凤凰山矿田成矿地质体三维结构与控矿地质因素分析

安徽铜陵凤凰山铜矿正面临资源保有程度严重不足的问题,建立凤凰山矿田成矿地质体三维结构和控矿地质因素模型,开展矿田深部隐伏矿体立体定位预测具有重要的现实意义.凤凰山矿田矿床矿体的定位主要受接触带和断裂构造的复合控制,新屋里岩体与围岩呈侵入接触,局部地段超覆于围岩之上,接触带的形态和产状控制了矿体的空间分布.在分析矿田地质...     

Influence of phosphate on the oxidation kinetics of nanomolar Fe(II) in aqueous solution at circumneutral pH

The oxygenation kinetics of nanomolar concentrations of Fe(II) in aqueous solution have been studied in the absence and presence of millimolar concentrations of phosphate over the pH range 6.0-7.8. At each phosphate concentration investigated, the overall oxidation rate constant varied linearly with pH, and increased with increasing phosphate concentration. A model based on equilibrium speciation of Fe(II) was found to satisfactorily explain the results obtained. From this model, the rate constants for oxygenation of the Fe(II)-phosphate species FeH₂PO₄⁺, FeHPO₄ and FePO₄⁻ have been determined for the first time. FePO₄⁻ was found to be the most kinetically reactive species at circumneutral pH with an estimated oxygenation rate constant of (2.2 ± 0.2) × 10 M⁻¹ s⁻¹. FeH₂PO₄⁺ and FeHPO₄ were found to be less reactive with oxygen, with rate constants of (3.2 ± 2) × 10⁻² M⁻¹ s⁻¹ and (1.2 ± 0.8) × 10⁻¹ M⁻¹ s⁻¹, respectively.     

乌鲁木齐河流域普通民众对冰冻圈变化的感知及适应性对策选择

基于乌鲁木齐河流域普通民众对气候变化及冰冻圈变化感知情况的问卷调查,结合有关监测研究结果,分析了普通民众对流域气候变化及冰冻圈变化的感知情况,探讨了环境变化对流域水资源和农业生产的可能影响.普通民众对气候变化和冰冻圈变化的感知基本与科学监测事实相符.对气候变化和冰冻圈变化条件下普通民众对水资源紧缺的适应措施的分析发现:...     

攀枝花市区5-7月人体舒适度变化趋势研究

选用攀枝花市区1977-2009年5-7月逐日平均气温、平均相对湿度和平均风速资料,计算擎枝花市区的人体舒适度指数,并利用线性趋势系数、多项式以及MK突变检验等方法分析攀枝花市区的舒适程度和舒适度指数变化规律.结果表明:攀枝花市区舒适度指数绝大多数处于5～6级,占到总统计天数的96.9％;攀枝花市区舒适度指数5级、6级...     

Review of geology, alteration and origin of iron oxide–apatite deposits in the Cretaceous Ningwu basin, Lower Yangtze River Valley, eastern China: Implications for ore genesis and geodynamic setting

In the Cretaceous Ningwu volcano-sedimentary basin in the Yangtze River Valley metallogenic belt, eastern China, there are three areas with a dense distribution of magnetite or hematite deposits: the Meishan deposit in the north; Washan, Nanshan and Taocun deposits in the center; and the Zhongjiu and Gushan deposits in the south. The mineralization in the Ningwu basin is associated mainly with subvolcanic intrusions, consisting of gabbro–diorite porphyry and/or gabbro–diorite. Alteration zoning of these deposits is pronounced, and includes: (1) an upper light colored zone of argillic, kaolinite, silica, carbonate and pyritic alteration (2) a middle dark colored zone of diopside, fluorapatite–magnetite, phlogopite, and garnet with fluorapatite–magnetite; (3) a lower light colored zone of extensive albitic alteration. However, at the Gushan iron deposit, the lower light colored zone and the middle dark colored zone are absent, whereas the principal alteration is represented by silicification, kaolinization, and carbonatization.The iron oxide–apatite deposits in the Ningwu basin are typically magmatic–metasomatic origin and are similar to the Kiruna-type deposits in Scandinavia, particularly with respect to mineral assemblages, fabric and structure of the iron ores, occurrence of the orebodies and wall rock alteration. The iron oxide–apatite deposits of the Ningwu basin contain magnetite and/or hematite, with diopside or actinolite and apatite gangue. They were formed in a rift or extensional environment and the mineralization is associated with alkaline magmatism. The time interval between magmatism and related mineralization is very short.     

Timing of skarn deposit formation of the Tonglushan ore district,southeastern Hubei Province,Middle–Lower Yangtze River Valley metallogenic belt and its implications

The Tonglushan ore district in the Middle–Lower Yangtze River Valley metallogenic belt includes the Tonglushan Cu–Fe, the Jiguanzui Au–Cu, and the Taohuazui Au–Cu skarn deposits. They are characterized by NE-striking ore bodies and hosted at the contact of Triassic carbonate rocks and Late Mesozoic granitoid deposits. New Sensitive High-Resolution Ion Microprobe (SHRIMP) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA–ICP-MS) zircon U–Pb, molybdenite Re–Os, and phlogopite ⁴⁰Ar–³⁹Ar ages indicate that these skarn deposits formed between 140.3 ± 1.1 and 137.3 ± 2.4 Ma. These dates are identical to the zircon U–Pb ages for host quartz diorites ranging from 140 ± 2 to 139 ± 1 Ma. These results confirm that both skarn mineralization and related intrusions were initiated during the Early Cretaceous. The high rhenium contents (261.4–1152 μg/g) of molybdenites indicate that a metasomatic mantle fluid was involved in the ore-forming process of these skarn ore systems. This conclusion is consistent with previously published constraints from sulfur, deuterium, and oxygen isotope compositions, and the geochemical signatures, and Sr–Nd isotopic data of the mineralization-hosting intrusions. Geological and geochronological evidence demonstrates that there were two igneous events in the Tonglushan ore district. The first resulted in the emplacement of quartz diorite during the Early Cretaceous (140 ± 2 to 139 ± 1 Ma), and the second is characterized by the eruption of volcanic rocks during the mid-Early Cretaceous (130 ± 2 to 124 ± 2 Ma). The former is spatially, temporally and genetically associated with skarn gold-bearing mineralization (140.3 ± 1.1 to 137.3 ± 2.4 Ma). The recognition of these two igneous events invalidates previous models that proposed continuous magmatism and associated mineral deposits in the Middle–Lower Yangtze River Valley metallogenic belt.     

Porphyry Cu–Au–Mo–epithermal Ag–Pb–Zn–distal hydrothermal Au deposits in the Dexing area, Jiangxi province, East China—A linked ore system

Based on previous studies and detailed field investigations of the Dexing porphyry copper deposit, the Yinshan Ag-Pb-Zn deposit and the Jinshan shear zone – hosted gold deposit in the Dele Jurassic volcanic basin, in the northeastern Jiangxi province, East China, we propose that the three deposits share spatial, temporal and genetic relationships and belong to the same metallogenic system. Dexing is a typical porphyry Cu–Au–Mo deposit in which both ore-forming fluid and metals are derived from the granite porphyry. The Yinshan deposit consists of a porphyry copper ore located in the cupola of a quartz porphyry stock, in the lower part, and Ag–Pb–Zn ore veins in the upper part. The hydrothermal fluids were mainly derived from the magma in the early stages of the mineralizing event and became mixed with meteoric waters in the late stages. Its ore metals are magma-derived. Both the Jinshan base metal veins and the Hamashi, Dongjie and Naikeng quartz vein-type gold deposit are hosted by brittle–ductile structures, which are distal in relation to the porphyry intrusions and were formed by mixed magmatic fluids and meteoric water, whereas the gold was mainly leached from the country rocks (Mesoproterozoic Shuangqiaoshan Group phyllite and schist). The deposits show a distinct spatial arrangement from porphyry Cu, to epithermal Ag–Pb–Zn and distal Au. We suggest a porphyry–epithermal–distal vein ore system model for this group of genetically related mineral deposits. They were formed in a back-arc setting in a Middle Jurassic active continental margin, with magmas derived from the subducted slab.     

Mesozoic metallogeny in East China and corresponding geodynamic settings — An introduction to the special issue

The giant East China Mesozoic metallogenic province hosts some of the World’s largest resources of tungsten, tin, molybdenum, antimony and bismuth. Ores of gold, silver, mercury, lead, zinc, copper, uranium and iron are also of major importance. The province and its constituent metallogenic belts or regions (South China; Middle–Lower Yangtze River Valley; East Qinling–Dabie; Interior of North China Craton; Yan-Liao and North-east China) are the products of several pulses of igneous activity and mineralisation between ~240 and ~80 Ma. Each successive stage has produced a distinctive suite of deposits that can be readily related to the geodynamic evolution of the region during the Mesozoic. This geodynamic evolution is linked to a complex series of tectonic events, involving far-field-subduction, plate collisions, crustal thickening, post-collision collapse and rifting.     

Single-crystal EPR and DFT studies of a [BO<Subscript>4</Subscript>]<Superscript>0</Superscript> center in datolite: electronic structure,formation mechanism and implications

A natural datolite CaBSiO₄(OH) (Bergen Hill, NJ, USA), before and after gamma-ray irradiation (up to ~70 kGy), has been investigated by single-crystal and powder electron paramagnetic resonance (EPR) spectroscopy from 10 to 295 K. EPR spectra of gamma-ray-irradiated datolite show the presence of a boron-associated oxygen hole center (BOHC) and an atomic hydrogen center (H⁰), both of which grow with increasing radiation dose. The principal g and A(¹¹B) values of the BOHC at 10 K are: g ₁ = 2.04817(3), g ₂ = 2.01179(2), g ₃ = 2.00310(2), A ₁ = −0.401(7) mT, A ₂ = −0.906(2) mT, A ₃ = −0.985(2) mT, with the orientations of the g ₁ and A ₁ axes approximately along the B–OH bond direction. These experimental results suggest that the BOHC represents hole trapping on the hydroxyl oxygen atom after the removal of the proton (i.e. a [BO₄]⁰ center): via a reaction O₃BOH → O₃BO^· + H⁰, where · denotes the unpaired electron. Density functional theory (DFT) calculations (CRYSTAL06, B3PW, all-electron basis sets, and 1 × 2 × 2 supercell) support the proposed structural model and yield the following ¹¹B hyperfine coupling constants: A ₁ = −0.429 mT, A ₂ = −0.901 mT, A ₃ = −0.954 mT, in excellent agreement with the experimental results. The [BO₄]⁰ center undergoes the onset of thermal decay at ~200°C and is completely annealed out at 375°C but can be restored readily by gamma-ray irradiation. Isothermal annealing experiments show that the [BO₄]⁰ center exhibits a second-order thermal decay with an activation energy of 0.96 eV. The confirmation of the [BO₄]⁰ center (and its formation from the O₃BOH precursor) in datolite has implications for not only understanding of BOHCs in alkali borosilicate glasses but also their applications to nuclear waste disposal.     

梨树断陷秦家屯-秦东断裂带构造特征及形成演化

本文研究认为,秦家屯断裂主要由两条右列侧接断裂组成,形成时间较早,主要活动期为早白垩世早期,对火石岭组地层沉积厚度具有明显的控制作用。秦东断裂发育的时间相对较晚,主要活动期应在登娄库期-泉头期早期,具有较明显的走滑特征。该断裂从早期已形成的两条秦家屯断裂之间切过。这两条断裂对该构造部位油气的运移和聚集具有重要控制作用。