values (>199.69 ppm) and depletions of Nb, Ta, and Ba make it different from typical A‐type granites. By comparative analysis of geochemical data, we believed that the ca. 1872.8 Ma porphyritic granodiorite formed in a tectonic environment resembling that of magmatic arc granites and the ca. 239.5 Ma alkali‐feldspar granite formed in syn‐collisional settings which is related to closure of Palaeo‐Asian Ocean. Our new data, combined with previous studies, allow us to speculate that the Triassic alkali‐feldspar granite is directly related to the Mo mineralization in this area. [ABSTRACT FROM AUTHOR]

The Dacaoping and Sadaigoumen Mo deposits were recently discovered along the northern margin of the North China Craton. The newly determined Re–Os isochronous age of molybdenite from the Dacaoping Mo deposit is ca. 147 Ma, and the Re–Os model age of molybdenite from the Sadaigoumen Mo deposit is ca. 248 Ma, which represents two of their respective mineralization stages. Combined with previous data, we suggest four phases of mineralization in the Dacaoping and Sabagaogoumen Mo deposits; these phases are 248, 236, 147, and 140 Ma. The Early Triassic monzogranite and Early Cretaceous granodiorite in the Dacaoping Mo deposit and the Middle Triassic monzogranite in the Sabagaogoumen Mo deposit are I‐type granite with similar geochemical characteristics. The Triassic granites formed in a collisional–post‐collisional setting between the North China Plate and the Siberian Plate, and the Cretaceous granodiorite formed from the rapid thinning of the lithosphere. The partial melting of the lower crust is the main reason for their formation, and small amounts of mantle‐derived components were added. Compared to other Mo deposits in the region, we can further divide these Mo deposits into three phases, namely, (a) Triassic (ca. 248–223 Ma), (b) Early–Middle Jurassic (ca. 187–165 Ma), and (c) Late Jurassic–Early Cretaceous (ca. 155–130 Ma), which are consistent with the times of magmatic activity. These activities occurred during the collision and post‐collision between the North China Plate and the Siberian Plate after the Paleo‐Asian Ocean's closure, intracontinental orogeny, and rapid thinning of the lithosphere, respectively. [ABSTRACT FROM AUTHOR]

The Southern Great Xing'an Range (SGXR) hosts a number of Early Cretaceous Sn and associated metal deposits, which can be divided into three principal types according to their geological characteristics: skarn type deposits, porphyry type deposits and hydrothermal vein type deposits. Fluid inclusion assemblages of different types of deposits are quite different, which represent the complexities of metallogenic process and formation mechanism. CH4 and CO2 have been detected in fluid inclusions from some of deposits, indicating that the ore‐forming fluids are affected by materials of Permian strata. Hydrogen and oxygen isotope data from ore minerals and associated gangue minerals indicate that the initial ore fluids were dominated by magmatic waters, some of which had clearly exchanged oxygen with wall rocks during their passage through the strata. The narrow range for the δ34S values presumably reflects the corresponding uniformity of the ore forming fluids, and these δ34S values have been interpreted to reflect magmatic sources for the sulfur. The comparation between lead isotope ratios of ore minerals and different geological units' also reveals that deeply seated magma has been a significant source of lead in the ores. [ABSTRACT FROM AUTHOR]

The Zhuanshanzi gold deposit lies in the eastern section of the Xingmeng orogenic belt and the northern section of the Chifeng‐Chaoyang gold belt. The gold veins are strictly controlled by a NW‐oriented shear fault zone. Quartz veins and altered tectonic rock‐type gold veins are the main vein types. The deposits can be divided into four mineralization stages, and the second and third metallogenic stages are the main metallogenic stages. In this paper, based on the detailed field geological surveys, an analysis of the orebody and ore characteristics, microtemperature measurement of fluid inclusions, the Laser Raman spectrum of the inclusions, determination of CHOSPb isotopic geochemical characteristics, and so on were carried out to explore the origin of the ore‐forming fluids, ore‐forming materials, and the genesis of the deposits. The results show that the fluid inclusions can be divided into four types: type I – gas–liquid two‐phase inclusions; type II – gas‐rich inclusions; type III– liquid inclusions; and type IV – CO2‐containing three‐phase inclusions. However, they are dominated by type Ib – gas liquid inclusions and type IV – three‐phase inclusions containing CO2. The gas compositions are mainly H2O and CO2, indicating that the metallogenic system is a CO2H2ONaCl system. The homogenization temperature of the ore‐forming fluid evolved from a middle temperature to a low temperature, and the temperature of the fluid was further reduced due to meteoric water mixing during the late stage, as well as a lack of CO2 components, and eventually evolved into a simple NaClH2O hydrothermal system. CHOSPb isotope research proved that the ore‐forming fluids are mainly magmatic water during the early stage, with abundant meteoric water mixed in during the late stage. Ore‐forming materials originated mostly from hypomagma and were possibly influenced by the surrounding rocks, suggesting that the ore‐forming materials were mainly magmatic hydrothermal deposits, with a small amount of crustal component. The fluid immiscibility and the CO2 and CH4 gases in the fluids played an active and important role in the precipitation and enrichment of Au during different metallogenic stages. The deposit is considered a magmatic hydrothermal deposit of middle–low temperature. The gold mine is a medium‐ and low‐temperature magmatic hydrothermal deposit. The ore‐forming fluid evolved from a CO2H2ONaCl system to a simple NaClH2O hydrothermal system later. The fluid immiscibility and the CO2 and CH4 gases in the fluids played an active and important role in the precipitation and enrichment of Au during the different metallogenic stages. [ABSTRACT FROM AUTHOR]

Earthworms are excellent indicators of landscape fragmentation due to their widespread distribution and poor dispersal abilities over water. Based on field studies conducted in the Shandong and Liaodong peninsulas and their associated islands during summer 2009, we analysed the genetic variation of Drawida japonica Michaelsen, 1892 (Oligochaeta, Moniligastridae) using DNA sequences of the 16S and 28S ribosomal genes in samples obtained from 13 localities, 12 of which were islands, one artificially connected to the mainland by man (Yangma SC). We identified 55 haplotypes among 79 samples, based on 1094 bp, including 47 unique haplotypes. The phylogenetic tree topologies showed two distinct clades. A multiple-apex Poisson distribution using a mismatch analysis of nucleotides was also detected. Results of a Tajima D neutral test were not significant (p > 0.05). Genetic divergence among populations was much larger than within populations. A positive relationship between genetic diversity and island area was revealed, but no significant correlation between genetic diversity and distance to the nearest larger landmass was found. These results indicate that the intraspecific genetic diversity of D. japonica has been influenced by geographic isolation (i.e. island habitat). Passive transport via anthropogenic activities or nonhuman vertebrates (birds or mammals) may also play a key role in dispersal. [ABSTRACT FROM PUBLISHER]

The Huangyangshan alkaline pluton is located within the southern part of the Eastern Junggar orogenic belt in Xinjiang Province, and forms part of the Kalamaili alkaline granite belt. The pluton hosts the Huangyangshan super-large graphite deposit, which develops unique spherical structure and coexists with metal sulfides. This study examines the genetic relationship between the alkaline magmatism that formed the pluton and the graphite mineralization using zircon LA–ICP–MS U–Pb dating, geochemical analysis for representative rock types in the Huangyangshan pluton, and new Re–Os isotope dating for the graphite in the Huangyangshan graphite deposit. Zircons from medium-grained arfvedsonite granite, medium–fine-grained amphibole granite, medium-grained biotite granite, and fine-grained biotite granite phases of the Huangyangshan pluton yield weighted mean U–Pb ages of 322.7 ± 4.5, 318.3 ± 4.0, 303.9 ± 2.1, and 301.1 ± 3.6 Ma, respectively, indicating that all of the granite phases were emplaced during the Late Carboniferous over a period of around 20 Myr. Six graphite samples from the deposit yield a Re–Os isochron age of 332 ± 53 Ma. Combining these ages with the genetic relationship between the graphite mineralization and magmatism in the study area and the relatively large uncertainty on the Re–Os isochron age for the graphite suggests that the mineralization formed at ca. 320 Ma. The graphite samples yield an initial 187Os/188Os value of 0.38 ± 0.2, indicative of carbon derived from a mixture of organic and mantle-derived sources. The different granite phases in the Huangyangshan pluton are geochemically similar with relatively high SiO 2 (75.6–78.2 wt%) and Na 2 O + K 2 O (8.01–9.04 wt%) and relatively low CaO (0.18–0.7 wt%), MgO (0.06%–0.13 wt%) and Fe 2 O 3 (T Fe2O3 = 1.08–2.06 wt%) contents. The granites are enriched in light rare earth elements (LREE), large-ion lithophile elements (LILEs) (e.g. Rb, Th, and K), and high field strength elements (HFSEs) (e.g. Zr and Hf), depleted in heavy rare earth elements (HREEs), and have negative Ba, Sr, P, Ti, and Eu anomalies. These geochemical characteristics are indicative of derivation from juvenile basaltic oceanic crustal materials in the lower crust. This suggests that the Huangyangshan pluton formed from magmas generated by partial melting caused by mantle-derived magma underplating, with the magmas then undergoing mixing, separation, and significant fractional crystallization. Diorite enclaves within the granites have weaker trace element anomalies that are indicative of magma mixing. In addition, the mantle-derived intermediate–basic end-member involved in the magma mixing is likely one of the important carriers of carbon and metal. In summary, the Late Carboniferous Huangyangshan pluton and its associated graphite mineralization formed in a post-collision extensional tectonic setting in the Kalamaili area. [ABSTRACT FROM AUTHOR]

Abstract: A 6-month study was carried out at the China Agricultural University greenhouse to determine the effects of organic amendments (fertilizer) on the abundance and community composition of soil organisms in saline alkali soils. Treatments with two different organic amendments (cattle dung and vermicompost) were compared with treatments with a chemical fertilizer. Results showed increased soil nutrient content with both organic amendments and chemical fertilizers without significant alteration of soil pH or electrical conductivity. Compared with the chemical fertilizer treatment, organic amendments led to higher levels of soil microbial biomass, nematode abundance, and mite abundance. The increased level of soil organisms could be attributed to the increased level of soil organic matter, although no significant effect was observed on plant cultivation. Soil organism community composition varied among the different organic amendment treatments. The findings of this study suggest that the application of an organic amendment to saline alkali soil may directly or indirectly improve the growth of salt-tolerant plants by elevating the soil nutrient content and the abundance of soil organisms. [Copyright &y& Elsevier]

Abstract: Terrestrial earthworm variously reported from China number amounts to 298 species with 84 of these, or 28%, non-natives for which 67% are Asiatic Megascolecidae and 22.6% are Lumbricidae of Holarctic origin. All the 298 species belong to 8 families and 27 genera. Among of them, 59 species are new species or new records after 1992. Using SPSS 12.0 to establish the distributional relationships among genera and species, we could draw a conclusion that the numbers and abundances of species in the South of China were more abundant and richer than that in the North of China. Megascolecidae was dominant in China, amounting to 243 species. The numbers of wide-range species and wide-range genera were 11 and 6, respectively, and about 3.7% of total species and 22.2% of total genera. Most species only are distributed in one or two Provinces, which indicates most genera and species have a bias to limitation of distribution. That Lumbricidae distributes in Oriental region still could not define its origin. It is not clear that the origin of earthworms among the seven Provinces, but the species abundance in Oriental region is much richer than that in Palaearctic region. Molecular (DNA and RNA) methods may solve the problems of identification and origin. [Copyright &y& Elsevier]