琼州7.5级地震区深部电性异常及地震活动性研究   总被引：1，自引：0，他引：1       下载免费PDF全文

胡久常  白登海  王薇华  林镇  向小娟  王立风 《地震学报》2007,29(3):258-264

通过对1605年琼州7.5级大地震震中区及邻近地区大地电磁探测,发现震中区地壳深部存在一低阻体.该低阻体自约13 km以下一直延伸到上地幔,推测其为正在上升的地幔柱,并由此认为地幔柱的存在及其热物质的上涌,使上部地壳产生断裂和粘滑活动,是产生琼州7.5级大地震的重要原因. 这次大地震后断裂活动表现为以蠕滑为主.推测未来再发生同等强度大地震的危险性将大大降低.   相似文献   

An internal-external optimized convolutional neural network for arbitrary orientated object detection from optical remote sensing images     

Sihang Zhang  Zhenfeng Shao  Xiao Huang  Linze Bai  Jiaming Wang 《地球空间信息科学学报》2021,24(4):654-665

Due to the bird's eye view of remote sensing sensors, the orientational information of an object is a key factor that has to be considered in object detection. ...  相似文献   

The maize evapotranspiration in the background of climate change: a case study in arid area     

Buchun Liu  Xurong Mei  Guohua Lv  Youlu Yang  Meilan Bai  Yongfeng Wu  Jiqing Song  Wenbo Bai 《水文研究》2012,26(5):633-639

  相似文献   

东秦岭商丹地区蛇绿岩中的角闪石研究   总被引：1，自引：0，他引：1  

白学让  原莲肖 《岩石矿物学杂志》1990,9(2):137-147

东秦岭蛇绿岩主要分布在北秦岭南缘、商丹断裂带以北的狭窄地带,断续逶迤呈带状作近东西向展布。分布于商丹地区的蛇绿岩是东秦岭蛇绿岩带的重要组成部分并具有代表性。 本文着重论述了商丹地区蛇绿岩中广泛分布的主要造岩矿物之一,角闪石的主要特征组份、微量元素、晶胞参数、阳离子占位度等成因矿物学特点。并据此说明了该蛇绿岩中的角闪石属于区域正变质的产物;形成的物质来源具有同源性,原岩为超镁铁质-镁铁质的岩浆岩和火山熔岩;形成的热力学条件基本相同,变质程度为绿帘角闪岩相或角闪岩相,变质温度为610℃左右,压力大于5×10~8Pa。 此外,根据商丹地区蛇绿岩中角闪石成因矿物学特征之相同性所提供的信息表明,东秦岭蛇绿岩带是华北和扬子两个板块俯冲、碰撞的构造边界变质带。  相似文献   

天山乌鲁木齐河源冰川与空冰斗辐射气候的计算结果   总被引：3，自引：0，他引：3  

白重瑗 《冰川冻土》1989,11(4):336-349

提要 在朝向、坡度和山体遮蔽度影响下,与水平面相比朝北冰川和朝南空冰斗在太阳偏角为15°,0°和-10°时的平均太阳辐射能量损失分别是40.6％和21.0％。1号冰川东支夏季消融期内自然冰雪面辐射场内辐射平衡各分量平均日总量值受地形因素和反射性能的控制而显示出由西北侧向东南侧逐渐降低的带状分布规律。晴朗少云天气下的总辐射和有效辐射的垂直梯度分别是14.52Wm~(-2)/100m和2.77Wm~(-2)/100m。  相似文献   

Types and distribution of silver ore deposits in China   总被引：2，自引：0，他引：2  

C. Y. Wu  G. Bai  L. M. Xu 《Mineralium Deposita》1993,28(4):223-239

Silver is generally recovered as a by- and co-product along with Au, Pb, Zn, Cu, Sb, Bi, Hg, Sn and W from polymetallic and gold mines in China. Chinese silver deposits can be classified into five principal types according to host rocks. These types and their host rocks are: (1) marine volcanic-sedimentary rocks hosting (la) massive sulfide Pb-Zn-(Cu)-Ag ores and (1b) stratiform Ag-(Au) ores; (2) continental volcanic-sedimentary rocks containing (2a) various polymetallic-silver veins and/or stockworks, and (2b) Ag-(Au) veins in pyroclastic rocks; (3) rocks affected by metasomatic processes including (3a) complex Sn-polymetallic-Ag ores, (3b) Pb-Zn-(Cu)-Ag skarns, (3c) associated W-Ag quartz veins and/or skarns, and (3d) Ag-(Au) zones and veins in altered carbonate rocks; (4) metamorphic-intrusive rocks, principally Ag-(Au) veins in sheared and brecciated metamorphic rocks; and (5) sedimentary rocks including (5a) stratiform Pb-Zn-Ag ores in carbonate rocks, (5b) Ag-V mantos in black shales, and (5c) Cu-(Ag) layers in red sandstones. A sixth grouping includes gossans. The tectonic settings, geological features, and temporal and spatial distribution of these different types of silver occurrences indicate that silver mineralization reflects to a great extent the evolution of tectonic environments in China throughout geological time. Type 1 is generally developed in association with several fold belts from the Caledonian to Yanshanian orogens, while types 2, 3 and 4 correlate with rejuvenation of the eastern China continent during the Mesozoic period. The three subgroups of type 5 are recognized in different stages and various sedimentry and diagenetic environments during the development of paraplatforms and fold belts. Type 6 results from recent weathering of existing sulfide ores or protores. Editorial handling: DR  相似文献   

华北板块北缘中段含铁变质岩系的时代和构造环境初探   总被引：15，自引：1，他引：15  

徐备  陈斌 《地质论评》1994,40(4):307-311

内蒙北部苏尼特右旗以北二道井、哈拉干和红格尔地区的含铁变质岩系中变质基性火山岩Ｓｍ－Ｎｄ全岩等时线年龄为１５１１±７６Ｍａ，这表明该岩系属中元古代而不是以往推测的早古生代，等时线的εＮｄ（ｔ）值为＋６．３±１．７，属亏损型地幔源区岩相学分析表明它形成于规模不大，具中等水深和较弱水动力条件的较封闭海域。据上述特征推测，华北板块北缘中曾存在中元古代初动型火山陆缘。  相似文献   

综合方法在勘查一个特殊的斑岩型铜银锡矿床中的应用     

刘光海  白大明 《物探与化探》1994,18(2):121-130

敖瑙达巴斑岩型铜银锡乡金属矿床既不同于大多数由幔源岩浆衍生物所形成的斑岩铜矿,也不同于大多由地壳重熔岩浆衍生物形成的斑岩型锡(钨钼)矿床。它是分布于过渡性地壳上的、由起源于下地壳-上地幔的过渡性岩浆的衍生物形成的斑岩型铜银锡矿床。根据已取得的资料,在矿区内磁法、电法、化探异常的展布与已知矿化蚀变带一致。凡磁、电、化探异常吻合一致的综合异常,经验证都已见到了矿体。  相似文献   

空间数据的拓扑关系及其自动生成   总被引：8，自引：0，他引：8  

白玲 《测绘学院学报》1993,(4)

本文讨论了空间数据的拓扑关系,对地图的基本图形元素作了更准确的表述;详细介绍和讨论了自动生成空间数据拓扑关系的原理和方法,重点研究和探讨了并列和嵌套的面域拓扑关系。本文所述的方法适用于多种复杂的空间实体关系。  相似文献   

Effects of chemical environment on the solubility and incorporation mechanism for hydrogen in olivine     

Quan Bai  D. L. Kohlstedt 《Physics and Chemistry of Minerals》1993,19(7):460-471

To investigate the solubility and the sites of incorporation of hydrogen in olivine as a function of point defect concentration, two-stage high-temperature annealing experiments have been carried out. The first annealing stage (the dry preannealing stage) was conducted at a total pressure of 0.1 MPa, a temperature of 1300° C and various oxygen fugacities in the range 10^?11–10^?4 MPa for times > 12 h. In these heat treatments, the samples were buffered against either orthopyroxene or magnesiowustite, or they remained unbuffered. The second annealing stage (the hydrothermal annealing stage) was performed at 300 MPa and 900–1050 ° C under a hydrogen fugacity of ～ 158 MPa for 1–5 h. Infrared spectra from the annealed samples revealed two distinct groups of bands. Group I bands occurred at wavenumbers in the range 3450–3650 cm^?1, while Group II bands occurred in the range 3200–3450 cm^?1. The hydrogen solubility associated with Group I bands is proportional to f _{O 2} to the 1/6 power for samples preannealed in contact with orthopyroxene, to the 1/3 power for samples preannealed in contact with magnesiowustite, and to the 1/13 power for samples preannealed in the absence of a solid-state buffer. The hydrogen concentration for Group II bands varies with f _{o 2} to the 1/3 power for opxbuffered samples, to the 1/2 power for mw-buffered samples, and to the 1/3 power for unbuffered samples. The dependence of hydrogen solubility on oxygen fugacity and orthopyroxene activity suggests that hydrogen is incorporated into the olivine structure via association with point defects. The presence of two distinct groups of absorption bands indicates that hydrogen is associated with two distinct lattice defects. The following point defect model for the mechanism of incorporation of hydrogen in olivine is consistent with these results: Hydrogen ions responsible for the Group I bands are associated with doubly charged oxygen interstitials, while hydrogen ions responsible for the Group II bands are associated with singly charged oxygen interstitials. Furthermore, the infrared bands observed in naturally derived olivines are present in spectra from our hydrothermally annealed crystals. Thus, the mechanisms of incorporation of hydrogen in olivine under geological conditions are the same as those operative under laboratory conditions. The maximum solubility reached in these experiments was ～ 360H/10⁶Si, which corresponds to ～ 0.002 wt% of H₂O. This value is a lower bound for the solubility of hydrogen in olivine under upper mantle conditions.  相似文献