安徽沙溪斑岩型铜金矿床成岩序列及成岩成矿年代学研究

沙溪矿床是长江中下游成矿带中典型的斑岩型铜金矿床,位于庐枞盆地北外缘、郯庐断裂内,矿床成岩成矿时代确定对该矿床成因研究及区域成矿规律的认识具有重要意义。在详细野外地质工作的基础上,采集沙溪矿床与成矿有关的主要岩浆岩样品(粗斑闪长玢岩、黑云母石英闪长玢岩、中斑石英闪长玢岩、细斑石英闪长玢岩和闪长玢岩)和与黄铜矿密切共生的辉钼矿,分别利用Cameca、LA-ICP-MS U-Pb和Re-Os同位素定年方法,获得矿床内主要岩浆岩的成岩年龄(130.60±0.97Ma、129.30±1.00Ma、127.10±1.50Ma、129.46±0.97Ma和126.7±2.1Ma)以及成矿年龄(130.0±1.0Ma),并重新厘定了沙溪岩体从早到晚岩浆的侵位序列。通过区域对比,提出长江中下游存在两阶段斑岩型铜金矿化,沙溪矿床为长江中下游成矿带第二阶段形成的斑岩型矿床,沙溪矿床的成岩成矿作用既不同于庐枞盆地,也不同于断隆区第一阶段的斑岩矿床,而是受郯庐断裂和长江断裂动力学演化联合作用的产物。     

Influences of mulching durations on soil erosion and nutrient losses in a peanut (Arachis hypogaea)-cultivated land

Plastic film mulching is widely employed to improve crop yields. Mulching for the entire crop growth period is a widespread practice. However, a shorter plastic film mulching duration is suggested for obtaining larger grain yield recently. To quantify the effects of plastic film mulching durations on soil erosion and nutrient losses, a three-treatment experiment with three replicates was constructed in field. The designed treatments were control (M0, non-mulched treatment), mulching from sowing to the end of the peanut pod-setting stage (M1) and pod-filling stage (M2). Plastic film mulching significantly increased the mean runoff and sediment yield. With film mulching, the mean runoff and soil losses among M1 and M2 treatments had no significant difference, and significantly larger than that in M0 treatment. After mulching removing, there were no significant differences between the mean runoff and soil losses of M0 and M1 treatments. Compared with the M2 treatment, the M0 treatment had significantly reduced mean runoff and soil losses of all the events. Non-mulching increased the total nitrogen (TN) and total phosphorus (TP) losses. The M0 treatment had the highest TN (23.0 mg m^?2) and TP (3.02 mg m^?2) losses in the three treatments. The M2 treatment significantly reduced the TN and TP losses. In conclusion, mulching from sowing to the end of pod-setting stage was suggested as the appropriate choice for the largest yield and less soil erosion. But, some soil conservation measurements should be taken in furrow areas to effectively reduce soil erosion, under the condition of film mulching.     

Late cretaceous radiolarians and age of flyschoid sediments in the Struganik section (Western Serbia)

The succession of radiolarian assemblages in the Struganik section of western Serbia is described for the first time. The following radiolarian beds are defined in carbonate flyschoid sequences represented by thin-platy limestones with calcarenite and bentonite clay intercalations (from the base upward): Theocampe urna-Dictyomitra koslovae (presumably lower Santonian); Afens perapediensis-Clathropyrgus titthium (presumably uppermost lower Santonian-basal upper Santonian); Alievium gallowayi-Crucella espartoensis (upper Santonian). The examined assemblages are characterized by high taxonomic diversity. The upper Santonian Alievium gallowayi-Crucella espartoensis Assemblage exhibits significant similarity with the coeval radiolarian assemblage of the Crimean Mountains (Ukraine). Archaeocenosphaera (?) karamatai sp. nov. is described.     

On strategy of the upcoming exploration phase in the North Caspian petroleum province

This paper gives a review of oil and gas resource potential of the North Caspian petroleum province. A new potential for finding several giants and large-size discoveries exists, respectively, in the presalt and postsalt sequences. Recommendations for future directions in exploration targeting at postsalt deposits (Upper Permian–Triassic and Jurassic–Paleogene petroleum systems) are given. It is emphasized that, given adequate exploration techniques, the postsalt sequence may provide stable and commercial production for decades. Most of the prospects are located within nonlicensed area. Therefore, the future exploration activity will have to be implemented through special-purpose governmental projects, namely, state-funded integrated projects aiming at investigation of the individual petroleum regions and zones.     

The κ-Cygnid Meteor Shower and Its Relationship with Near-Earth Asteroids

Astronomy Reports - This study is focused on the relationships between the κ-Cygnid meteor shower and different groups of asteroids crossing the Earth’s orbit (the so-called near-Earth...     

A Thermodynamic Model of the Water–Rock Interaction under Hydrothermal Exposure of the Bazhenov Formation

Thermodynamic modeling of the hydrothermal exposure of the rocks of the Bazhenov Formation resulted in revealing the equilibrium mineral associations at 50–350°C and the pressure of saturated water vapor. The calculation results show that mineral parageneses varied slightly with the increase of temperature. Thus, zeolites were characterized by the stilbite–laumontite–wairakite series; kaolinite, pyrite, dolomite, and brannerite were replaced by montmorillonite and/or albite, pyrrhotite, calcite, and uraninite, respectively. The modeling results were confirmed in experiments.     

Phase Relations in the Harzburgite–Hydrous Carbonate Melt at 5.5–7.5 GPa and 1200–1350°С

Phase relations are studied experimentally in the harzburgite–hydrous carbonate melt system, the bulk composition of which represents primary kimberlite. Experiments were carried out at 5.5 and 7.5 GPa, 1200–1350°С, and \({{X}_{{{\text{C}}{{{\text{O}}}_{2}}}}}\) = 0.39–0.57, and lasted 60 hours. It is established that olivine–orthopyroxene–garnet–magnesite–melt assemblage is stable within the entire range of the studied parameters. With increase of temperature and \({{X}_{{{\text{C}}{{{\text{O}}}_{2}}}}}\) in the system, Ca# in the melt and the olivine fraction in the peridotite matrix significantly decrease. The composition of silicate phases in run products is close to those of high-temperature mantle peridotite. Analysis of obtained data suggest that magnesite at the base of subcontinental lithosphere could be derived by metasomatic alteration of peridotite by asthenospheric hydrous carbonate melts. The process is possible in the temperature range typical of heat flux of 40–45 mW/m², which corresponds to the conditions of formation of the deepest peridotite xenoliths. Crystallization of magnesite during interaction with peridotite matrix can be considered as experimentally substantiated mechanism of CO₂ accumulation in subcratonic lithosphere.     

Diagenetic migration of sulfides in sediments accumulated in different sedimentation settings

Migration and accumulation of sulfides at the contact of lithologically and geochemically different layers are considered. The possible mechanisms (gravitational, diffusion, elision, and electrogeochemical) for sulfide transportation during diagenesis are discussed. Data are presented to explain the localization of sulfide minerals at the boundary of reduced and oxidized sediments. The paper considers examples of stratiform sulfide concentrations of not only ore grade, but also lower grade, which, however, are of great significance for understanding the formation conditions of some geochemical anomalies. Link between the diagenetic migration of sulfides and the formation of iridium anomaly is substantiated.     

Correlation analysis between drought indices and terrestrial water storage from 2002 to 2015 in China

Drought monitoring is a key topic in environmental monitoring and assessment although there is still a need to determine the correlation between drought monitoring indices and remote sensing products. We analyzed the correlation between the self-calibrating Palmer Drought Severity Index (sc_PDSI), the Standardized Precipitation Index and the Standardized Precipitation Evapotranspiration Index (SPEI) and terrestrial water storage monitored through the Gravity Recovery and Climate Experiment (GRACE) on a monthly timescale from 2002 to 2015 in China. As a consequence of anomalies in the soil water budget, the highly significant correlation between the sc_PDSI and the GRACE satellite-observed terrestrial water storage suggested that these two datasets are the most suitable for use in monitoring droughts. In comparing the three drought indices, the sc_PDSI was introduced as a means of drought monitoring in the Yangtze, Pearl, Huaihe, Southeast and Songhua River Basins, whereas the SPEI was found to be more applicable to other major river basins, such as the Inland River Basin. These diverse spatial behaviors are caused by the differences between the hydrological droughts characterized by these three drought indices.