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991.
东天山喀尔力克康古尔塔格组火山岩特征 总被引:2,自引:1,他引:2
准噶尔板块南缘喀尔力克古生代岛弧带内的中泥盆世火山活动较为频繁,喷发韵律主要为溢流-沉积及爆发-沉积,每次火山活动后均有停歇间断,间歇期沉积火山碎屑沉积岩和正常沉积岩.爆发相中岩石出现较多的熔结凝灰岩,沉积相中出现植物化石,是陆相火山-沉积体系的特点.火山喷发系数由西向东为61.94%~30%,其中具溢流相岩石减少,爆发岩相增多的演变特点,根据岩石化学、地球化学特征综合分析研究,反映火山活动具陆缘弧构造环境的特征.除上述火山岩相外,还存在古火山机构——火山颈相的岩石,具中心式火山喷发的特点. 相似文献
992.
Petrogenesis of a Late Jurassic Peraluminous Volcanic Complex and its High-Mg, Potassic, Quenched Enclaves at Xiangshan, Southeast China 总被引:20,自引:0,他引:20
JIANG YAO-HUI; LING HONG-FEI; JIANG SHAO-YONG; FAN HONG-HAI; SHEN WEI-ZHOU; NI PEI 《Journal of Petrology》2005,46(6):1121-1154
A late Mesozoic belt of volcanicintrusive complexes occursin SE China. Volcanic activity at Xiangshan in the NW of thebelt took place mainly in the Late Jurassic (158135 Ma).The volcanic rocks from the Xiangshan volcanic complex includerhyolitic crystal tuffs, welded tuffs, rhyolite lavas, porphyriticlavas, and associated subvolcanic rocks. Mineral assemblagesin these magmatic rocks include K-feldspar, plagioclase, quartz,Fe-rich biotite and minor amphibole, orthopyroxene and almandine.Mineral geothermometry indicates a high crystallization temperature(>850°C) for the Xiangshan magmas. The volcanic rocksare generally peraluminous; SiO2 contents are between 65·4%and 76·8% and the samples have high alkalis, rare earthelements (REE), high field strength elements and Ga contentsand high Ga/Al ratios, but are depleted in Ba, Sr and transitionmetals. Trace element geochemistry and SrNdO isotopesystematics imply that the Xiangshan magmas were probably derivedfrom partial melting of Middle Proterozoic metamorphic lower-crustalrocks that had been dehydrated during an earlier thermal event.These features suggest an A-type affinity. Quenched mafic enclaves,hosted by the subvolcanic rocks, consist mainly of alkali feldspar,plagioclase, clinopyroxene, phlogopite and amphibole. Geothermometrycalculations indicate that the primary magmas that chilled toform the quenched enclaves had anomalously high temperatures(>1200°C). The quenched enclaves have boninitic affinities;for example, intermediate SiO2 contents, high MgO and low TiO2contents, high Mg-numbers and high concentrations of Sc, Ni,Co and V. However, they also have shoshonitic characteristics,e.g. enrichment in alkalis, high K2O contents with high K2O/Na2Oratios, high light REE and large ion lithophile element contents,low initial Nd values (4·2) and high initial 87Sr/86Srratios (0·7081). We suggest a phlogopite-bearing spinelharzburgitic lithospheric mantle source for these high-Mg potassicmagmas. Underplating of such anomalously high-temperature magmascould have induced granulite-facies lower-crustal rocks to partiallymelt and generate the Xiangshan A-type volcanic suite. A back-arcextensional setting, related to subduction of the Palaeo-Pacificplate, is favoured to explain the petrogenesis of the Xiangshanvolcanic complex and quenched enclaves. KEY WORDS: volcanic complex; quenched enclaves; petrology; geochemistry; back-arc extension setting; Xiangshan; SE China 相似文献
993.
土壤湿度对东亚夏季气候潜在可预报性影响的数值模拟 总被引:5,自引:0,他引:5
利用全球大气环流模式NCARCAM3进行了在给定的观测海温条件下的22a(1979—2000年)5—8月的2组集合试验。运用方差分析方法,分析了在气候态和年际变化的表层土壤湿度情况下,CAM3模式模拟的东亚夏季气候潜在可预报性及其差异。结果表明:在给定的观测海温条件下,采用气候态的土壤湿度时,CAM3模式模拟的东亚夏季气候的潜在可预报性偏低;而采用年际变化的土壤湿度时,模拟的夏季气候潜在可预报性有所提高,尤其是在中国西北地区;后者模拟的中国西北地区夏季降水和气温的潜在可预报性比前者的模拟结果提高0.1以上。其原因可能是:采用年际变化的土壤湿度时,模式可以更好地模拟出中国西北地区的地表蒸发量和湍流热通量的年际变化,进而使得模式对该地区夏季气候的预报技巧得到提高。 相似文献
994.
With the methods of REOF (Rotated Empirical Orthogonal Function), the summer precipitation from 43 stations over eastern China for the 1901 - 2000 period was examined. The results show that South China and Southwest China, the middle and lower reaches of Changjiang River, North China and the southwestern of Northeast China are the three main areas of summer rainfall anomaly. Furthermore, correlation analysis is used in three time series of three mostly summer rainfall modes and four seasonal Pacific SSTA (Sea Surface Temperature Anomaly), and the results suggest that the Pacific SSTA which notably causes the summer rainfall anomaly over eastern China are the SSTA of the preceding winter over Kuroshio region of Northwest Pacific, SSTA of the preceding spring in the eastern and central equatorial Pacific, and SSTA of the current summer in the central region of middle latitude. The relationship between summer precipitation over eastern China and SSTA of Pacific key regions was further verified by SVD (Singular Value Decomposition) analysis.The composite analysis was used to analyze the features of atmospheric general circulation in the years of positive and negative precipitation anomaly. Its results were used to serve as the base of numerical simulation analysis. 相似文献
995.
样品采用过氧化钠熔融,酒石酸络合提取,电感耦合等离子体发射光谱法测定黑钨精矿和中矿中的锰含量,碱熔络合体系避免了酸处理样品时大量钨酸沉淀的生成,解决了钨酸沉淀导致的溶矿不完全和夹杂、吸附待测元素的问题。在优化的工作条件下,方法检出限为0.019μg/mL,精密度(RSD,n=11)为0.92%~1.50%,并且具有较高的回收率(97.5%~104.0%),单次测定结果与协同定值结果的偏差小于国家标准GB/T 6150.14—2008硫酸亚铁铵法实验室间允许差。方法简便快速,无明显基体干扰,满足了国家标准黑钨精矿中锰的检测要求,可用于高、中品位钨矿石样品中低含量锰的准确测定。 相似文献
996.
目前湖相碳酸盐岩是国内外沉积学研究的薄弱环节。本文在众多专家学者历年研究成果的基础上,综述了湖相碳酸盐岩的研究现状,其主要体现在岩石类型、分布及发育特点、相模式、储集层和生油岩几个方面;并阐明了湖相碳酸盐岩的研究具有重要的理论和经济意义。 相似文献
997.
998.
Research on the gully forming in the gully region of Yanhe River Basin and process of geological disasters
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In recent years, the frequency of geological disasters gradually increases in the gully region of the Loess Plateaus centred with Yanhe River Basin. The research on the forming of the geological disasters in gully region and the disaster process will help us further understand the development of geological disasters and the disaster process. According to the detailed survey of geological disasters in Yan’an City, the river and gully erosion is the main natural predisposing factor that caused the geological disasters in the river gully region. In the forming of ditches and gullies, the surface water system changes the stress form of the original slope and reduces the strength combination of the slope in ways of water erosion and gravity erosion. Gully’s forming stage and stratigraphic contact form have some influence on the geological disasters and disaster process. 相似文献
999.
1000.
铂族元素作为地球化学指示剂有关问题讨论 总被引:1,自引:0,他引:1
铂族元素在研究地球化学过程中发挥着越来越重要的示踪作用。根据铂族元素在不同圈层中的分布,可以探索地球的形成历史和地外撞击事件。根据铂族元素之间的分异性,可用来研究岩浆的部分熔融程度、岩石的形成过程以及大地构造环境的判别等。然而,多年来,由于分析手段和分析方法等的限制,对铂族元素在地质作用过程中的化学行为的认识尚欠深入,对其作为地球化学指示剂的研究还存在诸多问题,许多现象尚不能得到很好的解释。本文提出,应加强地质样品中超痕量铂族元素的高精度分析方法研究和铂族元素在地质作用过程中分异行为、分异规律的研究。 相似文献