Some Topics on the Auroras in Middle and Low Latitudes     

朱岗崑  洪明华 《极地研究(英文版)》2004,15(1):66-74

This paper consists of the following topics : (1) Significance of observing lower-latitude auroras. (2) Different kinds of atmospheric luminosity. (3) Chronological catalogues and maps of isochasms for auroral visibility. (4) Analysis of archaco-auroras in low latitudes during earlier centuries. (5) Aurora observing studies since International Geophysical Year (IGY). (6) Concerning prediction of auriora occurrence.  相似文献   

西秦岭阳山金矿带花岗斑岩元素及Sr-Nd-Pb同位素地球化学   总被引：12，自引：10，他引：2  

刘红杰  陈衍景  毛世东  赵成海  杨荣生 《岩石学报》2008,24(5)

甘肃阳山金矿带的花岗斑岩脉中含有石榴子石,A/CNK=1.65～3.65,属于强过铝质花岗岩类.花岗斑岩相对富集LILE和LREE,亏损Ba、Sr、Nb、Ta、P、Ti等,配分模式类似于典型同碰撞型花岗岩类;花岗斑岩ΣREE=54.35～124.01×10-6,(La/Yb)N=9.72-27.80,δEu=0.70～0.89,表明其岩浆形成时部分斜长石进入熔体,而非完全残留.花岗斑岩Isr值为0.70806～0.71756,平均0.71107;εNd(t)值变化于-2.9～-5.0,平均-3.4;Nd模式年龄(T2DM)为1.24～1.41Ga,平均1.34(Ga).以上同位素特征表明花岗斑岩岩浆应源自成熟度较低的中元古代基底地壳物质.花岗斑岩的(206pb/204Pb)220Ma、(207pb/204Pb)220Ma和(206pb/204Pb)220Ma的平均值分别为17.875、15.604和38.296,与秦岭微陆块的中元古代基底和碧口地体碧口群的Pb同位素组成一致.考虑到前人获得碧口群的年龄为1.235～1.367Ga,而秦岭微陆块沿勉略缝合带向南仰冲到碧口地体之上.我们认为由碧口群等组成的俯冲板片的变质脱水熔融作用导致了阳山金矿带花岗斑岩的形成.因此,阳山金矿带的花岗斑岩是扬子与华北大陆中生代碰撞造山过程中形成的同碰撞花岗岩类.  相似文献   

定向钻进泥浆后处理     

刘珍 《岩土钻凿工程》2008,(4):14-16

本文介绍了废弃泥浆的成分及其对环境的影响,探讨了处理废弃泥浆的一般方法和技术及定向钻进环空泥浆替换技术。  相似文献   

气象仪器装备类科技成果后效评估指标体系和方法     

储凌  邹立尧  王亚光  胡宜昌  荆国栋 《气象科技》2016,44(2):234-237

以气象仪器装备类科技成果为研究对象开展后效评估研究。基于评估对象的界定与特征分析,对此类成果后效评估的指标要素进行了探索研究,初步构建了相应的后效评估指标体系,并采用层次分析法(AHP)确定了评估体系中的各项指标权重。根据构建的指标体系和评估依据,确定了气象仪器装备类成果的综合评分方法,并进行了模拟评估。结果表明:此后效评估指标体系与评估方法具有实际可操作性。此研究工作为气象科技成果的科学评估、规范化管理提供方法途径。  相似文献   

西昆仑早中志留世埃达克岩的发现及地质意义     

杨绍  吕宏伟  屈小相  吝岩  曾忠诚  高成 《岩石矿物学杂志》2016,35(4):563-578

1∶5万地质调查在西昆仑北部库尔良地区库尔良群中首次发现了一套早中志留世花岗闪长岩体,通过锆石LA-ICP-MS U-Pb测年法获得其成岩年龄为429.6±1.4 Ma(MSWD=0.69)。岩石具有典型的埃达克岩地球化学特征:高SiO_2(68.85%~72.49%)、Al_2O_3(14.08%~15.36%)、Sr(480×10-6~812×10-6)、Sr/Y(53.2~111.0),低Y(7.31×10~(-6)~10.30×10~(-6))、Yb(0.34×10-6~0.48×10-6),重稀土元素强烈亏损,轻重稀土元素分异明显,38.4(La/Yb)N61.2,无显著Eu异常(0.86δEu1.03,均值0.98)。同时,岩石具有较高的K_2O(2.92%~3.48%)和较低的MgO(0.69%~0.84%)、Mg#(26.4~32.6)、Cr(15.1~28.2)、Ni(3.54~5.39)等特征,Na_2O/K_2O值为1.03~1.46(均值1.21)。地球化学特征显示其为加厚下地壳部分熔融的产物,暗示早中志留世西昆仑发生了一次地壳增厚事件,彼时地壳厚度50 km。结合区域地质资料,认为以库地-其曼于特蛇绿构造混杂岩带为标志的原特提斯洋在早中志留世之前已经闭合,并已进入板块碰撞、挤压造山阶段。研究成果为原特提斯洋闭合后碰撞作用导致的地壳增厚事件提供了可靠的岩石学证据和精确的年代学依据。  相似文献   

新疆西准噶尔北部和布克赛尔蛇绿混杂岩的厘定及其洋盆闭合时代限定   总被引：1，自引：0，他引：1  

杨亚琦  赵磊  徐芹芹  郑荣国  牛宝贵 《地质学报》2018,92(2):298-312

本文通过详细野外地质勘查,识别出新疆西准噶尔北部和布克赛尔蛇绿混杂岩中三种不同类型的岩石组合,即:由变质橄榄岩、辉长岩、辉绿岩墙、玄武岩和硅质岩组成的典型蛇绿岩单元;主要由洋岛玄武岩组成的大洋岛屿单元,在野外见与硅质岩、硅质泥岩和灰岩相伴产出;由变流纹岩组成的后碰撞期火山岩单元。蛇绿岩中的辉长岩和辉绿岩无明显Eu异常;(La/Yb)N值介于0.54~3.18之间,REE配分型式呈现微弱的轻稀土亏损或富集,兼具E-MORB和N-MORB的特征。洋岛玄武岩具有高的Al_2O_3(13.66%~15.83%)、TiO_2(2.62%~3.15%)和Na_2O+K_2O(5.71%~7%),稀土元素含量高,显示明显的右倾模式,高场强元素Ti、Zr相对富集。变流纹岩具有高硅和钾,极低的MgO,MnO和CaO,不相容元素(K,Rb,Th,U,Pb)强烈富集,Sr,P,Ti显著亏损,Nb和Ta相对弱亏损的特点,形成于造山后伸展环境,其LA-ICP-MS锆石U-Pb定年结果为435±2Ma。变流纹岩底垫贯穿或底垫侵入于蛇绿岩不同的单元组分中(橄榄岩、辉绿岩和玄武岩等),说明和布克赛尔蛇绿岩所代表的洋盆在早志留世晚期之前已经闭合。  相似文献   

Collisional mafic magmatism of the fold-thrust belts framing southern Siberia (Western Sangilen,southeastern Tuva)     

R.A. Shelepaev  V.V. Egorova  A.E. Izokh  R. Seltmann 《Russian Geology and Geophysics》2018,59(5):525-540

We consider geochemical features of mafic magmatism manifested during the evolution of a complex nappe-folded structure in Western Sangilen, resulted from the Cambrian-Ordovician collisional tectogenesis. There are abundant ultramafic-mafic and mafic associations of different types in this region: layered low-Ti low-alkali ultramafic-mafic intrusions, high-Ti medium-alkali gabbroids, gabbro-monzodiorite intrusions, and alkali basalts. Isotope-geochronological data showed that these complexes formed over a wide time interval, from 570 to 440 Ma. At this time, the geodynamic setting in Western Sangilen changed from an island-arc one via a collision one to an intercontinental rift setting. At the early and late stages of the evolution of Western Sangilen, the geochemical features of mafites were typical of their geodynamic settings. The properties of mafites that formed synchronously with the collision are of particular interest. The studies have shown that the chemical composition of collisional mafites of Western Sangilen changed with time. They became richer in alkalies, titanium, and incompatible elements. This fact indicates a change in the type of mantle source from suprasubductional in the Cambrian to enriched deeper-level one in the Ordovician.  相似文献   

松潘- 甘孜造山带南部江浪穹隆中侏罗世花岗岩及构造意义     

刘晓佳  许志琴 《地质学报》2021,95(6):1754-1773

新火山和乌拉溪花岗岩体侵位于松潘-甘孜造山带南部的江浪穹隆中,是理解松潘-甘孜造山带的构造演化的重要窗口.锆石U-Pb定年结果表明新火山和乌拉溪花岗岩体的结晶年龄为162±1～170±0.5 Ma.岩体主要由石英、斜长石、钾长石和少量黑云母组成,具有低A/CNK(1.10～0.99)、TFeO/MgO(8.55～2.83)和K2O/Na2O(1.34～0.51),较低的Zr+Nb+Ce+Y浓度(平均258×10-6),Al2O3、P2O5与SiO2呈负相关,相当于I型花岗岩的特征.一些主微量元素具有明显的关联性,说明在岩浆演化过程中发生了分离结晶(例如:角闪石和钛铁矿).富集轻稀土和大离子亲石元素,亏损高场强元素,并具有较低的Mg#值(38.7～17.3)和Y/Nb值(0.45～0.16)以及多数为负的εHf(t)值(-24.8～-7.6),证明岩浆可能起源于古老地壳的部分熔融并受到幔源或者新生地壳熔融混染.松潘-甘孜地块的中侏罗世岩浆活动是在造山运动向陆内伸展这一构造体制转化背景下,由于地壳伸展造成了古老中基性地壳的部分熔融.  相似文献   

Overland flow generation in chaparral ecosystems: temporal and spatial variability     

B. Valeron  T. Meixner 《水文研究》2010,24(1):65-75

Fire is an important and natural process in the lifecycle of chaparral systems, removing old growth and recycling nutrients. Recent catastrophic wildfires in southern California chaparral have heightened concerns about increased runoff and nutrient export. The goal of this study was to improve understanding of how overland flow is generated in unburned and post‐fire chaparral watersheds. Samples of overland flow were collected from burned and unburned watersheds after rainfall events and multiple regression analysis was used to examine the influence of individual storm characteristics and system moisture on overland flow volume. The results indicate that variation in overland flow generation in the unburned watershed is best explained by storm size, while overland flow in the burned watershed was positively related to storm size and time between storms. These findings suggest that the burned system had decreased infiltration rates and increased soil water repellency. In contrast, there is a statistically significant negative relationship between overland flow 1 year after a fire against different system and precipitation factors revealed a negative correlation with drying period and a positive relationship with rainfall intensity, a combination that suggests reduced repellency. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

滇西北中甸陆家村石英二长斑岩的锆石SHRIMP定年及其意义   总被引：2，自引：2，他引：0  

薛传东  骆少勇  宋玉财  杨志明  韩艳伟  黄琴辉  李敬  魏爱英 《岩石学报》2010,26(6):1845-1855

滇西北中甸陆家村石英二长斑岩位于义敦-中甸岛弧带最南端、金沙江断裂带与扬子地台交汇部位,侵入于中三叠统浅变质的砂泥质板岩、泥质粉砂岩及蚀变玄武岩中。锆石SHRIMPU-Pb定年结果表明,两件锆石增生边的年龄分别为35.6±1.4Ma(MSWD=0.36,N=4)、36.7±0.8Ma(MSWD=1.80,N=8),平均为36.2±1.3Ma(MSWD=0.35,N=12),代表了岩浆侵位结晶时代;继承性锆石年龄在413～61.2Ma之间变化,分别代表了早期岩浆侵位和捕获基底围岩碎屑锆石的年龄,反映其多种来源并经历了复杂的地质演化。结合岩体锆石SHRIMP定年结果、产出地质背景及区域对比,认为陆家村石英二长斑岩浆侵位于印-亚大陆晚碰撞阶段,是藏东-金沙江-红河新生代富碱斑岩带的组成部分,其形成与喜马拉雅期陆陆碰撞导致壳幔过渡层大规模侧向迁移引起的地幔上涌和中下地壳部分熔融有关,是青藏高原东缘构造转换带对主碰撞带造山作用过程响应的记录。该认识为深入了解中甸-丽江构造-岩浆-成矿作用提供了重要约束,也确认本区具有斑岩型矿床的找矿潜力。  相似文献