渭南市冰雹时空分布及天气条件分析

随着气候变暖,生态系统发生了变化,为此农作物的品种以及栽培方式也必须适应变化了的环境条件。以山西太原盆地南部的介休市为例分析了主栽作物冬小麦和玉米的适应性栽培应采取的对策,以达农作物高产、稳产、防灾、减灾,确保农业增效,农民增收之目的。     

Carboniferous porphyry Cu–Au deposits in the Almalyk orefield,Uzbekistan: the Sarycheku and Kalmakyr examples

The Almalyk porphyry cluster in the western part of the Central Asian Orogenic Belt is the second largest porphyry region in Asia and hence has attracted considerable attention of the geologists. In this contribution, we report the zircon U–Pb ages, major and trace element geochemistry as well as Sr–Nd isotopic data for the ore-related porphyries of the Sarycheku and Kalmakyr deposits. The zircon U–Pb ages (Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS)) of ore-bearing quartz monzonite and granodiorite porphyries from the Kalmakyr deposit are 326.1 ± 3.4 and 315.2 ± 2.8 Ma, and those for the ore-bearing granodiorite porphyries and monzonite dike from the Sarycheku deposit are 337.8 ± 3.1 and 313.2 ± 2.5 Ma, respectively. Together with the previous ages, they confine multi-phase intrusions from 337 to 306 Ma for the Almalyk ore cluster. Geochemically, all samples belong to shoshonitic series and are enriched in large-ion lithophile elements relative to high field strength elements with very low Nb/U weight ratios (0.83–2.56). They show initial (⁸⁷Sr/⁸⁶Sr)_i ratios of 0.7059–0.7068 for Kalmakyr and 0.7067–0.7072 for Sarycheku and low ε_Nd(t) values of ?1.0 to ?0.1 for Kalmakyr and ?2.3 to 0.2 for Sarycheku, suggesting that the magmas were dominantly derived from a metasomatized mantle wedge modified by slab-derived fluids with the contribution of the continental crust by assimilation-fractional-crystallization process. Compared to the typical porphyry Cu deposits, the ore-bearing porphyries in the Almalyk cluster are shoshonitic instead of the calc-alkaline. Moreover, although the magmatic events were genetically related to a continental arc environment, the ore-bearing porphyries at Sarycheku and Kalmakyr do not show geochemical signatures of typical adakites as reflected in some giant porphyry deposits in the Circum-Pacific Ocean, indicating that slab-melting may not have been involved in their petrogenesis.     

粤北诸广南铀矿聚集区岩浆、构造与铀成矿活动

粤北诸广南铀矿聚集区位于南岭诸广山岩体中东部,区内铀矿资源丰富,是中国重要的铀矿产基地。区内以发育花岗岩型铀矿化为主,整体上受中生代区域性岩浆—构造—热液活动"三位一体"联合控制。区域性花岗质岩浆活动对铀矿化有着预富集作用,断裂构造活动为成矿提供了有利空间,热液活动促使了花岗岩中铀的活化迁移和富集成矿。研究区的铀成矿作用具有同时性和多期性特征,形成于华南白垩纪—古近纪岩石圈伸展动力学背景下,统一受制于地壳的强烈拉张作用。由诸广山岩体与南雄盆地组成的盆山体系的白垩纪—古近纪构造演化可能是导致诸广南铀矿聚集区形成的重要因素之一。     

Middle Devonian Picrites of the Southern Margin of Altay Orogenic Belt and Implications for the Tectonic Setting and Petrogenesis

INTRODUCTION Inrecentyears,greatprogressonthegeologic tec tonicevolutionandmineralresourcesofXinjianghas beenachieved.However,manyissuesarestilldebated, suchasancienttectonicpatternsandtheclosuretimeof theancientoceanicbasin(LiandXu,2004).Theseis sueshavelimitedourknowledgeoftheformationande volutionofAsiancontinents,aswellastheexploration anddevelopmentofmineralresources. Recently,theHilaketehalasuporphyrycopperde positwasdiscoveredinthestrataoftheMiddleDevoni anBeitashanFormatio…     

Understanding the characteristic of GLONASS inter-frequency clock bias using both FDMA and CDMA signals

GPS Solutions - High-frequency global navigation satellite system (GNSS) observations are of great significance for structural health monitoring. At present, most studies on high-frequency GNSS...