内蒙古赤峰南窝铺铀矿床英安岩的SHRIMP锆石U-Pb年龄、地球化学特征及地质意义

南窝铺铀矿床位于西拉木伦缝合带以南、康宝—围场—赤峰断裂带（华北北缘断裂带的一部分）以北的白乃庙加里东期岛弧带和华北古板块北缘海西期俯冲—碰撞带,属沽源—红山子铀成矿带北东段红山子—广兴铀成矿亚带的一个铀矿床,铀矿体赋存在额里图组安山岩—英安岩—流纹岩组合中。该组合中的英安岩SHRIMP锆石n(206Pb)/n(238U)加权平均年龄为268.1±2.5 Ma（N=15,MSWD=0. 85）,结合安山质角砾凝灰岩的锆石U-Pb年龄为277.1±0.9 Ma,指示额里图组安山岩—英安岩—流纹岩的地质时代属早二叠世（乌拉尔世）—中二叠世（瓜德鲁普世）早期;英安岩SiO2=65. 49%~68.23%,K2O=1.83%~2.56%,Na2O=4.13%~5.01%,(K2O+Na2O)=5.96%~7.47%,K2O/Na2O=0.43~0.59,(FeO+Fe2O3)=3.13%~4.63%,MgO=1.25%~1.79%,在TAS图解上落入亚碱性系列英安岩区,在FAM图解上落入钙碱性系列范围,在SiO2—K2O图解上落入中钾钙碱性系列范围,在Na2O—K2O图解上落入I型花岗岩区;Al2O3=15. 74%~16. 77%,CaO=2. 87%~3. 59%,A/CNK=0. 95~1. 12（平均为1.04,<1.1）,标准矿物刚玉（C）的含量为0~1.74%,平均为0.96%,指示源岩为I型岩浆岩;英安岩稀土元素总量低,富集轻稀土,Eu无明显负异常,ΣREE=76.5×10-6~95.4×10-6,(La/Yb)N=4.97~12.5（平均8.95）,δEu=0.80~1.13（平均0.94）,稀土配分模式为右倾型,与安第斯型钙碱性系列火山岩基本一致。英安岩明显富集大离子亲石元素Rb、Th、U、K、Sr等和亏损高场强元素Nb、Ta、P、Ti等,微量元素蛛网图与安第斯型钙碱性系列火山岩的形式一致,在Ce—SiO2、Al2O3—Ga图解上均落入I型花岗岩区,在Ta—Yb、Nb—Y构造环境判别图解上落入火山弧花岗岩区域（VAG）及同碰撞花岗岩（syn- COLG）交界处,在Rb—(Y+Nb)、Rb—(Yb+Ta)构造环境判别图解上落入火山弧花岗岩区域（VAG）,指示英安岩形成于俯冲作用下的岛弧环境。南窝铺铀矿床英安岩地质时代、岩石系列和形成构造环境的确定,不仅证实了早二叠世—中二叠世早期额里图组是红山子—广兴铀成矿亚带一个新的赋矿层位,而且揭示了岛弧型安山岩—英安岩—流纹岩组合也赋存有与火山岩有关的热液型铀矿,为深入开展热液型铀矿成矿理论的研究和进一步扩大铀矿勘查范围提供了新的基础资料。     

Influence of sedimentary setting on the use of magnetic susceptibility: examples from the Devonian of Belgium

Bulk magnetic susceptibility measurements on sedimentological samples from all geological periods have been used widely in the last two decades for correlations and as a proxy for sea‐level variations. This paper explores the link between magnetic susceptibility, depositional setting and environmental parameters. These environmental parameters include distal–proximal transects, microfacies successions and fourth‐order trends on different carbonate platform types (platform, ramp, carbonate mound or atoll) during different Devonian stages (Eifelian, Givetian and Frasnian). Average magnetic susceptibility values over a distal–proximal‐trending facies succession vary markedly with depositional setting. On carbonate platforms, average magnetic susceptibility generally increases towards the top of shallowing‐upward sequences. On a distal–proximal transect, average magnetic susceptibility is intermediate for the deepest facies, decreases for the reef belts and increases to a maximum in the back‐reef zone. In ramps and atolls, magnetic susceptibility trends clearly differ; average magnetic susceptibility generally decreases towards the top of shallowing‐upward sequences and is highest in the deepest facies. The strong relationship between magnetic susceptibility, facies and sequences implies a strong environmental influence. However, the different responses in the different platform types suggest that sea‐level changes leading to variation in detrital input is not the only parameter controlling average magnetic susceptibility values. Other primary or secondary processes also probably influenced magnetic mineral distribution. Primary processes such as carbonate production and water agitation during deposition are probably key factors. When carbonate production is high, the proportion of magnetic minerals is diluted and the magnetic susceptibility signal decreases. High water agitation during deposition will also selectively remove magnetic minerals and will lead to low average magnetic susceptibility values. These parameters explain the lowest values observed on the reef platform, inner ramp and atoll crown, which are all in areas characterized by higher carbonate production and greater water agitation during deposition. The lowest values observed in the lagoon inside the atoll crown can be related to detrital isolation by the atoll crown. However, other parameters such as biogenic magnetite production or diagenesis can also influence the magnetic signal. Diagenesis can change magnetism by creating or destroying magnetic minerals. However, the influence of diagenesis probably is linked strongly to the primary facies (permeability, amount of clay or organic matter) and probably enhanced the primary signal. The complexity of the signal gives rise to correlation problems between different depositional settings. Thus, while magnetic susceptibility has the potential to be an important correlation tool, the results of this investigation indicate that it cannot be used without consideration of sedimentary processes and depositional environments and without strong biostratigraphical control.     

Geothermal structure revealed by curie isothermal surface under Guangdong Province,China

Guangdong Province in Southeast China is noted for its numerous geothermal resources due to tectonic episodes, mainly occurred during the Cretaceous. The surface heat flow and geothermal gradient are the most direct ways to understand the temperature of the Earth. However, geothermal resources are poorly utilized in Guangdong Province due to limited numbers of boreholes and surficial hydrothermal fluids. To improve the understanding of underground temperature distribution in Guangdong Province, we have applied power-density spectral analysis to aeromagnetic anomaly data to calculate the depth of the Curie isothermal surface. Upward continuation is applied and tested to the magnetic data. The calculated Curie isotherm is between 18.5 km and 25 km below surface. The fluctuation in the depth range reflects lateral thermal perturbations in the Guangdong crust. In particular, the eastern, northern, western and coastline areas of the province have a relatively shallow Curie isotherm. By comparing the surface heat flow, geothermal gradient, distribution of Mesozoic granite-volcanic rocks, and natural hot springs, we conclude that during Mesozoic, magmatism exerted great influence on the deep thermal state of Guangdong Province. A shallow Curie isotherm surface, as well as numerous natural hot springs and high heat flow,show clear signatures of shallow heat sources.     

甘南玛曲沼泽湿地土壤微生物量、理化因子与土壤酶活的关系

对甘南玛曲沼泽湿地6个样地的微生物量与土壤酶活性及其土壤理化性质之间的关系进行了研究.结果表明:纤维素酶活性在冬季达到高峰,其余5种土壤酶活性分别在春季和秋季达到高峰;硝化细菌数量与过氧化氢酶、纤维素酶、脲酶、碱性磷酸酶有较显著的负相关关系;微生物量与酶活性之间存在极显著相关关系,其中微生物量因子中的放线菌、氨化细菌、硝化细菌和土壤酶活性因子中的酸性磷酸酶、碱性磷酸酶、中性磷酸酶是引起相关性的主要因素;酸性磷酸酶活性与土壤含水率、pH值、硝态氮含量、氨态氮含量都有密切的关系,过氧化氢酶活性可以通过有机质的含量来反映,脲酶活性可以通过土壤的含水率来反映,碱性磷酸酶活性可以通过电导率来反映.     

冀北窟窿山流纹斑岩锆石SHRIMP U-Pb年龄、地球化学特征及地质意义

冀北窟窿山流纹斑岩位于赤峰—开原断裂以南、尚义—平泉断裂带以北的华北克拉通北缘隆起带和沽源—红山子铀成矿带的西南段,主要分布于窟窿山北西部,出露面积约25 km~2。本文通过SHRIMP锆石U-Pb定年和主量元素、微量元素、稀土元素、Sr—Nd—Pb—O同位素组成测试,查明流纹斑岩形成的地质时代,探讨流纹斑岩的物质来源和形成的构造背景,分析流纹斑岩与铀矿化的关系。分析结果显示:流纹斑岩SHRIMP锆石n(~(206)Pb)/n(~(238)U)年龄为138.4±1.3 Ma(n=12,MSWD=0.25),属早白垩世早期;流纹斑岩具有高硅、富钾、钠,高FeO~T/MgO值,贫Al、Mg、Ca、P的高分异特征,属准铝质—弱过铝质高钾钙碱性系列岩石,在SiO_2—[(Na_2O+K_2O)—CaO]和SiO_2—FeO~T/(FeO~T+MgO)图解中落于A型花岗岩区;∑REE含量较低,Eu负异常明显,具轻稀土富集型稀土配分曲线特征,富集Rb、Th、U、Nb、Ta、Zr、Hf、Y等元素,亏损Sr、Ba、P、Ti等元素,10000Ga/Al=3.74～4.29(2.6),Zr+Nb+Ce+Y=374×10~(-6)～402×10~(-6)(350×10~(-6)),显示A型花岗岩微量元素的特征。流纹斑岩的[n(~(87)Sr)/n(~(86)Sr)]_i值变化范围较大(=0.690385～0.724000),ε_(Nd)(t)值较低(=-16.2～-14.9)、T_(DM2)较大(=2163～2244 Ma),Pb同位素比值较低{[n(~(206)Pb)/n(~(204)Pb)]_i=16.893～16.922、[n(~(207)Pb)/n(~(204)Pb)]_i=15.393～15.424、[n(~(208)Pb)/n(~(204)Pb)]_i=37.716～37.771},在铅同位素图解中窟窿山流纹斑岩同时带有下地壳物质和富集地幔印记;δ~(18)O_(V-SMOW)=3.5‰～4.9‰,低于正常地幔的δ~(18)O_(V-SMOW)值(=5.3‰±0.3‰),具低氧流纹岩特征。Sr—Nd—Pb—O同位素特征显示,流纹斑岩可能是源于DMM型、EMI型地幔和少量古老下地壳混合形成的年轻下地壳部分熔融的产物,而且与高温热液蚀变有关。对比表明,窟窿山流纹斑岩与中国东部绝大多数与火山岩有关的热液型铀矿的赋矿围岩时代一致,特别是与沽源—红山子铀成矿带西南段张麻井铀矿的赋矿流纹斑岩特征一致,而且在流纹斑岩的接触带内已揭露到铀矿化,指示窟窿山流纹斑岩的内、外接触带具有良好的找矿前景。     

GSCORS不稳定站坐标时间序列分析

本文对114个GSCORS坐标时间序列予以分析,发现93％以上的GSCORS位置稳定,序列变化平稳.个别基准站位置不稳定,造成基准站不稳定的因素多种多样,其中基准站周边地质松软、地基不稳为主要因素,导致测站大幅沉降、倾斜.科学、精准地分析不稳定基准坐标时间序列对维护省级参考框架的稳定具有重要指导作用.     

2000年4月15日青海省杂多县5．3级地震

在杂多5．3级地震宏观烈度考察、划分的基础上,分析讨论了区域地震构造背景及发震构造,并对地震序列类型进行了划分。     

基于信号估计的高分辨率叠加速度分析

如何得到高分辨率的叠加速度谱是高分辨率地震资料处理的关键.本文在分析地震共中心点(CDP)道集的振幅随偏移距变化(AVO)特性的基础上,提出一种信号模型来逼近CDP道集,然后利用优化技术估计信号,并采用信号估计误差实现信号检测,从而提出一种新的基于信号检测和估计的高分辨率叠加速度谱分析方法.文中的方法充分利用地震信号波形中所包含的速度信息.     

地球自转与El Nio——海气耦合理论

从低纬的海气耦合的浅水模式方程组出发 ,运用正交模和特殊函数的方法进一步讨论地球自转速率变化对海气耦合系统的影响 .研究表明 :地球自转速率的变化通过海气耦合一方面使大气和海洋的Kelvin波和Rossby波的移动及稳定性发生变化 ,另一方面使纬向风、洋流和海表温度发生变化 .特别是在地球自转减慢时 ,通过海气耦合 ,出现纬向风和洋流异常和大洋东部海表温度增加 ,从而导致引起全球气候异常的ElNi no现象     

2002-2017年千岛湖浮游植物群落结构变化及其影响因素

为认识大型水库中浮游植物群落结构的演替特征及其驱动机制,以钱塘江流域新安江水库（下称"千岛湖"）为例,基于2002-2017年16年的水库浮游植物数据,结合同期千岛湖水质与水文气象资料,分析了千岛湖浮游植物结构及优势属的长期变化特征,探讨了影响浮游植物群落结构变化的主要因素.结果表明：2002-2017年千岛湖共鉴定出浮游植物7门93属,主要由硅藻门、绿藻门、蓝藻门及隐藻门种类组成.16年间,浮游植物年均丰度和群落结构经历了4个阶段：2008年前丰度持续低值且蓝藻不是主要类群,2009-2012年丰度较高且蓝藻成为主要类群,及2013-2015丰度降低且蓝藻占比降低,2016-2017年丰度增加且蓝藻再次成为主要类群.浮游植物门类变化的同时伴随着优势属的变化：浮游植物年优势属从2002-2008年的小环藻属（Cyclotella）、隐藻属（Cryptomonas）和蓝隐藻属（Chroomonas）转变为2009-2012年的颤藻属（Oscillatoria）、小球藻属（Chlorella）、小环藻属和蓝隐藻属,2013-2017年又转变为鱼腥藻属（Anabaena）、束丝藻属（Aphanizomenon）、小环藻属、针杆藻属（Synedra）、直链藻属（Melosira）、栅藻属（Scenedesmus）和蓝隐藻属.冗余分析表明,气温、风速、水位、入库流量等气象水文因子和总氮浓度、电导率、氮磷比、透明度等水质因子与浮游植物群落结构变化关系密切.研究结果表明,在千岛湖这种大型贫-中营养水库,浮游植物群落结构不仅受来水营养盐负荷的影响,还在很大程度上受水文、气象条件的影响,给水库藻类水华等生态风险的预测以及水库水质管理带来了挑战.