东疆库姆塔格—沙泉子地区岩屑地球化学异常优选排队方法   总被引：10，自引：0，他引：10       下载免费PDF全文

方维萱 徐杰刘正桃  李丰收 《地质与勘探》2003,39(5):57-62

化探异常中选优评价成为目前地质勘查中的关键技术难题之一，以东疆觉罗塔格成矿带库姆塔格—沙泉子测区岩屑地球化学综合异常优选排队为例，讨论了化探异常优选排队新方法。在区域成矿地质背景和地球化学背景研究的基础上，采用地质地球化学预测系统新技术思路和方法，对本区130个化探异常进行了优选排队，筛选出36个有望异常和7个成矿远景区。对优选出的有望异常进行检查评价和工程验证均发现地表含金铜蚀变矿(化)体，说明所提出的化探异常优选排队新方法是有效可行的。  相似文献   

青海省3次强震前地下流体短临异常的对比分析     

张敏  马延魁 《高原地震》2003,15(1):9-14

通过对发生于1999～2000年间库玛中东段地区3次5级以上地震前地下流体短临异常的分析对比，得出了该地区地下流体短临异常的时空强演化特征。  相似文献   

德令哈6．6级地震前地震活动及地震序列特征     

陈玉华马文静  崔国信 《高原地震》2003,15(3):1-8

德令哈6．6级地震发生在青海省地震局2003年度会商确定的应注意地区内，震前测震学出现多项中短期异常。该地震序列从其能量释放比、震级差均符合主震一余震型判断指标，为主震-余震型序列。序列跟踪工作总结出该序列早期阶段(20天内)预测强余震的几项指标。  相似文献   

Magnetic properties of a freshly fallen LL ordinary chondrite: the Bensour meteorite   总被引：1，自引：0，他引：1  

Jrme Gattacceca  Pierre Rochette  Michle Bourot-Denise 《Physics of the Earth and Planetary Interiors》2003,140(4):343-358

A comprehensive rock magnetic, magnetic anisotropy and paleomagnetic study has been undertaken in the brecciated LL6 Bensour ordinary chondrite, a few months only after its fall on Earth. Microscopic observations and electronic microprobe analyses indicate the presence of Ni-rich taenite, tetrataenite and rare Co-rich kamacite. Tetrataenite is the main carrier of remanence. Magnetization and anisotropy measurements were performed on mutually oriented 125 mm³ sub-samples. A very strong coherent susceptibility and remanence anisotropy is evidenced and interpreted as due to the large impact responsible for the post-metamorphic compaction of this brecciated material and disruption of the parent body. We show that the acquisition of remanent magnetization postdates metamorphism on the parent body and predates the entering of the meteorite in Earth’s atmosphere. Three components of magnetization could be isolated. A soft coherent component is closely related to the anisotropy of the meteorite and is interpreted as a shock remanent magnetization acquired during the same large impact on the parent body. Two harder components show random directions at a few mm scale. This randomness is attributed either to the formation mechanism of tetrataenite or to post-metamorphic brecciation. All components are likely acquired in very low (≈μT) to null ambient magnetic field, as demonstrated by comparison with demagnetization behavior of isothermal remanent magnetization. Two other LL6 meteorites, Kilabo and St-Mesmin, have also been studied for comparison with Bensour.  相似文献   

地浸砂岩型铀矿床微磁异常研究及其找矿意义   总被引：4，自引：0，他引：4  

江民忠  李名松  谢迎春  石岩 《地质科技情报》2003,22(3):49-54

通过认真研究中国新疆某盆地410，411和412三个已知地浸砂岩型铀矿床的航磁资料，发现这些矿床上方均存在航磁微磁异常。根据地浸砂岩型铀矿的成矿地球化学机制，对航磁微磁异常的形成机理作了进一步探讨，结合试验区的实际预测成果指出，与氧化一还原过渡带有关的地浸砂岩型铀矿床上方存在微磁异常，高精度航磁完全能探测得到它。航磁微磁异常是此类矿床的特征异常之一，对此类铀矿床具有直接的指示意义，可以作为一种直接标志信息运用于前期成矿预测。  相似文献   

给定内插高程异常值的精度时对GPS水准网格间距的考虑   总被引：7，自引：0，他引：7  

陈俊勇 《测绘学报》2003,32(2):130-133

在已布设GPS水准网的地区，若需内插其中任意一点的高程异常值时，应该了解该内插值的精度。导出了该内插点高程异常值的精度评定方法，并具体给出在我国C级GPS水准网中，该内插点高程异常推估值精度和该地区的地形和栅格重力异常分辨率的数学关系式和实例。在给定内插点高程异常值精度的局域大地水准面时，按不同地形和栅格重力异常分辨率的密度，根据这些数学关系式，可以设计间距合理的B级或C级GPS水准网。  相似文献   

Study of Aeromagnetic Data Over Part of Eastern Ghat Mobile Belt and Bastar Craton     

S.P. Anand  Mita Rajaram   《Gondwana Research》2003,6(4):859-865

A portion of the aeromagnetic anomaly map of India, from 17⁰ to 20⁰ N and 78^o to 84^o E has been analysed to understand the tectonics of the region. The distribution of magnetic sources in the study region are clearly brought out in the analytic signal map and found to be associated with charnockitic rocks, iron formation and trap flows. The Godavari Graben is devoid of any magnetic sources. High-grade charnockitic rocks on surface and sub-surface, flank the shoulders of the Godavari Graben on either side. From the analysis of magnetic data, Sileru Shear Zone (SSZ) is identified as the contact of the Bastar craton and the Eastern Ghat Mobile Belt (EGMB). The Eastern Ghat is divided into two blocks: Block-N north of Srikakulam is devoid of magnetic sources while the charnockitic rocks are the main magnetic carriers in Block-S. The difference in magnetic characteristics of the two blocks has been attributed to the difference in metamorphic history. Block-N has an over print of amphibolite facies metamorphism while Block-S to the south depicts granulite facies metamorphism. The Euler solutions within the EGMB shows that the magnetic sources along SSZ is shallower than the south east implying that the exhumation process in the EGMB has a differential rate.  相似文献   

Pull-down basin in the central part of Japan due to subduction-induced mantle flow     

Takeshi Kudo  Koshun Yamaoka   《Tectonophysics》2003,367(3-4):203-217

The driving force for the basin subsiding against isostatic balance in and around Lake Biwa in the Kinki district, Japan is discussed. The lake region is characterized by strong negative Bouguer anomalies, especially by a steep horizontal gradient zone of gravity anomaly running along the western margin of the lake. The large negative anomaly (>50 mgal) cannot be explained by low-density sediments beneath it. A down-warping structure extending to the Moho depth should be taken into account. This conjecture has been strongly supported by a short-period receiver function imaging, which shows a clear offset of about 8 km for the Moho discontinuity under the steep gravity gradient zone.A question arises as to what is the driving force to create such a large down-warping structure. We consider that the subduction of the shallow-dipping slab under the region (Philippine Sea Slab) may cause crustal deformation by dragging the viscous mantle downward. In order to verify this model, we simulated the induced mantle flow due to the subduction of the Philippine Sea Slab and the pressure distribution on the crust–mantle boundary. This numerical experiment showed that the induced flow makes a strong negative pressure zone under the lake region if the slab has a vertical offset along the direction of subduction. This offset of the slab is consistent with plate models deduced from hypocentral distributions and Sp phases of the deep-focus earthquakes.  相似文献   

冬季北极涛动和华北冬季气温变化关系研究   总被引：33，自引：6，他引：33  

何春  何金海 《南京气象学院学报》2003,26(1):1-7

利用北极涛动指数（AOI）、NCEP／NCAR40a再分析资料中的海平面气压（SLP）、850、500、200hPa等压面高度场资料及中国160站月平均气温资料，运用小波分析，经验正交函数（EOF）分析等方法，分析了华北冬季气温和冬季北极涛动指数的变化特征及其关系。结果表明它们之间存在有着显著相关，特别是在年代际尺度上关系尤其密切。华北在20世纪70年代初以前为持续冷冬，80年代中期之后变为持续暖冬，其间相对正常，而冬季北极涛运指数亦存在类似的3个阶段，冬季北极涛动高（低）低数年，华北地区为暖（冷）冬年。其原因在于，北极涛动在于对流层低层和高层都可激发类似EU遥相关型的异常，通过影响西伯利亚高压和东亚大槽影响华北地区气温。强（弱）涛运年大气环流具有弱（强）东亚冬季风特征，西伯利亚高压减弱（增强），亚洲大陆地面东北风减弱（增强），高空东亚大槽减弱（增强）。  相似文献   

欧亚冬季雪盖异常及其与ENSO循环的关系     

王静  孙照渤 《南京气象学院学报》2003,26(1):38-46

利用 NOAA- NESDIS提供的 1 973— 2 0 0 0年北半球雪盖面积资料 ,研究了欧亚冬季雪盖的时空特征 ,发现欧亚大陆中高纬地区积雪有明显的整体性分布特征 ,而50°N以南的冬季积雪随纬度的变率较大 ;欧亚大陆中高纬地区冬季积雪呈东西反位相分布。利用小波分析发现 ,冬季欧亚积雪具有显著的 3～ 4 a周期。最后指出 ,欧亚积雪异常引起的下垫面热力异常可能为次年 El Nino事件的爆发提供触发条件。  相似文献