甘肃北山地区怪石山含铜镍矿化镁铁质－超镁铁质杂岩体的地球化学特征及成因机制   总被引：1，自引：0，他引：1  

李丽  杨永强  王育习 《世界地质》2010,29(1):16-27

甘肃北山怪石山镁铁质－超镁铁质杂岩体为一具铜镍矿化的基性岩体。岩石地球化学数据显示, 基性岩相Mg#为74, 超基性岩相为84～90, 表明其具有原生岩浆及早期堆晶的特征。稀土和微量元素特征为ΣREE偏低; 球粒陨石标准化配分曲线属轻微右倾的平坦型, (La /Sm) _N为0.99～1.95, (La / Yb) _N为1.13～2.96, (Ce /Yb) _N为1.16～2.37, δEu为0.93～1.02, δCe为0.91～0.95, 基本无异常。结合该岩体产出的构造环境分析, 认为这一岩体应产于活动大陆边缘的构造背景下, 锆石SHRIMP U-Pb测年确定为泥盆纪。甘肃北山地区古生代的俯冲活动可能持续到泥盆纪, 在这一过程中上地幔的尖晶石橄榄岩相发生部分熔融, 产生的上升岩浆并未受到明显混染作用, 从而形成了怪石山镁铁质－超镁铁质岩体, 并伴随有铜－镍矿化。  相似文献   

黑龙江金厂金矿流体地球化学特征   总被引：6，自引：2，他引：4  

王永  席斌斌  张德会  张文淮 《矿床地质》2007,26(2):184-194

通过对黑龙江省金厂金矿床内包裹体的研究,对比不同矿化程度岩石中包裹体特征,认识到矿化程度与岩浆-流体的演化程度有密切的关系。矿化主要为黄铁矿化,还见有黄铜矿、方铅矿、闪锌矿、毒砂等硫化物矿物,主要呈脉状、条带状及浸染状产出。矿化程度高的钻孔岩芯内,包裹体类型发育完整,流体包裹体、熔融包裹体、熔-流包裹体均有发现。进一步研究发现,矿化与岩浆的结晶分异作用、流体的沸腾作用及流体的混合作用关系密切。分异作用使成矿物质得到富集,沸腾与混合作用使矿质进一步富集并沉淀析出。  相似文献   

Effects of grain size distribution on mineralogical and chemical compositions: a case study from size‐fractional sediments of the Huanghe (Yellow River) and Changjiang (Yangtze River)     

Xiaojing Zhou  Anchun Li  Fuqing Jiang  Jian Lu 《Geological Journal》2015,50(4):414-433

The influence of hydrodynamics on the chemical composition of sediments is based on the uneven distribution of element abundances in different size fractions. In this study, 72 size‐fractional sediments from the Huanghe (Yellow River) and Changjiang (Yangtze River) riverbeds were measured with XRD, SEM, ICP‐AES and ICP‐MS. The analysis results show that the mineral and chemical characteristics change with grain size in the Huanghe and Changjiang sediments. According to the principal components analysis, three independent geochemical factors were found. The first factor elements, Zr, Hf, Th, U, Y, La and TiO₂ are influenced by the existence of heavy minerals. The second factor elements, Al₂O₃, alkalis, alkaline earth (excluding Ca and Sr) and most of the transitional metals are dominated by clay minerals. The third factor group includes Ca and Sr, which were controlled by calcium‐bearing mineral contents and chemical weathering intensities. The various grain size distributions greatly affect the mineralogical and chemical compositions of bulk sediments. Compared to other size fractions, the 5–6PHI size fractions of the Huanghe and Changjiang sediments have special mineralogical and chemical compositions, and intermediate volume percentages. Weight or volume percentage of each size fraction may be more suitable than mean grain‐size of the bulk sediment to elucidate the grain size effects. Chemical Index of Alteration (CIA) values increase steeply with decreasing grain size, while Weathering Index of Parker (WIP) values are relatively stable. Because of the big influence of the abundance of clay minerals on CIA values, it is questionable to use CIA as a proxy of weathering intensity. Considering the clay mineral effects, stability in values and heterogeneous material properties, WIP has the potential to indicate the chemical weathering intensity of sediments. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

基于Local-BGM法的冷涡暴雨集合预报试验及评估检验北大核心          下载免费PDF全文

张海鹏  智协飞  李昊  黎振宇  张志强  黄晶 《气象科学》2023,43(1):36-45

基于传统增长模繁殖法(Breeding Growing Mode,BGM)和局地增长模繁殖法(Local Breeding Growing Mode,Local-BGM)生成初始扰动成员,对一次冷涡暴雨过程进行集合预报试验,从多方面比较两种方案的预报效果,并且在邻域概率法(Neighborhood Probability,NP)中引入时间邻域,评估概率预报结果。结果表明,引入局地化思想的Local-BGM方案能够生成比传统BGM方案更合理的初始扰动,具有很明显的局地特征。对于扰动变量的预报,Local-BGM方案在均方根误差和离散度等方面均表现更好,同时能够提高各量级降水的预报技巧。邻域集合概率法能够综合各个集合成员预报的降水信息得到优于集合平均的概率预报,分数技巧评分更高。并且在考虑时间不确定性后,无论是控制预报、集合平均还是邻域集合概率法,分数技巧评分均有很大改善,并且降水阈值越大改善效果越明显,能够为极端强降水天气提供较为客观的概率预报信息。  相似文献