1948—2001年全球大尺度区域 6～8月降水的长期变化     

黄先香  施能  顾骏强  高鸿 《地球科学进展》2004,19(5):824-830

研究了1948-2001年南、北半球及欧亚大陆、非洲大陆、澳洲大陆、北美大陆、南美大陆、南极大陆和中国 7个大尺度区域 6～8月降水的长期趋势变化和年代际变化。结果表明，南、北半球 6～8月的降水都为负趋势，但南半球降水的负趋势在统计上不显著。在54年的时间段内，南半球 6～8月降水的递减速度为 0．12 mm／a，仅为北半球同期降水减幅（0．24 mm／a）的一半。南、北半球 6～8月降水量年代际尺度的振荡都非常明显，但是，南、北半球年代际变化的特征明显不同。目前北半球仍是在少雨时间段，而南半球处在降水量正常或多雨的时间段。分析还表明，非洲大陆 6～ 8月降水的年代际特征最明显，降水的负趋势也最为显著；欧亚大陆 6～8月降水也有着明显的年代际变化与明显的负趋势变化；澳洲大陆 6～8月降水的年际变化明显，年代际变化相对来说要小得多；北美大陆 6～8月降水的年际变化明显，但无明显的趋势变化。此外，分析了大尺度区域 6～ 8月降水之间的相关关系，发现部分区域大尺度降水量之间有明显的联系；分析了中国夏季降水的长期变化，发现中国夏季降水的年代际变化明显，但无明显的趋势变化。  相似文献   

天山山区近40a年降水变化特征与南、北疆的比较   总被引：24，自引：2，他引：24       下载免费PDF全文

袁玉江  何清  喻树龙 《气象科学》2004,24(2):220-226

本文分析了天山山区近40 a来年降水变化的基本特征，并与南疆、北疆进行了比较，所得的主要结果如下：(1)天山山区在年降水量干湿变化阶段上与北疆的相似性强于南疆。(2)年降水量的空间分布的同步变化性以北疆为最好，南疆最差，天山山区居中，而年降水量的空间分布的反向变化性，以天山山区为最大，北疆最小，南疆居中。(3)天山山区与南疆从60年代到90年代，年降水均表现出了持续的增加的趋势，北疆年降水从60年代到90年代，除70年代外，不断增多。  相似文献   

陕南化探数据库的建设及开发应用     

李春兰  向婷婷  李文全  刘雁 《物探与化探》2004,28(3):280-282

利用现代化计算工具及《区域地球化学数据管理系统》、MAPGIS地理信息系统等软件,对陕南地区57357km²历年来1:5万化探数据进行建库、数据处理及成图,提取有用信息,分析研究陕南地区区域地球化学特征及各元素富集规律。结合地质、物探资料及时指导找矿预测、资料二次开发及二轮找矿。  相似文献   

陕西略阳铧厂沟金矿床地质与矿床类型   总被引：2，自引：3，他引：2  

宗静婷 《西北地质》2004,37(1):97-101

铧厂沟金矿床位于勉略缝合带中泥盆系三河口群郭镇岩组中。含矿与容矿岩系为泥盆系三河口群郭镇岩组中的细碧岩和结晶灰岩。主控矿构造为寨子湾韧-脆性剪切构造带。围岩蚀变包括退化蚀变和矿化蚀变。在矿区内产出南北两条矿化带，矿石类型为蚀变细碧岩型、黄铁绢英片岩型和石英脉型。主要的金属矿物为黄铁矿和黄铜矿，金矿物是自然金。韧脆性剪切构造叠加和岩石强烈变形、彻底退化蚀变以及后期含矿热液交代与充填是主要的成矿作用，属于火山-沉积岩系中的类卡林型金矿床。  相似文献   

赣南中侏罗世流纹岩地球化学及成因研究：上地壳成因的的微量元素和Pb-Nd-Sr同位素地球化学制约   总被引：4，自引：1，他引：4  

章邦桐凌洪飞  孔兴功 《岩石学报》2004,20(3):511-520

江西南部龙南-寻邬地区余田群菖蒲组的流纹岩形成于中侏罗世(164．8．1Ma～174．9Ma)，为双峰式火山岩组合的酸性端元，属弱过铝质(ACNK平均为1．04)钙碱性系列(σ平均为1．90)。稀土元素含量高(平均为278．9μg/g)，轻稀土富集(IMH平均为7．94)，Eu亏损中等(δEu平均为0．41)。微量元素以富集Rb，Ba，Th，U，Zr，Y，Pb，而亏损Sr，Nb为特征。Pb，Nd，Sr同位素组成为：(^206Pb/^204Pb)t=17．89～18．58，(^207Pb/^204Pb)t=15．58～15．70，(^208Pb/^204Pb)t=37．94～38．82；εNd(t)=-7．44～-11．9；ISr=0．71126～0．71228。对赣南流纹岩微量元素采用蛛网图和模糊聚类分析方法进行对比研究的结果及Pb-Nd-Sr同位素相关特征为其上地壳成因提供了地球化学佐证。赣南流纹岩是由进入上地壳内高位岩浆房的石英拉斑玄武岩浆的底侵作用直接使上地壳部分熔融形成的产物。  相似文献   

南太行山闪长岩的SHRIMP锆石U-Pb年龄及岩石成因研究   总被引：6，自引：13，他引：6  

彭头平王岳军  范蔚茗郭锋　彭冰霞 《岩石学报》2004,20(5):1253-1262

南太行山符山和东冶角闪闪长岩岩体的精细SHRIMP锆石U-Pb定年和元素-同位素地球化学研究表明:符山角闪闪长岩体形成于126.7±1.1Ma,东冶角闪闪长岩体形成于125.9±0.9Ma,与区内基性侵入岩和北太行地区侵入杂岩具有相似的形成年龄,表明晚中生代(±130Ma左右)太行山地区经历了与华北陆块同期的重要构造岩浆事件。区内闪长质岩石SiO_2=54.84％～65.75％,MgO=1.31％～3.89％,K_2O Na_2O=6.53％～11.40％,mg值=0.36～0.58,(La/Yb)_(cn)=9.86～22.77,(Gd/Yb)_(cn)=1.51～2.00;Eu/Eu=1.00～1.23,以富集LREE、LILE元素和明显亏损Nb-Ta、Zr-Hf-Ti等高场强元素为特征。~(87)Sr/~(86)Sr(t)=0.705363～0.706165,ε_(Nd)(t)=-13.8～-16.8,源自于EMI型富集岩石圈地幔,可解释为新生地幔底侵物质熔融后经过结晶分异作用的产物。与华北克拉通内部其他地区一样,早白垩世南太行山地区处于软流圈上涌的岩石圈伸展构造背景。  相似文献   

镇旬铅锌矿田热水沉积硅岩研究   总被引：4，自引：0，他引：4  

侯满堂  臧世权  李新林 《陕西地质》2004,22(1):45-54

从镇(安)旬(阳)铅锌矿田热水沉积硅岩的产状、形态、岩石结构、构造、矿物成分、化学成分、微量元素、稀土元素、硫同位素、氧同位素等研究表明，本区硅岩具有以热液为主兼有生物和正常沉积的特征，并非典型热水沉积岩。  相似文献   

陕西金矿床类型及其找矿方向   总被引：1，自引：2，他引：1  

齐文  侯满堂 《陕西地质》2004,22(2):1-8,106

通过对陕西金矿资源的分析、总结，将陕西金矿成因类型划分为7类14亚类；与金矿有关的成矿系列划分为3个矿床成矿系列组合，7个成矿系列类型，10个成矿系列和4个亚系列；金矿床空间分布严格受隐伏基底和出露基底，隐伏岩体、重磁吻合构造，构造和成矿时代的控制；与金成矿有关的Ⅲ级成矿区(带)有4条，有关的Ⅳ级成矿区(带)有10条，有关的Ⅴ级主要金成矿区(带)有16条；提出了金矿新的找矿方向，为今后本区金矿地质找矿的新突破提供信息。  相似文献   

Retrograded textures and associated mass transfer: evidence for aqueous fluid action during exhumation of the Qinglongshan eclogite, Southern Sulu ultrahigh pressure metamorphic terrane, eastern China   总被引：6，自引：0，他引：6  

T. N. Yang 《Journal of Metamorphic Geology》2004,22(7):653-669

The Qinglongshan eclogites in the Southern Sulu ultrahigh pressure metamorphic (UHPM) terrane show very different retrograded textures from their counterparts in the Northern Sulu terrane, implying a different thermal history. Scanning electron and optical microscope observations indicate that the peak assemblage of the Qinglongshan eclogite is anhydrous, composed of Grt + OmpI + Rt + (Ky + coesite). These primary minerals were replaced by second and third stage minerals, resulting in symplectite pseudomorphs or coronas. The following relationships are inferred: OmpI → OmpII + Ab + Fe‐oxide symplectite (type I) and Rt → Rt + Ilm intergrowth; and, Ky → Pg, OmpII (+Pl) → Amp (+Pl) symplectite (type II), and Grt → Prg (+Fe‐oxide). Mineral chemistry and mass‐balance demonstrate that the pseudomorphed textures were developed by metasomatism involving dissolution and precipitation intensified by fluids along grain boundaries. The formation of symplectite type I produced Fe, Mg and Na but consumed Ca and Si. The Mg and Fe diffused to garnet where exchange of (Mg, Fe) with Ca of the garnet resulted in compositional zonation with decreased Ca towards the edge of garnet grains where Ca was consumed during symplectite formation. The replacement of kyanite by paragonite consumed the extra Na. In the later stage, fluid infiltration partially transformed symplectite type I to type II, and narrow rims of pargasite resorbed garnet from their boundaries. Mass balance suggests that the transformation and resorption would have been coupled during fluid infiltration. In the latest stage, epidote and quartz were precipitated at very late stage as a result of fluid activity along microfractures. Tentative P–T conditions based on mineral reactions and thermocalc software suggest that the retrograded eclogite did not record the granulite facies retrograde evolution characteristic of eclogites from the Northern Sulu terrane. The difference in retrograde evolution between the Southern and Northern Sulu eclogites suggests a different exhumation history.  相似文献   

Neotectonic deformation in the transition zone between the Dead Sea Transform and the East Anatolian Fault Zone, Southern Turkey: a palaeomagnetic study of the Karasu Rift Volcanism     

O Tatar  J.D.A Piper  H Gürsoy  A Heimann  F Kobulut 《Tectonophysics》2004,385(1-4):17-43

In southern Turkey ongoing differential impingement of Arabia into the weak Anatolian collisional collage resulting from subduction of the Neotethyan Ocean has produced one of the most complex crustal interactions along the Alpine–Himalayan Orogen. Several major transforms with disputed motions, including the northward extension of the Dead Sea Fault Zone (DSFZ), meet in this region. To evaluate neotectonic motion on the Amanos and East Hatay fault zones considered to be northward extensions of the DSFZ, the palaeomagnetism of volcanic fields in the Karasu Rift between these faults has been studied. Remanence carriers are low-Ti magnetites and all except 5 of 51 basalt lavas have normal polarity. Morphological, polarity and K–Ar evidence show that rift formation occurred largely during the Brunhes chron with volcanism concentrated at 0.66–0.35 Ma and a subsidiary episode at 0.25–0.05. Forty-four units of normal polarity yield a mean of D/I=8.8°/54.7° with inclination identical to the present-day field and declination rotated clockwise by 8.8±4.0°. Within the 15-km-wide Hassa sector of the Karasu Rift, the volcanic activity is concentrated between the Amanos and East Hatay faults, both with left lateral motions, which have rotated blocks bounded by NW–SE cross faults in a clockwise sense as the Arabian Block has moved northwestwards. An average lava age of 0.5 Ma yields a minimum cumulative slip rate on the system bounding faults of 0.46 cm/year according with the rate deduced from the Africa–Arabia Euler vector and reduced rates of slip on the southern extension of the DSFZ during Plio-Quaternary times. Estimates deduced from offsets of dated lavas flows and morphological features on the Amanos Fault Zone [Tectonophysics 344 (2002) 207] are lower (0.09–0.18 cm/year) probably because they are limited to surface fault breaks and do not embrace the seismogenic crust.Results of this study suggest that most strike slip on the DSFZ is taken up by the Amanos–East Hatay–Afrin fault array in southern Turkey. Comparable estimates of Quaternary slip rate are identified on other faults meeting at an unstable FFF junction (DSFZ, East Anatolian Fault Zone, Karatas Fault Zone). A deceleration in slip rate across the DSFZ and its northward continuation during Plio-Quaternary times correlates with reorganization of the tectonic regime during the last 1–3 Ma including tectonic escape within Anatolia, establishment of the North and East Anatolian Fault Zones bounding the Anatolian collage in mid–late Pliocene times, a contemporaneous transition from transpression to transtension and concentration of all basaltic magmatism in this region within the last 1 Ma.  相似文献